Does bite-jumping damage the TMJ? A prospective longitudinal clinical and MRI study of Herbst patients

The aim of this prospective longitudinal study of 62 consecutively treated Class II malocclusions was to determine whether bite-jumping causes temporo mandibular disorders (TMD). The function of the temporomandibular joint (TM J) was assessed anamnestically, clinically, and by means of magnetic resona nce images (MRIs) taken before (TI), after (T2), and 1 year after (T3) Herb st treatment. Average treatment time with the Herbst appliance was 7.2 mont hs. In all subjects, Herbst treatment resulted in a Class I or overcorrecte d Class I dental arch relationship. Thereafter, treatment was continued wit h a multibracket appliance. The condyle was positioned significantly forwar d during treatment but returned to its original position after removal of t he Herbst appliance. A temporary capsulitis of the inferior stratum of the posterior attachment was induced during treatment. Over the entire observat ion period from before treatment to 1 year after treatment, bite-jumping wi th the Herbst appliance: (1) did not result in any muscular TMD; (2) reduce d the prevalence of capsulitis and structural condylar bony changes; (3) di d not induce disc displacement in subjects with a physiologic pretreatment disc position; (4) resulted in a stable repositioning of the disc in subjec ts with a pretreatment partial disc displacement with reduction; and (5) co uld not recapture the disc in subjects with a pretreatment total disc displ acement with or without reduction. A pretreatment total disc displacement w ith or without reduction did not, however, seem to be a contraindication fo r Herbst treatment, In conclusion, bite-jumping using the Herbst appliance does not have a deleterious effect on TMJ function and does not induce TMD on a short-term basis.