Are there bone dehiscences in maxillary canines
orthodontically moved into the grafted alveolar
cleft?
Marilia Sayako Yatabe, a Terumi Okada Ozawa,b Guilherme Janson,c Renato Andre de Souza Faco,d
and Daniela Gamba Garibe
Bauru, Sao Paulo, Brazil
Introduction: The aim of this study was to assess the bone morphology of teeth mesialized into the grafted region in patients with unilateral alveolar cleft. Methods: The sample comprised 30 patients with unilateral cleft lip and palate with a mean age of 20.5 years. High-resolution cone-beam computed tomography images of the maxilla were obtained 6 months to 2 years after comprehensive orthodontic treatment. The contralateral canines and lateral incisors were used as controls. Axial section was used to measure the bone thickness, and cross section was used to measure the alveolar crest height using the cementoenamel junction as a reference. Paired t tests andWilcoxon tests were used to compare the cleft and noncleft sides (P\0.05).Results: High individual variability was found. In general, the canines in the cleft side had statistically thinner buccal bone plates than the contralateral teeth. No differences between the cleft and noncleft sides were found for the lingual bone plate thickness. The canine on the cleft side showed a slightly greater distance between the lingual alveolar crest and the cementoenamel junction than the lateral incisor in the noncleft side. Conclusions: In patients with unilateral cleft lip and palate, mesial orthodontic movement of the maxillary canines into the grafted alveolar cleft results in acceptable buccal and lingual periodontal morphology. (Am J Orthod Dentofacial Orthop 2015;147:205-13)
aPhD student, Bauru Dental School, University of S~ao Paulo, Bauru, Sao Paulo, Brazil.
bChief, Dentistry Division, Hospital of Rehabilitation of Craniofacial Anomalies, University of Sao Paulo, Bauru, Sao Paulo, Brazil.
cAssociate professor, Bauru Dental School, University of Sao Paulo, Bauru, Sao Paulo, Brazil.
dBuccomaxillofacial surgeon, Hospital of Reahabilitation of Craniofacial Anomalies, University of Sao Paulo, Bauru, Sao Paulo, Brazil.
eAssociate professor of orthodontics, Hospital of Rehabilitation of Craniofacial
Anomalies, Bauru Dental School, University of S~ao Paulo, Bauru, Sao Paulo, Brazil.
All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported.
Address correspondence to: Marılia Sayako Yatabe, Alameda Octavio Pinheiro
Brisolla, 9-75, 17012-901 Bauru, S~ao Paulo, Brazil; e-mail, msyatabe@yahoo.com.br.
Submitted, March 2014; revised and accepted, October 2014. 0889-5406/$36.00
Copyright 2015 by the American Association of Orthodontists.
http://dx.doi.org/10.1016/j.ajodo.2014.10.027
Cleft lip and palate (CLP) is the most common congenital craniofacialmalformation in humans.1,2
The rehabilitation protocol of CLP includes lip and palate repair during the first months and year of life, respectively.3-5 During the late mixed dentition, an alveolar bone graft is indicated to rehabilitate the alveolar cleft.4,6-14 After the secondary alveolar graft surgery, the maxillary canines spontaneously erupt through the grafted region in most patients.6,14-16 Patientswith CLP often have agenesis of the maxillary lateral incisors.17-19 The gold standard treatment plan after alveolar bone graft surgery is to mesially move the maxillary canines to replace the missing lateral incisors.20-24 This procedure stimulates maintenance of the alveolar bone graft at the cleft region and avoids the need for tooth prosthesis. After canine substitution for missing maxillary lateral incisors, esthetic dentistry is performed to complete treatment similarly to that for noncleft patients with maxillary lateral incisor
agenesis.22,23,25
Orthodontic tooth movement into an edentulous alveolus is critical in terms of alveolar bone response.26 Bone remodeling around the tooth root depends on the magnitude of force, the amount of tooth movement, and the presence of bacterial plaque.27,28 Despite our knowledge of periodontal responses to orthodontic treatment, there is lack of information regarding the response of grafted bone to orthodontic therapy in cleft patients. Since the grafted alveolar cleft has buccolingual constriction of the alveolar ridge, during comprehensive orthodontic treatment for canine substitution, does movement of the maxillary canine toward the grafted area occur within the bone or through the bone?29,30 Previous studies have demonstrated that maxillary canines that erupt through the graft have similar periodontal conditions to canines erupted in normal bone.7,31-33 These studies, however, analyzed only the mesial and distal alveolar bone by means of periapical radiographs. No previous study has evaluated the buccal and lingual bone plates of maxillary canines moved into the grafted area. Therefore, the purposes of this study were to evaluate the buccal and lingual alveolar bone thicknesses and levels of canines moved into the grafted alveolar cleft, and to compare these characteristics with the contralateral teeth in patients with unilateral CLP. The null hypothesis is that the teeth on the cleft and noncleft sides have similar buccal and lingual alveolar bone morphology.
