Occlusal tooth wear in the general population of Germany: Effects of age, sex, and location of teeth Oliver Schierz, DDS, Dr Med Dent,a Sandra Dommel, DDS,b Christian Hirsch, DDS, Dr Med Dent Habil,c and Daniel R. Reissmann, DDS, Dr Med Dentd University of Leipzig, Leipzig, Germany; University Medical Center Hamburg-Eppendorf, Hamburg, Germany; University of Minnesota, Minneapolis, Minn Statement of problem. Tooth wear is an increasing problem in a society where people are living longer. Purpose. The purpose of this study was to assess the effect of age, sex, and location of teeth on the severity of tooth wear and to determine the prevalence of dentin exposure in the general population of Germany. Material and methods. Tooth wear was measured in casts of both jaws of 836 persons with a 6-point (0-5) ordinal rating scale. Linear random-intercept regression models with the covariates of age, sex, jaw, and tooth group (with the participant as a grouping variable) were computed to determine the association of these covariates with tooth wear of a single tooth. Results. The mean tooth wear score across all age groups, both sexes, and all teeth was 2.9 (standard deviation, 0.8), and the prevalence of teeth with exposed dentin was 23.4%. The participants’ age was correlated with the mean tooth wear scores (r¼0.51). The tooth wear level among women was on average 0.15 units lower than among men, and tooth wear was on average 0.59 units higher for anterior teeth than for posterior teeth. Conclusions. Increased tooth wear in anterior teeth may be due to the initially predominant guidance by anterior teeth, with age-related linear progress in tooth wear. Occlusal tooth wear scores and dentin exposure increase with age. (J Prosthet Dent 2014;-:---)
Clinical Implications Whether tooth wear is in the physiologic range or not, the age and location of the tooth should be taken into account. The differentiation for sex is of limited value. Over a lifetime, teeth are exposed to intrinsic factors (such as gastroesophageal reflux disease) and extrinsic factors (such as habits, environment, or occupation) that cause attrition, abrasion, abfraction, or erosion.1-5 As differentiating among these factors is challenging and tooth-surface loss in general is multifactorial, the umbrella term “tooth wear” has been established. a
Whereas severe tooth wear can substantially affect survival in some species, its consequences for humans are less serious. Nonetheless, premature tooth wear often causes hypersensitivity, esthetic (and therefore psychosocial) impairment, and, in severe situations, loss of tooth vitality or the need for extraction.6 Differentiating physiologic (normal) from pathologic tooth wear is
therefore essential. Knowing whether tooth wear is of a physiologic or pathologic nature might aid in early intervention, thereby preventing severe tooth wear or even tooth loss and minimizing the need for comprehensive restorations. In the near future, more elderly people will be living than ever before,7 meaning that preventing and treating severe tooth wear will be an ever-increasing problem.
Assistant Professor, Department of Prosthodontics and Materials Science, University of Leipzig. Research Associate, Department of Prosthodontics and Materials Science, University of Leipzig. c Professor and Chair, Department of Pediatric Dentistry, University of Leipzig. d Assistant Professor, Department of Prosthetic Dentistry, University Medical Center Hamburg-Eppendorf; Research Fellow, Department of Diagnostic and Biological Sciences, University of Minnesota. b
Schierz et al
2
