Inferior alveolar nerve injury after mandibular third molar extraction: a literature review

Association of indications for mandibular third molar coronectomy and the Pell and Gregory and the Winter classification systems

PURPOSE

The purpose of this study was to determine how the surgeon's decision to perform a mandibular third molar coronectomy or surgical removal is associated with the impaction pattern as classified using Pell and Gregory or Winter's system.

METHODS

This observational, cross-sectional study was conducted on 813 mandibular third molars belonging to 565 patients. All patients were referred for removal of the mandibular third molar and had radiographic signs indicating a close relationship with the inferior alveolar nerve. Panoramic images were classified according to the impaction pattern.

RESULTS

A coronectomy was performed on 492 (60.5%) mandibular third molars. Most impacted mandibular third molars were class IIB with a mesioangular inclination. A significant association was found between the Pell and Gregory classification and the surgeon's choice (p = 0.002). Winter's classification was not significantly associated with surgeon choice (p = 0.425).

CONCLUSION

Mandibular third molar coronectomy is chosen more frequently than surgical removal if molars are class III and position B.

TRIAL REGISTRATION NUMBER

Not applicable.

Evaluating Stromal Vascular Fraction As a Treatment for Peripheral Nerve Regeneration: A Scoping Review

PURPOSE

This study aims to investigate the potential of stromal vascular fraction (SVF) for peripheral nerve regeneration.

METHODS

A scoping review of Scopus and PubMed databases was conducted. Inclusion criteria were human or animal studies exploring the use of SVF for peripheral nerve regeneration. Studies were categorized by assessed outcomes: pain assessment, neural integrity, muscle recovery, and functional recovery. Level of evidence and study quality were assessed.

RESULTS

Nine studies met the inclusion criteria. SVF injection in humans with trigeminal neuropathic pain reduced pain scores from 7.5 ± 1.58 to 4.3 ± 3.28. SVF injection improved sensation in humans with leprosy neuropathy. Repairing transected rat sciatic nerves with SVF-coated nerve autografts improved wet muscle weight ratios (0.65 ± 0.11 vs 0.55 ± 0.06) and sciatic functional index (SFI) scores (-68.2 ± 9.2 vs -72.5 ± 8.9). Repairing transected rat sciatic nerves with SVF-coated conduits increased the ratio of gastrocnemius muscle weights (RGMW) (7-10% improvement), myelinated fibers (1,605 ± 806.2 vs 543.6 ± 478.66), and myelin thickness (5-20% increase). Repairing transected rat facial nerves with SVF-coated conduits improved whisker motion (9.22° ± 0.65° vs 1.90° ± 0.84°) and myelin thickness (0.57 μm ± 0.17 vs 0.45 μm ± 0.14 μm). Repairing transected rat sciatic nerves with SVF-coated nerve allografts improved RGMW (85 vs 50%), SFI scores (-20 to -10 vs -40 to -30), and Basso, Beatie, and Bresnahan locomotor scores (18 vs 15). All metrics mentioned above were statistically significant. The human studies were level 4 evidence due to being case series, while animal studies were the lowest level of evidence.

CONCLUSION

Despite initial promising results, the low-level evidence from the included studies warrants further investigation.

Clinical insights into traumatic injury of the inferior alveolar and lingual nerves: a comprehensive approach from diagnosis to therapeutic interventions

OBJECTIVES

This scoping review explores the risk and management of traumatic injuries to the inferior alveolar and lingual nerves during mandibular dental procedures. Emphasizing the significance of diagnostic tools, the review amalgamates existing knowledge to offer a comprehensive overview.

MATERIALS AND METHODS

A literature search across PubMed, Embase, and Cochrane Library informed the analysis.

RESULTS

Traumatic injuries often lead to hypo-/anesthesia and neuropathic pain, impacting individuals psychologically and socially. Diagnosis involves thorough anamnesis, clinical-neurological evaluations, and radiographic imaging. Severity varies, allowing for conservative or surgical interventions. Immediate action is recommended for reversible causes, while surgical therapies like decompression, readaptation, or reconstruction yield favorable outcomes. Conservative management, utilizing topical anesthesia, capsaicin, and systemic medications (tricyclic antidepressants, antipsychotics, and serotonin-norepinephrine-reuptake-inhibitors), proves effective for neuropathic pain.

CONCLUSIONS

Traumatic nerve injuries, though common in dental surgery, often go unrecorded. Despite lacking a definitive diagnostic gold standard, a meticulous examination of the injury and subsequent impairments is crucial.

CLINICAL RELEVANCE

Tailoring treatment to each case's characteristics is essential, recognizing the absence of a universal solution. This approach aims to optimize outcomes, restore functionality, and improve the quality of life for affected individuals.

Multislice computed tomography demonstrating mental nerve paresthesia caused by periapical infection: A case report

Components derived from an infected lesion within the bone can spread through various passages in the mandible, particularly via the mental foramen. Radiologically, the spread of infection is typically nonspecific and challenging to characterize; however, multislice computed tomography (MSCT) can effectively detect pathological changes in soft tissues and the bone marrow space. This report describes the case of a 55-year-old woman who experienced mental nerve paresthesia due to a periapical infection of the right mandibular second premolar. MSCT imaging revealed increased attenuation around the periapical lesion extending into the mandibular canal and loss of the juxtamental foraminal fat pad. Following endodontic treatment of the tooth suspected to be the source of the infection, the patient's symptoms resolved, and the previous MSCT imaging findings were no longer present. Increased bone marrow attenuation and obliteration of the fat plane in the buccal aspect of the mental foramen may serve as radiologic indicators of inflammation spreading from the bone marrow space.

Risk factor analysis for perioperative complications in impacted third molar surgery - a single center experience

BACKGROUND

The surgical removal of impacted third molars is usually carried out by an oral/maxillofacial surgeon. Two specific risks of surgical removal of impacted third molars are oroantral communication (OAC) when extracting ​​upper third molars and hypesthesia of the inferior alveolar nerve (IAN) ​​when extracting lower third molars. The aim of this study is to determine the distribution of complications in deeply impacted third molar surgery, to identify specific risk factors influencing the most common perioperative (OAC, IAN hypesthesia) and to compare these results with other studies.

MATERIALS AND METHODS

The clinical findings, digital panoramic radiographs, intra- and postoperative data of 80 patients with a total of 232 impacted third molars that had been subjected for tooth extraction, from December 2022 and August 2023, were collected and analyzed. Perioperative complications (IAN hypesthesia, OAC, hypesthesia lingual nerve, postoperative bleeding, postoperative infection) were identified. A risk analysis for OAC and IAN hypesthesia was performed regarding perioperative data.

RESULTS

Overall, the rate of OAC for the right upper third molar was 12.8% and for the left upper third molar 15.6%. The complication rates regarding transient hypesthesia were 8.1% for the left IAN and 7.3% for the right IAN. The distance to maxillary sinus, the depth score according to Pell and Gregory, the bone coverage score, the operation time, the tooth's angulation and the type of surgeon (oral surgeon, DMD) were identified as significant risk factors for the occurrence of OAC. The minimum distance to IAN, the bone coverage score, the total operation time and the operation by an oral surgeon (DMD) were identified as significant risk factors for hypesthesia of the IAN.

CONCLUSION

Next to the risk factors from above, the present study is one of the first showing that patients who were primarily operated on by an oral surgeon (DMD) and not a maxillofacial surgeon (MD, DMD) showed higher rates of OAC and IAN hypesthesia in impacted third molar extraction. The results of this study can serve as a baseline for further studies to investigate complication patterns in impacted third molar surgery.

