• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.3
• /
• pp.354-361
• /
• 2007

Statement of Problems. The precision of fit between the bearing surfaces of implant abutments and the prosthesis framework has been considered fundamental to implant prosthodontic protocol. Purpose. The study aimed to investigate the effect of laboratory procedure on the dimensional accuracy of cast implant bars. Material and methods Thirty implant bars were fabricated on a metal master model. The gap distances were measured at the right implant abutment replica-gold cylinder interface after casting procedure. The bar length data of precasting and postcasting state were collected and analyzed. Results. The mean gap distance found after casting was $106.3{\mu}m$ for buccal side, $122.1{\mu}m$ for distal side and $117.1{\mu}m$ for the lingual side. The mean bar length was $17964.7{\mu}m$ at precasting measurement, $17891.6{\mu}m$ at postcasting measurement. The mean change of bar length was $-73.1{\mu}m$. Conclusion. Even though the techniques used in this study strictly followed the guidelines established in the literature, the 30 cast implant bars evaluated all yielded gap distances that were beyond acceptable accuracy. There was a statistically significant difference between precasting and postcasting bar length (P<0.01). There was a decreasing tendency in bar length after casting procedure. It was necessary to correct this dimensional change from laboratory procedure by some corrective methods.

• The Journal of Korean Academy of Prosthodontics
• /
• v.33 no.3
• /
• pp.539-549
• /
• 1995

The purpose of this study was to determine the accuracy of 3 implant impression methods by using strain gauge. The models used for this study were partially edentulous mandibular acrylic resin casts Model A, with two abutment analogs in #46,47 extraction site, represented two implant parallel to to the adjacent natural tooth. Model B represent an anterior implant parallel to the adjacene natural tooth and a posterior implant exhibiting a 15-degree lingual inclination. Master framework were fabricated on the master model, and 3 strain gauges were attached to a master framwork to determine the passivity of fit of the framework to sample casts made by the three impression techniques. The master framework was attached to each sample cast with gold screws, which were tightened with the torque driver to ensure a consistent toque application of 10 Ncm. Universal Digital Measuring System UCAM-5BT was used for strain measuring. Impression techniques studid were : 1. unsplinted tapered impression coping, polyvinyl siloxane, stock tray 2. unsplinted squared impression coping, polyether, custom tray 3. squared impression coping splinted with Duralay resin, polyether, custom tray Through analysis on data from this study, the following conclusions were obtained. 1. There were no statistically significant differences between the mean strain recorded from the sample casts made with the tree impression. But only strain values of model A(parallel group) Y-axis was signifcantly differed between Technique 1 and 3(P<0.05). 2. There was no statistically significant difference between model A(parallel group) and model B(15-degree divergent group).

• The Journal of Advanced Prosthodontics
• /
• v.3 no.4
• /
• pp.177-185
• /
• 2011

PURPOSE. The aim of this study was to evaluate the effect of dimensional stability of splinting material on the accuracy of master casts. MATERIALS AND METHODS. A stainless steel metal model with 6 implants embedded was used as a master model. Implant level impressions were made after square impression copings were splinted using 5 different techniques as follows. (1) Splinted with autopolymerizing resin and sectioned, reconnected to compensate polymerization shrinkage before the impression procedure. (2) Splinted with autopolymerizing resin just before impression procedure. (3) Primary impression made with impression plaster and secondary impression were made over with polyether impression material. (4) Splinted with impression plaster. (5) Splinted with VPS bite registration material. From master model, 5 impressions and 5 experimental casts, total 25 casts were made for each of 5 splinting methods. The distortion values of each splinting methods were measured using coordinate measuring machine, capable of recordings in the x-, y-, z- axes. A one-way analysis of variance (ANOVA) at a confidence level of 95% was used to evaluate the data and Tukey's studentized range test was used to determine significant differences between the groups. RESULTS. Group 1 showed best accuracy followed by Group 3 & 4. Group 2 and 5 showed relatively larger distortion value than other groups. No significant difference was found between group 3, 4, 5 in x-axis, group 2, 3, 4 in y-axis and group 1, 3, 4, 5 in z-axis (P<.0001). CONCLUSION. Both Splinting impression copings with autopolymerizing resin following compensation of polymerization shrinkage and splinting method with impression plaster can enhance the accuracy of master cast and impression plaster can be used simple and effective splinting material for implant impression procedure.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.22 no.4
• /
• pp.317-328
• /
• 2006

Purpose: This study was performed to measure the accuracy of adjustable dental impression trays by a scanning laser three-dimensional digitizer. Materials and Methods: Metal stock tray and adjustable stock trays were used for 40 stone casts(10 casts each) duplicated a resin master model of mandible and maxilla. The type IV dental stone was poured in a allginate impressions and allowed to set for one hour. The casts were digitized using an optical digitizer. The distance between the reference points were measured and analyzed on the graphic image of 3-D graphic software (CATIA version 5.0). The statistical significance of the differences between the groups was determined by a two-way ANOVA. Results: There were no significant differences between the accuracies of the adjustable stock tray and the master model except anterior arch width of the upper arch and the diagonal arch length and arch length(one side) of the lower arch. Conclusion: The adjustable stock trays showed clinically acceptable accuracies of the study casts produced by them.

