Accuracy of one-step automated orthodontic diagnosis model using a convolutional neural network and lateral cephalogram images with different qualities obtained from nationwide multi-hospitals / 대한치과교정학회지

Objective@#The purpose of this study was to investigate the accuracy of one-step automated orthodontic diagnosis of skeletodental discrepancies using a convolutional neural network (CNN) and lateral cephalogram images with different qualities from nationwide multi-hospitals. @*Methods@#Among 2,174 lateral cephalograms, 1,993 cephalograms from two hospitals were used for training and internal test sets and 181 cephalograms from eight other hospitals were used for an external test set. They were divided into three classification groups according to anteroposterior skeletal discrepancies (Class I, II, and III), vertical skeletal discrepancies (normodivergent, hypodivergent, and hyperdivergent patterns), and vertical dental discrepancies (normal overbite, deep bite, and open bite) as a gold standard. Pre-trained DenseNet-169 was used as a CNN classifier model. Diagnostic performance was evaluated by receiver operating characteristic (ROC) analysis, t-stochastic neighbor embedding (t-SNE), and gradientweighted class activation mapping (Grad-CAM). @*Results@#In the ROC analysis, the mean area under the curve and the mean accuracy of all classifications were high with both internal and external test sets (all, > 0.89 and > 0.80). In the t-SNE analysis, our model succeeded in creating good separation between three classification groups. Grad-CAM figures showed differences in the location and size of the focus areas between three classification groups in each diagnosis. @*Conclusions@#Since the accuracy of our model was validated with both internal and external test sets, it shows the possible usefulness of a one-step automated orthodontic diagnosis tool using a CNN model. However, it still needs technical improvement in terms of classifying vertical dental discrepancies.

Comparison of one-jaw and two-jaw orthognathic surgery in patients with skeletal Class III malocclusion using data from 10 multi-centers in Korea: Part I. Demographic and skeletodental characteristics / 대한치과교정학회지

Objective@#To investigate demographic and skeletodental characteristics of one-jaw (1J-OGS) and two-jaw orthognathic surgery (2J-OGS) in patients with skeletal Class III malocclusion. @*Methods@#750 skeletal Class III patients who underwent OGS at 10 university hospitals in Korea between 2015 and 2019 were investigated; after dividing them into the 1J-OGS (n = 186) and 2J-OGS groups (n = 564), demographic and skeletodental characteristics were statistically analyzed. @*Results@#2J-OGS was more frequently performed than 1J-OGS (75.2 vs. 24.8%), despite regional differences (capital area vs. provinces, 86.6 vs. 30.7%, p 0.05). The most prevalent skeletal patterns in both groups were hyper-divergent pattern (50.0 and 54.4%, respectively) and left-side chin point deviation (both 49.5%).Maxillary spacing (odds ratio [OR], 3.645; p < 0.001) increased the probability of 2J-OGS, while maxillary crowding (OR, 0.672; p < 0.05) and normo-divergent pattern (OR, 0.615; p < 0.05) decreased the probability of 2J-OGS. @*Conclusions@#In both groups, males outnumbered females, and their mean operation age was older. The most frequent ALD was crowding in the 1J-OGS group, and spacing in the 2J-OGS group, while skeletal characteristics were not significantly different between the two groups.

Accuracy of artificial intelligence-assisted landmark identification in serial lateral cephalograms of Class III patients who underwent orthodontic treatment and two-jaw orthognathic surgery / 대한치과교정학회지

