Morphological variation in dentate and edentulous human mandibles

What we see is what we touch? Sex estimation on the skull in virtual anthropology

BACKGROUND

The increased use of virtual bone images in forensic anthropology requires a comprehensive study on the observational errors between dry bones and CT reconstructions. Here, we focus on the consistency of nonmetric sex estimation traits on the human skull.

MATERIALS AND METHODS

We scored nine nonmetric traits on dry crania and mandibles (n = 223) of archaeological origin and their CT reconstructions. Additionally, we 3D surface scanned a subsample (n = 50) and repeated our observations. Due to the intricate anatomy of the mental eminence, we split it into two separate traits: the bilateral mental tubercles and the midsagittal mental protuberance. We provide illustrations and descriptions for both these traits.

RESULTS

We obtained supreme consistency values between the CT and 3D surface modalities. The most consistent cranial traits were the glabella and the supraorbital margin, followed by the nuchal crest, zygomatic extension, mental tubercles, mental protuberance, mental eminence, mastoid process and ramus flexure, in descending order. The mental tubercles show higher consistency scores than the mental eminence and the mental protuberance.

DISCUSSION

The increased interchangeability of the virtual modalities with each other as compared to the dry bone modality could be due to the lack of tactility on both the CT and surface scans. Moreover, tactility appears less essential with experience than a precise trait description. Future studies could revolve around the most consistent cranial traits, combining them with pelvic traits from a previous study, to test for accuracy.

Immediate implant placement in the premolar maxillary area: a cone-beam computed tomography study

PURPOSE

This research aimed to investigate potential factors associated with the risk of perforation of the labial bone plate, nasal floor, or maxillary sinus floor during immediate implant placement (IIP) in the maxillary premolar area, utilizing a cone-beam computed tomography (CBCT) virtual study.

METHODS

CBCT exams from 179 eligible participants, encompassing 716 teeth, were included. Implants were virtually positioned in 2 orientations: along the long axis of the tooth (the prosthetically-driven position) and in an optimal position relative to adjacent anatomical structures (the bone-driven position). Binary logistic regression analysis was employed to assess potential associations between perforation or invasion and various covariates, including sex, age, tooth region, the distance from the tooth apex to the nasal floor or maxillary sinus floor, the angle between the prosthetically- and bone-driven positions (implant-line A angle [ILAA]), and the labial concavity angle (LCA).

RESULTS

The mean ILAA was 18.3°±8.0°, and the angle was significantly larger for the second premolar compared to the first premolar. The mean minimum implant length was 13.0±2.1 mm, with a bone anchorage of 4 mm. The incidence of perforation was 84.1% for the prosthetically-driven position and 40.5% for the bone-driven position. Factors associated with a higher risk of cortical bone wall perforation or invasion of the 2-mm safety margin from surrounding anatomical structures (in the bone-driven position) included female sex, older age, shorter distance from the tooth apex to the nasal cavity/maxillary sinus, and smaller LCA.

CONCLUSIONS

A high prevalence of cortical bone wall perforation or invasion of the 2-mm safety margin is anticipated when performing IIP in the maxillary premolar region.

Mental foramen and apical foramen: A dangerous anatomical proximity

The study evaluated the spatial position of the mental foramen (MF) using 300 cone-beam computed tomography. The spatial position was analyzed with the horizontal location and relative location (distance between apical foramen and MF). The horizontal location was assessed through three positions (positions 1, 2, and 3). The relative location was determined with the x, y, and x coordinates of the root apex of mandibular premolars and the MF. Student's t-test and chi-square were performed. The most common horizontal location (52%) was position 2, which means between the premolars (p < 0.05). The relative location of the MF to the root apex of the second premolar was closer than the first premolar (p < 0.05). The distance between the root tip of the second premolar and the MF was 5.27 mm, with a minimum value of 1.87 mm. Clinicians should be aware of the possible neural results to the mental nerve of an endodontic infection and the extrusion of irrigation solutions.

Evaluation of the validity of mental foramen USG measurements by comparison with CBCT and determination of blood flow

OBJECTIVES

To examine mental foramen (MF) morphology and morphometry in comparison with ultrasonography (USG) and cone-beam computed tomography (CBCT), and to determine the relationship between mental artery blood flow parameters and age, gender, dental status, alveolar crest height, mandibular cortical index (MCI) with USG.

METHODS

A total of 120 MF and mental arteries of 60 patients (21 males and 39 females), including 20 patients in each group, aged 18-39, 40-59, and 60 years and above, were evaluated. The horizontal and vertical diameter of the MF and the distance between it and the alveolar crest were evaluated with USG and CBCT. In addition, mental artery blood flow parameters were examined by USG.

RESULTS

When the horizontal diameter values of MF were compared in USG and CBCT measurements; the diameter was significantly lower in the measurements obtained by USG (p < 0.05). It was observed that there were no mental arteries whose blood flow could not be recorded, 31 (25.8%) had strong blood flow and 89 (74.2%) had weak blood flow. No significant correlation was observed between gender and blood flow parameters (p > 0.05).

CONCLUSIONS

Considering that CBCT images are used as gold standard in our study, it may be said that USG is not as reliable as CBCT in evaluating the MF dimensions in the maxillofacial region. Nevertheless, USG is a suitable technique for determining the visualizing and blood flow of the MF.

