Comparison of alveolar bone width and sagittal tooth angulation of maxillary central incisors in Class I and Class III canine relationships: a retrospective study using CBCT

Abstract

Background: Canine relationship is a key reference identifying anterior malocclusion and an important implication for evaluating preimplantation bone morphology at maxillary esthetic zone. This study aimed to compare the differences of maxillary central incisor-related measurements (alveolar bone thickness and tooth sagittal angulation) between Class I and Class III canine relationship and further explore the risk factors for immediate implant placement in the anterior maxilla based on cone beam computed tomography (CBCT) data.

Methods: CBCT digital imaging and communications in medicine (DICOM) files of 107 patients (54 with Class I canine relationship and 53 with Class III canine relationship) were collected and the alveolar bone thickness at mid-root (mid-root buccal thickness/MBT; palatal/MPT), apical regions (apical buccal thickness/ABT; palatal/APT) and sagittal angulation (SA) of the maxillary central incisor at the examined side were measured on the mid-sagittal observation plane. Descriptive statistical analysis and frequency distributions of the measurements based on Class I or Class III canine relationship were established. Statistical analyses were performed using Fisher's exact test, independent samples t test and Pearson correlation test with the significance level set at p < 0.05.

Results: The frequency distributions of maxillary central incisors' MPT, ABT, APT and SA showed significant differences between Class I and Class III canine relationships (p = 0.030, 0.024, 0.000 and 0.000, respectively). MPT (2.48 ± 0.88 mm vs. 3.01 ± 1.04 mm, p = 0.005), APT (6.79 ± 1.65 mm vs. 8.47 ± 1.93 mm, p = 0.000) and SA (12.23 ± 5.62° vs. 16.42 ± 4.49°, p = 0.000) were significantly smaller in patients with Class III canine relationship. Moreover, SA showed a strong positive correlation with APT (R = 0.723, p = 0.000) and a moderate negative correlation with ABT (R = - 0.554, p = 0.000).

Conclusions: In populations with Class III canine relationship, maxillary central incisors were significantly more labially inclined and have a thinner palatal bone plate at the apex compared with Class I relationship. Clinicians should avoid palatal perforation during immediate implantation at sites of originally protrusive maxillary incisors.

Keywords: Canine relationship; Cone-beam computed tomography; Immediate implant; Maxillary central incisor.

Fig. 1

a Example of neutral canine relationship (Class I) and corresponding maxillary central incisor; b Example of mesial canine relationship (Class III) and corresponding maxillary central incisor

Fig. 2

a Determination of panoramic curve after head position reorientation; b Observation plane (blue): mid-sagittal plane passes through chosen tooth’s long axis which was perpendicular to panoramic curve (yellow)

Fig. 3

a Measurements of bone thickness at different aspects; b Measuring the sagittal angulation of the maxillary central incisor based on the tooth axis and the axis of its respective alveolar process. MBT, mid-root buccal thickness; MPT, mid-root palatal thickness; ABT, apical buccal thickness; APT, apical palatal thickness

Fig. 4

Illustration of the frequency distributions of MBT, MPT, ABT, APT. MBT, mid-root buccal thickness; MPT, mid-root palatal thickness; ABT, apical buccal thickness; APT, apical palatal thickness. *Statistically significant difference between Class I and III canine relationships (p < 0.05)

Fig. 5

Illustration of the frequency distribution of sagittal angulation between the long axes of tooth and its associated alveolar bone. *Statistically significant difference between Class I and III canine relationships (p < 0.05)