Journal of

Oral Rehabilitation

Journal of Oral Rehabilitation 2014 41; 101--107

Occlusal tooth wear in Chinese adults with shortened dental arches Q. ZHANG*, D. J. WITTER†, E. M. BRONKHORST‡, D. W. BARTLETT§ & N. H. J. C R E U G E R S † *Department of Prosthetic Dentistry and Implantology, Key laboratory of Oral Medicine, School and Hospital of Stomatology, Guangzhou Medical University, Guangzhou City, China, †Department of Oral Function and Prosthetic Dentistry, College of Dental Science, Radboud University Nijmegen Medical Centre, Nijmegen, ‡Department of Preventive and Restorative Dentistry, College of Dental Science, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands and §Department of Prosthodontics, Kings’ College Dental Institute, Guys’ Tower London, London, UK

SUMMARY To assess associations between occlusal tooth wear and shortened dental arches (SDA) in Chinese 40 years and older subjects. From a sample of 1462 urban and rural adults, those presenting with SDA (n = 150) were compared with a control group of 65 randomly selected subjects with complete dentitions (CDA). Occlusal wear was assessed using a modified Smith and Knight index – the occlusal tooth wear index (OWTI) – and analysed using multivariate (logistic) regression. There was no significant effect from SDA on severe occlusal wear (OTWI score 3 or 4: OR = 2016; 95% CI = 0960–4231; P = 0064). Higher age was associated with severe occlusal wear (P values ≤0007) and with higher mean OTWI scores; urban had less often severe occlusal wear than rural residents (OR = 0519; P = 0008). Higher mean OTWI scores were associated with rural residents, except for anterior teeth. Females had lower mean

Introduction Data from a recent systematic review suggest that tooth wear is a common clinical phenomenon with cumulative effects during ageing (1). Some authors even state that human dentitions are ‘designed’ for tooth wear as compensation mechanisms that accompany the tooth wear eventually lead to an effectively adapted ‘occlusion’ (2, 3). Anthropological research has also documented a persistent feature of extensive tooth wear from prehistoric time until today. How© 2013 John Wiley & Sons Ltd

OTWI score for anterior teeth (effect = 0153; P = 0030). Premolars in SDA had higher mean OTWI scores compared with those in CDA (effect = +0213; P = 0006). In SDA, more posterior occluding pairs (POPs) were associated with lower mean OTWI sores for anterior teeth (effect: 0158; P = 0008) and higher scores for molars (effect: +0249, P = 0003). Subjects with SDA or CDA presented comparable occlusal wear, but premolars in SDA tend to have higher probability for having occlusal wear. Fewer numbers of POPs were associated with more wear in anterior teeth. KEYWORDS: occlusal tooth wear, dental occlusion, Chinese adults, shortened dental arch, epidemiologic study Accepted for publication 25 November 2013

ever, Kaifu (4) estimated a decrease has occurred in the severity of tooth wear since the beginning of the industrial revolution, when more refined and tender foods became available for larger parts of populations. Nevertheless, throughout the last decades, an increasing interest in tooth wear is noticeable in the dental literature. In contrast with the opinion of anthropologists and recent findings with respect to prevalence of tooth wear, contemporary tooth wear is considered an increasing clinical problem in dentistry. Given the increasing number of people that retain a natural doi: 10.1111/joor.12119

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Q . Z H A N G et al. dentition into old age, the requirement to manage tooth wear is also increasing (5). Tooth wear may result from tooth-to-tooth contacts (attrition), by mechanical forces from foreign elements (abrasion), or by chemical dissolution from acidic diets (erosion), occurring together or separately. As occlusion is considered a key factor in the management of reduced dentitions and wear affects mainly the occlusal or incisal surfaces of the teeth, a mutual relationship between reduced dentitions and wear might be expected. Evidence of such a relationship might have clinical consequences for the management of (specific types of) reduced dentitions, for example, splints for protection of the occlusal surfaces of the teeth, or teeth replacements to compensate for the presence of fewer teeth. Today’s knowledge regarding this relationship includes reported correlations between attrition and anterior spatial relationships, and between wear and number of teeth (6). Chewing tests on subjects with shortened dental arches (SDA) showed comparable bite forces; however, more chewing cycles and higher chewing frequencies were needed to pulverise test food to similar particle sizes than subjects with complete dentitions (7). These findings suggest that in SDA fewer teeth may be at an increased risk of developing higher levels of wear. The aim of this cross-sectional study was to assess the relationship of occlusal tooth wear and SDA in Chinese adults of 40 years and older. It was hypothesised that subjects with SDA present more occlusal tooth wear than subjects with complete dental arches (primary outcome). Furthermore, it was hypothesised that SDA with fewer posterior occluding pairs (POPs) present with more occlusal tooth wear (secondary outcome).

