Introduction
The purposes of this study were to identify buccolingual inclinations and alveolar bone thickness in patients with Class III dentofacial deformities and to compare these measurements with those from subjects with normal occlusions to verify, based on the correlation between these 2 variables, whether the natural process of bone remodeling provides uniformity of bone thickness or whether it varies around the roots due to tooth inclination.
Methods
The sample consisted of 35 adults with normal occlusions and 35 adults with Class III dentofacial deformities with no previous orthodontic treatment. Buccolingual inclinations and alveolar bone thickness were measured at 3 heights from the cementoenamel junction from 3-dimensional images generated by cone-beam computed tomography.
Results
The region corresponding to the maxillary canines appeared to be thinner, and the palatal area of the maxillary central incisors and the distobuccal region of the mandibular second molars appeared to be thicker. Greater tooth inclinations were observed in the maxillary incisors and mandibular canines, and smaller tooth inclinations were observed on the buccal roots of the mandibular second molars.
Conclusions
In subjects with Class III deformities, more statistically significant correlations were found between inclination and thickness in the mandibular teeth, whereas in subjects with normal occlusion, few statistically significant correlations were found between these 2 variables.
Highlights
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We measured buccolingual inclinations and alveolar bone thicknesses.
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We compared normal occlusion subjects and those with Class III dentofacial deformities.
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Greater buccolingual inclinations were observed in the maxillary incisors in both groups.
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Average thicknesses were lower in Class III subjects than in those with normal occlusion.
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Few significant correlations were found between alveolar thickness and tooth inclination.
The assessment of the anatomic relationships between craniofacial structures provides the data necessary for orthodontic treatment planning. However, when we specifically plan the orthodontic movement so that treatment goals are achieved regardless of the orthodontic technique, the patient’s biologic limits are extremely important. Part of the importance of evaluating the maxillomandibular alveolar bone morphology is that it defines the limits of orthodontic tooth movement, and overcoming this limit can result in iatrogenic side effects to periodontal support and protection, such as dehiscences and fenestration. Initial efforts to define the effect of tooth movement toward the buccal and lingual bone plates have focused on animal and human studies using lateral and frontal cephalometric radiographs. However, these radiographic methods are susceptible to intrinsic errors from overlapping anatomic structures, difficulties in identification of dental elements, and magnification errors caused by divergence of the radiation beam. Despite the methodologic limitations, the results of previous studies have shown that the cortical bone is a natural anatomic barrier to tooth movement.
Studies regarding the measurement of the buccal and lingual alveolar bone thicknesses had a great advance with cone-beam computed tomography (CBCT), because this method enables the examination of alveolar bone morphology with quality because 3-dimensional images are not subject to distortion or overlap. Furthermore, the secondary computerized reconstructions also facilitate the quantitative and qualitative evaluations of bone surfaces and the relationship between the alveolar bone and the teeth. The effect of tooth movement on the alveolar bone as evaluated by CBCT scans can change the usual planning, indicating the limits of the therapeutic possibilities in orthodontics.
Linear and angular measurements from CBCT images have been considered accurate for the evaluation of dental and maxillofacial structures. With this method of examination, it is possible to measure the thickness of alveolar bone around the roots. CBCT is more accurate than intraoral radiographs in detecting buccal and lingual periodontal defects and changes in bone level during orthodontic treatment. Periapical and interproximal radiographs and lateral cephalometric radiographs show image distortions that are inherent to the method because of divergence of the x-ray beam. Furthermore, because the cortical bone of the palate and the symphysis drawn on cephalometric radiographs represent a 2-dimensional visualization of a concave surface, the actual limit of these structures may be narrower than the image drawn on radiographs.
Because histologic cross sections are not a realistic option in patients and routine soft-tissue reflection is impractical and potentially damaging, CBCT imaging can be a good option for evaluating periodontal tissues, but some studies have shown that CBCT is not as reliable in assessing fenestrations and dehiscences, with measurement errors between direct measurements and CBCT-derived measurements. However, Timock et al concluded that mean errors between CBCT and direct measurements of buccal bone height and buccal bone thickness were small (0.30 and 0.13 mm, respectively) and showed no statistically significant differences or bias to underestimate or overestimate.
