Eugenio Jose Garcia

Evaporating solvents with a warm air-stream: effects on adhesive layer properties and resin-dentin bond strengths.

OBJECTIVES This study evaluated the effect of a warm or cold air-dry stream for solvent evaporation on the microtensile resin-dentin bond strength (muTBS), nanoleakage pattern (SEM), degree of conversion (DC) and solvent evaporation rates (SE) of an ethanol/water- (Adper Single Bond, [SB] 3MESPE) and an acetone-based (Prime & Bond 2.1, [PB] Dentsply), two-step etch-and-rinse adhesive system. MATERIALS AND METHODS Adhesives were applied on demineralized dentin surfaces. For SE, a warm or cold air-dry stream (10 s) was applied prior to light-activation (10 s). Bonded sticks (0.8mm2) were tested in tension (0.5 mm/min). Two bonded sticks from each tooth were immersed in a 50% (w/v) solution of silver nitrate (24 h), photodeveloped (8 h) and analyzed by SEM. The DC and solvent evaporation rate of the adhesives were evaluated under FTIR and analytical balance, respectively. Data were analyzed by two-way ANOVA and Tukey test (alpha=0.05). RESULTS Higher muTBS and lower nanoleakage were observed when the SE step was performed with warm air-dry stream. However, the DC of the adhesives was not altered by the use of a warm air-dry. CONCLUSIONS The use of a warm air-dry stream seems to be a clinical tool to improve the bond strength and the quality of the hybrid layer (less nanoleakage infiltration), since it might reduce the number of pores within the adhesive layer.

Antioxidant activity by DPPH assay of potential solutions to be applied on bleached teeth

The aim of this study was to assess, using the DPPH assay, the antioxidant activity of several substances that could be proposed to immediately revert the problems caused by bleaching procedures. The percentage of antioxidant activity (AA%) of 10% ascorbic acid solution (AAcidS), 10% ascorbic acid gel (AAcidG), 10% sodium ascorbate solution (SodAsS), 10% sodium ascorbate gel (SodAsG), 10% sodium bicarbonate (Bicarb), Neutralize(®) (NE), Desensibilize(®) (DES), catalase C-40 at 10 mg/mL (CAT), 10% alcohol solution of alpha-tocopherol (VitE), Listerine(®) (LIS), 0.12% chlorhexidine (CHX), Croton Lechleri (CL), 10 % aqueous solution of Uncaria Tomentosa (UT), artificial saliva (ArtS) and 0.05% sodium fluoride (NaF) was assessed in triplicate by 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical assay. All substances exhibited antioxidant activity, except for CL. AAcidS, AAcidG and VitE exhibited the highest AA% (p<0.05). On the contrary, CHX, NE, LIS and NaF showed the lowest AA% (p<0.05). In conclusion, AAcidS, AAcidG, SodAsS, SodAsG and VitE presented the highest antioxidant activity among substances tested in this study. The DPPH assay provides an easy and rapid way to evaluate potential antioxidants.

Evaluating resin-enamel bonds by microshear and microtensile bond strength tests: effects of composite resin

Objectives The aims of this study were to evaluate the effect of resin composite (Filtek Z250 and Filtek Flow Z350) and adhesive system [(Solobond Plus, Futurabond NR (VOCO) and Adper Single Bond (3M ESPE)] on the microtensile (µTBS) and microshear bond strength (µSBS) tests on enamel, and to correlate the bond strength means between them. Material and methods Thirty-six extracted human molars were sectioned to obtain two tooth halves: one for µTBS and the other one for µSBS. Adhesive systems and resin composites were applied to the enamel ground surfaces and light-cured. After storage (37ºC/24 h) specimens were stressed (0.5 mm/ min). Fracture modes were analyzed under scanning electron microscopy. The data were analyzed using two-way ANOVA and Tukeys test (α=0.05). Results The correlation between tests was estimated with Pearsons product-moment correlation statistics (α =0.05). For both tests only the main factor resin composite was statistically significant (p<0.05). The correlation test detected a positive (r=0.91) and significant (p=0.01) correlation between the tests. Conclusions The results were more influenced by the resin type than by the adhesives. Both microbond tests seem to be positive and linearly correlated and can therefore lead to similar conclusions.

