Effect of Simulated Dental Pulpal Pressure Using Fetal Bovine Serum for the Bonding Performance of Contemporary Adhesive to Dentin

This study evaluated the effect of simulated pulpal pressure (SPP) conditions and storage time on contemporary adhesive systems' microtensile bond strength (µTBS) to dentin. Extracted human molars were prepared and randomly divided into four groups according to the adhesives: Clearfil Megabond 2 (CSE), Beautibond Xtreme Universal (BXU), G2-Bond (G2B), and Scotchbond Universal Plus (SBP). Each adhesive group was further divided following the SPP conditions: control with no simulation (SPP-CTR), SPP with distilled water (SPP-DTW), and SPP with fetal bovine serum (SPP-FBS). Resin composite build-ups were prepared, and teeth were stored in water (37 °C) for 24 h (24 h) and 3 months (3 m). Then, teeth were sectioned to obtain resin-dentin bonded beams and tested to determine the µTBS. Data were analyzed using three-way ANOVA, Tukey post hoc tests (=0.05), and Weibull failure analysis. Failure mode was observed using scanning electron microscopy. The µTBS response was affected by adhesive systems, simulated pulpal pressure conditions, and storage time. SPP-CTR groups presented a higher overall bond strength than SPP-DTW and SPP-FBS, which were not significantly different from each other. Only for SBP, the SPP-FBS group showed higher µTBS than the SPP-DTW group. The Weibull analysis showed that the bonding reliability and durability under SPP-DTW and SPP-FBS were inferior to SPP-CTR, and the 24 h bonding quality of adhesives to dentin was superior to that of 3 m. SPP drastically reduced the µTBS of all adhesives to dentin regardless of solution (distilled water or fetal bovine serum). Storage after 3 m also decreased µTBS despite the SPP condition.

Bond Strength, Microleakage, Microgaps, and Marginal Adaptation of Self-adhesive Resin Composites to Tooth Substrates with and without Preconditioning with Universal Adhesives

PURPOSE

This study investigated and compared the bond strengths, microleakage, microgaps, and marginal adaptation of self-adhesive resin composites (SAC) to dentin with or without universal adhesives.

MATERIALS AND METHODS

Dentin surfaces of 75 molars were prepared for shear and microtensile bond strength testing (SBS and µTBS). Silicon molds were used to build up direct restorations using the following materials to form 5 groups: 1. Surefil One; 2. Prime&Bond active Universal Adhesive + Surefil One; 3. Vertise Flow; 4. OptiBond Universal + Vertise Flow; 5. Scotchbond Universal + Filtek Z500 (control group). Bonded specimens were thermocycled 10,000x before being tested either for SBS or µTBS using a universal testing machine at a crosshead speed of 0.5 mm/min. Direct mesial and distal class-II cavities were created on 100 sound premolars, with the gingival margin of distal cavities placed below CEJ and restored according to the five groups. After thermocycling, microleakage scores were assessed following immersion of restored premolars in 2% methylene blue dye for 24 h, while marginal gaps and adaptation percentages were investigated on epoxy resin replicas under SEM at magnifications of 2000X and 200X, respectively. Results were statistically analyzed with parametric and non-parametric tests as applicable, with a level of significance set at α = 0.05.

RESULTS

Bond strengths, microleakage scores, microgaps, and percent marginal adaptation of Surefil One and Vertise Flow were significantly (p < 0.001) inferior to the control group. Dentin preconditioning with universal adhesives significantly increased the study parameter outcomes of Surefil One and Vertise Flow, yet they were still significantly below the performance of the control group.

CONCLUSION

Conventional resin composite outperformed the SAC whether applied solely or in conjunction with their corresponding universal adhesives.

Comparative Evaluation of Microtensile Bond Strength in Three Different Dentin Luting Agents: An In vitro Study

Aim

Long-term clinical success on indirect restorations is largely determined by bonding efficiency of the luting agent, with adhesion to dentin being the main challenge. Therefore, aim of this study was to assess the microtensile bond strength when using flowable resin composite, preheated resin composite and dual self-adhesive resin cement as dentin luting agents.

Materials and Methods

Occlusal thirds of molar teeth were cut and randomly divided into 3 groups to be cemented: RelyX™U200, Filtek™ Z250 XT- preheated to 70° and Filtek Flow™ Z350XT. They were then thermocycled 5000 times between 5+/-2°C and 55+/-2°C. Subsequently, 10 microbars per group were prepared. The 30 samples were placed in saline solution for 24 hours at room temperature prior to microtensile test. This was performed with a digital universal testing machine at a crosshead speed of 0.5 mm/min. The bond strength values obtained were analyzed in Megapascals (MPa). Measures of central tendency such mean and measures of dispersion such standard deviation were used. In addition, the Kruskall Wallis non-parametric test with Bonferroni post hoc test was applied, considering a significance value of 5% (P < 0.05), with type I error.

Results

The dentin microtensile bond strengths of preheated resin composite, flowable resin composite and dual self-adhesive cement were 6.08 ± 0.66 Mpa, 5.25 ± 2.60Mpa and 2.82 ± 1.26Mpa, respectively. In addition, the preheated resin composite exhibited significantly higher microtensile bond strength compared to the dual self-adhesive cement (P < 0.001). While the flowable resin composite showed no significant difference with the dual self-adhesive cement (P = 0.054) and the preheated resin composite (P = 0.329).

Conclusions

The microtensile bond strength in dentin was significantly higher when using a preheated resin composite at 70°C as a luting agent compared to dual self-adhesive cement. However, the preheated resin composite showed similar microtensile bond strength compared to the flowable resin composite.

"No-Primer" Resin Cementation of Lithium Disilicate Ceramic: A Microtensile Bond Strength Evaluation

OBJECTIVE

The objective of this study was to evaluate the resin-ceramic adhesion of a long-carbon-chain silane (LCSI)-containing resin cement.

METHODS

Polished lithium disilicate ceramic discs were etched with hydrofluoric acid and randomly assigned into four groups; (PSAP), cemented using a silane-free resin cement with no prior priming; (PSAP-S), primed using a silane-containing primer before cementation using a silane-free resin cement; (PSAU), cemented using a LCSI-containing resin cement with no prior priming; (PSAU-S), primed as for the group (PSAP-S) and cemented using a LCSI-containing resin cement. The cemented blocks were sectioned into microbeams. The resin-ceramic microtensile bond strength (μTBS) was measured at 1 week and after thermocycling. The failure modes of the tested microbeams were evaluated.

RESULTS

The μTBS of the LCSI-containing and silane-free resin cements, either with or without a prior priming step, did not significantly differ. The adhesion of the LCSI-containing resin cement to lithium disilicate ceramic, either with or without a prior priming step, did not significantly deteriorate after artificial aging.

CONCLUSIONS

The long-carbon-chain silane (LCSI) monomer incorporated in the resin cement eliminated the need for a silane priming step of a hydrofluoric acid-etched lithium disilicate ceramic.

Effects of Short-Term Exposure of Chloramine-T Solution on the Characteristics of Light-Cured and Chemical-Cured Adhesives

This study evaluated the effect of a 0.5% chloramine T solution on a chemical-cured universal adhesive by comparing the light-cured, one-step, self-etch adhesive for the bonding performance, mechanical properties, and resin-dentin interfacial characteristics. Caries-free human molars were randomly assigned into eight groups based on the bonding systems employed (Bond Force II, BF and Bondmer Lightless, BL), the immersion solutions used before bonding (0.5% chloramine T solution and distilled water), and the immersion durations (5 and 60 min). Microtensile bond strength (μTBS), nanoleakage evaluation, and nanoindentation tests were performed, and the surface morphology of the resin-dentin interface was examined using a focus ion beam/scanning ion microscopy system. Immersion in chloramine-T for 5 min significantly decreased the μTBS of Bondmer Lightless (from 22.62 to 12.87 MPa) compared with that in distilled water. Moreover, there was also a decreasing trend after immersing in chloramine-T for 60 min (from 19.11 to 13.93 MPa). Chloramine T was found to have no effect on the hardness, elastic modulus, or morphological characteristics of the ion-beam milled resin-dentin interfacial surfaces in the tested adhesives, suggesting that chloramine T might reduce the bond strength by interfering with the interaction and the sealing between the adhesive resin and dentin in the chemical-cured universal adhesive, albeit without affecting the mechanical properties.

Effect of Aprotic Solvents on the Microtensile Bond Strength of Composite Core and Fiber-Reinforced Composite Posts

This investigation evaluated the effects of aprotic solvents, i.e., tetrahydrofuran, pyridine, and morpholine, compared with hydrogen peroxide, on the surfaces of fiber-reinforced composite posts with a composite core based on the microtensile bond strength. In total, 150 FRC Postec Plus posts and 150 D.T. Light-Posts were randomly divided into three groups (non-thermocycling, 5000-cycle, and 10,000-cycle thermocycling groups). Each group was divided into five subgroups according to the post-surface treatment: C, non-treatment group; H2O2, immersed in 35% hydrogen peroxide; THF, immersed in tetrahydrofuran; PY, immersed in pyridine; and MP, immersed in morpholine. The treated specimens were placed in the bottom of a plastic cap and filled with a composite core material in preparation for the microtensile bond test. The data were evaluated using one-way ANOVA and Tukey's test (p < 0.05) as well as an independent t-test (p < 0.05). For the surface roughness, white light interferometry was used for measurement, and the mean surface roughness was analyzed via one-way ANOVA and Tukey's test (p < 0.05). The results showed that, under non-thermocycling conditions, the PY subgroup with D.T. Light-Post had the highest microtensile bond strength, followed by THF, MP, H2O2, and the control groups. For FRC Postec Plus, the PY group had the highest microtensile bond strength, followed by MP, THF, H2O2, and the control groups. Although the thermocycling conditions decreased the microtensile bond strength in all groups, the PY subgroup still had the highest value. An independent t-test revealed that even under all non-thermocycling and 5000- and 10,000-cycle thermocycling conditions, D.T. Light-Post in the PY subgroup displayed significantly higher microtensile bond strengths than FRC Postec Plus in the PY subgroup. While the surface roughness of the fiber-reinforced composite posts showed that the posts treated with pyridine possessed the highest surface roughness for each material type, In conclusion, as an aprotic solvent, pyridine generates the highest microtensile bond strength between the interfaces of composite cores and fiber-reinforced composite posts.

