A study on the vertical augmentation of the alveolar ridge by distraction osteogenesis in dogs / 대한치과보철학회지

STATEMENT OF PROBLEM: Implant-type distractor uses a removable distraction device that has an appearance similar to that of a dental implant and utilizes many of the same techniques for placement as are used for dental implants. MATERIAL AND METHOD: In this study, 48 implant type titanium distractors were inserted into the osteotomized alveolar bone of 12 beagle dogs. After a 7-day latency period, the alveolar bone was augmented by 5mm vertically at a rate of 1.0 mm/day. The dogs were sacrificed after 4weeks, 8weeks and 12 weeks for radiographic, histologic, and histomorphometric analysis. RESULTS: Copper equivalent value showed significant difference between 4 weeks and the other weeks(8, 12 weeks)(p<0.05). But there was no significant difference between maxillary and mandibular groups. In the bone to metal contact analysis, there was a significant difference between 4 weeks and 12 weeks(p<0.05). On the contrary, there was no significant difference between maxilla and mandible. The bone area showed significantly higher values in 12 weeks compared to 4 weeks(p<0.05). Histologically mineralization began at the host bone margins. At 12 weeks, increasing accumulation of Ca++ element was confirmed. CONCLUSION: From the results above, the new bone formation was increased according to consolidation period. Especially there was significant difference between 4 weeks and 12 weeks(p<0.05). Implant type distractors used in this study to augment vertical ridge defect may prove to be a clinically useful treatment option in selected cases.

A study of the anti-rotating inner post screw system as a means of preventing abutment screw loosening / 대한치과보철학회지

STATEMENT OF PROBLEM: The most commonly reported problem associated with dental implant restoration is the loosening of the screws. PURPOSE: This study compared the efficacy of an implant system incorporating an anti-rotational locking sleeve(Anti-Rotating Inner Post Screw System(ARIPS-system)) with other, traditional implant systems as a means of minimizing vibration loosening. MATERIALS AND METHODS: Three implant systems were examined; the conventional external hex type, the ARIPS-system, and the internal taper type implant system. 30 specimens(10 samples per group)were fabricated and each abutment screw was secured to the implant fixture with 32Ncm of torque force and loosening torque was measured using a Torque Gauge. The procedure was repeated 3 times, recording initial loosening torque each time. The re-tightened abutment screw was subjected to a cyclic load having a maximum force of 200N and minimum of 20N at 2Hz over a period of 12,600 cycles, after which the loosening torque was measured. Measured values were calaulated for statistical analysis. Analysis of measured value was performed by 3 methods: (i) as a percentage average of the initial 3 loosening-torque values(initial loosening value) to the tightening torque of 32Ncm, (ii) as a percentage of the loosening torque value after a load of 200N(experimental value) to the initial loosening value, and (iii) as a percentage of the experimental value to the 32Ncm of tightening torque. The analyses shows the amount of initial loosening at the screw, loosening by repetitive load and the the final loosening value. RESULTS: The results of this study were as follows. (1) Percentage of initial loosening value to tightening-torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p<0.05). (2) Percentage of experimental value to initial loosening value was increased in order of external hex, ARIPS-system and internal taper. Value of internal taper showed significant difference with those of external hex and ARIPS-system (p <0.05). (3) Percentage of experimental value to tightening torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p <0.05). CONCLUSION: The results of the analysis of the final loosening level value, which are closely correlated to clinical use, show that the ARIPS-system can be a useful means of minimizing abutment screw loosening when compared to the external hex type system. Although further clinical studies need to be made, the ARIPS-system should be considered to maximize the long-term success of the implant prosthesis.

A study on the solubility and the water sorption of various resin cements / 대한치과보철학회지

