| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
RESEARCH REPORT |
1 Department of Prosthodontics, School of Dentistry, Martin Luther University Halle-Wittenberg, Große Steinstr. 19, 06097 Halle/Saale, Germany;
2 Department of Preventive Dentistry and Pediatric Dentistry, School of Dentistry, Martin Luther University Halle-Wittenberg, Harz 42-44, 06108 Halle/Saale, Germany;
3 Department of Oral Medicine and Department of Dental Public Health Sciences, School of Dentistry, University of Washington, Health Sciences Bldg., Box 356370, Seattle, WA 98195; and
4 Department of Dental Public Health Sciences, School of Dentistry, University of Washington, Health Sciences Bldg., Box 357475, University of Washington, Seattle, WA 98195;
*corresponding author, 4747 30th Ave. NE, #A102,Seattle, WA 98105, USA; mtjohn{at}u.washington.edu
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
|---|
KEY WORDS: temporomandibular disorders • dental occlusion • malocclusion • overbite • overjet
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Extreme overbite and overjet values such as open bite (Pullinger and Seligman, 2000), deep bite (Lieberman et al., 1985), mandibular prognathism (Tanne et al., 1993), and large overjet (Pullinger et al., 1993) have all shown an association with TMD, which is a necessary but not a sufficient criterion for a causal relationship. These findings indicate that there may be a ‘U-shaped’ relationship between overbite/overjet and TMD. This type of relationship implies that large negative as well as positive values for overbite/overjet may be related to TMD in comparison with a middle range, where the most common values for both variables are located. In addition, most dentists believe that occlusion is important in causing TMD (LeResche et al., 1993). On the other hand, most reviews of this topic concluded that malocclusion is not a cause of TMD (Tallents et al., 1991; Vanderas, 1993).
However, previous studies have suffered from methodological problems, such as small sample size, inadequate control for potentially confounding variables, inadequate case definitions, and a lack of demonstrated reliability in measurement of variables (Drangsholt and LeResche, 1999). Further limitations include problems with the selection of controls in case-control studies (Wacholder et al., 1992). A population-based study of TMD risk factors has the advantage that cases are not selected according to patient referral. Controls come from the same population as the cases, which reduces the possibility of selection bias (e.g., controls selected from a clinic population may be more likely to have had orthodontic treatment than cases, and, hence, more ideal overbite or overjet relationships).
Because of these methodological concerns in previous studies, the true association between overbite or overjet and TMD may be quite different than previously observed.
The aim of this cross-sectional study was to investigate the association between overbite or overjet and self-report of TMD symptoms by means of a population-based approach and improved analytical methodology in a large pool of subjects.
|
MATERIALS & METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Outcome, Exposure, and Confounding Variables
The primary outcome was self-report of TMD pain in the last month. It was defined as pain in the face, jaw, temple, in front of the ear, or in the ear according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) (Dworkin and LeResche, 1992). Secondary outcomes were self-report of joint noises (Have you ever had joint noises? Answer options: none, clicking, crepitus) and limitations of mouth-opening (Have you ever had difficulties in opening the mouth wide or jaw locking?), as defined by the Helkimo Index (Helkimo, 1974). The exposure variables "overbite" and "overjet" were defined and measured according to the RDC/TMD and the manual of the DMS III (Micheelis and Reich, 1999). Five dentists took part in both studies and were trained by one of the authors (M.T.J.). Reliability was assessed for overjet and overbite according to the intraclass correlation coefficient (ICC), which showed excellent inter-observer reliability (ICC = 0.95 for overjet, 0.92 for overbite in children/adolescents; 0.94 for overjet, 0.89 for overbite in adults/seniors) (Micheelis and Reich, 1999). Age and gender were considered as potential confounding variables, as well as self-report of orthodontic treatment (Have you ever had an orthodontic appliance?) or the presence of malocclusion in the clinical examination [malocclusion in the sagittal (Angle classification), vertical (open/deep bite), and median plane (cross-bite)] according to Korkhaus (1932), which were recorded only in children/adolescents.
