• The korean journal of orthodontics
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• v.28 no.5 s.70
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• pp.731-740
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• 1998

In the previous studies about prescription of preadjusted appliance, occlusal plane was used as a reference plane for crwon angulation (tip) measurement. But this reference plane is not parallel to the line connecting the facial axis points at which the centers of brackets are positioned (Andrews' plane), due to the curve of Spee. Therefore, we developed a new reference plane unaffected by the curve of Sun and more parallel to the Andrews' plane. It is an imaginary line connecting mesial and distal marginal ridges of each posterior tooth, and we named it 'marginal ridge plane'. In this study, crown angulations of posterior teeth of 29 normal occlusion samples were measured and measurements from both reference planes were compared. Crown angulation measurements measured from occlusal plane were different from crown angulation measurements from marginal ridge plane in the upper and lower 2nd molars (p<0.01), md 1st premolars (p<0.05). These results were analyzed as the crown angulation measurements from occlusal plane were affected by the curve of Spee. Crown angulations should be varied according to the amount of curve of Spee to maintain the continuity of marginal ridges. To solve this problem, determining bracket angulation as the bracket slot is parallel to the marginal ridge plane of each posterior teeth is recommended.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.2
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• pp.93-101
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• 2014

Purpose: The aim of this study is to investigate the typical shape of the curve of Spee in Korean and analyze the curve of Spee according to gender, age, and left and right. Materials and Methods: Among the patient of Wonkwang University Sanbon Dental Hospital taking cone beam computerized tomography, the images of 500 Koreans (311 males and 189 females) who qualifies the criteria of this study were selected and their curve of Spee were analysed in sagittal plane. Results: The mean radius of curve of Spee in Korean was 91.4 mm. There was statistically significant difference between male (94.6 mm) and female (86.1 mm) by gender, but not significant differences by age and between right and left side. Conclusion: Within the limitation of this study, the smaller radius (91.4 mm) of Korean than the 4-inch (101.6 mm) value advocated by Monson was meaned that it would be need to reconsider the application of the curve of Spee in all cases when occlusal plane is reconstructed in Korean.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.1
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• pp.108-113
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• 2004

This study was to evaluate and compare differences of the cervical vertebral skeletal maturity of normal occlusion and skeletal Class III malocclusion. Normal occlusion (172 girls) and skeletal Class III malocclusion(191 girls) were classified according to diagnosis stone model and lateral cephalogram of Korean girls aging from 8 to 12 years. The concavity of inferior border, vertico-horizontal ratio of cervical vertebrae were observed and measured according to age. Differences of the cervical vertebral skeletal maturity were evaluated. The results were as follows : 1. The concavity of inferior border of the 2nd to 6th vertebrae of normal occlusion and skeletal Class III had uniformly increased with age. 2. The vertico-horizontal ratio of the 3rd to 6th vertebrae of girls with normal occlusion and skeletal Class III had uniformly increased with age. 3. There was no significant difference in cervical vertebral skeletal maturity between normal occlusion and skeletal Class III malocclusion in the concavity of inferior border of the 2nd to 6th vertebrae and in the vertico-horizontal ratio of the 3rd to 6th vertebrae. The results in the study indicate that there is no significant difference of cervical vertebral skeletal maturity between girls with normal occlusion and skeletal Class III malocclusion.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.4
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• pp.371-383
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• 2012