System for automatically assessing the likelihood of inferior alveolar nerve injury

Inferior alveolar nerve (IAN) injury is a severe complication associated with mandibular third molar (MM3) extraction. Consequently, the likelihood of IAN injury must be assessed before performing such an extraction. However, existing deep learning methods for classifying the likelihood of IAN injury that rely on mask images often suffer from limited accuracy and lack of interpretability. In this paper, we propose an automated system based on panoramic radiographs, featuring a novel segmentation model SS-TransUnet and classification algorithm CD-IAN injury class. Our objective was to enhance the precision of segmentation of MM3 and mandibular canal (MC) and classification accuracy of the likelihood of IAN injury, ultimately reducing the occurrence of IAN injuries and providing a certain degree of interpretable foundation for diagnosis. The proposed segmentation model demonstrated a 0.9 % and 2.6 % enhancement in dice coefficient for MM3 and MC, accompanied by a reduction in 95 % Hausdorff distance, reaching 1.619 and 1.886, respectively. Additionally, our classification algorithm achieved an accuracy of 0.846, surpassing deep learning-based models by 3.8 %, confirming the effectiveness of our system.

Neurosensory Deficits of the Mandibular Nerve Following Extraction of Impacted Lower Third Molars-A Retrospective Study

BACKGROUND

Neurosensory deficits are one of the major complications after impacted lower third molar extraction leading to an impaired patient's quality of life. This study aimed to evaluate the incidence of neurosensory deficits after lower third molar extraction and compare it radiologically to the corresponding position of the inferior alveolar nerve.

METHODS

In a retrospective study, all patients who underwent impacted lower third molar extraction between January and December 2019 were compiled. Therefore, clinical data as well as preoperative radiological imaging were assessed.

RESULTS

In total, 418 patients who underwent lower third molar extractions (n = 555) were included in this study. Of these, 33 (5.9%) had short-term (i.e., within the initial 7 postoperative days) and 12 (1.3%) long-term (i.e., persisting after 12 months) neurosensory deficits documented. The inferior alveolar nerve position in relation to the tooth roots showed apical position in 27%, buccal position in 30.8%, lingual position in 35.4%, and interradicular position in 6.9%.

CONCLUSIONS

A statistically significant increased incidence of neurosensory deficits occurs when the inferior alveolar nerve is directly positioned lingually to the tooth roots (p = 0.01).

Three-dimensional positional relationship between impacted mandibular third molars and the mandibular canal

OBJECTIVE

To observe the three-dimensional positional relationship between impacted mandibular third molars (IMTMs) and mandibular canal close contacts using cone beam computed tomography (CBCT).

METHODS

A total of 101 patients with IMTMs were selected who met the diagnostic criteria for 142 teeth (no bone wall imaging area between IMTMs and the mandibular canal, a high-density bone cortical imaging area only, or a ≦1 mm bone imaging area). The parameters of the rotating CBCT anode were set as follows: 110 kV, 40-50 mA; the focal point and exposure field were set as 0.3 mmh and a high-resolution zoom, respectively; the exposure time and image layer thickness were set as 5.4 s and 0.25 mm. Three-dimensional reconstruction was performed, and the position of the mandibular canal through the IMTM area was observed continuously from the coronal, horizontal and sagittal planes.

RESULTS

We found that the mandibular canal was interrupted below the third molar (TM) in 85 cases, accounting for 59.86% of all cases. The mandibular canal was located below the buccal and lingual curvatures in 33 and 19 cases, respectively, accounting for 23.23% and 19%. In addition, a small number of mandibular canals were also located on the buccal side of the mandibular molars (2.82%). We also found one case of direct insertion of the mandibular third molar (MTM) into the mandibular canal. In addition, the mandibular canal passed through the IMTM region with 125 close contacts at the roots (88.03%); 14 mandibular canals were in contact with all teeth and 3 were in contact with the crown.

CONCLUSION

The use of CBCT can provide a dynamic and comprehensive understanding of the three-dimensional positional relationship of the mandibular alveolar nerve canal passing through the IMTM area, providing a high clinical reference value when extracting IMTMs and reducing the risk of injury to the inferior alveolar nerve.

Automatic classification of 3D positional relationship between mandibular third molar and inferior alveolar canal using a distance-aware network

The purpose of this study was to automatically classify the three-dimensional (3D) positional relationship between an impacted mandibular third molar (M3) and the inferior alveolar canal (MC) using a distance-aware network in cone-beam CT (CBCT) images. We developed a network consisting of cascaded stages of segmentation and classification for the buccal-lingual relationship between the M3 and the MC. The M3 and the MC were simultaneously segmented using Dense121 U-Net in the segmentation stage, and their buccal-lingual relationship was automatically classified using a 3D distance-aware network with the multichannel inputs of the original CBCT image and the signed distance map (SDM) generated from the segmentation in the classification stage. The Dense121 U-Net achieved the highest average precision of 0.87, 0.96, and 0.94 in the segmentation of the M3, the MC, and both together, respectively. The 3D distance-aware classification network of the Dense121 U-Net with the input of both the CBCT image and the SDM showed the highest performance of accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve, each of which had a value of 1.00. The SDM generated from the segmentation mask significantly contributed to increasing the accuracy of the classification network. The proposed distance-aware network demonstrated high accuracy in the automatic classification of the 3D positional relationship between the M3 and the MC by learning anatomical and geometrical information from the CBCT images.

The Influence of Slice Thickness, Sharpness, and Contrast Adjustments on Inferior Alveolar Canal Segmentation on Cone-Beam Computed Tomography Scans: A Retrospective Study

This retrospective study aims to investigate the impact of cone-beam computed tomography (CBCT) viewing parameters such as contrast, slice thickness, and sharpness on the identification of the inferior alveolar nerve (IAC). A total of 25 CBCT scans, resulting in 50 IACs, were assessed by two investigators using a three-score system (good, average, and poor) on cross-sectional images. Slice thicknesses of 0.25 mm, 0.5 mm, and 1 mm were tested, along with varying sharpness (0, 6, 8, and 10) and contrast (0, 400, 800, and 1200) settings. The results were statistically analyzed to determine the optimal slice thickness for improved visibility of IAC, followed by evaluating the influence of sharpness and contrast using the optimal thickness. The identified parameters were then validated by performing semi-automated segmentation of the IACs and structure overlapping to evaluate the mean distance. Inter-rater and intra-rater reliability were assessed using Kappa statistics, and inferential statistics used Pearson's Chi-square test. Inter-rater and intra-rater reliability for all parameters were significant, ranging from 69% to 83%. A slice thickness of 0.25 mm showed consistently "good" visibility (80%). Sharpness values of zero and contrast values of 1200 also demonstrated high frequencies of "good" visibility. Overlap analysis resulted in an average mean distance of 0.295 mm and a standard deviation of 0.307 mm across all patients' sides. The study revealed that a slice thickness of 0.25 mm, zero sharpness value, and higher contrast value of 1200 improved the visibility and accuracy of IAC segmentation in CBCT scans. The individual patient's characteristics, such as anatomical variations, decreased bone density, and absence of canal walls cortication, should be considered when using these parameters.

Accurate mandibular canal segmentation of dental CBCT using a two-stage 3D-UNet based segmentation framework

OBJECTIVES

The objective of this study is to develop a deep learning (DL) model for fast and accurate mandibular canal (MC) segmentation on cone beam computed tomography (CBCT).

METHODS

A total of 220 CBCT scans from dentate subjects needing oral surgery were used in this study. The segmentation ground truth is annotated and reviewed by two senior dentists. All patients were randomly splitted into a training dataset (n = 132), a validation dataset (n = 44) and a test dataset (n = 44). We proposed a two-stage 3D-UNet based segmentation framework for automated MC segmentation on CBCT. The Dice Similarity Coefficient (DSC) and 95% Hausdorff Distance (95% HD) were used as the evaluation metrics for the segmentation model.

