Vinyl Polysiloxane Impression Materials: A Status Report

The Effect of Usage of Antiasthmatic Inhalers on Color Stability and Surface Roughness of Dental Restorative Materials: An In Vitro Study

OBJECTIVES

 Increased demand for esthetics by parents and children has resulted in the use of tooth-colored restorative materials. Children with chronic respiratory conditions like asthma use inhalers which have shown to affect the surface of restorative materials. Hence, the aim of the present study was to evaluate the effect of antiasthmatic inhalers on color stability and surface roughness of three restorative materials.

MATERIALS AND METHODS

 Forty samples each of three dental restorative materials: group A: glass ionomer cement (GIC), group B: alkasite restorative material, and group C: composite resins were prepared. Each group was further divided into two subgroups of 20 samples each according to the inhaler used. All the specimens were polished using polishing discs and stored in artificial saliva in order to simulate the oral environment. The baseline color value and surface roughness of all the samples were measured using a spectrophotometer and a profilometer, respectively. Group 1 and group 2 were exposed to 0.31 mg of salbutamol sulfate and 20 mg formoterol fumarate in combination with budesonide, respectively, for every 12 hours, for a period of 15 days following which the samples were evaluated for color changes and surface roughness.

STATISTICAL ANALYSIS

 The data obtained was subjected to statistical analysis and level of significance was set at p < 0.05.

RESULTS

 Exposure to both the inhalers caused a change in color and surface roughness in all three restorative materials. There was a significant change in the color of GIC and composite resin (ΔE > 3.3), following exposure to both the inhalers (p < 0.05). The change in color of alkasite restorative material was not significant. A significant increase in the surface roughness of composite resin from 0.56 ± 0.14 to 0.67 ± 0.19 was seen following 15 days' exposure to formoterol in combination with budesonide inhaler (p < 0.05).

CONCLUSION

 Following exposure, both the inhalers had an equal effect on color and surface roughness of all three restorative materials. Alkasite restorative material showed greater resistance to change in color and surface roughness when exposed to antiasthmatic inhalers, compared to GIC and composite resin. Thus, children who use inhalers and nebulizers should be advised to implement more precautionary oral hygiene measures and periodic dental visits.

Comparison of Dimensional Accuracies Using Two Elastomeric Impression Materials in Casting Three-dimensional Tool Marks

The purpose of this study was to evaluate two types of impression materials which were frequently used for casting three-dimensional tool marks in China, namely (i) dental impression material and (ii) special elastomeric impression material for tool mark casting. The two different elastomeric impression materials were compared under equal conditions. The parameters measured were dimensional accuracies, the number of air bubbles, the ease of use, and the sharpness and quality of the individual characteristics present on casts. The results showed that dental impression material had the advantage of special elastomeric impression material in casting tool marks in crime scenes; hence, it combined ease of use, dimensional accuracy, sharpness and high quality.

Silicone impression materials and latex gloves. Is interaction fact or fallacy?

This review will explore the mechanism of delayed setting and inhibition of polyvinyl siloxane impression material by latex and examine the evidence for and against this phenomenon. Clinical implications are discussed and recommendations for clinical practice made.

CLINICAL RELEVANCE

The production of accurate polyvinyl siloxane impressions in the fabrication of indirect restorations/prostheses is vital for a good clinical outcome.

Effects of sulfur-based hemostatic agents and gingival retraction cords handled with latex gloves on the polymerization of polyvinyl siloxane impression materials

Objectives

This study investigated the possible interactions between three addition silicone materials (Express^®, Aquasil Ultra^® and Adsil^®), three hemostatic agents (ferric sulfate, StatGel FS^®; aluminum sulfate, GelCord^®; and aluminum chloride, Hemostop^®) and gingival retraction cords previously handled with latex gloves to determine whether direct contact with medicaments or indirect contamination by latex in conditions similar to those found in clinical practice inhibit or affect the setting of the impression materials.

Material and Methods

A portable device for the simultaneous test of several specimens was specifically developed for this study. Polymerization inhibition was analyzed by examination of the impressions and the molded surface. Ten trials were performed for each addition silicone material used in the study, at a total of 240 study samples.

Results

All the samples tested (N=240) were nonreactive regardless of the type of combination used.

Conclusions

Aluminum sulfate, ferric sulfate and aluminum chloride hemostatic solutions did not show any inhibitory potential on the addition silicone samples under study, and there were no changes in polymerization as a result of contact between addition silicone and retraction cords handled with latex gloves.

