• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.1
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• pp.60-69
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• 2016

Purpose: The objective of this study was to compare the accuracy of digital models from 3 dimentional (3D) optical scanner and cone beam computed tomography (CBCT). Materials and Methods: We obtained digital models from 11 pairs of stone casts using a 3D optical scanner and a CBCT, and compared the accuracy of the models. Results: The error range of average positive distance was 0.059 - 0.117 mm and negative distance was 0.066 - 0.146 mm. Statistically (P < 0.05), average positive distance was larger than $70{\mu}m$ and shorter than $100{\mu}m$, and that of negative distance was larger than $100{\mu}m$ and shorter than $120{\mu}m$. Conclusion: We concluded that the accuracy of digital models generated from CBCT is not appropriate to make final prostheses. However, it may be acceptable for provisional restorations and orthodontic diagnoses with respect to the accuracy of the digitalization.

• Imaging Science in Dentistry
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• v.33 no.3
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• pp.171-178
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• 2003

Purpose: The purpose of this study was to report the reproducibility of intra-observer and inter-observer consistency of cephalometric measurements using three-dimensional (3D) computed tomography (CT), and the degree of difference of the cephalometric measurements. Materials and Methods: CT images of 16 adult patients with normal class I occlusion were sent to personal computer and reconstructed into 3D images using V-Works 3.5/sup TM/(Cybermed Inc., Seoul, Korea). With the internal program of V-Works 3.5/sup TM/, 12 landmarks on regular cephalograms were transformed into 21 analytic categories and measured by 2 observers and in addition, one of the observers repeated their measurements. Intra-observer difference was calculated using paired t-test, and inter-observer by two sample test. Results: There were significant differences in the intra-observer measurements (p < 0.05) in four of the categories which included ANS-Me, ANS-PNS, Cdl-Go (Lt), GoL-GoR, but with the exception of Cdl-Go (Lt), ZmL-ZmR, Zyo-Zyo, the average differences were within 2 mm of each other. The inter-observer observations also showed significant differences in the measurements of the ZmL-ZmR and Zyo-Zyo categories (p < 0.05). With the exception of the Cdl-Me (Rt), ZmL-ZmR, Zyo-Zyo categories, the average differences between the two observers were within 2 mm, but the ZmL-ZmR and Zyo-Zyo values differed greatly with values of 8.10 and 19.8 mm respectively. Conclusion: In general, 3D CT images showed greater accuracy and reproducibility, with the exception of suture areas such as Zm and Zyo, than regular cephalograms in orthodontic measurements, showing differences of less than 2 mm, therefore 3D CT images can be useful in cephalometric measurements and treatment planning.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.5
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• pp.375-379
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• 2010

Introduction: In the management of dentofacial deformities, variable movement of the maxilla can be made possible by a Le Fort I osteotomy. Posterior impaction of the maxilla necessary for rotation of the maxillomandibular complex enhances the functions and esthetic results. In cases of posterior impaction of the maxilla, an increase in the figure of the occlusal plane angle and incisor inclination can occur. This study reports the relationship between the amount of posterior impaction and the change in the occlusal plane angle and incisor inclination in a Le Fort I osteotomy by preoperative and postoperative lateral cephalograms. Materials and Methods: Twenty patients who had undergone orthognathic surgery in Dong-A University Medical Center participated in this study. Lateral cephalometrics, within 3 weeks prior to surgery and 3 days after surgery, were used for analysis. Pre and postoperative measurements of the occlusal plane angle and incisal inclination based on the Frankfort horizontal (FH) plane were performed. X and Y were defined as the amount of vertical change in the upper incisor tip and the amount of vertical change in the upper first molar mesial cup tip through the operation. The amount of final posterior maxillary impaction was determined by subtracting Y from X, which is the difference in vertical height. According to the amount of posterior maxillary impaction, the change in the occlusal plane angle and incisal inclination was measured. Results: The average posterior maxillary impaction was 2.91 mm and the average change in the occlusal plane angle and incisal inclination was $6.54^{\circ}$after surgery. As a result, each mm of posterior maxillary impaction changed the occlusal plane angle and incisal inclination by $2.25^{\circ}$. Statistically, there was high significance. Two cases were observed: one with the same amount of posterior maxillary impaction performed on both the right and left showing $2.20^{\circ}$, and the other with a different amount of posterior maxillary impaction performed showing $2.35^{\circ}$. In this case, there was no significance difference between the two cases. Conclusion: Each mm of posterior maxillary impaction changes the occlusal plane angle and incisal inclination by an average of $2.25^{\circ}$. In posterior maxillary impaction, there was no significant difference in the amount of change in the occlusal plane angle and incisal inclination regardless of whether there was an equal amount of posterior maxillary impaction on both sides. This study is expected to help in the presurgical orthodontic preparation and presurgical treatment planning.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.1
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• pp.126-132
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• 2009

