An investigation of the association between overjet size, lip coverage, and traumatic injury to maxillary incisors.

This study investigated the association between overjet size and lip coverage when assessing the likelihood of traumatic injury to maxillary incisors. Eleven-hundred-and-thirty-seven 11- and 12-year-olds were examined in school for traumatic injury to their maxillary incisors. The size of overjet and the adequacy of lip coverage of the maxillary incisors was assessed for each child. One-hundred-and-sixty-seven (15 per cent) had experienced traumatic injury to their maxillary incisors. Both increased overjet and inadequate lip coverage of the maxillary incisors were found to be significant risk factors. However, inadequate lip coverage was the single most important independent predictor of traumatic injury (P < 0.001), with a relative odds ratio of 2.62. The results suggest that much of the predictive value of increased overjet may be explained by inadequate lip coverage.