• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.3
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• pp.340-347
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• 2022

Distal displacement of the tooth germ of the mandibular second premolar (MnP2) leads to its impaction and obturation of the eruption path of the mandibular first molar delaying its eruption. The present case report describes the treatment of 2 cases of eruption guidance for distally displaced developing MnP2 that caused delayed eruption of the mandibular first molar. Intentional extraction of primary predecessor results in the mesial shift of the displaced MnP2. However, unfavorable distal ectopic eruption of the mandibular first premolar after the premature loss of primary second molar has been previously reported. Hemisection and sequential extraction of the mandibular primary second molar were performed to mesially shift the distally displaced MnP2, while preventing unfavorable distal ectopic eruption of the mandibular first premolar.

• The Journal of the Korean dental association
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• v.26 no.10 s.233
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• pp.898-902
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• 1988

완전히 발육된 하악 제3대구치가 매복되어 있거나 또는 부분적으로 맹출된 상태일때는 임상증상을 일으키기 전에 발치하는 것이 치관주위염이나 이로 인한 합병증 및 치주질환 등을 예방할 수 있느느 가장 좋은 방법이며 이미 임상 증상을 유발한 매복 하악 제 3대구치는 대부분 재발방지를 위하여 발거하게 된다. 성공적인 발치의 기준을 1) 치아의 완전한 발치 2) 인접조직에 대한 최소한의 외과적 손상 3) 술후 합병증의 극소화 4) 가능한한 시술 시간의 단축 등이라 할때 매복 하악제 3대구치의 성공적인 발거를 위하여는 발치의 기본 원칙을 숙지하여야 함은 물론이며 더욱 면밀한 술전 평가와 외과적 발치술 시 필요한 기구의 완비 등이 필수적이라 할 것이다.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.2
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• pp.229-236
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• 2021

Eruption disturbances of the mandibular first molars can cause multiple problems in occlusal development although they are extremely rare. Early diagnosis and treatment are very important to prevent complications associated with eruption disturbances. The present case report describes the treatment of two cases of eruption disturbances of the mandibular first permanent molar. A fixed appliance composed of a cantilever spring with mandibular second deciduous molar as an anchor tooth was used to tract the impacted mandibular first permanent molar. The success of both cases shows that this novel traction appliance can be used to induce the eruption of an impacted mandibular first permanent molar within a short time in patients with intact mandibular second deciduous molar as an anchor tooth.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.3
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• pp.325-336
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• 2009

The purpose of this study was to investigate the eruption pattern of the mandibular first molar in sagittal, frontal and horizontal views using the cone beam CT scanning. CT images were obtained from healthy 83 children (42 boys, 41 girls) between 3 to 10 years of age with a normal dentition according to Nolla stage. 1. In the frontal and horizontal view, the intermolar width decreased continuously with stage and slightly increased at the last stage. 2. In the sagittal and frontal view, eruption distances from occlusal plane were observed the largest change between stage 5 and 7. 3. In the horizontal and sagittal view, mandibular first molar from distal surface of primary second molar moved distally between stage 4 and 6. 4. In the sagittal view, angle from occlusal plane to mesio-distal axis increased between stage 4 and 8. 5. In the frontal view, angle from occlusal plane to bucco-lingual axis increased continuously during all stage. 6. In the horizontal view, angle from midsagittal plane to long axis increased between stage 5 and 8.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.4
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• pp.373-384
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• 2023

This study aims to confirm the average chronologic age according to the developmental stages of the mandibular canine (L3), first and second premolars (L4, L5), and second and third molars (L7, L8) in children and adolescents, and to confirm the developmental stage of L3, L4, L5, and L7, which can estimate the development of L8. A total of 1,956 digital panoramic radiographs of healthy individuals aged between 6 and 15 years who visited Seoul National University Dental Hospital from January 2019 to December 2020 were selected. The developmental stages of L3, L4, L5, L7, and L8 on both sides were evaluated using the dental maturity scoring system proposed by Demirjian and Goldstein. The average age at which the follicle of L8 was first observed was around 9.34 ± 1.35 years and varied from 6 to 12 years. The possibility of agenesis of L8 was high when no traces of L8 were observed after the following stages: L3, L4, and L5 at the developmental stage F and L7 at the developmental stage E; the age was about 10 years. In estimating the development of L8, when only one tooth was considered, estimation accuracy with L5 was the highest, and there was no significant difference when all four teeth were included. This study showed the age distribution according to the developmental stages of L3, L4, L5, L7, and L8 in children and adolescents and confirmed the developmental stages of L3, L4, L5, and L7, which can be used to estimate the development of L8.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.2
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• pp.219-227
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• 2020

