In Vitro Evaluation of Candida albicans Adhesion on Heat-Cured Resin-Based Dental Composites.

Microbial adhesion on dental restorative materials may jeopardize the restorative treatment long-term outcome. The goal of this in vitro study was to assess Candida albicans capability to adhere and form a biofilm on the surface of heat-cured dental composites having different formulations but subjected to identical surface treatments and polymerization protocols. Three commercially available composites were evaluated: GrandioSO (GR), Venus Diamond (VD) and Enamel Plus HRi Biofunction (BF). Cylindrical specimens were prepared for quantitative determination of C. albicans S5 planktonic CFU count, sessile cells CFU count and biomass optical density (OD570 nm). Qualitative Concanavalin-A assays (for extracellular polymeric substances of a biofilm matrix) and Scanning Electron Microscope (SEM) analyses (for the morphology of sessile colonies) were also performed. Focusing on planktonic CFU count, a slight but not significant reduction was observed with VD as compared to GR. Regarding sessile cells CFU count and biomass OD570 nm, a significant increase was observed for VD compared to GR and BF. Concanavalin-A assays and SEM analyses confirmed the quantitative results. Different formulations of commercially available resin composites may differently interact with C. albicans. The present results showed a relatively more pronounced antiadhesive effect for BF and GR, with a reduction in sessile cells CFU count and biomass quantification.

Cytotoxic and Genotoxic Effects of Composite Resins on Cultured Human Gingival Fibroblasts.

The aim of the study was to evaluate the cytotoxic and genotoxic potential of five commercially available dental composite resins (CRs), investigating the effect of their quantifiable bisphenol-A-glycidyl-methacrylate (Bis-GMA) and/or triethylene glycol dimethacrylate (TEGDMA) release. Experiments were performed using the method of soaking extracts, which were derived from the immersion of the following CRs in the culture medium: Clearfil-Majesty-ES-2, GrandioSO, and Enamel-plus-HRi (Bis-GMA-based); Enamel-BioFunction and VenusDiamond (Bis-GMA-free). Human Gingival Fibroblasts (hGDFs) were employed as the cellular model to mimic in vitro the oral cavity milieu, where CRs simultaneously release various components. Cell metabolic activity, oxidative stress, and genotoxicity were used as cellular outcomes. Results showed that only VenusDiamond and Enamel-plus-HRi significantly affected the hGDF cell metabolic activity. In accordance with this, although no CR-derived extract induced a significantly detectable oxidative stress, only VenusDiamond and Enamel-plus-HRi induced significant genotoxicity. Our findings showed, for the CRs employed, a cytotoxic and genotoxic potential that did not seem to depend only on the actual Bis-GMA or TEGDMA content. Enamel-BioFunction appeared optimal in terms of cytotoxicity, and similar findings were observed for Clearfil-Majesty-ES-2 despite their different Bis-GMA/TEGDMA release patterns. This suggested that simply excluding one specific monomer from the CR formulation might not steadily turn out as a successful approach for improving their biocompatibility.

Wear properties of dental ceramics and porcelains compared with human enamel.

STATEMENT OF PROBLEM: Contemporary pressable and computer-aided design/manufacturing (CAD/CAM) ceramics exhibit good mechanical and esthetic properties. Their wear resistance compared with human enamel and traditional gold based alloys needs to be better investigated. PURPOSE: The purpose of this in vitro study was to compare the 2-body wear resistance of human enamel, gold alloy, and 5 different dental ceramics, including a recently introduced zirconia-reinforced lithium silicate ceramic (Celtra Duo). MATERIAL AND METHODS: Cylindrical specimens were fabricated from a Type III gold alloy (Aurocast8), 2 hot pressed ceramics (Imagine PressX, IPS e.max Press), 2 CAD/CAM ceramics (IPS e.max CAD, Celtra Duo), and a CAD/CAM feldspathic porcelain (Vitablocs Mark II) (n=10). Celtra Duo was tested both soon after grinding and after a subsequent glaze firing cycle. Ten flat human enamel specimens were used as the control group. All specimens were subjected to a 2-body wear test in a dual axis mastication simulator for 120000 loading cycles against yttria stabilized tetragonal zirconia polycrystal cusps. The wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm(3)). Antagonist wear (mm) was also recorded. Data were statistically analyzed with 1-way ANOVA tests (α=.05). RESULTS: The wear depth (0.223 mm) of gold alloy was the closest to that of human enamel (0.217 mm), with no significant difference (P>.05). The greatest wear was recorded on the milled Celtra Duo (wear depth=0.320 mm), which appeared significantly less wear resistant than gold alloy or human enamel (P<.05). CONCLUSIONS: The milled and not glazed Celtra Duo showed a small but significantly increased wear depth compared with Aurocast8 and human enamel. Wear depth and volumetric loss for the glaze-fired Celtra Duo and for the other tested ceramics did not statistically differ in comparison with the human enamel.

Adhesive Cementation of Indirect Composite Inlays and Onlays: A Literature Review.

