Inferior Alveolar Canal Research Articles

Evaluation of cone beam computed tomography imaging in placed dental implants: comparison between multiplanar reconstruction and parasagittal images / Avaliação de imagens de tomografia computadorizada de feixe cônico em implantes instalados: comparação entre reconstrução multiplanar e imagens parassagitais

This study aimed to compare multiplanar reconstruction (MPR) to parasagittal images of cone-beam computed tomography (CBCT) for localizing placed dental implants concerning adjacent anatomical structures (nasal fossa floor, maxillary sinus, inferior alveolar canal and nasopalatine canal).The CBCT exams of 164 placed implants were analyzed. All tomographic images were imported to Imaging Studio software to create parasagittal image templates. The images were randomized and analyzed by two oral and maxillofacial radiologists who classified whether or not there was perforation of the anatomical structure in question.According to Kappa coefficient of agreement, the results including, all anatomical structures for inter-observer assessment was 0.81 and for intra-observer assessment, 0.79 for observer one and 0.89 for observer two. For each anatomical structure, the agreement ranged from 'substantial' to 'almost perfect' (nasal fossa floor 0.72, nasopalatine canal 0.92, maxillary sinus 0.81, and inferior alveolar canal 0.81). Based on our findings, there was substantial to almost perfect agreement when comparing MPR and parasagittal images of CBCT regarding of implant position relationship with anatomical structures. Since both modalities did not differ in implant position, and the MPR represents the complete and original volume that enables analysis in three dimensions, they can be the first-choice imaging modality to analyze placed dental implants.

STAFNE BONE CYST OF MANDIBLE - A RARE PSEUDOCYST

Background: Stafne bone cyst (SBC) is a bone depression found on the lingual side of the mandible. It is usually asymptomatic and is usually diagnosed on the routine radiographs as an incidental nding. So it has an unknown prevalence. The lesion resembles many odontogenic pathologies and the entity remains a diagnostic challenge. The aim of this case report is to describe the clinical and radiological characteristics of a case of stafne bone cyst and the importance of cone beam computed tomography in conrming the diagnosis. Method: Analysis of orthopantomogram (OPG) and cone beam computed tomography (CBCT) was done on the basis of diagnostic criteria described by Stafne. Result : According to the clinical and radiographic ndings and based on the dental literature, it was concluded that the observed bony cavity was a Stafne bone defect, located in the angle of mandible below inferior alveolar canal. Conclusion: Differential diagnosis of SBC's from other possible pathologies that may require treatment and imaging technique selection according to case is signicant. The use of CBCT is highlighted because of the ne detail of imaging , low radiation dose and limited area exposure which is benecial for the diagnosis of SBC.

A CBCT Based Evaluation of The Varying Location of Mandibular Canal and Mental Foramen: An Original Research Study

Background and Aim: Iatrogenic injuries to inferior alveolar nerve (IAN) are a well known complication of implant placement, osteotomies and other surgical procedures. This study was at attempted to determine the most common position of the mental foramen and to estimate difference in position of mental foramen, occurrence of anterior loop and to evaluate the variation in the location of mandibular canal using cone-beam computed tomography (CBCT) radiographs. Materials & Methods: A total of 205 north Indian subjects were selected during a period of two years. Formerly exposed CBCT images of the selected subjects were studied by ‘iCAT Vision’ and ‘Anatomage’ Software. Measurements from the mandibular canal to the root apices of the first premolar, second premolar, first molar and second molar were obtained. Likewise the distance from the inferior alveolar canal to the buccal cortical plate (BCP) and lingual cortical plates (LCP) were also studied. The estimation of the horizontal and vertical positioning of mental foramen on the CBCT images was also done on both sides. Other inter-related dimensional parameters were also studied comprehensively. The incidence of Anterior Loop (AL) was also assessed and comparisons were done among both sides of the jaw and gender. Statistical Analysis and Results: A total of 205 subjects comprising of 108 (52.7%) males and 97 (47.3%) female participated in the study. The Unpaired t-test showed a statistically significant difference among males and females in the measurements of IAC. Among males Linear, Perpendicular and Anterior loop pattern was seen in 64 (59.3%), 34 (31.4%) and 10 (9.3%) subjects respectively. Among males prevalence of right sided anterior loop (Mental Foramen) was 10 (30.3%), left sided anterior loop was 10 (30.3%). The Unpaired t-test showed a statistically non-significant difference among males and females. (p>0.5) Anterior loop was seen on 17 (51.5%) occasions on the right side and 16 (48.5%) occasions on the left side. The Pearson’s Chi-square test showed a statistically non-significant difference among the genders on the right side. Conclusion: The most common configurations alveolar canal was the linear pattern followed by perpendicular pattern. Most frequent location of mental foramen was in continuity with second premolar in both the left and right sides as well as in both the genders. The anterior loop was the least common pattern of inferior alveolar canal.

