Coronectomy: A Surgical Option for Impacted Third Molars in Close Proximity to the Inferior Alveolar Nerve—A 5-Year Follow-Up Study

Residual enamel removal to improve outcomes of mandibular third molar coronectomy: A single-center retrospective cohort study

This study aimed to analyze post-coronectomy complications, chronological root survival rate (success rate) using Kaplan-Meier analysis, and postoperative radiographic signs for root extraction. A total of 555 mandibular third molar coronectomies were clinically and radiologically evaluated (mean follow-up period, 27.2 months; range, 1 month to 10.5 years). Complications were observed in 22 (4.0%) cases. Temporary inferior alveolar nerve damage was observed in one (0.2%) case, and 21 (3.8%) retained roots required extraction between 1 and 64 months after coronectomy due to dry socket (two cases, 0.4%), primary non-wound closure (10 cases, 1.8%), secondary root exposure (seven cases, 1.3%), and submucosal root eruption (two cases, 0.4%). Residual enamel after coronectomy was more significantly found on 13 (61.9%) of 21 extracted roots than on 30 (5.6%) of 534 surviving roots. Kaplan-Meier analysis revealed an overall survival rate of 93.8% at 5 years and 92.2% at 10 years. The 5-year survival rates differed significantly (p < 0.001) between the enamel-free (97.0%) and residual enamel-attached (58.3%) roots. The Cox proportional hazards model showed a hazard ratio of 20.87 (95% confidence interval, 8.58-50.72). The long-term outcomes of coronectomy were satisfactory, and a higher success rate is expected when the enamel is completely removed during coronectomy.

The success rates and outcomes of mandibular third molar coronectomy: 167 cases

PURPOSE

The purpose of this study was to assess success rates and to report complications of coronectomy of mandibular third molars (M3M), including intra-operative failure, pain, infection, dry socket, inferior dental alveolar (IAN) and lingual nerve (LN) injuries and re-operation rates.

METHODS

Retrospective analysis of 167 coronectomies completed between January 2017 to December 2022 was undertaken.

RESULTS

The success of coronectomy was 93%. Intra-operative failure was reported to be 3.6% (n = 8). Complications accounted for pain (15%, n = 24), infection (9%, n = 15) and dry socket (3.6%, n = 6). Three patients required removal of M3M root at 3 months (n = 2) and 24 months (n = 1), accounting for 1.8% re-operation rate. A total of number of patients who suffered a nerve injury was 12; three of these were permanent (LN - 1.2%, n = 2; IAN - 0.6%, n = 1), nine were temporary (IAN - 1.2%; n = 2, LN - 2.4%; n = 4; site not specified - 1.8%, n = 3). No patients with intra-operative failure and re-operation suffered IAN or LN injury post-operatively.

CONCLUSION

Coronectomy offers a successful strategy for management of high risk M3M. The treatment outcomes can be improved with careful case selection and adjusting surgical technique, including assessment of root morphology, incomplete crown sectioning technique and avoidance of lingual retraction. Reporting of coronectomy success as a factor of surgical outcome, presence or absence of permanent IAN injury, persistent symptoms or any other long-standing complications (such as LN injury), and the need for re-operation accounting for root migration status may be a useful tool to measure coronectomy outcomes.

Third Molar Coronectomy vs Total Removal in Second Molar Periodontal Healing

OBJECTIVES

The objective of this randomised controlled trial was to compare the periodontal healing at the distal of the adjacent second molar after coronectomy or surgical removal and the surgical morbidities of the 2 techniques.

METHODS

This is a pilot study of a split-mouth randomised clinical trial comparing the periodontal healing of the adjacent second molar after coronectomy or total removal of lower third molars, which was registered with the University of Hong Kong Clinical Trial Centre as HKUCTR-2948 on 21 February 2020. Cone beam computed tomography (CBCT) scans were taken preoperatively and at 6 months postoperatively. Changes in the bone level from the cemento-enamel junction, periodontal probing depth (PPD), and clinical attachment level (CAL) at the distal of the adjacent second molar were compared. Surgical morbidities in terms of pain, infection, neurologic deficit, root exposure, and need for second surgery for removal were assessed.

RESULTS

Forty patients (22 male, 18 female) with mean age of 26.7 years were evaluated at 6 months postoperatively. Both coronectomy and total removal groups demonstrated statistically significant reduction in PPD and CAL. There was an alveolar bone gain of 1.28 ± 0.88 mm in the coronectomy group and 1.13 ± 0.73mm in the control group, which was statistically significant (P < .001 for both groups).

