SUMMARY This was an in vitro study to evaluate the effect of sodium ascorbate on the microshear bond strength (MSBS) of resin composite to sodium perborate-bleached dentin. Molar dentin sections were ...divided into six groups: 1) control, 2) sodium perborate (SP) bleach and immediate bonding, 3) SP and 30 second sodium ascorbate (SA); 4) SP and 1 minute SA; 5) SP and 2 minute SA; and 6) SP and 7 day delay before bonding. They were further divided into two-step self-etching (Clearfil SE Bond) or all-in-one self-etching (Xeno IV) adhesive systems. Resin composite microtubes were bonded according to dentin location-center, pulp horn, and peripheral positions-and an MSBS test was carried out. Failure mode was determined using light microscopy and scanning electron microscopy. There were no significant differences between the treatment types/groups. MSBSs were significantly higher for two-step self-etching adhesive compared with all-in-one self-etching adhesive (p=0.028). For the all-in-one adhesive, MSBSs at the center and pulp horn positions were significantly lower than the peripheral positions (p<0.001). All-in-one groups had significantly more adhesive failures than two-step adhesive groups (p=0.015). The odds of adhesive failure were higher at the pulp horn position than the peripheral position (p=0.004). Sodium perborate bleaching of dentin had no effect on MSBS or mode of failure for either two-step or all-in-one self-etching adhesives; therefore, the effect of sodium ascorbate was negligible. The two-step adhesive groups demonstrated the highest MSBS, and the all-in-one groups, when bonded to center and pulp horn dentin, exhibited the lowest MSBS.
Tensile bond strength measurements are commonly used for the evaluation of dentin adhesive systems. Most tests are performed using extracted non-carious human or bovine dentin. However, the adhesion ...of resins to caries-affected dentin is still unclear. The objectives of this study were to test the hypothesis that bonding to caries-affected dentin is inferior to bonding to normal dentin, and that the quality of the hybrid layer plays a major role in creating good adhesion. We used a micro-tensile bond strength test to compare test bond strengths made to either caries-affected dentin or normal dentin, using three commercial adhesive systems (All Bond 2, Scotchbond Multi-Purpose, and Clearfil Liner Bond II). For scanning electron microscopy, the polished interfaces between the adhesive bond and dentin were subjected to brief exposure to 10% phosphoric acid solution and 5% sodium hypochlorite, so that the quality of the hybrid layers could be observed. Bonding to normal dentin with either All Bond 2 (26.9 ± 8.8 MPa) or Clearfil Liner Bond II (29.5 ± 10.9 MPa) showed tensile bond strengths higher than those to caries-affected dentin (13.0 ± 3.6 MPa and 14.0 ± 4.3 MPa, respectively). The tensile bond strengths obtained with Scotchbond Multi-Purpose were similar in normal and caries-affected dentin (20.3 ± 5.5 MPa and 18.5 ± 4.0 MPa, respectively). The hybrid layers created by All Bond 2 in normal dentin and by Clearfil Liner Bond II in normal or caries-affected dentin showed phosphoric acid and sodium hypochlorite resistance, whereas the hybrid layers created by All Bond 2 in caries-affected dentin and those created by Scotchbond Multi-Purpose to normal and caries-affected dentin showed partial susceptibility to the acid and sodium hypochlorite treatment. The results indicate that the strength of adhesion to dentin depends upon both the adhesive system used and the type of dentin. Moreover, the quality of the hybrid layer may not always contribute significantly to tensile bond strength.
Objectives: Limited information exists with regard to the adhesive ability of glass ionomer cements (GIC) and recently developed resin-based dentin bond systems to primary dentin. The aim of this ...study was to compare the microtensile bond strength of a conventional GIC (Fuji IX), a resin-modified GIC (Fuji II LC), and two resin-based dentin adhesives (Prime and Bond NT with NRC and Single Bond). The bonded interfaces were also observed using field emission electron microscopy(FE–SEM).
