New posteroanterior cephalometric norms: a comparison with craniofacial measures of children treated with palatal expansion.

Abstract

The aim of the study was to evaluate posteroanterior (PA) cephalometric characteristics in a normal longitudinal database and compare these measurements with corresponding measures in a group of patients treated with rapid maxillary expansion. Posteroanterior cephalographs of 16 girls and 14 boys from the Bolton-Brush growth study, taken at ages 10 and 18 years, were used to track growth in children with normal occlusion. Pretreatment PA cephalograms of 24 patients who had palatal distraction around age 10 were compared with the 10-year-old normal patients. Digitized landmarks included right and left jugale (J, at intersection of maxillary tuberosity and zygomatic buttress) and antegonion (AG, at notch of antegonial protuberance). Mandibular width (AG-AG) was similar in boys and girls at age 10 but not 18, when the difference between gender groups was statistically significant (P < .05). Maxillary width (J-J) was greater in boys than girls at both ages. The increase in AG-AG (5.5 mm, boys; 3.9 mm, girls) was more than twice that of J-J (2.4 mm, boys; 1.2 mm, girls). Arch width (at first molar) was nearly stable with age, indicating compensatory occlusal adaptation to differential changes between maxillary and mandibular widths. At age 18, the distance between the centers of the orbits, a surrogate measure of cranial width, was almost equal to J-J in girls and significantly correlated with AG-AG in boys (r = .71, P < .002) and girls (r = .77, P < .0001). The majority of treated children had both skeletal and dentoalveolar widths narrower than control values. Linear regressions between J-J and AG-AG revealed almost parallel slopes for control and treated groups in both genders, but the treated group was at a lower level, which is consistent with smaller maxillary widths.