The purpose of the present study was to estimate the frequency of the occurrence of intraoperative adverse events during the removal of impacted maxillary third molars and to correlate predictive variables. A prospective cohort study was carried out involving patients submitted to at least one surgical removal of an impacted maxillary third molar as part of a line of research on third molar surgery developed at the study university. Predictor variables indicative of the occurrence of adverse events during surgery were classified by their demographic, clinical, radiographic, and surgical features. Descriptive and bivariate statistics were computed. In total, 106 patients fulfilled the eligibility criteria, and 204 surgeries were performed. The mean patient age was 22.8 ± 2.2 years and the ratio of women to men was 3:1. Nine different adverse events occurring during surgery were recorded. These events occurred in approximately 6.9% of cases and were significantly associated with the second molar relationship ( P = 0.008) and periodontal space ( P = 0.05). The study revealed a low frequency of adverse events during the surgical removal of an impacted maxillary third molar. The results suggest that adverse events during surgery are associated with the second molar relationship and periodontal space.
Adverse events are involuntary consequences of health care and occur at an alarming frequency. A large number of these events could be avoided by the adoption of reliable evidence-based practices and the implementation of safety measures, such as the standardization and simplification of procedures and recognition of preoperative factors.
The estimation of possible adverse events is a frequent dilemma for surgeons. Moreover, studies on third molar surgery have focused on the occurrence and treatment of postoperative adverse events, with little consideration given to intraoperative events. An analysis of the PubMed database using the descriptors ‘adverse events’, ‘surgical complication’, and ‘maxillary third molar’ revealed no prospective studies beyond the preventive aspect of the occurrence of adverse events and/or surgical complications. Thus, severe adverse events that require complex management are often reported.
The best approach to adverse events is not to allow them to occur. For this purpose, it is important to develop a model of factors associated with surgical adverse events. Such a model should allow changes to be made during the act of surgery and assist in the decision as to whether the procedure should even be carried out.
Because of the scarcity of scientific evidence on this issue, the aim of the present study was to estimate the frequency of adverse events during the removal of impacted maxillary third molars. The researchers hypothesized that there are predictive variables for the occurrence of adverse events during surgery. The specific aim was to identify and clarify the variables of interest related to such occurrences.
Materials and methods
Study design, location, and eligibility criteria
To address the research purpose, the investigators designed and implemented a prospective cohort study. The study population comprised all patients presenting for the evaluation and management of an impacted maxillary third molar between January and September 2012. To be included in the study sample, patients had to fulfil the following eligibility criteria: (1) indication for surgery under local anaesthesia, and (2) American Society of Anesthesiology (ASA) category I or II. Patients were excluded as study subjects based on the following exclusion criteria: absence of the maxillary second molar, absence of the upper central incisor, absence of the lower central incisor, systemic and/or behavioural disorder that would render local anaesthesia unviable, pregnant or lactating women, recent irradiation, cognitive impairment that would render the comprehension of the study objectives impossible, and non-acceptance of the methodology. All patients signed statements of informed consent, and the study received approval from the university ethics committee.
Interpretation and recording of predictive variables
The predictor variables were categorized into the following groups: demographic (gender, age, and body mass index (BMI)), clinical (maximal mouth opening and associated pathologies), and radiographic (level of occlusal plane, available retromolar space, impaction angle, number of roots, root curvature, tooth relationship with maxillary sinus, relationship with the second molar, depth of the elevator tip, crown width, and periodontal space). Table 1 summarizes the predictor variables and their definitions. Predictor variables were recorded by a single examiner. Further data were obtained from digital orthopantomography (panoramic picture). After the initial examination, the patients were randomly sent to a single previously calibrated senior surgeon who had had no contact with the patients in the pre-selection phase and was blinded to the previously collected data.
