Mandibular skeletal posterior anatomic limit for molar distalization in patients with Class III malocclusion with different vertical facial patterns / 대한치과교정학회지

Objective@#The aim of this study was to compare the differences in mandibular posterior anatomic limit (MPAL) distances stratified by vertical patterns in patients with skeletal Class III malocclusion by using cone-beam computed tomography (CBCT). @*Methods@#CBCT images of 48 patients with skeletal Class III malocclusion (mean age, 22.8 ± 3.1 years) categorized according to the vertical patterns (hypodivergent, normodivergent, and hyperdivergent; n = 16 per group) were analyzed. While parallel to the posterior occlusal line, the shortest linear distances from the distal root of the mandibular second molar to the inner cortex of the mandibular body were measured at depths of 4, 6, and 8 mm from the cementoenamel junction. MPAL distances were compared between the three groups, and their correlations were analyzed. @*Results@#The mean ages, sex distribution, asymmetry, and crowding in the three groups showed no significant differences. MPAL distance was significantly longer in male (3.8 ± 2.6 mm) than in female (1.8 ± 1.2 mm) at the 8-mm root level. At all root levels, MPAL distances were significantly different in the hypodivergent and hyperdivergent groups (p < 0.001) and between the normodivergent and hyperdivergent groups (p < 0.01). MPAL distances were the shortest in the hyperdivergent group. The mandibular plane angle highly correlated with MPAL distances at all root levels (p < 0.01). @*Conclusions@#MPAL distances were the shortest in patients with hyperdivergent patterns and showed a decreasing tendency as the mandibular plane angle increased. MPAL distances were significantly shorter (~3.16 mm) at the 8-mm root level.

Mandibular skeletal posterior anatomic limit for molar distalization in patients with Class III malocclusion with different vertical facial patterns / 대한치과교정학회지

Objective@#The aim of this study was to compare the differences in mandibular posterior anatomic limit (MPAL) distances stratified by vertical patterns in patients with skeletal Class III malocclusion by using cone-beam computed tomography (CBCT). @*Methods@#CBCT images of 48 patients with skeletal Class III malocclusion (mean age, 22.8 ± 3.1 years) categorized according to the vertical patterns (hypodivergent, normodivergent, and hyperdivergent; n = 16 per group) were analyzed. While parallel to the posterior occlusal line, the shortest linear distances from the distal root of the mandibular second molar to the inner cortex of the mandibular body were measured at depths of 4, 6, and 8 mm from the cementoenamel junction. MPAL distances were compared between the three groups, and their correlations were analyzed. @*Results@#The mean ages, sex distribution, asymmetry, and crowding in the three groups showed no significant differences. MPAL distance was significantly longer in male (3.8 ± 2.6 mm) than in female (1.8 ± 1.2 mm) at the 8-mm root level. At all root levels, MPAL distances were significantly different in the hypodivergent and hyperdivergent groups (p < 0.001) and between the normodivergent and hyperdivergent groups (p < 0.01). MPAL distances were the shortest in the hyperdivergent group. The mandibular plane angle highly correlated with MPAL distances at all root levels (p < 0.01). @*Conclusions@#MPAL distances were the shortest in patients with hyperdivergent patterns and showed a decreasing tendency as the mandibular plane angle increased. MPAL distances were significantly shorter (~3.16 mm) at the 8-mm root level.

Three-dimensional assessment of upper lip positional changes according to simulated maxillary anterior tooth movements by white light scanning / 대한치과교정학회지

OBJECTIVE: Esthetic improvements during orthodontic treatment are achieved by changes in positions of the lips and surrounding soft tissues. Facial soft-tissue movement has already been two-dimensionally evaluated by cephalometry. In this study, we aimed to three-dimensionally assess positional changes of the adult upper lip according to simulated maxillary anterior tooth movements by white light scanning. METHODS: We measured changes in three-dimensional coordinates of labial landmarks in relation to maxillary incisor movements of normal adults simulated with films of varying thickness by using a white light scanner. RESULTS: With increasing protraction, the upper lip moved forward and significantly upward. Labial movement was limited by the surrounding soft tissues. The extent of movement above the vermilion border was slightly less than half that of the teeth, showing strong correlation. Most changes were concentrated in the depression above the upper vermilion border. Labial movement toward the nose was reduced significantly. CONCLUSIONS: After adequately controlling several variables and using white light scanning with high reproducibility and accuracy, the coefficient of determination showed moderate values (0.40-0.77) and significant changes could be determined. This method would be useful to predict soft-tissue positional changes according to tooth movements.

