Luis Alexandre Maffei Sartini Paulillo

Effect of surface treatments of laboratory-fabricated composites on the microtensile bond strength to a luting resin cement

The purpose of this study was to evaluate the influence of different surface treatments on composite resin on the microtensile bond strength to a luting resin cement. Two laboratory composites for indirect restorations, Solidex and Targis, and a conventional composite, Filtek Z250, were tested. Forty-eight composite resin blocks (5.0 x 5.0 x 5.0mm) were incrementally manufactured, which were randomly divided into six groups, according to the surface treatments: 1- control, 600-grit SiC paper (C); 2- silane priming (SI); 3- sandblasting with 50 mm Al2O3 for 10s (SA); 4- etching with 10% hydrofluoric acid for 60 s (HF); 5- HF + SI; 6 - SA + SI. Composite blocks submitted to similar surface treatments were bonded together with the resin adhesive Single Bond and Rely X luting composite. A 500-g load was applied for 5 minutes and the samples were light-cured for 40s. The bonded blocks were serially sectioned into 3 slabs with 0.9mm of thickness perpendicularly to the bonded interface (n = 12). Slabs were trimmed to a dumbbell shape and tested in tension at 0.5mm/min. For all composites tested, the application of a silane primer after sandblasting provided the highest bond strength means.

Influence of Additional Adhesive Application on the Microtensile Bond Strength of Adhesive Systems

This study evaluated microtensile bond strength (pTBS) when an additional adhesive layer was applied to the dentin surface. Thirty-five human third molars were flattened to expose the occlusal dentin surface. The teeth were randomly assigned to 7 experimental groups: G1-Single Bond (SB); G2-additional layer of SB; G3--a layer of Scotchbond Multi-purpose (SMP) adhesive applied over SB; G4-Clearfil SE Bond (CE); G5-additional layer of CE; G6-Adper Prompt (AP) and G7-additional layer of AP. For the G2, G3, G5 and G7 groups, the first adhesive layer was light-cured before application of the additional layer. After bonding procedures, 5-mm high composite crowns were incrementally built up. The samples were sectioned to obtain 0.9 x 0.9 beams, which were tested under tension at a crosshead speed of 0.5-mm/minute until failure. The failure mode and adhesive thickness were evaluated under SEM. The pTBS data were analyzed by 1-way ANOVA and post-hoc Ducans Test (a=0.05). Mean adhesive thickness was analyzed by 1-way ANOVA and post-hoc Tukeys test (a=0.05). The results indicated that G3 presented the highest microTBS and the thickest adhesive layer. G6 and G7 presented the lowest microTBS values. When solvent-free adhesives systems were used, microTBS values were not affected by the thicker layer.

Bond strength to high-crystalline content zirconia after different surface treatments

The aim of this study was to evaluate the effect of primers, luting systems and aging on bond strength to zirconium oxide substrates. Eighteen zirconia discs (19.5 x 4 mm) were polished and treated (n = 3) either with a MDP primer (Md) or with a MDP and VBATDT primer (MV). In the control group (n = 3) no surface chemical treatment was performed. Zirconia specimens were cemented to prepolymerized composite discs utilizing resin cements - RelyX Unicem or Panavia 21 (RU and Pa, respectively). After 24 h, samples were sectioned for microtensile testing and returned to water at 37 degrees C for two different periods before being tested: 72 h or 60 days + thermocycling (5-55 degrees C/5000 cycles). Bond strength testing was performed at 1 mm/min. Values in MPa were analyzed through ANOVA and Tukeys Studentized Range (HSD) (p > 0.05). The application of MV primer resulted in the highest bond strength (22.77 MPa), statistically superior to Md primer (12.78 MPa), and control groups presented the lowest values (9.17 MPa). When luting systems were compared, RU promoted the highest bond strength (16.07 MPa) in comparison with Pa (13.75 MPa). The average bond strength decrease after aging (9.35 MPa) when compared with initial values (20.46 MPa). The results presented by this in vitro study suggest that a chemical surface treatment based on the MDP and VBATDT combination may improve bond strength between zirconia and luting system, without any previous mechanical treatment, depending on the luting system used. This chemical treatment may result in a reliable alternative to achieve adequate and durable bond strength.

