• Journal of Periodontal and Implant Science
• /
• v.25 no.2
• /
• pp.397-406
• /
• 1995

The purpose of this study was to evaluate the changes of interproximal bone density by means of videodensitometer and to examine the clinical applicability of videodentitometer to assess the periodontal disease activity.Twelve interproximal sites, with periodontal pockets deeper than 5mm and vertical loss of bone on standard dental radiograph, were treated by subgingival curettage. The papilla bleeding index, the plaque index, the degree of mobility, the depth of pockets, and the level of attachment were measured. Standardized reproducible radiographs were taken by using the occlusal stent with parallelling film holder. The density of the interdental bone was measured on the radiographs by a videodensitometer at three levels: the most 'superficial' level; the 'deep' level, arbitrarily 1.5mm below: and the 'apical' level, where no bony changes were to be expected. The clinical parameter and the radiographical change were measured at initial, and 1 month, 3 months, and 6 months after treatment.The results were as follows :1. The papilla bleeding index and the degree of mobility decreased significantly until 3 months after subgingival curettage and showed the Same level in the remaining experimental periods. 2. The pocket depth mainly decreased due to the gingival recession until 1 month after treatment, but to the attachment gain after 1 month. 3. The density of the interdental bone did not show a significance increase until 1 month after treatment, but showed a steady increase throughout the 6 months of observation. 4. The close relationships were shown between the decrease in pocket depth and the gain of attachment and the improvement of bone density at 6 months after treatment.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.23 no.3
• /
• pp.667-673
• /
• 1996

The prevalence of class III malocclusion is approximately 5$\sim$9%, and about one fourth of this malocclusion is due to underdeveloped maxilla. Maxillary protraction appliance is an orthopedic device which promote the growth of a deficient maxilla by applying extraoral force to actively growing patients. The object of using maxillary protraction appliance is to guide a normal growth of maxilla and mandible and improve the occlusal relationship and also improve the facial profile. The author treated three patients whom were diagnosed as a class III malocclusion due to deficient maxilla using maxillary protraction appliance and the followings are the conclusions : 1. In these cases, anterior crossbite was corrected by anterior movement of maxilla and downward backward rotation of mandible and simultaneously, anterior facial height was increased. 2. The amount of dental change compare to skeletal change was greater as the patients got older. 3. When 500gm of force to each side was applied, the treatment period has been decreased. 4. As a result of applying the force between maxillary first primary molar and canine, there was a small degree of changes in palatal plane. So, it can be concluded that the maxillary protraction appliance is effective in treating growing patients with a deficient maxilla.

• Journal of Oral Medicine and Pain
• /
• v.24 no.2
• /
• pp.189-206
• /
• 1999

This study was performed to investigate the factors affecting muscle activity and cephalometric variables according to change of head postures. For this study, 150 patients with temporomandibular disorders and 80 dental students without any signs and symptoms of temporomandibular disorders were selected as the patients group and as the normal group, respectively. Head position to body-midline in frontal plane and upper quarter posture to body plumb line in sagittal plane were observed clinically and electromyographic(EMG) activity of anterior temporalis, masseter, sternocleidomastoideus, and trapezius on clenching were recorded with $BioEMG^{(R)}$ in four head postures, which were natural head posture(NHP), forward head posture(FHP), $20^{\circ}$ upward head posture(UHP), and $20^{\circ}$ downward head posture(DHP). Cephaloradiographs were also taken in the same head postures as in EMG taking, but that was taken only in NHP for the patient group. Cephalometric variables measured were SN angle, CVT angle, atlas inclination angle, occlusal plane angle, Me-C2 angle, pharyngeal width, occiput~axis distance, area of pharyngeal space, and cervical curvature. The data were analyzed by SAS statistical program. The results of this study were as follows : 1. Between the patient and the normal group, there were significant difference in distance from plumb line to acromion, eye-tragus angle, electromyographic activity of the four muscles, and cephalometric variables of linear measurement. 2. There was no consistent pattern of correlation between upper quarter posture, EMG activity and cephalometric variables in any case without relation to cervical curvature and head position in frontal plane. 3. Sternocleidomastoid muscle only showed variation of electromyographic activty with changes of head postures, but all the muscles did show correlation with head postures. 4. All the cephalometric variables measured in this study showed difference of mean value by head posture, and CVT angle, pharyngeal width, occiput-atlas distance, and area of pharyngeal space showed correlation between these variables with change from NHP to FHP, and from NHP to UHP.