Do the Microshear Test Variables Affect the Bond Strength Values

Little is known about the effect of specimen preparation and testing protocols on the micro-shear bond strength (μSBS) results. To evaluate whether variations in polyethylene rod use affect (μSBS)). Human dentin disks were randomly distributed into six groups (n = 5): polyethylene tube (3 levels) and adhesive system (2 levels). In Group 1, polyethylene tubes filled with polymerized composite) were placed on adhesive covered surfaces. Tubes were removed 24 h after water storage, leaving the rods only. In Group 2, the same procedure was performed; however, tubes were kept in place during testing. In Group 3, composite rods without tubes were placed on adhesive covered dentin. In all groups, adhesives were photoactivated after positioning filled tubes/rods on adhesive covered surfaces. Specimens were tested under shear mode and the data subjected to a two-way ANOVA and Tukeys tests. Groups 1 and 2 resulted in statistically similar mean μSBS (P > 0.05); however, a greater number of pretest failures were observed for Group 1. Higher μSBS values were detected for Group 3, irrespective of adhesive system used (P < 0.05). Removing the polyethylene tube before composite rod is placed on dentin affects μSBS values.

Reducing the incompatibility between two-step adhesives and resin composite luting cements.

PURPOSE To determine whether the adverse interaction between a two-step/acidic etch-and-rinse adhesive (One-Step Plus [OS], Bisco) and chemically cured resin luting cement [Variolink II, Ivoclar Vivadent] can improve adhesive coupling by reducing the dentin permeability with an oxalate desensitizer (BisBlock, Bisco). MATERIALS AND METHODS After exposing dentin on the occlusal surfaces of human third molars, bonding was performed on either oxalate treated (BB) or nontreated (NB) demineralized dentin. A resin luting cement was placed in the format of a crown following the light-curing mode (only with the base syringe [LC]) or the chemically curing mode (mixture of base and catalyst syringes [CC]). The activation of the LC or CC cements was either immediately [IM], meaning soon after the placement of LC and the initial set of CC cement (5 min), or after a delay of 20 min [DP] for both modes of polymerization. Five teeth were assigned to each experimental condition. Teeth were sectioned to obtain sticks with a cross-sectional area of 0.95 mm2, which were tested using the microtensile bond strength test soon after the specified periods of polymerization. The bond strength values of each adhesive were analyzed by three-way repeated measures ANOVA and Tukeys tests (α = 0.05). Fractographic analysis of the specimens was performed using SEM. RESULTS The delayed polymerization (for both LC and CC cements) produced low bond strength values compared to IM activation. When the BB was employed, the bond strength values of the CC cement was approximately doubled, while the BB did not affect the bond strength of the LC cement. Bond strength values of LC cements were higher than CC. The use of BB significantly improved the bond strength of CC cement only. The morphological observations confirmed the bond strength results. A myriad of voids could be detected in the luting cement side when BB was not applied, except for the immediately light-cured group. CONCLUSION The use of an oxalate desensitizer (BisBlock) reduced the incompatibility between a two-step etch-and rinse adhesive and chemically cured resin cements and light-cured systems in the delayed polymerization mode.

Six-month evaluation of a resin/dentin interface created by methacrylate and silorane-based materials