Three-dimensional symmetry and parallelism of the skeletal and soft-tissue poria in patients with facial asymmetry / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to examine the symmetry and parallelism of the skeletal and soft-tissue poria by three-dimensional (3D) computed tomographic (CT) imaging. METHODS: The locations of the bilateral skeletal and soft-tissue poria in 29 patients with facial asymmetry (asymmetric group) and 29 patients without facial asymmetry (symmetric group) were measured in 3D reconstructed models of CT images by using a 3D coordinate system. The mean intergroup differences in the anteroposterior and vertical angular deviations of the poria and their anteroposterior and vertical parallelism were statistically analyzed. RESULTS: The symmetric and asymmetric groups showed significant anteroposterior angular differences in both the skeletal and the soft-tissue poria (p = 0.007 and 0.037, respectively; Mann-Whitney U-test). No significant differences in the anteroposterior and vertical parallelism of the poria were noted (p < or = 0.05; Wilcoxon signed-rank test). CONCLUSIONS: In general, the skeletal poria are parallel to the soft-tissue poria. However, patients with facial asymmetry tend to have asymmetric poria.

Soft-tissue thickness of South Korean adults with normal facial profiles / 대한치과교정학회지

OBJECTIVE: To standardize the facial soft-tissue characteristics of South Korean adults according to gender by measuring the soft-tissue thickness of young men and women with normal facial profiles by using three-dimensional (3D) reconstructed models. METHODS: Computed tomographic images of 22 men aged 20 - 27 years and 18 women aged 20 - 26 years with normal facial profiles were obtained. The hard and soft tissues were three-dimensionally reconstructed by using Mimics software. The soft-tissue thickness was measured from the underlying bony surface at bilateral (frontal eminence, supraorbital, suborbital, inferior malar, lateral orbit, zygomatic arch, supraglenoid, gonion, supraM2, occlusal line, and subM2) and midline (supraglabella, glabella, nasion, rhinion, mid-philtrum, supradentale, infradentale, supramentale, mental eminence, and menton) landmarks. RESULTS: The men showed significantly thicker soft tissue at the supraglabella, nasion, rhinion, mid-philtrum, supradentale, and supraglenoid points. In the women, the soft tissue was significantly thicker at the lateral orbit, inferior malar, and gonion points. CONCLUSIONS: The soft-tissue thickness in different facial areas varies according to gender. Orthodontists should use a different therapeutic approach for each gender.

Comparison of palatal bone thickness between 3D model and lateral cephalometric radiograph / 대한치과교정학회지

OBJECTIVE: This study compared the bone thickness of the palate between lateral cephalogram and 3D model measurements. METHODS: The subjects consisted of 30 adults (15 men,15 women) with a normal skeletal pattern and occlusion. The CT images were transformed to a 3D model, and were compared with the cephalometric image. Descriptive statistics for each variable were calculated. RESULTS: In the 3D CT model, the mid-palatal area was the thickest part. It became thinner as the palate tapered laterally. In the male group, the thinnest portion was positioned 6 mm away from the mid-palate, while in the female group the thinnest portion was 8mm away from the mid-palate. Correlation analysis between the lateral cephalometric and 3D CT model revealed a significant correlation except in the mid palatal area and the area 2 mm lateral to the mid-palate in men, whereas there was a significant relationship in every area in the women. In both men and women, the highest correlation appeared in the area 8 mm lateral to the mid palate. CONCLUSIONS: Using regression analysis, an actual prediction of the bone thickness between the measured bone thickness of the lateral cephalometric radiograph and 3D model was made. This will provide useful information for mini-implant length selection when inserting into the palate.

