Micro-computed tomographic evaluation of the effect of fluoride agents on white spot lesions:An in vitro study / 대한치과교정학회지

Objective@#To investigate remineralizing effect of three fluoride regimens on artificially demineralized enamel around orthodontic bracket by analyzing mineral density (MD) acquired from micro-computed tomography (micro-CT). @*Methods@#Forty-eight bracket bonded bovine incisors were prepared to create demineralized enamel (DE) surface. The samples were divided into four groups according to the fluoride regimen: 1) no fluoridation, 2) 1.23% acidulated phosphate fluoride (APF) gel, 3) fluoridated toothpaste, and 4) 0.05% sodium fluoride mouthwash. Micro-CT was scanned after demineralization (T0), and 2 weeks (T1) and 4 weeks (T2) of fluoridation. @*Results@#APF gel showed highest remineralization of DE during T1–T0 interval among the groups (p < 0.05); followed by toothpaste, mouthwash and no fluoridation. APF gel and toothpaste demonstrated significant increase in MD after 4 weeks of application (p < 0.05). @*Conclusions@#Remineralization effects of three fluoride regimens were depicted through micro-CT analysis, of which APF gel was most effective.

Influence of changing various parameters in miniscrew-assisted rapid palatal expansion: A three-dimensional finite element analysis / 대한치과교정학회지

OBJECTIVE@#This study aimed to analyze the effect of changing various parameters of the bone-borne rapid palatal expander (RPE) using the finite element method (FEM).@*METHODS@#In eight experimental groups, we investigated the effect of the number, position, and length of miniscrews; positional changes of the expander; and changes in the hook length on maxillary expansion. In finite element analysis, we compared the magnitude and distribution of stress, and the displacement changes following expansion of the bone-borne RPE.@*RESULTS@#When we compared the number and position of miniscrews, placing miniscrews in the anterior and posterior sides was advantageous for maxillary expansion in terms of stress distribution and displacement changes. Miniscrew length did not significantly affect stress distribution and displacement changes. Furthermore, anteroposterior displacement of the expander did not significantly affect transverse maxillary expansion but had various effects on vertical changes of the maxilla. The maxilla rotated clockwise when the miniscrews were placed in the anterior region. The hook length of the expander did not show consistent results in terms of changes in stress distribution and magnitude or in displacement changes.@*CONCLUSIONS@#The findings of this study suggest that changes in the location and length of the miniscrews and displacement of the bone-borne RPE could affect the pattern of the maxillary expansion, depending on the combination of these factors.

Colorimetric evaluation of white spot lesions following external bleaching with fluoridation: An in-vitro study / 대한치과교정학회지

OBJECTIVE: This study was performed to investigate the effects of external tooth bleaching with flouridation on the appearance of white spot lesions (WSLs) in vitro. METHODS: In total, 125 bracket-bonded bovine incisor enamel blocks with artificial WSLs were randomly divided into a control group and four treatment groups (home bleaching, home bleaching + fluoridation, in-office bleaching, and in-office bleaching + fluoridation). A spectroradiometer (SR) and digital images (DIs) were used to evaluate colorimetric parameters (Commission Internationale l'Eclairage L*a*b*) for all specimens. Color measurements were obtained before WSL formation (T1), after WSL formation (T2), and after completion of the external tooth bleaching treatment (T3). RESULTS: The SR-based color change after bleaching was significantly greater in the treatment groups than in the control group (p 0.05). CONCLUSIONS: The findings of this study suggested that external tooth bleaching with fluoridation can alleviate the conspicuity of WSLs.

The relation between idiopathic scoliosis and the frontal and lateral facial form / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the relation between idiopathic scoliosis and facial deformity in the horizontal, vertical, and anteroposterior planes. METHODS: A total of 123 female patients aged 14 years or older, who visited the Spine Clinic at the Department of Orthopedics, Korea University Guro Hospital for treatment of idiopathic scoliosis, were enrolled. Whole-spine anteroposterior and lateral radiographs were taken with the patient in a naturally erect position, and frontal and lateral cephalograms were taken in an erect position with the Frankfort horizontal line parallel to the floor. Scoliosis was classified according to the Cobb angle and Lenke classification of six curve types. Cephalometric tracing in all cases was carried out with V-Ceph 5.5 by the same orthodontist. The Kruskal-Wallis test was performed to determine whether any relation existed between each group of the idiopathic scoliosis classification and the cephalometric measurements of frontal and lateral cephalograms. RESULTS: The measurements did not reveal any significant association between the Cobb angle and cephalometric measurements and between the curve type based on the Lenke classification and cephalometric measurements. CONCLUSIONS: Based on the results of this study, no apparent relation was observed between the severity of scoliosis and facial form variations in idiopathic scoliosis patients.

