• 대한치과교정학회지
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• 제48권3호
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• pp.133-142
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• 2018

Objective: The purpose of this study was to evaluate differences in three-dimensional (3D) morphology of the hard palate between Korean adults with and without mild-to-moderate obstructive sleep apnea (OSA) using cone-beam computed tomographic (CBCT) data. Methods: The protocol for the two-dimensional (2D) and 3D mathematical modeling was established by analyzing CBCT images of 30 adults with OSA and 30 matched controls without OSA, using MIMICS software. The linear and angular measurements were also determined using this software. The measurements were repeated for 30 palates, by the same operator, to assess reliability. Results: The palates of OSA patients were higher in the posterior part and narrower in the anterior-superior part than those of the control group (p < 0.05). The nasal cavities of patients with OSA were narrower (p < 0.05) than those of controls. The increasing angle of the first molar palatal root is a compensation of the upper dental arch to improve occlusion. However, for most palatal measurements, there were no significant differences between the OSA and control groups (p > 0.05). The results of 2D and 3D mathematical models were consistent for linear and angular measurements, indicating that 2D and 3D mathematical modeling of the palate is a reliable methodology. Conclusions: OSA is a multifactorial disease; the palates of adults with mild-to-moderate OSA do not have specific morphological features distinct from those of healthy controls.

• 대한치과교정학회지
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• 제15권1호
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• pp.67-74
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• 1985

The primary objective of this study is to make the prediction percentile tabulation of the sun of mesiodistal width of the unerupted permanent canines and premolars derived from the sum of mesiodistal width of the erupted permanent mandibular incisors in Korean population. The subjects were 316 individuals with normal occlusion aged 11 to 23 years. The sum of mesiodistal width of mandibular incisors, and the sum of mesiodistal width of maxillary canine, first and second premolars, and the sum of mandibular canine, first and second premolars were measured from the dental cast models using the sliding caliper (Mitutoyo Co.). From the study, the results are as follows: 1. The sum of M-D width of mandibular incisors and the sum of M-D width of maxillary canines, first and second premolars, and the sum of M-D width of mandibular canine, first and second premolars were smaller than those of American Caucasians and Negros. 2. The correlation coefficient between the sum of M-D width of mandibular incisors and that of maxillary or mandibular canines, first and second premolars was found to be 0.598 and 0.586, respectively. 3. The regression constants were determined to evaluate the sum of M-D width of the unerupted permanent canines and premolars derived from the sum of M-D width of the erupted permanent incisors. 4. The prediction percentile tabulation were made in an attempt to predict the total M-D width of the unerupted permanent canines and premolars derived from the total M-D width of the erupted permanent mandibular incisors.

• 대한치과교정학회지
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• 제15권2호
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• pp.341-352
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• 1985

The primary objective of this study is to estimate of the mesiodistal crown diameters of the unerupted permanent successors derived from the mesiodistal crown diameters of the deciduous teeth in Korean population. The subjects were 54 individuals (twenty nine boys and twenty five girls) with normal occlusion aged 6 to 13 years. The mesiodistal crown diameters of the deciduous and the successional permanent teeth were measured from the longitudinal dental cast models using the sliding calipers (Mitutoyo Co.). From the study, the results are as follows; 1. Sex differences of mesiodistal won diameters were less in the deciduous teeth, but male were more than that of female in the successional permanent teeth. 2. The mesiodistal crown diameters of the deciduous central incisors, lateral incisors, canines were smaller than that of the successional permanent teeth and the deciduous 1st molars, and 2nd molars were more larger than that of the successional permanent teeth. 3. Size differences between sum of the mesiodistal crown diameters of central incisors and lateral incisors in the decidous teeth and the successional permanent teeth were $7.20{\pm}1.79mm$ in upper, $5.38{\pm}1.64mm$ in lower and that of canine,1st molar and 2nd molar in the deciduous teeth and the successional permanent teeth were $0.56{\pm}1.19mm$ in upper, $2.22{\pm}1.19mm$ in lower. 4. In male, the correlation coefficients between the upper deciduous central incisor and the successional permanent tooth (r = 0.57) and in female, the correlation coefficients between the upper deciduous 1st molar and the successional permanent tooth (r=0.67) appeared the highest. 5. The regression constants were determined to estimate the mesiodistal crown diameters of the unerupted successional permanent teeth.

