Resin-dentin Microtensile Bond Strength Research Articles

Adhesive sonic agitation improves bonding durability to class-II cavity preparation.

The purpose of this study was to evaluate the effect of adhesive sonic agitation on resin-dentin micro-tensile bond strength (µTBS) and interfacial morphology at the gingival wall of class-II cavity preparation. Seventy-two molars with prepared class-II cavities were divided into six groups (n = 12) according to the bonding mode; etch-and-rinse (E&R) or self-etch (SE) and application protocol of the universal adhesive (UA) employed (Clearfil Universal Bond Quick, Kuraray Noritake); following the manufacturer instructions (MI), manual agitation for 20s (20s), or sonic agitation for 20s using a modified sonic micro-brush mounted on EndoActivator device, Dentsply Sirona, (sonic). Restored teeth were sectioned into resin-dentin beams and slaps and µTBS was evaluated at 1week (1w) and after thermocycling (10k). µTBS data were analyzed using the linear mixed-effects modeling with specific contrast (p < 0.05). The resin-dentin interfacial morphology was evaluated using ascanning electron microscope. Adhesive sonic agitation resulted in significantly higher µTBS means in both E&R and SE modes, compared to MI group. The µTBS of MI group showed significant reduction upon aging when applied in SE mode. Sonic agitation was associated with enhanced adhesive infiltration into dentin specially in E&R mode. Sonic agitation of UA using modified sonic micro-brush attached to EndoActivator device significantly improved the resin-dentin µTBS and interfacial morphology at the gingival wall of class-II cavity preparation.

Phosphoric acid containing proanthocyanidin enhances bond stability of resin/dentin interface.

Proanthocyanidin (PA) is a promising dentin biomodifier due to its ability to stabilize collagen fibrils against degradation by matrix metalloproteinases (MMPs); however, the most effective protocol to incorporate PA into bonding procedures is still unclear. This study evaluated the effect of dentin biomodification with a PA acid etchant on MMP activity, adhesive interface morphology and resin-dentin microtensile bond strength. Sound extracted human molars were flattened to expose dentin and acid-etched for 15 s according to the groups: EXP - experimental phosphoric acid; EXP+PA - experimental phosphoric acid 10% PA; TE - total-etching system; SE - self-etching system. Samples were restored with composite resin and stored in distilled water (37ºC). MMP activity and interface morphology were analyzed after 24 h by in situ zymography (n=6) and scanning electron microscopy (n=3), respectively. The resin-dentin microtensile bond strength (μTBS) was evaluated after 24 h and 6 months storage (n=6). Significantly higher MMP activity was detected in etched dentin compared with untreated dentin (p<0.05), but no difference among acid groups was found. Resin tags and microtags, indicative of proper adhesive system penetration in dentinal tubules and microtubules, were observed along the hybrid layer in all groups. There was no difference in μTBS between 24 h and 6 months for EXP+PA; moreover, it showed higher long-term μTBS compared with TE and EXP (p<0.05). The results suggest that 15 s of biomodification was not sufficient to significantly reduce MMP activity; nonetheless, EXP+PA was still able to improve resin-dentin bond stability compared with total- and self-etching commercial systems.

Effect of Dimethyl Sulfoxide wet bonding technique on the durability of resin-dentin bond of an etch-and rinse adhesive system under in-vivo simulating conditions

Purpose: This study assessed the influence of new dimethyl sulfoxide (DMSO) containing pretreatments on the aged resin-dentin micro-tensile bond strength (μTBS) of a two-step etch-and rinse adhesive system. Methods: Occlusal enamel of forty-eight sound molar teeth were ground to expose mid-coronal dentin. Prepared specimens were restored with AdperTM Single Bond2 (SB2) adhesive systems. Prior to the adhesive system application, specimens were randomly assigned into three groups according to dentin pretreatment [no treatment (control group), ethanol wet-bonding (EtOH), or 50 vol% DMSO dissolved in ethanol (DMSO/EtOH)]. Resin composite block was build-up for each specimen. Specimens were stored under simulated IPP 20 mmHg, immersed in artificial saliva at 37 oC for either 24h or 6m. Specimens were sectioned into sticks of 1mm2 for μTBS testing using a universal testing machine. Mode of failure was analyzed using a scanning electron microscope. Three extra sticks from each subgroup were prepared and assessed for the amount of silver nitrate penetration (wt%) using energy dispersive analytical x-ray (EDAX). Data were statistically analyzed by Two-way ANOVA of Variance. Results: (DMSO/EtOH) group revealed the highest statistically significant mean bond strength and the least silver nitrate penetration compared to the (control) and (EtOH) groups at 24h and 6m. Adhesive failures was most predominant for control group at 24h, with increased percentage of mixed failure for EtOH and DMSO/EtOH groups at 24h and 6m. Conclusions: DMSO/EtOH dentin pretreatment improved the immediate and delayed resin-dentin bond.

