Surface properties and Streptococcus mutans biofilm adhesion of ion-releasing resin-based composite materials.

OBJECTIVE: To evaluate the adhesion of Streptococcus mutans (S. mutans) and related surface properties of ion-releasing resin-based composite (RBC) restorative materials. METHODS: Two ion-releasing RBCs, Activa (ACT) and Cention-N (CN), were compared to a conventional RBC (Z350) and a resin-modified glass ionomer cement (Fuji-II-LC). Ten disk-shaped specimens were fabricated for each material (n = 40). After standardized surface polishing procedure, the surface properties of the specimens were evaluated using surface roughness measurements by a profilometer and hydrophobicity using water contact angle measurements. To assess bacterial adhesion, the number of S. mutans bacteria was calculated from colony-forming units (CFU). Confocal laser scanning microscope analysis was done for qualitative & quantitative assessment. The data were analyzed using One-way ANOVA followed by Tukey's post-hoc test to compare the mean values of surface roughness, water contact angle and CFU values. To compare the mean dead cell percentage Kruskal-Wallis rank test and Conover test were used. A p-value of ≤ 0.05 was used to report the statistical significance. RESULTS: Z350 and ACT had the smoothest surfaces, followed by CN, and the roughest surface was seen in FUJI-II-LC. The lowest water contact angles were seen in CN, and Z350, and the highest were in ACT. S. mutans counts were the highest in ACT and the lowest in Z350 and CN. CN and Fuji-II-LC registered the highest percentage of dead bacterial cells, while the lowest were in ACT. SIGNIFICANCE: Surface properties did not significantly influence bacterial adhesion. More S. mutans bacteria accumulated on ACT than on the nanofilled composite and on CN. CN had antibacterial effects against Streptococcus mutans biofilms.

Ion releasing direct restorative materials: Key mechanical properties and wear.

OBJECTIVES: To investigate the depth of cure (DoC), fracture toughness (KIC) and wear of ion releasing resin-based composite (RBC) restorative materials. METHODS: Two ion releasing RBCs, Activa (ACT) and Cention-N (CN) were compared to a conventional RBC (Z350) and a resin-modified glass ionomer cement (Fuji-II-LC). The DoC was measured in a 10-mm deep semi-circular metal mold with a 2-mm internal radius (n = 8). The molds were irradiated from one end for 20-s. The Knoop hardness (KH) was measured at 0.5-mm intervals from the surface after the specimens had been stored at 37 °C for 24-h. To measure the KIC, single-edge-notched specimens (n = 15/group) were prepared (25×5x2.5-mm) for a 3-point bending test and then stored for either 1 or 30-days in water at 37 °C. Disk-shaped specimens (n = 10) were subjected to 250,000-load cycles of 49-N using a chewing simulator against spherical steatite antagonists. DoC and wear data were analyzed by one-way ANOVA and Tukey post hoc tests (p ≤ 0.05). KIC data were analyzed by two-way ANOVA and one-way ANOVA, and the Tukey post hoc test (p ≤ 0.05). In addition, an independent t-test was used to determine if storage time had any effect (α = 0.05) on the KIC of each material. RESULTS: Maximum hardness value was the highest for Z350 and the lowest for ACT. The depth at which 80% of the maximum KH, was the highest for CN (9.2 mm) and the lowest for Z350 (2 mm). All tested materials met the manufacturers' claims for DoC. After 1-day, the highest KIC values were recorded for ACT and the lowest for Fuji-II-LC. Water storage (30-days) significantly reduced the KIC value for all materials except Fuji-II-LC. The highest wear rate values were recorded for CN followed by ACT. SIGNIFICANCE: All tested materials met their manufacturers' claims for DoC. Water storage for 30-days significantly reduced the fracture toughness for ACT and CN. Wear was significantly higher for ACT and CN.

Effect of a broad-spectrum LED curing light on the Knoop microhardness of four posterior resin based composites at 2, 4 and 6-mm depths.

OBJECTIVE: To measure the Knoop microhardness at the bottom of four posterior resin-based composites (RBCs): Tetric EvoCeram Bulk Fill (Ivoclar Vivadent), SureFil SDR flow (DENTSPLY), SonicFill (Kerr), and x-tra fil (Voco). METHODS: The RBCs were expressed into metal rings that were 2, 4, or 6-mm thick with a 4-mm internal diameter at 30°C. The uncured specimens were covered by a Mylar strip and a Bluephase 20i (Ivoclar Vivadent) polywave(®) LED light-curing unit was used in high power setting for 20s. The specimens were then removed and placed immediately on a Knoop microhardness-testing device and the microhardness was measured at 9 points across top and bottom surfaces of each specimen. Five specimens were made for each condition. RESULTS: As expected, for each RBC there was no significant difference in the microhardness values at the top of the 2, 4 and 6-mm thick specimens. SureFil SDR Flow was the softest resin, but was the only resin that had no significant difference between the KHN values at the bottom of the 2 and 4-mm (Mixed Model ANOVA p<0.05). Although the KHN of SureFil SDR Flow was only marginally significantly different between the 2 and 6-mm thickness, the bottom at 6-mm was only 59% of the hardness measured at the top. CLINICAL SIGNIFICANCE: This study highlights that clinicians need to consider how the depth of cure was evaluated when determining the depth of cure. SureFil SDR Flow was the softest material and, in accordance with manufacturer's instructions, this RBC should be overlaid with a conventional resin.

Tooth-bleaching procedures and their controversial effects: A literature review.

AIM: This review article will help clinicians improve their understanding of the history of bleaching procedures, bleaching types, components, mechanisms, and their effects on soft tissue, tooth structures, resin composite, and bonding. METHODS: The controversial issues about bleaching procedures and their effects are reviewed. Additionally, the consequences of pre- and post-bleaching on the bonding potential of composite resin restorations to tooth structure are discussed. CONCLUSION: The overall goal of the paper is to help reduce risks for patients.