Methods: Microtensile bond test specimens were prepared on superficial dentin of primary and permanent molars. The specimens were bonded according to each manufacturer's instructions except for Prime and Bond NT/NRC which used Silux Plus resin composite instead of Dyract. Hour-glass shaped specimens were created (diameter of 1.2±0.02
mm) and stressed in tension at a crosshead speed of 1
mm/min. Results were analyzed using two-way ANOVA and LSD test, fracture modes were analyzed using the Mann-Whitney
U-test and Kruskall-Wallis test. Twelve specimens were prepared for each material on primary and permanent dentin. Samples were prepared in the same manner, then critical point dried, fractured and sputter-coated for the FE–SEM observations.
Results: Two-way ANOVA showed the overall bond strengths were greater for the permanent dentin compared with primary dentin. However, for individual material comparisons no differences among the bond strengths to primary and permanent dentin for Fuji IX (9.7, 12.2
MPa), Fuji II LC (16, 20.1
MPa), Prime & Bond NT/NRC (18.1, 21.6
MPa) and Single Bond (18.2, 21.6
MPa), were detected. However, Fuji IX bond strengths were significantly lower than the other systems tested when bonded to either primary or permanent dentin (
p<0.05). Failure mode showed cohesive failure of GIC and mostly adhesive failure for the resin–based adhesives. The FE–SEM observations showed hybrid-like layer formation for the GIC materials and hybrid layer formation for the resin-based adhesives.
Significance: The materials tested would be suitable for bonding to either primary or permanent dentin, but the resin-modified GIC or resin-based systems are likely to provide a stronger bond than the conventional GIC, Fuji IX.
Background: Test method, substrate material and operator variability are factors known to affect bond strength test outcomes. The aim of this study was to determine if, with increasing experience, ...individual operator skill in material handling influenced microshear bond strength outcomes.
Methods: This retrospective study used data collected from six preliminary tests carried out successively on enamel microshear bond strength for two adhesives: Clearfil SE Bond (Kuraray) and Adper Single Bond 2 (3M ESPE) by one operator. Mean and median microshear bond strength values, standard deviations and coefficients of variation for each adhesive test group were calculated and assessed.
Results: A gradual increase in mean microshear bond strengths, a decrease in standard deviations and coefficients of variation over time for both adhesives and a progressively more uniform distribution of microshear bond strength results recorded in individual test sets was observed. The results suggest an improvement in bonding reliability as experience is gained.
Conclusions: Operator skill in material handling appears to play a critical role in determining the outcome of bond strength testing. This same skill is probably relevant when using an adhesive for the first time clinically. It is important that clinicians become familiar with new adhesives in order to achieve optimal outcomes.
Background
This study evaluated the effect of: (1) chemomechanical caries removal (CMCR); (2) dentine surface treatments and (3) dentine substrates on adhesion of resin‐modified glass ionomer cement ...(RMGIC) adhesives.
Methods
One hundred and twenty permanent molars exhibiting moderate cavitation on the occlusal surface into dentine were used. Seventy‐five carious molars were used for bond strength testing; the remaining 45 for micromorphological evaluation of the bonded interface. Caries was excavated with NaOCl‐based CMCR (Carisolv), enzyme‐based CMCR (Papacarie), or conventional rotary caries removal methods. Dentine surface treatment was performed using 37% phosphoric acid, 25–30% PAA or 20% PAA + 3% AlCl3.
Results
Three‐way ANOVA revealed that all three factors ‘caries removal methods’, ‘dentine surface treatments’ and ‘dentine substrates’ did not significantly affect bond strength (p > 0.05). Scanning electron microscopy micrographs showed that the acid‐base resistant layer was thicker in caries‐affected dentine compared to sound dentine.
Conclusions
NaOCl‐ and enzyme‐based CMCR methods have no adverse effect on adhesion of RMGIC adhesives to sound and caries‐affected dentine. Dentine surface treatment with 37% phosphoric acid for 5 s has no negative effect on bonding of RMGIC adhesives to dentine compared with using polyacrylic acid for 10 s. RMGIC adhesives bonded well to both sound and caries‐affected dentine.
