Inferior Alveolar Nerve Exposure Research Articles

Evaluation of Intraoperative Inferior Alveolar Nerve Exposure During and Postoperative Neurosensory Disturbances after Bilateral Sagittal Split Osteotomy: A Prospective Cross-sectional Study in Iran

Introduction: Inferior Alveolar Nerve (IAN) exposure and neurosensory disturbances (NSDs) following bilateral sagittal split osteotomy (BSSO) of the mandible are paramount. We aimed to assess intraoperative IAN exposure during and NSDs after BSOO surgery using different clinical assessment methods in a prospective study in a local setting.
 Materials and methods: The present study was a prospective cross-sectional study. We monitored the nerve exposure status during the BSSO. Our time points were: before surgery, one day after, one month later, three months after and six months after the BSSO surgery. We performed two-point discrimination test, static light touch test and pinprick test on both mental regions of the cases.
 Results: We included seven women and eight men. The average age of the participants was 25.13 ± 3.27 years. The results of the two-point discrimination test showed the following: the day after the BSSO compared to before the surgery, the sensation is significantly impaired in both mental regions. In addition, it is noted that during our study, the two-point discrimination test results showed a gradient healing, though not reaching the point before the surgery (P>0.05). The results of the Pinprick test also showed a gradual resolution of the NSDs; however, a significant sensation difference remained between six months after the BSSO and before the surgery.
 Conclusion: The BSSO surgery significantly impairs the IAN sensation, causing intraoperative IAN exposure and postoperative NSDs for the patients. A gradient resolution of the NSDs was observed in all the cases, though; the sensation of the mental region did not reach the pre-surgical levels.

A randomized controlled trial comparing conventional and piezosurgery methods in mandibular bone block harvesting from the retromolar region

BackgroundAlthough piezosurgery is now commonly used for various applications in maxillofacial surgery, its advantages over conventional rotary instruments in terms of postoperative edema, ecchymosis, postoperative morbidity, and prolonged osteotomy time have been questioned.Materials and methodsThis study aimed to compare the efficiency, postoperative morbidity, and complication rates of piezosurgery and conventional methods in harvesting autogenous ramus grafts. In this randomized controlled trial, 21 patients (32 sides) underwent autogenous graft harvesting from the ramus area, with 16 sites treated using piezosurgery and 16 using the conventional method. The primary outcomes measured were osteotomy time, total operation time, and postoperative morbidity. Complication rates were also evaluated.ResultsThe final analysis encompassed 19 patients, accounting for a total of 30 donor sites, following the exclusion of two patients who were unable to attend the scheduled follow-up visits. A total of 19 patients (30 donor sites) were included in the final analysis. No statistically significant difference was found in the mean osteotomy time between the piezosurgery group (mean: 10.35, SD: 2.74 min) and the conventional group (mean: 8.74, SD: 2.74 min) (95% CI: -3.67 to 0.442, p = 0.119). The total operation time, postoperative pain, and swelling were not significantly different between the two groups (p > 0.05). The complication rates, including wound dehiscence and inferior alveolar nerve exposure, were similar in both groups.ConclusionsPiezosurgery can be safely used for harvesting autogenous ramus grafts and does not increase osteotomy or total operation time compared to the conventional method. The postoperative morbidity and complication rates were also similar, indicating that both techniques can be effectively employed in clinical practice.Clinical Trial RegistrationThe protocol was registered on clinicaltrials.gov (ID: NCT05548049, First registration date: 21/09/2022).

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.