|Groups of variables, variable/definition||Classification|
|Age||(1) <25 years|
|(2) ≥25 years|
|BMI, kg/m 2 (weight divided by height squared)||(1) <18.5|
|Associated pathologies (condition associated with the third molar)||(1) None|
|(4) Bone resorption|
|Maximal mouth opening (distance between incisal edges of the upper and the lower central incisor during maximal mouth opening)||(1) <45 mm|
|(2) ≥45 mm|
|Level of the occlusal plane (occlusal plane of the third molar in relation to the second molar)||(1) High: crown of the third molar completely above the cemento-enamel junction of the second molar|
|(2) Medium: larger part of the crown of the third molar between the occlusal plane and the cemento-enamel junction of the second molar|
|(3) Low: larger part of the crown of the third molar below or at the same level as the second molar|
|Available retromolar space (distance between the distal-most point of the second molar crown and the cortex of the maxillary tuberosity)||(1) Sufficient: space greater than or equal to the mesiodistal distance of the third molar|
|(2) Reduced: space greater than half and less than the mesiodistal distance of the third molar|
|(3) Insufficient: space less than half of the mesiodistal distance of the third molar|
|Impaction angle (winter), measured in degrees (angle between the crossing of the long axis of the third molar and the occlusal plane)||(1) Horizontal, 0–30°
(2) Mesioangular, 31–60°
(3) Vertical, 61–90°
(4) Distoangular, >90°
|Number of roots||(1) One fused root|
|(2) ≥2 roots|
|(3) Tooth germ|
|Root curvature (angle between the long axis of the crown and the root of the third molar)||(1) Non-dilacerated, <10°|
|(2) Dilacerated, >10°|
|Tooth relation with maxillary sinus (distance, mm, from the root apex to the cortex of the maxillary sinus)||(1) Negative: apex with no contact with the cortex of the maxillary sinus|
|(2) Positive: apex in contact with the cortex of the maxillary sinus|
|Relation with the second molar (relation of the third molar crown with the second molar)||(1) No contact|
|(2) Contact with the crown alone|
|(3) Contact with the crown and the root|
|(4) Contact with the root alone|
|Depth of the elevator tip (length of the perpendicular line from the cemento-enamel junction of the distal face of the second molar and elevator application point)||(1) 0–3 mm|
|(2) 4–6 mm|
|(3) ≥6 mm|
|Crown width (mesiodistal distance of the third molar crown compared with the second molar)||(1) Non-bulbous: equal to or less than that of the second molar|
|(2) Bulbous: greater than that of the second molar|
|Periodontal space (status of the space between the root of the third molar and the alveolar cortex)||(1) Radiolucent: fully radiolucent space|
|(2) Mixed: radiolucent and radio-opaque|
|(3) Radio-opaque: totally radio-opaque space|
Interpretation and recording of adverse events
Adverse events (primary outcome variable) in the present study were defined as any undesirable, unintentional result affecting the patient at the time of surgery that would not have occurred if the operation had gone as planned, requiring additional management beyond that originally planned by the surgeon (yes/no). To avoid subjectivity and imprecision, qualitative terms (secondary outcome variables) such as small complication or large complication were purposely avoided in the reports. The revised definition suggests that an adverse event is not a fixed reality.
Record of adverse events
Immediately prior to surgery, the surgeon wrote down the entire surgical plan for the case, from incision to suturing. During the procedure, an examiner verified the technical manoeuvres used for the extraction and recorded any intraoperative event that required management beyond that which was originally planned. The duration of surgery from incision to suturing was also recorded (operative variable).
All procedures were carried out in the same surgery unit using the same instruments, high-speed drills (80,000–150,000 rpm, conical bit number 702), and materials. Local anaesthesia was administered (3% lidocaine with noradrenaline at 1:50,000) for the regional blocking of the greater palatine and posterior superior alveolar nerves following aspiration. No sedation method was used in the present study. All extractions were carried out with the standardized general method for the surgical removal of impacted third molars as described by Farish and Bouloux.
Descriptive and bivariate statistics were computed, and a model was adjusted to explain each of the predictor variables. A model was first adjusted for each predictor variable considering all independent variables with a level of significance up to 15% ( P < 0.15). Adjustment of the final model was performed using a backward stepwise procedure, maintaining only those variables with a level of significance up to 5.0% ( P < 0.05). SPSS version 15.0 software (SPSS Inc., Chicago, IL, USA) was used for the statistical calculations.