• Maxillofacial Plastic and Reconstructive Surgery
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• v.28 no.1
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• pp.49-57
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• 2006

Mandibular fractures have higher incidence rate compared to facial bone fractures because of relatively prominent form. Specially, mandibular angle fractures were known as common fracture site because of morphological anatomic structure. The mandibular third molar appears to be the most frequent impacted tooth. The mandibular third molar have influence on mandibular angle fractures according to it's eruption state. Also, the mandibular angle fracture including the third molar may influence on post operative infection whether the third molar is in impacted or extracted state when reduction of fracture site is operated. The presence or absence and degree of impaction of the mandibular third molar were assessed for each patient and were related to the occurrence of the mandibular angle fracture. The extraction or non extraction of the mandibular third molar were related to the occurrence of the post operative infection in the reduction of mandibular angle fractures. In the presence of mandibular third molar, the possibility of mandibular angle fractures were relatively common. When viewing the mandibular third molar at occlusal plane, the possibility of mandibular angle fractures were high in the class C group. The possibility of mandibular angle fractures were high in the mesial angulation and partial impaction. There was a statistically significant difference(P<0.05). In complete erupted mandibular third molar, the possibility of post operative infection occurs quite often, but there was no statistical significant difference(P>0.05). In the extracted or non extracted of mandibular third molar, the post operative infection showed no statistical significant difference(P>0.05). With the results mentioned above, mandibular third molar was significantly more susceptible to mandibular angle fracture. In the reduction of mandibular angle fracture, it was recommended that mandibular third molar should be extracted especially in case of pericoronitis, periodontitis and other infections.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.2
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• pp.161-167
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• 2006

Objectives: Pericoronitis was the most common indication for mandibular third molar surgery and there are no universally acceptable predictive criteria for pericoronitis occurrence. This study was designed to analyze the correlation of the pericoronitis and the eruption state of the mandibular third molar using panoramic radiographs statistically. Materials and Methods: 218 patients whose chief complaint was the extraction of the mandibular third molar were examined. The presence and absence of pericoronitis, age, sex, position of extraction site, angulation, impaction degree, position to the anterior border of mandibular ramus, distance between distal cementoenamel junction of second molar and mesial cementoenamel junction of the mandibular third molar were assessed. Then the correlation of pericoronitis and the eruption state of the mandibular third molar were analyzed by Student's t-test and chi-square test. Results: There was no correlation between Pericoronitis and age, sex, position of the mandibular third molar. The angulation(P=0.005), impaction degree(P=0.043), relation with anterior border of mandibular ramus(P=0.003), distance between distal cementoenamel junction of second molar and mesial cementoenamel junction of the mandibular third molar(P<0.05) were correlated with pericoronitis. Conclusions: The occurrence of the pericoronitis can be predicted by the eruption state of the mandibular third molar such as angulation, impaction degree, relation with anterior border of mandibular ramus, distance between distal cementoenamel junction of second molar and mesial cementoenamel junction of third molar.

• Imaging Science in Dentistry
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• v.37 no.4
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• pp.197-203
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• 2007

Purpose: To provide diagnostic information by evaluation of the positional relationship between the mandibular third molar and the mandibular canal. Materials and Methods: Eighty-nine mandibular third molars were classified as mesioangular, horizontal, vertical, distoangular groups. The distances between the mandibular third molar and the mandibular canal were measured in cone-beam computed tomographs. The height and width ratios of distances from the mandibular third molar and the mandibular canal to the mandibular inferior border and to the lingual cortical plate were calculated. Results: The vertical and buccolingual distances between the mandibular third molar and the mandibular canal were 0.03 mm, 2.96 mm in the mesioangular, 0.37 mm, 3.38 mm in the horizontal, -1.50 mm, 1.38 mm in the vertical, -1.10 mm, 4.20 mm in the distoangular group. There were significant differences in vertical (P < 0.05), but not in buccolingual (P>0.05). The height and width ratios of distances on the mandibular third molar were 47.1 %, 36.1 % in the mesioangular, 47.4%, 34.4% in the horizontal, 37.0%, 46.7% in the vertical, 40.9%, 37.4% in the distoangular group. There were significant differences between the mesioangular and the vertical group, and the horizontal and the vertical group in height ratio (P < 0.05), and also between the mesioangular and the vertical group in width ratio (P < 0.05). The height and width ratios of distances on the mandibular canal showed no significant differences between groups (P > 0.05). Conclusion : The mesioangular group showed the nearest distance between the mandibular third molar and the mandibular canal vertically. The root apex of the mandibular third molar was positioned more buccally in the vertical group than in the mesioangular group.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.12 no.1
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• pp.57-61
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• 1982

