Identification of Mutans Streptococci isolated from dental plaque between the bracket and tooth surface in orthodontic patients / 대한치과교정학회지

The aim of this study was to compare the species and biotypes of mutans streptococci isolated from dental plaques sampled from the interfaces between the bracket and tooth surface and smooth tooth surfaces in orthodontic patients. Dental plaque was collected from the interfaces between brackets and teeth (test group), and from smooth tooth surfaces distant from brackets by more than 2 mm (control group). The dental plaque collected by a sterilized curette was transferred into a vial of 1 X PBS. The sample in the vial was vigorously vortexed for 1 min and plated on mitis-salivarius bacitracin (MSB) agar plate using cotton tips. The agar plates were incubated at 37 degrees C in a candle jar for 2 days, and again incubated for 1 more day at anambient temperature. Individual colonies were cultured in TH broth at 37 degrees C CO2 incubator. The PCR-RFLP based on dextranase gene was performed for the identification of mutans streptococci at the species-level. For biotyping of mutans streptococci, biochemical tests were performed. There was no significant difference of the species of mutans streptococci isolated from both test and control groups. However, the biotypes of the mutans streptococci isolated from test and control groups were different. These results may offer the basic data to verify the relationship between the mutans streptococci biotype and enamel decalcification or dental caries in orthodontic patients with fixed appliances.

Expression of mRNAs characteristic of cartilage and bone in the developing mandibular condyle of mice / 대한치과교정학회지

It has not been elucidated whether the initiation of condylar development of the mandible is related with the periosteum of the mandible, or if it derives from a separate programmed blastema not related with the mandible. Also, although the mandibular condylar cartilage is known to promote growth, few studies have dealt with molecular-biologic mechanisms such as the expression of specific genes according to the differentiation of the mandibular condyle. To elucidate the unique cellular characteristics, development, and differentiation process of the mandibular condyle, an examination of expressions of genes characteristic of cartilage and bone were carried out using RT-PCR and mRNA in situ hybridization. 1. Type?collagen mRNA was detected with type II collagen mRNA in the differentiation and growth process of the cartilage of the mandibular condyle. Type II collagen mRNA was demonstrated in the whole resting and upper part of the proliferative zone, whereas type II collgen mRNA was observed in the resting, proliferative and upper hypertrophic cartilage zone of the mandibular condyle. 2. The condylar cartilage rapidly increased in size due to the accumulation of hypertrophic chondrocytes as characterized by the expression of type II collagen mRNA during postnatal development. 3. BMP-4 mRNA was present in the anlage of the future condylar process and also in the ossifying mandibular body. 4. IHH mRNA was limited exclusively to the lower part of the proliferative zone and the upper part of the hypertrophic cartilage zone during condylar development. These findings were different from those in the growth-plate cartilage of the long bone, indicating a characteristic feature of the differentiation of the chondrocytes in the condylar cartilage present in prenatal and postnatal development. Furthermore, it was also suggested that chondroblasts of condylar cartilage rapidly differentiate into hypertrophic chondrocytes with increased functional Load force such as muscle activity and mastication.

A meta analysis of maxillary expansion: comparisons of intercanine/intermolar expansion and rapid/slow expansion / 대한치과교정학회지

As a research method that weighs and combines evidence, meta analysis produces evidence that is more powerful than the original studies. The purpose of this study was to compare the intercanine/intermolar expansion and rapid/slow expansion in the maxillary expansion treatment using meta analysis. Medline was searched from 1979 to 2000 for all studies examining the stability of transverse expansion of the human maxilla, and 388 articles were found. Then these articles were reduced to 7 based on the defined inclusion and exclusion criteria, and a cumulative Meta evaluation score was computed for each study. The results were as follows; 1. The mean expansion in intermolar width was 6.0mm. Of the 6.0mm, 4.8mm was retained and 20.0%(1.2mm) was relapsed while wearing retainers. 2. In intercanines width, the mean expansion was 3.7mm. Of the 3.7mm, 2.6mm was retained and 29.7%(1.1mm) was relapsed while wearing retainers. 3. The differences in the amount of expansion and relapse between rapid expansion group and slow expansion group were less than 6%(0.1-0.3mm). But, there might be differences in the skeletal/dental exapnsion ratios according to the expansion method.

