Date of Graduation

2015

Document Type

Thesis

Degree Type

MS

College

School of Dentistry

Department

Orthodontics

Committee Chair

Peter Ngan

Committee Co-Chair

Chris Martin

Committee Member

Timothy Tremont

Abstract

Objectives: Orthopedic functional appliances have been shown to be effective in correcting Class II malocclusions with mandibular deficiency. However, most of the studies reported in the literature could not substantiate the effect of the appliance on mandibular growth because the appliance was worn for a short time and most of the studies were short term. In addition, there is also report on the breakage of the appliance with the use of the banded Herbst design. The objective of this study was to investigate the skeletal and dental changes of patients treated with the reinforced banded Herbst appliance during Herbst treatment and after completion of fixed appliance treatment. The results of this research should provide additional information on mode of action and the length of treatment when using the Herbst appliance. Methods: Thirty patients with Class II division 1 malocclusion (mean age = 12.34 years) treated by one of the investigator (M.R.) with Herbst followed by fixed appliance were compared to a matched control sample obtained from the Bolton-Brush study. Cephalometric radiographs were taken before treatment (T1), at the completion of Herbst treatment (T2), and following the removal of all fixed appliances (T3). Data was analyzed using a combination of ANOVA and Tukey-Kramer Test. Results: Treatment with the Herbst appliance (T2-T1) for an average of 1.5 years after growth is subtracted (t2-t1) resulted in a backward movement of the maxilla by 1.2 mm. The mandible moved forward 1.3 mm. The maxillary molars moved backward 4 mm and the maxillary incisors moved backward 4 mm. The mandibular molars moved forward 3.5 mm and the lower incisors moved forward 3.2 mm. The vertical changes were the maxilla moved downward 1.2 mm. The upper molars intruded 1 mm. The lower molar intruded 1mm and the lower incisors intruded 1.1 mm. The overbite decreased by 3.3 mm. The angular changes were SNB increased 3.6°. The SNA and ANB decreased 1° and 4.5°. The occlusal plane increased by about 5°. The upper incisor retracted 5.5° and the lower incisor proclined 8.6°. The Wits decreased by 4.2. The change in overjet was -7.2 mm. The skeletal contribution was -2.5 mm and the dental contribution was -4.7 mm. The change in molar relationship was -7.5 mm. The skeletal contribution was -2.5 mm and the dental contribution was -5 mm. The maxilla, maxillary molars, and maxillary incisors moved backwards. The mandible, mandibular molars, and mandibular incisors moved forward. The total treatment effect of the Herbst appliance and phase II treatment (T3-T1) after growth is subtracted (t3-t1) resulted in a backward movement of the maxilla by .4 mm. The mandible moved forward .9 mm. The maxillary molars moved backward 2.3 mm and the maxillary incisors moved backward 1.5 mm. The mandibular molars moved forward 2.7 mm and the lower incisors moved forward 2.9 mm. The vertical changes were the maxilla moved downward 1.2 mm. The upper molars extruded .3 mm and the lower molar extruded .8 mm. The overbite decreased by 4.2 mm. The angular changes were SNB increased 2.6°. The SNA and ANB decreased .2° and 3.3°. The occlusal plane increased by about 1.2°. The upper incisor retracted 5° and the lower incisor proclined 4.5 °. The Wits decreased by 3.2. The change in overjet was -4.4 mm. The skeletal contribution was -1.3 mm and the dental contribution was -3.1 mm. The change in molar relationship was -5 mm. The skeletal contribution was -1.3 mm and the dental contribution was -3.7 mm. The maxilla, maxillary molars, and maxillary incisors moved backwards. The mandible, mandibular molars, and mandibular incisors moved forward. Conclusions: The Herbst appliance when used for an average of 1.5 years was effective in correcting class II dental and skeletal malocclusions. The Herbst appliance when used for a longer period of time seems to allow for more over correction and less relapse.

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