RESULTS

The two-stage 3D-UNet model successfully segmented the MC on CBCT images. In the test dataset, the mean DSC was 0.875 ± 0.045 and the mean 95% HD was 0.442 ± 0.379.

CONCLUSIONS

This automatic DL method might aid in the detection of MC and assist dental practitioners to set up treatment plans for oral surgery evolved MC.

Extraction of impacted mandibular third molars in close proximity to the inferior alveolar canal with coronectomy-miniscrew traction to avoid nerve injury

OBJECTIVES

Extraction of impacted mandibular third molars (IMTMs) is the most common surgery performed in the Department of Oral and Maxillofacial Surgery. Inferior alveolar nerve (IAN) injury is a rare but severe complication, and the risk is significantly higher in cases of IMTM near the inferior alveolar canal (IAC). The existing surgical method to extract such IMTMs is either not safe enough or is time-consuming. A better surgical design is needed.

MATERIALS AND METHODS

From August 2019 to June 2022, 23 patients underwent IMTM extraction by Dr. Zhao at Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Nanjing University, and were found to have IMTMs in close proximity to the IAC. Due to high IAN injury risk, these patients underwent coronectomy-miniscrew traction to extract their IMTMs.

RESULTS

The time between coronectomy-miniscrew insertion and complete removal of the IMTM was 32.65 ± 2.110 days, which was significantly shorter than that of traditional orthodontic traction. Two-point discrimination testing revealed no IAN injury, and no injury was reported by patients during follow-up. Other complications, such as severe swelling, severe bleeding, dry socket, and limited mouth opening, were not observed. Postoperative pain levels were not significantly higher in the coronectomy-miniscrew traction group than in the traditional IMTM extraction group.

CLINICAL RELEVANCE

For IMTMs that are in close proximity to the IAC and must be extracted, coronectomy-miniscrew traction is a novel approach to minimize the risk of IAN injury in a less time-consuming way with a lower possibility of complications.

Early root migration after a mandibular third molar coronectomy

PURPOSE

This prospective cohort study aimed to assess early root migration after a coronectomy of the mandibular third molar at 2 and 6 months after surgery.

METHODS

We included all patients treated with a coronectomy of an impacted mandibular third molar. The primary outcome measure was the extent of postoperative root migration after 2 and 6 months. Migration was measured as the distance between the root complex and a fixed point on the inferior alveolar canal. The secondary aim was to identify factors (age, impaction pattern, and patient sex) that affected the extent of root migration.

RESULTS

One hundred and sixty-five coronectomies were performed in 141 patients (96 females and 45 males; mean age 33.1 years, SD 16.0). The 2-month checkup was completed by 121 patients that received 141 coronectomies. The 6-month check-up was completed by 73 patients that received 80 coronectomies. The mean root migrations were 3.30 mm (SD 2.53 mm) at 2 months and 5.27 mm (SD 3.14 mm) at 6 months. In the 2-6-month interval, the mean root migration was 2.58 mm (SD 2.07 mm). The extents of migration were similar during the 0-2-month interval and the 2-6-month interval (p = 0.529). Younger age was associated with greater root migration, and females experienced significantly greater migrations than males (p = 0.002).

CONCLUSION

Roots migrated more rapidly in the first two postoperative months, compared to the 2-6-month interval. Age was negatively correlated with the extent of root migration, and females showed significantly greater migrations than males.

Management of Temporomandibular Joint Reankylosis: A Case Series

Background Temporomandibular joint ankylosis is a severe debilitating clinical condition where there is fusion of the mandible with the temporal bone. It is often a challenge to the maxillofacial surgeon as the surgical treatment protocol must be tailored individually according to the time of presentation of the ankylosis, and proper postoperative aggressive physiotherapy must be advocated, which is essential for a successful outcome. This is a case series of six recurrent temporomandibular joint ankylosis, in which the historical Esmarch surgery was done, and the pterygomassetric sling was interposed between the osteotomized segments. Postoperative mouth opening and surgical outcome were satisfactory. In our cases, we created a pseudojoint, which was very successful using the Esmarch procedure. Aim We aim to improve mouth opening in patients presenting with temporomandibular joint reankylosis using the Esmarch procedure and evaluate the efficacy of the conventional and modified Esmarch procedure. Materials and methods We have included six cases of recurrent temporomandibular joint reankylosis. Five cases were operated on using the conventional Esmarch procedure in which the osteotomy was done at the angle region, below the inferior alveolar nerve canal, and one case using the modified Esmarch procedure, wherein the osteotomy was done above the inferior alveolar nerve canal. The patients included in the case series presented with temporomandibular joint reankylosis and had undergone multiple surgeries for the release of ankylosis. Results Satisfactory postoperative mouth opening was achieved in all six patients. It was observed that in the modified Esmarch osteotomy, where the cuts were placed above the inferior alveolar nerve canal, there was a massive hemorrhage intraoperatively. This was primarily attributed to the altered anatomy of the maxillary artery, which was very close to the ankylotic mass. When the osteotomy was done below the inferior alveolar nerve canal, it was found that by this technique, the intraoperative hemorrhage was minimal, but it carries a risk of postoperative inferior alveolar nerve paresthesia, which was managed conservatively. Conclusion With the abovementioned results, we proceeded with the conventional Esmarch procedure for five cases and the modified Esmarch procedure for one case. It was found that in temporomandibular joint reankylosis cases, where there is extensive ankylotic mass extending from the glenoid fossa to the coronoid process of the mandible, this Esmarch procedure provides promising results when the osteotomy cuts are placed below the nerve canal.

Post-Operative Complications and Risk Predictors Related to the Avulsion of Lower Impacted Third Molars

Background and Objectives: This prospective cohort study aimed to evaluate the onset and severity of pain and other complications following lower impacted third molar extraction and to identify potential risk predictors. Materials and Methods: Twenty-five patients were treated with at least one lower impacted third molar extraction. The primary outcome was the onset of post-operative pain, evaluated at 6 h, 12 h, 24 h, 48 h, 72 h, and 7 days. The secondary outcomes (trismus, edema, alveolitis, dehiscence, neuralgic injury, and suppuration) were recorded at 3, 7 and 21 days after oral surgery. A correlation analysis was performed to identify potential associations between patient- and tooth-related factors and VAS (Visual Analogue Scale) scale. When a statistically significant correlation was identified, a regression analysis was performed. Results: Most of the patients were female (84%) with a mean age of 25 ± 3 years; the reason for oral surgery was dysodontiasis in 60% of cases, while the most frequent Pell and Gregory class was BII (36%). The VAS scale showed the onset of mild pain at 6 h (44%), 12 h (48%), 24 h (68%) and 48 (68%) after surgery. Trismus, edema, and alveolitis were observed at 3-day (20%, 64% and 12%, respectively) and at 7-day (16%, 12% and 4%, respectively) follow-up. Neuralgic injury was reported in one case (4%). The linear regression analysis showed a statistically significant association (p < 0.05) between the duration of oral surgery and VAS scores at 6 and 12 h. Finally, the binary logistic regression identified systemic disease, Pell and Gregory classification, duration of oral surgery, VAS at 6 and 12 h, trismus, and edema at 3 and 7 days as predictive factors of post-operative complications. Conclusions: Within their limits, the results of this study suggest that the onset of post-operative complications increases in proportion to the duration of the surgical procedure.

Evaluation of the Anatomic Position of the Mandibular Canal Regarding to the Segments of the Mandibular Sagittal Split Ramus Osteotomy to Diminish the Possibility of Injuries: a Pilot Study

Objectives

This pilot study evaluated the relationship between inferior alveolar nerve location through computed tomography scan and intraoperative inferior alveolar nerve entrapment after bilateral sagittal split osteotomy.

