Recovery bone formation on radiographic palatal bone dehiscences after incisor retraction with microimplants

Abstract

Objectives: To investigate the difference in labial and palatal alveolar bone thickness and height during the retention period after incisor retraction treatment with microimplant.

Materials and methods: A sample of 21 patients (mean age: 17.80 ± 4.38 years) who underwent incisor retraction treatment using microimplants after premolar extraction was investigated. The cone-beam computed tomography images at pretreatment, posttreatment, and retention were used to measure anterior alveolar bone thickness (labial, palatal, and total; at three vertical levels) and height (labial and palatal) and differences in the incisor position during treatment or retention. Repeated-measures analysis of variance with Bonferroni correction was performed to compare the variables at T0, T1, and T2.

Results: The maxillary central incisor moved posteriorly by approximately 8.0 mm along with intrusive movement of 1.8 mm after treatment. The alveolar bone thickness significantly decreased on the palatal side and increased on the labial side after treatment. Thereafter, the palatal bone thickness significantly increased and labial bone thickness decreased during the retention period. The palatal interdental bone depressed by incisor retraction showed substantial bone deposition after retention.

Conclusions: Radiographic palatal bone dehiscences on the incisor root and palatal bone depression between the incisor roots were apparent after treatment. This palatal bone loss around the incisor roots noticeably recovered with newly formed bone during retention.

Keywords: Alveolar bone remodeling; Incisor retraction; Microimplant; Radiographic palatal bone dehiscence.

Figure 1.

Reference planes and measurements in cone-beam computed tomography image. (A) Midsagittal and horizontal reference planes of the maxilla. (B) Sagittal section. Vertical levels of the axial section based on the cementoenamel junction (CEJ) of the right maxillary central incisor at posttreatment. (C) Axial section. Alveolar bone thickness (along the anteroposterior line of the tooth) and interdental bone depression (distance between the labial/palatal interdental line and the most depressed point of the interdental bone). (D) Vertical bone level (distance from the alveolar bone crest to the CEJ). (E) Difference in the incisal tip position and tooth inclination on the sagittal sections between time points. (F) Difference in the tooth position on the axial sections between time points (at the labial or palatal root surface). ANS indicates anterior nasal spine; N, nasion; PNS, posterior nasal spine; T1, posttreatment.

Figure 2.

Alveolar bone assessment by cephalometric images. (A) Determination of palatal bone dehiscence of the central incisor at each vertical level (Lv). (B) Palatal vertical bone level of the incisor. CEJ indicates cementoenamel junction. Lv indicates level.

Figure 3.

Alveolar bone thickness (significant difference between time points; * P < .05, *** P < .01, *** P < .001). T0 indicates pretreatment; T1, posttreatment; T2, retention.

Figure 4.

Interdental bone depression (significant difference between time points; * P < .05, ** P < .01, *** P < .001). T0 indicates pretreatment; T1, posttreatment; T2, retention.

Figure 5.

Summary illustration of the difference in alveolar bone thickness, interdental bone depression, and tooth position. (A) Sagittal section. Alveolar bone thickness of the right maxillary central incisor. (B) Axial section. Interdental bone depression at level 1. Lv indicates level; T0, pretreatment; T1, posttreatment; T2, retention.

Figure 6.

Sagittal section views of three samples showing significant palatal bone apposition at retention. T1 indicates posttreatment; T2, retention.

Figure 7.

Palatal alveolar bone images of a sample (at retention). (A) Cephalometric image. (B) Cone-beam computed tomography (CBCT) image (grayscale mode). Landmarks of the interdental palatal bone depression. (C) CBCT image (bone mode). Landmarks of the interdental palatal bone depression. (D) Axial sections of CBCT image. Landmarks of the interdental palatal bone depression. Lv indicates level.