|Year : 2019 | Volume
| Issue : 2 | Page : 25-29
Association between impacted mandibular third molar and occurrence of mandibular angle fracture: A radiological study
Karpal Singh Sohal, Jeremiah Robert Moshy, Sira Stanslaus Owibingire, Elison N M. Simon
Department of Oral and Maxillofacial Surgery, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
|Date of Web Publication||1-Oct-2019|
Karpal Singh Sohal
Department of Oral and Maxillofacial Surgery, Muhimbili University of Health and Allied Sciences, P.O. Box 65014, Dar es Salaam
Source of Support: None, Conflict of Interest: None
Background: Presence of an impacted mandibular third molar contributes to the weakness of the angle region of the mandible and increases the risk of its fracture. The influence of the presence of impacted mandibular third molars on the occurrence of angle fractures is, however, imprecisely estimated despite boundless research on this subject. Aim: To determine the influence of impacted third molars on the incidence of mandibular angle fractures. Materials and Methods: This was a retrospective study of panoramic radiographs (orthopantomogram [OPG]) that were taken at the Radiology Unit of the Department of Oral and Maxillofacial Surgery, Muhimbili University of Health and Allied Sciences, for 2 years. The collected data included presence of fracture of mandibular angle, presence/absence of impacted lower third molar, and classification of impacted tooth. Data were analyzed using Statistical Package for the Social Sciences software Version 22. A significant level of P < 0.05 was considered. Results: Two-hundred and sixty-eight OPGs were studied. Fracture of the mandibular angle was in about a quarter (25.4%) of them. According to Winter's classification, 44.3% of the impacted teeth had mesioangular inclination, and by Pell and Gregory's classification, 72.2% and 60.8% of the impacted teeth were in Class II and Position A, respectively. In more than half (59.7%) of the fractures of mandibular angle, there was the presence of impacted mandibular third molars. The odds of sustaining fracture to the angle of mandible was about nine times higher in the presence of an impacted lower third molar (odds ratio 8.7, 95% confidence interval: 4.71–16.11). Conclusion: The presence of impacted third molars increases the risk of mandibular angle fracture; however, the classification of impacted tooth by Winter's or Pell and Gregory's methods had no significant role in occurrence of the mandibular angle fracture.
Keywords: Impacted third molar, mandibular angle fracture, panoramic radiograph
|How to cite this article:|
Sohal KS, Moshy JR, Owibingire SS, M. Simon EN. Association between impacted mandibular third molar and occurrence of mandibular angle fracture: A radiological study. J Oral Maxillofac Radiol 2019;7:25-9
|How to cite this URL:|
Sohal KS, Moshy JR, Owibingire SS, M. Simon EN. Association between impacted mandibular third molar and occurrence of mandibular angle fracture: A radiological study. J Oral Maxillofac Radiol [serial online] 2019 [cited 2020 Jan 17];7:25-9. Available from: http://www.joomr.org/text.asp?2019/7/2/25/268237
| Introduction|| |
In spite of being the strongest bone in the maxillofacial region, the mandible is one of the most commonly fractured bones due to its prominence in the face and presence of teeth, which weaken its corticocancellous framework., The pattern of mandibular fractures depends on multiple factors, including direction and amount of force, presence of soft tissue bulk, and biomechanical characteristics of the mandible, such as bone density and presence or absence of teeth., Although generally the mandible is a strong bone, some of its regions such as the mandibular angle, the mandibular condyle, and the parasymphysis are considered to be mechanically fragile.
The angle of the mandible is quite vulnerable due to the fact that it forms the junction between the ramus and the body and is influenced, to a great extent, by the masticatory sling of muscles attached to its medial and lateral aspects. In addition, it is the region where unerupted or partially erupted mandibular third molars are usually nested. By occupying an area that should be filled with bone, these teeth affect the local distribution of traumatic forces, which might render the region more susceptible to fractures.
