OBJECTIVES: This study aimed to assess the alterations in condylar positioning in adult skeletal Class I patients with unilateral posterior crossbite following microimplant-assisted rapid palatal expansion (MARPE) treatment. METHODS: This retrospective study involving 30 participants (10 males, 20 females) with an average age 22.9 ± 4.2 years, ranged from 18.1 to 30.9 years, who were treated with a customized microimplant-supported rapid palatal expander. Pre-expansion and post- comprehensive orthodontic treatment CBCT images (20-26 ±2.1months) were analyzed to assess the condylar changes before and after treatment. We measured the temporomandibular joint (TMJ) in the three dimension in terms of: (1) The position and angle of the mandibular condyles
(2) How centralized the condyles were in their particular mandibular fossae
and (3) The volume of the TMJ and the joint spaces. To evaluate the differences between the T1 and T2 samples, we used the paired t-test and the Wilcoxon signed rank test. RESULTS: Before treatment, minor differences were noted in the anterior joint space (AJS), superior joint space (SJS), and anteroposterior condylar joint position (APCJP) between the crossbite and non-crossbite sides, though these differences were not statistically significant. Post-treatment, the condyles on both sides assumed a more posterior position, yet significant asymmetry in the AJS persisted (P <
.05). The crossbite-side condyle also showed a tendency to rotate toward the non-crossbite side in the anteroposterior direction. While MARPE affected specific aspects of condylar positioning, achieving complete alignment remained challenging. CONCLUSION: This study provides insightful observations on the enduring impacts of MARPE on TMJ spaces and position in adult patients suffering from a unilateral posterior crossbite.