Volatilization of components from and water absorption of polyether impressions

OBJECTIVE

To evaluate the accuracy of stone dies produced from impressions with polyether impression materials and a vinyl polysiloxane reference material after prolonged storage at 0, 50, or 100% relative humidity.

METHODS

Impressions were taken with light and heavy-bodied types of the polyethers P2 (P2L/H; Heraeus Kulzer) and Impregum (IML/H; 3M ESPE) and vinyl polysiloxane Flexitime (FLL/H; Heraeus Kulzer) from a truncated steel master cone in cylindrical trays giving 4 mm layer thickness at the prominence line. Impressions were taken at 23 degrees C, and stone dies were poured after 1, 2, 3, 4, or 5 days storage at 23 degrees C and 0, 50, or 100% RH. Accuracy was determined as discrepancy between a steel ring with accurate fit on the master cone and the stone die and expressed as base diameter deviation Deltad (microm). One-way ANOVA and Duncan's post-hoc test were used for statistical data analysis (p<0.05).

RESULTS

P2L/H showed significant Deltad increase (30-240 microm) depending on storage time and humidity (p<0.05). Dies from IML/H at 0% RH were 90 through 180 microm enlarged, at 50% RH the maximum diameter increase was 60 microm, and at storage in 100% RH all dies were 25-120 microm smaller (p<0.05). Dies from FLL/H showed maximum Deltad deviations (55 to -10 microm).

CONCLUSIONS

P2 impressions release volatile substances during storage and should preferably be poured within less than 24 h. Impregum absorbs water and should be stored at <50% humidity. The accuracy of Flexitime is scarcely affected by storage time or by ambient humidity.

An Experimental Study on Particular Physical Properties of Several Interocclusal Recording Media. Part III: Resistance to Compression After Setting

PURPOSE

The purpose of this study was to evaluate the resistance to compression after setting of several elastomeric interocclusal recording materials.

MATERIALS AND METHODS

Testing of the resistance to compression after setting was performed following a modification of the method described in specification No. 19 (4.3.6) of the A.D.A., for the elastomeric impression materials-1 cylindrical stainless steel mold with an internal diameter of 20 mm and a height of 20 mm was constructed. Mixing of the interocclusal registration media was conducted according to manufacturers' instructions, and the materials were injected into the mold. Two subsequent loads, one of 100 g/cm2 and a second of 1000 g/cm2 were exerted on each sample. The deformation of each was calculated using a vertical traveling micrometer microscope with an accuracy of +/- 0.001 mm.

RESULTS

One-way ANOVA revealed significant differences among the materials (F=331.58, p <0.0005). Tukey's HSD (p <0.05) test was used to determine the significant differences between the materials.

CONCLUSIONS

Polyvinylsiloxane Blu Mousse displayed the greatest resistance to compression, as compared to other elastomeric interocclusal recording materials tested.

Optical modeling of extraoral defects

In order to reduce the stress caused to patients by conventional methods of modeling using computed tomography (CT) or magnetic resonance imaging (MRI), an optical modeling process has been developed for extraoral defects and body areas. The selected body part is digitized using optical 3-coordinate measuring technology, providing an extensive data record. This is adapted for further use by equalizing the point clouds to obtain a Computer Aided Design (CAD) model, which is converted to a physical model by means of a stereolithographic process. With this technology, the patient's physical and psychological stress may be reduced. This article describes a technique for optical modeling of an ocular prosthesis.

Evaluation of dental arch reproduction using three-dimensional optical digitization

STATEMENT OF PROBLEM

Numerous investigations have been done to determine the most accurate method to reproduce a dental arch. Investigations have used different definitive cast configurations, materials, and measuring techniques to evaluate dimensional change, leaving clinicians undecided as to the most accurate method to reproduce a dental arch.

PURPOSE OF STUDY

The purpose of this investigation was to evaluate the effect of impression tray selection on accuracy of reproductions of a dental arch using a 3-dimensional optical digitizer.

MATERIALS AND METHODS

Impressions were made of a stone cast of a dental arch using vinyl polysiloxane impression material in custom and stock impression trays (n=12). Custom trays, designed with full palatal coverage, were fabricated on a separate standard stone cast using 2 layers of pink baseplate wax as the spacer and tissue stops on 1 anterior tooth and both first molar teeth. Impressions were poured with type IV gypsum and allowed to set with the tray inverted (n=5) or not inverted (n=5). The standard cast and resulting casts were digitized using an optical digitizer. Custom software was used to align and process the 3-dimensional images created by the digitizer. Each image was superimposed onto the standard cast image, curves were created of the percent of points less than a defined distance between the 2 superimposed images, and the area under the curve was calculated. A weighted average area was calculated for each cast, and these values were analyzed using a 2-way ANOVA (alpha=.05).