STATEMENT OF PROBLEM: Among the physical properties of adhesion luting cement, the aspect that requires the most important factor is the degree of solubility and water sorption. Dissolution or an inadequate due to excessive water sorption inside the oral cavity compromises the while concurrently increasing the susceptibility to secondary dental caries. Susceptibility to dissolution and difficulty of removing remnant cement from the gingival sulcus have hindered the use of dental resin cement in the clinical practice, but the improved characteristics of newer generation resin cements have interest in and enabled resin cements to be widely used in adhesion of fixed prosthesis, such as laminate veneers and all-ceramic crowns. PURPOSE: The purpose of this study is to compare and analyze the degrees of solubility and water sorption of a variety of resin cements widely used for clinical purposes with different curing methods. MATERIALS AND METHODS: Self-curing resin cements, Avanto(R), CandB(TM) CEMENT and Superbond CandB cements comprised group 1, 2 and 3. The dual-curing resin cements Panavia(TM) F, Calibra(R) and Variolink(R) II were divided into groups 4, 5, and 6, respectively. The investigation was carried out using disc-shaped specimens as specified by ANSI/ADA Specification No. 27. The degree of water sorption, water solubility and lactic acid solubility of each test group was analyzed statistically leading to the following conclusion. RESULTS: The degree of water sorption was shown to increase in the following order : group 6, 5, 4, 2, 1 and 3. There were significant differences between the water sorption of each group. Results of the degree of water solubility were shown to increase in the following order : group 6, 5, 4, 2, 1 and 3. Statistically significant differences were found between each group, with the exception of groups 1 and 3. Finally, the degree of lactic acid solubility was found to increase in the following order : group 6, 5, 4, 2, 3 and 1. Significant differences were found between each group. In general dual-curing resin cements displayed substantially lower values than self-curing resin cements with regard to water sorption, water solubility, and lactic acid solubility. CONCLUSIONS: From the results of this study, dual-curing resin cements show a significantly lower degree of water sorption and solubility than their self-curing counterparts. Clinically, when selecting resin cements, the product with a lower degree of water sorption and solubility are preferred. The results of this study indicate that the use-of dual-curing resin cements is preferable to self-curing cements.

Color stability of ceromers in three food colorants / 대한치과보철학회지

STATEMENT OF PROBLEM: Ceramic and composite resin have been used to fulfill the demand for esthetic prosthesis. However, ceramic is easy to break and wears off the opposite natural teeth. Conventional composite resin also has low abrasive resistance and color stability. Ceramic Optimized Polymer (ceromer) was developed in mid-1990s to overcome the shortfalls of ceramic and composite resin. Ceromer has similar abrasiveness with the natural tooth and has relatively high strength. Color stability affects esthetics and long-term prognosis of the prosthesis. PURPOSE: The purpose of this study was to compare color stability of ceromers(2 types : Artglass., Targis.) with ceramics(Vintage.-polishing, Vintage.-glazing). MATERIAL AND METHOD: The color difference(E*) was measured by spectrophotometer with different immersion time. Twenty disks, 3mm in thickness and 10mm in diameter, were fabricated for each specimen in shade A2(Vita Lumin shade guide). Specimens(5 samples in each group) were immersed in the food colorants(Red no.3, Yellow no.4, Blue no.1, Distilled water) for 24 hours, 48 hours and 72 hours respectively. L*, a* and b* value were measured with spectrophotometer (CM 503i : Minolta Co., Japan) and mean E* value was calculated for statistical analysis. RESULTS: The results of this study were obtained as follows. 1. The E* values of all test samples increased with the time of immersion. 2. The E* values of all materials increased in order of Distilled Water, Yellow no.4, Blue no.1 and Red no.3. There was significant difference between Red no.3 and the other food colorants(p<0.05). 3. The E* values increased in order of Vintage-glazing, Vintage-polishing, Artglass and Targis. There was significant difference between Vintage.-glazing and the other materials (p<0.05). CONCLUSION: By means of the above results, immersion time was found to be a critical factor for color stability of ceromer. For the long-term color stability of prosthesis it is recommended patients having ceromer prosthesis(Artglass., Targis.) to reduce the habitual intake of Red no.3 colorants con taining foods.

A study on the measurement of the implant stability using resonance frequency analysis / 대한치과보철학회지