Objective@#To investigate the pattern of accuracy change in artificial intelligence-assisted landmark identification (LI) using a convolutional neural network (CNN) algorithm in serial lateral cephalograms (Lat-cephs) of Class III (C-III) patients who underwent twojaw orthognathic surgery. @*Methods@#A total of 3,188 Lat-cephs of C-III patients were allocated into the training and validation sets (3,004 Lat-cephs of 751 patients) and test set (184 Lat-cephs of 46 patients; subdivided into the genioplasty and non-genioplasty groups, n = 23 per group) for LI. Each C-III patient in the test set had four Lat-cephs: initial (T0), pre-surgery (T1, presence of orthodontic brackets [OBs]), post-surgery (T2, presence of OBs and surgical plates and screws [S-PS]), and debonding (T3, presence of S-PS and fixed retainers [FR]). After mean errors of 20 landmarks between human gold standard and the CNN model were calculated, statistical analysis was performed. @*Results@#The total mean error was 1.17 mm without significant difference among the four timepoints (T0, 1.20 mm; T1, 1.14 mm; T2, 1.18 mm; T3, 1.15 mm). In comparison of two time-points ([T0, T1] vs. [T2, T3]), ANS, A point, and B point showed an increase in error (p < 0.01, 0.05, 0.01, respectively), while Mx6D and Md6D showeda decrease in error (all p < 0.01). No difference in errors existed at B point, Pogonion, Menton, Md1C, and Md1R between the genioplasty and non-genioplasty groups. @*Conclusions@#The CNN model can be used for LI in serial Lat-cephs despite the presence of OB, S-PS, FR, genioplasty, and bone remodeling.

Effect of lower facial height and anteroposterior lip position on esthetic preference for Korean silhouette profiles / 대한치과교정학회지

Objective@#The purpose of this study was to evaluate the esthetic preference for various Korean silhouette profiles. @*Methods@#The Korean average male and female profiles were modified by changing the lower facial height and anteroposterior lip position to produce nine types of profiles. In order to test intrarater reliability, the average profile was copied once more to be included for evaluation. A questionnaire containing 10 profiles for each sex, each of which had to be rated for preference on a numerical rating scale from 0 to 10, was administered to 30 adult orthodontic patients, 30 dental students, 30 orthodontists, and 30 dentists excluding orthodontists. The data were statistically analyzed using the intraclass correlation coefficient (ICC), independent t-test, and one-way ANOVA. @*Results@#The ICC of overall intrarater reliability was 0.629. For several profiles, significantly higher scores were given to male profiles than to female profiles (p < 0.05). However, no significant differences were found in the scores for all profiles among the four rater groups.Among the short profiles, a significantly higher score was given to the retruded profile, and among the vertically average and long profiles, a significantly higher score was given to the horizontally average profile (p < 0.001). Among all the profiles, significantly lower scores were given to the protruded profile (p < 0.001). @*Conclusions@#This study revealed good overall intrarater reliability, with several types of male profiles being esthetically preferred over female profiles. Moreover, while retruded and horizontally average profiles were generally preferred, protruded profiles were not.

Comparison of slot sizes and parallelism of metal brackets manufactured through metal injection molding and computerized numerical control / 대한치과교정학회지

Objective@#To investigate and compare the slot sizes and parallelism of metal injection molding (MIM) and computerized numerical control (CNC) brackets. @*Methods@#The following four MIM bracket series with 0.022-inch (in) slots were selected for investigation: Di MIM mini Twin (Ortho Organizers), Mini Diamond Roth (Ormco), Gemini MBT (3M Unitek), and Formula R Roth (Tomy).The following four CNC bracket series with 0.022-in slots were selected for investigation: Econoline MBT (Adenta), Legend mini MBT (GC Orthodontics), Crown mini MBT (Adenta), and Evolve MBT (DB Orthodontics). The slot dimensions were measured using an optical microscope (XTCam-D310M;Mitutoyo) with a resolution of 1 μm. The results were statistically analyzed using one-way analysis of variance and the Tukey post-hoc test with a significance level of 0.05. @*Results@#The results indicated that all the investigated slot sizes were oversized with respect to the manufacturers’ specifications (0.022 in). Among the eight bracket series, the Di MIM bracket (MIM) was the most oversized by 10.4%, whereas the Evolve bracket (CNC) was the least oversized by 2.6%. The slots in seven of the bracket series had divergent walls instead of parallel ones. The Evolve bracket alone had parallel slot walls. @*Conclusions@#Regardless of the manufacturing method, all the slot sizes of the brackets investigated in this study were significantly oversized; most of the slot walls were nonparallel, except for those of the Evolve bracket. This study could not establish that the CNC method was more accurate than the MIM method in manufacturing bracket slots.