Shaping the root canal system to maintain original canal curvature is essential to clinical success in endodontic treatment. Opposed to most root canals that are curved, endodontic instruments are made from straight metal blanks. They have a tendency of straightening the root canal during preparation and frequently result in procedural errors. A new treatment method to maintain original canal curvature during shaping has been introduced for preventing procedural errors. The aim of this study was to compare the ability of instruments to maintain original canal curvature of continuous rotary system and single file system. Thirty ISO 15, 0.02 taper, Endo Training Blocks(Dentsplay Maillefer) were used. Specimens were assigned to 1 of 3 groups for shaping: specimens in group 1 were shaped with ProFile #20/.06 at the WL. Specimens in group 2 were shaped with Mtwo #35/.04 at the WL. Specimens in group 3 were shaped with WaveOne Primary reciprocating files at the WL after the glide path was achieved with PathFile. Pre- and postinstrumentation digital images were superimposed and processed with Matlab r2010b(The MathWorks Inc, Natick, MA) software to analyze the curvature-radius ratio(CRr), representing canal curvature modification. Data for comparison on the ability of instruments to maintain original canal curvature depending on each Ni-Ti file were analyzed with 1-way ANOVA(P<.05). Data for comparison on the ability of instruments to maintain original canal curvature depending on each Ni-Ti file system were analyzed with independent t-test(P<.05). A statistically significant difference(P<0.05) was noted on each Ni-Ti file. ProFile and WaveOne instrumentations maintained the original canal curvature significantly better(P<0.05) than Mtwo file. There were no significant difference(P>0.05) between continuous rotary system and single file system. Under the conditions of this study, ProFile and WaveOne instruments maintained the original curvature significantly better than Mtwo file and were less modification of the canal curvature compared. There was no significant difference between continuous rotary system and single file system in shaping of simulated canals. As clinical practitioners, it may be advantages to use hybrid approach when root canal shapes depending on the design and usage of Ni-Ti files.

• Journal of Technologic Dentistry
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• v.38 no.3
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• pp.217-224
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• 2016

Purpose: This study aimed to generate 3-D occlusal curvatures and evaluate the relationship between the occlusal curvatures and mandibular occlusal morphology factors. Methods: Mandibular dental casts from 25 young adult Korean were scanned as a virtual dental models with a 3-D scanner(Scanner S600, Zirkonzahn, Italy). The curve of Spee, curve of Wilson, and Monson's sphere were generated by fitting a circle/sphere to the cusp tips using a least-squares method. The mandibular mesiodistal cusp inclination, buccolingual cusp inclination, and tooth wear parameters were measured on the prepared virtual models using RapidForm2004(INUS technology INC, Seoul, Korea). Wilcoxon signed-rank test was performed to test side difference, and Spearman's rank correlation coefficients were investigated to verify the correlation between occlusal curvatures and correlated factors (a=0.05). Results: The mean radii of curve of Spee were $83.09{\pm}33.94$ in the left side and $79.00{\pm}28.12mm$ in the right side. The mean radii of curve of Wilson were $66.82{\pm}15.87mm$ in the mesial side and $47.87{\pm}9.40mm$ in the distal side with significantly difference between mesiodistal sides(p<0.001). The mean radius of Monson's sphere was $121.85{\pm}47.11mm$. Most of the cusp inclination parameters showed negative correlation for the radius of Monson' sphere(p<0.05). Especially, the buccolingual cusp inclinations in mesial side of molar showed high correlation coefficients among the factors(p<0.05). Conclusion: The radius of Monson's sphere was greater than the classical 4-inch values, and the buccolingual cusp inclinations in mesial side of molar can be considered as one of the main factors correlating with the radius of Monson's sphere.

• The korean journal of orthodontics
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• v.38 no.4
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• pp.283-298
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• 2008

Objective: The purpose of this study was to investigate changes in the mandibular dental arch from presurgical orthodontic treatment and orthognathic surgery, and to evaluate the relationships between the pretreatment records and changes of mandibular dental arch in skeletal Class III malocclusion individuals. Methods: Lateral cephalometric radiographs and mandibular study models of 31 adults with skeletal class III malocclusion were taken and measured. All measurements were evaluated statistically by ANOVA, Scheffe's Post Hoc, and paired t-test, and correlation coefficients were evaluated. Results: No significant difference in Mn-LMMC, Mn-LIE, Mn-MnOcc was detected between pretreatment and presurgical groups. Statistically significant but low correlations were demonstrated between the initial arch length discrepancy (ALD) and change in ICW, IPW1 (r = 0.492, 0.615) and change in arch length (r = 0.641). No association was seen between the initial depth of curve of Spee and change in mandibular incisor angle and arch width or arch length. Regression analysis showed that the amount of change for arch length and IPW1 could be explained by 64.0% and 75.8% of the pretreatment variables respectively. Conclusions: This study suggests that orthognathic surgery results can be predictable by measuring the pretreatment records.