STATEMENT OF PROBLEM: Successful osseointegration of endosseous threaded implants is dependent on many factors. These may include the surface characteristics and gross geometry of implants, the quality and quantity of bone where implants are placed, and the magnitude and direction of stress in functional occlusion. Therefore clinical quantitative measurement of primary stability at placement and functional state of implant may play a role in prediction of possible clinical symptoms and the renovation of implant geometry, types and surface characteristic according to each patients conditions. Ultimately, it may increase success rate of implants. PURPOSE: Many available non-invasive techniques used for the clinical measurement of implant stability and osseointegration include percussion, radiography, the Periotest., Dental Fine Tester. and so on. There is, however, relatively little research undertaken to standardize quantitative measurement of stability of implant and osseointegration due to the various clinical applications performed by each individual operator. Therefore, in order to develop non-invasive experimental method to measure stability of implant quantitatively, the resonance frequency analyzer to measure the natural frequency of specific substance was developed in the procedure of this study. MATERIAL AND METHOD: To test the stability of the resonance frequency analyzer developed in this study, following methods and materials were used: 1) In-vitro study: the implant was placed in both epoxy resin of which physical properties are similar to the bone stiffness of human and fresh cow rib bone specimen. Then the resonance frequency values of them were measured and analyzed. In an attempt to test the reliability of the data gathered with the resonance frequency analyzer, comparative analysis with the data from the Periotest was conducted. 2) In-vivo study: the implants were inserted into the tibiae of 10 New Zealand rabbits and the resonance frequency value of them with connected abutments at healing time are measured immediately after insertion and gauged every 4 weeks for 16 weeks. RESULTS: Results from these studies were such as follows: The same length implants placed in Hot Melt showed the repetitive resonance frequency values. As the length of abutment increased, the resonance frequency value changed significantly (p<0.01). As the thickness of transducer increased in order of 0.5, 1.0 and 2.0 mm, the resonance frequency value significantly increased (p<0.05). The implants placed in PL-2 and epoxy resin with different exposure degree resulted in the increase of resonance frequency value as the exposure degree of implants and the length of abutment decreased. In comparative experiment based on physical properties, as the thickness of transducer increased, the resonance frequency value increased significantly(p<0.01). As the stiffness of substances where implants were placed increased, and the effective length of implants decreased, the resonance frequencies value increased significantly (p<0.05). In the experiment with cow rib bone specimen, the increase of the length of abutment resulted in significant difference between the results from resonance frequency analyzer and the Periotest.. There was no difference with significant meaning in the comparison based on the direction of measurement between the resonance frequency value and the Periotest. value (p<0.05). In-vivo experiment resulted in repetitive patternes of resonance frequency. As the time elapsed, the resonance frequency value increased significantly with the exception of 4th and 8th week (p<0.05). CONCLUSION: The development of resonance frequency analyzer is an attempt to standardize the quantitative measurement of stability of implant and osseointegration and compensate for the reliability of data from other non-invasive measuring devices. It is considered that further research is needed to improve the efficiency of clinical application of resonance frequency analyzer. In addition, further investigation is warranted on the standardized quantitative analysis of the stability of implant.

Shade analysis of anterior teeth using digital shade analysis system / 대한치과보철학회지

STATEMENT OF PROBLEM: A scientific examination and understanding of overall aspects of the natural dentition is the first step involved in making a satisfactory selection in the shade of an aesthetic prosthesis. Proper natural shade selection of the prosthetic restoration that is in harmony with the remaining dentition is as important aesthetically, as harmony of form and function in the anterior dentition. Clinically, the most commonly applied method of shade selection has been visual, but because of the subjective nature inherent to this method, shade selection results are variable and can be influenced by such factors as the technician, the type of shade guide used, and the type and intensity of the lighting. PURPOSE: The purpose of this study was to develop a more objective and scientific approach to examining and understanding the shade of teeth, which has in turn lead to the development of a number of shade analysis devices that present a more objective method of shade analysis. MATERIAL AND METHOD: In this study, the shades of healthy anterior teeth were examined and analyzed using the recently developed digital shade analysis of the ShadeScan(TM) System. The study examined 80 individuals in their twenties, 40 males and 40 females, presenting 6 healthy, unrestored maxillary anterior teeth. Tooth brushing and oral prophylaxis were performed prior to evaluation. The ShadeScan handpiece was used to acquire images of the 6 maxillary anterior teeth. These images were analyzed using the Vita/Classical mode of the ShadeScan(TM) Software, and shade maps of each tooth were acquired and divided into cervical, middle, and incisal thirds. The shade distribution of each third, left and right symmetry, and gender differences were investigated and analyzed. RESULTS: The results of the study are as follows: 1. An overwhelming majority of the examined teeth were found to possess shades belong to Group A, with the greatest variations occurring at the middle and cervical thirds of the maxillary central and lateral incisors, in both male and female subjects. 2. Canines of both male and female subjects showed left and right symmetry with uniform shade distribution of A4 and C4, while the lateral and central incisors showed left-right symmetry of the incisal 1/3 with a uniform shade distribution of A2 and A3 shades. 3. No significant differences in shade distribution were seen between genders in maxillary canines, whereas maxillary central and lateral incisors showed differences at the middle and cervical thirds between male and female subjects. The results of this study show that with the exception of maxillary canines, maxillary anterior teeth display a diverse shade distribution as well as gender differences. CONCLUSION: Clinically, when making a shade selection using the existing shade guide, one must consider the fact that even a single tooth consists of a variety of shades. The results of this study show that when selecting a shade from a number of groups is difficult, shades from A group are the most consistent with the natural shade of maxillary anterior teeth.

