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.

OBJECTIVE: To investigate the impact of mineralized dentin matrix (MDM) on the prognosis on bone regeneration and migration of retained roots after coronectomy.
METHODS: Patients were divided into three groups based on the type of bone graft after coronectomy: Group C (n = 20, collagen), Group T (n = 20, tricalcium phosphate (TCP) + collagen), and Group D (n = 20, MDM + collagen). CBCT scans, conducted immediately and 6 months after surgery, were analyzed using digital software. Primary outcomes, including changes in bone defect depth and retained root migration distance, were evaluated 6 months after surgery.
RESULTS: After 6 months, both Groups D and T exhibited greater reduction of the bone defect and lesser retained root migration than Group C (p < 0.001). Group D had greater regenerated bone volume in the distal 2 mm (73 mm3 vs. 57 mm3, p = 0.011) and lesser root migration (2.18 mm vs. 2.96 mm, p < 0.001) than Group T. The proportion of completely bone embedded retained roots was also greater in Group D than in Group C (70.0% vs. 42.1%, p = 0.003).
CONCLUSIONS: MDM is an appropriate graft material for improving bone defect healing and reducing retained root migration after coronectomy.
CONCLUSIONS: MDM is an autogenous material prepared chairside, which can significantly improve bone healing and reduce the risk of retained root re-eruption. MDM holds promise as a routine bone substitute material after M3M coronectomy.

OBJECTIVE: 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.
CONCLUSIONS: 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.

OBJECTIVE: 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).
CONCLUSIONS: Mandibular third molar coronectomy is chosen more frequently than surgical removal if molars are class III and position B.
BACKGROUND: Not applicable.

OBJECTIVE: Of the study is to reduce the risk of postoperative neuropathy of the inferior alveolar nerve by improving diagnostic methods, assessment of individual topographic and anatomical features and extraction technique of impacted teeth adjacent to the mandibular canal.
METHODS: According to the CBCT examination, orthopantomography and macroscopic examination of removed third molars roots (n=140) the relative position of the mandibular canal and the roots of the third molars were studied.
RESULTS: Three variants of close mandibular canal and third molars position have been identified. In the lateral and apical nerve position, the root surface depressions were detected. With inter-radicular position fit, the mandibular canal and the nerve bundle form a «bed» in between impacted tooth roots.
CONCLUSIONS: The injury of neurovascular bundle prognosis during extraction with an interadicular mandibular position depends on roots anatomy and their convergence degree. If the interradicular distance is less than the diameter of the mandibular canal, nerve injury during tooth extraction is inevitable, in such cases coronectomy is indicated.
UNASSIGNED: Снижение рисков развития послеоперационной невропатии нижнего альвеолярного нерва путем совершенствования способов диагностики, учета индивидуальных топографо-анатомических особенностей и техники удаления ретинированных зубов с тесным прилеганием к нижнечелюстному каналу.
UNASSIGNED: По данным КЛКТ-обследования, ортопантомографии и макроскопии корней удаленных третьих моляров (n=140) проведено изучение взаиморасположения нижнечелюстного канала и корней третьих моляров.
UNASSIGNED: Выделено три варианта тесного прилегания третьих моляров к нижнечелюстному каналу. При боковом и апикальном прилегании на поверхности зубов выявлены вдавления, сформировавшиеся в результате развития зуба. При межкорневом прилегании нижнечелюстной канал и сосудисто-нервный пучок формируют подобие ложа в межкорневой области ретинированного зуба.
UNASSIGNED: Прогноз развития травмы сосудисто-нервного пучка при удалении зуба с межкорневым прилеганием нижнечелюстного канала зависит от анатомии корней и степени их схождения. В случае, если межкорневое расстояние меньше диаметра нижнечелюстного канала, травма нерва неизбежна при удалении зуба, в таких случаях оправдано проведение коронэктомии.

