Assessment of the Discoloured Tooth
Kyle D. Hogg
With the increased emphasis and importance placed on dento-facial aesthetics in today’s society, it comes as no surprise that many patients are seeking to change or improve the colour of their teeth. In a recent survey conducted in the UK asking 3215 subjects to self-assess their dentition, 50% of the population studied perceived that they had some type of tooth discoloration.1 This trend for patients desiring aesthetic improvement is not limited to young individuals. As people are maintaining more teeth longer into life, older individuals are also seeking out tooth whitening as a minimally invasive and safe way to improve their dental appearance.2
Performing a thorough pre-operative assessment of patients seeking tooth whitening is paramount to successfully identifying and treating patients who are suitable candidates. It is important to bear in mind that tooth colour is determined by both intrinsic qualities, such as the way in which enamel and dentine absorb and reflect light, and extrinsic qualities, such as external stains caused by smoking, diets rich in tannin-containing items or consumption of metal salts. There are also changes in the colour of teeth associated with the ageing process, as well as iatrogenic changes due to the patient’s restorative dental history. In fact, tooth discoloration may manifest itself differently on individual teeth within the same arch (Figure 10.1.1). A thorough investigation of the patient’s individual history and an understanding of the ways in which teeth become discoloured will allow the clinician to form a diagnosis for the type of discoloration and prescribe, where indicated, appropriate treatment protocols.
Perhaps the most frequent cause of tooth discoloration is via the process of cumulative extrinsic staining. This staining occurs when the organic material present in the interprismatic spaces located between enamel rods wicks pigments and dyes from the oral environment via capillary action. The organic material in these spaces is more susceptible to discoloration. Pigments present in the oral environment consist of a colour-bearing group (chromophore) in addition to another molecule(s). Pigments may or may not enter into the interprismatic space and adhere to the organic material located there. This is slightly different than a dye, which is a type of pigment that contains reactive hydroxyl or amine groups that more readily adhere to the inorganic material in these spaces.3 Dyes are ubiquitous and can be found in many commonly consumed food items such as tea, coffee, cola, berries and red wine, among many others. Figure 10.1.2 depicts how metal compounds can interact with dyes and pigments to form larger compounds and discolour the teeth.