Dental Material, Operative Dentistry and Prosthodontics

Suraj  Kumar

Dental Material, Operative Dentistry and ProsthodonticsCHAPTER 1

Topic

➢ Physical Properties
➢ Impression Material
➢ Gypsum Product
➢ Amalgam
➢ Pin Retained Restoration
➢ DFG
➢ Cements
➢ Composite
➢ Denture Base Resin
➢ Ceramic
➢ Metallurgy
➢ Caries
➢ Instruments and Miscellaneous
➢ Prosthodontics
➢ Some More Notable Points from Prosthodontics
➢ Some More Important Points from DM + OD + Prosthodontics

PHYSICAL PROPERTIES

Glass Transition Temperature:

Benzold – Bruck effect (PGI 11) vs Metamerism
BENZOLD – BRUCK effect
METAMERISM
Change in color due to change in BRIGHTNESS
different colour under different LIGHT SOURCE [Q]
Change in value of hue with change in luminance

(PGI june 11)
Munsell ‘s system measures and defines color quantitatively

(AIIMS Nov. 10, AIPG 07)

Water contact angle:

2Poisson's ratio:
Stress: It is the Internal [Q] resistance against applied force/load
Elastic Limit “Maximum stress” > proportional limit
Permanent distortion occurs when ELASTIC limit is exceede
Proportional limit = GREATEST stress
toughness

Toughness of dentine > enamel [Q]
e.g tempering of steel [Q]
Bingham Body behavior:
Fig 1.1: Bingham body behavior
- Concept: Viscoelastic deformation: applied force produces ELASTIC strain, plastic strain/combination of elastic + plastic strain.
- Plastic deformation: Is irreversible. new permanent shape taken up
- Elastic deformation: Is reversible and will be completely recovered
- Viscoelastic deformation: PARTIAL recovery [Q]. It is a characteristic of POLYMER that behave as elastic solids and viscous liquid. AMALGAM is also viscoelastic.
3Stress strain graph:

Fig 1.2: Stress strain graph
Moe:
- Enamel (83,000 MPa) > Amalgam (27, 000 MPa) > Dentine (17,000 MPa)

Cote of different material in comparison to enamel (11.4):

COMPRESSIVE strength of:
- Dentine (266 MPa) (KCET Q) < amalgam (310 MPa) < enamel (384 MPa)
ULTIMATE tensile strength:
- Co Cr > Au alloys { donot confuse with Tensile strength. it is a strength
High compressive strength + low tensile strength = Brittle (ceramic and amalgam)
Types of Stress and Force responsible:
Force
Stress
Fig 1.3: Shear
Shear stress – result of 2 set of forces parallel to each other

KHN values:
- Diamond (superabrasive) (7,000 to 10, 000) > porcelain (412) > enamel (340) (closest to porcelain PGI 05) > amalgam (90) > microfilled composite (25 to 35)

Hardness Test: Is the resistance to abrasion and indentation

HARDNESS TEST	MATERIALS used to measure
Knoop hardness test	Diamond of Rhombic shape (TRICK: Ke Da R)
Vicker's/diamond pyramid test (PGI 07, 11, 10)	Diamond of square base shape (136^°)
	Diamond of conical shape
	Steel ball

NOTE:

Gold is the most ductile and malleable
Ag is the 2^nd most ductile and malleable
Enamel is stiffer and brittle than DENTINE.dentine is flexible and tougher (resistance to fracture)
5Brazillian Test:

Measures the ultimate tensile strength of Brittle material
Fig 1.5: Brazillian test
Maxwell Voigt model:
- Determine Viscoelastic behavior
Solid solution:
Alloy with complete solubility in BOTH solid and liquid state
Most dental restoration are based on SOLID solution [Q]
Simplest alloy (KCET 10)

Eutectic alloy:

Peritectic alloys:
components have limited solid solubility, e.g Ag – Sn in amalgam and Ag-Pt in gold casting alloy
Liquid + β – solid solution → α solid solution (AIIMS)
Concept:
- Why there is high incidence of marginal caries around restoration? The surface energy of many restorative material is higher than tooth. so, increased tendency for surface and margins to accumulate debris.
M.p:
m.p of Ag – 960 ^°C
m.p of Au - 1063 ⁰ C
m.p of Ti – 1668 ⁰ C
b.p of Au – 2200 ^° C
Thermoset material – chemically set material
Thermoplastic material – temperature affects setting

LAST 5-YEAR QUESTIONS FROM THIS TOPIC

1. Angle between adhesive and aderend is zero. It me Ans.

(AIPG 08)

Ans. Complete wetting of surfaces (Ref: Craig's 12/e p18 -20)

2. The forces that hold atoms together are called:

(KCET 10)

Ans. Cohesive forces

3. If rate of loading is increased, the mechanical properties of a material:

(AIIMS Nov. 09)

Ans. Increases (Ref: Journal of the American Concrete Institute, 1980; 77: 1 – 212)

4. Which of the following decreases with strain hardening?

(PGI Dec 11)

Hardness
Strength
Proportional limit
Ductility

Ans. d. (Ref: phillip's 11/e p74)

5. Which decreases with surface hardening?

(PGI Dec 11)

Ans. Percentage elongation + corrosion resistance (Ref: Phillip's 11/e p576)

6. Wire hardening at low temperature of orthodontic wire would enhance all EXCEPT:

(PGI Dec 11)

Stiffness
Resiliency of wire
Brittleness
Ductility of wire

Ans. d. (Ref: Phillip's 11/e p576)

7. Tempering of steel:

(PGI Dec 10)

Ans. Increases it's toughness (Ref: Phillip's 10/e p641)

IMPRESSION MATERIAL (VERY IMPORTANT FOR AIPG)

Dustless alginate: is made by coating with glycerine (if glycerine Not given in option go for Glycol/Dihydric Alcohol)

(AIIMS Nov. 09)
Hysteresis is the temperature lag between gelation and liquefaction

(AIPG 07)
Hysteresis is exhibited by AGAR [Q] not by alginate
BUT syneresis by BOTH

Concept: Controlling S.T for alginate/ZnOE

7ZnOE:

Base paste
Reactor paste
ZnO
ZnOE:
Is Non – H₂O based cement (KCET 12), BUT requires water for it's setting reaction:

(AIIMS Nov. 09)
Produces Obtundant effect on pulp.

(AIPG 07)
for Dimensional Stability:
Of agar → stored in 2 % K₂SO₄/100 % relative humidity
Of alginate → stored in 100 % relative humidity
Agar and Gypsum Hardener:

(AIIMS Nov. 10, AIPG 07) (Important for KCET)

BORAX was introduced into agar to improve its strength BUT it has retarding effect on setting of gypsum
(AIIMS Nov. 10)
So, an accelerator K₂SO₄ is added to agar to counter act the retarding effect of borax (AIPG 07).this 2 %K₂SO₄ is called GYPSUM HARDENER.
(AIIMS Nov. 10, AIPG 07)
Type 2 silicone impression material → additional silicone
Type 1 ZnOE → HARD type 2 ZnOE → SOFT
In NON-eugenol → HV – EBA is a substitute for eugenol (KCET)
The MOST COMMON impression material for INDIRECT CASTING: additional polysilicone [Q]

(ALSO material of choice for OSMF patient) [Q]
FLUORIDE release: [Q]

GIC > RMGIC > Compomer > composite
Stages of addition polymerization:
Clinical implication of high tear strength of PolyS:

Allows their use in deep subgingival areas where removal is difficult
8Impression Compound:

(PGI 10)

The low thermal conductivity influences the cooling rate of this material because the outside of a mass of compound hardens fairly rapidly, whereas the inner regions remain soft. Impressions must be given adequate time to cool completely before they are removed from mouth (A favourite Q of PGI repeatedly asked)
Polysulfide vs additional Silicone:

Polysulfide
Additional Silicone
High W.T and S.T (advantage)
Reverse of PolyS
SNAP test:
- Polyether shows a clearly defined W.T with a sharp transition into setting phase. This is called SNAP test
W.T of dental materials:

Zn Polycarboxylate → 3 min
Zn PO → 5 min
Amalgam → 3-4 min
Multiple pour/multiple casts → Addition polysilicone/polyether
Optimal thickness of elastomeric impression material → 2-4 mm

(KCET Q)
Spacer thickness – 2 mm
Putty – Wash technique:
To minimize the effect of polymerization shrinkage
PUTTY Used 1^st → Then wash material used
distortion is associated with putty material
Surfactant → is added to polyvinyl siloxane to make it hydrophilic

(AIIMS Q)
Multiple mix technique → heavy + light body
Single Mix technique → medium viscocity of elastomer is used.so, single mix don't have high viscocity
Custom Tray: used in polysulfide. {advantage – less material required. So, less polymerization shrinkage} [Q]
Brush Heap → found in agar
ZnOE paste → most commonly used wash/final impression for edentulous jaw.

(BHU 07)

Main advantage - dimensional stability. so, used for final impression
Elastic Impression material: hydrocolloid + elastomer
BOTH silicones (addition and condensation) cannot be used with “Latex gloves”

Low W.T + S.T → disadvantage
Polysulfide vs Condensation Silicone:
Polysulfide
Condensation Silicone
Highest permanent deformation
high permanent deformation
High polymerization shrinkage
Highest polymerization shrinkage
C₂H₅OH [Q] is by product of condensation silicone is a larger molecule than H₂O [Q], a by product of PolyS (Remember)
9PolyS:
Highest tear strength
Trear strength: PolyS > Polyether

(PGI 11)
Biocompatible
High W.T + S.T (advantage)
Polyether:

highest cytoxicity
Stiffest (very rigid) → so, cast is difficult to remove
Too rapid polymerization + incomplete polymerization + improper P/L
Rough and irregular surface on impression (Very Important Q for NEET)

(AIPG 10, 07)
Catalyst:

PolyS – PbO₂
Condensation silicone – Sn octate
Addition silicone - chlorplatinic acid
Addition silicone:
Can be poured after several hours
Pour after 20 minutes as H₂ evolves to create voids if poured before
Called type 2 silicone impression
FLOW of type 1 impression compound:

At 37 ^°C - 6 %
(AIPG 07)
At 45 ^°C - > 85 %
Of type 2 impression compound:

At 37 ^°C
2 %
At 45 ^°C
75 to 85 %
Impression of hyperplastic tissue/flabby tissue:

Should be obtained with MUCOSTATIC technique to ensure intimate contact (AIPG 08 Q) and no pressure on tissue. So, tray with SPACER used. impression plaster used for this purpose
(AIIMS 05)
Additional silicone → material of choice for OSMF patient in closed mouth technique as it has excellent flow

(AIPG 08)

NOTE: (important for AIPG/AIIMS)

10Plasticizer:
In polyether
Glycol ether/pthalate

Accelerator vs retador:

Material	Accelerator	Retador
ZnOE/impression paste	Zinc acetate (AIPG), CaCl_2, ZnCl₂ (AIPG 07), MgCl_2, ZnSO_4, alcohol, H₂O [Q] PGI 11	TRICK all oily compound Mineral oil, waxes petroleum jelly, glycerine
agar	2% K₂SO₄ (also called gypsum hardener) Accelerate setting reaction of	Borax ses strength and Ces viscosity of agar
alginate	Ti fluoride (gypsum hardener	Trisodium PO₄
gypsum	K₂SO₄, Na₂SO_4, NaCl upto 2 %, gypsum (acts as nuclei of crystalisation)	TRICK:A B C A – Acetate B - Borax C - Citrate

NOTE:
* upto 2 % NaCl acts as accelerator in gypsum product BUT at higher concentration it acts as RETARDOR
* ZnOE used to make final/wash impression as it has DIMENSIONAL STABILITY [Q]
HYDROCOLLOIDS and ELASTOMERS should be removed by sudden jerky [Q] motion as they are viscoelastic material. This is to prevent permanent deformation [Q]

[PGI]
AGAR:

(AIPG)
Has brush heap structure
Liquefies at 70 ^°C to 100 ^°C

(AIPG 08)
Solidifies at 30 ^°C to 50 ^°C

Laminate/agar – alginate method:

In case of Polyether, stone cast can be easily poured but removed with difficulty.

(KCET 11)
In case of condensation silicone, polymerization is accompanied with repeated elimination of small molecules

(AIPG 10)

SUB TOPIC: IMPRESSION TECHNIQUES

Concept:

11“PPS”:

Buccal Frenum:
Maxilla
- Affected by levator anguli oris
- CANINUS
Fig 1.6: Buccal frenum
Remember: 8 muscles form modiolus EXCEPT zygomaticus MINOR and ala Nasi (COMEDK 07, PGI Dec 11)
For stability of denture tongue should rest on occlusal plane
Massetric notch:

(AIPG 12)
Formed by action of Masseter on Buccinator
(TRICK = it is “massetric notch”. so, action will be of “masseter”)
Influence of CORONOID process on maxillary denture:
- CORONOID process → limits DB flange → if DB flange too thick
- Denture falls during wide opening of mouth/lateral movement of mandible
12MOUTH temperature wax:
Used in fluid wax technique to record PPS
e.g Iowa wax; Korecta type 4(NOT type 1) { COMEDK 13 }; HL physiologic paste
Hamular Notch = pterygomaxillary notch
Retromylohyoid curtain formed by:

Fig 1.7: Retromylohyoid curtain
Influence of muscle on lingual flange:
Anterior region
Middle region
Posterior region
Genioglossus
Mylohyoid
Palatoglossus + superior constrictor

Points to Remember from Impression Materials (a final conclusion)

Polysulfide/mercaptan/thiokol:

1^st dental elastomer

PbO₂ → gives brown color to polyS and cross linking and oxidizing agent.