Immunohistochemical localization of several protein changes in periodontal ligament during tooth eruption and interdental separation of rats / 대한치과교정학회지

In this study, we attempt to investigate the mechanisms by which PDL cells regulate osteoclast formation and also to know whether PDL retained their characteristic phenotype during tooth eruption and interdental separation. Rats were prepared at developmental days 21 (pre-root formation), 27 (root development), 34 (advanced root formation/ eruption) and at later times(adult rats). To induce severe resorption state of alveolar bone and tooth root, interdental separation with brass wire was performed between the lower first and second molars for 2 weeks in adult rats. Rat mandibles were demineralized and embedded in paraffin, and horizontal and frontal section were prepared for immunohistochemical analysis using PDL-specific protein 22 (PDLs22), receptor activator of NFKB ligand (RANKL) and osteoprotegerin (OPG) antibodies. 1. Root formation and eruption stage of tooth development. 1) PDLs22 immunolocalization was observed in tooth follicle/PDL cells and osteoblasts throught out the root formation and eruption stages of tooth development. 2) RANKL expression became stronger at eruption stage than root formation stage of tooth development. 3) Strong expression of OPG was detected in follice/PDL cells of root formation stage but it was decreased with tooth eruption. 2. Interdental separation between lower first and second molar. 1) Comparared to normal animal, multinucleated osteoclasts and odontoclasts were markedly induced in the alveolar bone and tooth root with PDL remodeling in hematoxylin-eosin section. 2) PDLs22 expression was decreased with interdental separation. 3) RANKL expression was increased with interdental separation in PDL fibroblasts, osteoblasts, odontoclasts and it lacunae, resorbing dentin, cementum and bone matrix. 4) OPG expression was slightly decreased in the PDL cells adjacent to the alveolar bone and root surface with interdental separation. These results suggested that during tooth eruption and tooth movement, RANKL and OPG in the periodontal tissues are important determinants regulating balanced alveolar bone and tooth root resorption. And it is also suggested that PDL cells retained their characteristic phenotype during tooth eruption and interdental separation except for the short period of PDL remodeling.

Effect of Leaf-Extract from Camellia sinensis and Seed-Extract from Casia tora on Viability of Mutans Streptococci isolated from the interface between orthodontic brackets and tooth surfaces / 대한치과교정학회지

Mutans streptococci is the major causative factor in dental caries. Especially, orthodontic patients with fixed appliance are a risk group for dental caries. Because fixed appliances attached on teeth may change the environment of dental plaque, the enamel decalcification or dental caries around the bracket and band is a major side effect of orthodontic treatment. The aim of this study was to search plant extracts that have antimicrobial effect on mutans streptococci. Seed-extract of Casia tora were prepared with ethanol and CHMC-2032, the leaf-extracts from Camellia sinensis extract, was obtained extract, 2 type strains and 20 clinical isolates of mutans streptococci isolated from the interface between orthodontic brackets and tooth surfaces in the orthodontic patients were used in this study. The minimal inhibitory concentration of CHMC-2032 was 5 mg/ml on the S. mutans KCTC 3065, S. sobrinus KCTC 3088, and 8 clinical isolates of S. sobrinus. However, there was no antibacterial effect of seed-extract of C. tora on mutans streptococci. These data suggest that green tea may be more effective than the tea prepared from C. tora in the prevention of enamel decalcification or dental caries around brackets.

An epidemiologic study on the orthodontic patients who visited department of orthodontics, Chosun university dental hospital last 10 years (1990-1999) / 대한치과교정학회지

With socioeconomic development and change of esthetic recognition, the demand for orthodontic treatment and number of orthodontic patients has been increasing so rapidly. And frequency of malocclusion was changed. So this study was done in an attempt to provide an epidemiologic study so that we can accomodate their orthodontic needs adequately and to obtain the reliable quantitative information regarding the characteristics of orthodontic patients. Distribution and trends were examined in 3,070 malocclusion patients who had been examined and diagnosed at Department of Orthodontics, Dental Hospital, Chosun University over 10 year-period from 1990 to 1999. The results were as follows : 1.The number of patients per year was increasing trend and higher visiting rate in female(56.5%) than in male(43.5%). 2.Age distribution had shown 7~12 year-old group being the largest(37.9%) and each percentage of 13~18, 19~24, above-19, 0~6 year-old group was 32.0%, 19.6%, 7.1%, 3.4%. 3. Hellman dental age IVa which is completion of the permanent dentition showed the highest percentage in male and female. 4.Geographic distribution showed a majority of patients in Kwang Ju(71.0%). Group within the distance 10km from Chosun Dental Hospital was 56.3% and group within 20km was 14.7%. 5.Anterior cross bite showed the highest percentage in chief complaints and percentage of Mn. prognathism and protrusion of Mx. teeth was 12.6%, 12.2%. 6.Distribution in the types of malocclusion according to the Angle's classification had shown; 38.9% for Class I, 20.7% for Class II division 1, 2.0% for Class II division 2, 38.4% for Class III. 7.In the dental vertical dysplasia according to the Angle's classification, deep bite was the most frequent in Class II div.1 and div. 2(24.3%, 56.7%) and open bite in Class III(21.4%). 8.In the skeletal sagittal dysplasia, 39.3% of skeletal ClassII was due to the undergrowth of the mandible and 46.3% of skeletal ClassIII was due to the overgrowth of the mandible. 9.Distribution in orthodontic treatment accoding to the extraction and nonextraction had shown 66.9% for nonextraction case, 33.1% for extraction case, and four first bicuspids have been extracted in the highest percentage(38.6%). 10.Patients who had orthognathic surgery comprised 7.9%, with an increasing trend.

