Patterns of emergence of the human mental nerve

Radiographic Recognition of Mental Nerve for Secured Dental Implant Placement by Cone-Beam Computed Tomography in Mosul City Population

The study aims to estimate precisely the different levels of mental loop and foramina in the Mosul population of Nineveh governorate in Iraq. It is a cross-sectional study of a previously saved database in the cone-beam computed tomography device. The study sample was 357 patients selected randomly from the database of patients at the Oral Radiology Unit at the Maxillofacial Department in Al-Salam Teaching Hospital. The study variables are mental foramen (MF) position, shape, radiograph appearance, and mental loop presence and direction. The results show that the age group from 19 to 30 years shows the highest percentage (40.1%). Females show more than half of the cases (59.7%). The MF position's highest percentage is shown in 2 areas with the slight differences. These are the long axis of first premolar and the area between first premolar and second premolar (42.6%, 40.9). According to shape variation round shapes are the uppermost percent (53.8%). More than 60% of cases (66.1%) show continuity with the inferior alveolar canal and 50% show no loop presence, and the mental nerve leaves the foramen in a perpendicular direction. In conclusion localization of the MF, nerve, and its loop precisely in both horizontal and vertical directions, both hard and soft tissues in a continuous view. Before arranging any surgical procedure, anatomic markers are crucial. To reduce the danger of harm to the foramen region, the authors thus advised cone-beam computed tomography before scheduling implant surgery, particularly in the mental region of the jaw.

Accessory lingual mental foramen: A case report of a rare anatomic variation

INTRODUCTION

The mandibular nerve and the mental foramen have occasionally shown variations in its anatomy. This report aims to present a case of lingual mental foramen recognised on three-dimensional cone beam computed tomographic imaging (CBCT).

CASE REPORT

Routine Orthopantomogram (OPG) and CBCT images were evaluated to assess the status of impact third molars in a 31-year-old female who had visited the dental clinics in our institution. The OPG image failed to reveal any anatomic variation in the position of the mental foramen. On tracing the course of the mandibular canal in CBCT images, two foramina were traced at the region of premolar. One opened towards the buccal cortical plate at the normal position of the mental foramen and an accessory lingual mental foramen had an opening on the lingual cortical bone at the same level as the mental foramen.

CONCLUSION

Understanding variations of the mental foramen is extremely essential in dentistry to carry out successful anaesthetic or surgical interventions and to avoid complications such as nerve damage or excessive bleeding.

Assessment of the Anterior Loop and Pattern of Entry of Mental Nerve Into the Mental Foramen: A Radiographic Study of Panoramic Images

INTRODUCTION

The precise location of the mental foramina is an essential landmark in planning the position of dental implants in the anterior mandible. Injury to inferior alveolar nerve during anterior mandibular implant surgery causes altered sensation which greatly affects patient satisfaction.

METHODS

In this study, we assessed the prevalence of anterior loop of mental nerve and the pattern of entry of mental nerve into the mental foramen. Three hundred panoramic radiographs (600 hemimandibles) obtained from records maintained in the Department of Oral Medicine and Radiology were randomly selected for the study. The radiographs were evaluated by two independent observers for the pattern of entry of mental nerve into the mental foramen on either side of the mandible and for the presence or absence of anterior loop of mental nerve.

RESULTS

The most prevalent pattern of mental nerve observed was Straight pattern which totals to 67.5% followed by Anterior loop pattern (18.8%) and then the Perpendicular pattern (13.7%). There was no significant association between the gender and subtypes of looping pattern on the left and right side and a highly significant association between the side of the mandible and loop pattern was observed by Chi square test.

CONCLUSION

The Anterior loop pattern of mental nerve has been found in 18.8% of the population suggesting to accurate planning with three-dimensional imaging techniques to avoid injury to mental nerve during dental implant placement and other surgical procedure involving the interforaminal region of the mandible.

The Temporary Mental Nerve Paresthesia as an Outcome of Dentigerous Cyst Removal during Preparation for Dental Implant Placement: A Case Report

The usage of xenograft material is widely used in almost all oral cavity bone defects for regenerative and reconstructive purposes. The presented xenograft usage in the following care report enabled good bone defect healing and enabled the preservation of affected premolars. It is quite common to use any possible variations of bone materials to ensure bone defect improved healing. In some cases, the scope of surgeries requires the removal of each cyst within close proximity to various nerves and vessels. The inferior alveolar, infraorbital, lingual, and mental nerves are those most commonly adjacent to most operating sites in jaw bones. The usage of some additional materials such as collagen sponges, bone substitutes, resorbable membranes, or other additional materials are useful in each bone defect reconstruction but should be handled with care, as described in the following case. Before planning their usage, it is important to perform each surgery with close cone beam computed tomography imaging, which is very helpful to establish the scope of each lesion and the proximity of vital structures. There are a lot of factors that might influence any possible nerve damage, especially the different nerve anatomical variations. Even factors including the subperiosteal preparation and compression of adjacent tissues might influence later nerve function. When the lesion is expanding through the buccal cortical plate and when soft tissue fluctuation is present, some special care is needed. Similar to the presented case, a limitation in crushing, blowing, or any irritation of nerve fibers improves later postoperative outcomes. When the wound and surrounding tissues are handled with care, a limited possibility of any damage or paresthesia can occur. When the nerve itself is damaged or cut, loss of function can be permanent. Immediately after or even prophylactic prescription 1–2 days before the surgery of Vitamin B with NSAIDs (Non-steroidal anti-inflammatory drugs) (or other additional supplementary medicaments can improve nerve function in time. Possible nerve damage can be divided into many etiological factors. A quite different situation arises when the nerve is pulled in by the cyst growth into the cyst wall. The presented case report describes the outcomes of a cyst removal from the mandibular basis and treatment modalities.