Injuries of permanent teeth by trauma occur frequently in childhood and adolescence. Crown fractures are as frequent as 25-76% and especially maxillary incisors are prone to fractures. There have been numerous efforts to achieve both aesthetically and functionally satisfying restoration. When a mature tooth is fractured, porcelain crown or laminate veneer could be a choice of prosthodontic treatment. However, in a case of immature permanent incisor fracture, prosthodontic treatment is more complicated due to the immaturity of the tooth. Moreover, if endodontic treatment is accompanied with the prosthodontic treatment, the treatment period is prolonged. In the past, restoration using an orthodontic band, a ready-made crown, or glass ionomer cement did not exhibit esthetically satisfying result. As restorational materials have been improved, now more esthetic restoration is possible by reattaching fractured fragments or light-curing composite resin restoration. We reports cases of patients with fractured maxillary incisors and their successful treatment results through reattachment of fractured fragments and composite resin restoration.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.4
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• pp.422-428
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• 2010

Giomer is fluoride-releasing, resin-based dental materials that comprise PRG(pre-reacted glass ionomer) filler. The purpose of this study was to evaluate the shear bond strength of Giomer using self-etching primer systems to bovine dentin. Bovine incisors were mounted in self-curing orthodontic resin and the facial surfaces were wet ground on SIC paper to expose the dentin. Total 100 samples were made and divided randomly into 4 groups, Giomer group(I), Composite resin group(II) and Compomer group(III), Giomer and single bottle adhesive group(IV). The shear bond strengths of 25 samples per each group were measured using universal testing machine. And data were analyzed statistically with One-way ANOVA and Scheffe test. Giomer group(I) showed the significantly higher bond strength than Compomer group(III)(p<0.05). There was no significant difference between Giomer group(I) and Composite resin group(II)(p>0.05). And there is no significant difference between gourp(I) and group(IV). Based on the results of present study, the use of Giomer as an esthetic restorative material for primary teeth might be justified. It is considered that more study about the fluoride releasing ability is needed to evaluate the anticariogenic effect of giomer.

• The korean journal of orthodontics
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• v.25 no.5 s.52
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• pp.605-611
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• 1995

The purpose of this study was to evaluate effects of time on shear bond strengths of a light-cured glass ionomer cement and chemically cured resin cement to enamel, and to observe the failure patterns of bracket bondings. Shear bond strength of a light-cured glass ionomer cement were compared with that of a resin cement. Metal brackets were bonded on the extracted human bicuspids. Specimens were subjected to a shear load(in an Instron machine) after storage at room temperature for 5 and 15 minutes; after storage in distilled water at $37^{\circ}C$ for 1 or 35 days. The deboned specimens were measured In respect of adhesive remnant index. The data were evaluated and tested by ANOVA, Duncan's multiple range test, and t-test, and those results were as follows. 1. The shear bond strength of light-cured glass ionomer cement is higher than that of resin cement at 5 and 15 minutes. 2. The shear bond strengths of both light-cured glass ionomer cement and resin cement increase with time. There was no significant difference in those of both 1 day group and 35 day group 3. Light-cured glass ionomer cement is suitable as orthodontic bracket adhesives

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.371-377
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• 1998

To estimate the possibility of clinical application of TiN ion-Plated Elgiloy(Co-Cr wire), measurements of tensile strength and hardness were made on the four tempers on each of the manufactured Elgiloy, the (heat-treated) Elgiloy for 30 minutes at $250^{\circ}C$ and the TiN ion-plated Elgiloy. For comparison, the tensile strength and hardness of Stainless Steel wires were also measured. The following are the results of the study: $\cdot$In the 4 tempers, tensile strength was the greatest in the TiN ion-plated group, followed by the heat-treated Elgiloy group and the manufactured Elgiloy group, but no statistical difference was noticed between heat-treated and manufactured Elgiloy groups(p>0.05). $\cdot$In each temper, tensile strength of ion-plated Elgiloy increased about $10kgf/mm^2$ in comparison with the values of the manufactured Elgiloy $\cdot$In yellow, green and red tempers except the blue, hardness was the greatest in ion-plated group. In the blue temper, there was no statistical difference between heat-treated and manufactured Elgiloy groups(p>0.05). $\cdot$In each temper, hardness of ion-plated Elgiloy increased about 50-90VHN in comparison with the values of the manufactured Elgiloy. $\cdot$The tensile strength of Stainless Steel wire was similar to that of the red temper of manufactured Elgiloy and the green temper of ion-plated Elgiloy.