Photoelastic evaluation of mandibular posterior crossbite appliance / 대한치과교정학회지

This study was undertaken to demonstrate the forces in the mandibular alveolar bone generated by activation of the mandibular posterior crossbite appliance in the treatment of buccal crossbite caused by lingual eruption of mandibular second molar. A three-dimensional photoelastic model was fabricated using a photoelastic material ( PL-3 ) to simulate alveolar bone. We observed the model from the anterior to the posterior view in a circular polariscope and recorded photographically before and after activation of the mandibular posterior crossbite appliance. The following results were obtained : 1. When the traction force was applied on the buccal surface of the mandibular second molar, stress was concentrated at the lingual alveolar crest and root apex area. The axis of rotation also was at the middle third of the buccal root surface and the root apex, so that uncontrolled tipping and a buccal traction force for the mandibular second molar were developed. 2. When the traction force was applied on the lingual surface of the mandibular second molar, more stress was observed as opposed to those situations in which the force application was on the buccal surface. In addition, stress intensity was increased below the root areas and the axis of rotation of the mandibular second molar was lost. In result, controlled tipping and intrusive tooth movements were developed. 3. When the traction force was applied on either buccal or lingual surface of the second molar, the color patterns of the anchorage unit were similar to the initial color pattern of that before the force application. So we can use the lingual arch for effective anchorage in correcting the posterior buccal crossbite. As in above mentioned results, we must avoid the rotation and uncontrolled tipping, creating occlusal interference of the malpositioned mandibular second molar when correcting posterior buccal crossbite. For this purpose, we recommend the lingual traction force on the second molar as opposed to the buccal traction.

Photoelastic evaluation of maxillary posterior crossbite appliance / 대한치과교정학회지

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 1/4 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 may 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.

Periodontal tissue response following different types of fixed retainers in young adult dogs / 대한치과교정학회지

The purpose of this study was to evaluate the material for fixed type retainer, allowing physiologic tooth movement. and proper remodeling of periodontal tissue during retention period. The present study was performed to observe the histologic changes of periodontal tissue after application of different types of fixed type retainer after orthodontic tooth movement in young adult dogs. For this study, 4 young adult dogs were used as a experimental animal and experimental group was divided into three groups ; experimental group 1 contained right side maxillary third incisors and canines, experimental group 2 contained contralateral teeth of same animals, and control group contained mandibular premolars. And each dogs were applied the 4 different types of fixed type retainer to experimental group 1. The experimental teeth were ligated on the Sentalloy closed coil spring(R)(Tomy Co., Japan) from maxillary third incisors and canines and applied orthodontic force at initial 200gm-forced during 1 week. All the experimental animals were sacrificed on the 3rd week after the orthodontic teeth movement and then the specimens were taken, fixed in formalin, embeded in parafin, sectioned 6-8micrometer in thickness and stained with Hematoxylin-Eosin staining, and Masson's trichrome staining method. Examined under the light microscopy. The following results were observed. 1. There were observed that decreased infiltration of giant cells in pressure side and increased the new bone forming in tension side on the specimen of 6-stranded 0.0195' Respond(R)(G&H Co., U.S.A.) group. Periodontal ligament fibers were much compressed or elongated in 3-stranded 0.018', 0.020' Dentaflex(R)(Dentarum Co., Germany), and Superbond C&B(R)(Sun Medical Co., Japan) groups. 2. In experimental group 1, necrotic bone inside the alveolar bone of pressure side, forming of the sharpey's fiber in osteoid tissue, and remodeling of the periodontal ligament were observed in all animals. 3. In experimental group 2, it was observed that the amount of bone resorption was equal or decreased in pressure side, and increased new bone forming and significantly decreased infiltration of giant cell than the experimental group 1. By this results, it considered that 6-stranded Respond(R)(G&H Co., U.S.A.) wire was the most useful material allowing early periodontal tissue remodeling.

