Influence of Antibacterial Copper Glass Particles on Surface and Mechanical Properties of Flowable Composites

Copper oxide containing phosphate glasses showed an antibacterial action against streptococcus sanguis, streptococcus mutans and staphylococcus epidermidis. This study aimed to investigate the effect of adding copper glass particles (025 wt%) into flowable composites (Filtek Z350XT flowable and Fusio liquid dentin dental flowable) to induce antibacterial properties. Surface (contact angle and Vicker hardness number) and mechanical (flexure strength, strain and modulus) properties of modified composites have been tested throughout this study; the antibacterial action will be tested in the future. The results showed that both surface and mechanical properties were dependent on the original composite as well as the added filler content. Lower contact angles, indicating higher wettability of the composites, observed with the higher loading of copper glass particles in both resin composites; this high wettability was obvious with Fusio flowable composites. This would be beneficial in bacterial adhesion to the composite surface and hence the expected antibacterial activity of copper glass against the adherent bacteria during biofilm formation. Surface hardness was not negatively affected by adding copper glass particles, except at higher loading levels (25 wt%) particularly when added to Z350 composites. This could indicate that the copper glass at low wt% had no adverse effect on monomer conversion. Generally, the rigidity (indicated by flexure modulus) and strain % of both composites were not affected by the presence of copper glass particles. Finally, it can be concluded that addition of low wt% of copper glass particles (up to 10 wt%) could provide a restorative material with antibacterial action without compromising their surface and mechanical properties. Addition of high wt% of copper glass to Fusio flowable in particular could be beneficial in producing a more hydrophilic material that could potentially encourage bacterial adhesion and hence a significant antibacterial action of copper glass against adherent bacteria will be expected. (608) Dalia A. Abuelenain E.D. J. Vol. 64, No. 1 mostly bioinert to prevent the recurrent decays (1). This has therefore been documented as the main cause of failure in resin restorations (2). Two main mechanisms are needed to prevent secondary caries; suppressing biofilm acids and promoting remineralization (1). Researchers are diligent to modify the current resin restorative materials with antibacterial elements to prevent caries under dental restorations at the same time to allow for hard tissue remineralization without the need of several materials application. For this purpose, bioactive resins with anti-caries properties were developed and a new generation of bioactive/therapeutic materials has been introduced (1). Several materials with antibacterial actions were considered as modifiers for dental restorative materials (1,3–11). Examples of these materials include zinc methacrylate monomer, silver particle, titanium dioxide, calcium phosphate, zinc oxide and copper oxide. Silver particles known to have antimicrobial activity against Escherichia coli and Streptococcus mutans were added to resins in previous investigations (1,6) . The silver nanoparticles greatly reduced biofilm growth without negatively affecting the material’s color and bond strength. Incorporation of calcium phosphate particles with antibacterial activity into resins released calcium and phosphate ions and re-mineralized carious lesions (12). However, composites containing calcium phosphate particles were mechanically weak and cannot be handled as a restorative materials (1). Fluoride is a dual element, that can inhibit bacterial metabolism and enhance tooth remineralization (1). Topical fluoride application will provide remineralization of infected and affected dental tissues with the antibacterial action when applied as a glass ionomer restoration; this bacterial inhibition will diminish if fluoride is incorporated in resin based restorations (13). Regardless of the antibacterial action of fluoride, it was not proven that fluoride releasing restorative materials will reduce the incidence of recurrent caries (14). In several investigations (7,15), Copper oxide (CuO) delivered by phosphate based glass fibers, showed antibacterial action against streptococcus sanguis, the main cariogenic bacteria streptococcus mutans (16) and staphylococcus epidermidis. Furthermore, CuO