Relationship of the Degree of Nerve Exposure and Surgical Manipulation and Short-Term Neurosensory Disturbance Following Sagittal Split Ramus Osteotomy: A Prospective Study

BackgroundNeurosensory disturbance (NSD) is a common complication after sagittal split ramus osteotomy (SSRO) due to inferior alveolar nerve (IAN) injury. The impact of intraoperative nerve manipulation on NSD remains debated. PurposeThe purpose of this study was to evaluate the influence of IAN exposure and manipulation during SSRO on functional sensory recovery (FSR). Study designThis was a single-center, prospective cohort study of 40 patients undergoing SSRO at Mahidol University, from December 2020 to December 2021. The inclusion criteria were patients aged 20-34, ASA Class I-II. The exclusion criteria were patients with systemic bone disease, history of head and neck or neurological pathology, previous SSRO or incomplete data collection. Predictor variableDegree of intraoperative nerve manipulation was divided by the attending surgeon as follows; 1) Nerve fully encased in distal segment and not visible (NS); 2) Nerve encased in distal segment but partially visible (DS) ; 3) Nerve partially encased in proximal segment and fully dissected free (PS). Outcome variablesThe area of interest was divided into the lip and chin. The primary outcome was time to FSR. The secondary outcome was subjective patient report, using a visual analogue scale, compared to FSR. CovariatesThe covariates were sex, age, skeletal diagnosis, degree of movement, and concomitant genioplasty/subapical procedure. AnalysesKaplan-Meier survival analysis, Cox proportional hazards regression, and Mcnemar test were utilized. P-value < 0.05 was significant. ResultsIn the lip, the median times to FSR were; NS, 2 days; DS, 45 days; PS, 102 days. (Interquartile range: 77,127, 114, respectively) In the chin, the median times to FSR were; NS, 23 days; DS, 92 days; PS, 87 days. (Interquartile range: 77, 161, 101, respectively.) Nerve manipulation significantly affected FSR in the lip and chin (p= 0.001, <0.001, respectively. Cox hazard ratios for DS and PS were lower compared to NS. Patients consistently reported more NSD compared to FSR as per Mcnemar test. Conclusion and RelevanceAfter SSRO, FSR in the lip is prolonged when the IAN is partially encased in the proximal segment and released. This raises the question of the efficacy of surgically releasing a partially encased IAN.

Analyzing the Causes and Frequency of Early Dental Implant Failure among Iranians: An Epidemiological Study.

The rate of early dental implant failure (DIF) has increased in recent years, though the risk factors associated with this primary failure remain unclear. This study aimed to determine the rate of early implant failure and identify contributing factors. It was conducted from March 2018 to 2020 in Mashhad, Iran. This observational study examined the records of 983 implants from the Implant Department of Mashhad Dental School. Variables considered included age, gender, systemic diseases, smoking habits, implant type and size, and surgery-related factors. Data were analyzed using Chi-square, Mann-Whitney U, and Fisher exact tests in SPSS V22, with a p-value of 0.05 or less considered statistically significant. Of the 983 implants, 42 (4.3%) experienced early failure. The study population consisted of 555 (56.5%) females and 428 (43.5%) males, with an average age of 49.34 ± 13.67 years. A significant correlation was found between surgical complications (e.g., fracture of implant fixtures and inferior alveolar nerve exposure) and implant loading time (Yes or No) with early DIF (p=0.05 and p < 0.01, respectively). However, no significant correlation was observed between early failure and factors such as age, gender, smoking habits, systemic diseases, implant dimensions, or manufacturer. Surgical complications and loading time may be the most critical factors contributing to early implant failure. Therefore, we suggest dentists pay attention to the mentioned factors in the surgical protocols and their relationship. Further prospective studies on risk factors that could affect early implant failure are needed.

Radiographic factors associated with inferior alveolar nerve exposure during mandibular third molar surgery and their influence on neurosensory deficit: A prospective study.