Effectiveness of Different Application Modalities on the Bond Performance of Four Polymeric Adhesive Systems to Dentin

One of the major goals of adhesive dentistry is to improve the interaction of the already-existing adhesives with different substrates by using different application techniques. Thus, the objective of the present in vitro study was to assess the bond performance of four adhesive systems, Prime&Bond Universal (PBU), Clearfil SE Bond (CSE), OptiBond Universal (OBU), and OptiBond FL (OBFL), to dentin using various application modes: passive application (PA), active application (AA), Compo-Vibes modified application (CVM), and Compo-Vibes application (CV). Eighty extracted human molars were allocated into four groups based on the application modalities tested. The micro-tensile bond strength as well as fracture mode were tested in accordance with ISO/TS 11.405 after 24 h and 6 months of aging. Adhesive contact angle (CA) and scanning electron microscope analysis were also performed (n = 3). Statistical tests were performed with α = 0.05. After 24 h, a significant difference with a higher bond strength value was found for PBU in the AA modality and for CSE in the CVM modality (p < 0.05). However, no significant difference was shown between the techniques used among the other adhesives (OBFL and OBU). Moreover, at 24 h, only the PA demonstrated significant differences between the tested materials (p < 0.05). After 6 months, CSE, PBU, and OBU demonstrated significant differences between the techniques (p < 0.05), with a higher bond strength for CSE in AA and CVM modalities, for PBU in AA modality, and for OBU in AA and PA modalities. No significant differences were found between the techniques used among the OBFL (p > 0.05). In addition, only the CVM technique demonstrated significant differences between the tested materials after 6 months. CV and CVM showed a decreased value after aging for CSE and PBU, respectively. However, all the modalities decreased for OBU and OBFL after aging. All the adhesives showed marked resin infiltration into dentinal tubules in AA among all the modalities tested. Both universal adhesive systems (OBU and PBU) demonstrated statistically lower CA when compared to the other systems (CSE and OBFL) (p < 0.05) when applied in the PA mode. Concerning the AA mode, only CSE and OBFL were tested. The AA demonstrated lower CA values compared to the same adhesives in PA (p < 0.05). It could be concluded that the bond strength could be influenced by both materials and application techniques. It seems that the AA technique could be recommended as a gold standard for the application of an adhesive system to dentin. Plus, the CV and CVM modalities after 6 months of aging were considered stable for PBU and CSE, respectively. Consequently, the performance of these adhesive systems might vary when applied to other modalities. Future studies are needed to test this hypothesis.

Dentin Bonding Performance of Universal Adhesives in Primary Teeth In Vitro

(1) Background: The aim of this in vitro study was to evaluate the micro-tensile bond strength (µ-TBS) of universal adhesives to primary tooth dentin after different storage periods. (2) Methods: Dentin of 100 extracted primary molars was exposed. Dentin surfaces were bonded with six universal adhesives (Adhese®Universal [AU], All-Bond Universal® [ABU], G-Premio Bond [GPB], iBond®Universal [IBU], Prime&Bond active™ [PBa], and Prime&Bond®NT as control [PBN]) and restored with a resin composite build-up (Filtek™ Z250). After 24 h, 6 months, and 12 months of water storage, specimens were cut into sticks, and µ-TBS was measured and analyzed using one-way ANOVA (p < 0.05) for normal distributions and the Mann-Whitney U-test (p < 0.05) for non-normal distribution. Pretesting failures were recorded as 0 MPa. Fracture modes were analyzed under a fluorescence microscope; interfaces were visualized with SEM/TEM. (3) Results: Compared with the reference group (PBN: 32.5/31.2 MPa after 6/12 months), two adhesives showed a significantly higher bond strength after 6 months (AU: 44.1 MPa, ABU: 40.9 MPa; p < 0.05) and one adhesive after 12 months (AU: 42.9 MPa, p < 0.05). GPB revealed significantly lower bond strengths in all storage groups (16.9/15.5/10.9 MPa after 24 h/6 months/12 months; p < 0.05). AU and IBU did not suffer pre-test-failures [PTF]. (4) Conclusions: After 12 months, PBN, IBU, AU, and GPB showed significantly lower results compared ithw initial µ-TBS, whereas AU revealed the highest µ-TBS and no PTF.

Comparative evaluation of the effect of two natural collagen cross-linkers on microtensile bond strength of self-etch adhesive system to dentin after contamination with blood and hemostatic agent: An in vitro study

Background

Cavity preparation often causes gingival bleeding which can be controlled by hemostatic agents (HAs). These along with blood act as contaminants and hamper the bonding mechanism. Collagen cross-linkers (CCLs) are agents known to increase the bond strength (BS) to dentin. Hence, the purpose of this in vitro study was to determine the effect of two different CCLs, proanthocyanidin (grape seed extract [GSE]) and hesperidin on the microtensile BS (μTBS) of a self-etch adhesive (SEA) system to dentin which was contaminated with blood and a HA.

Materials and Methods

Thirty-six extracted human molars were collected, and their occlusal surfaces were sectioned to expose the dentin. The teeth were randomly divided into four groups: Group I - Control, Group II - Contamination with blood and HA, Group III - Application of GSE after contamination, and Group IV - Application of hesperidin extract after contamination. The SEA was applied, followed by the use of a nanocomposite. Dentin-composite rods were obtained from each group, and μTBS testing was done. The fracture pattern was visually classified as an adhesive failure at the interface, cohesive failure in composite, or dentin. The scanning electron microscope (SEM) analysis was done for two samples from each group. Statistical analysis was done using the Student's unpaired "t" and ANOVA test.

Results

Group II showed a statistically significant reduction in μTBS in comparison to Group I. This was overcome in Groups III and IV. Hesperidin showed marginally better results than GSE.

Conclusions

The use of GSE and hesperidin increases the μTBS of composite resin to dentin postcontamination with blood and ViscoStat Clear with Single Bond Universal Adhesive.

In Vitro Comparison of Surface Roughness, Flexural, and Microtensile Strength of Various Glass-Ionomer-Based Materials and a New Alkasite Restorative Material

This study aims to evaluate the physical properties of Cention N and various glass-ionomer-based materials in vitro. The groups were obtained as follows: Group 1 (LC-Cent): light-cured Cention N; Group 2 (SC-Cent): self-cured Cention N; Group 3 (COMP): composite (3M Universal Restorative 200); Group 4 (DYRA): compomer (Dyract XP); Group 5 (LINER): Glass Liner; Group 6 (FUJI): FujiII LC Capsule; and Group 7 (NOVA): Nova Glass LC. For the microtensile bond strength (μTBS) test, 21 extracted human molar teeth were used. The enamel of the teeth was removed, and flat dentin surfaces were obtained. Materials were applied up to 3 mm, and sticks were obtained from the teeth. Additionally, specimens were prepared, and their flexural strength and surface roughness (Ra) were evaluated. Herein, data were recorded using SPSS 22.0, and the flexural strength, μTBS, and Ra were statistically analyzed. According to the surface roughness tests, the highest Ra values were observed in Group 6 (FUJI) (0.33 ± 0.1), whereas the lowest Ra values were observed in Group 2 (SC-Cent) (0.17 ± 0.04) (p < 0.05). The flexural strengths of the materials were compared, and the highest value was obtained in Group 2 (SC-Cent) (86.32 ± 15.37), whereas the lowest value was obtained in Group 5 (LINER) (41.75 ± 10.05) (p < 0.05). When the μTBS of materials to teeth was evaluated, the highest μTBS was observed in Group 3 (COMP) (16.50 ± 7.73) and Group 4 (DYRA) (16.36 ± 4.64), whereas the lowest μTBS was found in Group 7 (NOVA) (9.88 ± 1.87) (p < 0.05). According to the μTBS results of materials-to-materials bonding, both Group 2 (SC-Cent) and Group 1 (LC-Cent) made the best bonding with Group 3 (COMP) (p < 0.05). It can be concluded that self-cured Cention N had the highest flexural strength and lowest surface roughness of the seven materials tested. Although the bond strength was statistically lower than conventional composites and compomers, it was similar to resin-modified glass ionomer cements. Additionally, the best material-to-material bonding was found between self-cured Cention N and conventional composites.

Evaluation of Chitosan-Oleuropein Nanoparticles on the Durability of Dentin Bonding

Purpose

To evaluate the effects of dentin pretreatment with chitosan-loaded oleuropein nanoparticles (CONPs) on the durability of resin-dentin bonding interfaces.

Methods

Eighty freshly extracted non-carious human third molars were randomly divided into four groups (n = 20 each): a de-ionized water (DW) group, a chitosan (CS) group, a chlorhexidine (CHX) group and a CONP group. The dentin in the DW, CS, CHX, and CONP groups were pretreated with de-ionized water, 1.0 mg/L CS solution, 2% chlorhexidine solution, and CONP suspension (prepared with 100 mg/L oleuropein), respectively, followed by the universal adhesive and resin composites. The bonded teeth of each group were randomly divided into two subgroups: an immediate subgroup and an aged subgroup. The bonded teeth of each group were then cut into the bonded beams. We measured their microtensile bond strength (μTBS), observed the characteristics of bonding interface by atomic force microscope, calculated the percentage of silver particles in a selected area for interfacial nanoleakage analysis, and evaluated the endogenous gelatinase activity within the bonding interface for in-situ zymogram analysis. Data were analyzed with two-way ANOVA and LSD multiple comparison test (P < 0.05).

