SHAPE-COORDINATE ANALYSIS OF SKELETAL CHANGES INDUCED BY RAPID MAXILLARY EXPANSION AND FACIAL MASK THERAPY

The aim of this study was to evaluate maxillary and mandibular shape/s ize changes by means of Bookstein's shape-coordinate and tensor analys is in children with Class III malocclusions treated with rapid maxilla ry expansion and a facial mask in order to define optimum timing of in tervention for this type of therapy. The treated group (46 subjects, 2 6 females and 20 males) was divided into two subgroups according to th e stage of dentitional development. The early-treated group consisted of 23 subjects treated in the early mixed dentition (mean age at Time 1, 6 years 9 months +/- 7 months); the late-treated group included 23 subjects treated in the late mixed dentition (mean age at Time 1, 10 y ears 3 months +/- 1 year). The mean treatment period was about 11 mont hs. The control group (32 subjects with untreated Class III malocclusi on, 18 females and 14 males) also was divided into two subgroups (an e arly control group, 17 subjects in the early mixed dentition, and a la te control group, 15 subjects in the late mixed dentition). Maxillary triangles (point T the most superior point of the anterior wall of sel la turcica, point FMN, the fronto-maxillary-nasal suture, and point A) and mandibular triangles (point Condylion, point Gonion, and point Po gonion) were digitized on cephalograms in both groups at Time 1 and Ti me 2. Combined facial mask and rapid maxillary expansion therapy produ ced a significant enhancement of the forward growth of the maxilla and significantly more upward and forward direction of growth of the mand ibular condyle (leading to smaller increments in mandibular total leng th, Co-Pg) in the early-treated group when compared with controls and to the late-treated group. Both maxillary size and mandibular size wer e significantly affected by treatment in the early mixed dentition. Th e results of this study indicate that orthopedic treatment of Class II I malocclusion induces favorable size and shape changes both in the ma xilla and mandible, and that this combined treatment approach is more effective in the early mixed dentition than in the late mixed dentitio n.