A radiographic study of location of mental foramen in a selected Turkish population on panoramic radiograph

Purpose of this study was to investigate the most common position of the mental foramen in a selected Turkish population. The study sample included three hundred and sixty one panoramic radiographs of selected Turkish population taken in Faculty of Dentistry, University of Gazi. The most common position of the mental foramen was between the first premolar and the second premolar (71.5%). The mental foramen was symmetrical in 90.4% of patients. In this study, the difference of the location of the mental foramen in different ethnics groups was discussed. Clinicians and anthropologists should expect to find the position of the mental foramen to be symmetrical and between the first premolar and the second premolar teeth.     

A clinical and anatomical study of the location of the mental foramen in adult Chinese mandibles

One hundred mandibles of adult Chinese cadavers of both sexes without missing teeth, alveolar bone resorption and malposition of teeth were studied. The anatomical location of each mandibular mental foramen was measured by using a combination of three previous methods. Our results showed that the location of the mental foramen below the apex of the lower second premolar (relation IV: 58.98%) was the most common. On average, the distance between the most anterior portion of the anterior border of the mental foramen and the mandibular symphysis was 28.06 mm, between the most anterior portion of the anterior border of the mental foramen and the posterior border of the ramus 74.14 mm, between the inferior border of the mental foramen and the lower border of the mandibular body 14.70 mm, between the superior border of the mental foramen and the bottom of the lower second premolar socket 2.50 mm. The distance across the mental foramen between the alveolar crest and the lower border of the mandibular body was 30.29 mm. Our results were compared with those of other investigators. The significance of identifying the anatomical location of the mental foramen in dental practice is discussed.     

The localization and anthropometry of mental foramen on late Byzantine mandibles

Comprehensive studies of the human skeletal features and variations between and within populations are beneficial both for clinical applications and determination of racial characteristics of populations. The aim of this study was to examine the location and anthropometric characteristics of the mental foramen in 36 adult male mandibles of the Late Byzantine period. The results demonstrated that the most common position of the mental foramen was in line with the longitudinal axis of the second premolar (50% right side; 47% left side) followed by a location between the first and second premolars (33% right side; 36% left side). When compared with the results of previous similar studies, the results obtained in the present study suggest that traits such as the localization of mental foramen may not only differ between populations of different geographic environment but also within the inhabitants of the same geography.     

A comparison of the position of the mental foramen in Chinese and British mandibles

The antero-posterior position of the mental foramen was studied in 68 Chinese and 44 British skulls of known or calculated age at death. All skulls showed low pre-mortem tooth loss and had a good occlusion. The position of the foramen was related to the body of the mandible as well as to the standing mandibular teeth using two previously published methods. There was no significant difference in the size of the Chinese and British mandibles. There was a significant difference between the two groups when measurements relating the foramen to the body of the mandible (symphysis menti) were considered, the foraminal position being more distal in the Chinese group. The modal position of the foramen in the Chinese sample was along the long axis of the second premolar, whereas in the British sample it lay between the apices of the first and second premolar. The foraminal position apparently moved distally in both groups with age and this was likely to be associated with mesial tooth drift and age-related attrition.     

Tooth wear and the position of the mental foramen

Variation in the position of the mental foramen with respect to the teeth ("apparent" position) seems to be associated with race, but in the determination of this position, factors which affect the disposition of the teeth plainly have a bearing on the results. The apparent position was investigated in a sample of southern Chinese skulls of known age which were classified by the degree of tooth wear. Controlling for "true" position and size of the mandible, a highly significant correlation between wear and position was found, age and tooth size having no significant contribution as additional explanatory variables. The effect of tooth wear on the apparent position of the foramen may partly explain racial variation.     