A photoelastic study of the stress distribution on canine retraction by segmented TMA T-loop spring / 대한치과교정학회지

The segmented TMA T-loop spring, used for reciprocal space closure and described by Burstone, was used to achievebodily movement of canine. Photoelastic analysis is a technique for the transformation of internal stress into visible light patterns. The two-dimensional photoelastic stress analysis was performed, and stress distribution was recorded by photography. The purpose of this study was to visualize photoelastically the distribution of forces transmitted to the alveolus and surrounding structures using new segmented TMA T-loop spring for canine retraction. The results were as follows: 1. Decreased activation produced decreased stress of upper 1st. premolar extraction site and increased intrusive stress of upper 1st. molar, regardless of T-loop position. 2. At 5mm activation, More posterior positioning of T-loop produced an increased stress in upper 1st. premolar extraction site. 3. At 3mm activation, More posterior positioning of T-loop produced an increased stress in upper 1st. premolar extraction site and mesial lower half of upper 1st. molar mesio-buccal root. 4. At 1mm activation, More anterior positioning of T-loop produced an increased stress in upper mesial and blew apex area of upper canine root. 5. 0.25 B/L ratio and 3mm activation produced bodily movement of canine. To summarize, desired tooth movement and anchorage requirement is possible by altering the activation and mesio-distal position of the T-loop spring.

Changes of bite force and occlusal contacts after stabilization splint therapy / 대한치과교정학회지

This study was done to identify the changes of bite force and occlusal contact between before and after stabilization splint therapy. 16 female patients, accepted for orthodontic treatment at the Department of Orthodontics, College of Dentistry, Chosun University, were selected as the sample of this investigation. For comparisons, the samples of 16 were divided into just before stabilization splint, 1 month after stabilization splint, 2months after stabilization splint, and 3 months after stabilization splint and used the T-scan system to identify the bite force and occlusal contact changes for each group. Statistical analysis of the data was carried out ANOVA tests, and Turkey test using SPSS/PC(+). The results were as follows : 1. Bite force change from just before treatment to 1 month after stabilization splint therapy was statistical significantly decreased (P0.05). 3. The changes of anterior occlusal contacts showed no statistical significance regardless of the wearing periods of stabilization splint (p>0.05). 4. The changes of posterior occlusal contacts from just before treatment to 1 month after stabilization splint therapy was statistical significantly decreased (p>0.05). 5. The changes of posterior occlusal contacts during 1 to 3 months after stabilization splint therapy showed no statistical significance (p>0.05). 6. Posterior teeth rather than anterior teeth were more influenced by the changes of the number of occlusal contacts. To sum up above results, we may respect to capturing and stabilizing centric relation position just 1 month after stabilization splint therapy.

A study on the reproducibility of the natural head position according to the skeletal malocclusion type and sex / 대한치과교정학회지

This study was performed to evaluate the reproducibility of natural head position according to skeletal malocclusion types and sex using cephalometric radiographs for establishing orthodontic diagnosis and treatment planing. The sample consisted of 90 young adults (male 45, female 45) who had the skeletal malocclusion. Cephalometric radiographs were taken on natural head position, and statistical analysis was performed and method error of 6 postural variables were estimated to evaluate the reproducibility of the natural head position. The following results were obtained: 1. In the reproducibility of the natural head position, postural variables had no statistical significance in male and female(P>0.05) 2. In the reproducibility of the natural head position, postural variables had no statistical significance in Class I, II, III and total group (P>0.05). 3. The reproducibility of natural head position using method error was excellent in all group.

The prevalence of temporomandibular disorders in 16~18 aged subjects at Yongin, Kyungkido, Korea / 대한치과교정학회지

An epidemiological investigation was carried out at Yongin, Kyungkido, South Korea to determine the prevalence of symptoms of temporomandibular disorders and parafunctional habits in adolescent aged 16, 17 and 18 years. 2,098 students(male 507, female 1,591) were randomly selected and investigated with the questionnaire. The results were obtained as follows. 1. The prevalence of symptoms of temporomandibular disorders was 80.9% total, 77.3% for male and 82.0% for female with significance between male and female(P<0.05). 2. The prevalence of symptoms of temporomandibular disorders was gradually increased according to increasing age with significant difference among ages(P<0.01) 3. The most frequent symptom in the temporomandibular disorders is pain on chewing(65.9), and then clicking(50.7%), pain on mouth opening(41.8%), and pain on TMJ(36.8%). 4. There was little corelationship between clenching habits and symptoms of temporomandibular disorders(r=0.166), and also between bruxing habit and those(r=0.057).

