Mandibular dimensional changes and skeletal maturity

Age estimation from mandibles in Malay: A 2D geometric morphometric analysis

Objectives

In this study, the sizes and forms of mandibles in various age groups of the Malay population were measured and compared.

Methods

Geometric morphometric (GM) analysis of mandibles from 400 dental panoramic tomography (DPT) specimens was conducted. The MorphoJ program was used to perform generalized Procrustes analysis (GPA), Procrustes ANOVA, principal component analysis (PCA), discriminant function analysis (DFA), and canonical variate analysis (CVA). In the tpsDig2 program, the 27 landmarks were applied to the DPT radiographs. Variations in mandibular size and form were categorized into four age groups: group 1 (15-24 years), group 2 (25-34 years), group 3 (35-44 years), and group 4 (45-54 years).

Results

The diversity in mandibular shape among the first eight principal components was 81%. Procrustes ANOVA revealed significant shape differences (P < 0.001) among age groups. Mahalanobis distances indicated substantial differences among all age groups; group 1 and group 4 scored highest, at 2.114. The ranges for the cross-validation and discriminant function tests were 90-72% and 81-49%, respectively.

Conclusion

GM analysis through radiography is a simple, non-invasive, and non-destructive method of estimating age by using the mandible. GM analysis is unique because it can visualize the changes in mandible shape among age groups. This method should aid in age identification in forensic odontology investigations.

Correlation of various dental parameters of mandibular first molar with age, body weight and breed in healthy dogs

The aim of this study was to investigate the relationship of different radiographic parameters of mandibular first molar with respect to age, body weight and breed in healthy dogs. Overall, 50 dogs with the age from 5 to 156 months and body weight from 6.00 to 45.00 kg of various breeds were made the subject of study. Animals were categorized into different groups based on age, body weight and breed. A new dental parameters measurement technique was standardised which was in line with modified Lind's measurement technique of human dentistry. A significant decrease in least square count means of dental parameters was observed in age group 1 (0 - 12 months) in comparison with group 2 (13 - 60 months) and group 3 (> 60 months). A significant decrease in least square count means of dental parameters was observed in group A (0.00 - 10.00 kg) in comparison with group B (11.00 - 25.00 kg) and group C (> 25.00 kg). The root canal width showed a significant decrease with an increase in age; therefore, it was difficult to approach pulp cavity in older dogs. Small breeds showed decline in root length/crown height (R/C) ratio and mandible height/first mandibular molar height (MH/M1H) ratio in comparison with medium and large breeds because of which there were more chances of tooth loosening in smaller breeds. Regression equations formulated with respect to body weight and age can act as a ready reference to calculate values of different dental parameters at places where dental radiography is not available.

A roadmap of craniofacial growth modification for children with sleep-disordered breathing: a multidisciplinary proposal

Craniofacial modification by orthodontic techniques is increasingly incorporated into the multidisciplinary management of sleep-disordered breathing in children and adolescents. With increasing application of orthodontics to this clinical population it is important for healthcare providers, families, and patients to understand the wide range of available treatments. Orthodontists can guide craniofacial growth depending on age; therefore, it is important to work with other providers for a team-based approach to sleep-disordered breathing. From infancy to adulthood the dentition and craniofacial complex change with growth patterns that can be intercepted and targeted at critical time points. This article proposes a clinical guideline for application of multidisciplinary care with emphasis on dentofacial interventions that target variable growth patterns. We also highlight how these guidelines serve as a roadmap for the key questions that will influence future research directions. Ultimately the appropriate application of these orthodontic techniques will not only provide an important therapeutic option for children and adolescents with symptomatic sleep-disordered breathing but may help also mitigate or prevent its onset.

Mandibular Ramus: An Indicator for Gender Determination

Background The goal of this study is to use digital orthopantomographs (OPGs) to find out the role the mandibular ramus plays in figuring out a person's gender. Methodology Six hundred digital OPGs of patients, aged 21 to 50 years of either gender, fulfilling the exclusion and inclusion criteria, were randomly selected from the department archives exclusively for this digital retrospective study. All the scans were anonymized before the analysis. A total of seven measurements (in mm) were performed on OPGs, namely, minimum and maximum widths of the ramus, minimum and maximum condylar heights, maximum height of the ramus and coronoid, gonial angle bilaterally, and bigonial width. The data obtained was statistically analyzed using IBM SPSS Statistics for Windows, Version 21.0. (IBM Corp., Armonk, NY, USA), by a stepwise discriminant functional analysis for gender determination. Results Linear measurements, including maximum and minimum widths of the ramus, maximum height of the condyle, height of the ramus, and coronoid and bigonial width, revealed more values in males than in females. However, the gonial angle showed higher average values in females than in males. Moreover, all seven parameters showed statistically insignificant age-related changes. Conclusions The mandibular ramus showed high sexual dimorphism, and its analysis on OPG can be a valuable aid in the determination of gender in the fields of forensic odontology and anthropology.

