Viscosity Of Impression Materials Research Articles

Addition Silicone Impressions in Fixed Prosthodontics: Clinical Standpoints.

Addition silicones have revolutionized the field of fixed prosthodontics because of their dimensional stability, sufficient tear strengthand excellent detail reproduction. This review study aims to provide a detailed description of the essential variables to be taken into account during the process of making addition silicone impressions in fixed prosthodontics. These variables include the selection of appropriate tray type, size, and fabrication; the use of tray adhesive; gingival displacement techniques; manipulation of the impression material; the choice of the impression material's viscosity; impression techniques; and the proper insertion, removal, disinfection, and pouring of the cast. Additionally, this review aims to help doctors produce high-quality impressions by empowering them to critically assess the impressions to spot mistakes and motivating them to redo impressions that have serious problems before submitting them to the laboratory.

Influence of Custom Trays, Dual-Arch Passive, Flexed Trays and Viscosities of Elastomeric Impression Materials on Working Dies.

Dual arch impression technique signifies an essential improvement in fixed prosthodontics and has numerous benefits over conventional impression techniques. The accuracy of working dies fabricated from dual arch impression technique remains in question because there is little information available in the literature. This study was conducted to compare the accuracy of working dies fabricated from impressions made from two different viscosities of impression materials using metal, plastic dual arch trays and custom made acrylic trays. The study samples were grouped into two groups based on the viscosity of impression material used i.e. Group I (monophase), whereas Group II consisted of Dual Mix technique using a combination of light and heavy body material. These were further divided into three subgroups A, B and C depending on the type of impression tray used (metal dual arch tray, plastic dual arch tray and custom made tray). Measurements of the master cast were made using profile projector. Descriptive statistics like mean, Standard Deviation (SD) were calculated for all the groups. One way analysis of variance (ANOVA) was used for multiple group comparisons. A p-value of 0.05 or less was considered statistically significant. The gypsum dies obtained with the three types of impression trays using two groups of impression materials were smaller than the master models in dimensions. The plastic dual arch trays produced dies which were the least accurate of the three groups. There was no significant difference in the die dimensions obtained using the two viscosities of impression materials.

The effect of tray selection and viscosity of impression materials on the accuracy of dies produced from dual arch impressions – An in-vitro study

Objectives :The aim of this in-vitro study was to compare the accuracy of dies generated from metal and plastic dual arch trays impressions using two different viscosities of polyvinyl siloxane impression material and comparing the results to that obtained using a conventional full arch custom impression technique. Materials and method: Seven set of impressions were made of an experiment model using different combinations of, dual arch trays and viscosities of impression materials and the dimensions of the dies thus obtained were compared with those obtained from conventional full arch custom arch tray and medium viscosity impression material. Results: The gypsum dies prepared, from the complete arch custom tray technique and the dual arch impression technique using plastic and metal dual arch trays were generally larger in bucco-lingual dimension and shorter in mesio-distal dimension. Conclusions: All the seven types of impression techniques produced clinically successful impressions of standard brass die and dies so developed were within clinical standards to produced clinically successful restorations.

Pontic site development and soft tissue transfer of the esthetic area: a case report

Soft tissue collapse around prepared teeth and pontic is inevitable after removal of the provisional restoration during the impression taking procedures. When inserting gingival retraction cord, soft tissue is displaced to an undesired contour. Viscosity of impression material also causes gingival displacement. Therefore, the consideration to transfer the prosthetically contoured soft tissue to master cast is required, especially in the esthetic area. In this report, the methods to maintain the soft tissue contour and transfer to the mastercast will be introduced. Harmonious contour of the soft tissue can be achieved with provisional restoration and be transferred to the master cast with two different techniques mentioned in this case report. (J Korean Acad Prosthodont 2013;51:323-31)

The effect of tray selection, viscosity of impression material, and sequence of pour on the accuracy of dies made from dual-arch impressions