• The Journal of Korean Academy of Prosthodontics
• /
• v.37 no.3
• /
• pp.383-394
• /
• 1999

The indirect technique for making cast restoration requires that dies be as accurate and durable as possible. Currently, stone is the most commonly used material for die. However, it has some problems such as the weakness in its strength and low abrasion resistance. Recently, epoxy resin die systems have become available. The purpose of this study was to examine two commercially available resin die systems and evaluate some characteristics for their clinical performance. This study evaluated the dimensional accuracy of epoxy resins and their wettability with impression materials. In this study, the first experiment was about dimensional accuracy of different die materials. The master model was made of stainless steel. 10 models were made of two epoxy resins (Die-epoxy, Tri-epoxy) and a die stone (Fujirock) each. Occlusal diameter (Dimension I), occluso-gingival height (Dimension II), and interabutment distance (Dimension III) were measured in each model. Next, the contact angles of die materials with impression materials were observed. The blocks were made of polyether, hydrophilic additional silicone, polysulfide impression materials. By drop-ping the same amount (0.05ml) of Tri-epoxy, Die-epoxy, and die stone on the blocks, 10 samples of each die material were made. After setting of materials, the contact angles were measured. The results of this study were as follows. 1. The expansion of stone die and the shrinkage of resin dies in occlusal diameter were observed, and stone and Tri-epoxy were expanded and Die-epoxy was shrinked in occluso-gingival height. There was little change among materials in interabutment distance (p<0.05). 2. In comparison with the master model Tri-epoxy had the least variation in measurement of the three die systems examined. Die-epoxy was next, and die stone showed the greatest variation. 3. The compatibility of die stone for polyether, hydrophilic additional silicone, polysulfide decreased in order, wherease epoxy materials had the decreased compatibility for polyether and polysulnde, hydrophilic additional silicone in order. It was not statistically different between polyether and polysulfide (p<0.05). 4. The contact angles of Tri-epoxy, Die-epoxy, die stone were getting bigger in order.

• The korean journal of orthodontics
• /
• v.28 no.1 s.66
• /
• pp.113-122
• /
• 1998

Stabilization splint therapy Precedes orthodontic intervention to enable the operator to find a 'true' centric(which is stable and comfortable), to test the patient's response to a change in the occlusion, prior to embarking upon a complex course of occlusal therapy : and finally, to see if the centric relation position can be stabilized. For this study, 47 malocclusion Patients enrolled for orthodontic treatment at the Department of Orthodontics, College of Dentistry, Chosun University comprised the malocclusion group, little variation of growth factor by the second molar eruption. They had Cr-Co discrepancy beyond normal range. For each patients the stabilization splint with mutually protected type of occlusal scheme was applied for 3 months. Condylar positions in CR and CO were measured using Penadent articulators, Panadent condylar position indicator(CPI), and transcranial projection before & after stabilization splint therapy. On the basis of this study, the results of this study were as follows 1. In all samples using CPI, there were statistical significances in CR-CO discrepancy(p<0.001) both before 8t after stabilization splint therapy. 2. In Rt and Lt+Rt/2 of superior joint space using transcranial projection, there were statistical significances in CR-CO discrepancy({<0.05) before & after stabilization splint therapy. 3. In supero-inferior components using CPI, there were statistical significances in CR-CO discrepancy(p<0.01) before & after stabilization splint therapy. 4. In all components except Rt using transcranial projection, there were no statistical significances in CR-CO discrepancy(p>0.05) before & after stabilization splint therapy. To sum up, CPI might be more effective than transcranial projection to reveal the changes between CR-CO discrepancies and stabilization splint might be more useful appliance for displaying the vertical changes, than the antero-posterior changes, of condylar position.