The inferior alveolar nerve (IAN) can occasionally be observed in the extraction socket of the mandibular third molar (M3M) intraoperatively. Exposure of inferior alveolar neurovascular bundle during surgery primarily depends upon the absence of bony cortex between the canal and root of impacted third molar or either by existence of a very thin cortical lining between two which gets broken during luxation of tooth. Accurate anatomical relationship of inferior alveolar canal with root apex of impacted (M3M) and the location of canal can be determined by Cone beam computed tomography (CBCT). Initially 200 patients evaluated by Orthopantomogram (OPG) for anatomical relationship of IAN with impacted (M3M) and various radiographic risk factors for nerve injury. Among these 200, 75 showed the presence of two or more than two risk factors for IAN injury which then were further evaluated by using CBCT for presence or absence of cortex of canal and location of canal on buccal, lingual, inferior, and interradicular position. Cortex of canal is an important barrier between the root apex and inferior alveolar neurovascular bundle. Interruption of cortex on CBCT, the interradicularly and lingually positioned neurovascular bundle become a strong affirmation for intra operative nerve exposure during (M3M) surgery. Although its exposure is affected by various factors such as bone density, sex and age of patient, surgeon's expertise, operative tissue damage, post operative edema, surgical procedure, but neurosensory deficit do not occur simply after the exposure of neurovascular bundle.

Influence of Inferior Alveolar Nerve Exposure During Sagittal Split Osteotomy on the Rate and Timing of Baseline Sensory Recovery

Neurosensory disturbance is the most common consequence of sagittal split osteotomy (SSO). The purpose of this study is to quantitatively assess neurosensory deficiency and recovery to the preoperative status when the inferior alveolar nerve (IAN) was exposed versus unexposed during SSO. This is a single-center, prospective, cohort study of all patients undergoing bilateral SSO between August 2018 and July 2019. Patients were included in the study sample if they underwent bilateral SSO with an intact intraoperative IAN and were received follow-up assessment for at least a year. The predictor variable was the intraoperative IAN status (exposed vs unexposed). The outcomes of interest were the rate and timing of recovery to the preoperative status. The covariates were age, sex, and the magnitude and direction of surgical movements. Neurosensory function was quantitatively evaluated using the Semmes-Weinstein monofilament test at follow-up intervals of 1, 3, 6, and 12months. Descriptive statistics, bivariate statistics, Cox proportional hazards regression, and Kaplan-Meier analyses were performed. P value <.05 was considered statistically significant. Of 90 patients, 86 patients who underwent 172 SSOs were included in this study. The mean age was 22.95±3.34years (range, 17 to 30), 65 were women, and the range of surgical movements was 3 to 8.3mm of advancement and 2 to 12mm of setback. Eighty-five nerves (49.4%) were allocated to the unexposed group, and 87 (50.6%) to the exposed group, with statistically significant differences in the rate and timing of recovery (hazard ratio= 2.368; 95% confidence interval, 1.662 to 3.376; P<.001). Among those with recovered nerves, the median time to recovery was 90days in the unexposed group and 364days in the exposed group (P<.0001). IAN exposure during SSO is associated with an increased risk of neurosensory deficiency and an increased time of sensory recovery to the baseline threshold in patients aged 17 to 30years. When the IAN remained fully enclosed in the canal of the distal segment, only 11% of patients had a measurable sensory deficit 1year after surgery. In those patients with any degree of IAN exposure, 36% had a residual sensory deficit 1year after surgery.

Risk factors of neurosensory disturbances at 1 year postoperatively after bilateral sagittal split osteotomy

To investigate morphologic and surgical risk factors causing neurosensory disturbances (NSDs) after bilateral sagittal split osteotomy (BSSO). A total of 237 patients (with 474 sides) who underwent BSSO were followed up for 1 year. Parameters examined included age, sex, asymmetry, mandibular movement direction, mandible cutting devices, split type, intraoperative exposure of the inferior alveolar nerve (IAN), contact between the IAN and screw, distance between mandibular canal and inner surface of the cortical bone (distance A), distance from lateral osteotomy to mental foramen (distance B), and NSD at 1 year postoperatively. NSD was observed in 62 (13.1%) sides of 51 patients. Exploratory factor analysis determined 4 factors (factor 1: distance A; factor 2: direction of mandibular movement; factor 3: distance B and cutting devices; factor 4: IAN exposure). Logistic regression analysis was performed using the above factors and age, sex, and asymmetry, making a total of 7 variables. Age, factor 1, and factor 4 were significant predictors of NSD. Advanced age, close distance between mandibular canal and inner surface of the cortical bone, and IAN intraoperative exposure are risk factors for NSD 1 year postoperatively. Cases at high risk for NSD must be treated with great care.