RESULTS

The main effect of tray type, laboratory setting technique, and the interaction between these 2 characteristics was analyzed. None of these effects was significant.

CONCLUSION

The differences in accuracy of reproductions of a dental arch, regardless of the impression and laboratory techniques, were not significant when evaluated using a 3-dimensional optical digitizer.

The effect of metallic radial head arthroplasty on radiocapitellar joint contact area

OBJECTIVE

This study determined the effect of metallic radial head arthroplasty on radiocapitellar joint contact area.

DESIGN

The contact area of eight intact radiocapitellar joints was assessed during simulated compressive loading. Subsequently, the same experiments were repeated after reconstruction with three different radial head implant sizes.

BACKGROUND

There has been an increasing use of metal radial head implants relative to silicone implants. However, the contact characteristics with the metal reconstruction have not been determined.

METHODS

A 100 N compressive load was applied to the radiocapitellar joint at three different flexion angles for the native joint and three different sizes of a metal head implant. An impression material was employed to quantify joint contact area.

RESULTS

Following metallic radial head arthroplasty, the contact area decreased by approximately two-thirds relative to the native radiocapitellar joint (P<0.001). Smaller implant sizes resulted in slightly larger contact areas (P<0.05). In addition, contact area decreased as joint flexion angle increased (P<0.04).

CONCLUSIONS

Selection of radial head implant size is likely not a significant factor with regard to contact area mechanics of the radiocapitellar articulation.

RELEVANCE

The effect of radial head implant size on the contact area produced with the native capitellum is not known. This study shows that the design or selection of a metallic radial head implant from the viewpoint of size is likely not an important factor with regard to minimizing joint contact stresses.

Wettability, imbibition, and mass change of disinfected low-viscosity impression materials

STATEMENT OF PROBLEM

There is an ongoing effort by dental manufacturers to create impression materials with improved wetting properties. Disinfection solutions may alter the surface characteristics of these newer materials.

PURPOSE

This study compared wettability, imbibition, and mass change of various recently introduced automixed low-viscosity addition silicone and polyether materials before and after immersion disinfection.

MATERIAL AND METHODS

The Wilhelmy technique was used for deriving wetting properties of 5 addition silicone materials (Clinician's Choice Affinity, Clinician's Choice Superhydrophilic [experimental], Kerr's Take One, 3M's Imprint II, and Dentsply's Aquasil LV) and 2 polyether materials (ESPE's Permadyne Garant and Impregum Garant). Conditions included a control with no disinfection (0 hours), as well as (1/2) hour of immersion disinfection in a full-strength solution of 2% acid glutaraldehyde disinfectant (Banicide). Weight changes before and after disinfection and weight loss in air were measured over an 18-hour period to detect imbibition and mass change over time. The data were analyzed with a 1-way analysis of variance at alpha=0.05, with n = 3 for advancing (ACA) and receding (RCA) contact angles and n = 2 for imbibition and mass change.

RESULTS

Statistical significant differences in wettability (P<.001) were found among nondisinfection control groups, as well as among (1/2)-hour disinfection groups. Polyethers were the most wettable materials overall. Impregum Garant polyether demonstrated significantly lower RCA for the control (48.4 degrees) and at (1/2) hour of disinfection (51.8 degrees). The 2 polyethers and Take One lost mass, whereas Aquasil LV gained mass in air; however, all materials exhibited some degree of imbibition during disinfection.

CONCLUSION

Within the limitations of this study, the 2 polyether materials tested exhibited significantly lower ACA's and RCA's compared with the 5 addition silicones tested. Imbibition for the 2 polyether materials was significantly higher (P<.001). Polyether materials lost significantly more (0.6% to 0.8%) and Aquasil LV gained significantly more (0.6%) mass in air.

Laser digitization of casts to determine the effect of tray selection and cast formation technique on accuracy

STATEMENT OF PROBLEM; Several studies have attempted to determine the ideal combination of dental materials and laboratory techniques to produce the most accurate dental cast. Most have made use of 2-dimensional manual measuring devices, which neglect to account for the dimensional changes that exist along a 3-dimensional surface.

PURPOSE

The purpose of this study was to determine the effect of impression tray selection and cast formation techniques on the dimensional change of a dental cast with the use of new, 3-dimensional optical digitizing technology.

