Mental Foramen Research Articles

REFERENCE AREAS SELECTION AFFECTS REGISTRATION OF AI-SEGMENTED MANDIBLES ACQUIRED WITH CBCT

Introduction Precise registration of sequential 3D datasets is crucial for accurate dimensional analysis. Utilizing the Local Best-Fit (LBF) algorithm and stable Registration Reference Areas (RRAs) facilitates the accurate alignment of 3D surface models. Currently, Cone-beam Computed Tomography (CBCT) and Deep Learning (DL) algorithms are at the forefront for segmenting CBCT scans to monitor morphological changes in the residual alveolar ridge. This study compares the effectiveness of different RRAs in registration sequential 3D surface models of partially edentulous mandibles. Methods DL-assisted software segmented two sequential CBCTs (T0 and T1) from 10 patients, producing sequential 3D mandibular models. These models were aligned using three distinct RRAs: (i) WHOLE, encompassing the entire surface model; (ii) MND_BODY, covering the mandibular body while excluding the unstable alveolar ridge; and (iii) SPIN_FOR, incorporating stable RRAs (mental foramina and mental spine). An innovative method assessed registration accuracy by generating centroids from cross-sectional outlines of the mandibular nerve canals at the anterior third (A), medial third (B), and posterior third (C) of the posterior edentulous areas. The distance between centroids at T0 and T1 quantified registration accuracy. Results The MND_BODY group exhibited superior accuracy, whereas the SPIN_FOR group showed the least, with accuracy decreasing from A to C, suggesting rotational misalignments. ConclusionsWhen selecting RRAs, both stability and spatial distribution must be taken into account. For optimal alignment, sequential 3D surface models should use RRAs that are both stable and widely distributed.

Evaluation of the Rostral Inferior Alveolar Nerve Block via the Mental Foramen in Equids: In Vivo Efficacy Testing.

The use of proper sedative and regional anesthetic protocols is essential when performing equine dental surgical procedures under standing sedation. The efficacy of the rostral inferior alveolar nerve block via the mental foramen has not been previously studied. Aims of this study included determining the efficacy of the block, investigating whether any region (labial mucosa, alveolar mucosa, or teeth) was more reliably anesthetized, and if differences in efficacy existed between bilateral and unilateral blocks. In this blinded trial, 10 horses each were randomly assigned to receive a left unilateral block, right unilateral block or bilateral blocks and 5 horses were bilateral controls. For unilateral groups, the contralateral side of the horse acted as its own unilateral control. Mechanical nociceptive stimulus methods were used to determine response to stimulus at time points pre-sedation, post-sedation, and post-injection at 10, 30, 60, and 90 min. Results were evaluated in 4 groups: unilateral blocks, unilateral controls, bilateral blocks and bilateral controls. Overall, all groups were significantly less likely to respond to stimulus at time points post-sedation, T10, and T30, whereas only blocked sites were less likely to respond at T60 and T90 compared to pre-sedation. There was no significant difference in response to stimuli of blocked sites between the 3 regions at all time points. Overall, at T60 and T90, blocks produced regional anesthesia in 73% and 55% of sites, respectively. This study demonstrated the equine mental foramen regional nerve block has varied efficacy, producing partial or incomplete regional anesthesia in some cases.