Quantitative evaluation and affecting factors of post-treatment relapse tendency / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to quantitatively evaluate relapse tendency after orthodontic treatment and determine the contributing factors by using the American Board of Orthodontics objective grading system (ABO-OGS). METHODS: The subjects were 80 patients with more than 2 years of retention period after completing orthodontic treatment at the dental hospitals of Busan University, Kyunghee University, and Dankook University. The posttreatment (T2) and post-retention (T3) ABO-OGS measurements were analyzed in relation to age, gender, Angle's classification, extraction, retention period, and pretreatment condition (initial peer assessment rating (PAR) index, T1) by multiple regression analysis. RESULTS: Among the 7 ABO-OGS criteria, alignment worsened but occlusal contact and interproximal contact improved in T3, but not in T2 (p < 0.01). The 4 other criteria showed no significant differences. Multiple regression analysis showed that alignment, occlusal relationship, overjet, and interproximal contact were significant linear models, but with a low explanation power. Age, gender, Angle's classification, extraction, retention period, and pretreatment condition (initial PAR index, T1) had little influence on the ABO-OGS changes between T3 and T2. CONCLUSIONS: An orthodontist's understanding of post-treatment relapse tendency can be useful in diagnosis and during patient consultation.

Factors affecting orthodontically induced root resorption of maxillary central incisors in the Korean population / 대한치과교정학회지

OBJECTIVE: Orthodontically induced root resorption (OIRR) involves partial loss of cementum and dentin of teeth caused by routine orthodontic treatment. It decreases root length and influences the function of affected teeth. In this study, the treatment and patient factors causing apical root resorption in Koreans were determined. The observed factors were extraction, gender, age, displacement of root apex, total treatment period, total teeth length, and shape of the root. METHODS: The records of 137 patients treated with full, fixed edgewise appliances were obtained from the Department of Orthodontics, Dankook University Dental Hospital, from November 2007 to December 2008. Periapical radiographs of the maxillary central incisors and cephalometric radiographs of each patient were used to assess apical root resorption and type of tooth movement. RESULTS: The mean amount of resorption was 1.62 +/- 1.58 mm. The amount of resorption in the extraction and non-extraction groups was 2.10 +/- 1.64 mm and 1.18 +/- 1.39 mm, respectively. The amount of root resorption increased with the total tooth length. Severe root resorption (> 4 mm) was related to abnormal root shape (blunt, pointed, or eroded). CONCLUSIONS: The variables significantly related to OIRR were extraction, initial tooth length, and root shape.

Expression of Heat Shock Protein 27 according to Gleason Score and Pathologic Stage of Prostate Cancer

PURPOSE: Heat shock protein 27 (HSP27) is induced by heat shock and other pathophysiologic stresses. We examined the relationship between HSP27 expression and Gleason score and pathologic stage of prostate cancer. MATERIALS AND METHODS: Fifty-three men were treated by radical prostatectomy for prostate cancer diagnosed from May 2004 to April 2007. Prostate tissues (n=53) were obtained from radical prostatectomy specimens of prostate cancer. The overall percentage of cancer cells showing staining (0% to 100%) was indicated by visual scoring. Specimens were graded from +1 to +3 intensity representing the range of staining area, for which below 5% is +1 grade, 5-50% is +2 grade, over 50% is +3 grade and focal reaction is +0.5 grade. RESULTS: An HSP27-positive reaction was seen in 2 of 11 cases (18.2%) with a Gleason score of 4-6, 11 of 19 cases (57.9%) with a Gleason score 7, 6 of 10 cases (60.0%) with a Gleason score 8, 12 of 13 cases (92.3%) with a Gleason score of 9 (p=0.001); the mean HSP27 reaction scores were 0.27, 0.86, 0.83, and 1.54 respectively (p=0.006). An HSP27-positive reaction was seen in 17 of 37 cases (46.0%) with pathologic stage T2, 10 of 12 cases (83.3%) with pathologic stage T3, and 4 of 4 cases (100%) with pathologic stage T4 (p=0.0032); the mean HSP27 reaction scores were 0.64, 1.17, and 2, respectively (p=0.007). HSP27 expression was not statistically significant according to age. CONCLUSIONS: There is correlation between HSP27 expression and Gleason score, pathologic stage of prostate cancer.