Effect of Non-Thermal Atmospheric Plasma on Micro-Tensile Bond Strength at Adhesive/Dentin Interface: A Systematic Review.

Objective: The objective of this review was to evaluate the effect of non-thermal atmospheric plasma (NTAP) on adhesives resin–dentin micro-tensile bond strength (μTBS) in previously published studies. Methods: Electronic search was conducted using the Medline, Cochrane library, and Scopus databases. The included studies were laboratory studies that investigated the effect of NTAP on adhesives μTBS to coronal dentin. Studies that evaluated the effect of NTAP on bond strength to indirect substrates, enamel or root dentin, were excluded. The methodological quality of included studies was assessed. Results: Thirteen studies were included in this systematic review. All the included studies were considered to have a medium risk of bias. NTAP significantly improved μTBS at 24 h or after short-term aging in five studies (38.5%) and both immediate and after long-term aging in 5 studies (38.5%). In two studies (15.4%), NTAP resulted in a short-term material-dependent effect that was not stable after long-term aging. Interestingly, in one study (7.7%), NTAP had a positive effect only in the etch-and-rinse (ER) mode after long-term aging. Conclusion: Within the limitations of this systematic review, NTAP application could enhance resin–dentin μTBS of ER adhesives or universal adhesives (UAs) applied in the ER mode. In the ER mode, the rewetting step after NTAP seems to be unnecessary. Because of the limited information currently available in the literature, further studies are required to evaluate the effect of the NTAP application on self-etch (SE) adhesives or UAs applied in the SE mode.

Effect of Alternative Self-Etch Applications on Dentin Bond Strength of “No Wait Concept” Universal Adhesives

Objective: This study evaluated the effects of alternative self-etch application modes on resin-dentin microtensile bond strength (µTBS) of three commercially available “no wait” concept universal adhesives. Materials and methods: In this study extracted impacted non-carious human third molars were used. The flat surfaces were prepared in mid-coronal dentin and prepared with a 600-grit SiC paper. The three universal adhesives that were used are as follows: Clearfil Universal Bond Quick (CUQ, Kuraray Noritake, Japan), G-Premio Bond (GPB, GC Corp, Japan), and a self-curing universal adhesive “Tokuyama Universal Bond” (TUB; Tokuyama Dental, Japan). The following three different application procedures were used for the dentin surfaces: the adhesives were applied and immediately subjected to air-dry; the adhesives were applied followed by a 10-second wait; or the adhesives were rubbed for 10 seconds. Then composite resin was applied to the dentin surface and light cured. After storage in 37°C distilled water for 24 h, all the bonded teeth were cut into 1mm² sections using a low-speed diamond saw (Micracut 125 Low Speed Precision Cutter, Metkon, Bursa, Turkey) under running water (n=15). The sections were subjected to a tensile force at a crosshead speed of 1mm/min in a testing apparatus (Microtensile Tester, Bisco, IL, USA) and µTBS values were measured. Data were analyzed using the Kruskal-Wallis test and Mann-Whitney U test. Failure modes were analyzed under a stereomicroscope. Results: Prolonged application time significantly affected the µTBS (p&lt;0.005). A significant increase of µTBS on active application was observed for CUQ and GPB. The TUB with an active application had a significantly lower µTBS value compared with the other adhesives. Conclusions: Prolonged application time caused significant improvement of bond strength in all adhesives. The active application is effective at increasing the dentin bond strength except for TUB.