This study was performed to determine the alveolar bone thickness and buccolingual inclinations of the maxillary and mandibular teeth from CBCT scans and to evaluate the correlations between these 2 variables in subjects with Class III dentofacial deformities and in periodontally healthy subjects with normal occlusion, balanced profiles, and no orthodontic treatment history. The purpose of determining the amplitudes of dental inclinations and alveolar bone thickness on the buccal and lingual areas corresponding to each tooth in our sample was to determine whether it is possible to assess whether the natural bone remodeling process provides uniformity in alveolar thickness or whether the alveolar thickness around the roots of the teeth varies with tooth inclination in subjects with Class III dentofacial deformities, no history of orthodontic treatment, and compensated teeth. The importance of this study in these 2 groups is that it provides the possibility of establishing normal values of alveolar bone thickness and buccolingual tooth inclination in subjects with normal occlusion, thereby determining the limits of orthodontic tooth movement; this is crucial for decompensation during the presurgical orthodontic phase in patients with Class III dentofacial deformities.
Material and methods
Our sample population was obtained from the collection of the orthodontic preparation for orthognathic surgery clinic of the University of São Paulo in Brazil; the DICOM data of these patients were retrospectively evaluated. Those with normal occlusion were dentists and dental students who were well informed about the radiation dose and consented freely to have CBCT scans. This project was submitted to the ethics committee of the Faculty of Dentistry and approved for subjects with Class I malocclusions (protocol 18/2010) and Class III malocclusions (protocol 19/2010).
The sample consisted of 70 men and women. They were divided into 2 groups according to facial profile and occlusion: group 1 had facial balance and normal occlusion, and group 2 had skeletal Class III malocclusion. Group 1 included 35 adults (16 men, 19 women) aged 19 to 31 years 5 months (mean, 26 years 1 month). The facial analysis was assessed through photo screening by 3 orthodontists (M.S., J.B.P., J.R.N.) previously calibrated. The inclusion criteria of the subjects in this group were lip competence and a balanced facial profile as assessed using the analysis of Arnett and Bergman ( Table I ), complete permanent dentition, good dental and periodontal conditions, Class I molar relationship with the maxillary mesiobuccal cusp tip within 1.5 mm posterior and 1.0 mm anterior of the mandibular molar buccal groove, overbite and overjet within normal limits, crowding less than 4 mm, and good sagittal and vertical relationships between bony bases ( Table II ). Records of patients in this group came from the Department of Orthodontics of the Faculty of Dentistry.
| Measurement | Norm | |
|---|---|---|
| Frontal facial analysis | ||
| Proportion of facial thirds | 55-65 mm | 55-65 mm vertically |
| Upper lip length | 19-22 mm | 19-22 mm |
| Lower lip length | 38-44 mm | 38-44 mm |
| Upper tooth to lip relationship | 1-5 mm | 1-5 mm |
| Interlabial gap | 1-3 mm | 1-5 mm |
| Profile facial analysis | ||
| Maxillary sulcus contour | Gently curved | Gently curved |
| Mandibular sulcus contour | Gently curved | Gently curved |
| Cheekbone contour | Not flat | Does not appear flat |
| Measurements | ||
|---|---|---|
| Group 1 | Group 2 | |
| ANB (°) | 2.69 ± 1.76 | −3.78 ± 4.07 |
| SNA (°) | 81.88 ± 3.88 | 82.18 ± 3.44 |
| SNB (°) | 79.20 ± 3.85 | 85.92 ± 3.72 |
| Nperp-A (mm) | 2.10 ± 3.44 | −0.96 ± 4.08 |
| Nperp-Pog (mm) | 1.54 ± 6.58 | 6.62 ± 7.48 |
| Co-A (mm) | 85.77 ± 12.27 | 92.28 ± 7.35 |
| Co-Gn (mm) | 115.45 ± 15.76 | 136.62 ± 9.3 |
| SN.GoGn (°) | 32.49 ± 4.68 | 32.5 ± 7.98 |
| IMPA (°) | 94.43 ± 5.69 | 81.92 ± 8.5 |
Group 2 included 35 adults (18 men, 17 women) aged 18 to 41 years 7 months (mean, 26 years 1 month), who were selected according to the following criteria: skeletal Class III malocclusion, complete permanent dentition, good dental and periodontal conditions such as no bleeding on probing and probing depths under 3 mm, indication for orthodontic-surgical treatment, finalized craniofacial growth, no previous orthodontic-surgical treatment, and no local or general contraindications for surgery ( Table II ). Their periodontal status was evaluated by a periodontic specialist (M.S.) using a Michigan periodontal probe. The probing depth was measured by the depth of penetration of the probe when held parallel to the vertical axis of the tooth. Another important clinical aspect of analyzing the periodontal condition is gingival bleeding on probing, which indicates acute gingival inflammation.