EVALUATION OF PATTERNS OF IMPACTED THIRD MOLARS AND THEIR ASSOCIATION WITH VITAL STRUCTURES BY RADIOGRAPHIC EXAMINATION

Objective: To assess the patterns of impacted 3rd molars and their proximity with adjacent vital structures.
 Study Design: Comparative cross-sectional study.
 Place and Duration of Study: Oral & maxillofacial department of Rawalpindi Dental Hospital, from Oct 2016 toFeb 2018.
 Methodology: Patient sample size was 956. Orthopantomograms (OPGs) were assessed to determine the presence, patterns of impacted third molars and their relation to maxillary sinus and inferior alveolar canal (IAC) in maxilla and mandible respectively.
 Results: Out of 956 Orthopantomograms with 3499 3rd molars examined, 808 (23.09%) were impacted. Frequency of impaction was much higher in mandible than maxilla. Out of 527 impacted mandibular 3rd molars 238 (45.16%) were mesio-angular, 370 (70.21%) had class 1 relation to mandibular ramus & 266 (50.47%) had level B depth, while among 281 impacted maxillary third molars 134 (47.69%) had vertical angulation and 162 (57.65%) had level B depth. Two hundred and eighty four (53.89%) impacted mandibular 3rd molars showed relationship with the inferior alveolar canal, out of which 187 (35.48%) impacted mandibular 3rd molars showed interruption of white line as the most common radiographic finding.
 Conclusion: Frequency of impacted third molars was more common in mandible and among females whereasthere is significant difference in patterns of impaction among mandible and maxilla. While most impacted teethhave approximation with IAC and maxillary sinus.

The outcome of postoperative paresthesia of inferior alveolar nerve after surgical removal of mandibular third molar using Orthopantomogram (OPG) versus Cone-beam CT

Background: Periapical and Orthopantomogram (OPG) are the most commonly used radiographs for assessment of the relationship of lower 3rd molar roots with the inferior alveolar canal. Panoramic radiographs provide inadequate information of the buccolingual relationship between the roots of the 3rd molar & mandibular canal being two-dimensional (2D) in nature. To verify the relationship in three (3D) dimensions and to make a predictable treatment plan, traditional investigations may be supplemented by using CBCT. Cone-beam computerized tomography (CBCT) is an office-based radiography technique used to assess the three-dimensional relationship of lower 3rd molar roots with inferior alveolar nerve.
 Patients and methods: This comparative-cross sectional study was conducted at the Department of Oral and Maxillofacial Surgery, Fatima Memorial Hospital (FMH), Lahore from 1st January 2019 till 30th June 2019. A total of 124 patients requiring removal of lower wisdom tooth were enrolled and then divided into two groups (62 in each) randomly. OPG was used for diagnosis of impacted lower 3rd molars in Group A patients while CBCT for diagnosis in Group B patients. A self-designed Performa was used to collect the data and final information was collected after 3 months of follow-up. Data analysis was performed using SPSS 20. A chi-square test was used to compare the postoperative paraesthesia between the OPG group and CBCT group patients. A p-value <0.05 was taken as significant.
 Results: The occurrence of postoperative paresthesia between the two groups is significantly different; being a low percentage in the CBCT group at 2nd, 7th day and after 3 months follow-up visits with a p-value of 0.019, 0.019, and 0.005 respectively. On 3 months follow up, the distribution of paraesthesia between the two groups is significantly different; 20 patients (32.25%) in OPG group A and those of 7 (11.29%) in CBCT group B experienced paresthesia with a p-value of 0.005.
 Conclusion: It is better to use CBCT to improve the postoperative paraesthesia for lower third molar surgical extraction.

