• 대한치과보철학회지
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• 제43권2호
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• pp.248-257
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• 2005

Statement of problem. Cortical bone plays an important role in the primary implant stability, which is essential to immediate/early loading. However, immediate load-bearing capacity and primary implant stability according to the change of the cortical bone thickness have not been reported. Purpose. The objectives of this study were (1) to measure the immediate load-bearing capacity of implant and primary implant stability according to the change of cortical bone thickness, and (2) to evaluate the correlation between them. Material and methods.48, screw-shaped implants (3.75 mm$\times$7 mm) were placed into bovine rib bone blocks with different upper cortical bone thickness (0-2.5 mm) and resonance frequency (RF) values were measured subsequently. After fastening of healing abutment. implants were subjected to a compressive load until tolerated micromotion threshold known for the osseointegration and load values at threshold were recorded. Thereafter, RF measurement after loading, CT taking and image analysis were performed serially to evaluate the cortical bone quality and quantity. Immediate load-bearing capacity and RF values were analyzed statistically with ANOVA and post-hoc method at 95% confidence level (P<0.05). Regression analysis and correlation test were also performed. Results. Existence and increase of cortical bone thickness increased the immediate load-bearing capacity and RF value (P<0.05) With the result of regression analysis, all parameter's of cortical bone thickness to immediate load-bearing capacity and resonance frequency showed significant positive values (P<0.0001). A significant high correlation was observed between the cortical bone thickness and immediate load-beating capacity (r=0.706, P<0.0001), between the cortical bone thickness and resonance frequency (r=0.753, P<0.0001) and between the immediate load-bearing capacity and resonance frequency (r=0.755, P<0.0001). Conclusion. In summary, cortical bone thickness change affected the immediate load-baring capacity and the RF value. Although RF analysis (RFA) is based on the measurement of implant/bone interfacial stiffness, when the implant is inserted stably, RFA is also considered to reflect implant/bone interfacial strength of immediately after placement from high correlation with the immediate load-baring capacity. RFA and measuring the cortical bone thickness with X-ray before and during surgery could be an effective diagnosis tool for the success of immediate loading of implant.

• 대한치과보철학회지
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• 제43권2호
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• pp.176-190
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• 2005

Statement of problem. The current trend in prosthodontics is the adoption of a conservative approach to preparing dental prostheses by minimizing the amount of sound tooth structure removal during preparation. Purpose. The major disadvantage of the adhesion bridge is the inherently poor resistance to dislodgement that its use in areas subjected to high occlusal load is limited. The purpose of this study was to compare the dislodgement resistance of $Bio-pin^{(R)}$, conventional 3-unit and adhesion bridges. Material and methods. The experimental groups were classified as follows : Group I : 3-unit bridge cemented using $Super-Bond^{(R)}$ C&B Group II : Adhesion bridge cemented using $Super-Bond^{(R)}$ C&B Group III : $Bio-pin^{(R)}$ design adhesion bridge without incorporation of $Bio-pin^{(R)}$ (cemented using $Super-Bond^{(R)}$ C&B) Group IV-1 : $Bio-pin^{(R)}$ retained adhesion bridge incorporating a single $Bio-pin^{(R)}$ (cemented using $Super-Bond^{(R)}$ C&B) Group IV-2 : $Bio-pin^{(R)}$ retained adhesion bridge incorporating a single $Bio-pin^{(R)}$ (cemented using $Panavia^{(R)}$ F) Group V : $Bio-pin^{(R)}$ retained adhesion bridge incorporating two $Bio-pins^{(R)}$ (cemented using $Super-Bond^{(R)}$ C&B) Results. The results of this study were as follows : 1. Significant differences in dislodgement resistance of the restorations were found between Group I, Group II and Group III (p<0.05). No significant differences in dislodgement resistance of the restorations were observed between Group I Group IV-1 and Group V. However, there were significant differences in dislodgement resistance between Group II and the other groups (p<0.05). 2. No significant differences in dislodgement resistance of the restorations were observed between GroupIV-1 and GroupIV-2, both of which utilized a single $Bio-pin^{(R)}$. However, significant differences were observed when Group III was compared to either GroupIV-1 or Group V (p<0.05). 3. No significant differences in dislodgement resistance relative to the type of dental cements used were found. Conclusion. From the above results, it is concluded that the dislodgement resistance of $Bio-pin^{(R)}$ bridge restorations utilizing a single $Bio-pin^{(R)}$ is similar to that of a conventional 3-unit bridge. The results also suggest that $Bio-pin^{(R)}$ bridge restorations using a single $Bio-pin^{(R)}$ are a viable alternative to the conventional 3-unit bridge when minimal removal of sound tooth structure and fulfillment of both function and esthetic aspects are considered.