Results

Regardless of after 24 h or after thermocycling, CONP exhibited better μTBS (P < 0.05) than the other three groups except that there was not a statistical significance (P > 0.05) in the CONP and CHX groups after 24 h. Besides, the CONP group presented significantly higher modulus of elasticity in the hybrid layers (P < 0.05), lower expression of nanoleakage (P < 0.05), and better inhibitory effect of matrix metalloproteinases than the other three groups before and after thermocycling.

Conclusion

Altogether, the CONPs had the potential to act as a dentin primer, which could effectively improve the dentin-resin binding durability.

Effect of Chlorhexidine-containing Etch-and-Rinse Adhesives on Dentin Microtensile Bond Strength after Biological Loading

PURPOSE

This study compared a 2%-CHX dentin pre-treatment with three CHX adhesives (experimentally admixed 0.1% CHX in primer or bonding agent, or industrially added 0.2% CHX in universal adhesive) by evaluating dentin bond strengths after biological loading in a fully automated artificial mouth model.

MATERIALS AND METHODS

The occlusal dentin of 50 freshly extracted human third molars was exposed, and the teeth were randomly assigned to 5 groups according to the adhesive protocol (n = 10): 1. control, Scotchbond Multipurpose (3M Oral Care; CTRL); 2. 2% CHX dentin pre-treatment (DENT); 3. 0.1% CHX experimentally admixed into the primer (PRIM); 4. 0.1% CHX experimentally admixed into the bonding agent (BOND); 5. Peak Universal Bond containing 0.2% CHX (Ultradent; PEAK). The teeth were restored with composite resin. Microtensile bond strength testing (bonding area 0.46 mm2 ± 0.04 mm2, crosshead speed 1 mm/min) was performed after 24-h storage in distilled water (baseline) or after 2-day biological loading with S. mutans (demineralization 1 h / remineralization 5 h). The mode of fracture was recorded and exemplary sticks were evaluated under SEM.

RESULTS

CTRL exhibited significantly higher μTBS at baseline in comparison to PRIM (p = 0.000), BOND (p = 0.002), and PEAK (p = 0.000). After undergoing the caries model, CTRL demonstrated significantly lower μTBS compared to DENT (p = 0.000), PRIM (p = 0.008), and PEAK (p = 0.000). The same behavior was observed for BOND vs DENT (p = 0.000), PRIM (p = 0.003), and PEAK (p = 0.001). After biological loading, DENT (p = 0.041), PRIM (p = 0.000), and BOND (p = 0.000) exhibited significantly fewer adhesive fractures than CTRL.

CONCLUSIONS

CHX addition to the primer protects dentin bond strength from declining after biological loading. Thus, it may offer some clinical advantage in terms of secondary caries inhibition around composite restorations. However, since loss of adhesion at baseline was less when 2% CHX was used as a dentin pre-treatment, it can be suggested as a safer option. so that bonding is not undermined by potential chemical interactions from CHX with the adhesives.

Bond Strengths of Universal Adhesives to Dentin Contaminated with a Hemostatic Agent

PURPOSE

To evaluate the microtensile bond strength (µTBS) of three universal adhesives to dentin contaminated with a hemostatic agent.

MATERIALS AND METHODS

Ninety-six human premolars were cut to expose mid-coronal dentin. The teeth were randomly divided into a control group (uncontaminated dentin) and an experimental group in which a hemostatic agent was applied (contaminated dentin). Each group was further divided into 6 subgroups according to universal adhesives - SBU (Single Bond Universal), OPU (OptiBond Universal), CBQ (Clearfil Universal Bond Quick) - and etching mode, either etch-and-rinse (ER) or self-etch (SE). Following adhesive application, composite was placed in two increments and light cured. The specimens were stored in distilled water at 37°C for 24 h. The µTBS test was performed using a universal testing machine. Failure mode was assessed using a light microscope. The data were statistically analyzed using three-way ANOVA followed by Scheffe's test (p < 0.05). The resin-dentin interface was observed using scanning electron microscopy.

RESULTS

Significantly lower bond strength was observed when the universal adhesives were bonded to contaminated dentin in SE mode (p < 0.05). In contrast, the µTBS of the universal adhesives in ER mode was not affected by contamination (p > 0.05). The µTBS of CBQ to contaminated dentin was significantly lower than that of the other adhesives. Observation of the resin-dentin interface revealed limited resin penetration when the universal adhesive was applied in SE mode on contaminated dentin.

CONCLUSION

Contaminating the dentin with a hemostatic agent significantly reduced the µTBS of the universal adhesives in SE mode. However, this adverse effect was not found when the universal adhesives were used in ER mode.

Long-term Evaluation of Bonding Performance of Universal Adhesives based on Different Dentinal Moisture Levels

PURPOSE

To evaluate the microtensile bond strength (μTBS) and silver nitrate uptake (SNU) of three universal adhesives used in etch-and-rinse (ER) and self-etch (SE) modes on dry, wet, and oversaturated dentin surfaces after 24 h and 1 year of water storage. The morphology of the hybrid layer (MHL) and the degree of conversion (DC) were also evaluated.

MATERIALS AND METHODS

Human molars were divided into 36 groups according to combinations of the following variables: (i) universal adhesives (Ambar Universal APS [AMB], Prime&Bond Active [PBA], Scotchbond Universal Adhesive [SBU]), (ii) adhesive strategies (ER or SE), (iii) moisture level (dry, wet, or oversaturated dentin surface), and (iv) storage time (24 h or 1 year). After restoration, the specimens were sectioned into resin-dentin sticks and tested for μTBS and SNU according to storage time. For MHL, the specimens were sectioned and evaluated after 24 h using SEM. DC was evaluated using FTIR. ANOVA and Tukey's test were used for statistical analyses (5%).

RESULTS

When 24-h vs 1-year data were compared, there was a significant decrease in μTBS and an increase in SNU values for the majority of experimental groups (p < 0.0001). On dry (ER) and oversaturated (ER and SE) dentin, AMB showed higher μTBS than did PBA (p < 0.00001). No significant decrease in μTBS was observed when universal adhesives were applied in the SE mode to dry dentin (p > 0.05). Regarding SNU, at all moisture levels, AMB showed lower SNU values than SBU (p < 0.001). Regarding MHL, SBU showed several imperfections when applied to oversaturated dentin in comparison with AMB and PBA. Regarding DC, when dentin was kept dry or was oversaturated, AMB showed a higher DC than PBA (p < 0.0001).

CONCLUSION

The behavior of the different universal adhesives evaluated did not vary when applied to wet or dry dentin. However, the results with oversaturated dentin were dependent on the universal adhesive. Independent of the moisture level and the universal adhesive evaluated, significant degradation of the bonding properties occurred after 1 year of water storage, with the exception of universal adhesives applied to dry dentin in the SE strategy.

Effect of Method of Removing Caries-Affected Dentin on the Bond Strength of Composite Resin to Root Canal Dentin

The adhesion of composite resin to caries-affected dentin differs from the adhesion of resin to sound dentin. We evaluated the bond strengths of dual-cure resin composites applied to caries-affected root canal dentin under various clinical conditions and using several caries removal indicators. In the dye stain 1 group, caries were removed to a pale pink stain level using a caries detector. In the dye stain 2 group, caries were removed to a stain-free level using a caries detector. In the probing group, caries were removed to the level of hardness based on probing with a sharp explorer. Additionally, a sound dentin group was used as a control. We compared the resin composite microtensile bond strengths and failure mode distribution among the groups. The bond strengths (MPa) of the probing (64.6 ± 11.9) and the sound dentin (68.7 ± 11.1) groups were significantly higher than those of the dye stain 1 (46.9 ± 7.9) and 2 (47.5 ± 8.4) groups (p < 0.05). The removal of caries-affected dentin using a dentin-hardness-based technique showed higher tensile strength than that using a dye stain technique involving removal to any color level. Thus, the caries removal technique used on root canal dentin affects the bond strength of the resin composite.

Comparative Assessment of Different Pre-Treatment Bonding Strategies to Improve the Adhesion of Self-Adhesive Composites to Dentin

The aim of this study is to compare the adhesive interface formed in dentin, using self-adhesive composites applied with different bonding strategies, by testing the microtensile bond strength (μTBS) and ultramorphology through the use of light microscopy. Permanent, sound human molars were randomly allocated to six experimental groups. The groups included a negative control group, where only etching was performed via EtchOnly; a positive control group where an adhesive was applied, OptiBondFL (OBFL); and an experimental group where a primer was applied using a co-curing strategy together with a composite (Primer_CoCuring). The samples were sectioned into microspecimens for μTBS (n = 8) and into 1-mm thick slabs for light microscopy using Masson’s trichrome staining protocol (n = 3). The statistical analysis included a two-way ANOVA for μTBS data and Tukey’s HSD was used as a post-hoc test (significance level of 5%; SPSS v. 26.0). The results of the μTBS revealed that the self-adhesive composite (F = 6.0, p < 0.018) and the bonding strategy (F = 444.1, p < 0.001) significantly affected the bond strength to dentin. However, their interactions were not significant (F = 1.2, p = 0.29). Etching dentin with no additional treatment revealed the lowest μTBS (VF_EtchOnly = 2.4 ± 0.8 MPa; CC_EtchOnly = 2.0 ± 0.4 MPa), which was significantly different from using a primer (VF_CoCu = 8.8 ± 0.8 MPa; CC_CoCu = 6.3 ± 1.0 MPa) or using the full adhesive (VF_OptiBondFL = 22.4 ± 0.3 MPa; CC_OptibondFL = 21.2 ± 0.4 MPa). Microscopy images revealed that the experimental Primer_CoCuring was the only group with no collagen fibers exposed to the dentin−composite interface. Overall, the use of a primer, within the limitations of this study, increased the bonding of the self-adhesive composite and provided sufficient infiltration of the collagen based on light-microscopic imaging.