Assessment of mental loop using cone beam computed tomography in a sample of Egyptians

ABSTRACT Introduction: Although the inferior alveolar nerve had been described as a single entity that travels through the mandibular canal and leaves it through the mental foramen directly giving rise to mental nerve, presence of mental loop was reported. Improper identification of mental loop led to increasing the incidence of nerve injury during surgical procedures especially implant placement. Objective of the study: The purpose of this study was to assess mental loop and its length among a sample of Egyptians, using cone beam computed tomography (CBCT). Materials and Methods: Two hundred and sixty-seven CBCTs were collected in which one hundred were males and one hundred and sixty-seven were females, then evaluated for the presence of the mental loop. The length of the loop was measured on reconstructed panoramic views of CBCT using on demand software. Results: Mental loop was present in one hundred and nine patients (40% of the patients), 63 females and 46 males. The minimum length observed was 2.27 mm. while the maximum length was 7.18mm and the mean length was 4.36±.96mm. There was no significant difference between males and females. Conclusions: High prevalence of mental loop was detected in Egyptians. Based on this finding proper identification of mental loop by the method explained in this study prior to surgical planning is essential. Keywords: Anatomical variant, CBCT, inferior alveolar canal, mental nerve loop

Degree of Compression of the Inferior Alveolar Canal on Cone-Beam Computed Tomography and Outcomes of Postoperative Nerve Injury in Mandibular Third Molar Surgery

Cone-beam computed tomography (CBCT) offers the advantage of a 3-dimensional representation of the anatomic relationship of the mandibular third molar tooth and the inferior alveolarcanal (IAC), as compared to a panoramic radiograph. We hypothesized that a novel method of categorizing the degrees of compression of the IAC were reliable predictors for postoperative nerve injuries. We conducted a retrospective analysis of the outcomes in third molar surgery for patients who obtained a CBCT scan in additional to a plain film radiograph over a 12months period and underwent surgical removal of their mandibular third molars; 257 consecutive patients were identified, and 416 mandibular third molars were surgically removed. Patients who had severe compression of the inferior alveolar canal (IAC) on CBCT imaging had a significantly increased risk of a postoperative IAN injury (P=.0068, OR=3.47, 95% CI: 1.40 to 8.54) and accounted for 52.17% of all IAN injuries. Ninety-one percent of all cases of postoperative nerve injury occurred in female patients. The mean age of patients with a postoperative IAN injury (30.2years) was significantly higher than those without injury 26.0years; (P=.016, 95%CI: 25.11 to 33.80) CONCLUSIONS: In addition to patient factors, assessment of the degree of compression on a preoperative CBCT image is a useful tool for predicting outcomes in mandibular third molar surgery. In cases of severe compression of the IAC, patients are at a significantly increased risk of postoperative IAN injury.

Can a panoramic radiograph predict the inferior alveolar nerve canal's position, or canal compression, near third molar root apices?

Background: Injury to the inferior alveolar nerve can occur during surgical removal of the mandibular third molars (M3Ms), resulting in numbness of the mandibular teeth, chin, and lower lip. This occurs when the roots of M3M compress the inferior alveolar canal (IAC) against the lingual cortical plate. Cone-beam computed tomography (CBCT) reveals the buccolingual relationship of the IAC and M3M, but the panoramic radiograph (PR) has not been evaluated to determine whether the plane film can reveal this relationship. Aims: The aim of the study is to determine whether PR could predict buccal or lingual IAC position or compression near M3M. Design: This retrospective study evaluated 200 M3M sites in 42 women and 67 men, aged 17–28 years. Ninety-one bilateral measurements were taken; 98 left and 102 right halves were analyzed. Methods: IAC position and degree of compression were interpreted from the CBCT. Utilizing imaging software, 13 different measurements were obtained. Statistical Analyses: Fisher's exact test, t-test, principal component analysis, and multivariate analysis were utilized. Results: Male and female canal positions significantly differed. Canal position was significantly different comparing partially erupted to erupted and fully bony impacted molars. Lingual canal position, versus buccal, was more frequently associated with moderate-to-severe IAC compression. “Anterior-posterior ramus at the occlusal plane” and “anterior ramus to anterior IAC at the occlusal plane” contributed most to the severity of IAC compression. Conclusion: The variables evaluated did not identify a significant relationship. A larger data set is needed to evaluate any role the dimension of the ramus has on IAC compression.

