Introduction
The aim of this study was to compare the presence of alveolar defects (dehiscence and fenestration) in patients with Class I and Class II Division 1 malocclusions and different facial types.
Methods
Seventy-nine Class I and 80 Class II patients with no previous orthodontic treatment were evaluated using cone-beam computed tomography. The sample included 4319 teeth. All teeth were analyzed by 2 examiners who evaluated sectional images in axial and cross-sectional views to check for the presence or absence of dehiscence and fenestration on the buccal and lingual surfaces.
Results
Dehiscence was associated with 51.09% of all teeth, and fenestration with 36.51%. The Class I malocclusion patients had a greater prevalence of dehiscence: 35% higher than those with Class II Division 1 malocclusion ( P <0.01). There was no statistically significant difference between the facial types.
Conclusions
Alveolar defects are a common finding before orthodontic treatment, especially in Class I patients, but they are not related to the facial types.
Orthodontic movement is achieved by biologic events in bone remodeling (resorption and apposition) of the alveolar process, which supports the teeth with involvement of the roots. Since bone resorption occurs in the direction of tooth movement, the reduced volume of the alveolar bone, sometimes with minimal thickness, sometimes even nonexistent, is a complicating factor for orthodontic treatment.
Previous studies and case reports have shown that, as the roots are displaced and move away from the center of the alveolar bone, there is increased risk of creating or exacerbating alveolar defects and producing consequent mucogingival changes, such as gingival recession. The lack of the facial or lingual cortical plate, which resulted in exposing the cervical root surface and affecting the marginal bone, represents an alveolar defect called dehiscence. When there is still some bone in the cervical region, the defect is called fenestration. The occurrence of dehiscence and fenestration during orthodontic treatment depends on several factors, such as the direction of movement, the frequency and magnitude of orthodontic forces, and the volume and anatomic integrity of the periodontal supporting tissues. To avoid these problems, the alveolar morphology must be determined before orthodontic treatment through imaging, which shows bone topography and anatomy. Currently, cone-beam computed tomography (CBCT) is the option chosen for most clinical dental situations, including the alveolar process, when a cross-sectional examination is indicated, because of its lower dose of radiation, better image resolution, and lower costs compared with multislice computed tomography.
To date, no study has been undertaken to compare the presence of alveolar defects in subjects with various malocclusions. The hypothesis we tested was that there is no difference in bone covering between the various malocclusions. Our aim was to compare the presence of dehiscence and fenestration between patients with Class I and Class II Division 1 malocclusions and different facial types by using CBCT.
Material and methods
This study was approved by the institutional review board of Medical School Charité, Berlin, Germany.
We used pretreatment CBCT examinations of orthodontic patients from the radiological files of the Mesantis private orthodontic clinic in Berlin, Germany. The sample was selected by 1 observer, trained in the use of sectional images, who did not participate in the study. The following inclusion criteria were considered: CBCT examinations of patients over 18, with no previous history of orthodontic treatment; and patient of both sexes with Class I or Class II Division 1 malocclusions, mild-to-moderate crowding, and different facial types. The Class I samples were confirmed by the bilateral Class I molar and canine relationships: ANB between 2° and 4°, and overjet between 1 and 4 mm. The criteria for selecting the Class II Division 1 subjects were bilateral Class II molar and canine relationships, ANB ≥4° and overjet >4 mm. The facial types were divided according to NS.GoGn proposed by Reidel, with the mesofacial group measuring from 27° to 37°; the brachyfacial group, <27°; and the dolichofacial group, ≥37°. All cephalometric measures used in the study were obtained from the original CBCT images. The exclusion criteria included patients with missing teeth and agenesis, and images suggesting periodontal disease such as horizontal or vertical proximal bone loss, furcal involvement, and calculus. Partial and low-resolution images were also excluded from the evaluation, as well as 133 teeth with extensive restorations involving the cementoenamel junction.
A total of 79 Class I and 80 Class II Division 1 malocclusion patients matched the inclusion criteria, giving 4319 teeth to be evaluated. The power analysis determined that a sample size of 139 patients would be sufficient to detect a 5% difference between malocclusion groups. The distribution of the malocclusion and facial types of all subjects is shown in Table I . Tables II and III show the sample characteristics according to malocclusion and facial type.
| Facial type Malocclusion |
Brachyfacial | Mesofacial | Dolichofacial | Total |
|---|---|---|---|---|
| Class I | 32 | 29 | 18 | 79 |
| Class II Division 1 |
27 | 30 | 23 | 80 |
| Total | 59 | 59 | 41 | 159 |
| Class I | Class II Division 1 | |
|---|---|---|
| Age (y) | 27.09 (7.46) | 26.48 (8.18) |
| ANB (°) | 2.52 (1.96) | 6.66 (1.96) |
| Overjet (mm) | 2.61 (0.86) | 5.72 (1.13) |
| NS.GoGn (°) | 29.32 (6.48) | 30.98 (6.63) |
| Brachyfacial | Mesofacial | Dolichofacial | |
|---|---|---|---|
| NS.GoGn(°) | 23.41 (3.28) | 31.07 (1.74) | 38.77 (2.86) |
The images were obtained by using i-CAT tomography (Imaging Sciences International, Hatfield, Pa), with 47.7 mA, 120 kV, 40-second exposure time, and isotropic voxel size of 0.25 × 0.25 × 0.25 mm. The imaging protocol was performed with a 6-in field of view to include the entire facial anatomy. The files were exported to 512 × 512 pixels matrix in DICOM 3 format and processed by using InVivoDental software (Anatomage, San Jose, Calif). The patient’s head was oriented by locating the Frankfurt plane parallel to the horizontal plane and in centric occlusion.