MATERIAL AND METHODS
Institutional research ethics committee and written patient and parent consents were obtained. The confidentiality and rights were protected. The sample size calculation was based on preliminary statistics including the first 5 patients of the sample. For a standard deviation of 0.13 mm for bone thickness and a minimal intergroup difference of 0.10 mm to be detected, a sample of 28 patients was required to provide statistical power of 80% with an a of 0.05.
From August 2011 to January 2012, a sample of 30 patients with unilateral alveolar cleft from 1 rehabilitation center was consecutively selected. Twenty-two patients had complete unilateral CLP, and 8 had unilateral cleft lip and alveolus. The patients were examined at the orthodontic department of the Hospital of Rehabilitation of Craniofacial Anomalies, University of S~ao Paulo, in Brazil during their appointments for retainer adjustment. The inclusion criteria were (1) minimum retention period of 6 months after debonding, (2) age between 15 and 25 years, (3) history of secondary alveolar bone graft surgery with iliac crest autogenous bone, (4) presence of canines and lateral incisors in the noncleft side, (5) agenesis of the lateral incisor at the cleft side, and (6) comprehensive orthodontic treatment including mesial movement of the maxillary canines toward the grafted alveolar cleft. The exclusion criteria were patients with syndromes. The final sample comprised 14 female and 16 male subjects with a mean age of 20.5 years and a mean retention
period of 1.8 years. The ratio between the right and left sides of the cleft was approximately 1:2.5. The mean age when the secondary alveolar bone graft was performed was 11.8 years. Three surgeons performed the bone graft procedure using the same technique. At the time of secondary alveolar bone graft,36%of the patients had their permanent canine partially erupted on the cleft side. In 58% of the patients, the permanent canine at the cleft side spontaneously erupted after the bone graft, whereas 7% of the patients needed canine traction. Orthodontic movement of the canine after the secondary alveolar bone graft began 2 months after surgery for patients who had the canine erupted at the time of surgery. For patients who had the secondary alveolar bone graft before canine eruption, comprehensive orthodontic treatment was initiated only after the cleft-side canine had erupted. Comprehensive orthodontic treatment started a mean of 18.6 months after the secondary alveolar bone graft surgery (SD, 17.1 months). No regrafting surgery was needed. Only 2 of the 30 patients underwent orthognathic surgery. This study had a split-mouth design. The experimental group consisted of the maxillary canines at the cleft side (C3). The control group consisted of the maxillary canines (NC3) and the lateral incisors (NC2) on the noncleft side. Cone-beam computed tomography (CBCT) was performed with an i-CAT cone-beam 3-dimensional system (Imaging Sciences International, Hatfield, Pa). The technical parameters for image acquisition were 120 kV, 23.87 mA, field of view of 16 3 6 cm, and voxel size of 0.25 mm.
Initially, the CBCT image was standardized in the sagittal view, positioning the palatal plane parallel to the horizontal plane. In the frontal view, the occlusal plane was coincident to the horizontal plane. Finally, in the axial sections, the vertical guideline was positioned at the midline of the central incisors (Fig 1).
In the frontal and sagittal images, an axial section passing through the trifurcation of the right first permanent molar was selected. On this image, the buccal and lingual alveolar bone thicknesses were measured on the C3 and on the NC3 and NC2 (Fig 2). The buccal and lingual alveolar crest heights were measured on cross sections passing through the center of the crowns of the C3, NC3, and NC2, with the cementoenamel junction (CEJ) as a reference (Fig 3).
Statistical analysis
Teeth were measured twice with an interval of at least 1 month by 2 examiners (M.S.Y., D.G.G.). Intrarater and interrater reliabilities were assessed with intraclass correlation coefficients.
