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

Abstract

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 x T3 (P = .317), T3 x T4 (P = .287), or T1 x T4 (P = .261). At T2, on average, the disc was positioned regressively. With the mouth open, no difference was observed between T1 x T3 (P = .223) or T1 x T4 (P = .082). We did observe a significant difference between T3 x T4 (P < .05). Significant changes in the disc form were found with the mouth closed between T1 x T2 (P < .001) and T2 x 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.

Figures

Figure 1

Case 9. Left (A) and right (B) temporomandibular joint magnetic resonance images (mouth closed). The disc is in its normal superior position at T1, T3, and T4, showing a retrusive tendency at T2. The disc form is biconcave.

Figure 2

Case # 9. Left (A) and right (B) temporomandibular joint magnetic resonance images (mouth open). The disc was interposed between the condyle and the articular eminence. The disc form is biconcave.