The authors conducted a literature review focused on materials and techniques used in adhesive cementation for indirect composite resin restorations. It was based on English language sources and involved a search of online databases in Medline, EMBASE, Cochrane Library, Web of Science, Google Scholar, and Scopus using related topic keywords in different combinations; it was supplemented by a traditional search of peer-reviewed journals and cross-referenced with the articles accessed. The purpose of most research on adhesive systems has been to learn more about increased bond strength and simplified application methods. Adherent surface treatments before cementation are necessary to obtain high survival and success rates of indirect composite resin. Each step of the clinical and laboratory procedures can have an impact on longevity and the esthetic results of indirect restorations. Cementation seems to be the most critical step, and its long-term success relies on adherence to the clinical protocols. The authors concluded that in terms of survival rate and esthetic long-term outcomes, indirect composite resin techniques have proven to be clinically acceptable. However, the correct management of adhesive cementation protocols requires knowledge of adhesive principles and adherence to the clinical protocol in order to obtain durable bonding between tooth structure and restorative materials.

The influence of adhesive thickness on the microtensile bond strength of three adhesive systems.

PURPOSE: To evaluate the effects of multiple adhesive layers of three etch-and-rinse adhesives on both adhesive thickness and microtensile bond strength (microTBS). MATERIALS AND METHODS: Midcoronal occlusal dentin of 36 extracted human molars was used. Teeth were randomly assigned to 3 groups (EB, XP, PQ) according to the adhesive system to be used: PQ1 (Ultradent) (PQ), EnaBond (Micerium) (EB), or XP Bond (Dentsply/DeTrey) (XP). Specimens from each group were further divided into three subgroups according to the number of adhesive coatings (1, 2, or 3). In all subgroups, each adhesive layer was light cured before application of each additional layer. After bonding procedures, composite crowns were incrementally built up. Specimens were sectioned perpendicular to the adhesive interface to produce multiple beams, approximately 1 mm2 in area. Beams were tested under tension at a crosshead speed of 0.5 mm/min until failure. Adhesive thicknesses and failure modes were evaluated with SEM. The microTBS data and mean adhesive thickness were analyzed by two-way ANOVA and multiple-comparison Tukey's test (alpha = 0.05). RESULTS: The mean bond strength (in MPa (SD)) of group EB gradually increased from 1 to 3 consecutive coatings (27.02 (9.38) to 44.32 (4.93), respectively) (p < 0.05). The highest mean bond strengths for the PQ (46.66 (12.95)) and XP groups (40.55 (5.69)) were obtained applying two adhesive coatings. The mean thickness of the adhesive layer (in microm (SD)) significantly increased with the number of coatings (p < 0.05), ranging from 29.45 (1.42) to 77.64 (1.10) for PQ, from 5.12 (0.68) to 37.75 (0.92) for EB, and from 12.64 (0.68) to 37.92 (0.71) for the XP group. Failure modes for EB specimens were mainly classified as adhesive failure between adhesive and dentin. The XP3 and PQ3 subgroups showed a greater number of total cohesive failure in adhesive. CONCLUSION: Multiple adhesive coats significantly affected bond strength to dentin. An excess of adhesive layer thickness can negatively influence the strength and the quality of adhesion.

Effect of three surface treatments on the adhesive properties of indirect composite restorations.

PURPOSE: To evaluate the effect of different surface treatments of composite resin blocks on the adhesive properties of indirect composite restorations. The null hypothesis tested was that none of the performed surface treatments would produce greater bond strength. MATERIALS AND METHODS: The crowns of 80 extracted molars were transversally sectioned next to the pulp to expose flat, deep dentin surfaces. Eighty-eight cylindrical composite specimens measuring 3.5 mm in diameter and 10 mm in height were prepared and randomly divided into 4 groups (CG, HFSiG, SaG, SaSiG), which respectively received the following treatments: control (CG): etching with 9.5% HF acid gel and application of a silane (HFSiG); sandblasting (SaG) with 50-microm Al2O3 from a distance of 10 mm at a pressure of 2.5 bars for 10 s; combination of sandblasting and silanization procedures (SaSiG). Two composite specimens of each group were analyzed with SEM, while the remaining twenty cylindrical specimen were bonded to dentin samples using a two-step adhesive system and a thin layer of composite. After 24 h storage and 5000 thermocycles, all specimens were loaded to failure under tension in a universal testing machine. The mean differences of each group were analyzed with the Kruskal-Wallis test, while multiple comparisons were made using the Ryan-Einot-Gabriel-Welsch Range test. P-values less than 0.05 were considered to be statistically significant in all tests. The fracture pattern of bonded specimens was also evaluated by SEM. RESULTS: SEM analysis showed morphological changes in each group. The mean values (in MPa) of TBS (+/- SD) for groups CG, HFSiG, SaG, and SaSiG were 11.17 +/- 3.48, 10.81 +/- 5.19, 16.51 +/- 3.45 and 16.55 +/- 3.16, respectively. Statistical analysis showed that the bond strength was significantly affected by surface treatment (p < 0.001). Multiple comparison analysis identified statistically significant differences for CG and HFSiG vs SaG and SaSiG (p < 0.05), while no significant differences were found for the comparisons CG vs HFSiG and SaG vs SaSiG (p > 0.05). Only a few adhesive failures were recorded (CG: 0.5%; SaG: 0.4%; HFSiG: 0.5%; SaSiG: 0.7%). The null hypothesis was rejected. CONCLUSION: Composite surface treatments are important for adhesion of indirect composite restorations. Roughening the composite area of adhesion, sandblasting, or both sandblasting and silanizing can provide statistically significant additional resistance to tensile load. Hydrofluoric acid etching with silane treatment did not reveal significant changes in tensile bond strength. These findings suggest that sandblasting treatment was the main factor responsible in improving the retentive properties of indirect composite restorations.