• 대한치과교정학회지
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• 제45권3호
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• pp.121-129
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• 2015

Objective: This study aimed to assess three-dimensional changes in the temporomandibular joint positions and mandibular dimensions after correction of dental factors restricting mandibular growth in patients with Class II division 1 or division 2 malocclusion in the pubertal growth period. Methods: This prospective clinical study included 14 patients each with Class II division 1 (group I) and Class II division 2 (group II) malocclusions. The quad-helix was used for maxillary expansion, while utility arches were used for intrusion (group I) or protrusion and intrusion (group II) of the maxillary incisors. After approximately 2 months of treatment, an adequate maxillary arch width and acceptable maxillary incisor inclination were obtained. The patients were followed for an average of 6 months. Intraoral and extraoral photographs, plaster models, and cone-beam computed tomography (CBCT) images were obtained before and after treatment. Lateral cephalometric and temporomandibular joint measurements were made from the CBCT images. Results: The mandibular dimensions increased in both groups, although mandibular positional changes were also found in group II. There were no differences in the condylar position within the mandibular fossa or the condylar dimensions. The mandibular fossa depth and condylar positions were symmetrical at treatment initiation and completion. Conclusions: Class II malocclusion can be partially corrected by achieving an ideal maxillary arch form, particularly in patients with Class II division 2 malocclusion. Restrictions of the mandible in the transverse or sagittal plane do not affect the temporomandibular joint positions in these patients because of the high adaptability of this joint.

• 대한치과교정학회지
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• 제46권5호
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• pp.290-300
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• 2016

Objective: This study aimed to (1) evaluate the effects of maxillary second and third molar eruption status on the distalization of first molars with a modified palatal anchorage plate (MPAP), and (2) compare the results to the outcomes of the use of a pendulum and that of a headgear using three-dimensional finite element analysis. Methods: Three eruption stages were established: an erupting second molar at the cervical one-third of the first molar root (Stage 1), a fully erupted second molar (Stage 2), and an erupting third molar at the cervical one-third of the second molar root (Stage 3). Retraction forces were applied via three anchorage appliance models: an MPAP with bracket and archwire, a bone-anchored pendulum appliance, and cervical-pull headgear. Results: An MPAP showed greater root movement of the first molar than crown movement, and this was more noticeable in Stages 2 and 3. With the other devices, the first molar showed distal tipping. Transversely, the first molar had mesial-out rotation with headgear and mesial-in rotation with the other devices. Vertically, the first molar was intruded with an MPAP, and extruded with the other appliances. Conclusions: The second molar eruption stage had an effect on molar distalization, but the third molar follicle had no effect. The application of an MPAP may be an effective treatment option for maxillary molar distalization.

• The Journal of Advanced Prosthodontics
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• 제4권4호
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• pp.218-226
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• 2012

PURPOSE. The purpose of this study was to propose finite element (FE) modeling methods for predicting stress distributions on teeth and mandible under chewing action. MATERIALS AND METHODS. For FE model generation, CT images of skull were translated into 3D FE models, and static analysis was performed considering linear material behaviors and nonlinear geometrical effect. To find out proper boundary and loading conditions, parametric studies were performed with various areas and directions of restraints and loading. The loading directions are prescribed to be same as direction of masseter muscle, which was referred from anatomy chart and CT image. From the analysis, strain and stress distributions of teeth and mandible were obtained and compared with experimental data for model validation. RESULTS. As a result of FE analysis, the optimized boundary condition was chosen such that 8 teeth were fixed in all directions and condyloid process was fixed in all directions except for forward and backward directions. Also, fixing a part of mandible in a lateral direction, where medial pterygoid muscle was attached, gave the more proper analytical results. Loading was prescribed in a same direction as masseter muscle. The tendency of strain distributions between the teeth predicted from the proposed model were compared with experimental results and showed good agreements. CONCLUSION. This study proposes cost efficient FE modeling method for predicting stress distributions on teeth and mandible under chewing action. The proposed modeling method is validated with experimental data and can further be used to evaluate structural safety of dental prosthesis.

• Journal of Periodontal and Implant Science
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• 제37권4호
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• pp.681-690
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• 2007

Mini implants had been used provisionally for the healing period of implants in the beginning. But it becomes used for the on-going purpose, because it is simple to use, economic and especially suitable for the overdenture. But there is few studies about the stability of mini implants, that is most important factor for the on-going purpose, and particularly the implant parameters affecting the initial stability. The purpose of this study was to evaluate the stress and the strain distribution pattern of immediate-loaded screw type orthodontic mini-implant and the parameters affecting the initial stability of immediate-loaded mini-implant. Two dimensional finite element models were made and contact non-linear finite element analysis was performed. The magnitude and distribution of Von Mises stresses were evaluated. The obtained results were as follows: 1. The stress was concentrated on the thread tip of an implant in the cortical bone. 2. The direction of load is the most important factor for the stress distribution in cortical bone. 3. The diameter of an implant is the most important factor for the stress distribution in the trabecular bone. In conclusion, if the horizontal load vector is successfully controlled, mini-implants, which diameter is under 3mm, can be used for the on-going purpose.