• 대한치과보철학회지
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• 제43권2호
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• pp.191-203
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• 2005

Statement of problem. In Korea, the preliminary impression trays for dental and edentulous maxillae are manufactured on the base of the statistical value of Westerners. There had been less study on the dental and edentulous arches of Koreans. Purpose. The purpose of this study was to evaluate an average dental cast, preliminary impression trays, three-dimensional relation of dental and edentulous maxilla of Koreans Material and methods. The subjects for this study were 173 dental casts of maxilla (dental: 52, edentulous : 146) with ages $18\{\sim}60$ years old. Each of the master casts was measured 69 measuring points on the dental cast or maxilla, and 46 measuring points on the edentulous cast of maxilla with three-dimensional digital measuring machine. Each measuring points were analysed and were overlapped, that three dimensional dental graphic manufactured by CAD/CAM system. Results. 1. A standard of distribution to alveolar bone were width between left and right buccal border lines of the standard 3/4 line. The mean value of dental and edentulous casts were 67.27mm, 63.49mm respectively. 2. Morphological classification of dental casts were divided into three groups or V-shape, O-shape, U-shape, that proportion of distribution were 17%, 16%, 67%, respectively. Dimensional classification of the dental casts were divided into five groups of less than 63mm, 63 up to 65mm, 65 up to 67mm. 67 up to 69mm, more than 69mm, respectively. 3. Morphological classification of edentulous casts were divided into three groups or V-shape, O-shape, U-shape, that proportion of distribution were 18%, 17%, 65%, respectively Dimensional classification of the edentulous casts were divided into five groups of less than 57mm, 57 up to 61mm, 61 up to 65mm, 65 up to 69mm, more than 69mm, respectively. 4. Mean dental and edentulous cast of maxilla were overlapped, the proportion of bone resorption to alveolar bone is higher than that of palatal bone, its difference were higher anterior 2/4 area than posterior 3/4 area. Conclusion. It obtains information of preliminary impression trays for dental and edentulous maxilla of Koreans.

• 대한치과보철학회지
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• 제38권6호
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• pp.757-764
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• 2000

Statement of the problem. All-ceramic post-and-core restorations offer a number of advantages compared with systems that use metal build-ups. In certain clinical cases, however, fractures at the joint between the post and core build-up have been reported. Purpose. The objective, therefore, is to improve the joint between the post and the core build-up. Material and methods. Three different methods were used to prepare all-ceramic post-and-core restorations; pressing IPS Empress core build-ups to CosmoPost zirconia posts, cement-ing IPS Empress core build-ups to CosmoPost zirconia posts and Celay-milling of zirconia blanks. A series of ten restorations was prepared for each of the three methods. The post-and-core complexes were tested to failure with the load applied perpendicular to the post axis. The load and deflection at fracture were recorded. Results. The highest breaking load and highest deflection were recorded for the cementing technique with values of 25.3 N and $394{\mu}m$, respectively, The corresponding values for the pressed core build-ups and the milled zirconia core build-ups were 22 N and $301{\mu}m$, and 13 N and $160{\mu}m$, respectively. All the differences are statistically significant (p=0.05). Regarding the load-dependence of the deflection, the cemented core build-ups again demonstrated the highest value with $15.5{\mu}m/N$. The difference in the values of $13.6{\mu}m/N\;and\;13{\mu}m/N$ recorded for the pressed-on and milled core build-ups, respectively, were statistically insignificant. Conclusion. In regard to the high fracture resistance of zirconia post, adhesive cementing the core build-up to the post offers a viable alternative to the conventional pressing technique. The elastic bond between the rigid high-strength zirconia post and the core build-up presents an additional advantage.