Efficacy and Safety of Intravenous Propofol Anesthesia during Transrectal Ultrasound-Guided Prostate Biopsy

PURPOSE: Transrectal ultrasonography (TRUS)-guided prostate biopsy causes fear and pain in 65% to 90% of patients. This study was designed to evaluated the use of intravenous propofol anesthesia during TRUS-guided prostate biopsy. MATERIALS AND METHODS: Between January 2006 and June 2008, 195 men undergoing a transrectal prostate biopsy were divided into 2 groups according to anesthetic technique. Group A consisted of 99 patients who received intravenous propofol infusion through an 18 gauge needle during TRUS-guided prostate biopsy. Group B consisted of 96 patients who intrarectally received 10 ml of 2% lidocaine gel 10 minutes before TRUS-guided prostate biopsy. Pain scores were assessed on a visual analogue scale immediately after prostate biopsy. RESULTS: The pain score was significantly reduced in group A compared with group B. There was a significant difference in the mean pain score between the 2 groups (1.0+/-1.3 in group A versus 2.9+/-2.0 in group B; p<0.01). Also, there was a significant difference in the willingness to undergo rebiopsy between the 2 groups (83.8% in group A versus 17.7% in group B; p<0.01). However, the complication rates were not significantly different between the 2 groups. Gross hematuria was found in 14% of group A patients and 18% of group B patients. CONCLUSIONS: Our results proved the advantage of intravenous propofol anesthesia during TRUS-guided prostate biopsy. Intravenous propofol infusion can be a safe and simple technique that significantly reduces pain during TRUS-guided prostate biopsy.

Consideration of maxillary sinus bone thickness when installing miniscrews / 대한치과교정학회지

OBJECTIVE: Miniscrews are widely used in orthodontic treatment for the purpose of anchorage control. Maximum anchorage can be acquired by the use of miniscrews. Maxillary miniscrew has many clinical advantage for orthodontic treatment. Maxillary sinus, tooth root can be an obstacle for maxillary miniscrew installation. The purpose of this study was to find the safest area and direction of miniscrew insertion in consideration of the maxillary sinus. METHODS: The maxillary sinus area of 40 patients (20 male, 20 female) was measured using 3D computed tomography and 3D reconstruction program. RESULTS: The maxillary sinus floor was located most inferiorly between the 1st molar and 2nd molar and located most superiorly between the 1st premolar and 2nd premolar. Buccal bone thickness from the maxillary sinus is significantly thicker between the 1st molar and 2nd molar and significantly thinner between the 1st premolar and 2nd premolar. The area between the 1st premolar and 2nd premolar has a significantly longer vertical distance from CEJ to sinus in consideration of buccal bone thickness. CONCLUSIONS: Considering maxillary bone thickness, the posterior area has advantages over the anterior area for installing miniscrews safely and preventing perforation.

Skeletal maturation associated with the fourth cervical vertebra and menarcheal timing / 대한치과교정학회지

OBJECTIVE: This study analyzed the morphologic changes of the fourth cervical vertebra body to determine the skeletal age of orthodntic patients during growth. METHODS: Eighty-one female patients aged from 11 to 14 who had cephalograms taken on the same day were examined. The subjects were divided into three groups depending on the depth of the concavity of the lower border of the fourth cervical vertebra (Group A: less than 1.05 mm, Group B: 1.05 - 2.07 mm, Group C: greater than 2.07 mm). Menarcheal timing, SMI stage, length, width and ratio of length and width of the fourth cervical vertebra body were analyzed and the following results were obtained. RESULTS: The average SMI stage of group A,B and C were 5.67 +/- 2.57, 8.73 +/- 2.41, and 10.00 +/- 1.47, respectively. Length, width, ratio of length and width, and SMI stage were greater in group B than group A and in group C than group B. Mean menarcheal timing was 11.64 +/- 0.92 years. Concavity depth, length, width, ratio of length and width showed a significant positive correlation with SMI stage, especially with the concavity depth. CONCLUSION: The results of this study propose a simple method for determining the timing of orthopedic treatment by measuring the concavity depth of the fourth cervical vertebra on the cephalogram.