• Restorative Dentistry and Endodontics
• /
• v.16 no.2
• /
• pp.43-61
• /
• 1991

Present - day inlay casting procedures have been developed for more than 100 years and experimentation has focused on the perfect adaptation to the cavity preparation. Marginal adaptation is considered to be an important indicator of the acceptability of the cast restotration, especially on the gingival margin. The purpose of this study was to evaluate the effects of a dissecting microscope and burnishing on vertical discrepancies, horizontal discrepancies, and cement thicknesson master die. Extracted premolars were prepared for class II gold inlays and master dies were made with conventional techniques. The experiments consisted of 4 groups. Group 1 : unaided eye, no burnishing on master die. Group 2 : unaided eye, burnishing on master die. Group 3 : microscope, no burnishing on master die. Group 4 : microscope, burnishing on master die. Cemented inlays were embedded in the hard resin and sectioned with microcutter through the gingival margins. The sectioned surfaces were polished with emery paper and finally with aluminum oxide powders. The results of the experiments were measured for vertical discrepancies, horizontal discrepancied and cement thickness under the scanning electron microscpe at the beveled gingival margin. The results of the study were summarized as follows. 1. Group 1 showed the vertical discrepancies of $81.6{\mu}m({\pm}48.6{\mu}m)$, horizontal discrepancies of $60.1{\mu}m({\pm}41.1{\mu}m)$, and cement thickness of $59.6{\mu}m({\pm}24.6{\mu}m)$. 2. Group 2 showed the vertical discrepancies of $78.6{\mu}m({\pm}30.9{\mu}m)$, horizontal discrepancies of $36.9{\mu}m({\pm}20.7{\mu}m)$, and cement thickness of $54.0{\mu}m({\pm}21.6{\mu}m)$. 3. Group 3 showed the vertical discrepancies of $57.5{\mu}m({\pm}26.4{\mu}m)$, horizontal discrepancies of $28.4{\mu}m({\pm}17.5{\mu}m)$, and cement thickness of $37.2{\mu}m({\pm}17.4{\mu}m)$. 4. Group 4 showed the vertical discrepancies of $56.7{\mu}m({\pm}35.0{\mu}m)$, horizontal discrepancies of $31.8{\mu}m({\pm}24.2{\mu}m)$, and cement thickness of $45.6{\mu}m({\pm}19.8{\mu}m)$. 5. Vertical discrepancies were not significantly different at any groups(p>.050). 6. Microscope groups(Group 3, 4) showed significantly improved horizontal marginal adaptation (p<.050). 7. Although cement thickness showed the subset of Group 3. 4, 2 and Group 4, 2, 1. Group 3 showed significantly smaller thickness than Group l(p<.050). 8. Finishing and polishing by means of a microscope produced significantly smaller discrepancies than doing so with the unaided eye(p<.050).

• The Journal of Advanced Prosthodontics
• /
• v.13 no.6
• /
• pp.373-384
• /
• 2021

PURPOSE. This study aimed to compare the marginal and internal fit of 3-unit monolithic zirconia restorations that were designed by using the data obtained with the aid of intraoral and laboratory scanners. MATERIALS AND METHODS. For the fabrication of 3-unit monolithic zirconia restorations using impressions taken from the maxillary master cast, plaster cast was created and scanned in laboratory scanners (InEos X5 and D900L). The main cast was also scanned with different intraoral scanners (Omnicam [OMNI], Primescan [PS], Trios 3 [T3], Trios 4 [T4]) (n = 12 per group). Zirconia fixed partial dentures were virtually designed, produced from presintered block, and subsequently sintered. Marginal and internal discrepancy values (in ㎛) were measured by using silicone replica method under stereomicroscope. Data were statistically analyzed by using 1-way ANOVA and Kruskal Wallis tests (P<.05). RESULTS. In terms of marginal adaptation, the measurements on the canine tooth indicated better performance with intraoral scanners than those in laboratory scanners, but there was no difference among intraoral scanners (P<.05). In the premolar tooth, PS had the lowest marginal (86.9 ± 19.2 ㎛) and axial (92.4 ± 14.8 ㎛), and T4 had the lowest axio-occlusal (89.4 ± 15.6 ㎛) and occlusal (89.1 ± 13.9 ㎛) discrepancy value. In both canine and premolar teeth, the D900L was found to be the most marginally and internally inconsistent scanner. CONCLUSION. Within the limits of the study, marginal and internal discrepancy values were generally lower in intraoral scanners than in laboratory scanners. Marginal discrepancy values of scanners were clinically acceptable (< 120 ㎛), except D900L.

