• Elastomers and Composites
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• v.44 no.2
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• pp.150-155
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• 2009

This study examined the effects of the concentration variation of the silyl hydride (Si-H) functional group in polymethylhydrogen siloxane cross-linker and the vinyl-functional group in silicone prepolymer on the physical properties of the dental polyvinylsiloxane impression materials (PVS). When the SiH/Vinyl ratio was 1.6 (Group $\underline{C6}$ containing ${\underline{C}}ross$-linker $\underline{6}$ parts), the setting rate was too slow even though their tensile strength was the highest within the tested groups. When the SiH/Vinyl ratio was 3.2 (Group C12), the setting rate was too fast to allow appropriate working time even though their mechanical properties were good. The C14 group showed rather lower tensile strength compared to the groups having lower cross-linker contents. Notably, too much incorporation of cross-linker, like C16 group, induced delay of the setting, by which the mechanical and manipulation properties were detrimentally affected.

• Elastomers and Composites
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• v.44 no.1
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• pp.76-83
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• 2009

The purpose of this study was to investigate the effects of combined use of several types of silicone polymers on the physical properties of the dental polyvinylsiloxane impression materials (PVS). Four types of silicone prepolymers having different molecular weight and vinyl group position, and two types of cross-linkers having differently located silyl hydride functional groups were used in various combinations for the formulation. The samples containing bimodal or trimodal prepolymers showed higher tensile strength, elongation at break, and elastic deformation than those containing only one type of prepolymer. The samples using CR210 cross-linker which has side- and terminal-silyl hydride groups showed higher elastic deformation and elongation at break than those using CR101 cross-liker which has side-only silyl hydride group. High vinyl content prepolymer having side vinyl group delayed setting even though it enhanced tensile strength. Further studies are needed to clarify the specific role of this component on setting time and to find appropriate controlling methods for making improved PVS with optimum workability.

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

• Journal of Technologic Dentistry
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• v.42 no.1
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• pp.27-33
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• 2020

Purpose: This study is to compare and analyze the precision of glass fiber resin dentures. Methods: A lower edentulous model was prepared. Ten study models were produced using Type IV stone. Ten wax lower resin dentures containing artificial teeth were prepared. The lower wax denture was buried with plaster and deflasking was performed to remove the wax. Five conventional lower resin dentures and five glass fiber lower resin dentures were produced. The scanning spray was coated on the impression surface and then scanned. Independent sample t-test were performed using statistical software. Results: In the color different map, which is a qualitative evaluation, the green area of the precision of the conventional lower resin denture occupied the whole. The glass fiber conventional resin dentures had many negative and positive area. In quantitative evaluation, the RMS of conventional lower resin was 89.83 ㎛ and that of fiberglass resin was 224.92 ㎛. The two groups showed statistically significant differences (p<0.05). Conclusion: Conventional lower resin dentures were superior in precision, and glass fiber resin dentures would have to improve the process.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.2
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• pp.55-63
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• 2019

The aim of this article was to review various methods used to evaluate the accuracy of digital dental models. When evaluating the accuracy of digital models, the errors can be reduced by educating examiners and using artificial landmarks. The accuracy evaluation methods of digital dental models are divided into linear measurement, 2-dimensional cross-sectional analysis, and 3-dimensional best fit measurement. As the technology of scanners develops, many studies have been conducted to compare the accuracy of digital impression and conventional impression. According to improvement of scan technologies and development of 3-dimensional model analysis software, the ability to evaluate the accuracy of digital models is becoming more efficient. In this article, we describe the methods for evaluating the accuracy of a digital model and investigate effective accuracy analysis methods for each situation.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.2
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• pp.207-218
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• 1993

The purpose of this study was to evaluate the reproducing accuracy of stone casts made from complete arch impressions using different impression materials. The impression materials studied were 1) polyether, 2) polysulfide, 3) polyvinyl siloxane, and 4) irreversible hydrocolloid. Impressions were made from a partially edentulous acrylic resin model with metal inserts in canine, first molar region bilaterally and mid palatal vault region. Each distance between 2 out of 5 meauring points was measured by using 3dimensional measuring machine. Impressions were poured at once with a type IV dental stone. Data were analyzed using t-test with a sample size of six. The results were as follow : 1. Polysulfide and polyether were significantly superior to polyvinyl siloxane and irreversible hydrocolloid in reproducing full arch model(p<0.05), but there were no statistical differences in amount of dimensional reproducing accuracy for full arch impression between polysulfide and polyether(p>0.05). 2. There were statistical differences in amount of dimensional reproducing accuracy between edentulous area and tooth bound area for polysulfide and polyether(p<0.05). but no statistical differences were observed for polyvinyl siloxane and irreversible hydrocolloid(p>0.05).