MATERIAL AND METHODS

Multiple impressions of a machined steel die that resembled a dental arch were made with custom and stock impression trays and vinyl polysiloxane impression material. The impressions were poured in type V artificial dental stone and allowed to set with the tray inverted or noninverted. The steel master die and stone casts were digitized with the Steinbichler Comet 100 Optical Digitizer, which was developed at the Minnesota Dental Research Center for Biomaterials and Biomechanics. Three-dimensional images of the stone casts were aligned to the 3-dimensional image of the master die and analyzed with AnSur-NT software. Multiple measurements of the master die and stone casts were analyzed to determine the accuracy of the 3-dimensional technology and of the impression and cast fabrication techniques. Planar distances between the center of each crown preparation were measured, as were crown heights. Data were analyzed with analysis of variance (P<.05), and root mean square error values were determined.

RESULTS

Casts were compared with a total of 45 significance tests, of which only 4 yielded P<.05. There was no pattern to these results, which suggests that they were false-positive findings.

CONCLUSION

Results obtained with the use of new optical digitizing technology indicated that neither impression tray type nor cast formation technique affected the accuracy of final casts.

The effect of the use of dental gloves on mixing vinyl polysiloxane putties

PURPOSE

The purpose of this study was to determine the delay in setting times that occurs with selected brands of gloves or residual powder from those gloves on eight popular brands of vinyl polysiloxane putties.

MATERIALS AND METHODS

The putties were mixed and rolled into a round 3-inch-long cylinder without gloves on hand, with gloves on hand, and with powder residue on hands, immediately after degloving. The end of a cement spatula was drawn over the putty at various intervals with a force of 3 ounces. The setting time was recorded to be when no permanent indentation of the putty occurred.

RESULTS

All materials set within 5 minutes without gloved hands. Eighty-eight percent of the putties set within 5 minutes when mixed with Friction Grip Powder Free and Medical Gloves on hands. When mixed with Pharmaseal gloves on hands, 50% of the putties set in 5 minutes. When mixed with Micro-Touch Latex Medical Gloves, 38% of the putties set in 5 minutes. When the putties were mixed with the residual powders left on ungloved hands, the same results occurred with the above-mentioned gloves. With residual powder on hands from Natraflex and Medical Exam Tex, 25% of the putties set in 5 minutes.

CONCLUSIONS

Gloved hands interfered with the setting of more brands of putties than did residual powder on hands immediately after degloving. There are gloves available that do not interfere with the setting of most of the vinyl polysiloxane putties.

Surface characteristics of polyether and addition silicone impression materials after long-term disinfection

It has been demonstrated that short-term disinfection can affect the surface properties of impression materials. This study evaluated advancing contact angle, receding contact angle, inhibition and mass loss of a polyether impression materials, and two different viscosities of an addition silicone impression material after long-term immersion disinfection (18 hours). The brand names of the impression materials tested were Impregum F, Extrude Extra, and Extrude Wash, and all were tested by use of the Wilhelmy technique; first, for the nondisinfected state, which served as controls, and then after 1 and 18 hours of disinfection in a full-strength solution of acid glutaraldehyde. Weight changes before and after the disinfection process were also measured to detect weight loss and mass change over time. All materials exhibited some degree of inhibition. Polyether lost 0.4% mass in air, which indicated loss of a volatile component. Polyether and addition silicone were both relatively hydrophobic and could be disinfected with acid glutaraldehyde for up to 18 hours without affecting wettability.

The effects of sterilization on addition silicone impressions in custom and stock metal trays

Five groups of addition silicone impressions (four made in custom autopolymerizing acrylic resin trays and one in stock metal rim-lock trays) were made of a stainless-steel master die. The first group (control group) was not sterilized. The second group was sterilized in an ethylene oxide gas autoclave, the third group in a steam autoclave, and the fourth and fifth groups by immersion for 12 hours in 2% glutaraldehyde. Casts made from each sterilization group were found to be significantly different from control impressions by multivariate analysis of variance and should not be used to fabricate prostheses.

Bond strengths between elastomeric impression materials and disinfected preliminary impressions

Bond strengths between disinfected putty impressions and subsequent wash applications were determined in specimens made to simulate clinically an interrupted two-step impression technique. The effect of a disinfectant on the bond strength between a disinfected wash impression and a subsequent wash application was also evaluated to simulate perfecting a disinfected final impression clinically. Vinyl polysiloxane (putty or wash) and polyether (wash only) impression materials were placed in perforated metal cylinders, allowed to set, and dipped in an iodine or glutaraldehyde disinfectant. Wash material was then applied to the disinfected material by use of another metal cylinder and allowed to set before the specimen was tested in tensile mode. Significant decreases in bond strengths were found in both clinical simulations but were limited to specific impression material and disinfectant combinations.