Etiological factors for mandibular fractures in transoperative period of tooth extraction : systematic review Fatores etiológicos para fraturas mandibulares no transoperatório de extração dentária : revisão sistemática

Objectives: to analyze the possible etiological factors associated with mandibular fractures occurring during tooth extractions. Methods the following data were collected: sex, age, the extracted tooth, tooth classification, angulation, level of bone impaction, pathological association, recognized technical errors, instruments used at the time of the fracture, and the surgeon’s experience and specialization, if applicable. An electronic search of the following databases was performed: PubMed/Medline, Lilacs, Embase, and Scopus. The data were tabulated and analyzed using the Chi-square test, a P-value less than 0.05 was considered significant. Results: a total of 80 cases were selected. Sex and age were not statistically significant (P>0.05). The teeth most associated with fractures were the mandibular third molars; however, the location was not significant. Pell & Gregory classes II, B, C, mesioangular teeth, partial bone impaction, teeth related to pathological process, application of Research, Society and Development, v. 9, n. 9, e721997856, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i9.7856 3 excessive strength, extractions with elevators, and non-specialists showed greater association with mandibular fractures during transoperative time (P<0.05).

10 The tooth to be removed at the time of the fracture was reported in 62 cases. The highest incidence of mandibular fractures occurred during the extraction of inferior third molars, which comprised 79.0% of the cases. Of these, the right inferior third molar was associated with the most associated mandibular fractures (26 cases; 41.9%); however, this was not significant when compared to the contra lateral side (37.1%; P = 0.06) ( Table 3). Research, Society and Development, v. 9, n. 9, e721997856, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i9.7856

Classification of the tooth
Pell & Gregory classification was reported in 27 cases. The most frequent classes were II, B, and C (Table 3).
The angulation of the tooth was reported in 30 of the reported cases of mandibular fractures. Mesio-angulation impaction was related to 14 cases of associated mandibular fracture (46.7%) followed by 7 (23.3%) related to vertical angulation (P < 0.05) ( Table 3).
There were 18 cases mandibular fracture was associated with periapical pathology. A follicular cyst or simply an increase of the follicle was associated with 12 cases of mandibular fracture (75.0%; P < 0.05) cases (Table 3).

Type of anesthesia
The type of anesthesia was reported in 24 cases of mandibular fracture associated with dental extraction and the surgery was performed under general anesthesia only in three cases (Table 4). Regarding the technical errors, a significant difference was found between excessive force and absence of bone removal (P = 0.04), as well as excessive force and use of improper instruments (P = 0.04). There was no significant difference between extensive bone removal and excessive force (P = 0.78) and between extensive bone removal and absence of ostectomies or utilization of improper instruments (P = 0.06) (Fig. 2). The type of instrument used during the procedure that resulted in the mandibular fracture was reported in 30 cases. The elevator was used in 21 (70.0%) cases, followed by the forceps (2 cases), chisel plus elevator (2 cases), chisel (2 cases), elevator plus forceps (2 cases), and chisel plus forceps (1 case) (P<0.05) ( Table 4).
Only 22 articles reported whether the surgeon was a specialist, 77.3% of the cases of the reported mandibular fractures occurred when the operator was a not a specialist (P = 0.01) ( fractures that occurred during the transoperative period; and a 3.9:1 ratio, with biggest incidence in the age group of 36-to 60-year for fractures that occurred during the postoperative period. In a review of mandibular fractures after third molar extractions by Pires Research, Society andDevelopment, v. 9, n. 9, e721997856, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i9.7856 age. These authors attributed these results to the major force of the mandible during chewing generated by the male patient in conjunction with a decrease of bone elasticity, osteoporosis, periodontal ligament narrowing, and ankylosis in the elderly. 9 In this review, the sex distribution was similar to that found by Ethunandan et al.,8 with regard to fractures that occurred during the transoperative period, with a male:female patient ratio of 1:1.2 (P > 0.05).
This showed there was no difference between the sexes. however, an analysis of the data in Table 2 showed a balanced distribution between the age groups. Therefore, the literature reviewed in this study showed no evidence for age significance to the occurrence of mandibular fractures during dental extraction.
We found no clinical trials or systematic reviews that exclusively analyzed the relationship between the extraction of a specific tooth and mandibular fractures. The review that provides results closest to this issue was described by Bodner et al., 1 which combined the incidence of fractures during the trans-and postoperative periods. The results were like those found in this review, in which the third molars had the highest association with mandibular fractures during the transoperative period. Regarding the fractures of the mandibular angle, the result of this review also resembles those described in the literature, 1,8,9 in which the difference between the sides is not significant. An interesting finding reported by Farish,12 was the fracture of the coronoid process during the extraction of the maxillary third molar (Table 3).
The literature describes the Pell and Gregory classes II/III and B/C as having the highest association with mandibular fractures during tooth extractions. 8,9,13 The disto-angular position is considered as more difficult to execute and often requires extensive bone removal. 14 Teeth that were totally impacted in bone have the highest incidence of mandibular fracture during extraction. 1,8,9 In this review, classes I/II and B/C were the most prevalent.
Although reports state that the most difficult position for extraction is the disto-angular, 15 the results of this review are consistent with other studies that show that the extraction of the mesio-angular and vertical teeth are more frequently associated with mandibular fractures. 1,8,9,16 This result can be justified by the fact these angulations occur more frequently in the general population. 17 Among the different results found in the literature, partial bone impaction had the highest association with fractures during a procedure (Table 3).
Teeth with a pathological lesion occupy bone space, leading to weakness at the region, which favors the occurrence of a fracture during extraction 5,18 (Table 3).