Introduction
This study aimed to evaluate the incidence and distribution of alveolar bone dehiscence and fenestration in skeletal Class III malocclusions with different vertical growth patterns in the anterior region using cone-beam computed tomography (CBCT).
Methods
In this retrospective study, 84 patients with skeletal Class III malocclusions who underwent CBCT were selected. This study included 28 patients with hypodivergence (mean age, 22.9 ± 3.9 years), 28 with normodivergence (mean age, 21.0 ± 3.0 years), and 28 with hyperdivergence (mean age, 21.0 ± 3.7 years). Teeth in the anterior region were examined using CBCT to detect dehiscence and fenestration. The incidences of dehiscence and fenestration in the anterior teeth region were recorded, and statistical analysis was conducted using SPSS software (version 25.0, IBM, Armonk, NY).
Results
Among the patients with skeletal Class III malocclusions, dehiscence and fenestration were prone to occur in the mandible. Dehiscence and fenestration were more prevalent in patients with hyperdivergence compared with in patients with hypodivergence and normodivergence.
Conclusions
Dehiscence and fenestration are prevalent among patients with skeletal Class III malocclusion. Furthermore, the occurrence of alveolar bone defects is higher in patients with hyperdivergence.
Highlights
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Alveolar bone dehiscence and fenestration are common in patients with a Class III relationship.
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The incidence of alveolar bone defects was higher in the mandible.
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The incidence of alveolar bone defects was higher among patients with hyperdivergence.
Class III malocclusion is relatively more common in Asian populations. Because of its adverse effects on facial esthetics, chewing function, and mental health, patients always have a strong willingness to undergo treatment. Both camouflage treatment and orthodontic orthognathic surgery involve labial or lingual movement of the teeth in the anterior region. However, this process is restricted to the morphology of alveolar bone, as inappropriate tooth movement beyond the limits of the bone causes root resorption, gingival recession, dehiscence, and fenestration. Therefore, it is essential to understand the morphologic features of the alveolar bone in skeletal Class III malocclusions.
Cone-beam computed tomography (CBCT) was first introduced in dentistry in 1998 and has been widely used in the field of orthodontics. , Compared with traditional intraoral radiography, CBCT provides a more accurate method to evaluate periodontal defects in 3 dimensions and shows a high diagnostic value in the detection of dehiscence and fenestration.
Previous studies have indicated that dehiscence and fenestration are prevalent among people who have not undergone orthodontic treatment. Recently, researchers have focused on the distribution of dehiscence and fenestration among those with different types of malocclusion. In 2010, Evangelista et al selected 79 patients with a Class I malocclusion and 80 patients with a Class II Division 1 malocclusion and evaluated the occurrence of dehiscence and fenestration using CBCT; of the 4319 teeth involved, 51.09% had dehiscence, and 36.51% had fenestration; fenestration was more frequently observed in the maxilla, whereas dehiscence occurred more frequently in the mandible. In 2013, Sun et al evaluated the distribution of labial dehiscence and fenestration in the anterior region of 44 patients with skeletal Class III malocclusions and reported that the incidences of dehiscence and fenestration were 61.57% and 31.93%, respectively. The authors also found that the occurrence of alveolar bone defects was higher in the mandible (58.52%) than in the maxilla (41.48%). Yagci et al grouped 123 patients with sagittal facial types to compare the distribution of dehiscence and fenestration among patients with Class I, II, and III malocclusions. Patients with Class II and III malocclusions had a higher incidence of alveolar bone defects than that of those with Class I malocclusions, and dehiscence was more prevalent in the mandible for all groups. These results suggested that sagittal facial type is one of the factors affecting the distribution of dehiscence and fenestration, and the distribution of dehiscence and fenestration was different in the maxilla and mandible.
Li et al found a negative correlation between lingual alveolar bone thickness in the anterior region and the Frankfort-mandibular plane angle among Asians, suggesting that vertical growth patterns may affect the incidence rates of lingual dehiscence and fenestration. Enhos et al used CBCT to compare the distribution of labial dehiscence and fenestration among patients with different vertical growth patterns and found that the incidence of dehiscence was lower among patients with hypodivergence; however, this study did not restrict the sagittal facial types of the included samples. It is unclear whether there are differences in the distribution of dehiscence and fenestration among skeletal Class III malocclusions with different vertical growth patterns.