Two calibrated examiners (an orthodontist K.E. and a dentist K.F.V.) visually examined all the sectional images in a dark room, using a 24.1-in LCD monitor with resolution of 1920 × 1200 pixels. Both observers evaluated the same tomographic views blindly without knowing either the malocclusion or the facial type, or each other’s results. First, the mesiodistal and buccolingual axes of each tooth were placed perpendicular to the horizontal plane. The total length of the root was evaluated in axial and cross-sectional slices at the buccal and lingual surfaces. Images that showed no cortical bone surrounding the root in at least 3 consecutive views were registered as having an alveolar defect. This lack of bone was classified as dehiscence when the alveolar bone height was more than 2 mm from the cementoenamel junction, based on the value for normal alveolar height. It was classified as fenestration when the defect did not involve the alveolar crest. The root length was divided into 3 equal parts, from the cementoenamel junction to apex, to locate the third of the root with the alveolar defect.
After 20 days, an observer repeated the analysis of 25% of the examinations, randomly selected, to verify the reproducibility of the method.
Statistical analysis
The levels of interobserver and intraobserver agreement were assessed by kappa statistics. A descriptive analysis was performed to show the prevalence of the alveolar defects and the most teeth, surfaces, and root thirds affected. Student t and Mann-Whitney tests were applied to compare the malocclusion groups. Analysis of variance (ANOVA) and Kruskal-Wallis tests were used to compare the facial types. The statistical analysis was performed by using an SPSS software package (version 16.0, SPSS, Chicago Ill) at the 0.05 significance level.
Results
Kappa values for interobserver and intraobserver agreement varied from 0.7 to 1.00, which represented good agreement of this method.
The hypothesis tested was not confirmed. Table IV shows the differences between the Class I and Class II Division 1 malocclusion and facial types. The samples with Class I malocclusion had a greater prevalence of alveolar defects, specifically dehiscences, which were 35% higher than in the patients with Class II Division 1 malocclusion ( P <0.01). No difference was found between facial types.
| Alveolar defect | Dehiscence | Fenestration | ||||
|---|---|---|---|---|---|---|
| Number of surfaces | P ∗ | Number of surfaces | P † | Number of surfaces | P ∗ | |
| Malocclusion | ||||||
| Class I | 30.01 (9.45) | <0.01 | 22.36 (12.26) | <0.01 | 11.08 (5.62) | NS |
| Class II Division 1 | 21.78 (10.34) | 14.43 (10.63) | 9.41 (5.52) | |||
| Facial type | ||||||
| Brachyfacial | 26.84 (10.78) | NS | 19.52 (12.19) | NS | 10.16 (5.49) | NS |
| Mesofacial | 24.90 (10.82) | 17.31 (12.33) | 10.45 (5.91) | |||
| Dolichofacial | 25.85 (10.56) | 18.27 (11.78) | 10.05 (5.49) | |||
Tables V, VI, and VII show the incidences of alveolar defects. There were more alveolar defects (75.65%) on the buccal root surfaces. Dehiscence was associated with 51.09% of all teeth, with greater prevalence in the mandible (57.35%). Dehiscence was also more predominant on the buccal root surface (69.43%), with the exception of the mandibular central incisors, which had equal distributions on the buccal and lingual surfaces. Large dehiscences involving the apical root third represented 10.43% of dehiscence defects and were more related to the mandibular incisors (32.19%), maxillary (14.77%) and mandibularr (14.39%) canines, and maxillary first premolars (8.33%). Figure 1 shows axial and cross-sectional views of dehiscence in the mandible in a Class I malocclusion patient. The teeth most affected in mandible were the central (24.33%) and lateral (17.51%) incisors, and the canines (17.13%). In maxilla, canines (18.73%), first premolars (18.45%), and first molars (18.27%) had more occurrences.
| Dehiscence | Fenestration | |||||||
|---|---|---|---|---|---|---|---|---|
| Maxilla | Mandible | Maxilla | Mandible | |||||
| Tooth | n | % | n | % | n | % | n | % |
| 1 | 204 | 9.46 | 706 | 24.33 | 174 | 10.51 | 161 | 21.05 |
| 2 | 288 | 13.35 | 508 | 17.51 | 302 | 18.24 | 194 | 25.36 |
| 3 | 404 | 18.73 | 497 | 17.13 | 296 | 17.87 | 171 | 22.35 |
| 4 | 398 | 18.45 | 481 | 16.58 | 299 | 18.06 | 95 | 12.42 |
| 5 | 226 | 10.48 | 266 | 9.17 | 124 | 7.49 | 68 | 8.89 |
| 6 | 394 | 18.27 | 287 | 9.90 | 269 | 16.24 | 30 | 3.92 |
| 7 | 243 | 11.26 | 156 | 5.38 | 192 | 11.59 | 46 | 6.01 |
| Total | 2157 | 100 | 2901 | 100 | 1656 | 100 | 765 | 100 |
| Buccal | Lingual | Total | ||||
|---|---|---|---|---|---|---|
| n | % | n | % | n | % | |
| Maxilla | 1450 | 28.67 | 707 | 13.98 | 2157 | 42.65 |
| Mandible | 2062 | 40.76 | 839 | 16.59 | 2901 | 57.35 |
| Total | 3512 | 69.43 | 1546 | 30.57 | 5058 | 100 |