Volume Data for tooth wear in the general population and related factors have not been extensively reported, and the comparability of study results is limited because of the variety of assessment indices.8-12 For most of the applied indices, no data for the general population or for validity or reliability are available. Although some data have been collected on skeletal material from nonindustrialized cultures (both ancient and contemporary),13-15 most researchers have quantified different scales measuring the prevalence of tooth wear in present-day industrialized populations.16-22 Most studies have reported that factors such as age and sex affect the severity of tooth wear.10,16,20,23 More challenging is to obtain information on the relevance of the location of teeth. However, the extent of the effect of all these factors is unclear, and no information is available as to which has the most influence. The purpose of this study was to investigate the effect of age, sex, and location of the teeth on the extent of occlusal tooth wear. A secondary purpose was to provide information on the distribution of tooth wear and the prevalence of dentin exposure in the general adult population of Germany.16,17,24-34
applied. Impressions were made with irreversible hydrocolloid, and hard stone plaster casts were fabricated. The casts were arranged in pairs and stored in a dry environment. The study protocol was approved by the Institutional Review Board of the Martin Luther University Halle-Wittenberg and conducted in accordance with the Helsinki Declaration. All participants gave signed informed consent. One trained examiner (R.H.) assessed occlusal tooth wear by using casts of both jaws of the participants. All occlusal surfaces and incisal edges were examined without magnification under a table lamp, and the tooth wear of each tooth was rated separately with the ordinal 6-point scale (range, 0-5) of the modified severity index described by John et al (Fig. 1).36 Teeth that were missing, involved with partial fixed dental prostheses, replaced, or otherwise not assessable (for example, where more than 75% of the occlusal surface had been replaced by restorations or air bubbles) were excluded from the rating (16% for the 20- to 29-year-old age group, 27% for the 30- to 39-yearold age group, 36% for the 40- to
MATERIAL AND METHODS This study was a secondary analysis of an epidemiologic study conducted in the metropolitan area of Leipzig and Halle (Saale), Germany.35 The original purpose of this survey was to determine the prevalence of symptoms of temporomandibular disorders in the general population. The residency registration offices of both Halle and Leipzig supplied the addresses of 1000 residents between the ages of 20 and 59 years. Of these individuals, 836 (mean age, 40.4 years; standard deviation, 11.7 years; 56% women) agreed to be examined and questioned by dentists at the universities of Halle (N¼388 participants) and Leipzig (N¼448 participants). Age was the only inclusion criterion (20 to 59 years); no exclusion criteria were
The Journal of Prosthetic Dentistry
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Issue
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49-year-old age group, and 46% for the 50- to 59-year-old age group). In total, 32% of the teeth were not assessable for tooth wear. Third molars were excluded from the analyses. A total of 17 302 teeth were assessable and included in the analyses (women, n¼9604 teeth; men, n¼7698 teeth; maxilla, n¼8289 teeth; mandible, n¼9013 teeth; anterior teeth, n¼8484; and posterior teeth, n¼8818). Analyses were performed on 2 levels: on a participant level (with mean scores of all assessable teeth in both jaws [casts] to compensate for the reduced number of assessable teeth associated with increasing age) and on a tooth level (that is, with the scores of each single tooth in the analysis and the participant as the grouping variable). Additionally, the single teeth were merged to anterior teeth (incisors and canines) and posterior teeth (premolars and molars without third molar teeth). The tooth wear scale was considered quasi-interval, based on the expected equal differences between 2 adjacent ordinal scores.36 Test-retest reliability (intraexaminer reliability) of the single examiner (R.H.) 2
2 1
1
3
3 4
4 5 5