Evaluation of Position of Mental Foramen in Dentulous Population by Digital Panoramic Radiography

Need for the Study

The mental branch of the trigeminal nerve, which supplies sensation to the lower lip, originates in the mandibular canal, making it an essential anatomical structure for dentists and oral surgeons to access. It is not well known that there is a spectrum of normal that includes variants in which there may be more than one nerve entry site, which means that if the mental foramen is not protected, normal feeling in the lower lip may be lost permanently. The diagnostic value of global radiographic landmarks like the mandibular trench and the dental foramen in identifying skeletal problems has been investigated.

Materials and Methods

Four hundred patients over 40 who fit the inclusion/exclusion criteria were chosen. Patients were recruited from Vananchal Dental College and Hospital, Garhwa's Out Patient section for Oral Medicine, Diagnosis, and Radiology. The following patients with their consent are subjected for digital orthopantomography (Cephalometric Device for Rotograph EVOD Ref 930790001, SN 14112930, Villa Sistem Medical) and the captured images are then interpreted for the variations in mandibular canal.

Result

The results of our study are as follows: In this study, the mean age of the subjects was 47.27 years, with a range of 40-75 yearsMajority of cases were females (53.75%) and 46.25% were males.The top of the residual ridge, located between the mental foramen and the mandibular canal, is clearly visible to all observers (grade I).Only 1.75% of the people surveyed had a bifid canal, despite the fact that the majority of the people surveyed had a single mandibular canal on both sides (98.25%).Right side mean was 18,682.017, whereas left side mean was 16,331.851; nevertheless, this difference was not statistically significant (P = 0.0860 NS).

Conclusion

The dental foramen was located close to where the mandible and the area housing the next premolar met. These findings may be utilized to improve the safety of peri-apical surgical procedures. Therefore, it is therapeutically relevant to get insight into the structural alterations of the mental foramen and locate its location in preoperative radiological scans.

Owner Survey of 55 Dogs That Underwent Full Mouth Extraction Procedures in a Referral Practice

Full mouth extraction (FME) in dogs is a common procedure performed in veterinary dental referral practice. Clients may be apprehensive to have FME performed, with concerns for ability to eat and quality of life. These concerns may be barriers to electing to proceed. This study used a cross-sectional survey to identify concerns clients had regarding FME. Medical records of 168 dogs that underwent FME at a referral practice from 2013 to 2019 were sent surveys. A total of 55 responses were obtained. This study demonstrated that after extractions, 52.7% of the patients ate the same diet as before the surgery. Regarding enthusiasm for eating, 12 (21.7%) reported an increase in enthusiasm, 15 (27.3%) reported slightly more enthusiasm, 25 (45.5%) reported the same enthusiasm, two (3.6%) reported less enthusiasm, and one (1.8%) showed a complete lack of interest. Fifty-one (92.7%) reported improved postoperative oral comfort. Twenty-five respondents (45.5%) had a great deal of anxiety before the procedure, specifically regarding eating postoperatively, 13 (24.1%) were extremely concerned, 31 (57.4%) were somewhat concerned. Twenty-six (47.3%) were extremely anxious about anesthesia. This study demonstrated high client satisfaction with 45 (81.8%) of the respondents reporting high satisfaction. This survey demonstrated that FME is a successful procedure with a high rate of client satisfaction.

Immediate Implant Placement in the Maxillary Aesthetic Zone: A Cone Beam Computed Tomography Study

This study aimed to investigate the factors that could be associated with the risk of labial cortical bone wall perforation with immediate implant placement (IIP) in the maxillary aesthetic zone, in a cone-beam computed tomography (CBCT) virtual study. CBCT exams from 126 qualified subjects (756 teeth) were included. Implants were virtually positioned in two different positions: in the long axis of the tooth (prosthetically-driven position) and in an ideal position in relation to adjacent anatomical structures (bone-driven position). Two different implant diameters were planned for each tooth position, namely, 3.75 and 4.3 mm for central incisors and canines, and 3.0 and 3.3 mm for lateral incisors. The incidence of perforation was nearly 80% and 5% for prosthetically- and bone-driven position, respectively. Factors associated with a higher risk of cortical bone wall perforation (bone-driven position), according to logistic regression analysis, were women, wider implants, Sagittal Root Position class IV, and decrease of the labial concavity angle. Perforation of the labial cortical bone wall can be greatly minimized when the implant is placed in a bone-driven position compared to a prosthetically-driven position. It is important to preoperatively evaluate the morphological features of the implant site for risk assessment and to individualize the treatment plan.

Sexual dimorphism of the mandibular conformational changes in aging human adults: A multislice computed tomographic study by geometric morphometrics

The aging process has an impact on mandibular bone morphology and can therefore affect shape sexual dimorphism. Understanding the effect of senescence on mandibular shape changes is particularly important to correctly estimate the sex of an individual and predict age-related conformational modifications. The purpose of this study was to assess age-related changes in mandibular shape and sexual dimorphism. The study sample comprised 160 Multi Slice Computed Tomography examinations of individuals aged 40 to 79 years. Geometric morphometric analysis of fourteen osteometric landmarks was used to examine sexual dimorphism and patterns of mandibular shape variation with age. Results showed that mandibular sexual dimorphism of shape remained significant with aging. Conformational changes occurred between 50 and 70 years and were different for male and female individuals. Females presented earlier and more marked age-related shape changes than males. These observations suggest that mandibular senescence is a sexually dimorphic process since its onset, rate, and the areas subjected to conformational changes differ from male to female individuals. Senescence-related changes present substantial variability, and further investigation is required to determine precisely the age that marks their onset.