Assessment of the anterior and caudal extent of inferior alveolar nerve canal, location of inferior alveolar canal and mental foramen, and the depth of submandibular fossa using computed tomography.

Background:A well-versed knowledge of the precise location of various anatomical landmarks is necessary to avoid complications during surgery. The study was conducted for the assessment of the anterior and caudal extent of the inferior alveolar nerve canal, location of inferior alveolar canal and mental foramen, and the depth of the submandibular fossa using computed tomography (CT).Materials and Methods:One hundred CT scans were randomly selected for this study accounting for 200 hemimandibles. Both axial and coronal images were obtained and evaluated concurrently. Results were subjected to statistical analysis for correct inferences.Results:A total of 200 hemimandibles (n = 200) from 100 patients with a mean age was 23.89 ± 1.75 years ranging from 21 to 33 years were evaluated. The mean length of the anterior loop was 0.95 mm for all of the observation combined and measurement range from 0 to 5.1 mm. The total frequency of type I, type II, and type III of mental nerve was found as 71%, 4.5%, and 24.5%, respectively. At the level of the first molar, the mean distance from the center of the inferior alveolar canal to the external surface of the buccal cortex (Q) was 5.44 ± 1.38 mm ranging from 2.4 to 10.4 mm. Furthermore, there was no statistically significant difference in MF-IMB (mental foramen to the inferior border of mandible) between the right and left sides of the mandible. (P = 0.87).Conclusion:Our study demonstrates that analyzing CT scans using the methods described in this study can be a useful tool in avoiding the iatrogenic injuries to inferior alveolar nerve and arteries during various maxillofacial surgical procedures.

Contrastive Characteristic Analysis of Mandibular First Molar Alveolar Bone Between Li Nationality and Han Nationality

Background/purpose: The present study was performed to compare the ethnic features of alveolar bone of Li and Han nationality in Hainan province. Methods: The lower first permanent mandibular molar tooth (L6) from patients with Li nationality and Han nationality were chosen. Cone-beam computed tomography (CBCT) examination technology was used to measure the vertical height of the middle point of the crown of L6 along the long axis of the tooth from the crest of alveolar bone to the inferior alveolar nerve canal (IANC), and the buccolingual width of alveolar ridge in the direction of this site. The vertical height and buccolingual width between Li nationality and Han nationality were compared. Results: The vertical height between the crest of alveolar bone to IANC of L6 in Li nationality was farther than that in Han nationality and the difference was statistically significant. There was no significant difference in the buccolingual width of alveolar ridge. At the same time, the comparison of the same gender group shows that the difference between the two indicators remains unchanged. Conclusion: Ethnicity-related variations exist in terms of the length of alveolar crest to IANC in the mandible. Longer implants could be considered in the restoration of L6 loss in Li nationality.

Multidetector computed tomography in preoperative planning for temporomandibular joint ankylosis: A pictorial review and proposed structured reporting format.

Ankylosis of the temporomandibular joint (TMJ) is a disabling disease resulting from fibrous or bony fusion of the mandibular condyle and the glenoid fossa. Early diagnosis and surgical treatment are essential to prevent facial deformity and other complications. Conventional radiography has limitations in demonstrating the true extent of ankylosis. It is important for surgeons to be aware of the size and degree of bony ankylosis in order to perform complete resection of the ankylotic mass. In addition, a detailed evaluation of the relationship with adjacent vital structures such as the internal maxillary artery, inferior alveolar nerve canal, external auditory canal, and skull base are crucial to avoid iatrogenic injury. Multidetector computed tomography (MDCT) is the current imaging modality of choice for preoperative assessments. Herein, the authors propose a structured CT reporting template for TMJ ankylosis to strengthen the value of the preoperative imaging report and to reduce the rates of intraoperative complications and recurrence.