Polyphenols and Brazilian red propolis incorporated into a total-etching adhesive system help in maintaining bonding durability

ObjectivesThe aim of this study was to evaluate the degree of conversion and bond strength of a commercial dental adhesive modified by the incorporation of quercetin, resveratrol (RES), and Brazilian red propolis (BRP). MethodsBRP markers were identified using ultra-performance liquid chromatography coupled with a diode array detector, and the antioxidant activity (AAO) of the three substances was analyzed. Single Bond 2 adhesive (3M ESPE) was modified by adding BRP, quercetin, and RES, separately, at 20 μg/mL, 250 μg/mL, and 500 μg/mL, respectively. The degree of conversion (DC) was measured using near-infrared spectroscopy 24 h after photopolymerization. Measurements of the resin-dentin microtensile bond strength (μTBS) were carried out after 1 day and 1 year. Student's t test and ANOVA with Tukey's test were used for data analysis (α = 0.05). ResultsThe markers daidzein, liquiritigenin, pinobanksin, isoliquiritigenin, formononetin, pinocembrin, and biochanin A were found in the ethanolic extract of BRP. Quercetin, RES, and BRP showed high AAO. The DC of the tested adhesives remained adequate for this category of material, with a slight increase in the DC of adhesives with quercetin and BRP (P > 0.05). Comparisons between μTBS measurements made at 1 day and 1 year showed that, contrary to the control group, μTBS values for all modified adhesives were maintained after 1 year in distilled water (P > 0.05). ConclusionsThese findings suggest that quercetin, RES, or BRP might be useful in adhesive dentistry to help improve hybrid layer resistance. Clinical significanceDentin bonding agents with quercetin, RES, and BRP have potential to increase the longevity of composite restorations.

Evaluation of the Bond Strength and Cytotoxicity of Alkasite Restorative Material

Cention N (CN; Ivoclar Vivadent, Schaan, Liechtenstein), advertised as an alkasite, is a bioactive bulk-fill resin-based composite (BF-RBC) with alkaline fillers. This study evaluated the resin-dentin micro-tensile bond strength (μTBS) and cytotoxicity of CN. Methods: Flat dentin surfaces were obtained, bonded with a universal adhesive, and randomly distributed into two groups. CN (group I) and a flowable BF-RBC, namely, Tetric N-Flow Bulk Fill, Ivoclar Vivadent, Schaan, Liechtenstein (group II), were used. After thermocycling, bonded samples were sectioned into micro-beams for μTBS evaluation. Resin-based composite (RBC) discs with a thickness of 2 and 4 mm were tested on human gingival fibroblast cells (HGFCs). Cytotoxicity was assessed by cell viability and growth using AlamarBlue® (Biosource, Camarillo, CA, USA) over a seven-day period. Independent t-test was utilized to statistically analyze μTBS data, while one- and two-way analysis of variance (ANOVA) and Tukey’s post-hoc tests were utilized to analyze the cell viability data. Results: There was no statistically significant difference (p &gt; 0.05) in the μTBS between the flowable BF-RBC and CN. For both materials, the HGFCs were viable, with constant growing over the seven-day period. Conclusion: CN provided a resin-dentin μTBS that was comparable to that provided by the flowable BF-RBC. Both materials showed acceptable cytotoxicity over the seven-day period at a thickness of both 2 and 4 mm.

The effect of chlorhexidine application on the microtensile bond strength and durability of a total-etch adhesive

Abstract Aim: The aim of this study was to evaluate the effect of chlorhexidine (CHX) on resin–dentin microtensile bond strength (μTBS) after 6-month aging and to compare with sodium hypochlorite. Materials and Methods: A total of 40 extracted human third molar teeth were mounted in the acrylic resin. Flat occlusal surfaces of dentin were exposed, and after acid etching, the samples were divided randomly into four groups as follows: (a) Control group: Single Bond adhesive resin was applied. (b) The dentin surfaces were exposed to 2% CHX, and then, Single Bond was applied. (c) Dentin surfaces were treated by 5.25% sodium hypochlorite; after rinsing and drying, Single Bond was applied. (d) At first, 5.25% sodium hypochlorite was applied for 30 s, and then, 2% CHX and Single Bond adhesive were applied. Finally, Filtek P60 composite was bonded on the dentin surface. The samples of each group were divided into two subgroups of 24 h and 6 months. μTBS tests were performed using universal testing machine. Afterward, modes of failures were investigated. The statistical analyses were carried out using ANOVA, t-test, and Dunnett’s test. Results: The mean of μTBS for the 24-h and 6-month groups was 15.19 and 10.99 MPa, respectively. Bond strength of all groups except Group D decreased after 6 months, and this bond strength reduction in Group C was more than other groups. Most failure modes were in adhesive type. Conclusions: The use of CHX did not have better preservation of μTBS when compared to control group. Use of hypochlorite is not recommended.

