Inferior Alveolar Canal Research Articles

Novel strategy to predict high risk of inferior alveolar nerve injury during extraction of lower third molars based on assessment of computed tomographic images of multiple anatomical features

Preoperative assessment is essential to prevent inferior alveolar nerve (IAN) injury during surgical extraction of the lower third molar (LM3). Here, we aimed to establish an assessment system to predict IAN injury during surgical extraction of the LM3. We conducted a retrospective cohort study on 115 patients diagnosed as ‘high-risk’ based on our previous risk assessment method involving three anatomical features of the inferior alveolar canal using computed tomographic (CT) images. We evaluated the occurrence of neurosensory impairment in these high-risk patients, and its association with novel anatomic features based on CT images. Neurosensory impairments were observed in 19 patients (16.5%). The inferior alveolar canal major diameter (p < 0.0001) and lingual bone thickness (p = 0.0039) were significantly associated with the occurrence of neurosensory impairment during LM3 extraction. Receiver operating characteristic curves were used to determine cut-off values of these quantitative factors to specifically predict IAN injury. Preoperative risk assessment with quantitative factors based on anatomical features observed on CT images may facilitate more appropriate surgical planning for patients at a high risk of IAN injury.

Case Report: Incidental Finding of an Osteoblastoma of the Mandible

Osteoblastoma is a rare, benign primary neoplasm of the bone. The reported incidence rate of osteoblastomas is 1% of all whole body bone neoplasms. According to radiologic literature, this entity is most commonly reported in the vertebral skeleton. Of these reported lesions, 15% arise in the gnathic skeleton, 36% occur in the vertebrae with the remaining in the long bones of the extremities.1 Osteoblastomas have a predilection for presenting in the second or third decade. Seldom these lesions occur at a more advanced age.2 This entity appears to affect males more frequently than females, with a gender predilection of 2:1. Among reported cases arising in the gnathic skeleton, medullary bone is the primary location. The hypothesized pathogenesis involves benign neoplastic proliferation of osteoblasts.1Clinically, osteoblastomas often present as a painful swelling of the mandible. Imagining of this entity may be variable with a differential diagnosis spanning both benign and malignant neoplasms. Often radiographic features include ossification with an increase in radiodensity.2 Additional radiographic characteristics may include sclerotic bone with a radiolucent halo. This presentation is similar to an osteoid osteoma. Histopathology of this entity includes anastomosing trabeculae set within a loose fibrovascular stroma.2 Key histologic features include osteoblastic rimming with varying degrees of calcification. Definitive diagnosis may be challenging because of the similar histological features seen with primary malignant bone neoplasms, especially osteosarcoma.2Traditionally, the treatment involves surgical intervention, which ranges from aggressive curettage to en-bloc resection. Reported surgical intervention is dependent on size and anatomic location. Recurrence of the entity is reported to be uncommon with a 20% recurrent rate. Malignant transformation secondary to radiation therapy has been reported.1The authors present the clinical course and treatment of a 68-year-old male who presented to the St. Barnabas Hospital Oral and Maxillofacial Surgery Clinic for evaluation and treatment of a painful mobile carious tooth. On review of his panoramic radiograph, an incidental finding of a lesion was noted in the lower left mandible. The patient complained of no pain in the left mandible, and clinical examination showed a mild lateral expansion of the lower left mandible. The radiographic examination was consistent with a well-defined radiolucent/radiopaque lesion of the left mandible below the inferior alveolar nerve canal. The patient underwent an incisional biopsy in the operating room and was subsequently diagnosed with an osteoblastoma.