Ontogenetic migration of the mental foramen in Neandertals and modern humans

Since the nineteenth century, researchers have noted that Neandertal and modern human adults differ in mental foramen position, although the ontogenetic changes in the position of this feature have only recently come under the scrutiny of paleoanthropologists. Research on mental foramen position has focused on whether this feature is inferior to a particular tooth. However, tooth position may not be a reliable indicator of mental foramen position because of variability in tooth size within and between taxa and during eruption events. As opposed to observing the mental foramen with respect to the postcanine teeth, we examined linear distances from the mental foramen to other mandibular landmarks. Modern human adults may appear truncated, or paedomorphic, in mental foramen position with respect to Neandertal adults. However, infants of the two taxa differ substantially in anterior mandibular form. The initial differences in the shape of the mental region may be related to the embryological position of the mental foramen in modern humans and its role in the development of the mental trigone. The shape changes that accrue thereafter, possibly from faster mandibular growth rates in Neandertals, further distinguish the adults from one another. Although mandibular shape differences exist from early infancy onwards, adults of the two taxa are broadly similar in bi-mental foramen breadth with respect to mandibular size. For this reason, qualitative assessments of mental foramen position may provide less taxonomic information than previously thought.     

Absence of the mental foramen in dry human mandibles.

The absence of the mental foramen was investigated in 1,435 dry human mandibles (2,870 sides). The foramen was absent twice in the right side (0.06%) and once in the left side (0.03%). The meaning of this anatomical variation was commented.     

Mental foramen and mental nerve: changes with age

In a study of 525 dry mandibles and dissections in 50 cadavers, the mental foramen (MF) was found: single in 94.67% of the cases and multiple in 5.33%. Its shape was round in 34.48% with an average diameter of 1.68 mm and oval in 65.52% with an average long diameter of 2.37 mm. In 43.66% the MF was located in front of the apex of the root of the second premolar. In children before tooth eruption, the MF is somewhat closer to the alveolar margin; during the eruption period, the MF descends to half way between the margins, and in adults with the teeth preserved, the MF is somewhat closer to the inferior border. With loss of teeth and bone resorption the MF moves upwards closer to the alveolar border. In extreme cases of resorption the MF and the adjacent part of the mandibular canal are open at the alveolar margin. In the dissections the findings were similar. The mental nerve emerged from the MF closer to or at the alveolar border, according to the degree of resorption. In extreme degrees of resorption, the mental nerve and the final part of the inferior alveolar nerve were found directly under the gums. In these cases, the vestibular grooves became very shallow, and the mucosa passed directly from the cheeks over the alveolar ridge. Practical implications of the changes of the MF and mental nerve are discussed.     

Dietary correlates associated with the mental foramen in primates: implications for interpreting the fossil record

The mandibular nerve is a sensory and motor nerve that innervates the muscles of mastication, the lower dentition, and the lower lip and surrounding structures. Although this nerve contains both efferent and afferent fibers, the mental nerve, a terminal branch of the mandibular nerve, is a strictly sensory nerve that exits the mental foramen and innervates the lower lip, the skin overlaying the mandible, and the oral mucosa around the mandible. Osteological foramina are often used as proxies for nerve cross section area and they often correlate well with some aspect of a primate's ecology (e.g., optic foramen and visual acuity). The primary objective of this study is to explore the correlation between the mental foramen and dietary preference among primates. The mental foramen of 40 primate species (n = 180) was measured from 3‐D surface models of the mandible. Both conventional and phylogenetic tests indicate that although frugivores have larger mental foramina than folivores, the differences were not significant. These results show that while structures like the infraorbital foramen correlate well with diet and touch sensitivity, the mental foramen does not. Based on these findings, the mental foramen is not a suggested morphological character for interpreting of the fossil record. J. Morphol. 277:978–985, 2016. © 2016 Wiley Periodicals, Inc.     

Metric dimensions of the proximal phalanges of the human hand and their relationship to side, position, and asymmetry

The anatomy of the proximal phalanges of the human hand has been widely described. Nevertheless, when consulting osteology and anatomy publications, the general opinion of researchers is that siding and allocating the proximal phalanges with regard to finger position is difficult, if not impossible. We provide morphological criteria for determining the side of the proximal phalanges and a metric means of allocating a phalanx to a specific finger. This paper also quantifies the absolute and directional asymmetry found in phalanges within this sample. The sample studied consists of three groups, one modern and two archaeological. To investigate these, three measurements were taken—maximum length, maximum width at the base and maximum width at the head. It was found that phalanges could be assigned correctly to the side and finger of origin in 100% of the cases when the five phalanges of a given hand were present, and that this result dropped to 92% when allocating isolated phalanges. The means of the measurements taken were larger in the modern group and a constant relationship between the greater basal width of the second and the fourth proximal phalanges was found.     

