Changes in temporomandibular joint disc position and form following Herbst and fixed orthodontic treatment

Objective:To determine the changes in the position and form of the temporomandibular joint articular disc in adolescents with Class II division 1 malocclusion and mandibular retrognathism treated with the Herbst appliance (phase I) and fixed orthodontic appliance (phase II).Materials and Methods:Thirty-two consecutive adolescents went through phase I of treatment and 23 completed phase II. The temporomandibular joints were evaluated qualitatively by means of magnetic resonance images at the beginning of treatment (T1), during phase I (T2), at the end of phase I (T3), and at the end of phase II (T4).Results:Significant changes in disc position were not observed with the mouth closed between T1 × T3 (P  =  .317), T3 × T4 (P  =  .287), or T1 × T4 (P  =  .261). At T2, on average, the disc was positioned regressively. With the mouth open, no difference was observed between T1 × T3 (P  =  .223) or T1 × T4 (P  =  .082). We did observe a significant difference between T3 × T4 (P < .05). Significant changes in the disc form were found with the mouth closed between T1 × T2 (P < .001) and T2 × T3 (P < .001).Conclusions:At the end of the two-phase treatment, in general terms, the position and form of the initial articular discs were maintained; however, in some temporomandibular joints some seemingly adverse effects were observed at T4.