Durability Of Resin Research Articles

Can Chlorhexidine enhance the Bond Strength of Self-etch and Etch-and-rinse Systems to Primary Teeth Dentin?

Introduction: Modifying the durability of resin bonding systems resulted in introducing materials with cross-link property, such as chlorhexidine (CHX) that can promote the strength of resin-dentin bonding. The aim of this study was evaluation of the effect of CHX on shear bond strength (SBS) of self-etch (SE) and etch-and-rinse (E&R) bonding systems to the primary teeth dentin. Materials and methods: In this in vitro study, 40 freshly extracted primary molars collected and were cut mesiodistally, and then the buccal and lingual surface enamel was grounded. The specimens were randomly divided into two groups: I: Single Bond adhesive and II: Clearfil SE Bond adhesive. Then, each group was divided into two subgroups: On the buccal surface of each sampleCHX was applied for 30 seconds and on the lingual surface of (I2, II2 groups), CHX was not applied. The SBS (MPa) of samples was assessed using the Zwick universal testing machine. Data were analyzed by paired t-test and independent t-test using Statistical Package for the Social Sciences (SPSS), version 16. Results: The mean SBS was significantly higher in the Single Bond group with CHX (66.45 ± 8.3) than without CHX (25.43 ± 12.94) in the nonaging group (p = 0.002). There was no significant difference in the mean SBS in the Clearfil SE Bond group with CHX and without CHX in the aging and nonaging groups. Conclusion: CHX had positive influence on immediate SBS of Single Bond adhesive to primary teeth dentin. In addition, no positive effect has been seen in the Clearfil SE Bond system. Clinical significance: Now more researches are needed about the recommendation of CHX in resin restorations of primary teeth. Keywords: Chlorhexidine, Etch-and-rinse adhesive, Failure pattern, Self-etch adhesive, Shear bond strength.

Fully Automated System for 99Tc Monitoring in Hospital and Urban Residues: A Simple Approach to Waste Management.

99Tc is an artificial beta emitter widely used in nuclear medicine for diagnostic tests. A fully automated and rapid system for 99Tc monitoring is introduced with the aim to improve hospital residues management. This system can also be helpful for controlling urban wastewater. Figures of merit similar to those obtained with liquid scintillation counting were achieved by exploiting a simple, economic, and portable system with spectrophotometric detection. The combination of flow analysis techniques, i.e., lab-on-valve (LOV) and multisyringe flow injection analysis (MSFIA), with a selective resin ((weak base extraction chromatographic (WBEC) resin) enables the analysis to be performed in a short time, achieving high selectivity and sensitivity levels. After elution with NH4OH (3 mol·L-1), 99Tc is derivatized with 1,5-diphenylcarbohydrazide (DPC) and finally detected by a miniaturized fiber optic CCD spectrophotometer at 520 nm, exploiting a long path-length liquid waveguide capillary cell (LWCC) of 100 cm path length. The proposed method was optimized by experimental design, achieving a limit of detection (LOD) of 4 ng of 99Tc (2.5 Bq), a reproducibility of 6%, and a resin durability of 78 injections. The microcolumn allows one to preconcentrate up to 100 mL of sample without deterioration of the analytical signal. The automated system was successfully applied to hospital residues and urban wastewater, and the attained recoveries were between 90% and 110%.

Effect of a novel quaternary ammonium silane cavity disinfectant on durability of resin–dentine bond

ObjectiveThe present study examined the effect of a quaternary ammonium silane (QAS) cavity disinfectant on the viability of human dental pulp cells, dentine bond durability and nanoleakage of simplified etch-and-rinse adhesives. MethodsEtched dentine surface of third molars were randomly divided into two adhesive groups, Adper™ Single Bond 2 and Prime & Bond® NT™. For each adhesive, the teeth were randomly assigned to five cavity disinfectant groups (N=6): Group 1: deionised water (control); Group 2: 2% chlorhexidine (CHX); Group 3: 2% QAS; Group 4: 5% QAS and Group 5: 10% QAS. The cavity disinfectants were applied on etched dentine surfaces for 20s, followed by adhesive application. The bonded teeth were sectioned for bond strength testing at 24h, 6 months and 12 months. Viability of human dental pulpal cells was examined using MTT assay. Bond strength data were analysed using 3-way ANOVA and Tukey test. Interfacial nanoleakage was evaluated after 24h and 12 months and analysed using Kruskal–Wallis test. ResultsSignificant differences in bond strength were observed for the factors disinfectants (p<0.001) and time (p<0.001); while the factor, adhesive, was not significantly different (p=0.203). The 2% QAS cavity disinfectant preserved bond strength of both adhesives and reduced interfacial nanoleakage after 12 months. Cell viability was the lowest for 2% CHX, followed by 2% QAS and the control. ConclusionsThe 2% QAS cavity disinfectant demonstrated greater cell viability compared to 2% CHX, with no adverse effect on immediate bond strength and preserved bond stability over time. Clinical significanceIncorporation of 2% quaternary ammonium silane cavity disinfectant in the resin–dentine bonding protocol enhances the success rate of bonded restorations.

