Position Of Inferior Alveolar Canal Research Articles

High- Risk Factors Associated with Inferior Alveolar Nerve Injury Following Removal of the Third Molars: A Preliminary Study

PURPOSE: This study aims to determine the incidence of inferior alveolar nerve (IAN) injury following the extraction of the lower third molars (LTMs) and to identify the demographic, radiographic, and intra-operative risk factors associated with this complication. MATERIALS & METHODS: Fifty LTMs from 47 patients were included in this prospective clinical study. Demographic data and intra-operative parameters including operation time, bone removal and duration, excessive bleeding and IAN exposure were recorded. Bone retention, anatomical position of LTMs (Pell&Gregory and Winter classification) and 5 radiographic criteria proposed by Rood and Shehab were evaluated on panoramic images, whereas the distance between roots and the inferior alveolar canal (IAC), the cortication status of IAC, and the buccolingual position of IAC were examined on CBCT images. Chi-square test was used to compare the presence of IAN injury with variables. A p-value < 0.05 was considered as statistically significant. RESULTS: The incidence of temporary IAN injury was 6% among study population. No permanent IAN injury was observed. Excessive bleeding (p=0.007), IAN exposure (p=0.007), the lingual position of IAC (p=0.035) and dumbbell-shaped IAC (p=0.002) were found to be associated with increased risk of temporary IAN injury. CONCLUSION: Identification of high-risk factors is essential for predicting the risk of IAN injury, and determining the most convenient treatment plan for each case. Further studies with larger study samples are needed both to confirm the risk factors that are proposed in the present study and to identify the other potential ones.

Radiological assessment of the inferior alveolar canal and mental foramen using cone beam computed tomography for pre-operative evaluation of surgeries in the mandible: A single-center five-year retrospective study

IntroductionCone beam computed tomography (CBCT) plays a significant role in studying the anatomical structures of the mandible. AimThis retrospective study aimed to assess the role of CBCT at the pre-assessment stage of mandibular surgery. Materials and methodsA total of 250 CBCT images were collected. The inferior alveolar canal (IAC) and mental foramen (MF) were measured bilaterally to the mandibular teeth apexes, including molars, premolars, and canines, to the buccal, lingual cortical bone, and to the inferior border of the mandible. ResultsThere were no differences in the average number of extracted teeth between the right and left sides (P-value > 0.05, median = three teeth). It was noticed that the average measures of each point of the IAC and MF on the right side were closely matched to the similar point on the left side (P-value > 0.05). T-tests showed that there were differences between males and females on the M2 and M3 on the right side (P-value < 0.05) and on the M1, M2, and M3 on the left side (P-value < 0.05). Using one-way ANOVA tests, results showed that there were some differences in measures at P0 (F = 3.376, P-value = 0.003), P4 (F = 3.782, P-value = 0.001) on the right side, and at P3 (F = 5.620, P-value = 0.019) on the left side of the mandible. ConclusionsThere were no significant differences in IAC and MF positions between the right and left sides.However, between males and females, MF measurements showed significant differences on some points on the right and left sides. Although the history of extracted teeth showed no statistically significant difference in the location of IAC and MF, the number of extracted teeth showed an effect in the IAC position on the right and left sides, but not with the MF.

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.

Do positional changes of the inferior alveolar canal after sagittal split mandibular osteotomy affect neurosensory recovery?

The purpose of this study was to assess the pre- and postoperative position and dimensions of the inferior alveolar canal (IAC) following sagittal split osteotomy (SSO) and identify any association with postoperative neurosensory deficit (NSD) at 1 year. This retrospective cohort study enrolled consecutive patients who had SSO performed to correct skeletal malocclusion. The pre- and postoperative cone beam computed tomography data were superimposed to visualize differences in IAC position and dimensions. Subjective and objective neurosensory tests were used to determine NSD in the inferior alveolar nerve distribution. A total of 20 subjects were included. The preoperative distance from the lateral cortex of the IAC to the inner aspect of the lateral cortex of the mandible was significantly greater in sides with NSD when compared to sides without NSD (P = 0.01). A significantly greater reduction in the postoperative distance measurement was seen in sides with NSD when compared to sides without NSD (P = 0.01). The magnitude of mandibular movement was significantly increased in sides with NSD (P = 0.02). The preoperative location of the IAC, as well as certain changes in the mediolateral and vertical positions as a result of SSO, are risk factors for postoperative NSD.