Which cells respond to gravitropic stimulus in the lentil root?

When roots of lentil ( Lens culinaris L., cv. Large blonde) were placed in horizontal position for 2 h, their upper side elongated faster than their lower side, and also faster than vertical controls. The length of the cortical cells was greater in the upper half than in the lower half of roots which had been horizontally stimulated for 2 h. The zone of curvature extended from the distal part of the meristem to the proximal part of the cell elongation zone. The curvature in the meristem was due to early differentiation of the cells of its upper part. In the proximal part of the cell elongation zone, bending took place due to inhibition of cell growth in the lower half of the root. The results obtained are in agreement with the hypothesis of lateral transport of an inhibitor in gravistimulated roots. This inhibitor should be present in greater amounts in the lower side of the stimulated root and in lower amounts in its upper side than in the vertical controls.     

Spatial relationship between the mental foramen and mandibular developing teeth in modern humans,chimpanzees, and hamadryas baboons

The mental foramen (MF) of adult human mandibles is characterized by its high position and posterosuperior opening orientation, compared with that of nonhuman primates. In this study, to examine when and how such interspecies variations in MF position/orientation are manifested in the context of dental development, positional relationships between the MF and nearby forming teeth (dc, dm1, C, P3) were assessed using CT‐scanned growth‐series mandibles of the following three species with various MF positions and anterior dental sizes: modern humans, chimpanzees, and hamadryas baboons. Results showed that modern humans have more antero‐superiorly located MF and dc than the two nonhuman samples during growth, whereas the MF and dm1 of hamadryas baboons are the most inferiorly positioned. Considering that the mandibular canal generally reaches the dc/dm1 position during infancy, the species differences in MF position can be attributed largely to the positions where the anterior deciduous teeth first appear. Specifically, the distinctive dental position of modern humans should stem eventually from the comparatively small anterior dental size. Furthermore, human MF position shifted slightly upwards with alveolar development, unlike in the nonhuman samples, accompanied by strong curvature and vertical elongation of the anterior mandibular canal. Meanwhile, the human MF shifted from a forward to a lateral/backward orientation in association with human‐specific growth‐related alveolar recession. The findings of this study, thus, collectively indicate that taxonomic variations in adult MF position/orientation can be interpreted partly by the positions of the surrounding developing teeth. Am J Phys Anthropol 154:594–603, 2014. © 2014 Wiley Periodicals, Inc.     

Anatomy and phylogenetic value of the mandibular and coronoid canals and their associated foramina in proboscideans (Mammalia)

Characters associated with the mandibular canal are differently distributed amongst proboscidean lineages and provide useful information on the systematics and relationships of proboscideans. The aim of this paper is to describe the pattern of the mandibular canal and its associated foramina in proboscideans in order to fully appreciate the extent of interspecific variation of these structures within the group and to discuss its systematic and phylogenetic value. Outgroup comparison indicates that the condition presented by the basal proboscidean Phosphatherium is morphotypic for proboscideans. Primitive proboscidean characters are: the low position of the mandibular foramen, and its crescent‐shaped outline, the occurrence of a coronoid foramen (canal), the occurrence of two lateral mental foramina, the posterior one at the level of (or slightly behind) the posterior margin of the symphysis, the anterior one in a more distal position, the absence of a medial mental foramen (MMF), the mandibular canal set just below the tooth row. The occurrence of a single lateral mental foramen may represent a shared derived character of Daouitherium, Numidotherium, and Barytherium. A unique derived feature of the Elephantinae mandible is the occurrence of a medial mental foramen on the medial side of the incisive part of the mandible. MMFs have never been observed in other proboscideans excluding elephantines. The very high frequency of MMFs observed in Mammuthus meridionalis–Mammuthus trogontherii–Mammuthus primigenius (>93 per cent of the studied specimens) could be considered a synapomorphy of this group. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 391–413.     

