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cosmetic dentistry_beauty & science No. 1, 2017

naturomimetic layering technique | products of major enamel protein amelogenin.8 The mature enamel is acellular and does not regenerate itself unlike other biomin­ eralised tissues such as bone and dentine.9 Enamel surface loss affects smile aesthetic Fig. 3a Fig. 3b Fig. 4 Enamel, being the outermost coverage of coronal portion of teeth, has to face various challenges of maintaining its integrity with constant deminerali­ sation and remineralisation within the oral environ­ ment, and it is susceptible to tooth surface loss (TSL) phenomenon. Tooth surface loss can be physio­ logical, occurring as a normal aging process.10 This process, accelerated by several endogenous and exogenous factors, is termed pathologic. Depend­ ing upon the cause, four types of surface loss have been identified: attrition, abrasion, erosion and abfraction.11­19 Each type of tooth surface loss and its effects on overall health, function and smile aesthetics are described below. Attrition (Fig. 1) is the loss of the tooth substance occurring as a result of mechanical wear between the opposing surfaces of teeth during masticatory and parafunctional activities.20­23 It is most often seen on the occlusal surfaces of posterior teeth and the incisal edges of the anterior teeth. Abrasion (Fig. 2) denotes mechanical wear of teeth due to causes other than tooth­to­tooth con­ tact.24­26 It occurs due to friction between teeth and exogenous agents like a hard toothbrush, abrasive toothpaste, intensive horizontal brushing motions etc.27, 28 Erosion (Figs. 3a & b) is the wearing of the teeth due to chemical processes that may involve intrinsic or extrinsic acids. The rate of the erosion is also affected by the quality of saliva (salivary flow, pH, and its constituents). The palatal surface seems to be the most commonly affected site.27, 28 Abfraction (Fig. 4) is the pathologic process of tooth surface loss in which repeated compression and flexure of teeth under occlusal loading will lead to fracture of thin enamel rods. It is mostly seen in the cervical region of teeth.29­32 Other than these four causes, developmental anom­ alies (Fig. 5a–c), especially amelogenesis imperfecta and dentinogenesis imperfecta, predispose teeth to rapid wear.33­35 This is because the enamel is very thin and/or friable in amelogenesis imperfect, while in dentinogenesis imperfect, the attachment of the enamel and dentine is weak, which results in easy separation.36 Tooth surface loss affects tooth anat­ omy, and various kinds of complications may arise if it is left untreated. Loss of the mineralised tooth substance results in a higher risk of tooth sensitivity, pulpal complications, and discoloration.37, 38 Loss of the vertical occlusal dimension (VOD) may result in dentoalveolar compensation or an increased interocclusal rest space.39 This will affect the neuromusculature, efficiency of masticatory function, and aesthetics, as the posi­ tion of the smile line, the horizontal occlusal plane changes.38­40 Loss of canine guidance and canine protection may increase horizontal stresses in the posterior occlusal surface and thereby cause loss and fracture of res­ torations.38 Moreover, instability of the occlusion will decrease masticatory function and increase the incidence of cheek and tongue biting.37, 41 The overall effects of tooth substance loss influence not only teeth anatomy and masticatory system, but also quality of life.42 Fig. 5a Fig. 5b Figs. 3a & b: Erosion. Fig. 4: Abfraction. Figs. 5a–c: Teeth with developmental defect: enamel hypoplasia (a), amelogenesis imperfecta (b), dental fluorosis (c). Fig. 5c 15 cosmeticdentistry 1 2017

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