• The korean journal of orthodontics
• /
• v.31 no.3 s.86
• /
• pp.347-355
• /
• 2001

Maxillary and mandibular anterior dental arches often have the problems of occlusal relation and esthetics by malformations of teeth, congenital missing, et at. Though the clinician usually use the anterior ratio to overcome this problems, he has the limitation of a direct application this ratio to the prediction of anterior occlusal relationship by the change of anterior ratio as dental arch form, intercanine width, segment depth and arch perimeter. So this study examine maxillary and mandibular anterior dental arch forms by least square method using Korean normal occlusion models(man : 20 casts, woman : 20 casts). Maxillary and mandibular anterior dental arches of Korean normal occlusion models are curve fitted to polynomial function, beta function, hyperbolic cosine function in order. And this accuracy of curve fitting is constant regardless of man/woman and maxilla/mandible. The relationships between intercanine width, segment depth, and arch perimeter based on this owe fitted dental arch form are acquired. This relationships will give the prediction of anterior dental arch form and the information of more accurate anterior ratio according to intercanine width.

• The korean journal of orthodontics
• /
• v.25 no.3 s.50
• /
• pp.247-261
• /
• 1995

The purpose of this study was to quantitate differences in the nature of the correction of Angle's Class II div 1 malocclusion dependent on the patient's age at the time of treatment. The sample consisted of 27 female patients in the adolescent group with a mean initial records age of 11.8 years and 25 female patients in the adult group with a mean starting age of 21.1 yrs. Lateral cephalometric head films were taken before and after orthodontic treatment with four bicuspid extraction. The results were obtained as follows. 1. None of maxillary skeletal parameters exhibited a significantly different in treatment change between adolescents and adults. But, in mandibular skeletal measurements, there were significant differences between two groups. (P<0.05) 2. Measures of vertical dimension in the adults remained unchanged during treatment, reflecting the effective absence of growth. 3. The steepness of occlusal plane in the adults changed significantly.(P<0.05) In contrast, the adolescents displayed stability of the occlusal plane. 4. According to the Johnston analysis, there was a significant difference in the total molar correction between two groups.(P<0.05) 5. According to the Johnston analysis, differential mandibular growth in the adolescents contrubuted $63\%$ of the total molar correction, with orthodontic tooth movement accounting for the remaining $37\%$. In the adults, dental movement comprised $99\%$ of the correction.

• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.1
• /
• pp.1-11
• /
• 2007

Statement of problems: The concept of CR has also changed continuously.?In order to find out the factors that affect the centric slide, studies were carried out to compare the forms of wisdom teeth eruption, lateral movement, premature contact in CR, and anterior movement. Research and statistical methods were based on the report by the 1980 Korean dental association. Material and method: In our study, 403 dentists in their twenties and dentistry students who could understand CR and CO (and who did not receive occlusal, orthodontic treatment, without extreme caries and large prosthodontic care) were compared with the 25 year old results. A segment of line parallel to the upper incisor was marked on the lower incisor. When seen laterally, a line perpendicular to the occlusal plane was drawn on the foremost area of the upper incisor. This line was extended to the lower incisor and the two points (points at the lower and upper incisors) were used as reference points for the CO. After guiding the occlusion to the CR, two lines were marked by using the same method that was used for the CO. The point in which these lines meet became the reference point of CR occlusion Results and conclusions: Results of the experiment completed in 1980 show that all 307 research members had anterior-posterior and upper-lower displacement. Displacement measurements were $0.7{\pm}0.4mm$ for the anterior-posterior displacement, $0.99{\pm}0.50mm$ for the upper-lower displacement,0.18{\pm}0.31 mm for the lateral displacement, and $1.32{\pm}0.67mm$ for the total displacement. Results of the 2006 experiment show that all 409 research members had anterior-posterior and upper-lower displacement. The anterior-posterior displacement was $1.12{\pm}0.86mm$, the upper-lower displacement was $1.02{\pm}0.71mm$, the lateral displacement was $0.61{\pm}0.56mm$, and the total displacement was $1.80{\pm}0.99mm$. No specific differences were found between each group when comparing displacement according to the forms of wisdom teeth eruption. Since 1980, the percentage of unerupted teeth has increased from 35.16% (111/307 people) to 57.5% (236/409 people). Westernization of the Korean cranial form and intraoral structure has brought about these results. In our experiment, 26.7% (109/409 people) of the subjects were cuspid guided, while 7.3% (30/409 people) were mutually guided. No specific differences were found in the amount of displacement between the two groups. Only the subjects with anteriors coming in contact made up the largest percentage group (42.3%, 173/409 people) in our study. No specific differences were found between each group.