Effect of the type of acidic monomer on the bond durability of two-bottle type ceramic primer.

Ceramic primers consisting of γ-methacryloxypropyl trimethoxysilane (γ-MPS) and either 4-methacryloyloxyethyl trimellitate (4-MET) or 10-methacryloyloxydecyl dihydrogen phosphate (MDP) are useful for facilitating bonding of resin cement to silica-based ceramic surfaces. However, bond stability at the resin-ceramic interface differs among commercial ceramic primers. To determine the ability of 4-MET or MDP to hydrolyze the methoxy group in γ-MPS, the author designed two-bottle experimental ceramic primers comprising γ-MPS solution and an activator solution of 4-MET or MDP. The effects of the type of acidic monomer on contact angle and ceramic bond durability of resin were investigated. MDP and 4-MET promoted chemisorption of γ-MPS on the ceramic surface and enhanced the ceramic bond strength of the resin. However, thermocycling decreased ceramic bond strengths, as reflected by the increased number of bonded specimens that exhibited interfacial resin failure. Bond strength was greater for 4-MET-activated ceramic primer than for the MDP-activated ceramic primer, although most bonded specimens exhibited interfacial resin failure. Degradation behavior differed between the 4-MET-activated and MDP-activated ceramic primers.

A Literature Review on the Correlation Between Shear Bond Strength and the Degree of Conversion of Orthodontic Adhesive Systems

Objectives: The purpose of this study is to provide a comprehensive literature review on the correlation between shear bond strength and the degree of conversion of the orthodontic adhesive systems. Thus, this is considered as a major issue for the success of the orthodontic bonding techniques. Material and Methods: Electronic searches were performed in Pubmed and Scopus databases using relevant keywords. Textbook searching was also applied. Following the selection, full-text English language papers were fully reviewed to ensure that they met both the inclusion and the exclusion criteria. Results: Recent studies suggest that when increasing the DC, the SBS will increase. Thus, this results to a stiffer and a more durable resin. Conclusions: There is a wide range of factors affecting the SBS, DC, and their correlation. Some of them are related to the tooth etching techniques, adhesive related factors, curing units, and bracket materials. More research is required to develop more understanding of the role of these factors in determining the bonding success. This is because there are no specific published papers which were directly linked to the correlation between the SBS and the DC of orthodontic adhesives.

Novel Cavity Disinfectants Containing Quaternary Ammonium Monomer Dimethylaminododecyl Methacrylate.

This study was set to assess the possible benefits of novel cavity disinfectants with 5% dimethylaminododecyl methacrylate (DMADDM); and compare the effectiveness of saliva microbial-aging method with water-aging in measuring the changing of resin–dentin bond strength. Three cavity disinfectants were tested: 0.2% Chlorhexidine (CHX); 5% DMADDM; and 5% DMADDM + 0.2% CHX. Microtensile bond strength (μTBS) test was performed after microbial-aging with saliva microbial or water aging for one month. Hydroxyproline (HYP), the production of collagen degradation, was measured spectrophotometrically. Additionally, the antibacterial effects of each reagent were evaluated. The 5% DMADDM exerted the least percentage of resin–dentin bond strength loss after one month microbial-aging (p < 0.05). There were no statistically significant differences of bond strength decrease after one month water aging among the tested groups (p > 0.05). Microbial-aging method yield more drop of bond strength than water aging in all groups except 5% DMADDM (p < 0.05). Meanwhile, 5% DMADDM had the same matrix metalloproteinases (MMPs) inhibitory effects as the other two agents (p > 0.05), but much stronger antibacterial capability than 0.2% CHX (p < 0.05). This indicated that a cavity disinfectant with 5% DMADDM is promising for improving the stability of resin–dentin bonds in appearance of saliva biofilm; and the saliva microbial-aging method is more promising for studying the durability of resin–dentin bonds than water aging.