The subjects underwent CBCT in an i-CAT device (Imaging Sciences International, Hatfield, Pa), at 120 kVp, 47.74 mAs, and extended height protocol. The image detector device consisted of an amorphous 20 × 25 cm flat panel in a 14-bit gray scale. All 3-dimensional models were reconstructed from images obtained with voxel dimensions of 0.4 mm. To obtain natural head position, subjects were positioned using Dolphin 3-dimensional software (version 10.5 premium; Dolphin Imaging and Management Solutions, Chatsworth, Calif) to show the soft tissues, primarily in the coronal view, and also in the sagittal and axial views. The position was defined and saved upon agreement of 4 calibrated orthodontists (M.S., J.B.P., J.A., J.R.N.). To minimize the potential positioning errors of the head while obtaining the CBCT scan, all images in groups 1 and 2 were reoriented using the protocol of Cevidanes et al, with the simulated natural head position orientation obtained without any guide planes but, rather, by each observer’s subjective interpretation of the plane of vision that best defined the true horizontal plane.
Measurements of alveolar bone thickness were performed by importing the DICOM files into the Dolphin software and selecting the axial, coronal, and sagittal visualization displays. All 3 displays were simultaneously selected, but only one was amplified, as shown in Figure 1 , A .
The next step involved magnification of the sagittal view and selection of the height of the measurement (in the maxilla or mandible), as indicated by the blue horizontal lines in Figure 1 , B and C . The measurements were performed 3, 6, and 8 mm from the cementoenamel junction in the apical direction as seen in the axial view ( Figs 1, D , and 2 ). The most buccal region of the tooth root, seen in the axial section of the CBCT image, was measured.
Buccolingual inclinations of the maxillary and mandibular posterior teeth (premolars and molars) and canines were examined in the coronal view using the horizontal line displayed by the program as a reference (Dolphin 3D), which represents the true horizontal line of the patient because the patient was positioned in natural head position. This line was positioned superior to the apex of the maxillary teeth and inferior to the apex of the mandibular teeth. The maxillary incisors (central and lateral) were measured in relation to the palatal plane and observed in the sagittal view.
The mandibular incisors were measured in relation to the mandibular plane, which was also observed in the sagittal view ( Figs 3 and 4 ).
After the initial CBCT scan, 20% of the sample was remeasured 14 days later. Intraclass correlation coefficients were used to evaluate agreement between evaluators, and Dahlberg’s formula was used to determine the random error.
Statistical analysis
To accomplish the study objectives, an average was first determined using measurements obtained from the right and left sides of the mouth. With the Kolmogorov-Smirnov test, the mean outcome measurements were examined for a normality probability distribution. Summary measurements, including the averages for each tooth, site, and height (3, 6, 8 mm), were calculated to describe the data (mean, standard deviation, range with 95% confidence intervals for the mean, median, minimum, and maximum) ( Tables III–VII ). The Pearson correlation test was used to confirm the correlation between inclination and thickness ( Tables VIII and IX ). The tests were performed at a 5% significance level.