On the marginal fidelity of all-ceramic core using CAD/CAM system / 대한치과보철학회지

Novel methods producing supplementary and prosthetic material by cutting or discharge processing via computer design have been proposed as alternatives for traditional casting methods and are being utilized for commercial purposes. The CAD/CAM system used in dentistry can be classified into three-dimensional input of target values, restoration design, and material processing. The marginal fidelity in production of In-Ceram core has important clinical implications and is a key consideration issue in CAD/CAM production as well. Through this research, the author arrived at the following conclusion after conducting comparison analysis of marginal fidelities between the In-Ceram core produced via CAD/CAM and that produced through the traditional method: 1. In the cases of mesial, distal, and lingual margins, the core margins via CAD/CAM produced lower values than those via the traditional method, but the differences were found to be statistically insignificant. 2. In the case of labial flange, the core margins via CAD/CAM produced lower values than those via the traditional method and the differences were found to be statistically significant. (p<0.05) 3. In comparision with overall marginal fidelity, the core margins via CAD/CAM produced lower values than those via the traditional method, but the differences were found to be statistically insignificant. 4. Among the core margins produced via the traditional method did not have statistically significant differences but for those produced via CAD/CAM had statistically significant differences between labial and lingual sides and between labial and mesial sides. (p<0.05)

A Comparative Study on the Accuracy of Master Casts by Implant Impression Techniques / 대한치과보철학회지

As the inaccuracy which was made in implant impression prevented passive fit,it needed to solder the sectioned framework at several locations to correct the inaccuracy. Many clinicians have suggested impression techniques which could make passive fit between implant and superstructure. The purpose of this research was to measure and compare the accuracy of three methods of taking impression with the strain amplifier. The experimental groups were classified as follows : Group I; splinted the two parts with Futar D Occlusion. Group II; splinted the two parts with DuraLay. Group III; didn't splint the two parts. The results were as follows ; 1.The values of strain in the vertical and horizontal surfaces were increased in the order of groupI,group II and group III. 2.Group I showed higher accuracy of the duplicated casts in the vertical and horizontal surfaces than group IIand group III(p<0.05). 3.There were no significant differences in the accuracy of the duplicated casts between group IIand groupIII. From the above results,it is considered that the splinting method of impression copings could make an influence on the accuracy of the master casts.To improve the accuracy of the master casts, splinting the squared impression copings with the additional silicone occlusion materials is recommendable.

A Study on the Void Formation And Detail Reproduction According to The Various Impression Materials And Mixing Methods / 대한치과보철학회지

Void-free impression taking is important for the fabrication of accurate dental restorations.One of the essential properties of an impression material used for indirect fabrication of precision castings is the reproduction of the fine detail. The objective in this study was to determine the influence of mixing methods on the number of voids and surface detail reproduction.The number of voids and surface detail reproduction were evaluated with the stereomicroscope SZ-PT and photographed. The results were as follows; 1.In comparison of the void formation according to mixing methods of all impression materials,mechanical mixing was better than hand mixing and there was significant difference(P<0.05). 2.In comparison of the void formation according to hand mixing of alginate impression materials(TOKUSO A-1 alpha ,CAVEX IMPRESSIONAL ,AROMA FINE DF III), there was no significant difference among alginate groups.But the number of void was increased in the order of Panasil contact,TOKUSO A-1alpha , Permlastic light bodied and there was significant difference(P<0.05). 3.In comparison of the void formation according to mechanical mixing of alginate impression materials(TOKUSO A-1 alpha, CAVEX IMPRESSIONAL, AROMA FINE DF III), there was no significant different among alginate groups.But the number of void was decreased in order of TOKUSO A-1 alpha, Permlastic light bodied,Panasil contact and there was significant difference(P<0.05). 4.In comparison of the surface detail reproduction according to mixing methods of 3 types of impression materials(TOKUSO A-1 alpha, Permlastic light bodied,Panasil contact), there was no significant difference between hand mixing and mechanical mixing method 5.The surface detail reproduction was only influenced by impression materials,and produced better in order of TOKUSO A-1alpha, Panasil contact,Permlastic light bodied.There was significat difference among 3 type of impression materials(P<0.05). From the above results,void formation is influenced by mixing methods and surface detail reproduction is influenced by impression materials than mixing methods.Therefore,to fabricate accurate restorations,proper impression material and mechanical mixing method are more effective and available clinically.