Neural networks for classification of cervical vertebrae maturation: a systematic review

OBJECTIVE

To assess the accuracy of identification and/or classification of the stage of cervical vertebrae maturity on lateral cephalograms by neural networks as compared with the ground truth determined by human observers.

MATERIALS AND METHODS

Search results from four electronic databases (PubMed [MEDLINE], Embase, Scopus, and Web of Science) were screened by two independent reviewers, and potentially relevant articles were chosen for full-text evaluation. Articles that fulfilled the inclusion criteria were selected for data extraction and methodologic assessment by the QUADAS-2 tool.

RESULTS

The search identified 425 articles across the databases, from which 8 were selected for inclusion. Most publications concerned the development of the models with different input features. Performance of the systems was evaluated against the classifications performed by human observers. The accuracy of the models on the test data ranged from 50% to more than 90%. There were concerns in all studies regarding the risk of bias in the index test and the reference standards. Studies that compared models with other algorithms in machine learning showed better results using neural networks.

CONCLUSIONS

Neural networks can detect and classify cervical vertebrae maturation stages on lateral cephalograms. However, further studies need to develop robust models using appropriate reference standards that can be generalized to external data.

Longitudinal evaluation of the association between Insulin-like growth factor-1, Bone specific alkaline phosphatase and changes in mandibular length

The aim of the current longitudinal study was to assess the levels of serum Bone-specific alkaline phosphatase (BALP) and serum Insulin like growth factor-1 (IGF-1) in different cervical vertebral maturation index (CVMI) stages and observe their association with the mandibular growth. Blood samples and lateral cephalograms of 63 subjects (age group of 11–17 years) were obtained at two time points, 12 months apart. On the basis of CVMI, all subjects were divided into six groups based on whether the subjects remained in same CVMI stage or transitioned to the next CVMI stage. Annual mandibular length was related with serum BALP and serum IGF-1 levels estimated using ELISA. Serum IGF-1 and BALP attained highest levels at CVMI stage 3 with peak BALP levels observed earlier than IGF-1. Although a positive correlation was determined between IGF-1 and BALP but BALP followed skeletal growth pattern more precisely. Overall IGF-1 and BALP were negatively correlated with mandibular length with notable growth in CVMI groups 3–3 (P < 0.01), 3-4 (P < 0.01), 4-4 (P < 0.001) and 5-5 (P < 0.001). In conclusion, BALP is a potential biomarker for skeletal growth assessment. However, the mandibular growth pattern was independent of changes in IGF-1 and BALP.

Associations between mandibular symphysis form and craniofacial structures

OBJECTIVES

This study aimed to (1) analyze the relationships between mandibular symphysis characteristics (height, prominence, inclination, concavity, and convexity) and facial pattern, skeletal class, lower incisor position, and sex, and (2) determine the associations between the symphysis soft tissue dimensions and the underlying osseous structures.

METHODS

Cone-beam computed tomography (CBCT) images were selected for 385 patients (206 women and 179 men). The patients were classified according to their skeletal class and vertical pattern. The lower incisor inclination (IMPA) was recorded. Twelve measurements were taken for each mandibular symphysis using Invivo5 software (Anatomage, San Jose, CA, USA).

RESULTS

Symphyseal measurements were larger in males than in females. Skeletal Class II and III hyperdivergent patients showed the highest symphysis height values. Hypodivergent individuals showed lower symphysis convexity angles. Concavity of the symphysis was greater for Class II hyperdivergent patients. Lower incisor inclination showed a positive correlation with symphysis concavity and inclination. Moderate and weak correlations were found between hard tissue and soft tissue parameters.

CONCLUSIONS

Only a few characteristics of symphysis morphology depend on sex, incisor position, skeletal class, and vertical pattern. More significant relationships are found when the vertical pattern and skeletal class are analyzed in combination. The shape of the symphysis soft tissue is not directly correlated with the underlying skeletal structures.