Influence of dimethyl sulfoxide used as a solvent on the physical properties and long-term dentin bonding of hydrophilic resins

ObjectiveTo examine the feasibility of dimethyl sulfoxide (DMSO) incorporation into relatively hydrophilic resins as a new potential method to improve the durability of resin–dentin bonds. MethodsSix experimental light-curing BisGMA/HEMA resins solvated in ethanol and DMSO with increasing concentrations of DMSO (0, 0.5, 1, 2, 4 and 10wt%) were prepared. The degree of conversion (DC) was evaluated by Fourier Transform Infrared Spectroscopy (n=8); water sorption (Wsp) and water solubility (Wso) were gravimetrically assessed (n=10); and flexural strength (FS) and elastic modulus (E) were determined by a three-point bending flexural test (n=10). Flat dentin surfaces on sound third molars (n=10/group) were bonded with resins containing 0, 2, 4 and 10wt% DMSO used as a two-step etch-and-rinse system. Dentin microtensile bond strength was determined at 24h and after two-year aging in artificial saliva at 37°C. ResultsDMSO significantly affected Wsp (p=0.0006), DC, Wso, FS, and E (p<0.0001). In general, the resins’ mechanical/physical properties were not affected by 2% or lower DMSO incorporation. Incorporation of 4% or higher DMSO content significantly increased DC, Wsp and Wso, but 2% or higher DMSO concentrations significantly reduced FS and E. No influence on immediate dentin bond strength occurred up to 4% DMSO incorporation. While 4% or higher DMSO concentrations impaired bond strength over time, the resin containing 2% DMSO presented significant higher dentin bond strength compared to the control resin after two year-aging. SignificanceThe use of DMSO as a new solvent in adhesive dentistry improves dentin bonding of relatively hydrophilic resins over time. 2% DMSO incorporation in BisGMA/HEMA resins should be sufficient to reduce bond strength loss without compromising polymer mechanical strength and physical properties.

Microtensile bond strength and micromorphologic analysis of surface-treated resin nanoceramics.

PURPOSEThe aim of this study was to evaluate the influence of different surface treatment methods on the microtensile bond strength of resin cement to resin nanoceramic (RNC).MATERIALS AND METHODSRNC onlays (Lava Ultimate) (n=30) were treated using air abrasion with and without a universal adhesive, or HF etching followed by a universal adhesive with and without a silane coupling agent, or tribological silica coating with and without a universal adhesive, and divided into 6 groups. Onlays were luted with resin cement to dentin surfaces. A microtensile bond strength test was performed and evaluated by one-way ANOVA and Tukey HSD test (α=.05). A nanoscratch test, field emission scanning electron microscopy, and energy dispersive X-ray spectroscopy were used for micromorphologic analysis (α=.05). The roughness and elemental proportion were evaluated by Kruskal–Wallis test and Mann–Whitney U test.RESULTSTribological silica coating showed the highest roughness, followed by air abrasion and HF etching. After HF etching, the RNC surface presented a decrease in oxygen, silicon, and zirconium ratio with increasing carbon ratio. Air abrasion with universal adhesive showed the highest bond strength followed by tribological silica coating with universal adhesive. HF etching with universal adhesive showed the lowest bond strength.CONCLUSIONAn improved understanding of the effect of surface treatment of RNC could enhance the durability of resin bonding when used for indirect restorations. When using RNC for restoration, effective and systemic surface roughening methods and an appropriate adhesive are required.

