• Restorative Dentistry and Endodontics
• /
• v.22 no.2
• /
• pp.731-738
• /
• 1997

A retrospective in vivo study of endodontically treated mandiblar molars was conducted. The radilographs and clinical records of mandibular molars that had been treated endodontically in the Dental hospital of Yonsei University from 1986 to July 1997 were reviewed and categorized. A total of 1751 cases were studied and following results were obtained. 1. The number of root canals in mandibular first permanent molar in a Korean population revealed three in 53.2 %, four in 23.0 %, two in 18.4 %, C-shaped canal in 5.0 %, and one in 0.4 %. 2. In mandibular second molar, three canals was observed in 53.2 %, four in 22.2 %, two in 14.9%, C-shaped canal in 9.1 %, and one in 0.6%. 3. In the results of the percentage of 4 canals of mandibular first molars at various age, before age 20, 37.7 % was obtained whereas 19.3 % after 30. 4. 7.94 % of mandibular first molars examined were found to have three roots. 5. The mandibular second molar had C-shaped canals in 9.1 %.

• The korean journal of orthodontics
• /
• v.51 no.3
• /
• pp.179-188
• /
• 2021

Objective: To evaluate the overall treatment effects in terms of the amount of uprighting with changes in the sagittal and vertical positions of mandibular molars after applying an orthodontic miniplate with a nickel-titanium (NiTi) reverse curve arch wire (biocreative reverse curve [BRC] system). Methods: A total of 30 female patients (mean age, 25.99 ± 8.96 years) were treated with the BRC system (mean BRC time, 10.3 ± 4.07 months). An I-shaped C-tube miniplate (Jin Biomed) was placed at the labial aspect for the alveolar bone of the mandibular incisors. A 0.017 × 0.025-inch NiTi reverse curve arch wire was engaged at the C-tube mini-plate anteriorly and the first and second premolars and molars posteriorly in the mandibular arch. Pre- and post-BRC lateral cephalograms were analyzed. A paired t-test was used to analyze the treatment effects of BRC. Results: The mandibular second molars were intrusively uprighted successfully by the BRC system. Distal uprighting with a controlled vertical dimension was noted on the first molars when they remained engaged in the BRC and the distal ends of the arch wire were laid on the second molars. The mandibular first and second premolars showed a slight extrusion. The changes in the mandibular incisors were unremarkable, while the mandibular molar angulation improved significantly. The lower occlusal plane rotated counterclockwise (MP-LOP: 1.13° ± 2.60°). Conclusions: The BRC system can provide very effective molar uprighting without compromising the position of the mandibular anterior teeth.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.32 no.5
• /
• pp.464-473
• /
• 2006

Purpose: This study was performed to evaluate relationship between the inferior alveolar nerve injury and the findings of panoramic and tomographic images for preventing inferior alveolar nerve injury after the 3rd molar extraction. Material and Method: From April, 2005 to June, 2005, The 190 patients who visited in the Department of Oral and Maxillofacia Surgery, Chonnam National University Hospital and the panoramic radiographies were taken for extraction of the mandibular third molar, was selected. Among 215 mandibular third molars, Scanora tomographic imagings were taken in the 90 teeth which were overlaped to the mandibular canal in the panoramic imagies. In panoramic radiographies, the angulation, the level, the root morphology, and the superimposition sign of the mandibular third molars with the mandibular canal were evaluated. In the tomographic radiographies, the location and distance of the mandibular third molar from the canal were also evaluated. The relationships between these findings and the inferior alveolar nerve injury were examined. Results: In the panoramic findings, the inferior alveolar nerve injuries were occurred in the darkened roots (5 molars, 7%), the uncontinuous radiopaque image (3 molars, 7%), and the depositioned mandibular canal (2 molars, 10%). In the tomographic findings of 90 molars, 20 molars also had the superimposition imagies. Five molars in those molars (25%) had the inferior alveolar nerve injury after extraction. There were 10 patients who had the inferior alveolar nerve injury. The sensory was began to be recovered in 9 patients, except 1 patient, within 2 weeks, then fully recovered within 3 months. Conclusion: These results indicate that the depth mandibular third molar and the superimposition sign may be related with the risk of the inferior alveolar nerve injury after extraction.

• The korean journal of orthodontics
• /
• v.50 no.2
• /
• pp.145-154
• /
• 2020

Moving the mandibular posterior teeth into a severely atrophic edentulous space is a challenge. A carefully designed force-and-moment system that results in bodily protraction of the posterior teeth with balanced bone resorption and apposition is needed in such cases. This report describes the treatment of a 19-year-old woman with missing mandibular first molars due to juvenile periodontitis. Miniscrews were used as absolute anchorage during protraction of the mandibular second and third molars. Bodily mesial movement of the mandibular second and third molars was achieved over a distance of 11 to 17 mm after 39 months of orthodontic treatment.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.48 no.3
• /
• pp.155-158
• /
• 2022

Objectives: The aim of this study was to observe the relationship between impacted mandibular third molars and development of temporomandibular joint (TMJ) disorders. Knowledge of the factors that have an adverse effect on the TMJ is necessary for proper diagnosis, treatment, and prognosis of TMJ disorders. Materials and Methods: The study was performed on 80 patients aged between 20 and 60 years with impacted mandibular third molars, over a period of two months. The patients were examined clinically and radiologically to determine the type of impaction and detect the associated TMJ symptoms or disorders. Results: In the 80 patients, 63.8% (51/80) of TMJ disorders were found in the horizontal group, 46.3% (37/80) in the mesioangular group, 42.5% (34/80) in the distoangular group, and 30.0% (24/80) in the vertical group of impacted mandibular third molars. Conclusion: The study concluded that type of impacted mandibular third molar is factor in the development of temporomandibular disorders.

