The effect of mandibular third molar presence and position on the risk of an angle fracture
Fracture of the mandible occurs more frequently than any other fracture of the facial skeleton (Banks P. 1993). This is due to its relatively prominent position in relation to common injuring forces. It has been compared with archery which is strong at its centre and weakest at the end where it breaks often. Mandible fractures occur at various locations like body, angle, condyle, coronoid, ramus and dentoalveolar area. Within which fracture incidence is 38% in body, condyle 29%, angle 25%, ramus 4%, dentoalveolar area 3% and coronoid 1% (Neelima A M 2002). As angle fracture comprises a large percentage of mandible fracture so lot of studies have been conducted in several countries.
The incidence of fracture is affected by several factors including the patients age, sex and socio-economic status as well as the aetiology. The direction and type of force is important in mandible fracture. Fracture mandible may result from direct violence, indirect violence and excessive muscular contraction. Fracture displacement at angle are influenced by medial pterygoid and masseter muscle sling of which medial pterygoid is the stronger component. Fracture in this region have been classified as vertically and horizontal favourable or unfavourable.
The causes of fracture of the mandible are chiefly road traffic accidents, interpersonal violence, falls, sports injuries and industrial trauma. For 30 years after the Second World War road traffic accidents were found to be the major cause of fracture of the mandible accounting for between 35 and 60% of fractures of the facial bones. In Bangladesh Molla M R 1994 reported that the major causes of mandible fracture was road traffic accident (58.4%), the other causes were falls (13.6%), work related (12.8%), sports related (4.8%), assault (0.8%) and pathological fracture (1.6%).
The angle is a unique anatomic subcomponent of the mandible. It serves as the transition zone between dentate and edentate regions and is commonly associated with impacted teeth. This qualities may be associated with an increased risk of fracture at the angle region. The teeth are most important in determining the sites, where fracture occurs. The long canine tooth and partially erupted third molar tooth both represent line of relative weakness.
Mandibular fracture patterns depend on multiple factors, including direction and amount of force, presence of soft tissue bulk and bio-mechanical characteristics of the mandible such as bone density and mass or anatomic structures creating weak areas (Amaratunga N A S 1988).
Since mandibular fractures frequently occur at or near the angle, some investigator felt that this may be related to the presence of an unerupted mandibular third molar. Multiple studies report a 2- to 3-fold increased risk for mandibular angle fractures, when third molars (M3s) are present (Tevepaugh DB et al 1995). According to hypothesis conducted by Reitzik et al in 1978, they showed that the impacted or unerupted third molar (M3) could weaken the mandible because the tooth occupies more osseous space.
In a study by Reitzik et al, experimental fractures were produced in monkeys and showed that mandibles containing unerupted third molars fractured with 60% of force where mandibles containing erupted third molars require 100% force These findings were supported by Lee J T et al 2000. in their studies they showed presence of third molars was associated with increased risk of mandibular angle fractures.
A deeply impacted third molar tooth will make an angle vulnerable to fracture as will do physiological or pathological conditions such as cyst or tumour. Safdar and Meechan concluded through their research that deeply impacted lower thied molar have the highest relative risk for angle fractures. This conclusion was later challenged by a secondary analysis (Dodson TB. 1996). Tevepaugh and Dodson failed to confirm their hypothesis that more deeply impacted M3s increased the risk for angle fracture, possibly due to an inadequate sample size. Using a larger sample size, Lee and Dodson suggested deeply impacted M3s were actually associated with a decreased risk of angle fractures.
However, it is not clear why impacted teeth are associated with an increased risk for angle fractures. The biomechanical argument is that impacted teeth occupy space in the mandible that would otherwise be occupied by bone, thereby reducing the total available bone mass and producing a relatively weaker jaw (Reitzik M 1978).
Because of the continuing controversy regarding the relationship of mandibular third molar presence and position and the risk of angle fracture, this study was designed to clarify the relationship. This study was done in different centre, with adequate sample size with an aim to find out the true relation of mandibular angle fracture and presence and position of the third molar.