Mechanisms of degradation of the hybrid layer in adhesive dentistry and therapeutic agents to improve bond durability—A literature review

ObjectiveSuccess in adhesive dentistry means long lasting restorations. However, there is substantial evidence that this ideal objective is not always achieved. Current research in this field aims at increasing the durability of resin–dentin bonds. The objective of this paper is to examine the fundamental processes responsible for the aging mechanisms involved in the degradation of resin-bonded interfaces and the potential approaches to prevent and counteract this degradation. MethodsPubMed searches on the hybrid layer degradation were carried out. Keywords were chosen to assess hybrid layer degradation for providing up-dated information on the basis of scientific coherence with the research objective. Approaches to prevent and counteract this degradation were also reviewed. Results148 peer-review articles in the English language between 1982 and 2015 were reviewed. Literature shows that resin–dentin bond degradation is a complex process, involving the hydrolysis of both the resin and the collagen fibril phases contained within the hybrid layer. Collagen fibers become vulnerable to mechanical and hydraulic fatigue, as well as degradation by host-derived proteases with collagenolytic activity (matrix metalloproteinases and cysteine cathepsins). Inhibition of the collagenolytic activity and the use of cross-linking agents are the two main strategies to increase the resistance of the hybrid layer to enzymatic degradation. SignificanceThis review analyzes the issues regarding the durability of the adhesive interface, and the techniques to create stable resin–dentin bonds able to resist the collagenolytic hydrolysis that are currently studied.

Durability of resin bond strength to dental noble metal–ceramic alloys conditioned with novel mercapto silane-based primer systems

The purpose of this study was to investigate the efficacy of novel mercapto silane-based experimental primers on the resin bonding and its durability to dental noble metal–ceramic alloys in comparison with that of commercial primers. Disc-shaped gold–platinum–palladium, gold–palladium–silver, and palladium–silver alloy specimens were used as the adherents after air-abrasion. One of three commercial primers (M.L. Primer, Single Bond Universal, and All-Bond Universal) and two experimental primer systems (2-step application with γ-mercaptopropyltrimethoxysilane and then γ-methacryloxypropyltrimethoxysilane and a blend of the two silanes) was applied to each alloy. Resin cylinders with a diameter of 2.38 mm were bonded to the surfaces and light-cured. All bonded specimens were stored in water at 37 °C for 24 h and then half of them additionally water immersed for 7 days (37 °C) and then thermocycled 10,000 times before the shear bond strength test (n = 10). The surface energy parameters for unprimed and primed alloy surfaces were calculated based on the contact angle measurements. The bond strength data were non-parametrically analyzed at α = 0.05. Regardless of the alloy type, both mercapto silane systems equally and consistently showed superior bonding durability to the commercial primers. Pearson correlation analyses revealed moderate to strong, significant correlations between the surface energy parameters and the bond strength values. The two novel mercapto silane systems are a promising alternative for enhanced durability of resin bonding to dental noble metal–ceramic alloys.

Effect of proanthocyanidin incorporation into dental adhesive on durability of resin–dentin bond

BackgroundProanthocyanidin has shown to have beneficial effects on dentin bonding via its collagen cross-linking and protease inhibitory effects. ObjectiveThis study evaluated the effect of incorporation of 1–3% PA into a dental adhesive on durability of resin–dentin bond. Materials and methodsThe experimental adhesive was first formulated by combining 50wt% comonomer mixtures with 50wt% ethanol. PA was then added to the ethanol-solvated adhesive to yield three groups of adhesives at concentrations of 1.0wt%, 2.0wt% and 3.0wt%. The PA-free adhesive served as control. Flat dentin surfaces from forty extracted third molars were etched with 32% phosphoric acid and the specimens were randomly assigned to one of the four adhesive groups. Two layers of experimental adhesives were applied to etched dentin and light-cured for 20s after solvent evaporation. Composite build-ups were performed using Filtek Z250 (3M ESPE). The bonded teeth were divided into three subgroups for different methods of storage: (1) 24h indirect water exposure (IE), (2) 6 M IE and (3) 6 M direct water exposure (DE). After the designated period of water storage, the bonded teeth were sectioned into 0.9mm×0.9mm beams for bond strength testing. Bond strength data were evaluated by two-way ANOVA and Tukey׳s tests (α=0.05). Interfacial nanoleakage was examined using a field-emission scanning electron microscopy. Two-way ANOVA and Tukey׳s tests were used to examine the effects of PA concentration and water exposure on bond strength and percentage of nanoleakage (α=0.05). ResultsTwo-way ANOVA showed that the factors, water exposure and PA concentration had a significant effect on bond strength (p<0.001). Interaction between the two factors was also significant (p<0.001). Bond strength of all four adhesives decreased with PA concentrations and ageing. Type of water exposure had no effect on the bond strength of PA-incorporated adhesive; while direct water exposure significantly reduced the bond strength of PA-free adhesive. Conversely, the factors, water exposure and PA concentration showed a significant effect on nanoleakage percentage (p<0.001). Interaction between the two factors was not significant (p>0.05). ConclusionIncorporation of proanthocyanidin into a dental adhesive did not prevent resin–dentin bond degradation over time.

