Orthodontics and Genetics

Prevalence of mandibular asymmetries in the pediatric population of Jazan: A radiographic analytical study

Background

Facial asymmetry results from variation in mandibular linear and angular dimensions on the right and left sides of the face. Mandibular asymmetry is of great significance to oral surgeons and orthodontists as it directly impacts the facial profile of an individual.

Aim

The present study aimed to measure the prevalence of mandibular asymmetry and its fluctuations during the mixed dentition growth phase in healthy children aged 6-8 years in the Jazan region of Saudi Arabia.

Method

This retrospective observational study was conducted by measuring linear asymmetrical measurements of mandible on orthopantomograms of 390 healthy children (182 boys and 208 girls, aged 6-8 years) with mixed dentition. Linear measurements from orthopantomograms were obtained using a standardized digitizer. Two sets of mandibular measurements were recorded, alongside subjective assessments of mandibular first molar development. An independent t-test was employed to assess the significance between measurements on both sides, while one-way ANOVA was used to demonstrate facial asymmetry significance among different age groups.

Result

The result of this study revealed a significant statistical difference (p-value≤ 0.05) for both sides of the mandible across two dimensions: condylar and ramus height (p value = 0.03) and mandibular length (p value = 0.04). The asymmetry index resulted in no asymmetry among most of the included subjects. However, compared to the other three linear measurements, many seven-year-old participants possess mandibular asymmetry on condylar height (54.5 %).

Conclusion

Within the limitation it could be concluded that children in growing age have a significant mandibular asymmetry (mainly 7 years), which, however, is only seldom clinically significant. Hence, treatment plan should be cautiously planned.

[Malocclusion in adolescents in the State of São Paulo: spatial and hierarchical analysis]

The scope of this study was to analyze the spatial distribution of malocclusion (MO), estimate the prevalence and evaluate the associated factors in adolescents. It was a study with results of 5,558 adolescents aged 15 to 19 from the São Paulo Oral Health (SB) 2015 survey. The outcome was MO. Sociodemographic aspects, access to dental services, dental caries and tooth loss were the independent variables. A total of 162 municipalities in the state of São Paulo were included and spatial statistics techniques were applied. Hierarchical logistic regression models were performed. The prevalence of MO was 29.3%. There was a spread pattern between the types of MO and positive detachment (p<0,05). Non-white adolescents (OR=1.32, 95%CI: 1.24-1.42), with less years of schooling (OR=1.30, 95%CI: 1.22-1.42), with teeth extracted due to caries (OR=1.40, 95%CI: 1.03-1.88) were more likely to have MO. Adolescent access to dental consultation did not contribute to reducing the chance of developing MO, regardless of whether the dental consultation occurred less (OR=2.02, 95%CI: 1.65-2.47) or more than one year before (OR=1.63, 95%CI: 1.31-2.03). Thus, the occurrence of MO is unequally distributed in the state of São Paulo and associated with sociodemographic conditions, access to consultations and tooth loss due to caries.

Three-Dimensional Analysis of Posterior Mandibular Displacement in Rats

Mandibular protrusion and its treatment is challenging for the orthodontist. The aim of the present research was to identify macroscopic changes in the mandible, based on three-dimensional Cone Beam Computed Tomography analysis. Seventy-two male Wistar rats were divided into two equal groups, experimental (group A) and control (group B). Each consisted of three equal subgroups of 12 rats (A1, A2, A3, B1, B2, B3). Full-cast orthodontic intraoral devices were attached to the maxillary incisors of the experimental animals, and effected functional posterior mandibular displacement. Throughout the experimental period, all animals were fed with mashed food. Animals were sacrificed at 30 days (A1, B1), 60 days (A2, B2) and 90 days (A3, B3). At the 60th day of the experiment, the orthodontic devices were removed from the remaining experimental subgroup A3. Measurements revealed significant differences in the anteroposterior dimensions between experimental and control subgroups. However, the observed changes in the vertical dimensions, Condylion/Go’–Menton and the Intercondylar distance proved insignificant. Posterior mandibular displacement of the mandible in growing rats affects the morphology of the mandible and culminates in the development of a smaller mandible at a grown age.

Genetic Factors That Affect Asymmetric Mandibular Growth—A Systematic Review

Facial asymmetry is a feature that occurs to a greater or lesser extent in the general population. As its severity is usually slight, facial asymmetry may not be noticeable to the patient. However, there are cases when severe facial asymmetry not only affects the facial aesthetics by distorting facial proportions, but also contributes to problems related to the function of the stomatognathic system. The nodal signalling pathway appears to be of particular importance in the process of mandibular asymmetry, as it affects not only structures formed from the first pharyngeal arch, but also other organs, such as the heart and lungs. Following the evaluation of the available literature, the inheritance of mandibular asymmetry is a very complex and multifactorial process, and the genes whose altered expression appears to be a more important potential aetiological factor for asymmetry include PITX2, ACTN3, ENPP1 and ESR1. This systematic review attempts to systematise the available literature concerning the impact of signalling pathway disruption, including the disruption of the nodal signalling pathway, on the development of mandibular asymmetry.