• 구강회복응용과학지
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• 제19권3호
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• pp.139-151
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• 2003

This study was to evaluate and to compare the compressive strength and the displacement effecting the abutment or the residual ridge which are transformed by the angle and the heights of the konus denture inner crown when restorating the unilateral konus denture by using the mandibular canine and the 1st premolar as an abutment. The author made 9 different models for different inner crown heights and konus angles. The inner crown height were divided to 5mm, 6mm, and 7mm and konus angles was divided to $4^{\circ}$, $6^{\circ}$, and $8^{\circ}$. And then in each model, 5kg of $15^{\circ}$ mesial load was stressed on the central fossa of the 1st premolar and the 1st molar. The stresses and displacement were measured using the finite element analysis. The results were as follows 1. The maximum compressive strength was shown on the connective area of the abutment and the denture base. 2. As the angle of the inner crown becomes increased, the compressive strength was shown smaller. 3. As the height of the inner crown becomes increased, the maximum compressive strength was shown smaller while the compressive strength of the root apex and the residual ridge showed larger. 4. When the stress was loaded only on the 1st premolar, the more compressive strength was concentrated on the root apex area of the 1st premolar. 5. When the stress was loaded only on the 1st premolar, the compressive strength was concentrated uniformly on the abutment and the residual ridge. 6. When the stress was loaded only on the 1st molar, the maximum displacement was shown on the distal part of the residual ridge.

• 대한치과보철학회지
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• 제30권4호
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• pp.582-610
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• 1992

The long-term success of any dental implant is dependent upon the optimization of stresses which occur during oral function and parafunction. Especially, it has been suggested that there is an unique set of problems associated with joining an osseointegrated implant and a natural tooth with a fixed partial denture. For this particular case, although many literatures suggest different ways to avoid high stress concentrations on the bone surrounding the implant under static and dynamic loading conditions, but few studies on the biomechanical efficacy of each assertion have been reported. The purpose of this investigation was to evaluate the efficacies of clinically suggested methods on stress distribution under static load and shock absorption under dynamic load, using two dimensional finite element method. In FEM models of osseointegrated implant-natural tooth supported fixed partial dentures, calculations were made on the stresses in surrounding bone and on the deflections of abutments and superstructure, first, to compare the difference in stress distribution effects under static load by the flexure of fastening screw or prosthesis, or intramobile connector, and second, to compare the difference in the shock absorption effects under dynamic load by intramobile connector or occlusal veneering with composite resin. The results of this analysis suggest that : 1. Under static load condition, using an implant design with fastenign screw connecting implant abutment and prosthesis or increasing the flexibility of fastening screw, or increasing the flexibility of prosthesis led to the .increase in height of peak stresses in cortical bone surrounding the implant, and has little effect on stress change in bone around the natural tooth. 2. Under static load condition, intramobile connector caused the substantial decrease in stress concentration in cortical bone surrounding the implant and the slight increase in stress in bone around the natural tooth. 3. Under dynamic load condition, both intramobile connector and composite resin veneering showed shock absorption effect on bone surrounding the implant and composite resin veneering had a greater shock absorption effect than intramobile connector.

• 대한치과교정학회지
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• 제51권3호
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• pp.157-165
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• 2021

Objective: This study aimed to identify the clinical effectiveness of two different penetration depths of micro-osteoperforations (MOPs) on the rate of orthodontic tooth movement. Methods: Twenty-four patients requiring the removal of the upper first premolar teeth were selected and randomly divided into two groups. The control group participants did not undergo MOPs. Participants in the experimental group underwent three MOPs each at 4-mm (MOP-4) and 7-mm (MOP-7) depths, which were randomly and equally performed to either the left or right side distal to the canine. The retraction amount was measured on three-dimensional digital models on the 28th day of retraction. MOP-related pain was measured using a visual analog scale (VAS). Between-group statistical differences in the VAS scores were determined using an independent t-test and those in canine retraction were determined using analysis of variance and post-hoc Tukey test. Results: No significant difference was found between the MOP-4 (1.22 ± 0.29 mm/month) and MOP-7 (1.29 ± 0.31 mm/month) groups in terms of the canine retraction rate. Moreover, both the groups demonstrated a significantly higher canine movement than the control group (0.88 ± 0.19 mm/month). MOPs did not significantly affect the mesialization of the posterior teeth (p > 0.05). Moreover, the pain scores in the MOP-4 and MOP-7 groups were similar and showed no statistically significant difference. Conclusions: Three MOPs with a depth of 4 mm can be performed as an effective method to increase the rate of tooth movement. However, three MOPs with depths of 4-7 mm does not additionally enhance tooth movement.