On the durability of resin–dentin bonds: Identifying the weakest links

Fatigue of resin–dentin adhesive bonds is critical to the longevity of resin composite restorations. ObjectivesThe objectives were to characterize the fatigue and fatigue crack growth resistance of resin–dentin bonds achieved using two different commercial adhesives and to identify apparent “weak-links”. MethodsBonded interface specimens were prepared using Adper Single Bond Plus (SB) or Adper Scotchbond Multi-Purpose (SBMP) adhesives and 3M Z100 resin composite according to the manufacturers’ instructions. The stress-life fatigue behavior was evaluated using the twin bonded interface approach and the fatigue crack growth resistance was examined using bonded interface Compact Tension (CT) specimens. Fatigue properties of the interfaces were compared to those of the resin–adhesive, resin composite and coronal dentin. ResultsThe fatigue strength of the SBMP interface was significantly greater than that achieved by SB (p≤0.01). Both bonded interfaces exhibited significantly lower fatigue strength than that of the Z100 and dentin. Regarding the fatigue crack growth resistance, the stress intensity threshold (ΔKth) of the SB interface was significantly greater (p≤0.01) than that of the SBMP, whereas the ΔKth of the interfaces was more than twice that of the parent adhesives. SignificanceCollagen fibril reinforcement of the resin adhesive is essential to the fatigue crack growth resistance of resin–dentin bonds. Resin tags that are not well hybridized into the surrounding intertubular dentin and/or poor collagen integrity are detrimental to the bonded interface durability.

The effects of the macroscopic conditions of a ceramic primer with high bond durability in a silica-based ceramic

An experimental ceramic primer was used to increase the bond durability of resin cement to computer-aided design and computer-aided manufacturing ceramics. Several factors influencing the bonding performance of the experimental ceramic primer were investigated, including the concentration of γ-methacryloxypropyltrimethoxysilane, the pH of the aqueous solution and the duration of the silanation reaction. An experimental primer A was prepared. Three types of primer B were obtained, leading to pHs of 1.0, 2.0 and 5.0. Ethanol was then mixed with three aqueous solutions at 50 vol.-%. The ceramic adherents were pre-silanated for 30 seconds, 1, 3 and 10 minutes, respectively. The strength of the resulting resin-to-ceramic bond was evaluated before and after thermo-cycling. High (p<0.05) bond strengths of 20.7 Mpa (before thermo-cycling) and 13.5 Mpa (after thermo-cycling) were obtained with a 3-minutes silanating period in 50 mg mL−1 γ-methacryloxypropyltrimethoxysilane at pH of 2.0. The experimental ceramic primer increases the bond durability of resin cements to silica-based ceramics.

Synthesis and characterization of degradable polyurethane based on poly(ether ester) polyols (PPG-2000 and ε-caprolactone/lactic acid) for marine antifouling

Poly(ether ester) polyols consisting of polypropylene glycol-2000 (PPG-2000) and different ratios of e-caprolactone and lactic acid (LA) had been prepared by polycondensation reactions. Degradable polyurethane (PU) films were prepared with poly (ether ester) polyols and hexamethylene diisocyanate trimer. Hydrolytic degradation experiments demonstrated that PU films could be degradable in artificial seawater. Importantly, the hydrolytic degradation of PU films in artificial seawater increased with the increase of LA content. The results also showed that the surfaces of PU films were renewed and kept active, as revealed by the scanning electron microscope micrographs of degradation PU coatings. Moreover, the copper ion release rates of PU coatings prepared with poly(ether ester) polyols reached steady state at about 35 days. The degradable polyurethanes based on poly(ether ester) polyols (PPG-2000, e-caprolactone, and LA) could be effective and durable resins for marine antifouling.

Effect of ethanol wet bonding technique on the durability of resin- dentin bond with contemporary adhesive systems.