Treatment effect of face mask therapy for Class III malocclusion patients according to low facial morphology / 대한치과교정학회지

OBJECTIVE: Improvements in jaw relationship through clockwise rotation of the mandible may be desirable in some Class III patients with short low facial height. The aim of this study was to examine the treatment effect of face mask for Class III malocclusion patients according to their low facial morphology. METHODS: Class III patients in their pubertal growth period were divided into two groups (Group 1, high LFH; Group 2, low LFH) according to lower facial height (LFH) by Ricketts (norm, 47). Treatment changes between groups after face mask treatment was compared not only for hard tissue but also for soft tissue. RESULTS: There were no significant differences between the two groups for the skeletal and soft tissues of the maxilla. There were no significant differences between the two groups for the skeletal posterior movement of the mandible, but posterior movement of the mandibular soft tissues in group 2 was larger than group 1. There were no significant differences between the two groups for the vertical hard tissue proportion changes of the mandible, but the vertical soft tissue proportion changes of the mandible in group 2 was larger than group 1. There was a significant correlation between the sagittal hard tissue and soft tissue changes of the maxilla and mandible, but there was no significant difference in the vertical changes. CONCLUSION: The clockwise rotation of the mandible occurred from use of the face mask, and posterior movement of soft tissues of the mandible was higher in Cl III patients with low LFH than with high LFH.

Changes in atlas position with Class II activator treatment in Class II malocclusion patients / 대한치과교정학회지

OBJECTIVE: Previous studies have reported that morphological features of the first cervical vertebra (atlas) have been associated with mandibular growth direction. The purpose of this study was to show the possible positional and morphological changes of the Atlas from activator treatment in Class II malocclusion patients. METHODS: Lateral cephalometric radiograph tracings were made at initial, middle and final stages of treatment. Angular and linear measurements of skeletal and morphological features were measured on the anatomical landmarks and reference planes. RESULTS: The skeletal effects of activator treatment on Class II malocclusion patients were evident on ramal height, body length, effective body length, ANB, and overjet. Clockwise rotation of the long axis of the Atlas was found in Group 1, but there was no inclination change of the Atlas in groups 2 and 3. There was no significant correlation between anterior and posterior positions of the atlas or morphological change in all groups. - except for posterior movements of the Atlas found in group 1. CONCLUSION: Clockwise rotation of the atlas axis resulted from activator treatment in Cl II malocclusion patients. Change in atlas axis can be thought of as an indicator for success of activator treatment.

A study on the correlation between airway space and facial morphology in Class III malocclusion children with nasal obstruction / 대한치과교정학회지

OBJECTIVE: The aim of this study was assessment of the relationship between airway space and facial morphology in Class III children with nasal obstruction. METHODS: For this study, 100 Class III children (50 boys and 50 girls) were chosen. All subjects were refered to ENT, due to nasal obstruction. Airway space measurements and facial morphology measurements were measured on lateral cephalometric radiograph. Pearson correlation analysis was used to assess the relationship between airway space and facial morphology. RESULTS: Ramal height, SNA, SNB, PFH, FHR and facial plane angle were positively related to upper PAS, and sum of saddle angle, articular angle, and gonial angle, SN-GoGn, Y-axis to SN and FMA negatively related to upper PAS. Gonial angle, FMA were positively related to lower PAS, and articular angle, facial depth, PFH and FHR negatively related to lower PAS. PCBL, ramal height, Mn. body length, Mn. body length to ACBL, facial depth, facial length, PFH and AFH were positively related to tonsil size. Sum of saddle angle, articular angle, gonial angle, facial length, AFH, FMA and LFH were positively related to tongue gap, and IMPA and overbite was negatively related to tongue gap. Upper PAS, related to size of adenoid tissue, was mainly related to posterior facial dimension following a vertical growth pattern of face and mandibular rotation. Lower PAS and tonsil size, related to anterior-posterior tongue base position, were significantly related to each other. Lower PAS was related to growth pattern of mandible, and tonsil size was related to size of mandible and horizontal growth pattern of face. Tongue gap was related to anterior facial dimension following a vertical growth pattern of face. CONCLUSION: Significant relationship exists between airway space and facial morphology.