Tooth eruption involves a complex developmental process of tooth migration from the dental follicular origin to the final occlusion position in the oral cavity via the alveolar process. Disturbance of tooth eruption can occur at any point in a series of eruption stages; however, horizontal impaction of the mandibular first molar and primary retention of the primary mandibular second molar are rarely observed simultaneously. This study describes the treatment for two cases of horizontally impacted first molar with primary retention of primary molar. The primary retention of the primary mandibular second molar was extracted, and orthodontic traction was applied to the horizontally impacted primary mandibular first molar. Subsequently, displacement of the premolar tooth bud was improved and space regaining for eruption was achieved, guiding to normal eruption of the first molar.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.1
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• pp.41-45
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• 2004

In the normal growth and development of the mandible, the molar tooth buds distal to the first permanent molar have a mesial inclination. This inclination is usually self-correcting, but, unfortunately, this self-correction does not always occur. The first case is about, 14-year-old female patient with familial history of lower second molar impaction. Her lower second molars were both impacted, and she was treated with sectional wires and open-coil springs. The second case, 14-year-old male, we treated his impacted #47 with Halterman appliance. The third case, 11-year-old male, his both mandibular second molars were impacted during full-fixed orthodontic treatment. They were treated with brass wire, sectional wire and open-coil spring.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.3
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• pp.415-430
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• 1996

The purpose of this study was to evaluate the stress distributions in the surrounding tissues of the teeth seated by indirect retainers in three different teeth of unilateral distal extension partial denture when the dislodging forces were applied on denture bases. Three dimensional photoelastic models were made. The teeth on which indirect retainers were seated were mandibular left lateral incisor (Model I), canine (Model II), and first premolar (Model III). The dislodging force with 860mg at $45^{\circ}$ angulation to occlusal plane was applied to each model. Three dimensional photoelastic stress analysis was done, and the records were diagramed and analysed. The results were as follows : The compressive stresses were shown the most on neck portions of buccal, mesial, and distal sides in all three models. Slight tensile stresses were shown on neck portions of lingual sides in all three models. The compressive stresses on buccal side were shown in strength in such order as model I, model II, and model III. The compressive stresses were shown on neck portion of mesial and distal sides of model I and mode II, with model I more than Model II. The compressive stresses were shown only on neck portion of mesial side on Model III. The general overall magnitude of compressive stresses were shown in strength in such order as Model I, Model II, and Model III.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.1
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• pp.167-174
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• 2008

Mandibular first molar and primary molars usually have two roots, on the mesial and distal sides. Occasionally, these molars have an extra root located in the distolingual aspect. Prevalence of the 3-rooted first permanent molar shows ethnic variation, ranging from about 3% in Caucasian to about 20% in Mongoloid group, which includes Chinese, Japanese, Eskimo, American and Canadian Indians. The frequency of the mandibular molar with three roots decreases in the order of the first permanent molar, the second primary molar, and the first primary molar. If the mandibular first or second primary molar has an additional distolingual root, the adjacent molars, including the first permanent molar, posterior to it also may have it. Coronal morphologic change can occur in the mandibular first primary molars with three roots: the crown had more triangular-shape compared to the one with two roots, possibly affected by the presence of additional distolingual root. Clinically, exact diagnosis and treatment should be taken with those teeth for pulp canal treatment, extraction, and SS Cr.

• The korean journal of orthodontics
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• v.34 no.2 s.103
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• pp.109-119
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• 2004

This study aimed at investigating the skeletal, dentoalveolar, and soft tissue changes of Class III malocclusion cases treated by second molar extraction. The lateral cephalograms of 15 subjects with moderate Class III malocclusion by average ANB $-1.4^{\circ}\;and\;IMPA\;85^{\circ}$ were traced and the computerized superimposition of average craniofacial change was made. The data was gathered and statistically analyzed. The results were as follows: 1 Lower anterior facial height/anterior facial height increased by 0.6%(P<0.01), mandibular plane increased by $1.5^{\circ}$(P<0.05). 2. There was a slightly downward & backward rotation of the mandible. 3. Lower first molar tipped distally by 4.nm(P<0.001), lower anterior teeth lingually tipped by $3.2^{\circ}$(P<0.05). 4. Retracted lower lip improved facial profile. This study may suggest that second molar extraction could be effective for a moderate Class III malocclusion to make distalization of the lower first molar easier and avoid severe lingual tipping of the lower incisor, if the lower third molar has a normal shape, good direction of eruption and adequate time for lower second molar extraction