Objective: The aim of this study was to assess the influence of overjet size and lip coverage on the prevalence and severity of incisor trauma.
Patients and methods: Dental records made on presentation of 1,367 patients were examined for data concerning the prevalence, type and severity of incisor trauma. Original overjet was measured on the pre-treatment study models and divided into two categories: normal overjet (0-3.0 mm) and increased overjet (> 3.0 mm). Lip coverage of the upper incisors was estimated with reference to photographs showing the patient's face and was then rated as adequate or inadequate. The patients were then divided into three groups: normal original overjet and adequate lip coverage (Group 1), increased original overjet and adequate lip coverage (Group 2), and increased original overjet and inadequate lip coverage (Group 3).
Results: Group 1 patients revealed a significantly lower prevalence of traumatic injuries than those in Group 2 (p = 0.028) or Group 3 (p = 0.003), and the odds ratios compared to Group 1 were 1.6634 for Group 2 and 2.0336 for Group 3. Regarding the type of trauma, Group 3 patients showed a significantly higher frequency of periodontal injuries than those in Group 1 (p = 0.018) or Group 2 (p = 0.015). Furthermore, Group 3 patients had significantly more in juries to two or more teeth per person than patients in Group 1 (p < 0.001) or Group 2 (p < 0.001).
Conclusions: Increased overjet and inadequate lip coverage increase the risk and severity of incisor trauma. Early orthodontic treatment might prevent dental trauma in these patients.