The Role of Retrograde Urethrography as a Predictor of Early Recovery of Urinary Continence after Radical Retropubic Prostatectomy

PURPOSE: This study is designed to explore the role of retrograde urethrography as a predictor of recovery of urinary continence after radical retropubic prostatectomy. MATERIALS AND METHODS: A total of 40 patients who underwent radical retropubic prostatectomy from January 2005 to April 2007 were investigated. Among them one neurogenic bladder patient and one follow up loss patient were excluded. Voiding pattern and urinary incontinence were investigated with voiding diary monthly after Foley catheter removal. Recovery of urinary continence was defined as usage of less than 1 diaper per day. Pericatheter urethrography was conducted 2 weeks after operation. If definite bladder-urethral extravasation was not detected, an retrograde urethrography was performed immediately. 30 patients with sufficient length of urethra, regular margin of urethra and beaky appearance were defined as Group A, and 8 patients without above mentioned characteristics were marked as Group B. Differences between two groups were compared in terms of age, prostate volume, prostate specific antigen, urodynamic parameters, and duration of urinary incontinence. RESULTS: No significant differences were found in age, prostate volume, PSA between two groups. In group A, recovery rates of urinary continence were 70% (21 persons), 100% (30 persons) at 1,3 months after removal of catheter, respectively. In group B, rates of urinary continence recovery were 16.6% (1 person), 37.5% (3 persons), 75% (6 persons) at 1,3,4 months, respectively and 1 person regained continence at 7 months. CONCLUSION: A catheter free retrograde urethrography can be easily added after confirmation of bladder urethra anastomosis site healing. It gives us some valuable informations about external sphincter. The characteristics of retrograde urethrography can be used as a predictor of early recovery of postoperative incontinence.

Post-treatment stability of the occlusal plane according to different vertical facial patterns / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to find changes in the occlusal plane related to different vertical facial patterns and suggest treatment goals and conduct possible treatment mechanisms. METHODS: 60 adult patients (28 males, 32 females) who had been diagnosed as Class I skeletal malocclusion and treated without extraction were selected. Patients were divided into three groups; short face type (group 1), average face type (group 2) and long face type (group 3), using the data on normal occlusion of Korean adults. RESULTS: The results were achieved by analyzing cephalometric tracings of each group at pre-treatment, end-treatment and post-treatment (about 1 year recall check). The inclination of the occlusion plane tends to gradually increase as the face becomes longer. In group 1, COP-X, FOP-X, L6/L1, MP-L6 were significantly decreased, and L1-FOP was significantly increased during the retention period (T3-T2). Group 2 showed no significant change. In group 3, FOP-X was significantly increased during the retention period (T3-T2). During the retention period, FOP-X showed significant change among each group, especially between group 1 and group 3. CONCLUSION: These results suggest that changes of occlusal plane inclination according to facial vertical pattern need to be considered during the retention period for intrusion, extrusion, and incisor overbite.