Periradicular Surgery Guided with Erbium Er Cr Laser:YSGG. Case Report

Purpose: The aim of the study is to observe the bone healing process of a guided periradicular surgery, performed in the endodontics postgraduate course of the University of Santo Tomas, in which an osteotomy was performed for a bone window with erbium, chromium: yttrium, scandium, gallium, garnet (Erbium,Chromium:YSGG) laser, and the healing process was evaluated by cone beam computed tomography (CBCT) during the first four months after surgery. Materials and Methods: After completing the clinical history and studying the CBCT scans, a patient was selected with a diagnosis of symptomatic apical periodontitis, periapical lesion less than 5mm with intact vestibular cortex that required periradicular surgery due to the presence of an adapted fixed prosthesis and the proximity of the mental foramen to the apex of the tooth to be treated. The treatment plan was established, the surgical guide was designed and the osteotomy was performed with Erbium,Chromium:YSGG laser. The size of the periradicular lesion and the bone density of the surgical area were measured at three points in time: pre-surgical (T0) and post-surgical at 24 hours (T1), at 4 months (T2) and at one year. Results: Bone density measured in Hounsfield units (HU) on CBCT in the axial section showed preoperative values in the vestibular apex of 1478 and 1435 HU, at 24 hours after surgery -95 and -210 HU, and in the control at 4 months of 992 and 860 HU. In the coronal slice in the mid vestibular area at the apex level, a preoperative value (T0) of 1335 HU was reported, at 24 hours (T1) -18 HU and at 4 months 1269 HU. At one year of evolution, greater bone density was evidenced comparing between month 4 and month 12. Conclusions: By performing a surgical procedure with guided technique and Erbium,Chromium:YSGG laser for the osteotomy, the adverse effects of the surgical procedures are reduced, achieving results with greater accuracy and better prognosis.

Mental Foramen as a Guide to Establish Sexual Dimorphism among Eastern Indian Population: An Observational Cross-sectional Study on Dry Bones

Abstract Context: The study deals with a role of mental foramen in determining the sexual dimorphism of mandibles as well as generating the sufficient data for the dental surgeons regarding location and measurements of the same. Aims: The aim of the study was to determine the location of mental foramen with respect to the different bony points of mandible and the presence of accessory foramen, if any and to establish sexual dimorphism among mandibles in relation to mental foramen and assessing the role of mento-submental angle for the same. Settings and Design: An observational cross-sectional study was conducted at Medical Colleges of West Bengal. Materials and Methods: Two hundred and eighty dry mandibles were used. Digital images were captured with digital camera after placing the bones in anatomical position for suitable views. Measurements were taken with the help of ImageJ software. Statistical analysis was performed using the SPSS software. Statistical Analysis Used: Measures of central tendency were determined. Significance was tested using the Chi-square test or unpaired Student’s t test, as applicable. Results: Most of the mental foramina were in line with the second premolar tooth or between the first and second premolars. Distance from the alveolar margin and the diameters of foramen were statistically significant among the genders. Mento-submental angle was significantly lower in males as compared to females being <115° and >115°, respectively. The prevalence of accessory mental foramen was very low in both genders. Conclusions: Sexual dimorphism can be well established from the morphometry of mental foramen of mandibles in the Eastern Indian population.

Evaluation of Injectate Distribution of the Middle Mental Nerve Block Within the Mandibular Canal in a Cadaveric Canine Model.

Awareness among veterinarians has increased regarding the need for comprehensive pain relief, but many companion animal veterinarians do not administer regional analgesia pre-emptively during dental procedures. The middle mental nerve (MMN) block desensitizes the ipsilateral mandibular incisor and canine teeth as well as soft tissues rostral to the delivery site. There is little published information on the efficacy of the MMN block in dogs. The objective of this study was to determine injectate distribution within the mandibular canal using a radiopaque contrast media/methylene blue solution. Half a milliliter of solution was injected within the opening of the middle mental foramen using a standard hypodermic syringe and a 25G x 25 mm needle. The course of the injectate was traced both via computed tomography (CT) and, in some cadavers, gross dissection. Post-treatment CT revealed that in 90% of the cases, the contrast diffused at least as far caudally as the mesial root of the third premolar tooth. The injectate was not identified within the canal of 5% of cadaveric mandibles examined. Although the solution used diffused caudally within the mandibular canal when injected using recommended clinical techniques, this may not completely represent the extent of clinical effects experienced in live patients. This technique also confirmed that the needle does not need to be advanced into the mandibular canal to achieve adequate diffusion to at least the mesial root of the third premolar tooth.