Morphological Investigation of Residual Ridge in Japanese Edentulous Elderly for Fabrication of Edentulous Stock Tray

The objective of this study was to determine the size of the residual ridge in edentulous elderly Japanese persons for preparation of edentulous stock trays and clarify any correlations among the items measured. The participants comprised 74 patients requesting construction of a complete denture for the maxilla, mandible, or both. The length, width, and anterior and posterior height of the maxillary and mandibular residual ridge was measured on a prepared working model using a caliper. For each of the maxillary and mandibular edentulous residual ridges, correlations among measurement items were analyzed employing Pearson's correlation coefficient. In participants who were edentulous in both the maxilla and mandible, correlations between the maxillary and mandibular measurement items were analyzed employing Pearson's correlation coefficient. The results revealed that the mean maxillary length of the residual ridge was 55.21±4.07 mm, while mean mandibular length was 56.03±4.04 mm. The mean posterior width of the maxillary jaw was 48.79±4.14 mm, while that of the mandibular jaw was 57.33±3.24 mm. A strong correlation was found between the length and width of the residual ridge in both the maxilla and mandible, but no strong correlation was detected between the height in the anterior tooth region and any other item measured. These findings suggest that the size of any given item can be estimated by measuring either the length or width of the residual ridge when selecting a stock tray. We also propose that it is necessary to prepare stock trays with several different heights in the anterior tooth region, regardless of the length and width of the tray, or to adjust the length of the tray.

Exploratory study of the three-dimensional morphological variation of the jaw associated to teeth loss

PURPOSE

The aim of this study is to evaluate the morphological variability in mandibles with different types of edentulism, comparing the use of traditional morphometrics and tridimensional geometric morphometrics.

METHODS

Traditional morphometrics and geometric morphometrics (GM) exploratory analysis, by principal components (PCs) and PC scores, were performed on a sample of 24 cadaveric hemi mandibles. A digital reconstruction of 3D surfaces of each specimen was obtained by CT scans segmentation. The mandibles were divided in three groups: full dentition (G1), partial edentition (G2) and total edentition (G3). The results of the two methods were compared in relation to the morphological variability determined with each method.

RESULTS

Both methods were consistent in terms of morphological variability between the defined groups. The main shape variations observed were a decrease in mandibular body height, a widening of the cross sectional morphology on the symphysis, a shorten-narrowed Ramus and a deeper sigmoid notch, in the partially or totally edentition groups, compared to the full dentition group.

DISCUSSION

The general patterns of morphological variations associated with edentulism that have been reported in literature could be visualized with GM method, which had not been previously used for this purpose. The GM methods could offer a more detailed definition of shape variations, which is critical in a clinical context. Moreover, GM allowed defining configurations of mean morphologies and an image library with different types of morphological variations.

The morphology of the human mandible: A computational modelling study

Cephalometric methods have been used to evaluate morphometric measurements of the mandible and quantify sex-related anatomical features; however, most studies to date employ a limited set of location-specific measurements without considering the entire three-dimensional anatomy of the mandible. The aims of this study were to develop statistical shape models (SSMs) of partially edentulous male and female mandibles to evaluate inter-subject morphological variability and secondly to assess the effectiveness of discrete clinical morphometric measurements in prediction of complete three-dimensional mandible geometry. Computed tomography images of forty partially edentulous female and twenty-five male subjects were obtained, and SSM developed using mesh fitting, rigid body registration and principal component analysis. Analysis of female and male SSMs showed that the variation along their first principal components was size-related. Sex-differentiating pure shape variations were found along the first principal component of size-normalised SSM and were observed to be most prominent in the symphysis and posterior ramus regions of the mandible. Seven morphometric measurements were found to characterise female and male shape prediction optimally. The capability to rapidly generate accurate patient-specific shape-predictive models of the mandible may be useful for implant development and pre-operative planning, particularly in the absence of bony structures following trauma or tumour resection.

Dental malocclusions are not just about small and weak bones: assessing the morphology of the mandible with cross-section analysis and geometric morphometrics

OBJECTIVES

Dental malocclusions in modern populations would be the result of small and weak jaws developing under low masticatory loads. We assess the validity of this by characterising the external and internal morphology of mandibles affected by class II and III malocclusions and comparing them with those from individuals with different masticatory load patterns.

MATERIALS AND METHODS

CTs from up to 118 individuals exerting intensive, medium and low masticatory loads with harmonic occlusion, and from class II and III individuals, were used to compare their external shape using geometric morphometrics, as well as their internal amount and distribution of cortical bone.

RESULTS

The low-load groups (harmonic, class II and III occlusion) are externally more gracile than the intense and medium load groups. But more relevant in shape variation is a marked allometric pattern, which differentiates class II (small) and III (large) mandibles. Despite gracility, the relative amount of cortical bone in the low-load groups is larger than in the remaining groups.

CONCLUSIONS

There is no evidence that the modern mandible, including class II and III individuals, is intrinsically small and weak. Instead, there is a rather large degree of morphological variation, which could be linked to a lack of constraints derived from low masticatory loads. Thus, the effect of other factors such as genetics, but also basal metabolism, should be looked in more depth.

CLINICAL RELEVANCE

Dental malocclusions are a common disorder whose aetiology has not been unravelled, and several to be considered in the prevention and therapy of malocclusion.

A 3D characterization method of geometric variation in edentulous mandibles

PURPOSE

The aim of this study was to perform an exploratory analysis of the morphological variations of mandibles at diverse states of edentulousness using tridimensional geometric morphometrics.