1 Modified assessment of occlusal tooth wear severity according to Pullinger and Seligman.42 Scale used: 0, no visible tooth wear; 1, minimal wear of cusps or incisal tips, enamel only; 2, facets parallel to normal planes of contour, enamel only; 3, noticeable flattening of cusp or incisal edges, enamel only; 4, total loss of contour and dentin exposure when identifiable, dentin exposure up to half of former crown of tooth; and 5, total loss of contour, dentin exposure over half of former crown of tooth. John et al added the fifth score.36
Schierz et al
-
2014
3 examiner provided similar results. Reliability and validity analyses were performed at the individual tooth level. Initially, a descriptive analysis of the data was performed. The prevalence of the tooth wear scores is presented in a graph. The mean wear scores and prevalence values of exposed dentin (proportions of teeth with a score of 4 or 5) are provided for all participants and for the subgroups according to age, sex, location of teeth (anterior or posterior), and jaw. Because age is a continuous variable, subgroups were defined in decades (20 to 29 years, 30 to 39 years, 40 to 49 years, and 50 to 59 years). Prevalence data were limited to assessable teeth, and all data excluded third molars. For the correlation analysis of participants’ tooth wear and age, the mean wear scores and the individual age were used to calculate the Pearson
Cumulative prevalence maxilla
was assessed at the start of the study by using repeated ratings of 60 arbitrarily chosen casts and considered sufficient (weighted kappa, 0.62).37 The validity of the ratings of the single examiner (R.H.) was assessed based on consistency with the median wear scores of 6 additional examiners, which were considered the external standard (convergent validity). Casts of 14 arbitrarily chosen participants were rated by all examiners. The additional examiners were not trained but were provided with a visual examination guide showing the severity index in detail. By using the median wear scores of the additional examiners, a weighted kappa of 0.54 was calculated, reflecting a sufficient convergent validity. The combined mean wear scores of the additional examiners were slightly higher (3.7) than the mean wear scores of the study examiner (3.4), meaning the study
product-moment correlation coefficient. Univariate linear random-intercept models were calculated with age, sex, jaw, and tooth group as predictor variables. The tooth wear scores of each single tooth was the criterion variable in these models, and the participant was used as grouping variable to account for the intercorrelation of the scores within a participant.38 A multivariate linear random-intercept model was developed by using a backward elimination technique, starting with all candidate variables mentioned previously as predictor variables and tooth wear scores as the criterion variable. Coefficients of determination (R2) were calculated to provide values for explained variance. Finally, a sensitivity analysis was performed to determine whether significant fluctuations of the results occur if the conditions are somewhat changed, allowing the robustness of
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 8
7
6
5
4
3
2
1
1
2
3
Right Cumulative prevalence mandible
8
7
6
5
4
4
5
6
5
6
7
8
Left 3
2
1
1
2
3
4
7
8
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% score 0
score 1
score 2
score 3
score 4
score 5
2 Distribution and cumulative prevalence of tooth wear scores in dental arch (both sexes, all age groups) (1, central incisor; 2, lateral incisor; 3, canine tooth; 4, first premolar; 5, second premolar; 6, first molar; 7, second molar; 8, third molar).
Schierz et al
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Issue
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Mean occlusal tooth wear (severity) and proportion of teeth with dentin exposure (prevalence) stratified by age, sex, tooth group in dental arch, and jaw (severity / prevalence)
Table I.
Jaw Sex and Age Group
Maxilla
Mandible
All
Anterior
Posterior
All
Anterior
Posterior
All
Anterior
Posterior
All
2.9/23.4
3.2/40.9
2.6/8.7
2.7/17.3
3.0/31.4
2.5/6.1
3.0/28.9
3.3/49.0
2.7/11.2
20-29
2.6/12.9
2.9/25.8
2.4/3.8
2.5/9.3
2.7/19.0
2.3/2.5
2.7/16.5
3.1/32.4
2.4/5.1
30-39
2.8/19.6
3.1/36.3
2.6/5.8