Retrospective Radiographic Analysis of Peri-Implant Bone Loss in Mandibular Full-Arch Implant Rehabilitations

Objectives: Can the type of implant rehabilitation influence peri-implant bone loss in case of full-arch mandibular prosthesis? The purpose of the study was to assess, using orthopantomograms (OPGs), the bone loss around implants in different types of implant-supported prosthetic rehabilitations and identify potential risk factors, associated with the number and location of implants, that may have an association with bone defects. Methods: A radiographic study was conducted on 22,317 OPGs from 2010 to 2024. All OPGs with implant-supported prosthetic mandibular rehabilitations were included in the study. Results: A total of 155 OPGs were evaluated, with peri-implant bone loss identified in 64 (41.3%). Distal implants (furthest from the center) across various positioning patterns were most susceptible to bone loss, with positions 3.6 and 4.6 demonstrating the most frequent occurrence (25 and 26 cases, respectively). The χ2 test revealed significant associations between both the implant positioning pattern (p < 0.001) and number of implants (p < 0.001) with peri-implant bone loss. Also, by updating the sample of OPGs, increased susceptibility to bone resorption was found for implants placed distal to the mental foramen compared to mesial ones in full-arch-implant-supported fixed prostheses. Conclusions: Prospective clinical studies will therefore be useful in investigating this finding further.

AI-Powered Identification of Osteoporosis in Dental Panoramic Radiographs: Addressing Methodological Flaws in Current Research.

Background: Osteoporosis, a systemic skeletal disorder, is expected to affect 60% of women over 50. While dual-energy X-ray absorptiometry (DXA) scans are the current gold standard for diagnosis, they are typically used only after fractures occur, highlighting the need for early detection tools. Initial studies have shown panoramic radiographs (PRs) to be a potential medium, but these have methodological flaws. This study aims to address these shortcomings by developing a robust AI application for accurate osteoporosis identification in PRs. Methods: A total of 348 PRs were used for development, 58 PRs for validation, and 51 PRs for hold-out testing. Initially, the YOLOv8 object detection model was employed to predict the regions of interest. Subsequently, the predicted regions of interest were extracted from the PRs and processed by the EfficientNet classification model. Results: The model for osteoporosis detection on a PR achieved an overall sensitivity of 0.83 and an F1-score of 0.53. The area under the curve (AUC) was 0.76. The lowest detection sensitivity was for the cropped angulus region (0.66), while the highest sensitivity was for the cropped mental foramen region (0.80). Conclusion: This research presents a proof-of-concept algorithm showing the potential of deep learning to identify osteoporosis in dental radiographs. Furthermore, our thorough evaluation of existing algorithms revealed that many optimistic outcomes lack credibility when subjected to rigorous methodological scrutiny.

Morphometric Analysis of the Dimension and Distance to Anatomical Structures From the Mental Foramen Using Cone Beam Computed Tomography

Morphometric Analysis of the Dimension and Distance to Anatomical Structures From the Mental Foramen Using Cone Beam Computed Tomography

The relationship between radiomorphometric indices and fractal dimension analysis: a cone-beam computed tomography study.

The purpose of this study is to evaluate the relationship between radiomorphometric indices and fractal dimension (FD) analysis in jawbone radiographic density using Cone-Beam Computed Tomography (CBCT). The study included 87 CBCT datasets from dental patients aged 50-79. Four radiomorphometric indices (Computed Tomography Cortical Index (CTCI), Computed Tomography Mental Index (CTMI), Computed Tomography Index-Superior (CTI-S), and Computed Tomography Index-Inferior (CTI-I)) along with age, gender, remaining teeth, and mandibular bone height were evaluated. FD was assessed in trabecular bone near the mental foramen (ROI 1) and on the mandibular cortical bone (ROI 2). Relationships between indices and variables were analyzed using Pearson chi-square, Fisher's exact, one-way ANOVA, Kruskal-Wallis, and Spearman's rho tests. ANOVA showed significant differences in mandibular bone height (p = .004) and FD at ROI 2 (p = .000) across three mandibular cortex types (C1, C2, C3). Spearman's rho indicated significant correlations between FD at ROI 2 and CTMI, CTI-S, CTI-I (p = .000), and between mandibular bone height and CTMI (p = .010). The correlations of FD at ROI 2 ranged from strongest to weakest with CTCI, CTMI, CTI-S, and CTI-I. High-risk osteoporosis radiomorphometric indices are associated with FD analysis of cortical bone.