CONCLUSIONS

Early findings show the periodontal healing at the adjacent second molar of coronectomy was as good as that of total removal of lower third molar. There were no differences in terms of surgical morbidities between both groups.

Surgical outcomes of the surgical techniques following management of iatrogenic trigeminal nerve injuries: A systematic review

Objective

To investigate the effectiveness of the microsurgical treatment in restoring full sensory recovery following trigeminal nerve injuries caused by iatrogenic oral and maxillofacial surgical interventions.

Methods

A detailed search was conducted on the Cochrane central register of controlled trials, Medline and Embase. Clinical studies with at least twelve months of follow up were included and assessment of risks of bias was made using the Robbin I assessment tool.

Results

Six studies were identified in the searches which include 227 patients. The lingual nerve was the most common injured nerve, followed by the inferior alveolar nerve. Third molar removal was the most frequent cause of nerve injury, followed by root canal treatment, pathology excision, coronectomy, orthognathic surgery, dental implants and then local anaesthetic injections. Overall, surgical interventions for nerve injuries showed neurosensory improvement postoperatively in the majority of patients.

Conclusion

Direct neurorrhaphy is still the gold-standard technique when the tension at the surgical site is minimal. Promising results have been noted on conduit applications following traditional repair or grafting. Further research is needed on the efficacy of allografting and conduit applications in nerve repair.

Benefits of Coronectomy in Lower Third Molar Surgery: A Systematic Review and Meta-analysis

PURPOSE

The purpose of this study was to measure and compare coronectomy versus extraction in patients at increased risk for inferior alveolar nerve (IAN) injuries associated with third molar removal in terms of IAN injury and other complications.

METHODS

The review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses checklist. We conducted a comprehensive literature search across six databases and the gray literature from July 15 to August 01, 2022. We employed Rayyan software to identify and remove duplicate articles to ensure data integrity. Our research followed the strategy patient (P), intervention (I), comparison (C), outcome (O), and study (S): (P) patients needing lower third molar surgery at higher risk of IAN injury; (I) surgery options, coronectomy or complete extraction; (C) comparisons included reduced risks of nerve injuries, postoperative complications (pain, infection, alveolitis), and increased risks of reoperation, root migration, and extraction; (O) desired outcomes were preventing nerve injuries and reducing other surgical complications; and (S) observational study designs (cohort, case-control). Excluded from consideration were studies involving teeth other than lower third molars, as well as reviews, letters, conference summaries, and personal opinions. To gauge the certainty of evidence, we employed the Grading of Recommendation, Assessment, Development, and Evaluation instrument, selecting the most current papers with the highest levels of evidence for inclusion. The primary outcome variable of our study centered on evaluating the incidence of IAN injury, and secondly, the lingual nerve (LN) injury, the postoperative pain, infection, localized alveolitis, the necessity for surgical reintervention, root migration, and extraction. These assessments were carried out with respect to their chosen operative technique for managing third molars, either coronectomy or extraction, as predictor variables. We also considered covariates such as age, gender, and the presence of systemic diseases in our analysis to account for potential confounding factors. The pooled data underwent rigorous analysis utilizing an inverse variance method with both random and fixed effect models by the "metabin" function in the R program's meta-package. Additionally, we assessed the risk of bias in the selected studies by utilizing the Joanna Briggs Institute's Critical Appraisal Checklist for Studies Reporting Prevalence Data and the Critical Appraisal Checklist for Case Reports.

RESULTS

Of the 1,017 articles found, after applying the inclusion and exclusion criteria, 42 were included in this study (29 cohort and 13 case-control studies), including 3,095 patients from 18 countries. The meta-analysis showed that coronectomy reduced the risk of IAN injury [OR (Odds Ratio): 0.14; 95% CI (confidence intervals): 0.06-0.30; I2 (inconsistency index) = 0%; P = .0001], postoperative pain (OR: 0.97; 95% CI: 0.33-2.86; I2 = 81%; P = .01), and alveolitis (OR: 0.38; 95% CI: 0.13-1.09; I2 = 32.2%; P = .01) when compared to complete tooth extraction. However, it also highlighted a greater risk of reintervention (OR: 5.38; 95% CI: 1.14-25.28; I2 = 0.0%; P = .01).

