Comparison of temporomandibular joint changes in Twin Block and Bionator appliance therapy: a magnetic resonance imaging study.

Background: The objective of the present study was to evaluate and compare temporomandibular joint changes especially disk-condyle-fossa relationship following functional treatment of skeletal class II division 1 malocclusion using Twin Block and Bionator appliances.

Methods: The total sample consisted of 30 subjects (13 males and 17 females) with class II division 1 malocclusion having mandibular retrognathism, in the age group of 9 to 14 years. Two treatment groups, i.e., Twin Block and Bionator groups, were formed which comprised ten subjects each, while a group of ten subjects served as the control group. The treatment effects were evaluated using magnetic resonance imaging (MRI). For the treatment groups, pretreatment MRI with wax construction bite was taken. For all subjects, MRI images with corrected sagittal T1 images were recorded in a maximal intercuspation position at pretreatment (R1) and in an unstrained retruded position at the end of a 6-month observation period (R2).

Results: At the end of 6 months of treatment, the condyles occupied a more anterior position in the fossa to its pretreatment position, while the disk moved more posteriorly in relation to the condyle. The control group showed no changes in the condyle and disk position over a period of 6 months.

Conclusions: Although the treatment group showed consistent forward positioning of the condyle and backward movement of the disk, long-term MRI findings in these groups will further clarify the adaptations between the condyle fossa and articular disk.