2.7/14.5
3.0/27.9
2.5/4.2
3.0/24.4
3.2/43.7
2.7/7.3
40-49
3.0/24.8
3.3/43.0
2.7/8.4
2.8/19.1
3.2/34.8
2.5/5.2
3.1/29.7
3.4/49.9
2.8/11.5
50-59
3.3/40.4
3.5/60.2
3.0/20.5
3.1/31.1
3.3/47.6
2.8/16.0
3.4/47.8
3.7/69.6
3.1/24.5
Men
3.0/26.7
3.3/46.4
2.7/10.8
2.9/20.8
3.2/38.5
2.6/7.3
3.1/32.0
3.5/53.2
2.8/14.3
20-29
2.6/13.0
3.0/26.0
2.4/4.3
2.6/10.6
2.9/22.2
2.3/3.0
2.7/15.4
3.1/29.8
2.4/5.7
30-39
2.9/21.2
3.3/39.9
2.6/6.4
2.8/15.9
3.1/30.9
2.5/5.3
3.0/26.4
3.4/48.2
2.7/7.7
40-49
3.1/28.9
3.4/50.1
2.8/11.4
3.0/23.6
3.3/44.5
2.6/5.9
3.2/33.5
3.5/54.9
2.9/16.3
50-59
3.3/44.0
3.6/65.7
3.0/23.2
3.2/35.0
3.5/55.2
2.9/17.3
3.4/51.1
3.7/73.6
3.1/28.5
Women
2.8/20.7
3.1/36.6
2.6/6.9
2.7/14.5
2.9/25.9
2.5/5.1
3.0/26.3
3.2/45.7
2.7/8.6
20-29
2.6/12.9
2.9/25.7
2.4/3.4
2.5/8.5
2.7/17.2
2.3/2.2
2.7/17.2
3.0/34.0
2.4/4.7
30-39
2.8/18.3
3.0/33.6
2.6/5.2
2.7/13.3
2.9/25.6
2.9/3.4
2.5/22.9
3.1/40.4
2.7/7.1
40-49
2.9/20.7
3.2/36.5
2.6/5.4
2.7/14.7
3.0/25.6
3.0/4.5
2.5/26.0
3.3/45.4
2.7/6.4
50-59
3.2/36.8
3.4/55.1
2.9/17.8
3.0/27.2
3.2/40.5
3.3/14.8
2.5/44.5
3.6/65.8
3.0/20.6
the results to be tested. Therefore, the tooth wear scores 1 and 2 were merged, eliminating the qualitative component of the score. All analyses were performed with a statistical software package (Stata, v12; StataCorp LP) and with the probability of a Type I error set at the .05 level.
RESULTS The distribution and cumulative prevalence of tooth wear scores for single teeth are presented in Figure 2. The mean tooth wear score across all age groups, both sexes, and all teeth was 2.9 (standard deviation, 0.8), ranging from 2.6 in young women (20 to 29 years) to 3.3 in older men (50 to 59 years). The minimal individual mean score of 1.6 was found in a 35-year-old woman, whereas the most severe individual mean score of 4.4 was present in a 55-year-old man. Posterior teeth had lower mean attrition scores than anterior teeth. The prevalence of teeth with exposed dentin (a score of 4 or 5) across all age groups, both sexes, and all teeth
was 23.4%, ranging from 12.9% in young women (20 to 29 years) to 44.0% in older men (50 to 59 years). In 16.3% of the participants (n¼132; 65% women), no tooth with exposed dentin was present, whereas 2.0% of the participants (n¼16; 44% women) had exposed dentin in all assessable teeth. More details are presented in Table I. For example, a prevalence of 25.7% in the anterior teeth of women between 20 and 29 years of age indicates that a fully dentate woman in this age range has on average 3 anterior teeth with exposed dentin. Participants’ ages correlated with mean tooth wear scores (r¼0.51; Fig. 3). The tooth wear level increased on average approximately 0.22 wear units in each decade of life (regression model; P
Clinical Implications Whether tooth wear is in the physiologic range or not, the age and location of the tooth should be taken into account. The differentiation for sex is of limited value. Over a lifetime, teeth are exposed to intrinsic factors (such as gastroesophageal reflux disease) and extrinsic factors (such as habits, environment, or occupation) that cause attrition, abrasion, abfraction, or erosion.1-5 As differentiating among these factors is challenging and tooth-surface loss in general is multifactorial, the umbrella term “tooth wear” has been established. a
Whereas severe tooth wear can substantially affect survival in some species, its consequences for humans are less serious. Nonetheless, premature tooth wear often causes hypersensitivity, esthetic (and therefore psychosocial) impairment, and, in severe situations, loss of tooth vitality or the need for extraction.6 Differentiating physiologic (normal) from pathologic tooth wear is
therefore essential. Knowing whether tooth wear is of a physiologic or pathologic nature might aid in early intervention, thereby preventing severe tooth wear or even tooth loss and minimizing the need for comprehensive restorations. In the near future, more elderly people will be living than ever before,7 meaning that preventing and treating severe tooth wear will be an ever-increasing problem.
