Twin-Block Patients Showed More Mandibular Advancement and Condylar Growth on CBCT

Edited by Dentaltown staff

Class II patients treated with a Twin-block functional appliance followed by fixed appliances showed more forward movement of the chin and more condylar growth per year than matched patients treated with Class II elastics, according to a case-control study published online Sept. 11 in the American Journal of Orthodontics and Dentofacial Orthopedics.

Investigators analyzed cone beam computed tomography records of 22 Twin-block patients at three points: before treatment, at completion of the functional appliance phase, and after fixed appliance treatment. Twenty-two matched patients treated with Class II elastics, scanned before and after treatment, served as controls. Images were oriented and registered on the anterior cranial base and the mandibular corpus.

After adjustment for sex, skeletal maturation, vertical facial pattern, age at the first scan, and total treatment time, the Twin-block group averaged 1.39 mm per year more anterior displacement of pogonion and 1.79 mm per year more at B-point than controls. Anterior displacement of the anterior fossa was 1.38 mm per year greater, and superior condylar growth was 1.35 mm per year greater.

The timing was concentrated. Within the Twin-block group, most posterior condylar growth occurred during the functional appliance phase, with minimal additional growth during the fixed appliance phase that followed.

Dentoalveolar effects accompanied the skeletal changes. Mandibular incisors extruded 2.99 mm per year more in the Twin-block group and mandibular molars 2.07 mm per year more than in the control group.

Sophie M. Isaksson, Paolo M. Cattaneo, Lucia S. Cevidanes, Paul M. Schneider, and Marie A. Cornelis conducted the study at the Melbourne Dental School at the University of Melbourne, with a coauthor at the University of North Carolina Adams School of Dentistry. Outcomes were quantified with point-to-point measurements and compared using linear mixed-effects models.

The design was a matched case-control study rather than a randomized trial, with 22 patients per group, and the comparison group received Class II elastics rather than no treatment. The findings describe differences between two active treatment approaches, not the effect of functional appliance therapy against untreated growth.

Sources:
American Journal of Orthodontics and Dentofacial Orthopedics, “Three-dimensional changes in patients with Class II malocclusion treated with the Twin-block functional appliance: A case-control study,” published online Sept. 11, 2026: doi.org/10.1016/j.ajodo.2026.06.024
PubMed record, PMID 42726031: pubmed.ncbi.nlm.nih.gov/42726031