Effects of surface treatment and artificial aging on the shear bond strength of orthodontic brackets bonded to four different provisional restorations.

OBJECTIVE: To evaluate the combined effects of material type, surface treatment, and thermocycling on the bond strength of orthodontic brackets to materials used for the fabrication of provisional crowns. MATERIALS AND METHODS: Four materials were included in this study (ProTemp, Trim Plus, Trim II, and Superpont C+B). Sixty cylindrical specimens (1 × 3 cm) were prepared from each material and equally divided into three groups. The first group was ground with silica carbide paper, the second was polished with pumice, and the last group was sandblasted with 50-µm aluminum oxide particles. Stainless-steel maxillary central incisor brackets (Victory Series, 3M) were bonded to the provisional material specimens with Transbond XT light-cured composite resin, and half of the specimens from each group were thermocycled 500 times in 5°C and 55°C water baths. Then the brackets were debonded with shear testing, and the results were statistically analyzed by three-way analysis of variance and Tukey's multiple-comparison tests at α  =  0.05. Adhesive Remnant Index (ARI) was also identified. RESULTS: Before and after thermocycling, ProTemp materials showed the highest shear bond strength with orthodontic brackets (10.3 and 13.1 MPa, respectively). The statistical analysis indicated an interaction among the three independent variables (P < .05) and statistically significant differences in bond strength among provisional materials (P < .001), surface treatments (P < .001), and thermocycling (P < .05). According to the ARI, most groups demonstrated adhesive failure. CONCLUSIONS: The provisional material type, surface treatment, and artificial aging have a significant effect on bond strength. Sandblasting treatment exerts a beneficial effect on shear bond strength.

Effect of exposure time on the polymerization of resin cement through ceramic.

PURPOSE: This study measured the effects of using three different exposure times to cure one resin cement through two types of ceramic. MATERIALS AND METHODS: One light-curing resin cement (Variolink II, Ivoclar Vivadent) was exposed for 20 s, 40 s, or 60 s with a BluePhase G2 light (Ivoclar Vivadent) on the high power setting through 1.0 mm of either ZirPress (ZR) or Empress Esthetic (EST) ceramic (Ivoclar Vivadent). The degree of conversion (DC) of the resin was measured 100 s after light exposure. The Knoop microhardness (KHN) was measured 5 min after light exposure and again after 24 h. The DC and KHN results were analyzed with ANOVA followed by Scheffe's post-hoc multiple comparison tests at α = 0.05. RESULTS: Increasing exposure time had a significant effect on the KHN and DC values for the resins exposed through both ceramics. As exposure times increased, the influence of the ceramic was reduced; however, the microhardness values were greater for the cement exposed through EST ceramic. When the exposure time was increased from 20 s to 40 s, microhardness values for the resin increased by 39.6% through the EST ceramic. When exposed for 60 s, there were no differences between the 100-s DC values or 5-min KHN values using either ceramic (p > 0.05). There was an excellent correlation between the DC at 100 s and the microhardness values measured at 5 min. CONCLUSION: Resin polymerization was greater through EST than ZR ceramic. At least 40 s to 60 s from the Blue- Phase G2 on high power mode is required to cure this resin cement through 1.0 mm of ceramic.

Effects of single-peak vs polywave light-emitting diode curing lights on the polymerization of resin cement.

PURPOSE: This study examined the effect of selecting a single-peak blue vs a polywave blue/violet emission LED curing light on the degree of conversion (DC) and Knoop microhardness (KHN) of resin cements when light cured through a ceramic disk. MATERIALS AND METHODS: Two shades (A1 and A4) of resin cement (Variolink II) were placed in a 0.5-mm-thick ring. The top surfaces were covered with a Mylar strip and further covered with a disk of 1-mm-thick Empress Esthetic ceramic, shade A2. The specimens were light cured by means of an Elipar-S10 (3M ESPE, single-peak blue LED) or BluePhase-G2 (Ivoclar Vivadent, polywave blue/violet LED) curing light, both for 20 s, directly on the surface of an attenuated total reflectance FT-IR plate at 30°C. The DC of the resin was calculated after 100 s. The specimens were removed, and the Knoop microhardness was tested immediately and again after 24-h storage in the dark at 37°C and 100% humidity. Five specimens were made in each group. The DC and Knoop microhardness results were analyzed with ANOVA and Fisher's PLSD at α = 0.05. RESULTS: The choice of curing light had no significant effect on the DC and only a small effect on the immediate and 24-h KHN values. Shade A4 of the resin cement was harder and had a higher DC than shade A1. CONCLUSION: When light cured for 20 s, Variolink II resin cement can be light cured with either the single-peak or the polywave curing light. Shade A4 of the cement was slightly harder than A1.

The effects of different shades of resin luting cement on the color of ceramic veneers.

The purpose of this study was to quantitatively evaluate the effects of different shades of light-polymerized resin cement on the color of two different thicknesses (0.5 mm and 0.7 mm) of three different ceramic materials (Esthetic, e.max, and ZirPress). A spectrophotometer (Color Eye 7000A - CIE (L*a*b*) was used to measure the color of specimens on the control substrate without cement, and then on (Translucent, White Opaque, B0.5, A1, and A3 of RelyX™ Veneer cement). The mean values of color difference (ΔE) were higher for Esthetic, followed by ZirPress, with the lowest values for e.max. The mean values of ΔE decreased when the thickness of ceramic increased from 0.5 mm to 0.7 mm. It was observed that the White Opaque had significantly increased ΔE values when compared with (TR, B0.5, A1, and A3), whereas no significant difference between B0.5 and TR, and between B0.5 and A3.