Mandible Length Research Articles

Enlarged occipital spur and craniofacial morphology: a cephalometric analysis.

This cross-sectional study aimed to investigate the association between the occipital spur length and craniofacial morphology in individuals with occipital spur (OS). The study included cephalometric images from 451 individuals (196 females, 255 males, age range was 9-84years). The spur length and craniofacial characteristics were evaluated using cephalograms. Based on spur length, subjects were divided into two groups: the OS group (N = 209) and the enlarged occipital spur (EOS) group (N = 242). Descriptive statistics, Independent T-test, Mann-Whitney U test, chi-square test, Kruskal-Wallis test, and age- and sex-based stratified analyses were performed. The level of significance was set at p < 0.05. Males had significantly larger spur length than females. Spur length was shorter in individuals under 18 than the groups over 18. After adjusting for gender and age, ramus height, mandibular body length, effective length of maxilla, effective length of mandible, anterior cranial base length, posterior cranial base length, anterior facial height, posterior facial height, facial height index, and lower anterior facial height had statistically significant differences between OS group and EOS group. Males exhibit greater spur length than females. Patients under 18 had a shorter spur length than adults. Linear craniofacial measurements were found to be greater in subjects with EOS than the individuals with OS. The craniofacial growth and development of an individual might be associated with EOS. The causal relationship between EOS and craniofacial development requires further longitudinal studies.

Association Between Growth Hormone Receptor Gene Polymorphisms rs6180, rs6182, and rs6184 and Craniofacial Parameters in Indian Population

Objective/Background Craniofacial growth and development is influenced by growth hormone, which is in turn facilitated by the growth hormone receptor (GHR). GHR gene polymorphisms have been found to be associated with mandibular morphology and skeletal facial profiles in various populations. The aim of this study was to determine the association of single nucleotide polymorphisms (SNP) of GHR gene rs6180, rs6182, and rs6184 with maxillomandibular parameters in the Indian population. Setting and Sample Population A cross sectional study was conducted on 174 male and female Indian subjects in the age range of 20 to 32 years who reported for orthodontic treatment. Material and Methods Venous blood and lateral cephalogram were collected from each participant for genetic and cephalometric analysis. Genotypes of each SNP were identified by polymerase chain reaction—restriction fragment length polymorphism. Independent t test and Analysis of Variance (ANOVA) were done for intra and inter group comparisons with SPSS software. Results SNPs rs6180, and rs6182 were found to be associated with sagittal position and length of maxilla and mandible, anterior facial height, and growth pattern. SNP rs6184 did not have any significant association with the craniofacial parameters. Conclusion The results suggest that the GHR gene might be a candidate gene for maxillomandibular morphology in the Indian population.

New data on the cranial morphology of the tapejarid Sinopterus from the Early Cretaceous Jehol Biota

ABSTRACT Here, we describe a new Jehol tapejarid skeleton tentatively referred to Sinopterus dongi, revealing some valuable cranial information about the palate and mandibular symphysis of this species. In the palate, the absence of the lateral process of the pterygoid indicates that the subtemporal fenestra is undivided, in contrast to the well-developed lateral process that subdivides the subtemporal and secondary subtemporal fenestrae in other azhdarchoids. The mandibular symphysis is elongated to about 58.7% of the mandible length, significantly longer than the other two Jehol tapejarids (52.9–53.7%) and much longer than other tapejarids (38.0–51.0%), except for the basal tapejarid Caupedactylus ybaka (~65%). The symphyseal shelf is extensive, flattened, and sculptured by sinuous ridges and pits. The ratio of its length to the symphysis is 34.4%, between that of the possible tapejarid Bakonydraco galaczi (43.9%) and the coexistent chaoyangopterid Eoazhdarcho liaoxiensis (26.7%), and much distinct from the well-reduced condition in other tapejarids. This discovery highlights the variation of the cranial morphology in the Tapejaridae and even the Azhdarchoidea.

