Introduction
The aim of this study was to evaluate the thickness and the height of the maxillary central incisors’ alveolar bone near the grafted alveolar cleft area, after comprehensive orthodontic treatment.
Methods
The sample comprised 30 patients with unilateral alveolar cleft with a mean age of 20.5 years (range, 17-25.8 years). High-resolution cone-beam computed tomography images of the maxilla were obtained 6 to 24 months after the comprehensive orthodontic treatment. The contralateral maxillary central incisor was used as a comparison group. Axial sections at the level of the central incisor root were used to measure the labial and lingual alveolar bone thicknesses. Cross sections were used to measure the bone crest heights using the cementoenamel junction as the reference. Paired t and Wilcoxon tests were used to compare the cleft and noncleft sides.
Results
The labial and lingual bone thicknesses of the maxillary central incisors’ alveolar bone were significantly thinner (0.16 and 0.39 mm, respectively), and the labial alveolar crest height distance was significantly greater on the cleft side compared with the noncleft side (−1.2 mm).
Conclusions
In patients with unilateral cleft lip and palate, the maxillary central incisors adjacent to the grafted alveolar cleft had thinner labial and lingual alveolar bones and an apically displaced labial alveolar crest level than the controls.
Highlights
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Maxillary central incisor alveolar bone thickness and height were evaluated.
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Measurements were compared between cleft and noncleft sides.
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Bone was thinner and alveoloar crest height greater on the cleft side.
An important clinical implication of cleft lip and palate in orthodontics relates to bone defects in the alveolar ridge. Bone defects in the alveolar ridge cause changes in tooth position. The canines assume a more angulated position, and the central incisors are rotated and angulated in the opposite direction, to avoid the bone defect and keep their roots inside the bone. The ideal time to perform secondary alveolar bone graft surgery is in the mixed dentition, before eruption of the permanent canines. This procedure aims to restore bone morphology and provide healthy bone for eruption of the permanent canines.
Lateral incisor agenesis is common on the cleft side. Agenesis of the permanent lateral incisor in the cleft area has an important role in orthodontic treatment planning. The treatment plan involves movement of the maxillary permanent canines to the grafted area, replacing the nonexistent maxillary lateral incisor. This orthodontic movement should be carefully performed and followed by periodontal and imaging controls due to the narrow mesial and distal bone plates adjacent to the cleft or graft. During comprehensive orthodontic treatment, the central incisors are also moved into the grafted area, especially when midline, tooth rotation, and angulation need to be corrected.
Comparing the alveolar bone support ratio from the maxillary permanent canine between the cleft and noncleft sides using periapical radiographs, Boyarskiy et al concluded that although the noncleft side had statistically significant greater alveolar bone support, there was a good level of alveolar bone support for the permanent canine in the cleft side after the secondary bone graft. Yatabe et al evaluated, with cone-beam computed tomography (CBCT), the labial and lingual alveolar bone thicknesses and the levels of the canines moved into the grafted alveolar cleft. Their findings showed statistically significant thinner labial bone in the cleft side. The alveolar crest level showed statistical similarity between the canines in the cleft and noncleft sides.
No previous studies have evaluated the labial and lingual alveolar bones of maxillary central incisors moved into the neighboring region of the grafted alveolar cleft. Are there bone defects at these regions after comprehensive orthodontic treatment? The purpose of this study was to evaluate the labial and lingual alveolar bone thicknesses and the levels of the maxillary central incisors in patients with unilateral alveolar cleft, by comparing the cleft and noncleft sides. The null hypothesis was that the maxillary central incisors in the cleft and noncleft sides have no differences in quantitative alveolar bone parameters.
Material and methods
This retrospective study was approved by the ethical committee in research of the Hospital of Rehabilitation of Craniofacial Anomalies, University of São Paulo, Bauru, São Paulo, Brazil (process number 16269913.0.0000.5441). The sample was obtained from a previous study. The test power was calculated with the sample of 30 subjects, to detect a minimum intergroup difference of 0.5 mm in bone thickness, with a standard deviation of 0.33 mm (labial alveolar bone thickness), and an alpha of 0.05. The paired t test power was higher than 99%.
The patients were examined at the Department of Orthodontics, Hospital of Rehabilitation of Craniofacial Anomalies, University of São Paulo, Bauru, São Paulo, Brazil, from August 2011 to January 2012 during their appointments for retainer adjustment and consecutively selected according to the following criteria: (1) retention period of at least 6 months, (2) age from 15 to 25 years, (3) history of secondary alveolar bone graft surgery using autogenous bone from the iliac crest, (4) no tooth agenesis at the anterior region of the noncleft side, (5) agenesis of the lateral incisor at the cleft side, and (6) comprehensive orthodontic treatment closing the spaces of the lateral incisor agenesis at the cleft side by mesial movement of the maxillary canines. The exclusion criteria were patients with syndromes. Right side clefts comprised 30% of the sample, and left side clefts comprised 70%. The secondary alveolar bone graft was performed by 3 buccomaxillofacial surgeons at a mean age of 11.8 years (SD, 1.64 years; minimum age, 8.3 years; maximum age, 15.2 years) using the technique of Boyne and Sands.