| Variable | Group 1 | Group 2 | Total | P |
|---|---|---|---|---|
| Sex, n (%) | 0.632 ∗ | |||
| Female | 19 (54.3) | 17 (48.6) | 36 (51.4) | |
| Male | 16 (45.7) | 18 (51.4) | 34 (48.6) | |
| Age (y) | 0.365 † | |||
| Average (SD) | 26.1 (3.3) | 27.1 (5.7) | 26.6 (4.6) |
| Maxillary teeth | 3 mm Average and SD |
6 mm Average and SD |
8 mm Average and SD |
||||||
|---|---|---|---|---|---|---|---|---|---|
| MB | DB | P | MB | DB | P | MB | DB | P | |
| First molar | 0.5 ± 0.1 | 0.8 ± 0.4 | 0.6 ± 0.2 | 0.6 ± 0.2 | 1.0 ± 0.6 | 0.8 ± 0.2 | 0.6 ± 0.3 | 1.1 ± 0.7 | 1.1 ± 0.4 |
| Second molar | 0.6 ± 0.4 | 0.9 ± 0.5 | 0.9 ± 0.2 | 1.4 ± 0.5 | 1.6 ± 0.6 | 1.1 ± 0.5 | 1.9 ± 0.7 | 1.9 ± 0.8 | 1.3 ± 0.6 |
| Buccal | Palatal | Buccal | Palatal | Buccal | Palatal | |
|---|---|---|---|---|---|---|
| First premolar | 0.4 ± 0.1 | 0.5 ± 0.1 | 0.6 ± 0.3 | 0.8 ± 0.2 | 0.7 ± 0.3 | 1.3 ± 0.5 |
| Second premolar | 0.6 ± 0.3 | 0.6 ± 0.2 | 1.0 ± 0.5 | 1.1 ± 0.4 | 1.2 ± 0.7 | 1.7 ± 0.6 |
| Canine | 0.4 ± 0.0 | 0.6 ± 0.3 | 0.5 ± 0.2 | 1.0 ± 0.6 | 0.6 ± 0.3 | 1.4 ± 0.7 |
| Lateral incisor | 0.5 ± 0.2 | 0.5 ± 0.2 | 0.7 ± 0.3 | 0.8 ± 0.5 | 0.8 ± 0.4 | 1.2 ± 0.8 |
| Central incisor | 0.5 ± 0.1 | 0.7 ± 0.3 | 0.7 ± 0.2 | 1.3 ± 0.6 | 0.8 ± 0.3 | 2.1 ± 0.8 |
| Mandibular teeth | 3 mm Average and SD |
6 mm Average and SD |
8 mm Average and SD |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| MB | DB | ML | DL | MB | DB | ML | DL | MB | DB | ML | DL | |
| First molar | 0.4 ± 0.0 | 0.5 ± 0.2 | 0.9 ± 0.3 | 1.5 ± 0.5 | 0.5 ± 0.1 | 1.0 ± 0.7 | 1.7 ± 0.5 | 2.6 ± 0.6 | 0.8 ± 0.5 | 1.6 ± 0.9 | 2.4 ± 0.6 | 3.2 ± 0.8 |
| Second molar | 1.2 ± 1.1 | 2.7 ± 1.7 | 1.2 ± 0.6 | 1.7 ± 0.7 | 2.6 ± 1.4 | 4.4 ± 1.5 | 2.1 ± 0.6 | 2.4 ± 0.7 | 3.7 ± 1.5 | 5.2 ± 1.4 | 2.5 ± 0.7 | 2.6 ± 1.0 |
| Buccal | Lingual | Buccal | Lingual | Buccal | Lingual | |
|---|---|---|---|---|---|---|
| First premolar | 0.4 ± 0.02 | 0.8 ± 0.55 | 0.4 ± 0.05 | 1.5 ± 0.75 | 0.4 ± 0.11 | 1.9 ± 0.76 |
| Second premolar | 0.4 ± 0.06 | 0.8 ± 0.40 | 0.5 ± 0.15 | 1.8 ± 0.69 | 0.6 ± 0.30 | 2.4 ± 0.75 |
| Canine | 0.4 ± 0.02 | 0.4 ± 0.11 | 0.4 ± 0.03 | 0.7 ± 0.33 | 0.4 ± 0.04 | 0.9 ± 0.43 |
| Lateral incisor | 0.4 ± 0.01 | 0.4 ± 0.09 | 0.4 ± 0.02 | 0.4 ± 0.17 | 0.4 ± 0.06 | 0.6 ± 0.38 |
| Central incisor | 0.4 ± 0.04 | 0.4 ± 0.04 | 0.4 ± 0.05 | 0.4 ± 0.12 | 0.5 ± 0.25 | 0.5 + 0.22 |
| Maxillary teeth | 3 mm Average and SD |
6 mm Average and SD |
8 mm Average and SD |
||||||
|---|---|---|---|---|---|---|---|---|---|
