Morphological relationship analysis of impacted maxillary canines and the adjacent teeth on 3-dimensional reconstructed CT images

Abstract

Objective: To examine whether there is a relationship between maxillary canine impaction and the morphologic characteristics of the maxillary dentition, especially the root of the lateral incisor.

Materials and methods: In this study, we selected only patients with unilateral maxillary canine impaction to compare the morphologic characteristics of the dentition on the impaction side and the clinically normal eruption side. The sample size was decided to be 40 based on the pilot study. To minimize bias depending on sex and location of the maxillary canine impaction, we selected equal numbers (20) of boys and girls, and equal cases (20) of buccal impaction and palatal impaction. Under the aforementioned conditions, the mean age was 13.5 ± 2.3 years. The multislice spiral computed tomography images of these 40 subjects were converted into three-dimensional (3D) reconstructed images using the OnDemand 3D program (Cybermed Co, Seoul, Korea). Then we measured the morphologic characteristics of the individual teeth on the obtained 3D teeth images.

Results: Length and volume of the maxillary lateral incisor's roots were significantly smaller on the impaction side compared with the normal eruption side (P = 0.001 and P = 0.006, respectively). The width and volume of the canine's crown were significantly greater on the impaction side compared with the normal eruption side (P = 0.020 and P < .0001, respectively).

Conclusion: These results might help to prove the hypothesis that the smaller-sized lateral incisor roots and greater-sized canine crowns are the influential etiologic factors in maxillary canine impaction.

Keywords: 3D reconstruction; Guidance theory; Lateral incisor morphology; Maxillary canine impaction.

Figure 1.

Reconstructed 3D MSCT DICOM images with the surrounding structures removed using the OnDemand 3D program (a). Maxillary right canine separated from the reconstructed 3D image (b). Maxillary right lateral incisor (c). Maxillary right central incisor (d). Maxillary left central incisor (e). Maxillary left lateral incisor (f). Maxillary left canine (g).

Figure 2.

Mesiodistal width of the crown (mm) measured from the widest point of the crown (a). Anatomic height of the crown (mm) measured from the lowest buccal CEJ point to the incisal tip in the lateral view image. Length of the root (mm) measured from the lowest buccal CEJ to the root apex in the lateral view image (b).

Figure 3.

The tooth was separated into the crown part and the root part using a line made by connecting the lowest buccal CEJ and lowest palatal CEJ (a). Then, the crown and root volume were measured using the OnDemand 3D program. This cross-sectional image of the root was obtained by separating the crown and root part (b).

Figure 4.

Statistical comparison of central incisors' morphologic features between the impaction side group and the eruption side group using a Wilcoxon signed rank test.

Figure 5.

Statistical comparison of lateral incisors' morphologic features between the impaction side group and the eruption side group using a Wilcoxon signed rank test (*P < .05).

Figure 6.

Statistical comparison of canines' morphologic features between the impaction side group and the eruption side group using a Wilcoxon signed rank test (*P < .05).