Experimental hydrophilic vinyl polysiloxane (VPS) impression materials incorporating a novel surfactant compared with commercial VPS

Reproduction of Fine Details and Compatibility of Vinyl Polysiloxane Impression Materials

The purpose of this study was to develop novel experimental (Exp) vinyl polysiloxane (VPS) impression materials (ab initio) and to evaluate their reproduction of fine details and compatibility with pouring materials. The Exp materials were compared with three commercial VPSs (Aquasil Ultra Monophase (Aq M), Extrude Medium-Bodied (Extr M), Elite HD Monophase (Elt M)) under dry, moist and wet conditions. Five VPSs (Exp-I–V) were developed, out of which Exp-I and II were hydrophobic while Exp-III, IV and V were hydrophilic. In the current study, Exp-II is the control for Exp-III, IV and V. Exp-I was the control for Exp-II, in which tear strength of the VPS was improved by adding a novel cross-linking agent. This part of the study has already been published by the authors. Under dry conditions, all commercial and Exp materials reproduced the 20 µm line satisfactorily. Under moist conditions, all commercial and some of the Exp (III, IV and V) materials reproduced the 20 µm line satisfactorily, with the exception of Exp-I and II. Under wet conditions, Aq M, Extr M and Exp-IV and V reproduced the continuous line, while Elt M and Exp-I, II and III failed to produce the line. For compatibility, all commercial and Exp VPSs, under dry conditions, reproduced the 50 µm line on the cast. Under moist conditions, Elt M and Exp-I and II did not record the line, while Aq M, Extr M and Exp-III, IV and V reproduced this line. Under wet conditions, Aq M, Extr M and Exp-IV and V reproduced the continuous line of 50 µm, while Elt M and Exp-I, II and III failed to record this line. Performance of the materials depends on the type and amount of surfactant incorporated. These data provide useful knowledge for clinicians on recording and pouring impressions with greater accuracy of reproduction of fine details and compatibility with cast/die materials.

Comparison of the Hardness of Novel Experimental Vinyl Poly Siloxane (VPS) Impression Materials with Commercially Available Ones

Purpose

To determine the hardness and Young's moduli of both commercial and experimental vinyl poly siloxane (VPS).

Methods

The purpose of this study was to develop a medium-bodied experimental (Exp-I, II, III, IV, and V) VPS impression materials and to analyse their effects on hardness and Young's modulus and compare them with three commercial VPS materials (Aquasil, Elite, and Extrude) using Shore A hardness tester. Measurements were recorded after 1, 24, 72, and 168 hours of mixing. The results were analysed with one-way ANOVA and post hoc Tukey's test using the SPSS PASW statistical 22 software.

Results

Commercial and experimental vinyl polysiloxane exhibited higher Shore A hardness values with time (i.e., 1 hour after mixing, 24 hours after mixing, 72 hours after mixing, and 1 week after mixing). All Comml and Exp VPS demonstrated a significant increase (ANOVA, p < 0.05) in hardness at increasing time points. Generally, all commercial VPS exhibited significantly higher values for Shore A hardness compared to all Exp formulations. For commercial products, Elt M presented significantly highest values at all-time points followed by Aq M then Extr M. Exp-I was significantly harder than all other Exp VPS at all-time points. Young's modulus values were directly related to Shore A hardness; materials with higher Shore A hardness values had higher Young's moduli.

Conclusion

Continued polymerisation of elastomeric impression materials results in increased hardness over time. Hardness, Young's moduli, and rigidity of the set commercial and experimental VPS materials were within the required limits. Shore A hardness and Young's moduli were directly proportional to each other, and commercial and experimental materials had enough rigidity to contain the stone during pouring.

Improved water absorption behaviour of experimental hydrophilic vinyl polysiloxane (VPS) impression materials incorporating a crosslinking agent and a novel surfactant

OBJECTIVES

To study the effects of incorporating a further crosslinking agent and a novel surfactant on the water absorption behaviour of experimental VPS impression materials.

METHODS

Part 1: The water uptake behaviour of Aquasil-Ultra-Monophase (AqM) was studied gravimetrically in three media (DW, 1%NaOCl and Perform ID), at 23 °C and 37 °C, over a period of one and four-months (n = 5) to gain information on long-term immersion. Part 2: Five experimental materials were formulated: Exp-I and II as hydrophobic and Exp-III-V as hydrophilic, containing an additional cross-linking agent (TFDMSOS) and Rhodasurf CET-2 surfactant. Their water uptake and desorption (both at 23 °C) properties (gravemetrically), solubility, pH and diffusion coefficient (DC) data were compared with three commercial, hydrophilic VPS impression materials, over seven days (n = 5). The results were analysed statistically.