| MB | DB | P | MB | DB | P | MB | DB | P | |
| First molar | 1.0 ± 0.4 | 1.5 ± 0.5 | 1.3 ± 0.4 | 1.1 ± 0.5 | 1.6 ± 0.6 | 1.4 ± 0.4 | 1.2 ± 0.6 | 1.7 ± 0.9 | 1.5 ± 0.5 |
| Second molar | 1.3 ± 0.6 | 1.4 ± 0.6 | 1.4 ± 0.6 | 2.0 ± 0.7 | 1.8 ± 0.7 | 1.3 ± 0.5 | 2.4 ± 1.2 | 2.1 ± 1.0 | 1.2 ± 0.5 |
| Buccal | Palatal | Buccal | Palatal | Buccal | Palatal | |
|---|---|---|---|---|---|---|
| First premolar | 0.7 ± 0.3 | 0.9 ± 0.3 | 1.0 ± 0.4 | 1.7 ± 0.5 | 1.0 ± 0.4 | 2.4 ± 0.7 |
| Second premolar | 1.3 ± 0.5 | 1.2 ± 0.4 | 1.5 ± 0.5 | 2.0 ± 0.5 | 1.5 ± 0.6 | 2.9 ± 0.9 |
| Canine | 0.6 ± 0.2 | 0.9 ± 0.5 | 0.8 ± 0.3 | 2.0 ± 0.6 | 0.9 ± 0.3 | 2.7 ± 0.8 |
| Lateral incisor | 0.8 ± 0.3 | 1.1 ± 0.4 | 1.0 ± 0.4 | 2.0 ± 0.7 | 1.0 ± 0.4 | 2.8 ± 0.8 |
| Central incisor | 0.9 ± 0.2 | 1.5 ± 0.5 | 1.0 ± 0.3 | 2.6 ± 0.8 | 1.1 ± 0.4 | 3.6 ± 0.9 |
| Mandibular teeth | 3 mm Average and SD |
6 mm Average and SD |
8 mm Average and SD |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| MB | DB | ML | DL | MB | DB | ML | DL | MB | DB | ML | DL | |
| First molar | 1.0 ± 0.4 | 1.7 ± 0.7 | 2.1 ± 0.8 | 2.5 ± 0.7 | 1.6 ± 0.7 | 2.8 ± 1.2 | 3.2 ± 0.8 | 3.6 ± 0.8 | 2.3 ± 1.0 | 3.5 ± 1.5 | 3.8 ± 0.8 | 4.1 ± 1.0 |
| Second molar | 2.8 ± 1.5 | 4.6 ± 2.0 | 2.2 ± 0.6 | 2.8 ± 0.8 | 4.5 ± 1.6 | 6.4 ± 1.7 | 3.0 ± 0.7 | 3.2 ± 1.0 | 5.6 ± 1.6 | 7.1 ± 1.6 | 3.3 ± 1.0 | 3.3 ± 1.2 |
| Buccal | Lingual | Buccal | Lingual | Buccal | Lingual | |
|---|---|---|---|---|---|---|
| First premolar | 0.5 ± 0.1 | 2.2 ± 1.2 | 0.8 ± 0.4 | 3.3 ± 1.3 | 1.2 ± 0.7 | 3.7 ± 1.4 |
| Second premolar | 0.8 ± 0.3 | 2.1 ± 0.9 | 1.4 ± 0.6 | 3.3 ± 1.1 | 1.8 ± 0.8 | 3.8 ± 1.3 |
| Canine | 0.5 ± 0.1 | 1.3 ± 0.8 | 0.6 ± 0.2 | 2.0 ± 1.0 | 0.9 ± 0.4 | 2.4 ± 0.9 |
| Lateral incisor | 0.5 ± 0.1 | 0.7 ± 0.2 | 0.7 ± 0.2 | 1.1 ± 0.4 | 1.0 ± 0.5 | 1.5 ± 0.6 |
| Central incisor | 0.5 ± 0.1 | 0.5 ± 0.2 | 0.8 ± 0.4 | 0.9 ± 0.4 | 1.5 ± 0.7 | 1.3 + 0.6 |
| Variable | Correlation | n | P |
|---|---|---|---|
| Inclination of mesiobuccal root of mandibular second molar | |||
| Mesiobuccal alveolar thickness of second molar at 3 mm | −0.447 | 35 | 0.007 |
| Mesiobuccal alveolar thickness of second molar at 6 mm | −0.355 | 35 | 0.037 |
| Mesiolingual alveolar thickness of second molar at 3 mm | 0.368 | 35 | 0.030 |
| Inclination of mandibular second premolar | |||
| Lingual alveolar thickness of second premolar at 3 mm | 0.559 | 35 | <0.001 |
| Inclination of mandibular canine | |||
| Lingual alveolar thickness of canine at 3 mm | 0.528 | 35 | 0.001 |