CONCLUSIONS

This study has demonstrated that coronectomy is associated with a decreased risk for IAN injury and decreased pain and localized alveolitis when compared to complete tooth extraction. However, it is essential to acknowledge the higher likelihood of requiring reintervention with coronectomy. Therefore, clinicians should carefully consider the advantages and potential drawbacks of both techniques and tailor their choices to the unique clinical circumstances of each patient.

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.

What is the Incidence of Late Complications Associated With Lower Third Molar Coronectomy? 10-Year Follow-Up Results

PURPOSE

Coronectomy is an operation to manage impacted third molars (M3s) considered at high risk for mandibular nerve injury but long-term outcomes are still lacking. The purpose of this study was to estimate the risk of late complications occurring within 10 years following lower M3 coronectomy.

METHODS

The investigators designed a prospective cohort study and enrolled a sample of 94 patients treated with coronectomy of third mandibular molars at the Unit of Oral and Maxillofacial Surgery of the University of Bologna, from 2009 to 2012. This follow-up study included all of the patients from the original study who completed 10 years of follow-up. The primary outcome variables is postoperative late complication occurring between 5 and 10 years after coronectomy coded as present or absent. Late complications were defined as root exposure, nerve injury, pulpitis, periapical infection, and reoperation. The secondary outcome variable was probing pocket depth. Covariates examined were age, smoking and type of M3 impaction. Descriptive statistical analyses were performed.

RESULTS

The inception cohort was composed of 94 subjects who had 116 coronectomies (k) completed. The study cohort was composed of subjects with 10 years of follow-up and included 48 subjects (k = 60) with a mean age of 28.99 ± 8.9 years. Between years 5 and 10 of follow-up, 2 subjects (4%) have complications; all root exposures diagnosed at years 8 or 9 after surgery. In another case root removal was required for orthodontics reason. No case of nerve injury to the inferior alveolar nerve occurred, and no periapical infection was observed around the residual roots. The mean 10-year probing pocket depth was 3.31 ± 0.92 mm (1,66-5,66 mm). There were too few complications to identify risk factors for late complications.

CONCLUSIONS

Within all the limitations of this study, the results of this prospective study imply that coronectomy is a useful surgical technique for the treatment of M3s at high neurological risk, to avoid nerve injury to the inferior alveolar nerve. In addition, after coronectomy, retained roots did not develop late infection or periapical infection in the long term. However, in a few cases, removal of retained roots was required at 10 years, due to root migration in the oral cavity. The risk for late complications is uncommon, but persistent.

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.

Does the Coronectomy a Feasible and Safe Procedure to Avoid the Inferior Alveolar Nerve Injury during Third Molars Extractions? A Systematic Review

This systematic review aimed to review the literature on the coronectomy technique and evaluate the incidence of success and complications as a surgical approach for inferior third molars. Online databases were searched for data on the frequency of inferior alveolar nerve damage, lingual nerve damage, root migration, pain, infection, dry socket, and extraction of the remaining root, and data on the necessity of reintervention were also extracted. Randomized clinical trials, controlled clinical trials, prospective cohort studies, and prospective and retrospective studies with or without the control group were intercepted. This systematic review was registered in PROSPERO (CDR 42020135485). Sixteen papers analyzed 2176 coronectomies in total, and only five of them were judged as appropriate according to methodological quality assessment. The incidence of inferior alveolar nerve injury was documented in 0.59% of the procedures, lingual nerve injury in 0.22%, infection 3.95%, dry socket 1.12%, extraction of the root 5.28%, and reintervention 1.13%. The pain was the most reported, in 22.04% of the population. This study provides an overview of the clinical success and complications of coronectomy, and their prevalence. A coronectomy may be considered a low-risk procedure and an option for treatment to avoid potential damage to nervous structures. However, patients should still undergo a full screening and evaluation of postsurgical procedures.