Morphometric Measurements of Red Foxes (Vulpes vulpes) in Somogy County, Hungary

The red fox (Vulpes vulpes) has the widest natural distribution of any terrestrial carnivore. Sexual dimorphism in this species is well known and is frequently observed in body and skull measurements. Morphological analysis is essential because the skull and body morphologies reflect many population/individual characteristics, genetic distances, environmental effects, and growth-affecting factors. Our study presents the first comprehensive analysis of red fox body and skull morphometry in Hungary. We performed morphometric measurements on 200 red foxes at two developmental stages, juvenile and adult, of different sexes, male and female, from Somogy County, Hungary, between January 2021 and January 2022. Statistical tests showed significant differences in all seven body measurements (body weight, total body length, tail length, head length, wither height, hind leg (left) length, and neck circumference of adult red foxes between the sexes, being significantly lower in the case of females than males. Significant differences were also found between the sexes in adult red fox skull measurements (total skull length, zygomatic width, and mandible length). In the case of juvenile red foxes, not all body dimensions differed significantly between the sexes (body weight, head length, and neck circumference did not differ significantly). We also found significant differences between the sexes in skull dimensions, except for zygomatic width. Regarding significant differences, the values for females were lower than those for males. Concerning the red foxes in Hungary, we found evidence of sexual dimorphism in all body and skull measurements in adult red foxes, which were larger in males, but not in all of the dimensions in juveniles.

The role of morphological traits in predicting the functional ecology of arboreal and ground ants in the Cerrado–Amazon transition

There is often a vertical stratification of the vegetation in tropical forests, where each forest stratum has a unique set of environmental conditions, including marked differences in habitat heterogeneity, physical complexity, and microclimate. Additionally, many tropical forests are highly seasonal, and we need to consider the temporal variation in environmental conditions when assessing the functional aspects of their organisms. Here, we tested the hypothesis that vertical stratification and seasonality shape tropical ants' functional ecology and that there are differences in the functional trait diversity and composition between arboreal and ground-dwelling ant communities. We collected ants in the arboreal and ground strata in the rainy and dry seasons in six different areas, measuring seven morphological traits to characterize their functional ecology and diversity. Irrespective of the season, we found a distinct functional composition between arboreal and ground-dwelling ants and a higher functional richness on the ground. However, ground ants were more functionally redundant than arboreal ants. The differences in functional richness and redundancy between ant inhabiting strata and season could also be observed in the community-weighted mean traits: arboreal and ground ant traits can be distinguished in Weber's length, mandible length, eye length, and eye position on the head capsule. The differences in these functional traits are mainly related to the ants' feeding habits and the complexity of their foraging substrates. Overall, by providing the first systematic comparison of continuous traits between arboreal and ground-dwelling ants, our study opens new investigation paths, indicating important axes of functional diversification of tropical ants.

Ant communities in disturbed subtropical landscapes: is climate more important than stochastic processes?

Functional trait-based approaches have provided advances in the understanding of community assembly rules. Broad generalisations remain, however, limited due to the idiosyncratic nature of taxa and ecosystems, especially in tropical regions. We use fine scale resolution (30m grid) environmental variables and community surveys from nearly 100 secondary tropical forest sites to study niche-based or neutral assembly mechanisms in ground dwelling ants. This provides a unique opportunity for understanding fine scale drivers of taxonomic, functional and phylogenetic diversity in a region characterized by large topographic and climatic differences on a relatively small geographic scale. Precipitation emerged as the most consistent environmental correlate, in shaping taxonomic, phylogenetic and functional aspects of the communities. Functional diversity was weakly associated with topography and temperature related variables. The fourth corner model revealed that femur, scape and mandible length were key traits in response to precipitation, and that communities showed a functional homogenization towards shorter appendages at wetter sites. Our results suggest that neutral and deterministic assembly processes act in concert to shape the taxonomic, phylogenetic and functional aspects of leaf litter ant assemblages. The use of multiple complementary metrics and approaches along environmental gradients are powerful to reveal the subtilities of assembly processes and provide insight into the ways future communities might change.