Influence of extended light exposure time on the degree of conversion and plasticization of materials used as pit and fissure sealants

AIM To evaluate the conversion and plasticization of fissure sealer materials, as influenced by extended curing time. METHODS Twenty specimens (n=5) of a pit and fissure sealant and a flowable composite at two curing times (20 and 60 sec) were photocured with the Bluephase 16i light-emitting diode. The conversion was determined by Fourier transform infrared/attenuated total reflection spectroscopy 24 h after polymerization. Hardness was measured, and samples were stored in absolute ethanol for 24 h. A second hardness measurement was executed after storage to assess plasticization by the percentage of hardness decrease. Data were analyzed by analysis of variance and Pearsons correlation (α=0.05). RESULTS The pit and fissure sealant showed lower degree of conversion than the flowable composite. The 60-sec curing time increased the conversion only for the flowable composite. Plasticization was lower for the flowable composite than for the pit and fissure sealant. The 60-sec light exposure time showed a similar percentage of hardness decrease of 20 sec. A low correlation between the conversion and plasticization was found. CONCLUSION Extended curing time improved the conversion only for the flowable composite. The pit and fissure sealant presented lower conversion and higher plasticization than the flowable composite.

Influence of composite restorative materials and light-curing units on diametrical tensile strength

The aim of this study was to evaluate the diametrical tensile strength (DTS) of three light-curing photo-activated composites with two different light curing units (LCU). Three types of dental restorative composites were used in this study: micro filled A110 (3M Espe); P60 (3M Espe) for posterior restorations, and micro-hybrid Charisma (Heraeus-Kulzer). The two LCUs were: halogen light (HAL) (Degulux, Degussa) and blue light emitting diode (LED) (Ultrablue, DMC). Resin composite specimens were inserted incrementally into a Teflon split mold measuring 3 mm in depth and 6 mm in internal diameter, and cured using either LCU (n = 10). Specimens were placed into a dark bottle containing distilled water at 37 degrees C for 7 days. DTS tests were performed in a Universal Testing Machine (0.5 mm/min). Data were submitted to two-way ANOVA and Tukeys test. Results were (MPa): A110/HAL: 276.50 +/- 62.94a; A110/LED: 306.01 +/- 65.16a; P60/HAL: 568.29 +/- 60.77b and P60/LED: 543.01 +/- 83.65b; Charisma/HAL: 430.94 +/- 67.28c; Charisma/LED: 435.52 +/- 105.12c. Results suggested that no significant difference in DTS was obtained with LCUs for the same composite. However, resin composite restorative materials presented different DTS.

Effect of surface roughness on amalgam repair using adhesive systems

The objective of this in vitro study was to evaluate the effect of three surface treatments and two adhesive systems on the shear bond strength of old and freshly placed amalgam. The results suggested that the intact amalgam showed a significantly higher strength than repaired groups and the strongest repaired specimens were made when the amalgam surfaces were roughened with a diamond bur or microetcher. The adhesive systems showed no significant differences on bond strength with the same superficial texture.

Color Stability and Polymerization Behavior of Direct Esthetic Restorations

OBJECTIVES The current study evaluated the effect of accelerated artificial aging (AAA) on the color stability (CS) and degree of conversion (DC) of nanofilled and nanohybrid resin composites associated to different adhesive systems in direct esthetic restorations. MATERIAL AND METHODS Eighty bovine incisors were used to obtained dentin blocks (4 × 4 × 1 mm). The restorative systems were bonded to the blocks and photoactivated according to the manufacturers instructions. Three adhesive systems were used: Adper Scotchbond Multi-Purpose (conventional of three steps), Tetric N-Bond (conventional of two steps) and ClearFill SE Bond (self-etching). Also, two composites were used: Filtek Z350 XT (nanofilled) and IPS Empress Direct (nanohybrid). The restorations were made using a silicone mold placed on top of the prepared dentin blocks (N = 10). CS was measured after 300 hours of AAA by means of ultraviolet light using a spectrophotometer and CIE L*a*b* parameters on the top surface of the composite and at the bonded interface. The DC was performed using Fourier transform infrared spectroscopy (N = 10). Data were analyzed using two-way analysis of variance and Tukeys test (α = 0.05). RESULTS The adhesive systems had no significant influence on the color stability (ΔE) of either the restoration surface (α = 0.90) or the bonded interface (α = 0.78). However, composite influenced the color as measured by ΔE and isolated coordinates (α < 0.001). The nanohybrid composite showed increased DC values (67%) compared with the nanofilled (61%) with statistically significant differences (α < 0.001). CONCLUSIONS The adhesive system did not affect the final color of direct esthetic restorations. The nanohybrid composite demonstrated a higher DC and increased color stability after AAA compared to the nanofilled composite. CLINICAL SIGNIFICANCE The long-term color stability of composite restorations is a critical aspect of esthetic restorative procedures. Optimal Polymerization behavior of resin composite as indicated by the degree of conversion also influence on the color stability after artificial aging of composite restorations.