Three-dimensional assessment of root migration and rotation patterns after coronectomy: bone-embedded roots versus soft tissue-covered roots

In this study, a three-dimensional evaluation was performed to explore differences between bone-embedded and soft tissue-covered roots after mandibular third molar (M3M) coronectomy. Patients were recruited according to the results of cone-beam computed tomography, 6 months after coronectomy. Completely bone-embedded M3Ms were assigned to group B, while completely soft tissue-covered M3Ms were assigned to group S. Data were recorded using digital software. A total of 213 M3Ms in 181 patients were investigated, of which 170 were assigned to the two study groups. Age was the primary factor influencing root migration (P<0.001). The smaller the degree of angulation of the M3M, the more likely was the root complex to rotate distally (r=-0.37, P<0.001). The depth of the impacted M3M contributed to the regeneration of new bone (P≤0.008). The length of the root complex (odds ratio 0.82, P=0.048) and distance from the root to the alveolar crest (odds ratio 1.23, P=0.026) were two critical factors influencing whether the root complex was bone-embedded. Ensuring that the length of the root complex is <7.6mm and the distance between the root and alveolar crest is ≥5mm were both found to be critical to the remaining root being completely bone-embedded and thus preventing eruption and the need for secondary surgery.

Computer-aided three-dimensional assessment of periodontal healing distal to the mandibular second molar after coronectomy of the mandibular third molar: a prospective study

Background

The periodontal healing distal to the mandibular second molar (M2M) after coronectomy of the M3M has shown controversial results. We aimed to combine a digital method with cone-beam computed tomography (CBCT) and estimate periodontal healing of M2M after M3M coronectomy. An accurate and stable indicator in three dimensions was also explored tentatively.

Methods

Patients with a M3M in contact with the inferior alveolar canal were included. CBCT was applied immediately after coronectomy (baseline) and 6-months later. Data were investigated with digital software for registration. Previously reported and coronectomy-related factors were included for univariate and multivariate analyses.

Results

A total of 181 patients (213 M3Ms) completed 6-month follow-up. Significant reduction in the distal intra-bony defect (DBD) depth of the M2M was shown (1.28 ± 1.24 mm, P < 0.001). DBD depth of the M2M at baseline was the most influential factor (r = 0.59), followed by preoperative M3M condition, age, rotation and migration of the root complex. Remaining enamel (OR = 6.93) and small retromolar space (0.67) contributed to re-contact of the root complex and M2M. Bone volume regenerated in the distal 2 mm was associated significantly with DBD-depth reduction (r = 0.74, P < 0.001).

Conclusions

Bone volume regenerated in the distal 2 mm of the M2M denoted stability of distal periodontal healing of the M2M. DBD depth at baseline was the most influential factor for healing of a DBD of the M2M after M3M coronectomy. The remaining enamel and a small retromolar space could contribute to re-contact of the root complex and the M2M.

Trial registration

China Clinical Trial Center, ChiCTR1800014862. Registered 10 February 2018,

Does the Use of Cone-Beam Computed Tomography Before Mandibular Third Molar Surgery Impact Treatment Planning?

PURPOSE

We aimed to investigate whether cone-beam computed tomography (CBCT) alters the treatment decision for impacted mandibular third molar (M3M) surgery when the third molars show proximity to the inferior alveolar canal (IAC) on panoramic radiography (OPG) and to examine surgeons' confidence in the various treatment options.

METHODS

We performed a retrospective study evaluating a series of randomized OPG and CBCT images and answering a set of questions regarding impacted M3Ms. The anatomic risk factors studied included the proximity of M3M roots to the IAC, vertical relationship between the M3M and the IAC, and interruption of the IAC cortex by M3M roots. The primary outcome variable was the treatment decision of whether to observe, extract under local anesthesia, extract under general anesthesia, or perform coronectomy. The secondary outcome variable was confidence in the proposed treatment plan. The χ² test was used to compare proportions and to test the differences in the treatment plan according to the studied independent variables. Binary logistic regression was used to determine the effect of anatomic factors. P < .05 was considered statistically significant.

RESULTS

The study sample consisted of 132 impacted M3Ms in 71 patients. No significant differences in the proposed treatment plan were found when the imaging modalities (OPG and CBCT) were compared (P > .05). Examination of CBCT enabled detection of anatomic risk factors (P < .001). Binary logistic regression showed the absence of IAC cortex interruption to be the most significant determinant toward planning for extraction on OPG (odds ratio, 3.1; P < .005) and on CBCT (odds ratio, 5.0; P < .001). Surgeons were more confident when planning for extraction (P < .001).

CONCLUSIONS

The use of CBCT provides a better understanding of the anatomic relationship between M3M roots and the IAC. However, experienced surgeons dealing with impacted M3Ms with evidence of proximity to the IAC on OPG can decide on the treatment modality without CBCT.