Topographic, Morphological and Morphometric Investigation of Mandible in Norduz Sheep

In order to contribute to animal welfare, veterinary maxillofacial surgery is one of the fields of science that requires deep anatomical knowledge about the region. Therefore, in this study, it was aimed to define the mandible by using macroanatomical, morometric and topographic methods to understand the morphophysiology of the mandible in Norduz sheep. Norduz sheep mandibles of 10 male animals were used. Mandibles were first examined with classical morphometric and topographic methods. It was seen that the mandible consisted of corpus, ramus and angulus parts. It was observed that the foramen mentale was oval and round in shape and in different numbers on the lateral edge of the mandible. It was observed that the foramen mandible was elliptical. According to the statistical analysis, mandible length was measured as 149.12±4.75 mm on the right side and 148.12±4.50 mm on the left side in Norduz sheep. Mandible height was analyzed as 160.81±4.72 mm on the right side and 160.74 mm on the left side. The distance of the foramen mandible to the infradental space was 127.85±4.62 mm on the right and 125.31±4.11 mm on the left. Diastema length was analyzed as 38.05±1.34 on the right side and 40.87±2.81 on the left side. The length of the premolar and molar teeth on the margo alveolaris of the mandible was 56.69±2.38 mm on the right side and 54.13±2.73 mm on the left side. The distance of the foramen mentale to the gonion caudale was analyzed as 118.34±4.22 mm on the right and 118.90±4.12 mm on the left. According to the statistical analysis, L17 measured over the right and left mandibles was statistically significant (p

Record of New Termite (Blattodea, Termitidae) Species in Togo West Africa.

Simple SummaryIn the sub-Saharan regions of Africa, there are many termite species, of which very few have been correctly identified and described. The large majority of these species is either wrongly identified or waiting to be found and described because of the lack of identification keys and the errors within the existing keys. One way to overcome this problem is the use of reference works that contain illustrated parts of the body of termites along with accurate measurements of the features involved in termite identification. The purpose of this study is to provide pictures of the heads of soldiers (commonly used in termite identification) along with measurements of parts of the head and leg. A total of 12 termite species were examined. Seven of these species were already described, while the other five appear to have not been described before. Ten out of the twelve species are new records for the country.In Africa, despite their economic and ecological importance, termites are still relatively unknown. Their systematic remains uncertain, the approximate number of species for many biogeographic areas is underestimated, and there is still confusion in the identification of the species for many genera. This study combined morphological traits with morphometric measurements to determine several species collected in Togo and provided head illustrations of soldiers. Termites were sampled within the frame of transects laid in several landscapes inside three different parks including: Fosse aux Lions, Galangashie, and Fazao Malfakassa. Samples were grouped by morphospecies and measurements of part of the body (length and/or width of head, mandible, pronotum, gula, and hind tibia) were conducted. Twelve termite species including Foraminitermes corniferus, Lepidotermes sp., Noditermes cristifrons, Noditermes sp. 1 and Noditermes sp. 2, Promirotermes holmgren infera, Promirotermes sp., Unguitermes sp., Amitermes evuncifer, A. guineensis, A. truncatus, and A. spinifer were separated and pictured. Ten new species were added to the check list of the country, including five unidentified ones. Further studies such as biomolecular analysis should be carried out in order to clarify the status of these unknown species.

Stag beetle Cyclommatus mniszechi employs both mutual- and self-assessment strategies in male-male combat

Animals may base contest decisions on their fighting ability alone (self-assessment) or also their opponents’ (mutual assessment). Many male stag beetles develop disproportionately enlarged mandibles and use them as weapons. Information on their assessment strategy is limited. To investigate their assessment strategy and whether they adopt the same strategy at different stages of contests, we used food to encourage male Cyclommatus mniszechi of different (random pairings) or similar (ML-matched pairings) mandible length (ML) to interact. For the random pairings, losers had shorter mandibles than winners and were faster to feed. Overall contest duration and the tendency to escalate to tussles associated positively with winners’ ML and average ML in the random and the ML-matched pairings, respectively, consistent with self-assessment. Non-tussle phase duration associated positively with average ML in the ML-matched pairings, consistent with self-assessment. Tussle phase duration, however, positively associated with losers’ ML in the random pairings and had no association with average ML in the ML-matched pairings, consistent with mutual assessment. These results show that (1) the males employ both assessment strategies, (2) winners have more control over contest intensity than losers, and (3) males with shorter mandibles are quicker to feed and also more likely to lose fights.