Prevalence, Patterns and Variations of Anterior Loop of Inferior Alveolar Nerve-A CBCT Based Retrospective Study

The fragment of inferior alveolar nerve (IAN) existing anterior to the mental foramen (MF), before dividing the canal, is known as the "Anterior Loop of the IAN". The presence of anterior loop (AL) is important when placing the implant in inter foraminal area of the mandible or during any other surgical procedure. It is imperative to precisely determine the position and dimensions of these anatomical variations on a cone-beam CT (CBCT) scan. To estimate the prevalence and pattern of anterior loop of IAN and establish any corelation between dimension of the MF with length and angulation of the AL of the IAN. Total 178 CBCT samples were collected fulfilling the inclusion criteria from a private diagnostic centre in Bhubaneswar, Odisha. The greatest diameter of the mental foramen was measured along with anterior loop length and angulation in the panoramic section of the CBCT scan. The angulation formed and the length was corelated with the greatest diameter of the mental foramen and analysed. Our study reveals that the AL was more frequently seen among males, predominantly on the left side of the mandible. The relationship between length of the anterior loop and diameter of the mental foramen demonstrated a mild negative corelation. There was no possible corelation present between angle formed by anterior loop with inferior alveolar canal and diameter of mental foramen. A small positive corelation was established between length of anterior loop and angle formed by the anterior loop with inferior alveolar canal. CBCT scans should be recommended for pre-surgical evaluation of anatomical variations in the mandibular region. Also, a safe margin of 3-4 mm anterior to mental foramen should be maintained while working in the premolar area.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-021-02691-w.

Assessment of the position and level of mental nerve for placement of implants using cone-beam computed tomography & panoramic radiograph in the Saudi population

Background and objective

In surgical dentistry, shape, location, position, and extent of the anterior loop of mental foramen plays a deliberately imperative landmark during an osteotomy procedure. To evade any neurological disturbance during implant surgery radiological assessment is compulsory. Therefore, the aim of the study was to assess the position and level of mental nerve for placement of implants using Cone-beam computed tomography & Panoramic radiography in the Saudi population.

Materials and methods

A total of 150 CBCT and Panoramic radiographs were taken from the patients who visited the Department of Oral Medicine and Radiology. The data collection was done by using the same radiographic pieces of equipment for both CBCT and Panoramic radiographs. CBCT images taken from Kodak 9000 3D, Carestream Health, Inc., New York, USA, and Panoramic Radiographs taken from Panoramic Planmeca ProMax, Helsinki, Finland (Vujanovic-Eskenazi et al., 2015). The Chi-square test student test was used for statistical analysis.

Results

The most frequent shape and location of mental foramen in both CBCT and Panoramic radiographs were oval and in between the first and second premolar, both in CBCT & PR views. The visibility of mental loop on CBCT & PR view showed that; visibility of mental loop in CBCT was higher with 42(56%) as compared with PR view 26(34.66%) with statistically significant p-value 0.014. The mean length of the mental loop on CBCT was statistically significant (p = 0.001). But the mean distance from the lower point of the mental foramen to the lower border of the mandible was not statistically significant.

Conclusion

Based on the results of the present study; the visibility of the mental loop and its extension is more in CBCT as compared with PR views. Therefore, we recommended CBCT, during of implant surgery.

A Rare Anatomical Finding: Bilateral Accessory Mental Foramen

Aim

Accessory mental foramen (AMF) is a not common anatomical variation. During the surgical procedures involving the mandible such as implant surgery, periapical surgery, jaw surgeries, and periapical surgery and enucleation of pathologies at the mental region, obvious attention should be given to prevent postoperative sequelae. Case Report. Orthopantomograph (OPG) is routinely taken to visualize the maxillofacial region at a dental clinic. OPG shows exactly upper and lower jaw and teeth but superficially reveals some pathology or anatomic variation. It misses sometimes an anatomic landmark such as AMF. As the surgery is planned to a maxillofacial region, a detailed knowledge should be known before going into surgery to not interfere with anatomic landmarks. A 52-year-old male patient was referred to Kütahya Health Science University Dental Hospital, Turkey, to rehabilitate his bilateral partial edentulous lower jaw region. Implant surgery was planned in our patient. OPG was taken to evaluate the maxillofacial region but was unremarkable. Before the implant surgery, CBCT was obtained from our patient. CBCT and a three-dimensional reconstructed model of the male patient showed bilateral accessory mental foramen (AMF).

Conclusion

Accessory mental foramen (AMF) carries additional innervation to the chin, mandibular anterior gingiva, and mental region. Reflection and protection of the AMF during the surgery can prevent hemorrhage and neurosensory disturbance at the mental region and can improve quality of life for the patient. CBCT has higher precision but also a higher price and radiation dose. Although anatomical variations are uncommon, they can be found on digital panoramic radiographs but in limited percentage.

Tomographic evaluation of the mandibular nerve in the mental region and its surgical implications: a cross-sectional study

The aim of this study was to evaluate the prevalence and length of the anterior loop (AL) of the inferior alveolar nerve, nerve emergence from the mental foramen, and prevalence of sensory disorders after implant placement in the interforaminal region. Four hundred and fifty hemimandibles (225 patients) were evaluated using cone beam computed tomography and panoramic radiographs. Information on the presence of sensory disorders was obtained from the medical records. AL prevalence was 13.6% and mean AL length was 1.25 mm. The false-negative rate for the identification of the AL using panoramic radiography was 58.6%. Straight nerve emergence from the mental foramen was the most prevalent (62.7%), followed by anterior (21.8%) and posterior (15.6%) emergence. The incidence of sensory disorders was 4.4%, and 1.1% were related to the presence of the AL. When implants were placed within the planned distance of the mental foramen or further, 1.2% had sensory problems associated with the presence of the mandibular incisive canal. In cases of distances smaller than planned, 12.9% had sensory alterations. Only five (1.1%) had the AL, with a length between 0 and 4.5 mm. However, in four cases, the planned distance was respected and, even so, there was a sensory disorder. Posterior nerve emergence from the mental foramen was associated with a higher prevalence of AL.