In Maxillofacial Surgery Department of Dhaka Dental College and Hospital large amount of injured patient attended both in indoor and outdoor for treatment. A great portion of them sustained trauma in mandible especially in angle and most of them are young and have third molar. In other countries several studies have shown the increased risk of mandibular angle fracture associated with third molar. In Bangladesh no study has done about this issue till now. So this study might help maxillofacial surgeon to take proper decision regarding preventive treatment of trauma prone patient.
In the present studies, the prevalence of mandibular angle fracture is seen on the basis of presence and position of the mandibular third molar. The result is still remains controversial and a lot more studies have been conducted in different countries to resolve the issue. So such a study in our country is an attempt to resolve the issue definitely that might help the maxillofacial surgeons to prophylactically remove mandibular third molars who are prone to trauma as a preventive measurement.
Aims and objectives
To evaluate the cause of mandibular angle fracture.
To observe the relationship between various types of mandibular third molar impactions and their relations with mandibular angle fracture.
To asses the socio-demographic characteristics of mandibular angle fracture.
To evaluate the association between mandibular third molar status and risk of an angle fracture.
Review of Literature
One study conducted by N. Safdar et al in 1995 on relationship between fractures of the mandibular angle and the presence and state of eruption of the lower third molar. The records and radiographs of 200 patients with mandibular fractures were examined. The presence and degree of impaction of lower third molars were assessed for each patient and related to the occurrence of fractures of the mandibular angle. Data were analyzed by chi-square statistic and the Students t test. Their study provided clinical evidence to suggest that unerupted third molar weaken the mandibular angle both quantitatively and qualitatively.
Another study conducted by Joice T. et al in 2000 about the effect of mandibular third molar presence and position on the risk of an angle fracture. Their aim was to asses the relationship between the presence and position of mandibular third molars and angle fractures. A retrospective cohort study design and a sample composed of patients admitted for treatment of mandible fractures between January 1993 and April 1998 were used. Data sources were the patient’s medical records and radiographs. The predictor variables were the presence and position of third molar. The outcome variable was the presence of an angle fracture. Other study variables included age, sex, race, mechanism of injury and fracture location. Mandibular third molar position was grouped into 9 categories based on the Pell and Gregory classification. Their study results confirmed other reports that patients with mandibular third molar present have an increased risk for angle fractures. Furthermore, they also showed that the risk for an angle fracture varied depending on third molar position.
A similar study was conducted in Jordan about the topic that whether mandibular third molar a risk factor for mandibular angle fracture or not. The objective of their study was to evaluate the association of mandibular angle fractures with the presence and state of the eruption of the mandibular third molar. The medical records panoramic radiographs of 615 patients with mandibular fractures were examined. Data were analyzed as previous method .The results of their study showed that the mandibular angle that contains an impacted third molar is more susceptible to fracture when exposed to an impact than an angle without an third molar (Jasser Ma’aita et al 2000).
V. I. Ugboko et al studied about an investigation into the relationship between mandibular third molars and angle fractures in Nigerians in 2000. Their study concluded that angle fractures are more likely to occur in people with unerupted lower third molars than in those in whom they have erupted.
James C. Fuselier et al studied in 2002 in heading do mandibular third molars alters the risk of angle fracture. They used a multicentre retrospective cohort study design and a sample composed of patients treated for mandibular fractures. The predict tor variable were 1) the presence of an mandibular third molar and 2) the position of an third molar classified according to the Pell and Gregory system. The outcome variable was the presence or absence of an angle fracture. Their study sample was composed of 1210 patients. Patients with mandibular third molar present had a 2.1 times greater chance of an angle fracture than did patients without third molars (p<.001). There was a statistically significant variation in the risk for an angle fracture depending on mandibular third molar position. They concluded that in patients who sustain a mandible fracture, the presence of third molars significantly increases the likelihood of an angle fracture. In addition, the risk for an angle fracture depends on third molar position.
