Determination of the Effects of Removable Orthodontic Appliances Used in Orthodontic Treatment on the Axis Angles of Molars

BACKGROUND Tooth morphology and crown angulations are among the anatomical factors that can influence orthodontic outcomes. This study aimed to compare the changes in molar base angle (MBA), the angle of molar teeth relative to the jaw axis, in individuals using different removable functional orthodontic appliances. MATERIAL AND METHODS A total of 40 patients were included. Images taken from each patient were collected from the orthodontic patient archive and categorized into 4 groups, as follows: group A, maxillary expansion appliance; group B, twin-block/monoblock appliances; group C, face mask appliances; and group D, chin cup appliances, with 10 samples in each group. This retrospective study evaluated pre-treatment and post-treatment panoramic radiographs of individuals who met the criteria for removable functional orthodontic appliance therapy. RESULTS Our findings revealed a statistically significant increase in MBA values in the maxillary teeth across all 4 groups (P<0.05). In contrast, MBA values in the mandibular teeth showed a significant decrease in groups A and B, while groups C and D showed a significant increase (P<0.05). CONCLUSIONS In groups A and B, a decrease in mandibular MBA and an increase in maxillary MBA were observed. This effect appeared to be associated with the specific characteristics of the appliances. In groups C and D, an increase in MBA was observed, leading to slight angular changes of the teeth in the mesial direction. Such angular inclinations can adversely affect orthodontic treatment outcomes. Therefore, angular changes in the teeth during treatment with these appliances should be considered when choosing an appliance.