Author/Authors :
Souki, Bernardo Quiroga Department of Orthodontics - Pontifical Catholic University of Minas Gerais School of Dentistry - Bela Horizonte, Brazil , Cheib, Paula Loureiro Department of Orthodontics - Pontifical Catholic University of Minas Gerais School of Dentistry - Bela Horizonte, Brazil , Oliveira, Dauro Department of Orthodontics - Pontifical Catholic University of Minas Gerais School of Dentistry - Bela Horizonte, Brazil , Braga, Wagner Fernando Moyses Department of Orthodontics - Pontifical Catholic University of Minas Gerais School of Dentistry - Bela Horizonte, Brazil , Cevidanes, Lucia Helena Soares Deparment of Orthodontics and Pediatric Dentistry - University of Michigan School of Dentistry - Ann Arbor, USA , Franchi, Lorenzo Deparment of Orthodontics and Pediatric Dentistry - University of Michigan School of Dentistry - Ann Arbor, USA , Ruellas, Antonio Carlos de Oliveira Department of Orthodontics and Pediatric Dentistry - Federal University of Rio de Janeiro School of Dentistry - Rio de Janeiro, Brazil
Abstract :
To test the following two hypotheses regarding the consequences of Herbst appliance (HA) insertion: 1) a significant
clockwise mandibular rotation will occur and 2) the displacement of the condyles will follow the same magnitude of the changes of
overjet (OJ) and overbite (OB).
Methods: Virtual 3D surface models of 25 patients were generated from cone-beam computed tomographs taken before treatment
and immediately after HA insertion. Scans were registered on the cranial base and were analyzed using point-to-point measurements,
color-coded maps, and semitransparent overlays. Statistical tests included correlation and simple regression analysis.
Results: Pitch rotation, ranging from −2.2° to 2.2° (mean, 0.2°), was observed in clockwise and counterclockwise directions. Condylar
sagittal displacement presented a positive correlation with OJ changes. Each millimeter of OJ correction resulted in an anterior condylar
displacement of approximately 0.95 mm. Vertical condylar displacement correlated with OB changes and varied mostly between
2 mm and 4.5 mm.
Conclusion: Immediately after HA insertion, no significant clockwise mandibular rotation was observed. The condyles were displaced
anteriorly and inferiorly. Condylar anterior displacement and OJ correction presented a ratio close to 1:1. The vertical displacement of
the condyles did not follow the same magnitude of OB changes.