Unsupervised learning for detection of possible sexual dimorphism in larvae of Belgica antarctica Jacobs (Diptera, Chironomidae)

Belgica antarctica is one of the two native chironomid species of the Antarctic Peninsula. In this species, adult males and females are considerably different, yet the question of larval sex differences in morphometric parameters remains unanswered. In this paper, we analyze five morphometric parameters: head capsule length, head capsule width, mandible width, mandible length, mentum length of 140 fourth-instar larvae of B. antarctica from seven study plots in the south of Petermann Island, Wilhelm Archipelago, Antarctic Peninsula. To infer possible sexual dimorphism, we use the methods of unsupervised analysis (PCA and hierarchical clusterization). Our results suggest that the selected morphometric features of width and length are highly intercorrelated and cannot differentiate sex in the sampled larvae of B. antarctica.

Morphometric and Genetic Description of Trophic Adaptations in Cichlid Fishes.

Simple SummarySkull and jaw shape are critical to how an animal eats. The goal of this work was to examine how facial variation evolves and the genetic basis of these changes. We used two species of Lake Malawi cichlids with different facial shapes, one which has evolved to eat prey by suction feeding, a second that bites algae from rocks, as well as hybrid individuals generated by artificial mating of the two species. We found a series of changes in craniofacial structure including the shape of the lower jaw and throat region that impact how animals perform at suction feeding and biting. We then identified genetic regions that regulate these facial shapes. These genetic regions suggested that evolution of the senses, among other traits, may play an important role in facial evolution. Also, evolution of different parts of the face are controlled by distinct genetic regions. Despite this, cichlids that eat similar ways have similar facial shapes, suggesting that the function of jaw movement places certain limits on facial evolution in cichlid fishes. Overall, this work provides insights into how the face evolves, how these changes relate to feeding, and the genes and molecules that regulate craniofacial variation.Since Darwin, biologists have sought to understand the evolution and origins of phenotypic adaptations. The skull is particularly diverse due to intense natural selection on feeding biomechanics. We investigated the genetic and molecular origins of trophic adaptation using Lake Malawi cichlids, which have undergone an exemplary evolutionary radiation. We analyzed morphological differences in the lateral and ventral head shape among an insectivore that eats by suction feeding, an obligate biting herbivore, and their F2 hybrids. We identified variation in a series of morphological traits—including mandible width, mandible length, and buccal length—that directly affect feeding kinematics and function. Using quantitative trait loci (QTL) mapping, we found that many genes of small effects influence these craniofacial adaptations. Intervals for some traits were enriched in genes related to potassium transport and sensory systems, the latter suggesting co-evolution of feeding structures and sensory adaptations for foraging. Despite these indications of co-evolution of structures, morphological traits did not show covariation. Furthermore, phenotypes largely mapped to distinct genetic intervals, suggesting that a common genetic basis does not generate coordinated changes in shape. Together, these suggest that craniofacial traits are mostly inherited as separate modules, which confers a high potential for the evolution of morphological diversity. Though these traits are not restricted by genetic pleiotropy, functional demands of feeding and sensory structures likely introduce constraints on variation. In all, we provide insights into the quantitative genetic basis of trophic adaptation, identify mechanisms that influence the direction of morphological evolution, and provide molecular inroads to craniofacial variation.

A new istiodactylid pterosaur, Lingyuanopterus camposi gen. et sp. nov., from the Jiufotang Formation of western Liaoning, China.

The Istiodactylidae is a group of pterodactyloids characterised by large nasoantorbital fenestrae and labiolingually compressed teeth, with several records reported from the Early Cretaceous of northeastern China and western Europe. Here we report a new istiodactylid, Lingyuanopterus camposi gen. et sp. nov. from the Jiufotang Formation of Lingyuan, Liaoning, northeastern China. The holotype is represented by a near-complete skull, mandible and atlas-axis complex. It is distinguished from other istiodactylids by several characters, including two autapomorphies: short triangular tooth crowns with sharp mesial and distal carinae limited to the distal teeth, mandibular symphysis occupying approximately a quarter the mandible length. We also report the presence of helical jaw joints in istiodactylids, and provide a revised diagnosis of the clade Istiodactylidae, which includes five genera: Istiodactylus, Liaoxipterus, Nurhachius, Luchibang and Lingyuanopterus. Four pellets containing fish fragments were observed and are tentatively interpreted as bromalites of Lingyuanopterus. Although members of this clade possess similar skull morphologies, istiodactylids vary in terms of their dentition, with at least three forms from the Jiufotang Formation alone. This may represent different feeding strategies, and also indicate a similarity between the pterosaur assemblages of northeastern China and Britain during the Early Cretaceous.