Long-term microtensile bond strength of self-etch adhesives and influence of 7-s phosphoric acid etching on adhesion of a 3-step etch-and-rinse adhesive to the dentine of primary teeth

BACKGROUND

The immediate microtensile bond strength (µTBS) of self-etch (SE) adhesives to primary dentine is promising, but evidence about the durability is scarce.

AIM

To assess the long-term µTBS of SE adhesives to primary dentine and to examine the effect of 7-s etching on µTBS of a 3-step etch-and-rinse (ER) adhesive.

DESIGN

The enamel of 115 caries-free human primary teeth was ground flat, and bonding was performed according to group assignment: G-aenial™ Bond/GC [GB], Clearfil™ SE Bond/Kuraray [CS], OptiBond™ XTR/Kerr [OX], Scotchbond™ Universal/3M™ [SU], Prime&Bond^® NT™/Dentsply [PB], and OptiBond™ FL/Kerr [OF]. After storage (24 h, 6 mos., 12 mos.), 1,762 beams were cut for µTBS testing. Fracture analysis was performed using light/fluorescence microscopy. Resin-dentine interfaces were exemplarily analyzed using SEM.

RESULTS

After 24 h, OX and SU showed significantly higher estimated mean µTBS than GB, which exhibited the lowest µTBS at all stages (p < .05). μTBS within each adhesive group showed slight variations over time (p > .05). OF_SE produced acceptable µTBS. Etching increased the mean immediate µTBS for OF (p > .05) and the percentage of cohesive fractures.

CONCLUSIONS

SE adhesives achieved durable μTBS to primary dentine. 7-s etching may improve the immediate µTBS of a 3-step ER adhesive.

Cause-Effect Relationship of Varying Bonding Thicknesses in Dentin Adhesion of Universal Adhesives

PURPOSE

To evaluate whether varying thicknesses of universal adhesives utilizing the additional coating strategy would affect their microtensile bond strength (µTBS) to dentin, hardness, and elastic modulus (mechanical properties).

MATERIALS AND METHODS

Ninety-nine human maxillary premolars were cut to expose coronal dentin, ground with regular-grit diamond burs, and randomly distributed into 9 groups based on 1. adhesive: Scotchbond Universal Adhesive (SB; universal), G Premio Bond (GP; universal) and Clearfil Megabond 2 (MB; two-step self-etch; control); and 2. application strategy (one, two or three coats; each coat light cured). After adhesive application and resin composite buildup, the bonded teeth were stored in distilled water (37°C; 24 h). Resin-dentin sticks from eight premolars per group (each premolar yielded 3 sticks; n = 24 sticks altogether) were prepared for the µTBS test, followed by measurement of the adhesive thicknesses at their fractured ends using SEM. The mechanical properties of the adhesive layers produced by different coats were evaluated on separate resin-dentin slices (n = 3 teeth per group).

RESULTS

Two coats significantly increased the µTBS (p < 0.001) of all the adhesives. The correlation between adhesive thickness and bond strength was positive for GP but negative for SB. MB did not show any correlation. Additional coating significantly increased the mechanical properties of GP (p < 0.05) but did not affect SB and MB (p < 0.05).

CONCLUSION

An additional adhesive coating over the manufacturers' recommendations improved the bond strength of all the adhesives tested. However, the increased mechanical properties of the adhesives with additional curing was material dependent.

Application of Sulfinate Agent in Conjunction with HOCl Smear-Layer Deproteinization Improves Dentin Bonding Durability of One-step Self-etch Adhesives

PURPOSE

To evaluate the effect of a sulfinate agent on the bonding durability of one-step self-etch adhesives (1-SEAs) to smear-layer-covered dentin deproteinized with hypochlorous acid (HOCl).

MATERIALS AND METHODS

Human coronal dentin disks with a standardized smear layer were deproteinized with 100 ppm HOCl solution for 0 s (control), 15 s or 30 s. After rinsing with water for 30 s and air drying, half of the specimens were treated with a sulfinate agent (Scotchbond Universal Dual Cure Activator; SDA) prior to the application of a 1-SEA (Bond Force II [Tokuyama Dental] or Clearfil Universal Bond Quick [Kuraray Noritake]). Microtensile bond strength (µTBS) was measured after 24 h or 10,000 thermal cycles (TC). The data were analyzed by three-way ANOVA with Tukey's post-hoc tests and t-tests at the 0.05 significance level.

RESULTS

The 24-h µTBS of both adhesives increased statistically significantly with the HOCl pretreatment for 15 s or 30 s (p < 0.05), but it was not statistically significantly affected by the application of SDA (p > 0.05). However, after TC, the groups treated with the combination of HOCl and SDA maintained their µTBS (p > 0.05), as opposed to untreated dentin and dentin treated with either HOCl or SDA, whose µTBS decreased significantly (p < 0.05).

CONCLUSION

The application of the sulfinate agent did not statistically significantly affect the immediate bond strength of 1-SEAs, and it could not prevent a significant decrease in the bond strength to untreated dentin after thermocycling. However, the sulfinate agent significantly improved the bonding durability of 1-SEAs to HOCl smear-layer deproteinized dentin.

Influence of Dentin Surface Roughness, Drying Time, and Primer Application on Self-adhesive Composite-Cement Bond Strength

PURPOSE

To investigate the effect of roughness and drying time of dentin as well as the number of coats of a self-adhesive composite-cement primer on the bond strength of self-adhesive composite cement.

MATERIAL AND METHODS

Sixty human teeth were prepared and assigned to 12 groups (n = 5), according to three experimental factors: 1) dentin surface roughness, rough or fine, as achieved by 250- and 600-grit silicon carbide papers, respectively; 2) dentin wetness based on air-drying time (5 or 10 s); and 3) the self-adhesive composite-cement primer applications (no-coat, 1-coat, and 2-coat). Composite resin blocks were made with hybrid composite resin (M1 GraceFil) and cemented with G-CEM ONE (both GC). Cement-dentin sticks (12) were prepared, and the microtensile bond strength (μTBS) test was performed. Failure modes were observed with a stereomicroscope (40X), and bonding interfaces were evaluated with confocal laser scanning microscopy (CLSM). Statistical analysis was performed using three-way ANOVA and Tukey's post-hoc comparisons test (α = 0.05).

RESULTS

Dentin roughness (250-grit > 600-grit, p = 0.000), drying time (5-s drying > 10-s drying, p = 0.000), and primer application (no-coat < 1-coat = 2-coat, p = 0.000) had significant effects on bond strength. These factors also showed significant interactions with each other (p = 0.003). The highest μTBS (31.8 ± 3.1 MPa) was observed in the 1-coat/fine roughness/10-s drying group and the lowest μTBS (13.4 ± 2.7 MPa) in the no-coat/coarse roughness/5-s drying group. CLSM showed higher penetration of cement in the primer-coated groups compared to that in the no-coat groups.

CONCLUSION

Bond strength between the self-adhesive composite cement and dentin was higher in the fine-roughness dentin group than in the coarse-roughness dentin group, and in the 5-s drying group compared to the 10-s drying group. Applying a primer to dentin improved bond strength of the self-adhesive composite cement.

Enhancing the Stability of the Resin-Dentin Bonding Interface with Ag+- and Zn2+-Exchanged Zeolite A

Enhancing the stability of the resin-dentin bonding interface via simultaneously improving the antibacterial, mechanical, and adhesive properties of a dental adhesive is the key to prolonging the longevity of dental restoration for caries treatment. Herein, we present the stabilization effect of Ag⁺- and Zn²⁺-exchanged zeolite A (denoted as Ag-A and Zn-A, respectively) on the resin-dentin bonding interface. Ag-A and Zn-A zeolites exhibited sustained ion release capability, outstanding biocompatibility to L929 cells (<2 mg/mL), and excellent antibacterial ability to Streptococcus mutans (minimum inhibitory concentration: 100 μg/mL for Ag-A and 200 μg/mL for Zn-A). One-step self-etching adhesives modified by Ag-A, Zn-A, or Ag-/Zn-A (1/1 in weight) zeolites with an ultralow loading of 0.2 wt % exhibited favorable antibacterial activity with the inhibition of biofilm formation by 70.33, 56.47, and 62.54%, respectively. Compared to the control group, Zn-A- and Ag-/Zn-A-modified adhesives significantly increased the wettability properties of the adhesive and the long-term resin-dentin bond strength (by ∼25%) after 5000 thermocycles of aging. The current data demonstrated that the introduction of 0.2 wt % Zn-A or Ag-/Zn-A into the adhesive remarkably enhanced the stability of the resin-dentin bonding interface. Our findings provide a new strategy to modify the dental adhesive for further optimizing the longevity of dental restorations for caries.

Effect of the thicknesses of bulk-fill composites on bonding strength

OBJECTIVES

This work evaluated the effects of thickness on resin bonding strength.

METHODS

We set the two bulk-fill composites Filtek Bulk Fill Posterior (FBF) and Tetric N-Ceram Bulk Fill (TBF) as the experimental groups and the two conventional composites Filtek Z100 (Z100) and Spectrum TPH (ST) as the control groups. The translucency parameter (TP), color difference, Vickers hardness (HV), and microtensile bond strength (μTBS) of dentine and the resin composites were measured at different depths.

RESULTS

In each group, TP and HV decreased with the increase in thickness. At the same depth, the TP of the bulk-fill composites was higher than that of the conventional composites. At the same depth, the HV of the four different resin composites followed the order of Z100>FBF>TBF>ST (except for the upper surface). Except for FBF at 3 and 4 mm, all of the other groups showed no visible color change at all the tested thicknesses. Although the μTBS values of the four different composites obtained through the bulk-fill technique were lower than those of composites obtained through the incremental fill technique, the μTBS of the bulk-fill composites obtained through the bulk-filling technique can reach 30 MPa.

