• Imaging Science in Dentistry
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• v.51 no.4
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• pp.373-382
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• 2021

Purpose: Cone-beam computed tomography (CBCT) reconstructions were analysed to elucidate factors affecting the anatomical relationship between tooth roots and the mandibular canal(MC). Materials and Methods: Images of 300 volumetric tomography scans of patients aged between 20 and 79 years old (167 women and 133 men) were analysed. The mean distances between 2,053 dental root apices and the internal border of the MC were obtained by measuring the horizontal and vertical distances on coronal CBCT images. The actual distance was then calculated mathematically with the Pythagorean formula. The statistical significance of differences between men and women was assessed using the Mann-Whitney test. Correlations with patient age were evaluated with the Spearman rank correlation coefficient. Results: The mean distances ranged from 2.17 mm, for single right third molar roots in women, to 8.02 mm for single left third molar mesiolingual roots in men. The mean distances measured for the mandibular right second molar mesial roots and the right second premolar roots were larger in men than in women. Age showed a significant positive correlation with the measured distances for mesial and distal roots of the first and second molar on both sides and the right third molar, mesiolingual roots of the left third molar, and single roots of the right third molar. Conclusion: The root-to-mandibular canal distance depended on age and the type of tooth. In 2 root types, this distance was impacted by sex.

• 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.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.1
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• pp.35-44
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• 2022

The aim of this study is to evaluate the development of the left mandibular third-molar development with modified Demirjian method and its relation to chronological age. A total of 1653 digital panoramic radiographs of healthy individuals aged between 7 and 23 years who visited Yonsei University Dental hospital were selected. The developmental status of the left mandibular third molars was assessed using dental maturity scoring proposed by Demirjian et al. The mean age of the first appearance of mineralization, complete crown formation, and complete root formation were around 9, 14, 21 years respectively. Statistically significant differences between males and females in the development stage of D and G were revealed that crown formation and root length completion were attained earlier in males than in females. There was significant positive relationship between age and third molar development in both sexes, and new formula was presented to estimate age of children and adolescents based on their developmental stages of third molars. In this study, the use of left mandibular third molar as a developmental marker is appropriate, and age estimation can be attained with dental maturity stage.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.36 no.5
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• pp.201-206
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• 2014

Purpose: To establish management protocol for mandibular angle fracture, we describe pertinent factors including cause, impacted third molar and recent treatment tendency. Methods: We examined the records of 62 patients who had unilateral mandibular angle fracture. Sixty patients who had open reduction surgery were examined at postoperative weeks 1, 4, 8, 12, and 28. Results: Left mandibular angle fracture is frequent in younger males. Presence of the mandibular third molar can increase fracture risk. Because of attached muscle, favorable fractures occurred primarily in the mandibular angle area. Conclusion: Extracting the mandibular third molar can prevent angle fractures, and open reduction with only one plate adaptation is generally the proper treatment method for mandibular angle fracture.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.40.1-40.7
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• 2019

Background: Through the analysis of clinical data, we attempted to investigate the etiology and determine the risk of severe iatrogenic lingual nerve injuries in the removal of the mandibular third molar. Methods: A retrospective chart review was performed for patients who had undergone microsurgical repair of lingual nerve injuries. The following data were collected and analyzed: patient sex, age, nerve injury side, type of impaction (Winter's classification, Pell and Gregory's classification). Ratios for the respective lingual nerve injury group data were compared with the ratios of the respective data for the control group, which consisted of data collected from the literature. The data for the control group included previous patients that encountered various complications during the removal of the mandibular third molar. Results: The lingual nerve injury group consisted of 24 males and 58 females. The rate of female patients with iatrogenic lingual nerve injuries was significantly higher than the control groups. Ages ranged from 15 to 67 years, with a mean age of 36.5 years old. Lingual nerve injury was significantly higher in the patient versus the control groups in age. The lingual nerve injury was on the right side in 46 and on the left side in 36 patients. There was no significant difference for the injury side. The distoangular and horizontal ratios were the highest in our lingual nerve injury group. The distoangular impaction rate in our lingual nerve injury group was significantly higher than the rate for the control groups. Conclusion: Distoangular impaction of the mandibular third molar in female patients in their 30s, 40s, and 50s may be a higher risk factor of severe lingual nerve injury in the removal of mandibular third molars.

• Restorative Dentistry and Endodontics
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• v.49 no.1
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• pp.2.1-2.12
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• 2024

Objectives: This study aimed to determine the effects of 1-rooted mandibular second molar (MnSM) teeth on root canal anatomy complexities of the mandibular central incisor (MnCI), mandibular lateral incisor (MnLI), mandibular canine (MnCn), mandibular first premolar (MnFP), mandibular second premolar (MnSP), and mandibular first molar (MnFM) teeth. Materials and Methods: Cone-beam computed tomography images of 600 patients with full lower dentition were examined. Individuals with 1-rooted MnSMs were determined, and the complexity of root canal anatomy of other teeth was compared with individuals without 1-rooted MnSMs (Group-1; subjects with at least one 1-rooted MnSM, Group-2; subjects with more than a single root in both MnSMs). A second canal in MnCIs, MnLIs, MnCns, MnFPs, and MnSPs indicated a complicated root canal. The presence of a third root in MnFMs was recorded as complicated. Results: The prevalence of 1-rooted MnSMs was 12.2%, with the C-shaped root type being the most prevalent (9%). There were fewer complicated root canals in MnCIs (p = 0.02), MnLIs (p < 0.001), and MnFPs (p < 0.001) in Group 1. The other teeth showed no difference between the groups (p > 0.05). According to logistic regression analysis, 1-rooted right MnSMs had a negative effect on having complex canal systems of MnLIs and MnFPs. Left MnSMs were explanatory variables on left MnLIs and both MnFPs. Conclusions: In individuals with single-rooted MnSMs, a less complicated root canal system was observed in all teeth except the MnFMs.

