• The korean journal of orthodontics
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• v.34 no.3 s.104
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• pp.219-227
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• 2004

The purpose of this study was to evaluate the spatial changes of mesial-in rotated maxillary molar and opposite anchor tooth during derotation by the precision transpalatal arch (TPA) with the use of a new typodont simulation system, the Calorific machine system, which was designed to observe the whole process of tooth movement. The maxillary right first molar was used for the anchor tooth and the maxillary left first molar was used for the mesial-in rotated tooth, and the angle of rotation was increased to 20,40, and 60. A passive precision TPA was fabricated and then activated by bending the left arm to 20, 40, and 60. Each experiment was repeated five times under the same conditions and analyzed by ANOVA and Tucky's Studentized Range (HSD) test. In the occlusal plane, when the bending angle of precision TPA was increased, the mesiobuccal cusp of the rotated molar moved more buccally (p<0.001) and less distally (p<0.001) while the distolingual cusp moved in the mesiopalatal direction. In the sagittal plane, the palatal roots of the derotated molar moved mesially (p<0.001). In the traverse plane, the derotated molar showed slight extrusion (p<0.001). The upper right first molar, which was used as an anchor tooth, showed clinically insignificant movement across all three planes.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.89-100
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• 2005

The purpose of this study was to analyze the morphometrics of primary second molar and permanent first molar. Samples were consisted of normal occlusion in the primary dentition(50 males and 50 females) and permanent dentition(43 males and 43 females). Their upper and lower plaster casts were used and their measuring points were decided, through 3-dimensional laser scanning(3D Scanner, DS4060, LDI, U.S.A.), fitting standard horizontal plane were made for measuring the intercuspal distance, volume of intercuspal area and section curve. The results were as follows; 1. Average distance from the fit plane to the cusp tips of mandibular primary second molar was smaller than any other tooth. (0.05-0.09 mm in male and 0.04-0.09 mm in female). 2. Intercuspal distances of mandibular primary second molar and permanent first molar were larger in male than in female. Especially, there was statistical significance in primary second molar(p<0.05). 3. Intercuspal distance between distobuccal and distolingual cusp was larger in maxillary primary second molar, except cross intercuspal distances. And distances between distal and distolingual cusp, in mandibular primary second molar, between mesiolingual and mesiobuccal cusp, in maxillary first molar, and between distolingual and mesiolingual cusp, in mandibular first molar were larger than any other intercuspal distance. 4. Volume of intercuspal area of primary second molar and permanent first molar was larger in mandible than in maxilla and that of permanent first molar was 1.40-1.75 times of primary second molar (p<0.05). Also it was larger in male than in female, but there was no statistical significance. 5. In most cases, section curves were wider and deeper in permanent dentition than in primary dentition. Except cross intercuspal distances, in maxilla, section curve between mesiobuccal and mesiolingual cusp was the deepest in both dentition. In mandible, section curve between distobuccal and distal cusp was the deepest in permanent dentition and between distolingual and distal cusp was the deepest in primary dentition.

• Restorative Dentistry and Endodontics
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• v.23 no.2
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• pp.647-655
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• 1998

심미도재수복시의 와동의 폭과 교두의 capping이 응력의 분포에 미치는 영향을 비교하기 위하여 연속사진 촬영술을 이용하여 상악제1소구치의 3차원 유한요소 모델을 제작하였다. 법랑질, 상아질, 도재 및 복합레진시멘트의 각각의 재질에 대한 물성치를 부여하고, 140N의 하중을 가하여 Super SAP 프로그램으로 해석하여 다음과 같은 결과를 얻었다. 1. 응력은 탄성계수값이 큰 법랑질과 도재를 따라 분포되고, 연질의 상아질에는 적게 발생된다. 2. 와동의 협측치수선각부위에서는 인레이모델의 경우에는 와동폭의 증가에 따른 응력의 증가는 관찰되지 않으나, 온레이모델에서는 응력의 증가가 관찰된다. 3. 온레이모델의 경우에는 근심협측교두를 피개하고 있는 도재부위에 최대주응력이 크게 나타나고, 치은변연부의 도재에서는 교두를 피개하지 않은 인레이모델의 해당되는 법랑질에 비해 응력이 1/2정도로 감소된다. 4. 하중이 증가되면 잔존치질의 파절은 근심와동의 협측치은선각부위에서 협측보다는 치은을 향해 경사지게 일어날 것이다. 5. 교두를 피개하면 교두피개부위에서의 도재의 파절가능성은 증가되고, 치은변연에서는 도재와 하부의 치질의 파절가능성은 감소된다. 6. 도재를 이용하여 교두를 피개할 경우에는 응력을 견딜 수 있는 도재의 두께를 부여할 수 있도록 교두를 충분히 삭제하여야 하고, 충분한 강도를 갖는 도재를 선택하여야 한다.