Patterns of Root Morphology of Mandibular Third Molars and Their Clinical Implications in a Cohort of Sri Lankan Patients

Background: Mandibular third molar surgeries garnered recognition as one of the common treatment procedures provided by Oral & Maxillofacial practices across the globe. Mandibular third molars are not only impacted, often giving rise to bothering issues to patients ranging from pain to difficulty in opening mouth but create challenges in their surgical removal. Postoperative complications of those surgeries such as pain, swelling, trismus and alveolar osteitis (dry socket) could be prevented and controlled by meticulous preoperative assessment of tooth-related and patient-related factors. Pattern of root morphology could be one important tooth- related factor connected to difficulties and subsequent postoperative complications of mandibular third molar surgeries. Aim: Against this backdrop, the aim of this study was to explore the patterns of root morphology of mandibular third molars and to elucidate their associations with selected attributes of the surgeries, self-reported preoperative pain and selected postoperative complications among a cohort of Sri Lankan patients. Materials & Methods: A hospital based, descriptive cross-sectional study was conducted among 715 patients (represented wider age range from adolescents to older adults) who underwent surgical removal of mandibular third molars at the Department of Oral & Maxillofacial Surgery, Faculty of Dental Sciences, University of Peradeniya, Sri Lanka. Of extensive socio-demographic, clinical and radiological investigation data collected, those data on root morphology and numbers of roots, inferior dental canal relationship, self-reported preoperative pain, duration of the surgery, flap design, tooth sectioning and postoperative pain and swelling complications were used for the present analysis. Data entry and analysis was done using SPSS-21 Statistical Software Package. Results: Based on our findings on patterns of root morphology, straight two roots were the most common (34.4%) across all age groups, followed by convergent two- roots (19.3%) fused straight- roots (16.3%) and distally curved two- roots (13.8) among Sri Lankan patients. Almost half (46.8%), of patients had inferior dental nerve canal placed away from mandibular third molar roots. Moreover, root morphology was significantly associated with presence of preoperative pain, duration of the surgery as well as occurrence of postoperative swelling (p<0.05). Conclusions: Patterns of root morphology of mandibular third molars may implicate on certain processes of their surgical removal and its outcomes. Therefore, careful preoperative assessment of root morphology and related factors of those teeth becomes useful in tailored patient care for minimal postoperative complications, better patient experience and quality-of-life.

A Suspected Metastatic Liposarcoma of the Inferior Alveolar Nerve Canal: A Case Report and Literature Review

Introduction: Liposarcoma is the most common soft tissue sarcoma, but it is relatively scarce in the head and neck. The metastatic liposarcoma is more infrequent than the primary one. Case Presentation: Here is presented a suspected case of metastatic liposarcoma in the inferior alveolar nerve canal in a 40-year-old female patient with a chief complaint of the chin and lower lip numbness and medical history of liposarcoma in the thigh. The present study was a case report for metastatic liposarcoma in the head and neck regions, according to the English language literature found in PubMed and Google Scholar. The search was performed using the keywords "Metastatic Liposarcoma" and "Head" and "Neck". Conclusions: According to the findings, the reported case may be the first case of the metastasis of liposarcoma in the inferior alveolar nerve canal. Ominous signs, such as numbness, should be considered in patients with a history of cancer, due to their warning for metastasis or recurrence of the tumor.

Is There a Safe Zone for Lateral Border Fixation of Mandibular Angle Fractures?