METHODS

Twelve cadaveric mandibles were selected and divided in three groups: dentate (G1), partially edentate (G2) and totally edentate (G3). CT scans, segmentation and digital reconstruction of 3D surfaces of each specimen was made. Thirteen landmarks were defined; the measurement error was determined and 3D morphometrics exploratory analysis by principal components (PCs) and PC scores was performed.

RESULTS

The principal shape variations in G2 and G3 compared to G1 can be summarized as follows: (1) decrease in the mid body mandibular height of 24% in G2 and 41% in G3, (2) decrease of symphysis height of 16% in G2 and 37% in G3, (3) a decrease in posterior mandibular height of 30% in both G1 and G2, (4) a deeper sigmoid notch also in both groups and finally (5) a widening of 7.7% in the cross sectional morphology on the symphysis in G3.

CONCLUSIONS

The 3D morphometric methods, combined with surface morphing tools confirmed the main patterns of bone changes in edentulous mandibles, referenced in the literature. The average 3D mandibular morphologies of each edentulousness state group was also defined. These methods could offer more accurate definition of shape variations, which is critical in a clinical context. This study provides clinicians with highlights of 3D morphological mandibular variations at different states of edentulism and not only in 2D projections as they are currently described. The 3D surface model for each group in PDF3D file format, are include in supplementary material.

Locating the mental foramen at the bedside with point of care ultrasound imaging

Introduction

Ultrasound guided neuro-anaesthesia is a developing field of interest to clinicians from various disciplines. The objective of this proof of concept study was to explore the ability, ease and rapidity of ultrasonography in locating the mental foramen.

Methods

A convenience sample of 100 patients aged 18 years or older, with no known pathology to the mandibular region, that presented to a single urban ED were enrolled. All patients underwent an ultrasound examination on both sides of the face to locate the mental foramina.

Results

A total of 100 patients' mental foramina were studied. Mean age was 35.7 years (SD 9.1 years), 50% were black and 25% each were asian and white. The mental foramina were ultrasonographically identified in all (100%) of the subjects in the study group. Although requiring a larger quantity of ultrasound gel, the mental foramina were also visualized in all twelve subjects with facial hair. Three out of the 100 subjects were noted to have accessory mental foramina. The overall mean time taken to locate the first mental foramen in each patient was 16.1 seconds (SD 12.9 seconds). For the first 25 subjects studied, the mean time taken was 34.7 seconds (SD 13.4 seconds), whereas for the next 75 subjects studied, the mean time taken was 9.9 seconds (SD 3.0 seconds).

Conclusion

Bedside ultrasound imaging is a potentially reliable method to identify and locate the mental foramen. With practice and experience, the mental foramen can be more easily identified.

Anatomical landmarks of mandibular interforaminal region related to dental implant placement with 3D CBCT: comparison between edentulous and dental mandibles

BACKGROUND

Anterior mandibular (interforaminal) region is important in implant applications as it serves a basis for neurovascular bedding and holds the prosthesis for patients. Treatment planning for dental implant patients is often complicated by the unknown extent of the anterior loop of the neurovascular bundle. Anatomical structures including mandibular incisive canal (MIC) and lingual foramen (LF) should also be examined as part of the detailed analysis for their neurovascular structures. This study aimed to detect the positions of LF and MIC as well as the prolongation of interforaminal region in Anatolian population to supply the reference data of the surgical safe zone in chin for the clinicians.

MATERIALS AND METHODS

Mandibles of 70 adult specimens (35 edentulous + 35 dentate) were retrieved from the Department of Anatomy, Ege University. Images of the dry mandibles were obtained using a cone beam computed tomography unit applying a standardized exposure protocol. Afterwards, mandibles were sawn into vertical sections according to the respective tomographic cross-sections. Images were evaluated for the absence/presence of the MIC, its dimensions and antero-posterior length for both edentulous and dentate groups. In addition; the presence, number, location, labial canal and LF diameter and height of the LF were determined for both groups.

RESULTS

The MIC was observed in 80 and 68.6% of the dentate and edentulous groups, consecutively (p > 0.05). The MIC continued towards the incisor region in a slightly downward direction. The LF was observed in all dentate mandibles (100%), while it was present in 94.3% of the edentulous mandibles (p > 0.05). For the dentate group, 62.9% of the specimens had two foramens and 20% had three foramens in the mandibular midline. Mean length of the MIC in dentate groups and edentulous groups was measured as 2.55 ± 0.809 and 3.08 ± 1.745 mm, respectively. Well-defined MIC mean diameter in dentate groups and edentulous groups were measured as 2.44 ± 0.702 and 2.35 ± 0.652 mm, respectively. Significant difference was found between dentate and edentulous group in most of the parameters except for the LF and the diameter of the MIC (p > 0.05). The correlation between observers' measurements ranged between 0.742 and 0.993 for all anatomical landmarks and mandible groups.

CONCLUSION

The MIC and LF are associated with neurovascular bundle variations in number, location and size. Therefore, clinicians should determine each of these anatomical structures on a case-by-case basis to recognize their presence and to take measures for the possible implications of various treatment options. These guidelines included leaving a 2 mm safety zone between an implant and the coronal aspect of the neurovascular bundle. To avoid neurovascular injury during surgery in the interforaminal area, guidelines were developed with respect to validating the presence of an anterior loop of the neurovascular bundle.