Statistical Analysis
To describe the relationship between self-reported TMD and overbite/overjet, we computed the frequencies of overbite/overjet separately for subjects with and without TMD pain, joint noises, or limited mouth-opening. Chi-squared tests with seven degrees of freedom assessed statistical significance. Logistic regression analysis was used for the computation of odds ratios for each TMD outcome separately for overbite and overjet, adjusted for gender and age (10 to 18, 35 to 44, or 65 to 74 yrs). In the logistic regression analyses, overbite and overjet were grouped into five categories (
-1 mm, 0 to 1 mm, 2 to 3 mm, 4 to 5 mm, 
6 mm) to reduce the number of odds ratios being estimated and to increase the statistical power. Additional analyses were performed which included both overbite and overjet in the same regression model, and analyses based on only children/adolescents, also adjusted for report of orthodontic treatment or the presence of malocclusion. Hosmer-Lemeshow tests were used for the assessment of overall model goodness-of-fit (Hosmer and Lemeshow, 2000).
To ensure that the descriptive summaries and odds ratio estimates were not unduly influenced by the cut-offs chosen for overbite/overjet, we repeated similar analyses controlling for age and gender, using fractional polynomial regression (Royston and Altman, 1994), which avoids specification of cut-off values, since overbite/overjet are treated as continuous measures. Because this method estimates both the number of polynomial terms and the power of the terms that gives the best fitting relationship between an outcome variable and a continuous exposure variable, the method can detect both linear and (complex) non-linear relationships. A component-plus-residual plot is used to illustrate the best-fitting relationship between overbite/overjet and TMD pain by means of a two-polynomial-term model. The y-axis of these plots describes the magnitude of the TMD risk (= partial linear predictor) from overbite/overjet. These graphs can be interpreted as follows: If there is an increased risk from any overbite or overjet value, then the partial linear predictor will be a greater value compared with the other values. If there is a decreased risk, then the predictor will be less than the other values. Any shape of the overbite or overjet-TMD risk relationship would indicate a risk, except for a straight line.
Statistical analyses were carried out with the statistical package STATA (Release 7.0 StataCorp. 1999, Stata Statistical Software, College Station, TX, USA), with a probability level of 0.05 considered statistically significant.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Open bite was rare (38 out of 2976 subjects: 1.3%). More than twice as many subjects were prognathic (n = 84, 2.8%). Subjects with a large overjet ( 6 mm) were more prevalent (n = 249, 8.4 %), as were subjects with a large deep bite ( 6 mm; n = 398, 13.4%) (Tables 1 and 2
). Overbite and overjet were positively correlated (r = 0.52).
|
|
). Logistic regression analysis, which controlled for age and gender, indicated no association between exposure (overbite or overjet) and TMD outcome (pain, joint noises, or limited opening) (all p-values 0.16). The odds ratios ranged from 0.66 to 1.42, except for an open bite or mandibular prognathism and TMD pain (odds ratio = 0.31 and 0.36, respectively). None of the odds ratios was statistically significant (Table 3).
|
0.20).
The multivariable fractional polynomial regression analyses also showed no association between self-reported TMD pain and overbite or overjet. Searching through 44 possible statistical models for each overbite or overjet analysis, we found that the best-fitting curve was not better compared with a statistical model without overbite or overjet (p-value = 0.72 and 0.75, respectively). For overbite, the best function with the two polynomial terms overbite-1 and overbite3 (adjusted for age and gender) showed no increased or decreased risk from -5 to 15 mm of overbite (Fig. 1, Panel A). The narrow 95% confidence interval around the best-fitted curve indicated that this result was unlikely due to chance alone. Because of the rareness of overbites -5 mm (only four subjects), there is some uncertainty of the relationship between TMD pain and overbite for values of overbite between –8 and –5 mm, as indicated by the wide confidence interval. Overjet presented the same pattern (Fig. 1, Panel B). In children/adolescents, further adjustment (above age and gender) for report of orthodontic treatment or for the presence of malocclusion did not indicate an association between overbite/overjet and TMD pain self-report (all p-values 0.80; data not shown). Overbite/overjet relationships with self-report of joint noises or limited mouth-opening were also not statistically significant in fractional polynomial regression analyses adjusted for age and gender (all p-values 0.67; Fig. 1, Panels C-F).
