• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.1
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• pp.130-135
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• 2010

Ectopic eruption is caused by an abnormal direction of eruptive path, most common in maxillary first molar, mandibular lateral incisor, and maxillary canine, and sometimes mandibular first molar. Ectopic eruption of first molar leads to abnormal root resorption of second deciduous molar, which, if left untreated, could cause premature loss of second deciduous molar; mesial tilting and rotation of first permanent molar; lack of space for eruption of second premolar; and occlusal problems. Therefore early treatment is advised when diagnosed as ectopic eruption. Treatment of ectopic eruption in the first permanent molar involves providing proper guidance for the direction of eruption using interproximal wedging and distal tipping methods while preserving second deciduous molar. This case report shows satisfactory results of the ectopic eruption of mandibular first molars in young patients who were treated with Humphrey appliance and Halterman appliance.

• The korean journal of orthodontics
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• v.35 no.3 s.110
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• pp.227-237
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• 2005

Eruptive disturbance of the permanent lower first molar is an uncommon condition caused by physical barriers on the eruption path or failure of the eruptive mechanism. Once eruptive disturbance of the permanent lower first molar is diagnosed. treatment should be started as soon as possible to establish a normal eruption pathway and to avoid any detrimental effects on the developing occlusion A case of primary retention of the mandibular first permanent molar treated with operculectomy and forced eruption which showed good treatment results and stability is described

• 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.

• The korean journal of orthodontics
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• v.47 no.2
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• pp.142-147
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• 2017

The purpose of this study was to investigate immediate changes in the mandibular dentition after maxillary molar distalization using headgear in non-growing patients. Sixteen patients (mean age, $18.9{\pm}2.0$ years) with Class II molar relationship and crowding were included in the present study. To correct the molar relationship, headgear was used for maxillary molar distalization. Cone-beam computed tomography-generated half-cephalograms (CG Cephs) and dental casts were used to evaluate dental changes for each subject before and immediately after molar distalization using headgear. The mean duration that subjects wore the headgear was 6.3 months. CG Cephs showed that the first maxillary molars were distalized $4.2{\pm}1.6\;mm$ with $9.7^{\circ}{\pm}6.1^{\circ}$ of distal angulation. The intercanine, interpremolar, and intermolar widths of the mandible increased after maxillary molar distalization. The present study's results suggest that maxillary molar distalization using headgear induces a spontaneous response in the untreated mandibular dentition of non-growing patients.

• Journal of Technologic Dentistry
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• v.11 no.1
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• pp.65-70
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• 1989

The development of the lobe pattern in the human dentition plays a part in the form and function of each individual teeth. In order to determin the morphological categories used to describe the occlusal surfaces of the maxillary and mandibular molars, the variation of the developmental grooves which separate each lobe in the molars was examined and analysed. The obtained conclusions were as follow. 1. Most of the maxillary first molars with more distinct and more developmental grooves than the other molars but in most cases of the third molar, a heart-shaped outline due to poorly developed or abscent distolingual cusp was most frequent and in this case the third molar had the 3 cusps separated by the central developmental groove and the buccal developmental groove. 2. In most cases, the mandibular first molar had the 5-cusp type that the groove patter resembles a Y, the second molar the 4-cusp type arranged in such a way that the buccal and lingual developmental grooves meet the central developmental groove at right angle on the occlusal surface and many instances of the mandibular third molars had the 5-cusp thpe with a+groove pattern which separatess the mesiolingual cusp from the distobuccal cusp and the 4-cusp type with a+groove pattern. 3. The maxillary and mandibular third molar were most variable in the developmental groove.

• The korean journal of orthodontics
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• v.47 no.5
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• pp.277-288
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• 2017

Objective: Treating Class II subdivision malocclusion with asymmetry has been a challenge for orthodontists because of the complicated characteristics of asymmetry. This study aimed to explore the characteristics of dental and skeletal asymmetry in Class II subdivision malocclusion, and to assess the relationship between the condyle-glenoid fossa and first molar. Methods: Cone-beam computed tomographic images of 32 patients with Class II subdivision malocclusion were three-dimensionally reconstructed using the Mimics software. Forty-five anatomic landmarks on the reconstructed structures were selected and 27 linear and angular measurements were performed. Paired-samples t-tests were used to compare the average differences between the Class I and Class II sides; Pearson correlation coefficient (r) was used for analyzing the linear association. Results: The faciolingual crown angulation of the mandibular first molar (p < 0.05), sagittal position of the maxillary and mandibular first molars (p < 0.01), condylar head height (p < 0.01), condylar process height (p < 0.05), and angle of the posterior wall of the articular tubercle and coronal position of the glenoid fossa (p < 0.01) were significantly different between the two sides. The morphology and position of the condyle-glenoid fossa significantly correlated with the three-dimensional changes in the first molar. Conclusions: Asymmetry in the sagittal position of the maxillary and mandibular first molars between the two sides and significant lingual inclination of the mandibular first molar on the Class II side were the dental characteristics of Class II subdivision malocclusion. Condylar morphology and glenoid fossa position asymmetries were the major components of skeletal asymmetry and were well correlated with the three-dimensional position of the first molar.