Material and Methods

Overall, 20 helicoidal computed tomography scans were evaluated in patients with facial deformities who underwent to bilateral sagittal split osteotomy (BSSO). The distance from the mandibular canal to the internal surface of the buccal and lingual cortical bone, mandibular thickness, bone density and proportion of medullary and cortical bone in 3 regions were evaluated. During the intraoperative period, the segment to which the nerve remained adhered after performing BSSO was analysed, and the data correlated.

Results

The distance from the mandibular canal to the buccal cortical bone showed a mean of 2.6 mm when the inferior alveolar nerve was adhered to the distal segment and mean of 0.7 mm when the nerve was adhered to the proximal segment. The thickness was 11.2 mm and 9.8 mm when the nerve was adhered the distal the proximal segments respectively. Mandibular thickness, distance from the mandibular canal to the buccal and lingual cortical were statistically related to intraoperative nerve entrapment (P < 0.05).

Conclusions

Narrow jaws and the distance from the mandibular canal to buccal cortical bone less than 2 mm increases the risk of the inferior alveolar nerve entrapment in bilateral sagittal split osteotomy.

Piezoelectric Surgery Is Effective in Reducing Pain, Swelling, and Trismus After Removal of Impacted Lower Third Molars: A Meta-Analysis

PURPOSE

Surgery of impacted lower third molars may be associated with postoperative complications. The aim of this study is to determine whether piezoelectric surgery is effective in reducing pain, swelling, and trismus compared to conventional rotary instruments during extraction of impacted lower third molars.

METHODS

For this systematic review, the searches were performed independently by 2 researchers. Randomized clinical trials that used the piezoelectric instrument for the removal of impacted lower third molars in humans were included. The predictor variable was the study group (piezo surgery vs rotary instruments). The main outcome was the analysis of postoperative pain, swelling, and trismus. Data analysis included risk of bias assessment (RoB 2 Cochrane) and meta-analysis with heterogeneity based on random effects I² and 95% confidence interval.

RESULTS

In the initial results, 956 articles were revised and after applying inclusion/exclusion criteria, the final sample was composed of 18 publications, all being randomized clinical trials. The results of this meta-analysis demonstrated a significant reduction in pain scores with a Cohen's d of -0.95 [CI 95% = -1.23 to -0.67] of high clinical impact (P < .001). In the piezo group there was a significant increase in mouth opening of 4.29 [CI 95% = 2.33 to 6.25] mm (P < .001). Regarding swelling, Tragus-Ang and Go-eye, both showed a significant reduction in the piezo group (P < .001). There was a significant increase of 7.32 [CI 95% = 4.40 to 10.24] minutes in the piezo group (P < .00001), and none of the studies showed a significant risk of bias.

CONCLUSIONS

Piezo proved to be effective in reducing pain, swelling, and trismus in third molar surgeries even with longer surgical time, but due to the lack of standardization in primary studies regarding swelling, new, controlled and standardized studies should be carried out with the objective of proving the effectiveness of this therapeutic modality in the reduction of postoperative swelling.

Bilateral ‘kissing’ molars: A case report

‘Kissing molars’, were described by Van Hoof in 1973 as when the occlusal surfaces of impacted molars are united by the same follicular space and the roots point in the opposite direction. There are very few published cases in the literature, and it is an extremely rare form of impaction.

This manuscript concerns the diagnosis and management of a rare dentoalveolar clinical and radiographic presentation, which may be encountered by and be of interest to dental practitioners in both primary and secondary care.

Assessment of the Proximity of the Inferior Alveolar Canal with the Mandibular Root Apices and Cortical Plates-A Retrospective Cone Beam Computed Tomographic Analysis

Various endodontic interventions often lead to iatrogenic damage to the inferior alveolar nerve present in the inferior alveolar canal (IAC). The purpose of the present study was to analyze the relationships of IAC with the root apices of mandibular teeth and with the mandibular cortical plates.

MATERIALS

116 cone beam computed tomography (CBCT) scans were examined and the shortest distance of IAC with the root apices of mandibular canines, premolars and molars, and with cortical plates was analyzed. The data were statistically analyzed using SPSS.

RESULTS

The shortest mean distance between IAC and lingual cortical plate (LCP) was found in the third molar area, and between IAC and buccal cortical plate (BCP) in the second premolar area. A high incidence of 60% direct communication (DC) was present in mandibular second molars; 38% in mandibular third molars; 13% in mandibular second premolars; 12% in mandibular first molars; and 1% in mandibular first premolars.

CONCLUSION

Anteriorly, IAC was found to be significantly present in close approximation to the roots of mandibular canines. Posteriorly, IAC was found to be in significant proximity to the distal roots of mandibular second molars.

Top 100 cited publications in the field of third molar surgery: A bibliometric analysis

This study aimed to identify and rank the top 100 cited papers related to third molar surgery METHODS: This bibliometric analysis was performed through the Clarivate Analytics' Web of Science database intended to find the top 100 most cited papers. The search was conducted on 18^th November 2021 with MeSH terms related to the third molar surgery. Extracted Data included title, main author, institution, publication year, a total of citations, citation average per year, country, the journal paper was published, journal impact factor, the number of citations of the three most-cited journals, study design, and field related to third molar surgery RESULTS: The top-cited paper was a retrospective cohort related to complications after the third molars surgery, published in 2003 in the Journal of Oral and Maxillofacial Surgery. The total number of citations was 9026. Thirty-nine percent of the papers included were randomized clinical trials. The USA is the main country responsible for the best publications in the field of third molar surgery. European researchers had the main expressive citation score, and "surgery" related to the third molar was the most critical field of research CONCLUSIONS: 1) The United States of America was the leading country that contributed to third molar field research 2) The Universities of Barcelona and the University of North Carolina were the most productive institutions regarding this research field; 3) Complications after third molar surgery was the most researched field. Compared to the other fields in dentistry such as Oral pathology and Cariology, the number of citations regarding third molar surgery was low.

Canal-Net for automatic and robust 3D segmentation of mandibular canals in CBCT images using a continuity-aware contextual network

The purpose of this study was to propose a continuity-aware contextual network (Canal-Net) for the automatic and robust 3D segmentation of the mandibular canal (MC) with high consistent accuracy throughout the entire MC volume in cone-beam CT (CBCT) images. The Canal-Net was designed based on a 3D U-Net with bidirectional convolutional long short-term memory (ConvLSTM) under a multi-task learning framework. Specifically, the Canal-Net learned the 3D anatomical context information of the MC by incorporating spatio-temporal features from ConvLSTM, and also the structural continuity of the overall MC volume under a multi-task learning framework using multi-planar projection losses complementally. The Canal-Net showed higher segmentation accuracies in 2D and 3D performance metrics (p < 0.05), and especially, a significant improvement in Dice similarity coefficient scores and mean curve distance (p < 0.05) throughout the entire MC volume compared to other popular deep learning networks. As a result, the Canal-Net achieved high consistent accuracy in 3D segmentations of the entire MC in spite of the areas of low visibility by the unclear and ambiguous cortical bone layer. Therefore, the Canal-Net demonstrated the automatic and robust 3D segmentation of the entire MC volume by improving structural continuity and boundary details of the MC in CBCT images.

Can CBCT change the level of confidence of oral maxillofacial surgeons in mandibular third molar management?