The predictability of dentoskeletal factors for soft-tissue chin strain during lip closure / 대한치과교정학회지

OBJECTIVE: To investigate the dentoskeletal factors which may predict soft-tissue chin strain during lip closure. METHODS: The pretreatment frontal and lateral facial photographs and lateral cephalograms of 209 women (aged 18-30 years) with Angle's Class I or II malocclusion were examined. The subjects were categorized by three examiners into the no-strain and strain groups according to the soft-tissue chin tension or deformation during lip closure. Relationships of the cephalometric measurements with the group classification were analyzed by logistic regression analysis, and a classification and regression tree (CART) model was used to define the predictive variables for the group classification. RESULTS: The lower the value of the overbite depth indicator (ODI) and the higher the values of upper incisor to Nasion-Pogonion (U1-NPog, mm), overjet, and upper incisor to upper lip (U1-upper lip, mm), the more likely was the subject to be classified into the strain group. The CART showed that U1-NPog was the most prominent predictor of soft-tissue chin strain (cut-off value of 14.2 mm), followed by overjet. CONCLUSIONS: To minimize strain of the soft-tissue chin, orthodontic treatment should be oriented toward increasing the ODI value while decreasing the U1-NPog, overjet, and U1 upper lip values.

The effect of silver ion-releasing elastomers on mutans streptococci in dental plaque / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to investigate the antimicrobial effect of silverized elastomers on mutans streptococci in dental plaque. METHODS: Forty patients undergoing orthodontic treatment were randomly placed into 1 of 2 groups. We examined the maxillary right and left central incisors and premolars, and the mandibular right and left canines of all participants. We ligated the right maxillary and left mandibular teeth of the participants in group 1 with silverized elastomers and ligated their contralateral teeth with conventional elastomers. We ligated the left maxillary teeth and right mandibular teeth of group 2 participants with silverized elastomers. Each participant visited the clinic 4 times at 3-week intervals. We applied the elastomers to the teeth on one side of each patient's mouth during their first visit. During the second visit, the elastomers were removed for microbiological analysis and replaced with steel ligatures. During the third visit, we used silverized elastomers to ligate the teeth contralateral to those treated on the first visit. The elastomers were removed during the fourth visit, and microbiological analyses were performed. We compared the quantity of bacteria on silverized and conventional elastomers at the 0.05 level of significance. RESULTS: The percentage of mutans streptococci was not significantly different in cultures of dental plaque from the silverized and the conventional elastomers (p > 0.05). CONCLUSIONS: There was no significant difference between the antimicrobial effect of the silverized elastomers and that of the conventional elastomers.

Comparison of bony changes between panoramic radiograph and cone beam computed tomographic images in patients with temporomandibular joint disorders / 대한치과교정학회지

OBJECTIVE: This study was designed to assess the diagnostic validity of digital panoramic radiographs compared to cone beam computed tomography (CBCT) in patients with temporomandibular joint disorders. METHODS: Panoramic radiograph and CBCT were taken from a total of 212 joints from 106 subjects. The joints were examined by two dentists and divided into the following six groups: normal, flattening, osteophyte formation, erosion, sclerosis, and unclassified. The sensitivity and specificity of each observer and inter-observer reliability were statistically analyzed. RESULTS: The results showed relatively high intra-observer reliability in the diagnosis of both panoramic and CBCT images and the weighted Kappa indices of panoramic and CBCT images were 0.714 and 0.727, respectively. The sensitivities of panoramic images of observer A and B to CBCT images was 82.35% and 84.30%, respectively, while the specificity of observer A and B was 58.06% and 61.54%, respectively. However, guided diagnosis from panoramic and CBCT images were statistically different (p < 0.05). CONCLUSIONS: The present study suggests that the panoramic radiograph could be used as a primary diagnostic device to detect bony changes of temporomandibular joints in clinical orthodontics, because panoramic images showed relatively high sensitivity compared to CBCT images. However, CBCT images may be one of the best choices when a more accurate diagnosis is necessary.