CONCLUSIONS

Bulk-fill composites applied in single 4 mm increments can meet the requirements of clinical application. However, the color stability of some bulk-fill composites cannot be maintained.

Effect of Clinically Relevant Smear Layers and pH of Universal Adhesives on Dentin Bond Strength and Durability

PURPOSE

To evaluate the effects of different smear layers on the microtensile bond strength (µTBS) of a reference two-step self-etch adhesive and two universal adhesives.

MATERIALS AND METHODS

Mid-coronal dentin of 90 teeth was exposed and divided into three bur groups (coarse diamond, fine diamond, or tungsten carbide). Each bur-prepared group was further divided into three adhesive groups: Clearfil SE Bond (SE, Kuraray Noritake), Single Bond Universal (SB; 3M Oral Care), and G-Premio Bond (GP, GC). After adhesive application, 4-mm-thick resin composites were built up. Half of the teeth in each bur-adhesive group were used in immediate µTBS testing, and the others were tested after thermal aging (n = 5). Rectangular sticks were prepared using a low-speed diamond saw. For each tooth, 6 central sticks were used in the µTBS test. Statistical analysis was performed using three-way ANOVA and Bonferroni tests (α = 0.05).

RESULTS

SE presented higher µTBS than universal adhesives and SB presented higher µTBS than GP regardless of dentin surface preparation and thermal aging (p ˂ 0.05). For SE and SB, the tungsten carbide bur demonstrated higher immediate and aged µTBS than did the extra-fine diamond bur (p ˂ 0.05). The immediate µTBS was similar for GP with all bur types (p ˃ 0.05); the tungsten carbide and extra-fine diamond burs presented higher µTBS than did the coarse-diamond bur after thermal aging (p ˂ 0.05).

CONCLUSION

Dentin surface preparation and adhesive type had significant effects on µTBS. The smear layer created with an extra-fine diamond or tungsten carbide bur is favorable when mild and ultra-mild self-etch adhesives are used.

Flowable fiber-reinforced versus flowable bulk-fill resin composites: Degree of conversion and microtensile bond strength to dentin in high C-factor cavities

OBJECTIVES

To compare flowable fiber-reinforced and flowable bulk-fill resin composites regarding their degree of conversion (DC) and microtensile bond strength (μTBS) to dentin in high C-factor class I cavities.

MATERIALS AND METHODS

One flowable fiber-reinforced (EverX Flow, GC) and two flowable bulk-fill composites (SDR, Dentsply, and Tetric N-flow Bulk fill, Ivoclar Vivadent) were tested. Regarding DC, 10 cylindrical-shaped specimens were prepared from each material (N = 30), measured using Fourier-Transform Infrared Spectroscopy (FTIR). Regarding µ TBS , class I cavities (4.5 × 4.5 × 3) were prepared on flat dentin surfaces of 30 molars, divided into three equal groups, restored with the three restorative materials, thermocycled, sectioned to create 1 mm × 1 mm cross-sectional beams, then tested using a universal testing machine. Failure mode was assessed using a stereomicroscope. Two-way ANOVA and Tukey's HSD post-hoc tests were used in DC, while One-way ANOVA was used for µ TBS .

RESULTS

The used materials showed statistically significant differences in DC with the fiber-reinforced composite having the highest value. No statistically significant differences were found between the materials regarding their µ TBS .

CONCLUSIONS

Flowable fiber-reinforced composite provided the most DC performance compared to the flowable bulk-fill composites. The three used restorative materials provided comparable bonding ability to dentin in high C-factor cavities.

CLINICAL SIGNIFICANCE

Flowable fiber-reinforced resin composite is preferred as a dentin-replacement material in high-stress bearing areas. However, both flowable fiber-reinforced and bulk-fill resin composites are equally effective in bonding to dentin in high C-factor cavities.

Dimethyl Sulfoxide Dentin Pretreatments Do Not Improve Bonding of a Universal Adhesive in Etch-and-Rinse or Self-etch Modes

PURPOSE

To evaluate the influence of dimethyl sulfoxide (DMSO) solutions used as dentin pretreatments on microtensile bond strength (µTBS), as well as the dentin/restoration interface micromorphology of a universal adhesive in etch-and-rinse or self-etch mode.

MATERIALS AND METHODS

Eighty blocks of dentin were submitted to acid conditioning with 35% phosphoric acid (etch-and-rinse), or not (self-etch), and distributed among the treatments (n = 10): CON: Scotchbond Universal/3M Oral Care; DMSO: pretreatment with DMSO; DMSO/water: pretreatment with DMSO in water (1:1); DMSO/ethanol: pretreatment with DMSO in ethanol (1:1). Microtensile bond strength and failure tests were performed after 24-h and 6-month storage. The tooth-restoration interface was evaluated using scanning electron microscopy to assess the hybrid layer formed.

RESULTS

The interaction between treatments, storage time, and etching modes was not significant for µTBS (p = 0.2469). The DMSO, DMSO/water and DMSO/ethanol pretreatments did not affect µTBS values at either time point (p = 0.8732). Aging decreased µTBS over time only for the etch-and-rinse strategy, although the groups presented higher microtensile bond strengths in etch-and-rinse mode than in self-etch mode at both time points (p < 0.0001). The micromorphological images of the interface showed that different DMSO pretreatment solutions did not impair hybrid layer formation.

CONCLUSION

The use of dentin pretreatments containing DMSO did not improve the bonding or the micromorphology of a universal adhesive in etch-and-rinse or self-etch modes.

Effects of C-Factor on Bond Strength of Universal Adhesives to Floor and Wall Dentin in Class-I Composite Restorations

PURPOSE

To evaluate the effects of C-factor on the bond strength of universal adhesives to floor and wall dentin in class-I composite restorations using a bulk-fill composite.

MATERIALS AND METHODS

108 non-carious humans third molars were randomly divided into four groups as follows: flat wall, flat floor, cavity wall, and cavity floor (n = 36). Then, each group was subdivided into three subgroups according to the type of adhesive used: Single Bond Universal, G-premio Bond (both universal adhesives), or Adper Single Bond 2 (an etch-and-rinse adhesive). After the bonding procedure, X-tra fill resin composite was applied in bulk to build up the flat surfaces or fill the cavities.Then the teeth were sectioned into 1-mm2 sticks and microtensile bond strength (µTBS) was measured using a universal testing machine. µTBS (MPa) was analyzed by one-way, two-way, and three-way ANOVA using SPSS Version 23 (a = 0.05).

RESULTS

Interactions between adhesives and bonding surfaces, as well as C-factor and bonding surfaces showed statistically significant differences, but the interaction between the C-factor and type of adhesive was not statistically significant. The comparison of bonded surfaces including the flat wall and the flat floor in Adper Single Bond 2 was statistically significant (p < 0.05), except for the cavity wall and cavity floor.

CONCLUSION

Regardless of the type of adhesives, the C-factor reduced the µTBS of the composite resin to dentin. Adper Single Bond 2 mediated higher µTBS than did the universal adhesives G-premio Bond and Single Bond Universal.

Effects of different concentrations of sodium hypochlorite on dentine adhesion and the recovery application of sodium erythorbate

OBJECTIVES

Root canal therapy is the most effective and common method for pulpitis and periapical periodontitis. During the root canal preparation, chemical irrigation plays a key role. However, sodium hypochlorite (NaOCl), the widely used irrigation fluid, may impact the bonding strength between dentin and restorative material meanwhile sterilization and dissolving. Therefore, it's important to explore the influence of NaOCl on the adhesion between dentin and restoration materials to ensure clinical efficacy. This study aims to explore the effect of NaOCl on dentine adhesion and evaluate the effect of dentine adhesion induced by sodium erythorbate (ERY), and to provide clinical guidance on dentin bonding after root canal therapy.

METHODS

Seventy freshly complete extracted human third molars aged 18-33 years old, without caries and restorations were selected. A diamond saw was used under running water to achieve dentine fragments which were divided into 10 groups with 14 fragments in each group: 2 control [deionized water (DW)±10% ERY] and 8 experimental groups (0.5%, 1%, 2.5%, and 5.25% NaOCl±10% ERY). The dentine specimens in the control group (treated with DW) and the experimental groups (treated with 0.5% NaOCl, 1% NaOCl, 2.5% NaOCl, and 5.25% NaOCl) were immersed for 20 min using corresponding solutions which were renewed every 5 min. The other 5 groups were immersed in 10% ERY for 5 min after an initial washing with DW for 1 min. Then, we selected 4 dentine fragments from all 14 fragments in each group and the numbers and diameters of opening dentinal tubules were observed under scanning electron microscope (SEM). The other 10 dentine fragments from each group were used to make adhesive samples by using self-etch adhesive wand composite resin. All the above adhesive samples were sectioned perpendicular to the bonded interface into 20 slabs with a cross-sectional area of 1 mm×1 mm using a diamond saw under the cooling water, and then the morphology of 10 slabs in each group's bonding interface was observed from aspects of formation of resin tags, depth of tags in dentin, and formation of hybrid layer under SEM. The other 10 slabs of each group's microtensile bond strength and failure modes were also analyzed.