Cranial base measurements in different anteroposterior skeletal relationships using Bjork-Jarabak analysis.

To assess the linear and angular cranial base measurements (Bjork polygon) in different anteroposterior (AP) skeletal relationships using Bjork-Jarabak analysis. Pretreatment lateral cephalograms of 288 (146 women, 142 men, mean ages 21.24 ± 2.72 years and 22.94 ± 3.28 years, respectively) adult patients were divided into Class I, II, and III skeletal relationships according to their ANB angle. Linear and angular measurements of Bjork polygon were measured and compared among different skeletal relationships. Analysis of variance was performed to detect the differences among groups. Independent-sample t-test was used to detect differences between men and women. The Class II skeletal relationship has a significantly larger saddle angle than Class III does (P < .05), whereas Class III has a significantly larger gonial angle than Class II does (P < .05). The articular angle and sum of Bjork polygon angles were not significantly different among groups (P > .05). Anterior (N-S) and posterior (S-Ar) cranial base lengths were similar in the different AP skeletal relationships (P > .05). The ramal height and body of the mandible length were significantly larger in Class III compared with Class I and II (P < .05). Women had a significantly larger articular angle than men did (P < .05), although men had significantly larger linear measurements of Bjork polygon than women did (P < .05). The Class III skeletal relationship has a smaller saddle angle and larger mandibular length and gonial angle. Men have a larger cranial base and mandibular linear measurements and a smaller articular angle compared with women.

Reference ranges of fetal mandible measurements: Inferior facial angle, jaw index, mandible width/maxilla width ratio and mandible length in Thai fetuses at 15 to 23 weeks of gestation.

ObjectivesTo determine the normal distribution of 1) inferior facial angles (IFA), 2) jaw index, 3) mandible width/maxilla width ratio (MD/MX ratio), and 4) mandible length (ML) in second trimester Thai fetuses.MethodsA prospective study was performed between April 1 and October 31, 2020, at the Maternal-Fetal Medicine Unit of Songklanagarind Hospital. Transabdominal ultrasonography was performed on Thai singleton pregnant women at 150/7 to 236/7 weeks of gestation to measure IFA, jaw index, MD/MX ratio and ML. All women received standard antenatal care and were followed up until delivery. The exclusion criteria were multifetal gestation, congenital anomaly, chromosomal abnormality, fetal growth restriction, abnormal amniotic fluid volume, suspected abnormality of fetal mandible, maxilla or jaws based on the proposed criteria from previous studies and suspected neonatal structural or genetic abnormalities postnatally. Quantile regression was used to estimate changes in the median, 5th and 95th percentiles of each parameter across gestational ages and to generate formulas for predicting the 5th percentile value for each parameter.ResultsThe results of 291 women were analyzed. Scatter plots and reference ranges of each parameter were generated. IFA, jaw index and ML values significantly increased, while the MD/MX ratio value significantly decreased, with increasing gestational age. The formulas calculated for predicting the 5th percentile value for each parameter were IFA = 55.12 + 0.045*(GA in days—136) jaw index = 37.272 + 0.01693*(GA in days—136) MD/MX ratio = exp(0.027–0.00110*(GA in days—136)) ML = 20.83 + 0.243*(GA in days—136).ConclusionsThe reference ranges and formulas to calculate the 5th percentile values of mandible parameters in Thai fetuses were developed.Trial registrationThis study has been reviewed and approved by the Thai Clinical Trials Registry with identification number TCTR20210602003.