• 대한치과보철학회지
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• 제39권3호
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• pp.243-249
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• 2001

Statement of the problem. The interest in all-ceramic restorations has increased as more techniques have become available. With the introduction of machinable dental ceramics and CAD/CAM systems or Copy-milling systems there is a need for evaluating the quality levels of these new fabrication techniques. Purpose. This study was to evaluate the fitting accuracy of machined all-ceramic crowns made out of an industrially prefabricated feldspathic porcelain. Material and Methods. Three master models with different cutting depth (0.8mm/1.0mm/1.2mm)were produced using a palladium-silver alloy. A total of 36 working dies, 12 of each form, was used for the modellation of prototype resin copings and 36 additional crowns, 12 of each cutting depth, were produced by using the $CEREC^{(R)}2$ system for all crowns. The maginal fit of all 72 crowns was then evaluated on their respective master die at 54 circularly staggered points of measurement per crown under a fixation pressure of 30 N by using a computerized video image system. Results. The medians of the copy-milled $CELAY^{(R)}$ crowns ranged from 29 to $36{\mu}m$. The highest value for the marginal gap was found in group B (cutting depth 1.0mm) at $107{\mu}m$. The median for the $CEREC^{(R)}2$ crowns was found between 43.5 and $70{\mu}m$. The maximum values for all three groups ranged from $181{\mu}m$ to $286{\mu}m$. With $286{\mu}m$ the highest value for marginal gap was found in group C. the Kruskal-Wallis test and multiple comparisons analysis procedure revealed a significant influence of the production technique on the marginal fit in all three groups (p<0,02). Conclusion. 1. The $CELAY^{(R)}$ system is capable to produce all-ceramic crowns with a significantly better marginal fit than the $CEREC^{(R)}2$ system. 2. As far as premolar crowns produced with the $CEREC^{(R)}2$ system are concerned, the cutting depth has a significant influence on fitting accuracy. 3. The production of crowns with an acceptable marginal fit is possible with both systems. However, adhesive luting is recommended for milled feldspathic porcelain crowns.

• 대한치과보철학회지
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• 제43권2호
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• pp.264-279
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• 2005

Statement of problem. Intraoral corrosion not only affects the esthetic and function of metallic dental restoration, but also has biologic consequences as well. Therefore, corrosion is considered a primary factor when choosing the dental alloy and laboratory technique. Purpose. The objective of this study was to compare the effects of solder and laser weld on corrosion Material and methods. Test specimens were made of 2 types of gold alloys, Co-Cr and Ni-Cr alloy and fabricated 3 methods, respectively: as cast, solder, and laser weld. For the analysis of corroding properties, potentiodynamic polarization test and immersion test conducted. The potentiodynamic polarization scan curve were recorded in 0.9% NaCl solution(pH 7) using Potentiostat/Galyanostat Model 273A. All specimens were exposed to 0.9% NaCl solution(pH 2.3) during 14 days. Elemental release into corrosive solution was measured by atomic emission spectrometry Differences in corrosion potential and mass release were determined using ANOVA. Results and conclusion. Through analyses of the data, following results were obtained. 1. In Pontor MPF and Wiron 99, corrosion potential of the solder group was statistically lower than as cast and laser weld group (p<0.05) , but there was no difference between corrosion potential of solder group and laser weld group in Pontor MPF and no differences between as cast and laser weld group (p>0.05). In Jel-Bios 10 and Wirobond, there was no difference of corrosion potential according to joining methods(p>0.05). 2. In all tested alloys, the amount of released metallic ion was greatest in the solder group(p<0.05). There was no difference between as cast group and laser weld group in Jel-Bios 10 and Wirobond(p>0.05). 3. In scanning electron microscopic examination. except soldered Wiron 99 specimens, it is impossible to discriminate the corrosive property of solder and laser weld. 4. Under the this experimental circumstances, laser weld appears superior to the solder when corrosion is considered.