Clinical Significance of Intraoperative Exposure of Inferior Alveolar Nerve during Surgical Extraction of the Mandibular Third Molar in Nerve Injury.

During extraction surgery, the inferior alveolar nerve (IAN) can occasionally be observed in the extraction socket of the mandibular third molar (M3). The purpose of this study was to investigate and compare the incidence of IAN injury in groups with and without intraoperative IAN exposure during surgical extraction of M3, and to identify additional risk factors for the IAN injury in addition to the IAN exposure. A total of 288 cases in 240 patients, who underwent surgical extraction of M3 by a single surgeon, were divided into the exposed group (n = 69) and the unexposed group (n = 219). The surgeon recorded the information regarding the procedure when the clinical observation of IAN exposure was made during the surgery. The incidence of IAN injury after the extraction surgery was significantly higher in the exposed group than in the unexposed group (4.3% versus 0%, p < 0.05). Paresthesia was recognized in three cases of the exposed group, but it showed complete recovery within three postoperative months. No case of permanent paresthesia was detected in both groups. According to the logistic regression, the only significant risk factor of IAN injury in the exposed group was the increase of age (OR 1.108, p < 0.05). Intraoperative IAN exposure during surgical extraction of M3 may show a higher incidence of IAN injury than the case without IAN exposure, representing an incidence of 4.3%. Even if the paresthesia associated with IAN exposure occurs, it is likely to be a temporary injury, and this risk may increase with age.

Diagnostic accuracy of CBCT compared to panoramic radiography in predicting IAN exposure: a systematic review and meta-analysis.

The aim of this study is to verify whether the diagnostic accuracy of cone beam computed tomography (CBCT) is superior to panoramic radiography (PR) in predicting inferior alveolar nerve (IAN) exposure during the lower third molar extraction. Eight electronic databases were searched up to September 2020. Studies that evaluated the accuracy (sensitivity, specificity, positive-predictive value, and negative predictive value) of both imaging methods were included. The gold standard was the visualization of the IAN exposure during the extraction of lower third molars. The gray literature was also used to include any other paper that might meet the eligibility criteria. The meta-analysis was performed with OpenMeta-Analyst and ReviewManager v.5.3 software. The methodology of the studies was evaluated using QUADAS-2. Among the search, three studies met all the eligibility criteria and were included in the qualitative and quantitative synthesis. The meta-analysis was conducted with all included studies. Accuracy values for CBCT were 95.1% for sensitivity (p=0.666) and 64.4% for specificity (p<0.001). For PR sensitivity and specificity, we observed 73.9% (p=0.101) and 24.8% (p<0.001), respectively. Both exams were reliable for detecting positive cases of exposure of the IAN. However, CBCT had a better performance compared to PT in predicting IAN exposure during surgery. To better understand the CBCT accuracy in predicting the IAN exposure during surgery, since this event can increase the likelihood of IAN injury and, consequently, cause neurosensory disturbances.

Preoperative imaging findings as predictors of postoperative inferior alveolar nerve injury following mandibular cyst surgery.

The purpose of the present study was to predict inferior alveolar nerve (IAN) exposure and associated neurosensory deficits after mandibular cyst surgery based on imaging findings. The study includes 193 sites in 184 consecutive patients who underwent enucleation of cystic lesions around a mandibular third molar (MM3) and extraction of the associated MM3. Absence/presence of white lines on panoramic radiographs (PR) and absence/presence of cortication surrounding the mandibular canal on computed tomography (CT) are evaluated as predictor variables. Outcome variables are operative IAN exposure and postoperative lower lip and/or chin dysesthesia. There is a significant correlation between interruption of white lines and loss of cortication. The predictor variables are statistically associated with IAN exposure and dysesthesia. Positive predictive values of CT findings (loss of cortication) for each outcome variable are slightly higher than those of PR findings (interruption of white lines). When considering the variables, type IV, with interruption of white lines and loss of cortication, shows a statistically significant difference compared to the other groups. White lines on PR images and cortication status of the mandibular canal on CT images predict operative IAN exposure and postoperative dysesthesia in mandibular cyst surgery.