The relationship between maxillary and mandibular lengths of ethnic Bataks of chronological age 9–15 years

Background: Maxillary and mandibular growth have an important role in determining diagnosis and treatment plans. Knowledge of the growth of the maxilla and mandible becomes very important in designing a proper treatment plan and knowing the mean maxillary and mandibular lengths from the ages of 9–15 means malocclusion can be treated at the appropriate age. Purpose: The aim of this study was to determine the relationship between 9–15-year-old males and females and the length of the maxilla and mandible. Methods: This study used a cross-sectional design. The subjects consisted of 35 male and 45 females aged 9–15 years and 80 cephalometric radiograms were collected using a purposive sampling method from Universitas Sumatera Utara (USU) Oral and Dental Hospital based on inclusion and exclusion criteria. Data were collected by tracing the lateral cephalogram, the maxillary length and mandible lengths being measured on the cephalogram based on the McNamara method through a computer program, CorelDRAW. Pearson’s correlation coefficient was used for statistical analysis. Results: The average maxillary length for 9–15-year-olds was 96.35 ± 7.56 mm. The mean mandibular length for 9–15-year-olds was 122.29 ± 10.43 mm. Based on assessment and result, using the Pearson correlation coefficient test between maxillary length and mandibular length and chronological age, a maxillary length of p=0.003 and mandibular length of p=0.00 were obtained. Conclusion: There was a significant positive relationship between chronological age and maxillary length and mandibular length in 9–15-year-olds of Batak ethnicity.

Class II Treatment in Growing Patients: Preliminary Evaluation of the Skeletal and Dental Effects of a New Clear Functional Appliance

Objective: The purpose of this retrospective preliminary study was to analyze the skeletal and dentoalveolar effects of a new clear functional appliance in a sample of patients close to growth spurt with class II malocclusion attributable to mandibular retrusion. Materials and methods: A sample of growing patients underwent functional Class II correction using F22® (Sweden and Martina, Due Carrare (PD), Italy) Young, realized combining the aesthetic characteristics of the F22® clear aligner with the structural features of a functional appliance. For each patient, a digital setup was performed by a single operator to plan a mandibular advancement to the therapeutic position. Cephalometric analysis before and after treatment was performed. The purpose of the statistical analysis was to evaluate dental and skeletal changes associated with F22® Young device, and whether there were statistically significant differences in anatomical measurements between the beginning and end of treatment. Results: 15 patients, 7 females and 8 males of average age 10.3, were treated with the F22® Young appliance for an average period of 10 months ± 0.5 (maximum 11.5 months, minimum 10.5 months). The data showed that the SNB angle increase was statistically significant from T0 to T1, leading to a reduction in the ANB angle. Values for the mandible length, both total (Co-Gn) and at the base (Go-Pg), significantly increased. Conclusions: According to this preliminary study, F22® Young appliance is effective in promoting mandibular advancement when used near the pubertal growth peak. The device is comfortable and aesthetic, which certainly promoted patient compliance, a key factor for treatment success.

Topography of the location of mental foramen in dried edentulous human mandible and its clinical implication

The mental foramen is an oval or round opening on external surface of mandible and transmits mental nerve and vessels. Mostly located at apex of second mandibular premolar or between the apices of premolars. The study was commenced on 60 dried edentulous mandibles with the aim to determine location of mental foramen(MF) with reference to surrounding anatomical landmarks. By measuring its distance from midline (symphysis menti), posterior border of ramus of mandible, lower border of mandible. Length of lower border (Base) of mandible was also measured. In present study most common shape of mental foramen was round (70%). The mean distances of MF from midline are 24.36mm on right side and 24.15mm left side. From posterior border of ramus are 64.45mm on right side and 64.15mm on left side. From base of mandible are 12.29mm on right side and 12.48mm on left side. Length of base mandible (midline to angle of mandible) is 83.27mm right side and 83.12mm left side. Ratio of distance from symphysis menti to MF and length of base of mandible are same on both sides that are 0.29. There is statistically significant positive correlation between distance from symphysis menti to MF and length of base of mandible.The MF plays a very important role in treatment planning and its location needs to be considered prior to placement of dental-implants, regional anesthesia, osteotomy-surgeries and during complete denture-fabrication in order to avoid MN injury and related complications.