A study was conducted in 2002 T. Meisami et al about the impacted third molars and risk of angle fracture. The purpose of their study was to asses the influence of the presence, position and severity of impaction of the mandibular third molars, on the incidence of mandibular angle fracture. A retrospective cohort study was designed for patients presenting to the division of Oral and Maxillofacial Surgery,Toronto General hospital (Toronto, Canada), for treatment of mandibular fractures from January 1995 to June 2000. The independent variables in that study were the presence, position and severity of impaction of third molars. The outcome variable was the incidence of mandibular angle fractures. Hospital charts and panoramic radiographs were used to determine and classify those variables. The study sample comprised 413 mandibular fractures in 214 patients. The incidence of angle fractures was found to be significantly higher in the male population and was most commonly seen in the third decade of life. Their study provided evidence that patients with retained impacted third molars are significantly more susceptible to angle fracture than those without. The risk for angle fracture, however, does not seem to be influenced by the severity of impaction.
David R. et al studied in 2004 about mandibular third molars and angle fractures. They concluded that the presence of mandibular third molars was associated with a 2-8 fold increased risk for angle fractures. Mandibular third molar position was associated with a variable risk for angle fracture. Notably, the deep impactions were not associated with an increased risk for fracture.
Beate P. Hanson et al studied in 2004 about the association of third molars with mandibular angle fractures: a meta analysis. The objective of their study was to estimate the relative risk of mandibular angle fractures among people with a lower third molar compared with those without a lower third molar. They concluded that the presence of a lower third molar may double the risk of an angle fracture of the mandible. That could have a bearing on any clinical decision on whether to extract the molar.
In 2005 Seiji IIDA et al studied about relationship between the risk of mandibular angle fractures and the status of incompletely erupted mandibular third molar. They showed that incompletely erupted mandibular third molars close to the inferior border of the mandible have a high risk of angle fractures.
Murat Metin et al studied in 2007 about impacted teeth and mandibular fracture. In that retrospective study, they measured the relationship between the presence s of impacted or unerupted teeth in the mandible and mandibular fractures. The records and radiographs of 41 patients with mandibular fracture associated with impacted or unerupted teeth were examined. The presence of impacted or unerupted teeth were assessed for each patient and related to the occurance of fractures of mandible. Their result showed that patients with fracture in the impacted or unerupted teeth area present had a 1.73 times greater chance of an mandibular fracture than patients with no fracture in the impacted or unerupted teeth area. Their was a statistically significant variation in the risk for a mandibular fracture depending on impacted or unerupted teeth presence (x =5.29, p<.05).Their study showed that the presence of an impacted or unerupted teeth significantly increases the likelihood of an mandibular fracture.
In 2008 D. H. Duan and Y. Zhang studied in a heading as ‘Does the presence of mandibular third molars increase the risk of angle fracture and simultaneously decrease the risk of condylar fracture? The incidence of fractures was compared in 700 patients with and without impacted third molars. Their results showed that patients with lower impacted third molar had a lower risk of condylar fracture and a higher risk of angle fracture than those without impacted third molar when injured by moderate trauma force.
Type of Study:
Cross Sectional Observation.
Period of Study:
July 2009 to June 2010.
Places of Study:
Department of Oral and Maxillofacial Surgery in Dhaka Dental College and Hospital, Bangabandhu Sheikh Mujib Medical University, Shaheed Suhrawardy Medical College and Hospital, Casualty Deptartment of Dhaka Medical college Hospital.
Sample size: 100
Patients attended to OPD or admitted to hospitals with angle of the mandible fracture (Patients having with or without presence or absence of mandibular third molar) irrespective of age and sex.
Recruitment Procedure: Among all patients admitted / attended to hospital with angle of the mandible fracture with or without mandibular third molar. Study subjects were recruited on the basis of inclusion and exclusion criteria.
Patients having mandibular angle fracture with third molar
Patients having mandibular angle fracture without third molar
Age limit of the patients were 17 years to 65 years of both sex
Patients who refused to be included in this study
Patients having pathological angle fracture due to Tumor, Cyst, Peri-apical pathoses, Hyperparathyroidism, Pagets, Osteoporosis and other metabolic conditions.