A Modified Technique of Mandibular Ramus Sagittal Split Osteotomy for Prevention of Inferior Alveolar Nerve Injury: A Prospective Cohort Study and Outcome Assessment.

Postoperative functional impairment of the inferior alveolar nerve (IAN) has been a common and well-recognized complication. Our study introduced a modified Obwegeser-Dal Pont bilateral sagittal split osteotomy (BSSO) technique and evaluated the subsequent incidence of postoperative neurosensory disturbance of IAN. In this prospective cohort study, 57 patients receiving our modified BSSO during orthognathic surgery were enrolled. The technique contained opening the 2 ramus cortices and inserting the osteotome bypassing the IAN to avoid nerve injury. A 5-point scale self-assessment questionnaire was used to evaluate IAN neurosensory disturbance one week, six months and 12 months postoperatively. Differences between groups were analyzed using χ test for categorical and Wilcoxon signed-rank test for pairwise categorical data. Complete ramus splitting could be achieved in 109 (95.6%) sides. Lower lip or chin neurosensory disturbances presented in 72 (63.2%) sides 1 week postoperatively and gradually reduced to 9 (7.9%), and 4 (3.5%) at postoperative months 6 and 12, respectively. This BSSO technique could be safely performed with low rates of IAN exposure and injury and a low incidence of persistent neurosensory disturbance in 3.5% of patients 12 months postoperatively.

Does additional cone beam computed tomography decrease the risk of inferior alveolar nerve injury in high-risk cases undergoing third molar surgery?Does CBCT decrease the risk of IAN injury?

The objectives of this study were to evaluate the efficacy of additional cone beam computed tomography (CBCT) imaging on decreasing the risk of inferior alveolar nerve (IAN) injury during third molar removal in patients at high risk and to assess the surgical outcomes. The study sample included patients considered at high risk for IAN injury based on panoramic radiography (PAN) evaluation. The primary predictor was the type of imaging method (PAN only or with additional CBCT). The other variables were demographic and anatomical/radiographic factors. The primary outcome variable was IAN injury. The secondary outcome variables were the preoperative surgical plan and surgical results including IAN exposure and duration of surgery. The sample comprised 122 patients (139 teeth) aged 18–48 years. Postoperative temporary IAN injury was present in three (4.2%) cases in the CBCT group and 11 (16.4%) in the PAN group at 7 days after surgery. However, none of the patients had a permanent IAN injury at the 6-month follow-up. Additional CBCT imaging was not superior to PAN in reducing IAN injury after third molar surgery during long-term follow-up. Nonetheless, CBCT may decrease the prevalence of temporary IAN injury and improve the surgical outcomes in high-risk patients.

Diagnostic value of cone beam computed tomography and panoramic radiography in predicting mandibular nerve exposure during third molar surgery

The aim of this study was to evaluate the diagnostic accuracies of cone beam computed tomography (CBCT) and panoramic techniques in predicting inferior alveolar nerve (IAN) exposure. The sample size was determined based on a pilot study. This prospective clinical series study included 59 third molar extraction sites with any of seven previously suggested panoramic signs of IAN exposure. The diagnosis of nerve exposure was done on panoramic and CBCT images. Molars were extracted and nerve exposure was evaluated clinically. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CBCT method, and sensitivity and PPV of panoramic method were estimated). The panoramic and CBCT methods correctly classified 67.7% and 93.3%, respectively, of 60 cases. This difference was statistically significant (χ2=13.333, P=0.000). The sensitivity, specificity, PPV, and NPV for CBCT were 97.4%, 85.7%, 92.7%, and 94.7%, respectively. The sensitivity and PPV of panoramic radiography were 67.8% and 97.6%, respectively. The signs with the highest sensitivity were interruption of the mandibular canal border and abrupt canal narrowing. None of the Pell and Gregory criteria, molar angulations, or three-dimensional canal–apex relationships was significantly associated with clinically confirmed IAN exposure. Panoramic radiography may miss about one-third of exposure cases, but a positive panoramic diagnosis is most likely to be a real exposure and should be taken seriously.

