• The Journal of the Korean dental association
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• v.21 no.12 s.175
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• pp.1005-1010
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• 1983

To study the eruption process of the permanent tooth, esp., 1st molar, the author took 303 cases of oblique cephalogram (Male. 162 cases, Female: 141 cases) from age 3 to 8 yea old children, and observed the vertical change and axial change. The result were as follow: 1. The mesial end of upper 1st molar was closer to the occlusal plane than the distal, and they were erupting toward the occlusal plane by aging. In the case of lower 1st molar, the distal end was closer to the occlusal plane than the mesial and the occlusion showed the tendency to accord with the plane to be settled by aging. 2. Eruption rate of the upper and lower 1st permanent molar increased rapidly at 5 or 6 years of age. 3. Axial inclination of lower 1st permanent molar to the mandibular plane decreased gradually from 3 years of age, except for 6 years of age. There was some increase at 5 or 6 years of age.

• Korean Journal of Cleft Lip And Palate
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• v.16 no.1
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• pp.25-35
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• 2013

We report the treatment of an adult Class II malocclusion with severe crowding and a hopeless lower second molar. According to the treatment plan, 4 premolars and 4 third molars were to be extracted for 2-jaw surgery. To replace the hopeless lower second molar, one upper third molar was successfully autotransplanted during the pre-surgical orthodontic treatment. Multiple teeth are frequently extracted for treatment purposes in adult surgical cases. Under precise diagnosis, the reuse of extracted teeth to replace missing teeth can be a successful alternative even in adult surgical patients.

• The korean journal of orthodontics
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• v.24 no.3 s.46
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• pp.709-719
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• 1994

The aim of this investigation was to identify which suing is more suitable for uprighting of the 30 degree inclined lower second molar in different situations. Between four different molar uprighting springs which were A, B, C type and T-loop spring, the author tested T-loop suing as a control material and the other springs were experimental group. Each spring was fabricated from .017' $\times$ .025' TMA wire and preactivated with 40 degree tip-back bend. Stabilizing unit included from the lower right central incisor to the lower right second premolar which were made by acrylic resin. The photoelastic overview of the lower right quadrant showed that stress concentrations were observed in its photoelastic model. The obtained results were as follows. 1. Higher concentration of compression can be seen clearly at the distal curvature than the mesial of the lower second molar when A type uprighting spring was applied, which can be used as a space regainer. 2. Higher level compression was presented at the mesial root apex area than the distal of the lower second molar in B type uprighting spring, which can be used as a space closer. 3. Areas of higher compression and tension were observed about the mesial and distal root of the lower second moalr than A and B type in C type uprighting spring, which can be used as a partial space regainer.

• Journal of Oral Medicine and Pain
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• v.3 no.1
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• pp.11-22
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• 1977

In order to evaluate the normal eruption time of the Korean permanennt teeth, the author had examined the eruption phases of permanent first molars in 778 males and 653 female children aged from 5 to 9-year old and analysed. The eruption was divided into 4 phases; the tip of the crown can be seen, the dull occlusal surface of the crown can be easily seen, the crown is not in contact with its antagonist, and the crown is in contact with its antagonist. The obtained results were as follows : 1. It seemed that percentage of the eruptingand erupted permanent first molar in female by age was higher than that of male. 2. In general, percentage of the erupting and erupted permanent first molar by age was higher than that of upper first molar. 3. In the correlation of age with the eruption phase, the regression equation were "y=0.43x+5.61" on male upper first molar, "y=0.41x+5.60" on male lower first molar, "y=0.44x+5.47" on female upper first molar, and "y=0.38x+5.57" on female lower first molar respectively.n female lower first molar respectively.

• Journal of the korean academy of Pediatric Dentistry
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• v.8 no.1
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• pp.103-117
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• 1981

The data about dental caries obtained from 1438 preschool children (male 797, female 641) in Seoul aged from 3 to 6 were analyzed by their sexes, ages, jaws and teeth surfaces. The results were as follows. 1. dmf rate : 92.63% 2. dmft index : 6.06 dmft rate 30.81 % dmfs index : 11.82 dmfs rate 12.02 % 3. d,m & f rate d rate: 79.45% m rate: 8.15% f rate : 12.40 % 4. dft index : 5.94 5. The order of caries susceptible tooth 1. Lower deciduous 2nd molar 2. Lower deciduous 1st molar 3. Upper deciduous 2nd molar 4. Upper deciduous lateral incisor 5. Upper deciduous cental incisor 6. Upper deciduous lateral incisor 7. Lower deciduous canine 8. Upper deciduous canine 9. Lower deciduous central incisor 10. Lower deciduous lateral incisor 6. Predilection sites of each tooth A) Deciduous central incisor ; Max. : Mesial cavity Mand. : Mesio-distal cavity B) Decidous lateral incisor ; Max. : Mesial cavity Mand. : Distal cavity=Mesial cavity C) Deciduous canine; Max. : Labial cavity Mand. : Distal cavity D) Decidous 1st molar ; Max. : Disto-occlusal cavity Mand.: Disto-occlusal cavity E) Deciduous 2nd molar ; Max. : Linguo-occlusal cavity Mand.: Occlusal cavity 7. All the values in caries criteria in 1981 were somewhat lower than in 1968, but m & f rate were increased.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.1
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• pp.25-33
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• 2017