Materials and methods The study was conducted in the Qingdao area, located at the east coast of Shandong Province, situated in Eastern China. Shandong is one of the largest provinces in China in terms of population and economy. Qingdao City has approximately 3 million inhabitants and has direct jurisdiction over the surrounding rural territory in Shandong Province, including 5 countylevel cities (approximately 200 000–400 000 residents each) and the counties surrounding these cities. Each rural county comprises 40–80 small rural villages. The

total area of Qingdao (urban and rural) is approximately 10 000 km2 with a coastline of 730 km, and approximately 8 million inhabitants. Sampling method From a cross-sectional survey, a sample of 1462 subjects aged 40 years and older, dentate in upper and lower jaw were selected from administrative lists of residents of communities or villages provided by local authorities and lists of employees of factories. Inclusion aimed at proportional distribution according to age, gender and place of residence (urban or rural). Data were collected in 2009 and 2010. The urban sample was constructed on the basis of accessibility and comprised 11 communities and 4 factories in Qingdao City. Administrators of the communities informed and invited their residents for participation in the study. The examination venue usually was a neighbourhood community office or a social centre for elderly. A total of 570 community inhabitants and 193 employees from factories were included on the basis of voluntary participation. A truly representative sampling was not feasible, so the pathfinder sampling method was adopted incorporating sufficient examination sites to cover relevant groups of the population intended (8). For the rural sample, one county (Zhugou) was considered representative for north-east Shandong Province and was chosen on the basis of accessibility and cooperation from local authorities. This county (a predominantly agrarian area with a low population density and a total population of approximately 36 000) is located approximately 120 km north-west from Qingdao City and comprises 56 villages. Subjects from these villages were randomly selected using administrative name lists. A detailed description of the sampling method can be found in Zhang et al. (9). For the present analysis, a subsample was created consisting of all subjects in the survey sample that was identified with having a shortened dental arch [SDA group; n = 150 (which is 10% of the total sample)]. Next, a control group was created by random selection from all subjects in the survey sample that had a complete dental arch (CDA group; n = 65; 13% of all subjects with complete dental arches). A shortened dental arch was defined as a reduced dentition with complete anterior regions and absent POPs starting from posteriorly. Subjects with SDA with fixed © 2013 John Wiley & Sons Ltd

OCCLUSAL WEAR IN SHORTENED DENTAL ARCHES dental prostheses that restored tooth bounded arch interruptions were also included. Complete dental arches were defined as complete dentitions with or without third molars. Of subjects with SDA, 43% (n = 64) reported that the most recent extraction was less than 5 years before examination; 24% (n = 36) between 5 and 10 years, 11% (n = 17) between 10 and 15 years, and 21% (n = 32) more than 15 years before examination. One subject was unaware of the time of the most recent extraction. The study was carried out in compliance with the Helsinki Declaration and was approved by the ethics committee of the medical school at Qingdao University, Qingdao, China. Clinical examination After obtaining verbal consent from the participants, a calibrated and trained examiner conducted a clinical examination using good lighting and followed the procedures and diagnostic criteria recommended by the World Health Organization (10). In this study, of all variables recorded, only the presence of teeth (including 3rd molars), tooth type, number and location of natural POPs, and occlusal tooth wear were considered. For these variables, interobserver agreements between the principal investigator and experienced researchers in the field were good to excellent (unweight overall kappa’s ≥ 063). Occlusal tooth wear was assessed after drying the teeth using the index described by Smith and Knight (11) [occlusal tooth wear index (OTWI): score 0 = no loss of occlusal enamel surface characteristics; score 1 = loss of occlusal enamel surface characteristics; score 2 = loss of occlusal enamel, exposing dentine for less than 1 ⁄ 3 of the surface/incisal loss of enamel and minimal dentine exposure; score 3 = loss of occlusal enamel, exposing dentine for more than 1 ⁄ 3 of the surface/ incisal loss of enamel and substantial loss of dentine; score 4 = complete loss of occlusal/incisal enamel, pulp exposure or exposure of secondary dentine]. Missing teeth and teeth with heavily restored occlusal surfaces were not recorded. Retained roots were considered non-functional teeth and therefore considered as missing teeth. Subjects with SDA presented with different number of teeth and POPs, ranging from extremely shortened without any premolar and molar POP to slightly shortened with only second molar © 2013 John Wiley & Sons Ltd