Case series of cleidocranial dysplasia: Radiographic follow-up study of delayed eruption of impacted permanent teeth

This report describes 3 cases of cleidocranial dysplasia (CCD) and presents relevant findings on long-term follow-up radiographic images of impacted permanent teeth with delayed eruption. Radiographic images of 3 CCD patients were reviewed retrospectively. These images were mainly composed of panoramic and skull radiographs, and the follow-up periods were 3, 13, and 13 years, respectively. The distinct features revealed by the images were described, and the eruption state of impacted permanent teeth was evaluated. The features common to the 3 cases were multiple supernumerary teeth, the presence of Wormian bone, underdevelopment of the maxilla and the maxillary sinus, and clavicular hypoplasia. The eruption of impacted permanent teeth was not observed without proper dental treatment in adult CCD cases, even after long time periods had elapsed. When proper orthodontic force was applied, tooth movement was observed in a manner not significantly different from the general population.

Three-dimensional analysis of tooth movement in Class II malocclusion treatment using arch wire with continuous tip-back bends and intermaxillary elastics / 대한치과교정학회지

OBJECTIVE@#The aim of this study was to analyze three-dimensional (3D) changes in maxillary dentition in Class II malocclusion treatment using arch wire with continuous tip-back bends or compensating curve, together with intermaxillary elastics by superimposing 3D virtual models.@*METHODS@#The subjects were 20 patients (2 men and 18 women; mean age 20 years 7 months ± 3 years 9 months) with Class II malocclusion treated using 0.016 × 0.022-inch multiloop edgewise arch wire with continuous tip-back bends or titanium molybdenum alloy ideal arch wire with compensating curve, together with intermaxillary elastics. Linear and angular measurements were performed to investigate maxillary teeth displacement by superimposing pre- and post-treatment 3D virtual models using Rapidform 2006 and analyzing the results using paired t-tests.@*RESULTS@#There were posterior displacement of maxillary teeth (p < 0.01) with distal crown tipping of canine, second premolar and first molar (p < 0.05), expansion of maxillary arch (p < 0.05) with buccoversion of second premolar and first molar (p < 0.01), and distal-in rotation of first molar (p < 0.01). Reduced angular difference between anterior and posterior occlusal planes (p < 0.001), with extrusion of anterior teeth (p < 0.05) and intrusion of second premolar and first molar (p < 0.001) was observed.@*CONCLUSIONS@#Class II treatment using an arch wire with continuous tip-back bends or a compensating curve, together with intermaxillary elastics, could retract and expand maxillary dentition, and reduce occlusal curvature. These results will help clinicians in understanding the mechanism of this Class II treatment.

Relationship between maturation indices and morphology of the midpalatal suture obtained using cone-beam computed tomography images / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to determine whether predicting maturation of the midpalatal suture is possible by classifying its morphology on cone-beam computed tomography (CBCT) images and to investigate relationships with other developmental age indices. METHODS: The morphology of the midpalatal suture was assessed by using CBCT images of 99 patients. Axial plane images of the midpalatal suture were classified into five stages according to the classification scheme. To make the assessment more accurate, the morphology and fusion of the midpalatal suture were additionally investigated on coronal cross-sectional planar images and volume-rendered images. Bone age was evaluated using the hand and wrist method (HWM) and cervical vertebrae method (CVM); dental age (Hellman's index), sex, and chronological age were also assessed. To evaluate relationships among variables, Spearman's rho rank test was performed along with crosstabs using contingency coefficients. RESULTS: The HWM and CVM showed strong correlations with the maturation stage of the midpalatal suture, while other indices showed relatively weak correlations (p < 0.01). Through crosstabs, the HWM and CVM showed high association values with CBCT stage; the HWM demonstrated slightly higher values (p < 0.0001). Based on the HWM, the midpalatal suture was not fused until stage 6 in both sexes. CONCLUSIONS: Among developmental age indices, the HWM and CVM showed strong correlations and high associations, suggesting that they can be useful in assessing maturation of the midpalatal suture.