An Update on Endodontic Microsurgery of Mandibular Molars: A Focused Review

Endodontic microsurgery is a highly predictable treatment option in most cases when conventional endodontic treatment is not feasible. Nevertheless, mandibular molars are still considered by clinicians to be the most difficult type of teeth, with the lowest success rate. In recent years, endodontic microsurgery has been attempted more frequently with the emergence of modern cutting-edge technologies such as dental operating microscopes, various microsurgical instruments, and biocompatible materials, and the success rate is increasing. This review describes the current state of the art in endodontic microsurgical techniques and concepts for mandibular molars. Notably, this review highlights contemporary equipment, technology, and materials.

The Proximity of Mental Foramen to Mandibular First Premolar Teeth: Cone Beam Computed Tomography Analysis in Turkish Population

Background/Aim: The aim of this study was to evaluate the proximity of the mental foramen (MF) to the roots of the mandibular first premolar teeth in the Turkish population according to gender and different age groups.

Material and Methods: The study was conducted on 385 samples of 242 patients who presented at the Dicle University, Faculty of Dentistry, Department of Dentomaxillofacial Radiology. The proximity of the MF to mandibular first premolar teeth was examined on cone beam computed tomography (CBCT) images. Two-way Anova variance analysis was used in the statistical analyses of the data.

Results: According to the analysis results, no statistically significant difference was determined between the age and gender groups (p>0.05). In the evaluation of the gender groups, the mean value was 6.6997 mm for females and 6.5445 mm for males.

Conclusions: With 3-dimensional imaging technology, the CBCT system provides detailed information about the MF localization. This method has shown that the localization of the MF could change associated with variables such as age and gender.

Cone beam CT-based measurement of the accessory mental foramina in the Chinese Han population

Anatomical data of accessory mental foramina (AMFs) were investigated in a Chinese Han population using cone beam CT (CBCT). A retrospective analysis was performed on 527 selected sets of CBCT images. The average frequency and diameter of AMFs, the diameter of the ipsilateral mental foramen (MF), and the center distance and relative position between the AMFs and MF were measured and calculated by three professional dentists. Among the 527 patients, AMFs were identified in 36 cases (frequency 6.83%), of which 68.75% of AMFs were larger than 1 mm. The mean diameters of the AMFs and the ipsilateral MF were 1.32±0.61 mm and 3.26±0.90 mm, respectively. The average distance from the AMFs to the alveolar ridge crest (ARC) was 15.05±3.50 mm, and the average distance to the mandibular plane was 15.87±3.64 mm. The positions of the AMFs relative to the MF varied widely. The AMFs were mostly positioned distal-inferior to the ipsilateral MF and under the mandibular second premolars. Nutrient foramina around the MFs were distinguished from AMFs. The reference plane for measuring AMFs was suggested to be the mandibular plane to increase the repeatability and accuracy of the experiment. Standard planes were proposed to determine the relative position between AMFs and the MFs. Based on our results, we propose that for implant surgeries, the safety region of 2 mm above the MFs should be reevaluated. CBCT examination is recommended before the operation to identify important anatomical structures around the MF region and their variations and set the safety distance on an individual basis.

Momentousness of the Mental Loop: A Comparative Study

Background and Purpose

To assess the anterior (aAL) and caudal (cAL) extensions of Anterior loop (AL) of Inferior alveolar nerve (IAN) using Digital Panoramic (DP) and Cone Beam Computed Tomography (CBCT) for its presence and dimensions in various age groups, genders, right and left sides of the mandible and between dentulous and edentulous patients.

Methods

A 1-year retrospective comparative study between DP and CBCT to assess the extensions of AL of IAN was conducted on individuals referred to a private imaging center located in Bengaluru, South India. 360 mandibular sites were examined using DP and CBCT to assess the presence and dimensions of AL.

Results

Results showed higher frequency of AL in CBCT compared to DP. Also there was a decreasing frequency of AL with increasing age and an insignificant difference in frequency between males and females. Bilateral looping was most common, aAL was more frequent on the left side and cAL on the right of the mandible. Statistically higher frequency in dentate group compared to edentulous. A decreasing mean value with increasing age and higher mean values in CBCT than DP. No significant difference in mean values among males and females or between the dentulous and edentulous groups. Higher mean values in CBCT compared to DP on the left side of the mandible compared to the right.

Conclusion

Choosing mental foramen as reference for termination of IAN could result in injury to AL; low sensitivity and specificity of DP compared to CBCT in assessing frequency and extent of AL underlines its inadequacy, while CBCT can be performed with comparable resolution, to accurately analyze AL.

Variation in accessory mental foramen frequency and number in extant hominoids

Nerves providing sensation to the lower face and jaw exit the mandibular canal via the mental foramen. In humans, there are many documented occurrences of additional foramina (accessory mental foramina, AMFs) on the lateral mandibular surface that may also contain nervous structures. There are large discrepancies in the literature regarding how often AMFs occur in humans, and investigations of non-human hominoid AMFs are rare. Consequently, the causes of interspecific diversity in this variable have not been explored. This project seeks to compare the frequency and number of AMFs between males and females, and among human regional groups and hominoid subspecies and species, and to investigate possible causal factors for any differences identified. No significant differences were found between males and females in any group. Gorillas and orangutans had the highest percentages of individuals with AMFs and the highest mean number of foramina, while modern humans and siamangs had the lowest figures for these variables. Significant differences (p < .05) were found for the mean number of foramina between most pairs of species. The results also showed that species with mandibles that are larger overall, have a larger area anterior to mental foramen, and a longer mandibular canal typically present more AMFs. The strongest correlation was found between the mean number of mental foramina and mandibular canal length. We suggest that these results provide preliminary support for the hypothesis that increasing mandibular canal length increases the likelihood that that nerves will ramify, leading to greater frequencies of accessory mental foramina.

Available bone morphology and status of neural structures in the mandibular interforaminal region: three-dimensional analysis of anatomical structures

PURPOSE

This study aimed to clarify the size and morphology of the mandible and to determine state of neural structures for the planning of the dental implantation using cone-beam computerized tomography (CBCT).

