Experimental fractures of monkey mandibles

Relationship between the risk of mandibular angle fractures and the status of incompletely erupted mandibular third molars

BACKGROUND

Several studies have shown the increased risk of mandibular angle fractures associated with incompletely erupted mandibular third molars. But only a few reports analysed in detail the relationship of the status of eruption of this tooth and this type of fracture.

OBJECTIVES

The purpose of this study was to clarify the influence of the eruption status of incompletely erupted mandibular third molars on the incidence of mandibular angle fractures.

METHODS

Four hundred and thirty-six mandibular halves in 218 patients with mandibular fractures, aged between 15 and 40 years old, were analysed using panoramic radiographs.

RESULTS

The incidence of angle fractures in the mandibular halves with incompletely erupted mandibular third molars was 30.8% and this was statistically significantly higher than that in another group (p<0.0001). Deeply located mandibular third molars clearly showed a higher incidence of this fracture when compared with the adjacent second molar (p<0.0001).

CONCLUSION

The results of this investigation showed that incompletely erupted mandibular third molars close to the inferior border of the mandible have a high risk of angle fractures.

Relationship between lower wisdom tooth position and cyst development, deep abscess formation and mandibular angle fracture

AIM

There is an ongoing controversy about indications for prophylactic removal of third molars. The purpose of this retrospective study was to clarify the risk of preservation of lower third molars.

MATERIAL AND METHOD

In a 5-year period, 316 patients were registered who had received in-patient treatment for deep abscess formation, cyst formation or mandibular angle fracture in relation to lower third molars. A radiological analysis (panoramic radiographs) was performed to determine whether major pathological changes associated with lower wisdom teeth are related to their position. Third molar positions were studied in this in-patient group and in an out-patient group. The latter consisted of 300 consecutive patients with prophylactically removed impacted third molars without any pathology. The relationship between the positions and the different pathological changes associated with impacted lower wisdom teeth was analysed statistically using a new 'position score'.

RESULTS

The study revealed that the highest 'position scores' corresponding to a leading aberrant position correlated significantly with cyst formation. Lower scores corresponding to moderately aberrant or slightly irregular position were found with angle fractures, abscess formation, and in the control group as a whole.

CONCLUSION

This study indicates that prophylactic third molar surgery for teeth with high and strongly elevated 'position scores' is appropriate in order to prevent cyst formation or mandibular angle fractures in a population at risk for facial trauma. In addition to other factors, 'position score' data could be useful for development of a model for predicting severe complications related to (removal of) impacted lower wisdom teeth.

Relationship between the presence of unerupted mandibular third molars and fractures of the mandibular condyle

Previous studies have shown that the presence of unerupted mandibular third molars predisposes the mandible to angle fractures. This study attempted to relate the presence of unerupted mandibular third molars with the incidence of condyle fractures. The authors compared the proportion of fractures in 439 patients who had unerupted third molars or no unerupted third molars. Fractures at the condylar region showed a significantly higher incidence in patients without unerupted third molars than in those patients with unerupted third molars. This study provides solid clinical evidence to suggest that the removal of unerupted mandibular third molars predisposes the mandible to condyle fractures.

Mandibular third molars and angle fractures

PURPOSE

The study purpose was to measure associations between mandibular third molar (M3) status/position and risk for angle fracture.

MATERIALS AND METHODS

We designed a multicenter retrospective cohort study composed of patients who presented for operative management of mandible fractures. The primary predictor variable was M3 (present/absent). The secondary predictor variable was M3 position classified using the Pell and Gregory system. The outcome variable was angle fracture (present/absent). Appropriate univariate, bivariate, and multivariate logistic regression analyses were computed. The level of statistical significance was set at P </=.05.

RESULTS

The study sample was composed of 1,450 subjects with a mean age of 30.6 +/- 10.4 years (range, 2 to 87 years). The risk of an angle fracture with and without M3s was 30.1% and 13.7%, respectively (adjusted odds ratio, 2.8; 95% confidence interval, 2.3 to 3.4; P <.001). Based on the Pell and Gregory classification, varying M3 position was associated with varying risks of angle fracture (P <.001).

CONCLUSION

The presence of M3s was associated with a 2.8-fold increased risk for angle fractures. M3 position was associated with a variable risk for angle fracture. Notably, the deep impactions were not associated with an increased risk for fracture.