Cross-sectional study design. There are multiple accepted treatment options for internal fixation of mandibular angle fractures. The purpose of this study was to determine if there is a safe zone for lateral border fixation of mandibular angle fractures. One hundred coronal images of facial computed tomography (CT) scans were reviewed on patients between the ages of 18 to 48. Measurements were taken in the area of the second and third molar region related to the inferior border to the superior extent of the inferior alveolar canal and apex of the second molar root, along with buccal cortical measurements to the inferior alveolar canal and apical third of the second molar root. The average measurement of the inferior border in the second molar area to the inferior alveolar canal and apex of the root was 1.12 cm (0.70-1.77) and 1.39 cm (0.91-2.30), respectively. The average measurement of the inferior border of the third molar to the inferior alveolar canal was 1.26 cm (0.78-1.83). The average measurement of the buccal cortex of the second molar to the inferior alveolar canal and apical one-third of the root was 0.64 cm (0.34-1.25) and 0.59 cm (0.33-0.98), respectively. The average measurement of the third molar buccal cortex to the inferior alveolar canal was 0.45 cm (0.18-0.98). In the area of the second molar region, there is no ubiquitous safe zone for screw placement, cortical bone thickness is more critical than vertical placement of the fixation plate and screws. In the third molar region, cortical bone thickness and vertical orientation may provide a safe zone for screw placement.

Evaluation of artificial intelligence for detecting impacted third molars on cone-beam computed tomography scans

PurposeThe aim of this study was to evaluate the diagnostic performance of artificial intelligence (AI) application evaluating of the impacted third molar teeth in Cone-beam Computed Tomography (CBCT) images. Material and methodsIn total, 130 third molar teeth (65 patients) were included in this retrospective study. Impaction detection, Impacted tooth numbers, root/canal numbers of teeth, relationship with adjacent anatomical structures (inferior alveolar canal and maxillary sinus) were compared between the human observer and AI application. Recorded parameters agreement between the human observer and AI application based on the deep-CNN system was evaluated using the Kappa analysis. ResultsIn total, 112 teeth (86.2%) were detected as impacted by AI. The number of roots was correctly determined in 99 teeth (78.6%) and the number of canals in 82 teeth (68.1%). There was a good agreement in the determination of the inferior alveolar canal in relation to the mandibular impacted third molars (kappa: 0.762) as well as the number of roots detection (kappa: 0.620). Similarly, there was an excellent agreement in relation to maxillary impacted third molar and the maxillary sinus (kappa: 0.860). For the maxillary molar canal number detection, a moderate agreement was found between the human observer and AI examinations (kappa: 0.424). ConclusionsArtificial Intelligence (AI) application showed high accuracy values in the detection of impacted third molar teeth and their relationship to anatomical structures.

Boon to dentistry of CBCT use: A lingual mandibular bone defect – A radiographic incidental finding

Objective: Since many decades we are using conventional radiography as it is commonly used world-wide. Conventional radiographs lacks many important features which needs to be enhanced in terms of quality of equipment, radiographic techniques used, to interpret accurately and radiation exposure risk, so it is a need of the day to confirm the hidden lesion with accuracy. So recent we came across a radiographic incidental finding of lingual mandibular bone defect by using CBCT. Results: We incidentally found stafne’s bone cyst below the IAN canal on left side of the jaw in mandible with the help of CBCT. Conclusion: We concluded according to our observation, we observed that CBCT is useful and will have potential value when introduced in routine day to day life examination imaging method in dentistry to confirm the unknown hidden lesions that are most common finding. Keywords: Cone beam CT, CT, Inferior alveolar nerve canal, Stafne’s bone cysts.

Neurapraxia in an infected radicular cyst and its management

Radicular cysts are the most common inflammatory odontogenic cyst of jaw that emanates from the epithelial cell rests of malassez in the periodontal ligament. 60% of cases are found in maxilla, most commonly around incisors and canines with male predilection. Most of the cases remain silent until secondarily infected. Treatment modalities of Radicular cyst according to their size and severity are extraction of the associated tooth, endodontic treatment, apical surgery, enucleation and/or marsupialization. Though, radicular cyst involving inferior alveolar nerve may cause paraesthesia due the neurosensory disturbance caused by mechanical compression or stress. Here, we report a case of neurapraxia occurred in an infected radicular cyst involving roof of the inferior alveolar nerve canal. Keywords: Radicular cyst, Inferior alveolar nerve, Paraesthesia, Neurosensory disturbance, Compression, Stress.