Evaluation of Accessory Infraorbital Foramen with Cone Beam Computed Tomography

Objective: to assess the incidence, number and position of accessory infraorbital foramina (AIOF) according to cone beam computed tomography (CBCT).Material and methods. CBCT data from 156 patients who received dental care at a private medical center in Minsk (The Republic of Belarus) in 2018–2023 were analyzed.Results. In 29 (18.6%) patients, 38 AIOF were found. Unilateral doubling of the infraorbital foramen was more common than bilateral (21 patients compared to 8). In 1 case, the presence of two AIOF simultaneously on one side was noted. They were located medial and superior relative to the main infraorbital foramen at a distance 3.73–14.5 mm from it. In 2 of 13 patients with simultaneously visualized upper and lower jaws, an accessory mental foramen was found on the AIOF side. AIOF were more often identified on the left side (p<0.05); no gender differences in their occurrence were detected.Conclusion. The obtained results demonstrate a high frequency of infraorbital foramen doubling. To increase the effectiveness of surgical manipulations in the middle third of the face and prevent iatrogenic neurological complications, it is recommended to conduct a preoperative CBCT to clarify the localization of the main and accessory infraorbital foramina.

Evaluation of mandibular bone structure changes in phenylketonuria patients through fractal analysis and radiomorphometric indices

ObjectivesThe aim of this study was to evaluate the effect of phenylketonuria (PKU) on mandibular bone structure by comparing the bone of PKU patients with healthy controls using fractal analysis and the radiomorphometric indices of mandibular cortical width (MCW) and mandibular cortical index (MCI). Study DesignIn total, 32 patients with PKU were analyzed and compared with the control patients. Regions of interest in panoramic radiographs were selected and the fractal dimension (FD) obtained from fractal analysis was calculated. MCW was defined as the cortical thickness of the inferior border of the mandible at the level of the mental foramen. MCI classified the endosteal edge of the mandibular cortex as C1: straight and sharp, C2: the presence lacunar resorption spaces, and C3: distinctly porous and severely eroded. The significance level was P<0.05. ResultsAll FD and MCW values were significantly lower in the PKU patients. The prevalence of C1 was significantly lower and prevalence of C2 was significantly higher in the PKU group. ConclusionThe differences in fractal dimension and radiomorphometric indices between patients with PKU and healthy controls may indicate a potential impact of PKU on mandibular bone structure.

Integrative approach for supernumerary teeth: a single-center retrospective analysis.

This study aimed to provide a comprehensive case analysis from a single center, with the objective of clarifying the optimal timing and recommendations for a preferred treatment strategy customized to the specific presentation of each type of supernumerary tooth identified in the research. A retrospective study was conducted on patients who presented with a supernumerary tooth and were treated interdisciplinarily at the clinic. In total, 55 patients with 81 supernumerary teeth of the permanent dentition were analyzed, 30 males and 25 females. The dentition status of the patients was as follows: 31 patients with mixed dentition, no patients with primary dentition, and 24 patients with permanent dentition. The diagnosis of supernumerary tooth was primarily made by general or pediatric dental practitioners and/or orthodontists. Patients were then referred to maxillofacial surgeons for treatment decision. The timing of treatment was mainly determined by the oral surgeon, based on the recommendations of the other specialists involved. Cases involving maleruption or malalignment of permanent teeth required both surgical and orthodontic treatment. Patients over 9 years old were treated either under local anesthesia or sedation, whereas those under 9 years old were treated under deep sedation or general anesthesia. A comprehensive investigation of cases involved the utilization of CBCT at the supernumerary tooth site to facilitate treatment planning. There was a significant correlation between younger age and the preference for treatment under sedation or general anesthesia (P &#61; .01, t test). Similarly, a strong association was found between younger age and the need for additional orthodontic treatment (P &#61; .016, t test). Cases of surgical removal of a supernumerary tooth at a young age typically did not require orthodontic traction of the permanent tooth, in contrast to cases of late surgical intervention (patients over 11 years old), which often did necessitate such traction. There was a strong tendency for treating supernumerary teeth in the maxilla. The proximity of supernumerary teeth to vital anatomical landmarks significantly influenced treatment decisions. Patients with supernumerary teeth near the mental foramen or the inferior dental canal in the premolar area were exclusively placed under follow-up care (P &#61; .002, Pearson chi-square test). However, in the maxilla, the proximity of supernumerary teeth to vital structures such as the floor of the nose and the incisive nerve did not affect the treatment approach, and those supernumerary teeth were mostly removed. A team approach for managing supernumerary teeth is recommended. The timing of treatment should carefully consider the advantages and disadvantages of early versus late intervention. Early surgical treatment in cases where eruption is disturbed might result in spontaneous eruption, eliminating the need for orthodontic traction of the permanent teeth.