Objectives: This study aimed to compare the micro-tensile bond strength of methacrylate resin systems to a silorane-based restorative system on dentin after 24 hours and six months water storage. Material and Methods: The restorative systems Adper Single Bond 2/Filtek Z350 (ASB), Clearfil SE Bond/Z350 (CF), Adper SE Plus/Z350 (ASEP) and P90 Adhesive System/Filtek P90 (P90) were applied on flat dentin surfaces of 20 third molars (n=5). The restored teeth were sectioned perpendicularly to the bonding interface to obtain sticks (0.8 mm2) to be tested after 24 hours (24 h) and 6 months (6 m) of water storage, in a universal testing machine at 0.5 mm/min. The data was analyzed via two-way Analysis of Variance/Bonferroni post hoc tests at 5% global significance. Results: Overall outcomes did not indicate a statistical difference for the resin systems (p=0.26) nor time (p=0.62). No interaction between material x time was detected (p=0.28). Mean standard-deviation in MPa at 24 h and 6 m were: ASB 31.38 (4.53) and 30.06 (1.95), CF 34.26 (3.47) and 32.75 (4.18), ASEP 29.54 (4.14) and 33.47 (2.47), P90 30.27 (2.03) and 31.34 (2.19). Conclusions: The silorane-based system showed a similar performance to methacrylate-based materials on dentin. All systems were stable in terms of bond strength up to 6 month of water storage.

Influence of different test parameters on the microshear bond strength of two simplified etch-and-rinse adhesives.

PURPOSE To evaluate the effect of different test parameters on the resin-dentin microshear bond strength (μSBS). MATERIALS AND METHODS A 1.5-mm-thick dentin disk was prepared in each of 140 human molars. The disks were divided into five groups to test the following variables: time of adhesive light polymerization (n = 20), storage time (n = 40), bonding area (n = 40), Tygon tube removal (n = 20), and time of composite placement (n = 20). The adhesives were applied and each specimen was subjected to μSBS testing. All fractured specimens were observed with SEM. The data from each experiment were subjected to two-way ANOVA and Tukeys test (α = 0.05). RESULTS The storage time, bonding area, and Tygon tube removal did not influence the μSBS. Higher μSBS values were found when empty Tygon tubes were filled after positioning and when the adhesive was light polymerized before Tygon tube placement (p < 0.05). CONCLUSIONS Differences in test parameters affected the μSBS of adhesives, especially the time of adhesive light polymerization and composite placement.

Effect of Two Microshear Test Devices on Bond Strength and Fracture Pattern in Primary Teeth

This in vitro study evaluated the influence of two devices for application of shear load in microshear tests on bond strength and fracture pattern of primary enamel and dentin. Eighty primary molars were selected and flat enamel (40 teeth sectioned mesio-distally) and dentin (40 teeth sectioned transversally) surfaces were obtained. Both surfaces were polished to standardize the smear layer. Two-step etch-and-rinse adhesive systems (Adper Single Bond and XP Bond) were used. Polyethylene tubes was placed over the bonded surfaces and filled with composite resin. The microshear testing was performed after storage in water (24 h/37 °C) using two devices for application of microshear loads: a notched rod (Bisco Shear Bond Tester) or a knife edge (Kratos Industrial Equipment). Failure modes were evaluated using a stereomicroscope. Bond strength data were subjected to ANOVA and chi-square test to compare the failure mode distributions (α=0.05). No significant differences were observed between the groups for dentin and enamel bond strength or fracture patterns (p>0.05). The predominant failure mode was adhesive/mixed. In conclusion, the devices for application of shear loads did not influence the bond strength values, regardless of adhesive system and substrate.

Use of flowable composite as intermediary layer in non-carious cervical lesions restored with composite resin: 48-month follow-up

Purpose: In this case report study, the clinical performance of a microhybrid resin composite was compared with lined class V restorations or with restorations performed without a flowable resin composite, over a 48-month period. Case description: The patient of this case report presented 2 pairs of equivalent cervical abfraction lesions, under occlusion. Four restorations were placed in teeth 34, 35, 44 and 45. The restorations were divided into groups (Single Bond + Filtek-Flow + Filtek Z250 or Single Bond + Filtek Z250) and the materials were applied according to the manufactures instructions. Two previously calibrated operators placed the restorations and two other independent examiners evaluated the restorations at baseline and after 48 months, according to the USPHS criteria and modified criteria for color match. Conclusion: After 48 months of evaluation the lesions restored with Filtek-Flow as a liner under Filtek Z250 did not show better clinical performance than the restorations without Filtek-Flow. All the groups showed a trend toward dark yellowing after 48 months.