• The korean journal of orthodontics
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• v.31 no.6 s.89
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• pp.549-558
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• 2001

This study was undertaken to demonstrate the forces in the maxillary alveolar bone generated by the activation of the maxillary posterior crossbite appliance In the treatment of posterior buccal crossbite caused by buccal ectopic eruption of the maxillary second molar. A photoelastic model was fabricated using a Photoelastic material (PL-3) to simulate alveolar bone and ivory-colored resin teeth. The model was observed throughout the anterior and posterior view in a circular polariscope and recorded photographically before and after activation of the maxillary posterior crossbite appliance. The following conclusions were reached from this investigation : 1. When the traction force was applied on the palatal surface of the second molar, stresses were concentrated at the buccal and palatal root apices and alveolar crest area. The axis of rotation of palatal root was at the root apex and that of the buccal root was at the root li4 area. In this result, palatal tipping and rotating force were generated. 2. When the traction force was applied on the buccal surface of the second molar, more stresses than loading on the palatal surface were observed in the palatal and buccal root apices. Furthermore, the heavier stresses creating an intrusive force and controlled tipping force were recorded below the buccal and palatal root apices below the palatal root surface. In addition, the axis of rotation of palatal root disappeared whereas the rotation axis of the buccal root moved to the root apex from the apical 1/4 area. 3. When the traction force was simultaneously applied on the maxillary right and left second molars, the stress intensity around the maxillary first molar root area was greater than the stress generated by the only buccal traction of the maxillary right or left second molar. As in above mentioned results, we should realize that force application on the palatal surface of second molars with the maxillary posterior crossbite appliance Produced rotation of the second molar and palatal traction, which nay cause occlusal Interference. That is to say, we have to escape the rotation and uncontrolled tipping creating occlusal interference when correcting buccal posterior crossbite. For this purpose, we recommend buccal traction rather than palatal traction force on the second molar.

• Journal of Periodontal and Implant Science
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• v.32 no.2
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• pp.379-388
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• 2002

For the success of dental implant, accurate radiographic evaluation is prerequisite for planning the location of the osseointegrated implants and avoiding injury to vital structures. CT/MPR(computed tomography/multiplanar reformation) shows improved visualization of inferior alveolar canal. In order to obtain cross-sectional images parallel to the teeth, the occlusal plane is used to orientate for the axial plane. If the direction of axial plane is not parallel to the occlusal plane, the reformatted cross-sectional scans will be oblique to the planned fixture direction and will not show the actual dimension of the planned fixture's location. If the available bone height which measured in the cross-sectional view is much greater than the actual available bone height, penetration of canal may occur. The aim of this study is to assess the effect of the axial plane to measurement of available bone height for dental implant in computed tomography of the mandible. 40 patients who had made radiographic stents and had taken CT were selected. The sites that were included in the study were 45 molar regions. In the central panoramic scan, the length from alveolar crest to superior border of inferior alveolar canal(available bone height, ABH) was measured in direction of reformatted cross-sectional plane(uncorrected ABH). Then, length from alveolar crest to superior border of canal was measured in direction of stent(corrected ABH). The angle between uncorrected ABH and corrected ABH was measured. From each ABH, available fixture length was decided by $Br{{\aa}}nemark$ system. The results were following ; the difference between two ABHs was statistically significant in both first and second molar(p< 0.01). The percentage of difference more than 1 mm was 8.7% in first molar and 15.5% in second molar. The percentage of difference more than 2 mm was 2.0% in first molar and 6.6% in second molar. The maximum value of difference was 2.5 mm in first molar and 2.2 mm in second molar. The correlations between difference of 2 ABHs and angle was positive correlations in both first and second molar. The correlation coefficient was 0.534 in first molar and 0.728 in second molar. The second molar has a stronger positive correlation. The percentage of disagreement between 2 fixture lengths from two ABHs was 24.4% in first molar and 28.9% in second molar.