Assistant Professor, Department of Prosthodontics and Materials Science, University of Leipzig. Research Associate, Department of Prosthodontics and Materials Science, University of Leipzig. c Professor and Chair, Department of Pediatric Dentistry, University of Leipzig. d Assistant Professor, Department of Prosthetic Dentistry, University Medical Center Hamburg-Eppendorf; Research Fellow, Department of Diagnostic and Biological Sciences, University of Minnesota. b
Schierz et al
2
Volume Data for tooth wear in the general population and related factors have not been extensively reported, and the comparability of study results is limited because of the variety of assessment indices.8-12 For most of the applied indices, no data for the general population or for validity or reliability are available. Although some data have been collected on skeletal material from nonindustrialized cultures (both ancient and contemporary),13-15 most researchers have quantified different scales measuring the prevalence of tooth wear in present-day industrialized populations.16-22 Most studies have reported that factors such as age and sex affect the severity of tooth wear.10,16,20,23 More challenging is to obtain information on the relevance of the location of teeth. However, the extent of the effect of all these factors is unclear, and no information is available as to which has the most influence. The purpose of this study was to investigate the effect of age, sex, and location of the teeth on the extent of occlusal tooth wear. A secondary purpose was to provide information on the distribution of tooth wear and the prevalence of dentin exposure in the general adult population of Germany.16,17,24-34
applied. Impressions were made with irreversible hydrocolloid, and hard stone plaster casts were fabricated. The casts were arranged in pairs and stored in a dry environment. The study protocol was approved by the Institutional Review Board of the Martin Luther University Halle-Wittenberg and conducted in accordance with the Helsinki Declaration. All participants gave signed informed consent. One trained examiner (R.H.) assessed occlusal tooth wear by using casts of both jaws of the participants. All occlusal surfaces and incisal edges were examined without magnification under a table lamp, and the tooth wear of each tooth was rated separately with the ordinal 6-point scale (range, 0-5) of the modified severity index described by John et al (Fig. 1).36 Teeth that were missing, involved with partial fixed dental prostheses, replaced, or otherwise not assessable (for example, where more than 75% of the occlusal surface had been replaced by restorations or air bubbles) were excluded from the rating (16% for the 20- to 29-year-old age group, 27% for the 30- to 39-yearold age group, 36% for the 40- to
MATERIAL AND METHODS This study was a secondary analysis of an epidemiologic study conducted in the metropolitan area of Leipzig and Halle (Saale), Germany.35 The original purpose of this survey was to determine the prevalence of symptoms of temporomandibular disorders in the general population. The residency registration offices of both Halle and Leipzig supplied the addresses of 1000 residents between the ages of 20 and 59 years. Of these individuals, 836 (mean age, 40.4 years; standard deviation, 11.7 years; 56% women) agreed to be examined and questioned by dentists at the universities of Halle (N¼388 participants) and Leipzig (N¼448 participants). Age was the only inclusion criterion (20 to 59 years); no exclusion criteria were
The Journal of Prosthetic Dentistry
-
Issue
-
49-year-old age group, and 46% for the 50- to 59-year-old age group). In total, 32% of the teeth were not assessable for tooth wear. Third molars were excluded from the analyses. A total of 17 302 teeth were assessable and included in the analyses (women, n¼9604 teeth; men, n¼7698 teeth; maxilla, n¼8289 teeth; mandible, n¼9013 teeth; anterior teeth, n¼8484; and posterior teeth, n¼8818). Analyses were performed on 2 levels: on a participant level (with mean scores of all assessable teeth in both jaws [casts] to compensate for the reduced number of assessable teeth associated with increasing age) and on a tooth level (that is, with the scores of each single tooth in the analysis and the participant as the grouping variable). Additionally, the single teeth were merged to anterior teeth (incisors and canines) and posterior teeth (premolars and molars without third molar teeth). The tooth wear scale was considered quasi-interval, based on the expected equal differences between 2 adjacent ordinal scores.36 Test-retest reliability (intraexaminer reliability) of the single examiner (R.H.) 2