Fracture resistance of ceramic brackets to arch wire torsional force / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to estimate the fracture resistance of commercially available ceramic brackets to torsional force exerted from arch wires and to evaluate the characteristics of bracket fracture. METHODS: Lingual root torque was applied to maxillary central incisor brackets with 0.022-inch slots by means of a 0.0215 x0.027-inch stainless steel arch wire. A custom designed apparatus that attached to an Instron was used to test seven types of ceramic brackets (n = 15). The torque value and torque angle at fracture were measured. In order to evaluate the characteristics of failure, fracture sites and the failure patterns of brackets were examined with a Scanning Electron Microscope. RESULTS: Crystal structure and manufacturing process of ceramic brackets had a significant effect on fracture resistance. Monocrystalline alumina (Inspire) brackets showed significantly greater resistance to torsional force than polycrystalline alumina brackets except InVu. There was no significant difference in fracture resistance during arch wire torsional force between ceramic brackets with metal slots and those without metal slots (p > 0.05). All Clarity brackets partially fractured only at the incisal slot base and the others broke at various locations. CONCLUSION: The fracture resistance of all the ceramic brackets during arch wire torsion appears to be adequate for clinical use.

Shear bond strength of brackets bonded with different self etching primers / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the clinical usefulness of 4 self etching primers by measuring the shear bond strength of orthodontic brackets and examining the failure pattern of bracket-tooth interfaces. METHODS: Seventy-five, defect-free, premolars were randomly assigned into five groups: control group (37% phosphoric acid + Transbond XT primer) and self etching primer treated groups (Transbond Plus self etching primer, Unifil bond, Clearfil SE bond, and Adhese). The shear bond strength was measured with a universal testing machine and the amount of residual adhesive remaining on the brackets after debonding was assessed by the adhesive remnant index (ARI). RESULTS: The results showed that the groups conditioned with self etching primer had significantly lower shear bond strength than the control group (p 0.05). Evaluation of the ARI scores indicated there was less resin remnant on the teeth in the groups conditioned with self etching primers, although not statistically significant. CONCLUSION: The results of this study suggest that all four of the self etching primers have shown acceptable bond strength for clinical use.

Evaluation of friction of esthetic brackets according to different bracket-wire angulations / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate how the friction that occurs during the sliding movement of the archwire through esthetic brackets is differently affected by bracket materials, slot designs, and tip angulations of the archwire. METHODS: Eight types of brackets with 0.018 inch slots (composite: Brillant (BR); composite with metal slot: Spirit MB (SP); ceramic: Inspire (IN), Signature (SI), Cristaline V (CR); ceramic with metal slot: Clarity (CL), Luxi II (LU); and metal bracket: Integra (IT)), and placed into groups of 20 brackets in each group, were tested in artificial saliva with 0.018 inch stainless steel wire. The wire tip angulations were given as 0, 4 and 8 degrees. RESULTS: CR group significantly showed the lowest frictional force with all wire tip angulations of 0, 4, and 8 degrees. IN significantly showed the highest frictional force (p < 0.001). BR (polyoxymethylene) had significantly less frictional force than SP (polycarbonate) (p < 0.001) and showed no significant difference between metal brackets. Friction was increased as the wire tip angulations were increased, but no notches were observed on any parts of the archwire. CONCLUSIONS: According to the results of this study, esthetic brackets are superior or similar to SS brackets from a frictional point of view.

Distribution and clinical features of patients with degenerative change of the mandibular condyle / 대한치과교정학회지

OBJECTIVE: This study was carried out to evaluate the distribution and clinical features of patients with degenerative change of the mandibular condyle. METHODS: Six thousand and seventy patients with TMD (temporomandibular disorder) were selected for this study, who had complete initial clinical records and radiographs. Panorama and TMJ panorama radiographs were used to screen the degenerative change in the condyle, and the patients were divided into DJD (degenerative joint disease) and non-DJD groups. RESULTS: The distribution and clinical features of the two groups were compared. Out of the total number of patients, 31.7% were in the DJD group, and 68.3% were in the non-DJD group. The portion of females was larger in the DJD group (80.8%) than in the non-DJD group (67.5%), and the DJD group had high prevalence in the second and third decades. Lack of incisal contact, retrusive chin, facial asymmetry, and mouth opening limitation were the chief complaints of the patients who had positive relation to DJD. CONCLUSION: Patients with an orthodontic treatment history, CO-CR discrepancy and crepitation were at possible risk of having DJD.

