• The Journal of Korean Academy of Prosthodontics
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• v.41 no.1
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• pp.48-60
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• 2003

The purpose of this study was to compare the fracture strength of the IPS Empress ceramic crown according to the occlusal depth (1.5mm, 2.0mm, 2.5mm) and axial inclination ($4^{\circ},\;8^{\circ},\;12^{\circ}$) of the lower First Molar. After 10 metal dies were made for each group, the IPS Empress ceramic crowns were fabricated and cemented with resin cement(Bistite resin cement, Tokuyama Soda Co. LTD., Japan). The cemented crowns were mounted on the testing jig with inclination of 30 degrees and the universal testing machine(Zwick Z020, Zwick, Germany)was used to measure the fracture strength. The results of this study were as follows : 1. The fracture strength of the ceramic crown with 2.5mm depth and $12^{\circ}$ inclination was the highest (1789 N). Crowns of 1.5mm depth and $4^{\circ}$ inclination had the lowest strength (1091 N). 2. There were no significant differences in the fracture strength by axial inclination of the same occlusal depth group. 3. Most fracture lines began at the loading area and extended through proximal surface perpendicular to the margin, irrespective of occlusal depth. Size of fragment was affected by the amount of occlusal reduction.

• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.239-249
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• 1999

In orthognathic surgery to obtain proper functional and esthetic form after skeletal discrepancy treatment, precise diagnosis and treatment plan are essential. Especially in two jaw surgeries that have serious upper and lower jaw problems, maxilla and mandible are arranged in three dimensions. Based on the maxillary rearrangement, mandibular sagittal and transverse positions are determined, and thus new occlusal plane is established. The object of this study is to evaluate the stability of the indiviual ideal occlusal plane based on the architectural and structural craniofacial analysis of Delaires. The subjects of this study were 48 patients who underwent two jaw surgeries, and they were equally divided into two groups, A and B. A group was operated with ideal occlusal plane and B group was not. Two groups were compared at the preoperative, immediate postoperative (average 4.3days), and long-term postoperative (average 1.3years) lateral cephalometric radiographs. The following results were obtained: 1. ANS was lower than that of PNS for both A and B after the surgery. That is, maxilla and mandible are rotated in posterior and superior direction. 2. Significances were found between $T_2$ and $T_3$ for both A and B are HRP-Me at vortical measurements, articular angle(p<0.01), gonial angle(p<0.01), and Mn. plane angle(p<0.05) at angular measurement. Mn. plane angle is increased at HRP-Me is decreased for both A and B. 3. There is no significance in skeletal stability aster the surgery between group A and B. 4. Horizontal movements of B and Pog by surgery have statistically significant inverse correlations with horizontal relapse of B and Pog, and vertical relapse of PNS, as well as Mn. Plane angle, and gonial angle after the surgery.

• The korean journal of orthodontics
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• v.40 no.5
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• pp.334-341
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• 2010

Objective: The purpose of this study was to evaluate morphologic differences in the mandibular arch between Egyptian and Korean subjects. Methods: The Egyptian sample consisted of 94 mandibular casts (35 Class I, 32 Class II and 27 Class III). The Korean sample consisted of 462 mandibular casts (114 Class I, 119 Class II, and 135 Class III). The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth. The subjects were grouped according to arch form to compare the frequency distribution of the 3 arch forms between the ethnic groups in each Angle classification. Results: Egyptians had significantly narrower intermolar and intercanine widths ($p$ < 0.001), and shallower intermolar and intercanine depths ($p$ < 0.001) than Koreans. There was an even frequency distribution of the 3 arch forms within the Egyptian group ($p$ = 0.46). However, in the Korean group, the most frequent arch form was the square arch form (46.7%), while the frequency of the tapered arch form was significantly lower (18.8%). Conclusions: These results might provide helpful information in evaluating morphologic differences between ethnic groups in selection of preformed superelastic archwires.

• The korean journal of orthodontics
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• v.30 no.2 s.79
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• pp.143-157
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• 2000

