Dentofacial parameters explaining variability in retroclination of the maxillary central incisors

Abstract

Background and aim: The interrelation between retroclination of the maxillary central incisors and dentofacial parameters is a controversial subject in the literature. In contrast to comparisons between malocclusion and control groups, the objective of the present study was to identify skeletal, dentoalveolar or perioral (soft-tissue) factors which primarily determine how severely retroclination is individually manifested.

Materials and methods: For this purpose we evaluated the pretherapeutic lateral cephalograms of 83 patients with an inclination of the maxillary central incisors ranging from physiological values to very severe retroclination (inclination to anterior cranial base between 104 degrees and 64 degrees ). A detailed analysis of the skeletal, dentoalveolar, and soft-tissue morphology was performed using lateral cephalograms taken prior to therapy. The statistical analysis included the calculation of multiple regression models for maxillary central incisor inclination and different parameters describing the lip-to-incisor relationship as dependent variables.

Results: A regression model including 1) the lip-line level measured at the dorsal upper-lower lip contact point, 2) the sagittal intermaxillary relationship, and 3) the inclination of the mandibular central incisors explained 81% of the variability in maxillary central incisor inclination (p < 0.0001 for all three parameters). Statistical analysis of the morphologic base of a high dorsal lip-line level (i.e., the predominant characteristic in the retroclination cases) revealed the significance of soft-tissue, dentoalveolar, and skeletal variables (p < 0.001).

Conclusions: Complementary to results of previous resting lippressure measurements, this cephalometric study suggests that a high lip-line level is the predominant causative factor for a cover- bite or Class II, Division 2 malocclusion. Therefore, we conclude that (1) lip-line measurements should be included in routine cephalometric diagnostics, and (2) that a high lip-line must be eliminated by therapeutic measures in these malocclusions to prevent a post-orthodontic relapse.