Pretreatment characteristics of adolescents with Class II malocclusion treated by maxillary second molar extraction / 대한치과교정학회지

The purpose of this retrospective study was to estimate the pretreatment characteristics of growing patients with Class II malocclusion, who had been treated with maxillary second molar extractions. The sample comprised of 51 subjects; 18 subjects were classified into the molar extraction group, and 33 subjects were treated without extraction and classified into the nonextraction group. Pretreatment lateral cephalograms were calculated and analyzed by independent t-test and stepwise discriminant analysis. In measurements for skeletal pattern, no anteroposterior measurements and proportions of various vertical dimensions were significantly different, and only some measurements such as AB-MP (degree), Na-Me (mm), AVD (mm) were significantly different between the two treatment groups (p < 0.05). In measurements for dentoalveolar pattern, some measurements, which were related to the position and angulation of the upper and lower permanent first molars, and the angulation of the upper third molars, were significantly different between the two treatment groups. In particular, the maxillary second molar extraction group exhibited more mesial angulation of maxillary first molar to the occlusal plane.

Shear bond strength of orthodontic adhesive to amalgam surface using light-cured resin / 대한치과교정학회지

This study was performed to compare the shear bond strength of orthodontic adhesive to amalgam according to different light sources (halogen-based light and light emitting diode (LED)) and amalgam surface treatments. Ninety extracted human premolars were randomly divided into 6 groups (4 experimental and 2 control groups) of 15 by light sources and surface treatments. Orthodontic brackets were bonded and shear bond strength was measured with an Instron universal testing machine. The findings were as follows: The bond strength of adhesive to amalgam surface was 3-5.5 MPa which was lower than that of acid-etched enamel (19 MPa) control. In the sandblasted amalgam surface, the shear bond strength of the halogen light group was higher than that of the LED group (p 0.05). Within the same light source, sandblasting had no significant effect on the shear bond strength of the adhesive bonded to amalgam surface (p > 0.05). There was no significant difference in shear bond strength according to the light sources in acid-etched enamel control groups. This results suggest that there can be a limit in using light curing adhesives when brackets are bonded to an amalgam surface. Additional clinical studies are necessary before routine use of halogen light and LED light curing units can be recommended in bonding brackets to an amalgam surface.

Three-dimensional finite element analysis on the effect of maxillary incisor torque / 대한치과교정학회지

The purpose of this study was to investigate the stress distribution in the periodontal tissue and the displacement of teeth when active torque was applied to the maxillary incisors by three-dimensional finite element analysis. A three-dimensional finite element model consisted of the maxillary teeth and surrounding periodontal membrane, .022 x .028 Roth prescription bracket and stainless steel, NiTi and TMA rectangular ideal arch wires which were modeled by hexahedron elements. Applied active torques were 2, 5 and 10 degrees. The findings of this study showed that the reaction force acting on the bracket was the extrusion force on the mesial side of the incisors and canine and the intrusion force on the distal side of the incisors and canine. The amount of force and moment was greatest at the lateral incisor. When active anterior labial crown torque was applied, labial crown and distal tipping and intrusion of the incisors took place, and lingual crown distal tipping and extrusion of the canine occured. An excessive force was concentrated on the lateral incisor, when the stainless steel wire was used. NiTi or TMA wire is desirable for torque control.

The stability in the adolescent Class III malocclusion treated by fixed appliances / 대한치과교정학회지

The purpose of this study was to investigate the predictors of relapse in orthodontic treatment of skeletal Class III malocclusion in growing patients. A total of 55 patients were studied and all subjects were divided into two groups according to their stability in the post-treatment stage. Of the sample, 33 patients were included in the stable group and the remaining 22 were assigned to the relapse group. Cephalometric data of the pre-treatment stage was taken and compared between the stable and relapse group. The following results were obtained through t-test: 1. This study presented statistical evidence to show that the major skeletal determinant of prognosis in Class III orthodontic treatment was not anteroposterior discrepancy but vertical discrepancy, especially within the AB-maxillo-mandibular triangle. Vertical angular measurements that showed statistically significant differences were AB-MP and ODI(P<0.01) and the vertical ratio measurements were MP-P/AL and PP-P/AL(P<0.05). 2. Relapse tendency increased with the steep occlusal plane, especially the steep lower occlusal plane. As to occlusal plane, there were statistically significant differences in OP(L)-PP, OP-PP, AB-OP(L) and Wits appraisal(P<0.05). This study claimed that anteroposterior discrepancy was not necessarily the proper criteria to predict relapse. Vertical discrepancy had a significant effect on post-treatment stability.