• The Journal of Korean Academy of Prosthodontics
• /
• v.26 no.1
• /
• pp.51-61
• /
• 1988

The recently introduced castable glass ceramics incorporate properties characteristic of natural teeth and they are regarded as an ideal material to restore lost tooth structure. The purpose of this study was to compare the marginal fit of castable ceramic crown with that of the metal-ceramic crown in the process of heat treatment. Two master dies for castable ceramic crowns and metal-ceramic crowns were fabricated from being cast with the base metal. Each master die was duplicated with addition silicone and hard stone. Ten castable ceramic crowns were made on each hard stone die and their marginal openings were measured three times first, after casting; second, after ceramming; third, after shading. The other ten metal-ceramic crowns were made on each hard stone die and their marginal openings were measured three times : first, after casting; second, after degassing; third, after porcelain veneering. Each crown was seated on its master die with the constant force delivered by loading jig. And then, marginal openings were measured on four locations by optical projector at X50 magnification. The results were as follows: 1. The mean marginal openings of castable ceramic crowns were $31.1{\pm}12.7{\mu}m$ after casting; $44.6{\pm}12.8{\mu}m$ after ceramming; $51.2{\pm}16.8{\mu}m$ after shading. 2. The mean marginal openings of the metal-ceramic crowns were $26.2{\pm}13.8{\mu}m$ after casting; $29.8{\pm}10.3{\mu}m$ after degassing; $38.0{\pm}14.5{\mu}m$ after porcelain veneering. 3. There was significant increase in the marginal opening of castable ceramic crowns after ceramming, while metal-ceramic crowns sho(wed significant increase after porcelain veneering (p<0.05). 4. Marginal fit of metal-ceramic crown was better than that of castable ceramic crown (p<0.01).

• The Journal of Korean Academy of Prosthodontics
• /
• v.32 no.3
• /
• pp.445-454
• /
• 1994

Osseointegrated implant prostheses are to provide normal function without compromising the unique interaction between the tissue and the implant. The essential requirement for the osseointegrated implant prostheses is passive fit of abutment. Therefore, the impression must be accurate and reproduciable since the resultant master cast precisely duplicates the clinical condition. The purpose of this study was to compare the accuracy of the master casts obtained from five impression techniques. Group 1 : To take impression with indirect technique and Impregum F. Group 2 : To take impression with unsplinted direct technique and Impregum F. Group 3 : To take impression with splinted direct technique and Impregum F. Group 4 : To take impression with unsplinted direct technique and Xanthano. Group 5 : To take impression with splinted dierct technique and Xanthano. The results were as follow : 1. In taking impression of Impregum F, there was no significant difference between to use of indirect technique and unsplinted direct technique.(p<0.05) 2. Unsplinted direct technique with Impregum F is less accurate than splinted direct technique with Impregum F or Xanthano and unsplinted direct technique with Xanthano.(p<0.05). 3. There was no significant difference between splinted direct technique with Impregum F and unsplinted direct technique with Xanthano.(p<0.05) 4. Splinted direct technique reproduce more accurate than unsplinted direct technique.(p<0.05) 5. Impression plaster produced less distortion than polyether.(p<0.05) As a result, splinted direct technique with Xanthano was the most accurate technique. As a result, splinted direct technique with Xanthano was the most accurate technique in this study. In addition to dimensinal changes in the materials used, positional errors were also attributed to the mechanical components used in the transfer porocess. Although the errors measured were relatively small, this study demonstrates the potential for distortions with the transfer technique used. Further study is indicated that ?the technique will be able to reproduce the intraoral relationship of implant fixtures reliably and predictably.

• Journal of Korea Foundry Society
• /
• v.12 no.4
• /
• pp.346-354
• /
• 1992

In Al-Pb monotectic alloys Pb particles are difficult to uniformly distribute over the Al matrix because of the gravity segregation of pb element. Therefore the effects of centrifugally spray casting process on microstructures and distributions of Pb particle were investigated. As the preform thickened the sine of Pb particle became larger, the amount of porosity became lower and microstructures showed the change from spray-deposition microstructures in the lower part of the preform to spray-casting microstructures in the upper part of it. The size of Pb particles, amount of porosity and splat layer boundaries in hot forged preform showed still less than of as-deposited preform.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.05a
• /
• pp.299-302
• /
• 2005

Semisolid A356 slurries were prepared by electromagnetic stirring casting and by inoculation of Al-5Ti-B master alloy. As stirring time and addition of Al-5Ti-B are different, the grain size of the primary phase is different. Through the experiment of rheocast in a Buhler horizontal die casting machine, it was found that the finer the equiaxed primary dendrites, the smoother the die filling and better cast quality. Small equiaxed primary dendrite also results in less liquid segregation on the surface.