The process of diagnosis and current criteria for dental erosion 23 26 1 52 12 Fig. 1 a b c d  12 The diagnosis of tooth wear in general and erosion in particular is made from its lesion characteristics, from the results of nutritional, medical and occupational analysis, and from dietary records. The diagnostic process can be more differentiated with the individual patient, whereas in field trials it is restricted to the classification of lesion shape. 12 14 The early signs of erosive tooth wear appear as changes of the optical properties of enamel resulting in a smooth silky–shining glazed surface. When the tissue loss continues, changes in the original morphology occur. On smooth surfaces, convex areas flatten or concavities develop, the width of which clearly exceeds the depth. Lesions are located coronal from the enamel–cementum junction (CEJ) with an intact enamel rim along the gingival margin. On occlusal and incisal surfaces, rounding and cupping of the cusps and grooving of the incisal edges occur, and restorations may rise above the level of the adjacent tooth surfaces. In advanced cases, the whole occlusal morphology disappears. 24 The implementation of current diagnostic criteria 43 47 31 Stafne and Lovestedt presented their observations in subjects with known acid exposure, amongst them 50 patients with frequent consumption of lemon juice. They did not give a concrete description of lesion shape, but attributed hypersensitivity, absence of stain and defects with rounded margins as effect of the action of the acids. Their most important sign of diagnostic value was the presence of fillings projecting above the surface of the tooth. In their publication, a number of clinical images were included, presenting lesions clearly matching current erosion criteria. 40 It appears noteworthy, that Pindborg, as well as Robinson, ascribed cupping of the cusps, loss of the occlusal morphology or loss of crown height, and incisal grooving to attrition which in their publications was defined as result of mastication. 8 10 8 1 Table 1 10 8 Diagnostic criteria for dental erosion Initial Absence of developmental ridges of the enamel, smooth glazed surface Advanced  Facial/oral surfaces Concavities whose breadth greatly exceeds their depth Lesion ovoid or crescentic in outline, concave in cross section or Lesion entirely in the crown, irregular in outline, punched out appearance  Occlusal/incisal surfaces Surfaces appear flattened, depression of the cusps (cupping) and on the incisal edges (grooving), edges of restorations raising above the level of the adjacent tooth surface Conclusions from epidemiological studies using current diagnostic criteria 8 9 16 32 39 50 15 17 21 25 34 38 44 48 51 2 Table 2 Prevalence of lesions in risk groups deriving from the use of current diagnostic criteria for dental erosion   Index Group size Prevalence risk group Prevalence control group Intrinsic acid exposure 34 Eccles and Jenkins index n 28/117 = 24% No control group 44 Eccles and Jenkins index n 22/35 = 63% 12/105 = 11% 38 Lussi index n 79/81 = 98% Minor, less severe Incisal/occlusal Incisal/occlusal Grade 1: 93% Grade 1: 73% Grade 2: 52% Grade 2: 23% Buccal Buccal Grade 1: 30% Grade 1: 19% Grade 2: 9% Grade 2: 6% Palatal Palatal Grade 1: 21% Grade 1: 10% Grade 2: 5% Grade 2: 0% Extrinsic acid exposure 25 Eccles and Jenkins index n 16/26 = 60% 0/26 = 0% 51 Eccles and Jenkins index n 14/19 = 74% No control group 15 Lussi index n 127/130 = 98% 66/76 = 87% These observations support the finding that subjects with continuous exposure to acids have a higher rate of lesions with a specific characterisation. This is, however, not enough support for the assumption that, vice versa, subjects presenting with such defects must be exposed to acids. 