Research on plaque removal by sonic toothbrush for patients with a fixed orthodontic appliance / 대한치과교정학회지

The purpose of this research is to evaluate and compare the plaque removal ability of sonic brushing and manual brushing in order to present a method for continuous and effective oral hygiene control during orthodontic treatment. Nonextracted adolescent patients (male : 23 persons, female : 37 persons) and adult patients (male : 15 persons, female : 45 persons) outfitted with a fixed orthodontic appliance from their incisors to second molar, in both the maxilla and mandible, were divided into manual brushing and sonic brushing groups. A Philips oral healthcare HX-4401 sonic toothbrush was used, and the application of brushing for the two groups was standardized at two minutes. After brushing the plaque score was measured with a modified Wilkin's PHP. The following results were achieved after comparing each group's plaque score. 1. In patients with a fixed orthodontic appliance when age was not accounted for, the application of sonic brushing exerted a beneficially decreased effect on the plaque score. (adolescents : p<0.01, adults : p<0.05) 2. When comparing the adolescent and adult groups in regard to plaque score, the adolescent group showed a more decreased effect. 3. When using the same toothbrush type, there was no difference between the adolescent and adult groups.

A comparative study on bond strength and adhesive failure pattern in bracket bonding with self-etching primer / 대한치과교정학회지

A self-etching primer that combines the etchant and primer in one chemical compound saves time and should be more cost-effective to the clinician and patient. The purpose of this study was to evaluate the clinical effectiveness of a self-etching primer by measuring shear bond strengths according to various conditions and observing adhesive failure patterns. For this investigation, 120 upper and lower premolars extracted for orthodontic purposes were used and randomly divided into six groups of twenty teeth each. Human premolars were embedded in a metal cylinder with orthodontic resin. Metal brackets and ceramic brackets were bonded with XT primer and self-etching primer by means of XT adhesive. Upon curing, plasma arc light and visible light were used. After bonding, the shear bond strength was tested by Instron universal testing machine, and the amount of residual adhesive that remained on the tooth after debonding was measured by stereoscope and assessed with an adhesive remnant index. The results were as follows: 1. When brackets were bonded, if other conditions remained the same, there was no significant difference in shear bond strength due to the type of primer - either self-etching primer or XT primer. 2. When metal brackets were bonded, there was no significant difference in shear bond strength according to the source of light - plasma arc light or visible light - and type of primer. 3. There was a very significant difference in shear bond strength according to the type of brackets - metal or ceramic brackets. The shear bond strength of ceramic brackets was stronger than metal brackets. 4. When the adhesive failure patterns of metal brackets bonded with self-etching primer were observed by using the adhesive remnant index, the bond failure of the metal bracket occurred more frequently at the bracket-adhesive. The failure of the ceramic bracket, however, occurred more frequently at the enamel-adhesive interface. The adhesive failure patterns of metal brackets bonded with XT primer observed the same patterns. The above results suggest that self-etching primer can be clinically useful for bonding the brackets without fear of a decrease in shear bond strength.

A photoelastic study on the initial stress distribution of the upper anterior teeth retraction using combination loop archwire and sliding mechanics / 대한치과교정학회지

An unfavorable tipping movement can occur during the retraction of anterior teeth because orthodontic force is loaded by brackets positioned far from the center of resistance. To avoid this unfavorable movement, a compensating curved wire or lingual root torque wire is used. The purpose of this study is to investigate, using photoelastic material, the distribution of initial stress associated with the retraction of the incisors according to the degree of the compensating curve, to model changes associated with tooth and alveolar bone structure. The following results were obtained by analysis of the polarizing plate of the effects of initial stress resulting from retraction of the anterior teeth: 1. When the incisors were retracted using combination archwire or sliding mechanics, the maximal polarizing pattern of the apical area decreased as the degree of the compensating curve increased from 0 to 15 to 30. 2. When the incisiors were retracted by the combination archwire or sliding mechanics, the maximal polarizing pattern of t he canine and premolar area increased as the degree of the compensating curve increased from 0to 15to 30. 3. A lower degree of polarizing patterns were associated with the combination archwire technique than the sliding mechanics technique at a given force. The above results indicate that there is no significant difference between the combination loop archwire technique and sliding mechanics, for the retraction of maxillary anterior teeth with decreased lingual tipping tendency by a compensating curve on the arch wire. However, the use of sliding mechanics is more effective for the prevention of lingual inclination of the anterior teeth, because the hook used in sliding mechanics is closer to the center of resistance of the maxillary anterior teeth.