METHODS

Of the 252 patients, CBCT images of 48 selected patients were evaluated. The bone height and width were measured and the type of the mental portion of the inferior alveolar canal, the anterior loop length (ALL), the location of the incisive canal and lingual foramen were identified with cross-sectional and multiplane reformatted CBCT images. According to buccal and lingual concavities, the shape of the mandible is classified as type A, B and C.

RESULTS

Bone widths of males were significantly higher than female (p < 0.05). The thickest part of the alveolar bone was measured in the middle triple zone (d line) and the thinnest part was measured in the area near the alveolar crest (b line). The most seen type of mandible was type B (45.8%) that mandible was concave on the buccal side. Bone heights had a tendency to increase towards to the anterior mandible, and bone height in male patients was slightly but not significantly greater than that in female patients. ALL was 4.2 ± 1.2 mm and visible incisive canal length on CBCT was 9.7 ± 3.8 mm.

CONCLUSION

CBCT assessment of morphological features of the alveolar bone and locations of nerve canals and foramina in the anterior-premolar region of mandible represent useful practical anatomical information about the interforaminal region. This information is the guide to the dentist before implant surgery.

Prevalence and Length of the Anterior Loop of the Inferior Alveolar Nerve in Iranians

The anterior loop of the inferior alveolar nerve is a sensitive anatomical feature that should be taken into account during installation of dental implants anterior to the mental foramen. This study was conducted to explore the controversy regarding prevalence and length. A total of 452 mandible quadrants of 234 patients (age: 50.1 ± 13.3 years, 113 males, 121 females) were studied using cone-beam computerized tomography. After reconstructing axial, frontal, and sagittal slices, the region between the most anterior point on the mental foramen and the most anterior part of the mandibular nerve was inspected for signs of anterior loop presence. If positive, the length of the anterior loop was measured in mm as the distance between the anterior border of mental foramen and the anterior border of the loop. Prevalence and length of the anterior loop were compared statistically between sexes and age groups. The anterior loop was observed in 106 quadrants (23.5% of 451 quadrants) of 95 patients (40.6% of 234 patients), of whom 11 had bilateral anterior loops. Prevalences were similar in males (41%) and females (39%, chi-square P =.791). The mean anterior loop length was 2.77 ± 1.56 mm (95% CI: 2.5–3.1 mm), without significant sex (regression beta = −0.159, P = .134) or age (beta = −0.059, P = .578) differences. The anterior loop might exist in about 40% of patients, regardless of their gender. The mean safe anterior distance from the anterior loop is about 3 mm + (2.5–3.1 mm) = 5.5–6.1 mm, regardless of age.

Inferior alveolar nerve trajectory, mental foramen location and incidence of mental nerve anterior loop

OBJECTIVES

Injury of the inferior alveolar nerve (IAN) is a serious intraoperative complication that may occur during routine surgical procedures, such as dental implant placement or extraction of impacted teeth. Thus, the purpose of this study was to analyze the trajectory of the mandibular canal (MC), the location of the mental foramen (MF) and the presence and extension of an anterior loop of the mental nerve (AL).

STUDY DESIGN

In this cross-sectional study, a total of 348 CBCTs were analyzed. Distances from MC to the surface of the basal, medial and lateral cortical of the mandible were measured at the level of the second molar, first molar and second premolar. Location of the MF relative to the apices of the premolars, as well as incidence and anterior extent of the AL were also determined.

RESULTS

Significant and clinically relevant correlations were found between the position of the MC in women, which was located more caudal (r=-0.219, p=0.007; r=-0.276, p<0.001; right and left, respectively) and lateral (r=-0.274, p=0.001; r=-0.285, p<0.001; right and left, respectively), particularly at the level of the premolars. Additionally, the presence (r=-0.181, p=0.001; r=-0.163, p=0.002; right and left, respectively) and anterior extension (r=-0.180, p=0.009; r=-0.285, p=0.05; right and left, respectively) of the AL was found to be inversely correlated with the age of the patient.

CONCLUSIONS

This analysis of a Caucasian population has found that the older the patient, the lower the incidence of the loop and the shorter its anterior extension.

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.

The assessment of accessory mental foramen in a selected polish population: a CBCT study

Background

Accessory mental foramen (AMF) is a rare anatomical variation. When accessory mental foramen is present, the nerves and vessels that go through the mental foramen (MF) must follow alternative courses and special care must be taken during dental treatment planning. The purpose of this study was to evaluate the occurrence and the location of AMF in a selected Polish population using cone-beam computed tomography (CBCT).

Methods

Two hundred CBCT (105 males and 95 females) examinations were evaluated for the presence of AMFs. The location and side of AMFs were reported. The mean distance between MF and AMF was also calculated. The vertical size of MF on the side with and without AMF was measured. The obtained variables were statistically analyzed.

Results

AMFs were observed in 7% of the patients. There was no statistically significant difference between the appearance of AMF and sex (p > 0.05). We found no significant difference in the vertical size of MF between individuals with and without AMFs (p < 0.05).

Conclusion

Twenty-eight AMFs (7%) were observed from 400 sides of 200 patients. AMFs occurred more often in males (18 AMFs) than in females (10 AMFs). Twenty AMFs (71.4%) were located anteriorly, and eight (28.6%) - posteriorly. Fifteen AMFs (53.6%) were on the right side and thirteen (46.4%) - on the left.

Panoramic radiographs underestimate extensions of the anterior loop and mandibular incisive canal

Purpose

The purpose of this study was to detect the anterior loop of the mental nerve and the mandibular incisive canal in panoramic radiographs (PAN) and cone-beam computed tomography (CBCT) images, as well as to determine the anterior/mesial extension of these structures in panoramic and cross-sectional reconstructions using PAN and CBCT images.

Materials and Methods

Images (both PAN and CBCT) from 90 patients were evaluated by 2 independent observers. Detection of the anterior loop and the incisive canal were compared between PAN and CBCT. The anterior/mesial extension of these structures was compared between PAN and both cross-sectional and panoramic CBCT reconstructions.

