Tooth-wear patterns in subjects with Class II Division 1 malocclusion and normal occlusion



Tooth-wear patterns in subjects with Class II Division 1 malocclusion and normal occlusion




American Journal of Orthodontics and Dentofacial Orthopedics, 2010-01-01, Volume 137, Issue 1, Pages 14.e1-14.e7, Copyright © 2010 American Association of Orthodontists


Introduction

The aim of this study was to investigate the prevalence of tooth wear in adolescents with Class II malocclusion, compared with those with normal occlusion.

Methods

The sample consisted of dental casts obtained from 310 subjects, divided into 3 groups: group 1, 110 subjects with normal occlusion (mean age, 13.51 years); group 2, 100 complete Class II Division 1 patients (mean age, 13.44 years); and group 3, 100 half-cusp Class II Division 1 patients (mean age, 13.17 years). Dental wear was assessed by using a modified version of the tooth-wear index. The 3 groups were compared by means of the Kruskal-Wallis and Dunn tests, considering the frequency and the severity of wear on each surface of each group of teeth. The level of statistical significance was set at 5%.

Results

The normal occlusion group had statistically greater tooth wear on the palatal surfaces of the maxillary central incisors and the incisal surfaces of the maxillary canines than the corresponding surfaces in both Class II malocclusion groups. The complete and half-cusp Class II Division 1 malocclusion groups had statistically greater tooth wear on the occlusal surfaces of the maxillary second premolar and first molar, the occlusal surfaces of the mandibular premolars, and the buccal surfaces of the mandibular posterior teeth compared with the normal occlusion group. The half-cusp Class II Division 1 malocclusion group had significantly greater tooth wear on the incisal surfaces of the mandibular incisors compared with the complete Class II Division 1 malocclusion group.

Conclusions

Subjects with normal occlusion and complete or half-cusp Class II Division 1 malocclusions have different tooth-wear patterns. Tooth wear on the malocclusion subjects should not be considered pathologic but rather consequent to the different interocclusal tooth arrangement.

Because of decreasing dental caries in many societies, more attention has been focused on tooth wear from erosion, abrasion, and attrition. Tooth wear is the loss of mineralized tooth substance from the tooth surface as a result of physical or chemical attack.

Masticatory movements by cooperative interactions among various stomatognathic organs, their proprioceptors, and higher brain centers are closely related to the functional occlusal system. A change in any information related to occlusion, the temporomandibular joint, or the masticatory muscles affects the patterns of the chewing movements. Some researchers have argued that occlusion might influence the masticatory path ; this is supported by 1 investigation. Gradual attrition of the occlusal surfaces of the teeth appears to be a general physiologic phenomenon in all mammals, in every civilization, and at all ages. There are relatively few studies of tooth wear in the literature. This lack of detailed research is partly because of problems involved in measuring techniques.

Measurement of tooth wear is difficult because some wear is normal throughout life, and no single index has been universally accepted. Studies that aimed to analyze dental wear initially focused on clinical evaluation of the lesions, through estimation of their severity and then began to report the distribution of the lesions. Smith and Knight introduced the tooth-wear index (TWI), which attempted to provide a solution to some problems associated with measuring wear at the individual and community levels. The TWI and modified versions of it have been used in many studies; this suggests widespread acceptance. However, it was described as flawed when used in an aging population, because it does not take into account teeth that were restored due to wear.

Some studies indicate that masticatory forces and malocclusion are the primary etiologic factors for noncarious lesion development ; others did not find this correlation. Because of the high prevalence of malocclusions in children and the controversies in the literature, it is relevant to verify the pattern of tooth wear in different occlusal relationships to help professionals to differentiate between physiologic and pathologic processes. The absence of previous studies of tooth wear on specific malocclusions encouraged us to compare the patterns of tooth wear in subjects with complete and half-cusp Class II Division 1 malocclusions, and compare them with subjects with normal occlusion.


Material and methods

The study protocol was approved by the Ethics Committee on Human Research of Bauru Dental School, University of São Paulo, Brazil.