RESULTS

Among the 0.5% NaOCl, 1% NaOCl, 2.5% NaOCl, and 5.25% NaOCl groups, the number and diameter of patent dentinal tubules gradually increased with the rise of concentration of NaOCl solution (all P<0.05). Among the DW, 0.5% NaOCl, 1% NaOCl, 2.5% NaOCl, and 5.25% NaOCl groups, the number and diameter of patent dentinal tubules increased after using ERY, but without significant difference (all P>0.05). Among the DW, 0.5% NaOCl, 1% NaOCl, and 2.5% NaOCl groups, the scores of formation of resin tags under SEM gradually increased with the increase of concentration of NaOCl solution, while the score in the 5.25% NaOCl group decreased significantly compared with the score of the 2.5% NaOCl group (P<0.05). There was no significant difference between using 10% ERY groups and without using 10% ERY groups (all P>0.05). The scores of length of the tags under SEM in the 5.25% NaOCl group was significantly higher than the scores of DW, 0.5% NaOCl, and 1% NaOCl groups (all P<0.05), and it was also higher than the score of the 2.5% NaOCl group, but without significant difference (P>0.05). There was no significant difference between using 10% ERY groups and without using 10% ERY groups (P>0.05). The scores of formation of hybrid layer under SEM in the 2.5% NaOCl and 5.25% NaOCl groups significantly decreased compared with the score of the DW group (all P<0.05). There were significant differences between the 2.5% NaOCl±10% ERY groups and between the 5.25% NaOCl±10% ERY groups (all P<0.05). Microtensile bond strength was greater in the 0.5% NaOCl, 1% NaOCl, and 2.5% NaOCl groups, but lower in the 5.25% NaOCl group than that in the DW group (all P<0.05). There were significant differences between the 2.5% NaOCl±10% ERY groups and between the 5.25% NaOCl±10% ERY groups (all P<0.05). The incidence of type "Adhesive" of failure modes in the 5.25% NaOCl group was significantly higher than that in other groups (all P<0.05), while the incidence of type "Adhesive" in the 5.25% NaOCl+10% ERY group was lower than that in the 5.25% NaOCl group (P<0.05).

CONCLUSIONS

The bonding strength to dentine increases with the increase of NaOCl concentration when the concentration lower than 2.5%; whereas it is decreased at a higher concentration (such as 5.25%). 10% ERY has a definite recovery effect on attenuated bonding strength to 5.25% NaOCl-treated dentine.

Influence of Application of Dimethyl Sulfoxide on the Bonding Properties to Eroded Dentin

PURPOSE

To evaluate the effect of dimethyl sulfoxide (DMSO) on the microtensile bond strength (µTBS), nanoleakage (NL), and degree of conversion (DC) of universal adhesives on eroded dentin.

MATERIALS AND METHODS

One hundred thirty-four extracted (134) human third molars were selected for the study. After the dentin surface was exposed, 128 teeth were randomly assigned to 16 experimental groups as follows: dentin surfaces (sound dentin and eroded dentin), application of DMSO (without or with the application of DMSO), and adhesive strategies (etch-and-rinse [ER] and self-etch [SE]). The universal adhesive systems iBond Universal (IBU) and Scotchbond Universal (SBU) were applied and the teeth were restored using a resin composite. After 24 h in distilled water at 37°C, the samples were sectioned and evaluated for μTBS. Selected sticks from each tooth were used for evaluating NL and DC. The remaining six teeth were used to measure the thickness of the collagen layer of the artificially eroded dentin using scanning electron microscopy. Data on μTBS, NL, and DC (%) were analyzed using three-way ANOVA and Tukey's test (α = 0.05).

RESULTS

Significantly lower μTBS (p = 0.0001) and DC (p = 0.01) were observed for eroded dentin than for sound dentin. However, a significant increase in the μTBS (p = 0.0007) and DC (p = 0.001) was observed for both substrates when DMSO was applied. Moreover, the application of DMSO decreased the concentration of silver nitrate at the bottom of the hybrid layer for both sound and eroded dentin (p = 0.002). Eroded dentin showed enlarged tubules with the presence of a collapsed collagen fibril layer approximately 5.0 ± 2.0 mm of thickness.

CONCLUSION

The bonding performance of both tested universal adhesives improved on both sound and eroded dentin with DMSO pretreatment.

Influence of Heated Hydrofluoric Acid Surface Treatment on Surface Roughness and Bond Strength to Feldspathic Ceramics and Lithium-Disilicate Glass-Ceramics

PURPOSE

To evaluate the effect of heated and room-temperature hydrofluoric (HF) acid on surface roughness parameters (Ra and Rq) and microtensile bond strength (μTBS) on feldspathic ceramic and lithium-disilicate glass-ceramics.

MATERIALS AND METHODS

Disk-shaped samples made from both ceramics were divided into groups according to surface treatment: feldspathic ceramic polished surface (FP), feldspathic ceramic + 60 s of 9% HF acid etching at room temperature (FC), feldspathic ceramic + 60 s of 9% HF acid etching heated to 70°C (F70), lithium-disilicate polished surface only (LP), lithium disilicate + 20 s of 9% HF acid etching at room temperature (LC), and lithium disilicate + 20 s of 9% HF acid etching heated to 70°C (L70). To evaluate Ra and Rq, non-overlapping readings were taken on the surface of each sample with a contact stylus profilometer. To measure microtensile bond strength (μTBS), samples of groups FC, F70, LC and L70 received their corresponding surface treatment, were silanized and then bonded using a dual-cure composite cement to resin composite disks. After 24 h, samples were sectioned to obtain specimens for μTBS. Representative samples from each group were examined using scanning electron microscopy (SEM) to analyze the morphology of the etched surface. The data were analyzed for statistical significance using Welch's ANOVA with the Games-Howell multiple-comparison post-hoc test.

RESULTS

For both surface roughness parameters and HF acid etching at room temperature (FC and LC) showed a significant increase (p < 0.001) in surface roughness when compared to polished surfaces (FP and LP). Furthermore, the use of heated HF acid etching significantly increased (p < 0.001) the surface roughness of the ceramic when compared to their counterpart sample of HF acid etching at room temperature. Group L70 obtained the highest μTBS of all groups (29.11 ± 8.26 MPa) and was significantly higher (p < 0.001) than that of the other experimental groups. There were no statistical differences (p > 0.05) between groups FC (19.94 ± 4.14), F70 (18.24 ± 5.29), and LC (17.87 ± 6.96).

CONCLUSION

The use of 9% HF acid etching heated to 70°C resulted in significantly higher surface roughness and improved bond strength onto lithium-disilicate glass-ceramic compared to surface HF acid etching at room temperature.

Can a New HEMA-free Two-step Self-etch Adhesive Improve Dentin Bonding Durability and Marginal Adaptation?

PURPOSE

A new two-step self-etch adhesive (2-SEA) free of hydrophilic monomers was evaluated. Its microtensile bond strength (µTBS) to dentin under various aging conditions, interfacial gap formation, water sorption/solubility, and formation of an acid-base resistant zone (ABRZ) were evaluated and compared with a gold-standard 2-SEA.

MATERIALS AND METHODS

The new 2-SEA G2-Bond Universal (G2; GC) was compared to Clearfil SE Bond 2 (CSE2, Kuraray Noritake). Their µTBS to sound coronal dentin was tested after 1 week, 10,000 thermal cycles (TC), 20,000 TC, 6 months and 1 year. Failure mode was determined using scanning electron microscopy (SEM). Gap formation at the interface of 2-mm deep tapered cavities with an enamel border was observed using swept-source optical coherence tomography after 1 day, 1 week, 10,000 TC, and 20,000 TC. In addition, water sorption and solubility of the bonding agents was measured, and ABRZ formation was evaluated using SEM.

RESULTS

There was no significant difference in µTBS between G2 and CSE2 (p > 0.05), and the aging conditions had no significant effect on µTBS (p > 0.05). In all groups, cohesive failures prevailed (55%-95%). Interfacial gap formation was initially similar for both adhesives (p > 0.05), but G2 exhibited a significantly lower gap formation than CSE2 after TC (p < 0.05). The water sorption of G2 was significantly lower compared to CSE2 (p < 0.05), and their solubility was statistically similar (p > 0.05). ABRZ of similar thickness was observed with both adhesives.

CONCLUSION

The new 2-SEA exhibited stable dentin bonding and increased hydrophobicity resulting from the absence of hydrophilic monomers.

The Effect of Different Condition of Pulpal Pressure on Microtensile Bond Strength of Several Dentin Bonding Agents on Deep and Superficial Dentin

The objective of this study was to examine the effect of different conditions of simulated hydrostatic pulpal pressure on the μTBS of HEMA-based and HEMA-free dentin bonding agents (DBAs). The influence of dentin location (deep and superficial) on μTBS was also evaluated. Flat coronal dentin surfaces of extracted human molars were prepared. Three groups of resin-bonded specimens were exposed to different pulpal pressures. Pulpal pressure was maintained for 20 min for each group. A flowable resin composite was used for coronal build-up. The bonded teeth were sectioned and, after 24 h of water storage, stressed to failure using the microtensile tester (μTBS). Failed samples were analyzed by SEM inspection. HEMA-based DBAs were much more sensitive to pulpal pressure conditions than non-HEMA-containing DBAs. Pulpal pressure had a greater influence in deep dentin. The HEMA-free DBA was insensitive to the presence or absence of pulpal pressure condition. SEM inspection confirmed a relationship between the presence of voids inside the HEMA-based DBAs layer and the lower μTBS results. HEMA-based DBAs are more sensitive to pulpal pressure conditions than HEMA-free DBAs. Interestingly, HEMA-free DBA showed a greater number of water droplets at resin–dentin interface in all tested conditions.

Eight-year Microtensile Bond Strength to Dentin and Interfacial Nanomechanical Properties of a One-step Adhesive

PURPOSE

To evaluate the microtensile bond strength (µTBS) of a one-step self-etch adhesive (1-SEA) to dentin and its interfacial nanomechanical properties after 8 years of water storage.

MATERIALS AND METHODS

Flat coronal dentin surfaces of extracted human third molars were bonded with a 1-SEA (Clearfil S3 Bond Plus, CS3+) and built up with a hybrid resin composite (Clearfil AP-X). After storage in water for 24 h or 8 years, non-trimmed stick-shaped specimens were fabricated from the central part of each bonded tooth and subjected to the µTBS test at a crosshead speed of 1.0 mm/min. Failure modes and the morphology of debonded interfaces were analyzed using a scanning electron microscope (SEM). In addition, the elastic modulus (E) and hardness (H) of the adhesive layer and the resin composite were determined by an instrumented nanoindentation test. The acquired µTBS, E, and H data were statistically analyzed using t-tests to examine the effect of storage time (α = 0.05).