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Measurement error might possibly mask true differences that may exist between cases and controls (Armstrong et al., 1992). However, we found sufficient reliability of overbite/overjet measurement in this study and for TMD pain report asked in this fashion (Wahlund et al., 1998). Therefore, measurement error is not a likely explanation for our findings.
The statistical methodology, such as fractional polynomial regression, which has not been previously used for this research question, should detect linear trends, biologically plausible U-shaped curves, or even more complex relationships between an exposure variable and outcome. It is especially suitable for investigating the potential risk of a continuous exposure variable (Hosmer and Lemeshow, 2000). Such "power models" where multiple power terms for the exposure are chosen have several advantages as compared with an analysis based on exposure categories. These statistical models include the use of information about the differences within exposure categories and provide a smooth picture of the overall relationship between exposure and outcome. These two features are especially useful for the analysis of the relationship between overbite/overjet and TMD, because it is expected that the TMD risk from these variables should vary smoothly over the full variable range. Previously used cut-off points for overbite/overjet (Pullinger et al., 1993; Kahn et al., 1998), where the TMD risk is expected to change substantially, are probably not an accurate reflection of any biologically plausible gradually increasing or decreasing relationship between exposure and outcome.
Our study has several limitations. Although it was a cross-sectional study of the German adult population, it is possible that the people who did not participate in the study were different enough from the participants that our study findings would be altered. However, the findings about the relationship of both variables to self-reported TMD would be distorted only if people with specific levels of overbite or overjet and with and without TMD were less likely to participate, indicating a differential non-response, and this is unlikely. We used self-report of TMD because TMD may be viewed as a self-limiting chronic pain illness not necessarily associated with progressive physical deterioration (Dworkin, 1994), and symptom report is the major focus, as is the case for other chronic pain conditions (Crombie and Davies, 1999). In addition, most clinical signs, such as muscle and joint palpation, are influenced by the subject's perception and therefore are not entirely objective. However, it is possible that if the outcome measure was instead ‘TMD’, by meeting specific diagnostic criteria including examination findings, a different relationship could be found among overbite, overjet, and this disorder. On the other hand, our pain outcome—self-reported pain of the face, jaw, temple, in front of the ear, or in the ear in the past month—is a necessary criterion for TMD pain diagnoses in frequently used TMD classification systems, such as the Research Diagnostic Criteria for Temporomandibular Disorders (Dworkin and LeResche, 1992).
We grouped all self-reported TMD pain or joint noise conditions into one category. Therefore, it is also possible that relationships may exist between overbite/overjet and specific TMD subgroups.
Our confidence in the risk for very extreme negative values of overbite/overjet is limited, due to the small number of subjects in this range. However, based on a population perspective, the public health importance would also be limited due to the rareness of these values.
Description of basic epidemiological characteristics like gender, age, and racial distributions can provide important clues about disease determinants (Hennekens and Buring, 1987). TMD pain is more common in females and peaks in the third and fourth decades of life (List and Dworkin, 1996). Such a profile is not present for overbite/overjet, which is similar for both genders (Brunelle et al., 1996) and is stable over life (Carter and McNamara, 1998). Racial differences in TMD pain (Lipton et al., 1993) do not have a counterpart in overbite or overjet patterns (Brunelle et al., 1996). Therefore, the observed lack of an association between overbite/overjet and TMD is supported by several epidemiological characteristics.