Age below 17years.
Un-cooperative and psychic patient.
Data were collected by a preformed questionnaire containing
Radiographs – Orthopantomogram.
Clinical records from hospital charts.
100 patients treated for mandibular angle fractures by the Maxillofacial Surgery Department in Dhaka Dental College and Hospital, Bangabandhu Seikh Mugib Medical University, Saheed Suhrawardy Medical College and Hospital, Casualty Department in Dhaka Medical College and Hospital between July 2009 to June 2010. Data on age, sex and etiology of the fractures were collected from case records and radiographs. To asses the predictor variable, Panoramic radiographs were used (Presence or absence of lower third molar, impacted or not impacted) and outcome variable (presence or absence of mandibular angle fracture). In addition, with the help of patient’s hospital charts and OPG, their age gender, type of fracture, radiographic evaluation and type of impaction were assessed.
We used the definition of a mandibular angle fracture given by Kelly and Harrigan: a fracture located posterior to the second molar extending from any point on the curve formed by the junction of the body and the ramus in the retromolar area to any point in the curve formed by the inferior border of the body and posterior border of the ramus of the mandible.
The position of the impacted third molars were analysed according to Pell and Gregory. The horizontal space available for M3 was grouped based on the amount of space as measured between the anterior border of the ascending ramus and the posterior border of the second molar as follows : Class 1, adequate space available; Class 2, inadequate space available ; Class 3 , M3 located all or mostly within the ascending ramus.
The vertical space was classified based on the highest position of the M3 crown as follows: Class A, level at or above the occlusal plane; Class B, between the cemento enamel junction of the adjacent second molar and the occlusal plane :Class C, below the cement-enamel junction.
In addition, the angulation of M3 was measured for all unerupted third molars except root formation. The angulations were defined as angle of intersection between the long axis of the tooth and the mandibular occlusal plane and were classified as distoangular, vertical, mesioangular , horizontal.
Data were analysed with the use of chi- square test. Statistical significance was considered when p < 0.05. Software used is SPSS 16 version for statistical analysis.
Table 1: Distribution of the study subjects by age (n=100)
Table shows the distribution of the mandibular angle fracture patient by age. Among them most of the patients were within the age range between 30 -39 years. Mean age of the subjects was 44.36±21.9 years.
Table 2: Distribution of the study subjects by sex (n=100)
Table shows the distribution of the study subjects by sex. Among them 68% were male and 32% were female.
Figure 1: Distribution of the study subjects by occupation (n=100)
Chart illustrates the distribution of the mandibular angle fracture patients by occupation. Among them most patients (42%) were service holders.
Figure 2: Distribution of the study subjects by cause of injury (n=100)
Figure shows the distribution of the mandibular angle fracture patients by cause of injury. Within 100 patients majority (66%) reported road traffic injury.
Table 3: Status of third molar
|Status of third molar||Frequency||Percent|
Table shows the distribution of the mandibular angle fracture patients by status of third molar teeth. Among 100 patients 75% reported to have third molar teeth and 25% didn’t have third molar teeth. The finding signifies that, Presence of third molar teeth might precipitate the fracture in the angle of mandible.
Table 4: Condition of third molar teeth (n=75)
|Condition of teeth||Frequency||Percentage|
Table shows the distribution of the study subjects by condition of third molar. Among the 75 patients with third molar teeth, 64 (85.3%) had the teeth impacted and in 11 (14.7%) cases the teeth was erupted.
Figure 3: Type of impacted teeth (n=64)
Figure shows the types of impacted teeth in mandibular angle fracture patients. Among the 64 patient with impacted teeth most of them (64.1%) were of mesio-angular type.
Figure 4: Type of erupted teeth (n=11)
Among the 11 patients with erupted teeth, 7 (63.6%) were completely erupted and 4 (36.4%) were partially erupted.