RESULTS

The 8-year µTBS was slightly lower than that after 24 h, but the difference was not significant (p = 0.123). The SEM observation of debonded surfaces after 8 years revealed extrusions and lacunas. E and H of the adhesive layer and the resin composite significantly decreased over the 8-year water storage (p < 0.001).

CONCLUSIONS

Although 8 years of water storage did not decrease the µTBS of CS3+ significantly, the observed failure mode patterns and significantly decreased nanomechanical properties indicated resin degradation of the adhesive and the resin composite.

Influence of the resin-coating technique on the bonding performance of self-adhesive resin cements in single-visit computer-aided design/computer-aided manufacturing resin restorations

OBJECTIVE

This in vitro study investigated the influence of resin coating on the bonding performance of self-adhesive resin cements in single-visit computer-aided design (CAD)/computer-aided manufacturing (CAM) resin restorations.

MATERIALS AND METHOD

CAD/CAM resin (1.5-mm thick) was mounted on 20 noncoated and 20 resin-coated human dentin surfaces using dual-cured self-adhesive resin cements (Panavia SA Cement Plus or Panavia SA Cement Universal, Kuraray Noritake Dental) in either self-curing or dual-curing mode. These specimens were sectioned into beam-shaped sticks and subjected to microtensile bond strength tests after 24 h of water storage. The obtained data were statistically analyzed with three-way analysis of variance (ANOVA) and t tests (α = 0.05).

RESULTS

The three-way ANOVA results revealed the significant influence of resin coating, resin cement, and curing mode. Resin coating and light curing led to higher bond strengths in almost all groups. Resin-coated dentin with Panavia SA Cement Plus exhibited a mean bond strength greater than 35 MPa in both self-curing and dual-curing modes.

CONCLUSIONS

In single-visit CAD/CAM resin restorations, resin coating, resin cement selection, and curing mode influenced the bonding performance of self-adhesive resin cements. In addition, resin coating and light curing increased the bond strength of self-adhesive resin cements. Resin coating and light curing are encouraged for predictable bonding performance of dual-cured self-adhesive resin cements in single-visit CAD/CAM resin restorations.

Water-Airborne-Particle Abrasion as a Pre-Treatment to Improve Bioadhesion and Bond Strength of Glass-Ceramic Restorations: From In Vitro Study to 15-Year Survival Rate

The purposes of this study were to evaluate the efficacy of water-airborne-particle abrasion (WAPA) as pre-etching procedure for tooth surfaces to increase bond strength, and to compare the survival rate of WAPA vs. non-WAPA glass-ceramic restorations with a 15-year follow-up. The occlusal surfaces of 20 human molars were sectioned and flattened. The prepared surfaces areas were subdivided into two parts: one received WAPA treatment (prophy jet handpiece with 50 µm aluminium oxide particles) followed by acid etching (37% phosphoric acid for 20 s/3-step etch-and-rinse); the other one was only acid-etched. In total, 108 specimens were obtained from the teeth, of which 80 were used to measure the micro-tensile bond strength (μTBS) in the WAPA (n = 40) and control (n = 40) groups, while the remaining specimens (n = 28) were investigated via SEM to evaluate the micromorphology and roughness (Ra) before and after the different treatment steps. The survival rate (SR) was performed on 465 glass-ceramic restorations (131 patients) comparing WAPA treatment (n = 183) versus non-WAPA treatment (n = 282). The bond strength was 63.9 ± 7.7 MPa for the WAPA group and 51.7 ± 10.8 MPa for the control group (p < 0.001). The Ra was 98 ± 24 µm for the enamel control group, 150 ± 35 µm for the enamel WAPA group, 102 ± 27 µm for the dentin control group and 160 ± 25 µm for the dentin WAPA group. The Ra increase from the WAPA procedure for enamel and dentin was statistically significant (p < 0.05). Under SEM, resin tags were present in both groups although in the WAPA they appeared to be extended in a 3D arrangement. The SR of the WAPA group (11.4 years) was 94%, while the SR of the non-WAPA group (12.3 years) was 87.6% (p < 0.05). The WAPA treatment using aluminium oxide particles followed by a 3-step etch-and-rinse adhesive system significantly improved bioadhesion with an increased bond strength of 23.6% and provided superior long-term clinical performance of glass-ceramic restorations.

Bonding Performance of Self-etching Adhesives to Bur-cut Dentin with Active Application Mode

PURPOSE

This study evaluated whether active application of self-etching adhesives would influence their microtensile bond strength (µTBS) to dentin cut with burs of different grit sizes.

MATERIALS AND METHODS

Eighty-four human premolars were divided into 12 groups according to 1) two dentin surface preparations with either superfine- or regular-grit diamond burs; 2) three adhesives - Clearfil SE Bond 2 (SE2), Scotchbond Universal (SBU, 3M Oral Care) and G-Premio Bond (GPB, GC); and 3) two application modes of each adhesive (active or passive). Six bonded teeth per group were sectioned into sticks for µTBS testing. Statistical analyses were performed using 3-way ANOVA followed by Duncan's test (p < 0.05). Additional teeth were prepared to observe the interaction between the dentin smear layer obtained from each bur with adhesives under different application modes using transmission electron microscopy (TEM).

RESULTS

Active application significantly increased the dentin bond strength of SE2, irrespective of the kind of bur used (p < 0.05). The highest bond strength of SBU was observed when bonded to superfine-grit diamond bur-cut dentin with the active application. There was, however, no influence of the tested factors on GPB group (p > 0.05). TEM observation showed that active application promoted dentin smear layer dissolution in all adhesive groups.

CONCLUSIONS

Bond strengths of self-etching adhesives to dentin are influenced by bur-cut smear layers and mainly by application mode of adhesive materials. Active application improves µTBS of self-etching adhesives by enhancing smear layer modification and resin penetration into bur-cut dentin.

Effect of Silane-Containing Universal Adhesives on the Bonding Strength of Lithium Disilicate

The purpose of this study was to investigate the effect of silane-containing universal adhesives on the bonding strength of lithium disilicate. Two-hundred-and-forty lithium disilicate blocks were divided into 16 groups according to the following surface treatments: hydrofluoric acid (HF)-treated or not, silane-treated or not, and the type of universal adhesive used (All-Bond Universal (ABU); Prime & bond (PB); Clearfil Universal Bond (CU); Single bond Universal (SBU)). After surface treatment, resin discs were bonded to each lithium disilicate using dual-cure resin cement. Bonded specimens were stored in distilled water for 24 h and then subjected to microtensile bond strength (μTBS) test. Failure modes were examined under stereomicroscope. Microscopic observation of bonded interfaces was analyzed using scanning electron microscopy. The μTBS data were statistically analyzed. Regardless of silane treatment, all groups treated with HF showed higher bonding strengths compared to those that were not treated with HF (p < 0.05). In groups treated with HF, the bonding strength increased after silane application (p < 0.05) except PB and CU (p > 0.05). Adhesive failures were dominant in all groups, but some mixed failures were observed in ABU treated with HF and silane. While most of the specimens that were not treated with silane after HF application only showed loose bonding between the ceramic and resin cement due to partial gaps, the specimens treated with silane application after HF showed a tight ceramic–resin interface. In conclusion, the silane in universal adhesives did not effectively improve the bonding strength between lithium disilicate and resin cement.

Self-etch Approach of Universal Adhesives as an Alternative to Minimize Bond Degradation on Sound Dentin vs Caries-affected Dentin over Time

PURPOSE

To investigate the influence of the etching strategy of universal adhesives on bond degradation to sound and artificially-induced caries-affected dentin.

MATERIALS AND METHODS

The universal adhesives (Scotchbond Universal Adhesive; All-Bond Universal; Prime&Bond Elect) and adhesives used as controls (Adper Single Bond 2 and Clearfil SE Bond) were applied to sound and artificially-induced caries-affected bovine dentin. Microtensile bond strength was evaluated immediately (24 h) and after one year of water storage (1 year). Representative specimens were also prepared to assess nanoleakage. Bond strength data (MPa) were analyzed using three-way ANOVA and post-hoc Tukey's test (α = 0.05), considering each substrate separately.

RESULTS

Bonding degradation was observed for all universal adhesives on caries-affected dentin, irrespective of the etching strategy. On sound dentin, bonding degradation was observed when adhesives were used on the etch-and-rinse strategy.

CONCLUSION

The universal adhesives were not capable of maintaining bond stability over time on caries-affected dentin. The self-etch strategy seems better able to maintain the durability of adhesive interfaces created on sound dentin.

Effect of chemical cross-linkers on surface topography and microtensile bond strength of sound dentin: An in vitro study

AIM AND OBJECTIVES

The aim of the study was to investigate the effect of two different collagen cross-linking agents proanthocyanidin (Grape seed extract [GSE] and 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide) on the surface topography of etched dentin and microtensile bond strength (μTBS) of resin dentin bond.

MATERIALS AND METHODS

Fifty-two sound human 3rd molars were collected, and their occlusal surfaces were ground flat to expose dentin. Dentin surfaces were etched using phosphoric acid and then teeth were randomly divided into four groups, according to the dentin treatment: Group 1: wet bonding technique, Group 2: dry bonding technique, Group 3: 6.5% proanthocyanidin, and Group 4: 0.1M carbodiimide. Scanning electron microscope analysis was done for twenty specimens (n = 5 per group) at ×10,000 and ×30,000 magnification. Remaining 32 specimens were restored with TETRIC N-Bond adhesive systems and resin composite. After 24 h, teeth were sectioned to produce a cross-sectional surface area of 1.0 mm2 and tested for μTBS.

