Effect of Spherical Silica Filler Addition on Immediate Interfacial Gap-formation in Class V Cavity and Mechanical Properties of Resin-modified Glass-ionomer Cement

Modifications of Glass Ionomer Cement Powder by Addition of Recently Fabricated Nano-Fillers and Their Effect on the Properties: A Review

The aim of this article is to provide a brief insight regarding the recent studies and their recommendations related to the modifications to glass ionomer cement (GIC) powder in order to improve their properties. An electronic search of publications was made from the year 2000 to 2018. The databases included in the current study were EBSCOhost, PubMed, and ScienceDirect. The inclusion criteria for the current study include publication with abstract or full-text articles, original research, reviews or systematic reviews, in vitro, and in vivo studies that were written in English language. Among these only articles published in peer-reviewed journals were included. Articles published in other languages, with no available abstract and related to other nondentistry fields, were excluded. A detailed review of the recent materials used as a filler phase in GIC powder has revealed that not all modifications produce beneficial results. Recent work has demonstrated that modification of GIC powder with nano-particles has many beneficial effects on the properties of the material. This is due to the increase in surface area and surface energy, along with better particle distribution of the nano-particle. Therefore, more focus should be given on nano-particle having greater chemical affinity for GIC matrix as well as the tooth structure that will enhance the physicochemical properties of GIC.

Effects of adding silica particles on certain properties of resin-modified glass-ionomer cement

OBJECTIVE

This study was conducted to evaluate the effect of incorporation of silica particles with different concentrations on some properties of resin-modified glass ionomer cement (RMGIC): Microleakage, compressive strength, tensile strength, water sorption, and solubility.

MATERIALS AND METHODS

Silica particle was incorporated into RMGIC powder to study its effects, one type of RMGIC (Type II visible light-cured) and three concentrations of silica particles (0.06, 0.08, and 0.1% weight) were used. One hundred and twenty specimens were fabricated for measuring microleakage, compressive strength, tensile strength, water sorption, and solubility.

STATISTICAL ANALYSIS

One-way analysis of variance and Tukey's tests were used for measuring significance between means where P ≤ 0.05.

RESULTS

RMGIC specimens without any additives showed significantly highest microleakage and lowest compressive and tensile strengths.

CONCLUSION

Silica particles added to RMGIC have the potential as a reliable restorative material with increased compressive strength, tensile strength, and water sorption but decreased microleakage and water solubility.

Effect of silanized nanosilica addition on remineralizing and mechanical properties of experimental composite materials with amorphous calcium phosphate

OBJECTIVES

Experimental composite resins with amorphous calcium phosphate (ACP) have the potential to regenerate demineralized tooth structures. The aim of the study was to investigate the effect of the addition of silanized silica nanofillers to the ACP-based composites on their mechanical properties and the kinetics of calcium and phosphate release.

MATERIALS AND METHODS

The test materials comprised 5 wt% (5-ACP) or 10 wt% (10-ACP) of silanized silica admixed to the 40 wt% ACP and 50 or 55 wt% resin. The ACP control (0-ACP) contained 40 wt% ACP and 60 wt% resin. Additionally, composite material CeramX (Dentsply, Germany) was included as control. Three-point bending test was performed to calculate flexural strength and modulus of elasticity. Inductively coupled plasma atomic emission spectroscopy was used for measurement of ion release. The micromorphology of calcium phosphate depositions on composite samples has been qualitatively evaluated using a scanning electron microscope. The results were analyzed using Mann-Whitney and Wilcoxon rank sum tests (α < 0.05).

RESULTS

Ion release was enhanced by the silica fillers, when compared to the 0-ACP. Although not statistically significant, flexural strength of 10-ACP was improved by 46 % compared to 0-ACP. Flexural modulus of 5-ACP was significantly higher than 0-ACP.

CONCLUSIONS

The admixture of silanized fillers seems to be a promising approach for the improvement of mechanical and remineralizing properties of ACP composite resins.

CLINICAL RELEVANCE

ACP-based composite resins with modified composition could serve as an effective remineralizing aid as base materials in restorative dental medicine.

Setting kinetics and shrinkage of self-adhesive resin cements depend on cure-mode and temperature

OBJECTIVE

To investigate the influence of curing mode and temperature on the shrinkage kinetics of self-adhesive resin cements in comparison to a conventional multi-step resin cement.

METHODS

The shrinkage of self-adhesive resin cements Maxcem Elite (MX), Speedcem (SPC), Smartcem2 (SMC), iCem (IC) and RelyX Unicem (RX) and Nexus Third Generation (NX3) as a multi-step resin cement was measured continuously for 1h using the bonded disk method. All materials were tested with dual-curing (dc) and self-curing (sc) mode. All measurements (n=5 per group) were conducted at room temperature (23°C) as well as at body temperature (37°C). Shrinkage time constants were obtained from a simple exponential growth model. Data were statistically analyzed by ANOVA and the p-values were adjusted for multiplicity according to Hothorn et al. (2008) using the R-package "multcomp".

RESULTS

Shrinkages ranged between 1.84 (RX sc23) and 7.09 (IC sc37). The curing-mode changing from sc to dc had the dominant effect for several materials, especially RX, both on final shrinkage and time constant for setting. Temperature increase had an effect on setting and shrinkage for all materials except RX. Final shrinkage for SPC, SMC and NX3 was statistically equivalent (p>0.05).

SIGNIFICANCE

The 3-fold variation in final shrinkage for these materials is significant for clinical material selection. Light curing can lead to a 10-fold increase in the rate of setting. A self-adhesive universal resin cement (RX) had the lowest shrinkage in the groups examined.

Evaluation of a newly developed polymethyl methacrylate powder for brush-dip technique

PURPOSE

The aim of this study is to evaluate a newly developed polymethyl methacrylate (PMMA) powder.

METHODS

The particle size distribution, surface area, and particle shape of both new and traditional powders were compared. The shear bond strength of the resin cement with the new powder to a silver-palladium-copper-gold alloy was determined and compared to that for a cement with the traditional powder. Also, the weight of mixture held by the brush at one time of both powders was also calculated and compared as an index of mixability.

RESULTS

The surface area of the new powder was smaller than that of the traditional powder, while the particles size distributions were similar. The new powder included various-sized spherical particles as well as irregular particles, while the traditional powder consisted of only irregular particles. The new powder showed significantly higher mixability, although its bond strength was not significantly different from that of traditional powder.

CONCLUSION

The results of this study show that the interminglement of spherical and irregular particles cannot influence the bond strength to the alloy but is helpful to improve the working properties.

Effect of Thermocycling on Interfacial Gap-formation in Class V Cavities and Mechanical Properties of Spherical Silica Filler Addition to Resin-modified Glass Ionomer Restorations

The effects of thermocycling at 20,000 cycles and addition of silanized spherical silica filler (SF) on resin-modified glass ionomer cement (RMGIC) restorations were investigated. A RMGIC added with an untreated spherical silica filler (UF) was used as a comparison. Marginal gaps in Class V tooth cavities, compressive strength, diametral tensile strength, flexural strength, and shear bond strengths to enamel and dentin were examined. All thermocycled samples showed decreased frequency of marginal gap formation as compared to the 24-hour samples, with reduction of 73% to 95%. At the immediate condition, after 24 hours, and after thermocycling, the addition of 10 wt% SF yielded the most favorable results in terms of marginal gap formation in Class V cavities, compressive strength, flexural strength, and shear bond strength to enamel. Diametral tensile strength and flexural strength were also increased significantly by the addition of 5 wt% SF. Further, shear bond strength tests showed that the addition of SF had no effect on bonding capability to enamel and dentin.