Comparison of the bonding strengths of second- and third-generation light-emitting diode light-curing units / 대한치과교정학회지

OBJECTIVE: With the introduction of third-generation light-emitting diodes (LEDs) in dental practice, it is necessary to compare their bracket-bonding effects, safety, and efficacy with those of the second-generation units. METHODS: In this study, 80 extracted human premolars were randomly divided into eight groups of 10 samples each. Metal or polycrystalline ceramic brackets were bonded on the teeth using second- or third-generation LED light-curing units (LCUs), according to the manufacturers’ instructions. The shear bond strengths were measured using the universal testing machine, and the adhesive remnant index (ARI) was scored by assessing the residual resin on the surfaces of debonded teeth using a scanning electron microscope. In addition, curing times were also measured. RESULTS: The shear bond strengths in all experimental groups were higher than the acceptable clinical shear bond strengths, regardless of the curing unit used. In both LED LCU groups, all ceramic bracket groups showed significantly higher shear bond strengths than did the metal bracket groups except the plasma emulation group which showed no significant difference. When comparing units within the same bracket type, no differences in shear bond strength were observed between the second- and third-generation unit groups. Additionally, no significant differences were observed among the groups for the ARI. CONCLUSIONS: The bracket-bonding effects and ARIs of second- and third-generation LED LCUs showed few differences, and most were without statistical significance; however, the curing time was shorter for the second-generation unit.

Three-dimensional evaluation of tooth movement in Class II malocclusions treated without extraction by orthodontic mini-implant anchorage / 대한치과교정학회지

OBJECTIVE: The aim of this study was to analyze tooth movement and arch width changes in maxillary dentition following nonextraction treatment with orthodontic mini-implant (OMI) anchorage in Class II division 1 malocclusions. METHODS: Seventeen adult patients diagnosed with Angle's Class II division 1 malocclusion were treated by nonextraction with OMIs as anchorage for distalization of whole maxillary dentition. Three-dimensional virtual maxillary models were superimposed with the best-fit method at the pretreatment and post-treatment stages. Linear, angular, and arch width variables were measured using Rapidform 2006 software, and analyzed by the paired t-test. RESULTS: All maxillary teeth showed statistically significant movement posteriorly (p 0.05) and the intercanine, interfirst premolar, intersecond premolar, and interfirst molar widths increased significantly (2.2 mm, p < 0.01; 2.2 mm, p < 0.05; 1.9 mm, p < 0.01; 2.0 mm, p < 0.01; respectively). CONCLUSIONS: Nonextraction treatment with OMI anchorage for Class II division 1 malocclusions could retract the whole maxillary dentition to achieve a Class I canine and molar relationship without a change in the vertical position of the teeth; however, the second molars were significantly extruded. Simultaneously, the maxillary arch was shown to be expanded with distal-in rotation of the molars.

Cone-beam computed tomography based evaluation of rotational patterns of dentofacial structures in skeletal Class III deformity with mandibular asymmetry / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to assess rotational patterns of dentofacial structures according to different vertical skeletal patterns by cone-beam computed tomography (CBCT) and analyze their influence on menton deviation in skeletal Class III deformity with mandibular asymmetry. METHODS: The control group consisted of 30 young adults (15 men, 15 women) without any severe skeletal deformity. The asymmetry group included 55 adults (28 men, 27 women) with skeletal Class III deformity and at least 3-mm menton deviation from the midsagittal plane; it was divided into the hyperdivergent and hypodivergent subgroups using a mandibular plane angle cutoff of 35degrees. Fourteen rotational variables of the dental arches and mandible were measured and compared among the groups. Correlations between menton deviation and the other variables were evaluated. RESULTS: The asymmetry group showed significantly larger measurements of roll and yaw in the mandible than the control group. The hypodivergent subgroup showed significant differences in maxillary posterior measurements of yaw (p < 0.01) and maxillary anterior shift (p < 0.05) compared with the hyperdivergent subgroup. All the mandibular measurements had significant correlations with menton deviation (p < 0.01). Most measurements of roll were positively correlated with one another (p < 0.01). Measurements of yaw and roll in the posterior regions were also positively correlated (p < 0.05). CONCLUSIONS: Menton deviation in skeletal Class III deformity with mandibular asymmetry is influenced by rotation of mandibular posterior dentofacial structures. The rotational patterns vary slightly according to the vertical skeletal pattern.