Polymerization shrinkage minimized by taking minimal material in tray. [Q]

Shows highest tear strength. So, used in subgingival area

(PGI 11)

Stains clothes + unpleasant odour

(AIPG 10,07)

POLYETHER:

Cross linking agent is ESTER derivative of AROMATIC sulfonic acid

(BOUCHER MCQ)

Condensation silicones polymerise by repeated elimination of small molecules

(AIPG 10)

Single mix materials have lower viscosity

(AIPG 08)

LAST 5-YEAR QUESTIONS FROM THIS TOPIC:

1. Working time of elastomeric impression material is defined as:

(AIPG 10, 07)

Ans. Time from start of mixing till just BEFORE the elastic properties have developed (Ref: Phillips 10/e p142)

2. For ZnOE, all of the following are true EXCEPT:

(AIPG 08)

Olive oil is used as plasticizer
Addition of methylmethacrylate increases strength.
Addition of o – EBA in concentration of 37 – 50 % increases strength
Rosin decreases the brittleness of set cement

Ans. c (Ref: Craig's 12/e p498)

133. All of the following is used as accelerator in ZnOE except?

(PGI Dec 11)

Acetic acid
Znic acetate dehydrate
Bromoglycerine
Calcium chloride

Ans. c (Ref: phillips 10/e p181)

GYPSUM PRODUCT

ADA number = 25

(COMED K 11)

Property	Type 1	Type 2	Type 3	Type 4	Type 4
Other Name	Impression Plaster	Model plaster P.O.P dental plaster	dental stone hydrocal class 1 stone	Densite	Dental stone with high strength and expansion
W/P	0.5	0.5	0.28 – 0.30	0.22 – 0.24	0.18 – 0.22
S.T	4 to 5 min	All	Others have	12 to 15	min
S.E	0.15 %	0.30 %	0.20 %	0.10 %	0.30 %
Compressive Strength	800>	1300 >	3000 >	5000 >	7000
Use	Final wash	To fill flask	Construct-ion Of cast	BEST die material	Improved die material

TRICK
to remember S.E:
TYPE 2 = TYPE 5 = 0.30% (highest)
Next remember Type 3 < type 1 < type 4
Minimum requirement of SE for GP:
ALL except type 4 and 5
Type 4 and 5
“0”
0.10 %
Type 5 = 0.10 %

(KCET 11)

14Factors affecting S.E of G.P: (ALL points have been asked as Q)

H₂O of reaction for setting of G.P = 18.6 ml
Gauzing H₂O does not react. So, S.T of G.P independent of it
Soluble plaster:
Impression plaster + potato starch
Facilitates removal of impression from cast

(COMEDK 11)

Setting reaction of G.P:

Cynoacrylate:

Low viscosity resin. Initiation of polymerization in presence of H₂O
USE:
Major: DIE hardener
Fluidity measurements:
Type 1 and 2 (Slump Test)
Type 3, 4, 5 (CORE penetration test)
Terra Alba: set CaSO₄. 2H₂O act as accelerator [Q]

LAST 5-YEARS QUESTIONS FROM THIS TOPIC

1. The safest method for soaking dental cast is:

(COMED K 11)

Ans. Placing in a saturated solution of calcium sulfate

2. The strength of gypsum products is generally expressed in terms of:

(KCET 10)

Ans. Compressive strength

AMALGAM (IMPORTANT TOPIC FOR ANY MDS EXAM)

Composition of amalgam: (a favourite topic of PGI)
15HIGH Cu amalgam is formed by irregular + spherical particles

(KCET 10)

HIGH Cu
Low Cu
Admixed
Unicompositional (Best)
Ag – 65 %
Ag – 69 %
Ag – 60 %
Sn – 29 % (PGI 11)
Sn – 17 %
Sn – 27 %
Cu - < 6 %
Cu – 13 %
Cu – 13 – 30 %
Zn - < 1 %
Zn - 1 %
Zn – 0 %
NOTE: Zn containing amalgam alloys last 20 to 50 % longer than Zn free though they cause delayed expansion

(KCET 10)
Zn containing amalgam alloy has Zn > 0.01 %
Hg content of “precapsulated Amalgam” – 40 to 45 %

(AIIMS Nov 11)
Spherical alloy = 42 – 45 % Hg [Q]
Lathe cut = 50 % Hg [Q]

Delayed Expansion:

Delayed Contraction:

NOTE: In composition of amalgam only Sn ↓ses expansion while Ag and Cu ↑Ses expansion.
SPHERICAL amalgam requires less condensation force than lathe cut

Phases in amalgam alloy:

Order of Corrosion Resistance:

γ1 > γ > η > γ2
so, η is least corrosion resistant phase in high Cu amalgam as < 1% of γ2 phase in high Cu amalgam (DONOT confuse)
Lathe cut vs Spherical alloy:
All properties of lathe cut inferior to spherical
Lathe cut achieves lowest compressive strength at 1 hr (AIIMS 06)
Indisper:

10 % In admixed → ↓ses release of Hg vapour during polishing (AIPG 09)

Compressive strength of amalgam:

Tensile strength of amalgam:
In 1 week = 48 to 70 MPa
Tensile strength of admixed < low Cu
Appearance of amalgam:
Undermix amalgam = dull
Adequate mix amalgam = shiny [Q]
Over mix amalgam = soupy/sticky
Under/Over Trichuration:

In lathe cut
in spherical
Ses strength
ses strength
BUT

↑ Ses CREEP in BOTH lathe cut and spherical

Creep and Mercuroscopic Expansion:

NOTE: Content of Hg is 2-3 % higher at margin

Hg CONTENT and EFFECT:

Degradation of high and low copper amalgam:

most common evidence of degradation of LOW Cu amalgam
↓
MARGINAL deterioration
(AIPG 07)
Of high Cu amalgam → BULK fracture (due to mechanical fatigue For 10 to 15 yrs)
Marginal defect best measured by Mahler's scale

Range of value – 1 to 11 for amalgam
Corrosion Products:

LOW Cu
HIGH Cu
SnO + SnCl
CuO
Penetrating type of corrosion NOT seen in high Cu AMALGAM

(AIPG 10, 09, AIIMS Nov. 09)
Facts About Hg:
Maximum exposure of Hg (occupational) considered safe is 50 μg/m³ of air [Q] { according to OSHA safe level for Ni is 1 mg/m³ } { PGI 11 }
Hg absorbed from GIT, LUNGS, SKIN NOT KIDNEY [Q]
- Absorbtion efficiency for different for Hg:
  
  FORM
  SKIN
  LUNG
  GIT
  Elemental
  ---
  80 %
  ----
  Inorganic
  ---
  80 %
  7 %
  organic
  ---
  ---
  95 to 98 %
  
  Methyl Hg is most toxic form and absorbed 90 – 95 % from GUT [Q]
  14 times denser than H₂O
  65 – 85 % inhaled Hg vapour is retained in body
  Half life 55 days (NBDE Q)
18
NORMAL level in:

Urine – 15 μg/l
Blood – 4 μg/ml
Lower blood Hg level at which earliest non – specific symptom starts 35 ng/ml (AIPG 07) and urine is 30 μg/ml

SUB TOPIC: CAVITY PREPARATION

Cavity width for class 1 and 2

Material
DFG
AMALGAM
INLAY
ONLAY
Width
1/5^th intercuspal (I.C) distance (most conservative)
1/4^th the I.C distance
1/3^rd I.C distance
>1/3^rd I.C distance
Axial wall pulpal depth (into dentine): for class 2
Crown – 0.5 to 0.6 mm
Root – 0.7 to 0.8 mm

20 retention in class 2:

2⁰ retention feature in class 3

Fig 1.8: Secondary retention feature in class 3
2⁰ retention in class 5:
- Is by placing 2^° retention grooves on AXIAL WALL (AIIMS 11) (i.e A-G and A-I line angle)
- OR 4 coves on point angles
Fig 1.9: Retention in class 5
19

Fig 1.10: Retention in class 5

Internal and External line angle:

Locks and high Cu amalgam:

Does not require locks as they exhibit less creep

Butt joint vs Slide fit:

BUTT JOINT	SLIDE
900 butt joint for amalgam, silicate, ceramic (all 3 brittle material)	>900 cavosurface angle for CAST restoration
NOTE: 900 BUTT joint is done for silver amalgam as it has poor strength in thin sections. (COMEDK 11)

Number of line angle and point angles for class 1, class 2 and MOD:

TRICK = number of line angle increases by 3 and point angle by 2 when cavity transforms from class 1 to class 2 and class 2 to MOD
CAVITY
Class 1
Class 2
MOD
POINT ANGLE
4
6
8
LINE ANGLE
8
11
14
Supporting cusp = centric holding/stamp cusp/functional cusp

(KCET 12)
cavosurface angle of amalgam cavity preparation should be at right angle

(AIPG 07)
BEVELS:

Produces stronger enamel margin
Provides marginal adaptation [Q]
In amalgam
In CAST restoration
Bevels are included under RESISTANCE form
NOT included in 10retention and resistance form BUT given during final cavity preparation (i.e FINISHING)
Clearance with adjacent tooth:
Of gingival seat
Of facial and lingual proximal wall
0.5 mm
0.2 mm
20In class 3 preparation it is acceptable to place enamel margin in area of contact
Reverse ‘S’ curve:

Has role in Esthetic → so, placed on buccal surface
Cavity preparation in class 1:
In amalgam/DFG when proximal residual ridge thickness is < 1.6 mm, mesial and distal wall must Diverge Occlusally
But if this is > 1.6 mm, mesial and distal wall should converge occlusally.
Gingival extension of restoration:

Atleast 3 mm above alveolar crest [Q]
Concept:

Resistance form:

For class 2 cavity preparation on maxillary permanent 1^st molar:
Increased chances of exposure of “MB and ML pulp horns” (NBDE Q)
“MB” pulp horn exposed in case of 1° 1^st molar

(PGI 12)

class 5 cavity

(Important for NEET and AIIMS):

Class 3 cavity (Important for NEET and AIIMS):
- Facial, lingual and gingival walls should meet the axial walls at 90^°
- Retention coves placed at axio-facio-incisal point angle.this points are placed entirely in dentine
  
  (AIPG 07)
- “lingual dove tail” indicated if ADDITIONAL retention needed for larger restoration, e.g CANINE
Fig 1.11: Lingual dove tail

LAST 5-YEARS QUESTION FROM THIS TOPIC

1. Pre carve burnishing is useful for all except:

(AIPG 12)

Removes old amalgam restoration
removes excess Hg
initiates carving
margin of amalgam is well condensed.

Ans. a. (Ref: Sturdevant 4/e p682 – 683)

2. When bonding of amalgam is required in orthodontic practice which of the following is selected for the purpose:

(AIIMS Nov 12)

Ans. 4 – META (Ref: Orthodontics – current principle and practice by grabber 4/e)

3. Discoloured areas seen through the enamel in the teeth that have amalgam restoration are known as:

(KCET 11)

Ans. Amalgam blues.