Risk stratification against inferior alveolar nerve injury after lower third molar extraction by scoring on cone-beam computed tomography image.

The study aimed to stratify the risk of inferior alveolar nerve injury (IANI) after lower third molar (LM3) surgery with a scoring system using identified predictive factors based on cone-beam computed tomography (CBCT) images. In a case-control study, the primary outcome was IANI occurrence. The control group included randomly selected patients without IANI. Predictor variables included patient demographics, surgical situations, Pell-Gregory classification, and inferior alveolar canal (IAC)-associated factors on CBCT. Study variables were analyzed using logistic regression models. Risk stratification was assessed by a scoring system that was constructed using independent predictors. The 858 patients who underwent LM3 surgery (1177 teeth) after CBCT scan were divided into case (25 patients, 2.9%, 27 teeth) and control (235 patients, 300 teeth) groups. In the multivariate model, lingual/inter-radicular position of IAC [odds ratio (OR) 7.21; P < 0.001; assigned score, 2], multiple roots closed to the IAC with cortical perforation (OR 3.72; P = 0.015; 1), and age > 30years (OR 4.99; P = 0.008; 2) were associated with an increased IANI-risk. The IANI-risk scoring system could be stratified into low- and high-risk groups at a cutoff score of 3 (sensitivity, 68.0%; specificity, 90.6%; positive predictive value, 17.8%; positive likelihood ratio, 7.23). In conclusion, the high-risk group of IANI after LM3 surgery corresponded to individuals with multiple factors: lingual/inter-radicular IAC position to LM3, multiple roots with perforated IAC, and increased age (> 30years). Raising awareness of the higher probability for IANI is needed for patients with multiple aforementioned factors.

Efficacy of digital volume tomography in the preoperative assessment of position of inferior alveolar canal with impacted mandibular third molars in a subset of Indian population

Context: Choosing an imaging source, which provides minimum radiation exposure to the patient, to facilitate surgical removal of impacted mandibular third molars (MTMs), thereby avoiding unwanted neurological complications. Aim: The aim of the study was to assess the efficacy of digital volume tomography (DVT) in evaluating the position of inferior alveolar canal (IAC) in relation to impacted MTMs and comparing it with conventional radiography (CR) in a subset of the Indian population. Materials and Methods: Four experienced observers assessed two groups: 33 DVT and 33 CR images, for the position of root-tips of impacted MTM in the proximity to IAC, in both vertical and horizontal planes. The diagnostic information was compared in both the groups. Statistical Analysis: Chi-square test, Mann–Whitney U-test, and Kappa statistics were used. Results: Comparison between DVT and CR revealed no statistically significant variation in assessing relationship in the vertical plane. There was, however, a significant difference between the groups, while comparing the diagnostic information for the horizontal dimension, for both the mesial and the distal roots, with an advantage for DVT (P

Combined preoperative measurement of three inferior alveolar canal factors using computed tomography predicts the risk of inferior alveolar nerve injury during lower third molar extraction