Influence of the Incompletely Erupted Lower Third Molar on Mandibular Angle and Condylar Fractures

BACKGROUND

Several studies have shown an increased risk of mandibular angle fractures by the presence of the lower third molar (M3), especially the incompletely erupted M3. The presence of M3s might influence condylar fractures, which is one of the most common fracture sites, as well as the angle fracture.

METHODS

Six hundred ninety-two mandibular sides among 346 patients with mandibular fracture were analyzed. They were classified into two groups according to the presence of incompletely erupted M3s and were analyzed according to fracture site, age, and cause of injury.

RESULTS

Among these patients with mandibular fractures, the frequency of occurrence of the mandibular angle fracture was higher in the group with incompletely erupted M3s (p < 0.0001) and that of the condylar fracture was higher in the group without it (p < 0.001).

CONCLUSION

The result of this retrospective investigation shows that an incompletely erupted M3 decreases the risk of condylar fractures and increases the risk of mandibular angle fractures.

Ballistic Impact to the Forehead, Zygoma, and Mandible: Comparison of Human and Frangible Dummy Face Biomechanics

BACKGROUND

Currently, there is a greater use of nonlethal force in law enforcement and military operations. Because facial injuries have been observed, there is a need to understand the human response to ballistic impacts involving various regions of the face. This study aimed to establish blunt ballistic response corridors for high-speed, low-mass facial impacts to the forehead, zygoma, and mandible, and to determine how these responses compare with those of the frangible Hybrid III headform. Correlation of the human and dummy responses allows injury risk assessment for munitions used in the field.

METHODS

Facial impacts to the forehead, zygoma, and mandible of six cadavers at 42 +/- 10 m/sec were conducted using a 25- to 35-g projectile 37 mm in diameter that was instrumented with an accelerometer to determine impact force. High-speed video analysis determined penetration of the projectile, and autopsy determined the facial fractures. Force and deflection were normalized for the 50% tile response, and corridors were determined for blunt ballistic impacts. Similar tests were conducted on the frangible face of the Hybrid III dummy.

RESULTS

Peak normalized force of 3.5 +/- 0.9 kN on the forehead and 3.0 +/- 1.0 kN on the mandible did not result in fractures, whereas an impact force of 2.3 +/- 0.5 kN on the zygoma caused anterior maxilla fractures. The frangible Hybrid III face developed similar force levels, but with less penetration of the projectile. Its stiffness was 43% greater than that of the cadaver.

CONCLUSIONS

Higher impact force can be tolerated on the forehead and mandible than on the zygoma. Normalized force-deflection and force-time corridors were established for the human response. The frangible Hybrid III face is an effective surrogate for assessing ballistic injury risks, but greater compliance would make it more biofidelic. Initial human tolerance levels of 6.0 kN for the forehead, 1.6 kN for the zygoma, and 1.9 kN for the mandible have been established for ballistic impacts to the face.

An Unusual Traumatic Fracture of the Mandibular Symphysis Resembling Horizontal Osteotomy for Genioplasty

The authors report a rare case of mandibular fracture caused by a flying object, discuss the mechanism of the fracture, and review the literature. The patient was a 40-year-old male soldier in the Self Defense Force (SDF). During a mock battle of the SDF Agency, a shell splinter penetrated his mentum and caused a fracture of the mandibular symphysis that resembled horizontal osteotomy for genioplasty. A horizontal fracture of the mandibular symphysis is very rare, and on clinical inspection, the authors found the general course of the clinical fracture line coincided with the weakest portion of the mandible. A powerful blast can cause an object to become airborne and injure persons in the vicinity, as did the metallic fragments that caused the mandibular fracture in patient reported here. Thus, when examining victims of such traumas, the possibility that a foreign object might have penetrated the body should be kept in mind. A thorough inspection of injuries resulting from explosions is mandatory.

Do mandibular third molars alter the risk of angle fracture?

PURPOSE

In this study, we measured the relationship between the presence of mandibular third molars (M3s) and angle fractures. In addition, the study examined the relationship between M3 impaction level and angle fracture susceptibility.

PATIENTS AND METHODS

We used a multicenter retrospective cohort study design and a sample composed of patients treated for mandibular fractures. The predictor variables were 1) the presence of an M3 and 2) the position of an M3 classified according to the Pell and Gregory system. The outcome variable was the presence or absence of an angle fracture.

