Comparison of mandibular morphology in Korean and European-American children with Class III malocclusions using finite-element morphometry

Does osteotomizing the lower border of the mandible affect the lingual split pattern in a sagittal split ramus osteotomy?

AIM

The purpose of this study was to evaluate the effect of adding a fourth osteotomy at the lower border of the mandible on the lingual cortical fracture pattern in bilateral sagittal split ramus osteotomies.

PATIENTS AND METHODS

The sample of the study consisted of 20 patients (12 male and 8 female, with a mean age of 26.79 ± 7.12 years) with mandibular deformities who needed bilateral sagittal split ramus osteotomy. One side underwent a traditional sagittal split ramus osteotomy, and the procedure was modified on the other side by adding a 1 cm horizontal osteotomy at the lower border of the mandible, just distal to the caudal end of the vertical buccal osteotomy cut. A 3D CBCT was used to identify the split pattern.

RESULTS

In the total sample, 40% of the lingual splits ran vertically toward the lower border of the mandible (LSS1), 20% of the splits passed horizontally to the posterior border of the mandible (LSS2), 32.5% of the splits took place along the inferior alveolar canal (LSS3), and 7.5% of the splits were unfavourable fractures (LSS4). On the inferior border osteotomy sides, the distribution of LSS1, LSS2, LSS3, and LSS4 was 10 (25%), 6 (15%), 4 (10%), and 0 (00), respectively. Their distribution on the sides without inferior border osteotomy was 6 (15%), 8 (20%), 13 (32.5%), and 3 (7.5%), respectively. Statistical analysis revealed a significant difference between the two groups (p < 0.05).

CONCLUSION

Inferior border osteotomy tends to direct the lingual split fracture line toward the lower and posterior borders of the mandible and minimizes bad splits; however, further studies are needed to confirm our findings.

The influence of maxillary incisor angles on the stress distributions of temporomandibular joints under incisal biting

BACKGROUND AND OBJECTIVE

The incisal biting was one of the most regular jaw activities. The direction of bite force on the incisor tip and the mandible position were relevant to the incisor angle as biting. This study was carried out to explore the influence on the temporomandibular joint (TMJ) caused by the incisor angle.

METHODS

Twenty individuals belonging to three incisor subtypes of the buccal type were recruited. In addition, the 3D models including the maxillary, mandible and discs were established based on their cone-beam computed tomography and magnetic resonance imaging scannings. Then, the mandibular ligaments and the discal attachments were simulated in the finite element models to analyze the stress distributions of the TMJs under incisal biting.

RESULTS

The TMJ stresses of subtype I showed normal range and distribution. The stresses of the intermediate temporal bone tended to increase in subtype II. The intermediate and posterior bands of the discs sustained greater tensile stresses in subtype III.

CONCLUSIONS

Abnormal stress distributions are harmful to TMJs, so the incisor cusp was not suggested to incline to the palatal side too much.

Role of matrilin-1 (MATN1) polymorphism in class III skeletal malocclusion with mandibular prognathism in Deutero-Malay race: a case-control study

Background

Several studies have identified different genes that control the final dimension and structure of the mandible. Prognathism of the mandible is thought to correlate with these genes; however, no specific gene has been assigned as a risk factor due to various genome-wide scan results in different races. Previous studies that involved the Han ethnic group in China and Korea suggested matrilin-1 (MATN1) polymorphism as the contributor for mandibular prognathism. To date, no study has been conducted to understand the role of MATN1 in Deutero-Malay population. This study aimed to detect MATN1 gene polymorphism in the promoter and exon 5 regions, which is a proposed risk factor in class III skeletal malocclusion with mandibular prognathism in Deutero-Malay population. This was a case-control study with purposive sampling method that involved 47 class III skeletal malocclusion subjects with mandibular prognathism (case group) and 47 class I skeletal relation subjects (control group) performed in the Molecular Genetics Laboratory of Faculty of Medicine, Universitas Padjadjaran, Indonesia. DNA isolated from buccal mucous epithelia and MATN1 gene was amplified using the polymerase chain reaction (PCR) and sequencing technique. Data were then analyzed statistically to observe the frequency of allele/genotype MATN1 in class III skeletal malocclusion and mandibular prognathism patients in comparison with the normal mandibular as well as to identify the risk factor of mandibular prognathism.

Result

The frequency of the 354 T > C(rs20566) CC genotype gene polymorphism in the case group was significantly higher than in the control group. The odd ratio (OR) value of the case group was also higher than in the control group (χ2 = 4.89; p = 0.027; OR = 6.27).

Conclusions

Our results show that the polymorphism of 354 T > C in the exon 5 region of the CC genotype MATN1 gene is a risk factor for class III skeletal malocclusion with mandible prognathism in Deutero-Malay population.

Effects of rapid palatal expansion (RPE) and twin block mandibular advancement device (MAD) on pharyngeal structures in Class II pediatric patients from Cluj-Napoca, Romania

Objective: To compare cephalometric changes of pharyngeal structures after rapid palatal expansion (RPE) with those induced by a twin block mandibular advancement device (MAD) with palatal expansion capability. Methods: This retrospective study investigated 55 Class II pediatric patients, divided into two groups: 29 patients treated with RPE and 26 patients treated with MAD. Lateral cephalometric measurements were compared before and after treatment. Results: Changes in pharyngeal airway space were statistically significant in both groups (p < 0.001) from a pre-treatment mean distance measured between the lower posterior pharyngeal wall and the hyoid bone (LPF-H) of 25.42 mm in the MAD group and 28.62 mm in the RPE group, to a post-treatment mean LPF-H of 27.96 mm in the MAD group and 31.52 mm in the RPE group. Conclusion: Significant changes in pharyngeal space may be obtained in Class II patients through both rapid palatal expansion and mandibular advancement devices with palatal expansion capability.

Inheritance of craniofacial features in Colombian families with class III malocclusion

Introduction

The inheritance of class III malocclusion has been well documented, but the inheritance of craniofacial structures in Colombian families with this malocclusion has been not yet reported.

Patients and methods

The study sample of 25 families comprised 186 untreated orthodontic individuals from 8 to 60 years old. Pedigrees were drawn using Cyrillic software. Complete family histories for each proband were ascertained and the affection status of relatives was confirmed by lateral cephalograms and facial and dental photographs. Analysis of variance and odds ratio test for each parameter was performed to estimate inheritance from parents to offspring and to determine similar phenotypic features in relatives.

Results

The analysis of the pedigrees suggests autosomal dominant inheritance. The craniofacial characteristics that showed more resemblance between parents and offspring were middle facial height, shorter anterior cranial base and mandibular prognathism. In contrast the protrusion of upper lip and maxillary retrusion were the phenotypic features that contributed to class III in the majority of families.

Conclusion

Knowledge of the inheritance of craniofacial phenotypes in class III malocclusion will enable the design of new therapies to treat this malocclusion.