Ethical considerations
This study was approved by the Medical Ethical Committee of Amsterdam University Medical Center (reference number 266#21.292) and the ACTA Ethics Committee (reference number 2023-49571). Every patient was given detailed information about the study, and all patients gave signed consent to be included in the study and agreed to appear for the surgery and follow-up session(s).
Eligible patients
All patients included in this study were referred by their dental general practitioner to the Oral and Maxillofacial department of the Amstelland Hospital in Amstelveen, The Netherlands, for MTM management between March 2015 and September 2023. This study included patients of all ages and genders who were scheduled for surgical treatment of an impacted MTM with an increased risk of IANI and who had a (histopathological) diagnosis of a dentigerous cyst or caries. Exclusion criteria were as follows: age of <18 years; failure to show up for postoperative follow-up; history of kidney failure, hematological disorder, or any form of chronic hepatic disease; history of gastric ulcers; diagnosis with uncontrolled diabetes; current pregnancy or lactation; infection with human immunodeficiency virus (HIV); prior radiation therapy to the maxillofacial region; prior organ or marrow transplantation (donors and recipients); and corticosteroid use within 15 days before surgery.
Radiographical assessment
Every patient underwent preoperative radiographic orthopantomography (X-OPT) assessment with the Orthopantomograph ® OP100 D (GE Healthcare, Dental, Tuusula, Finland) used for all recordings before January 22, 2021, and the Sirona Orthophos SL 2D (Dentsply Sirona, Charlotte, USA) used for recordings after January 22, 2021. X-OPT imaging was essential for analyzing the grade of MTM impaction, determined based on Pell & Gregory’s classification [16], the proximity of the MTM to the inferior alveolar canal, and the extent of MTM pathology.
When X-OPT revealed the proximity of the MTM to the inferior alveolar canal, the following seven radiographic signs were used to evaluate the likelihood of IANI [17, 18]:
- darkening of the root
- deflected roots
- narrowing of the root
- dark and bifid root
- interruption of the white opaque line(s) representing the inferior alveolar canal
- diversion of the inferior alveolar canal, and
- narrowing of the inferior alveolar canal.
Patients having one or more of these radiographical indicators were referred for additional computed tomography (X-CT) (Philips Ingenuity 128 CT Scanner, Integrity Medical, Fort Myers, Florida, USA) to visualize the relationship of the MTM to the inferior alveolar canal in all three dimensions [19-21]. The DICOM X-OPT and X-CT files were viewed using Phillips Healthcare software for Picture Archiving and Communication System (PACS, Phillips Healthcare, Phillips IntelliSpace PACS Enterprise 4.4).
Total removal carried a higher likelihood of IANI when X-CT confirmed one of the following three anatomical situations [22-25]:
- lingual position of the inferior alveolar canal relative to the radices of the MTM with flattening of the inferior alveolar canal;
- flattening of the inferior alveolar canal at the contact surface with the MTM’s radices; and
- inter-radicular position of the inferior alveolar canal surrounded by the MTM’s radices.
In this study, when X-CT confirmed one of these situations, coronectomy was performed as an alternative to total removal to prevent IANI [2, 3]. Subjects without increased risk of IANI based on X-CT imaging were treated with complete removal. The radiographical findings and treatment planning were explained to the patients, and treatment was initiated with the patient’s consent.
X-OPT was also used to investigate the pathology of MTMs. In cases where dentigerous cysts were suspected on the MTMs, X-OPT revealed a well-defined unilocular crown-related radiolucency. The radiolucency size was estimated using the ruler measuring tool of the PACS, following the method described by Damante & Fleury [26]. Two perpendicular lines (A-A' and B-B') were drawn on the molar; one across the molar's long axis and the other mesiodistally across the crown. Line C-C' was drawn through the junction of A-A' and B-B' to the widest point of the radiolucency, and the distance in millimeters from the crown's edge to the outermost radiolucency was estimated using the digital ruler in line with C-C' (Fig. 1a). The MTMs were classified into two groups according to the cyst‘s extensiveness: <1 cm and >1 cm. X-OPT was also used to diagnose caries and to determine the extent of the lesion in three grades: A, radiolucency restricted to the enamel; B, radiolucency extending into dentin; and C, radiolucency extending into the pulp (Fig. 1b-d).
Surgical procedure
The surgical procedures were performed using a similar technique by two oral and maxillofacial surgeons with over twenty years of experience in dentoalveolar surgery. Every patient received a mandibular nerve block injection and buccal nerve infiltration. Hospital protocol included standardization of the anesthesia type- and dosage (40 mg articaine/hydrochloride with 0.01 mg epinephrine, administered with a 1.7 mL syringe, Ultracain D-S forte; Sanofi-Aventis, Netherlands BV, Gouda, the Netherlands), type of needle (27 gauge/0.40 × 35 mm), area of administering, temperature, and repository.