Normal distribution was evaluated with the Kolmogorov-Smirnov test (P\0.05). Intergroup comparisons were performed using the paired t test when there was normal distribution or the Wilcoxon test when there was nonnormal distribution (P\0.05).
Fig 1. Standardization of image position before measurements: A, vertical guideline coincident with the midline in the axial section; B, palatal plane parallel to the horizontal plane in the sagittal view; C, molar occlusal plane parallel to the horizontal plane in the frontal view; and D, 3D reconstruction view.
Fig 2. Measurement of buccal and lingual bone plate thicknesses.
Fig 3. Measurement of buccal and lingual alveolar crest heights.
RESULTS
Alveolar bone thickness measurements showed excellent intrarater correlations of 0.91 to 1.00. The alveolar crest level assessments demonstrated good intrarater correlations of 0.7 to 0.89. Intergroup comparisons are shown in the Table. The canines’ buccal bone in the cleft area was thinner than that of the controls, and the lingual bone thickness was similar (Table and Fig 4).
Cross-sectional images of the experimental and control teeth from the complete sample are shown in Figures 5, 6, and 7. Despite the large individual variations (Fig 5), the buccal alveolar crest level of the maxillary canines moved into the grafted alveolar cleft was similar to that of the contralateral teeth (Table). In the whole sample, only 1 patient showed severe buccal bone dehiscence, and 6 patients had moderate buccal bone dehiscences. The lingual alveolar crest height of the C3 was similar to the control canines but more apically located than were the NC2 (Table). Two of the 30 patients showed severe lingual bone dehiscences, and 1 patient had moderate lingual bone dehiscence.
Fig 4. Axial sections passing at the level of the first molar trifurcation of all patients.
DISCUSSION
Until the advent of CBCT, the only imaging method to assess periodontal morphology was the periapical radiograph, which allowed visualization of only the mesial and distal aspects. Currently, CBCT is an imaging method that allows complete assessment of the buccal and lingual bone plates34 and may be recommended for diagnosis in patients with oral clefts.35,36 The SEDENTEXCT document stated that 3-dimensional information can be used to determine the adequacy of bone filling after graft surgery in patients with palatal clefts and recommended that CBCT should be preferred instead of medical computed tomography.35 The American Academy of Oral and Maxillofacial Radiology also recommended CBCT images in orthodontics for
evaluation of compromised dentoalveolar boundaries including reduced buccal and lingual alveolar widths and clefts of the alveolus.36 In these patients, the smallest volume size compatible with the situation should be selected because of the reduced radiation dose.35,36 Although the measurement accuracy of CBCT has been shown to be within 0.1 to 0.2 mm, conclusions based on dimensions smaller than the scanner’s spatial resolution, such as the alveolar bone, should be made with caution.37 Ballrick et al38 found that the 0.2-mm voxel size has an average spatial resolution of 0.4 mm, which means that it can distinguish 2 objects with a minimum distance of 0.4 mm. However, the spatial resolution can be influenced by other factors in addition to
voxel size, such as partial-volume averaging and scatter level. Partial-volume averaging is the capability of 1 voxel to display an average density when it represents 2 structures with different densities.37 The scatter level increases as the size of the field of view increases.37 The easiest way to control it is to use the smallest field of view that encompasses the region of interest.37 In this study, to evaluate small structures such as the buccal and lingual bone plates, a voxel size of 0.25 mm with a field of view of 6 cm was used. The goal was to minimize the partial-volume effect and the scatter level. Falsepositive
results for bone dehiscences were not a concern because most of the buccal and lingual bone plates were visible in the images (Figs 5-7). Additionally, the intraclass correlation coefficient results showed that the measurements were reliable. Orthodontic movement of the maxillary canines through grafted alveolar bone is considered the gold standard in oral rehabilitation of young patients with CLP, primarily to stimulate the bone graft. Moreover,
better results can be achieved with canine substitution instead of opening the space for future prosthetic rehabilitation. 32 On the other hand, there is evidence that the bone graft shows some resorption in buccolingual width over time.29,30 In the interval between the bone graft procedure and comprehensive orthodontic treatment, some resorption may occur. In this way, the buccolingual width of the alveolar ridge at the grafted area may have some constriction by the time the maxillary canines are mesially moved. The question is whether this possible atrophy can compromise the final
periodontal bone support of the maxillary canines at the cleft side.