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.4
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• pp.404-411
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• 2012

Tooth impaction is defined as a failure of tooth eruption resulting from the physical obstacles in the eruption path or the abnormal position of the tooth germ. Impaction of mandibular second molar is relatively rare, and it may incite pathologic conditions such as dental caries, periodontitis, or root resorption of adjacent first molar. Thus, early diagnosis and treatment is recommended. In the first case, a 10-year-old male patient, was treated by brass wire to separate the bilaterally impacted mandibular second molars. In the second case, a 12-year-old female patient, was treated with Humphrey appliance for impacted mandibular left second molar, which was detected during a periodical dental examination. In the third case, a 17-year-old female patient with impacted mandibular right second molar, was treated by uprighting spring with mini-implant anchorage around premolar area. In the last case, an 18-year-old male patient, was treated with mini-implant placed on the ramus of mandible connected to the orthodontic buttons bonded on impacted mandibular left second molar by elastic thread.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.22 no.2
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• pp.185-193
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• 1992

The purpose of this study was to evaluate the prevalence and distribution of tooth number anomaly by means of the analysis of panoramic radiographs in 6,531 patients visited the Dental Infirmary of Kyungpook National University Hospital from January 1983 to May 1992. The results were as follows: 1. The prevalence of congenitally missing teeth except third molar was revealed to be 10.8%, and there was a hihger prevalence in females(44.6%) than in males(55.4%). Mandibular 2nd premolars(23.2 %) were absent most frequently, followed by maxillary lateral incisors(18.4 %), mandibular lateral incisors(18.3%), and maxillary second premolars(15.4 %) in descending order of frequency. As to the number of congenitally missing teeth, the percentage of missing one tooth was 48%, missing two teeth was 35.4 %, missing three teeth was 6.6%. 2. he prevalence of congenitally missing third molars was revealed to be 39.7%. There was a higher prevalence n the maxilla(60.3%) than in the mandible(39.7%). Maxillary right 3rd molars(30.6%) were absent most frequently, followed by maxillary left 3rd molar(29.7%), mandibular right 3rd molar(202%), mandibular left 3rd molar(19.5%) in descending order of frequency. 3. The prevalence of supernumerary teeth was revealed to be 4.2%, and there was a higher prevalence in males(65.7%) than in females(34.3 ). They were ound most frequently in maxillary central incisor area(64.8%), followed by maxillary lateral incisor area(132%), posterior area of maxillary third molar(8.7%) in descending order of frequency. As to the number of supernumerary teeth; The percentage of one supernumerary tooth was 79.9%, two supernumerary teeth was 8.9%, three supernumerary teeth was 1.2 %.

• Imaging Science in Dentistry
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• v.46 no.1
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• pp.1-7
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• 2016

Purpose: This study assessed the accuracy of age estimates produced by a regression equation derived from lower third molar development in a Thai population. Materials and Methods: The first part of this study relied on measurements taken from panoramic radiographs of 614 Thai patients aged from 9 to 20. The stage of lower left and right third molar development was observed in each radiograph and a modified Gat score was assigned. Linear regression on this data produced the following equation: Y=9.309+1.673 mG+0.303S (Y=age; mG=modified Gat score; S=sex). In the second part of this study, the predictive accuracy of this equation was evaluated using data from a second set of panoramic radiographs (539 Thai subjects, 9 to 24 years old). Each subject's age was estimated using the above equation and compared against age calculated from a provided date of birth. Estimated and known age data were analyzed using the Pearson correlation coefficient and descriptive statistics. Results: Ages estimated from lower left and lower right third molar development stage were significantly correlated with the known ages (r=0.818, 0.808, respectively, $P{\leq}0.01$). 50% of age estimates in the second part of the study fell within a range of error of ${\pm}1year$, while 75% fell within a range of error of ${\pm}2years$. The study found that the equation tends to estimate age accurately when individuals are 9 to 20 years of age. Conclusion: The equation can be used for age estimation for Thai populations when the individuals are 9 to 20 years of age.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.39
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• pp.29.1-29.5
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• 2017

Background: The surgical extraction of the third molar is the most frequently encountered procedure in oral and maxillofacial surgery and is related with a variety of complications. This study examined the efficacy of intentional partial odontectomy (IPO) in the third molars which have no periapical lesions and are located near important anatomical structures such as inferior alveolar nerve. Methods: Seven patients (four males, three females, $39.1{\pm}11.6years$), who received IPO to reduce the risk of inferior alveolar nerve injury (IANI), were followed long-term. The treated teeth were horizontally impacted third molars in the mandibular left (n = 5) or mandibular right (n = 4) areas and were all ankylosed with the surrounding alveolar bone. During the IPO, the bone around the crown was removed to expose the crown, and then the tooth was resected at cement-enamel junction (CEJ). Any secondary trauma to the healthy root was minimized and remained intact after primary suture. Results: The mean follow-up time was $63.2{\pm}29.8months$, and all sites showed good bone healing after the crown removal. Also, sensory abnormality was not found in any patients after IPO. In one patient, the bone fragments erupted 4 months after IPO. In other patient, an implant placed on second molar site adjacent to the third molar that received IPO was explanted about 2 years after the patient's persistent discomfort. Conclusions: In case where high risk of IANI exists, IPO may be chosen alternatively to surgical extraction to reduce the risk of nerve damage.