Application of Tribology Concept in Dental Composites Field: A Scoping Review

Evaluation of the Mechanical Properties of Different Dental Resin-Based Materials After Submersion in Acidic Beverages

Background: The aim of this study was to evaluate the influence of acidic beverages on the mechanical properties of various dental resin-based materials. Methods: A total number of 160 samples were prepared using four types of resin-based materials-Group A (n = 40): flowable composite, Group B (n = 40): heavy-flow composite, Group C (n = 40): resin-based sealant and Group D (n = 40): nano-hybrid composite. Then, the samples were distributed into four subgroups according to the submersion solution: a (n = 10): artificial saliva, b (n = 10): coffee, c (n = 10): cola and d (n = 10): red wine. The Vickers microhardness, Young's modulus of elasticity and scratch resistance were assessed using a CETR UMT-2 tribometer. Results: The obtained results showed that 14-day submersion of the resin-based materials in coffee, cola and red wine solutions significantly (p < 0.05) decreased the microhardness values (VHN), Young's modulus of elasticity and scratch resistance. Fourteen days of storage in coffee decreased the microhardness values of flow resin from 117.5 to 81.59 VHN (p < 0.001) whereas the values of the nanohybrid resin decreased from 125.5 to 89.4 (p < 0.001). The elasticity modulus of the heavy flow resin showed a decline from 15.57 to 10.50 GPa after 14 days' submersion in coffee (p < 0.001), and from 21.29 to 13.10 GPa for the nanohybrid resin after immersion in cola (p < 0.001). For the scratch test, the resin-based sealant showed a significant decrease after 14 days of storage in coffee, from 0.34 to 0.02 units. Conclusions: The submersion of conventional nanohybrid, flowable, heavy-flow composite resins and resin-based sealants in coffee, cola and red wine solutions changes the mechanical properties (Young's modulus of elasticity, Vickers microhardness and scratch resistance). The most resistant resin-based material to acid attack was the conventional nanohybrid composite resin, followed by heavy flow resin, flowable resin and resin-based sealant.

Mechanical Properties of Nano-Crystalline Glass-Carbomer Cements Used in Dentistry

The main aim of this study was to assess the impact of the environment on the mechanical and tribological properties of glass-carbomer cements used in dentistry. The properties of the Glass Cements Polyalkene (GCP) Glass Fill material, belonging to glass-polyalkene cements, were tested after placing it in various environments: air, distilled water, artificial saliva simulating a neutral environment (pH = 7), and simulating inflammation (pH = 4). The research material included four samples and a two-year reference material. The analysis of volumetric consumption and the assessment of the impact of solubility on the stability of glass-carbomer cements were carried out using tribological measurements and Vickers hardness measurements. In addition, microstructural characterization of the materials was performed using scanning electron microscopy (SEM). It was observed that the lowest wear (0.04%), the most stable microstructure, and the lowest average hardness (21.52 HV 0.1) were exhibited by the material stored in artificial saliva simulating a neutral environment (pH = 7). The least stable microstructure and statistically the highest hardness (77.3 HV 0.1) was observed in the test sample, which was stored in air for two years and then in distilled water. The highest consumption (0.11%) was recorded in the case of cement placed in artificial saliva simulating inflammation (pH = 4). The results obtained in this study indicate specific trends in the influence of the environment in which the tested cement is located, such as air, distilled water, air/distilled water, artificial saliva simulating a neutral environment, and simulating inflammation, on its structure, hardness, and wear.

An In Vitro Study regarding the Wear of Composite Materials Following the Use of Dental Bleaching Protocols

Composite materials used in dental restorations are considered resistant, long-lasting and aesthetic. As the wear of restorations is an important element in long-term use, the aim of this study was to evaluate the surface condition of nanohybrid and microfilled composite resins, after being subjected to the erosive action of dental bleaching protocols. This paper reflects a comparative study between one nanofilled composite and three microfilled composites used in restorations. For each composite, three sets of samples (under the form of composite discs) were created: a control group, an "office bleach" group with discs bleached with 40% hydrogen peroxide gel, and a "home bleach" group with discs bleached with 16% carbamide peroxide gel. Wear was numerically determined as the trace and the coefficients of friction obtained using a tribometer, the ball-on-disk test method, and two balls: alumina and sapphire. For all composite groups, there were statistically significant differences between the wear corresponding to the control and bleaching groups, for both testing balls. Regarding the composite type, the largest traces were recorded for GC Gradia direct anterior, for all groups, using the alumina ball. In contrast, for the sapphire ball, 3M ESPE Filtek Z550 was characterized by the largest traces. With respect to the friction coefficients, the "office bleach" group recorded the largest values, no matter the composite or the ball type used. The 3M ESPE Valux Plus composite recorded the largest friction coefficients for the alumina ball, and 3M ESPE Filtek Z550 for the sapphire ball. Overall, the "office bleach" group was characterized by higher composite wear, compared to the "home bleach" protocol or control group. Nanofilled composite resins showed superior wear resistance to microfilled resins after undergoing a bleaching protocol.