The compensatory adaptation of anterior teeth according to the skeletal rolation / 대한치과교정학회지

The purpose of this study was to identify the compensatory adaptation of dentoalveolar structure according to the various skeletal relation though the statistical correlation between the anteroposterior, vertical skeletal and dentoalveolar relation, For this study, the sample were consisted of 101 adult subjects (51male and 50 female, mean age; male 23.6 years, female 21.5 years) who had good occlusion with the range of normal overjet and overbite and acceptable Angle's class I molar relationship which had not been related orthodontically. The results were as follows : 1. Even though acceptable normal occlusion, the range of measurements which represent anteroposterior, vertical skeletal relation and dentoalveolar relation were very wide. 2. Upper and lower incisor axis were significantly correlated with anteroposterior skeletal relation, which means the more lingual inclination of upper anterior teeth and the more labial inclination of lower anterior teeth according to the more anterior position of mandible to the maxilla (p0.05). 5. The correlation between the incisor axis and vertical skeletal was more closely related in upper anterior teeth than the lower anterior teeth. To summarize the above results, even though acceptable normal occlusion, skeletal and dentoalveolar relation was very widely ranged, and there were close relationship between the anteroposterior skeletal relation and the inclination of upper and lower anterior teeth and between the vertical skeletal relation and upper and lower anterior alveolar bone height. These finding can be concluded as compensatory adaptation to the different skeletal relationship

Changes of lateral cephalometric values according to the rotation of head / 대한치과교정학회지

This study was performed to find out the effect projection errors on cephalometric linear and angular measurements according to head rotation during taking lateral cephalometric radiography. Seventeen skulls with permanent dentition and on gross asymmetry were obtained from the Department of Anatomy, Medical School, Chosun University. Total 527 x-ray films were taken with 1degrees interval from the reference position(0degrees) to 15degrees around the vertical axis (Z axis) which is perpendicular to the midpoint of the connecting the center of two ear rods in submento-vertex direction. Statistical analysis was performed by paired t-test if there were statistically significant differences between the mean of the reference position(0degrees) and that of each rotation angle. The following results were obtained. 1. The projection errors of angular measurements were smaller than those of linear measurements. 2. The projection errors of angular measurements including midline landmarks were smaller than those including bilateral landmarks. 3. The horizontal linear measurements were gradually decreased when the skull was rotated toward the film, but slightly increased and then decreased when the skull was rotated toward the focal spot. However, the changes were smaller in focal direction. 4. The projection errors of horizontal linear measurements were larger than those of vertical linear measurements. 5. The projection errors of vertical linear measurements were increased with increased distance form the rotation axis to vertical measurements. It is concluded that the use of angular measurements rather than linear measurements is recommended to minimize the projection errors.

Effect of fluoride releasing orthodontic sealants on enamel demineralization in vitro / 대한치과교정학회지

The purpose of this study was to evaluate the effects of fluoride releasing orthodontic sealants, light-cured(Group L1 & L2) and self-cured (Group S1 & S2) FluoroBond(R) , on enamel microhardness under artificial carious solution in vitro 112 extracted human premolar teeth were collected for experiments and divided into seven groups. A Tukon microhardness tester equipped with a Knoop diamond indenter was employed to determine microhardness. Tukon 23 program converted the number of microhardness into KHN(Knoop hardness number). The results were as follows : 1. The microhardness of enamel depth of all groups were the least at the depth of 50micrometer and that of all groups except L2 group, the greatest at the depth of 200micrometer, were the greatest at the depth of 300micrometer. And as the enamel depth of all groups except L2 and S2 group increased, the microhardness value also increased. 2. There was a little preventive effect in enamel decalcification both light-and self-cured orthodontic sealant groups, but had no statistical significance between the groups(p>0.05). 3. Light-cured ortodontic sealant groups had a progressive inhibiting effect in enamel decalcification at the depth of 100micrometer, 150micrometer, and 200micrometer(p0.05).

