| | Brief Description
This is the most conventional method of dental examination, where the dentist detects the presence of caries and diseases in the mouth via sight (visual inspection) or touch (usually using a dental explorer).
Caries occur when the tooth surface is damaged due to prolonged exposure to acids. These acids can arise from bacteria, or from our diet. The destruction of the tooth structure (dentine, enamel, and finally the pulp) leads to irreversible pathological changes in the tooth, which can be detected by visual inspection or by the sense of touch. Ideally, dentists should look out for good visual indicators that involve features which are purely associated with caries itself. This is to prevent misdiagnosis and confusion over the patient’s oral health condition.
The initial stage of caries is the dissolution of surface enamel crystals, leading to a change in its optic behaviour. Healthy enamel should be slightly translucent, but partially dissolving enamel is opaque. Dissolving enamel is more porous due to the acidic effect on the tooth, and hence scatters more light to give rise to it its opaque appearance.
The difference between air’s refractive index (1.00) and that of hydroxyappatite (1.66) (the substance which enamel is made of) is larger than that between hydroxyappatite and water (1.33). This means that a mildly demineralised tooth covered with water might not appear opaque, but might appear so when it is air dried. In other words, a lesion that has to be dried before opacities are observed has loss less minerals than a tooth which appears opaque even when wet (Ekstrand, 2004). This highlights the importance of drying all teeth during a dental examination, so as to detect caries in their early stages. Early stage caries (before cavitation and the loss of tooth structure occurs) are reversible, and early detection plus excellent oral hygiene might lead to a reversal of the cavitation process. (Ismail, 2004)(Picture Source: Pesqui, Odonto. 2003)
The demineralization of dentine weakens tooth structure and exposes dentine, giving rise to the “tackiness” found on carious teeth. Dentists make use of this tactile property in the diagnosis of caries as well.
Lastly, there are also colour changes that occur as teeth decay. The crowns of such teeth can appear black or brown, while carious roots might have a yellow/orange/tan/light brown appearance. The Method
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