Accuracy of three-dimensional printing for manufacturing replica teeth / 대한치과교정학회지

OBJECTIVE: Three-dimensional (3D) printing is a recent technological development that may play a significant role in orthodontic diagnosis and treatment. It can be used to fabricate skull models or study models, as well as to make replica teeth in autotransplantation or tooth impaction cases. The aim of this study was to evaluate the accuracy of fabrication of replica teeth made by two types of 3D printing technologies. METHODS: Fifty extracted molar teeth were selected as samples. They were scanned to generate high-resolution 3D surface model stereolithography files. These files were converted into physical models using two types of 3D printing technologies: Fused deposition modeling (FDM) and PolyJet technology. All replica teeth were scanned and 3D images generated. Computer software compared the replica teeth to the original teeth with linear measurements, volumetric measurements, and mean deviation measurements with best-fit alignment. Paired t-tests were used to statistically analyze the measurements. RESULTS: Most measurements of teeth formed using FDM tended to be slightly smaller, while those of the PolyJet replicas tended to be slightly larger, than those of the extracted teeth. Mean deviation measurements with best-fit alignment of FDM and PolyJet group were 0.047 mm and 0.038 mm, respectively. Although there were statistically significant differences, they were regarded as clinically insignificant. CONCLUSIONS: This study confirms that FDM and PolyJet technologies are accurate enough to be usable in orthodontic diagnosis and treatment.

Short-term and long-term treatment outcomes with Class III activator / 대한치과교정학회지

OBJECTIVE: The purpose of this retrospective study was to investigate short-term and long-term skeletodental outcomes of Class III activator treatment. METHODS: A Class III activator treatment group (AG) comprised of 22 patients (9 boys, 13 girls) was compared with a Class III control group (CG) comprised of 17 patients (6 boys, 11 girls). The total treatment period was divided into three stages; the initial stage (T1), the post-activator treatment or post-mandibular growth peak stage (T2), and the long-term follow-up stage (T3). Cephalometric changes were evaluated statistically via the Mann-Whitney U-test and the Friedman test. RESULTS: The AG exhibited significant increases in the SNA angle, ANB angle, Wits appraisal, A point-N perpendicular, Convexity of A point, and proclination of the maxillary incisors, from T1 to T2. In the long-term follow-up (T1-T3), the AG exhibited significantly greater increases in the ANB angle, Wits appraisal, and Convexity of A point than the CG. CONCLUSIONS: Favorable skeletal outcomes induced during the Class III activator treatment period were generally maintained until the long-term follow-up period of the post-mandibular growth peak stage.

Comparing esthetic smile perceptions among laypersons with and without orthodontic treatment experience and dentists / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to examine whether orthodontic treatment experience affects the individual's perception of smile esthetics and to evaluate differences among orthodontically treated laypersons, non-treated laypersons, and dentists by using computerized image alterations. METHODS: A photograph of a woman's smile was digitally altered using a software image editing program. The alterations involved gingival margin height, crown width and length, incisal plane canting, and dental midline of the maxillary anterior teeth. Three groups of raters (orthodontically treated laypersons, non-treated laypersons, and dentists) evaluated the original and altered images using a visual analog scale. RESULTS: The threshold for detecting changes in maxillary central incisor gingival margin height among laypersons was 1.5 mm; the threshold of dentists, who were more perceptive, was 1.0 mm. For maxillary lateral incisor crown width and height, the threshold of all three groups was 3.0 mm. Canting of the incisal plane was perceived when the canting was 3.0 mm among non-treated laypersons, 2.0 mm among treated laypersons, and 1.0 mm among dentists. Non-treated laypersons could not perceive dental midline shifts; however, treated laypersons and dentists perceived them when the shift was > or = 3.0 mm. CONCLUSIONS: Laypersons with and without orthodontic treatment experience and dentists have different perceptions of smile esthetics. Orthodontically treated laypersons were more critical than non-treated laypersons regarding incisal plane canting and dental midline shifts. Based on these findings, it is suggested that orthodontic treatment experience improved the esthetic perceptions of laypersons.

