• Imaging Science in Dentistry
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• 제43권4호
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• pp.219-225
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• 2013

Purpose: The purpose of this study was to determine the prevalence of missing and impacted third molars in people aged 25 years and above. Materials and Methods: The study sample of 3,799 patients was chosen randomly from patients who visited Pusan National University Dental Hospital and had panoramic radiographs taken. The data collected included presence and impaction state, angulation, and depth of impaction of third molars, and radiographically detected lesions of third molars and adjacent second molars. Results: A greater percentage of men than women retained at least one third molar. The incidence of third molars decreased with increasing age. The incidence of partially impacted third molars greatly declined after the age of 30. Vertically impacted maxillary third molars and horizontally impacted mandibular third molars were most frequent in all age groups. Among the maxillary third molars, those impacted below the cervical line of the second molar were most frequent in all age groups, and among the mandibular third molars, deeply impacted third molars were most frequent in those aged over 40. Dental caries was the most common radiographic lesion of the third molars. Mesioangularly impacted third molars showed radiographic lesions in 13 (9.5%) adjacent maxillary second molars and 117 (27.4%) mandibular second molars. Conclusion: The number of remaining third molars decreased and the percentage of Class C depth increased with age. Caries was the most frequent lesion in third molars. Partially impacted mesioangular third molars showed a high incidence of caries or periodontal bone loss of the adjacent second molar. Regular oral examination will be essential to keep asymptomatic third molars in good health.

• Imaging Science in Dentistry
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• 제44권3호
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• pp.185-191
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• 2014

Purpose: This study investigated the developmental stages of third molars in relation to chronological age and compared third molar development according to location and gender. Materials and Methods: A retrospective analysis of panoramic radiographs of 2490 patients aged between 6 and 24 years was conducted, and the developmental stages of the third molars were evaluated using the modified Demirjian's classification. The mean age, standard deviation, minimal and maximal age, and percentile distributions were recorded for each stage of development. A Mann-Whitney U test was performed to test the developmental differences in the third molars between the maxillary and mandibular arches and between genders. A linear regression analysis was used for assessing the correlation between the third molar development and chronological age. Results: The developmental stages of the third molars were more advanced in the maxillary arch than the mandibular arch. Males reached the developmental stages earlier than females. The average age of the initial mineralization of the third molars was 8.57 years, and the average age at apex closure was 21.96 years. The mean age of crown completion was 14.52 and 15.04 years for the maxillary and the mandibular third molars, respectively. Conclusion: The developmental stages of the third molars clearly showed a strong correlation with age. The third molars developed earlier in the upper arch than the lower arch; further, they developed earlier in males than in females.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제28권1호
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• pp.46-52
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• 2002

Purpose : We examined the relationships between the root curvatures of the mandibular third molars and their locations on the mandible, so that it might be contributed to elucidate the origin of the formation and development of the Korean mandibular third molar and help many clinicians to treat the mandibular third molars. Materials and Methods : Panoramic radiographs of 237 patients who had been treated at Korea University Ansan Hospital from March, 2000 to April, 2001 and had bilateral mandibular third molars were examined and analyzed. Results : There was no statistically significant difference between men and women (p<0.05). But there were significantly fewer subjects with bilateral curved roots in bilateral third molars regardless of their status (p<0.01) and were statistically significant differences between the groups with bilateral curved roots in the mandibular third molars with same status and with unilateral curved roots in the mandibular third molars with different status and between the groups with unilateral curved roots in the mandibular third molars with same status and with bilateral curved roots in the mandibular third molars with different status(p<0.05). Subjects with bilateral curved roots in the mandibular third molars with bilateral partial impacted status and with bilateral curved roots in the mandibular third molars with bilateral complete eruption status were significantly fewer (p<0.01) and subjects with the mandibular third molars with partial impacted and complete impacted status and with the mandibular third molars with complete erupted and partial impacted status had significantly fewer bilateral curved roots (p<0.05). Conclusions : When we postulate that it is genetic and environmental factors that affect the root formation, it seems that environmental factors have more effects on the formation of the mandibular third molars than on that of the mandibular first and second molars

• 대한치과교정학회지
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• 제20권1호
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• pp.123-133
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• 1990

The work was undertaken to evaluate the calcification of the second and the third molars in skeletal Class II and III malocclusions. The differences in the calcification stages between skeletal Class II and III malocclusion were evaluated and statistically analysed from panoramic radiographs of 202 males and females ranging in age from 11 to 15 years old. The results were as follows, 1. The calcification stages of the second and the third molars were not different between the skeletal Class II and III malocclusions in each age groups of both sexes. 2. The calcification stages of lower second and third molars of the skeletal Class III malocclusion are more advanced than those of the skeletal Class II malocclusion in male. 3. The clacification stages of upper second and third molars are more advanced than those of lower second and third molars in skeletal Class II malocclusion. 4. The calcification stages of lower second and third molars are more advanced than those of upper second and third molars in skeletal Class III malocclusion.

