EVALUATION OF SKELETAL AND DENTAL CHANGES CONCURRENT TO USE Of HAAS AND HYRAX RME IN VERTICAL AND SAGITTAL DIRECTION

Aim: The main goal of this research was to evaluate the sagittal and vertical effects of Hyrax (tooth born) and Haas (tooth-tissue born) rapid palatal expanders on dentoskeletal structures of patients with maxillary constriction characterized by bilateral posterior cross bite. Materials and methods: A nonrondomized clinical trail of ۲۲ patients ۱۲ to ۱۴ years old (mean age ۱۲.۵ years) with maxillary constriction, who were divided into two groups, was undertaken. Group-I consisted of ۱۱ patients who received treatment by Hyrax type rapid palatal expander (RPE). Group- II composed ۰۱۱۱ patients who received treatment by Haas RPE. Two lateral cephalograms were taken, one before and the other after the palatal cusps of the upper posterior teeth reached the buccal cusps of lower posteriors consequent to expansion. The activation period lasted from ۱۲-۱۶ days with a mean value of ۱۳.۵ days. On each lateral cephalogram ۸ linear and ۱۰ angular parameters were measured, recorded and compared to a nearest of ۰.۵ mm and ۰.۵ degree respectively. Statistical analyses were performed using Kolomogrovsmirnov and paired t-test. A student t-test was used for comparison of two group. Results: In both groups significant increases in lower anterior facial height were observed. The value (ANS-ME) was increased ۱.۳۰mm in Hyrax (P=۰.۰۰۹) and ۱.۸۰mm in Haas group (P=۰.۰۳۲). Statistically neither of the appliances showed a significant effects on sagital position of the maxilla. The mandible was rotated downward and backwards. SNB angle decreases ۰.۶۵ and ۰.۴۳ degrees in Hyrax and Haas group respectively. ANB angle was increased by means of ۰.۶۰ degree (p= ۰.۰۳۰) in Hyrax and ۰.۵۳ degree (p=۰.۰۸) in Haas group. Conclussion: The maxilla kept its position sagitally, pre to post treatments, but showed inferior displacement in both groups. The mandible displayed a tendency to rotate downward and backward in both groups. Upper anteriors tipped palatally. (IJO ۲۰۰۶; ۱: ۶۱ - ۶۵) 

کلیدواژه ها:

Rapid Maxillary Expansion ، Haas ، Hyrax ، dentofacial structure