Effect of malocclusion or orthodontic treatment on oral health-related quality of life in adults / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the effect of malocclusion or orthodontic treatment on oral health-related quality of life (OHRQoL) in adults. METHODS: The sample consisted of 860 adults (378 men and 482 women, aged 18-39 years) who were clinically evaluated for malocclusion or orthodontic treatment experience. Participants were divided into 4 groups as follows: normal occlusion, malocclusion, fixed treatment, and retention. OHRQoL was assessed with the short form of the Oral Health Impact Profile (OHIP-14) and Psychosocial Impact of Dental Aesthetics Questionnaire (PIDAQ). RESULTS: The malocclusion group and the fixed treatment group had significantly higher OHIP-14 scores than the normal occlusion group and the retention group (p < 0.001). The malocclusion group had the highest PIDAQ score, while the normal occlusion group and the retention group had the lowest PIDAQ score (p < 0.001). Women had higher OHIP-14 and PIDAQ scores than men. A significant positive correlation was found between OHIP-14 and PIDAQ scores (p < 0.01). CONCLUSIONS: Malocclusion has a negative impact on OHRQoL, but this could be improved in adults through orthodontic treatment. These OHRQoL questionnaires can provide additional useful information on specific aspects of orthodontic patients' psychological state.

Effects of various toothpastes on remineralization of white spot lesions / 대한치과교정학회지

OBJECTIVE: The purpose of this in vitro study was to examine the effects of fluoridated, casein phosphopeptide.amorphous calcium phosphate complex (CPP-ACP)-containing, and functionalized beta-tricalcium phosphate (fTCP)-containing toothpastes on remineralization of white spot lesions (WSLs) by using Quantitative light-induced fluorescence (QLF-D) Biluminator(TM) 2. METHODS: Forty-eight premolars, extracted for orthodontic reasons from 12 patients, with artificially induced WSLs were randomly and equally assigned to four treatment groups: fluoride (1,000 ppm), CPP-ACP, fTCP (with sodium fluoride), and control (deionized water) groups. Specimens were treated twice daily for 2 weeks and stored in saliva solution (1:1 mixture of artificial and human stimulated saliva) otherwise. QLF-D Biluminator(TM) 2 was used to measure changes in fluorescence, indicating alterations in the mineral contents of the WSLs, immediately before and after the 2 weeks of treatment. RESULTS: Fluorescence greatly increased in the fTCP and CPP-ACP groups compared with the fluoride and control groups, which did not show significant differences. CONCLUSIONS: fTCP- and CPP-ACP-containing toothpastes seem to be more effective in reducing WSLs than 1,000-ppm fluoride-containing toothpastes.

Evaluation of the relationship between upper incisor exposure and cephalometric variables in Korean young adults / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to classify Korean young adults into 3 groups on the basis of upper incisor exposure rates (UIERs) and to compare the skeletal, dental, and soft tissue variables. METHODS: Samples were obtained from 127 students at the College of Dentistry, Wonkwang University in South Korea. Facial photographs of frontal posed smiles and lateral cephalograms of the subjects were taken. The subjects were divided into 3 groups on the basis of UIERs and 20 measurements were compared among the 3 groups. The correlations between the variables were determined. RESULTS: Male and female subjects showed significant differences in the group distribution. Male subjects showed higher frequencies of low smiles, and female subjects showed higher frequencies of high smiles. The vertical height of the anterior alveolar process of the maxilla directly correlated with the UIER. However, the UIER showed no significant correlation with the vertical height of the anterior basal bone or the inclination of the upper incisor axis. In female subjects, the upper central incisor clinical crown length showed an inverse correlation with the UIER. However, this variable showed no significant correlation with the UIER in male subjects. CONCLUSIONS: The UIER was directly correlated with the levator muscle activity of the upper lip and inversely correlated with the upper lip thickness, yet there was no correlation between the UIER and upper lip length at rest.

