ARCH LENGTH CHANGES FROM 6 WEEKS TO 45 YEARS

The purpose of this study was to evaluate, on a longitudinal basis, ch anges in maxillary and mandibular arch length over a 45-year period. S ubjects were drawn from two pools of normal individuals. Twenty-eight male and 33 female infants were evaluated longitudinally at 6 weeks, 1 year, and 2 years (before the eruption of the deciduous dentition). F ifteen males and 15 females from the lowa Facial Growth Study were eva ulated at 3, 5, 8, 13, 26, and 45 years. Arch length measurements were obtained independently by two investigators. Intra-and interexaminer reliabilities were predetermined at 0.25 and 0.5 mm, respectively. The greatest incremental increases occurred during the first two years of life. Arch length continued to increase until 13 years in the maxilla ry arch, and until 8 in the mandibular. Then significant and consisten t decreases occurred in both arches mesial to the permanent first mola rs.