• Journal of Korean Dental Science
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• v.7 no.1
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• pp.6-15
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• 2014

Purpose: The purpose of this retrospective study is to investigate the degree of coincidence between the peer assessment rating (PAR) index and American Board of Orthodontics objective grading system (ABO-OGS) in the assessment of orthodontic treatment outcomes of Class I malocclusion cases. Materials and Methods: The sample consisted of 26 Class I patients. The PAR index was used for evaluation of pre-(T0) and posttreatment (T1) casts, and the ABO-OGS for assessment of T1 casts. If there was a reduction in PAR scores from T0 to T1 of more than 30%, the label 'PAR+' was given to the case, and if not, it was labeled 'PAR-'. If the ABO-OGS was less than 27, the label 'OGS+' was given to the case and if not, it was labeled 'OGS-'. 'A PAR-only qualified group' (PAR+), 'ABO-OGS-only qualified group' (OGS+), 'both indices qualified group' (PAR+/OGS+), and 'both indices disqualified group' (PAR-/OGS-) were compared with a Wilcoxon rank-sum test, sensitivity/specifi city test and Spearman's correlation test. Result: PAR scores for T0, T1, and percentage reduction were 21.1, 6.4, and 65.9%, respectively, and 35.4 for ABOOGS. The distribution of the 'PAR+/OGS+', 'PAR+', and 'PAR-/OGS-' group was 19.3%, 76.9%, and 3.8%, respectively. The T0-PAR, T1-PAR and PAR point reductions for the 'PAR+' group were significantly higher than those of 'PAR+/OGS+' groups (23.1 vs. 15.6; 6.7 vs. 4.6; and 16.5 vs. 11.0; all P<0.05). However, the PAR-percentage reduction and treatment duration between the two groups were not statistically different (70.0% vs. 67.0%, P=0.4325; 24.1 months vs. 25.0 months, P=0.4057). The T1-ABO-OGS score for 'PAR+' group was significantly higher than that of the 'PAR+/OGS+' groups (38.2 vs. 24.0, P<0.001). Conclusion: Since the fraction of the 'PAR+/OGS+' group was less than 20% and there was no significant correlation between PAR-percentage reduction and T1-ABO-OGS, development of a new index system for the accurate evaluation of treatment outcome is needed.

• The korean journal of orthodontics
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• v.28 no.6 s.71
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• pp.927-935
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• 1998

The purpose of this study is to investigate the changes of mechanical properties and surface topography of various nickel titanium wires after heat sterilization for recycling with quantitative method. The materials used were four kinds of nickel titanium orthodontic wires including a Korean product. Experimental specimens were treated with two kinds of heat sterilization methods ; dry heat ($180^{\circ}C$, 60min) and autoclave ($121^{\circ}C$, 15-20psi, 30min). Mechanical properties were evaluated by tensile test with Instron 4466 (load cell capacity:.1000 kg, cross head speed:5mm/min, grip distince:40mm in room temperature). Surface topography of various wires was compared with each other qualitatively by using scanning electron microscopy and quantitatively by using profilometer. The findings were analyzed statistically with student t-tests. The results were as follows; 1. Neither method of heat sterilization had any effects on tensile properties of the nickel-titanium wires used in this experiment. 2. Before heat sterilization, the surface smoothness was highest in Optimalloy, followed by Align and Sentalloy, with NiTi showing the lowest smoothness value. 3. In surface topography, Align and Optimalloy were not influenced by heat sterilization. NiTi, on the other hand, had increased roughness after dry heat sterilization and Sentalloy showed the same tendency after each of the two heat sterilization procedures.

• Imaging Science in Dentistry
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• v.34 no.3
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• pp.151-157
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• 2004

Purpose : To evaluate the quantitative accuracy of three-dimensional (3D) images by means of comparing distance measurements on the 3D images with direct measurements of dry human skull according to slice thickness and scanning modes. Materials and Mathods : An observer directly measured the distance of 21 line items between 12 orthodontic landmarks on the skull surface using a digital vernier caliper and each was repeated five times. The dry human skull was scanned with a Helical CT with various slice thickness (3, 5, 7 mm) and acquisition modes (Conventional and Helical). The same observer measured corresponding distance of the same items on reconstructed 3D images with the internal program of V-works 4.0/sup TM/(Cybermed Inc., Seoul, Korea). The quantitative accuracy of distance measurements were statistically evaluated with Wilcoxons' two-sample test. Results: 11 line items in Conventional 3 mm, 8 in Helical 3mm, 11 in Conventional 5mm, 10 in Helical 5mm, 5 in Conventional 7mm and 9 in Helical 7mm showed no statistically significant difference. Average difference between direct measurements and measurements on 3D CT images was within 2mm in 19 line items of Conventional 3mm, 20 of Helical 3mm, 15 of Conventional 5mm, 18 of Helical 5mm, II of Conventional 7mm and 16 of Helical 7mm. Conclusion: Considering image quality and patient's exposure time, scanning protocol of Helical 5mm is recommended for 3D image analysis of the skull in CT.