Enhanced Osteoporosis Detection Using Artificial Intelligence: A Deep Learning Approach to Panoramic Radiographs with an Emphasis on the Mental Foramen.

Osteoporosis, a skeletal disorder, is expected to affect 60% of women aged over 50 years. Dual-energy X-ray absorptiometry (DXA) scans, the current gold standard, are typically used post-fracture, highlighting the need for early detection tools. Panoramic radiographs (PRs), common in annual dental evaluations, have been explored for osteoporosis detection using deep learning, but methodological flaws have cast doubt on otherwise optimistic results. This study aims to develop a robust artificial intelligence (AI) application for accurate osteoporosis identification in PRs, contributing to early and reliable diagnostics. A total of 250 PRs from three groups (A: osteoporosis group, B: non-osteoporosis group matching A in age and gender, C: non-osteoporosis group differing from A in age and gender) were cropped to the mental foramen region. A pretrained convolutional neural network (CNN) classifier was used for training, testing, and validation with a random split of the dataset into subsets (A vs. B, A vs. C). Detection accuracy and area under the curve (AUC) were calculated. The method achieved an F1 score of 0.74 and an AUC of 0.8401 (A vs. B). For young patients (A vs. C), it performed with 98% accuracy and an AUC of 0.9812. This study presents a proof-of-concept algorithm, demonstrating the potential of deep learning to identify osteoporosis in dental radiographs. It also highlights the importance of methodological rigor, as not all optimistic results are credible.

Assessment of anterior loop of mental foramen with cone beam computed tomography-An institutional based study

Cone beam computed tomography (CBCT) is a specialized imaging technology designed to create accurate 3D images of craniofacial anatomy while using significantly less radiation than traditional CT scans. This advancement allows clinicians to closely examine dental and maxillofacial structures, forensic analysis, and modern therapeutic techniques.To evaluate several anatomical variants of the anterior loop of the mental foramen using cone-beam computed tomography (CBCT).The study involved 30 randomly selected patients aged 20-60 year from the departmental OPD, who underwent CBCT of the anterior mandibular region to assess the mental foramen. After obtaining a detailed history, a diagnosis was made and explained to the patients. Data were analyzed according to the classification by Solar et al. (1994).Type 1 mental nerve loop presence was 6.6% greater on the right side (13.3%) than on the left side (6.7%), while Type 3 mental nerve loop presence was 6.6% higher on the left side (63.3%) than on the right side (56.7%) based on a comparison of the anterior loop of the mental foramen.However, Type 2 was similar on both the right (30.0%) and the left (30.0%) sides. The anterior loop of the mental foramen is an important anatomical feature and was comparable (Type 1/Type 2/Type 3) in patients on the right and left side (p &amp;#62; 0.05) (χ2=0.78, p = 0.678), showing no significant difference. Understanding its anatomy and occurrence has a significant impact on therapeutic strategies.

Assessing the Prevalence and Length of the Anterior Loop of Inferior Alveolar Nerve and the Position and Dimension of Mental Foramen Using Cone Beam Computed Tomography.