Predictive factors of the dimensions and location of mental foramen using cone beam computed tomography

Objective

The mental foramen (MF) hosts main neurovascular structures, making it of crucial importance for surgical procedures. This study aimed to analyze the factors influencing the dimensions and location of the MF.

Materials and methods

Cone beam computed tomography (CBCT) scans of 344 patients were examined for MF dimensions, as well as for the distances from the MF to the alveolar crest (MF-MSB), and to the inferior mandibular border (MF-MIB).

Results

Gender, mandibular side and presence of accessory mental foramina (AMF) significantly influence MF area. Males, left hemimandibles, and hemimandibles with no AMF had a higher rate of large MF areas (B = − 0.60; p = 0.003, females; B = 0.55; p = 0.005; B = 0.85; p = 0.038). Age, gender and dental status significantly influence MF-MSB distance. The distance decreased as age increased (B = −0.054; p = 0.001), females showed a lower rate of long MF-MSB distances (B = −0.94, p = 0.001), and dentate patients showed a higher rate of long MF-MSB distances (B = 2.27; p = 0.001). Age, gender and emerging angle significantly influenced MF-MIB distance. The distance decreased as age and emerging angle increased (B = −0.01; p = 0.001; B = −0.03; p = 0.001), and females had a lower rate of long MF-MIB distances (B = −1.94, p = 0.001).

Conclusions

General and local factors influence the dimensions and location of MF. MF dimensions are influenced by gender, mandibular side, anteroposterior position, and the presence of AMF. Distance from MF to alveolar crest is influenced by gender, age and dental status, while the relative MF position is influenced by age and dental status. CBCT images make it possible to analyze the MF in order to avoid complications during surgical procedures.

Assessing age-related change in Japanese mental foramen opening direction using multidetector computed tomography

OBJECTIVE

The purpose of this study was to investigate how the opening direction of the mental foramen (MF) changes with age in a Japanese population using multi-detector computed tomography (MDCT).

METHODS

Post-mortem MDCT scans of 121 Japanese subjects (66 males and 55 females) were carried out where all subjects possessed at least twenty teeth, including molar teeth, in the upper and lower jaws. Two angles of the mental foramen opening were measured, namely the superior-inferior angle in the coronal plane and anterior-posterior angle in the transverse plane, on the CT reconstructed images. The associations between age and these two angles were evaluated using a multiple regression analysis.

RESULTS

For male subjects, the relationship between the superior-inferior angle and age was a quadratic curve (p < 0.001). This angle increased until the subject reached their early 50s and then the angle decreased with age. In the transverse plane, there was a linear relation between the anterior-posterior angle and age (p=0.002).It was noted also that the angle decreased with age. By contrast, however, no significant associations between the two angles and age for either measurement were noted for female subjects. This study demonstrated that the opening direction of the mental foramen changes with age in Japanese male subjects. By contrast this change in the opening direction of the mental foramen was not demonstrated in Japanese female subjects. In male subjects, the opening direction moves superiorly until the individual reaches their early 50s, and then moves inferiorly with advancing age. It also shifts from a posterior to an anterior position with age.

CONCLUSION

These observed change differ from the results of previous studies. The findings could be useful for forensic science as they demonstrate a change in the position of mental foramen in a sample of contemporaneous male Japanese subjects.

Ultrasonographically locating the mental foramen and its soft tissue relations

OBJECTIVES

This ultrasound-based cross-sectional study aimed to visualize, locate and compare the position of the mental foramen with regard to its relationship to various soft tissue landmarks.

METHODS

100 Black and Caucasian subjects were included. An ultrasound transducer was used to locate the mental foramina. Distances to various landmarks were measured and compared.

RESULTS

All mental foramina were visualized. The mean soft tissue distance of the entire group from the mental foramen on the right and left sides, respectively, were as follows: (a) 3.4 mm [standard deviation (SD) 1.7 mm] and 3.4 mm (SD 1.5 mm) lateral to a vertical line passing through the chelion; (b) 20.1 mm (SD 2.6 mm) and 20.1 mm (SD 2.6 mm) distal to a horizontal line bisecting the chelions; (c) 15.1 mm (SD 2.4 mm) and 15.0 mm (SD 2.4 mm) proximal to the inferior border of the mandible. We found no statistically significant differences between race groups, between gender group and between age categories with regard to the horizontal soft tissue distance from a vertical line passing through the chelion to the mental foramen on the right or left sides. There were statistically significant (but not clinically significant) differences between race groups and between gender groups but not between age groups with regard to the vertical soft tissue distance from a horizontal line bisecting the chelions to the mental foramen as well as from the inferior border of the mandible to the mental foramen on both the right and left sides.

CONCLUSIONS

This study suggests that ultrasound is a feasible imaging modality that can be utilized to locate the mental foramen. Differences in the position of the mental foramen with regard to various soft tissue landmarks are minor and clinically insignificant.

Investigation of influence of different implant size and placement on stress distribution with 3-dimensional finite element analysis

PURPOSE

The purpose of this study was to analyze the biomechanical behavior of implants with varying number, inclination, and size, using 3-dimensional finite element (FE) analysis.

MATERIAL AND METHODS

A total of 10 FE models were constructed to simulate 5 implant placement configurations: 4 and 5 axial implants, 4 implants inclined with 17.5 degrees mesial and 35 degrees distal, and 2 axial and 2 distal implants inclined with 17.5 and 35 degrees, using implants of 3.5 and 5.5 mm diameters. A vertical load of 300 N was applied to the distal portion of a standardized size metal framework.