Detection of Mandibular Canal in Human Dry Mandibles with Cone Beam Computed Tomography using 270° and 360° Protocols under Continuous and Pulse Modes – A Comparative Study

Background: Cone beam computed tomography (CBCT) enables practitioner to accurately localize and mark the nerve canal. The rotation of the X-ray tube and the detector around the patient's head produces multiple projection images. A high number of projections is associated with increased radiation dose to the patient, higher spatial and contrast resolution. Shorter scan arc results in reduced scan time, reduced dose and smaller file sizes. The pulsed X-ray beam reduces the actual exposure time than the scanning time and the patient radiation exposure. Aim: (1) To assess and compare the diagnostic efficacy between pulse mode and continuous mode (2) To assess and compare the diagnostic efficacy between 270° and 360° CBCT rotational protocols Subjects and Methods: A total of 30 Intact Dentate or Partially dentate dry human mandibles consisting first, second, and third molars were subjected to a total of 4 CBCT scans: 270° rotation scans under continuous and pulse mode, 360° rotation scans under continuous and pulse mode using two CBCT units. Distance from the inferior cortical border of mandible (ICBM) to the roof of the inferior alveolar nerve canal (IANC) was measured at four locations: mental foramen, first, second and third molar. The results were then compared. Results: Comparison of the IANC length measurements for the two modes revealed no significant difference. Conclusion: Shorter scan arc and pulse mode can be adopted in patients finding it difficult to remain stable for prolonged periods of time, while maintaining appreciable clarity and quality of image. This could apply to geriatric patients, children, mentally challenged, in patients with trauma, neurological diseases, anxiety, claustrophobia, wherein the patient's movements might need re-scanning, which would lead to an extra radiation dose to the patient.

The neurosensory deficit of inferior alveolar nerve following bilateral sagittal split osteotomy: a prospective study.

Investigation in Saudi Arabia or the Arab Gulf States to assess the unfavorable impacts of the bilateral sagittal split osteotomy (BSSO) is non-existent, so questions have been raised about the success rate of this operation and the frequency of unwilling outcome. To address these worries, we directed a case series study to evaluate the hypoesthesia, a type of neurosensory deficit (NSD) of the inferior alveolar nerve (IAN) after BSSO, and if the hypoesthesia outcome will improve if the surgeries performed by a single surgeon. This was a prospective case series study for the patient who underwent BSSO in a medical complex that is considered one of the largest in Saudi Arabia (Riyadh). The inclusion criteria include patient aged 18-40years, any gender, and American Society of Anesthesiologists (ASA) class I. They will undergo BSSO for either mandibular, retrognathia, prognathic, or to follow the maxilla. The outcome will be measured after evaluating the neurosensory by four means light touch (LT), pinprick (PP), 2-point discrimination (2PD), and thermal sensations (TT) in four repeated measurements (preoperatively, 1week, 1month, 3months postoperatively) as the primary outcome. Other confounding factors were the secondary outcome (age, gender, visualization of the I.A.N, the type of mandibular movement, split favorability, mandibular canal location, and patient reports about paresthesia or dysesthesia on any given side); these data analyses were carried out using SPSS ver. 25 data processing software. The nerve was visible in 93% of cases. During the operation, none of the nerves was transected. Hypoesthesia on the first follow-up was 94% of cases for LT, 92% for PP, 82% for TT, and 100% for the 2PD. On the last follow-up, the patients still had hypoesthesia for the LT 51%, PP 35%, TT41%, and 2PD 55%; age and sex did not significantly affect hypoesthesia outcomes. Nerve visibility and inferior alveolar nerve canal (IAC) distance did not influence the results. The level of confidence for all tests was set at p < 0.05. The 2PD sensation was the most affected sense on the last visit, and the right side of the chin and lower lip was affected most both on early and long-term follow-up due to several reasons. A 3-month period was enough as a recovery time to restore 100% of neurological sensation for 45% of the sample, which is similar to several studies in the literature. A single surgeon did not show superior result compared to two surgeons' literature papers. Advancement movement was associated with a high percentage of hypoesthesia.

Evaluation of the Course of Inferior Alveolar Canal and its Relation to Anatomical Factors on Digital Panoramic Radiographs.

