Dentoskeletal effects of Class II malocclusion treatment with the Twin Block appliance in a Brazilian sample: A prospective study

OBJECTIVE: The aim of this study was to assess the dentoskeletal effects of Class II malocclusion treatment performed with the Twin Block appliance. METHODS: The experimental group comprised 20 individuals with initial mean age of 11.76 years and was treated for a period of 1.13 years. The control group comprised 25 individuals with initial mean age of 11.39 years and a follow-up period of 1.07 years. Lateral cephalograms were taken at treatment onset and completion to assess treatment outcomes. Intergroup comparison was performed by means of the chi-square and independent t tests. RESULTS: The Twin Block appliance did not show significant effects on the maxillary component. The mandibular component showed a statistically significant increase in the effective mandibular length (Co-Gn) and significant improvement in the maxillomandibular relationship. The maxillary and mandibular dentoalveolar components presented a significant inclination of anterior teeth in both arches. The maxillary incisors were lingually tipped and retruded, while the mandibular incisors were labially tipped and protruded. CONCLUSIONS: The Twin Block appliance has great effectiveness for correction of skeletal Class II malocclusion in individuals with growth potential. Most changes are of dentoalveolar nature with a large component of tooth inclination associated with a significant skeletal effect on the mandible.

研究目的：本研究旨在评估采用双块矫治器（Twin Block appliance）治疗安氏II类错颌畸形（Class II malocclusion）的牙颌骨骼效应。
研究方法：实验组纳入20名初始平均年龄为11.76岁的受试者，治疗周期为1.13年；对照组纳入25名初始平均年龄为11.39岁的受试者，随访周期为1.07年。于治疗起始与结束两个时间点拍摄头颅侧位片（lateral cephalograms）以评估治疗效果，组间比较采用卡方检验（chi-square test）与独立样本t检验（independent t test）完成。
研究结果：双块矫治器对上颌骨组分未产生显著影响。下颌骨组分的有效下颌长度（Co-Gn）呈现统计学意义上的显著增加，且上下颌骨间的颌骨关系得到显著改善。上下颌牙牙槽骨组分的前牙在两颌均出现显著倾斜：上颌切牙呈舌向倾斜且后移，而下颌切牙则呈唇向倾斜且前突。
研究结论：双块矫治器对于具备生长潜力的个体，在矫正骨性安氏II类错颌畸形方面具有良好疗效。绝大多数矫治改变为牙牙槽骨源性，伴随大量牙齿倾斜相关变化，且对下颌骨产生了显著的骨骼效应。