• The korean journal of orthodontics
• /
• v.21 no.3
• /
• pp.481-493
• /
• 1991

The purpose of this study was to obtain the norm of the crown shape (tip, torque, in/out) and arch form, and to provide basic data for fabricating straight wire bracket and ideal arch wire for Korean. 100 subjects aged from 17 to 26 (50 females, 50 males) were selected with a normal occlusion. By measuring the size, angulation, inclination, arch width, facial prominance of the teeth and the molar offset, the following results were obtained. 1. Average, standard deviation, minimum, maximum of each measuring item for each teeth were obtained. 2. Intermolar width (${\underline{6}}$ to ${\underline{6}}$) of upper arch before occlusal surface cutting and intermolar width of upper arch (${\underline{6}}$ to ${\underline{6}}$, ${\underline{7}}$ to ${\underline{7}}$) after occlusal surface cutting showed statistical difference. There was no difference between sexes in any other measuring items. 3. Arch form and specification of straight wire bracket for Korean who have normal occlusion was obtained.

• The korean journal of orthodontics
• /
• v.27 no.5 s.64
• /
• pp.815-824
• /
• 1997

The purpose of this study is to develop the basic algorithm for the finite element method modeling of individual malocclusions. Usually, a great deal of time is spent in preprocessing. To reduce the time required, we developed a standardized procedure for measuring the position of each tooth and a program to automatically preprocess. The following procedures were carried to complete this study. 1. Twenty-eight teeth morphologies were constructed three-dimensionally for the finite element analysis and saved as separate files. 2. Standard brackets were attached so that the FA points coincide with the center of the brackets. 3. The study model of a patient was made. 4. Using the study model, the crown inclination, angulation, and the vertical distance from the tip of a tooth was measured by using specially designed tools. 5. The arch form was determined from a picture of the model with an image processing technique. 6. The measured data were input as a rotational matrix. 7. The program provides an output file containing the necessary information about the three-dimensional position of teeth, which is applicable to several finite element programs commonly used. The program for a basic algorithm was made with Turbo-C and the subsequent outfile was applied to ANSYS. This standardized model measuring procedure and the program reduce the time required, especially for preprocessing and can be applied to other malocclusions easily.

• The Journal of Korean Academy of Prosthodontics
• /
• v.37 no.1
• /
• pp.104-126
• /
• 1999

The purpose of this study was to compare and evaluate the stress distribution and displacement developed in the abutment teeth and residual ridge area by madibular unilateral distal extension removable partial denture with 2 different retainer designs. The retainers on right and left canine and right 2nd molar were Alters clasp in one model and telescopic crown in the other model. The stress distribution of abutment teeth and residual ridge area on two model were compared and analyzed with 3-dimensional finite element method. 150N and 400N forces were applied vertically, 30 degree and horizontally on the central fossa area of left 1st molar of the removable partial denture, and then stress distribution patterns were analyzed and compared. The results were as follows 1. As the magnitude and angulation of applied force were increased, the magnitude of stress on the right and central residual ridge area and the right canine of the telescopic type increased and comparing to those of the Alters clasp type. 2. As the magnitude and angulation of applied force were increased, the mesial direction of displacement on the right residual ridge area and the right tooth of the telescopic type increased and the distal direction of displacement on left residual ridge area and the left canine increased comparing to those of Akers clasp type. 3. As the vertical force was applied, the distal direction of the displacement of the right tooth were greater and that of the left canine was smaller and the upward displacement of the right canine was greater in telescopic partial denture than those of Akers clasp type. 4. As the 30 degree force was applied, the mesial direction of the displacement of the right tooth were greater and the distal direction of the displacement of the left canine was smaller and the upward displacement of the right canine was greater in telescopic partial denture than those of Akers clasp type. In the horizontal force the results were same in right area tooth but the distal direction of displacement was greater in left canine. 5. In both removable partial dentures, as the magnitude and degree of force were increased, the stress and displacement were increased. The compressive force was dominative than the ten sile force. 6. In both removable partial dentures, the magnitude of stress was greater on mucosal tissue area than that of the alveolar bone area on distal extension residual ridge area but the result was reversed on anterior residual ridge area. The displacement was always greater on mucosal tissue area than that of alveolar bone area.