A Cross-Sectional Evaluation of Self-Perceived Orthodontic Treatment Needs Amongst Tribal Adolescent With Remote Access to Orthodontic Treatment Using a Simplified Malocclusion Index

Background:

Self-perceived orthodontic treatment need is strongly influenced by what is perceived to be the esthetic norm amongst a community, and reluctance toward treatment amongst adolescents with clinically ascertained malocclusion may often be due to readily remediable factors. Of particular interest is the prevalence of malocclusion amongst such communities as a probable indicator of the role of diet and genetics in establishing a predominant clinical phenotype that may also play a role in the construct of what is perceived as the esthetic norm amongst the community, thereby influencing the self-perceived need for treatment. Studies aimed at evaluating the association between self-perceived esthetics, and self-perceived treatment need have not been performed amongst a population with no prior exposure to orthodontic treatment

Objectives:

The purpose of this study was to evaluate the self-perceived orthodontic treatment need amongst the tribal adolescents belonging to regions with remote access to orthodontic treatment by way of a verbally assigned index and to also identify the reasons of reluctance toward treatment to better understand how to make orthodontic treatment readily accessible to such populations.

Participants, Materials, and Methods:

The agency areas of Paderu located at 18.0833°N 82.667°E and Parvathipuram located at 18°46'N 83°25'E are 2 revenue districts of Visakhapatnam and Vizianagaram, respectively, in the state of Andhra Pradesh, India, that are home to various tribal populations with remote access to orthodontic treatment. A total of 2,016 school-going tribal adolescents of the Paderu revenue division and 819 tribal adolescents of the Parvathipuram revenue division were examined to ascertain the prevalence of malocclusion. Necessary consent and permissions were obtained from the tribal authorities, the school authorities, parents, and the institutional ethical clearance committee. The screening was done utilizing natural daylight in compliance with infection prevention and control protocol. Clinical examination aimed at categorizing the observed occlusion into either ideal occlusion or one of the three classes of Angle’s class I, II, and III malocclusions. The Simplified Malocclusion Index For Layperson Evaluation (SMILE) was verbally assigned in the vernacular language while interacting with each child and the findings made note of for calculation of relevant scores related to their orthodontic awareness, self-esteem as related to self-perceived esthetics, and their self-perceived need for treatment. Reasons for reluctance to undergo treatment were noted down if expressed. An initial group of 31 adolescents categorized as presenting with clinical malocclusion were randomly picked up and assigned the SMILE index a second time to assess the reliability of the index by way of Cohen’s kappa statistic.

Results:

The initial test group of 31 individuals assigned the SMILE twice showed a Cohen’s kappa of 0.93 validating almost perfect intraoperator agreement. The SMILE index revealed that 80.95% of the adolescents of Paderu revenue division had orthodontic awareness and 79.51% had self-perceived esthetics but only 15.97% felt a need for orthodontic treatment. Pearson’s Chi squared statistical analysis indicated a gender bias related to the self-perceived need for orthodontic treatment ( X 2 [1, N = 1,371] = 19.71, P < .001). The Index assigned to the Parvathipuram division revealed that 77.04% had orthodontic awareness and 78.38 had self-perceived esthetics but only 6.95% felt the need for orthodontic treatment. Pearson’s Chi squared statistical analysis indicated a gender bias related to the self-perceived need for orthodontic treatment ( X 2 [1, N = 764] = 4.95, P = .02).

Conclusion:

The self-perceived need for orthodontic treatment is often based on the self-perceived esthetics of an individual or the self-esteem as influenced by the perceived esthetic norm of the community. Orthodontic treatment of adolescents with borderline malocclusion derangements requires careful ascertaining of the actual perceived need of the patient to enable the rendering of a justifiable orthodontic treatment with the complete trust of the young patient. This helps build community trust in regions where orthodontic treatment has not yet made in roads and may help ensure higher end of treatment satisfaction levels.

Retrognathic maxilla in individuals born with oral clefts is due to intrinsic factors and not only due to early surgical treatment

OBJECTIVES

To determine if the skeletal form of individuals born with oral clefts was associated with maxillary position.

MATERIALS AND METHODS

Lateral cephalometric radiographs of 90 individuals 8 to 12 years old born with or without cleft lip and palate paired by age and sex were used. Skull base length, cranial base angle, cranial deflection angle, and maxillary skeletal length and position were studied. Also, mandibular skeletal length and position, lower anterior facial height, and dental position were defined. Individuals were divided into three groups: 30 individuals born with cleft lip and palate with Class III malocclusion (UCLP Class III), 30 individuals born with cleft lip and palate with Class I malocclusion (UCLP Class I), and 30 individuals born without cleft lip and palate with Class III malocclusion (non-cleft Class III).

RESULTS

When comparing the UCLP Class III group with the UCLP Class I group, there were differences in maxillary position (P < .001) and mandibular position (P = .004) found. No differences were found when comparing the UCLP Class III group with the non-cleft Class III group.

CONCLUSIONS

There are intrinsic factors that affect craniofacial morphology of individuals born with cleft lip and palate.

Posterior Mandibular Displacement-A Systematic Review Based on Animal Studies

Treating extreme mandibular growth is challenging. The mandible is pushed backwards to address itsprotrusion. Nevertheless, conclusions after such displacement in animals have been contradictory. The aim of the present review is to present measurable alterations of the mandible and the condyle following retractionin healthy rats or rabbits. PubMed, Scopus and Web of Science were accessed for relevant studies up to October 2020. Eligibility was determined by the PICOS process, while the risk of bias was estimated with SYRCLE's risk of bias tool. Retraction resulted in a more distal molar occlusion and the condyle rested more posteriorly. Mandibular anteroposterior bilateral growth restriction was achieved, the condylar process measured smaller and its angulation increased. The condylar neck thickened, its posterior surface flattened, the coronoid process was measured longer, and enlarged retromolar density was registered. Differences in the ramus height and the intercondylar distance were insignificant. Changes persisted for the period of study and subsequently the mandible resumed its inherited growth pattern. The timing of mandibular shaping and TMJ outcomes might depend on the properties of the applied force. Stability is of concern and well-structured, long-term studies are expected to resolve the issue and further clarify the results of posterior mandibular displacement.

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.