To evaluate the effect of ethanol wet bonding technique on the immediate and long term bond strength of simplified etch and rinse adhesive systems to dentin. 96 extracted human permanent molars were ground to expose the flat dentin surface. The teeth were divided into four groups (n=24) according to the adhesives used, either Tetric N Bond or Solobond M and bonding techniques i.e. water wet bonding or ethanol wet bonding (EWB). Composite cylinder was bonded to each specimen using the respective adhesive technique. Ten samples from each group were then tested immediately for shear bond strength evaluation and two samples for SEM analysis. The remaining samples (12) were tested after 6 month storage in distilled water. Upon immediate testing, there was no significant difference in the mean shear bond strength of the groups regardless of the bonding technique or adhesive used. The bond strength fell dramatically in the water wet bonded specimens after 6 months water storage, while the bond strength of both the adhesives was maintained when EWB technique was used. SEM observation revealed good interfacial adaptation in EWB groups even after six months. For both simplified etch and rinse adhesives used, ethanol wet bonding technique led to significant preservation of the resin dentin bond over 6 months.

An overview of solvents in resin–dentin bonding

Resin bonding to dentin is less durable than bonding to enamel. Bonding to dentin had been a great challenge till date. Though the current dental adhesive systems have tremendously improved the complex dentin bonding, there are still challenges that need to be addressed. Improper handling of the dental adhesive systems is one of the several reasons for the decrease in durability of resin–dentin bonds over time. Improper handling includes inappropriate storage and inaccurate method(s) of application. Solvents incorporated in the dental adhesive systems are known to dissolve methacrylate monomer/co-monomer blends and the initiator/co-initiator systems. These solvents are volatile and they play several important roles in achieving successful and durable bond to dentin. Lack of knowledge about the role of solvents used in dental adhesives could be one of the reasons for improper handling of the dental adhesive systems. This overview discusses the solvent aspects of current dental adhesive systems and their applications in bonding. The overview consists of published literature retrieved from “Pubmed”, by using specific key words “solvents”, “resin adhesives”, “dentin”, “bonding”. The relevant literature was retrieved after screening the titles and the abstracts. Further relevant articles that were included for the overview were retrieved from the reference lists of the initially retrieved articles. The literature seems to indicate that solvent type, solvent content and other factors, like storage of the adhesives and methods of application play a major role in dentin bonding. The knowledge acquired on the solvents and their roles in dentin bonding would enable the users of the dental adhesives to handle them appropriately and consequently achieve strong and durable resin–dentin bonds.

Durability of an industrial epoxy vinyl ester resin used for the fabrication of a contemporary art sculpture

In this study we report on an assessment of the conservation condition of a sculpture partially made of synthetic polymers, and on the prediction of its long term durability. Compositional analysis, largely based on IR spectroscopy and Raman spectrometry, identified the epoxy vinyl ester resin used for modelling the lower part of the sculpture as the most critical component. Accelerated degradation tests of the epoxy vinyl ester resin possibly employed by the artist were performed in a photodegradation device and separately in a forced-air circulation oven at 140 °C, to simulate natural degradation. The results obtained by monitoring structural and molecular changes by FTIR and UV-Vis spectroscopy, thermogravimetry (TGA) and differential scanning calorimetry (DSC) allowed us to propose a comprehensive mechanism of oxidation. The validity of the prediction of the durability of the resin was corroborated through a comparison with the results obtained evaluating the actual state of conservation of the artwork. © 2014 Elsevier Ltd. All rights reserved.

Evaluation of four surface coating treatments for resin to zirconia bonding

ObjectivesTo compare the effects of four surface coating methods on resin to zirconia shear bond strength. Material and methodsEighty pre-sintered zirconia discs were prepared and randomly divided into five study groups according to the corresponding methods of surface treatments as follows: group C (control group, fully sintered without any surface treatment), group S (fully sintered and then sandblasted with silica coated alumina powder), group G (fully sintered and then coated with glazing porcelain followed by acid etching), group Si (pre-coated with silica slurry then fully sintered), and group Z (coated with zirconia particles and then fully sintered). The observation of surface morphology and elemental composition analysis were conducted by SEM and EDX. Self-adhesive resin cement stubs (diameter 3.6mm and height 3mm) were then bonded on the zirconia discs with a cylindrical shape. Both initial and artificial aged (including 30-day water storage, thermal cycling for 3000 and 6000 cycles) shear bond strengths were then evaluated. ResultsAll the tested coating methods showed significantly higher shear bond strengths than the control group, in both dry and aged conditions. Group S produced the strongest initial zirconia/resin bonding (19.7MPa) and the control group had the lowest value (8.8MPa). However, after thermal cycling, group Z exhibited the highest mean value. All the samples in the control group failed in the thermal cycling. Both different coating methods (p<0.001) and various aging treatments (p<0.001) produced significant influence on resin–zirconia shear bond strength. ConclusionsA reliable and durable resin zirconia bonding is vital for the longevity of dental restorations. Silica coating might be a reliable way in enhancing adhesion between resin and zirconia.