• The korean journal of orthodontics
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• v.38 no.1
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• pp.52-59
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• 2008

Objective: This study analyzed the morphologic changes of the fourth cervical vertebra body to determine the skeletal age of orthodontic 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 $5.67{\pm}2.57,\;8.73{\pm}2.41,\;and\;10.00{\pm}1.47$, 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 $11.64{\pm}0.92$ 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.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.1
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• pp.99-107
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• 2011

The main objective of nonsurgical retreatment is to disinfect the root canal space for periradicular healing. Thus, efficient removal of the filling material from the root canal system is essential to ensure a favorable outcome. Traditionally, the removal of root canal filling material was performed by stainless steel hand instrument and this procedure is time and effort-consuming. Recently, rotary NiTi retreatment instruments are developed to effective removal of root canal filling material. The aim of this study was to evaluate the effectiveness of stainless-steel hand instrument and rotary NiTi retreatment instrument when removing gutta-percha in curved root canals. For the remaining materials, there were no significant differences between groups. But the rotary NiTi system proved to be faster than hand instruments in removing root filling materials.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.4
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• pp.389-403
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• 2008

In Angle's Class III malocclusion, which has higher incidence in Korean than Western, depressed midfacial profile with protruded lower lips and mandible may give rise to many functional, esthetic, psychological, social problems. Due to the different malocclusion incidence according to racial differences, many previous studies focused on the relationship between Class II malocclusion and nasal airway obstruction. Previous studies used lateral cephalography which has limitations of 2 dimensional image with projection error and identification error. Therefore, the purpose of this study was to analyze morphologic differences in the nasal airway between normal occlusion and Angle's Class III malocclusion patients using 3-dimensional facial computed tomography. Thirteen normal occlusion(7 men and 6 women) and sixteen skeletal Class III(7 men and 9 women) patients were selected and 3-dimensional facial computed tomography taking was performed. Comparison between two group in volume and sectional area of nasal airway were carried out. The results were followed. 1. In the comparison of absolute nasal airway volume, oropharyngeal space of experimental group were larger than control group but there are no significant difference in other. 2. In the comparison of relative nasal airway volume, oropharyngeal space of experimental group were larger than control group but there are no significant difference in other. 3. In the oropharyngeal space width on frontal and lateral view, the similar tendency was revealed between two groups. 4. In the lateral curvature of nasal airway, the similar tendency was revealed between two groups.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.3
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• pp.245-252
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• 2012

The purpose of this study was to evaluate the influence of glide path on canal centering ratio after instrumentation with different single file systems; WaveOne and Reciproc. Reciproc R25 (VDW), WaveOne Primary (Dentsply Maillefer) and PathFile #13, 16, 19 (Dentsply Maillefer) were used in this study. In no glide path groups, Reciproc files and WaveOne files used for canal preparation without glide path. In glide path groups, the PathFile were used before canal preparation. Methylene blue dye was introduced into the canal to obtain a clear pre-instrumentation image. Pre-instrumentation images and post-instrumentation images were scanned using Epson Perfection V700 Photo scanner (Epson, Nagano, Japan). Transparencies of post-instrumentation images were changed and superimposed on pre-instrumentation images using Adobe Photoshop CS 3 (Adobe Systems Incorporated, San Jose, CA, USA). The centering ratio was calculated for each instrumented canal using the following formula: CR=|X1-X2|/Y. It was statistically analyzed using two-way ANOVA at 95% confidential level. The centering ratio in glide path groups were significant less than it in no glide path groups at 3, 4, 5 and 6 mm level. Except 1 and 6 mm level, WaveOne groups had significant less centering ration than Reciproc groups. At 6 mm level, there was no significant difference between WaveOne and Reciproc. In the limitation of this study, creation of a previous glide path before reciprocating motion instrumentation in curved canal appears to be appropriate and WaveOne system can be used for preparation of curved canal without severe aberrations.