This was a split-mouth study. The experimental group comprised the maxillary central incisors at the cleft side, and the control group included the maxillary central incisors at the noncleft side.
CBCT was performed using i-CAT 3-dimensional system (Imaging Sciences International, Hatfield, Pa) using a protocol of 120 kV, 23.87 mA, 6-cm field of view, and a voxel size of 0.25 mm.
Using the Nemoscan Software (Nemotec, Madrid, Spain), the CBCT image was standardized in the sagittal view, positioning the palatal plane parallel to the horizontal plane; in the frontal view, leveling the occlusal plane with the horizontal plane; and in the axial view, positioning the vertical guideline on the midline of the central incisors ( Fig 1 ).
An axial section passing through the trifurcation of the right permanent first molar was selected. On this image, the labial and lingual alveolar bone thicknesses of the maxillary central incisors were measured on the cleft and noncleft sides ( Fig 2 ).
The labial and lingual alveolar crest heights were measured on cross sections passing through the center of the maxillary central incisor crown on both sides, using the cementoenamel junction as the reference ( Figs 3-5 ). Incisor tipping was compensated by turning the panoramic image until the incisor’s long axis was upright . After this step, the cross section was obtained.
All variables were remeasured after at least 30 days by the same examiner (G.M.N.). Intraexaminer reproducibility was evaluated with intraclass correlation coefficients (ICC).
Statistical analyses
Kolmogorov-Smirnov tests were used to assess normal distribution. Normal distribution was found only for lingual alveolar bone thickness and crest height. Intergroup comparisons of the labial and lingual alveolar bone variables were performed by Wilcoxon and paired t tests, respectively. The significance level was regarded as 5%.
Results
The data from all 30 patients are shown in Figure 6 .
The ICC values varied from 0.73 to 1, showing good to excellent measurement reproducibility ( Table I ).
| First measurement mean (mm) | Second measurement mean (mm) | Difference | ICC | |
|---|---|---|---|---|
| Cleft side | ||||
| LaABT | 0.27 | 0.31 | 0.04 | 0.73 |
| LiABT | 1.31 | 1.34 | 0.03 | 0.87 |
| LaACH | 2.96 | 2.98 | 0.02 | 1 |
| LiACH | 1.2 | 1.22 | 0.02 | 0.96 |
| Noncleft side | ||||
| LaABT | 0.42 | 0.49 | 0.07 | 0.79 |
| LiABT | 1.68 | 1.76 | 0.08 | 0.74 |
| LaACH | 1.76 | 1.77 | 0.01 | 0.99 |
| LiACH | 0.97 | 0.9 | −0.07 | 0.75 |
The hypothesis that the maxillary central incisors in the cleft and noncleft sides have no differences in quantitative alveolar bone parameters was not confirmed. The labial and lingual bone thicknesses of the maxillary central incisors were significantly thinner at the cleft side compared with the noncleft side. The labial alveolar crest height distance was significantly greater on the cleft side compared with the noncleft side ( Table II ).
| Cleft side (mm) | Noncleft side (mm) | Difference mean (SD) | Median difference | P | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean | SD | Min-max | Median | Mean | SD | Min-max | Median | ||||
| LaABT | 0.31 | 0.35 | 0.0-1.02 | 0.19 | 0.47 | 0.44 | 0.0-1.28 | 0.44 | 0.16 (0.33) | 0.25 | 0.017 ‡ ∗ |
| LiABT | 1.33 | 0.81 | 0.0-3.32 | 1.31 | 1.72 | 0.84 | 0.0-3.81 | 1.63 | 0.39 (0.90) | 0.32 | 0.023 † ∗ |
| LaACH | 2.97 | 2.4 | 0.57-11.7 | 2.33 | 1.77 | 0.96 | 0.0-4.98 | 1.63 | −1.2 (2.12) | −0.7 | 0.002 ‡ ∗ |
| LiACH | 1.21 | 0.71 | 0.0-3.10 | 1.09 | 0.94 | 0.53 | 0.0-1.80 | 0.97 | −0.27 (0.84) | −0.12 | 0.084 † |
Results
The data from all 30 patients are shown in Figure 6 .
The ICC values varied from 0.73 to 1, showing good to excellent measurement reproducibility ( Table I ).
| First measurement mean (mm) | Second measurement mean (mm) | Difference | ICC | |
|---|---|---|---|---|
| Cleft side | ||||
| LaABT | 0.27 | 0.31 | 0.04 | 0.73 |
| LiABT | 1.31 | 1.34 | 0.03 | 0.87 |
| LaACH | 2.96 | 2.98 | 0.02 | 1 |
| LiACH | 1.2 | 1.22 | 0.02 | 0.96 |
| Noncleft side | ||||
| LaABT | 0.42 | 0.49 | 0.07 | 0.79 |
| LiABT | 1.68 | 1.76 | 0.08 | 0.74 |
| LaACH | 1.76 | 1.77 | 0.01 | 0.99 |
| LiACH | 0.97 | 0.9 | −0.07 | 0.75 |
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