RESULTS

The study sample was composed of 1,210 patients. Patients with M3s present had a 2.1 times greater chance of an angle fracture than did patients without M3s (P <.001). There was a statistically significant variation in the risk for an angle fracture depending on M3 position (P <.001).

CONCLUSIONS

In patients who sustain a mandible fracture, the presence of M3s significantly increases the likelihood of an angle fracture. In addition, the risk for an angle fracture depends on M3 position.

Impacted third molars and risk of angle fracture

The purpose of this study was to assess the influence of the presence, position, and severity of impaction of the mandibular third molars, on the incidence of mandibular angle fractures. 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 this 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 these variables. The demographic data included age, sex, mechanism of injury and number of mandibular fractures. 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. Assault remained the most significant aetiological factor. Patients with third molars had thrice the increased risk of angle fractures when compared to patients without (P<0.001). Impaction of third molars significantly increased the incidence of angle fractures (P<0.001). The severity and angulation of third molar impactions were not significantly associated with angle fractures. This study provides 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.

An investigation into the relationship between mandibular third molars and angle fractures in Nigerians

We examined the relationship between the presence or absence of mandibular third molars and angle fractures in Nigerians between January 1976 and July 1997. Information was obtained from patients' case records and radiographs.A total of 490 patients were seen during the study period, 408 of whom (83%) had their third molars present, and 76 of whom had angle fractures. Road traffic accidents (n =304, 62%) were the main cause of the fractures. Of these, 44 (14%) had angle fractures compared with 14/75 (19%) patients in whom the mechanism of injury was a fight or assault.Sixty-five of the 408 patients whose third molars were present (16%) had angle fractures, as did 11/82 (13%) who did not have third molars (p =0.57). Of the 77 patients whose lower third molars were not erupted, 24 (31%) had angle fractures compared with 52/331 (16%) in whom the lower third molars were erupted (p =0.002). These findings suggest that angle fractures are uncommon in this population because of their particular mechanism of injury. In addition, the presence of a lower third molar does not necessarily predispose to fractures of the angle of the mandible. However, angle fractures are more likely to occur in people with unerupted lower third molars than in those in whom they have erupted.

The effect of mandibular third molar presence and position on the risk of an angle fracture

PURPOSE

This study assessed the relationship between the presence and position of mandibular third molars (M3) and angle fractures.

PATIENTS AND METHODS

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 patients' medical records and radiographs. The predictor variables were the presence and position of M3. M3 position was grouped into 9 categories based on the Pell and Gregory classification. The outcome variable was the presence of an angle fracture. Other study variables included age, sex, race, mechanism of injury, and fracture location.

RESULTS

The eligible sample was composed of 437 patients, of whom 367 had data available for analysis. Patients with M3 present had a 1.9 times (95% confidence interval = 1.2 to 2.9) greater chance of an angle fracture than patients without M3s (P = .003). There was a statistically significant variation in the risk for an angle fracture, depending on M3 position (P = .049).

CONCLUSION

The study results confirm other reports that patients with M3 present have an increased risk for angle fractures. Furthermore, it also showed that the risk for an angle fracture varied depending on M3 position.

Is the mandibular third molar a risk factor for mandibular angle fracture?

OBJECTIVES

The objective of this study was to evaluate the association of mandibular angle fractures with the presence and state of the eruption of the mandibular third molar (M3).

METHODS

The medical records and panoramic radiographs of 615 patients with mandibular fractures were examined. The presence or absence and degree of impaction of the M3 were assessed for each patient and related to the occurrence of fracture of the mandibular angle. Data were also collected for age, sex, mechanism of injury, number, and location of mandibular fracture. Data were analyzed by a chi-square statistic test and Student t test.

RESULTS

The incidence of mandibular angle fracture was found to be significantly greater when an unerupted M3 was present (P <.05). Of the 426 patients with an M3, 127 (29.8%) had angle fractures. Of the 189 patients without an M3, 25 (13.2%) had angle fractures.

CONCLUSIONS

The results of this study showed that the mandibular angle that contains an impacted M3 is more susceptible to fracture when exposed to an impact than an angle without an M3.

