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At least 145 records · Page 8Linked to original sources
PubMed1991

Properties of the tray adhesive of an addition polymerizing silicone to impression tray materials.

Adhesive bond strength studies for the tray adhesive of an addition vinyl polysiloxane (President) impression material were conducted with an acrylic resin, chromium-plated brass, and plastic trays. Tensile and shear stress studies were performed on the Instron Universal testing machine. Acrylic resin specimens roughened with 80-grit silicon carbide paper exhibited appreciably higher bond strengths compared with different types of tray material and methods of surface preparation.

Acrylic Resins↗
PubMed1992

The bond strength of elastomer tray adhesives to thermoplastic and acrylic resin tray materials.

This study evaluated the bond strength of selected impression materials (Permlastic, Express, and Hydrosil) to a thermoplastic custom tray material as a function of drying time of the adhesive after application to a tray material. In addition, bond strengths of a polysulfide impression material to an acrylic resin tray material and to a thermoplastic tray material made directly against wax were evaluated. Bond strengths were obtained directly from values of applied load at failure and important conclusions were drawn.

Acrylic Resins↗
PubMed1991

Effects of strain rate on the behavior of elastomeric impression.

The effects of strain rate on the ultimate tensile strength, ultimate elongation at fracture, and elastic recovery of five commonly used elastomeric dental impression materials were studied. Each specimen was prepared by standard mixing techniques, placed for setting in a standard ASTM mold, removed, trimmed, and mounted in an Instron testing unit. Tensile load was applied and plotted on a load versus displacement curve as the specimen was stretched axially until rupture. Five specimens of each material were tested, respectively, at strain rates of 100, 200, and 500 mm/min crosshead speed. Specimens were then removed, reassembled, and measured with an electronic caliper to assess the elastic recovery; measurements were repeated after 1 minute, 30 minutes, 1 hour, and 24 hours. Findings of this study indicated that (1) polysulfide materials exhibited the greatest amount of deformation, and the lowest tensile strengths of the materials studied; (2) higher tensile strengths were observed with higher strain rates; and (3) polysulfide materials showed the greatest amount of elongation at rupture, with the highest values occurring at the higher strain rates.

Analysis of Variance↗
PubMed1992

Dimensional stability of condensation silicone rubbers.

The linear shrinkage during 24 h after setting of a number of proprietary condensation silicone dental impression materials was studied. Weight loss and change in volume were measured over the same time period by weighing similar specimens in air and water. The weight-loss data conformed to a linear t1/2 plot, indicating that the loss of volatile material was diffusion controlled. From the diffusion coefficient so determined, linear shrinkage values predicted from the weight loss data were compared with the experimental results. For all except the highly-filled putty materials, the correspondence between theoretical and experimental data was reasonable; in the case of the putty materials, the shrinkage was very much greater than that predicted theoretically. This is possibly due to elastic memory effects consequent on moulding the putty materials.

Biocompatible Materials↗
PubMed2000

An in vitro comparison of 5 techniques for impressing dowel space preparations.

PURPOSE: This in vitro study compared 5 different dowel space impression techniques using polyvinyl siloxane impression material to determine which method produced fewer voids in the dowel space impression. MATERIALS AND METHODS: Five techniques were used to make impressions of a prepared dowel space in a simulated endodontically treated tooth. Technique I used a 25-gauge anesthetic needle to act as a vent at the apex of the preparation to reduce voids produced during the expression of light body impression material. The anesthetic needle was removed after the impression material was injected, and an impression post was then inserted to the depth of the preparation. Twenty impressions made using this technique were compared with other techniques that used the vent without a post, no vent with a post, no vent without a post, and a lentulo spiral with a post (Techniques II through V, respectively). The percentage of impressions with voids from each group was compared to determine which technique consistently produced a void-free impression of the complete preparation length. If voids were observed in the impression, the specimen was considered inadequate. RESULTS: The percents of void-free impressions using Techniques I through V were 100%, 70%, 40%, 60%, and 20%, respectively. CONCLUSIONS: Using a 25-gauge needle as a vent while expressing impression material into the dowel space followed by placing the impression post consistently produced void-free dowel space impressions.