Effects of chlorhexidine-containing adhesives on the durability of resin–dentine interfaces

ObjectivesThis study evaluated the effect of addition of diacetate CHX in different concentrations into two simplified etch-and-rinse (ER) adhesive systems (XP Bond [XP] and Ambar {AM}) on the ultimate tensile strength (UTS), degree of conversion (DC), 60-day cumulative water sorption (WS), solubility (SO) and CHX release (CR) as well as the immediate (IM) and 1-year (1Y) resin–dentine bond strength (μTBS) and nanoleakage (NL). MethodsTen experimental adhesive systems were formulated according to the addition of CHX diacetate (0 [control], 0.01, 0.05, 0.1 and 0.2%) in the two ER. For UTS and DC, specimens were constructed and tested after 24h. For WS, SO and CR, after specimens build-up, they were stored in water and the properties measured after 60 days. The occlusal enamel of fifty molars was removed and the adhesives were applied in dentine surface after 37% phosphoric acid etching. After composite resin build-ups, specimens were longitudinally sectioned to obtain resin–dentine bonded sticks (0.8mm2). Specimens were tested in tension at 0.5mm/min in the IM or 1Y. For NL, 2 bonded sticks from each tooth were prepared and analyzed under SEM. The data were submitted to appropriate statistical analysis (α=0.05). ResultsThe addition of CHX did not influence UTS, DC, WS and SO (p<0.05). Higher CR was observed in adhesives with higher concentration of CHX (p<0.05). After 1Y, significant reductions of μTBS and increases of NL were observed in the control groups (p<0.05). Reductions of μTBS and increase of NL over time were not observed (AM) for CHX-containing adhesives or it was less pronounced than the control (XP) regardless of the CHX concentration. ConclusionsThe addition of CHX diacetate in concentrations until 0.2% in the simplified ER adhesive systems may be an alternative to increase the long-term stability of resin–dentine interfaces, without jeopardizing the adhesives’ mechanical properties evaluated.

Dicalcium phosphate (CaHPO4·2H2O) precipitation through ortho- or meta-phosphoric acid-etching: Effects on the durability and nanoleakage/ultra-morphology of resin–dentine interfaces

ObjectivesTo compare the effects of two etching procedures using meta-phosphoric (MPA) or ortho-phosphoric acid (OPA) on dentine demineralisation, resin–dentine bonds durability and interface nanoleakage/ultra-morphology. MethodsMiddle-dentine specimens were etched using 37% OPA (15s) or 40% MPA (60s) and submitted to infrared spectroscopy (FTIR) or ultra-morphology dye-assisted (calcium-staining) confocal microscopy (Ca-CLSM). A three-step etch-and-rinse adhesive was formulated, applied onto dentine and light-cured for 30s before composite build-up. After 24h, the dentine-bonded specimens were cut into 1mm2 beams; half were immediately submitted to microtensile bond strength (μTBS) and half stored in DW for six months. The μTBS results were analysed with repeated-measures ANOVA and Tukey's test (p<0.05). Further teeth were bonded and prepared for interface nanoleakage/ultra-morphology confocal evaluation. ResultsFTIR and Ca-CLSM analyses showed dicalcium phosphate dihydrate (Brushite) precipitation in MPA-etched dentine and on the bottom (front of demineralisation) of the OPA-etched dentine. Statistical analysis showed similar μTBS for both etching procedures after 24h. The μTBS of specimens in OPA-group dropped significantly (p<0.05) after six month; the specimens in the MPA group showed no statistically difference (p>0.05). CLSM depicted no evident sign of nanoleakage within the resin–dentine interface of the MPA-treated specimens, while the specimens in OPA-group presented intense nanoleakage and interface degradation. ConclusionThe use of MPA (60s) as an alternative dentine conditioning agent in etch-and-rinse bonding procedures may be a suitable strategy to create more durable resin–dentine bonds.