A retrospective cohort study was performed to assess the clinical usefulness of combination assessment using computed tomography (CT) images in patients undergoing third molar extraction. This study included 85 patients (124 extraction sites). The relationship between cortication status, buccolingual position, and shape of the inferior alveolar canal (IAC) on CT images and the incidence of inferior alveolar nerve (IAN) injury after third molar extraction was evaluated. IAN injury was observed at eight of the 124 sites (6.5%), and in five of 19 sites (26.3%) in which cortication was absent+the IAC had a lingual position+the IAC had a dumbbell shape. Significant relationships were found between IAN injury and the three IAC factors (cortication status, IAC position, and IAC shape; P=0.0001). In patients with the three IAC factors, logistic regression analysis indicated a strong association between these factors and IAN injury (P=0.007). An absence of cortication, a lingually positioned IAC, and a dumbbell-shaped IAC are considered to indicate a high risk of IAN injury according to the logistic regression analysis (P=0.007). These results suggest that a combined assessment of these three IAC factors could be useful for the improved prediction of IAN injury.

Determination of Proximity of Mandibular Third Molar to Mandibular Canal Using Panoramic Radiography and Cone-beam Computed Tomography

Objectives: Position of inferior alveolar canal with respect to an impacted third molar reveals certain radiographic signs, but three-dimensional relationship to the canal can be provided with cone-beam computed tomography (CBCT). The purpose of this study was to determine which radiographic signs on panoramic radiography indicate a true relationship on CBCT. Materials and Methods: Forty samples with signs or symptoms of impacted mandibular third molar and panoramic radiograph showing signs of a close relationship with the mandibular canal as described by Félez-Gutiérrez et al. were included in the study and subjected to CBCT. Radiographic signs on panoramic radiography were compared with the relationship on CBCT. Statistical analysis was done using Chi-square test. Results: Twenty-one samples (52.5%) showed darkening of the apex, which was the most frequent type of radiographic sign of a close relationship on panoramic radiography. Twenty-three samples (57.5%) revealed a true relationship on CBCT. Darkening of the apex and narrowing of the canal were the signs most frequently associated with a true relationship. On CBCT, coronal and axial sections better predicted a true relationship. Conclusion: This study showed that the presence of any of the radiographic signs cannot definitely predict a true relationship; however, the presence of a close sign on panoramic radiography is often associated with a true relationship to the canal.

Radiographic features of anatomic relationship between impacted third molar and inferior alveolar canal on coronal CBCT images: risk factors for nerve injury after tooth extraction.

IntroductionThe present study was aimed to identify the radiographic signs between impacted third molar root and inferior alveolar canal (IAC) on cone-beam CT (CBCT) images as risk factors and prognostic predictors associated with inferior alveolar nerve (IAN) damage following tooth removal.Material and methodsA retrospective clinical study was performed involving 136 patients with 257 impacted lower third molars from January 2013 to December 2014. The neurosensory function of the lower lip and chin was subjectively evaluated and assessed by neurosensory tests before and after surgery. The preoperative CBCT data were retrieved and analyzed to identify the radiographic signs associated with postoperative IAN injury.ResultsThe overall incidence of IAN injury in our patient cohort was 13.2%. Multiple radiographic features on coronal CBCT images including contact between IAC and root, IAC position relative to root, IAC shape and cortication status were found to be significantly associated with IAN damage (p < 0.05, χ2 test). Furthermore, buccolingual position, teardrop/dumbbell shape and cortication status of IAC were identified as independent prognostic predictors for IAN damage.ConclusionsOur findings indicate that radiographic signs including direct contact between IAC and root, buccal/lingual IAC position relative to root, teardrop/dumbbell shape and cortication absence of the IAC on presurgical CBCT images are associated with high risk of IAN injury and postoperative neurosensory disturbance.

Variations in the buccal-lingual alveolar bone thickness of impacted mandibular third molar: our classification and treatment perspectives.