| Lingual alveolar thickness of canine at 6 mm | 0.481 | 35 | 0.003 |
| Lingual alveolar thickness of canine at 8 mm | 0.412 | 35 | 0.014 |
| Inclination of mandibular central incisor | |||
| Lingual alveolar thickness of central incisor at 6 mm | 0.412 | 35 | 0.014 |
| Inclination of the distobuccal root of maxillary second molar | |||
| Distobuccal alveolar thickness of second molar at 3 mm | 0.560 | 35 | <0.001 |
| Inclination of the palatal root of maxillary second molar | |||
| Palatal alveolar thickness of second molar at 8 mm | −0.469 | 35 | 0.004 |
| Inclination of palatal root of maxillary first molar | |||
| Palatal alveolar thickness of first molar at 8 mm | −0.392 | 35 | 0.020 |
| Inclination of maxillary canine | |||
| Palatal alveolar thickness of canine at 6 mm | 0.394 | 35 | 0.019 |
| Variable | Correlation | n | P |
|---|---|---|---|
| Inclination of the distobuccal root of maxillary second molar | |||
| Distobuccal alveolar thickness of second molar at 8 mm | −0.403 | 35 | 0.016 ∗ |
| Inclination of the palatal root of maxillary second molar | |||
| Palatal alveolar thickness of second molar at 6 mm | −0.433 | 35 | 0.009 ∗ |
| Palatal alveolar thickness of second molar at 8 mm | −0.400 | 35 | 0.017 ∗ |
| Inclination of maxillary central incisor | |||
| Palatal alveolar thickness of central incisor at 8 mm | −0.375 | 35 | 0.026 ∗ |
| Inclination of mesiobuccal root of mandibular first molar | |||
| Mesiobuccal alveolar thickness of first molar at 8 mm | −0.348 | 35 | 0.041 ∗ |
| Inclination of mandibular second premolar | |||
| Buccal alveolar thickness of second premolar at 3 mm | 0.341 | 35 | 0.045 ∗ |
We expected to identify correlations of at least 0.5 between the measures studied; thus, with 80% power and 95% confidence, the sample required for the study was 30 people for each group.
Results
The normal distribution test results showed that most measurements had a normal probability distribution that resulted in the use of parametric correlations.
The thickness measurements were highly reproducible, as indicated by the intraclass correlation values that were greater than 0.9. The error measurements, which obtained using Dahlberg’s formula, did not exceed 0.2 mm for any measurement. The reproducibility of the tooth inclination measurements was nearly perfect, as indicated by intraclass correlation values greater than 0.99 and the error measurements of 0.4° or less, obtained with Dahlberg’s formula.