This study analyzed the impact of CBCT on the level of confidence in diagnostic and treatment thinking in mandibular lower molar (M3M) clinical management. Thirty cases for which panoramic radiographs and CBTC images were available were selected and classified according to radiologic signs indicating the proximity of the M3M to the mandibular canal (interruption of the radiopaque borders of the canal of the mandibular canal wall, darkening of the roots, and diversion or narrowing of the canal, n = 10 for each classification). Twelve oral and maxillofacial surgeons (OMS) contributed to this study by answering two questionnaires. The first questionnaire contained a clinical description of the case and a panoramic radiograph. After 30 days, a second questionnaire with the same clinical illustrations and tomographic multiplanar reconstruction images was administered. Both questionnaires asked specialists to rate diagnostic confidence, the surgical complexity, chosen treatment, and surgical confidence. In approximately 40% of answers, CBCT images had a positive impact on ratings of diagnostic confidence and treatment thinking confidence, and in 24.4%, they increased the surgical complexity score. There was no change in the treatment plan following the use of CBCT, but the CBCT examination was a determining factor for diagnosis and treatment planning in 72.8% of the answers CBCT improved the confidence level in diagnostic and treatment thinking of the M3M management while also increasing the perceived level of surgical complexity. The findings of this study support the need to consider using CBCT in diagnosis and treatment planning for M3Ms with radiographic signs such as darkening of the roots, interruption of the radiopaque borders of the mandibular canal, or deviation of the mandibular canal and narrowing of the roots.

The effect of extraction of the lower first permanent molar on the developing third molar in children

Objective:

To find the effect of extraction of the lower first permanent molar in children (aged 8–11 years) on the position and angle of the developing third molar.

Design:

Retrospective radiographic analysis.

Participants:

Two cohorts of participants were identified: an extraction group, who had extraction of one or more first permanent molars aged 8–11 years; and a non-extraction group, who retained all mandibular teeth. Both cohorts previously had panoramic radiographs taken at mean ages of 9.7 years (T1), before extraction, and 12.12 years (T2). In total, there were 61 third molars with an associated extracted first permanent molar and 60 third molars with an associated retained first permanent molar.

Methods:

A digital radiographic analysis was carried out on the panoramic radiographs to measure the movement of the third molar, vertically and horizontally, and its angle. The magnification of the T1 and T2 radiographs was calibrated. Reliability of the radiographic analysis was confirmed via intra- and inter-rater reliability tests. The extraction and non-extraction groups were compared via independent sample tests

Results:

The third molar moved significantly more mesial in the extraction group (P < 0.001) and the angle uprighted significantly more than the non-extraction group (P < 0.001). Vertically, the third molar moved inferiorly in both cohorts with no significant difference.

Conclusion:

In the developing dentition, extraction of the lower first permanent molar encouraged mesial movement and uprighting of the developing third molar. This may improve the likelihood of future eruption of the third molar.

Mandibular Canal Location and Cortical Bone Thickness in Males and Females of Different Age Groups: A Cone-beam Computed Tomography Study

AIM: The purpose of the study was to measure and compare the prevalence of mandibular canal (MC) location variations in regard to mandibular first molars in both genders at different age groups. METHODS: A retrospective study was performed on 80 cone-beam computed tomography scans. Distance between MC and apical apices of first molars, buccal and lingual cortical plates was measured in both sides. RESULTS: 80 scans with 160 sides were analyzed. Distances was measured bilaterally for all scans with mean (5.22 ± 0.77) in men versus (4.1 ± 0.7) in women at group age 31–40 apical to apices of first molars. The mean was (3.77 ± 0.62) in men versus (2.81 ± 0.47) in women at same age group at buccal side, lingually the mean was (4.02 ± 0.67) in men versus (3.67 ± 0.26) in women in the same age group. CONCLUSION: Our study showed that there were decrease in measurements in older age group in both genders and in female groups more than male groups but with no statistical significant difference.

Resolution of lower second molar impaction through miniscrew-supported biomechanics: A proposal for a simplified classification

Two case reports are presented showing how the strategic use of skeletal anchorage via orthodontic miniscrews manages to solve the complex problems of orthodontic disimpaction of second mandibular molars with excellent anchorage control and reduction of the adverse effects common to the use of conventional methods. The temporary anchorage device (TAD)-mediated biomechanics used can be categorized as both "pulling from the distal side" and "pushing from the mesial side" techniques in which both direct and indirect anchorage mechanics were employed. Each of these mechanics has its advantages and disadvantages, which must be weighed and considered on a case-by-case basis. Based on the force application side and the type of anchorage, a simplified classification of TADs supported biomechanics for the recovery of fully or partially impacted second molars is proposed.

Prediction of post-traumatic neuropathy following impacted mandibular third molar removal

OBJECTIVES

The extraction of impacted mandibular third molars is a common surgical procedure often associated with complications including post-traumatic neuropathy. Previous work has focused on identifying confounding factors, but a robust preoperative risk prediction model remains elusive.

METHODS

Using a dataset of 648 patients and 812 impacted mandibular third molars, we used least absolute shrinkage and selection operator (LASSO) to fit prediction models based on risk factors assessed at both the tooth and patient levels. In addition, we fitted multivariable logistic regression models with the Firth correction for generalized estimating equations (GEE).

RESULTS

The LASSO model for post-traumatic neuropathy identified distoangular impaction of ≥ 45° (odds ratio [OR] = 2.9), proximity to the inferior alveolar nerve of ≤ 3 mm (OR = 1.9), disadvantageous curving (OR = 1.4), and psychiatric conditions (OR = 2.1) as predictors [area under the receiving operator characteristic curve (AUC) = 0.75]. Among other complications analyzed, the LASSO model for bleeding identified deep embedding or full impaction (OR = 1.8), psychiatric conditions (OR = 1.3), and age (OR = 0.9) as predictors (AUC = 0.64). These associations between predictors and postoperative complications were fundamentally reinforced by the corresponding GEE models.

CONCLUSIONS

Our findings point to the predictability of post-traumatic neuropathy and bleeding based on tooth anatomy and patient characteristics, overall suggesting that preoperatively identifiable factors can predict the risk of adverse outcomes in the extraction of impacted mandibular third molars.

CLINICAL SIGNIFICANCE

Mandibular third molar extraction is both a routine procedure and a leading cause of trigeminal neuropathy. Prevention of post-traumatic neuropathy, aided by individualized preoperative risk prediction, is of high clinical relevance.

Deep Learning-Based Prediction of Paresthesia after Third Molar Extraction: A Preliminary Study

The purpose of this study was to determine whether convolutional neural networks (CNNs) can predict paresthesia of the inferior alveolar nerve using panoramic radiographic images before extraction of the mandibular third molar. The dataset consisted of a total of 300 preoperative panoramic radiographic images of patients who had planned mandibular third molar extraction. A total of 100 images taken of patients who had paresthesia after tooth extraction were classified as Group 1, and 200 images taken of patients without paresthesia were classified as Group 2. The dataset was randomly divided into a training and validation set (n = 150 [50%]), and a test set (n = 150 [50%]). CNNs of SSD300 and ResNet-18 were used for deep learning. The average accuracy, sensitivity, specificity, and area under the curve were 0.827, 0.84, 0.82, and 0.917, respectively. This study revealed that CNNs can assist in the prediction of paresthesia of the inferior alveolar nerve after third molar extraction using panoramic radiographic images.