Effect of orthodontic force on the amount of tooth movement and root resorption in rat / 대한치과교정학회지

This study was undertaken to investigate the relation between orthodontic force magnitude and the amount of tooth movement. And more light force application for reducing root resorption. Twenty-four rats were divided into three experimental groups(A, B, C) based on force magnitude and application method. Springs of 50g force were applied to A group, spring of 100g force were applied to B group and springs of 25g force were applied to C group initially, and after 4 days springs of C group were changed to springs of 50g force. Two kinds of sentalloy(R) (GAC U.S.A) closed coil spring, 50g and 100g, were used. And we made 25g springs by heat treatment process of 50g spring. Each spring was inserted between the maxillary central incisor and the maxillary left first molar. Amounts of tooth movement were measured everyday by digital caliper(Digimatic(R) , Mitutoyo, Japan) under inhalation anesthesia for 15 days, all rats were sacrificed and histological sample were obtained with Hematoxyline-Eosin stan and Masson's trichrome stain. Following conclusion were made : 1. Group B showed the mean cumulative tooth movement of 2.19+/-0.41mm at 15th day, which was greatest among three groups, followed by group C(2.06+/-0101mm), group A(1.90+/-0.49mm) respectively. However, there was no statistically difference among three groups. 2. All groups showed general tooth movement pattern and A, B, C group finished lag phase at 9th, 8th, 7th day, but three was no statistical significance. 3. Group A, B, C showed root resorption and especially group B showed the most severe root resorption and group C showed milder root resorpting than other groups. According to the above results, large initial force with the development of a fairly widespread hyalinized zone may cause severe root resorption, so initial force should be applied lightly to reduce hyalinized area and eventually root resorption and then increased force will induce efficient tooth movement.

A comparative study on head posture and craniofacial morphology between Koreans and Scandiavian caucasians / 대한치과교정학회지

The purpose of this study was to evaluate racial differences in head posture and the influence of head posture to the craniofacial morphology. The sample group of this study was made up of 51 Korean males and 120 Scandinavian Caucasian males. From the comparison of the cranio-cervical angels and the variables of craniofacial morphology between them, the following results were obtained. 1. the cranio-cervical angle (NSL/OPT) was on average 9.28 degrees larger in Koreans. 2. The length of the anterior cranial base (N-S) was on average 4.66mm shorter in Koreans. 3. The length of the maxillary base (sp-pm and ss-pm) were on average 2.75mm and 4.65mm shorter in Koreans respectively, the anterior maxillary height (n-sp) was on average 2.60mm longer, the posterior dimension (s-pm) was found to be 2.06mm longer in Koreans, and the maxillary inclination (NSL/NL) was identical in both samples. 4. The mandibular body length (pg-tgo) and ramus height (ar-tgo) were identical in the two groups, but the gonial angle (ML/RL) was 3.22 degrees smaller and the mandibular plane inclination (NSL/ML) was 2.44 degrees larger in Koreans. 5. The maxillary prognathism (s-n-sp and s-n-ss) and the mandibular prognathism (s-n-ss) were identical in both samples. 6. The sagittal jaw relationship (ss-n-pg) was 1.44 degrees larger in the Koreans sample, but the vertical jaw relationship (NL/ML) was not significantly different. 7. The anterior facial height (n-gn) was 5.57mm longer in the Koreans sample. 8. The mandibular alveolar prognathism (CL/ML) was 5.71 defrees greater and the interincisal angle (ILs/ILi) was 3.08 degrees more acute in Koreans. Taken together these results, craniofacial morphology can be influenced by the head posture defined by cranio-cervical angulation.

Arch forms & dimensions after orthodontic treatment by premolar extraction / 대한치과교정학회지

This study was done to estimate arch forms and dimensions at the bracket level where archwire was placed in Angle's Class I first premolars extraction cases. 60 post-treatment dental casts which had attained good orthodontic treatment results were used in this study. Many landmarks and linear measurement items to describe arch forms and dimensions were determined and measured. With a computer system and digitizer, arch forms were described and linear measurement items were statistically analysed. The following results were obtained. 1. The average labial and lingual arch forms at the bracket level were obtained. 2. Arch forms were expressed by parabolic equations and coefficients of determination. 3. Arch widths were larger in male than in female. 4. There were statistical significances in upper intercanine width, upper interfirst molar width, upper intersecond molar height, lower intercanine width and lower interfirst molar width between both sexes (p<0.05, p<0.01). 5. Interfirst molar width differences between maxilla and mandible were 6.43mm in male and 6.05mm in female

A study of condylar positional changes before & after stabilization splint therapy / 대한치과교정학회지

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 Panadent 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(P0.05) 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.