4. In case of deep carious lesion incomplete debridement is done to:

(COMEDK 11)

Ans. Prevent pulp exposure and allow a thin layer of a dentine to remain (Ref: Sturdevent 4/e p128)

5. In class 2 cavity for amalgam in case of permanent teeth, axiopulpal line angle is?

(PGI Dec 11)

Ans. Beveled in permanent teeth (Ref: Sturdevant 5/e p746)

6. LCOTE of amalgam as compared to tooth structure is about:

(PGI june 10)

Ans. 2.5 times (Ref: Phillips 11th ed pf 55, 419)

PIN RETAINED RESTORATION

Provide MAINLY 1° retention [Q]
SELF threaded pin:

Most retentive
Less microleakage
Causes more pulpal stress (minimal with cemented pins)
(NOTE: hole diameter 0.001 inch larger in cemented pin and 0.001 inch smaller in friction locked)
{1 inch = 25 mm}
Cemented pin:

Indicated in RCT treated tooth as NO stress during pin placement
(AIPG 07, AIIMS 07)
Contraindication for pin retained restoration is hypoplastic tooth. [Q]
Advantage of PIN retained restoration:
Conservative tooth preparation
Single visit finishing
PIN retained restoration (Rule of Thumb)
Pin should be 2 mm into dentine
2 mm within amalgam
22
- 1 mm from DEJ (to be safe)
- Ideal ratio = 2: 1
  
  (AIPG 07)
- Optimal = 1: 1
- Two pins should not be parallel to each other [Q]
- Pin should be placed parallel to external tooth surface
  
  (AIPG 07)
- 0.5 mm clearance around pin should given for amalgam condensation
- 2 pins should be placed 3-5 mm apart
- 3 or more pins should be located at different vertical level
- 1 pin/missing line angle
Fig 1.12: PIN retained restoration
Pin retained restoration ↓ses strength of amalgam

(AIPG 11, 09)

LAST 5-YEARS QUESTIONS FROM THIS TOPIC

1. One of the following is not true regarding pin retained restoration:

Pin holes should never be prepared at different levels on the tooth
A minimum of 0.5 mm clearance should be provided around the circumference of the pin for adequate condensation of the amalgam
Pin hole should be located on a flat surface that is perpendicular to the proposed direction of the pin hole
The pin hole should be positioned no closer than 1 mm to DEJ and no closer than 1.5 mm to the external surface

Ans. a

2. In pin – retained amalgam restoration, failure is more likely to occur at the:

(COMEDK 11)

Ans. Pin dentine interface (Ref: sturdevent 4/e p783)

DFG

It is an ideal material for class 5 cavity preparation
Bridging:
Voids are inherent to DFG
Void are spaces created due to improper compaction of DFG
Difference of cavity for DFG from that of amalgam:
Reverse bevel + sharp line and point angle + more conservative cavity than amalgam.
REST features are same

23Classification of DFG:

24 karat gold = 1000 fineness
Material providing BEST marginal seal/intergrity = DFG
Electra alloy RV:

Gold + 0.1% Ca
(COMEDK 11)
(increases strength of DFG by dispersion strengthening)

CEMENTS

Concept:

Silicate cement has highest compressive strength while resin cement has highest tensile strength.
both GIC and silicate are contraindicated in mouth breadthers
Classification of GIC:

Type 1 – Luting cement
Type 2 – Restorative cement
Type 3 – Liner
Type 4 – Fissure sealent
Type 5 – Orthodontic cement
Type 6 – Core build up cement
Metal Reinforced Gic:
Miracal mix/Ag cermet
Glass cermet, e.g ‘ketac Ag’
Ag – Sn alloy used
Pure metal sintered
NONE of the properties improved
Fracture toughness and wear resistance improved.
Esthetic value maintained

24Type 3 GIC i.e GIC Liner:

GIC:

GIC liquid composition:

Itaconic acid, malic acid, tricarballyic acid → Plasticiser
Tartaric acid → increases W.T and decreases S.T., modifies handling properties

(AIPG 07)

Ionic bond present in completely set GIC

(AIPG)

Carboxyl group reacts with calcium in enamel and dentine

(AIPG 09, AIIMS May 11)

Bonding improves on clean surface provided the cleansing does NOT remove an excessive amount of Ca from tooth surface

So, etching with weak acids like polyacrylic acid is recommended and stronger

Acids like phosphoric acid is contraindicated

Treating dentine with an acidic conditioner followed by dilute solution of ferric chloride

Stages of GIC setting:

Decomposition → migration → gelation → hardening → maturation

GIC should be protected against moisture and dessication
- If excess moisture present
- Ions like Ca^2+, Sr^2+, Al³⁺ will be lost in environment
- Will Not be available for reaction
- If dessicated
- Ions will not have aqueous medium
- Will Not migrate/react

Bond strength = 2-7 MPa

Fluoride released from GIC is replaced by Hydroxyl ion

(AIIMS May 11)

High Viscosity GIC = RMGIC/light hardened GIC introduced in 1990

(PGI)
GIC adheres to tooth surface by carboxyl group of polymer chain

(AIIMS May 10)
Compomer:
- Properties inferior to composite BUT superior to GIC and RMGIC fluoride content:
  
  Silicophosphate > silicate > GIC
GIC has maximum fluoride releasing capacity BUT silicate has maximum fluoride content. So, minimum 2⁰ caries associated with GIC
bilayered/sandwich/laminated technique:
Given by Mclean
Increases retention form as GIC bonds both to tooth and composite
Main disadvantage of GIC → film thickness (thick film)
Remember: GIC recommended in root caries because of anticariogenic property
After 24 hrs of setting GIC has greater tensile strength BUT less compressive strength than ZnPO₄
Concept:
If sufficient dentine thickness is available ZnPO₄ cement is ideal base
If excavation is deep/very close to pulp then Ca(OH)₂ liner is indicated
25Zynomer/buffered GIC:

ZnO is added in the powder to increase pH
Advantage of RMGIC over GIC:
Rapid setting
Increased esthetic { as resin increases esthetic}
Can be finished at the time of placement (early finishing) and are
Recommended for class 5 and class 1and2 of 1^°teeth
Vitrabond/vitrebond:
RMGIC base/liner

(PGI 12)
Resin cement = flowable resin base composite material
NON–eugenol cement → Vanilate ester
CERAMIC restoration/laminates are cemented using resin cement.
e.g of chelation reaction:

ZnOE and Zn Polycarboxylate

ZnPO₄ cement:

Silicate cement:

Luting agent and their chief concern:

Luting Agent (PGI 11)
Concern
ZnOE
Less strength. so, replaced as permanent cementation agent
(PGI 10, 11)
GIC
Solubility
ZnPO₄
Solubility
Composite
Film thickness
Varnish:
2 – 5 μm thick
Composition: copal rosin + 90% organic solvent, e.g CHCl₃[Q], C₂H₅OH
Is semipermeable like J.E
Concept:

Varnish and liner must for ALL cavities but base optional (only for deep cavities)
27Base:
Maximum value for thermal protection: (0.5 – 0.75 mm)
Base does NOT prevent microleakage and acid penetration

Liners

THIN film liner (1-50 μm)		THICK liners/cement liner[Q]
Solution liner	suspension liner	0.2 to 1 mm
Varnish	20 – 25 μm	0.2 to 1 mm
2-5 μm (AIIMS Nov 09)		also called ‘cement liner’
		used for both pulpal Medication and thermal Protection

VARNISH and ZnOE contraindicated under composite
W.T of dental materials:

Cement
Working time
Zn Polycarboxylate
3 min
ZnPO₄
5 min
Amalgam
3-4 min

LAST 5-YEAR QUESTIONS FROM THIS TOPIC:

1. A radiopaque area is observed in the dentine underlying a 3 month old class 2 amalgam restoration. Which base was used in this restoration?

(AIIMS Nov 10, Nov 08, AIPG 08)

Ans. Ca(OH)₂ (NBDE Q)

2. To prevent damage to pulp in a deep cavity from acid etching, the cavity is lined by:

(AIIMS Nov 10, May 09)

Ans. RMGIC (Ref: sturdevant 4^/e p175-76)

3. Sequence of setting of GIC is:

(AIPG 09)

Ans. Decomposition, migration, gelation, hardening

4. Which of the following is true for hybrid ionomers:

(AIPG 08)

Release of fluoride more than compomer
Fluoride release is comparable to conventional GIC
More sensitive to water contamination compared to conventional GIC
More ionic activity compared to conventional GIC

Ans. a.

5. A diagnosis of small occlusal cavities is most readily made by:

(AIPG 08)

Ans. An explorer and compressed air

6. Which GIC developes early resistance to water intake on setting?

(KCET 11)

Ans. RMGIC (Ref: Phillips science of dental materials 11/e p482)

7. For accurate interocclusal records the material of choice is:

(COMEDK 11)

Ans. ZnOE bite registration material

8. Which dental cement is most kind to pulp?

(AIIMS Nov. 09)

Ans. Zinc polycarboxylate (Ref: Albers. Tooth colored restoratives: Principles and Techniques 9th ed pg 71 – 73)

COMPOSITE

Composition:

Powder (initiator)	liquid – activator and inhibitor [Q]
Initiator – benzoyl peroxide (self cure) Camphroquinone (light cure, activated at 474 nm) (PGI Dec 11)	Activator – 30 amine (in self cure) Diketone (VL cure) Benzoin methyl ether (in UV – cure)
	Inhibitor - hydroquinone

Radio opacifier added to composite → TiO2 + Zr oxide

(PGI Dec 11)
BIS – GMA in composite replaced methacrylate based matrix.

(KCET 10)
higher filler content → reduced H2O absorption
Coupling agent → provides HydrolytiC stability (organic silanes)
Filler size: (favourite Q of PGI)
Mega fill/inserts = 0.5 to 2 mm [Q]
Inserts/mega fill are added posterior composite to improve wear resistance [Q]
Visible light composite:
λ range of 400 nm – 500 nm (PGI 11), i.e BLUE region predominantly at 474 nm used.
shrinkage occurs towards light source [Q]
Shade matching should be done within 5 sec to avoid fatigue to eye

(AIPG 12)
Bond:

Covalent bonds are seen in dental resins

Filler content: (favourite Q of PGI)

	MICRO fill	Flowable	Packable	Conventional	Hybrid
Wt %	35 % – 60% ↓ –5%	40 % – 60% [Q] ↓ – 10%	65% – 80% [Q] ↓ –15%	75% – 80 %	75% – 85%
Volume%	30 % -–45%	30% – 55 %	48% – 67 %	75% – 80%	75% – 85 %

Microfilled composite shows more water absorption as compared to light cure composite/conventional/hybrid composite

(AIPG 07).

Compomer:

29Flowable composite: Used in

(KCET 12)
Pit and fissure
Class 1 restoration
Concept:

Cavity preparation for composite for caries extending to root surface:
When a cavity extends on to root, class 2 conventional cavity(without bevels), as bevels are only given on enamel.

NOTE: Etching time for:

Curing time – 20 sec
Enamel rod gets dissolved by acid the most in head region

(AIIMS Nov 09)
NOTE: Etching
Increases surface area
Increases surface free energy of enamel
Decreases surface free energy of dentine
Creates microporous layer (5 – 50 μ deep)
brings about reduction in microlekage

(AIIMS 08)
In Acid etching GEL form is preffered over solution form for providing ease of placement over area to be etched

(AIIMS May 12, Nov. 10, 08)
Type of acid etching:

Type – 1 → intact periphery + removal of core
Fig 1.13: Acid etching type 1
Type – 2 → intact core + removal of periphery
Fig 1.14: Acid etching type 2

30

Type – 3 → generalized roughening
Fig 1.15: Acid etching type 3
Etchant concentration:

> 50 % H₃PO₄ → MONO Calcium phosphate MONO hydrate
< 30 % H₃PO₄ → Di Calcium phosphate MONO hydrate
(AIIMS Nov 09)
Etchant removes/modifies smear layer primer:
HEMA used [Q]
increases surface free energy of dentine+ wets the dentine surface

(AIIMS Nov. 10, AIPG 09)
HYBRID layer – formed by bonding agent by co – polymerization with primer
Concept:

Bond strength of DBA is greater BUT clinical longevity is not as long as EBA due to H₂O content { donot confuse: in other restorations, bond strength with enamel is always greater }
Amalgam bonding system:

4 Used
(AIIMS Nov 12)
In PMMA P/L ratio:

= 3: 1 by volume
(AIIMS May 12)
= 2.5: 1 by wt.
(AIIMS May 12)

Class 5 cavity:

Among lasers, only Argon laser is used to cure composite (AIPG 10, COMEDK 11). it emits single wavelength [Q]
Curing:
Slow/soft start polymerization = QTH curing unit

(KCET 10)
Rapid polymerization = PAC light cure unit
Depth of curing of composite by light → upto 2 mm (can correlate it with the effective depth of topical LA which is upto 2-3 mm)
Copolymerisation:
2 Different monomers combine to yield a polymer with desirable property (kcet 10)
Remember in addition and condensation polymerization, same monomer condenses with elimination of small molecules.
31Smear layer thickness:
Conservative approach for restoration:

Composite >> GIC

Bonding Agents (favourite Q of KCET)

Etching:
Head of rod → Dissolves more (more prone to acid dissolution) [Q]
Tail and periphery → More resistant to acid dissolution
Uses of DBA:

(PGI Dec 11)
Create hybrid layer for micromechanical bonding
For desensitization of hypersensitive dentine by forming resin tags, hybrid layer and precipitation of protein/denature protein
Permeability of dentine depends on:
Smear layer
Diffusion coefficient of fluid
Length of dentinal tubules
Not on convection of fluid
(AIIMS 07)
Fluoride release:

GIC > RMGIC > compomer > composite
Curing:
Intensity/energy required for polymerization of composite → above
400 Mw/cm² [Q]
QTH → minimum energy shouldn't be less than 300 Mw/cm² (300 – 1200)

(PGI 10)

Polymerization Shrinkage:

32Polymerization stress can be minimized by:
Soft start polymerization
Ramped – up curing (intensity is gradually increased)
Delayed curing (stress relaxation takes place) [Q]
INCREMENTAL build – up

C – Factor:

We have to minimize C – factor to reduce polymerization shrinkage

Class 1 = 5 class 2 = 2 class 3 = 1 class 4 = 0.5 class 5 = 0.25

[Trick = 521 number ki BUS 0.5, 0.25]

[in KCET 2012 class 5 was asked but the answer was given as 0.5. we are sorry to say but even if it is given in sturdvent, you need to mark the same answer if Q is asked in future in KCET as they keep following their own key]

Microleakage in composite → more as LCTE is 3 times of teeth
Polishing:

Amalgam
Composite
SnO₂, ZnO, precipitated chalk (PGI 10), silex (COMEDK 07)
Al₂O₃, SiO₂

LAST 5-YEARS QUESTIONS FROM THIS TOPIC

1. While restoring a cavity, C factor is associated with:

(AIPG 12)

Ans. Polymerization shrinkage (Ref: Sturdevant 4/e p203, 243, 479)

2. Shade matching should be done within _______________ seconds to avoid fatigue of eyes to color.

(AIPG 12)

Ans. 5 seconds (Ref: Rosensteil, land, fujimoto 06, p724)

3. While restoring a tooth with composite resin, the etched surface gets contaminated with saliva accidently. what would be done next:

(AIPG 11,09)

Ans. Wash with water, dry area and continue restoration.

