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

Comparison of the elastic recovery and strain-in-compression of commercial and novel vinyl polysiloxane impression materials incorporating a novel crosslinking agent and a surfactant

This study aims to formulate experimental vinylpolysiloxane (VPS) impression materials and compare their elastic recovery and strain-in-compressions with three commercial VPS materials (Aquasil, Elite, and Extrude). Five experimental materials (Exp), two hydrophobic (Exp-I and II) and three hydrophilic (Exp-III, IV and V) were developed. Exp 1 contained vinyl-terminated poly-dimethyl siloxane and a conventional cross-linking agent (poly methylhydrosiloxane), while Exp- II contained a novel cross-linking agent that is tetra-functional dimethyl-silyl-ortho-silicate (TFDMSOS). Exp III-V (hydrophilic materials) were formulated by incorporating different concentrations of non-ionic surfactant (Rhodasurf CET-2) into Exp II formulation. Measurement of elastic recovery and strain-in-compression for commercial and experimental materials were performed according to ISO4823 standard using the calibrated mechanical testing machine (Tinius Olsen). One-way analysis of variance (one-way ANOVA) and Tukey's post-hoc (HSD) test were used for statistical analysis and a p-value of ≤ 0.05 was considered significant. Exp-I has statistically similar values to commercial VPS. The Exp-II showed the highest elastic recovery, while % elastic recovery was reduced with the addition of the non-ionic surfactant (Rhodasurf CET-2). The % reduction was directly related to the concentration of Rhodasurf CET-2. In addition, Exp II had significantly higher strain-in-compression values compared to Exp-I and commercial materials. These values were further increased with the addition of a non-ionic surfactant (Rhodasurf CET-2) was added (Exp-III, IV and V).

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.