RESULTS

Part 1: Significant differences in water absorbed by AqM were observed in the three media at 23 °C. Aq M had a significantly higher uptake in 2% Perform ID, than in DW and NaOCl. At 37 °C, over four-months the uptake profiles were more enhanced and differed. Part 2: All Exp and commercial materials significantly increased in weight in both media (DW and 1% NaOCl at 23 °C), with differing uptake profiles and non-reached equilibrium. Exp-VPS absorbed significantly less water than commercial-VPS. Desorption of all VPS from both parts was faster than absorption, followed Fickian diffusion kinetics and reached equilibrium within 1-3 days. Desorption DCs for Exp-VPS were higher than commercial materials (10^-10 versus 10^-11 m² s^-1). The solubility was higher in 1% NaOCl compared to DW. The pH of DW after immersion of samples significantly increased compared to 1% NaOCl.

SIGNIFICANCE

The incorporation of novel cross-linking agent, TFDMSOS and non-ionic surfactant, Rhodasurf CET-2, (ethoxylated-cetyl-oleyl alcohol) improved the dimensional stability of hydrophilic Exp-VPS in DW and 1% NaOCl. These materials merit further research in producing accurate casts of the patient's anatomy following disinfection.

Disposable plastic trays and their effect on polyether and vinyl polysiloxane impression accuracy-an in vitro study

OBJECTIVES

To evaluate the dimensional accuracy of impressions taken by use of disposable stock plastic trays and to compare performance with that of metal trays.

MATERIALS AND METHODS

From a metallic model incorporating three precision balls and three abutment teeth, one-step dual-phase polyether (PE) and vinyl polysiloxane (VPS) impressions were taken using either metal or disposable plastic trays (n = 10 for each of the resulting four test groups). Respective plaster cast scans were aligned with the reference dataset to evaluate global (distance and angle deviations) and local (trueness and precision) accuracy. Analyses of variance (ANOVA) were conducted to determine group differences.

RESULTS

For all impression tray and material combinations, global accuracy was good (mean distance changes < 100 μm) with greatest deviations being observed for distances exceeding one quadrant of the dental arch. In general, distances measured in the plaster casts were too short. Only VPS impressions with plastic trays showed a different behavior with a large percentage of cross-arch distances exceeding the reference value. Mean local accuracy ranged between 6 and 14 μm (trueness), and 6 and 16 μm (precision). On abutment tooth level, metal trays were associated with a significantly better precision (p = 0.015).

CONCLUSIONS

The observed distortions of the studied impression trays and materials are small and should enable satisfying clinical impression-taking.

CLINICAL RELEVANCE

Cleaning and processing of metal trays before re-use are time-consuming. Especially for patients' management with single crowns and small fixed dental prostheses, disposable plastic trays can be a viable and cost-effective alternative.

The effects of cross-linking agent and surfactant on the tear strength of novel vinyl polysiloxane impression materials

OBJECTIVES

To formulate experimental hydrophobic and hydrophilic vinyl polysiloxane (VPS) impression materials ab initio, comprising a novel cross-linking agent, tetra-functional (dimethylsilyl) orthosilicate (TFDMSOS), and a non-ionic surfactant, Rhodasurf CET-2 (ethoxylatedcetyl-oleyl alcohol), and to investigate their effects on tear strength (TS).

METHODS

Five experimental formulations (Exp I-V) were prepared and compared with three medium bodied commercial VPS impression materials (Aq M, Elt M, Extr M). Tear test was performed on trouser test specimens (n=12 per material), at four time points (immediately, 24, 72 and 168 hours after setting). FTIR spectroscopy was used for identifying functional bonds and cross-linking. The results were analysed with one-way ANOVA, two-way ANOVA and post hoc Tukey's test using the SPSS PASW statistical 22 software.

RESULTS

The material with novel cross-linking agent (Exp II) had significantly higher TSs at all-time points compared to Exp I (control; p˂0.05). Materials incorporating both TFDMSOS and surfactant (Exp III, IV and V), had further significantly increased TS at all-time points, which were concentration dependent. Extr M had a significantly lower TS (immediately after setting and at 24 hours) compared to all Exp and other commercial materials, with the exception of Elt M (difference not significant). The TSs of Exp II-V, after 72 and 168 hours, were significantly higher for than all commercial products and Exp I. FTIR spectra showed the consumption of Si-H groups indicating crosslinking had taken place with the addition of TFDMSOS and surfactant which contributed to an increase in the TS.

SIGNIFICANCE

TFDMSOS cross-linking agent increased the TS of Exp II significantly at all-time points compared to the control. Novel surfactant further significantly increased TS, and it was also concentration dependent. Exp VPS with improved TS have been developed, addressing one of the drawbacks of commercial VPS materials.