Accuracy of cone-beam computed tomography in defining spatial relationships between third molar roots and inferior alveolar nerve.

Objective:Cone-beam computed tomography (CBCT) has been proposed in surgical planning of lower third molar extraction. The aim of the present study was to assess the reliability of CBCT in defining third molar root morphology and its spatial relationships with the inferior alveolar nerve (IAN).Materials and Methods:Intraoperative and radiographic variables of 74 lower third molars were retrospectively analyzed. Intraoperative variables included IAN exposure, number of roots, root morphology of extracted third molars, and presence/absence of IAN impression on the root surface. Radiographic variables included presence/absence of the cortex separating IAN from the third molar roots on CBCT examination, number of roots and root morphology on both orthopantomography (OPG) and CBCT. The statistical association between variables was evaluated using the Fisher's exact test.Results:In all cases of intraoperative IAN exposure, the cortex appeared discontinuous on CBCT images. All cases, in which the cortical bone was continuous on CBCT images, showed no association with nerve exposure. In all cases in which nerve impression was identified on the root surface, the IAN cortex showed interruptions on CBCT images. No nerve impression was identified in any of the cases, in which the cortex appeared continuous on CBCT images. CBCT also highlighted accessory roots and apical anomalies/curvatures, not visible on the OPG.Conclusions:CBCT seems to provide reliable and accurate information about the third molar root morphology and its relationship with the IAN.

Inferior Alveolar Nerve Mobilization Using Ultrasonic Surgery With Crestal Approach Technique, Followed by Immediate Implant Insertion: Evaluation of Neurosensory Disturbance.

Many techniques are described for atrophied mandibles rehabilitation. This article reports on 12 clinical patients of severely atrophied posterior mandibles. In all the patients, a cone beam is performed before the crestal surgical approach to inferior alveolar nerve (IAN) mobilization. For the realization of this technique the piezosurgery device was used to minimize IAN injuries. With the help of this device the selective cutting of the bone has been possible until IAN exposure, in the implant placement site. At the same time, the authors performed the implant osteotomy and implant placement. After 4 months of healing, all implants were osseointegrated and the implant-supported bridges were done.Evaluation by means of neurosurgery function test over a 36-months period found that all patients had a return to normal sensation, after a brief period of neurosensory disturbance.

Quantitative pixel grey measurement of the “high-risk” sign, darkening of third molar roots: a pilot study

Our aim was to examine the panoramic darkening of the root, which is a "high-risk" sign, using quantitative measurements of pixel grey values to determine different aetiological backgrounds, namely inferior alveolar nerve (IAN) exposure with or without groove formation of the third molar roots or thinning/fenestration of the lingual cortex (LCTF). 38 impacted third molars that had been surgically removed and had darkened roots on panoramic radiographs were included in this retrospective case-control study. 15 IAN exposure cases were selected for the case group, and 23 cases with proven lingual cortical thinning or fenestration were chosen for the control group. The mean pixel grey values of selected areas in the dark band (D) and control areas within the same roots (R) were determined with the ImageTool (University of Texas Health Science Center, San Antonio, TX) software. The differences in pixel values (R-D) of the IAN and LCTF groups were analysed using the Mann-Whitney U-test and Pearson's χ(2) test. The medians of the R-D pixel values were 45.7 in the IAN group and 34.3 in the LCTF group, whereas the interquartile ranges were 12.0 (IAN) and 18.3 (LCTF) (p<0.001). The R-D critical value at which the outcomes differed significantly was 38. If the differences in pixel grey values (R-D) were higher than 38, the chance of IAN exposure was approximately 32 times higher than the chance of LCTF (χ(2) test, p < 0.001; odds ratio, 32.0; 95% confidence interval, 3.5-293.1). The pre-operative prediction of IAN exposure or lingual cortical thinning in cases with "darkening" is possible based on pixel grey measurements of digital panoramic radiographs.