The course of the inferior alveolar nerve in the normal human mandibular ramus and in patients presenting for cosmetic reduction of the mandibular angles

This study was undertaken to quantify the path of the inferior alveolar nerve in the normal human mandible and in the mandibles of patients presenting for cosmetic reduction of the mandibular angles. The goals were: (1) to provide normative information that would assist the surgeon in avoiding injury to the nerve during surgery; (2) to characterize gender differences in the normal population; and (3) to compare the course of the nerve in the normal population to its course in a group of patients who presented with a complaint of "square face." The study was based upon the computerized tomographic scans of 10 normal patients (six men, four women) and 8 patients (all women) complaining of "square face." Using AnalyzePC 2.5 imaging software, the mandibles were segmented and the position of the nerve was recorded within its osseous canal in the mandibular ramus on each axial slice in which it was identifiable. Distances were calculated between the nerve and the anterior, posterior, lateral, and medial cortices. The positions of the lateral ramus prominence and the lowest point on the sigmoid notch were also recorded. The position of the mental foramen was recorded in relation to the nearest tooth, and the three-dimensional surface distances from the foramen to the alveolar bone, the inferior border of the mandible, and the mandibular symphysis were determined. The distances from the entrance of the nerve into the mandible to the lateral ramus prominence and the lowest point on the sigmoid notch were calculated. Summary statistics were obtained, comparing differences in gender. The nerve was identifiable in each ramus over a mean distance of 12.7 mm. On average, the lateral ramus prominence was 0.3 mm higher on the caudad-cephalad axis than the point at which the nerve entered the bone, whereas the location of the lowest point on the sigmoid notch was 16.6 mm above the nerve. The average distances from the nerve to the anterior, posterior, medial, and lateral cortices were 11.6, 12.1, 1.8, and 4.7 mm, respectively. Gender differences were significant for all of these except the medial cortex to nerve distance. On average, the mental foramen exited the body of the mandible immediately below the second premolar and the average surface distances from the foramen to the symphysis, the most cephalad alveolar bone, and the inferior border of the body were 30.9, 14.2, and 19.3 mm, respectively. With regard to the patients presenting for mandibular angle reduction, there were a few statistically significant but small scalar differences from normal controls.     

Requirement for the gravity-controlled transport of auxin for a negative gravitropic response of epicotyls in the early growth stage of etiolated pea seedlings

Gravity-controlled transport of auxin was studied for a negative gravitropic response in the early growth stage of etiolated pea (Pisum sativum L. cv. Alaska) seedlings, in which epicotyl bending was observed near the cotyledon nodes of the seedlings grown continuously from seeds germinated in a horizontal or an inclined position. Increased expression of an auxin-inducible gene, PsIAA4/5, was observed in the elongated side of epicotyls grown in a horizontal or an inclined position. Regardless of the conditions of seed germination, polar auxin transport in the proximal side of the first internodes of the seedlings was significantly higher than in the distal side. Polar auxin transport in the proximal side of epicotyls grown in an inclined position was significantly lower than in those grown in a horizontal position. In contrast, lateral auxin distribution from the proximal to distal sides in epicotyls grown in an inclined position was significantly higher than in epicotyls grown in a horizontal position. Accumulation of PsPIN1 mRNA encoding a putative auxin efflux facilitator, which was observed in vascular tissue, cortex and epidermis in the proximal and distal sides of epicotyls, was markedly influenced by gravistimulation. These results strongly suggest that gravistimulation induces changeable polar auxin transport and one-way lateral auxin distribution in epicotyls as well as asymmetric auxin accumulation in the proximal and distal sides of epicotyls, resulting in a negative gravitropic response of epicotyls in the early growth stage of pea seedlings.     