Table 5: Position of impacted teeth.
|Status of third molar||No of patients||Percentage|
Table shows type of impaction and their percentage of fracture.
Table 6: Position of tooth according to radiological finding (n=75)
|Position of tooth||Frequency||Percentage|
|Tooth in fracture||57||76.0|
|Tooth outside the fracture||18||24.0|
Table shows the distribution of the mandibular angle fracture patient by position of teeth in the fracture line. Among them 76% had their tooth in fracture line and 24% had their tooth out of fracture line.
Table 7: Cross tabulation of age and sex with status of third molar
|Status of third molar||c² &
|<= 30 years||12(16.0)||5(20.0)||c²=10.1
|30 – 39 years||37(49.3)||6(24.0)|
|40 – 49 years||07(09.3)||8(32.0)|
|50 – 59 years||09(12.0)||4(16.0)|
|>= 60 years||10(13.3)||2(08.0)|
Statistically significant association between age and status of third molar teeth is present showing that angle fracture patient with third molar teeth are younger than patient without third molar (P< .05). Statistically significant association is also apparent between sex of the patient and the status of third molar illustrating that among the angle fracture patient maximum patients having 3rd molar were male than female (P< .001).
Figure 5: Cause of injury and status of third molar teeth
Figures shows the distribution of the respondents by Cause of injury and status of third molar teeth. Among the mandibular angle fracture patient with third molar teeth 66.7% reported to have RTA, 22.7% suffered assault and 10.7% had fallen from height. In the mandibular angle fracture patient without third molar teeth 64% reported to have RTA, 24% suffered assault and 12% had fallen from height.
The Maxillofacial region (especially head and neck) may frequently uphold trauma due to various factors such as road traffic accidents (RTA), political violence, assault, fall, industrial injury and sport injury. In developing countries like Bangladesh RTA remain the commonest causes of maxillofacial trauma. It is due to overcrowding, unsecured road, violation of traffic rules and unskilled driving. In case of mandible, fracture prevalence is the most in the body of the mandible, it is 38%; then comes condyle 29%; angle 25%; ramus 4%; dentoalveolar 3%, coronoid 1%, that is angle fracture shares a large amount of fracture in mandible.
This study evaluated 100 noted patients with mandibular angle fracture and compares the results of previous studies. Within 100 angle fractured patients 75% have mandibular third molar, majority of the patients were male, maximum patients age was between (30-39) years, their mean age was ( 44.36±21.9) years and road traffic accidents was the main cause of fracture. Among 75 patients with third molar, 85.3% have impacted third molar.
The angle is a unique anatomic subcomponent of the mandible that serves as the transition zone between dentate and edentate regions. Mandible fractures are frequently located in the angle region. The increased frequency of mandibular angle fractures relative to other locations has been hypothesized to be attributable to the presence of mandibular third molars (Ailling CC 1988). In fact, some investigators have advocated removing impacted mandibular third molars to prevent mandibular angle fractures (Peterson L J 1992).
Several factors have been proposed to influence the location of mandible fractures, including site, force and direction of impact, systemic disease, bony pathology, and the presence of impacted teeth. Many reports have also implicated mandibular third molars as a risk factor for mandibular angle fractures (Peterson L J 1993). The purpose of the current study was to evaluate mandibular third molars as a risk factor for angle fracture in collected patients. In human clinical studies, the presence of the M3 has been repetitively shown to be associated with higher relative risk for angle fracture (Safdar N, Meechan JG 1995).
Data of the current study shows that, within 100 patients with mandibular angle fracture 75% have lower third molar teeth and 25% have no third molar. Similar result was found by Joyce T. Lee et al 2000, in their study, among 99 angle fracture patients, 79 had lower third molar teeth. According to V. I. Ugboko et al in 2002, they found within 76 patients with mandibular angle fracture, 65 had lower third molar. An explanation for this relationship is that mandible third molars may weaken the mandible by decreasing the cross-sectional area of bone.