This study aimed to describe the distribution of dehiscence and fenestration on the labial and lingual sides in the anterior region of skeletal Class III malocclusions and compare differences in the incidence of dehiscence and fenestration among patients with different vertical growth patterns with the overarching aim of providing a theoretical basis for orthodontic treatment. The null hypothesis of our study was that among patients with skeletal Class III malocclusions with different vertical growth patterns, the incidence and distribution of dehiscence and fenestration were not different.
Material and methods
In this retrospective study, between January 2021 and December 2022, Chinese patients who visited the Orthodontic Department of Tianjin Stomatological Hospital and underwent CBCT were screened. The inclusion criteria were as follows: (1) aged 18-30 years, (2) ANB <0°, (3) no obvious crowding (the difference between the required and available space was <2 mm) in the maxillary and mandibular anterior regions, (4) no obvious tooth wear, and (5) no history of orthodontic treatment. The exclusion criteria were (1) imaging suggesting periodontal disease, such as horizontal or vertical bone loss; (2) craniofacial syndromes; (3) history of restorations, trauma, or surgery in the anterior region; or (4) disturbances in the eruption or number of teeth.
A total of 84 patients (39 women and 45 men) with skeletal Class III malocclusion were enrolled. Patients were divided into 3 groups on the basis of their vertical growth patterns, according to the following criteria: hypodivergent group (Mp-SN ≤29° or Mp-FH ≤22°), normodivergent group (29°< Mp-SN <40° and 22°< Mp-FH <32°), and hyperdivergent (Mp-SN ≥40° or MP-FH ≥32°). Each group consisted of 28 patients.
G∗Power (version 3.1.9.7; Franz Faul, Universität Kiel, Kiel, Germany) was used to calculate the sample size; 36 teeth (at least of 18 patients, including bilateral sides) were required for each group on the basis of a power analysis with α = 0.05, 80% power, and an effect size of 0.3.
The study protocol was approved by the Research Ethics Committee of Tianjin Stomatological Hospital (certificate no. PH2023-W-003). All participants signed an informed consent form.
CBCT images were collected using a KaVo 3D eXam CBCT scanner (KaVo Dental, Biberach, Germany) at the Department of Radiology of Tianjin Stomatological Hospital. The reference scanning parameters were as follows: 120 kV, 5 mA, 7-second scanning time, a field of vision of 170 mm, and a voxel size of 0.3 mm. The patient’s head position was adjusted such that the Frankfort plane was parallel to the ground during centric occlusion. The CBCT images were stored in digital imaging and communications in medicine file format and reconstructed in 3 dimensions using Dolphin 3D imaging software (version 11.8; Dolphin Imaging and Management Solutions, Chatsworth, Calif).
In this study, bilateral orbitales (the most inferior point of the orbital rim) and the right porion (the highest point on the upper margin of the external auditory meatus) were selected to build the Frankfort plane. A 3-dimensional reconstruction of the head position was performed and adjusted to ensure that the Frankfort plane was parallel to the horizontal reference line ( Fig 1 ).
With reference to the method introduced by Sun et al, the largest labiolingual section of the tooth was chosen as the measurement plane ( Fig 2 ). The same researcher measured the selected measurement plane, and the reference points and variables are shown in Figure 3 and Table I .
| Reference points and variables | Definition |
|---|---|
| A/A’ | CEJ at the labial or lingual side |
| B/B’ | Alveolar bone crest at the labial or lingual side |
| C/C’ | Coronal boundary of the fenestration |
| D/D’ | Apical boundary of the fenestration |
| d/d’ (mm) | Distance between A and B or A’ and B’ |
| f / f’ (mm) | Distance between C and D or C’ and D’ |
Established criteria were applied to diagnose dehiscence and fenestration. Dehiscence was diagnosed when the alveolar bone defect involved the alveolar bone crest and the distance between the bottom of the V-shaped defect and the cementoenamel junction (CEJ) was >2 mm (ie, d/d’ >2 mm). Fenestration was diagnosed when the alveolar bone was present near the CEJ on the largest labiolingual section and extended toward the root; however, the continuity was interrupted between the alveolar bone crest and root apex (ie, f/f’ >0 mm). , The process of measurement and diagnosis is illustrated in Figure 4 .
