Jutting the jaw forward in different stages of temporomandibular joint internal derangements: A multiple comparison study

Introduction: Oral jaw habits including jutting the jaw forward are directly or indirectly related with pathological changes in the temporomandibular joints. There is scarcity of studies about this relationship. Goals: Evaluate the frequency of jutting the jaw forward in a large sample of Craniomandibular disorders subjects with specific internal derangements of the TMJs. Methods: Retrospective investigation of clinical charts of 543 subjects previously examined in the last sixteen years. Clinical examination, self-report, palpation of joint and masticatory muscles, questionnaires, criteria for Craniomandibular disorders, bruxing behavior, and biomechanical tests were used to determine the type of temporomandibular internal derangements. Subjects were allocated to different clinical subgroups with unilateral capsulitis (n=27), bilateral capsulitis (n=73), unilateral retrodiskal pain (n=94), bilateral retrodiskal pain (n=68), unilateral disk-attachment pain (n=112), bilateral disk-attachment pain (n=84), unilateral arthralgia (n=35), bilateral arthralgia (n=17), unilateral osteoarthritis (n=19) and bilateral osteoarthritis (n=14). A simple questionnaire was used to determine the presence and type of jutting the jaw forward. Fisher ́s exact test, Kruskal-Wallis statistics, X-squared for independence and trends were utilized to analyze data. Results: We report data abou jutting the jaw forward only in subgroups with bilateral TMJs-IDs:The frequency of jutting the jaw forward was about 182/543=33,5% in the Craniomandibular Disorder subgroup as compared with the control one, 8/30=26,6%, but the difference was not statistically significant: (Fisher ́s exact test p=0,55). The frequencies of jutting the jaw forward were higher but non significant in most subgroups as compared with the control one: bilateral capsulitis 30/73=41,1% versus control subgroup 8/30=26,6% (Fisher ́s exact test p=0,18); bilateral retrodiskal pain 27/68=39,7% versus control subgroup 8/30=26,6% (Fisher ́s exact test p=0,25); bilateral disk attachment pain 37/84=44% versus control subgroup 8/30=26,6% (p=0,12). The frequency of jutting the jaw forward in subjects with bilateral arthralgia (10/17=58,8%) was higher as compared with the control subgroup (8/30=26,6%) and the difference was statistically significant: Fisher ́s exact test (p=0,05). A statistically significant difference in the frequency of jutting the jaw forward was observed only when the subgroup unilateral capsulitis (7/27=25,9%) was compared with the bilateral arthralgia subgroup (10/17=58,8%): Fisher ́s exact test (p=0,05). When the frequency of jutting the jaw forward in subjects with unilateral internal derangements (78/287=27,2%) was compared with the frequency in those with bilateral internal derangements (104/256=40,6%), the difference was statistically significant: Fisher ́s exact test (p<0,001). When tests for independence and trends for jutting the jaw forward in subgroups with different internal derangements types were evaluated, X-squared statistics demonstrated that the subgroups were independent (p<0,02) whereas X-squared for trends (p=0,09) showed that there was no a trend for higher frequency of jutting the jaw forward with the severity of bilateral internal derangements. Conclusion: The highest frequency of jutting the jaw forward was observed in bilateral arthralgia of the temporomandibular joint. CMDs subjects with internal derangements of the TMJ compared with the control group did not demonstrate a higher frequency of jutting the jaw forward. The frequency of jutting the jaw forward was higher in bilateral internal derangements of the TMJ. Because bilateral internal derangements of the Temporomndibular joint are associated with higher frequency of disk disorders, disk displacement is associated with higher frequency of jutting the jaw forward.