Is a Shortened Dental Arch a Risk Factor for TMD?

Objectives: Reduced occlusal posterior support is generally considered a risk factor for temporomandibular disorders (TMD). The aim of this study was to investigate this factor in subjects with shortened dental arches (SDA) without molar support on the long-term. Methods: In a 9-year follow-up, 42 subjects with SDA (mean age 41.8 ± 10.0 yrs; 14 males and 28 females) were compared with 41 subjects with complete dental arches (CDA: mean age 38.5 ± 9.8 yrs; 20 males and 21 females) with respect to signs and symptoms related to TMD. At visits with 3-yrs intervals, objective signs (palpated clicking/crepiting and maximal mouth opening) and subjective symptoms (pain, noises/clicking and restricted mobility of the mandible) were measured on ordinal scales, varying from no signs/symptoms to heavy expression. Average scores of symptoms/signs over the four observations were calculated. Changes over time were determined as the mean of the four slopes of the 3-year regression lines. The SDA and CDA groups were compared by T-tests on average scores and on mean slopes. Pearson correlation coefficients were calculated for symptoms and signs within a subject. Results: At each observation, the percentage of subjects without any symptom varied from 65 to 79% in the SDA group and from 70 to 75% in the CDA group. Average scores varied between .07±.26 (restricted mobility) and .48±.72 (palpated clicking/crepiting) and the differences between the groups were not significant (p>.05). Mean slopes also did not differ between groups (p>.05). Within subjects, symptoms fluctuated, but similar patterns were observed for both groups. Correlations between symptoms and signs were weak except between reported noises and palpated clicking/crepiting (r=.62, p<.001) and between reported restricted mobility and measured maximal mouth opening (r=.43, p<.001). Conclusion: It is concluded that a shortened dental arch is not a risk factor for TMD.