During polymerization of resin composites, shrinkage stresses compete with resin-dentin bonds in a manner that can cause failure of the bond, depending upon the configuration of the cavity, its ...depth, and the restorative technique. The hypothesis tested in this study was that the effect of cavity configuration (C) and remaining dentin thickness (RDT) influence resin bond strength to the dentin of Class I cavity floors. The occlusal enamel was ground to expose a flat superficial dentin surface as a control (superficial dentin, C-factor = 1) in human extracted third molars. Cavities 3 mm long x 4 mm wide were prepared to a depth 2 mm below the ground dentin surfaces (deep dentin within cavity floor, C-factor = 3). To assess the relationship between C-factor and RDT, we removed the walls of cavities, making a deep flat surface for bonding (deep dentin, C-factor = 1). The teeth were restored with either Clearfil Liner Bond II (LB II), One-Step (OS), or Super-Bond D Liner (DL), followed by Clearfil Photo Posterior resin composite. After 24 hrs' storage in water, the teeth were sectioned vertically into 3 or 4 slabs (0.7 mm thick) and trimmed for the micro-tensile bond test so that we could determine the strength of the resin bonds to the pulpal floor. All groups gave high bond strengths to superficial dentin, but OS and DL gave significantly lower bond strengths to flat deep dentin when the C-factor was 1. When the C-factor was increased to 3 by the creation of a three-dimensional cavity preparation, the bond strengths of all materials fell (range, 21 to 35%), but the difference was significant (p < 0.05) only with DL. SEM observations of failure patterns showed that specimens with high bond strengths tended to exhibit cohesive failures within the hybrid layer, while specimens exhibiting low bond strengths showed failures at the top of the hybrid layer. Some adhesives do not bond well to deep dentin, making them more susceptible to polymerization shrinkage stress that develops in cavities with high C-factors.
Summary
Background
Erythromycin (ERY) induces anhidrosis in foals. Azithromycin (AZI) and clarithromycin (CLA), often combined with rifampicin (RIF), are commonly used to treat Rhodococcus equi ...infections, but effects on sweating have not been investigated.
Objective
To determine the effects of AZI, CLA and RIF on sweat responses in normal foals.
Study design
Each experiment was a blinded, duplicated, six foal × three period counterbalanced within subjects design (12 foals/experiment).
Methods
Antimicrobials were given orally for 5 days. In Experiment 1, ERY, AZI and CLA were given. In Experiment 2, ERY, RIF and ERY/RIF combination were used. Quantitative intradermal terbutaline sweat tests were performed daily for 3 days before and 1, 2, 5, 9, 24, and 39 days after treatment. Data were analysed by repeated measures analysis of variance procedures. Significance was P≤0.05.
Results
In Experiment 1, all macrolides suppressed sweating although CLA and AZI were less potent than ERY. In Experiment 2, significant sweat suppression occurred in foals given ERY with or without RIF, but there was no effect of RIF alone. Rifampicin reduced sweat suppression by ERY on Day 1 of treatment but not thereafter.
Main limitations
Because ERY blood concentrations were not measured, effects of RIF on ERY‐induced anhidrosis could not definitively be ascribed to altered ERY bioavailability.
Conclusions
All macrolides commonly used to treat R. equi pneumonia, i.e. ERY, AZI and CLA, induce anhidrosis in foals. The potent anti‐sudorific effect of ERY is delayed, but not substantially affected by concurrent RIF administration.
Background: Resin‐based cements are brittle materials and the major shortcomings of these materials are manifested in their sensitivity to flaws and defects. Although various mechanical properties ...of resin luting cements have been described, few fracture toughness test data for resin‐based luting cements using the short rod design have been published.