Statement of the Problem: The inferior alveolar canal (IAC) is a bony canal that starts from mandibular foramen at the inner surface of the mandibular ramus and extends along the ramus and body of mandibular bone in forward and downward directions to the mental foramen. Inside the mandibular canal, there are lower alveolar artery and a nerve with the same name. Understanding the anatomical details of the lower alveolar canal, including position, pathway and morphology to prevent complications in surgical procedures in the lower jaw such as mandibular impacted molar surgeries, mandibular nerve block injection, or even root canal treatment of mandibular teeth is important. Purpose: The purpose of this study was to investigate the course and direction of IAC in mandibular bone and its relation to anatomical factors such as gonial angle and location of entrance of IAC in the mandibular ramus.Materials and Method: This cross-sectional study evaluated a sample of 280 digital panoramic images. All samples were Iranian. The pattern and direction of the IACs were recorded according to age and gender and the relation of these patterns to the gonial angle of mandible and the entry point of the IAC in mandibular ramus were evaluated.Results: The results showed that the course of canal, the entrance point of the canal and the gonial angle were the same between different age groups and between two genders. There was no significant relation between the course of canal and the two anatomical variables mentioned (p> 0.05).Conclusion: Considering the increasing frequency of implant surgeries and presence of different courses of the mandibular canal and concerning the important complications such as paresthesia caused by damage to the mandibular nerve, panoramic radiography is necessary before any surgery in this area to avoid unwanted injuries to the neurovascular system if other advanced modalities are not available.

Radiographic Features of the Maxillofacial Anomalies in Beta-Thalassemia Major: With New View.

BACKGROUNDBeta- thalassemia major causes the basic skeletal changes due to ineffective erythropoiesis in suffering patients. The aim of the study was to determine the frequency of maxillo-facial anomalies and the hemoglobin and ferritin levels in patients with beta-thalassemia major compared to the healthy control group. METHODSThe present study was performed on 72 beta- thalassemia major patients and 70 healthy control group in Ahvaz, Southwest Iran, from Jan 2014 to Mar 2015. Panoramic radiographs were taken using a standard procedure. The frequency of abnormalities including enlargement of bone marrow spaces, small maxillary sinuses, thickness of inferior mandibular cortex, prominent antegonial notch, absence of inferior alveolar canal and thin lamina dura, were determined by two Oral and Maxillofacial Radiologist. We also paid to identification of the relationship between abnormalities frequency and hemoglobin and ferritin levels during previous 6 months in thalassemia patients. RESULTSThe mean age of case and control groups was 18.6±7.25 and 17 ± 6. 55 yr, respectively. The frequency of abnormalities in the case and control groups was as follows, enlargement of bone marrow spaces [69 (95.8%) vs 3 (4.3%)], small maxillary sinuses [45 (62.5%) vs 1(1.4%)], reduced thickness of inferior mandibular cortex [21(29.2%) vs 6 (8.6%)], prominent antegonial notch [10 (13.9%) vs 2 (2.9%)], absence of inferior alveolar canal [68(94.4%) vs 41(58.6%)] and thin lamina dura [40 (55.6%) vs 5 (7.1%)]. CONCLUSIONThe all above mentioned abnormalities in patients with beta-thalassemia major was higher than the control group. Moreover, the frequency of maxillo-facial abnormalities decreased by increasing hemoglobin and decreasing ferritin.

Does the extent of cortical perforation of the inferior alveolar nerve canal by the roots of third molar teeth seen on cone beam computed tomography predict postoperative paraesthesia? - A prospective clinical study