Dental adhesive microtensile bond strength following a biofilm-based in vitro aging model.

Laboratory tests are routinely used to test bonding properties of dental adhesives. Various aging methods that simulate the oral environment are used to complement these tests for assessment of adhesive bond durability. However, most of these methods challenge hydrolytic and mechanical stability of the adhesive- enamel/dentin interface, and not the biostability of dental adhesives. Objective To compare resin-dentin microtensile bond strength (μTBS) after a 15-day Streptococcus mutans (SM) or Streptococcus sobrinus (SS) bacterial exposure to the 6-month water storage (WS) ISO 11405 type 3 test.Methodology A total of 31 molars were flattened and their exposed dentin was restored with Optibond-FL adhesive system and Z-100 dental composite. Each restored molar was sectioned and trimmed into four dumbbell-shaped specimens, and randomly distributed based on the following aging conditions: A) 6 months of WS (n=31), B) 5.5 months of WS + 15 days of a SM-biofilm challenge (n=31), C) 15 days of a SM-biofilm challenge (n=31) and D) 15 days of a SS-biofilm challenge (n=31). μTBS were determined and the failure modes were classified using light microscopy.Results Statistical analyses showed that each type of aging condition affected μTBS (p<0.0001). For Group A (49.7±15.5MPa), the mean μTBS was significantly greater than in Groups B (19.3±6.3MPa), C (19.9±5.9MPa) and D (23.6±7.9MPa). For Group D, the mean μTBS was also significantly greater than for Groups B and C, but no difference was observed between Groups B and C.Conclusion A Streptococcus mutans- or Streptococcus sobrinus-based biofilm challenge for 15 days resulted in a significantly lower μTBS than did the ISO 11405 recommended 6 months of water storage. This type of biofilm-based aging model seems to be a practical method for testing biostability of resin-dentin bonding.

Biological, mechanical and adhesive properties of universal adhesives containing zinc and copper nanoparticles

ObjectivesTo evaluate the effect of addition of zinc oxide and copper nanoparticles (ZnO/CuNp) into universal adhesives, on antimicrobial activity (AMA), cytotoxicity (CTX), water sorption (WS) and solubility (SO), microhardness (MH) and in vitro degree of conversion (DC), as well as resin-dentin microtensile bond strength (μTBS), nanoleakage (NL) and in situ DC. MethodsZnO/CuNp (0% [control]; 5/0.1 and 5/0.2 wt%) were added in Prime&Bond Active (PBA) and Ambar Universal (AMB). The AMA was evaluated against Streptococcus mutans. For CTX, Saos-2 cell-line was used. For WS and SO, specimens were tested for 28d. For MH, specimens were tested after 24 h and 28d and for in vitro DC, specimens were evaluated after 24 h. After, the adhesives were applied to flat dentine surfaces, composite resin build-ups, specimens were sectioned to obtain resin–dentine sticks. It was evaluated in μTBS, NL and in situ DC after 24 h of water storage. ANOVA and Tukey’s test were applied (α = 0.05). ResultsThe addition of 5/0.2 ZnO/CuNp increase AMA and WS, but decrease the SO when compared to control (p < 0.05). The CTX and μTBS were maintaining with adhesive-containing ZnO/CuNp (p > 0.05). MH, in vitro DC and in situ DC was significant increase (AMB) or maintaining (PBA) with ZnO/CuNp addition. However, significantly lower NL was observed for ZnO/CuNp groups (p < 0.05). ConclusionsThe addition of ZnO/CuNp in the tested concentrations in universal adhesive systems may be an alternative to provide antimicrobial activity and improves the integrity of the hybrid layer, without jeopardizing biological, adhesives and mechanical properties. SignificanceThis is the first study that demonstrates that the addition of zinc oxide and copper nanoparticles in concentrations up to 5/0.2 wt% in two universal adhesive systems is a feasible approach and may be an alternative to adhesive interfaces with antimicrobial properties and less defects in the resin-dentin interface.