4. Class 5 cavity prepared for amalgam and composite differs in:

(AIPG 09)

Ans. Cavosurface margin (Ref: Sturdevant 4/e p528 – 531)

5. HOW long does it take for an etched enamel to return to normal condition?

(COMEDK 11)

Ans. 30 days (Ref: Charbeneau's principle and practice of operative dentistry 3/e p163)

6. In etching of enamel, the depth achieved is:

(AIIMS Nov 10)

Ans. 5–50 μ (Ref: Heasmen. Restorative dentistry, pediatric dentistry and orthodontics p104)

DENTURE BASE RESIN

COMPOSITION:

In PMMA:
33If acrylic resin is packed in sandy state → Porosity occurs
Properties:

All properties of heat cure are better than self cure acrylic EXCEPT greater polymerization shrinkage [Q] in heat cure acrylic. So, less stable
Residual Monomer:

Heat cure
Self cure
0.2 to 0.5 %
OR
< 1 % (PGI 12)
3 to 5 %
Concept:

In heat cure more polymerization
↓
More polymerization shrinkage
↓
Less residual monomer
Most important disadvantage of Acrylic resin is polymerization shrinkage like composite
Resin packed in dough state because the material will be more homogeneous and occurrence of porosity is minimized
Curing of denture base resin:
SLOW curing →
74°C maintained for 8 hrs
FAST curing →
74 °C maintained for 1 ½ hrs and increased upto 100 ^°C
For 1 ½ hrs
BENCH curing –
30 to 60 min
Repair of fractured denture base:

Chemically cured resin → MORE stable → but durability decreased

Properties of PMMA:

34Disadvantage of PMMA:

Thermal properties are poor
In resin gas inclusion porosity → seen in fluid resin porosity due to air incorporation [NOT due to heating of resin]
Self cure are more porous than heat cure. So, to prevent porosity, self cure resins are cured under “VACUMM” pressure
Insufficient closure of flask during packing of denture base resin results in increase in vertical dimension (AIPG 07)

LAST 5-YEAR QUESTIONS FROM THIS TOPIC

1. During polymerization of acrylic resin above what temperature benzoyl peroxide form free radicals:

(AIIMS Nov 12)

Ans. 60°(Ref: Phillips 11/e p730)

CERAMIC

Composition:

Feldspar → Basic glass former

Kaolin → Binder

Quartz → Strengthener, glass former

Metal oxide → Provide color

Metallic oxide gives color to porcelain

(AIIMS 11)

The metal alloy used in PFM should NOT contain Cu/Ag as they discolor porcelain

↓

Causes greenish Discoloration

(KCET 10)

Flux → boric oxide. Present in LOW fusing ceramic. It reduces fusion

Temperature → improves fluidity, increases Cote

e.g. boric oxide + (Na, K, Ca) oxide

TiO₂ + ZrO₂ → opacifier in ceramic

Major advantage – Resistance to discoloration under U-V light

PFM:
Chemical bonding is 1° bonding
In base metal – CrO₂ helps in bonding
In noble metal – In and Sn oxide helps in bonding
Porcelain teeth:

When used, sufficient interocclusal clearance should be present, i.e sufficient overjet and over bite
Bonding of ceramic to metal occurs both by mechanical and Chemical
Self Glazed Porcelain
More permanent than apllied glaze
APF gel/other topical fluorides can cause staining
investment used for casting of ceramic → phosphate bonded
Castable glass ceramic/machinable glass ceramic → DICOR
Injection moulded ceramic → IPS empress
Glass infiltrated ceramic → inceram

(KCET 10)
35Method of decresing porosities in ceramic:
Vacuum firing
When porcelain is self glazed by reheating, It is the BEST method of reducing voids
Firing in porcelain: (stages)

Low bisque – minimal polymerization shrinkage
Medium bisque
HIGH bisque – high polymerization shrinkage
(AIPG 07)
High fusing = 1290 °C – 1370 °C (1300)
(Used for denture teeth)
Medium fusing = 1090 °C – 1260 °C (1300 – 1100)
Low fusing = 870 °C – 1090°C (900 – 110
Condensation shrinkage during porcelain firing is determined by particle size and shape (AIIMS Nov. 10, AIPG 07)
NOTE:

Vaccumm firing/diffusible gas like He/H₂ firing reduces porosity

Strengthening of porcelain

In aluminous porcelain alumina interrupts the crack propagation by the process of dispersion strengthening
CAD – CAM → No need for “impression” and “casting” procedure [Q]

LAST 5-YEAR QUESTIONS FROM THIS TOPIC

1. Common between amalgam and ceramic is:

(AIPG 12)

Ans. High compressive strength and low tensile strength (Ref: Manapalli 2/e p372)

2. For a cast porcelain inlay, the facial wall should:

(AIPG 09)

Ans. Diverge facially (Ref: Sturdevant 4^/e p579 – 580)

3. Ceramics fired to metals are processed by:

(KCET 11)

Ans. Sintering (Ref: craig's 11/e p553-554)

METALLURGY

Co – Cr/elgiloy:

Co – 60 %
Cr – 30 %
In austenite (18 – 8 steel):
18 % Cr and 8 % Ni
Fe is in γ form
Zn: Scavenger of O₂ (Deoxidizing agent added to dental alloys)

(PGI Dec 11)
Ti: Most corrosive resistant

Others – Al, Cr
(KCET 13)

Casting Difference between base metal and Au alloy:

BASE METAL	Au ALLOY
FLUX - fluoride (to dissolve any oxide formed e.g CrO₂) (AIPG 07)	FLUX – borax + boric acid
CRUCIBLE – quartz [Q]	CRUCIBLE – carbon/clay (for high noble alloy > 40 % Au)
SOLDER – silver	SOLDER - Au
PICKLING – sand blasting with Al₂O₃	PICKLING solution – 50 % HCl (BEST), also H₂SO₄
Casting shrinkage – 2.3 %	Casting shrinkage – 1.5 %
FINAL polishing - electropolishing	FINAL polishing – rouge (Fe₂O₃)

Sensitization and stabilization of stainless steel:
The only nearly pure metal used for dental casting is PURE titanium (Cp Ti) [Q] [donot confuse with DFG. It is pure Direct restorative material]
Cp Ti is most biocompatible

(PGI 11)
Noble metal alloy (casting) classification:

Predominantly base metal alloy → noble metal < 25 %
Noble metal are resistant to corrosion because they have positive EMF

Implant material:

(KCET Q)

37Fluoride flux:

has KF: boric acid = 1: 1
(PGI 09 Q)

Types of flux:

Antiflux:
Graphite, Pb, rouge
Restricts flow of solder (COMEDK 11)
Base metal vs Noble metal (e.g Au)
Base Metal
Noble Metal
Increased hardness, strength
Increased sag resistance (resistance against thermal stress)
Increased density, castability,
ductility

GRAIN refiners:

Nickel:

Added to cast gold alloy
↓
Strengthener
(AIIMS Nov. 09)
Soldering vs Brazing:

Soldering
Brazing
Fusion temperature of filler material < 450 ⁰F
Fusion temperature of filler material 450 ⁰F
Ideal temperature of H₂O bath for softening fluid wax 51 – 54°C

Heat treatment

Softening Heat Treatment	Hardening Heat Treatment/Age Hardening	Cold Working/Strain Hardening/Work Hardening
All Strength (Including Tensile Strength) Decreases Except Ductility (It Increases)	All strength increases EXCEPT ductility which decreases (PGI 11)	Increases strength BUT decreases ductility (PGI 11) (same improvement properties as after hardening heat treatment.
		Grain elongation is the result of cold working
		Corrosion resistance reduces (PGI 10)
	Usually For Au Alloys	Done for DFG, stainless steel wire

38NOTE: With surface hardening percentage elongation reduces

Cold working of Dfg:

Tempering of steel increases hardness

(PGI 10)
Wrought alloy → “cold worked” metal → hardness and tensile strength increases but ductility reduces
Ni added to cast Au alloy → Strengthner
Berrilium increases castability of BASE metal alloys
Fig 16: change in properties with cold working and annealing

Fig 1.16: Change in properties with cold working and annealing
Grain elongation seen in cold working:

It is the measure of ductility which increases rapidly in recrystallization phase of anneling
Wax Patern
Type 1/type B
Type 2/type C
“DIRECT”
“INDIRECT”
Best technique: Direct – indirect

(PGI 12)

Wax Composition:

Impression wax is: Bite registration/corrective wax
Incomplete wax elimination → leaves CARBON → causes Shiny surface on cast
Distortion is most serious problem of pattern, due to release of Internal stress
Method to prevent Warpage in wax pattern:

(AIPG 08)

Uniform heating of wax at 50 °C
Use of warm instrument for carving
Use of warm die
Adding wax to die in small amount
Invest the pattern immediately – Most practical method (COMEDK 11)
Non – True wax:

Cocoa butter (to protect GIC from moisture), japan wax
PKT -2 is wax adding instrument

(KCET)
Indirect spruing:

Extra Spruing → Minimizes Localized Shrinkage Porosity
Fig 1.17: Indirect spruing
Most common cause of incomplete casting → narrow sprue
Turbulence of alloy in sprue → due to position of sprue
Ideal Sprue: Hollow metal sprue
sprue attachment:
Cusp tip gives good result
In posterior teeth ideal position is near proximal surface [Q]/just below the non functional cusp

40Investment material:

Gypsum bonded:
- Binder – α – hemihydrates [Q], provides strength
  
  (AIPG 07)
- Used – casting Au alloys
- Heating above 700 °C → SO₂ released
  
  (NEET 13)
- S.E:
- N.S.E – 0.5 %
- E – 1-2 %
- Thermal expamsion – 1-2 %
- BEST pickling material for this investment is HCl
  
  (COMED K 11)

Phosphate bonded:
- Binder – MgO + mono ammonium phosphate
- Used – high melting Co – Cr and metal ceramic
- Phosphate bonded + carbon → for gold
- Phosphate bonded without carbon → for base metal, Ag Pd Alloys
Refractory material: quartz, cristobalite

Silica bonded:
- Binder – ethyl silicate/silica gel
- Use – high fusing base metal partial denture alloys
- GREEN shrinkage seen
- Refractory material: silica
- Heated upto 1200 °C

Concept:

Refractory and investment material:
- During heating, investment material is expected to Expand thermally to compensate casting shrinkage.
- But gypsum shrinks considerably when it is heated (due to release of sulphur gas)
- This refractory material (Silica) eliminates this contraction during heating and changed into an expansion (AIPG 07)
- “SILICA” exists in its 4 allotropic form: quartz, tridymite, crystoballite
  
  Best choice as refractory material
  
  As of low inversion temperature.

Ring Liner:
Permit expansion of mold
e.g. Asbestos, cellulose, Al silicate
Success of removable die system associated to precise relocation on working cast

(PGI 09)
DIE material:
Gypsum/die stone: Least abrasion resistance [Q]
Epoxy resin: Most commonly used in laboratory
Electroplated Ag: lethal due to Ag

Poly S can be electroplated

Porosity in cast restoration

(Very Important Topic)

Back pressure porosity: “escape of air is prevented” due to excessive thickness of investment, too short sprue, incomplete removal of wax pattern, Inadequatecasting Pressure (AIPG 11,09). So, adjust the sprue such that there is only 6 mm (¼ inch) distance between casting ring and wax pattern

Suck back porosity → Due to creation of “HOT SPOT” [Q]
- Cause → short sprue, sprue attachment at 90°

Localized shrinkage porosity: Due to long sprue

Microporosity: Due to rapid solidification shrinkage. So, increases melting temperature
- NOTE: Localized shrinkage porosity and microporosity are Not seen in denture Base Resin

Common Cause of porosity in denture:

Cavity preparation for Cast restoration:

Pulpal floor of class 2 of cast and amalgam at same level

Bevels: Types

Most important bevel for cast inlay → Gingival bevel

(AIPG 11, 09)
Width of gingival bevel = 0.5 to 1 mm and merging with 2° flare
Onlay:
It is partly INTRACORONAL and partly EXTRACORONAL type
At intracoronal portion → Hollow ground bevel given
At extracoronal portion → Counter/reverse bevel given
In inlay:

1⁰and 2⁰ flare given for same function as bevel
In onlay:
class 2 metal restoration:
Here A-P line angle slightly beveled
To increase thickness of wax at this area to prevent wax pattern distortion
[NOTE: In amalgam this bevel prevents fracture of restoration]
42Inlay vs Amalgam
Inlay
Amalgam
Cavosurface angle: 130⁰ - 140⁰
90⁰ - 100⁰
Marginal metal angle: 30⁰ - 40⁰
80⁰ - 90⁰
In inlay lap – joint present:

Fig 1.18: Inlay lap – joint
Certain Clinical conditions and choice of restoration:

If no caries
→
Inlay/onlay not indicated
Short clinical crown
→
Full crown best as has better retention
RCT treated tooth
→
Ideal – crown
Minimally – onlay acceptable
Contraindicated – inlay
For Inlay:

If marginal gaps/discrepancy exceeding 0.3 mm → should Not be burnished But discarded. repeat the cast
Where to keep gingival seat?