The study represents a preliminary evaluation of the accuracy of the dynamic navigation system (DNS) in coronectomy of the mandibular third molar (M3M).
The study included participants with an impacted M3M near the inferior alveolar canal. The coronectomy planes were designed before the surgery using cone-beam computed tomography (CBCT) imaging data and then loaded into the DNS program. Intraoperatively, the navigation system was used to guide the complete removal of the target crown. Postoperative CBCT imaging was used to assess any three-dimensional deviations of the actual postoperative from the planned preoperative section planes for each patient.
A total of 12 patients (13 teeth) were included. The root mean square (RMS) deviation of the preoperatively designed plane from the actual postoperative surface was 0.69 ± 0.21 mm, with a maximum of 1.45 ± 0.83/-1.87 ± 0.63 mm deviation. The areas with distance deviations < 1 mm, 1-2 mm, and 2-3 mm were 71.97 ± 5.72 %, 22.96 ± 6.57 %, and 4.52 ± 2.28 %, respectively. Most patients showed extremely high convexity of the surface area located in the mesial region adjacent to the base of the extraction socket. There was no observable evidence of scratching of the buccolingual bone plate at the base of the extraction socket by the handpiece drill.
These results provide preliminary support for the use of DNS-based techniques when extracting M3M using a buccal approach. This would improve the accuracy of coronectomy and reduce the potiential damage to the surrounding tissue.
DNS is effective for guiding coronectomy.

OBJECTIVE: The aim of this in vitro study was to evaluate the effect of a 3D-printed drill sleeve (DS) on the precision and duration of coronectomy sections.
METHODS: Thirty-six trainees and oral surgeons performed 72 coronectomy cuts in a 3D-printed, entirely symmetric mandible model. Coronectomy was performed freehand (FH) on one side and with a DS on the other side. The occurrence of \"too superficial\" (≥ 4 mm unprepared lingual tooth tissue) and \"too deep\" (drilling ≥ 1 mm deeper as tooth contour) cuts and sectioning times were registered.
RESULTS: In 7 cases, the sections were \"too deep\" with FH, while none with DS (OR: 18.56; 95%CI: 1.02-338.5; p = 0.048). The deviation between virtually planned and real cut depths was significantly greater in the FH group (1.91 ± 1.62 mm) than in DS group (1.21 ± 0.72 mm) (p < 0.001). A total of 18 \"too superficial\" buccolingual sections occurred with FH, while 8 cases with DS (OR: 3.50; 95%CI: 1.26-9.72; p = 0.016). Suboptimal sections did not correlate with experience (p = 0.983; p = 0.697). Shortest, suboptimal drillings were most frequently seen distolingually (OR: 6.76; 95% CI: 1.57-29.07; p = 0.01). In the inexperienced group, sectioning time was significantly longer with FH (158.95 ± 125.61 s vs. 106.92 ± 100.79 s; p = 0.038).
CONCLUSIONS: The DS effectively reduced tooth sectioning times by less experienced colleagues. Independently from the level of experience, the use of DS obviated the need for any preparation outside the lingual tooth contour and significantly decreased the occurrence of \"too superficial\" cuts, leaving thinner unprepared residual tooth tissue lingually.
CONCLUSIONS: Coronectomy sections may result in lingual hard and soft tissue injury with the possibility of damaging the lingual nerve. The precision of the buccolingual depth-control can be improved, while surgical time can be reduced when applying a drilling sleeve.

OBJECTIVE: The aim of this research was to evaluate the surgical complications and neurosensory deficits after coronectomy and the complete removal of mandibular third molars.
METHODS: The study sample included patients requiring surgical removal of mandibular third molars. A coronectomy was conducted on 220 teeth showing signs of close proximity to the inferior alveolar canal. A complete extraction was performed on 218 teeth with no risk signs. The patients were evaluated at 1 week and 1, 3, 6, 12, and 24 months after surgery for pain, swelling, neurologic deficit, dry socket, postoperative bleeding, infection, root migration, and eruption.
RESULTS: No significant difference was noted in pain and swelling; however, bleeding and dry socket were significantly higher in the odontectomy group (P = .017). The inferior alveolar nerve deficit was higher in the odontectomy group (3.7%) than the coronectomy group (0.5%) (P = .017). The percentage and distance of root migration of coronectomised teeth at 3, 6, and 12 months were 60% (2.37 ± 0.96 mm), 66% (3.35 ± 0.86 mm), and 74% (3.85 ± 0.93 mm), respectively.
CONCLUSIONS: Coronectomy is a safe procedure and should be performed when the roots are closely associated with the mandibular canal. Although root migration is common, the likelihood of root exposure is low and roots rarely need removal.

OBJECTIVE: 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.
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.
CONCLUSIONS: 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.

Impacted mandibular third molar removal is the most common procedure performed by oral and maxillofacial surgeons. An array of alternative procedures have been suggested, like operculectomy in cases of pericoronitis and coronectomy in certain cases. However, these procedures pose several disadvantages, and we propose a relatively non-invasive \'straight lift technique\'. This technique is specifically useful in straightening abnormally positioned mesioangular third molars as a substitute of complete removal. This can improve tooth function, eliminate the need for surgical intervention, and reduce the risk of complications associated with third molar removal.