The sample consisted of dental casts obtained from 310 untreated subjects from the files of the Department of Orthodontics at Bauru Dental School, University of São Paulo, Bauru, Brazil, and from the Burlington Growth Centre, Faculty of Dentistry, University of Toronto, Toronto, Canada, divided into 3 groups: group 1 included 110 subjects with normal occlusion (54 girls, 56 boys; mean age, 13.51 years; minimum, 10.31 years; maximum, 17.53 years); group 2 included 100 complete Class II Division 1 patients (51 girls, 49 boys; mean age, 13.44 years; minimum, 11.08 years; maximum, 17.26 years); and group 3 included 100 half-cusp Class II Division 1 patients (56 girls, 44 boys; mean age, 13.17 years; minimum, 10.54 years; maximum, 16.88 years). The dental casts were obtained of subjects with permanent maxillary and mandibular teeth up to the first molars. Additional inclusion criteria included no parafunctional habits, and no temporomandibular joint and airway problems, ascertained from the subjects' charts. Patients with open bite were not selected.

We used a modification of the TWI, described by Sales-Peres et al. The modifications matched the World Health Organization standard, thus allowing application of the index in broad epidemiologic surveys for both for deciduous and permanent dentitions. The modifications made calibration easier and resulted in greater reproducibility, because the modified TWI does not differentiate the depth of dentin involvement, as does the original TWI. In addition, the modified version includes a code for teeth that have been restored due to wear (code 4) and another code for teeth that cannot be assessed (code 9). The form sheet used to record the evaluations is shown in the Figure . The amount of permanent tooth wear was scored in numbers ( Table I ). A previously calibrated examiner (R.B.S.O.) performed the dental-cast evaluations.

Modified TWI (reprinted from Public Health 122, S.H. de Carvalho Sales-Peres et al, Prevalence of dental wear among 12-year-old Brazilian adolescents using a modification of the tooth wear index, 942-8, Copyright 2008, with permission from Elsevier. 22
Fig
Modified TWI (reprinted from Public Health 122, S.H. de Carvalho Sales-Peres et al, Prevalence of dental wear among 12-year-old Brazilian adolescents using a modification of the tooth wear index, 942-8, Copyright 2008, with permission from Elsevier.

Table I
Criteria used for tooth-wear evaluation, according to the modified TWI
Degree Criterion Description
Deciduous teeth Permanent teeth
A 0 Normal, no evidence of wear No loss of surface features
B 1 Incipient, tooth wear into enamel Loss of enamel giving a smooth, glazed, shiny appearance; dentin is not involved
C 2 Moderate, tooth wear into dentin Extensive loss of enamel with dentin involvement; exposure of dentin
D 3 Severe, tooth wear into pulp Extensive loss of enamel and dentin with secondary dentin or pulp exposure
E 4 Restored, tooth wear leading to restoration Tooth received restorative treatment because of wear
9 Could not be assessed Extensive caries, large restoration, fractured tooth, or missing tooth
Reprinted from Public Health 122, S.H. de Carvalho Sales-Peres et al, Prevalence of dental wear among 12-year-old Brazilian adolescents using a modification of the tooth wear index, 942-8, Copyright 2008, with permission from Elsevier.

A benchmark dental examiner (gold standard) (S.H.C.S.), skilled in epidemiologic surveys, trained and calibrated the examiner. The calibration process lasted 28 hours. Theoretical activities with discussions on diagnostic criteria of dental wear were performed.


Statistical analyses

To assess the reproducibility of the dental-cast analysis, 30 days after the first evaluation, 10 casts were reevaluated and demonstrated an intraexaminer kappa of 0.80 ( Table II ).

Table II
Intraexaminer analysis (kappa statistics)
Tooth wear Percentage of agreement (%) Coefficient value Strength of agreement
Dental casts 92.85 0.80 Almost perfect

Tooth surfaces were excluded from the statistical analysis if they were missing, or had extensive caries, large restorations, or fractures (code 9). The amount of tooth wear in the groups was compared with the Kruskal-Wallis test followed by the Dunn post-hoc test. The 3 groups were compared by considering the frequency and severity of wear on each surface of each group of teeth (incisors, canines, premolars, and molars). The level of statistical significance was set at 5%.