• Restorative Dentistry and Endodontics
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• v.39 no.2
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• pp.132-136
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• 2014

The presence of radix entomolaris (RE) in a mandibular first molar is a common occurrence in certain ethnic groups, but the presence of RE in a mandibular second molar is a rare occurrence. In the present case, RE was identified from preoperative radiographs and confirmed using cone-beam computed tomography (CBCT). The access cavity was modified to locate the RE. Cleaning and shaping were performed with nickel-titanium rotary instruments. Obturation was completed with gutta-percha cones using AH Plus (Dentsply Detrey GmbH) as sealer. From the CBCT axial images, the RE was determined to have a Type III curvature by the De Moor classification, Type B separate RE by the Carlsen and Alexandersen classification, and radiographically, a Type i image by the Wang classification. The presence of RE in the mandibular second molar makes it essential to anticipate and treat the distolingual root canal. This case report highlights the usefulness of CBCT for assessing RE in the mandibular second molar, which can help the clinician in making a confirmatory diagnosis and assessing the morphology of the root canal.

• 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 Association of Oral and Maxillofacial Surgeons
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• v.40 no.5
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• pp.225-232
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• 2014

Objectives: The purpose of this retrospective study is to find the differentiating characteristics of cystic and cystic-appearing lesions that involve the impacted mandibular third molar by analyzing panoramic radiographs and computed tomography images, and to aid the preoperative diagnosis. Materials and Methods: Eighty-one patients who had a mandibular cystic or cystic-appearing lesion that involved impacted mandibular third molar and underwent cyst enucleation were included in the study. The preoperative panoramic radiograph and computed tomography findings were analyzed in accordance to the histopathologic type. Results: Most of the cystic lesions containing the mandibular third molar were diagnosed as a dentigerous cyst (77.8%). The occurrence of mesio-distal displacement of the third molar was more frequent in the odontogenic keratocyst (71.4%) and in the ameloblastoma (85.7%) than in the dentigerous cyst (19.1%). Downward displacement was primarily observed in each group. Odontogenic keratocyst and ameloblastoma showed more aggressive growth pattern with higher rate of bony discontinuity and cortical bone expansion than in dentigerous cyst. Conclusion: When evaluating mandibular cystic lesions involving the impacted mandibular third molar, dentigerous cyst should first be suspected. However, when the third molar displacement and cortical bone absorption are observed, then odontogenic keratocyst or ameloblastoma should be considered.

• The korean journal of orthodontics
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• v.48 no.5
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• pp.339-345
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• 2018

Objective: The purpose of this study was to clarify the effects of continuous force application for extrusive tipping movement and occlusal interference on periapical root resorption in the rat mandibular first molar. Methods: We constructed an appliance comprising a titanium screw implant with a cobalt-chromium post as the anchorage unit and a nickel-titanium closed coil spring (50 cN) as the active unit. Force was applied on the mandibular left first molar of rats for 8 (n = 10) and 15 days (n = 10; experimental groups), with the tooth in occlusion. Five rats were included as a non-treated control group to examine the body effect of the appliance. Active root resorption lacunae, identified using tartrate-resistant acid phosphatase, were evaluated in terms of the length, depth, and area. Results: The rat mandibular first molars were mesially tipped and extruded in the occlusal direction. This mesio-occlusal tipping movement and occlusion resulted in the formation of a compression zone and active root resorption lacunae in the distoapical third of the distal roots. However, there was no significant difference in the amount of root resorption between the two experimental groups. The control group did not exhibit any active root resorption lacunae. Conclusions: Periapical root resorption was induced by continuous extrusive tipping force and occlusal interference in rat mandibular molars. These data suggest that we orthodontists had better take care not to induce occlusal interference during our orthodontic treatment.