Effect of epigallocatechin-3- gallate solutions on bond durability at the adhesive interface in caries-affected dentin

Hydrolytic and enzymatic degradation by matrix metalloproteinases (MMPs) reduces the durability of composite resin restorations on caries-affected dentin (CAD). The use of MMP inhibitors such as epigallocatechin-3-gallate (EGCG) could increase the longevity of the bond to dentin. This study aimed to evaluate the use of EGCG at different aqueous concentrations on the resin-dentin microtensile bond strength (μTBS), fracture pattern and nanoleakage (NL) in immediate (IM) time interval and after 12-months of water storage (1Y) when using a two-step etch-and-rinse adhesive system on CAD. Dentin surfaces of 40 human molars were submitted to a microbiological caries induction protocol and randomized into 5 groups (n = 8) (0.02% EGCG; 0.2% EGCG; 0.5% EGCG; 2% Chlorhexidine [CHX] and no treatment as Control Group - [NT]). After acid etching, the solutions were applied for 60 s followed by application of dental adhesive (Adper Single Bond 2, 3 M ESPE) to CAD surfaces. Subsequently, a resin composite (4 mm) block was built on the dentin. After 24 h, the teeth were sectioned into beam-shaped specimens (cross-sectional area of 1 mm2 and 8-mm high). Half of the specimens were tested in IM and the other half after 1Y. Two samples per tooth were submitted to SEM for NL evaluation. Data were statistically analyzed by two-way ANOVA and Tukey tests (α = 0.05). The results showed that use of EGCG and CHX did not affect μTBS in IM (p > 0.05). After 1Y, there was a reduction in μTBS for all experimental groups (p < 0.05). Adhesive fractures predominated in IM in all groups, except for 0.05% EGCG and NT. After 1Y, there was an increase in these adhesive fractures in all groups. For NL, all agents applied reduced NL in comparison with CT (p < 0.001). CHX showed lower NL (p < 0.001), followed by 0.02% and 0.5% EGCG. NT showed highest NL for both time intervals (p < 0.001). Thus, although the use of EGCG at different concentrations and CHX reduced the NL, they were unable to reduce degradation of μTBS to CAD over time.

Influence of povidone-iodine on micro-tensile bonding strength to dentin under simulated pulpal pressure

BackgroundPrevious studies had reported that bond strength deteriorate over time following the dentin surface pretreatment with chlorhexidine. Therefore, further investigations are needed to evaluate the effect of other materials such as povidone iodine.The purpose of this study was to investigate the effects of 10% povidone-iodine pretreatment on the resin-dentin micro-tensile bond strength of a single bond adhesive system in permanent teeth over time, and compare it with 2% chlorhexidine.MethodsFlat dentin surfaces were prepared in 63 extracted permanent teeth. Teeth were randomly assigned to a 10% povidone-iodine pretreatment, a 2% chlorhexidine pretreatment, or a control group. Composite resin blocks were built up over treated surfaces under pulp pressure simulation. The prepared specimens were assigned to three storage time, 24 h, 1 week, and 2 months. Samples were vertically sectioned to obtain specimens of 0.7 to 1.2 mm2 cross-sectional area.ResultsNo significant reduction of bond strength of povidone iodine group was found among the three storage times (p = 0.477). A significant reduction of bond strength for both chlorhexidine and control groups was found in the three storage times (p < 0.001).ConclusionPovidone iodine pretreatment of etched dentin was effective in reducing the loss of bond strength over time, while the chlorhexidine pretreatment and negative control showed significant deterioration in micro-tensile bond strength over time in permanent teeth.

Two-year Effects of Chlorhexidine-containing Adhesives on the In Vitro Durability of Resin-dentin Interfaces and Modeling of Drug Release.

To evaluate the effects of addition of diacetate chlorhexidine (CHX) at different concentrations into two etch-and-rinse adhesive systems on CHX release, as well as the immediate (IM) and two-year (2-Y) resin-dentin microtensile bond strength (μTBS) and nanoleakage (NL). CHX was added to XP Bond (XP) and Ambar (AM) at concentrations of 0.0 wt% (control); 0.01 wt%; 0.05 wt%; and 0.1 to 0.2 wt%. To assess the cumulative CHX release, adhesive disks were made in a metallic matrix and after light-curing were stored in water. Ultraviolet spectrophotometric measurements of the storage solution were performed to examine the release kinetics of CHX. For μTBS and NL, the occlusal enamel of molars was removed and the adhesives were applied to the dentin surface after acid etching. After composite resin build-up, specimens were sectioned to obtain μTBS sticks. The specimens were subjected to μTBS and NL at IM and after 2-Y. In addition, specimens underwent examination for CHX using micro-Raman spectroscopy. All data were submitted to statistical analysis (α=0.05). With regard to CHX release, AM showed a slower and gradual release of CHX while XP released CHX more quickly ( p<0.05), and CHX was still present in the hybrid layers after 2-Y. Both adhesives showed CHX release at 2-Y water storage. Both CHX-containing adhesives showed higher μTBS values than did the control group ( p<0.05).