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Tooth-wear patterns in subjects with Class II Division 1 malocclusion and normal occlusion Guilherme Janson , Paula Vanessa Pedron Oltramari-Navarro , Renata Biella Salles de Oliveira , Camila Leite Quaglio , Sílvia Helena de Carvalho Sales-Peres and Bryan Tompson American Journal of Orthodontics and Dentofacial Orthopedics, 2010-01-01, Volume 137, Issue 1, Pages 14.e1-14.e7, Copyright © 2010 American Association of Orthodontists Introduction The aim of this study was to investigate the prevalence of tooth wear in adolescents with Class II malocclusion, compared with those with normal occlusion. Methods The sample consisted of dental casts obtained from 310 subjects, divided into 3 groups: group 1, 110 subjects with normal occlusion (mean age, 13.51 years); group 2, 100 complete Class II Division 1 patients (mean age, 13.44 years); and group 3, 100 half-cusp Class II Division 1 patients (mean age, 13.17 years). Dental wear was assessed by using a modified version of the tooth-wear index. The 3 groups were compared by means of the Kruskal-Wallis and Dunn tests, considering the frequency and the severity of wear on each surface of each group of teeth. The level of statistical significance was set at 5%. Results The normal occlusion group had statistically greater tooth wear on the palatal surfaces of the maxillary central incisors and the incisal surfaces of the maxillary canines than the corresponding surfaces in both Class II malocclusion groups. The complete and half-cusp Class II Division 1 malocclusion groups had statistically greater tooth wear on the occlusal surfaces of the maxillary second premolar and first molar, the occlusal surfaces of the mandibular premolars, and the buccal surfaces of the mandibular posterior teeth compared with the normal occlusion group. The half-cusp Class II Division 1 malocclusion group had significantly greater tooth wear on the incisal surfaces of the mandibular incisors compared with the complete Class II Division 1 malocclusion group. Conclusions Subjects with normal occlusion and complete or half-cusp Class II Division 1 malocclusions have different tooth-wear patterns. Tooth wear on the malocclusion subjects should not be considered pathologic but rather consequent to the different interocclusal tooth arrangement. Because of decreasing dental caries in many societies, more attention has been focused on tooth wear from erosion, abrasion, and attrition. Tooth wear is the loss of mineralized tooth substance from the tooth surface as a result of physical or chemical attack. Masticatory movements by cooperative interactions among various stomatognathic organs, their proprioceptors, and higher brain centers are closely related to the functional occlusal system. A change in any information related to occlusion, the temporomandibular joint, or the masticatory muscles affects the patterns of the chewing movements. Some researchers have argued that occlusion might influence the masticatory path ; this is supported by 1 investigation. Gradual attrition of the occlusal surfaces of the teeth appears to be a general physiologic phenomenon in all mammals, in every civilization, and at all ages. There are relatively few studies of tooth wear in the literature. This lack of detailed research is partly because of problems involved in measuring techniques. Measurement of tooth wear is difficult because some wear is normal throughout life, and no single index has been universally accepted. Studies that aimed to analyze dental wear initially focused on clinical evaluation of the lesions, through estimation of their severity and then began to report the distribution of the lesions. Smith and Knight introduced the tooth-wear index (TWI), which attempted to provide a solution to some problems associated with measuring wear at the individual and community levels. The TWI and modified versions of it have been used in many studies; this suggests widespread acceptance. However, it was described as flawed when used in an aging population, because it does not take into account teeth that were restored due to wear. Some studies indicate that masticatory forces and malocclusion are the primary etiologic factors for noncarious