Results

In CBCT, the anterior loop and the incisive canal were observed in 7.7% and 24.4% of the hemimandibles, respectively. In PAN, the anterior loop and the incisive canal were detected in 15% and 5.5% of cases, respectively. PAN presented more difficulties in the visualization of structures. The anterior/mesial extensions ranged from 0.0 mm to 19.0 mm on CBCT. PAN underestimated the measurements by approximately 2.0 mm.

Conclusion

CBCT appears to be a more reliable imaging modality than PAN for preoperative workups of the anterior mandible. Individual variations in the anterior/mesial extensions of the anterior loop of the mental nerve and the mandibular incisive canal mean that is not prudent to rely on a general safe zone for implant placement or bone surgery in the interforaminal region.

The inferior alveolar nerve's loop at the mental foramen and its implications for surgery

BACKGROUND

In this study, the authors aimed to identify and measure the anterior extension of the alveolar loop (aAL) and the caudal extension of the alveolar loop (cAL) of the inferior alveolar nerve by using cone-beam computed tomography (CBCT). They also aimed to provide recommendations for surgery in the anterior mandible.

METHODS

In this retrospective case study of the frequency and extension of aAL and cAL, the authors evaluated 1,384 mandibular sites in 694 CBCT scans of dentate and partly edentulous patients, performed mainly for further diagnosis before removal of the mandibular third molars between January 2009 and February 2013, by using multiplanar reconstructions.

RESULTS

The frequency of aAL was 69.73 percent and of cAL was 100 percent. The mean value for aAL was 1.16 millimeters, with a range of 0.3 to 5.6 mm; the mean value for cAL was 4.11 mm, with a range of 0.25 to 8.87 mm. For aAL, 95.81 percent of the sites showed values of 0 to 3 mm; for cAL, 93.78 percent of the sites showed values of 0.25 to 6 mm. Dentate patients showed statistically significantly higher values for cAL than did partly edentulous patients (P = .043). CBCT resolution had a statistically significant impact on cAL measurements (P = .001), with higher values at higher resolution.

CONCLUSIONS

This study showed a high frequency of and large variations in aAL and cAL. In contrast to panoramic radiography, CBCT has been shown to be a reliable tool for identifying and measuring the AL. Therefore, preoperative diagnosis with CBCT is recommended for planning three-dimensional tasks such as implant placement in the vicinity of the mental foramen.

PRACTICAL IMPLICATIONS

Owing to the variability of aAL and cAL measurements, it is difficult to recommend reliable safety margins for surgical procedures such as implant placement, bone harvesting or genioplasty Depending on the indication, the clinician should consider preoperative diagnosis by means of CBCT.

Anterior Loop of the Inferior Alveolar Canal: A Cone-Beam Computerized Tomography Study of 494 Cases

The aim of this study was to use cone-beam computerized tomography (CBCT) images of patients to assess the prevalence of different types, especially anterior loop, of the mental portion of the inferior alveolar canal and to evaluate the anterior loop lengths. CBCT images of 494 patients providing inclusion criteria were examined by 2 oral radiologists. Sagittal, axial, and multiplanar reformatted images were used to detect the type of mental portion of the inferior alveolar canal. The anterior loop length was measured in the respective sections of each CBCT image. Statistical analysis was performed using SPSS v. 15, and t tests were used for statistical analysis. Of the 494 patients, 217 anterior loops were detected in 141 (28.5%) patients. The mean anterior loop lengths for the right side and the left side were 2.19 ± 1 mm and 2.08 ± 0.89 mm, respectively. The difference between males and females in the mean anterior loop length was statistically significant for both sides (Right: P < .05; Left: P < .05). A presurgical CBCT image examination is necessary prior to implant insertion to reveal the presence of anterior loop and to detect actual anterior loop length.

Assessment of the Anterior Loop of the Mental Nerve Using Cone Beam Computerized Tomography Scan

The purpose of this study is to use cone-beam computerized tomography (CBCT) scans with oblique-transverse reconstruction modality to measure and compare the anterior loop length (AnLL) of the mental nerve between gender and age groups and to compare the difference between the right and left sides. Sixty-one female and 61 male CBCT scans were randomly selected for each age group: 21–40, 41–60, and 61–80 years. Both right- and left-side AnLLs were measured in each subject using i-CATVision software to measure AnLLs on the oblique transverse plane using multiplanar reconstruction. The anterior loop was identified in 85.2% of cases, with the mean AnLL of the 366 subjects (732 hemimandibles) being 1.46 ± 1.25 mm with no statistically significant difference between right and left sides or between different gender groups. However, the mean AnLL in the 21–40 year group (1.89 ± 1.35 mm) was larger than the AnLL in the 41–60 year group (1.35 ± 1.19 mm) and the 61–80 year group (1.13 ± 1.08 mm). In conclusion, when placing implants in close proximity to mental foramina, caution is recommended to avoid injury to the inferior alveolar nerve. No fixed distance anteriorly from the mental foramen should be considered safe. Using CBCT scans with the oblique-transverse method to accurately identify and measure the AnLL is of utmost importance in avoiding and protecting its integrity.

Cone-Beam Computed Tomography Evaluation of Mental Foramen Variations: A Preliminary Study

Background. Mental foramen is important in surgical operations of premolars because it transfers the mental nerves and vessels. This study evaluated the variations of mental foramen by cone-beam computed tomography among a selected Iranian population. Materials and Methods. A total number of 180 cone-beam computed tomography projections were analyzed in terms of shape, size, direction, and horizontal and vertical positions of mental foramen in the right and left sides. Results. The most common shape was oval, opening direction was posterior-superior, horizontal position was in line with second premolar, and vertical position was apical to the adjacent dental root. The mean of foremen diameter was 3.59 mm. Conclusion. In addition to the most common types of mental foramen, other variations exist, too. Hence, it reflects the significance of preoperative radiographic examinations, especially 3-dimensional images to prevent nerve damage.

Computed tomographic analysis of the mental foramen and nerve in Japanese patients

PURPOSE

The aims of this study were to investigate the anatomical features of the mental foramen in Japanese patients through computed tomography (CT) imaging to reduce inadvertent damage to the mental nerve during implant placement.