RESULTS

Increasing the number of implants decreased the stress in the bone for axially placed implant models. The short implants with a large diameter resulted in lower stress values in the bone, but higher stresses in the implant/abutment assembly than the long implants with a small diameter. Increasing diameter of implants decreased high stress concentration in the cortical bone, resulting from increasing cantilever length.

CONCLUSIONS

Decreasing cantilever length with distal implant inclination decreases the stress values in the implant, cortical bone, and framework.

The Ultrasonographic Determination of the Position of the Mental Foramen and its Relation to the Mandibular Premolar Teeth

INTRODUCTION

The position of the mental foramen has been well researched in cadaver specimens, radiographically as well as intraoperatively. To our knowledge, this landmark study is the first to make use of ultrasonography in a study population to determine the position of the mental foramen in relation to the mandibular premolar teeth. Ultrasonography has great potential to further revolutionize the practice of medicine and dento-maxillofacial surgery.

AIM

To make use of ultrasound to determine the position of the mental foramen and its relation to the mandibular premolar teeth.

MATERIALS AND METHODS

One hundred Black and Caucasian subjects were enrolled. A high frequency (8MHz) transducer (PLF.805ST) of a diagnostic ultrasound system (model SSA-510A) was applied above the inferior border of the mandible, just lateral to the mentum. With the marker of the transducer pointing cranially, the position of the mental foramen in relation to the closest mandibular premolar tooth was determined. The position was compared across race, sex and age groups.

RESULTS

All mental foramina (100%) were visualised. Overall the most frequent position of the mental foramen was in line with the long axis of the second premolar on the right (44%) and between the first and second premolars on the left (44%). There were no statistical differences (p >0.05) between race groups, sex and age groups with regard to the position of the mental foramen in relation to the mandibular premolars. However, in Blacks, the most frequent position of the mental foramen was in line with the long axis of the second premolar and in Caucasians the most common position was between the first and second premolars. The most frequent position of the mental foramen in females was in line with the long axis of the second premolar on the right and between the first and second premolars on the left. In males, the most frequent position of the mental foramen was in line with the long axis of the second premolar bilaterally. The most common position of the mental foramen in the age group category 18-30 years was between the first and second premolars. In patients aged 31-60 years the most frequent position was in line with the long axis of the second premolar.

CONCLUSION

Ultrasound is a sensitive modality to locate the mental foramen. There are differences in the most common position of the mental foramen with regard to the long axis of the premolar teeth. Ultrasonography has the potential to revolutionize the practice of dento-maxillofacial surgery.

A morphometric analysis of the mandibular canal by cone beam computed tomography and its relevance to the sagittal split ramus osteotomy

PURPOSE

The aim of the present study was to morphometrically analyze the mandibular canal through the mandibular ramus by cone beam computed tomography (CBCT) and to relate the findings to performing sagittal split ramus osteotomy.

METHODS

CBCT of 200 patients were analyzed. Five parameters were measured at the axial scan, from the mandibular foramen to 21 mm below it (3-mm intervals). The canal was classified according to the position within the bone marrow space. Variations were evaluated according to age, sex, side, and number of mandibular teeth.

RESULTS/CONCLUSIONS

The following measurements increased gradually towards the most inferior level of measurement: the total thickness of the mandibular ramus through the center of the mandibular canal, the width of the bone marrow space (both buccal and lingual), and the narrowest width from the mandibular canal inner cortical to the mandibular ramus external cortical. The inner diameter of the mandibular canal slightly decreased to the same direction. Concerning the mandibular canal position within the bone marrow space, the percentage of the separate type increased towards the most inferior level of measurement, and the contact and fusion types decreased. Age, number of teeth, and sex had no significant influence on the total thickness of the mandibular ramus and on the narrowest width from the mandibular canal inner cortical to the mandibular ramus external cortical.

Anatomical characteristics and visibility of mental foramen and accessory mental foramen: Panoramic radiography vs. cone beam CT

Background

The mental foramen (MF) is a small foramen located in the anterolateral region of the mandible through which the mental nerve and vessels emerge. The knowledge on the anatomic characteristics and variations of MF is very important in surgical procedures involving that area. The aim of this study was two-fold: firstly, to analyze the anatomic characteristics of MF and the presence of accessory mental foramen (AMF) using CBCT and, secondly, to compare the capability of CBCT and PAN in terms of MF and AMF visualization, as well as influencing factors.

Material and Methods

A sample of 344 CBCT scans was analyzed for presence and characteristics (i.e. diameter, area, shape, exit angle) of MF and AMF. Subsequently, corresponding PANs were analyzed to ascertain whether MF and AMF were visible.

Results

Out of the 344 patients, 344 (100%) MFs and 45 (13%) AMFs were observed on CBCT. Regarding gender, MF diameter and area, MF-MIB and MF-MSB distances, and exit angle were all significantly higher in males. Also, statistically significant differences were found in terms of age and dental status. Statistically significant differences in MF long and short diameters and MF area were found with respect to AMF presence (p=.021, p=.008, p=.021). Only 83.87% of the MFs and 45.83% of the AMFs identified on CBCT were also visible on PANs. MF diameter, shape, exit angle, and age had a significant influence on MF visualization on PAN (B=.43, p=.005; B=-.55, p=.020; B=.20, p=.008; B=.61, p=.005).

Conclusions

PAN is not an adequate technique to properly identify MF and AMF. Diameter, shape, exit angle, and age are all factors influencing MF visualization on PAN images. For surgery involving the MF anatomical region, a preoperative radiological study with CBCT is of crucial importance to avoid complications.