lesion development ; others did not find this correlation. Because of the high prevalence of malocclusions in children and the controversies in the literature, it is relevant to verify the pattern of tooth wear in different occlusal relationships to help professionals to differentiate between physiologic and pathologic processes. The absence of previous studies of tooth wear on specific malocclusions encouraged us to compare the patterns of tooth wear in subjects with complete and half-cusp Class II Division 1 malocclusions, and compare them with subjects with normal occlusion. Material and methods The study protocol was approved by the Ethics Committee on Human Research of Bauru Dental School, University of São Paulo, Brazil. The sample consisted of dental casts obtained from 310 untreated subjects from the files of the Department of Orthodontics at Bauru Dental School, University of São Paulo, Bauru, Brazil, and from the Burlington Growth Centre, Faculty of Dentistry, University of Toronto, Toronto, Canada, divided into 3 groups: group 1 included 110 subjects with normal occlusion (54 girls, 56 boys; mean age, 13.51 years; minimum, 10.31 years; maximum, 17.53 years); group 2 included 100 complete Class II Division 1 patients (51 girls, 49 boys; mean age, 13.44 years; minimum, 11.08 years; maximum, 17.26 years); and group 3 included 100 half-cusp Class II Division 1 patients (56 girls, 44 boys; mean age, 13.17 years; minimum, 10.54 years; maximum, 16.88 years). The dental casts were obtained of subjects with permanent maxillary and mandibular teeth up to the first molars. Additional inclusion criteria included no parafunctional habits, and no temporomandibular joint and airway problems, ascertained from the subjects' charts. Patients with open bite were not selected. We used a modification of the TWI, described by Sales-Peres et al. The modifications matched the World Health Organization standard, thus allowing application of the index in broad epidemiologic surveys for both for deciduous and permanent dentitions. The modifications made calibration easier and resulted in greater reproducibility, because the modified TWI does not differentiate the depth of dentin involvement, as does the original TWI. In addition, the modified version includes a code for teeth that have been restored due to wear (code 4) and another code for teeth that cannot be assessed (code 9). The form sheet used to record the evaluations is shown in the Figure . The amount of permanent tooth wear was scored in numbers ( Table I ). A previously calibrated examiner (R.B.S.O.) performed the dental-cast evaluations. Fig Modified TWI (reprinted from Public Health 122, S.H. de Carvalho Sales-Peres et al, Prevalence of dental wear among 12-year-old Brazilian adolescents using a modification of the tooth wear index, 942-8, Copyright 2008, with permission from Elsevier. Table I Criteria used for tooth-wear evaluation, according to the modified TWI Degree Criterion Description Deciduous teeth Permanent teeth A 0 Normal, no evidence of wear No loss of surface features B 1 Incipient, tooth wear into enamel Loss of enamel giving a smooth, glazed, shiny appearance; dentin is not involved C 2 Moderate, tooth wear into dentin Extensive loss of enamel with dentin involvement; exposure of dentin D 3 Severe, tooth wear into pulp Extensive loss of enamel and dentin with secondary dentin or pulp exposure E 4 Restored, tooth wear leading to restoration Tooth received restorative treatment because of wear — 9 Could not be assessed Extensive caries, large restoration, fractured tooth, or missing tooth Reprinted from Public Health 122, S.H. de Carvalho Sales-Peres et al, Prevalence of dental wear among 12-year-old Brazilian adolescents using a modification of the tooth wear index, 942-8, Copyright 2008, with permission from Elsevier. A benchmark dental examiner (gold standard) (S.H.C.S.), skilled in epidemiologic surveys, trained and calibrated the examiner. The calibration process lasted 28 hours. Theoretical activities with discussions on diagnostic criteria of dental wear were performed. Statistical analyses To assess the reproducibility of the dental-cast analysis, 30 days after the first evaluation, 10 casts were reevaluated and demonstrated