• The Journal of Advanced Prosthodontics
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• 제1권2호
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• pp.85-90
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• 2009

STATEMENT OF PROBLEM. Over the years, resin-bonded fixed partial dentures (RBFPDs) have gone through substantial development and refinement. Several studies examined the biomechanics of tooth preparation and framework design in relation to the success rate of RBFPDs and considered retention and resistance form essential for increase of clinical retention. However, these criteria required preparations to be more invasive, which violates not only the original intentions of the RBFPD, but may also have an adverse effect on retention due to loss of enamel, an important factor in bonding. PURPOSE. The object of this in vitro study was to compare the dislodgement resistance of the new types of RBFPDs, the conventional three-unit fixed partial denture, and conventional design of RBFPD (Maryland bridge). MATERIAL AND METHODS. Fifty resin mandibular left second premolars and second molars were prepared on dentiforms, according to the RBFPD design. After model fabrication (five group, n = 10), prostheses were fabricated and cemented with zinc phosphate cement. After cementation, the specimens were subjected to tensile loading at a cross head speed of 4 mm/min in a universal testing machine. The separation load was recorded and analyzed statistically using one-way analysis of variance followed by Duncan's multiple range test. RESULTS. Group V, the pin-retained RBFPDs, had the highest mean dislodgement resistance, whereas specimens of group II, the conventional RBFPDs, exhibited a significantly lower mean dislodgement resistance compared to the other 4 groups (P <.05). There were no significant differences between group I, III, and IV in terms of dislodgement resistance (P>.05). Group V had the highest mean MPa (N/$mm^2$) (P <.05). There was no significant difference between groups I, II, III and IV (P > .05). CONCLUSION. Within the limits of the design of this in vitro study, it was concluded that: 1. The modified RBFPDs which utilizes the original tooth undercuts and requires no tooth preparation, compared with the conventional design of RBFPDs, has significantly high dislodgement resistance (P < .05). 2. The modified RBFPDs which utilizes the original tooth undercuts and requires minimal tooth preparation, compared with the conventional FPDs, has significantly no difference in retention and dislodgement resistance)(P>.05). 3. The pin-retained FPDs showed a high dislodgement resistance compared to the conventional three-unit FPDs (P<.05).

• The Journal of Advanced Prosthodontics
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• 제1권2호
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• pp.63-67
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• 2009

STATEMENT OF PROBLEM. Use of custom tray and tray adhesive is clinically recommended for elastomeric impression material. However there is not clear mention of drying time of tray adhesive in achieving appropriate bonding strength of tray material and impression material. PURPOSE. This study is to investigate an appropriate drying time of tray adhesives by evaluating tensile bonding strength between two types of polyvinylsiloxane impression materials and resin tray, according to various drying time intervals of tray adhesives, and with different manufacturing company combination of impression material and tray adhesive. MATERIAL AND METHODS. Adhesives used in this study were Silfix (Dentsply Caulk, Milford, Del, USA) and VPS Tray Adhesive (3M ESPE, Seefeld, Germany) and impression materials were Aquasil Ultra (monophase regular set, Dentsply Caulk, Milford, Del, USA) and Imprint II Garant (regular body, 3M ESPE, Seefeld, Germany). They were used combinations from the same manufacture and exchanged combinations of the two. The drying time was designed to air dry, 5 minutes, 10 minutes, 15 minutes, 20 minutes, and 25 minutes. Total 240 of test specimens were prepared by auto-polymerizing tray material(Instant Tray Mix, Lang, Wheeling, Il, USA) with 10 specimens in each group. The specimens were placed in the Universal Testing machine (Instron, model 3366, Instron Corp, University avenue, Nowood, MA, USA) to perform the tensile test (cross head speed 5 mm/min). The statistically efficient drying time was evaluated through ANOVA and Scheffe test. All the tests were performed at 95% confidence level. RESULTS. The results revealed that at least 10 minutes is needed for Silfix-Aquasil, and 15 minutes for VPS Tray Adhesive-Imprint II, to attain an appropriate tensile bonding strength. VPS Tray Adhesive-Imprint II had a superior tensile bonding strength when compared to Silfix-Aquasil over 15 minutes. Silfix-Aquasil had a superior bonding strength to VPS Tray Adhesive-Aquasil, and VPS Tray Adhesive-Imprint II had a superior tensile bonding strength to Silfix-Imprint II at all drying periods. CONCLUSION. Significant increase in tensile bonding strength with Silfix-Aquasil and VPS Tray adhesive-Imprint II combination until 10 and 15 minutes respectively. Tray adhesive-impression material combination from the same company presented higher tensile bonding strength at all drying time intervals than when using tray adhesive-impression material of different manufactures.