• The korean journal of orthodontics
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• v.38 no.3
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• pp.175-186
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• 2008

Objective: To evaluate the discrepancies between initial STO and final STO in Class III malocclusions and to find which factors are related to the discrepancies. Methods: Twenty patients were selected for the extraction group and 20 patients for the non-extraction group. They were diagnosed as skeletal Class III and received presurgical orthodontic treatment and mandibular set-back surgery at Pusan National University Hospital. The lateral cephalograms were analyzed for initial STO (T1s) at pretreatment and final STO (T2s) after presurgical orthodontic treatment, and specified the landmarks 3s coordinates of the X and V axes. Results: Differences in hard tissue points (T1s-T2s) in the X coordinates of upper central incisor edge, upper first molar mesial end surface, lower central incisor apex, lower first molar mesial end surface and mesio-buccal cusp and Y coordinates of upper central incisor edge, upper central incisor apex, upper first molar mesio-buccal cusp were statistically significant in the extraction group. Differences in hard tissue points (T1s-T2s) in the X coordinates of upper central incisor edge, lower central incisor apex, lower first molar mesial end surface and Y coordinates of lower central incisor apex were statistically significant in the non-extraction group. In the extraction group, the upper arch length discrepancy (UALD) had a statistically significant effect on maxillary incisor and first molar estimation. Lower arch length discrepancy and IMPA had statistically significant effects on mandibular incisor estimation in both groups. Conclusions: Discrepancies between initial STO and final STO and factors contributing to the accuracy of initial STO must be considered in treatment planning of Class III surgical patients to increase the accuracy of prediction.

• The korean journal of orthodontics
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• v.40 no.6
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• pp.373-382
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• 2010

Objective: The purpose of this study was to assess the dentoalveolar compensation in facial asymmetry individuals using an integration of a CBCT image and a laser scanned dental cast image. Methods: The subjects consisted of 30 adults with asymmetric mandibles and 20 adults with symmetric mandibles. The CBCT and laser scanned dental cast images were integrated with a registration technique. Canine and first molar position and angulation were assessed from reference coordinates. The differences between deviated and non-deviated sides were analyzed with the paired t-test. The differences shown according to menton deviation were also statistically analyzed using Pearson correlation analysis. Results: The experimental group showed deviated and non-deviated side differences (dev.-ndev.) in the position and angle of the canine and first molars. Menton deviation showed positive correlation with the deviation side (dev.-ndev.) for the maxillary and mandibular 1st molar angles, negative correlation with the deviation side for the vertical position of the maxillary 1st molars, transverse position of the mandibular canine, transverse position and vertical position of the mesio-lingual cusp of the mandibular 1st molars. Conclusions: The upper and lower canine and first molars of facial asymmetry individuals were compensated, so the transverse position, vertical position, and angle showed differences between the deviated/non-deviated sides.

• Restorative Dentistry and Endodontics
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• v.33 no.1
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• pp.28-38
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• 2008

This study was to investigate the influence of composite resins with different elastic modulus, cavity modification and occlusal loading condition on the stress distribution of restored notch-shaped noncarious cervical lesion using 3-dimensional (3D) finite element (FE) analysis. The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. A notch-shaped cavity and a modified cavity with a rounded apex were modeled. Unmodified and modified cavities were filled with hybrid or flowable resin. After restoration, a static load of 500N was applied in a point-load condition at buccal cusp and palatal cusp. The stress data were analyzed using analysis of principal stress. The results were as follows: 1. In the unrestored cavity, the stresses were highly concentrated at mesial CEJ and lesion apex and the peak stress was observed at the mesial point angle under both loading conditions. 2. After restoration of the cavity, stresses were significantly reduced at the lesion apex, however cervical cavosurface margin, stresses were more increased than before restoration under both loading conditions. 3. When restoring the notch-shaped lesion, material with high elastic modulus worked well at the lesion apex and material with low elastic modulus worked well at the cervical cavosurface margin. 4. Cavity modification the rounding apex did not reduce compressive stress, but tensile stress was reduced.