The shear bond strength and adhesive failure pattern in bracket bonding with different light-curing methods / 대한치과교정학회지

The purpose of this study was to evaluate the clinical effectiveness of a plasma arc light and light emitting diode (LED), compared with shear bond strength and the failure pattern of brackets bonded with visible light in direct bonding. Brackets were bonded with Transbond XT to 60 human premolars embedded in the resin blocks according to different light-curing methods. Then, the shear bond strength of each group was measured using a universal testing machine (Instron) and the adhesive failure pattern after debonding was visually examined by light microscope. The results were as follows: 1. The shear bond strength showed no significant difference between the visible light and light emitting diode, but the plasma arc light exhibited a significantly lower shear bond strength compared with the visible light and light emitting diode. 2. In the visible light and light emitting diode, adhesive failure patterns were similar. Bond failure occurred more frequently at the enamel-adhesive interface. 3. The bonding failure of brackets bonded with plasma arc light occurred more frequently at the bracket-adhesive interface. The results of this study suggest that plasma arc light, light emitting diode and visible light are all clinically useful in the direct bonding of orthodontic brackets.

Comparison of computer-based treatment prediction with true results in bimaxillary protrusion cases / 대한치과교정학회지

This study was performed to assess the accuracy of computer-based treatment prediction for soft tissue profile using Quick Ceph Image Pro(TM) & Quick Ceph 2000(TM) in bimaxillary protrusion cases. The pre- and post-treatment lateral cephalograms of 21 female adults treated by four first premolar extraction were imaged and 9 landmarks and 27 specific soft tissue mesurements were digitized for comparing actual treatment results with computer simulations. The results of this study showed that Quick Ceph Image Pro(TM) & Quick Ceph 2000(TM) tends to overestimate horizontal changes and underestimate vertical changes. In the computer simulation, upper lip showed rolling tendency. The upper lip measurements were disposed to be regular direction but lower lip measurements were varied case by case even if it was statistically insignificant.

Eruption failure of teeth / 대한치과교정학회지

The purpose of this study was to present the causes and their mechanisms of eruption failure of teeth and to investigate the treatment modalities. There are so many reports about eruption failure, but most of them are dealing with mechanical interferences. But, we have patients suffered from eruption failure of another causes. Many developmental failures show eruption problems of teeth, although in some cases, the primary failure of eruption (failure of the eruption mechanism itself) can be the primary cause. We have to know about the causes, differences, and the treatment modalities for those abnormalities.

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.

A study on long-term soft tissue changes after superior repositioning of the maxilla / 대한치과교정학회지

ft tissue changes that occurred between presurgery to 5-years post-surgery in 49 orthognathic surgery patients whose maxillae were moved upward by Le Fort I osteotomy were examined by lateral cephalometric film. The objective of the paper was to document soft tissue changes at long-term follow-up after superior repositioning of the maxilla and to relate soft tissue and hard tissue changes in the group. The results were as follows. 1. On average, soft tissue landmarks in the nose and the upper lip were not changed statistically significantly except superior movement of superior labial sulcus and forward movement of pronasale between presurgery and 5 years postsurgery. 2. Upward and forward movement of the lower lip were found at 5 years postsurgery in comparison with presurgery and genioplasty added this effects. 3. Upper lip length and vertical dimension of upper vermilion didn't show any significant changes, but increase of lower lip length and decrease of vertical dimension of lower vermilion were statistically significant between presurgery and 5 years post-surgery. 4. The decrease of upper incisor exposure and interlabial distance from presurgery to 1 year were continued from 1year to 5years and the amount of the decrease was more than that of vertical movement of the maxilla by surgery. 5. Long term changes in soft tissue landmarks from 1 to 5 years postsurgery exceeded hard tissue changes, meaning soft tissue moved down more than skeletal changes.