Dental Impression Materials↗
PubMed2000

Effect of 3 medicaments on the dimensional accuracy and surface detail reproduction of polyvinyl siloxane impressions.

OBJECTIVE: The purpose of this study was to determine the effect of retraction cord medicaments (aluminum chloride, ferric sulfate, and ferric subsulfate/ferric sulfate) on the dimensional accuracy and surface detail reproduction of polyvinyl siloxane impressions. METHOD AND MATERIALS: Polyvinyl siloxane impressions were made of standardized metal dies (American Dental Association [ADA] specification No. 19) treated with 1 of the 3 retraction cord medicaments. Dimensional accuracy was evaluated by comparing the average length of a line in the impressions to the standard die. Surface detail reproduction was evaluated by viewing the impressions under low-angle illumination at x10 magnification. Reproduction was considered satisfactory if 2 of 3 horizontal lines were reproduced continuously. The dies were also evaluated under the microscope before the impression was made. RESULTS: The medicaments did not significantly effect the dimensional accuracy; mean shrinkage was within ADA guidelines in the treatment groups. All of the medicaments had an adverse effect on surface detail reproduction. These effects were statistically significant compared to the untreated control. CONCLUSION: Although the changes in dimensional accuracy were within ADA guidelines, the surface detail reproduction was modified such that the impression would be considered clinically unacceptable. For optimal results, care must taken to remove all traces of these retraction cord medicaments prior to recording of a polyvinyl siloxane impression.

Aluminum Chloride↗
PubMed1994

Custom impression trays. Part II: Removal forces.

When choosing a material for making custom impression trays, it is important to understand the forces to which the tray will be subjected during removal of the completed impression from the oral cavity. Such forces have not been recorded in the dental literature. The purpose of Part II of this three-part series was to record these forces in vitro, using two different tray-removal methods. A polymethyl methacrylate custom tray was used during this study. Results from this investigation indicated that it is easier to remove a completed impression, made with a custom tray, by a single point of anterior force application (224 N) than by force application evenly around the tray (514 N). The recorded force values from this investigation will be used in Part III of this series.

Acrylic Resins↗
PubMed1991

The accuracy of polyvinyl siloxane impressions made with standard and reinforced stock trays.

A laboratory investigation was done to assess the influence of proprietary stock trays on the accuracy of impressions recorded with heavy light-body (HL) and putty light-body (PL) wash impression techniques. Two brands of trays were tested and the same trays were reinforced with acrylic resin. Individual die accuracy and overall distortion of the resultant casts were assessed. PL impressions in both stock trays gave undersized buccolingual dimensions at the preparation finishing lines whereas reinforcing the trays reduced this distortion. Significant inaccuracy at the second molar was found for all trays when PL impressions were made. These distortions would have resulted in clinically unacceptable dies. HL impressions, regardless of tray type, produced highly accurate dies at this critical site. Resultant overall cast distortion was reduced, but not eliminated, by using reinforced trays with either PL or HL techniques.

Acrylic Resins↗
PubMed2002

A study on the adhesion of restorative materials to irreversible hydrocolloid impression materials.

AIM: The purpose of this study was to evaluate the adhesion of restorative materials to irreversible hydrocolloid impression materials. MATERIALS AND METHODS: Three irreversible hydrocolloid impression materials were tested with four restorative materials: a base metal alloy, an amalgam, an autopolymerising resin composite and a heat polymerising resin. Samples were prepared with and without a collar. Half of the samples were cleaned with methanol by wiping. The other half were not methanol-wiped. All the samples were submerged into the impression materials and were subsequently placed in an impression- holding device in two different positions. A pullout test using a Hounsfield machine was used after the impression materials were set. RESULTS: Variance analysis was used in comparing the results obtained. Statistically, the four restorative materials showed different values regarding the adherence of the impressions materials to them (composite resin 52.47N, metal 26.36N). Samples with adherence to a collar were found to be more retentive than those without a collar. Samples with impression materials with a full collar were more retentive than those without a collar, and the samples cleaned with methanol were again less retentive than those which were not methanol wiped. CONCLUSION: The results of this study show that adhesion may be seen between restorative materials and irreversible hydrocolloid impression materials, and this adhesion may affect the accuracy of the impression.

