Nanoclay-Reinforced Glass-Ionomer Cements: In Vitro Wear Evaluation and Comparison by Two Wear-Test Methods

The Wear Behavior of Glass-Ceramic CAD/CAM Blocks against Bovine Enamel

The wear of enamel and crown restorative materials often occur by occlusion. The purpose of this study was to evaluate the wear volume between glass-ceramics used for CAD/CAM blocks (lithium disilicate: Initial LiSi block (LIS), IPS e.max CAD (IPS), zirconia-reinforced lithium silicate glass-ceramics: Celtra DUO (DUO), VITA Suprinity (VITS) and feldspar-based glass-ceramics: Vitablocs Mark II (MAK)) and bovine tooth enamel using a two-body wear test, the hardness, three-point bending strength, micro-structure and the element components of glass-ceramics. The data were analyzed using a one-way analysis of variance and Tukey's multiple comparison test (α = 0.05). IPS and DUO with relatively large size crystal gain had significantly larger abrader wear volumes. Zirconia-reinforced lithium silicate glass-ceramics (DUO, VITS) caused significantly greater wear volume in antagonist enamel. MAK with scale-shape crystals grains produced distinct scratches after wear tests, both in the material itself and in the enamel. A strong correlation between the mechanical properties (hardness, three-point bending strength) and wear volume could not be confirmed. The type of glass-ceramic, size, and shape of the crystal grains affected the wear behavior of the glass-ceramics for CAD/CAM blocks. Therefore, dentists should consider that wear behavior varies with crystal structure, size, and shape in glass-ceramics for CAD/CAM blocks.

Incorporation of Nanomaterials in Glass Ionomer Cements-Recent Developments and Future Perspectives: A Narrative Review

Glass ionomer cements (GICs), restorative materials with commercial availability spanning over five decades, are widely applied due to their advantages (including bio-compatibility, fluoride release, or excellent bonding properties). However, GICs have shortcomings. Among the disadvantages limiting the application of GICs, the poor mechanical properties are the most significant. In order to enhance the mechanical or antimicrobial properties of these materials, the addition of nanomaterials represents a viable approach. The present paper aims to review the literature on the application of different types of nanomaterials for the enhancement of GICs' mechanical and antimicrobial properties, which could lead to several clinical benefits, including better physical properties and the prevention of tooth decay. After applying the described methodology, representative articles published in the time period 2011-present were selected and included in the final review, covering the modification of GICs with metallic nanoparticles (Cu, Ag), metallic and metalloid oxide nanoparticles (TiO₂, ZnO, MgO, Al₂O₃, ZrO₂, SiO₂), apatitic nanomaterials, and other nanomaterials or multi-component nanocomposites.

Evaluation of a Method to Determine Wear Resistance of Class I Tooth Restorations during Cyclic Loading

The aim of this study was the development of a test regime to determine the wear resistance and predict the clinical performance of conventional glass ionomer cement (GIC) restorations in Class I tooth cavities. Cavities were prepared in excised human teeth and restored using three conventional glass ionomer restorative materials: DeltaFil, Fuji IX GP and Ketac Universal. The restored teeth were mechanically and thermally stressed using a chewing simulator with a maximum number of 1,200,000 load cycles. Besides determining the number of cycles achieved, the abrasion volume after termination of the chewing simulation was calculated using µCT images. All teeth restored with DeltaFil reached 1,200,000 cycles without any restoration failure. Only 37.5% of the restorations each with Ketac Universal and Fuji IX GP were able to achieve the maximum cycle number. A significant lower abrasion volume for restorations with DeltaFil compared to Ketac Universal (p = 0.0099) and Fuji IX GP (p = 0.0005) was found. Laboratory chewing simulations are a useful tool to study basic wear mechanisms in a controlled setting with in-vivo related parameters. DeltaFil shows an improved wear resistance compared to other conventional GICs, indicating the high potential of this material for long-lasting Class I restorations.

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.