A study of sports-related mandibular angle fracture: relation to the position of the third molars

Mandibular angle fractures have been considered attributable to the presence of unerupted third molars. We examined the relationship between the incidence of sports-related mandibular angle fractures and the presence of a mandibular third molar with emphasis on the position of the third molar. The incidence of angle fracture was significantly higher in the sports-related injury group than in the group with fracture due to other causes (P < 0.05). The incidence of angle fracture in the athletes with higher impaction scores was significantly higher than that in the subjects with higher scores who did not have sports-related fractures (P < 0.05). The percentage of rugby athletes with third molars was significantly higher than that of those without third molars (P < 0.001), and a high proportion of young athletes (89.5%) was considered to belong to a potential high-risk group for angle fractures. Our findings suggest that mandibular angle fractures are influenced by the presence and characteristics of the third molar in sports-related injuries.

Relationship between fractures of the mandibular angle and the presence and state of eruption of the lower third molar

OBJECTIVES

This study attempted to relate the incidence of fractures at the mandibular angle with the presence and state of eruption of lower third molars.

STUDY DESIGN

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 Student's t test.

RESULTS

The incidence of angle fractures was found to be significantly greater when unerupted lower third molars were present (p < 0.001). Bilateral unerupted third molar teeth predisposed to a fracture at the angle significantly more than unilateral unerupted third molars (p < 0.01). Furthermore, the amount of bony space occupied by an unerupted third molar tooth directly related to the weakness of that area of bone (p < 0.001).

CONCLUSIONS

This study provides clinical evidence to suggest that unerupted third molar teeth weaken the mandibular angle both quantitatively and qualitatively.

Are mandibular third molars a risk factor for angle fractures? A retrospective cohort study

PURPOSE

Anecodotal reports suggest that the presence of mandibular third molars predispose the mandible to angle fractures. The purpose of this study was to evaluate mandibular third molars as risk factors for angle fractures in a patient sample with fractured mandibles.

MATERIALS AND METHODS

The medical records and panoramic radiographs of a patient cohort with mandible fractures was retrospectively reviewed. Data were collected for the following variables: age, sex, race, mechanism of injury, number and location of mandible fractures, and the presence and position of the mandibular third molars.

RESULTS

Of the 73 patients with mandibular third molars, 30 (41.1%) had angle fractures. Of the 28 patients without mandibular third molars, 3 (10.7%) had angle fractures (P = .004).

CONCLUSION

The results of this study demonstrate that patients with fractured mandibles and mandibular third molars are 3.8 times more likely to have an angle fracture than patients without mandibular third molars.

Orofacial injuries and international rugby players' attitudes to mouthguards

This is the first such study of British rugby and the third yet published, the other two involving the 1984 Australian Wallabies and the 1987 United States Eagles. The report shows that while all 30 players believed mouthguards provided local protection, nine did not wear a mouthguard. Only one of the 21 who wore a mouthguard was willing to play without it, while eight mouthguard wearers felt mouthguards should be compulsory for adult rugby players. Twelve players had previously sustained an orofacial injury playing rugby which required treatment, only one of whom was wearing a mouthguard at the time. The full results are presented and compared with those of the previous two reports.

Mouthguards and the role of sporting team dentists

With the increased popularity of contact sports and encouragement to participate at an early age, the role of the dental profession in relation to prevention of dental and other orofacial sporting injuries has become more important. Provision of professionally-fitted (custom) mouthguards for persons involved in contact sports, recognition of the 'injury prone dentition', and expertise in immediate management of dental injuries form the basis of sports dentistry. The aim of this review paper is to increase professional awareness and interest. Additionally, it is hoped to stimulate dentists to become involved as sporting club consultants.

Impacted third molars: a contributing factor in mandibular fractures in contact sports

Studies have shown that the presence of impacted third molars places the mandible at increased risk for fracture. Individuals participating in high contact sports are subject to maxillofacial trauma; therefore, participants with impacted third molars are at increased risk for fractured mandibles. Three cases are reviewed to illustrate this problem.

Yield point of monkey mandible

Stress-strain curves were developed for monkey mandibles using an Instron Tensiometer. It was found that the yield point (elastic limit) was proportional to the breaking load.

Fractures of the mandible involving the impacted third molar tooth: an analysis of 47 cases

An attempt is made to correlate mesio-angular, horizontal, disto-angular and vertical tooth impaction with the incidence, displacement and management of fractures in the region of the mandibular third molar. Evidence was taken principally from a radiographic study of 47 cases of fracture of the mandible at this site. No particular single mandibular third molar angulation showed itself more commonly in this series of fractures. However, fractures involving unerupted mesio-angular third molard tended to remain undisplaced and could, therefore, be treated by simpler measures.