The aim of this study was to assess the extent of cortical perforation in millimetres (mm) in inferior alveolar nerve (IAN) canal on coronal section of cone beam computed tomography (CBCT) to predict IAN injury in high risk patients. We also analysed relation of position of canal and number of roots with likelihood injury to IAN. We conducted a prospective clinical study of 100 high risk patients in which 78 patients had cortical perforation which was verified by CBCT. 13/78 of 3rd molars were associated with IAN injury at 1 month post extraction. Out of those, only 3 had a permanent decrease in sensation and remaining 10 had temporary paraesthesia. Owing to the large number of patients with cortical defects, we further sub-categorised them into five groups based on cortical perforation: Type 1 – No involvement, Type 2–1 - 3 mm, Type 3–4 - 6 mm, Type 4–7 - 9 mm, Type 5 – more than 9 mm. All of the 8 patients who had more than 6 mm (Type 4 and Type 5) had some sensory disturbance whereas no IAN injury was found in patients of type 1 and type 2. There were 5/23 who had nerve injury in type 3. The association between cortical perforation and IAN injury was statistically significant (p - <0.0001). Extent of cortical perforation can be a reliable predictor to predicate IAN injury prior to lower third molar extraction. In addition, the presence of abnormal sensation was significantly associated with different canal positions (p - <0.0001) whereas association of number of roots and IAN injury was statistically insignificant (p - 0.3112).

DANG (Depth-Adjusted Nerve Guide) – A Technical Note

Traditional surgical approaches to the inferior alveolar nerve (IAN) pose a technical challenge and risk iatrogenic damage to healthy, uninvolved nerve tissue. The use of computer-assisted virtual surgical planning and fabrication of surgical guides has shown efficacy in various craniomaxillofacial surgical procedures, and may provide greater precision in accessing the inferior alveolar canal and allow for a more conservative approach. The addition of a depth control feature to a tooth-borne and bone-borne surgical guide, with the use of a standard contra-angle handpiece, provides safe and efficient access for IAN repair. This report describes this novel technique involving a guided transoral approach to the IAN for excision of a neurofibroma of the inferior alveolar nerve, with immediate peripheral nerve allograft IAN reconstruction.

MORPHOLOGIC VARIATIONS OF THE INFERIOR ALVEOLAR NERVE CANAL THROUGH THREE-DIMENSIONAL COMPUTED TOMOGRAPHY

<h3>BACKGROUND</h3> The Inferior alveolar nerve is the main nerve supply to the mandible, and its location and position related to the surrounding structures are critical during surgical procedures. The introduction of cone beam computed tomography (CBCT) with low radiation dose and high resolution has improved the anatomic visualization of the canal. <h3>OBJECTIVE(S)</h3> The aim of this study was to investigate the morphologic variations of the inferior alveolar canal in 10 CBCT data sets through 3D computed tomography assessment. <h3>STUDY DESIGN</h3> Ten CBCT scans were randomly selected from the archived cases database of the Oral and Maxillofacial Radiology Department at The University of Iowa. Institutional review board approval was obtained. The inclusion criteria consisted of visualization of the complete inferior alveolar canal and the third molar bilaterally, no pathosis associated with the mandible, and no motion or metallic artifacts that might affect the image quality. The distance between 10 fixed anatomic landmarks (lingula, sigmoid notch, angle of mandible, mental foramen, buccal cortex of the mandible, symphysis, mandibular foramen, posterior surface of the most distal molar, condyle, and inferior border of the mandible) were measured and the length and angulation of the inferior alveolar canal were measured. All measurements were performed by an OMR twice with at least 1 week between measurements. <h3>RESULTS</h3> There were variations in the inferior alveolar canal length and angulation between the right and left sides of the mandible. The right mental foramen was located slightly posteriorly from the symphysis compared with the left side. The mandibular canal was around 30 mm away from the distal aspect of the presented molars on the both sides. <h3>DISCUSSION/CONCLUSIONS</h3> Three-dimensional imaging obtained from CBCT scans provides comprehensive knowledge of the anatomic location and the course of the canal within the mandible.

A RADIOLUCENCY IN THE RAMUS OF THE MANDIBLE: WHAT IS THIS?

