• Imaging Science in Dentistry
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• v.43 no.4
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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.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.28 no.1
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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

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

• Journal of Korean Dental Science
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• v.9 no.1
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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.

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

• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.6
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• pp.492-498
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• 2009

We sought to evaluate the relationship between the mandibular canal and impacted mandibular third molars by using dental cone beam computed tomograph(CBCT) for third molar surgery. A total of 111 patients(177 teeth) offered the images through CBCT and panoramic radiography for the extraction of the mandibular third molars. In CBCT, the accurate relationship between the third molar and the mandibular canal were evaluated. In panoramic radiographies, we evaluated the impacted level and superimposition sign of the mandibular third molar with the mandibular canal, and also, the radiopacity of the white line in the canal. Data were statistically analyzed and estimated by $X^2$-test. In CBCT finding, high prevalence of contact between the mandibular canal and roots occured in the deep impacted third molars, narrowing mandibular canals, bending mandibular canals and cases where the radiopacity of white line of canals were "absence" on panoramic images. It showed statistical significance (P<0.05). When evaluating the mandibular canal and the roots through the panoramic radiography for third molar extraction, it could be difficult to diagnosis accurately. Thus, it is required to have an accurate diagnostic approach through CBCT that could evaluated the location between mandibular canal and root.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.28 no.6
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• pp.565-569
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• 2006

The purpose of this study was to assess the influence of the presence and impacted state of the mandibular third molars on the incidence of mandibular condyle fracture. A retrospective study was designed for patients presenting to the Department of Oral and Maxillofacial Surgery, Kyungpook National University Hospital and Tae-gu Fatima Hospital for treatment of mandibular fractures from January 2003 to January 2006. The independent variables in this study were the presence, degree of impaction of third molars, and the outcome variables were the incidence of mandibular condyle fractures. Hospital charts and panoramic radiographs were used to determine and classify these variables. The demographic data included age, sex, mechanisms of injuries and number of mandibular condyle fractures. The study sample comprised 136 mandibular condyle fractures in 105 patients. Result of this study demonstrated a statistically significant difference in ipsilateral condyle fractures and mandibular third molar absence(P=0.032) and bilateral condyle fractures without another fracture and mandibular third molar absence(P=0.028).

• The korean journal of orthodontics
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• v.11 no.2
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• pp.77-83
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• 1981

The author analyzed the morphological pattern of mandibles and lower third molars in order to study and predict the impaction of the developmental third molars. The subjects consisted of 37 males and 87 females with malocclusion. The following results were obtained: 1. The mandible was shown to be shorter in the impacted third molar group than in the erupted group, both in over-all length and in body length. 2. The developmental mesial angulation of the third molar to the mandibular plane was higher in the impacted third molar group. 3. There was a tendency for impacted third molars to be slightly larger than those which erupted except Class II malocclusion in female. 4. In the available space for the eruption of the third molar, significant space deficiency was found in association with the impacted third molar group compared with the erupted group.

• Imaging Science in Dentistry
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• v.51 no.1
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• pp.9-16
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• 2021

Purpose: The purpose of this study was to analyze the reliability of 7 panoramic radiographic signs for predicting proximity of the root apices of mandibular third molars to the mandibular canal using cone-beam computed tomography and to correlate these findings with the Pell and Gregory and the Winter classification systems. Materials and Methods: An observational, cross-sectional, descriptive study was conducted on 74 patients with bilateral impacted mandibular third molars. Four panoramic radiographic signs were observed in the tooth root (darkening, deflection, and narrowing of the root apices, and bifid apices), and another 3 in the mandibular canal (diversion, narrowing, and interruption of the mandibular canal). Cone-beam computed tomography images were analyzed to identify disruption and diversion of the mandibular canal and root deflection. Results: Binary logistic regression showed that only 4 of the 7 panoramic radiographic signs were able to predict proximity of the root apices of the mandibular third molars to the mandibular canal: darkening of the root, deflection of the root, narrowing of the root, and interruption of the mandibular canal(P<0.05). Conclusion: Darkening, deflection, and narrowing of the root, in tandem with the interruption of the mandibular canal on panoramic radiographs, indicate that cone-beam computed tomography should be performed when planning the extraction of impacted mandibular third molars. Proximity between mandibular third molars and the mandibular canal is correlated with the Winter classification.

• Imaging Science in Dentistry
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• v.42 no.3
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• pp.121-127
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• 2012

Purpose: This study evaluated the association between cone beam computed tomography (CBCT) and panoramic radiographs in the assessment of a superimposed relationship between the mandibular canal and impacted third molars. Materials and Methods: The study samples consisted of 175 impacted third molars from 131 patients who showed a superimposed relationship between the mandibular canal and third molars on panoramic radiographs and were referred for the examination of the mandibular canal with CBCT. Panoramic images were evaluated for the darkening of the root and the interruption of the mandibular canal wall. CBCT images were used to assess the buccolingual position of the mandibular canal relative to the third molar, the proximity of the roots to the canal, and lingual cortical bone loss. The association of the panoramic and CBCT findings was examined using a Chi-square test and Fisher's exact test. Results: Panoramic radiographic signs were statistically associated with CBCT findings (P<0.01). In cases of darkening roots, lingual cortical bone loss or buccally positioned canals were more frequent. In cases in which the mandibular canal wall was interrupted on panoramic radiographs, contact or lingually positioned canals were more frequent. Conclusion: The results of this study suggest that contact between the mandibular third molar and canal and a lingually positioned canal could be more frequently observed in cases of the interruption of the white line of the mandibular canal and that there could be more lingual cortical loss in cases of darkening roots.