• The Journal of Advanced Prosthodontics
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• v.14 no.4
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• pp.236-249
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• 2022

PURPOSE. The present study compared the accuracy between digital and conventional implant impressions. MATERIALS AND METHODS. The experimental models were divided into six groups depending on the implant location and the scanning span. Digital impressions were captured using the intraoral optical scanner TRIOS (3Shape, Copenhagen, Denmark). Conventional impressions were taken with the monophase impression material based on addition-cured silicones, Honigum-Mono (DMG, Hamburg, Germany). A high-precision laboratory scanner D900 (3Shape, Copenhagen, Denmark) was used to obtain digital data of resin models and stone casts. Surface tessellation language (STL) datasets from scanner were imported into the analysis software Geomagic Qualify 14 (3D Systems, Rock Hill, SC, USA), and scan body deviations were determined through two-dimensional and three-dimensional analyses. Each scan body was measured five times. The Sidak t test was used to analyze the experimental data. RESULTS. Implant position and scanning distance affected the impression accuracy. For a unilateral arch implant and the mandible models with two implants, no significant difference was observed in the accuracy between the digital and conventional implant impressions on scan bodies; however, the corresponding differences for trans-arch implants and mandible with six implants were extremely significant (P<.001). CONCLUSION. For short-span scanning, the accuracy of digital and conventional implant impressions did not differ significantly. For long-span scanning, the precision of digital impressions was significantly inferior to that of the traditional impressions.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.1
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• pp.117-123
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• 2011

Impression taking procedure is very important for support, retention and stability of denture, and it affects the success of denture in completely edentulous patients. Various materials and methods have been used for impression taking in complete denture, while dynamic impression method is more physiological and functional method than the others. We had satisfying results with fabrication and relining of dentures after taking impression in the most physiological condition with recovery of deformed soft tissue by dynamic impression method using Coe-comfort$^{(R)}$ (GC America, IL, USA), tissue conditioner, in edentulous patients in this case report.

• The Journal of Advanced Prosthodontics
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• v.11 no.5
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• pp.262-270
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• 2019

PURPOSE. The purpose of this in vitro study was to evaluate the marginal misfits of three-unit frameworks fabricated with conventional and digital impressions techniques. MATERIALS AND METHODS. Thirty brass canine and second premolar abutment preparations were fabricated by using a computer numerical control machine and were randomly divided into 3 groups (n=10) as follows: conventional impression group (Group Ci), Cerec Omnicam (Group Cdi), and 3shape TRIOS-3 (Group Tdi) digital impression groups. The laser-sintered metal frameworks were designed and fabricated with conventional and digital impressions. The marginal adaptation was assessed with a stereomicroscope at ${\times}30$ magnification. The data were analyzed with 1-way analysis of variances (ANOVAs) and the independent simple t tests. RESULTS. A statistically significant difference was found between the frameworks fabricated by conventional methods and those fabricated by digital impression methods. Multiple comparison results revealed that the frameworks in Group Ci (average, $98.8{\pm}16.43{\mu}m$; canine, $93.59{\pm}16.82{\mu}m$; premolar, $104.10{\pm}15.02{\mu}m$) had larger marginal misfit values than those in Group Cdi (average, $63.78{\pm}14.05{\mu}m$; canine, $62.73{\pm}13.71{\mu}m$; premolar, $64.84{\pm}15.06{\mu}m$) and Group Tdi (average, $65.14{\pm}18.05{\mu}m$; canine, $70.64{\pm}19.02{\mu}m$; premolar, $59.64{\pm}16.10{\mu}m$) (P=.000 for average; P=.001 for canine; P<.001 for premolar). No statistical difference was found between the marginal misfits of canine and premolar abutment teeth within the same groups (P>.05). CONCLUSION. The three-unit frameworks fabricated with digital impression techniques showed better marginal fit compared to conventional impression techniques. All marginal misfit values were clinically acceptable.

• The Journal of Advanced Prosthodontics
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• v.11 no.3
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• pp.155-161
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• 2019

PURPOSE. Although dental impression disinfection is determinant to reduce the cross-infection risk, some studies have shown that, in real practice, the disinfection procedures vary considerably. Thus, the aim of this study was to evaluate the antimicrobial effectiveness and the impact on the dimensional stability of addition silicone' impressions of water wash and the most clinically used disinfection solutions: 3% hydrogen peroxide, commercial disinfectant MD520 (Durr) and 1% and 5.25% sodium hypochlorite. MATERIALS AND METHODS. For this investigation, dental impressions were taken on 16 volunteer dental students. The antimicrobial effectiveness of each procedure was evaluated by pour plate method. The dimensional stability was evaluated using a standardized stainless-steel model, according to ANSI/ADA nº19 specification. RESULTS. The study results showed that water wash does not alter the dimensional stability of addition silicone impressions but doesn't reduce the microbial load of the material (P>.05). On the other hand, addition silicone disinfection by immersion with 3% hydrogen peroxide, MD520 (Durr), or sodium hypochlorite at 1% and 5.25% does not alter the dimensional stability significantly but reduces > 99.9% of the microbial load of the impressions (P<.001). CONCLUSION. Addition silicone impressions should always be disinfected after water wash in order to reduce effectively the cross-infection risk. All disinfectants tested showed high antimicrobial efficiency without significant changes in three-dimensional shape of impressions. Hydrogen peroxide and sodium hypochlorite are of particular importance because are easily accessible in dental setting. The less explored hydrogen peroxide could be a valuable alternative for silicone impressions disinfection.