Comparison of dental arch measurements in the primary dentition between contemporary and historic samples

The purpose of this study was to investigate secular changes that may have occurred in dental arch dimensions by comparing a sample of contemporary No rth American white children (born between 1992 and 1995) in the primary den tition to those children found in an earlier study of North American white children (born between 1946 and 1948). The sample of contemporary children has been followed prospectively since birth and was assessed at 41/2 to 5 y ears of age. Data for the historic sample were obtained from 5-year-old chi ldren who were enrolled in the Iowa Growth Study. The 2 samples were simila r in terms of geographic location, racial and ethnic backgrounds, and socio economic status. To further enhance the comparison and to match the 2 group s, the 2 samples were restricted to white children with a normal overjet (< 4 mm) and normal anteroposterior molar relationship, no anterior open bite, and no crossbite. In addition, individuals were excluded if any permanent teeth were erupted. Measurements of maxillary and mandibular arch lengths a nd intercanine and intermolar arch widths were made, with measurements of o verjet and overbite. The results indicated that maxillary and mandibular ar ch lengths in both sexes were significantly shorter in the contemporary sam ple; ail arch widths were significantly smaller in contemporary boys, but n ot in girls. These findings suggest that average arch dimensions may be sma ller in contemporary children than in past generations. Further research is needed to determine whether smaller arch dimensions are associated with mo re crowding in the primary, mixed, and permanent dentitions.