an intraexaminer kappa of 0.80 ( Table II ). Table II Intraexaminer analysis (kappa statistics) Tooth wear Percentage of agreement (%) Coefficient value Strength of agreement Dental casts 92.85 0.80 Almost perfect Tooth surfaces were excluded from the statistical analysis if they were missing, or had extensive caries, large restorations, or fractures (code 9). The amount of tooth wear in the groups was compared with the Kruskal-Wallis test followed by the Dunn post-hoc test. The 3 groups were compared by considering the frequency and severity of wear on each surface of each group of teeth (incisors, canines, premolars, and molars). The level of statistical significance was set at 5%. Results In total, 22,320 dental surfaces were evaluated; 73.9% did not have dental wear (code 0), 20.5% had incipient lesions (code 1), 0.3% had moderate lesions (code 2), and 5.3% were excluded (code 9). No severe lesions were found. The normal occlusion group had statistically greater tooth wear on the palatal surfaces of the maxillary central incisors ( Table III ) and the incisal surfaces of the maxillary canines ( Table IV ) than the corresponding surfaces in both Class II malocclusion groups. Table III Intergroup anterior tooth-wear comparisons (Kruskal-Wallis followed by Dunn tests): means, standard deviations, and P values Tooth † Normal occlusion Complete Class II Division 1 Half-cusp Class II Division 1 P value Mean SD Mean SD Mean SD Inicisal surfaces Maxillary teeth 12 0.35 a 0.50 0.28 a 0.45 0.33 a 0.47 0.5472 11 0.54 a 0.50 0.49 a 0.52 0.59 a 0.53 0.4130 21 0.50 a 0.52 0.48 a 0.54 0.68 b 0.51 0.0108 ∗ 22 0.35 a 0.48 0.36 a 0.50 0.44 a 0.50 0.2770 Mandibular teeth 42 0.83 a 0.44 0.68 b 0.47 0.83 a 0.40 0.0333 ∗ 41 0.91 a 0.42 0.65 b 0.50 0.86 a 0.38 0.0003 ∗ 31 0.85 a 0.43 0.63 b 0.49 0.90 a 0.33 0.0000 ∗ 32 0.69 a 0.48 0.70 a 0.48 0.89 b 0.35 0.0018 ∗ Palatal surfaces Maxillary teeth 12 0.26 a 0.44 0.24 a 0.43 0.23 a 0.42 0.8595 11 0.37 a 0.49 0.19 b 0.39 0.24 ab 0.43 0.0375 ∗ 21 0.46 a 0.50 0.19 b 0.42 0.25 b 0.44 0.0000 ∗ 22 0.31 a 0.46 0.15 a 0.36 0.25 a 0.43 0.0501 ∗ Labial surfaces Mandibular teeth 42 0.05 a 0.21 0.02 a 0.14 0.01 a 0.10 0.2399 41 0.02 a 0.14 0.01 a 0.10 0.04 a 0.20 0.3454 31 0.04 a 0.19 0.01 a 0.10 0.01 a 0.10 0.2598 32 0.03 a 0.13 0.04 a 0.20 0.04 a 0.20 0.5657 Different letters represent statistically significant differences. ∗ Statistically significant at P <0.05 † FDI 2-digit system. Table IV Intergroup canine tooth-wear comparisons (Kruskal-Wallis followed by Dunn tests): means, standard deviations, and P values Tooth † Normal occlusion Complete Class II Division 1 Half-cusp Class II Division 1 P value Mean SD Mean SD Mean SD Inicisal surfaces Maxillary teeth 13 0.58 a 0.53 0.24 b 0.43 0.39 b 0.49 0.0000 ∗ 23 0.67 a 0.67 0.20 b 0.40 0.37 b 0.49 0.0000 ∗ Mandibular teeth 43 0.72 a 0.58 0.68 a 0.47 0.60 a 0.55 0.2455 33 0.66 a 0.56 0.70 a 0.48 0.68 a 0.53 0.8128 Palatal surfaces Maxillary teeth 13 0.10 a 0.30 0.08 a 0.27 0.14 a 0.34 0.4906 23 0.14 a 0.35 0.12 a 0.32 0.19 b 0.40 0.3950 Labial surfaces Mandibular teeth 43 0.08 a 0.28 0.13 a 0.34 0.13 a 0.34 0.4550 33 0.03 a 0.16 0.14 b 0.35 0.07 ab 0.26 0.0091 ∗ Different letters represent statistically significant differences. ∗ Statistically significant at P <0.05 † FDI 2-digit system. The complete and half-cusp Class II Division 1 malocclusion groups showed statistically greater wear on the occlusal surfaces of the maxillary second premolar and first molar, the occlusal surfaces of the mandibular premolars, and the buccal surfaces of the mandibular posterior teeth compared with the normal occlusion group ( Table V ). In addition, there was a tendency of greater tooth wear on the palatal surfaces of the maxillary first molars ( Table V ). Table V Intergroup posterior tooth-wear comparisons (Kruskal-Wallis followed by Dunn tests): means, standard deviations, and P values Tooth † Normal occlusion Complete Class II Division 1 Half-cusp Class II Division 1 P value Mean SD Mean SD Mean SD Occlusal surfaces Maxillary teeth 16 0.74 a 0.44 0.90 b 0.35 0.91 b 0.29 0.0001 ∗ 15 0.13 a 0.33 0.36 b 0.48 0.29 b 0.46 0.0003 ∗ 14 0.40 a 0.49 0.41 a 0.50 0.47 a 0.52 0.6091 24 0.42 a 0.50 0.50 a 0.50 0.45 a 0.50 0.5226 25 0.17 a 0.37 0.40 b 