Background To prevent harm to the neurovascular bundle during clinical and surgical operations, it is crucial to understand the position and dimension of the mental foramen, as well as the prevalence and length of the anterior loop (AL). Methods An iCAT Vision (CT Dent, London, UK) was used to take a cone beam computed tomography (CBCT) scan. Measurement of height, length of anterior loop, position and width of mental foramen was examined. Results Assessed prevalence of anterior loop and saw difference among genders, which was found to be more among males than females; anterior loop decreased as age advances. Mean anterior loop length of study subjects in different age group on right side was more than the left side, and the most common location of the mental foramen (61.87% in females and 61.36% in males) is located below the apex of the second premolar. The mean value of the distance from inferior border was 9.72mm in females and 10.78mm in males. Conclusion The current study was done with all of these characteristics in mind to assess the effectiveness of CBCT in determining anterior looping of the inferior alveolar nerve (IAN) and the position and dimension of mental foramen. In more than half of the cases analyzed, an anterior loop was discovered.

Does mandible ramus height asymmetry affect postoperative skeletal stability in orthognathic surgery patients?

BackgroundRelapses following orthognathic surgery have been reported to exceed 2% to 50%, depending on multiple factors. This study aimed to analyze the stability after orthognathic surgery in patients with mandibular ramus height asymmetry through 3D reconstruction using Cone-beam CT.MethodsThis retrospective cohort study investigated patients who underwent mandibular setback surgery using bilateral sagittal split ramus osteotomy. Three-dimensional CT scans were taken at three different time points. Evaluation of the postoperative stability involved measuring changes in the x, y, and z axes as well as roll and yaw rotations of the mandible at specific landmarks (B point, mental foramen) on 3D CT scans obtained immediately after surgery and 6–12 months postoperatively. They were categorized into four groups based on bilateral mandibular height asymmetry through Asymmetry index (AI). The one-way ANOVA was implemented to compare the intergroup differences and Tukey's post hoc test was employed. Additionally, the Pearson correlation coefficient was also calculated.ResultsA total of 24 patients were included in this study. The corresponding AI, representing the degree of asymmetry in both mandibles, were calculated as Group 1 was 1.25 ± 0.64%, Group 2 was 2.89 ± 0.47%, Group 3 was 5.03 ± 0.51%, and Group 4 was 9.40 ± 1.99%. The x-axis change in Group 4 was significantly larger at 1.71 mm compared to Group 1 at 0.64 mm. The mandibular roll, Group 4 showed a statistically significant increase at 1.33° compared to Group 1 at 0.35°. And there was a significant positive correlation observed between x-axis change and AI (p = 0.019), as well as between mandibular roll and AI (p = 0.025).ConclusionAfter orthognathic surgery, stability was influenced by numerous factors, with the findings of this study suggesting that the degree of ramus height asymmetry in the mandible can be considered one contributing factor.

A new approach: Cervical approach for marginal resection of the posterior mandible

Gingival squamous cell carcinoma (SCC) of the posterior mandible often requires marginal resection of the mandible in conventional surgery. However, the posterior location of the lesion can limit surgical visibility, which is critical for complete tumor removal and minimizing recurrence. Typically, marginal resection of the posterior mandible is achieved through a midline lower lip incision and mental nerve transection, providing adequate exposure but resulting in nerve damage, lip numbness, and facial scarring. In this paper, we describe a case using a submandibular incision for neck dissection, extending from the mandibular angle to the mental foramen, to fully expose the posterior mandible. The intraoral incision, extending 1 cm beyond the tumor margin, connected with the submandibular incision. Under direct vision, we performed a marginal resection of the mandible, preserving the inferior alveolar neurovascular bundle and the mental nerve, and maintaining at least 1 cm of the inferior mandibular margin. This technique achieved complete tumor removal while preserving mental nerve function and lower lip integrity, reducing surgical difficulty and patient trauma. This approach maintains nerve function and aesthetics as much as possible, with a faster postoperative recovery. In treating gingival SCC of the posterior mandible, it is essential to preserve surrounding healthy tissue and critical anatomical structures, minimizing postoperative complications while ensuring complete tumor resection.

Morphometric Analysis of the Mandibular Canal and Its Anatomical Variants in a Chilean Subpopulation: Cone Beam Computed Tomography Study.

