Growth hormone receptor gene variant and three-dimensional mandibular morphology

Role of the Growth Hormone Receptor (GHR) Gene in Skeletal Class II Malocclusion and Its Significant Influence on the Skeletal Facial Profile in Both the Sagittal and Vertical Dimensions: A Systematic Review

This systematic review aims to determine the role of the growth hormone receptor (GHR) gene in skeletal malocclusion and its significant influence on the growth of the maxilla and the mandible in both sagittal and vertical dimensions. A search of the electronic databases of PubMed, Google Scholar, and Cochrane up to and including the year 2023 was made. In addition to this, a hand search of orthodontic and dentofacial orthopaedic journals was carried out. This search included randomized control trials. The Mesh terms used were "skeletal class II malocclusion", "mandibular retrognathism", "sagittal malocclusion", "genetic expression", "genetic factors", "genetic study", "genetic polymorphism", and "single nucleotide polymorphism". The inclusion criteria included studies such as clinical trials and orthopaedic appliances in the presurgical phase. The exclusion criteria for the study were studies not in the English language, case reports, case series, and studies with irrelevant data. It has been cited in various literature that polymorphic variations of the GHR gene could cause variations in mandibular morphogenesis affecting both the mandibular body length and ramal height. However, its effects are quite variable and are based on different population groups. Polymorphism of the GHR gene can be considered a reliable indicator predicting variations in affecting the growth of the mandible with greater significance in affecting the vertical ramal height compared to the body length of the mandible. Its effects on the maxillary skeletal base are rather limited comparatively.

Three-dimensional evaluation of mandibular condyle and coronoid process according to sex, age, and skeletal deformities

OBJECTIVE

To correlate the volume of the mandibular condyle (MC) and the coronoid process (CP) with sex, age, and skeletal deformities.

METHODS

The structures were visualized through semi-automatic segmentation of the 3D model and complemented with manual segmentation, using the ITK-SNAP 3.0 software. Mann-Whitney, Kruskal-Wallis, and the Dunn test were performed (p < 0.05).

RESULTS

The MC volume showed statistical differences between sex and skeletal deformities. Men and Class III patients showed higher values. CP volume was not influenced by age or skeletal deformities. However, statistical differences were found between sex, with higher values for men.

CONCLUSION

MC volume was influenced by sex and skeletal deformities, while CP was influenced only by sex. Women have smaller volumes for these structures. Age is not correlated with the volume of MC and CP. The highest and lowest values of condylar volume were found for Class III and II individuals, respectively.

Volumetric Analysis of the Jaws in Skeletal Class I and III Patients with Different Facial Divergence Using CBCT Imaging

Aim

The main objective was to evaluate any possible maxillary or mandibular volumetric difference between hyperdivergent skeletal Class III (CIII), normodivergent skeletal CIII, hypodivergent skeletal CIII, and normodivergent skeletal Class I (CI) patients using cone-beam computed tomography (CBCT) images. Also, the secondary objective was to investigate any possible correlation between CBCT-derived lateral cephalometric variables and the mandibular and maxillary volumes (MdV and MxV, respectively).

Materials and Methods

80 CBCT images of patients between 18 and 32 years of age were taken with one CBCT imaging device (Scanora 3D®, Soredex, Tuusula, Finland). The sample consisted of four groups: 20 hypodivergent skeletal CIII (11 males and 9 females), 20 normodivergent skeletal CIII (7 males and 13 females), 20 hyperdivergent skeletal CIII (8 males and 12 females), and 20 normodivergent skeletal CI (5 males and 15 females). The volumes of both jaws and the ratio of MxV/MdV were obtained using Mimics™ 19 software (Materialise, NV, Belgium), and 2D variables were obtained from CBCT-derived lateral cephalogram using AudaxCeph™ software (Orthodontic software suite, Ljubljana, Slovenia). One-way ANOVA test and Kruskal–Wallis analysis were employed to detect any possible significant difference between the volumetric variables, whereas Pearson's and Spearman's correlation coefficients were calculated to detect any possible relationship between the 2D variables and the volumetric measurements.