• Imaging Science in Dentistry
• /
• v.49 no.3
• /
• pp.213-218
• /
• 2019

Purpose: The aim of this study was to evaluate the relationship between the mandibular canal and impacted mandibular third molars using cone-beam computed tomography (CBCT) and to compare the CBCT findings with signs on panoramic radiographs(PRs). Materials and Methods: This retrospective study consisted of 200 mandibular third molars from 200 patients who showed a close relationship between the mandibular canal and impacted third molars on PRs and were referred for a CBCT examination of the position of the mandibular canal. The sample consisted of 124 females and 76 males, with ages ranging from 18 to 47 years (mean, $25.75{\pm}6.15$ years). PRs were evaluated for interruption of the mandibular canal wall, darkening of the roots, diversion of the mandibular canal, and narrowing of the mandibular canal. Correlations between the PR and CBCT findings were statistically analyzed. Results: In total, 146 cases(73%) showed an absence of canal cortication between the mandibular canal and impacted third molar on CBCT images. A statistically significant relationship was found between CBCT and PR findings (P<0.05). The absence of canal cortication on CBCT images was most frequently accompanied by the PR sign of diversion of the mandibular canal(96%) and least frequently by interruption of the mandibular canal wall(65%). Conclusion: CBCT examinations are highly recommended when diversion of the mandibular canal is observed on PR images to reduce the risk of mandibular nerve injury, and this sign appears to be more relevant than other PR signs.

• Imaging Science in Dentistry
• /
• v.43 no.4
• /
• pp.219-225
• /
• 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.

• Restorative Dentistry and Endodontics
• /
• v.41 no.3
• /
• pp.182-188
• /
• 2016

Objectives: The purpose of this study was to evaluate the proximity of the mandibular molar apex to the buccal bone surface in order to provide anatomic information for apical surgery. Materials and Methods: Cone-beam computed tomography (CBCT) images of 127 mandibular first molars and 153 mandibular second molars were analyzed from 160 patients' records. The distance was measured from the buccal bone surface to the root apex and the apical 3.0 mm on the cross-sectional view of CBCT. Results: The second molar apex and apical 3 mm were located significantly deeper relative to the buccal bone surface compared with the first molar (p < 0.01). For the mandibular second molars, the distance from the buccal bone surface to the root apex was significantly shorter in patients over 70 years of age (p < 0.05). Furthermore, this distance was significantly shorter when the first molar was missing compared to nonmissing cases (p < 0.05). For the mandibular first molars, the distance to the distal root apex of one distal-rooted tooth was significantly greater than the distance to the disto-buccal root apex (p < 0.01). In mandibular second molar, the distance to the apex of C-shaped roots was significantly greater than the distance to the mesial root apex of non-C-shaped roots (p < 0.01). Conclusions: For apical surgery in mandibular molars, the distance from the buccal bone surface to the apex and apical 3 mm is significantly affected by the location, patient age, an adjacent missing anterior tooth, and root configuration.

• Restorative Dentistry and Endodontics
• /
• v.43 no.3
• /
• pp.33.1-33.8
• /
• 2018

Objectives: This study aimed to investigate the prevalence of a separate distolingual root and to measure the thickness of the buccal cortical bone in mandibular first molars in Koreans using cone-beam computed tomography (CBCT) images. Materials and Methods: High-quality CBCT data from 432 patients were analyzed in this study. The prevalence of a separate distolingual root of the mandibular first molar was investigated. The distance from the distobuccal and distolingual root apices to the outer surface of the buccal cortical bone was measured. We also evaluated the thickness of the buccal cortical bone. Results: The prevalence of a separate distolingual root (2 separate distal roots with 1 canal in each root; 2R2C) was 23.26%. In mandibular first molars with 2R2C, the distance from the distobuccal root apex to the outer surface of the buccal cortical bone was 5.51 mm. Furthermore, the distance from the distolingual root apex to the outer surface of the buccal cortical bone was 12.09 mm. In mandibular first molars with 2R2C morphology, the thickness of the buccal cortical bone at the distobuccal root apex of the mandibular first molar was 3.30 mm. The buccal cortical bone at the distobuccal root apex was significantly thicker in the right side (3.38 mm) than the left side (3.09 mm) (p < 0.05). Conclusions: A separate distolingual root is not rare in mandibular first molars in the Korean population. Anatomic and morphologic knowledge of the mandibular first molar can be useful in treatment planning, including surgical endodontic treatment.

• Journal of Periodontal and Implant Science
• /
• v.32 no.1
• /
• pp.61-68
• /
• 2002

The objective of this study was to determine the incidence and distribution of root fusion as well as its sexlinkage in maxillary and mandibular molars. One hundred fifty patients who had eight maxillary and mandibular molars (third molars excluded) were consecutively selected for the study subjects. The subjects provided a total of 1200 molars, i.e., 600 maxillary and 600 mandibular molars. A decision about root fusion was made on the radiographic examination. If a molar had one root and/or roots fused at any part in the root surface, it was considered as having root fusion. The results showed that : (1) 14.1 % of the maxillary molars and 5.8 % of the mandibular molars had a fused root, (2) the prevalence of root fusion in the male was 33 % and 56.4 % in the female, (3) 60 % in the male and 48.8 % in the female had bilaterally paired root fusion, (4) the root fusion was most frequently observed in the maxillary second molar position, but none in the mandibular first position in this study. Within limitations of this study, it can be concluded that, in management of molars with a furcation problem, treatment options such as hemisection and root amputation should be chosen after careful evaluation of root fusion. Further studies are needed to investigate a possible relationship between root fusion and periodontal disease progression.