• The korean journal of orthodontics
• /
• v.36 no.3 s.116
• /
• pp.207-217
• /
• 2006

Although ceramic brackets have been used widely for improved esthetics during treatment, ceramic brackets have some inherent problems; brittleness, attrition of the opposing teeth and high frictional resistance. This study was performed to understand the frictional resistance of the ceramic brackets, as well as to be a helpful reference for finding the solutions to the problem of frictional resistance. Three different kinds of brackets were used; metal bracket, polycrystalline ceramic brackets with a metal slot to reduce the high frictional resistance and monocrystalline ceramic brackets. The brackets were tested with a $.019{\times}.025$ stainless steel wire with a second order angulation of $0^{\circ}\;and\;10^{\circ}$, and the static and kinetic frictional forces were measured on the universal testing machine. The results of this study showed that the ceramic brackets, especially the monocrystalline ceramic bracket without a metal slot, generated higher frictional resistance than the metal bracket, and the frictional resistance was increased as the angulation between the bracket slot and the wire increased. Therefore, the development of the ceramic bracket with reduced frictional resistance and the prevention of excessive crown tipping during orthodontic treatment will lead to the simultaneous attainment of more efficient and improved esthetic treatment goals.

• Imaging Science in Dentistry
• /
• v.43 no.3
• /
• pp.191-196
• /
• 2013

Purpose: This study assessed the accuracy of linear and angular measurements on panoramic radiographs taken at different positions in vitro. Materials and Methods: Two acrylic models were fabricated from a cast with normal occlusion. Straight and $75^{\circ}$ mesially and lingually angulated pins were placed, and standardized panoramic radiographs were taken at standard position, at an $8^{\circ}$ downward tilt of the occlusal plane compared to the standard position, at an $8^{\circ}$ upward tilt of the anterior occlusal plane, and at a $10^{\circ}$ downward tilt of the right and left sides of the model. On the radiographs, the length of the pins above (crown) and below (root) the occlusal plane, total pin length, crown-to-root ratio, and angulation of pins relative to the occlusal plane were calculated. The data were subjected to repeated measures ANOVA and LSD multiple comparisons tests. Results: Significant differences were noted between the radiographic measurements and true values in different positions on both models with linear (P<0.001) and those with angulated pins (P<0.005). No statistically significant differences were observed between the angular measurements and baselines of the natural head posture at different positions for the linear and angulated pins. Conclusion: Angular measurements on panoramic radiographs were sufficiently accurate and changes in the position of the occlusal plane equal to or less than $10^{\circ}$ had no significant effect on them. Some variations could exist in the pin positioning (head positioning), and they were tolerable while taking panoramic radiographs. Linear measurements showed the least errors in the standard position and $8^{\circ}$ upward tilt of the anterior part of the occlusal plane compared to other positions.

• The Journal of the Korean dental association
• /
• v.58 no.2
• /
• pp.83-92
• /
• 2020

In the anterior maxillary area, dental implants for tooth replacement are challenging due to the need to satisfy high esthetic level as well as functionality. Immediate implant placement and provisionalization can dramatically reduce the edentulous period, and then fulfill patient's demand for esthetics. The aim of present case report is to demonstrate two cases that successfully restored single tooth with immediate implant placement and provisionalization in the anterior maxillary area. A 47 years old female was scheduled to replace her maxillary right central incisor due to crown-root fracture by trauma. Another 54-year-old female was planned to place dental implant following tooth extraction of maxillary right lateral incisor owing to continuous pus discharge despite repetitive treatments including apicoectomy. In these two cases, surgical and prosthetic procedures progressed in a similar way. After minimal flap elevation, atraumatic tooth extraction was performed. Implant was placed in proper 3-dimensional position and angulation with primary stability. Bone graft or guided bone regeneration for peri-implant bone defect was conducted simultaneously. Provisionalization without occlusal loading was carried out at the same day. Each definitive crown was delivered at 7 and 5 months after the surgery. Two cases have been followed uneventfully for 2 to 5 years of loading time. In conclusion, Immediate implant placement and provisionalization could lead to esthetic outcome for single tooth replacement with dental implant under proper case selection.

• The korean journal of orthodontics
• /
• v.53 no.1
• /
• pp.26-34
• /
• 2023

Objective: The purpose of the present study was to compare the root positions in virtual tooth setups using only crowns in a simulated treatment with those achieved in the actual treatment. Methods: Pre- and post-treatment intraoral and corresponding cone beam computed tomography (CBCT) scans were obtained from 15 patients who underwent orthodontic treatment with premolar extraction. A conventional virtual tooth setup was used for the treatment simulation. Pre- and post-treatment three-dimensional digital tooth models were fabricated by integrating the patients' intraoral and CBCT scans. The simulated root positions in the virtual setup were obtained by merging the crown in the virtual setup and root in the pre-treatment tooth model. The root positions of the simulated and actual post-treatment tooth models were compared. Results: Differences in root positions between the simulated and actual models were > 1 mm in all teeth, and statistically significant differences were observed (p < 0.05), except for the maxillary lateral incisors. The differences in the inter-root angulation were > 1° in all teeth, and statistically significant differences were observed in the maxillary and mandibular canines. Conclusions: The virtual tooth setup using only crown data showed errors over the clinical limits. The clinical application of a virtual setup using crowns and roots is necessary for accurate and precise treatment simulation, particularly in extraction treatment.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.4 s.175
• /
• pp.907-915
• /
• 2000

