Cephalometric Evaluation of Skeletal and Dentoalveolar Changes Induced by Twin Block Appliance in Skeletal Class II Malocclusion

Abstract

Background: Skeletal Class II malocclusion is one of the most common orthodontic cases and is often associated with retrognathic mandible. Functional orthopedic appliances such as Twin Block, which are designed to aid the growth of the mandible and improve the dentofacial relationships, are popular among orthodontists. The changes to the mandible and dentofacial relationships can be evaluated using cephalometric analysis.

Objective: The purpose of this study was to assess the skeletal and dentoalveolar changes of Class II malocclusion patients after the use of the Twin Block appliance, with the use of cephalometric analysis.

Methodology: The study sample consisted of 100 children with Class II malocclusion, with a mean age of 12, and retrognathic mandible, utilizing the Twin Block appliance. Lateral cephalometric radiographs were taken prior to the use of the Twin Block (T1) and after the use of the Twin Block (T2). The following cephalometric measurements (i.e. SNA, SNB, ANB, mandibular length) were evaluated and the changes in dentoalveolar relationship and overbite and overjet were also measured. The skeletal changes and measurements of overbite, overjet, and dentoalveolar relationships were all done using paired-sample t-tests with the statistical significance set at p < 0.05.

Results: Significant skeletal and dentoalveolar changes occurred due to Twin Block therapy. The mean SNB angle increased and the mean ANB angle decreased. The mean SNB angle was 76.4° ± 2.8 pre-treatment and 79.1° ± 2.5 post-treatment (p < 0.001). The mean ANB angle was 6.2° ± 1.4 pre-treatment and 3.5° ± 1.2 post-treatment (p < 0.001). Mandibular length increased by 4.8 ± 1.6 mm. Statistically significant changes were noted with the following measurements: overjet, which reduced from 8.1 ± 1.9 mm to 3.2 ± 1.1 mm (p < 0.001); and overbite, which also reduced, from 5.1 ± 1.4 mm to 2.8 ± 0.9 mm (p < 0.001). An observed treatment effect for the maxillary incisors was retroclination, whereas proclination was noted for the mandibular incisors.

Conclusion: Twin Block appliance therapy addressed the skeletal Class II malocclusion by promoting growth of the mandible, improving the maxillomandibular relationship, and producing favorable dentoalveolar adaptations. Cephalometric evaluation confirmed significant reductions in overjet and overbite, supporting the effectiveness of Twin Block therapy during the growth phase.