Evaluation of the anterior dentoalveolar relationship in skeletal Class III malocclusion patients with different vertical facial patterns using cone-beam computed tomography.

OBJECTIVES: To measure and compare labiolingual inclinations of the teeth and alveolar bone and the anterior dentoalveolar inclination in patients with skeletal Class III malocclusions with different vertical facial patterns using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Based on the inclusion and exclusion criteria, 84 CBCT images of patients with untreated skeletal Class III malocclusion were selected. There were 28 patients each in the hypo-, normo-, and hyperdivergent groups. The labiolingual inclinations of the teeth, the corresponding alveolar bone, and the anterior dentoalveolar inclinations were measured and analyzed statistically. RESULTS: The inclinations of the mandibular canine and corresponding alveolar bone were smaller in the hypodivergent group than in the hyperdivergent group. The inclination of the alveolar bone and the maxillary dentoalveolar inclination were smaller in the hyperdivergent group than in the hypodivergent group. CONCLUSIONS: There were differences in the inclination of the teeth, corresponding alveolar bone, and dentoalveolar inclinations at different positions among skeletal Class III patients with different vertical facial patterns. The roots were generally located on the labial side of the alveolar bone.

Dehiscence and fenestration of skeletal Class III malocclusions with different vertical growth patterns in the anterior region: A cone-beam computed tomography study.

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.

Analysis of dental and basal bone arch form correlations in skeletal Class â ¡ malocclusion.

INTRODUCTION: This study aimed to establish mathematical equations to describe the dental and basal arch forms in skeletal Class II malocclusion and to investigate correlations between these forms to facilitate clinical diagnosis and treatment design. METHODS: Cone-beam computed tomography images of 60 patients (30 each with skeletal Class II malocclusion and normal occlusion) were subjected to 3-dimensional volume rendering, image reconstruction, and measurement. Using a computer program written in Java on the Eclipse platform (Eclipse Foundation, Ottawa, Canada), a beta function was used to establish mathematical models of dental and basal bone arch forms, and model-fitting was performed. RESULTS: A mathematical model was developed to describe the dental and basal arch forms in skeletal Class II malocclusion. The maxillary and mandibular dental arch lengths were significantly longer in skeletal Class II malocclusion than in normal occlusion, whereas the width of the maxillary molar segment was smaller. The maxillary molar and mandibular intercranial segments in the basal arch were significantly longer in skeletal Class II malocclusion than in normal occlusion, whereas the mandibular intercranial segment width was smaller. CONCLUSIONS: The dental arch and basal bone arch forms in the maxilla and mandible follow individual curves, described by a beta function. In skeletal Class II malocclusion, the dental and basal arches are discrepant in horizontal and anteroposterior dimensions, which should be considered during orthodontic treatment planning to improve arch matching.

Effect of orthodontic removal of mandibular first molar on the position change of third molar / 口腔疾病防治

Objective@#To investigate the effects of the first molar on the eruption of the third molar by comparing the changes of the third molar position after orthodontic treatment in different tooth extraction modes. @*Methods@#39 cases of adolescent patients were selected and divided into three groups:the first molar extraction, first premolar extraction and non-extraction.The pretreatment, posttreatment panoramic radiographs were measured to analyze the change of the third molar position among these groups.@*Results@# There were significant differences (P< 0.05) in the average annual variation of the third molar eruption space and angle. The changes in first molar extraction group were larger than that in premolar extraction group and non-extraction group. The average annual variation of the third molar eruption space, three groups were (2.38 ± 1.62) mm, (1.61 ± 0.90) mm and (1.08 ± 1.49) mm; the average annual variation of eruption angle, the three were 1.89° ± 1.93°, 1.37° ± 1.16° and 0.83° ± 1.74°.@*Conclusion @#Compared with conventional treatment, mandibular first molar extraction can significantly increase the third molar eruption space and improve its eruption angle, which is beneficial to the eruption of the third molar.