Table III shows no statistically significant association in terms of sex between the groups ( P = 0.632) and that the mean ages were statistically similar between groups ( P = 0.365). The thinnest alveolar bone was observed in the regions of the mesiobuccal roots of the first molars and the buccal surfaces of the first premolars and canines in the maxilla, and over the mesiobuccal roots of the first molars and the buccal surfaces of the first and second premolars, canines, and incisors in the mandible. The greatest alveolar bone thickness was observed in the distobuccal region of the mandibular second molar at any height evaluated. These data suggest lower values of the measurements at 3 mm from the cementoenamel junction in group 2 subjects (Class III) ( Tables IV and V ).
The maxillary incisors had the highest inclinations; in the mandible, the canines had the highest inclinations. Smaller inclinations were observed for the buccal roots of the maxillary and mandibular second molars in subjects with Class III dentofacial deformities.
Few statistically significant correlations were observed between the inclination and thickness of the maxillary teeth in subjects with Class III dentofacial deformities ( P <0.05). Statistically significant inverse correlations were observed in the palatine surfaces of the first and second molars at 8 mm; direct correlations were observed in the palatine surface of the maxillary canine at 6 mm and in the distobuccal region of the maxillary second molar at 3 mm ( Table VIII ). In subjects with Class III dentofacial deformities, there were more statistically significant correlations between inclination and thickness on the mandibular teeth ( P <0.05) compared with the maxillary teeth ( Table VII ). Similar results were observed in subjects with normal occlusion because few statistically significant correlations between inclination and thickness ( P <0.05) were observed in the maxillary and mandibular arches ( Table IX ).
For a comparison of bone thicknesses between the 2 groups, we evaluated the heights at 3 and 8 mm from the cementoenamel junction, where heights of 3 and 8 mm corresponded to the cervical portion and the apical region, respectively. The average thickness at 3 mm was significantly less in Class III subjects compared with those with normal occlusion ( Table X ). Moreover, the alveolar thickness at 8 mm had lower values in subjects with Class III dentofacial deformities compared with those with normal occlusion except in the area corresponding to the palatal root of the second molar. All evaluated regions were statistically significant ( P <0.05), except for the distobuccal and palatine areas of the maxillary second molar and the buccal area of the maxillary lateral incisor ( Table XI ).
| Variable | Group 1 | Group 2 | Average difference | 95% CI | P | |||
|---|---|---|---|---|---|---|---|---|
| Average | SD | Average | SD | Lower | Upper | |||
| Mesiobuccal maxillary first molar | 1.0 | 0.4 | 0.5 | 0.1 | 0.5 | 0.36 | 0.70 | <0.001 |