Key words:Mental foramen, accessory mental foramen, mandibular anatomy, cone beam computed tomography, panoramic radiography.

Importance of teeth in maintaining the morphology of the adult mandible in humans

Edentulism can negatively affect both masticatory performance and dietary intake by altering the patterns of biomechanical stress and strain, which in turn modifies the morphology of the different regions of the mandible. The morphological changes in the mandible caused by these stressors are unknown when comparing mandibles across varying dentition states. This study investigated differences in the morphology of human mandibles across various states of the dentition. In total, 498 mandibles of individuals between 20 and 80 yr of age at death were sourced from the Raymond A. Dart Collection of Human Skeletons. These included fully dentate (n = 95), partially edentulous (n = 333), and fully edentulous (n = 70) mandibles. Twelve linear anthropometric measurements of the mandible were derived from digitized landmarks located on its external surface. Data analysis included geometric morphometrics and multivariate analyses. Compared with dentate and partially edentulous mandibles, fully edentulous mandibles showed a shorter alveolar height (-0.4 mm), a shorter mandibular body length (-4 mm), a larger gonial angle (+4°), a more obtuse mental angle (+4.7°), a broader bicondylar width (+3.8 mm), and a taller ramus height (+1.6 mm). Thus, edentulous states are associated with an altered mandibular morphology, which may result from a reduction in jaw function.

Multidisciplinary care in severe pediatric electrical oral burn

Oral burns in pediatric patient are commonly due to electrical injuries, representing an important reconstructive issue even for functional than esthetic reason. Different classification, surgical management and even oral device were described to allow the best long-term result. In most case a multidisciplinary approach is necessary to achieve a satisfactory outcome. A severe case of pediatric oral burn with germinative teeth damage is presented, describing a multispecialist team approach that guarantee a satisfactory outcome by reconstructive surgery, careful progressive evaluation of dental and soft tissue healing and speech recovery. The use of acellular dermal substitute template within traditional reconstructive surgery had provided a good functional and esthetic result joint to valid preservation of germinative dental element as shown at long-term X-ray evaluation. Intensive rehabilitation speech program has also avoided phonetic impairment in an important speech develop period. It was so evident that the necessity of a multispecialist care in such difficult injury to achieve the best long-term result.

Key local and surgical factors related to implant failure

The concept of osseointegration has revolutionized the treatment options for the replacement of missing teeth in both partially and completely edentulous patients. Dental implants are widely used because clinical practice and studies have documented its successful outcomes. However, implants can occasionally fail, and such failures can be classified as early or late. Measures that can aid in the early recognition of failing osseointegrated implants are needed, as are measures that can facilitate appropriate treatment methods aimed at saving failing implants by determining the probable etiologic factors. This article summarizes our current understanding of the local factors that can be linked to implant failure.

Morphometric study of mandibular foramen in macerated skulls to contribute to the development of sagittal split ramus osteotomy (SSRO) technique

PURPOSE

The aim of this study was to provide morphometric data, obtained from macerated mandibles, which might facilitate the topographic location of the mandibular foramen, considering aspects such as gender, age and ethnicity.

MATERIALS AND METHODS

One hundred and eighty-five macerated mandibles of adult black and white individuals of both sexes were analyzed. Initially, 5 points were established: MF, the lowest point of the mandibular foramen; S, greatest concavity of the mandibular notch; A, anterior margin of the ramus of mandible; P, posterior margin of the ramus of mandible; and Go, gonion. Then the following measurements were performed bilaterally: MF-S, MF-A, MF-P and MF-Go.

RESULTS

The following mean values were found: MF-S: 21.02 mm for white females (WF) and 22.00 mm for black females (BF); 24.40 mm for white males (WM) and 24.35 mm for black males (BM); MF-A: 17.05 mm for WF and 18.09 mm for BF; 17.18 mm for WM and 18.11 mm for BM; MF-P: 11.11 mm for WF and 12.24 mm for BF; 13.10 mm for WM and 14.15 mm for BM; MF-Go: 19.00 mm for WF and 19.44 mm for BF; 23.13 mm for WM and 22.12 mm for BM.

CONCLUSIONS

The values found in this study, considering gender, age and ethnic group, can be used as a parameter to carry out the sagittal split ramus osteotomy technique, making it more predictable and with less risk of complications.

Reasons for failures of oral implants

This study reviews the literature regarding the factors contributing to failures of dental implants. An electronic search was undertaken including papers from 2004 onwards. The titles and abstracts from these results were read to identify studies within the selection criteria. All reference lists of the selected studies were then hand-searched, this time without time restrictions. A narrative review discussed some findings from the first two parts where separate data from non-comparative studies may have indicated conclusions different from those possible to draw in the systematic analysis. It may be suggested that the following situations are correlated to increase the implant failure rate: a low insertion torque of implants that are planned to be immediately or early loaded, inexperienced surgeons inserting the implants, implant insertion in the maxilla, implant insertion in the posterior region of the jaws, implants in heavy smokers, implant insertion in bone qualities type III and IV, implant insertion in places with small bone volumes, use of shorter length implants, greater number of implants placed per patient, lack of initial implant stability, use of cylindrical (non-threaded) implants and prosthetic rehabilitation with implant-supported overdentures. Moreover, it may be suggested that the following situations may be correlated with an increase in the implant failure rate: use of the non-submerged technique, immediate loading, implant insertion in fresh extraction sockets, smaller diameter implants. Some recently published studies suggest that modern, moderately rough implants may present with similar results irrespective if placed in maxillas, in smoking patients or using only short implants.

