Date of Award

5-2013

Document Type

Thesis

Degree Name

Master of Dental Science (MDS)

Program

Orthodontics

Research Advisor

Edward F. Harris, Ph.D.

Committee

Daniel Merwin, D.D.S., M.S. William Parris, D.D.S., M.S.

Keywords

CBCT, Class II, Functional, MARA, Orthodontic, TMJ

Abstract

Introduction: An ongoing debate exists in orthodontics about the amount of condylefossa remodeling and growth seen in Class II patients using functional appliance therapy. Some clinicians and researchers have found that that the use of functional appliances increases the amount of condylar growth and subsequent Class II skeletal correction; others believe that the mandible has a preset amount of growth and that conventional orthodontics will result in a similar amount of condylar growth to functional appliance therapy. Purpose: The aim of this study was to compare condylar remodeling in functional appliance treatment using the mandibular anterior repositioning appliance (MARA) to conventional fixed orthodontic therapy by measuring changes using Cone Beam Computed Tomography (CBCT).

Methods: This retrospective study was an analysis of cone beam computed tomography images taken on 65 subjects with Class II division 1 malocclusions at the beginning and end of their comprehensive orthodontic treatment. Thirty-three subjects (13 females, 20 males; average age 11.93 years) were treated with the MARA plus edgewise mechanics, and a sample of thirtyone subjects (18 females, 13 males; average age 12.37 years) were treated with full fixed conventional orthodontic appliances and class II intermaxillary elastics. The CBCT scans were evaluated using Dolphin3D©. Temporomandibular joint (TMJ) measurements were recorded in the sagittal, axial, and coronal axes, and lateral cephalograms were extracted to compare groups and evaluate treatment differences. A total of 98 variables were measured.

Results: Slightly more mandibular advancement was seen in the MARA group versus the conventional group. In looking at the TMJ dimensions, the joint spaces were relatively constant throughout treatment, but more resorption of the condylar head was observed in the MARA group versus conventional treatment. The condylar head angle decreased for both treatment groups, showing a forward remodeling. Lengthening of the condylar process was statistically greater in the MARA group than the conventional Edgewise treatment group, although both increased on average. The slope of the posterior border of the articular eminence became more acute in the MARA group and more obtuse in the conventional Edgewise group. Overall, there was a relative increase and forward advancement of the temporomandibular apparatus in both treatment groups.

Conclusions: Both treatment groups were successful in correcting the Class II malocclusion skeletally and dentally. However, the MARA group had slightly more mandibular advancement and condylar growth than the conventional treatment group. In both groups, the TMJ structures increased and came downward and forward partly due to treatment and, to some extent, growth in the adolescent subjects.

DOI

10.21007/etd.cghs.2013.0112

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