Alveolar Growth in Japanese Infants : A Comparison between Now and 40 Years ago.

To investigate differences in alveolar growth during the primary dentition period among different age groups, dental arch width, length, and height were measured in 93 dental arch plaster models obtained from 4-year-olds born between 1968 and 1974, 88 from 5-year-olds born between 1968 and 1974 (70s group), 61 from 4-year-olds born between 2007 and 2009, and 56 from 5-year-olds born between 2006 and 2008 (2000s group). A comparison was also performed to determine whether there was any difference in change between 4 and 5 years of age. The results showed age- and sex-dependent differences in growth patterns in primary dental arch width, length, and height. The amount of change was greater in the 2000s group than in the 70s group, suggesting that yearly growth between 4 and 5 years of age has increased over the last 40 years.