Evaluation of the morphological changes in the mandible for dentate and totally edentate elderly population using cone-beam computed tomography

PURPOSE

The loss of teeth considerably modifies the mandibular shape. The aim of this study was to compare the morphological changes in the mandible for dentate and totally edentate elderly subjects using cone-beam computed tomography.

METHODS

In total, 50 cone-beam computed tomography patients (25 dentate, 25 edentate) without any maxilla-mandibular dysmorphosis were analyzed retrospectively. Panoramic representations of the mandible with superimposed axial slices and cross-sectional slices were developed with the cone-beam computed tomography scans. Values of the mandibular cortical index, bone quality index, gonial angle, antegonial angle, antegonial depth and condyle angle in the left and right side were measured.

RESULTS

There was a significant difference in the mandibular cortical index between the total edentate group and the dentate group in the left side of the mandible (p < 0.001). There was a significant difference in the bone quality index between the total edentate group and the dentate group in the right side and the left side (p < 0.001). There was a significant difference in the bone quality index between the right side and the left side (p < 0.005). When comparing gender, there was only a difference in the right side (p < 0.05).

CONCLUSIONS

Our study concluded that the mandibular basal bone morphology changes as a consequence of tooth loss. Cone-beam computed tomography is shown to be a good tool in investigating and achieving these results.

Dentition, bone loss, and the aging of the mandible

BACKGROUND

Facial aging is a dynamic process with impact on both the soft tissues and the bones. Despite a growing body of evidence, controversy still exists regarding absolute characteristics of the aging facial skeleton.

OBJECTIVE

The purpose of this study was to investigate various mandibular measurements in different age groups and to delineate the relation of the dentition to these parameters.

METHODS

Ninety Caucasian mandibles were assessed for the following distance landmarks: gonion-gonion, infradentale-gnathion, mental foramen-mandibular crest, mental foramen-inferior mandibular border, gnathion-gonion, condyle-gonion, and gonial angle. The measurements were compared according to age, sex, and dentition.

RESULTS

The number of teeth decreased significantly with increasing age in males (P = .002) and females (P < .001). There were no other statistically significant differences between age groups for the rest of the parameters. The infradentale-gnathion distance (P = .005) and the mental foramen-mandibular crest distance (P < .001) was found to increase with total number of teeth. Other parameters did not show a significant relation to dentition. All parameters were significantly larger in the male subgroups with the exception of gnathion-gonion distance and gonial angle. Bilateral mandibular measurements were symmetric except for the gonial angle, which was more obtuse on the right side in males (P = .007) and females (P = .018).

CONCLUSIONS

Our findings support previous evidence that dentition is the main determinant of the morphology of the mandible. The skeletal characteristics are variable among individuals, and a longitudinal study is required to better understand age-related changes of the mandible.

Topography of the mental foramen in human skulls originating from different time periods

The location of the mental foramen is used in a number of maxillofacial surgical procedures and in anthropological examinations. The position of the mental foramen has been reported to vary in different ethnic groups and in different historical populations. The aim of this work was to analyse the topography of the mental foramen in mandibles from selected historical populations from the Pomeranian region in Poland. The material consisted of three groups: 92 skulls from the beginning of the 20th century from Szczecin (earlier name Stettin), and two Mediaeval groups -31 skulls from Rurka (historic Rörchen), 18th-19th centuries, and 50 skulls from Sypniewo (historic Zyppnow), 11th-13th centuries. Distances of the mental foramen in relation to the midline, and to the second corresponding point were measured. Additionally, non-metric traits of the mental foramen were recorded. No significant differences in average diameters of the mental foramina measured on the right and the left sides were observed between historical populations. On both sides, in all groups, the foramen was mainly located between positions of the lower first and lower second premolars. In all three groups the direction of the opening of the mental foramen was superoposterior. The similar level of epigenetic variation was observed in all groups. The position and the direction of the exit were similar to other previously studied European populations.

Morphological analysis of the maxillary arch and hard palate in edentulous maxilla of South Indian dry skulls

PURPOSE

The purpose of this study is to demonstrate the role of aging\edentulousness on the maxillary arch, the size of the alveolar process, the shape and thickness of the hard palate in the South Indian dry skulls to customize more appropriate treatment of elderly edentulous patients.

METHODS

One hundred dry skulls were divided into dentate and edentulous groups and were subgrouped into male and female. They were subjected to various morphological and morphometrical analyses.

RESULTS

The data have revealed a more significant reduction in the depth and width (p < 0.001) of the arch corresponding to the reduction in the size and thickness of the alveolar process (p < 0.001) in the edentulous skull. Further, a significant reduction in the size and thickness (p < 0.001) of the hard palate was observed in the edentulous skull. The data clearly indicate the effect of tooth loss in the horizontal regression of the maxilla. Furthermore, it may enhance the bone resorption that can ultimately result in the marked reduction of the width and depth of the alveolar arch concomitant with the alteration of the hard palate. These changes may subsequently alter the facial appearance in the elderly population.

CONCLUSION

The observed data from specific group of population may provide relevant data for their comparative analysis between different populations for a better understanding of their regional differences with respect to environmental and social influence. Moreover, the data can provide a better idea to evaluate a promising treatment strategy in prosthodontics and orthodontics in South India.