0.5 mm below contact area for finishing
Gingival extension of restoration:

At least 3 mm above alveolar crest

For any Cast restoration (gold/porcelain):

LAST 5-YEARS QUESTIONS FROM THIS TOPIC

1. Most common reason for incomplete casting when using a centrifugal casting machine is:

Ans. Narrow sprue

2. Which Zone of flame is used for melting alloys:

(AIPG 10, 07)

Ans. Reducing zone (Phillips 10/e p510, 627)

3. Fins and spines in casting may occur because of:

(AIPG 10)

Ans. Rapid heating (Ref: Phillips 11/e p328)

4. Which is not a noble metal?

(AIPG 08)

Au
43Ru
Ag
Osmium

Ans. c

5. One of the following is NOT true about gypsum bonded investment:

(AIPG 08)

Used for gold alloys
50 – 65% gypsum changes to form α – hemihydrates
Heating range is 500 – 700 ⁰C
Heating of investment above 700 ⁰C causes formation of SO₂ from calcium sulfate

Ans. b (Ref: Phillips 10/e p472 – 473)

6. Which is not used as antiflux:

(AIIMS Nov 12)

Graphite
Boric acid
Iron oxide
Calcium carbonate with alcohol

Ans. b (Ref: Textbook of orthodontics – gowri Shankar 1^st ed pg 761)

7. Solder and flux used for joining Elgiloy wires are:

(KCET 11)

Ans. Silver solder and fluoride flux

8. The ideal temperature for water bath for softening fluid wax is about:

(KCET 10)

Ans. 51 – 54 degree F

9. A casting shows round margins and smooth and shiny surface due to?

(PGI june 11)

Ans. Inadequate wax elimination (Ref: Dental materials and their selection by William J.O’Brien 3^/e p435)

CARIES

Difoti/Diagnodent

Pit and fissure caries vs smooth surface carie.

Fig 1.19: Pit fissure caries
Fig 1.20: Smooth surface caries
44Forward caries:

Caries cone broad in enamel than dentine
(KCET 10, 11)
Affected dentine has no bacteria
Earliest changes in incipient caries:

Loss of interprismatic/inter rod substance with increased prominence of rods
Eburnation/sclerotic dentine:

seen in arrested caries
The non active carious lesion is distinguished by no pain on excavation of caries

(AIIMS May 10, May 07, AIPG 07)
Reparative and sclerotic dentine deposition

Reparative
Sclerotic dentine
NOTE: In response trauma/irritant all 3 types of dentine, i.e. reparative, 2°, and sclerotic are formed
minimum depth of demineralisation of carious lesion to be detected radiographically = 500 μm
Minimum dentinal destruction to be evident radiographically = 40 μm
dental caries associated with 8 serotypes of S. mutAns.

S. rattus (AIIMS/AIPG), S. cricetus, S. ferus, S. soberinus
Streptococcus mutans and Lactobacillus:

Both are acidogenic andaciduric (AIPG 08)and 1° organism associated with caries
Active caries → light brown
Non – active caries → dark brown/black
Root caries:
Shows rapid spread
2° to gingival recession
Often asymptomatic
Arrested Caries:

Occlusal and proximal mostly

45Location of caries predominant organism: (very important in any examination)

TIME of progression from incipient to cavitated clinical caries on smooth surface = 18 month 6 month for deep pit and fissure caries:

If non cavitated
(AIPG 12)

Caries Diagnosis: Newer method of caries diagnosis

Different theories of caries:

Stephen Curve:

46Generation of sealants:
1^st – uv based
2^nd-chemical cure
3^rd-visible
4^th-F‾ releasing. [Q]
Caries activity test:
Synder's test:
- Colorimetric test. [Q]
- Principle – measures salivary microorganism ability to form acid in carbohydrate media.
- Medium has indicator – Br (green ph -5.4 → yellow ph 3.8) [Q]
- Measures
  
  Color change
  yellow
  yellow
  yellow
  Caries activity
  marked
  Definite
  Limited
  
  Time
  After24 hrs
  48hrs
  72 hrs
- Advantage: Simple, low cost.
- Synder test – Measure speed/rate of acid production. [PGI].
- Method/Yard Stick of detection is by Ph change. [PGI]

Lactobacillus count test:

Dyes used in staining fracture line in a suspected tooth – 2% iodine [Q]
Carisolv vs Caridex: They are alternative chemico-mechanical method for removal of caries.
Carisolv
x [PGI]
0.5% NaOcl,
1%Naocl

(AIIMS 12)
Leucine, lysine, glutamic acid and erythrosine dye.
Glycine
PH - 11
PH -11(alkaline PH)
Gel
Sol
5-15 mints required
5-15 mints

Caries Vaccine:

47Caries activity studies:

Vipeholm Study: Gustafsson 1954
- -5 yr study of 436 adult in a mental institution of the Vipeholm Sweden.
- Purpose of study: to find out does the increase in carbohydrate intake increases dental caries effect of Sticky form of sugar on caries.
  
  Effect of non sticky form of sugar on caries.
- Conclusion-physical form of sugar is more important than amount of sugar.

Hopewood study: Sullivan and Harries.
- Studies of dental status of children b/w 7-14 yrs at Hopewood house,
- New South wales → longitudinal studies for 10 yrs.
- Conclusion: Sparten diet (without fluoride and unfavourable oral hygiene) reduces dental caries.

3. Turku Sugar Study: Scheinin and Makinen
- AIM – compare cariogenicity of Sucrose, Fructose and Xylitol.
- Basis of study – Xylitol not metabolized by plaque microorganism. [Q]

Conclusion:

Fructose –less cariogenic than sucrose.
Xylitol - Non Cariogenic/Anticariogenic.

Inhibits growth of st. Mutans

Sorbitol:
Poly alcohol sugar substitute.
Lack enzyme to metabolize except mutans (But Even Slow)
BEST method to reduce caries. [Q]

LAST 5-YEAR QUESTIONS FROM THIS TOPIC:

1. Streptococci is important organism in causing dental caries as it :

(NEET 13, AIPG 12)

Ans. Produces extracellular polysaccharides

2. Streptococci are acidophilic and aciduric. In this acidophilic means.

(AIPG 12)

Ans. Can survive in acid (Ref: Jawetz 23^/e p65)

3. Which of the following is false regarding dental caries:

(AIPG 12)

Infectious and transmissible
Not caused by microbes
Causes breakown of organic structure
Possible without sucrose

Ans. b. (well known fact)

4. Bacteria are normally most populated in which area of teeth:

(NEET 13, AIPG 12)

Ans. Proximal

5. Caries assessment tool CAT developed by AAPD defines high risk group as all except:

(AIPG 12)

Visible plaque on anterior teeth
Atleast 1 area of demineralization
Enamel hypoplasia
Children with special health care needs

Ans. b (Ref: Mcdonnald)

6. Interproximal lesion Usually Begins:

(AIPG 11, 09)

Ans. Gingival to contact area (NBDE Q)48

7. Which is NOT true regarding S. mutAns.

(AIPG 10)

Acidogenic and aciduric
Requires specific conditions for growth
Requires carbohydrate for metabolism
Do not multiply easily

Ans. d (Ref: Clinical textbook of dental hygiene and therapy by Ireland, 2006 p77)

8. Which of the following is cariostatic?

(KCET 10)

Ans. Molybdenum and vanadium

9. Which of the following translucent area on hydration of tooth surface disappears?

(PGI Dec 10)

Ans. Incipient carious lesion (Ref: Sturdevant 4/e p408)

10. Best method for caries reduction is:

(AIPG 08)

Ans. Substitute sugar by alcohol based sugar.

Ex-sorbitol.

11. Most cariogenic sugar is:

(AIPG 08)

Ans. Sucrose

12. Bacteria which adhere to tooth andcause caries is due to:

Ans. They produce extracellular polysaccharides.

INSTRUMENTS AND MISCELLANEOUS

Bur Description:
Bur Number
Length
Diameter
No. 245 (inverted cone)
3 mm
0.8 mm (COMEDK 11)
No. 330 (smaller and pear shaped bur)
Used for the most conservative amalgam preparation.
1 mm
0.8 mm
Antirust agent:
- 2 %Na Nitrite [it's NITRITE not NITRATE] (AIPG 07)
Formula for instruments:

3 unit formula - W L B
W ~ width is in 10^th of mm
L ~ length in mm
49Caries:

HARD caries
SOFT caries
Removed at high speed
Removed by bur at slow speed
Enamel Bevel – given by GMT which is a type of Chisel [Q]
Noise levels in excess of 75 decible → causes hearing damage

(AIIMS 06)
Enamel hatchet + GMT → chisel
Angle former → excavator
Thickness of matrix band (CLASS 2):
Burs:
Carbide
Steel
Increases cutting efficiency
Decreased cutting efficiency
Used at high speed
Used at low speed
Less heat production
Produce more heat
Used for finishing
Thickness of rubber dam:
Rubber Dam
Thickness
Trick to Remember
Thin
0.006 inch (AIPG 07)
6
Medium
0.008 inch
8
Thick
0.010 inch
10
Distance between 2 holes in rubber dam = 6.3 mm
Thick rubber dam provides better retraction of gingiva → so, used in class 5 cavities
Concept: A rubber dam does not require anything to pass
Isolation:
Isolate at least 3 teeth at a time for operative procedure
For RCT isolation of the tooth being treated is enough
Size of diamond abrasive:

“coarse” = 125 μ to 150 μ
(AIPG 07)
Abrasive hardness:

Diamond > boron carbide > SiC

Macro Abrasion
Air Abrasion
Micro Abrasion
12 fluted composite finishing bur
95% alumina in powder
Average particle size = 27 μ/even
20 μ given in AIPG, AIIMS may 09
[25 μ to 30μ given in Philips]
50Air Abrasion:
- Contraindicated where risk of embolism e.g extraction socket, subgingival caries and pulmonary disease. Not deep caries

Limit of Eccentricity:

Principal of Balance (for instrument)
The cutting edge of the blade should be nearer to the long axis of the handle for proper balance
For optimum “ANTIROTATIONAL tendency” the blade edge must not be off the axis by more than 2 mm [Q]
Pressure applied:
SLOW speed rotator instrument → 2-5 pound
HIGH speed → 1 pound with H₂O coolant as high heat is generated
Ideal pressure → 2 – 4 pounds
Condensation pressure for amalgam → 3 – 4 pounds
Cavity preparation and temperature rise:

↓

Not > 60 °C/130 °F
factor influencing cutting efficiency of a bur:

Fig 1.21: Factor influencing cutting efficiency of a bur
Rake angle:
Negative rake angle = good for bur (long life)
Positive rake angle = increased cutting efficiency
[H – file has positive rake angle → so, good cutting efficiency]
Cracked tooth syndrome:
Diagnosed by – Best by rubber wheel test
Immediate Rx – splinting and relieve occlusion

(COMEDK 13)
Rx of choice – Cast restoration
Bitewing with RVG:

Best for detecting proximal caries
Crocus cloth = Pumice
Heat content of propane [Q] and butane is highest

51Sterilisation:

Important Values:

(Very Important)

Wedge:
Fig 1.22: PIGGY back – used in gingival recession
Double wedge:
- Useful in facio – lingually wide proximal box
  
  (AIPG 12)
- One wedge facially and other lingually
Wedge wedging:
- Used in maxillary 1^st premolar
- One wedge placed perpendicular to other
Seperator:
SLOW
RAPID
Use of rubber/Cu Wire/orthodontic wire
Wedge principle
Traction principle
e.g. ELLIOT Separator [Q]
e.g. ferrier double bow separator
Chisel:
Straight/curved/biangle chisel:

e.g. Wedelstat chisel [Q] with 4 unit formula
Enamel hatchet:

Cutting edge parallel to long axis of handle and beveled on 1 side
GMT
52Differentiating features of enamel hatchet from chisel:

(AIIMS 06)
It has a larger, Heavier blade.
It has a cutting edge in a plane that is parallel with the axis of the handle.
The blade does not curve (this curve is seen in GMT).
Excavator:
Ordinary hatchet
Hoe
Angle former:

Spoon excavator
Speed:
Low - < 8000 rpm
Medium – 20, 000 to 45,000 rpm
High – 45, 000 to 1 lakh rpm
Ultra high → 1 lakh rpm
Horning machine: Mechanical sharpener

(KCET 02)
In Bur → increased edge angle → decreases chances of bur to
Fracture
Change in bur neck diameter, shape and size of the bur and clearance angle affects efficiency of bur But not taper of bur head/height of bur head

(AIIMS 06)
For better efficiency and longer shelf life of a carbide bur, it should be rotated fast before entering cavity.

