Effectiveness of twin blocks and extraoral maxillary splint (Thurow) appliances for the correction of Class II relationships.

Aim: The aim of this study was to evaluate the skeletal and dentoalveolar changes due to treatment with twin block and Thurow appliances in patients with Class II occlusions.

Method: The sample consisted of 19 randomly selected patients in each group, as well as 20 individuals in the control group. All patients were treated during the prepubertal growth spurt for 12 months. Lateral cephalograms were analyzed at the beginning of active treatment and 12 months later. All data were tested with the ANOVA and Bonferroni tests.

Results and conclusion: These tests showed that the twin block promotes a significant increase (P<.001) in the total length of the mandible, as well as an increase in anterior facial height. In contrast, ANB and NAPog were reduced. In both treatment groups, the maxillary incisors retruded significantly (P<.001), although more so in the twin block group. In the Thurow appliance group, the mandibular incisors protruded significantly (P<.001). All other differences between the two treated groups were not significant.