46 3 2 3 5 7 20 30 35 37 49 22 1 27 35 Table 3 Analytical epidemiological studies attempting to relate the occurrence of (erosive) wear to aetiological factors   Index, group size, age and prevalence Conclusion 22 Eccles & Jenkins index Citrus fruits: odds ratio (OR) 2 n Soft drinks: OR 4 13–83-year-olds 27 Lussi index Significant relation to the consumption of fruit, acidic drinks, yoghurt, vomiting n 26–30- and 46–50-year-olds at least 36 and 43% resp. with any erosion 5 TWI (Smith and Knight) No significant relation to drinks or other acidic food n Significant relation to heart burn 11–14-year-olds 57% had wear in enamel on more than 10 teeth 20 Lussi index No relation to any aetiological factor n 19–25-year-olds at least 82% with erosion 1 TWI (Smith and Knight) Significant relation to drinks and fruit, but also to milk, yoghurt and beer n 14-year-olds 48% low, 51% moderate 1% severe lesions 2 TWI (Smith and Knight) modified for erosion No association to erosive drinks for the total sample n n 12–14-year-olds 95% with erosion 30 Lussi index No relation to the intake of sport drinks n 18–28-year-olds 37% with erosion 49 Modified Lussi index No relation to acidic drinks and fruits n 15–16-year-olds 30% with visible smooth wear 3 Modified Lussi index No significant association to risk factors n 15-year-olds 72% grade 1 24% grade 2 5% grade 3 37 TWI (Smith and Knight) modified for erosion No significant association with dietary factors n = 1726 Significant relationship with gastro-oesophageal symptoms 4–18-year-olds 36, 56 and 34% with any erosion on buccal and palatal surfaces of the incisors, and first permanent molars resp. 7 TWI (Smith and Knight) modified for erosion Drinking fizzy pop: odds ratio 1.59–2.52 depending on amount and frequency n 12-year-olds No relation to eating apples, citrus fruit 56% with erosion 35 TWI (Smith and Knight) on labial and lingual surfaces in front teeth, occlusal surfaces of first molars No association to apples, fresh oranges n Weak association (OR 1–1.4) to yoghurt, grapefruit, salad dressing, vinegar, fruit juice, fizzy drinks 14-year-olds Strong association to herbal/lemon tea (OR 3.97) 53.5% with exposed dentine 15 It must, however, also be taken into consideration that current diagnostic criteria might not be valid enough to really reflect the effect of a chronic acid exposure. 19 28 2 Fig. 2 a b a b c 13 15 d c  Comparative studies on lesion characteristics of wear 6 13 6 13 4 4 11 36 18 41 42 Table 4 n 13   Abrasive diet (medieval group) Acidic diet (raw food group) Average western diet   Incisal/occlusal surfaces Incisors/canines Grooving 93% 96% 90% n.s.  Molars/premolars Shallow cupping (<0.5 mm) 87% 59% 47% p Deep cupping (>0.5 mm) 78% 45% 4% p  Smooth surfaces (all teeth) Concavity coronal to the CEJ 0% 63% 8% p V-shaped defects 0% 38% 10% p 4 3 45 Fig. 3 a 13 c b 15 c d 4  As to the occlusal/incisal surfaces, grooving and cupping was common in all groups even though most often in the medieval group, followed by the raw food group, and the western diet group. The conclusion from this study was that shallow defects on smooth surfaces might be a valid criterion for dental erosion, whereas cupping, and especially incisal grooving, was common in all groups and therefore not valid for a differential diagnosis. 29 33 Hence, the occlusal/incisal substance loss observed in individuals prone to dietary acids may be explained as pronounced abrasion/demastication of acid softened surfaces. Therefore, it is questionable if the occlusal morphological criteria used for the diagnosis of occlusal erosion per se are valid. 4 Fig. 4 a 15 b c d e f  Conclusion The validity of current diagnostic criteria for dental erosion has not been systematically studied, even though there is consensus about their definition. Grooving of incisal surfaces is a common phenomenon and possibly the effect of any physical or chemical impact. It should be considered to abandon grooving of anterior teeth and canines as a clinical criterion for dental erosion. Shallow defects located coronal from the CEJ may predominantly occur as effect of chronic acid exposure and might be pathogonomic for dental erosion. This assumption is supported by the finding that these types of lesions are not present in ancient remains even in cases of severe wear. Cupping of cusps is the most uncertain criterion because it can be an effect of abrasion as well as of erosion. In industrialised countries, abrasion is not expected to be a significant factor in young people. Cupping occurring at younger ages can therefore be an effect of erosion. At older ages, however, physical and chemical impacts add up increasingly and cupping will therefore be of little diagnostic value in adults. These conclusions are drawn from very few studies; therefore systematic research on this issue is needed. Nevertheless, there is enough support for a criticism of current diagnostic criteria particularly in the light of the development of a new index.