Effectiveness of two universal adhesives using two different bonding approaches

Objectives: The aim of the current study was to evaluate the resin-dentin micro-tensile bond strength (μ-TBS) using 2 types of universal adhesives with etch-and-rinse and self-etch approaches after 24 hours and 6 months of water storage. Materials and Methods: A total of 20 extracted non-carious human molars were used in this study. Teeth were equally and randomly divided into 2 groups (N= 10 teeth) according to the type of adhesive used; Group I; Adhese® Universal and Group II; Single Bond Universal. Each group was further subdivided into 2 equal subgroups (n=5 teeth) according to the bonding approach used; Subgroup A; using the self-etch (SE) approach and Subgroup B; using the etch-and-rinse (ER) approach. After bonding, each tooth was built up by resin composite, cut into sticks (0.9 mm x 0.9 mm) and stored in distilled water at 37˚C for 24 hours and 6 months. Then, each stick was stressed under tension until failure using a simplified universal testing machine at a crosshead speed of 1 mm/min. Data were statistically analyzed using One-Way ANOVA, Two-Way ANOVA and Tukey HSD Tests. After μ-TBS testing, all debonded surfaces were observed using a stereomicroscope at 50X magnification to determine the modes of failure, which were categorized as adhesive, cohesive or mixed failure. Results: After 24 hours of water storage, there was no significant difference between the μ-TBS exhibited by Adhese Universal using both SE and ER approaches while both approaches differed significantly when using Single Bond Universal (P=0.0003). Furthermore, there was no significant difference when comparing the μ-TBS means of SE groups or ER groups of both adhesive systems. After 6 months of water storage at 37˚C, there was a significant decrease in the μ-TBS values of all groups (p<0.0001) except when Adhese Universal was used with SE approach, there was no difference between the 24 h and the 6 month-groups (p=0.1449). The failure mode analysis was consistent with the μ-TBS test results as the number of adhesive failures increased with decreased bond strength values.Conclusions: When bonding resin-based composite restoratives to dentin, a separate acid-etching step is not required when using Adhese Universal, but it is preferred with Single Bond Universal adhesive. Aging markedly contributes to bond degradation of universal adhesives.

Role of dentin cross-linking agents in optimizing dentin bond durability

The present work compared the effects of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC-HCl) and ultraviolet (UV)- or blue light-activated riboflavin cross-linking agents on resin–dentin micro-tensile bond strength and nanoleakage in bonds produced using a two-step, etch-and-rinse adhesive after three storage intervals (24 h, 6 months, and 12 months). Forty eight extracted human third molars were used to investigate micro-tensile bond strength and interfacial nanoleakage in resin–dentin bonds created using Adper Single Bond 2, with or without pretreatment of acid-etched dentin surfaces. Either 0.5 M EDC-HCl or 1% riboflavin-5-phosphate activated by blue or UV light were used as cross-linking agents. Samples were evaluated after storage for 24 h, 6 months, or 12 months in distilled water at 37 °C. Statistical analyses revealed that 12 months of storage resulted in significant decreases in the bond strength of the controls (p < 0.003), with significant increases in their silver nanoleakage (p < 0.05), compared with the groups subjected to dentin pretreatment with either EDC-HCl or light-activated 1% riboflavin. Despite the significant drop in bond strength after 6 months’ storage in all experimental groups compared with the 24-h bond strength (p < 0.05), there was a further non-significant drop in bond strength after 12 months in samples treated with EDC-HCl and UV-activated 1% riboflavin (p > 0.05). Dental collagen cross-linking induced by UV- or blue light-activated 1% riboflavin or EDC-HCl enhanced the durability and strength of the resin–dentin bond.