Effect of light curing modes and ethanol immersion media on the susceptibility of a microhybrid composite resin to staining.

The aim of this in vitro study was to evaluate the susceptibility of a hybrid composite resin (Filtek Z250 – 3M ESPE) to staining, when light cured in four different modes and immersed in two different media. Composite resin specimens were randomly prepared and polymerized according to the experimental groups (conventional - 550 mW/cm2 / 30 seconds; soft start - 300mW/cm2/ 10 seconds + 550 mW/cm2 / 20 seconds; high intensity - 1060 mW/cm2 – 10 seconds; pulse delay – 550 mW/cm2 – 1 seconds + 60 seconds of waiting time + 550 mW/cm2 – 20 seconds) and immersed in one of two media (distilled water or absolute ethanol) for 24h. Next, the specimens were immersed in a 2% methylene blue solution for 12 hours. Afterwards, the specimens were washed and prepared for the spectrophotometric analysis. For statistical analysis, two-way ANOVA (4×2) and Tukeys test were performed on the data at 0.05 confidence level. Soft start showed the least staining, and was statistically different from the high intensity and pulse delay light curing modes (p<0.05). Conventional light curing unit did not show statistically significant differences from any other groups (p>0.05). There were no significant differences between the two immersion media (p>0.05). The soft start polymerization mode showed lower susceptibly of the composite resin to staining than high intensity and pulse delay, irrespective of the immersion medium.

Effect of irradiation mode and filling technique on resin/dentin bonding strength in class I cavities

Factors such as light-curing mode, filling technique and cavity configuration may affect the bonding strength to dentin. This study evaluated the effect of irradiation mode and filling technique on resin/dentin bonding strength on the buccal wall of Class I cavities in human teeth. Occlusal enamel was removed to expose a flat dentin surface. Occlusal cavities (4 x 3 x 3 mm) were prepared in dentin. The adhesive Single Bond was applied according to the manufacturers instructions and TPH Spectrum composite resin was placed using the following: oblique incremental, horizontal incremental or bulk filling techniques. The composite resin was light-cured either by continuous (600 mW/cm2 for 40 s) or Soft-Start (250 mW/cm2 for 10 s + 600 mW/cm2 for 30 s) modes. Specimens of the control group were obtained by bonding the material to the flat exposed buccal wall of the cavity (C-factor = 1). The teeth were stored in water at 37 degrees C for 24 h and prepared for microtensile testing. Bonded beams of approximately 0.8 mm2 were obtained from the buccal wall and tested with a tension of 0.5 mm/min. Results were analyzed by two-way ANOVA, Tukeys test and Dunnetts test (alpha = 0.05). Incremental placement techniques with both irradiation modes produced higher bonding strength values than the bulk technique (p < 0.05). Bonding strength tested in the cavities had lower values than those obtained in flat dentin surfaces (control group) (p < 0.05), except for incremental fillings using stepped irradiation. Bonding strength to the cavity walls depends on the filling technique and on the irradiation mode of composite resins.

Nanoleakage evaluation of resin luting systems to dental enamel and leucite-reinforced ceramic

Purpose: The aim of this study was to evaluate the nanoleakage patterns between dental enamel and reinforced leucite ceramic, bonded with resin luting systems and a flowable composite resin. Materials and Methods: Twelve crowns of bovine incisors were randomly divided into four groups (n = 3) according to the luting procedure: Excite/Variolink II, Clearfil SE Bond/Panavia F, Scotchbond Multi‐Purpose Plus/RelyX ARC, and Single Bond 2/Filtek Z350 Flow. To evaluate the nanoleakage patterns, IPS Empress Esthetic disks (5 mm Ø and 1.2‐mm thick) were bonded to enamel, and, after 24 h, the specimens were immersed in a 50% (w/v) solution of silver nitrate (24 h), fixed, dehydrated, and processed scanning electron microscopy (SEM). Results: None nanoleakage on interface of the groups that Single Bond 2 followed by the flowable composite were used. The highest percentage of nanoleakage was shown by the Excite/Variolink II protocol. Also, in all conditions tested, none silver nitrate uptake was observed between the leucite‐reinforced ceramic and the resin luting cement. Conclusions: The use of a two‐step etch‐and‐rinse adhesive with flowable composite was able to promote an adequate seal of the bond interface at the enamel. Moreover, the conventional dual‐cured resin cements associated with simplified and dual‐cured adhesives tested are also indicated to bond thin ceramics to enamel, since all presented low silver nitrate uptake. Microsc. Res. Tech., 2012.