Objective:

The aim of this study was to assess the effects of twin block functional appliance three dimensionally on mandibular third molars angulation and eruption space.

Methods:

This retrospective study included cone beam computer tomography (CBCTs) of 34 Class II females (11.84 ± 0.94 years) who were divided into 2 groups. The first group received a standard twin block appliance (intervention group), while the other was considered as a control. CBCT images were obtained for all patients before the start of the intervention (T0) and after the active phase (9.4 ± 1.33 months) in the intervention group and at the beginning (T0) and after the observation period (T1) in the control group (8.12 ± 2.72 months). Measurements for the retromolar space were performed on the axial views, while those for molar angulation were performed on sagittal views as well as CBCT panoramic reformatted images.

Results:

Both twin block and control groups showed non-significant changes in the angular measurements (sagittal L8/MP° and panoramic L8/MP°) denoting lack of change in the angulation of the third molars in relation to the mandibular plane after treatment. On the other hand, retromolar spaces showed a statistically significant increase (P ≤ .05) in both groups. The change was much significant for the twin block group, measuring 1.95 mm and 1.56 mm on the right and left sides, respectively, as compared to the control group which revealed less than 1 mm increase in the retromolar space on both the right and left sides.

Conclusions:

In spite of their positive impact on the retromolar space, twin block bite jumping appliances have a non-significant influence on the angulation of the developing mandibular third molars.

Keywords: Cone beam CT, functional orthodontic appliance, third molar, three-dimensional imaging