All measurements were performed by 1 examiner (S.B.H.), and all of the samples were remeasured at a 2-week interval by another examiner (X.F.F.). The kappa coefficient was used to evaluate interoperator reliability and confirm the reproducibility of the diagnostic method.
Statistical analysis
The incidence of dehiscence and fenestration on the labial and lingual sides of each tooth in the anterior region of the samples was recorded. SPSS software (version 25.0; IBM, Armonk, NY) was used to perform the statistical analysis. χ 2 or Fisher exact tests were used to compare differences in the incidence of dehiscence and fenestration among different vertical growth patterns, and the Bonferroni method was used if multiple comparisons were necessary. P <0.05 was defined as statistically significant.
Results
In regard to demographics, the kappa value was 0.804, indicating a good level of interoperator reliability. The demographic information of the included patients according to different vertical growth patterns is presented in Table II .
| Variable | Hypodivergent | Normodivergent | Hyperdivergent |
|---|---|---|---|
| Sex | |||
| Females | 12 | 14 | 13 |
| Males | 16 | 14 | 15 |
| Total | 28 | 28 | 28 |
| Age, y | 22.9 ± 3.9 | 21.0 ± 3.0 | 21.0 ± 3.7 |
| ANB,° | −2.2 ± 1.9 | −1.9 ± 1.4 | −2.2 ± 2.1 |
| Mp-SN,° | 25.5 ± 2.7 | 33.4 ± 2.0 | 41.3 ± 2.6 |
| Mp-FH, ° | 17.4 ± 2.7 | 24.4 ± 2.2 | 31.1 ± 2.8 |
The results for the distribution of dehiscence and fenestration in the anterior region are presented in Table III . The incidences of labial fenestration and dehiscence in the maxilla were 42.26% and 13.89%, and those in the mandible were 48.81% and 38.29%, respectively. The incidences of palatal fenestration and dehiscence in the maxilla were 0.20% and 4.17%, respectively, and those in the mandible were 1.98% and 25.99%, respectively. Among the included patients with skeletal Class III malocclusions, alveolar bone defects were prone to occur in the mandible.
| Tooth type | Labial side | Palatal/lingual side | ||
|---|---|---|---|---|
| Fenestration | Dehiscence | Fenestration | Dehiscence | |
| Maxillary central incisor | 13 (7.74) | 7 (4.17) | 0 (0.00) | 0 (0.00) |
| Maxillary lateral incisor | 104 (61.90) | 24 (14.29) | 1 (0.60) | 7 (4.17) |
| Maxillary canine | 96 (57.14) | 39 (23.21) | 0 (0.00) | 14 (8.33) |
| Mandibular central incisor | 82 (48.81) | 40 (23.81) | 5 (2.98) | 39 (23.21) |
| Mandibular lateral incisor | 102 (60.71) | 50 (29.76) | 4 (2.38) | 44 (26.19) |
| Mandibular canine | 62 (36.90) | 103 (61.31) | 1 (0.60) | 48 (28.57) |
| Total in maxilla | 213 (42.26) | 70 (13.89) | 1 (0.20) | 21 (4.17) |
| Total in mandible | 246 (48.81) | 193 (38.29) | 10 (1.98) | 131 (25.99) |
| Total | 459 (45.54) | 263 (26.09) | 11 (1.09) | 152 (15.08) |
The incidence of labial fenestration was the highest in the maxillary lateral incisors (61.90%) and the lowest in the maxillary central incisors (7.74%). The incidence of labial dehiscence was the highest at the mandibular canines (61.31%) and the lowest at the maxillary central incisors (4.17%). The incidence of lingual fenestration was the highest in the mandibular central incisors (2.98%), and no palatal fenestration was observed in the maxillary central incisors or maxillary canines. The incidence of lingual dehiscence was the highest in the mandibular canines (28.57%), and no palatal dehiscence was observed in the maxillary central incisors. Compared with the lingual side, the incidence of labial alveolar bone defects was higher.
The distributions of labial and lingual dehiscence and fenestration in the different vertical growth patterns are presented in Tables IV and V . Among all the included patients with hypodivergence, normodivergence, and hyperdivergence with skeletal Class III malocclusions, the incidence of alveolar bone defects was higher in the mandible than in the maxilla. Compared with patients with hypodivergence and normodivergence, dehiscence and fenestration were more prevalent in patients with hyperdivergence.
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