Further exploration of status of the 3rd molar teeth reveals that among the 75 patients with third molar teeth, 64 (85.3%) had the teeth impacted and in 11 (14.7%) cases teeth was erupted. According to study by N Safdar and J. G Meechan in 1995 they showed that within total angle fractured patients 68.8% had impacted third molar, the remaining were either erupted or absent. In angle fracture patients as maximum patients contain impacted third molar, it may suggests an increased chance of fracture among subjects with impacted 3rd molar. Possible explanation is that impacted teeth may be associated with an increased risk for angle fractures which was reported by Reitzik et al. their report showed that impacted teeth occupy space in the mandible that would otherwise be occupied by bone, thereby reducing the total available bone mass and producing a relatively weaker jaw (Reitzik M, Lownie J F, Cleaton-Jones P, et al 1978).
Of the patients with impacted teeth, 64.1% were of mesio-angular type, 12.5% were of disto-angular type, 7.8% were of vertical type and 15.6% were of horizontal type. In present study, mesioangular impaction is more (64.1%). One study conducted by T Meisami et al in 2002, percentage of mesioangular impaction was more in their study. As the similar study conducted by Jasser Ma’aita at el in 2000, their result shows that vertical impaction is more (59%) in their study, they have demonstrated that increased type of vertical impaction causes mandible more susceptible to fracture. This result differs from their study, it may be due to our small sample size and short duration of time. So another study taking the control group can be carried out further.
Regarding age distribution it was found that highest percentage of (43%) of patients were in the age ranges between 30 to39 years with mean age 44.36+ 21.9 years. According to study by Ma’aita mean age of angle fracture patient was 33.2 years. The collected patients were mostly male (68%). The findings accords with most of the findings of the studies where sex was considered as variables (Jasser Ma’aita 2000). Statistically significant association of age and sex with status of third molar teeth is present showing that mandibular angle fracture patients with third molar teeth are younger than patients without third molar teeth (P<.05) and among such patients more male were found to have 3rd molar than female. (P< .001).
Regarding cause of injury leading to the fracture, among the mandibular angle fracture patient with third molar teeth, 66.7% reported to have RTA, 22.7% suffered assault and 10.7% had fallen from height. In the mandibular angle fracture patient without third molar teeth, 64% reported to have RTA, 24% suffered assault and 12% had fallen from height. The study by Jasser Ma’aita in 2000 showed the main cause of fracture was road traffic accidents (60.5%) followed by falls (19.7%). No statistically significant relation was evident between cause of fracture and 3rd molar status in this study.
Data regarding occupation didn’t show any specific pattern to suggest particular occupation as risk. Among them 42% were service holders, 13 % were engaged in business 23% were housewives and 22% were engaged in other occupation.
Data of the current study shows that among the patient with angle fracture, 76% had their 3rd molar tooth in fracture line and 24% had their tooth out of fracture line.
The ultimate causative factor the relationship between 3rd molar presence and increased risk of angle fracture in mandible is still not been documented, However decreased osseous structure within the mandibular angle region may still thought to be the primary etiology. Popular theory has typically been that the more impacted a tooth, the less is the cross-sectional region of bone in the angle region and therefore less bone is available to resist outside stresses.
The major limitation of the current study is its smaller sample size and absence of control group. However the evidence suggests a significant role of 3rd molar teeth in increasing the risk of fracture in the angle and specially mesioangular type of impaction mostly influence angle fracture. The fact has also been supported by structural phenomenon and biomechanics of the region. Our finding is in line with several other studies done in the field.
Based on the study finding the following conclusions are made.
Presence of 3rd molar teeth significantly increases the risk of fracture at the angle of mandible irrespective of the nature of impact leading to fracture. In angle fracture more patients presented with an impacted teeth, suggesting an increasing likelihood of fracture with the presence of an impacted tooth, particularly of mesio-angular teeth. Position of the tooth also seems to alter the risk of angle fracture.
Suggestion for the further studies
Further study with larger sample sizes with appropriate control is strongly recommended.
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