0.49 0.33 b 0.47 0.0006 ∗ 26 0.79 a 0.41 0.93 b 0.28 0.88 ab 0.33 0.0044 ∗ Mandibular teeth 46 0.82 a 0.38 0.88 a 0.34 0.93 a 0.26 0.0986 45 0.13 a 0.33 0.55 b 0.50 0.30 c 0.46 0.0000 ∗ 44 0.30 a 0.46 0.63 b 0.49 0.48 b 0.50 0.0000 ∗ 34 0.29 a 0.46 0.54 b 0.50 0.45 b 0.50 0.0007 ∗ 35 0.14 a 0.35 0.55 b 0.52 0.15 a 0.35 0.0000 ∗ 36 0.89 a 0.32 0.87 a 0.37 0.92 a 0.28 0.6115 Palatal surfaces Maxillary teeth 16 0.00 a 0.00 0.05 b 0.22 0.01 ab 0.10 0.0213 ∗ 15 0.00 a 0.00 0.00 a 0.00 0.02 a 0.14 0.1228 14 0.00 a 0.00 0.01 a 0.09 0.00 a 0.00 0.3499 24 0.00 a 0.00 0.03 b 0.17 0.00 a 0.00 0.0426 ∗ 25 0.00 a 0.00 0.00 a 0.00 0.00 a 0.00 1.0000 26 0.00 a 0.00 0.07 b 0.26 0.06 ab 0.24 0.0214 ∗ Buccal surfaces Mandibular teeth 46 0.07 a 0.26 0.42 b 0.50 0.24 c 0.43 0.0000 ∗ 45 0.00 a 0.00 0.14 b 0.35 0.10 b 0.30 0.0004 ∗ 44 0.02 a 0.13 0.07 ab 0.26 0.13 b 0.34 0.0072 ∗ 34 0.01 a 0.10 0.14 b 0.35 0.12 b 0.33 0.0014 ∗ 35 0.00 a 0.00 0.12 b 0.33 0.09 b 0.29 0.0013 ∗ 36 0.06 a 0.25 0.34 b 0.48 0.24 b 0.43 0.0000 ∗ Different letters represent statistically significant differences. ∗ Statistically significant at P <0.05 † FDI 2-digit system. The half-cusp Class II Division 1 malocclusion group had significantly greater wear on the incisal surfaces of the mandibular incisors compared with the complete Class II Division 1 malocclusion Group ( Table III ). There was also a tendency of more pronounced wear on the occlusal surfaces of the posterior teeth in this group when compared with the normal occlusion patients ( Table V ). Discussion We used a modified version of the universally used TWI, with high intraexaminer agreement (kappa, 0.80). The modified TWI does not differentiate the depth of dentin involvement as does the original TWI. Thus, the modified TWI has greater intra- and interexaminer agreement, even when working in field conditions. Some reports in the literature have suggested an association between greater tooth wear and malocclusion, although others did not corroborate this premise. Our results showed that the normal occlusion patients and those with complete or half-cusp Class II malocclusion had some tooth wear. However, the groups showed different wear patterns ( Tables III-V ). In the normal occlusion group, tooth wear was greater on the palatal surfaces of the maxillary central incisors and the incisal surfaces of the maxillary canines, compared with the 2 malocclusion groups ( Tables III and IV ). Greater tooth wear in the anterior region in the normal occlusion group ( Table III ) probably occurred because of normal vertical and horizontal anterior tooth relationships, establishing immediate anterior and lateral guidance during protrusion and lateral mandibular excursions, respectively. Since these teeth disclude the posterior teeth during mandibular functional movements, it seems logical that they would have greater wear. However, this should be considered physiologic wear because of the amount observed. To be considered pathologic, the amount of wear should have been much greater. Following the same rationale, since Class II Division 1 malocclusion patients have greater overjets, the amount of wear on the incisors would also be expected to be less than in the normal occlusion group ( Table III ). During lateral excursions, because of unfavorable anteroposterior positioning of the canines, these teeth also do not frequently disclude the posterior teeth as in normal occlusion, due to interferences of the posterior teeth. Therefore, this is the reason for less wear on the incisal surfaces of the maxillary canines in the malocclusion groups ( Table IV ). Complementing that explanation, the complete Class II Division 1 malocclusion group showed greater tooth wear on the posterior teeth; this can be explained by 2 factors. One is the large overjet that increases the likelihood of interferences of the posterior teeth during protrusion until the incisors make contact as the mandible is advanced ( Table V ). The other is that, because the canines are not in a favorable position to disclude the posterior teeth, these take the role of the canines during lateral mandibular excursions and are therefore subjected to greater wear. On the other hand, half-cusp Class II Division 1 patients had greater tooth