Results

There were no statistically significant differences in the maxillary volume or maxillary/mandibular ratio between the four groups (p=0.081 and 0.432, respectively). There was a significant difference in MdV between CIII hypodivergent (higher mean) and CIII hyperdivergent (p=0.039). There were some correlations between the MdV and 2D variables in the four studied groups especially in the posterior facial height (S-Go) and the facial depth (N-Go). There were some weaker correlations between the MxV and some 2D variables in the CIII hypodivergent and hyperdivergent groups.

Conclusions

The mandibular volume of the Class III hypodivergent patient was significantly greater than that of the Class III hyperdivergent patients. Correlations between the maxillary or mandibular volumes were found with some of the 2D variables. The volume of both jaws increased when the maxillofacial complex moved toward a horizontal growth pattern.

The Role of GH/IGF Axis in Dento-Alveolar Complex from Development to Aging and Therapeutics: A Narrative Review

The GH/IGF axis is a major regulator of bone formation and resorption and is essential to the achievement of normal skeleton growth and homeostasis. Beyond its key role in bone physiology, the GH/IGF axis has also major pleiotropic endocrine and autocrine/paracrine effects on mineralized tissues throughout life. This article aims to review the literature on GH, IGFs, IGF binding proteins, and their respective receptors in dental tissues, both epithelium (enamel) and mesenchyme (dentin, pulp, and tooth-supporting periodontium). The present review re-examines and refines the expression of the elements of the GH/IGF axis in oral tissues and their in vivo and in vitro mechanisms of action in different mineralizing cell types of the dento-alveolar complex including ameloblasts, odontoblasts, pulp cells, cementoblasts, periodontal ligament cells, and jaw osteoblasts focusing on cell-specific activities. Together, these data emphasize the determinant role of the GH/IGF axis in physiological and pathological development, morphometry, and aging of the teeth, the periodontium, and oral bones in humans, rodents, and other vertebrates. These advancements in oral biology have elicited an enormous interest among investigators to translate the fundamental discoveries on the GH/IGF axis into innovative strategies for targeted oral tissue therapies with local treatments, associated or not with materials, for orthodontics and the repair and regeneration of the dento-alveolar complex and oral bones.

Methods in Genetic Analysis for Evaluation Mandibular Shape and Size Variations in Human Mandible

ABSTRACT

The human mandible has been investigated from both clinical and evolutionary perspectives. Recent advances in genome science have identified the genetic regulation of human mandibular shape and size. Identification of genes that regulate mandibular shape and size would not only enhance our understanding of the mechanisms of mandibular growth and development but also help define a strategy to prevent mandibular dysplasia. This review provides a comprehensive summary of why and how the mandible was evaluated in the human mandible genome study. The variation in human mandibular shape and size has been progressively clarified, not only by focusing on the mandible alone but also by using extremely diverse approaches. The methods of data acquisition for evaluating human mandibular shape and size variation are well established. Furthermore, this review explains how to proceed with future research.

Assessment of Correlation of Growth Hormone Receptor Gene with Tooth Dimensions: A CBCT and Genotyping Study

Aim:

Assessment of root morphology, size, and amount of bone around tooth is essential before starting the orthodontic treatment. The present study aimed to assess the relationship between tooth dimensions with two gene variants of growth hormone (GH), namely rs6184 and rs6180.

Materials and Methods:

This study was conducted on 218 subjects (males: 104, females: 114) requiring orthodontic treatment. All underwent cone beam computed tomography (CBCT) scan for orthodontic treatment planning with Kodak CBCT machine. In all teeth, crown height (CH), root length (RL), and crown–root ratio were evaluated. Two growth hormone receptor (GHR) variants (rs6184 and rs6180) were genotyped using the TaqMan genotyping assay.

Results:

The mean CH and RL of all teeth, that is, maxillary and mandibular central incisors, lateral incisor, canine, first premolar, second premolar, first molar, and second molar, were measured. There was no significant difference in males and females (P > 0.05). Allele frequencies of GHR variants for rs6180 and rs6184 were 48.1% and 8.92%, respectively. Multiple regression analysis showed GHR rs6184 association with maxillary central incisor CH, maxillary canine RL, mandibular canine CH, and mandibular first premolar RL (P < 0.05).

Conclusion:

There was correlation of CH of maxillary and mandibular canine and RL of maxillary canine and mandibular first premolar with GHR rs6184.

