Prevalence of upper lip posture and incisor overjet

1,159 children (612 girls and 547 boys) aged 11-12 years were examined to determine the range and mean overjet values in four defined upper lip-maxillary central incisor relationships. No clinically significant differences were found on comparison of the data relative to each upper lip position. The findings suggest that upper lip posture is adaptive to the maxillary central incisor angulation and that the upper lip musculature is unlikely to influence the development of the incisor occlusion.