Subjects with an increased risk of IANI were treated with coronectomy following the procedure described by Pogrel et al. [4]. In all cases, a triangle flap design was performed. While the MTM was being exposed, subjects suspected to have a dentigerous cyst were biopsied for histological examination. Next, a round surgical bur was used to remove bone overlaying the impacted MTM until the cementoenamel junction was exposed. A steel surgical fissure bur separated the MTM's crown from the roots. The roots were reduced to 3-4 mm below the alveolar crest height. Excessive irrigation with a sterile distilled water solution was used when using the surgical handpiece.
Subjects without increased risk of IANI, based on X-CT, were treated with complete surgical MTM removal using the techniques described by Pell & Gregory [16]. In all cases, a triangle flap design was performed. While the impacted MTM was being exposed, subjects suspected of having a dentigerous cyst were biopsied for histological examination. Next, a round steel surgical bur was used to remove all bone overlaying the impacted MTM until the cementoenamel junction was. A surgical steel fissure bur was used to slice the molar into pieces to be removed. Excessive irrigation with sterile distilled water was used when using the surgical handpiece.
In both treatments, dental follicular soft tissue was eliminated before closing the surgical site, and the postoperative socket was excessively rinsed with sterile sodium chloride to remove debris. The surgical site was primarily sutured with 3/0 Undyed Vicryl Rapide (Ethicon, Somerville, MA, USA). Directly after surgery, the biopsy was documented and sorted for transportation to the histopathological department of the Free University Medical Center Amsterdam, Amsterdam, The Netherlands. Details about the surgery were reported in the digital patient record immediately after the procedure.
Postoperative management
Every patient was given strict postoperative instructions to bite on gauze for 30 minutes and not to rinse their mouth or spit for 24 hours. Subjects were prescribed ibuprofen (Brufen 600 mg, Abbott BV, Hoofddorp, the Netherlands) as an analgesic to take three times daily starting within two hours after surgery, and 0.12% chlorhexidine mouthwash (Perio•Aid Intensive Care ®, Dentaid Benelux BV, Houten, the Netherlands) to use as an antiseptic, for one minute three times daily, for five days, starting 24 hours postoperatively. The patients in the surgical removal group were given a Monoject Curved 412 Tip Syringe (Tyco/Healthcare-Kendall, Mansfield, MA) to rinse the surgical site three times daily starting on postoperative day three. Antibiotics were not provided in a standardized fashion but were instead prescribed only to patients with large cysts, deep caries, and those with a related health status. Postoperative instructions were given verbally and in writing to every patient.
Data collection
After either surgical procedure, patients were assessed for the following postoperative complications:
- sensibility disorder of the IAN
- alveolar osteitis
- surgical site infection
- persistent pain
- excessive bleeding, and
- the need for retreatment.
Postoperative clinical and radiographical follow-up was assessed by the two oral- and maxillofacial surgeons who performed the surgery. Patients were examined for sensibility disorders of the IAN at two-, six- and twelve months postoperatively. A two-point discrimination and static light touch detection test [27] examined sensory abnormalities such as pain, numbness, paresthesia, or dysesthesia. Alveolar osteitis, postoperative infection, bleeding, and persistent pain for longer than one week were examined and recorded after reviewing the patients’ self-reported problems, which participants had agreed to complete. The need for retreatment after coronectomy was analyzed using X-OPT to determine coronal migration of the roots and a periodontal probe was used to assess the roots’ impaction by overlying bone [28].
Data were collected and stored in a database. The variables were primarily used for descriptive purposes and secondary for data analysis. The demographic variables were age, computed as the interval in years between the date of surgery and the participant’s date of birth, and gender, noted as the gender recorded at the participant’s birth (male/female). The medical anamnesis was completed on paper, including the variables of smoking and health status (ASA: American Society of Anesthesiologists). The demographic and medical data at the first consultancy were documented in the digital patient record. Anatomic variables included the MTM’s impaction degree according to the classification of Pell & Gregory [16]: the cyst size estimated with X-OPT (Fig. 1a): and the extent of caries determined with X-OPT (Fig. 1b-d).
Statistical analysis
Fisher’s exact test was used to assess the significance of the relationship between treatment (coronectomy or complete removal) and the incidence of postoperative complications (IANI, alveolar osteitis, surgical site infection, persistent pain, and bleeding). These analyses were performed individually for the dentigerous cyst and caries groups. The relationships between the incidence of postoperative complications and patient- and molar-related factors were statistically assessed using Fisher’s exact test for the factors age, gender, smoking, impaction degree, and the cyst size; and with the Mann Whitney U test for the factors ASA score and extent of caries. The use of postoperative antibiotics was statistically assessed using the Mann-Whitney U test for the factors of ASA score and extent of caries, the Chi-square test for the impaction degree, and Fisher’s exact test for the cyst size.
When the Chi-square test’s statistical outcomes had an expected count of less than 5 in more than 20% of the cells, the P-value of the Fisher’s Exact Test was used to assess the significance. Statistical analyses were performed at the MTM level, not the patient level. For patients who underwent treatment for both left and right pathological MTMs, the analyses included both MTMs. All statistical analyses were performed using the software Statistical Package for Social Sciences-SPSS (IBM Inc., USA) version 27.0. A significance level of less than 0.05 was applied to the probability.