Clinical negligence claims in oral and maxillofacial surgery over the last 10 years

According to NHS Resolution, the cost of harm from clinical activity in the last year was £8.3 billion. The steady increase in litigation within the National Health Service (NHS) has led to concerns being raised regarding the sustainability of the NHS, the increasing practice of defensive medicine, and the psychological impact on healthcare professionals. To our knowledge, litigation within oral and maxillofacial surgery has not been investigated in the UK since 2010, therefore our aims were to identify the trends within our specialty and the common reasons for negligence claims over the last 10 years. A freedom of information request was made to NHS Resolution for all clinical negligence claims from 2010 to 2020. A total of 1,122 claims were registered and the total for damages paid was £32,631,131. The claims were categorised by the primary injury and further divided into groups of cause codes. Four types of primary injury comprised 65.4% (n = 734) of all negligence claims and were as follows: additional or unnecessary operations (n = 313, 27.9%), unnecessary pain (n = 156, 13.9%), nerve damage (n = 139, 12.4%), and dental damage (n = 126, 11.2%). The damages associated with nerve damage were the costliest, with a total of £8,033,737 being paid. The significant increase in the number and cost of clinical negligence claims is concerning. The lessons from these claims must be shared and implemented to reduce the burden on the NHS, and ensure that we are providing a high quality of care with improved patient outcomes.

Factors affecting root migration after coronectomy of the mandibular third molar

Nerve injury especially inferior alveolar nerve (IAN) is the one of the complications that occur when the mandibular third molar (M3) is extracted and in case of high risk patients, coronectomy might be an alternative to tooth extraction. The purpose of this retrospective study was to analyze root migration and its influencing factors at 6 months after coronectomy in both 2- and 3-dimensions using periapical view and cone-beam computed tomography (CBCT). We analyzed 33 cases of root remnant after coronectomy and measured the amount of migration in CBCT. The following factors that could possibly affect root migration were also analyzed: age, gender, number of M3 roots, shape of M3s, Pell, and Gregory classification, mesiodistal (MD) angulation, buccolingual (BL) angulation, contact point with the second molar, root curvature, and complete removal of the coronal portion. Migration of greater than 2 mm was found in 64% of the roots in the 2-dimensional (2D) analysis, and the average root migration was 4.11 mm in the 3-dimensional (3D) analysis. The factors affecting migration were the root morphology, complete removal of the coronal portion, impaction depth, and MD angulation in the 2D analysis, and MD and BL angulation in the 3D analysis. Ensuring sufficient space for root migration especially considering angulation, depth and complete removal of the coronal portion might be important factors after coronectomy of the M3. Root remnant after coronectomy of M3 may migrate in young patients who has sufficient empty coronal space and this may reduce the nerve damage by the separation of IAN and M3.

Photobiomodulation Therapy for the Management of Patients With Inferior Alveolar Neurosensory Disturbance Associated With Oral Surgical Procedures: An Interventional Case Series Study

Introduction: Inferior alveolar nerve (IAN) injury is a serious complication during intraoral surgeries. We aimed to evaluate the outcome of photobiomodulation (PBM) therapy in patients with IAN injury associated with third molar or implant procedures. Methods: Eight patients with an alteration of sensory function of the IAN after third molar or implant surgeries were enrolled in this case series study. The patients received 10 sessions of PBM therapy (810 nm diode laser, 200 mW, 10 J/cm² per point, three times a week). Pinprick (PP) and visual analogue scale (VAS) neurosensory tests were recorded at each treatment session and 14 days after the last treatment. The association between explanatory variables and the outcome of interest was analyzed using generalized estimating equations. Results: The median percentage change of outcomes from the first to the last visit was as follows: VAS score: +125.00% (range: 50.00 to 166.67); PP score: +350% (range: 150 to 800). The duration of paresthesia was inversely correlated with changes in VAS and PP scores. No significant association was found between patients' gender or age and changes in VAS and PP scores. Conclusion: Considering the limitations of this study, PBM with the parameters used in this study presented positive effects on neurosensory recovery in patients suffering from IAN injury associated with routine intraoral procedures. Patients with shorter duration of paresthesia tended to respond more favorably to PBM therapy.

Buccal corticotomy using piezosurgery as a surgical approach for removal of deeply impacted mandibular teeth: An alternative procedure to avoid pitfalls associated with the conventional technique

PURPOSE

To describe and evaluate the use of buccal corticotomy (BC) using a piezosurgical approach for the removal of deeply impacted mandibular teeth.

PATIENTS AND METHODS

The charts of all patients who underwent BC for the removal of impacted mandibular teeth between 2011 and 2019 at the University Hospital of Geneva were reviewed. The primary outcome variables were (1) the indication for the removal of impacted mandibular teeth by BC, (2) complications. Other variables included age, gender, teeth involved, indication for tooth removal and radiological features. Follow-up was at 1, 3, 6 and 12 months, and we noted the status of healing and complications, if any.

RESULTS

Twenty-three mandibular-impacted teeth in 6 patients were extracted using BC (8 third molars, 6 second molars, 1 first molar, 4 second premolars and 4 first premolars). The indications for using the BC approach included (1) deeply impacted teeth closely related to the inferior alveolar nerve (IAN) that runs either lingually or inferior to the dental roots (4 patients); or (2) deeply impacted teeth closely related to the IAN and located anterior to the second molar region (2 patients). No complications were observed during the follow-up period.

CONCLUSION

The present study showed that the BC approach is a valuable method for removing deeply impacted teeth in close proximity to the mandibular canal and is associated with no complications and sound bone healing.

Influence of Surgical Flap Design (Envelope and Szmyd) for Removal of Impacted Mandibular Third Molars on Clinical Periodontal Parameters: A Clinical Trial

The aim of the study was to assess the influence of flap designs (Envelope flap (EF) and Szmyd flap (SF)) for impacted mandibular third molar extraction, on periodontal pocket depth (PPD), clinical attachment loss (CAL) and bone levels (BL) of second molar. Sixty patients indicated for third molar extractions with healthy second molars were allocated into two groups: EF and SF (n = 30). Third molars were assessed for angulation, root patterns, depth of impactions and relation with ramus (Pell and Gregory classification). Extraction of third molars was performed and PPD, CAL and BL around second molars at 0, 3 and 6 month (mon) follow-ups (FU) were assessed clinically and radiographically. ANOVA, Chi-square and Fisher’s exact test were employed to compare periodontal factors between EF and SF groups, considering p ≤ 0.05 as significant. Sixty participants with a mean age of 23.22 ± 3.17 were included in the study. Based on angulation, the most common impaction in the EF and SF groups was mesio-angular (EF, 50%; SF, 36.7%). Buccal and distal PPD showed a significant increase (p < 0.001) in both EF and SF patients from baseline to 6 mon. EF patients showed significantly higher distal and buccal CAL (6.67 ± 0.18 mm; 6.91 ± 0.17 mm) and BL (7.64 ± 0.16 mm; 7.90 ± 0.15 mm) as compared to SF patients (CAL, 6.76 ± 0.26 mm; 6.91 ± 0.17 mm-BL, 7.42 ± 0.38 mm; 7.34 ± 0.34 mm) at 6 mon FU. SF showed better soft tissue attachment (PPD and CAL) and bone stability (less bone loss) around second molars compared to EF after third molar extractions regardless of the patient, tooth and operator factors.

Reliability of panoramic radiography in predicting proximity of third molars to the mandibular canal: A comparison using cone-beam computed tomography

Purpose

The purpose of this study was to analyze the reliability of 7 panoramic radiographic signs for predicting proximity of the root apices of mandibular third molars to the mandibular canal using cone-beam computed tomography and to correlate these findings with the Pell and Gregory and the Winter classification systems.

Materials and Methods

An observational, cross-sectional, descriptive study was conducted on 74 patients with bilateral impacted mandibular third molars. Four panoramic radiographic signs were observed in the tooth root (darkening, deflection, and narrowing of the root apices, and bifid apices), and another 3 in the mandibular canal (diversion, narrowing, and interruption of the mandibular canal). Cone-beam computed tomography images were analyzed to identify disruption and diversion of the mandibular canal and root deflection.

