Discussion
Before their operations the three patients did not have mandibular pathologies or lesions or systemic disease that would compromise osseous structural integrity. They reported that they had undergone very difficult surgery to remove left mandibular M3s (third molars) (under local anesthesia, which had been performed by three different dentists who had more than 10 years of professional experience.
A distinct cracking noise, swelling in the mandibular angle region and pain were reported by the patients during chewing approximately 3 weeks after surgery.
At admission to our clinic, they presented with clinical signs and symptoms typical of mandibular angle fractures: swelling, occlusal alteration, pain, and functional reduction in opening their mouth.
Panoramic radiographs showed the fracture lines in the sites of extraction of the left inferior M3s, with evidence of their configuration and the position of the osseous fragments. All fractures were oblique, unfavorable (mesiodistal orientation), parallel to the long axis of the tooth removed, and without dislocation of the fragments. In two cases a CT study was also utilized. Panoramic radiographs executed before the M3 surgery were also available to evaluate radiological parameters such as tooth spatial position (dental angle), crown position and degree of impaction, according to Winter’s and Pell and Gregory’s classifications. The analysis of impacted teeth before surgery (Table
1) showed, respectively: mesioangular variety, class II-C; mesioangular variety, class II-B; and vertical variety, class II-C.
Table 1
Features of impacted teeth
1 | 3.8 | Mesioangular | II | C | 7 |
2 | 3.8 | Mesioangular | II | B | 6 |
3 | 3.8 | Vertical | II | C | 8 |
We have treated the fractures with open surgical reduction, IF by titanium miniplates and IMF in normal occlusion using elastic bands, removed after 6 weeks.
The patients were recommended a soft diet for another 4 weeks. Panoramic radiographs, taken after 4 days, 3 and 6 months, 1 and 3 years postsurgery, revealed good evolution of osseous repair and complete structural recovery. Patients also showed a good functional recovery of mandibular movements and mastication. In one case (Case 3), on request of the patient the titanium miniplate was removed 16 months after surgery.
The removal of the inferior wisdom teeth is one of the most common procedures for oral and maxillofacial surgeons. Common complications of this procedure include alveolar osteitis (dry socket), secondary infection, neurological injuries, and hemorrhage. Iatrogenic damage or luxation of the second molar and locked trisma are less common complications. Frequent postoperative events are edema and swelling of the soft tissues, and pain. Excessive force for the mobilization of the impacted tooth can cause an incomplete or a complete iatrogenic intraoperative mandibular fracture, a rare but severe complication [
13].
Pathological (late) mandibular fracture after M3 surgery is more uncommon but it is a major event, sometimes complicated. There are 94 cases reported in the literature (Table
2); cases associated with osseous pathologies such as osteomyelitis or any local and systemic diseases that may compromise mandibular bone strength have not been included [
15].
Table 2
Cases of late fractures of mandibular angle after lower third molar surgery reported in the literature
| 1971 | 3 |
Haunfelder and Tetsch [ 2] | 1972 | 4 |
| 1980 | 4 |
| 1984 | 1 |
Litwan and Goetzfried [ 5] | 1987 | 4 |
| 1988 | 4 |
| 1997 | 13 |
| 2000 | 28 |
| 2000 | 6 |
| 2002 | 10 |
| 2005 | 17 |
Some elements that represent predisposing factors, related factors and risk are reported below. Certainly the excessive weakening of the mandibular angle, compared with the bone condition after routine M3 surgery, plays a decisive role. The following factors should be considered by the surgeon in the pre-operative time:
Dental mass and relative volume of impacted tooth. In our clinical experience there are cases in which an impacted tooth occupies a mandibular space of more than 50%.
Type and class of tooth bone inclusion. The risk for total inclusions (class II-III, type C) in which the M3 occupies a greater volume of bone and its removal requires ostectomies more generous than those for partial inclusions is twice that of partial inclusions. This implies a significant weakening of mandibular bone structure.
Age of patients. Osborne
et al. [
16] reported that 68% of patients included in his study were less than 25 years; Sisk
et al. [
15] and Goldberg
et al. [
17] indicate an average age, respectively, of 19 and 19.3 years. The incidence of complications of lower M3 surgical removal increases significantly after the third decade of life, in relation to the lower elasticity and compliance of the bone structure, and the frequent ankylosis of the impacted tooth; this makes the surgical procedure more difficult. In the cases reported by Harnisch [
1], Iizuka
et al. [
7] and Wagner
et al. [
11], the average age at which surgery of M3 was performed was 49 ± 3 years and for these authors there is an increase in the incidence of fractures and their possible risk, especially in males with full dentition, for those patients older than 40 years. By contrast, in some studies no difference in incidence between patients who are 40 years old or older and those under 40 years emerges [
18].