Hypodontia: Prevalence and pattern amongst the living Druze population – A Near Eastern genetic isolate

The Druze population is a small-sized Near Eastern genetic isolate with high rates of consanguineous marriages. The present study aimed at investigating prevalence, pattern and distribution of hypodontia in the permanent dentition, excluding wisdom teeth, amongst this population. Panoramic radiographs, dental casts, and anamnestic records of 85 un-admixed Druze schoolchildren (45 males, 40 females; age range = 14–18 years, mean age = 16 years, SD = 0.5 years) were examined for evidence of hypodontia. Those with any type of facial clefts or craniofacial syndromes were excluded. Hypodontia prevalence was 11.8% (11.1% for males, 12.5% for females) with no statistically significant difference between sexes. The average number of missing teeth per child was 1.4 (1.2 for males, 1.6 for females). The majority (90%) of affected individuals exhibited minor hypodontia (one or two teeth missing). The most commonly missing teeth were upper lateral incisors and canines, followed by lower and upper second premolars. Asymmetrical hypodontia was more prevalent. Maxillary, left side, and anterior segment predominance were observed. The distinct features of hypodontia among the Druze population are the relatively high prevalence of minor hypodontia, and the upper lateral incisors and canines being the most commonly missing teeth.     

Tooth replacement in the teleost fish Prionurus microlepidotus Lacépède

Previous studies on tooth replacement in lower vertebrates have been plagued by a lack of common integrative approaches and methods, making it impossible to furnish a phylogenetic synthesis. This study is based on serial sections of the jaw of Prionurus microlepidotus. Each Toothgerm was characterized by its developmental stage and its position in the jaw. The relationship between the developmental stage of toothgerm and position in the jaw has been studied and expressed in several graphical illustrations. The following conclusions have been made: (1) The initiation of toothgerms in P. microlepidotus is governed by two Zahnreihen, which respectively initiate toothgerms on the lingual and labial side of the functioning teeth in an alternating pattern. (2) Therefore, functioning teeth in one locus are supplied by the alternate eruption of lingual and labial toothgerms. (3) Advancing of tooth replacement in each locus is independent of functioning teeth and their successors in adjacent loci. (4) The disorders of replacement patterns are caused by an alternated rate of eruption of successive toothgerms as a response to unusual shedding of the functioning teeth.     

Scanning electron microscopic observations on the head morphology of seven different leptocephali belonging to six eel families (Anguilliformes)

Scanning electron microscopy observation was carried out on head morphology, number and construction of teeth, nostril position and the presence of neuromasts of seven species of leptocephali from six families of the Anguilliformes. The number and form of the teeth vary within the different families, from 76 teeth inGnathophis sp. (Congridae) to 32 teeth inAnarchias yoshiae (Muraenidae). In most of the genera the number of teeth on upper and lower jaws is almost equal, except inGnathophis sp.,Anguilla anguilla andKaupichthys hyoproroides. The unusual size and form of the leptocephali's teeth led us to speculate on the feeding behaviour of these larvae. Tentatively we suggest that the tooth formation of the leptocephali may act as a filtering system, rather than as a predatory apparatus, as its vicious appearance might suggest. Given the largely passive nature of a filtering system, the larvae would be able to concentrate on their migration. Of all the investigated leptocephali, onlyNemichthys scolopaceus shows one olfactory opening on each side of the head, whilst all the other species show two openings. The data obtained from these investigations suggest that teeth form as well as form and position of the nostrils are characteristics of the genera, and possibly also of the species.     

The relation of nerves to multiple regeneration in a single newt limb.

Three amputation surfaces were formed on the lower arm of a single newt. Growth occurred on all combinations of these surfaces. The proximal surface (the only single surface to form regenerates) produced more regenerates (76% of the cases) than the two more distal surfaces. Blocking the proximal surface with whole skin greatly stimulates the production of accessory structures on the first and/or second more distal surfaces. The mean number of nerve fibers on the proximal surface is considerably higher than the nerve counts of the first more and second most distal surfaces. Limbs possessing a notch or digit(s) on the proximal surface and the absence of growth on the first more and second distal surfaces also show a decrease in nerve number on the first more and second most distal surfaces. An analysis of the mean number of nerve fibers on the blocked (proximal) surface shows a noticeable decrease in comparison with nerve fibers in an equivalent level on normal limbs. Nerve fiber counts on the first more and second most distal surfaces are markedly increased on those limbs where the proximal surface was blocked with whole skin. Threshold experiments suggest that the irregular occurrence of accessory structures on the first more distal and second most distal surfaces may be related to an insufficient number of nerve fibers on these surfaces. Similarly, a possible explanation for the regular occurrence of accessory structures on the proximal surface is that nerve number on this surface is always above threshold.