Growth hormone receptor gene is related to root length and tooth length in human teeth

OBJECTIVES

To examine the relationship between tooth length and growth hormone receptor (GHR) gene variants in a healthy Japanese population.

MATERIALS AND METHODS

The subjects consisted of 193 Japanese adults (69 men, 124 women), aged 13 to 56 years. Genomic DNA was extracted from saliva and genotyped GHR rs6184 and rs6180 variants using the Taqman genotyping. Computed tomography (CT) images were acquired using a dental cone-beam CT scanner and reconstructed using open-source OsiriX medical image processing software. The maxillary (upper; U) and mandibular (lower, L) central incisors (1), lateral incisors (2), canines (3), first premolars (4), second premolars (5), first molars (6), and second premolars (7) were evaluated. Teeth were assessed for crown height (CH), root length (RL), overall tooth length (C+R), and crown to root ratio (C/R). The relationships between GHR variants and CH, RL, C+R, and C/R were statistically examined.

RESULTS

The GHR variant rs6184 was associated with the root lengths and tooth length for the upper and lower lateral incisors and upper canines (U2 RL; U3 RL, C+R; L2 RL [ P < .05]).

CONCLUSIONS

The results indicate that the GHR rs6184 variant is associated with tooth length and ratio dimensions in a Japanese cohort. Further studies utilizing a larger sample size are needed to confirm this finding.

The correlation between growth hormone receptor (GHR) polymorphism and obstructive sleep apnea syndrome among the Han and Hani population in China

Obstructive sleep apnea syndrome (OSAS) is a common health problem that is associated with abnormality in craniofacial morphology. The growth hormone receptor (GHR) belongs to the cytokine receptor superfamily and mediates the majority of growth hormone signaling, which, among other functions, determines mandibular growth and development. The aim of this study was to determine if correlations exist between single nucleotide polymorphisms (SNPs) in the GHR gene and OSAS in the Han or Hani ethnic groups in China. A total of 274 Han subjects (106 with OSAS and 168 without OSAS) and a total of 270 Hani subjects (64 with OSAS and 206 without OSAS) were enrolled in our study. Genomic DNA was extracted from peripheral blood obtained from all subjects. Genotyping was undertaken for eight SNPs in the GHR gene (rs3756416, rs7727047, rs2910875, rs12153009, rs2972781, rs12518414, rs4410646, and rs6451620) using PCR amplification and Sanger sequencing. The genotype frequency of rs12518414 was associated with OSAS in both the Han and Hani groups, and the A allele frequency was remarkably lower in Hani OSAS patients compared with Hani controls (16.7 vs 29.9%). In addition, the G allele frequency of the rs3756416 SNP was significantly lower in OSAS patients compared with normal controls in the Hani ethnic group (12.5 vs 24.6%). In a comparison between ethnic groups, genotype frequencies of four SNPs (rs2972781, rs6451620, rs12518414, and rs7727047) differed between Han and Hani OSAS patients, with the A allele frequency of the rs12518414 and G allele frequency of the rs7727047 were significantly higher in the Han OSAS patients. In conclusion, significant associations were detected between some SNPs in the GHR gene and OSAS occurrence while others appeared to be ethnicity-dependent.

Bilateral coronoid hyperplasia causing painless limitation of mandibular movement

The coronoid process is a beaklike process in the ramus of the mandible. Coronoid process hyperplasia (CPH) is a rare possible cause of reduced mouth opening. An overgrown process interferes with mandibular rotation and lateral excursion and hence leads to restricted mouth opening (RMO). Although some factors are suggested, etiology of CPH is not completely known. Prescription of suitable radiography is necessary for an accurate diagnosis. This article reports a 30-year-old man with bilateral CPH and progressive RMO since childhood. This disorder affected his oral hygiene and quality of life. With the help of different types of radiography, CPH was diagnosed and coronoidectomy was the only treatment option. The patient showed normal jaw movements after the surgery and postoperative physiotherapy. General dentists have an important role in noticing RMO and referring the patients to maxillofacial radiologists. Although it is a rare phenomenon, general dentists need to keep CPH in mind as a possible cause. Panoramic imaging accompanied by computed tomography or cone beam computed tomography is the best imaging option in such cases.