<h3>BACKGROUND</h3> A small radiolucent lesion is challenging for radiologists to make an accurate diagnosis, especially if it is asymptomatic and an incidental finding. It could go under the umbrella of the odontogenic or nonodontogenic cyst or tumor. We present a well-defined, corticated, expansile, unilocular radiolucency in the ramus of the mandible at the mandibular foramen level that proved to be a simple bone cyst. <h3>CASE REPORT</h3> An 18-year-old female patient presented to our clinic following referral by her orthodontist for an incidental finding of a radiolucency in the left mandibular ramus. A panoramic radiograph and cone beam computed tomography (CBCT) were taken. No changes in size were noted on panoramic radiographs 3 months apart. On CBCT, the lesion was well-defined, corticated, ellipsoidal, mildly expansile, unilocular, and uniformly radiolucent. It was located in the left ramus, below the sigmoid notch, buccal and superior to the inferior alveolar canal and displacing the canal and the mandibular foramen with dissipation of the canal wall. The medial and lateral cortices of the ramus were thinned and expanded. The findings were consistent with less aggressive, slowly growing lesions including odontogenic keratocyst, ameloblastoma, and neurovascular lesions. On surgical exploration, the lesion was devoid of any epithelial lining and was completely empty. <h3>DISCUSSION/CONCLUSIONS</h3> Simple bone cysts are nonneoplastic "pseudocysts" that are found in the mandible. Only 2% are found in the maxilla and a very small number have been reported in the condyle toward the ramus, and no radiographic images located solitary in the ramus. This is the first report showing a simple bone cyst in the middle of the ramus of the mandible.

Prevalence of bifid and trifid mandibular canals with unusual patterns of nerve branching using cone beam computed tomography.

Lack of knowledge concerning the inferior alveolar canal anatomical variations had proven to increase the incidence of surgical complications, so the study aimed to assess the configuration and prevalence of bifid and trifid mandibular canals using cone beam CT in Egyptian subpopulation. Cone beam CT scans of 278 patients (530 hemi-mandibles) were included in the study, in which bifid and trifid mandibular canals or any other branching patterns were recorded and evaluated. Bifid canals were categorized following Naitoh classification, and the diameter of the main mandibular and accessory canals was measured. Bifid canals were detected in 181 canals (34%) while trifid canals in 46 canals (8.7%). Upon classifying the bifid canals, 78 canals showed forward type, 40 retromolar type, 33 dental type, and 7 canals showed buccolingual type. Two special bifid canals subtypes were reported in 23 canals and nine distinct patterns of trifid canals were reported in our study. In addition, unusual patterns of canal branching were reported in 5 cases. The mean diameter of the accessory canals was 1.18 ± .54mm and the main canal was 3.98 ± 1.31mm. This study reported a high prevalence (54%) of canal branching, which reinforces the importance of cone beam CT in pre-surgical planning.

Mandibular Third Molar Surgery: Intraosseous Localization of the Inferior Alveolar Nerve Using 3D Double-Echo Steady-State MRI (3D-DESS).

The aim of this study was to evaluate the inferior alveolar nerve’s (IAN) intraosseous position within the inferior alveolar canal (IAC) using a 3D double-echo steady-state MRI sequence (3D-DESS). The IAN position was prospectively evaluated in 19 patients undergoing mandibular third molar (MTM) surgery. In the coronal reference layer, the IAC was divided into six segments. These segments were checked for the presence of hyperintense tubular MRI signals representing the IAN’s nervous tissue and assessed as visible/non-visible. Furthermore, the IAN in MRI and the IAC in MRI and CBCT were segmented at the third and second molar, determining the maximum diameter in all planes and a conversion factor between the imaging modalities. Regardless of the positional relationship at the third and second molar, the IAN showed the highest localization probability in the central segments (segment 2: 97.4% vs. 94.4%, segment 5: 100% vs. 91.6%). The conversion factors from IAC in CBCT and MRI to IAN in MRI, respectively, were the following: axial (2.04 ± 1.95, 2.37 ± 2.41), sagittal (1.86 ± 0.96, 1.76 ± 0.74), and coronal (1.26 ± 0.39, 1.37 ± 0.25). This radiation-free imaging modality, demonstrating good feasibility of accurate visualization of nervous tissue within the nerve canal’s osseous boundaries, may benefit preoperative assessment before complex surgical procedures are performed near the IAC.