Optical Effects Of Nonmetallic Post And Core Systems On All-Ceramic Crowns / 대한치과보철학회지

Recently as the esthetic concerns about dental prosthesis have been increased, the nonmetallic post and core systems have been introduced clinically to improve the color and the low optical transmittance of conventional casting metal post and core systems. The purpose of this study was to compare and analyze the optical transmittance and the shade changes of all-ceramic crowns with two nonmetallic post and core systems. The experimental groups were classified as follows: Total 27 specimens(9 samples in each group) were evaluated. Group I: Natural teeth as a control group. Group II: CosmoPost and Empress(R) core (Ivoclar-Vivadent, Liechtenstein). Group III: LIGHT-POST(TM) and LIGHT-CORE(TM)(Bisco, U.S.A.). In all groups, all-ceramic crowns were fabricated with the same shade of IPS Empress(R)II(Ivoclar-Vivadent, Liechtenstein) after abutment preparation, and then two kinds of spectrophotometers, UV 3101 PC(Shimadzu,Japan) and CM 503i(Minolta Co., Ltd., Japan), were used to measure the optical transmittance and the color value. The following results were obtained: 1. The optical transmittance of each group without all-ceramic crowns, was siginificantly decreased in order of Group III, I and II(p<0.05). 2. The optical transmittance of each group with all-ceramic crowns cemented, were siginificantly decreased in order of Group I, II and III(p<0.05). 3. In comparison with the shade of all-ceramic crowns, there were no significant differences between groups regardless of the cementation. 4. In comparison with the shade changes in each group after the cementation of all-ceramic crowns, there were no significant differences between groups. From the above results, it is thought that the selection among materials used in this study doesn't influence greatly the esthetic restoration, because the differences of optical transmittance were so small that those were clinically insignificant.

A STUDY THE SHADE CHANGE OF SEVERAL KINDS OF ALL CERAMIC CROWNS USED FOR METAL DOWEL CORE / 대한치과보철학회지

The purpose of this study is to compared and analyze the shade changes(deltaE)about In-Ceram(R),IPS-Empress(R),OPC(R) by using of the spectrophotometer arising from initial status and before and after cementation of the resin cement mounted on the metal core. We used a couple of statistics such as 'One-Way ANOVA'and Multiple Range Test. We could be able to verify significantly what is being discussed here up to 95%. The results drawn from our research are as follows: 1. At the time of our experiments regarding the initial shapes of all-ceramic and mounting status of all-ceramic on the metal crown(deltaE1), and a comparison of mounting of all ceramic on the metal crown with all-ceramic cemented on the metal core(deltaE2), at the time of shade change of initial shapes and after we cemented on the metal core. (1) no significant difference among all-ceramics was found. (2) no particular difference was found regarding the In-Ceram(R) (3) a significant difference between the deltaE1 and deltaE2 regarding the IPSS-Empress(R) was found (P<0.05). (4) a significant difference between the deltaE1 and deltaE2 regarding the OPC? was found (P<0.05). 2. When we compared the shade changes (deltaE) resulted from before and after the cementation on each of the parts involved of some all-ceramic . we could be able to find shape change increase from incisal third, middle third, and cervical third in that order in In-Cream(R)(spinell), IPS Empress(R) and OPC(R) all. In addition , we could be able to find a siginificant difference between cervical third and incisal third, middle third. (P<0.05) From what we have just seen, we might conclude that there is a significant shade change difference before and after the cementation with respect to IPS-Empress(R)and OPC(R). In addition, we could also be able to find more shade change difference at the cervical third rather than incisal third and middle third depending on the parts involved.