Biostability of the Proanthocyanidins-Dentin Complex and Adhesion Studies

Oligomeric proanthocyanidins (OPACs) are potent and renewable natural bioactives possible to be refined into chemically standardized mixtures for biological applications. Herein, we found that multiscale interactions of OPACs with the dentin matrix create tight biointerfaces with hydrophobic methacrylate adhesives on wet surfaces. An enriched mixture of OPACs, with a known phytochemical profile, was produced from grape seed crude extract (Vitis vinifera; enriched grape seed extract [e-GSE]) and applied to dentin matrices to determine changes to the mechanical properties and biodegradability of the dentin matrix and favorable resin adhesion mechanisms. Methods included a 3-point flexural test, quantification of hydroxyproline (collagen solubilization), static and dynamic nanomechanical analyses, resin-dentin microtensile bond strength, and micropermeability at the adhesive interface. The e-GSE-modified dentin matrix exhibited remarkably low collagen solubilization and sustained the bulk elastic properties over 12 mo. Tan δ findings reveal a more elastic-like behavior of the e-GSE-modified dentin matrix, which was not affected by H-bond destabilization by urea. Dentin-methacrylate biointerfaces with robust and stable adhesion were created on e-GSE-primed dentin surfaces, leading to a dramatic decrease of the interfacial permeability. Standardized OPAC mixtures provide a new mechanism of adhesion to type I collagen–rich tissues that does not rely on hydrophilic monomers. The bioadhesion mechanism involves physicochemical modifications to the dentin matrix, reduced tissue biodegradation, and bridging to methacrylate resins.

Influence of pH cycling and mechanical loading on the resin-dentin microtensile bond strength

The durability of adhesive interfaces is still a problem in adhesive restorations in dentistry. Laboratorial ageing methods have been proposed to predict the performance of materials, but they still require standardization. The objective of this study was to evaluate the resin-dentin microtensile bond strength of composite restorations subjected to pH cycling and different levels of mechanical loading. Resin blocks were built over a flat superficial dentin of bovine incisors (n = 40), using a three-step adhesive system. Half of the specimens were submitted to 10 cycles of pH cycling, followed by mechanical loading (0, 500,000; 1,000,000; 2,000,000 cycles – 98 N, 4 Hz). The other half was directly subjected to mechanical loading. After ageing, all groups were subjected to a microtensile bond test. Data were analyzed using two-way ANOVA and Tukey’s test (α = 0.05). The frequency of the early de-bonding was compared using the Chi-square test (α = 0.05). The statistical analysis revealed that the cross-product interaction ‘pH cycling’ vs. ‘number of mechanical loading cycles’ (p = 0.72) as well as the main factor ‘pH cycling’ (p = 0.49) was not statistically significant, and they were not able to reduce the resin–dentin bond strength values. Regarding the number of mechanical loading cycles, the groups subjected to 2,000,000 cycles showed lower bond strength values than the others (p = 0.003). The frequency of debonded specimens increased with mechanical loading. Therefore, it can be concluded that in this restorative model, at least 2,000,000 mechanical cycles are need to decrease the microtensile strength and simulate the ageing of the interface.

Dentin bond optimization using the dimethyl sulfoxide-wet bonding strategy: A 2-year in vitro study

ObjectiveThis study evaluated a new approach, named dimethyl sulfoxide (DMSO)-wet bonding, to produce more desirable long-term prospects for the ultrafine interactions between synthetic polymeric biomaterials and the inherently hydrated dentin substrate. MethodsSound third molars were randomly restored with/without DMSO pretreatment using a total-etch (Scocthbond Multipurpose: SBMP) and a self-etch (Clearfil SE Bond: CF) adhesive systems. Restored teeth (n=10)/group were sectioned into sticks and submitted to different analyses: micro-Raman determined the degree of conversion inside the hybrid layer (DC); resin–dentin microtensile bond strength and fracture pattern analysis at 24h, 1year and 2 years of aging; and nanoleakage evaluation at 24h and 2 years. ResultsDMSO-wet bonding produced significantly higher 24h bond strengths for SBMP that were sustained over the two-year period, with significantly less adhesive failures. Similarly, DMSO-treated CF samples presented significantly higher bond strength than untreated samples at two years. Both adhesives had significant less adhesive failures at 2 years with DMSO. DMSO had no effect on DC of SBMP, but significantly increased the DC of CF. DMSO-treated SBMP samples presented reduced silver uptake compared to untreated samples after aging. SignificanceBiomodification of the dentin substrate by the proposed strategy using DMSO is a suitable approach to produce more durable hybrid layers with superior ability to withstand hydrolytic degradation over time. Although the active role of DMSO on dentin bond improvement may vary according to monomer composition, its use seems to be effective on both self-etch and etch-and-rinse bonding mechanisms.

