Correction of the transverse discrepancy-induced spontaneous mandibular protrusion in Class II Division 1 adolescent patients.

Background: A Class Il malocclusion is the most frequent sagittal skeletal disharmony presenting for orthodontic treatment. A transverse interarch discrepancy ITID) may be considered as a possible functional cause of a Class 11 relationship.

Objective: The purpose of the present study was to determine transverse interarch width dimensions before and after orthodontic therapy and their possible relationship with increased mandibular projection following treatment.

Methods: The sample included 40 adolescent patients who were divided into two groups, one possessing and one without a transverse discrepancy. Interarch width differences (including ICWD, IPWD, IMWD, IAWD) were measured before and after treatment, and Pogonion (Pog) to Nasion (NJ perpendicular was similarly measured in each group.

Results: The differences in arch and alveolar width dimensions between the two groups (including ICWD, IPWDI, IPWDII, IMWD, IAWD) before treatment were statistically significant (p < 0.05). A comparison of Pog to N perpendicular between the two groups showed that mandibular protrusion after treatment in the transverse discrepancy group was 2.6 ± 1.3 mm, while mandibular protrusion after treatment in the group without a transverse discrepancy was 0.6 ±0.3 mm. The statistical comparison showed that the differences were significant (p < 0.01).

Conclusion: A transverse interarch discrepancy may have a functional relationship with mandible retrusion. If a transverse discrepancy is corrected via orthodontic treatment, the mandible may spontaneously protrude.