Predictive scoring model for inferior alveolar nerve injury after lower third molar removal based on features of cone-beam computed tomography image

IntroductionThis study aimed to construct a predictive scoring system for inferior alveolar nerve injury (IANI) following lower third molar (LM3) surgery based on cone-beam computed tomography (CBCT) images. Material and MethodsOf the 1573 patients who underwent LM3 removal following the CBCT, 39 with IANI and 457 randomly selected patients without IANI were enrolled. We collected information regarding the demographic characteristics of the patients, surgical situations, and inferior alveolar canal (IAC)-related CBCT factors. The association with IANI-risk was evaluated with a backward stepwise logistic regression model as per the Akaike information criterion. Scoring models’ abilities of discrimination (area under the curve) and calibration (Hosmer–Lemeshow test and calibration plots) were assessed, followed by evaluation of the clinical usefulness using decision curve analysis. ResultsAs per the multivariate analysis, the coronal positioned IAC on the enlarged root (odds ratio [OR], 3.78; P = 0.001), the length of perforated IAC (>3.4 mm) (OR, 3.05; P = 0.012), lingual/inter-radicular position of the IAC (OR, 3.96; P = 0.001), multiple roots closed to the perforated IAC (OR, 2.78; P = 0.025), and age >30 y (OR, 2.31; P = 0.076) were identified in the extended scoring model ranging from 0 to 12. This model was compared with our previously constructed baseline model that involved the latter three variables mentioned above, resulting in superior performance than that of the baseline model. ConclusionThe extended model would be a useful tool for reliable determination of the preoperative probability of IANI.

Cone Beam Computer Tomography and Histological Evaluation of Dental Follicle of Impacted Lower Third Molar Germs in Teens: A Histo-Radiographic Correlation Study in a Case Series

The dental follicle (DF) is the tissue that surrounds the crown of the developing tooth. In X-ray, images it appears as a radiolucent area. The removal of an impacted mandibular third molar is a common procedure in oral surgery. The radiographic evidence of pathology, commonly defined as a pericoronal radiolucency measuring at least mm 2.5 mm in any dimension, is accepted for the extraction of impacted mandibular third molars. Mesioangular impactions are usually more closely placed to the inferior alveolar canal, and the use of cone beam computer tomography (CBCT) before the removal of impacted mandibular third molars has been reported to be appropriate in these cases. The aim of this study was to evaluate the microscopic features of radiographically normal DFs associated with mesioangular impacted mandibular third molars examined through CBCT. Thirteen mesioangular impacted third molars from ten patients (5 males and 5 females, mean age ± SD: 15.1 ± 1.66) with a maximum width of the DF &lt;2.5 mm, as digitally established by CBCT, were included in this study. All the DFs associated with the removed third molars were examined histologically through the analysis of different variables. The mean (±SD) and range of the maximum width of the DFs were 1.35 (±0.47) mm and 0.71–2.21 mm, respectively. Nine (69.23%) DFs showed odontogenic remnants, five (38.46%) showed focal squamous metaplasia and eight (61.53%) mild mesenchymal myxoid degeneration. The maximum width of the DF failed to show any significant correlation with all the histological variables considered in this study. Aware of the limited number of patients included in this study, the histo-radiographic correlation in our case series confirm data in the literature, according to which normal pericoronal imaging may be associated with DF tissue changes/variations that in turn are potentially associated with the development of pathologies including odontogenic cysts and tumors. Whether these changes/variations are enough to make prophylactic germectomy of impacted third molars the standard by themselves remains to be established. However, they require accurate correlations with the radiographic data for the appropriate histologic assessment of a DF.

Neurosensory Deficits of Inferior Alveolar Nerve Following Impacted Mandibular Third Molar Extraction: Comparison of One-Stage Complete Extraction with Two-Stage Partial Coronectomy Surgical Technique.