wear on the incisal surfaces of the mandibular incisors than did the complete Class II malocclusion patients, but it was similar to the normal occlusion group ( Table III ). This is probably because the overjet in these patients is not large enough and allows contact between the anterior teeth during protrusion. Nevertheless, the amounts of wear on the occlusal posterior surfaces of the maxillary and mandibular teeth were also greater than in the normal occlusion group for the same reason as in the complete Class II Division 1 malocclusion, as explained above ( Table V ). Considering these results, tooth wear in the malocclusion subjects cannot be considered pathologic. No severe lesions (into pulp or secondary dentin) were found on the dental casts, and only 5.3% had moderate dental wear (exposure of dentin). The most tooth wear was considered to be incipient lesions (20.5%), corroborating a previous study. There is growing evidence that the major causes of severe wear in patients are systemic disease and intense parafunction. It seems that the difference between the studied groups is consequent to the different interocclusal tooth arrangement. In addition, it is not always possible to differentiate between erosion, attrition, and abrasion, because these conditions are frequently combined. However, if occlusal factors are involved in the cause of dental wear, they are probably related to attrition—tooth wear caused by the rubbing together of opposing occlusal surfaces. Attrition has specific characteristics. First, if attrition is the only cause of tooth wear, all wear will be located in areas of occlusal contact. There will be no wear on the buccal and lingual surfaces of teeth unless mandibular movement can make the opposing tooth touch in these areas. Second, attrition creates wear facets with a specific appearance: shiny, flat, and sharp edged. Third, attrition produces similar amounts of wear on the opposing teeth. In other words, it is impossible for tooth grinding to produce significant tooth wear on the maxillary anterior teeth but not on the mandibular anterior teeth. Finally, if attrition is the cause, the worn teeth must have occlusal contact in some mandibular position. The entire sample in this study was evaluated according to this reasoning. Some controversies in the literature regarding the amounts of wear in malocclusions are probably because of investigations in unspecific malocclusion groups. This study was specifically performed to investigate the differences in tooth wear between normal occlusion and complete and half-cusp Class II Division 1 malocclusions. Thus, it included many observations in each group. In addition, the groups had similar ages; this is essential when analyzing tooth wear, which increases with age. It could be speculated that patients with Class II subdivision malocclusions would have similar wear patterns to those with normal occlusion and complete Class II malocclusion on each side, but future studies must be developed to confirm this. Tooth-wear patterns in patients with Class II Division 2 malocclusion would also be probably different. We intend to investigate tooth wear in these malocclusion types in future studies. Further clinical studies should be undertaken with subjects of different age ranges to confirm these results and overcome the limitations of dental casts. The assessment of tooth wear at the epidemiologic level might be desirable in the near term, because of the increase in the prevalence and severity of dental lesions. Conclusions Subjects with normal occlusion and complete or half-cusp Class II Division 1 malocclusions have different tooth-wear patterns. Tooth wear in malocclusion patients should not be considered pathologic but, rather, a consequence of the different interocclusal tooth arrangement. The authors report no commercial, proprietary, or financial interest in the products or companies described in this article. References 1. Marthaler T.: Changes in dental caries 1953-2003. Caries Res 2004; 38: pp. 173-181 2. Vehkalahti M., Tarkkonen L., Varsio S., and Heikkila P.: Decrease in and polarization of dental caries occurrence among child and youth populations, 1976-1993. 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