(AIPG 11, 09)
Rubber dam clamp:

1° teeth
Incisor and canine
1^st Molar
2^nd Molar
‘O’ ivory
2, 2A ivory
26, 27
3 ivory

2° Teeth
Premolar
Partially erupted Molar
Fully erupted molar
2, 2A ivory
154 A, 8A ivory
14, 8 ivory

Critical/Non Critical instrument:

53Laser:

Argon laser:	Used in composite curing (PGI Dec 11) Greater degree of polymerization/greater depth of Polymerization.
ND – YAG	1064 nm 1^st laser used for dentistry Pulsed Nd – YAG ideal for soft tissue procedure and root Canal sterilization Converts dentine debris into an ionized gas leaving Debris on wall of canal (Plasma Effect) Used in Devitalisation pulpotomy + canal preparation + Laser welding
CO₂	Used in laser welding Ideal for soft tissue and useful in cutting Fibrous tissue as in gingivectomy
Er YAG (2.94 μ)	+ Er, Cr: YAG (2.79 μ) Highest absorption of H₂O Ideal for hard tissue
YSGG	Waterlase system (AIIMS May 09)

Polishing Agent:

Restoration	Polishing Agent
Amalgam	TiO, ZnO, Chalk (PGI)
Composite	Al₂O₃, SiC
Noble metal alloy	Fe₂O₃ (rouge)
Co–Cr (base metal)	Electropolishing
Natural teeth	Zr Si [Q]
Stainless steel	CrO → Whitening agent
Denture/artificial teeth	Pumice

After amalgam polishing, the metal surface is flattened. This layer is called as Beilby's layer

(AIIMS May 11, 08)
Agents for treating hypersensitivity are: NaF, SnF₂, potassium nitrate

(AIIMS 08)
2 % NaF is commonly used in iontophoresis

(AIIMS 06)

While restoring a tooth, following rules should be followed for maintaining aesthetics:

(AIIMS 06)

LAST 5-YEAR QUESTIONS FROM THIS TOPIC

1. It is essential to lubricate dam before applying it. Which of these is not a suitable lubricant?

(AIIMS May 11, AIPG 09)

Shaving gel
Liquid soap
Scrub gel
Vaseline

Ans. d (Ref: Sturdevant 5/e p467)

2. Which is the wrong way to apply dam using a wingless clamp?

(AIIMS May 11, AIPG 09)

Put the clamp on the tooth, and then pull the dam over it.
Place the dam on the tooth with fingers and then position the clamp over it.
Attach the dam over the clamp and frame outside the mouth, and then put the assembly over the tooth using clamp holders over the dam.
54Place the dam over the clamp and frame outside the oral cavity and then on tooth using a holder under the dam.

Ans. c. (Ref: Sturdevant 5/e p471)

3. Interdental papilla are seen protruding beneath the rubber dam mostly when:

(AIIMS Nov 11)

Ans. Holes are placed too close (Ref: Sturdevant 5/e p469)

4. FACIAL occlusal line in maxillary arch is formed by:

(KCET 11)

Ans. Non supporting cusps (Ref: Sturdvent 4/e p38)

5. Right rear operator position refers to:

(KCET 11)

Ans. 11 O'clock position

6. The disadvantage of winged rubber dam retainer is that it interferes with the placement of:

(KCET 11)

Ans. Matrix band

7. Which of the following items in the dental operatory cannot be classified as a semi critical item?

(KCET 11)

Suction tip
Hand piece
Endodontic file
Water syringe tip

Ans. c.

8. Function of water retraction system is:

(KCET 10)

Ans. Retracts water whenever spray is stopped

9. Rubber dam is particularly adaptable to primary 2^nd molar because the:

(KCET 10)

Ans. Cervical constriction of crown favours its retention

10. Which of the following laser is is having a wavelength in the visible light spectrum?

(PGI Dec 11)

Ans. Argon (Ref: Skinner's 11/e p412)

11. Safe level of Ni according to OSHA in clinics is?

(PGI June 11)

Ans. 1 mg (Ref: Sturdevant 5/e p165)

PROSTHODONTICS

Working condyle/laterotrusive condyle
Non-working condyle/mediotrusive condyle
Bennet movement
- concerned with Working Side
- It is 1-1.5 mm/side
Fig 1.23: Bennet movement
55Bennet angle:
Concerned with Non-working condyle [angle with saggital plane]
Bennet angle in edentulous patient is set at 30°
Border Movements:

Fig 1.24: Border movements

Vertical jaw relation:

Centric Relation:
Patterson and Needle house method = functional method
Graphic/arrow point tracing

Apex should be sharp
Pantograph → 3D → 6 styli used
Discrepency between centric relation and centric occlusion:

0.5 to 1.5 mm → also called freedom from centric
(AIIMS 05, Nov 11)
Thickness of inter – occlusal record – 2 mm
Orbitoaxial opening is determined by lateral pterygoid relining technique:
Open Mouth Method
Functional Method
Boucher
Winkler
Tissue conditioner used
ZnOE used
56Note: If there is CR and CO discrepancy then it needs NEW denture face bow:

Arbitary Facebow
Kinematic Facebow
Attached to maxilla
Attached to mandible
↓
UNSTABLE
↓
So, not used in CD
↓
Used in FPD
Used in CD patient
Used in FPD
Tissue conditioner:

Tend to harden and roughen in 4 – 8 weeks due to loss of plasticizer
Main disadvantage of relining and rebasing:

Change in “CR”
Main disadvantage of SCD:
Natural tooth wear
Denture fracture
The main reason for sequel with SCD is difficulty in obtaining balanced occlusion
Immediate denture:
No anterior try in
Frequent need of relining
Occlusal correction done after 48 hrs when swelling, inflammation subsides
Jiffy denture is interim immediate denture hinge movement possible upto:
20 – 25 mm
12° – 15° (13°) → Rotation of condyle in TMJ
Condylar inclination – 20 - 25°
Average intercondylar distance in CD patient = 110 mm
Relationship of denture base that resists the dislodgement of denture in horizontal direction is stability (AIIMS 06)

Problems in new denture bearers:

Problem	Cause
Soreness on slope of ridge	Deflective occlusal contact
Soreness on crest	Increased vertical dimension resulting in heavy contact
Generalized soreness of basal seat area	Increased vertical dimension
Increased salivation following insertion of CD	Due to reflex parasympathetic stimulation of salivary gland

Deflective occlusal contacts results in denture becoming loose several hours after wearing.

(AIPG 08)

57Anterior deprogramming device:

NOTE: Ideal support for implant – lamellar bone in patients requiring lingual frenectomy:

Denture fabricated before surgery to act as stent and prevent relapse
Biting Force: Measured by Gnathodynometer [Q]

In natural teeth – 20 kg (KCET 11)/44 pound/600 N
Maximum biting force in natural teeth - 45 kg
Metallic Denture:
Advantage
Disadvantage
Increased weight enhances stability of the denture
Increased weight of a maxillary denture causes denture to fall
Less margin of error permissible in PPS area
Appointment of Asthmatic patient is preffered in LATE morning/afternoon (AIIMS 06) patient type:

Phylosophical
Critical/exacting
Skeptical/hysterical
Indifferent
Best patient
Precise
Unrealistic expectation
Blaming nature
Above intelligent
Most difficult to manage [Q]
Little concern for treatment
Denture cleanser:

Na perborate is the main component (AIIMS May 12. direct pick from a Q bank)
Denture adhesive:
Synthetic salt of gontrez

(AIIMS Nov 12)
Good ionic adherence
Shunting effect in CD:

If occlusal plane is lowered in posterior region → denture instability
Die hardener:

Improves abrasion resistance of dies BUT not hardness
e.g. cynoacrylates (AIPG 10, 07 Q), acrylic resin, lacquers, polystyrenes
58Mastication vs bruxism:
Mastication
Bruxism/Parafunctional Habits
Force generated in vertical direction
Force generated in horizontal + vertical direction
Intermittent and light force
Prolonged + excessive force
Contraindication for relining and rebasing: [Q]

Excessive ridge resorbtion + change in vertical dimension >> discrepancy between centric relation and centric occlusion
Haspburg Jaw:

Class 3 → Progressive malocclusion
Arrangement of artificial teeth depends on ridge shape and arch form

(AIPG 08)
Atwood classification of ridge:

Classification
Description of ridge
1
Pre – extraction
2
Post extraction
3
High well rounded
(COMEDK 11)
4
Knife edge [Q]
5
Low well rounded
6
Depressed

Implant:

(Very Important Topic for PGI)

Epulis fissuratum is the tissue reaction commonly seen due to overextension of labial flanges of complete denture

(AIPG 08)
Rx of papillary hyperplasia:

Cryosurgery
Rx for hyperplastic ridge:

Use of tissue conditioner for several week before making impression

59Factors affecting tooth preparation:

Factor	Higher resistance → Lower resistance
Dislodging forces	Habits → eccentric interference → anterior guidance
Taper [Q]	Minimum → 6° → Excessive
Diameter [Q]	Small (premolar) → Large (molar)
Height [Q]	Long → average → short
Type of preparation [Q] NOTE: U grooves are more resistant than V type	Complete coverage ↓ Partial coverage ↓ Pnlay coverage
Luting agent [Q]

For abutment selection:

Shape of root + crown: Root [most important factors]
Crown: Root
Minimal = 1: 1
Optimum = 2: 3 (COMED 13)
Ideal = 1: 2
Lateral incisor cannot be used as abutment as it has insufficient pericemental area.

(AIPG 07)
Concept:

“B – L width” of occlusal surface of constructed crown should be narrow to transmit forces parallel to long axis of root of abutment. so, that better tolerated by pdl.
Taper:
Taper of 3° - 6° is allowable (KCET 11) (3°/wall) in tooth preparation for crown
For ceramic inlay taper > 2 - 5° (KCET 12)
Occlusal offset → given for structural durability [Q]
Functional cusp bevel→ provides adequate bulk to the restoration in area of heavy occlusal contact→ provides structural durability
Good ridge support required for FPD [Q]
If canine is missing abutments used is:

Central incisor + lateral incisor + 1^st premolar [Q]
Resistance:

Increased length/height + decreased diameter = “greater resistance” So, premolar has a greater resistance than molar
Grove should be atleast 1 mm wide
60Cusp Reduction:

Material
Functional Cusp
Non – Functional Cusp
Cast gold
3.5 mm
↓+ 0.5 mm
1 mm
↓+ 0.5 mm
Metal ceramic + amalgam
2 mm
1.5 mm
All ceramic
2 mm
2 mm
Angulation of functional cusp bevel:
Full veneer crown
3/4^th crown
Parallel to inner Inclines of cusp of opposing teeth
45degree angle to long axis of tooth
Indication of partial veneer crown:
Tilted tooth
Where aesthetic is desired [with normal length and shape of tooth]
Concept:

If full veneer given in tilted tooth larger destruction of tooth material may take place.