The author has made a study on the classification of the mandibular 3rd molars of Korean youths through dental radiography by means of Pell & Gregory's classification and on the prevalence of the dental caries of distal surface of the mandibular 2nd molar adjacent to the mandibular 3rd molars turned anteriorly. The results are as follow; 1. It was found that the largest case number was class I (272 cases, 52.9%) in the relation of the tooth to the ramus of the mandible and 2nd molar. 2. The mesio-angular position was the largest number (239 cases, 46.5%) in the relation of the long axis of the impacted mandibular 3rd molar to the long axis of the 2nd molar. 3. The mesio-angular position of class I was the largest number (140 cases, 27.2 %) in the relation of the tooth to the ramus of the mandible and 2nd molar and the long axis of the impacted mandibular 3rd molar to the long axis of the 2nd molar. 4. The average angle of the long axis of mandibular 3rd molar in mesioangular position or horizontal position to the occlusal plane was 143° 5. Mandibular 3rd molar with lesion such as dental caries or pericoronitis was 73 cases (14.2). 6. The caries incidence rate of the distal surface of the 2nd molar was about 3.1%.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.2
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• pp.242-255
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• 1999

The purpose of this study was to estimate the morphology and the size of permanent mandibular molar in Korean Adult. The 100 dental college students with a normal dentition and without any dental prosthesis and severe caries were selected for this study The subjects were taken impression to make study model. On the study model, the 5 dentists measured those sizes and estimated morphological structures with a calipers, a Boley gauge and a protractor. The results were as follows; 1. The clinical crown height, width, thickness and the other anatomical structures had symmetrical relationship between the left and right mandibular molar. 2. In the clinical crown height aspect, the buccal crown heights always were higher than the lingual crown height. The heights of the each surface, the buccal or lingual surface, were gradually decreased from the 1st molar to the 2nd molar and the difference on the buccal surface was higher than that on the lingual surface. 3. In the clinical crown width aspect, the mesiodistal measurement of the mandibular 1st molar was higher than that of the mandibular 2st molar. 4. In the clinical crown thickness aspect, the mesial buccolingual measurement was highest on the mandibular 1st molar and the distal buccolingual distance was lowest on the mandibular 2nd molar. This distal thickness of the mandibular molar always was higher than that of the mesial half. 5. The well-developed mesiobuccal groove of the 1st molar was observed more often than that of the 2nd molar. The buccal pit was also observed more frequently at the 1st molar, but the frequency(35%) was not high. 6. The occlusal type according to the number of cusp was almost 5-cusp(98%) in the 1st molar and was also 5-cusp(63%) in the 2nd molar. The frequency of the 6th cusp was 31% in the 1st molar and was 22% in the 2nd molar. The frequency of the 7th cusp was below 2of in the both teeth. 7. In the buccolingual intercuspal distance aspect of the mesial and distal half, the intercuspal distance of distal half was higher than that of the mesial half on the 1st and 2nd molar, but the difference on the 1st molar was higher than that on the 2nd molar. 8. The difference between the widths of the buccal and lingual half was 1.5mm in the 1st molar and 0.8mm in the 2nd molar. Therefore the lingual convergency of the occlusal surface was more higher in the 1st molar. 9. On the mandibular 1st and 2nd molar, the distobuccal external angle was more acute than the mesiobuccal external angle. But the mesiobuccal internal angle was more acute than the distobuccal internal angle. 10. When the mandibular molar was a 5-cusp type, the development of the distal cusp on the 1st molar was better than that on the 2nd molar. The difference between the cusps was around 0.4mm.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.40 no.6
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• pp.278-284
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• 2014