Inferior alveolar nerve neurosensory deficit is a worrisome complication of surgical extraction of impacted mandibular third molars. A novel approach using two-stage partial coronectomy has been proposed as an alternative surgical procedure to reduce this complication. This study compared neurosensory deficits of inferior alveolar nerve following impacted mandibular third molar extraction using one-stage complete extraction with the two-stage partial coronectomy technique. Subjects with mesioangular or horizontal impacted mandibular third molar with an intimate relationship with inferior dental canal who met the inclusion criteria were recruited for the study. Subjects were divided into one-stage and two-stage partial coronectomy techniques. The subjects were evaluated for the presence of inferior alveolar neurosensory deficit, and the relationships of neurosensory nerve deficit with sex, age and type of impaction. Neurosensory deficit was observed in 5 subjects (7.8%), with all cases seen in the one-stage group. This difference was statistically significant (p = 0.03). The relationship between the incidence of neurosensory deficit and age, sex, type of impaction, surgical difficulty, operating time and root morphology was not statistically significant (p > 0.05). Findings from this study suggest partial coronectomy compared to one-stage complete extraction reduces the incidence of Inferior alveolar nerve neurosensory deficit.

Is it possible to filter third molar cases with panoramic radiography in which roots surround the inferior alveolar canal? A comparison using cone-beam computed tomography

Inferior alveolar nerve (IAN) entrapment in third molar (M3) roots bears a significant risk for nerve injury. The aim of this study was to identify specific panoramic radiographic (PR) signs that can reliably identify IAN entrapment (IANE) root conformations. In a retrospective case-control study, 10 IANE and 218 non-IANE third molar risk cases were examined by PR and CBCT. The collected data included “classic” specific high-risk panoramic signs, number of M3 roots, extent of inferior alveolar canal (IAC)−root tip overlap, rotated position of M3 and impaction pattern. After bivariate analysis, sensitivity, specificity, positive and negative predictive values, positive likelihood ratios (LR+) and accuracy (AC) were calculated for the most significant predictive variables. Interruption of both cortical lines (LR+: 43.6; AC: 96.0%) and upward diversion of the IAC (LR+: 36.3; AC: 96.5%) were the most accurate single signs indicating IANE. Upward diversion combined with root darkening and interruption of the IAC (AC: 97.4%) and the combination of darkening with interruption and with a rotated M3 (LR+:130.8; AC: 97.8%) were the most accurate combinations predicting IANE. IANE may be correctly filtered with PR when focusing on the signs of upward diversion, darkening, interruption and rotated M3 position, especially in cases involving their multiple (≥3) presence. CBCT evaluation is highly recommended in these cases before partial and total tooth removals.

Penetration of inferior alveolar nerve canal increased by bicortical fixation after bilateral sagittal split osteotomy in mandibular prognathism

The purpose of this three-dimensional cone beam computed tomography (CBCT) study was to identify the difference between monocortical fixation (MCF) and bicortical fixation (BCF) in mandibular canal penetration after bilateral sagittal split osteotomy (BSSO) to correct mandibular prognathism, where interosseous fixation was done by BCF or MCF. CBCT was performed 1 week postoperatively and Dolphin 3D software was used to assess direct penetration of the mandibular canal by either type of screw. The primary outcome variable was the presence or absence of mandibular canal penetration and was categorized as a binary coded variable. The BCF and MCF groups were compared by χ2 test, and the odds ratio for canal penetration was estimated. Multiple logistic regression was performed to identify factors related to canal penetration. A total of 118 patients were included. The MCF group had only 6% canal penetrations (3/50 patients) and the BCF group had 58.8% canal penetrations (40/68 patients). The regression model showed that BCF was the only factor causing mandibular canal penetration, with an adjusted odds ratio of 52.5. Awareness of the increased risk of canal penetration with BCF and potential nerve injury might influence case selection.

Mandibular canal versus inferior alveolar canal: A Delphi study.