The effect of proanthocyanidin-containing 10% phosphoric acid on bonding properties and MMP inhibition

ObjectivesThis study evaluated the effect of etching using 2% proanthocynidin-containing 10% phosphoric acid 2% PA/10% PhA vs. 35% phosphoric acid 35% PhA on immediate (IM) and 6-months (6M) resin–enamel microshear bond strength (μSBS), resin–dentin microtensile bond strength (μTBS), nanoleakage (NL) and as well as in situ MMP inhibition potential. MethodsThe dentin surface of human were exposed and then etched using 35% phosphoric acid for 15s or 2% PA/10% phosphoric acid for 30s. After rinsing with water, the dentin was bonded with Single Bond Plus (3M ESPE) and composite build-ups were constructed, followed by polymerization. The teeth were sectioned and the bonds were testing for microtensile bond strength (μTBS) and by SEM for NL analysis at IM and 6M. For MMP activity, resin–dentin slices were prepared for in situ zymography, and analyzed under confocal microscopy. For μSBS, others teeth had flattened enamel surfaces etched according the experimental groups and prepared to microshear procedure. The specimens were tested IM and after 6M by microshear bond strength. The data were submitted to two-way repeated measures ANOVA and Tukey's test (α=0.05). ResultsAcid-etching using the 2% PA/10% phosphoric acid did not lower the μTBS in IM (p>0.05) compared to the control 35% phosphoric acid group. However, after 6M, only the 2% PA/10% PhA etched dentin had remained stable the resin–dentin bond strength (p<0.05). Bonds made with 35% PhA showed significant increase in NL% after 6M (p<0.05). Dentin bonds made with 2% PA/10% phosphoric acid showed no increase in NL% after 6 months. The MMP activity within the resin–dentin interface was almost completely reduced after 2% PA/10% PhA etching, while the 35% PhA exhibited intense MMP activity. For μSBS, the type of etchant and the storage period did not affect the resin–enamel bond strengths (p>0.05). SignificanceTen percent phosphoric acid containing 2% PA can produce stable resin–dentin and enamel–resin interfaces, without requiring additional steps in the bonding procedure. Future studies for longer evaluation time are required.

Influence of casein phosphopeptide-amorphous calcium phosphate application, smear layer removal, and storage time on resin-dentin bonding

The aim of this study is to evaluate the influence of Tooth Mousse (TM) application, smear layer removal, and storage time on resin-dentin microtensile bond strength (µTBS). Dentin specimens were divided into two groups: (1) smear layer covered; (2) smear layer removed using 15% EDTA for 90 s. In each group, half the specimens were treated once with TM for 60 min. After bonding procedures using a two-step self-etching adhesive (Clearfil SE Bond (CSE); Kuraray Medical, Tokyo, Japan), an all-in-one adhesive (G-Bond (GB); GC Corp, Tokyo, Japan), and a total-etch adhesive (Adper Single Bond 2 (SB); 3M ESPE, St. Paul, MN, USA), the specimens were stored for 3 d or 6 months in deionized water at 37 °C, and µTBS was tested and analyzed. With the exception of SB (no TM application) and GB, the μTBS was significantly increased for CSE and SB using EDTA pre-conditioning and 3 d of storage (P≤0.001). Bond strength of GB decreased significantly when using EDTA (3 d storage, P<0.05). TM application only increased the μTBS of GB (no EDTA) and SB (with EDTA) after 3 d (P≤0.02). Comparing the adhesives after 3 d of storage, CSE exhibited the greatest μTBS values followed by GB and SB (P≤0.02). The factors of adhesive, EDTA, and TM did not show any significant impact on μTBS when specimens were stored for 6 months (P>0.05). The additional application of TM and EDTA for cavity preparation seems only to have a short-term effect, and no influence on µTBS of dentin bonds after a period of 6 months.