A comparison of the accuracy of the cervical vertebrae maturation stage method and Demirjian’s method on mandibular length growth

Background: Malocclusion is one of the most familiar dental problems, with a high prevalence among the population. Understanding the patient’s craniofacial growth and development is crucial in diagnosis, as are the planning and subsequent success of the treatment. Malocclusion needs to be treated early to optimise the outcome achieved by the treatment. One of the most common types of malocclusions observed in clinics is crowding. The craniofacial bone relevant to the treatment of crowding is the mandible, defined as the mandibular length from the condylion to gnathion areas. When planning treatment, clinicians may experience difficulties in determining the biological age of patient, particularly when supporting diagnostic tools are not available. The indicators of biological age can be observed by the assessment of bone maturation using the cervical vertebrae maturation (CVM) method and by the analysis of tooth maturation using Demirjian’s method. However, limited studies are available regarding the accuracy of these methods as diagnostic tools. Purpose: This study aims to analyse the accuracy of the CVM method compared with Demirjian’s method concerning mandibular length growth. Methods: An analytic research method and a cross-sectional design are employed. The research sample comprised 50 lateral cephalometric and panoramic photos of children aged 8-16 years. Data were collected by analysing the maturity level of the cervical vertebrae and the teeth, and measuring the mandible length of the children in the photos. The statistical test used was the Wilcoxon test. Results: The results of the Wilcoxon test for the asymptotic sign had a p-value of 0.116 &gt; 0.05, indicating no significant difference between the CVM and Demirjian methods. Conclusion: Both of the methods noted above yielded equally accurate results for determining mandibular length growth.

An investigation into the total mandibular length and its potential correlation with the intraoral forces

ObjectivesIntraoral forces can be affected by several factors, including craniofacial dimensions, muscles, teeth status, and age. This study aims to reveal a possible correlation between maximum vertical interocclusal bite and masticatory forces and the total mandible length. Materials and methodsThe law of the lever was used to elucidate the mastication function by recording the occlusion and phases of mastication movements. A total of 115 people, 18 females, and 97 males, participated in the study. The midpoints of Gnathion (Gn), and Condyle (Co) were selected on the digital radiographs, and line connecting these points were used. Bite, and masticatory forces were measured in the anterior (intercanine) and posterior (premolar-molar) segments. Pearson correlation and multiple regression analyses were performed to evaluate the relationship between mandibular measurements and masticatory force. ResultsTotal mandible length varied between 11.0 and 13.0 cm in females and between 10.3 and 13.9 cm in males. The bite force of the anterior segment was found to be 34.2–52.1 kg in females and 27.0–61.2 kg in males, whereas posterior segment masticatory forces were determined between 45.0 and 69.0 kg in females and 36.8–93.6 kg in males. A weak positive correlation was found between the posterior segment and total mandibular length (p = 0.016) in the study. However, no correlation was found between the anterior segment and total mandibular length (p = 0.733). ConclusionThe results of the current study point to the fact that, as the total length of the mandible increase, the posterior segment masticatory forces increase as well. However, this relationship is relatively weak.

Darwin’s and Wallace’s Fascinations With Oversized Morphology and the Question of Developmental Plasticity

AbstractDarwin in his book, The Descent of Man and Selection in Relation to Sex, described his fascination with a male Chiasognathus grantii Stephens (Coreptera, Lucanidae), a stag beetle species with enormous mandibles. Wallace in his book, The Malay Archipelago, recorded his enchantment with a male Euchirus longimanus L. (Coreptera, Scarabaeoidae), a ‘chafer’ species with ‘immense fore-arms’ (tibia or femora). These oversized traits have been interpreted as the results of allometry through sexual selection. Both Darwin and Wallace were aware that there was a large variation in these oversized traits intraspecifically, leading to the question of the role of variability in species-level evolution. To answer this question, I studied the variation in developmental plasticity (DP; the individual ability to react to external environment) of the stag beetles, which shows a great variation in external morphology. These observations indicated that 1) DP (measured in body length) is independent of allometry of the mandibles, 2) allometry of the mandibles had been ingrained in most members of the Family before the differentiation of DP took place, 3) DP is indirectly related to sexual selection through elongated mandibles that are used for fighting or securing the mate, as evidenced by the close correlation of DP with the mandible length, and 4) the enormous mandibles of stag beetles are the product of enlarged DP through allometry and sexual selection. From these results, I add enhanced DP as an independent element in the evolution of seemingly oversized traits seen in many beetle species.