Side. The late fractures are more frequent in the left side than in the right side (for example as in the 70% of the patients reported by Wagner
et al.). Most surgeons are right-handed and their control of the left surgical area is difficult; they have a poor view of the impacted 3.8, which makes it difficult to calibrate the forces applied on the mandibular structure [
11].
Time event. Reports of the time at which the highest incidence of fracturative event occurs in the postoperative period include: in the second and third week (67.8% of 28 cases), with an average of 13 days [
8]; in the first, second and fourth weeks (64.7% of 17 cases), with an average of 19 ± 4 days [
11]. In our three cases, the fractures occurred 20, 22 and 25 days respectively after surgery with an average of 22.3 days. However, the event usually occurs within the first 4 weeks postsurgery [
8]. In this period, in fact, the effect of surgery decreases and the patients feel better and begin to chew more easily, but in the surgical site the granulation tissue is replaced by connective tissue and in some cases two-thirds of the osteoid and bone tissue does not appear before the 38
th day [
17]. So, after surgical removal of M3, especially if an extensive ostectomy has been performed, the mandibular angle region is not able to bear the normal masticatory loads from the second to the fourth week.
Gender. Late fractures occur because patients restart the full activity of chewing too early in relation to the osseous structural conditions. Men are more affected because they generally have greater muscular strength than women and they produce higher peak levels of biting forces than women [
19].
All these aspects are usually not considered because of the low frequency of late mandibular angle fractures. Accordingly, after M3 surgical removal, surgeons do not give patients appropriate instructions on eating behavior. The regime of a soft diet should be extended beyond the end of the phenomena related to the intervention [
11].
Conclusions
Pathological (late) fractures of the mandibular angle after lower M3 surgical removal are an infrequent event [
1‐
11]. The real percentage of late fractures is more difficult to define.
The preexistence of pathological bone alterations that cause a weakening of the mandibular structure such as periodontal disease, recurrent pericoronitis, osteoporosis, osteitis, and osteolytic lesions, that are more frequently present in patients who are 40 years or older, should also be considered.
The degree of tooth impaction and the ratio of tooth space to mandibular area are factors that indicate whether it is important to make an accurate preoperative diagnosis, obtained by panoramic radiography, but especially by CT Dentascan (CTD) or Cone Beam CT (CBCT), to avoid pathological (late) fractures of the mandibular angle. In fact, these advanced diagnostic methods show accurately in all planes of space, with axial scans and tridimensional reconstructions, the dental anatomy, the position of the impacted tooth and the ratio of tooth volume to mandibular angle volume. We utilize CTD or CBCT with all patients who are candidates for surgery of lower M3. In fact, it is also very important to always evaluate the relationship between lower M3 with the mandibular canal, regarding possible injuries of the alveolar nerve that could expose the surgeon to clinical and legal problems.
In conclusion, in cases of lower M3 surgical removal, it is appropriate that the surgeon:
a)
before surgery, makes a proper assessment of the case and explains to the patient that, besides the usual complications, there is the possibility of a pathological (late) fracture of the mandibular angle that could occur during chewing;
b)
during surgery, uses proper instrumentation, pays special attention to the procedure for 3.8 removal because it is usually more difficult than 4.8 surgery, performs a surgery that is conservative as possible, and does not exercise excessive force on the bone;
c)
after surgery (especially after a difficult operation with severe bone removal and impairment), explains to the patient the importance of an appropriate food style for an adequate period of time (for at least 4 to 5 weeks).
The possibility that the patient will not follow these recommendations must often be considered a determinant factor for a fracturative event. Surgeons should also explain to the patient how to recognize the symptoms of a late fracture and the need to treat it surgically.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
TC designed and coordinated the work and was the main surgeon who collected the data and corrected the manuscript. TB analyzed and interpreted the patient data regarding the anamnesis. DDF was a major contributor in writing the manuscript. SS supervised the translation of the manuscript. EP wrote the bibliography. PC prepared the images and revised the article. LJ supervised the discussion and the conclusions. All authors read and approved the final manuscript.