The lower $2^{nd}$ molar eruption is beginning to mesiolingually, then rotate to distobuccally so it has a tendency to be tilted and impacted mesially. Signs and symptoms of impacted $2^{nd}$ molar are similar to impacted $3^{rd}$ molar's. However, treatment plan for impacted $2^{nd}$ molar is different from that of impacted $3^{rd}$'s. The former is the preservation and uprighting of $2^{nd}$ molar so that it could act to recovery of mastication, symmetrical facial growth, maintaining the symmetry of dental arch, stable occlusion, while the latter is the extraction of tooth. If the uprighting treatment is planned, most proper protocol of treatment and the additional treatment opition should be applied with consideration for it's crown exposure, present of $3^{rd}$ molar which interrupt the uprighting process, extrusion of opposite tooth. Although it could not improve the esthetic result, it could prevent many dental problems. Therefore, uprighting for impacted lower $2^{nd}$ molar is meaningful treatment.

• Journal of Oral Medicine and Pain
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• v.19 no.1
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• pp.57-72
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• 1994

This study was undertaken to obtain the data age determination following the eruption of individual cusps of the first molars in the point of forensic odontology. 532 children (294 male and 238 female, born between April, 1989 and March, 1986) from a kindergarten and a primary school in a reesidential district in Seoul were studied. The eruption state of the first molar was divides into 6 stages according to the degree of exposure of individual cusps, and correlation between the stage and age was stastically analysed. The results of the study lead to following conclusions : 1. The most frequently seen eruption sequence of cusps for the upper first molar was mesibuccal cusp, mesiopalatal cusp, distobuccal cusp, mesiodistal cusp, distopalatal cusp. As for the lower first molar : mesiobuccal cusp, mcsiolingual cusp, distobuccal cusp, distolingual cusp. 2. The time of eruption was earlier in the female ethan in the male, but it was stastically remarkable only in upper and lower parts of the right and the left teeth of subjects age between 6.0 and 6.5 and upper part of the right and the left teeth of subjects age over 7.5 3. The eruption of the lower first molar was comparatively earlier than that of the upper first molar and there was no significant stastical difference between the right and the left first molars in the time of eruption. 4. There was no noticeable difference in the eruption sequence of cusps, irrespective of sex and side. 5. The eruption of the upper first molar is started at the age of about 6.4 and complete the age of about 7.1 and as for the lower first molar, it is from 6.3 to 7.0

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.1
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• pp.47-59
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• 2016

Purpose: The aim of this study was to investigate the changes in occlusal force after loss of the lower first molar depending on the inclination and extrusion of the adjacent and opposing teeth by using a strain gauge. Materials and Methods: Anatomic teeth were used to reconstruct the normal dental arch with loss of the lower right first molar. A uniformly thick layer of silicone was applied to the root to mimic the periodontal ligament. Four stages of dies with varying degrees of inclination and extrusion of the adjacent and opposing teeth were constructed and attached to master model interchangeably by using a CAD/CAM fabricated customized die system. The strain gauges were attached to teeth and a universal testing machine was used to determine the changes in occlusal force. An independent t-test and one-way ANOVA were performed (${\alpha}=.05$). Results: While simulating chewing food, the upper first, second premolar and lower second molar showed greater occlusal force than before extraction. When the change of adjacent teeth's occlusal force with their progressive movement after molar loss was evaluated, the difference among four die models was significant and was in the decreasing aspect (P < 0.05). Conclusion: When the lower first molar was lost and the adjacent teeth did not move yet, the occlusal force in adjacent teeth was higher than that when the lower first molar still existed. In addition, the occlusal force in the upper premolars and lower second molar decreased significantly with the progressive movement of adjacent teeth.

• The korean journal of orthodontics
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• v.17 no.2
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• pp.321-333
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• 1987

The purpose of this study was to observe the changes of the lower 3rd molars following the extraction of the lower 2nd molars by Lateral Cephalograms and Orthopantomograms. The subjects consisted of twenty malocclusion, 7 males 13 females, were 19 year 5 month old at the removal of the lower 2nd molars, 19 year 1 month old at the end of the orthodontic supervision after the removal of the lower 2nd molars (mean age) The obtained results were as follows, 1 It is recommended to extract the lower 2nd molars when the lower 3rd molars are Nolla's Stage 4 or 5 2 With the pre-extraction variables obtained by factor analysis, it was possible to predict the long axis of the lower 3rd molars after 2nd molar extraction. 3 There were no impacted 3rd molars.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.6
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• pp.505-511
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• 2011

Purpose: This study evaluated correlation and risk factors between position of the mandibular third molars and mandibular angle fractures using clinical and radiographic findings. Methods: Medical records and panoramic radiographs of 188 patients with mandibular fractures were retrospectively reviewed. The presence and position of the third molars were assessed for each patient and were related to the occurrence of mandibular angle fractures. Results: The incidence of mandibular angle fracture was found to be greater when a lower third molar was present, particularly at the occlusal plane positioned on the $2^{nd}$ molar occlusal surface (by Archer system) and the third molar is impacted in mandibular ramus (by Pell & Gregory system). Of the 192 sites with a lower third molar, 32 (16%) had an angle fracture. Of the 184 site without lower third molars, 16 (8%) had an angle fracture. Conclusion: This study confirmed an increased risk of angle fractures in the presence of a lower third molar as well as variable risk for angle fracture, depending on positioning of the third molar.