Results

Binary logistic regression showed that only 4 of the 7 panoramic radiographic signs were able to predict proximity of the root apices of the mandibular third molars to the mandibular canal: darkening of the root, deflection of the root, narrowing of the root, and interruption of the mandibular canal (P<0.05).

Conclusion

Darkening, deflection, and narrowing of the root, in tandem with the interruption of the mandibular canal on panoramic radiographs, indicate that cone-beam computed tomography should be performed when planning the extraction of impacted mandibular third molars. Proximity between mandibular third molars and the mandibular canal is correlated with the Winter classification.

Removal of Horizontally Impacted Mandibular Third Molars With Large Root Bifurcations Using a Modified Tooth Sectioning Method

PURPOSE

The purpose of this study was to introduce the method and first results of a modified tooth sectioning technique for the extraction of horizontally impacted mandibular third molars (M3Ms) with large root bifurcation.

PATIENTS AND METHODS

A total of 300 horizontally impacted M3Ms with large root bifurcation in medically healthy patients were included in this prospective study. Patients were divided into 2 groups: the modified method group (test group), in which the M3M was sectioned between the distal root and the remainder of the tooth at the point of root bifurcation; and the conventional method group (control group), in which the M3M was sectioned between the crown and the root at the cementoenamel junction. Operation duration, postoperative reactions, complications, and patient satisfaction were analyzed and compared between the 2 groups.

RESULTS

Each group included 150 M3Ms which were all successfully extracted. Operation durations in the test and control group were 10.48 ± 3.78 and 15.09 ± 4.24 minutes, respectively (P < .05). The test group had significantly better results than the control group with regard to postoperative reactions and complications (P < .05). Patients in the test group had higher satisfaction ratings regarding operation duration and the healing process than those in the control group (P < .05).

CONCLUSIONS

The modified method of tooth sectioning between the distal root and the remainder of the tooth can efficiently eliminate resistance from the bone and adjacent mandibular second molar and allow for just 1 sectioning of the M3M in most cases, which could make the operation straightforward and safe.

Reliability of Orthopantamogram in Lower Third Molar Surgery: Inter- and Intra-observer Agreement

Context:

The evaluation of relationship between the roots of impacted lower third molar (IL3M) and inferior alveolar nerve injury (IAN) with orthopantamogram (OPG) is mandatory before performing de-impaction surgery. An investigation is considered reliable if it can be reproduced by various examiners. Assessment of OPG is subjective and varies among examiners. OPG is reliable to clinicians if the interpretation is not a product of guess work.

Aim:

The aim of this study was to evaluate the magnitude of agreement among oral surgeons and oral radiologist in observing intimate relationship between IL3M and mandibular canal.

Materials and Methods:

OPGs were evaluated by two oral surgeons and one oral radiologist for nerve root relationship. All the three were from different institutions with 10–15 years of experience. The three observers were blinded from each other’s findings. A total of 127 OPGs were evaluated for inter-observer agreement. Fifty OPGs were evaluated after 60 days for intra-observer agreement.

The agreement was evaluated based on Cohen’s κ statistics.

Results:

Our results denote that the interpretation of OPG among specialists is not in good agreement. We suggest development of methods to standardize evaluation of OPG and the exposure technique to improve inter-observer agreement among the dental specialists.

Prophylactic removal of impacted mandibular third molars: a systematic review and economic evaluation

BACKGROUND

Impacted third molars are third molars that are blocked, by soft tissue or bone, from fully erupting through the gum. This can cause pain and disease. The treatment options for people with impacted third molars are removal or retention with standard care. If there are pathological changes, the current National Institute for Health and Care Excellence guidance states that the impacted third molar should be removed.

OBJECTIVE

The objective of this study was to appraise the clinical effectiveness and cost-effectiveness of the prophylactic removal of impacted mandibular third molars compared with retention of, and standard care for, impacted third molars.

METHODS

Five electronic databases were searched (1999 to 29 April 2016) to identify relevant evidence [The Cochrane Library (searched 4 April 2016 and 29 April 2016), MEDLINE (searched 4 April 2016 and 29 April 2016), EMBASE (searched 4 April 2016 and 29 April 2016), EconLit (searched 4 April 2016 and 29 April 2016) and NHS Economic Evaluation Database (searched 4 April 2016)]. Studies that compared the prophylactic removal of impacted mandibular third molars with retention and standard care or studies that assessed the outcomes from either approach were included. The clinical outcomes considered were pathology associated with retention, post-operative complications following extraction and adverse effects of treatment. Cost-effectiveness outcomes included UK costs and health-related quality-of-life measures. In addition, the assessment group constructed a de novo economic model to compare the cost-effectiveness of a prophylactic removal strategy with that of retention and standard care.

RESULTS

The clinical review identified four cohort studies and nine systematic reviews. In the two studies that reported on surgical complications, no serious complications were reported. Pathological changes due to retention of asymptomatic impacted mandibular third molars were reported by three studies. In these studies, the extraction rate for retained impacted mandibular third molars varied from 5.5% to 31.4%; this variation can be explained by the differing follow-up periods (i.e. 1 and 5 years). The findings from this review are consistent with the findings from previous systematic reviews. Two published cost-effectiveness studies were identified. The authors of both studies concluded that, to their knowledge, there is currently no economic evidence to support the prophylactic removal of impacted mandibular third molars. The results generated by the assessment group's lifetime economic model indicated that the incremental cost-effectiveness ratio per quality-adjusted life-year gained for the comparison of a prophylactic removal strategy with a retention and standard care strategy is £11,741 for people aged 20 years with asymptomatic impacted mandibular third molars. The incremental cost per person associated with prophylactic extraction is £55.71, with an incremental quality-adjusted life-year gain of 0.005 per person. The base-case incremental cost-effectiveness ratio per quality-adjusted life-year gained was found to be robust when a range of sensitivity and scenario analyses were carried out.

LIMITATIONS

Limitations of the study included that no head-to-head trials comparing the effectiveness of prophylactic removal of impacted mandibular third molars with retention and standard care were identified with the assessment group model that was built on observational data. Utility data on impacted mandibular third molars and their symptoms are lacking.

CONCLUSIONS

The evidence comparing the prophylactic removal of impacted mandibular third molars with retention and standard care is very limited. However, the results from an exploratory assessment group model, which uses available evidence on symptom development and extraction rates of retained impacted mandibular third molars, suggest that prophylactic removal may be the more cost-effective strategy.

FUTURE WORK

Effectiveness evidence is lacking. Head-to-head trials comparing the prophylactic removal of trouble-free impacted mandibular third molars with retention and watchful waiting are required. If this is not possible, routine clinical data, using common definitions and outcome reporting methods, should be collected.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42016037776.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 30. See the NIHR Journals Library website for further project information.

Factors Influencing the Localization of Mandibular Third Molars in Twins

PURPOSE

The aim of the present study was to evaluate the genetic and environmental factors influencing the localization of mandibular third molars by analyzing the panoramic radiographs of twins. We examined the mandibular third molars of Japanese monozygotic (MZ) and dizygotic (DZ) twins recruited by the Osaka University Center for Twin Research.

MATERIALS AND METHODS

The present study included 49 pairs (98 participants) of MZ twins and 11 pairs (22 participants) of DZ twins. Using panoramic radiography, we evaluated the degree of eruption of mandibular third molars according to the height of the alveolus bone and the third molar space/crown width ratio. Using co-twin control analysis and a generalized linear mixed model, we evaluated the effects of various factors, including gender, age, body height, number of teeth, length of the lower dental arch, existence of a second molar, bruxism, and previous orthodontic therapy.

RESULTS

Body height, third molar space/crown width ratio, and length of the mandibular dental arch were related to the degree of mandibular third molar eruption and were strongly influenced by genetic factors rather than common or unique environmental factors.