The influence of impacted mandibular third molars on the occurrence of angle fractures is imprecisely estimated, despite boundless research on this subject. Several studies have reported that the presence of mandibular third molar contributes to the weakness of the angle region of the mandible and increases the risk of its fracture by twofold to fourfold., The presence of an unerupted mandibular third molar is associated with an increased risk of fracture of the mandibular angle, based on the hypothesis that there is a decrease of bone and absorption of the impact in this area.,, Yet still, other studies have failed to confirm the relationship between the third molar position and the risk of mandibular angle fractures.
Despite the existing controversy, no studies have been carried out in Tanzania to investigate this debate. Therefore, this study was designed to determine the influence of the presence, position, and angulation of impacted third molars on the incidence of mandibular angle fractures.
| Materials and Methods|| |
This was a retrospective study of panoramic radiographs (orthopantomogram [OPG]) that were taken over 2 years. The radiographs were obtained from the archives of the Radiology Unit of the Department of Oral and Maxillofacial Surgery, School of Dentistry, Muhimbili University of Health and Allied Sciences (MUHAS). All projections were made with the same radiographic equipment (Instrumentarium Dental OP200 D [Tuusula-Finland] with the maximum KVP of 85, mA = 16, 110–230 VAC, 50/60 Hz, and all radiographs were taken by the same radiographer. The images were exported and saved in Joint Photographic Experts Group file, and no adjustment of contrast, brightness, and magnification was performed. All the images were reviewed by two expert oral and maxillofacial surgeons under conducive identical conditions.
A mandibular angle fracture was considered when a fracture line was located posterior to the second molar and at any point on the curve formed by the junction of the horizontal and the anterior border of the ascending ramus of the mandible. While the Pell and Gregory's classification was used to classify the ramus and occlusal position of the mandibular third molars, the Winter's classification was used to classify their angulation.,
The inclusion criteria included all OPGs of patients with mandibular fractures taken within the study period. The exclusion criteria were images with pathological fracture of the mandible and presence of incompletely formed third molars.
To ensure efficiency and consistency, two researchers independently examined a sample of radiographs and Cohen's Kappa statistics were performed. There was almost perfect agreement between the two examiners in reporting the presence of fractures (κ = 0.842 [95% confidence interval (CI), 0.542–1.142], P < 0.001) and a substantial agreement in reporting the presence of impacted teeth (κ = 0.7 [95% CI, 0.316–1.084], P < 0.007).
During data collection, the right and left sides of the mandible were assessed and considered separately. The information that was collected included the presence of fracture of mandibular angle, presence/absence of lower third molar, and presence/absence of an impacted lower third molar. Furthermore, the angulation, the vertical position in relation to the occlusal plane, and the horizontal position relative to the ramus of the mandible for the impacted tooth were recorded.
The data obtained from this study were entered in the computer and analyzed using Statistical Package for the Social Sciences software Version 22 (IBM Corp. Released 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp). Statistical analysis was done using Chi-square test and Z-test for proportions and significant level of P < 0.05 was considered statistically significant. Ethical clearance was obtained from the MUHAS Research and Ethical Committee. Permission to conduct this study was sought from the Department of Oral and Maxillofacial Surgery, MUHAS.
| Results|| |
OPGs of 12,348 patients were taken during the study period, in 262 (2.12%) of which there were radiological features of mandibular fractures. Unilateral fractured sites on the mandible were observed in 246 (93.9%) OPGs and the rest (6.1%) had bilateral fractured sites. The right and left sides of the mandible were considered separately, hence a total of 278 sites were studied. Of these sites, the third molar was present in 269 (95.1%) sites. Impacted mandibular third molars were found in 79 (29.4%) sites and 72 (25.4%) sites had fracture of mandibular angle [Figure 1].
|Figure 1: Orthopantomogram showing mandibular angle fracture (red arrow) in the presence of and impacted mandibular last molar (yellow arrow)|
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According to the Winter's classification, 35 (44.3%) impacted teeth had mesioangular inclination, and by Pell and Gregory's classification, 57 (72.2%) and 48 (60.8%) impacted teeth were in Class II and Position A, respectively [Table 1].
|Table 1: Percentage distribution of impacted lower 3rd molar according to different classifications. (n=79)|
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The presence of impacted mandibular third molars was associated with more than half (43, 59.7%) of the fractures of mandibular angle. A statistically significant association between the occurrence of fracture of the angle of mandible and presence of an impacted mandibular third molar (P < 0.001) was observed. The odds of sustaining fracture to the angle of the mandible was about nine times higher in the presence of an impacted mandibular third molar (odds ratio 8.7, 95% CI: 4.71–16.11).