To investigate the developmental stages of dental and skeletal maturation by ages and the correlations among dental maturity, skeletal maturity of cervical vertebrae, and that of hand-and-wrist, the author used the cephalograms, orthopantomograms, and hand-and-wrist radiograms of 1055 patients (male 458, female 597) aged 7 to 20 years old. In the cephalograms, the skeletal maturity stages of each bone were mainly assessed by Hassel and Farman's cervical vertebrae maturation indicators (CVMI) method. In the orthopantomograms, the dental maturity stages of each tooth were mainly assessed by Nolla's tooth calcification stages method. In the hand-and-wrist radiograms, the skeletal maturity stages of each bone were mainly assessed by Fishman's skeletal maturity indicators (SMI) method. The results were as follows. 1. There was a high correlation among dental maturity, skeletal maturity of cervical vertebrae, and that of hand-and-wrist in the both sexes (P<0.001). 2. There was a high correlation (r=0.91-0.93) between skeletal maturity of cervical vertebrae and that of hand-and-wrist. 3. There was a high correlation (r>0.8) between skeletal maturity of hand-and-wrist and maturity of upper and lower canine, first premolar, and second premolar. 4. There was high a correlation(r=0.8) between skeletal maturity of cervical vertebrae and maturity of upper canine. 5. By the ages, dental maturity, skeletal maturity of cervical vertebrae, and that of hand-and-wrist were obtained in the both sexes. In summary, dental maturity, skeletal maturity of cervical vertebrae, and that of hand-and-wrist we of sufficient diagnostic worth as an index to predict adolescent growth.

• Restorative Dentistry and Endodontics
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• v.35 no.1
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• pp.13-19
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• 2010

The purpose of this study was to compare the microshear bond strength of a self-etching primer adhesive to dentin prepared with different diamond points, carbide burs and SiC papers, and also to determine which SiC paper yield similar strength to that of dentinal surface prepared with points or burs. Fifty-six human molar were sectioned to expose the occlusal dentinal surfaces of crowns and slabs of 1.2 mm thick were made. Dentinal surfaces were removed with three diamond points, two carbide burs, and three SiC papers. They were divided into one of eight equal groups (n = 7); Group 1: standard diamond point(TF-12), Group 2: fine diamond point (TF-12F), Group 3: extrafine diamond point (TF-12EF), Group 4: plain-cut carbide bur (no. 245), Group 5: cross-cut carbide bur (no. 557), Group 6 : P 120-grade SiC paper, Group 7: P 220-grade SiC paper, Group 8: P 800-grade SiC paper. Clearfil SE Bond was applied on dentinal surface and Clearfil AP-X was placed on dentinal surface using Tygon tubes. After the bonded specimens were subjected to uSBS testing, the mean uSBS (n = 20 for each group) was statistically compared using one-way ANOV A and Tukey HSD test. In conclusion, the use of extrafine diamond point is recommended for improved bonding of Clearfil SE Bond to dentin. Also the use of P 220-grade SiC paper in vitro will be yield the results closer to dentinal surface prepared with fine diamond point or carbide burs in vivo.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.3
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• pp.205-215
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• 2002

This study investigated the compressive fracture strength of Targis ceromer crown by the difference of occlusal thickness on a maxillary first premolar. Control group was a castable IPS-Empress all-ceramic crown with occlusal thickness of 1.5 mm constructed by layered technique. Experimental groups were Targis crowns having different occlusal thicknesses of 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, respectively. The classification of Targis group is T10, T15, T20, T25 and T15N (for no-thermocycling and occlusal thickness of 1.5mm). Ten samples were tested per each group. Except occlusal thickness, all dimension of metal die is same with axial inclination of $10^{\circ}$and marginal width 0.8mm chamfer. All crowns were cemented with Panavia F and thermocycled 1,000 times between $5^{\circ}$ and $55^{\circ}$ water bath with 10 sec dwelling time and 10 sec resting time. The compressive fracture strength was measured by universal testing machine. The results were as follows : 1. Fracture strength was increased as the occlusal thickness increased : compressive fracture strength of Group T10, T15, T20, T25 was $66.65{\pm}4.88kgf$, $75.04{\pm}3.01kgf$, $87.07{\pm}7.06kgf$ and $105.03{\pm}10.56kgf$, respectively. 2. When comparing material, Targis crown had higher fracture strength than IPS-Empress crown : the mean compressive strength of group T15 was $75.04{\pm}3.01kgf$ and the value of group Control was $37.66{\pm}4.28kgf$. 3. Fracture strength was decreased by thermocycling : the compressive fracture strength of T15 was $75.04{\pm}3.01kgf$, which is lower than $90.69{\pm}6.88kgf$ of group T15N. 4. The fracture line of crowns began at the loading point and extended along long axis of tooth. IPS-Empress showed adhesive failure pattern whereas Targis had adhesive and cohesive failure. In the SEM view, stress was distributed radially from loading point and the crack line was more prominent on Targis crown.