• 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.28 no.3
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• pp.488-495
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• 2001

Treatment of class II malocclusions require distalization of maxillary molars into class I relationship. Intraarch distal molar movement techniques have recently assumed an important role in young patients. In this study, the dental and skeletal effects of the pendulum appliance were evaluated by means of cephalometric radiographs. The samples were consisted of 19 patients: 11 females and 8 males, mean age $11.68{\pm}1.52$ years. Measurements were obtained from cephalometric prior to and the day of removal of the pendulum appliance. Treatment changes were analyzed. The following results were obtain. 1. The pendulum appliance produced $2.94{\pm}1.54mm$ distal molar movement with a mean intrusion of $1.17{\pm}0.97mm$, mean period $18.13{\pm}7.95$ weeks. 2. The anchor tooth was $1.34{\pm}1.40mm$ forward movement and $0.48{\pm}0.99mm$ extrusion, and labial tilting of incisors. 3. The angle between palatal plane and mandibular plane increased significantly. 4. There was no significant difference in according to 2nd molar position. 5. Total movement was consisted of 74% distal movement of 1st molar and 26% forward movement of the anchor tooth.

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.61-74
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• 1998

The Purpose of this study was to investigate the stress distribution and tooth displacement at the initial phase produced by 5 types of molar uprighting springs using finite element method. The three dimensional finite element model of lower dentition, bone and springs was composed of 5083 elements and 2071 nodes. The results were as follows: 1. In case of helical spring and root spring, intrusion of lower canine and first premolar were observed md distal tipping, translation and extrusion of lower second molar were observed. 2. In case of T-loop, modified T-loop and box loop, intrusion and distal translation of lower second premolar were observed, and the largest crown distal tipping and translation of lower second molar were observed in T-loop and the smallest were observed in box loop. 3. In case of T-loop with cinch-bact crown distal tipping and translation of lower second molar were decreased, but extrusion was also decreased. 4. With increase of activation in T-loop, mesial translation and won distal tipping of lower second molar were increased and edentulous space was closing, but distal translation of second premolar was also increased. 5. With increase of tip-back bend in T--loop, distal tipping and translation of lower second molar were increased, but extrusion was also increased more largely.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.4
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• pp.324-330
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• 2014

In case of implant-tooth connected prosthesis, a natural tooth tends to intrude. There are several mechanisms that explain an intrusion phenomenon. So it is reco mmended not to connect an implant with a natural tooth. A 68-year-old female had upper left $2^{nd}$ premolar and $2^{nd}$ molar extracted and underwent implant surgery on the missing area. We made an implant prosthesis and treated upper left $1^{st}$ molar with a gold crown. 2.5 year later, the patient complained about loose proximal contact and food impaction between upper left $1^{st}$ molar and $2^{nd}$ molar. Mesial side of upper left $2^{nd}$ molar implant prosthesis was soldered so that proximal contact became tight again. But after 7 months, about 2 mm intrusion of upper left $1^{st}$ molar occurred, and the patient felt periodontally originated pain on intruded upper left $1^{st}$ molar. After the gold crown on upper left $1^{st}$ molar was removed, extrusion occurred and pain was relived.

• 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.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.2
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• pp.147-153
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• 2017

This study assessed the association between ectopic eruption of the maxillary first permanent molar and skeletal malocclusion in 5- to 10-year-old children. As subjects, 786 children who attended the Wonkwang University Dental Hospital for orthodontic diagnosis were included. Children with unerupted first permanent molars or fully erupted second permanent molars were excluded. The study group demonstrated ectopic eruption of the maxillary first permanent molar, while the control group did not. Cephalometric radiographs taken between January 2003 and August 2015 were analyzed. Skeletal class III malocclusion was detected in 57.0% of the study group, which differed significantly from that in the control group (p<0.05). The SNA, ANB angles, and A to N-perpendicular distance were significantly smaller, whereas the A-B plane angle and APDI were significantly greater in the study group than in the control group (p<0.05). The SNB and mandibular plane angles were not significantly different between the groups. Thus, maxillary undergrowth is a risk factor for ectopic eruption of the maxillary first permanent molar.

• 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.

• 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