The comparison of the frictional force by the type and angle of orthodontic bracket and the coated or non-coated feature of archwire / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the difference in frictional resistance among metal, ceramic, self-ligation brackets and coated or non-coated Ni-Ti archwires at various bracket-archwire angulations during the sliding movement of an orthodontic archwire, using an orthodontic sliding simulation device. METHODS: Four types of bracket (Micro-arch Perpect Clear2 Clippy-C and Damon3 and 5 types of orthodontic archwire (0.014", 0.016", and 0.016" x 0.022" inch coated Ni-Ti, and 0.016" and 0.016" x 0.022" inch Ni-Ti) were used. Further, the bracket-archwire angles were set at 4 different angulations: 0degrees, 3degrees, 6degrees, and 9degrees. RESULTS: The frictions from all the experimental groups were found to be significantly increased in order of self-ligation brackets, Micro-arch and Perpect Clear2 (p < 0.001). The presence of a coat had no effect on the friction of the same sized archwires at 0degrees and 3degrees bracket-archwire angles (p < 0.001). Coated archwires had significantly higher frictions than the same sized non-coated archwires at 6degrees and 9degrees bracket-archwire angles (p < 0.001). The frictions increased significantly as the bracket-archwire angles were increased (p < 0.001). CONCLUSIONS: The use of self-ligation brackets will be beneficial in clinical situations where a low frictional force is required. Further, in cases where crowding is not severe, the use of coated archwires should not cause problems. However, more additional explanation is required considering the fact that the damage of coated archwire and exposure of the metal portion in case of binding and notching and the effects of saliva were not taken into account.

Shear bond strength of ceramic brackets bonded with antimicrobial monomer-containing self-etching primer / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to determine (1) the shear bond strength (SBS) of an antimicrobial monomer-containing self-etching primer according to ceramic bracket types and (2) the bracket-adhesive failure mode using an adhesive remnant index (ARI). METHODS: A total of 90 extracted human teeth were randomly divided into 6 groups. Each group consisted of one of two ceramic brackets (monocrystalline, polycrystalline) and one of three primers (Transbond XT primer, Transbond Plus SEP, Clearfil Protect Bond) with each group containing 15 specimens. The SBS was measured, and adhesive residues left on the tooth surface were assessed. RESULTS: The SBS of polycrystalline ceramic bracket groups was significantly higher than that of the monocrystalline ceramic bracket groups (p < 0.001). The SBS of Transbond XT primer groups was significantly higher than those of Transbond Plus SEP groups and Clearfil Protect Bond groups (p < 0.001). All the groups showed bonding failures between the bracket base and adhesive. CONCLUSIONS: The combination of a self-etching primer with a monocrystalline bracket is recommended for clinical use, considering its acceptable SBS and mode of failure.

Shear bond strength of rebonded ceramic brackets / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the shear bond strength of rebonded ceramic brackets according to each condition and find an appropriate method to rebond ceramic brackets with proper shear bond strength in clinical practice. METHODS: The study consisted of 12 experimental groups, according to the types of brackets, debonding methods, and treatment methods of the bracket base. Shear bond strength was measured, and adhesive residues left on the tooth surface were assessed. The base of the bracket was examined under scanning electron microscopy. RESULTS: The shear bond strength of the monocrystalline ceramic bracket group was significantly higher than thatof the polycrystalline bracket group with only sandblasting (p 0.05). The shear bond strength of the sandblasted/silane group was significantly higher than that of the selectively grinded group with a low-speed round bur and the sandblasted only group (p < 0.001). The retentive structure was more presented in groups where laser was applied than in groups where shear force was applied to debond brackets prior to rebonding. The bracket bases which were treated before rebonding presented smoother surfaces than new brackets. CONCLUSIONS: Shear bond strength could be increased by applying a silane coupling agent after sandblasting before rebonding. Also, the bond strength of the selectively grinded group with a low-speed round bur and the sandblasted group showed acceptable bond strength for clinical orthodontic treatment.