The effects of clefting on crown-root length, eruption, height and weight in twins discordant for cleft of lip and/or palate.

Within-twin differences for crown-root length and eruption of the mandibular buccal teeth were examined for 14 DZ and 14 MZ like-sexed twins discordant for cleft of lip and/or palate. The differences were found to be greater between DZ twins than between MZ and seldom statistically significant. Relatively large variances associated with the differences are attributed to widely varying levels of postnatal care for this sample. The within-twin differences were also analyzed according to type of cleft. Cleft of lip only was found to have a lesser effect on root-crown length and percent eruption differenes than cleft or palate (or cleft of lip and palate) although again not a statistically significant difference. Height and weight were found to follow a similar pattern including large variances associated with the within-twin differences. It is therefore concluded that a dysmorphogenic effect of clefting on crown-root length, eruption, height and weight cannot be demonstrated in this sample because of large associated variances due in turn to varying levels of post-natal health care and multiple other aspects of the syndrome.