Comparison of Inter-Twin Concordance in Symptoms of Temporomandibular Disorders: A Preliminary Investigation in an Adolescent Twin Population

Abstract

There is controversy as to the genetic contribution to the pathogenesis of temporo-mandibular disorders (TMD). Several reports reveal a marked familial aggregation in the signs and symptoms of TMD, while others do not. Therefore, our goal was to investigate the hypothesis using a sophisticated research design, which was a well-known genetic survey inter-twin concordance assessment in the symptoms of TMD. This study is the first step to survey TMD symptoms of a twin group in junior and high schools as a preliminary trial. The 63 twins were asked to participate in this study in junior and senior high schools affiliated with the University of Tokyo, Japan, schools which kept ten twins in each grade for the purpose of several genetic survey programs. After excluding incomplete filling out of questionnaire sheets and data from male-female pairs, 43 monozygotic (MZ) (15.3+/-1.7 yrs, male/female = 17/26 pairs) and nine dyzygotic (DZ) (15.2+/-1.8 yrs, male/female = 6/3 pairs) twins were studied. Outcomes consisted of a prevalidated 14-item self-administered questionnaire, which assessed proband- and pair-wise concordance levels in the MZ and DZ twins. These results demonstrated that the MZ twins had a higher tendency of inter-twin concordance than DZ twins in terms of jaw pain in wide mouth opening (proband-wise concordance = 66.7% in MZ, 0% in DZ), difficulty in mouth opening (20% in MZ, 0% in DZ) and difficulty in mouth closing (50.0% in MZ, 33.3% in DZ), while there was no significant difference between the MZ and DZ concordance levels in other general health-related and behavior-related items, except toothache. However, the pair-wise concordance rates of jaw pain in wide mouth opening and difficulty in mouth opening in the MZ twins were not significantly higher compared to the DZ rate. Possibly, a genetic factor contributed to the pathogenesis of TMD in an adolescent population. The sample size needs to be increased, and there are plans to survey the next sample in the same schools.

Genetic Factors Account for Half of the Phenotypic Variance in Liability to Sleep-Related Bruxism in Young Adults: A Nationwide Finnish Twin Cohort Study

“…Still, only little evidence exists that TMD aggregate in families or has a strong genetic component (Smith et al, 2011). For example, Michalowicz et al (2000) found no evidence in heritability of TMJ signs or symptoms while Matsuka et al (2007) reported that genetic factors may affect TMD in an adolescent population, although their findings were not statistically significant. The observed substantial genetic components in liability to sleep-related bruxism compared to the rather minor genetic component of other disorders in the TMJ area gives important knowledge about the possible difference in the mechanism of these disorders.…”

Temporomandibular disorders and bruxism in childhood and adolescence: Review of the literature

“…Reared-together MZ twins were no more similar than reared-apart MZ twins, suggesting a negligible effect of the family environment on these outcomes. Matsuka et al [26] demonstrated that the MZ twins had a higher tendency of inter-twin concordance than DZ twins in terms of jaw pain in wide mouth opening, difficulty in mouth opening and difficulty in mouth closing, while there was no significant difference between the MZ and DZ concordance levels in other general health-related and behavior-related items, except toothache. Liljeström et al [27] observed no association between children's and mother's TMD signs, agreeing with others [25,28].…”

Clustering of symptoms associated with fibromyalgia in a Finnish Twin Cohort

“…A change in central pain modulation has been shown in both conditions, too. For temporomandibular disorder (TMD) the results for heritability are inconsistent (Matsuka et al, 2007;Michalowicz et al, 2000).…”