The general principles of anatomical terminology indicate that the "mandibular canal" should be named the "inferior alveolar canal" as it accommodates the inferior alveolar neurovascular bundles. Therefore, we performed a Delphi study to evaluate the current understanding and use of the terminology in different geographical regions and areas of expertise and to determine the appropriate terminology for this bony canal. A Delphi panel was formed and questions sent and answered via email about: field of expertise (anatomy, oral surgery/oral and maxillofacial (OMF) surgery, oral radiology/OMF radiology, plastic surgery, ENT surgery, or dentistry with the exception of oral/OMF surgery and oral/OMF radiology), years of experience in the field of expertise, country currently working in, "what is the name of the bony canal that contains the inferior alveolar neurovascular bundle," and "what should the structure above be called, in general?" A total of 52 participants responded to the questionnaire. Half or more of the experts in anatomy, oral/OMF surgery, and ENT/plastic surgery considered "mandibular canal" to be the most appropriate name for this bony canal. In contrast, more than half of all experts in oral/OMF radiology and dentistry, that is, most fields of dentistry, considered "either mandibular canal or inferior alveolar canal" to be the appropriate name. The results of the Delphi study and general principles suggest that an alternative term for the "mandibular canal" should be "inferior alveolar canal."

Ecomorphology and Morphological Diversity of Trigeminal Nerve‐mediated Somatosensation in Sauropsids

Understanding the morphology of tissues mediating sensory perception is essential to understanding organismal behavior. Cranial somatosensation in living reptiles requires dense innervation of the mandibles by the trigeminal nerve to receive and discriminate between the range of stimuli experienced during sensory behaviors including prey acquisition, feeding, and navigation. Morphological diversity of both the soft tissue and osteological trigeminal system is unexplored across reptiles, and thus relationships between form and function are unknown. Additionally, inferences of facial sensation in extinct vertebrates are often loosely based on qualitative descriptions of bony features of the trigeminal system. Using CT and hand-measured data, we explore morphometric relationships between and among soft tissue (i.e., trigeminal ganglion, inferior alveolar nerve, terminal sensors) and osteological (i.e., trigeminal fossa, inferior alveolar canal, rostral foramina) trigeminal structures of extant representatives from each major clade of sauropsids with diverse sensory strategies. Exploring the trigeminal mandibular division, we find relatively larger trigeminal structures in crocodylians than most birds and lepidosaurs, implying differing levels of sensory ability among taxa. We show canal branching patterns reflect sensory ecologies as well, with only tactile-foraging taxa exhibiting dendritic canals. Finally, we identify phylogenetic and ecologic factors influencing osteological correlate utility and predict sensory ecologies of extinct reptiles, supporting a trend of increasing trigeminal sensation along the crocodylian line. Overall, these findings describe some of the diversity of the reptilian trigeminal system and establish evolutionary patterns of reptile trigeminal ecomorphology.

ASSESSMENT OF MANDIBULAR 3RD MOLAR APICES TO THE INFERIOR DENTAL CANAL USING CONVENTIONAL RADIOGRAPHY AND CBCT

Conventional radiographs provide only a 2 dimensional view of complicated three dimensional structures. The proximity, angulations, location of impacted teeth, related to the IAN can be adequately determined using conventional 2-D periodical and panoramic radiographs. Computed tomography necessitates the administration of a high dose radiation, especially when the slice width is shortened to increased cost are the negative aspects of computed tomography compared with conventional imaging.&#x0D; Cone beam computed tomographies are becoming more readily available for use in maxilla facial applications. CBCT provides better image quality of teeth and their surrounding structures, compared with conventional CT and offers high spatial resolution. CBCT seems to be more accurate data about inferior alveolar canal. Hence the present study was undertaken to assess and select roots of third molar with close proximity to inferior dental canal in panoramic radiograph having radiographic signs of darkening of root, disruption of canal cortex and canal deviation and to evaluate the same roots with CBCT using trans axial and coronal sections which is angulated parallel to long axis to tooth, axial and coronal sections for proximity of inferior dental canal with the apices of third molar root.&#x0D; Keywords: CBCT, IAN