The aim of this chapter is to focus on the various aids including advanced diagnostic techniques. This chapter covers the aids used in clinical diagnosis, aids used in radiographic diagnosis, aids in microbiological diagnosis, methods/aids in immunological diagnosis, biochemical diagnosis, and other diagnostic aids. Periodontal probes are used to measure the pocket depth, quantification of bacterial plaque and gingival inflammation, determination of mucogingival relationship, measurement of gingival recession, location of calculus, and identification of tooth irregularities. Radiographs are used to obtain a visual image of the bone support around a tooth or dental implant. The radiographic image is the result of X-ray beam passing through the area of interest and exposing the silver halide emulsion on the radiographic film. The most commonly used radiographs in periodontal diagnosis are transmission radiographs. Aids in microbiological diagnosis are based on the concept of bacterial specificity.