• Restorative Dentistry and Endodontics
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• v.31 no.5
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• pp.359-370
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• 2006

The objective of this study was to investigate the effect of excessive occlusal loading on stress distribution on four type of cervical lesion, using a three dimensional finite element analysis (3D FEA). The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. Four different lesion configurations representative of the various types observed clinically for teeth were studied. A static point load of 500N was applied to the buccal and lingual cusp (Load A and B). The principal stresses in lesion apex, and vertical sectioned margin of cervical wall were analyzed. The results were as follows 1. The patterns of stress distribution were similar but the magnitude was different in four types of lesion 2. The peak stress was observed at mesial corner and also stresses concentrated at lesion apex. 3. The compressive stress under load A and the tensile stress under load B were dominant stress. 4. Under the load, lesion can be increased and harmful to tooth structure unless restored.

• Restorative Dentistry and Endodontics
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• v.34 no.1
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• pp.8-19
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• 2009

The purpose of this study was to investigate the effects of four restorative materials under various occlusal loading conditions on the stress distribution at the CEJ of buccal. palatal surface and central groove of occlusal surface of endodontically treated maxillary second premolar, using a 3D finte element analysis. A 3D finite element model of human maxillary second premolar was endodontically treated. After endodontic treatment, access cavity was filled with Amalgam, resin, ceramic or gold of different mechanical properties. A static 500N forces were applied at the buccal (Load-1) and palatal cusp (Load-2) and a static 170N forces were applied at the mesial marginal ridge and palatal cusp simultaneously as centric occlusion (Load-3). Under 3-type Loading condition, the value of tensile stress was analyzed after 4-type restoration at the CEJ of buccal and palatal surface and central groove of occlusal surface Excessive high tensile stresses were observed along the palatal CEJ in Load-1 case and buccal CEJ in Load-2 in all of the restorations. There was no difference in magnitude of stress in relation to the type of restorations. Heavy tensile stress concentrations were observed around the loading point and along the central groove of occlusal surface in all of the restorations. There was slight difference in magnitude of stress between different types of restorations. High tensile stress concentrations around the loading points were observed and there was no difference in magnitude of stress between different types of restorations in Load-3.

• Restorative Dentistry and Endodontics
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• v.32 no.1
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• pp.69-79
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• 2007

The purpose of this study was to investigate the effects of composite resin restorations on the stress distribution of notch shaped noncarious cervical lesion using three-dimensional (3D) finite element analysis (FEA). Extracted maxillary second premolar was scanned serially with Micro-CT (SkyScan1072 ; SkyScan, Aartselaar, Belgium). The 3D images were processed by 3D-DOCTOR (Able Software Co., Lexington, MA, USA). ANSYS (Swanson Analysis Systems, Inc., Houston, USA) was used to mesh and analyze 3D FE model. Notch shaped cavity was filled with hybrid or flowable resin and each restoration was simulated with adhesive layer thickness ($40{\mu}m$) A static load of 500 N was applied on a point load condition at buccal cusp (loading A) and palatal cusp (loading B). The principal stresses in the lesion apex (internal line angle of cavity) and middle vertical wall were analyzed using ANSYS. The results were as follows 1. Under loading A, compressive stress is created in the unrestored and restored cavity. Under loading B, tensile stress is created. And the peak stress concentration is seen at near mesial corner of the cavity under each load condition. 2. Compared to the unrestored cavity, the principal stresses at the cemeto-enamel junction (CEJ) and internal line angle of the cavity were more reduced in the restored cavity on both load con ditions. 3. In teeth restored with hybrid composite, the principal stresses at the CEJ and internal line angle of the cavity were more reduced than flowable resin.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.221-239
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• 2010

Bone loss may occur depending on the loading conditions. careful treatment planning and prosthetic procedures are very important factors for the proper distribution of stress. Evaluate the stress distributions according to numbers and location of implants in three-unit fixed partial dentures. A mandible missing the right second premolar, first molar and second molar was modeled. Using the CT data. we modeled a mandible with a width of 15mm, a height of 20mm and a length of 30mm, 2mm-thickness cortical bone covering cancellous bone mallow. An internal type implant and A solid type abutment was used. A model with 3 implants placed in a straight line, offset 1.5 mm buccally, offset 1.5 mm lingually and another model with 3 implants offset in the opposite way were prepared. And models with 2 implants were both end support models, a mesial cantilever model and a distal cantilever model. Three types of loading was applied; a case where 155 N was applied solely on the second premolar, a case where 206 N was applied solely on the second molar and a case where 155 N was applied on the first premolar and 206 N was applied on the first and second molar. For all the cases, inclined loads of 30 degrees were applied on the buccal cusps and vertical loads were applied on the central fossas of the teeth. Finite element analysis was carried out for each case to find out the stress distribution on bones and implants. This study has shown that prostheses with more implants caused lower stress on bones and implants, no matter what kind of load was applied. Furthermore, it was found out that inclined loads applied on implants had worse effects than vertical loads. Therefore, it is believed that these results should be considered when placing implants in the future.