• The korean journal of orthodontics
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• v.28 no.5 s.70
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• pp.763-774
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• 1998

The purpose of this study was to evaluate the morphology of mandibular symphysis and location of lower incisor under the influence of the craniofacial skeleton in skeletal Class III malocclusion. The sample consisted of 132 adults who have severe Class III malocclusion(prognathism group, 33 males and 33 females), and who have normal occlusion(normal group, 33 males and 33 females). They had not received any orthodontic treatment or orthognathic surgery. The lateral cephalograms were evaluated. The results were as follows : 1. Prognathism group were larger than normal group in comparison of facial skeleton (p<0.05) with the exception of ${\angle}FH-Pal$, ${\angle}SNA$. 2. In the morphology of symphysis, measurements of anteroposterior width(LaABBW, LiABBW, SW) of prognathism group were significantly less than that of normal group(p<0.001). 3. In the correlative analysis between the craniofacial skeleton and symphysis measurements of prognathism group, vertical measurements in relation with cranial base and mandibular plane showed reverse correlationship with anteroposterior width of symphysis(LiACBW, LaACBW, LiABBW, SW)(p<0.05). But, there was not distinct difference between horizontal skeletal measurements and symphysis measurements(p>0.05). 4. The probability by regression test between vertical measurements(${\angle}SN-Mn,\;{\angle}FMA,\;{\angle}Pal-Mn,\;{\angle}LFH$) and symphysis measurements(LiACBW, LiABBW, SW, ${\angle}LISA$) were very high(p<0.001).

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.29-41
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• 1998

Despite orthodontic treatment(tooth moving) is dynamic act many orthodontists have used mainly static evaluation method for evaluating effectiveness of the orthodontic appliances. They want to find which is better appliance, especially in the treatment results and treatment period when they chose one appliance from sugessted appliances for obtaining same treatment goal. The author and colleagues invented and manufactured new machine for getting information about the relative effectiveness from many suggested orthodontic appliances and we named it Calorific machine. We used this Calorinc machine to find the relative differences about tooth moving mechanism and tooth moving time between the Burstone's PLA(single force mechanism) and Molar-up's PLA(couple mechanism) for correcting the posterior cross bite. We measured the distance of tooth moving on the occlusal X-ray film and recorded the moving time of the anchored(control elctro-thermal tooth) and lingually tipped lower second molars(experimental electro-thermal tooth) and then processed paired t-est by SAS program. The results were as follows. 1. Molar-up's PLA showed more extrusive and horizontal movement than Burstone's PLA at the lingually tipped molar(p=0.0000). 2. There is no finding of tooth movement by Molar-up's PLA at the uprighted molar(p=o.3475) but Burstone's PLA showed a little change(0.2 m) at the same molar(p=0.0001). 3. Burstone's PLA took 17.8 minutes for tooth moving but Molar-up's PLA took only 3.8 minutes(p=0.0001)

• The korean journal of orthodontics
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• v.38 no.6
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• pp.427-436
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• 2008

Objective: The purpose of this study is to compare landmark position between cephalometric radiography and midsagittal plane projected images from 3 dimensional (3D) CT. Methods: Cephalometric radiographs and CT scans were taken from 20 patients for treatment of mandibular prognathism. After selection of land-marks, CT images were projected to the midsagittal plane and magnified to 110% according to the magnifying power of radiographs. These 2 images were superimposed with frontal and occipital bone. Common coordinate system was established on the base of FH plane. The coordinate value of each landmark was compared by paired t test and mean and standard deviation of difference was calculated. Results: The difference was from $-0.14{\pm}0.65$ to $-2.12{\pm}2.89\;mm$ in X axis, from $0.34{\pm}0.78$ to $-2.36{\pm}2.55\;mm$ ($6.79{\pm}3.04\;mm$) in Y axis. There was no significant difference only 9 in X axis, and 7 in Y axis out of 20 landmarks. This might be caused by error from the difference of head positioning, by masking the subtle end structures, identification error from the superimposition and error from the different definition.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.143-152
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• 2003

The aims of the present study was to observe resin tag of the resin/enamel, dentin interface produced by self-etching adhesive systems and evaluate effect of additional acid etching on resin tag formation. Three self-etching primer(SE bond, AQ bond and L Pop) and an one bottle adhesive(Single bond) were used. Flat occlusal enamel and dentin disks were obtained from extracted human molars. A total of 20 surfaces were collected and divided into four groups of 5 samples. One-half of each specimen in each group was etched with 35% phosphoric acid prior to the application of each adhesive system, with the second half being kept unetched. Subsequently, resin composite was placed and polymerized. The samples were sliced and immersed into HCl and NaOCl solutions, followed by drying and sputter coating for examination with a SEM. The results were as follows; 1. Additional etching side of dentin displayed longer and thicker resin tag than unetched side in all self-etching adhesive groups. 2. In enamel, additional etching side displayed deeper and more distinct etching pattern than unetched side except L Pop. There is no difference between etched and unetched enamel in L Pop. The results obtained suggest the self-etching adhesive did not etch enamel and penetrate into dentinal tubule as deeply as did additional etching. Further research should include the evaluation of the relationship of boding strength, microleakage and resin tag morphology.