Statement of problem Dual-arch trays are often used to generate impressions of prepared teeth and of the opposing arch simultaneously. There is concern that accuracy of the casts generated with this technique can be affected by the type of tray, viscosity of the impression material, and sequence of pouring the cast. Purpose This study compared the accuracy of working dies made from impressions with metal and plastic dual-arch trays, for 2 different viscosities of impression tray material and by altering which side of the impression was poured first. Material and methods Impressions were made of a typodont mandibular arch containing a circular stainless steel crown preparation (standard). There were 3 variables: type of dual-arch tray, impression material viscosity, and order of pour of the impressioned arches. A balanced design with independent samples was used (n=10). Two types of dual-arch trays, plastic (Triple Tray) and metal (COE Impression Tray), and 2 viscosities of addition silicone for the tray were used (Aquasil Rigid and Aquasil Monophase). Type IV gypsum (Fuji-Rock) with a ratio of 20 mL of distilled water to 100 g of powder was hand-mixed for 10 seconds then mixed under vacuum for 40 seconds and poured into the trays while being vibrated. One side of the dual-arch impression was poured with 35 g of stone and allowed to set for 1 hour before the other side was poured with 35 g of stone. The order of pour was randomized, and all casts were allowed to set for 24 hours at room temperature before removal. The dies were measured in 3 dimensions (buccolingual, mesiodistal, and occlusogingival) with a measuring microscope. The gypsum working dies were placed into a custom jig fabricated to permit measurement at a fixed, reproducible position under the microscope. Each dimension of the working dies was measured 3 times, and the mean was used for the sample value. The same 3 aspects of the stainless steel standard were measured multiple times, before and then at the conclusion of measuring all working dies, to arrive at the 3 standard values to which all working die means were compared. The means for the standard used in the statistical analysis were those taken at the conclusion of the study. The intraexaminer variation for measuring the standard was 0.001 mm. A 3-factor analysis of variance was used for the statistical analysis with hypothesis testing at α=.05. Results Statistically significant differences were found with viscosity selection for the buccolingual and occlusogingival dimensions of the working die. The rigid material produced working dies slightly taller (1 μm) than the standard, and those from the monophase material were 4 μm shorter. Regarding tray selection, metal trays were slightly more accurate in the mesiodistal dimension, and when monophase was used in a plastic tray, gypsum dies were nearly 30 μm smaller in the mesiodistal dimension ( P<.05). Differences were not detected for sequence of pouring impressions. Conclusion Within the limitations of this study, the monophase material, when compared with the rigid impression material, was most accurate for the occlusogingival and mesiodistal dimensions, although not as accurate in the buccolingual. This buccolingual difference (0.002 mm-0.006 mm) would be clinically inconsequential with the application of die spacer. The rigid impression material was also unaffected by tray selection for the mesiodistal, whereas monophase was affected. When a monophase impression material was used, plastic dual-arch trays yielded gypsum dies which were significantly smaller (0.029 mm) than the ones generated from the metal trays (0.006 mm). Thus rigid impression materials can be recommended for use in dual-arch trays; however, the magnitude of the differences would generally not be clinically significant because they could be compensated for with several coats of die spacer.

A clinical pilot study of the dimensional accuracy of double-arch and complete-arch impressions

Statement of Problem. It has been suggested that articulated casts fabricated with the double-arch impression technique may have superior occlusal accuracy than those fabricated with a single complete-arch impression. However, lack of tray rigidity may lead to flexure of the impression/tray complex, resulting in inaccurate dies in the bucco-lingual dimension. Purpose. This clinical pilot study compared the dimensions of dies fabricated with 3 types of double-arch impressions to dies fabricated with the conventional complete-arch, custom tray method. Material and Methods. Thirty-five addition silicone impressions were made of cast metal copings cemented onto natural teeth prepared as complete-crown abutments. Four combinations of tray types and impression material viscosity were used: (1) complete-arch, custom acrylic trays loaded with heavy-bodied material; (2) double-arch, disposable plastic trays loaded with heavy-bodied material; (3) double-arch, disposable plastic trays loaded with putty material; and (4) double-arch, reusable brass metal trays loaded with heavy-bodied material. Immediately prior to tray insertion, light-bodied impression material was syringed over all copings as a wash. The 4 copings were fabricated from cast gold and simulated metal-ceramic complete-crown thimbles with polished collars and had “projections” on the occlusal surfaces. The impressions were poured in type IV die-stone. Bucco-lingual and inter-abutment dimensions were measured. The differences between the stone dimensions and cast metal control dimensions were calculated and converted to percent dimensional change. The data were analyzed with 1-way analysis of variance, Student t tests, and Mann-Whitney tests (P<.05). Results. The plastic double-arch tray loaded with heavy-viscosity addition silicone and a low-viscosity wash produced the least accurate combination inter- and intra-abutment dimensions. For this protocol, 1.17% mean dimensional change was recorded. This result was significantly different than that obtained for the other 3 impression methods tested. No significant differences were found between the complete-arch method and protocols in which putty was loaded in a plastic or metal tray. Conclusion. Within the limitations of this pilot study, the more rigid tray/impression material combinations more accurately replicated stone dies. (J Prosthet Dent 2002;87:510-5.)

Measurement of internal voids in impression material using a digital image analyzer. Part 2. Influence of the difference of impression material and mixing method on internal voids

We investigated the measurement system of internal voids in impression material using a digital image analyzer explained in previous paper.In this paper, we investigated the influence of the difference of impression material and mixing method on internal voids.Nine impression materials were used to evaluate internal voids. They were mixed and injected into a cylindrical plastic ring. After setting, disk specimens were made by cutting them into a same thickness. Area and the number of internal voids that emerged on the surface of specimen were measured.Quantitative measurement of fine internal voids was made possible by using the digital image analyzer. Each impression material had a large number of internal voids which were less than 0.025mm2. In hand mixing, there were significant differences among impression materials with regard to the area and number of internal voids. Alginate impression material had the maximum value and medium-viscosity polyvinyl silycone elastomer had minimum value. Viscosity of impression material was correlated with the distribution of internal voids. In mechanical mixing, the number of internal voids increased slightly and the area decreased significantly in comparison with hand mixing. Using a syringe caused internal voids even in a void-free impression material. Internal voids were produced by mixing more than by the syringe.

Effect of viscosity on the accuracy and stability of elastic impression material.

A ram and cylinder penetrometer was designed to measure the viscosity of impression materials at their time of placement. Viscosity had no effect on accuracy or stability of the impression materials within the viscosity ranges studied.