A STUDY ON THE EFFECT OF THERMOCYCLING TO THE PHYSICAL PROPERTIES OF DENTURE LINERS / 대한치과보철학회지

For the improvement of denture fitness of changed residual ridge, denture liner can be used. Denture liner should be very stable physically in various environments of the mouth as well as be bonded strongly with denture resin. In this study, the specimens bonded with four kinds of soft denture liner and three kinds of hard denture liner were used to test the physical properties of the liners. All experimental groups were stored in 37+/-1degrees C distilled water for 24hours, followed by thermocycling between 15degrees C and 45degrees C with 15 second dwell time. 1000, 2000, 3000 cycles of thermocycling were excuted and physical properties were measured by Instron Universal Testing Machine. The obtained results were as follows: 1. In tensile bond test of soft liners, it was shown that both of Molloplast-B(R) specimens before and after thermocycling had the highest tensile strength, and in case of hard liners, Dura-liner II(R)speimen had the highest tensile strength before and after thermocycling. Depending on thermocycling, Soft-Relining(R), Denture-Relining(R),Molloplast-B(R), Coe-soft(R) and Kooliner(R) specimen showed significant difference(p<0.05). 2. In strain test of soft liners, it was shown that Molloplast-B(R) specimen before thermocycling and the Coe-soft(R) after thermocycling showed highest results, and in case of hard liners, the Dura-Liner II(R) speimen before and after thermocycling had the highest result. Depending on thermocycling. Denture-Relinig(R). Molloplast-B(R) and Dura-Lner II(R) specimen showed significant difference(p<0.05). 3. In Maximum distance test of soft liners, the Molloplast-B(R) specimen before thermocycling and the Coe-soft(R) after thermocycling showed highest results, and in case of hard liners, the Dura-Liner II(R) specimen before and after thermocycling showed highest results. Depending on thermocycling, Denture-Relining(R), Molloplast-B(R) specimens showed significant difference(p<0.05). 4.In elasticity test of soft liners , the Molloplast-B(R) specimen before and after thermocycling showed highest results, and in case of hard liners, the Dura-Liner II(R) specimen before thermocycling and the Tokuso-Rebase (R) after thermocycling showed highest results. Depending on thermocycling, Soft-Relining(R) , Molloplast-B(R) specimens showed significant difference(p<0.05).

A Study On The Color Stability Of Porcelain For Porcelain Fused To Metal Crown / 대한치과보철학회지

Dental porcelain should have adequate strength and similar esthetics as natural teeth. Recently esthetics has become a high priority in clinical dentistry. Thus the evaluation of color stability of dental porcelain has become an important part in dental research. The purpose of this study was to evaluate the difference in color stability of 3 types of porcelain (Vintage, VMK 95, CERAMCO II). The porcelain were divided into groups by 2 types of treatment (Glazing or non-glazing and thermocycling or non-thermocycling). The porcelain wee dyed with methylene blue and distilled water, and then the color stability was evaluated with a spectrophotometer. The results were as follow ; 1. The color change of porcelain increased in the order of VMK 95, Vintage, CERAMCO II. But there was no significant difference. 2. The color change decreased in the glazing group compared to the non-glazing group(p<0.05). 3. The color change increased after thermocycling But there was no significant difference. 4. The color change according to dye method was significantly larger with methylene blue copared to distilled water(P<0.05).

A STUDY ON THE ACCURACY OF THE IMPRESSION BODY ACCORDING TO MATERIALS AND FORMS OF THE INDIVIDUAL TOOTH TRAY / 대한치과보철학회지

Accurate impression is very important to achieve desirable prosthesis and there are many factors in taking a good impression. For example, types of impression material, types of impression tray, impression taking methods and so on. Recently individual tooth tray technique is accepted as obtaining good impression that can be applied to multiple abutment impression, heavy salivated patient, to minimize the effect of natural teeth' s undercuts and to reduce pain during cord packing procedures. The purpose of this study was to compare the accuracy according to materials and forms of the individual tooth tray which is clinically applied nowadays. Used materials in experiment were divided into 3 types (acrylic resin, Futar' occlusion, Blu-mousse) and forms were divided into 2 types (forming occlusal vent hole or not and forming marginal vent space or not). Stone master model from impression body and metal master model were measured by X-PLAN360d to compare occlusal surface discrepancy and marginal discrepancy. The results were as follows 1. In comparison of occlusal surface discrepancy and marginal discrepancy according to materials, groups with three materials showed no statistical difference. 2. In comparison of occlusal surface discrepancy and marginal discrepancy according to occlusal vent hole, groups with occlusal vent hole showed significantly less marginal discrepancy than groups with no occlusal vent hole(p<0.05). 3. In comparison of occlusal surface discrepancy and marginal discrepancy according to 0.5mm marginal-vent-space, groups with no 0.5mm-marginal-vent-space showed significantly less mar ginal discrepancy than groups with 0.5mm-marginal-vent-space(p<0.05). In summary, these results suggest that individual tooth tray made of 3 types of materials with occlusal vent hole and individual tooth tray made of acrylic resin with no marginal vent space showed good accuracy of impression. In addition, individual tooth tray which is made of bite registration materials may be more useful because of advantage in facility and timesaving aspect of fabrication.