Modifications 3/4th crown: (facial surface intact)

Reverse 3/4^th	Proximal/mesial half crown	7/8^th crown with extension on buccal surface
Lingual surface intact	Distal surface intactsurface	Mesio buccal cusp intact
Indication – lingually Inclined tooth to prevent excess tooth reduction due to complete veneer crown	Indication – tilted abutment (mesio – distally)	Retention and Resistance is better than 3/4^th as more surface is Covered

So, in tilted tooth → go for 3/4 th crown→ beter aesthetic + conservative
Compared to ALL ceramic, poor colour matching is main disadvantage of PFM
Fracture of PFM→ mainly due to inadequate design fabrication of restoration (NBDE Q)
Tooth Reduction:

PFM
- Labial and incisal “more”
- less lingual reduction
- metal thickness – 0.5 mm cervical and 0.3 mm elsewhere
ALL CERAMIC
“less” [1.2 to 1.4 mm]

Finish line:

61Any crown is indicated in case of gross carious destruction but contraindicated in case of uncontrolled caries
All ceramic → incisal edge sloping towards lingual (not straight)
This bevel (17°) necessary for stress distribution
PFM → wing formation/vertical wall → increases retention and resistance

Aesthetic laminates:

Stainless steel:
Occlusal clearance – 1 mm
Margin – feather edge + subgingival
For temporary restoration: among various material ZnOE is most commonly used
Natural glaze/self glaze → more permanent than applied glaze

For gingival retraction under chemicomechanical method:

Types of FPD:

Fixed – fixed most commonly used
Cantilever:
RCT treated tooth with short root is contraindicated as abutment

Resin bonded bridge:

62Connector: Non rigid

Fig 1.25: Non rigid connector
Fig 1.26: Pier abutment (AIIMS Nov O7,05, definition)
Pier abutment has a mesial and distal pontic
Conclusion: Key hole should always be prepared on mesial abutment tooth on their distal side
(PGI 11)

Pontic:

Modified ridge lap used in:
- Anterior (AIPG 08) + premolar of both maxilla and mandible (AIIMS 06)
- Maxillary posterior
- So, pontic of choice in both anterior and posterior maxilla [Q]

Ovate pontic:
- Only maxillary anteriors + premolar
- Both modified ridge lap and ovate pontic have Good aesthetic and good hygiene

Spheroidal/egg shaped/conical/heart shaped/bullet shaped pontic:
- Design of choice in Posterior Mandible [Q]

Sanitary/hygienic/fish belly[Q] ponitic for posterior mandible

Prefabricated pontic:
- Truepontic and long pin pontic – for maxillary posterior

Saddle pontic is the Least hygienic pontic (KCET 11)

Faciolingual width of pontic should be smaller (2/3^rd of missing tooth) while Mesio – Distal width should be same

Pontic in gingival area should be convex Mesio Distally and concave Bucco Lingually (for cleaning)

Post and Core:

DIE:
Epoxy resin (most commonly used in laboratory) and electroplated dies are dies with improved Abrasion Resistance
Die spacer: 25 μ to 40 μ for luting cement
Bucco lingual edentulous space requiring cross arch stability RPD preffered
Too great bone resorbtion → RPD preffered as FPD requires proper ridge support
Pulp capped tooth should not be used as Abutment
Tooth with greatest pericemental area:
Maxillary 1^St Molar (433 mm²) (Manipal)

in RPD:

Principals of Design of Rpd:

Major Connector: (very important)

Mandibular
- Lingual bar: 1^st prefferance in mandibular major connector
  - 8 mm of vertical space is required
Modifications:
- Sublingual bar: Used when height of floor of mouth does'nt allow superior margin to place 4 mm below the gingival margin. So, place inferior to lingual bar
  - Contraindicated in high frenal attachment (NEET 13) and tori
- Lingual plate: Lingual bar with thin metal extension on the tooth.
  - Used when sufficient vestibular depth is Not available/High frenal attachment (NEET 13)
  - Advantage: Stabilizes periodontally weakened teeth and where there is need for addition of one/more anterior teeth (AIIMS 05). In case of excessive ridge resorbtion in kennedy class 1 (AIIMS 07)
  - Cingulum bar: Used in case of anterior crowding, diastema and when some indirect retention is required [splint the periodontally weekened teeth]
  - Double lingual bar: Cingulum bar attached with lingual bar
- Labial bar: Used when severe lingual inclination [Q]
Swing lock bar: Modification of the lingual plate which is hinged to labial bar.
Indication: Missing key abutment, teeth with questionable prognosis, unfavourable teeth contour, anterior teeth with excessive labial inclination [Q]

Maxillary:
- Antero: Posterior strap/closed Horse Shoe: is Best design
- Can use in almost any situation
  
  Fig 1.27: Closed horse shoe shaped major connector
- Horse Shoe shape/U shaped:
  - Least rigid so, least desirable.also least desirable in case of Distsal extension RPD (KCET 11). can't use in any situation
  - Only used in case of Tori (KCET 11)
    
    Fig 1.28: U shaped major connector
- Single palatal strap → suitable rigidity without bulk
  
  (KCET 11)
- Used in kennedy class 3
- Single Palatal bar → most commonly used but least logical
- Complete Palate/Palate Plate → maximum retention [Q]
- Indicated when anterior and posterior teeth are to be replaced Bilaterally

Repair of fractured major connector is contraindicated

Relief under maxillary major connector is generally not required

(KCET 11)

Co – Cr is best suited for major connector as it has adequate strength in thin sections

Tissue stops should be prepared on Distal extension RPD to stabilize the framework. It's an integral part of minor connector. Is of 2 mm² dimension

If major connector is flexible:

(AIIMS O7, 05)
- Causes pdl breakdown
- Residual ridge resorbtion seen because of no distribution of force

The purpose of “beading” in major connector:
- Formed by scraping the maxillary cast creating a groove not more than 0.5 mm [Q]
- It provides intimate tissue contact of the major connector. so, prevents food entrapement

65Retention in RPD:
Primary retention
2°^/passive retention
Direct retainer
By intimate relation between minor connector and Guiding plane [Q]
Proximal plate [Q]
Direct retainer

(Important topic for KCET)
- TYPES:
  - Extracoronal
  - Intracoronal/internal attachment:
    
    Mainly given for aesthetic reasons. abutment tooth shoud have a sound pdl + should fill all the criteria of abutment tooth + should be avoided in Distal extension cases without stress breaker (i.e can be given in distal extension cases with stress breaker)
    Used in tooth supported prosthesis
    
    (PGI 12)
- Clasp Passivity: It should be passive until dislodging force is applied
- Circumferential clasp provides greater Stability due to “Rigid Shoulder” which is absent in bar clasp
- Distal extension case and choices of direct retainer:
  - As in distal extension case there are high forces on abutment. So, we have to protect it from damage. choice of direct retainer are as follows:
    
    Circumferential clasp:
    
    Fig 1.29: Circumferential clasp
    
    Fig 1.30: Circumferential clasp
    
    Single circlet clasp:
    
    High forces on abutment as very Rigid. So, can't be used
    Reverse circlet clasp:
    
    Can be used with opposite rest, i.e. MesiaL rest involving distobuccal undercut.
    Bar Clasp:
    
    Fulcrum line shifts mesially so, less force on the abutment.
    But if only mesio – buccal undercut is retentive, then use
    
    RING clasp:
    
    Fig 1.31: Ring clasp
    
    66
    
    Fig 1.32: Combination clasp
    
    Indications are:
    
    Tipped molar (KCET 12)
    Mandibular molar tipped mesio – lingually [Q]
    Maxillary molar tipped mesio – buccaly [Q]
    Back action clasp is a modification of ring clasp
  - Hair Pin/Reverse action/Fish Hook clasp: Uses mesial rest and engages same mesio – buccal undercut
  - Combination clasp:
    
    Flexible retentive arm of wrought alloy. So, less force on the abutment
  - Embrassure clasp: is always used with 2 occlusal rest
  - Multiple clasp: indicated when denture replaces entire half of the dental arch/when EXTRA retention is needed (KCET) as in case of periodontally weakened principle abutment (KCET 08)
  - HALF and HALF clasp: 2 minor connector for retentive and reciprocal arm
  - Advantage is DUAL retention [Q]
  - Indication is the isolated rotated abutment
Circumferential vs bar clasp:
Aker's/Circumferential clasp (Trick: Ac)
Bar clasp/Roach
Most logical
Plaque accumulation and gingivitis due to increased food accumulation
BUT decalcification of enamel and risk for caries is increased

Contraindication of BAR clasp:

Shallow vestibule
Large soft tissue undercut

Rest and Rest seat:

Indirect Retainer:
- Distal extension is subjected to Additional rotational forces. So, it requires additional unit (other than Direct Retainer) to resist these forces away from edentulous ridge [Not towards ridge]
- So, Indirect Retainer Is given
- [NOTE: in tooth supported kennedy class 3 and 4, movement of denture away from soft tissue is prevented by direct retainer]
- Fracture of Indirect Retainer: It is the 1^st visual indicator of need for relining and rebasing
- Forms of indirect retainer:
  
  Positive rugae support: It is less effective. tooth support is always better than soft tissue support
  Auxillary occlusal rest: Given on mesial fossa of 1^st premolar (most commonly)
Location: as far as possible from fulcrum line (AIIMS O7,05). This provides BEST leverage advantage against dislodgement.
Fig 1.33: TRIPOD effect is best seen in kennedy class 2
- E.g of indirect retainer:
  
  Proximal plate of minor connector
  Linguo plate/cingulam bar
  Reciprocal arm of clasp
Mechanism of action of Indirect retainer → Class 2 lever
Where as
Distal extension case is an, e.g. of class 1 lever
Non–anatomic teeth:

Ideal for FLAT ridge (AIIMS 07, AIPG 07) and Parkinsonism

SOME MORE NOTABLE POINTS FROM PROSTHODONTICS

PPS + fovea palatine + vibrating line → Movable soft palate

68Acrylic teeth vs Porcelain teeth

Acrylic Teeth	Porcelain Teeth
Chemically bond with denture base (greatest advantage)	Mechanically via pins/diatoric holes
Less brittle High resilience and toughness [Q]	Very brittle/chipping occurs on impact [Q]
Wear can result in decreased VDO	Excellent abrasion resistance
Tooth contouring/occlusal adjustment/repolishing is relatively easy	Tooth contouring/occlusal adjustment is Difficult and may loose glaze
Easy to grind	Difficult to grind Difficult to position/retain in limited interarch space

The mesial inner inclines of lingual cusp of maxillary 1^st premolar is the most common initial Supracontact at resting centric position.
Selective grinding:
“cusp” should be reduced only when the interference is in Both centric and eccentric position [Q]
Prematurity in centric position only – requires reduction of opposing Fossa and Ridge [Q]

Curve of occlusion:

Curve of Wilson:
- Medio-lateral curve
- Formed due to lingual inclination of mandibular posteriors
- Concave in mandible
- Convex in maxilla
- Is a transverse curve

Curve of spee:
- AP curve
- Runs through cuspal tip of canine, buccal cusp of premolars and molars and passes through head of condyle

Curve of monsoon [Q]:
- Lateral curve
- Each cusp and incisal edge forms a cicle of 8 inch diameter with center at glabella
- Has concavity facing upwards

Curve of antimonsoon:
- Lateral curve
- Teeth anterior to 2^nd premolars involved
- Convexity facing upwards

Pleasure curve:
- Monsoon + Antimonsoon curve in posterior region

Incisal guidance:

Denture will be more stable as the angle approaches closer to “zero”
For selective grinding and for clearly detecting discrepancy in occlusion
Remount on articulator with new inter-occlusal record
NOTE: It's an NBDE Q which has been asked in NEET 13. So, be thorough with all NBDE questions to crack NEET/AIIMS
69Interim immediate denture/JIFFY denture:
- Single visit extraction
In Overdenture:
- Anterior abutments are preffered over posterior abutments because anterior region is more prone to resorbtion
Concept: Implant placement
- Implant placement without surgical template, which is based on the ideal diagnostic wax-up, leads to loss of control of exact implant positioning during the surgical intervention and will lead to increased aesthetic failure. Thus, surgical template is the most important tool for accurate placement of implant (also angulation)
Tooth most likely causing lateral balancing interferences: premolars (NBDE Q)
CD patients have a preference for which tooth while chewing hard food – premolars
Denture stomatitis/denture papillary hyperplasia:
Usually associatedwith wearing denture at night
More common in Diabetics and Women
Proximal groove :
For anterior tooth
Posterior tooth
Parallel to incisal 2/3^rd
Parallel to long axis of tooth
MOLAR 3/4^TH crown placed in buccal half with bucco lingual divergence
Ferrule: Main advantage is to prevent vertical root fracture
New Concept:
The use of Single Tooth Implants in restoring missing tooth is an attractive option Both for patient and Dentist
Today is even preffered over 3 unit bridge
In Co – Cr – Ni alloy/elgiloy:

Minimum of 12 % Cr is required for passivation [don't confuse with 18/8 stainless steel]
The average distance between upper and lower sulcus in anterior region is 36 – 39 mm (38 mm) (AIPG Q, AIIMS 05)
Anterior lingual border forms 2° peripheral seal in mandible (NBDE Q)
The posterior determinant of occlusion has the greatest effect on the restoration of which tooth? (NBDE Q)

Ans. Mandibular 2^nd molar
Indication for Non-Rigid Fpd:
Short span FPD replacing 1 tooth
Retainers cannot be prepared to be drawn together without excessive tooth reduction
Tilted FPD abutment
Pier abutment

70Occlusion:

GROUP function/unilateral balanced occlusion: Non balancing side contacts Working side contacts from canine to 3^rd molar Distribution of occlusal load E.g ceramic veneer and aesthetic laminates Seen in middle age group (30 – 40 years)
Canine protected occlusion/canine guided occlusion: Also called as mutually protected/organic occlusion Cuspid rise in protrusion Working side contact occurs mostly in canine Disocclusion of posterior teeth on working side Used in porcelain veneer Usually seen in young adults
Conclusion:	Keneddy class 1 → Keneddy class 2 →	Bilateral balanced occlusion Unilateral balanced occlusion and Balanced occlusion
In FPD in posterior pontic avoid Balancing side contact (AIIMS 06)

The usual 1st STEP in occlusal adjustment is to eliminate prematurities in centric relation (NBDE Q)
NESBIT appliance:

It is single tooth replacement/unilateral partial denture

While recording protrusive interocclusal record:

Height of contour:
Term height of contour was given by “Kennedy”
1^ST device to measure height of contour was used by Fortunati
Minimum width of palatal strap – 8 mm
Width < 8 mm → then it is a palatal bar
Width of lingual bar → 4 mm
Abutment tilted > 20°
Extract/Modify

Implant:

Applegate's Rule for classification of edentulous span:

(Very Important for KCET and COMEDK)

Rule 1: Classification should follow rather precede extraction

Rule 2: If 3^rd molar is missing and not to be replaced then it should not be considered in classification.

