Alveolar bone morphology in patients with a unilateral palatally displaced maxillary lateral incisor: A cone-beam computed tomography study.

INTRODUCTION: Lingual displacement of the maxillary anterior teeth is 1 of the most common forms of malocclusion. The labial alveolar bone is thinner for the maxillary lateral incisor than for the central incisor and canine; however, the alveolar bone width at the actual position of the maxillary lateral incisor has not been examined. We investigated the morphologic characteristics of the alveolar bone around palatally displaced maxillary lateral incisors using cone-beam computed tomography and a split-mouth model. METHODS: Twenty-seven patients with a unilateral palatally displaced maxillary lateral incisor were included. Axial, sagittal, and horizontal measurements were recorded at 3 levels (ie, 25%, 50%, and 75% of the root length) using cone-beam computed tomography. All obtained data were statistically analyzed using paired t tests. RESULTS: The labial alveolar bone width at 25% of root length was significantly lesser on the affected side. At all 3 levels, the distance between a line tangential to the labial alveolar bone of the central incisor and canine and the position of the labial alveolar bone of the lateral incisor was significantly greater on the affected side. At 50% and 75% of root length, the horizontal distance between the posterior nasal spine and the labial alveolar bone of the lateral incisor was significantly lesser on the affected side. CONCLUSIONS: Palatal displacement of maxillary lateral incisors is significantly associated with decreased alveolar bone width at the apical level and asymmetry. However, a further elaborate investigation is necessary to determine the clinical relevance of the study.

A cone-beam computed tomographic assessment of the proximity of the maxillary canine and posterior teeth to the maxillary sinus floor: Lessons from 4778 roots.

INTRODUCTION: When tooth roots protrude into the maxillary sinus, apical root resorption and tipping may occur during horizontal tooth movement across the sinus floor. Three-dimensional cone-beam computed tomography (CBCT) images may provide detailed information without distortion and overlap. We evaluated the relationships between the maxillary tooth root apices and the maxillary sinus floor using CBCT. METHODS: We evaluated 4778 roots from 76 men (aged 27.6 ± 10.4 [mean ± standard deviation] years; range, 18-69 years), and 225 women (aged 30.4 ± 12.0 years; range, 18-68 years). The positional relationships between the maxillary tooth root apices, including the canine, premolar (first and/or second), and molar (first and/or second), and the inferior wall of the maxillary sinus were comprehensively evaluated on 2 cross-sectional CBCT images (ie, the sagittal and coronal planes). These distances were measured in both images simultaneously. RESULTS: The sagittal plane distances were significantly larger than coronal plane distances, except for the distobuccal root of the first molar. Pearson correlation test revealed a significant negative correlation between the distance and the patient's age. CONCLUSIONS: Our study provides valuable information for planning orthodontic tooth movement through the maxillary sinus, which may help to predict the occurrence and severity of root resorption.

Quantitative analysis of the relationship between maxillary incisors and the incisive canal by cone-beam computed tomography in an adult Japanese population.

BACKGROUND: In setting goals for orthodontic treatment, determining the morphologies of the alveolar bone and maxillary incisor root is important for avoiding root resorption, dehiscence, and fenestration. This study aimed to analyze the configurational relationships among maxillary incisors, the alveolar border, and the incisive canal by cone-beam computed tomography (CBCT). METHODS: Cone-beam CT images of 93 orthodontic patients were evaluated for length of the incisive canal (L); angles between the palatal plane and the maxillary alveolar border (θ1), the incisive canal (θ2), and maxillary incisor (θ3); distance from the left maxillary incisor to the incisive canal (D); and cross-sectional areas of the incisive canal (CSAs) at three vertical levels. Comparison of variables between male and female patients was performed with the two-sample t test. Correlations between parameters were examined by Pearson's correlation analysis and Bonferroni correction for multiple comparisons. RESULTS: Male patients exhibited significantly greater values of L than female patients. There were significant positive correlations between θ1 and θ2, θ2 and θ3, and θ3 and θ1. While the value of D was the lowest at the oral opening, that of the cross-sectional area of the incisive canal (CSA) was the greatest at the incisal root apex. CONCLUSIONS: This study demonstrated that the incisive canal had large inter-individual variability, and the proximity between the incisive canal and the incisal root could not be precisely predicted by the conventional cephalograms. Therefore, pre-treatment CBCT examination should be recommended when a large amount of maxillary anterior retraction and/or intrusion is planned in orthodontic diagnosis.