MATERIALS AND METHODS

The mandibles of 100 patients were observed on CT imaging. The location, shape, number, and size of the mental foramen were evaluated. Furthermore, the vertical and horizontal dimensions of the anterior loops were measured.

RESULTS

The mental foramen was mainly located by the apex of the second mandibular premolar in male, whereas the mental foramen was mainly located by the apex of the second mandibular premolar and between the apex of the second premolar and the first mandibular molar in female. With exception of a few hemi-mandibles, its shape was oval and the number of the mental foramen was 1. There was no significant difference in the size of the mental foramen between male and female. There was a significant difference in the vertical dimension of the anterior loops between the males and females.

CONCLUSION

In general, altered lip sensations are preventable if the mental foramen is located, and this knowledge is employed when performing surgical procedures in the foraminal area.

Branching Pattern of the Extraosseous Mental Nerve in a Kenyan Population

Knowledge of the branching pattern of the mental nerve is an important consideration during placement of tooth implants and reconstructive plates. It is known to display population variations and data for the same is scarce form the sub-Saharan region. With the recent increase in surgical interventions in the mandibular region in Kenya, a detailed description of mental nerve is warranted. A total of 64 mental nerves were dissected and branching pattern was noted. Single mental nerve was present in 60 (93.7%) cadavers while double mental nerves occurred in 3 (4.7%) and accessory in 1(1.6%). Most common pattern was bifurcation (39%) followed by trifurcation (34%), single (19%), and quadrification (8%). The double and triple branches were seen to further divide into two to three subbranches with diverse patterns. Side symmetry in branching was seen in four (6.25%). These are important anatomical considerations during placement of reconstructive plates for mandibular trauma and administration of mental nerve blocks.

Accuracy of Cone Beam Computerized Tomography and a Three-Dimensional Stereolithographic Model in Identifying the Anterior Loop of the Mental Nerve: A Study on Cadavers

The objective of this ex vivo cadaver study was to determine the accuracy of cone beam computerized tomography (CBCT) and a 3-dimensional stereolithographic (STL) model in identifying and measuring the anterior loop length (ANLL) of the mental nerve. A total of 12 cadavers (24 mental nerve plexus) were used for this study. Standardized CBCT scans of each mandible were obtained both with and without radiographic contrast tracer injected into the mental nerve plexus, and STL models of the two acquired CBCT images were made. The ANLL were measured using CBCT, STL model, and anatomy. The measurements obtained from the CBCT images and STL models were then analyzed and compared with the direct anatomic measurements. A paired sample t test was used, and P values less than .05 were considered statistically significant. The mean difference between CBCT and anatomic measurement was 0.04 mm and was not statistically significant (P = .332), whereas the mean difference between STL models and anatomic measurement was 0.4 mm and was statistically significant (P = .042). There was also a statistical significant difference between CBCT and the STL model (P = .048) with the mean difference of 0.35 mm. Therefore, CBCT is an accurate and reliable method in determining and measuring the ANLL but the STL model over- or underestimated the ANLL by as much as 1.51 mm and 1.83 mm, respectively.

A review of the mandibular and maxillary nerve supplies and their clinical relevance

Mandibular and maxillary nerve supplies are described in most anatomy textbooks. Nevertheless, several anatomical variations can be found and some of them are clinically relevant. Several studies have described the anatomical variations of the branching pattern of the trigeminal nerve in great detail. The aim of this review is to collect data from the literature and gives a detailed description of the innervation of the mandible and maxilla. We carried out a search of studies published in PubMed up to 2011, including clinical, anatomical and radiological studies. This paper gives an overview of the main anatomical variations of the maxillary and mandibular nerve supplies, describing the anatomical variations that should be considered by the clinicians to understand pathological situations better and to avoid complications associated with anaesthesia and surgical procedures.

The anterior loop of the inferior alveolar nerve: prevalence, measurement of its length and a recommendation for interforaminal implant installation based on cone beam CT imaging

OBJECTIVES

Interforaminal implant surgery requires anatomical knowledge of the area and adequate information on the location of the various landmarks of significance such as the mental foramen, the anterior loop of the inferior alveolar nerve and the mandibular incisive canal. Cone beam computed tomography (CBCT) is a relatively new imaging modality that provides a multi-dimensional view of the facial skeleton with, in most instances, lower radiation dose to the patient compared to medical CT. The present study aims to use CBCT to identify and measure variation in the presence and extent of the anterior loop of the inferior alveolar nerve. This information may be used to provide recommendations to the surgeon without access to a 3D scan of the dento-alveolar region.

MATERIAL AND METHODS

Ninety-three patients scanned with a Newtom VG device for a variety of clinical indications were included in this retrospective study. Using the multiplanar capabilities of the device's software the prevalence and length of the anterior loop was assessed.

RESULTS

The results show that an anterior loop could be identified in 48% of the cases with a mean length (range) of 0.89 mm (0-5.7).

CONCLUSIONS

In almost half of the surveyed cases an anterior loop was present. Even though in 95% of the study cases the loop was <3 mm, a 100% safety margin in the placement of anterior mandibular implants, in the absence of a CBCT scan, would only be achieved with a distance of 6 mm between the anterior border of the mental foramen and the most distal interforaminal implant fixture.

Morphological variation in dentate and edentulous human mandibles

PURPOSE

The aim of the study was to examine the different morphometric variations of the human mandibles, comparing between males and females in dentate and edentulous mandibles.

METHODS

Eighty adult human dry mandibles were studied. Thirty-two variations were evaluated according to the presence and absence of teeth. Kolmogorov-Smirnov test was performed to evaluate the normal distribution of the morphometric variables. Levene test evaluated homoscedasticity. Student t tests and Mann-Whitney U tests, when indicated, were performed to compare each of the morphometric variables between dentate and edentulous mandibles. Statistical differences were considered when the P value was less than 0.05.

RESULTS

Considerable numbers of measurements were statistically significantly different when comparing the influence of dental status on the anatomical measurements; the position and anatomical relations of the mental foramen and overall dimensions of the mandible are especially influenced. Only a few measurements were statistically significantly different in the comparison between males and females.