The association between the presence of fracture of the angle of the mandible with the presence of mandibular third molar, the angulation, the relative depth of the impacted tooth, and the relation of tooth to ramus is shown in [Table 2].
|Table 2: Presence of mandibular angle fracture in relation to presence of lower third molar and impacted lower 3rd molar|
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| Discussion|| |
This study was carried out at the only oral and maxillofacial unit which receives patients with mandibular fractures from Dar es Salaam city and most of the nearby regions. It is the biggest public facility with dental imaging facilities in the country. The X-rays and other patients' records are digitalized and stored in a secured computer system which assures quality and security.
The merits of the study include the fact that the sample was obtained from a huge pool of panoramic radiographs, independent examination of radiographs was done by qualified oral and maxillofacial surgeons, and two different systems of classification of impacted teeth was used to study not only the influence of angulation but also the depth of impaction on occurrence of mandibular angle fractures.
The mandibular angle has been described as a transitional zone between the mandible's dentulous and edentulous parts and the area where impacted teeth are most commonly found. Due to the presence of the lower third molars which are considered to cause a reduction in bone mass, this region is considered to be prone to fractures.,, Understanding the role of the lower third molars in the mandibular fractures is paramount in providing insight to the prevention, clinical approach, and management of patients at “risk.”
In some studies, the presence of impacted mandibular third molar was seen to increase the risk of fracture of the mandible by two to four-folds., Remarkably, in the current study, the odds of sustaining fracture to the angle of the mandible was about nine-folds higher in the presence of an impacted lower third molar [Figure 1] and [Figure 2]. This retrospective radiological study demonstrates a greater incidence of angle fractures in patients with impacted mandibular third molars, thus emphasizing its importance in the occurrence of mandibular angle fractures. The rationale behind this finding could be attributable to the fact that lower third molars weaken the mandibular angle by reducing the total available bone mass in the region.,,
|Figure 2: Orthopantomogram showing mandibular angle fracture (red arrow) in the presence of and impacted mandibular last molar (yellow arrow) on the left side, and a radiolucent lesion on the distal aspect of lower right second molar (green arrow) in the presence of an impacted mandibular last molar|
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The partially erupted third molars disrupt the cortical integrity of the external oblique ridge which weakens the mandibular angle, thus decreasing the resistance to angle fractures. Superficially impacted third molars, therefore, are associated with an increased risk of angle fracture compared to deeply impacted molars. In the current study, however, the association between mere presence of mandibular third molar and presence of fracture of the angle of the mandible was not statistically significant (P = 0.357). Furthermore, the angulation, the relative depth of the impacted tooth, and the relation of tooth to ramus had no statistically significant association with occurrence of fracture of the angle of the mandible.
Nevertheless, the pattern of mandibular fractures cannot be explained solely on the basis of an impacted mandibular third molar, but consideration should be put on other factors such as age and sex of the patient, anatomy of the mandible, and etiology of the fracture. Panneerselvam et al. studied the influence of mandibular gonial angle in occurrence of angle fractures and concluded that individuals with high gonial angle are at a greater risk of sustaining mandibular angle fractures. Considering that other relevant factors may play a causative or modifying role in the occurrence of mandibular angle fractures, the available evidence from this study may not sufficiently determine whether third molar presence is the main causative factor for mandibular angle fractures. Hence, a decision for prophylactic extraction of a third molar should be made on a case-by-case basis rather than as a protocol.
| Conclusion|| |
The present study showed that the presence of impacted third molars increases the risk of occurrence of mandibular angle fracture significantly; however, the class/type of impacted tooth by both Winter's or Pell and Gregory's methods did not seem to play a significant role.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]