The Condyle–Fossa Relationship After Maxillary Expansion with Tooth-Borne and Tooth-Bone-Borne Appliances: A Retrospective Cone-Beam Computed Tomography Study at the End of Retention

Background/Objectives: Maxillary expansion changes the occlusion and may alter the position of the mandibular condyle. Most cone-beam computed tomography (CBCT) studies have assessed the joint shortly after tooth-borne expansion and in the sagittal plane only. This study evaluated the condyle–fossa relationship from before expansion to the end of passive retention in the sagittal and coronal planes. Methods: In this retrospective study, 33 adolescents aged 12–17 years (66 condyles) treated with a tooth-borne Hyrax appliance (n = 16) or a tooth-bone-borne microimplant-assisted rapid palatal expander (MARPE; n = 17) were analysed. CBCT scans obtained before expansion (T0) and at the end of retention (T1; mean T0–T1 interval 6.3 months) were used to measure five joint spaces, the Pullinger concentricity index, intermolar width, overjet and overbite. Changes were assessed with paired tests and equivalence testing (±0.5 mm). Results: No joint space changed significantly (largest mean change 0.25 mm), and nine of ten were equivalent to no change within ±0.5 mm. The Pullinger index did not change, although individual category changes were frequent. Intermolar width increased by 5.07 mm (p < 0.001). No difference between appliances was detected in exploratory, baseline-adjusted analyses. Conclusions: No systematic group-level change in the condyle–fossa relationship was detected at the end of retention; individual variability was considerable.