A previous study in noncleft patients found a mean buccal alveolar bone thickness varying between 0.33 and 0.60 mm, similar to the control teeth.39,40 The cleft-side canines in this study showed a mean buccal alveolar bone thickness of 0.2 mm (Table). Despite being thinner, the buccal bone plate was seen in most of the maxillary canines moved into the grafted area. In other words, the buccal aspect of the maxillary canine was protected by a bone cover after orthodontic treatment. The lingual bone plate of the maxillary canines at the cleft-side showed a mean thickness of 1.4 mm at the molar furcation level, similar to the control teeth (Table). Bone plate thickness is reported to vary between 0.89 and 6.0 mm on the lingual aspect of the maxillary canines.39,40
Fig 5. Cleft-side canine cross sections in the complete sample.
Fig 6. Noncleft side canine cross sections in the complete sample.
Fig 7. Noncleft side lateral incisor cross sections in the complete sample.
The maximum distance from the CEJ to the alveolar crest is 2 mm.41-43 In the absence of periodontal disease, greater distances between the CEJ and the buccal or lingual alveolar crest are recognized as bone dehiscences. The average of the buccal alveolar crest heights of the cleft-side canines was 2.58 mm, with no differences with the control teeth, which showed buccal alveolar crest heights of 1.95 and 2.06 mm for the NC3 and NC2, respectively (Table). A normal bone crest level in the teeth close to the cleft has been observed before alveolar graft procedures.44 However, the movement of
maxillary canines, with great root volumes, into the grafted area, which may have a certain buccolingual atrophy, could have caused bone dehiscence. Figure 5 shows that buccal bone dehiscence (distance between CEJ and alveolar crest .2 mm) on the cleft-side canines occurred in 17 of the 30 patients. However, only 4 patients showed moderate to severe buccal bone dehiscences, whereas 13 had mild dehiscences. Previous studies have analyzed
teeth near the cleft after an alveolar bone graft with periapical radiographs and found no significant bone loss in the mesial and distal spects.13,33,45,46 On the other hand, a recent study showed the development of gingival recessions on the labial aspect of the anterior teeth of patients with unilateral CLP in the long term after compensatory orthodontic treatment.47 In our sample, most patients with complete unilateral CLP were treated with orthodontic camouflage and labial tipping of the maxillary anterior teeth. Therefore, it is not clear whether the mild buccal bone loss was due to mesial
movement into the grafted area or to labial tipping of the anterior teeth. The lingual alveolar crest height of the C3 was within normal values (1.87 mm). However, comparison with the control group showed decreased lingual alveolar crest heights for the NC2 (1.02 mm, Table). This difference has a small clinical relevance and might be related to the different root diameters between maxillary canines and lateral incisors. Only 7 of the 30 patients had a
lingual alveolar crest height greater than 2 mm, and the maximum lingual alveolar crest height was 8.76 mm. It is known that bone dehiscences are a predisposing factor for gingival recessions48,49 and that the prevalence of gingival recession of the permanent canines at the cleft side is 10 times higher than in patients with no oral clefts.50 In this perspective, a gingival graft should be recommended when a deficient amount of keratinized mucosa is observed in teeth with bone dehiscences near the cleft. In other words, the posttreatment CBCT examination had a clinical benefit for our patients because the 3-dimensional images may change the periodontal treatment planning. When buccal bone dehiscences were diagnosed in the CBCT
images, the periodontist could indicate gingival graft procedures in patients with deficient keratinized mucosa and also consider frenulum removal and buccal sulcoplasty for these patients. On the other hand, in patients with a normal alveolar crest level, the periodontist could be more conservative and avoid a gingival graft against a deficiency of keratinized mucosa when a good level of oral hygiene is observed.
CONCLUSIONS
Our findings suggest that orthodontic movement of maxillary canines into grafted alveolar bone is a viable treatment option with satisfying periodontal results. The orthodontist should work with the periodontist in an interdisciplinarymanner to provide slow tooth movement in the absence of precipitant factors for gingival recessions, such as gingival inflammation, a deficient amount of keratinized mucosa, and a low labial frenulum.51-54 The null hypothesis was rejected. Maxillary canines moved into the grafted alveolar cleft have different buccal and lingual alveolar bone morphologies than
noncleft side canines and lateral incisors. However, the differences are slight and do not contraindicate canine substitution during comprehensive orthodontic treatment. Future studies should also assess the mesial and distal alveolar bone of canines moved into the grafted alveolar area by means of CBCT.
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