Rule 3: If 3^rd molar present and to be used as abutment then it should be considered in classification.

Rule 4: If 2^nd molar missing and not to be replaced then should not be considered in classification.

Rule 5: The most posterior edentulous area always determines classification.

Rule 6: Edentulous areas other than those which determine classification are considered as “Modification” space.

Rule 7: Extent of modification is not considered. It is the number of additional edentulous areas which are taken into account.

(AIIMS Nov 07)

Rule 8: There can be no modification area in class 4 [Q]

LAST 5-YEAR QUESTIONS FROM THIS TOPIC

1. While setting condylar guidance on a 3 pin articulator, the incisal pin is:

(AIPG 12)

Ans. Out of contact with the guide table (NBDE Q)

2. The chamfer finish line is used in:

(AIIMS May 10, May 08, AIPG 07)

Ans. Lingual surface of PFM (Ref: Shillinburg 3/e p132)

3. The replacement of missing part/artificial substitute is called as:

(AIIMS May 10, May 08, May 07, AIPG 07)

Ans. Prosthesis (Ref: Nallaswamy 1/e p810)

4. A porcelain laminate veneer during adhesion gets bonding interface from:

(AIIMS May 10)

Ans. Composite resin matrix, luting agent, etched enamel and silane coupling agent

5. A patient with complete denture complains of pain while swallowing. There is overextension of the denture in the distolingual aspect. The muscle involved is:

(AIIMS Nov O9)

Ans. Superior constrictor (Ref: Winkler, prosthodontics 1988 p76)

6. A complete denture patient with poor neuromuscular control wants correction of denture. it may be achieved by which of the following?

(AIIMS Nov O9)

Ans. Interocclusal records are made and corrected on articulator (winkler. essentials of complete denture prosthodontics 2/e p328)

7. After complete denture fabrication, if teeth are in end to end relation in patient, it can be corrected by:

(AIIMS Nov O9)

Ans. Grinding of the inclines so that the upper teeth move buccally and lower tooth move lingually.

8. A patient has come for relining and rebasing. You do relining if:

(AIIMS Nov O9)

Ans. If the patient is poor and cannot afford new denture (Ref: Nallaswamy 1/e p2003, p239-48)

9. In an edentulous patient, the average distance between the upper and lower sulcus in the anterior region is:

(AIPG 08)

Ans. 38 mm

10. To transfer the axis orbital plane we require:

(AIPG 08)

Ans. Either arbitrary/kinematic face bow (Ref: Bouchers 8/e p243)

11. Retentive arm in a clasp always points towards:

(AIIMS Nov 11)

Ans. Occlusal (Ref: Stewart. Textbook of RPD 2/e p67 – 68)

12. For strength and rigidity, the vertical height of a finished lingual bar should be atleast:

(KCET 11)

Ans. 4 mm

7213. A reliable guide for positioning maxillary anterior teeth in CD patient is:

(KCET 11, NEET 13)

Ans. Incisive papilla

14. Articulated diagnostic casts help in the following EXCEPT:

Diagnostic wax up to evaluate outcome
Detailed analysis of occlusal plane and occlusion
Fabrication of wax patterns for casting
Performing mock tooth preparation

Ans. c.

15. Height of contour term was coined by:

(KCET 11, COMEDK 11)

Ans. Kennedy

16. The functional occlusal force applied to the periodontal tissues during one deglutition is for a duration of:

Ans. 1 sec

17. The 1^st person to employ mechanical device to determine the relative parallelism of tooth surface was:

(KCET 11)

Ans. Fortunati

18. Occlusal offset in an anterior partial veneer crown may generally be necessary to provide:

(KCET 11)

Ans. Structural durability

19. Mode of failure during dislodgement of prosthesis cemented with zinc polycarboxylate cement is usually seen at the:

(COMEDK 11)

Ans. Cement prosthesis interface (Ref: Phillips 11/e p112)

20. Hanau H₂ articulator has an intercondylar distance of:

(KCET 11)

Ans. 110 mm (Ref: Wrinkle 2/e p23)

21. The technique to produce limited removal of epithelial tissue in the sulcus while a chamfer finish line is being created in tooth structure is called:

(COMEDK 11)

Ans. Gingettage (Ref: Shillingburg 3/e p268)

22. The ultimate finish line which produces an acute margin of metal is:

(COMEDK 11)

Ans. Knife edge (Ref: Shillingburg 3/e p132)

23. Schubiger attachment has a screw base common to the:

(COMEDK 11)

Ans. Gerber attachment (Ref: Wrinkler 2/e p23)

24. While arranging artificial teeth, the labial surfaces of the maxillary central incisors are usually ___________ in front of the posterior border of the incisive papilla:

(NEET 13, KCET 10)

Ans. 8–10 mm

25. Torus mandibularis is common on which area:

(KCET 10)

Ans. Lingual, premolar area

26. Functional cusp bevel has to be placed in following cusps EXCEPT:

(KCET 10)

Mesiopalatal cusp
Distopalatal cusp
Distolingual cusp of mandibular molar
Distobuccal cusp of mandibular molar

Ans. c.

27. Wing preparation for metal ceramic restoration helps in:

(KCET 10)

Ans. Retention and resistance.

28. During recording centric relation, compound occlusion rims with styli in maxillary arch are used in:

(KCET 10)

Ans. Needles house technique

7329. Mechanism of action of indirect retainers resembles:

(KCET 10)

Ans. 2^nd class lever.

NOTE: Distal extension RPD is an example of 1^st order lever.

30. Which of the following case is contraindication for FPD?

(PGI Dec 11)

Ans. Patients with high caries index

31. Which of the following is the most biocompatible material for dental prosthesis?

(PDI June 11)

Ans. Commercially pure titanium (Ref: Peterson 2/e p189)

32. Margins for all ceramic are?

(PGI June 11)

Ans. Shoulder on both buccal and lingual (Ref: Rosenstiel 3/e p175)

33. Which of the following position of mandible is in non-interfering occlusion?

(PGI June 11)

Ans. Centric occlusion (Ref: Boucher's 12/e p277)

34. In tooth preparation procedure, the foremost principle is:

(PGI Dec 10)

Ans. Conservation of what is remaining (Ref: Nallaswamy 1/e p567)

35. During jaw relations protrusive records are used for:

(PGI Dec 10)

Ans. Condylar measurement of both side (Ref: Winkler 2/e p195)

36. Golden proportion rule applies:

(PGI Dec 09)

Ans. 62 % (Ref: Sturdevant's 5/e p628)

37. The success of removable die system is based upon:

(PGI Dec 09)

Ans. Precies relocation of the die in the working cast (Ref: Shillinburg 3/e p314)

38. Inter papillary distance is equivalent to:

(PGI June 09)

Ans. Distance between the corners of mouth (Ref: Nallaswamy 1/e p234)

SOME MORE IMPORTANT POINTS FROM DM + OD + PROSTHODONTICS

Addition polysilicones → type 2 silicone impression
Silicone impression materials → have Low W.T and S.T
In ZnPO₄ cement → ‘Al’ present in liquid which is essential for cement forming reaction
Activator in composite:
Diketone in VL cure composite
Benzoin methyl ether in UV cure composite
Glycol ether/phthalate:

Plasticizer in polyether
Glycol dimethacrylate → cross linking agent in denture resin → provide craze resistance [Q]
Bevel:
LONG bevel → most commonly used
Reverse/counter bevel → given in Onlay/DFG
Microporosities and localized shrinkage porosities are Not seen in dentine base resin
Tooth Reduction:
In all ceramic → labial and incisal reduction → 1.2 – 1.4 mm
In PFM → labial and incisal reduction → 1.5 – 2 mm
Functional cusp bevel = 2 mm
Wing formation in PFM → for retention and resistance (Not aesthetic)
74Resin Bonded bridge: main advantage is that it is Conservative [Q]
Rochette → is 1^st design [conical perforations seen]
Maryland → tissue surface of retainer is etched
Virginia → based on “Lost Salt technique” [Q]
Pontic:
Sanitary/hygienic/fishbelly pontic → posterior mandible [Q]
Ovate/spheroidal/heart shaped → posterior mandible [Q]
Prefabricated pontic (true/long pontic) → posterior maxilla

Major connector:

Tissue stops and beading:

Tissue stops
Beading
Part of minor connector [Q]
Given in distal extension Cases
For positive intimate contact
2 mm² in dimension [Q]
0.5 mm [Q] of wax is removed
Palatal strap width → 8 mm
Lingual bar → 4 mm
Tripoding is used in → class 3 keneddy

[PGI Q]
Indirect retainer based on → class 2 lever [Q]
Implant:

(Very important for PGI)
Minimum width of keratinized gingival around an implant → 1.5 mm [Q]
Minimum width of bone around implant periphery > 0.5 mm [Q]
Hardness test:
Only microhardness test is suitable for brittle material, i.e. Knoop and Vicker's method.
Brinnel used to measure proportional limit and ultimate tensile strength of dental gold alloys.
Mercury/(Hg):
Compressive strength of dentine (268) < amalgam (310) < enamel (384)
75Denture:
During lateral excursion:

Working side contact occurs on → LUB ^* BLL
Interferences in centric relation:

Antero posteriorly (A-P ly)
Fig 1.34: Mesial inclines of maxillary teeth and distal inclines of mandibular teeth
Loosening of denture while smiling → inadequate relief of buccal frenum [Q]
Gauze of wax:

Relief wax → 20 gauze
Gauze of sprue used for casting → 8 – 12
Disadvantage of autoclave → causes fibro optic dimming
24 karat = 1000 fineness
Fluoride flux → KF + boric acid (1: 1) [Q]
Bennet movement → 1 – 1.5 mm/side
Bennet angle → 15° [30° in edentulous patient]
Lingual flange in mandibular denture is characteristic ‘S’ shaped due to action of mylohyoid muscle [Q]
Tissue Conditioner → tends to harden in 4-8 weeks
Fluidity measurement of gypsum product:

β – hemihydrate
α – hemihydrate
Slump test
core penetration test
Stages in addition polymerization: (KCET Very Important)

Termination → by direct coupling/exchange of hydrogens
Chain Transfer → active stage is transferred from active radical to inactive molecule
Indisperse → 10 % indium admix → decreases Hg vapour

Rounding of internal line angle → reduces stress on TOOTH
Rounding of external line angle →	reduces stress on restoration
(angle with apex directed outward)	i.e prevents fracture of restoration i.e rounding/beveling of axiopulpal line angle prevents fracture of amalgam restoration (AIIMS Nov 11, 06)

Total ETCH	Self ETCH Primer	All In One
3 steps(E + P + BA) 4^th generation Multibottle (KCET 12)	EP + BA 6^th generation	7^th generation
2 step/1 bottle (E + PBA)(KCET 10) 5^th generation	No rinsing for etchant. so, does'nt remove smear layer. incorporates smear plug into resin tag
E = etchant P = primer BA = bonding agent

Development of residual Compressive stress	Distribution of crack propagation
Aluminous porcelain (Na K⁺⁾	Ion exchange/chemical tempering
Thermal tempering	Transformation toughening, e.g. tetragonal ZrO₂ monoclonal ZrO₂
Thermal compatibility (increased cote of metal slightly)

Lactobaccilus →	Deep pit and fissure (AIIMS 05), deep dentinal caries.
S. mutans →	Pit and fissure caries (most predominant) Smooth surface caries (most predominant) Root surface caries (2^nd common after Actinomyces)
Root caries →	A. Viscosus(most predominant) (AIPG 11) A. Naselundi(most predominant) (AIPG 11) S. Mutans (2^nd most common)
Deep Dentinal caries →	Lactobacillus (most predominant) A. Naselundi (most predominant)

No of organism/c.c	Degree of caries activity
0-1000	Little or none
1000-5000	Slight
5000-10000	Moderate
>10000	Marked [KCET]

Of gingival seat	Of facial and lingual proximal wall
0.5 mm	0.2 mm

BENZOLD – BRUCK effect	METAMERISM
Change in color due to change in BRIGHTNESS	different colour under different LIGHT SOURCE [Q]
Change in value of hue with change in luminance (PGI june 11)

At 37 ^°C	2 %
At 45 ^°C	75 to 85 %

Anterior region	Middle region	Posterior region
Genioglossus	Mylohyoid	Palatoglossus + superior constrictor

Chapter Notes

Dental Material, Operative Dentistry and ProsthodonticsCHAPTER 1