CONCLUSIONS

The results of this research showed that the presence or absence of the teeth can alter mandibular shape and that mandibular edentulism may be associated with specific shape changes in the mandible. The dental status has a higher influence on the mandibular anatomy than the difference in gender.

Evaluation of bone thickness around the mental foramen for potential fixation of a bone-borne functional appliance: a computer tomography scan study

AIM

A mandible bone-borne Herbst appliance (MBBHA) would avoid the proclination of the lower incisors that occurs with any teeth-borne functional appliance. But mapping of the bone characteristics at potential fixation areas around the mental foramen has not been carried out so far. The aim of this computer tomographic (CT) study was to evaluate bone thickness at specific positions around the mental foramen.

MATERIAL AND METHODS

CT scans of 60 randomly chosen adult Hong Kong Chinese subjects (mean age 28 ± 6.3 years) were used to measure the bi-cortical bone thickness in the mandible in the mental foramen area. The thickness of buccal and lingual cortical and cancellous bone was assessed at the following locations: 10 mm (A10 mm) and 5 mm (A5 mm) anterior, 10 mm (P10 mm) and 5 mm (P5 mm) posterior, and 5 mm (Inf5 mm) below the mental foramen.

RESULTS

The amount of buccal cortical bone thickness ranged between 1.89 mm, 10 mm anterior of the mental foramen, and 2.16 mm, 10 mm posterior to its location. At the A10 mm level, cortical thickness showed a marginal statistically significant difference between A5 and A10 mm. The total amount of bone thickness ranged from 10.19 to 12.06 mm.

CONCLUSION

At the locations studied around the mental foramen, a mean bicortical bone thickness of 10-12 mm was measured. No large variation in the thickness was found between bicortical bone thicknesses in the measured locations around the mental foramen. Thorough evaluation on a case-by-case basis is advisable.

The role of cone-beam computed tomography in the planning and placement of implants

BACKGROUND

Three-dimensional imaging, particularly cone-beam computed tomography (CBCT), has made significant contributions to the planning and placement of implants to replace missing teeth. The accuracy of CBCT data can be used to fabricate a surgical guide that transfers the implant planning information to the surgical site to facilitate implant placement. The authors describe a method for applying CBCT data to aid in the planning and placement of implants.

METHODS

The authors outline clinical goals for implant planning and placement and describe the anatomical and prosthetic requirements for successful implant placement. They also present imaging solutions, including CBCT scanning and software analysis, to the clinical goals.

CONCLUSIONS

Virtual implant planning using CBCT data allows the clinicians to create and visualize the end result before initiating treatment. CBCT scans are accurate and cost effective and can be used to improve communication and coordination of a multidisciplinary team to achieve the desired clinical outcome. Virtual planning allows clinicians to investigate multiple treatment scenarios until the optimum treatment plan is attained. The optimized virtual plan may be converted through modeling to create a surgical guide for clinical implementation.

CLINICAL IMPLICATIONS

The precise planning and delivery of implants to replace missing teeth can avert recognized and concealed treatment problems. This process aids the clinician and benefits the patient.

Identification of the mandibular vital structures: practical clinical applications of anatomy and radiological examination methods

Objectives

The purpose of this article was to review the current available clinical techniques and to recommend the most appropriate imaging modalities for the identification of mandibular vital structures when planning for oral implants.

Material and Methods

The literature was selected through a search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were mandibular canal, mandibular incisive canal, mental foramen, anterior loop of the mental nerve, radiography, dental implants. The search was restricted to English language articles, published from January 1976 to January 2010.

Results

In total 111 literature sources were obtained and reviewed. The peculiarities of the clinical anatomy of mandibular canal, mandibular incisive canal, mental foramen and anterior loop of mental nerve were discussed. Radiological diagnostic methods currently available for the identification of the mandibular vital structures when planning for oral implants were presented. Guidelines for the identification of the mandibular vital structures in dental implantology were made.

Conclusions

The proposed guideline provides clinicians a tool in proper identifying the important mandibular vital structures thus minimizing the potential complications during implant surgery.

Anatomy of Mandibular Vital Structures. Part II: Mandibular Incisive Canal, Mental Foramen and Associated Neurovascular Bundles in Relation with Dental Implantology

Objectives

The purpose of the present study was to review the literature of how to identify the mental foramen, mandibular incisive canal and associated neurovascular bundles during implant surgery and how to detect and avoid the damage of these vital structures during implant therapy.

Material and Methods

Literature was selected through a search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were mandibular incisive canal, mental foramen, mental nerve, anterior mental loop. The search was restricted to English language articles, published from 1979 to November 2009. Additionally, a manual search in the major anatomy, dental implant, and periodontal journals and books was performed.

Results

In total, 47 literature sources were obtained and reviewed. The morphology and variations of the mandibular incisive canal, mental foramen and associated neurovascular bundles were presented as two entities. It suggested that clinicians should carefully assess these vital structures to avoid nerve/artery damage.

Conclusions

The mandibular incisive canal, mental foramen and associated neurovascular bundles exist in different locations and possess many variations. Individual, gender, age, race, assessing technique used and degree of edentulous alveolar bone atrophy largely influence these variations. It suggests that the clinicians should carefully identify these anatomical landmarks, by analyzing all influencing factors, prior to their implant surgical operation.

Measurement of anterior loop length for the mandibular canal and diameter of the mandibular incisive canal to avoid nerve damage when installing endosseous implants in the interforaminal region: a second attempt introducing cone beam computed tomography

PURPOSE

To measure and compare the anterior loop length (ALL) for the mandibular canal and the mandibular incisive canal diameter (ICD) at its origin in cadavers using anatomy and cone beam computed tomography (CBCT) to safely install endosseous implants in the most distal area of the interforaminal region.

MATERIALS AND METHODS

The ALL and ICD were measured using CBCT in 4 cadavers, and using anatomy in 71 cadavers.