Darkening of third molar roots on panoramic radiographs: is it really predominantly thinning of the lingual cortex?

This study investigated the exact intra-alveolar aetiology of a panoramic high-risk sign, darkening of the third molar roots. 83 mandibular third molar surgical removals demonstrating dark bands on the third molar roots in preoperative radiographs were included in this prospective study. Exposure of the inferior alveolar nerve (IAN), the root morphology of the third molar (e.g. groove or hook) and the integrity of the mandibular canal or lingual cortical wall were observed. Differences between single (increased radiolucency alone) and multiple darkening cases (increased radiolucency with accompanying ‘high risk’ signs) and between IAN exposure and groove formation were analysed. In 38 cases (45.8%), the IAN was visible during the operation. Groove was present in 37.4% of cases. 26.5% of the cases showed lingual cortical thinning, while specious root conformation explained the formation of darkening on the radiographic images of an additional 9.6% of the cases. IAN exposure (P<0.001) and groove formation (P<0.001) were significantly more frequent in multiple darkening cases than in single darkening cases. According to these findings, darkening of the third molar roots is more often the result of fenestration of the inferior alveolar canal wall or groove formation of the root than lingual cortical thinning.

Inferior Alveolar Nerve Sensory Disturbance After Impacted Mandibular Third Molar Evaluation Using Cone Beam Computed Tomography and Panoramic Radiography: A Pilot Study

To measure sensory disturbances of the inferior alveolar nerve (IAN) after removal of impacted mandibular third molars using cone beam computed tomography (CBCT) and dental panoramic radiography (PAN) for preoperative assessment in a randomized controlled trial and to measure the efficacy of the observers' prediction of IAN exposure at surgery based on CBCT compared with PAN. The sample consisted of 86 impacted third molars (from 79 consecutive patients) in close relation to the IAN as determined by PAN and judged as showing a "moderate" risk of IAN damage. Cases presenting with no close relation between the IAN and roots and extremely risky cases with an obvious interrelation were excluded. Potential neurosensory disturbances of the lip and chin were assessed before surgery and during the postoperative recall by measuring the function of the IAN with the light-touch sensation method. Postoperative sensory disturbances occurred in 1 patient in the CBCT group and 1 patient in the PAN group. The light-touch sensation test showed no significant differences at the lip (P = .10) and chin (P = .17) levels for CBCT- versus PAN-based surgery. Significant differences in making a correct diagnosis of neurovascular bundle exposure at the extraction of impacted teeth were found between the 2 modalities (P = .029). Within the limits of the present pilot study, CBCT was not superior to PAN in predicting postoperative sensory disturbances but was superior in predicting IAN exposure during third molar removal in cases judged as having "moderate" risk.

Risk assessment of inferior alveolar neurovascular bundle by multidetector computed tomography in extractions of third molars

This study aimed to assess the reliability of multidetector computed tomography (MDCT) in determining the surgical risk of the inferior alveolar neurovascular bundle in extractions of third molars. The sample comprised thirty-three individuals (63 third molars) who underwent preoperative evaluation by MDCT before extraction of impacted mandibular third molars. MDCT was used to determine the relationship between the roots of the third molars and the mandibular canal, and the course of the mandibular canal. Inferior alveolar nerve (IAN) exposure and the presence of hemorrhage were analyzed after removal of the teeth. IAN neurosensory deficit was recorded after 7 days. Clinical and MDCT findings were compared using Fisher's exact test (P < 0.05). There was a statistically significant association between IAN exposure and the tomographic relationship between the roots of third molars and the mandibular canal (P = 0.015). Conventionally, all cases of IAN neurosensory deficit and hemorrhage occurred when the roots of the third molar presented in an at-risk relationship with the mandibular canal, however, this association was not statistically significant (P > 0.05). A statistically significant association was found between the lingual course of the mandibular canal and IAN exposure (P = 0.03). MDCT is an effective tool for determination of the surgical risk to the inferior alveolar neurovascular bundle in extraction of mandibular third molars.