It is difficult to compare our study with other work in this area, since other studies used many different measures of association that are difficult to summarize. Among the reported positive associations with TMD, large overjet is mentioned most often in case-control studies (Pullinger et al., 1993; Kahn et al., 1998; Pullinger and Seligman, 2000) or cohort studies (Henrikson et al., 2000). However, these studies had small sample sizes, or the effects were not consistent across different TMD measures. In addition, the magnitude of these relationships was small, and some authors emphasized that their role should not be overstated (Pullinger and Seligman, 2000).
Currently, there is consensus that the cause of TMD is multifactorial, but centrally acting factors, like depression and somatization, have more evidence to support them as risk factors than peripheral (local) factors (Drangsholt and LeResche, 1999). Nevertheless, because local factors occur with notable prevalence and may be accessible to prevention, they could still have a major public health impact. Although extreme measures of overbite/overjet have been related to changes in masticatory muscle (Lowe, 1980) and TMJ function (Anders et al., 2000), chronic factors like overbite/overjet, which do not exceed the adaptive capacity of the stomatognathic system, may not necessarily translate into TMD as perceived by the patient.
Our findings support the idea that wide ranges of overbite/overjet are compatible with a normal function of masticatory muscles and the TMJ as perceived by the individual. From that viewpoint, attempting to prevent TMD by creating ‘more normal’ values of overbite or overjet with dental treatment is not supported by this study.
|
ACKNOWLEDGMENTS |
|---|
The authors thank the Institute of German Dentists (IDZ, Cologne, Germany) and the director, Dr. W. Micheelis, for allowing us to analyze the findings of the DMS III study about overbite/overjet and TMD self-report symptoms.
Received September 17, 2001; Last revision January 10, 2002; Accepted January 14, 2002
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Armstrong BK, White E, Saracci R (1992). Principles of exposure measurement in epidemiology. Oxford: Oxford University Press.
Brunelle JA, Bhat M, Lipton JA (1996). Prevalence and distribution of selected occlusal characteristics in the US population, 1988-1991. J Dent Res 75:706–713.
Carter GA, McNamara JA Jr (1998). Longitudinal dental arch changes in adults. Am J Orthod Dentofac Orthop 114:88–99.[Medline]
Crombie IK, Davies HTO (1999). Requirements for epidemiological studies. In: Epidemiology of pain. Crombie IK, Croft PR, Linton SJ, LeResche L, Von Korff M, editors. Seattle: IASP Press, pp. 17-18.
Drangsholt M, LeResche L (1999). Temporomandibular disorder pain. In: Epidemiology of pain. Crombie IK, Croft PR, Linton SJ, LeResche L, Von Korff M, editors. Seattle: IASP Press, pp. 203-233.
Dworkin SF (1994). Behavioral, emotional, and social aspects of orofacial pain. In: Biological & psychological aspects of orofacial pain. Stohler CS, Carlson DS, editors. Ann Arbor: Center for Human Growth & Development, The University of Michigan. pp. 93-112.
Dworkin SF, LeResche L (1992). Research diagnostic criteria for temporomandibular disorders: review, criteria, examinations and specifications, critique. J Craniomandib Disord 6:301–355.[Medline]
Helkimo M (1974). Studies on function and dysfunction of the masticatory system. II. Index for anamnestic and clinical dysfunction and occlusal state. Swed Dent J 67:101–121.
Hennekens CH, Buring JE (1987). Epidemiology in medicine. Boston/Toronto: Little, Brown and Company.
Henrikson T, Nilner M, Kurol J (2000). Signs of temporomandibular disorders in girls receiving orthodontic treatment. A prospective and longitudinal comparison with untreated Class II malocclusions and normal occlusion subjects. Eur J Orthod 22:271–281.
Hosmer DW, Lemeshow S (2000). Applied logistic regression. 2nd ed. New York: John Wiley & Sons, Inc.
Kahn J, Tallents RH, Katzberg RW, Moss ME, Murphy WC (1998). Association between dental occlusal variables and intraarticular temporomandibular joint disorders: horizontal and vertical overlap. J Prosthet Dent 79:658–662.[Medline]
Korkhaus G (1932). Prophylaxe und Frühbehandlung der Zahnstellungs- und Kieferanomalien. In: Moderne orthodontische Therapie. Korkhaus G, editor. Leipzig & Berlin: Hermann Meusser Verlag, pp. 387-432.