• Imaging Science in Dentistry
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• 제45권4호
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• pp.233-240
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• 2015

Purpose: This study investigated maxillary third molars and their relation to the maxillary sinus using panoramic radiography and cone-beam computed tomography (CBCT) Materials and Methods: A total of 395 maxillary third molars in 234 patients were examined using panoramic radiographs and CBCT images. We examined the eruption level of the maxillary third molars, the available retromolar space, the angulation, the relationship to the second molars, the number of roots, and the relationship between the roots and the sinus. Results: Females had a higher frequency of maxillary third molars with occlusal planes apical to the cervical line of the second molar (Level C) than males. All third molars with insufficient retromolar space were Level C. The most common angulation was vertical, followed by buccoangular. Almost all of the Level C molars were in contact with the roots of the second molar. Erupted teeth most commonly had three roots, and completely impacted teeth most commonly had one root. The superimposition of one third of the root and the sinus floor was most commonly associated with the sinus floor being located on the buccal side of the root. Conclusion: Eruption levels were differently distributed according to gender. A statistically significant association was found between the eruption level and the available retromolar space. When panoramic radiographs showed a superimposition of the roots and the sinus floor, expansion of the sinus to the buccal side of the root was generally observed in CBCT images.

• Journal of Korean Dental Science
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• 제9권1호
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• pp.42-48
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• 2016

Prophylactic removal of impacted third molars is a common procedure in dentistry, but the necessity of routine extraction is still controversial. When impacted third molars caused severe apical root resorption of the second molars, orthodontic traction of the third molars after extraction of the damaged second molars could minimize alveolar bone defect and preserve the patient's natural teeth. By well-planned orthodontic treatment, functional occlusion was established avoiding extraction of the impacted teeth and eliminating the possibility of a large bone defect after extraction.

• 치과방사선
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• 제6권1호
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• pp.59-65
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• 1976

The author obtained the following results through the studies on 1012 roentgenograms of lower third molar regions of Korean female; 1. The rate of presence of lower third molars was 78.9 percent. 2. The period that crowns of lower third molars become completed was 16.1 years. 3. The period that completion of apices of lower third molars become completed was over 27 years.

• 대한치과의사협회지
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• 제25권11호통권222호
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• pp.1069-1077
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• 1987

Two brothers aged 15 1/6 and 12 2/3 years were diagnosed as Class I malocclusion with ectopic eruption of the upper left central incisor in the elder brother and etopic eruption in the upper right second premolar in the younger. All 4 second molars were extracted at the same time in both brothers. The treatment results were as follows. 1. In the elder brother, the third molars were fully erupted and their angulations were excellent at 3 years post-treatment. 2. In the younger brother, the lower right third molar was mesially erupted and upper third molars were still undergoing eruption at 3 years post-treatment. 3. Assessment of panex films of both brothers at aged 15 showed an earlier eruption of the third molars in the younger brother. 4. A longer post-treatment supervision of the third molars was required in the younger brother. 5. The facial probiles were enhanced and the ectopic eruptions were corrected in both brothers.

• 대한치과교정학회지
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• 제24권3호
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• pp.695-707
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• 1994

This study investigates the effects of third molar on the occlusal plane in Angle's class El malocclusion with possibilities of posterior crowding and the interrelationships of occlusal plane inclinations to other skeletal patterns. Above investigations might showed that considerations should be given to third molars with possibilities of posterior crowding in establishing diagnosis and treatment plans for Angle's class III malocclusion patients. The following conclusions were obtained 1. In events of third molars causing possible posterior crowding, maxillary third molars showed more mesial inclinations than second molars, and compared to those with third molar missing cases, first molars were more mesially inclined and displaced more inferiorly from the palatal plane and OP-MP was increase , thus the occlusal plane was less steep. 2. In events of third molars causing possible posterior crowding, the anglulation between AB line and mandibular plane was decreased and ANB showed negative values. Thus chin points were more protruded, ramus were more anteriorly displaced, and increase in lower facial height, genial angle, effective mandibular length and mandibular plane angle were observed. This in all caused more vertical opening and more severe skeletal disturbance. 3. OP-MP was increased as the maxillary first molars were more inferiorly displaced from the palatal plane. As this angle was increased mandibular planes were more inferiorly inclined and LFH, genial angle, effective mandibular length were more increased and mandibular ramus was more anteriorly placed. 4. As the maxillary first molars were more inferiorly placed from the palatal plane, more increased OP-MP/PP-MP ratio made the occlusal plane less steep. As OP-MP/PP-MP was increased, mandibular ramus was more anteriorly placed and made longer, and facial angle and effective mandibular length were increased.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제20권3호
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• pp.207-213
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• 1998

Purpose : This study attempted to relate the incidence of fractures at the mandibular angle with the presence and state of eruption of lower third molars, and to find out the real risk factors for angle fractures in the states of lower third molars. Materials and Methods : Medical records and radiographs of 395 patients with mandibular fractures were retrospectively reviewed. The presence and states of third molars were assessed for each patients and related to the occurrence of angle and other mandibular fractures. Results : Of 395 patients with mandibular fractures, 142 had angle fractures. The incidence of angle fractures was found to be significantly greater when partial erupted lower third molars were present and it had a definite role for risk factors for angle fractures. But there were no clear relationship between the incidence of angle fracrtures and states of without, fully erupted lower third molars. Furthermore, the states of patial and unerupted lower third molar had an effect on bony segment displacement. Conclusions : This study provides clinical evidence to suggest that patial erupted third molar teeth weaken the mandibular angle both quantitatively and qualitatively.