Methods: Specimens were prepared from five resin luting cements. For each material a total of 36 disc‐shaped specimens were prepared using a custom‐made mould. Specimens were randomly divided into six groups of six, immersed in two solutions: distilled water and 0.01 mol/L lactic acid at 37 °C for 24 hours, 1 month or 3 months. The specimens were loaded using a universal testing machine. The maximum load at specimen failure was recorded and the KIc (MPa. M 0.5) was calculated.
Results: There was a relationship between material, storage solution and time (p < 0.05). Nexus 3 showed the highest KIc followed by Panavia F, Calibra, Smart Cem2 and seT.
Conclusions: The fracture toughness of the resin luting cements was affected by both time and storage solution. Comparable fracture toughness of conventional resin cement and self‐adhesive resin cements was observed.
Background
A systematic review was undertaken to determine the clinical outcomes of resin modified glass‐ionomer cement or glass‐ionomer cement‐resin composite (RMGIC/GIC‐RC) laminate restorations ...and flowable resin composite (FRC)‐lined RC restorations compared to that of non‐laminate RC restorations.
Methods
Electronic databases were searched and filtered for relevant papers by assessing titles, s and full‐text articles. Randomized controlled clinical trials (RCTs) were included, comparing the clinical performance of RMGIC/GIC‐RC laminate restorations and FRC‐lined restorations with RC restorations as the control. The articles were categorized and critically appraised. Raw data were used for a fixed effects meta‐analysis.
Results
Thirteen articles were included in the review. Five evaluated FRC‐lined restorations, and eight studies evaluated RMGIC/GIC‐RC laminate restorations, comparing with non‐laminate RC restorations. Three of eight RMGIC/GIC‐RC laminate restorations assessed only postoperative sensitivity. A meta‐analysis could only be conducted in three studies with the FRC‐lined restorations as the intervention. The meta‐analysis found no significant difference in clinical failures between FRC‐lined RC restorations and RC restorations with no lining (p > 0.05).
Conclusions
Based on current clinical evidence, a FRC lining is no more advantageous than RC restorations with no FRC lining. More long‐term RCTs are required, particularly for evaluating RMGIC/GIC‐RC laminate restorations.
Abstract Objectives To evaluate the quality of bonded resin–dentine interfaces produced by two self-etching primer adhesives after casein phosphopeptide–amorphous calcium phosphate (CPP–ACP) ...treatment, in comparison to untreated dentine. Methods Thirty-four adult molar teeth were sectioned to obtain dentine with tubule orientations parallel/oblique or perpendicular to the surface. The specimens were divided into ‘smear layer’ (1A, 1B) and ‘no smear layer’ groups, after treatment with 15% EDTA (2A, 2B). The specimens were then left either untreated (1A, 2A) or treated (1B, 2B) with CPP–ACP paste (Tooth Mousse, GC Corp.) for 60 min × 7 days. Each treatment group was divided into three subgroups and specimens etched/conditioned (no conditioning; 30–40% phosphoric acid (H3 PO4 ); 20% polyacrylic acid) and bonded with either a 2-step self-etching primer adhesive (Clearfil SE Bond, Kuraray Medical) or an ‘all-in-one’ adhesive (G-Bond, GC Corp.) and a hybrid resin composite. After 24-h water storage, the bonded specimens were sectioned, polished up to 4000-grit abrasive silicon carbide paper and 0.25-μm diamond paste, prepared for FE-SEM using the acid–base technique, critical point-dried, gold-coated and examined. Bonded and fractured dentine interfaces were also prepared and examined. Results The 2-step adhesive produced a similar appearance of bonded resin–dentine interface irrespective of smear layer group, treatment or etching/conditioning. After polyacrylic acid conditioning, the ‘all-in-one’ adhesive exhibited more areas with bond failures. The bond failures were within the hybrid layer and more pronounced following CPP–ACP treatment. Conclusion The quality of the bonded resin–dentine interface produced after CPP–ACP treatment may depend on the adhesive system used.
PDF