POPs absent. Variations in numbers of POPs reflect different arch lengths. Only few people reported signs of parafunction; they were not excluded. Data analyses Differences in occlusal tooth wear between the SDA and CDA groups were expressed as differences in severe tooth wear (OTWI score 3 or 4) and in mean tooth wear scores. Differences in severe tooth wear were analysed in multivariate logistic regression models. Firstly, the influence of SDA on at least one tooth with OTWI score 3 or 4 was analysed: ‘OTWI score 3 or 4’ score was the dependent variable; ‘shortened dental arch’ (yes/no) and the background variables ‘age group’ (4 age groups: 40–49, 50–59, 60–69, and ≥70 years), ‘gender’ and ‘place of residence’ (urban/ rural) were the independent variables. For shortened dental arch subjects, the variables ‘number of teeth’ and ‘number of POPs’ were analysed in a second analysis. In this model, OTWI score 3 or 4 was the dependent variable and, ‘number of POPS’ and the background variables ‘number of teeth’ ‘age group’, ‘gender’ and ‘place of residence’ were the independent variables. Mean OTWI scores for different tooth types and for the whole dentition were analysed in regression models. In the first model, mean OTWI score was the dependent variable; ‘shortened dental arch’ (yes/no) and the background variables ‘age group’, ‘gender’ and ‘place of residence’ were the independent variables. For subjects with SDA, the effects of ‘number of POPs’ were further analysed: in this model, again mean OTWI score was the dependent variable with ‘number of POPs’, and the background variables ‘number of teeth’, ‘age group’, ‘gender’ and ‘place of residence’ as the independent variables. IBM SPSS Statistics (IBM, Armonk, New York, USA), version 20 was used for statistical analyses.

Results Table 1 shows the gender distribution of both groups with 487% and 60% female and a mean age of 582 and 551 years old in the SDA and CDA groups, respectively. The mean number of teeth in the SDA group was approximately four teeth less than in the CDA group. Shortened dental arches subjects had on average 55 POPs, and CDA subjects had 87. Of all subjects in the SDA group, 28% had maximum OTWI

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Q . Z H A N G et al. Table 1. Characteristics of the shortened dental arch (SDA) and complete dental arch (CDA) groups

Number of subjects Percentage females Percentage urban residents Mean age (s.d.) Mean number (s.d.) of teeth including third molars Mean number (s.d.) of teeth excluding third molars Mean number (s.d.) of posterior occluding pairs

SDA

CDA

150 487 540 582 (102) 259 (28)

65 600 554 551 (111) 299 (15)

239 (29)

277 (07)

55 (20)

87 (07)

score 3 versus 19% in the CDA group; for maximum OTWI score 4, these percentages were, respectively, 10 versus 1 (Table 2). Mean overall OTWI score for the SDA group was 149 (s.d. = 047); for the CDA group, this was 127 (s.d. = 046). The multivariate logistic regression analyses demonstrated (Table 3) that the chance for having OTWI Table 2. Number (%) of subjects according to maximum occlusal tooth wear index (OTWI) score per subject and mean OTWI scores for shortened dental arches (SDA) and complete dental arches (CDA) OWTI score

SDA (n = 150)

CDA (n = 65)

Maximum 0 1 2 3 4

1 10 81 42 16

0 (0) 6 (9) 46 (71) 12 (19) 1 (1)

(1) (7) (54) (28) (10)

Table 3. Odds Ratios (OR) for having occlusal tooth wear index (OTWI) score 3 or 4, P values and 95% confidence intervals (CI) for the variables shortened dental arch, age group, gender and place of residence (n = 215)

Shortened dental arch* Age 50–59 years† Age 60–69 years† Age ≥70 years† Female‡ Urban§ *Complete dental arch. † Age 40–49 years. ‡ Male. § Rural.

OR

P

95% CI

2016 4018 8254 11895 0705 0519

0064 0007

Occlusal tooth wear in Chinese adults with shortened dental arches.

To assess associations between occlusal tooth wear and shortened dental arches (SDA) in Chinese 40 years and older subjects. From a sample of 1462 urb...
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