Foreign body surgery in the inferior alveolar nerve canal following endodontic treatment

Endodontic treatment can result in the extrusion of dental sealant material beyond the apex of a tooth. Dental sealant materials are known to have potentially cytotoxic properties and can cause damage to biological structures. This article describes the case of a patient who had experienced a sustained painful dysaesthesia of the left inferior alveolar nerve as a result of extrusion of material beyond the apex of the tooth into the nerve canal, and the surgical approach taken to directly treat the nerve and improve her symptoms. CPD/Clinical Relevance: Awareness of the potential and sustained effects of dental sealant material on biological tissue, as well as the proximity of important anatomical structures, such as the inferior alveolar nerve, will help practitioners in the safe treatment of patients. Additionally, an awareness of the signs and symptoms of foreign body reactions within soft tissues will aid diagnosis and prompt onward referral for specialist treatments.

Variability associated with mandibular buccal shelf area width and height in subjects with different growth pattern, sex, and growth status

The primary objective of the study was to quantitatively analyze the width and height of the mandibular buccal shelf area (MBS) at 3 different potential locations for mini-implant placement. In addition, we aimed to compare and contrast the bone parameters of the MBS to study the correlation between different growth status (growing or nongrowing), facial types (hypodivergent, normodivergent, and hyperdivergent), and sex differences (male or female). In this retrospective cone-beam computed tomography study, 678 subjects were included. They were divided into groups according to growth status, facial type, and sex. Scans were imported into the reconstruction program and were aligned in 3 different steps. Measurements were made at 6 different coronal sections: mandibular first molar distal root, secondmolar mesial root, and secondmolar distal root (bilaterally). The roots of mandibular molars were used as a reference to measure the width and the roof of the inferior alveolar canal to measure the height of the buccal shelf area. Intraobserver reliability was assessed by measuring the width and height of MBS in 20 randomly selected subjects. No significant difference (P>0.05) was found in the width of MBS between males and females. MBS width increased, and height decreased (P<0.0001) as moved distally from the first molar distal root to the secondmolar distal root in all 3 facial types irrespective of age or sex. The hypodivergent facial type had significantly greater bone width than the hyperdivergent facial type at all the 3 locations in both males and females. The hypodivergent facial type had significantly less (P<0.0001) bone height than the hyperdivergent group at all the 3 locations irrespective of age or sex. The optimal site for MBS mini-implant is the buccal region of the distal root of mandibular secondmolars. Hypodivergent patients have more width and less height of MBS compared with hyperdivergent patients. MBS mini-implants are not advised for growing patients because of proximity to developing roots.

Anatomical Position of Lower Third Molar in Relation to Mandibular Canal on Cone-Beam Computed Tomography Images in A Tertiary Care Hospital: A Descriptive Cross-sectional Study.

The positional relationship between the mandibularcanal with impacted mandibular third molar is the main factor of inferior alveolar nerve injury. The purpose of this study wasto classify the anatomical three dimensional relationship between the proximity of impacted mandibular third molars to the inferior alveolar canal. The descriptive cross-sectional study was conducted inthe Department of Oral and Maxillofacial Surgery of a tertiary care hospital from July 2020 to August 2020 after obtaining ethical approval from the Institutional Review Committee (Reference number 2506202001). Cone-beam computed tomography images of 200 patient's mandibular third molars were used. A convenient sampling method was used. Data were analyzed using Statistical package for the Social Sciences. Mandibular canal relative to the roots of the mandibular third molar was observed on the apical side in 104 (52.0%) and 173 (86.5%) third molars had direct contact with the mandibular canal. About 36 (97.3%) lingually placed mandibular third molars had contact with the mandibular canal. The findings of the study conclude that most of the mandibular third molars situated lingually had a higher occurrence of mandibular nerve involvement. The anatomic structures of the mandibular third molar and the mandibular canal may be helpful to draw upon the adequate surgical plan to avoidor reduce nerve involvement.