The movement of teeth and initial stress associated with the treatment of orthodontics have been successfully studied using the finite element method. To reduce the effort in preprocessing of finite element analysis, we developed two types of three-dimensional finite element models based on the standard teeth model. Individual malocclusions were incorporated in the finite element The movement of teeth and initial stress associated with the treatment of orthodontics have been successfully studied using the finite element method. To reduce the effort in preprocessing of finite element analysis, we developed two types of three-dimensional finite element models based on the standard teeth model. Individual malocclusions were incorporated in the finite element models by considering the measuring factors such as angulation, crown inclination, rotation and translations. The finite element analysis for the wire activation with a T-loop arch wire was carried out. Mechanical behavior on the movement and the initial stress for the malocclusion finite element model was shown to agree with the objectives of the actual treatment. Finite element models and procedures of analysis developed in this study would be suitably utilized for the design of initial shape of the wire and determination of activation displacements.

• The korean journal of orthodontics
• /
• v.34 no.5 s.106
• /
• pp.417-428
• /
• 2004

The purpose of this study was to evaluate the stress distributions at the periodontal ligament (PDL) and displacements of the maxillary first molar when mesially directed force was applied under various molar angulations and rotations. A three dimensional finite element model of the maxiilary first molar and its periodontal ligament was made Upright position, mesially angulated position by $20^{\circ}$ and distally angulated position of the same degree were simulated to investigate the effect of molar angulation. An anteriorly directed force of 200g countertipping moment of 1,800gm-mm (9:1 moment/force ratio) and counterrotation moment of 1,000gm-mm (5:1 moment/force ratio) were applied in each situation. To evaluate the effect of molar rotation on the stress distribution, mesial-in rotation by $20^{\circ}$ and the same amount of distal-in rotation were simulated. The same force and moments were applied in each situation. The results were as follows: In all situations, there was no significant difference in mesially directed tooth displacement Also, any differences in stress distributions could not be found, in other words. there were no different mesial movements. Stress distributions and tooth displacement of the $20^{\circ}$ mesially angulated situation were very similar with those of the $20^{\circ}$ distal-in rotated situation. The same phenomenon was obserned between the $20^{\circ}$ distally angulated situation and $20^{\circ}$ mesial-in rotated situation. When the tooth was mesially angulated, or distal-in rotated, mesially directed force made the tooth rotate in the coronal plane. with its roots moving buccally, and its crown moving lingually. When the tooth was distally angulated, or mesial-in rotated, mesially directed force made the tooth rotate in the coronal plane, with its roots moving lingually and its crown moving buccally. When force is applied to au angulated or rotated molar, the orthodontist should understand that additional torque control is needed to prevent unwanted tooth rotation in the coronal plane.

• The korean journal of orthodontics
• /
• v.47 no.5
• /
• pp.277-288
• /
• 2017

Objective: Treating Class II subdivision malocclusion with asymmetry has been a challenge for orthodontists because of the complicated characteristics of asymmetry. This study aimed to explore the characteristics of dental and skeletal asymmetry in Class II subdivision malocclusion, and to assess the relationship between the condyle-glenoid fossa and first molar. Methods: Cone-beam computed tomographic images of 32 patients with Class II subdivision malocclusion were three-dimensionally reconstructed using the Mimics software. Forty-five anatomic landmarks on the reconstructed structures were selected and 27 linear and angular measurements were performed. Paired-samples t-tests were used to compare the average differences between the Class I and Class II sides; Pearson correlation coefficient (r) was used for analyzing the linear association. Results: The faciolingual crown angulation of the mandibular first molar (p < 0.05), sagittal position of the maxillary and mandibular first molars (p < 0.01), condylar head height (p < 0.01), condylar process height (p < 0.05), and angle of the posterior wall of the articular tubercle and coronal position of the glenoid fossa (p < 0.01) were significantly different between the two sides. The morphology and position of the condyle-glenoid fossa significantly correlated with the three-dimensional changes in the first molar. Conclusions: Asymmetry in the sagittal position of the maxillary and mandibular first molars between the two sides and significant lingual inclination of the mandibular first molar on the Class II side were the dental characteristics of Class II subdivision malocclusion. Condylar morphology and glenoid fossa position asymmetries were the major components of skeletal asymmetry and were well correlated with the three-dimensional position of the first molar.