| Distobuccal maxillary first molar | 1.5 | 0.5 | 0.8 | 0.4 | 0.7 | 0.51 | 0.99 | <0.001 |
| Palatal maxillary first molar | 1.3 | 0.4 | 0.6 | 0.2 | 0.6 | 0.51 | 0.83 | <0.001 |
| Mesiobucca maxillary second molar | 1.3 | 0.6 | 0.6 | 0.4 | 0.6 | 0.39 | 0.92 | <0.001 |
| Distobuccal maxillary second molar | 1.4 | 0.6 | 0.9 | 0.5 | 0.5 | 0.24 | 0.81 | 0.001 |
| Palatal maxillary second molar | 1.4 | 0.6 | 0.9 | 0.2 | 0.5 | 0.27 | 0.74 | <0.001 |
| Buccal maxillary first premolar | 0.7 | 0.3 | 0.4 | 0.1 | 0.3 | 0.18 | 0.42 | <0.001 |
| Palatal maxillary first premolar | 0.9 | 0.3 | 0.5 | 0.1 | 0.4 | 0.31 | 0.54 | <0.001 |
| Buccal maxillary second premolar | 1.3 | 0.5 | 0.6 | 0.3 | 0.6 | 0.41 | 0.83 | <0.001 |
| Palatal maxillary second premolar | 1.2 | 0.4 | 0.6 | 0.2 | 0.5 | 0.43 | 0.74 | <0.001 |
| Buccal maxillary canine | 0.6 | 0.2 | 0.4 | 0.0 | 0.2 | 0.17 | 0.34 | <0.001 |
| Palatal maxillary canine | 0.9 | 0.5 | 0.6 | 0.3 | 0.3 | 0.16 | 0.58 | 0.001 |
| Buccal maxillary lateral incisor | 0.8 | 0.3 | 0.5 | 0.2 | 0.3 | 0.20 | 0.49 | <0.001 |
| Palatal maxillary lateral incisor | 1.1 | 0.4 | 0.5 | 0.2 | 0.6 | 0.45 | 0.81 | <0.001 |
| Buccal maxillary central incisor | 0.9 | 0.2 | 0.5 | 0.1 | 0.3 | 0.21 | 0.44 | <0.001 |
| Palatal maxillary central incisor | 1.5 | 0.5 | 0.7 | 0.3 | 0.8 | 0.59 | 1.03 | <0.001 |
| Mesiobuccal mandibular first molar | 1.0 | 0.4 | 0.4 | 0.0 | 0.6 | 0.46 | 0.75 | <0.001 |
| Distobuccal mandibular first molar | 1.7 | 0.7 | 0.5 | 0.2 | 1.2 | 0.94 | 1.48 | <0.001 |
| Mesiolingual mandibular first molar | 2.1 | 0.8 | 0.9 | 0.3 | 1.1 | 0.83 | 1.49 | <0.001 |
| Distolingual mandibular first molar | 2.5 | 0.7 | 1.5 | 0.5 | 0.9 | 0.64 | 1.28 | <0.001 |
| Mesiobuccal mandibular second molar | 2.8 | 1.5 | 1.2 | 1.1 | 1.5 | 0.91 | 2.21 | <0.001 |
| Distobuccal mandibular second molar | 4.6 | 2.0 | 2.7 | 1.7 | 1.9 | 1.00 | 2.81 | <0.001 |
| Mesiolingual mandibular second molar | 2.2 | 0.6 | 1.2 | 0.6 | 1.0 | 0.76 | 1.37 | <0.001 |
| Distolingual mandibular second molar | 2.8 | 0.8 | 1.7 | 0.7 | 1.0 | 0.69 | 1.43 | <0.001 |
| Buccal mandibular first premolar | 0.5 | 0.1 | 0.4 | 0.0 | 0.1 | 0.11 | 0.17 | <0.001 |
| Lingual mandibular first premolar | 2.2 | 1.2 | 0.8 | 0.5 | 1.4 | 0.94 | 1.88 | <0.001 |
| Buccal mandibular second premolar | 0.8 | 0.3 | 0.4 | 0.0 | 0.4 | 0.32 | 0.53 | <0.001 |
| Lingual mandibular second premolar | 2.1 | 0.9 | 0.8 | 0.4 | 1.2 | 0.88 | 1.61 | <0.001 |
| Buccal mandibular canine | 0.5 | 0.1 | 0.4 | 0.0 | 0.1 | 0.11 | 0.24 | <0.001 |
| Lingual mandibular canine | 1.3 | 0.8 | 0.4 | 0.1 | 0.8 | 0.58 | 1.15 | <0.001 |
| Buccal mandibular lateral incisor | 0.5 | 0.1 | 0.4 | 0.0 | 0.1 | 0.13 | 0.22 | <0.001 |
| Lingual mandibular lateral incisor | 0.7 | 0.2 | 0.4 | 0.0 | 0.2 | 0.17 | 0.38 | <0.001 |
| Buccal mandibular central incisor | 0.5 | 0.1 | 0.4 | 0.0 | 0.1 | 0.11 | 0.22 | <0.001 |
| Lingual mandibular central incisor | 0.5 | 0.2 | 0.4 | 0.0 | 0.1 | 0.09 | 0.26 | <0.001 |
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