• The Journal of Korean Academy of Prosthodontics
• /
• v.36 no.2
• /
• pp.203-244
• /
• 1998

The human mandible is always under the condition of loading by the various forces extorted by the attached muscles. The loading is an important condition of the stomatognathic system. This condition is composed of the direction and amount of forces of the masticatory muscles, which are controlled by the neuromuscular system, and always influenced by the movement of both opening and closing. Mandible is a strong foundation for the teeth or various prostheses, nevetheless it is a elastic body which accompanies deformation by the external forces on it. The elastic properties of the mandible is influenced by the various procedures such as conventional restorative treatments, osseointegrated implant treatments, reconstructive surgical procedures and so forth. Among the treatments the osseointegrated implant has no periodontal ligaments, which exist around the natural teeth to allow physiologic mobility in the alveolar socket. And so around the osseointegrated implant, there is almost no damping effect during the transmission of occlusal stress and displacements. If the osseointegrated implants are connected by the superstructure for the stabilization and effective distribution of occlusal stresses, the elastic properties of mandible is restricted according to the extent of 'splinting' by the superstructure and implants. To investigate the change of elastic behaviour of the mandible which has osseointegrated implant prosthesis of various numbers of implant installment and span of superstructre, a three dimensional finite element model was developed and analyzed with conditions mentioned above. The conclusions are as follows : 1. The displacements are primarily developed at the area of muscle attachment and distributed all around the mandible according to the various properties of bone. 2. The segmentation in the superstructure has few influence on the distribution of stress and displacement. 3. In the load case of ICP, the concentration of tensional stress was observed at the anterior portion of the ramus($9.22E+6N/m^2$) and at the lingual portion of the symphysis menti($8.36E+6N/m^2$). 4. In the load case of INC, the concentration of tensional stress was observed at the anterior portion of the ramus($9.90E+6N/m^2$) and the concentration of tensional stress was observed at the lingual portion of the symphysis menti($2.38E+6N/m^2$)). 5. In the load case of UTCP, the relatively high concentration of tensional stress($3.66E+7N/m^2$) was observed at the internal surface of the condylar neck.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.49 no.1
• /
• pp.45-56
• /
• 2022

The purpose of this study is to evaluate changes of occlusion following the placement of preformed metal crown in the permanent first molar affected by severe caries or hypomineralization. The study was conducted on 24 patients who met the criteria among the patients with occlusion in the permanent first molar reaching the occlusal plane. Restorative treatment was performed on one first molar using preformed metal crown. Before treatment, immediately after treatment, after 4 weeks, and after 8 weeks, the T-scan III was used for measuring distribution of bite force at the maximum intercuspal position, and overbite was measured with digital vernier calipers and change of dental midline was surveyed. After 8 weeks, questionnaires survey was conducted. In most cases, immediately after treatment, the distribution of bite force between the restored side and non-restored side of arch was reversed compared to before treatment, and the overbite was decreased. However, after 4 weeks, bite force of the left and right side was balanced and the distribution of bite force on the restored and non-restored permanent first molars had similar values. Also, the changed overbite and midline were returned to pre-treatment status and there was no significant temporomandibular joint and masticatory discomfort after treatment. In this study, it was confirmed that spontaneous occlusal equilibrium was achieved one month after the placement of preformed metal crown.