RESULTS

The ranges and mean +/- SD for the anatomic measurements were: ALL, 0.0 to 9.0 mm and 1.9 +/- 1.7 mm; ICD, 1.0 to 6.6 mm and 2.8 +/- 1.0 mm. The average discrepancies between CBCT and anatomic measurements were 0.06 mm or less for both the ALL and the ICD, which were less than the resolution of CBCT.

CONCLUSIONS

Because large variations in measurements were observed, both for ALL and ICD, no fixed distance mesially from the mental foramen should be considered safe. The ALL and the ICD can be estimated from the CBCT measurement. The preoperative CBCT measurement yields important information for each case.

The Mental Foramen and Nerve: Clinical and Anatomical Factors Related to Dental Implant Placement: A Literature Review

BACKGROUND

The mental foramen is a strategically important landmark during osteotomy procedures. Its location and the possibility that an anterior loop of the mental nerve may be present mesial to the mental foramen needs to be considered before implant surgery to avoid mental nerve injury.

METHODS

Articles that addressed the position, number, and size of the mental foramen, mental nerve anatomy, and consequences of nerve damage were evaluated for information pertinent to clinicians performing implant dentistry.

RESULTS

The mental foramen may be oval or round and is usually located apical to the second mandibular premolar or between apices of the premolars. However, its location can vary from the mandibular canine to the first molar. The foramen may not appear on conventional radiographs, and linear measurements need to be adjusted to account for radiographic distortion. Computerized tomography (CT) scans are more accurate for detecting the mental foramen than conventional radiographs. There are discrepancies between studies regarding the prevalence and length of the loop of the mental nerve mesial to the mental foramen. Furthermore, investigations that compared radiographic and cadaveric dissection data with respect to identifying the anterior loop reported that radiographic assessments result in a high percentage of false-positive and -negatives findings. Sensory dysfunction due to nerve damage in the foraminal area can occur if the inferior alveolar or mental nerve is damaged during preparation of an osteotomy.

CONCLUSIONS

To avoid nerve injury during surgery in the foraminal area, guidelines were developed based on the literature with respect to verifying the position of the mental foramen and validating the presence of an anterior loop of the mental nerve. These guidelines included leaving a 2 mm zone of safety between an implant and the coronal aspect of the nerve; observation of the inferior alveolar nerve and mental foramen on panoramic and periapical films prior to implant placement; use of CT scans when these techniques do not provide clarity with respect to the position of the nerve; surgical corroboration of the mental foramen's position when an anterior loop of the mental foramen is suspected of being present or if it is unclear how much bone is present coronal to the foramen to establish a zone of safety (in millimeters) for implant placement; once a safety zone is identified, implants can be placed anterior to, posterior to, or above the mental foramen; and prior to placing an implant anterior to the mental foramen that is deeper than the safety zone, the foramen must be probed to exclude the possibility that an anterior loop is present. In general, altered lip sensations are preventable if the mental foramen is located and this knowledge is employed when performing surgical procedures in the foraminal area.

Morphometric Analysis of Implant-Related Anatomy in Caucasian Skulls

BACKGROUND

Sequelae related to implant placement/advanced bone grafting procedures are a result of injury to surrounding anatomic structures. Damage may not necessarily lead to implant failure; however, it is the most common cause of legal action against the practitioner. This study aimed to describe morphological aspects and variations of the anatomy directly related to implant treatment.

METHODS

Morphometric analyses were performed in 22 Caucasian skulls. Measurements of the mental foramen (MF) included height (MF-H), width (MF-W), and location in relation to other known anatomical landmarks. Presence or absence of anterior loops (AL) of the inferior alveolar nerve (IAN) was determined, and the mesial extent of the loop was measured. Additional measurements included height (G-H), width (G-W), thickness (G-T), and volume (G-V) of monocortical onlay grafts harvested from the mandibular symphysis area, and thickness of the lateral wall (T-LW) of the maxillary sinus. The independent samples t test, and a two-tailed t test with equal variance were utilized to determine statistical significance to a level of P < 0.05. Multiple regression analyses were performed to determine if each one of these measurements was affected by age and gender.

RESULTS

The most common location of the MF in relation to teeth was found to be below the apices of mandibular premolars. The mean MF-H was 3.47 +/- 0.71 mm and the mean MF-W was 3.59 +/- 0.8 mm. The mean distance from the MF to other anatomical landmarks were: MF-CEJ = 15.52 +/- 2.37 mm, MF to the most apical portion of the lower cortex of the mandible = 12.0 +/- 1.67 mm, MF to the midline = 27.61+/- 2.29 mm, and MF-MF = 55.23 +/- 5.34 mm. A high prevalence of AL was found (88%); symmetric occurrence was a common finding (76.2%), with a mean length of 4.13 +/- 2.04 mm. The mean size of symphyseal grafts was: G-H = 9.45 +/- 1.08 mm, G-W = 14.5 +/- 3.0 mm, and G-T = 6.15 +/- 1.04 mm, with an average G-V of 857.55 +/- 283.97 mm3 (range: 352 to 1,200 mm3). The mean T-LW of the maxillary sinus was 0.91 +/- 0.43 mm.

CONCLUSION

Implant-related anatomy must be carefully evaluated before treatment due to considerable variations among individuals, in order to prevent injury to surrounding anatomical structures and possible damage.

Intrabony course of the inferior alveolar nerve in the edentulous mandible

The purpose of this study was to investigate the vertical positioning and intrabony branching patterns of the inferior alveolar nerve (IAN) in 39 edentulous human cadaveric mandibles by buccal microdissection. Dissected mandibles were classified on the basis of the height of the IAN within the body of the mandible and the branching pattern of the IAN. The IAN was located in the superior part of the body of the mandible in 30.7% (12/39) of cases, all of which showed a small posterior molar plexus of branches. In 69.2% (27/39) of cases the IAN was half-way or closer to the inferior border of the mandible. Of these latter cases, 41% demonstrated a small, posterior molar plexus of branches, 37% showed posterior and anterior plexuses, and 22% showed either no branches or a single trunk with a small number of single branches directed at the superior border of the mandible. These findings were rendered in 3D computer format for instructional purposes.