Objectives: This study used cone-beam computed tomography (CBCT) images to categorize the relationships between the mandibular canal and the roots and investigated the prevalence of nerve damage. Materials and Methods: Through CBCT images, contact and three-dimensional positional relationships between the roots of the mandibular third molar and the mandibular canal were investigated. With this data, prevalence of nerve damage according to the presence of contact and three-dimensional positional relationships was studied. Other factors that affected the prevalence of nerve damage were also investigated. Results: When the mandibular third molar and the mandibular canal were shown to have direct contact in CBCT images, the prevalence of nerve damage was higher than in other cases. Also, in cases where the mandibular canal was horizontally lingual to the mandibular third molar and the mandibular canal was vertically at the cervical level of the mandibular third molar, the prevalence of nerve damage was higher than in opposite cases. The percentage of mandibular canal contact with the roots of the mandibular third molar was higher when the mandibular canal was horizontally lingual to the mandibular third molar. Finally, the prevalence of nerve damage was higher when the diameter of the mandibular canal lumen suddenly decreased at the contact area between the mandibular canal and the roots, as shown in CBCT images. Conclusion: The three-dimensional relationship of the mandibular third molar and the mandibular canal can help predict nerve damage and can guide patient expectations of the possibility and extent of nerve damage.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.6
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• pp.640-643
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• 2008

Distal caries of the second molar is common indication for the mandibular third molar surgery and there are no universally acceptable predictive criteria for distal caries of the second molar. To analyze the correlation of the distal caries of the second molar and the eruption state of the mandibular third molar using panoramic radiographs statistically and propose the acceptable guideline for preventive extraction of the mandibular third molar. 786 patients who were extracted the mandibular third molar from 2002 to 2006 at Samsung medical center were examined. The presence and absence of distal caries of mandibular second molar, age, gender, angulation, impaction degree, distance between distal cementoenamel junction of the second molar and mesial cementoenamel junction of the mandibular third molar were assessed. 79.6% of third molars had a mesial angulation of between $40^{\circ}$ and $80^{\circ}$. The mean age of third molar removal for distal caries of second molar was $33.86{\pm}9.81$. The prophylactic removal of a mesio-angular third molar about $40^{\circ}$ and $80^{\circ}$ could prevent distal cervical caries forming in the mandibular second molar.

• Journal of the korean academy of Pediatric Dentistry
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• v.6 no.1
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• pp.53-63
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• 1979

To Study the eruption pattern of the mandibular second permanent molar, the author took 425 cases of Oblique Cephalogram from 6 to 13 years old children and observed the vertical and mesiodistal directional change and tooth axis change. The following results were obtained. : 1. The eruption pattern of the mandibular second permanent molar was changed at about 10.0~10.1 ages or calcification stage IX. 2. At the early stage, the path of eruption of the mandibular second parmanent molar directed upward and forward and after calcification stage IX it changed to the direction of upward. 3. At the early stage, the distance from the distal end of the mandibular first permanent molar to the anterior portion of the ascending ramus was 0.9~1.0 times larger than the mesio-distal diameter of the mandibular second molar, but at the later stage it was increased 1.4 times larger than the mesio-distal diameter of the mandibular second permanent molar.

• Journal of dental hygiene science
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• v.7 no.4
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• pp.275-279
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• 2007

The purpose of this research, which was executed with 200 patients whose chief complaint was the extraction of the mandibular third molar, was to examine the effect that eruption state of the mandibular third molar has on the growth of pericoronitis. The conclusion about distribution of left and right mandibular third molar, angulation, impaction degree, anterior border of mandibular ramus and the interval from mandibular second molar to mandibular third molar was drawn by chi-square test. 1. There was correlation between pericoronitis and position of the mandibular third molar according to age. 2. In angulation of mandibular third molar, mandibular third molar most likely to be afflicted with pericoronitis is mesioangular. 3. The impaction degree between mandibular third molar and the growth of pericoronitis was given in the order of Level a, Level c and Level b. 4. In the anterior border of mandibular ramus with mandibular third molar, pericoronitis was easily generated in the order of Class II, Class I and Class III. 5. The shorter the interval from distal cementoenamel junction of mandibular second molar to mesial cementoenamel junction of third molar became, the more easily pericoronitis was generated.

• Imaging Science in Dentistry
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• v.41 no.3
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• pp.135-137
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• 2011

Impaction of third molar is a common developmental abnormality. However, ectopic impaction of the mandibular third molar in condylar region is an extremely rare condition. This report describes a case of impacted tooth in the mandibular condyle without any associated pathologic condition. Also, this report presents the spatial relationship of the impacted mandibular third molar to the surrounding anatomic structures using cone beam computed tomography.