Alginates↗
PubMed1995

Bond strength of two nonaqueous elastomeric impression materials bonded to two thermoplastic resin tray materials.

Investigations indicate that custom impression trays enhance the accuracy of the fabrication cast. Multiple materials and techniques exist for custom tray fabrication, and variability in the bonding strength of adhesive agents supplied with nonaqueous elastomeric material have been reported. Bonding between two nonaqueous impression materials and two thermoplastic resin tray materials was assessed in this study. Standard tensile specimens were fabricated and the combinations of Hydrotray resin (smooth) with Hydrosil impression material recorded the greatest bonding strength, 797 kPa. Adhesion to resin tray materials was found to vary with material type and surface preparation.

Adhesiveness↗
PubMed1991

Adhesive properties of several impression material systems: Part II.

The effect of saliva contamination on the tensile adhesive bond strengths of four impression adhesive systems, (1) polysulfide, (2) polyether, (3) polyvinylsiloxane, and (4) condensation silicone impression adhesive, was studied. Standard acrylic resin tray samples of 1-inch square surface were made. Tray surfaces were contaminated with saliva either before or after the application of tray adhesives. Tensile tests were performed with a Universal Load testing machine. The tensile adhesive bond strengths of contaminated tray surface and contaminated adhesive were compared with a group of control. Contamination of all impression adhesives resulted in significantly lower bond strength. Except for the polyvinylsiloxane and polysulfide impression adhesive systems, saliva contamination of tray material significantly decreased adhesive bond strengths. Impression trays should be tried in the mouth, rinsed, and dried before adhesive is applied.

Adhesiveness↗
PubMed1989

[The influence of disinfectants on colloidal impression materials and dental stones].

In view of prophylaxis against hospital infections, following tests were performed: Two kinds of alginate impression materials (ALGIACE and Aligix-S) and two kinds of agar impression materials (CARTRIILLOID and RUBBERLLOID) were immersed for 30 minutes in the following six kinds of disinfectants; 0.1% benzethonium chloride (benzethonium), 1% chlorhexidine gluconate (hexidine), 1% chlorhexidine gluconate added with surfactants (hexidine surfactant), 1% sodium hypochlorite (hypochlorous acid), 2% glutaraldehyde (glutaral) and 1% formaldehyde (formalin). Changes in size of the impression materials with time were then measured. Three kinds of dental stones (SHIMOMURA DENTAL PLASTER, NEW PLASTONE and SURSTONE) were infused into the impression surfaces after treatment with disinfectants, and the surface roughness and hardness of the yielded surfaces of the samples were measured. The results obtained are as follows: 1) As to ALGIACE, although the rates of changes in size lay within the range of +/- 0.3% when immersed in hexidine, hexidine surfactant and hypochlorous acid, the infusion of either one of SHIMOMURA DENTAL PLASTER, NEW PLASTONE or SURSTONE into the impression showed an effect on the stone surface. 2) As to Algix-S, the rate of changes in size lay within the range of +/- 0.3% when immersed in all the disinfectants, and the influsions of NEW PLASTONE and SURSTONE after immersing in benzethonium, hexidine surfactant and glutaral gave a slight effect on the stone surface. 3) As to CARTRILLOID, the rates of change in size lay within the range of +/- 0.3% except for the immersion in hexidine; the influsion of SHIMOMURA DENTAL PLASTER into the impression, the influsion of NEW PLASTONE after immersing in benzethonium and formalin and the influsions of NEW PLASTONE and SURSTONE after immersing in glutaral gave a slight effect on teh stone surface. 4) As to RUBBERLLOID, the rates of changes in size lay within the range of +/- 0.2% when immersed each disinfectant; the influsion of SHIMOMURA DENTAL PLASTER after immersing in hypochlorous acid and that of either one of SHIMOMURA DENTAL PLASTER, NEW PLASTONE or SURSTONE after immersing in benzethonium, glutaral and formalin gave a slight effect on the stone surface.

Calcium Sulfate↗