A STUDY ON THE ACCURACY OF THE IMPRESSION BODY ACCORDING TO MATERIALS AND FORMS OF THE INDIVIDUAL TOOTH TRAY / 대한치과보철학회지

Accurate impression is very important to achieve desirable prosthesis and there are many factors in taking a good impression. For example, types of impression material, types of impression tray, impression taking methods and so on. Recently individual tooth tray technique is accepted as obtaining good impression that can be applied to multiple abutment impression, heavy salivated patient, to minimize the effect of natural teeth' s undercuts and to reduce pain during cord packing procedures. The purpose of this study was to compare the accuracy according to materials and forms of the individual tooth tray which is clinically applied nowadays. Used materials in experiment were divided into 3 types (acrylic resin, Futar' occlusion, Blu-mousse) and forms were divided into 2 types (forming occlusal vent hole or not and forming marginal vent space or not). Stone master model from impression body and metal master model were measured by X-PLAN360d to compare occlusal surface discrepancy and marginal discrepancy. The results were as follows 1. In comparison of occlusal surface discrepancy and marginal discrepancy according to materials, groups with three materials showed no statistical difference. 2. In comparison of occlusal surface discrepancy and marginal discrepancy according to occlusal vent hole, groups with occlusal vent hole showed significantly less marginal discrepancy than groups with no occlusal vent hole(p<0.05). 3. In comparison of occlusal surface discrepancy and marginal discrepancy according to 0.5mm marginal-vent-space, groups with no 0.5mm-marginal-vent-space showed significantly less mar ginal discrepancy than groups with 0.5mm-marginal-vent-space(p<0.05). In summary, these results suggest that individual tooth tray made of 3 types of materials with occlusal vent hole and individual tooth tray made of acrylic resin with no marginal vent space showed good accuracy of impression. In addition, individual tooth tray which is made of bite registration materials may be more useful because of advantage in facility and timesaving aspect of fabrication.

A Study on the Accuracy of the record base of the Complete Denture to the Master Cast according to Kinds of Resin and Polymerization Method / 대한치과보철학회지

STATEMENT of THE PROBLEM: The record base in fabricating procedures of the complete denture, as a temporary form for reproducing denture base, is used to record upper and lower jaw relation and to align artificial teeth and try-in it in the mouth. The accuracy of jaw relation record is affected by the accuracy, stiffness and stability of the record base. So, the accuracy of record base is the most important requirements of jaw relation records. PURPOSE of STUDY: The purpose of this study was to evaluate the gap that occurred over the palatal area of a maxillary record base fabricated with autopolymerizing resin and light-curingresin. METHODS AND MATERIAL: The maxillary record bases were fabricated out of autopolymerizing resin that is used the most frequently in clinics and light-curing resin that attracts special attentionfor its several merits. The light-curing resin was made by two kinds of polymerization methods, which are one step curing method and multiple step curing method. All record bases were cut in certain positions of the master cast 1 hour and 1 day later after fabrication and the accuracy of the master cast was measured and analyzed with a microscope. RESULTS: A pattern of gap formation between the record base and the maxillary cast was observed in all specimens. According to kinds of resins, autopolymerizing resin was significantly more accurate than light-curing resin. There was no statistical difference according to time lapse, and in all three groups, the maximum discrepancy occurred at the posterior border in the midpalatal region. CONCLUSLON: The autopolymerizing resin is better than light-curing resin, and multiple step curing method is more accurate than one step curing method when using light-curing resin.

A Study On The Tensile Strength Between Metal Denture Base And Relining Materials / 대한치과보철학회지

Relining and rebasing are essential for long-term success and oral health in removable prosthodontics. Major features of failures between metal base and relining resins are adhesive failure due to lack of chemical bonding. The purpose of this study was to find a better metal primer and metal surface treatment method that enhance the bonding strength with relining resin materials. The surfaces of ticonium alloys were treated with 25micrometer sandblasting (Group A), stone wheel (Group B), stone wheel and EZ oxisor (Group C), 75micrometer sandblasting (Group D) and EZ oxisor application after 75micrometer sandblasting (Group E). They were subdivided into no primer application (Group I), MR bond application (Group II) and Metafast bonding liner (Group III). Then specimens were completed though being bonded with relining resins. The specimens were stored in 38degrees C water for 48 hours and tensile strength was measured using the universal testing machine. The results were as follows, 1. Primer application groups showed higher bond strength than no primer application group(p<0.05). 2. In comparison with primer application groups, MR bond group showed higher bond strength than Meta fast bonding liner application group(p<0.05). 3. In comparison with surface treatment methods. Bond strengths of group A and B were significantly different with group C, D, and E, and group C were significantly different with group D, and E in no primer application group(p<0.05). In primer application groups, group A, B, C were significantly different with group D and E(p<0.05). According to results of this study, Metal primer application and metal surface roughening were considered to be advantageous for relining of metal base dentures.