2 1
1
3
3 4
4 5 5
1 Modified assessment of occlusal tooth wear severity according to Pullinger and Seligman.42 Scale used: 0, no visible tooth wear; 1, minimal wear of cusps or incisal tips, enamel only; 2, facets parallel to normal planes of contour, enamel only; 3, noticeable flattening of cusp or incisal edges, enamel only; 4, total loss of contour and dentin exposure when identifiable, dentin exposure up to half of former crown of tooth; and 5, total loss of contour, dentin exposure over half of former crown of tooth. John et al added the fifth score.36
Schierz et al
-
2014
3 examiner provided similar results. Reliability and validity analyses were performed at the individual tooth level. Initially, a descriptive analysis of the data was performed. The prevalence of the tooth wear scores is presented in a graph. The mean wear scores and prevalence values of exposed dentin (proportions of teeth with a score of 4 or 5) are provided for all participants and for the subgroups according to age, sex, location of teeth (anterior or posterior), and jaw. Because age is a continuous variable, subgroups were defined in decades (20 to 29 years, 30 to 39 years, 40 to 49 years, and 50 to 59 years). Prevalence data were limited to assessable teeth, and all data excluded third molars. For the correlation analysis of participants’ tooth wear and age, the mean wear scores and the individual age were used to calculate the Pearson
Cumulative prevalence maxilla
was assessed at the start of the study by using repeated ratings of 60 arbitrarily chosen casts and considered sufficient (weighted kappa, 0.62).37 The validity of the ratings of the single examiner (R.H.) was assessed based on consistency with the median wear scores of 6 additional examiners, which were considered the external standard (convergent validity). Casts of 14 arbitrarily chosen participants were rated by all examiners. The additional examiners were not trained but were provided with a visual examination guide showing the severity index in detail. By using the median wear scores of the additional examiners, a weighted kappa of 0.54 was calculated, reflecting a sufficient convergent validity. The combined mean wear scores of the additional examiners were slightly higher (3.7) than the mean wear scores of the study examiner (3.4), meaning the study
product-moment correlation coefficient. Univariate linear random-intercept models were calculated with age, sex, jaw, and tooth group as predictor variables. The tooth wear scores of each single tooth was the criterion variable in these models, and the participant was used as grouping variable to account for the intercorrelation of the scores within a participant.38 A multivariate linear random-intercept model was developed by using a backward elimination technique, starting with all candidate variables mentioned previously as predictor variables and tooth wear scores as the criterion variable. Coefficients of determination (R2) were calculated to provide values for explained variance. Finally, a sensitivity analysis was performed to determine whether significant fluctuations of the results occur if the conditions are somewhat changed, allowing the robustness of
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 8
7
6
5
4
3
2
1
1
2
3
Right Cumulative prevalence mandible
8
7
6
5
4
4
5
6
5
6
7
8
Left 3
2
1
1
2
3
4
7
8
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% score 0
score 1
score 2
score 3
score 4
score 5
2 Distribution and cumulative prevalence of tooth wear scores in dental arch (both sexes, all age groups) (1, central incisor; 2, lateral incisor; 3, canine tooth; 4, first premolar; 5, second premolar; 6, first molar; 7, second molar; 8, third molar).
Schierz et al
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Volume
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Issue
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Mean occlusal tooth wear (severity) and proportion of teeth with dentin exposure (prevalence) stratified by age, sex, tooth group in dental arch, and jaw (severity / prevalence)
Table I.