[Occlusal planes of Angle's class III malocclusion impact by anterior overbite].

OBJECTIVE: To investigate the correlation between Angle's class III patients' occlusion plane and anterior overbite by controlling the changes in occlusion plane during orthodontic treatment. METHODS: In total, 90 Angle's class III adult orthodontic patients were selected as the experimental group, and 30 normal adults were selected as the control group. According to the overbite, the class III patients were divided into three groups, and 14 indicators were measured. ANOVA and multiple comparison analysis were used to analyze the difference between class III patients, and linear analysis was used to analyze the correlation between anterior overbite and anterior-posterior occlusion plane. RESULTS: In class Ill patients, posterior occlusion plane and anterior overbite size were negatively correlated (r = -0.24, P < 0.05), whereas anterior occlusal plane and anterior overbite size were positive correlated (r = 0.23, P < 0.05). CONCLUSION: The shape of the occlusion plane varies in different anterior overbite patients. During orthodontic treatment in different overbite class III patients, the vertical height of the posterior teeth and the rotation of the occlusion plane should be controlled.

[The characteristics of the arch form of skeletal Class II malocclusion].

OBJECTIVE: To study the characteristics of the arch form of skeletal Class III malocclusion and provide references for diagnosis and treatment plan. METHODS: 7 indexes in dental casts of 47 patients with skeletal Class III malocclusion and 50 individuals with normal occlusion were measured respectively. And differences between corresponding upper and lower measurements were calculated. Independent samples t-test was employed for comparing between the two groups by SPSS 17.0. RESULTS: Compared with normal occlusion sample, Class III malocclusion group had smaller anterior segment lengths and larger canine angles (P<0.05). Differences between upper and lower first premolar widths were larger in males with skeletal Class III malocclusion. And differences between upper and lower anterior segment lengths were smaller in males with skeletal Class III malocclusion (P<0.05). CONCLUSION: Arch widths of patients with skeletal Class III malocclusion are basically normal. The lengths of anterior segment are smaller and the anterior arch forms are straighter.

Craniofacial morphological characteristics of Chinese adults with normal occlusion and different skeletal divergence.

The aim of the present study was to examine the craniofacial morphologic characteristics of different vertical dysplasias in a population of Chinese adults with normal occlusion. Sixty-nine subjects (39 males and 30 females) were selected from 800 healthy students between 18 and 24 years of age. Lateral cephalograms were obtained and 27 hard and 10 soft tissue measurements were analysed. The subjects were then divided into three groups: high angle, low angle, or control according to the value of FH-MP. Intraclass correlation coefficient was determined for the repeated measurements. One-way analysis of variance was used to determine the differences between the groups. The results showed that the low-angle group had a larger cranial basis angle (N-S-Ar) and the high-angle group had a shorter maxilla (Ans-Ptm; P < 0.01). The high-angle group displayed vertical hyperdivergency with increased PP-OP, OP-MP, gonial, and lower gonial angles, whereas the low-angle group showed significant hypodivergence with decreased values for all variables (P < 0.01). The low-angle group displayed a more protrusive chin and the high-angle group a more retrusive chin (P < 0.01). Differences in dentoalveolar measurements in the divergent groups were mainly in the anterior region. Moreover, the low-angle group had a thicker and the high-angle group a thinner lower dentoalveolus (P < 0.01). For face height measurements, the main differences in the divergent groups were at the anterior lower third (P < 0.01). Soft tissue deviations were less obvious in the high-angle group and in general less significant than those of the hard tissues in both divergent groups. Significantly different morphological characteristics exist in Chinese adults with vertical dysplasia but normal occlusion. Major skeletal cephalometric changes were found for the lower facial third. The soft tissues showed a well-adapting mechanism of soft tissue coverage for the skeletal dysplasia.

Effects of tensile stress on the alpha1 nicotinic acetylcholine receptor expression in maxillofacial skeletal myocytes.