LeResche L (1997). Epidemiology of temporomandibular disorders: implications for the investigation of etiologic factors. Crit Rev Oral Biol Med 8:291–305.
LeResche L, Truelove EL, Dworkin SF (1993). Temporomandibular disorders: a survey of dentists' knowledge and beliefs. J Am Dent Assoc 124:90–106.[Abstract]
Lieberman MA, Gazit E, Fuchs C, Lilos P (1985). Mandibular dysfunction in 10-18 year old school children as related to morphological malocclusion. J Oral Rehabil 12:209–214.[Medline]
Lipton JA, Ship JA, Larach-Robinson D (1993). Estimated prevalence and distribution of reported orofacial pain in the United States. J Am Dent Assoc 124:115–121.[Medline]
List T, Dworkin SF (1996). Comparing TMD diagnoses and clinical findings at Swedish and US TMD centers using research diagnostic criteria for temporomandibular disorders. J Orofac Pain 10:240–253.[Medline]
Lowe AA (1980). Correlations between orofacial muscle activity and craniofacial morphology in a sample of control and anterior open-bite subjects. Am J Orthod 78:89–98.[Medline]
Micheelis W, Reich E (1999). Dritte Deutsche Mundgesundheitsstudie (DMS III) [Third German Oral Health Study]. Cologne: Deutscher Ärzte-Verlag.
Pullinger AG, Seligman DA (2000). Quantification and validation of predictive values of occlusal variables in temporomandibular disorders using a multifactorial analysis. J Prosthet Dent 83:66–75.[Medline]
Pullinger AG, Seligman DA, Gornbein JA (1993). A multiple logistic regression analysis of the risk and relative odds of temporomandibular disorders as a function of common occlusal features. J Dent Res 72:968–979.
Reichart PA (2000). Oral mucosal lesions in a representative cross-sectional study of aging Germans. Community Dent Oral Epidemiol 28:390–398.[Medline]
Royston P, Altman DP (1994). Regression using fractional polynomials of continuous covariates: parsimonious parametric modelling (with discussion). Appl Statist 43:429–467.
Tallents RH, Catania J, Sommers E (1991). Temporomandibular joint findings in pediatric populations and young adults: a critical review. Angle Orthod 61:7–16.[Medline]
Tanne K, Tanaka E, Sakuda M (1993). Association between malocclusion and temporomandibular disorders in orthodontic patients before treatment. J Orofac Pain 7:156–162.[Medline]
Vanderas AP (1993). Relationship between malocclusion and craniomandibular dysfunction in children and adolescents: a review. Pediatr Dent 15:317–322.[Medline]
Wacholder S, McLaughlin JK, Silverman DT, Mandel JS (1992). Selection of controls in case-control studies. I. Principles. Am J Epidemiol 135:1019–1028.
Wahlund K, List T, Dworkin SF (1998). Temporomandibular disorders in children and adolescents: reliability of a questionnaire, clinical examination, and diagnosis. J Orofac Pain 12:42–51.[Medline]
This article has been cited by other articles:
|
|
 |
|
  L. Sonnesen and P. Svensson Temporomandibular disorders and psychological status in adult patients with a deep bite Eur J Orthod, August 5, 2008; (2008) cjn044v1. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Farella, A. Michelotti, G. Iodice, S. Milani, and R. Martina Unilateral Posterior Crossbite is Not Associated with TMJ Clicking in Young Adolescents J. Dent. Res., February 1, 2007; 86(2): 137 - 141. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Relevant research from non-orthodontic journals J. Orthod., December 1, 2002; 29(4): 321 - 323. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| IADR Journals | Advances in Dental Research ® |
| Journal of Dental Research ® | Critical Reviews (1990-2004) |