A STUDY ON THE EFFECT OF UV LIGHT ABSORBER ON THE COLOR CHANGE OF MAXILLOFACIAL SILICONE / 대한치과보철학회지

The color change of maxillofacial silicone has been attributed to certain environmental factors such as exposure to the UV component of natural sunlight, wetting and drying of the elastomer, and surface abrasion resulting from the application and removal of cosmetics. The purpose of this study was to evaluate the color change of maxillofacial silicone (Silastic MDX4-4210) according to type of pigment (cadmium yellow, titanium white, cosmetic red), and UV absorber application method after 200, 400, and 600 hours of 350nm UV light irradiation. The results were as follows. 1. According to type of pigments, after 200 hours cosmetic red showed significantly larger color change than cadmium yellow and titanium white, and after 400 and 600 hours color change significantly decreased in the order of cosmetic red, cadmium yellow, and titanium white (p<0.05). 2. In the cadmium yellow group, after 200 hours, the non-treatment group showed significantly larger color change, but after 400 and 600hours, color change significantly decreased in the order of non-treatment, surface application and mixed group (p<0.05). 3. In the titanium white group, there was no significant color change difference between the three groups after 200 and 400 hours, but after 600 hours, the mixed group showed significantly smaller color change than the non-treatment and surface application groups (p<0.05). 4. In the cosmetic red group, there was significant decrease in color change in the order non-treatment, surface application and mixed group (p<0.05). From the results above, the effect of UV light absorber differed according to the type of pigment, but mixing UV light aborber with maxillofacial silicone is thought to give superior resistance against UV light irradiation in the long run.

A STUDY ON ACCUARACY AND DIMENSIONAL STABILITY ACCORDING TO IMPRESSION METHODS / 대한치과보철학회지

Accurate reproduction of intraoral tissue is essential in the fabrication of fixed prosthesis. This selection of impression material and method is very important. In this study, vinyl polysiloxane type impression material Panasil was used. Three impression methods ; one-step technique, individual tray technique, and individual tooth tray technique using the vinyl polysiloxane type bite registration material Futar Occlusion, were used to take horizontal and vertical impression. Improved stone models were fabricated. The amount of occlusal surface discrepaneies, interabutment distance discrepancies, amount of marginal defect were evaluated with the X-PLAN360d and photoscanning. The results were as follows. 1. There was no significant difference in occlusal surface according to the directions and techniques of impression taking. 2. There was no significant difference in interabutment distance discrepancies according to the directions and techniques of impression taking 3. There was no significant difference in marginal discrepancies according to the direction of impression taking but there was significant difference between one-step technique and individual tray technique, individual tooth tray technique (P<0.05). Taken together, these results suggest that individual tray technique and individual tooth tray technique are more accurate for impression taking than one-step technique.

MARGINAL FIDELITY AND FRACTURE STRENGTH OF IN-CERAM CROWNS ACCORDING TO VARIOUS RESIN CEMENTS / 대한치과보철학회지

In-Ceram system is one of contemporary esthetic all ceramic restorations and has relatively high flexural strength. The purpose of this study was to evaluate the marginal fidelity according to type of resin cement and measuring position, and to evaluate fracture strength according to type of resin cement. In this study, twenty seven In-Ceram crowns were fabricated on the metal master die of prepared maxillary right central incisor and devided into three groups. All specimens were cemented with Panavia 21 (group PV), Super-bond (group SB) and Lute-it (group LI) on the metal master die. After cementation, specimens were measured marginal gap between the margin of the In-Ceram crown and the finishing line of metal master die by using a stereomicroscope (SZ-ST, Olympus, Japan). Marginal gaps were recorded at the labial, lingual, mesial and distal measuring points on the metal master die. For the mesurement of fracture strength, lingual surfaces of cemented specimens were loaded at a distance of 1mm from incisal edge by using the Autograph S-2000 (Shimadzu, Japan). The results of marginal fidelity and fracture strength were statistically analyzed with the SPSS version 8.0 programs. The results of this study were as follows: 1. In comparison of marginal fidelity according to the measuring points, there was no significant difference. 2. The marginal fidelity according to the type of resin cement was decreased in order of group LI (63.75micrometer), SB (77.78micrometer), PV (86.53micrometer), and there was significant difference between group LI and PV (p<0.05). 3. The fracture strength according to the type of resin cement was showed descending order of group LI (60.00kg/cm2), SB (56.80kg/cm2), PV (56.11kg/cm2), but there was no significant difference.