This study was to investigate the alterations of the alpha1 nicotinic acetylcholine receptor (nAChR) levels under tensile stress stimulation in maxillofacial skeletal myocytes. The skeletal muscle satellite cells from two to three days post-natal BALB/C mice's maxillofacial muscle were collected for primary cell culture. The second passage cells in the loaded groups were subjected to cyclic tensile stress (0.5 Hz, 2000 micro strain) produced by a four point bending system for 2, 4, 6, 8, or 12 h. In the control groups, cells were cultured on similar plates and kept in the same incubator without mechanical stress loading. The examination of nAChR alpha1 receptor expression was performed by receptor binding of [125I] a-bungarotoxin. The nAChR alpha1 mRNA transcript level was analyzed by semi-quantitative RT-PCR. The result showed that the nAChR alpha1 receptor expression was elevated significantly in stress-stimulated group (P < 0.05). An increase of nAChR alpha1 in mRNA transcript level was also observed in stress groups as compared with controls (P < 0.05). It is concluded that nAChR was a possible molecular mechanism which might play an important role in mechanotransduction of tensile stress loading on maxillofacial skeletal myocytes.

[Effects of Fränkel II appliance on sagittal dimensions of upper airway in children].

OBJECTIVE: The purpose of this study was to investigate the effects of Fränkel II appliance on the upper airway of children. METHODS: The subjects consisted of 20 patients with Angle Class II, division I malocclusion (10 males and 10 females). The ages of all cases were ranged in 9-10 years. Each experimental subject was also served as self-control and cephalometric analysis was conducted. RESULTS: Compared with the results of pretreatment, the distance of PNS-Ba, SPP-SPPW, P-T, V-LPW and the Mcnamara line increased remarkably. CONCLUSION: The Fränkel II appliance can improve the sagittal dimensions of the upper airway in children.

[Comparison of craniofacial skeletal structures in adult high-angle and low-angle facial skeletal types].

OBJECTIVE: The purpose of this study was to compare the differences of craniofacial characteristics of adult high-angle and low-angle facial skeletal types. METHODS: The subjects consisted of 37 yellow race adults (17 high-angle, 20 low-angle). Fifty-three items of cephlometic radiographs were analyzed. RESULTS: The angle of N-S-Ar and N-S-Ba, the distance of Ptm-A, Co-Go, Po-NB, and S-Go, and the thickness of the mandibular symphysis in high-angle group were smaller than these in low-angle group. The angles of SN-OP, FH-OP, PP-OP, SN-MP, FH-MP, PP-MP, S-Ar-Go, mandibular angle(Ar-Go-Me), Y-angel and SUM, the distance of S-Co, N-Me, and ANS-Me in high-angle group were greater than these in low-angle group. The index of FHI, N-ANS/N-Me, and N-ANS/ANS-Me were smaller, and ANS-Me/N-Me larger in high-angle group. Although the means of Go-Po and FH-RP were smaller in high angle group, but no statistical difference were found. CONCLUSION: The craniofacial morphology of adult high-angle and low-angle facial skeletal types demonstrated significant differences, especially in lower facial form.

Comparison of superficial masseter muscle morphology between adult high-angle and low-angle facial skeletal types / 实用口腔医学杂志

Objective: To study the differences of the superficial masseter muscle morphology characteristics between adult high-angle and low-angle facial skeletal types. Methods: The subjects consisted of 37 yellow race adults,17 of them with high-angle facial skeletal type and 20 with low-angle. Ultrasound scanning was used to measure the perimeter, area, width, thickness, and length of masseter muscle. All the items were measured under relaxed, maximal clenching and maximal protrusive mandibular position.Results:①In the various mandibular positions, the masseter muscle size of adults with high-angle facial skeletal type was smaller than that of those with low-angle.②Except for the changes of width from the relaxed to maximal clenching position and from the relaxed to maximal protrusive position(P0.05).③Stature and weight influenced the size of the masseter muscle.Conclusion:The masseter muscle size of adult with high-angle facial skeletal type is smaller than that of those with low-angle.