The inferior alveolar nerve (IAN), contained within the mandibular canal (MC), is a structure prone to damage in clinical and surgical procedures on the mandible. This study aimed to analyze the MC morphology and its anatomical variants in a Chilean subpopulation using cone beam computed tomography (CBCT). In total, 342 images from patients with the following parameters were observed: 120 kV, 9 mA, field of view 12 × 9 MC, and voxel size 0.12 mm. The average length of the MC recorded a mean value of 70.493 ± 4.987 mm on the right side and 70.805 ± 5.177 mm on the left side. The location of the mental foramen (MF) was most frequently found between the mandibular first and second premolar. The greatest bone thickness was found at the level of the basilar border of the 2MPM. The root closest to the MC was distal from the mandibular second molar. The lowest thickness was in the lingual area at 1MM. The prevalence of the anterior loop (AL) (61.5%) and the retromolar canal (RC) (17.5%) showed no significant differences between men and women. The results obtained showed that the morphology of the MC in the Chilean subpopulation can vary.

Are different screw lengths associated with osteosynthesis quality in the region of the mental foramen?

AbstractIntroductionThe use of two monocortical malleable 04‐hole miniplates, placed above and below the mental foramen, has been indicated to prevent the adverse effects of tension and torsion forces on fracture healing. To obtain good fixation in the mandible's outer cortex screws, 5–8 mm long have been recommended. However, studies have shown thicknesses in the mental foramen region of up to 3 mm, meaning the length of the screw could be a risk to nerve or tooth root damage. The purpose of this study is to identify the influence of screw length on osteosynthesis quality in the region of the mental foramen.Materials and Methods10 synthetic polyurethane human lower jaw replicas were subjected to a linear loading test to evaluate fixation techniques with 5 and 10 mm of displacement. In the photoelastic analysis, 02 lower jaw models were made of photoelastic resin and subjected to linear loading in the fixation technique with 10 mm of displacement. Two 04‐hole miniplates in the region of the mental foramen either fixed completely with 4 mm screws (group 1) or with 5 mm screws in the tension zone and 8 mm screws in the compression zone (group 2). The variables were registered for peak load and peak displacement, and final load and final displacement. One‐way analysis of variance (ANOVA) was applied, followed by the Tukey test, with a significance of 5% (p = 0.05) for the comparisons between the means.ResultsConsidering 95% confidence intervals, the mechanical test showed no statistical differences in peak load between the fixations groups. In the photoelastic analysis, the fringes were concentrated on the distal segment of the fracture in both groups.ConclusionDue to the lack of statistical difference in the biomechanical and photoelastic tests, considering the methodologic limitation, our study indicates a tendency of advantage toward the treatment of fractures with two 04‐hole plates, fixed with 4 mm screws, to minimize complications like tooth or nerve damage. In vivo studies are needed to verify the convergence of the results of in vitro studies to evaluate the resistance and stability in real masticatory forces.

New Early Cretaceous zalambdalestid stem placental mammal from Mongolia and evolution of Zalambdalestidae

ABSTRACT Prozalambdalestes cratodus gen. et sp. nov. is based on a fragmentary dentary from the Lower Cretaceous (Aptian–Albian) Khovoor locality in Gobi Desert, Mongolia. This is the largest eutherian in the Khovoor mammal assemblage. It shows dental specializations of Zalambdalestidae such as procumbent, ever-growing gliriform first lower incisor with restricted enamel and reaching posteriorly p5, and mesiodistally compressed lower molar trigonids. The enamel is restricted to the ventrolabial and ventrolingual sides of the mesial half of the incisor and the enamel band is higher on the labial side. The new taxon retains five lower premolars, with p1 smaller than p2 and p3 smaller than adjacent premolars, and the Meckelian groove. It also differs from other zalambdalestids by position of mental foramina (under p3 and p5), p1–3 obliquely set in dentary, and lower molar talonids wider than trigonids. Phylogenetic analysis places Prozalambdalestes gen. nov. in a polytomy with Albian Zhangolestes, Turonian Kulbeckia, and the clade of Campanian zalambdalestids from Mongolia and Kazakhstan. CT data in Zalambdalestes and comparison with Prozalambdalestes gen. nov. show that the four lower premolars in Zalambdalestes are p2, p3 (variable present), p4, and p5. Consequently, the three lower premolars of Barunlestes and Zofialestes are p2, p4, and p5. The other diagnostic characters of Zalambdalestidae are reviewed.