particles were proved to be more potent against streptococcus mutans, compared to zinc oxide particles as confirmed by Ramazanzadeh et al (7). Therefore, adding CuO particles to restorative materials may lower the risk of bacterial accumulation on restorative materials and then reducing the potential of recurrent decays in restored teeth. Incorporation of bioactive elements into dental resins are still within its experimental stage and it needs further investigations. The influence of added antibacterial elements into resin materials on surface and mechanical properties is an essential factor to determine the applicability of these restorative materials. Therefore, the aim of the present study was to evaluate the effect of adding copper glass particles to flowable composites on contact angle, surface hardness, flexure strength and modulus. MATERIALS AND METHODS Composite materials used in the present study (Filtek Z350 XT flowable, Fusio Liquid dentin) are presented in table 1. The filler used in this study was copper containing phosphate based glass particles of approximately 60200 mm in diameter. These particles have the composition of 50 mol% P2O5, 30 mol% CaO, 10 mol% NaO and 10 mol% Cu (15). Copper glass was added at 0, 1, 5, 10 and 25 wt % to each composite material; this resulted in 10 experimental groups, 5 groups (n=3 for each group) for each composite material. Samples were coded as Z350, 1% Cu Z350, 5%Cu Z350, 10% Cu Z350 and 25% Cu Z350. Fus, 1%Cu Fus, 5%Cu Fus, 10%Cu Fus, 25%Cu Fus. INFLUENCE OF ANTIBACTERIAL COPPER GLASS PARTICLES ON SURFACE (609) Contact Angle Measurements Discs of 10 mm diameter and 2 mm height were prepared using a split Teflon mold (n=3). Experimental materials were backed into the Teflon mold and sandwiched between two celluloid strips and glass slides. Samples were then light cured from each side for 20 seconds using LED light (3M ELEBAR) with a wave length range between 430480 nm and light intensity of 1200Mw/cm2. Three samples from each composition were subjected to wettability measurement using a drop shape analyzer (Kruss). Contact angle was performed using distilled water as the test liquid. Drop Shape Analysis [DSA4] software was used to measure the contact angle. Vickers Hardness Number Discs of 10 mm diameter and 2 mm height were prepared using a split Teflon mold (n=3) as described above. Vickers hardness numbers were determined using a micro-hardness tester (Micromet 6040, Buehler, USA) under a load of 100 g and dwell time of 10 seconds. Three readings were recorded for each surface; the hardness number was presented as the average of these readings. Relative hardness (ratio of bottom to top hardness) for each experimental group was also recorded. Three-point Bending Test Thirty specimens were prepared (n=3 for each composition), by backing composite into a rectangular split Teflon mold (2x2x25 mm3) according to ISO 4049 specification for polymerbased restorations (17). Molds with composite materials were sandwiched between two celluloid strip and glass slides and tightened at both ends using paper clamps. Each specimen was then subjected to 4 overlapping 40 seconds curing cycles from one side. The cured specimen was then removed from the mold; excess materials were removed with a sharp scalpel. The prepared specimens were then stored for 24 hours in dry container at room temperature (22oC±1) prior to testing. Before flexure testing, dimension of each specimen was determined with a micrometer accurate to 0.01 mm. The threepoint bending test was carried out using the Instron testing machine (Instron 5944, USA) with a span of 20 mm at a crosshead speed of 0.25mm/ min and 2 KN load. The flexure strength (MPa), modulus (GPa) and strain at break (%) were measured using Bluehill 3 software. Statistical Analysis The data were collected and analyzed using oneway ANOVA and Tukey’s post hoc test to delineate areas of significance. Data collection and analysis was done using SPSS (Version 20.0, IBM, and New York, USA). TABLE (1) Details of restorative resin materials used in the study. Resin material Manufacturer Composition Filler loading Filtek Z350 XT flowable composite 3M ESPE Organic: bis-GMA, UDMA, TEGDMA, and bis-EMA(6) resins, In-organic: a combination of silica, zirconia, and zirconia/silica cluster filler 78.5% by weight 63.3% by volume Fusio Liquid dentin dental flowable composite PENTRON Organic: UDMA, TEGDMA, HEMA, 4-MET, In-organic: Silane treated barium glass, Silica. 65% by weight 52% by volume (610) Dalia A. Abuelenain E.D. J. Vol. 64, No. 1