• The Journal of Advanced Prosthodontics
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• 제1권2호
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• pp.107-112
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• 2009

STATEMENT OF PROBLEM. Macroscopic and especially microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Dental implants with modified surfaces have shown stronger osseointegration than implants which are only turned (machined). Advanced surface modification techniques such as anodic oxidation and Ca-P application have been developed to achieve faster and stronger bonding between the host bone and the implant. PURPOSE. The purpose of this study was to investigate the effect of surface treatment of titanium dental implant on implant stability after insertion using the rabbit tibia model. MATERIAL AND METHODS. Three test groups were prepared: sandblasted, large-grit and acid-etched (SLA) implants, anodic oxidized implants, and anodized implants with Ca-P immersion. The turned implants served as control. Twenty rabbits received 80 implants in the tibia. Resonance frequencies were measured at the time of implant insertion, 2 weeks and 4 weeks of healing. Removal torque values (RTV) were measured 2 and 4 weeks after insertion. RESULTS. The implant stability quotient (ISQ) values of implants for resonance frequency analysis (RFA) increased significantly (P <. 05) during 2 weeks of healing period although there were no significant differences among the test and control groups (P >. 05). The test and control implants also showed significantly higher ISQ values during 4 weeks of healing period (P < .05). No significant differences, however, were found among all the groups. All the groups showed no significant differences in ISQ values between 2 and 4 weeks after implant insertion (P >. 05). The SLA, anodized and Ca-P immersed implants showed higher RTVs at 2 and 4 weeks of healing than the machined one (P < .05). However, there was no significant difference among the experimental groups. CONCLUSION. The surface-modified implants appear to provide superior implant stability to the turned one. Under the limitation of this study, however, we suggest that neither anodic oxidation nor Ca-P immersion techniques have any advantage over the conventional SLA technique with respect to implant stability.

• 대한치과보철학회지
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• 제47권4호
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• pp.385-393
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• 2009

연구목적: 임플란트 경부 디자인의 차이가 경부 치밀골의 응력분포에 미치는 영향을 유한요소법을 이용하여 분석하고자 한다. 연구재료 및 방법: 몸체 형상은 유사 (직경 4.3 mm, 길이 10 mm)하나 경부 디자인이 internal형, external형, 및 submerged형으로 다른 3종의 임플란트 시스템 ((주)덴티스, 대구, 대한민국)에 대하여 축대칭 유한요소모델을 사용하여 해석하였다. 악골 폭경은 7 mm로 동일하게 모델링하였고 하중 조건으로는 임플란트 장축에 평행한 수직하중 50 N, 임플란트 장축에 $45^{\circ}$방향으로 작용하는 경사력 50N을 설정하였다. 결과: 해석한 3종의 임플란트 모두 경부 피질골에 응력집중을 발생시켰으며 디자인 차이에 따른 응력 수준의 차이가 관찰되었다. 경부 피질골의 최대 응력은 수직력 조건에서 internal형, submerged형, external형의 순으로 컸으며, 그 값은 각각 2.71, 2.60, 2.48 MPa였다. 경사력 조건에서는 internal형, external형, submerged형의 순으로 컸으며 그 값은 각각 9.30, 9.14, 8.97 MPa였다. 결론: 임플란트 경부 디자인이 주위 치밀골의 응력 분포에 영향을 미칠 수 있지만 그 차이는 크지 않은 것으로 분석되었다.