Selecting either buccal or lingual approach for the mandibular third molar surgical extraction has been an intense debate for years. The aim of this observational retrospective study was to classify the molar based on the proximity to the external cortical bone, and analyze the position of inferior alveolar canal (IAC) of each type. Cone-beam CT (CBCT) data of 110 deeply impacted mandibular third molars from 91 consecutive patients were analyzed. A new classification based on the mean deduction value (MD) of buccal-lingual alveolar bone thickness was proposed: MD≥1 mm was classified as buccal position, 1 mm>MD>−1 mm was classified as central position, MD≤−1 mm was classified as lingual position. The study samples were distributed as: buccal position (1.8%) in 2 subjects, central position (10.9%) in 12 and lingual position (87.3%) in 96. Ninety-six molars (87.3%) contacted the IAC. The buccal and inferior IAC course were the most common types in impacted third molar, especially in lingually positioned ones. Our study suggested that amongst deeply impacted mandibular third molars, lingual position occupies the largest proportion, followed by the central, and then the buccal type.

Buccolingual course of the inferior alveolar canal in different mental foramen locations: A cone beam computed tomography study of an Iranian population.

Context:Better understanding of the anatomical location and course of the mandibular canal is necessary to avoid damaging inferior alveolar nerve.Aims:The aim of this study was to investigate the buccolingual course of the inferior alveolar canal (IAC) in different mental foramen locations, using cone beam computed tomography.Materials and Methods:Three hundred and twelve hemimandibular images were evaluated in this study. The location of mental foramen in relation to the apices of mandibular premolar and molar teeth were recorded. Nine measurements (in millimeters) were taken at the level of the IAC and posterior mandibular premolar and molar root apices. Relative distances of IAC to buccal and lingual mandibular cortex were calculated for different mental foramen types.Statistical Analysis Used:Data were analyzed by one-way analysis of variance and P < 0.05 was considered to be statistically significant.Results:The distribution of subjects according to the type of mental foramen includes: Type 1 = 50.3% (at the level of second premolar apex), Type 2 = 33% (between the apices of first and second premolars), and Type 3 = 16.7% (between the apices of second premolars and first molars). The buccolingual ratio of the IAC position was statistically significant in different mental foramen types (P = 0.00).Conclusion:The position of IAC was affected by the location of the mental foramen. The direction of IAC gradually changed from lingual to buccal and from posterior to anterior.

Cone-beam Computed Tomography for Analyzing Variations in Inferior Alveolar Canal Location in Adults in Relation to Age and Sex*

Previous studies have indicated that the relative position of the inferior alveolar canal and its mental and mandibular foramina in adults vary with age and show sexual dimorphism. Conceivably, these purported differences could be of forensic value for determining identity of human remains. This study was designed to determine the influence of age and sex on the relative position of inferior alveolar canal and its foramina in cone-beam computed tomography (CBCT) studies of adults. Existing CBCT studies of the maxillofacial region from dentate adult patients selected at random and ranging in age from 18 to 80 years (110 women and 55 men) were acquired, and the location of the inferior alveolar canal was assessed at three points: the mandibular foramen in axial view, the inferior alveolar canal in coronal view, and the mental foramen in coronal view. Measurements were also expressed for the mental foramen as the percentile position from the nearest superior bony crest to the inferior border; corresponding position of the mandibular foramen from the anterior to the posterior border of the mandibular ramus; and for the inferior alveolar canal at the level of first permanent molar from the nearest buccal bony surface to the lingual surface and from the superior alveolar crest to the inferior border. Regression analyses were performed on the variables with regard to the effects of age and sex. Most analyses resulted in no statistical significance (p<0.05). A few of the sex-specific traits demonstrated near-statistically significant effects; however, these characterizations generally resulted in a 1% or less change per age decade. Overall, the results demonstrated that the relative location of the inferior alveolar canal and associated foramina in adults remain fairly constant without regard to age and sex.

下顎管の異常走行に対して下顎枝逆Ｌ字型骨切り術変法を施行した下顎前突症の１例

We report on a 20-year-old Japanese man with mandibular prognathism and an abnormal position of inferior alveolar canal. This paper describes the surgical technique and modified intraoral inverted L ramus osteotomy used for mandibular setback. With this technique and examination by computed tomographic scanning, we could perform osteotomy as initially planned and avoid damage to the inferior alveolar nerve.