CONCLUSIONS

The degree of third molar eruption was more similar among MZ twins than among DZ twins; therefore, genetic factors can be expected to have more significant influence than will environmental factors. These results can help identify the trend of third molar eruption from a young age, allowing us to advise the early extraction of mandibular third molars for patients with a short stature, narrow retromolar space, or short mandibular dental arch. In addition, if the genes that influence the degree of eruption were identified, we would be better equipped to predict an individual's risk of impaction, and indications for extraction might change.

Piezoelectric bone surgery for impacted lower third molar extraction compared with conventional rotary instruments: a systematic review, meta-analysis, and trial sequential analysis

The aim of this study was to evaluate whether piezoelectric bone surgery (PBS) for impacted lower third molar extraction reduces the surgical time and risk of intra- and postoperative complications in comparison with conventional rotary instruments. This meta-analysis followed the PRISMA guidelines and was registered in the PROSPERO database. The PubMed, Embase, Scopus, and OpenGrey databases were screened for articles published from January 1, 1990 to December 31, 2018. Selection criteria included randomized controlled trials (RCTs) comparing PBS with conventional rotary instruments for impacted lower third molar extraction and reporting any of the clinical outcomes (intra- and postoperative complications and duration of surgery) for both groups. A risk of bias assessment was performed using the Cochrane Collaboration tool. A meta-analysis was performed, and the power of the meta-analytic findings was assessed by trial sequential analysis (TSA). Strong evidence suggests that PBS prolongs the duration of surgery and low evidence suggests that PBS reduces postoperative morbidity (pain and trismus) in comparison with rotary instruments. Data were insufficient to determine whether PBS reduces neurological complications and postoperative swelling in comparison with burs.

Automatic mandibular canal detection using a deep convolutional neural network

The practicability of deep learning techniques has been demonstrated by their successful implementation in varied fields, including diagnostic imaging for clinicians. In accordance with the increasing demands in the healthcare industry, techniques for automatic prediction and detection are being widely researched. Particularly in dentistry, for various reasons, automated mandibular canal detection has become highly desirable. The positioning of the inferior alveolar nerve (IAN), which is one of the major structures in the mandible, is crucial to prevent nerve injury during surgical procedures. However, automatic segmentation using Cone beam computed tomography (CBCT) poses certain difficulties, such as the complex appearance of the human skull, limited number of datasets, unclear edges, and noisy images. Using work-in-progress automation software, experiments were conducted with models based on 2D SegNet, 2D and 3D U-Nets as preliminary research for a dental segmentation automation tool. The 2D U-Net with adjacent images demonstrates higher global accuracy of 0.82 than naïve U-Net variants. The 2D SegNet showed the second highest global accuracy of 0.96, and the 3D U-Net showed the best global accuracy of 0.99. The automated canal detection system through deep learning will contribute significantly to efficient treatment planning and to reducing patients’ discomfort by a dentist. This study will be a preliminary report and an opportunity to explore the application of deep learning to other dental fields.

Envisioning Post-treatment Occlusions after Space Closure Using Temporary Skeletal Anchorage Devices

Missing posterior teeth and posterior tooth extractions are commonly seen and needed within orthodontic practices. With the invention of temporary skeletal anchorage devices (TSADs), clinicians can now effectively close posterior tooth spaces. Various molar occlusions are discussed to help clinicians envision post-treatment occlusions after posterior teeth space closure using TSADs.

An analysis of the first and second mandibular molar roots proximity to the inferior alveolar canal and cortical plates using cone beam computed tomography among the Saudi population

Objectives:

To evaluate the relationship of the first and second mandibular molar roots to the inferior alveolar canal (IAC) and cortical plates using cone beam computed tomography (CBCT) in the Saudi population.

Methods:

Scans of 60 patients were collected retrospectively from the dental hospital database in King Saud University, Riyadh, Kingdom of Saudi Arabia. Measurements of the right and left first and second mandibular molars for each dental root and the mandibular bone thickness were determined. The position of the IAC was estimated using axial, coronal, and sagittal views. Three examiners performed the measurements independently.

Results:

The mean distance between the root apices of the mandibular molars and the IAC ranged from 1.68-4.79 mm, whereas the mean distance from the outer surface of the buccal cortical plate to the buccal root surface ranged from 2.33-6.72 mm. Similarly, the mean distance from the outer surface of the lingual cortical plate to the lingual root surface ranged from 2.62-4.80 mm. Finally, the mean distance from the outer surface of the lingual cortical plate to the outer surface of the buccal cortical plate was 11.93-13.19 mm.

Conclusion:

The measurements reported in this study may be of value to practitioners treating Saudi patients, as they need to be familiar with the distance of the mandibular first and second molars in relation to the IAC and surrounding cortical plates to accurately assess and plan endodontic surgeries, surgical extractions, and implant placements.

A Novel Orthodontic Extraction Method for Removal of Impacted Mandibular Third Molars in Close Proximity to Inferior Alveolar Nerve

PURPOSE

The present study has proposed a novel orthodontic extraction method with a removable appliance to avoid inferior alveolar nerve (IAN) injury during impacted mandibular third molar removal.

PATIENTS AND METHODS

In the present study, 16 patients were enrolled and divided into 2 groups per patient choice. In the orthodontic extraction group (n = 8), a removable appliance was first applied to move the root tips away from the IAN, and the tooth was subsequently removed. In the traditional extraction group (n = 8), each patient had the tooth removed immediately by the same surgeon.

RESULTS

All teeth were extracted successfully. All 8 patients in the orthodontic extraction group had had their impacted mandibular third molar removed without IAN injury after surgery. In contrast, 4 patients in the traditional extraction group had experienced transient IAN injury, and the symptoms persisted for 2 to 8 weeks. None of the patients experienced permanent IAN damage.

CONCLUSIONS

Orthodontic extraction with a removable appliance to separate the IAN and impacted mandibular third molar could be a good alternative treatment option to avoid IAN injury in high-risk cases.

Nerve Injury After Surgical Excision of Mandibular Third Molars Under Local Anesthesia: An Audit

Background

Injury of the inferior alveolar nerve (IAN) sustained during surgical removal of an impacted lower third molar may cause paresthesia of the lower lip, chin, lower gingivae and anterior teeth. Lingual nerve (LN) injuries may result in ipsilateral paresthesia of the anterior two thirds of the tongue, mucosa of floor of mouth and lingual gingivae. A close anatomic relationship between the roots of the third molar and mandibular canal places the IAN at risk of damage.

Purpose

The primary aim of this retrospective audit was to ascertain the incidence of IAN and LN damage after mandibular third molar surgery in National Dental Centre Singapore. A secondary aim was to identify the contributory factors for the risk of IAN and LN nerve injury on the basis of the data collected.

Methods

This retrospective audit included 1276 mandibular third molar surgical removals performed in the local anesthesia operating theatre (LAOT) at the National Dental Centre Singapore (NDCS) from April to December 2013. Data included patient details, clinical characteristics, and 1 week postoperative presence/absence of sensory alteration as reported by the patient.

Results

Summary of results- Out of 1276 third molar sites audited, 8 (0.62%) sites had altered sensation of the IAN and 1 (0.078%) had altered sensation of the LN at 1 week postoperative review.

Conclusion

The incidence of IAN injury (0.62%) and lingual Nerve injury (0.08%) after one week from surgery in our audit was low compared to similar studies. This retrospective audit did not show any correlation of nerve injury to age, gender, race, site, angulation of tooth, grade of operator, removal of bone or tooth division. There was no single radiological sign associated with paresthesia, although the most common radiological signs were interruption of the canal line and darkening of the roots.