Assessment of Degree of Conversion and Volumetric Shrinkage of Novel Self-Adhesive Cement

The degree of monomer conversion and polymerization shrinkage are two of the main reasons for potential adhesion failure between the tooth structure and the restoration substrate. To evaluate the degree of conversion and polymerization shrinkage of a newly developed self-adhesive resin cement, the degree of conversion (DC) was measured using FTIR under different activation modes, temperatures, and times. Volumetric shrinkage was tested using the AcuVol video imaging method. The experimental cement showed a higher DC than other cements under self-curing. The DC of the experimental cement was higher than that of other cements, except SpeedCem Plus under light curing. The experimental cement had a higher DC than other cements, except SpeedCem Plus in some conditions under dual curing. All self-adhesive cements had a higher DC at 37 °C than at 23 °C under self-curing, and there was no statistical difference between 23 °C and 37 °C under light curing. All self-adhesive cements showed a significantly higher DC at 10 min than at 5 min under self-curing. There was no statistical difference between 5 min and 10 min for most cements under dual curing. All self-adhesive cements statistically had the same volumetric shrinkage under light curing and self-curing. The newly developed self-adhesive resin cement exhibited a higher degree of conversion and similar volumetric shrinkage compared to these commercial self-adhesive resin cements

Multiscale mechanical characterization of biobased photopolymers towards sustainable vat polymerization 3D printing

In vat polymerization (VP) 3D printing, there is an urgent need to expand characterization efforts for resins derived from natural resources to counter the increasing consumption of fossil fuels required to synthesize conventional monomers. Here, we apply multiscale mechanical characterization techniques to interrogate a 3D printed biobased copolymer along a controlled range of monomer ratios. We varied the concentration of two dissimilar monomers to derive structural information about the polymer networks. Current research primarily considers the macroscale, but recent understanding of the process-induced anisotropy in 3D printed layers suggests a multiscale approach is critical. By combining typical macroscopic techniques with micro- and nanoscale analogues, clear correlations in the processing-structure-property relationships appeared. We observed that measured moduli were always greater via surface-localized methods, but property differences between formulations were easier to identify. As researchers continue to develop novel sustainable biopolymers that match or exceed the performance of commercial resins, it is vital to understand the multiscale relationships between the VP process, the structure of the formed polymer networks, and the resultant properties

Physical, Mechanical, and Adhesive Properties of Novel Self-Adhesive Resin Cement

Objective. To evaluate a newly developed self-adhesive resin cement on physical, mechanical, and adhesive properties and compare it with other commercial self-adhesive resin cements. Materials and Methods. Experimental self-adhesive resin cement (SARC) was formulated by our proprietary adhesive resin and filler technology. Maxcem Elite, RelyX Unicem 2, SpeedCem Plus, SmartCEM 2, and Calibra Universal 2 were selected for comparison. Working and setting times, film thickness, water sorption and solubility, flexural strength, and modulus were measured in accordance with ISO-4049. Consistency was tested according to modified ISO 4823. Shear bond strengths were conducted according to ISO 29022. The data were analyzed by one-way ANOVA and post hoc Tukey’s tests (p ≤ 0.05). Results. All cements showed about 2–4 min working time and about 3–6 min setting time except that RelyX Unicem 2 has a longer working time (9’58”) and setting time (10’18”). All cements meet ISO standards for film thickness (≤50 µm), water sorption (≤40 µg/mm3) except Maxcem Elite (46.19 µg/mm3), and water solubility (≤7.5 µg/mm3) except SmartCEM 2 (11.35 µg/mm3) and Calibra Universal (9.87 µg/mm3). Experimental SARC showed significantly higher flexural strength and modulus than other cements (p  0.05). For light-curing, Experimental SARC showed significantly higher bond strength than other cements (p  0.05). For dual-curing, the bond strength of Experimental SARC is significantly higher than that of other cements (p < 0.001). Conclusion. The newly developed self-adhesive resin cement exhibited favorable bonding capability and physical and mechanical properties compared to other commercial self-adhesive resin cements and is a good option for cementation of indirect restorations with potential long-term clinical success