Jaw Sex and Age Group
Maxilla
Mandible
All
Anterior
Posterior
All
Anterior
Posterior
All
Anterior
Posterior
All
2.9/23.4
3.2/40.9
2.6/8.7
2.7/17.3
3.0/31.4
2.5/6.1
3.0/28.9
3.3/49.0
2.7/11.2
20-29
2.6/12.9
2.9/25.8
2.4/3.8
2.5/9.3
2.7/19.0
2.3/2.5
2.7/16.5
3.1/32.4
2.4/5.1
30-39
2.8/19.6
3.1/36.3
2.6/5.8
2.7/14.5
3.0/27.9
2.5/4.2
3.0/24.4
3.2/43.7
2.7/7.3
40-49
3.0/24.8
3.3/43.0
2.7/8.4
2.8/19.1
3.2/34.8
2.5/5.2
3.1/29.7
3.4/49.9
2.8/11.5
50-59
3.3/40.4
3.5/60.2
3.0/20.5
3.1/31.1
3.3/47.6
2.8/16.0
3.4/47.8
3.7/69.6
3.1/24.5
Men
3.0/26.7
3.3/46.4
2.7/10.8
2.9/20.8
3.2/38.5
2.6/7.3
3.1/32.0
3.5/53.2
2.8/14.3
20-29
2.6/13.0
3.0/26.0
2.4/4.3
2.6/10.6
2.9/22.2
2.3/3.0
2.7/15.4
3.1/29.8
2.4/5.7
30-39
2.9/21.2
3.3/39.9
2.6/6.4
2.8/15.9
3.1/30.9
2.5/5.3
3.0/26.4
3.4/48.2
2.7/7.7
40-49
3.1/28.9
3.4/50.1
2.8/11.4
3.0/23.6
3.3/44.5
2.6/5.9
3.2/33.5
3.5/54.9
2.9/16.3
50-59
3.3/44.0
3.6/65.7
3.0/23.2
3.2/35.0
3.5/55.2
2.9/17.3
3.4/51.1
3.7/73.6
3.1/28.5
Women
2.8/20.7
3.1/36.6
2.6/6.9
2.7/14.5
2.9/25.9
2.5/5.1
3.0/26.3
3.2/45.7
2.7/8.6
20-29
2.6/12.9
2.9/25.7
2.4/3.4
2.5/8.5
2.7/17.2
2.3/2.2
2.7/17.2
3.0/34.0
2.4/4.7
30-39
2.8/18.3
3.0/33.6
2.6/5.2
2.7/13.3
2.9/25.6
2.9/3.4
2.5/22.9
3.1/40.4
2.7/7.1
40-49
2.9/20.7
3.2/36.5
2.6/5.4
2.7/14.7
3.0/25.6
3.0/4.5
2.5/26.0
3.3/45.4
2.7/6.4
50-59
3.2/36.8
3.4/55.1
2.9/17.8
3.0/27.2
3.2/40.5
3.3/14.8
2.5/44.5
3.6/65.8
3.0/20.6
the results to be tested. Therefore, the tooth wear scores 1 and 2 were merged, eliminating the qualitative component of the score. All analyses were performed with a statistical software package (Stata, v12; StataCorp LP) and with the probability of a Type I error set at the .05 level.
RESULTS The distribution and cumulative prevalence of tooth wear scores for single teeth are presented in Figure 2. The mean tooth wear score across all age groups, both sexes, and all teeth was 2.9 (standard deviation, 0.8), ranging from 2.6 in young women (20 to 29 years) to 3.3 in older men (50 to 59 years). The minimal individual mean score of 1.6 was found in a 35-year-old woman, whereas the most severe individual mean score of 4.4 was present in a 55-year-old man. Posterior teeth had lower mean attrition scores than anterior teeth. The prevalence of teeth with exposed dentin (a score of 4 or 5) across all age groups, both sexes, and all teeth
was 23.4%, ranging from 12.9% in young women (20 to 29 years) to 44.0% in older men (50 to 59 years). In 16.3% of the participants (n¼132; 65% women), no tooth with exposed dentin was present, whereas 2.0% of the participants (n¼16; 44% women) had exposed dentin in all assessable teeth. More details are presented in Table I. For example, a prevalence of 25.7% in the anterior teeth of women between 20 and 29 years of age indicates that a fully dentate woman in this age range has on average 3 anterior teeth with exposed dentin. Participants’ ages correlated with mean tooth wear scores (r¼0.51; Fig. 3). The tooth wear level increased on average approximately 0.22 wear units in each decade of life (regression model; P