STATISTICAL ANALYSIS

Data were statistically analyzed using ANOVA and post hoc least significant difference test (P < 0.05).

CONCLUSION

When acid-etched dentin is treated by 6.5% proanthocyanidin (GSE) and 0.1M carbodiimide, followed by application of adhesives, it results in increased μTBS due to cross-linking of collagen fibrils.

Effects of Dentine Pretreatment Solutions Containing Flavonoids on the Resin Polymer-Dentine Interface Created Using a Modern Universal Adhesive

The aim of the present study was to evaluate the influence of several experimental pretreatment crosslinker solutions on the resin polymer–dentine interface created using a representative universal adhesive system, by means of microtensile bond strength testing (μTBS), nanomechanical properties and ultramorphology confocal laser scanning microscopy (CLSM). Five experimental solutions containing different flavonoids were applied as dentine pretreatment after acid etching. A control pretreatment group containing no flavonoid was also employed. A representative modern universal adhesive was then applied, followed by a 3 mm thick composite built up. Specimens were sectioned into sticks and submitted to a μTBS test or nanoindentation analysis along the interface (24 h or 25,000 thermocycles). The ultramorphology of the polymer–resin interface was also evaluated using CLSM. The results were analyzed using two-way ANOVA and Bonferroni’s post hoc test (α = 0.05). All flavonoids improved short- and long-term μTBS values (p < 0.01), while only some specific such solutions improved the nanomechanical properties (p < 0.05) and preserved the structural morphology of the interface after aging. Pretreatment of acid-etched dentine using specific flavonoid-containing solutions may be a promising approach to improve both the nanomechanical properties and the durability of modern universal adhesive systems.

Effect of Varying Working Distances between Sandblasting Device and Composite Substrate Surface on the Repair Bond Strength

This study investigates the effect of defined working distances between the tip of a sandblasting device and a resin composite surface on the composite–composite repair bond strength. Resin composite specimens (Ceram.x Spectra ST (HV); Dentsply Sirona, Konstanz, Germany) were aged by thermal cycling (5000 cycles, 5–55 °C) and one week of water storage. Mechanical surface conditioning of the substrate surfaces was performed by sandblasting with aluminum oxide particles (50 µm, 3 bar, 10 s) from varying working distances of 1, 5, 10, and 15 mm. Specimens were then silanized and restored by application of an adhesive system and repair composite material (Ceram.x Spectra ST (HV)). In the negative control group, no mechanical surface pretreatment or silanization was performed. Directly applied inherent increments served as the positive control group (n = 8). After thermal cycling of all groups, microtensile repair bond strength was assessed, and surfaces were additionally characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The negative control group reached the significantly lowest microtensile bond strength of all groups. No significant differences in repair bond strength were observed within the groups with varying sandblasting distances. Composite surfaces sandblasted from a distance of 1 mm or 5 mm showed no difference in repair bond strength compared to the positive control group, whereas distances of 10 or 15 mm revealed significantly higher repair bond strengths than the inherent incremental bond strength (positive control group). In conclusion, all sandblasted test groups achieved similar or higher repair bond strength than the inherent incremental bond strength, indicating that irrespective of the employed working distance between the sandblasting device and the composite substrate surface, repair restorations can be successfully performed.

Characterization of an Experimental Two-Step Self-Etch Adhesive's Bonding Performance and Resin-Dentin Interfacial Properties

This study evaluated an experimental two-step self-etch adhesive (BZF-29, BZF) by comparing it with a reference two-step self-etch adhesive (Clearfil Megabond 2, MB) and a universal adhesive (G-Premio Bond, GP) for microtensile bond strength (μTBS) and resin-dentin interfacial characteristics. Twenty-four human third molars were used for the μTBS test. Bonded peripheral dentin slices were separated to observe the resin-dentin interface and measure the adhesive layer thickness with SEM. μTBS data of the central beams were obtained after 24 h and 6 months of water storage. Fracture modes were determined using a stereomicroscope and SEM. Nine additional third molars were used to determine the elastic modulus (E) employing an ultra microhardness tester. Water storage did not affect μTBS of the tested adhesives (p > 0.05). μTBS of BZF and MB were similar but significantly higher than GP (p < 0.05). BZF achieved the highest adhesive layer thickness, while GP the lowest. E of BZF and MB were comparable but significantly lower than GP (p < 0.05). Except for GP, the predominant fracture mode was nonadhesive. The superior bonding performance of BZF and MB could be attributed to their better mechanical property and increased adhesive thickness imparting better stress relief at the interface.

The effect of different surface preparation methods and various aging periods on microtensile bond strength for composite resin repair

Aims

To evaluate the effect of various aging periods and different surface preparation methods on microtensile bond strength (μTBS) for composite repair.

Materials and Methods

One hundred twelve composite resin blocks were formed using a nanohybrid composite resin. The samples were distributed into four groups according to surface preparation methods (n = 28): control (sound composite blocks); Er, Cr: YSGG laser; air abrasion; silicone carbide. All samples were then divided into four subgroups according to various aging periods: (i) No aging, (ii) 10,000 thermocycling, (iii) 30,000 thermocycling, and (iv) 50,000 thermocycling. Following surface preparation and aging procedures, surface topography of one sample from each group was evaluated under scanning electron microscope (SEM). The repair composites were bonded to the sample surfaces, using a three-step etch&rinse adhesive. Finally, thirty beams of size 1 × 1 × 8 mm from each group were subjected to μTBS test and failure modes were determined. The data were analyzed using two-way ANOVA, Post-hoc Bonferroni, and Chi-square tests (P = 0.05).

Results

When different surface preparation methods were evaluated together, no aging and 10,000 thermocycling groups displayed higher μTBS values (P < 0.05). When all aging periods were evaluated together, the surface preparation with air abrasion provided higher μTBS (P < 0.05). The interactions of various aging periods with different surface preparation methods revealed significant variations in repair μTBS (P < 0.05). There were statistically significant differences on failure mode distributions among surface preparation methods (P < 0.001). SEM evaluations provided valuable outcomes that help to comment on the μTBS findings.

Conclusions

Different surface preparation methods, various aging periods, and the interaction of both affected the repair μTBS of the tested nanohybrid composite resin.

Significance of immediate dentin sealing and flowable resin coating reinforcement for unfilled/lightly filled adhesive systems

BACKGROUND

Immediate dentin sealing implies applying an adhesive system to dentin directly after tooth preparation, before impression. The technique is universal (inlays, onlays, veneers, crowns) and well documented clinically and experimentally. Different types of dentin bonding agents (DBAs) are available on the market. Major differences lie in the thickness of the hybrid layer and overlaying adhesive resin (filled vs. unfilled/lightly filled adhesives).

OBJECTIVE

The objective of this work is to provide precise clinical instructions and present new experimental data about the bond strength of five DBAs (Optibond FL, Scotchbond MP, Single Bond Plus, Clearfil SE Bond, and Scotchbond Universal) used conventionally (dentin sealed at the time of restoration delivery) or with immediate dentin sealing, as well as with an additional flowable resin coating.

METHODS

Seventy-five human molars were selected, restored/tested according the microtensile bond strength method. Fifteen groups (n=5) were obtained from the combination of the five DBAs and three application modes: delayed dentin sealing, immediate dentin sealing and immediate dentin sealing with flowable resin coating.

RESULTS

It appears that immediate dentin sealing was confirmed to significantly improve the bond strength of all tested adhesives. The use of a flowable resin coating reinforcement after immediate dentin sealing increased the microtensile bond strength of all unfilled/lightly filled adhesives (from 233% of increase for ScotchBond MP, up to 560% for Clearfil SE Bond) and maintained the performance of the 3-step golden standard adhesive. Optibond FL used with (52.51 MPa) or without (54.75 MPa) additional flowable resin coating and Clearfil SE Bond (45.64 MPa) used with flowable resin coating provided the best results.

CLINICAL SIGNIFICANCE

The original immediate dentin sealing (IDS) technique implies the use of a filled DBA. With unfilled/lightly filled adhesives, it is suggested to reinforce IDS with an additional flowable resin coating. This seems especially paramount to the performance of simplified adhesive systems to protect the thin bonding interface from oxygen inhibition and preserve IDS layer during predelivery cleaning of the preparation. The clinical reinforcement of unfilled/lightly filled IDS with flowable resin composite is encouraged for more predictable bonding.

Dentin Bond Integrity of Hydroxyapatite Containing Resin Adhesive Enhanced with Graphene Oxide Nano-Particles-An SEM, EDX, Micro-Raman, and Microtensile Bond Strength Study

The aim was to synthesize and characterize an adhesive incorporating HA and GO nanoparticles. Techniques including scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), micro-tensile bond strength (μTBS), and micro-Raman spectroscopy were employed to investigate bond durability, presence of nanoparticles inside adhesive, and dentin interaction. Control experimental adhesive (CEA) was synthesized with 5 wt% HA. GO particles were fabricated and added to CEA at 0.5 wt% (HA-GO-0.5%) and 2 wt% GO (HA-GO-2%). Teeth were prepared to produce bonded specimens using the three adhesive bonding agents for assessment of μTBS, with and without thermocycling (TC). The adhesives were applied twice on the dentin with a micro-brush followed by air thinning and photo-polymerization. The HA and GO nanoparticles demonstrated uniform dispersion inside adhesive. Resin tags with varying depths were observed on SEM micrographs. The EDX mapping revealed the presence of carbon (C), calcium (Ca), and phosphorus (P) in the two GO adhesives. For both TC and NTC samples, HA-GO-2% had higher μTBS and durability, followed by HA-GO-0.5%. The representative micro-Raman spectra demonstrated D and G bands for nano-GO particles containing adhesives. HA-GO-2% group demonstrated uniform diffusion in adhesive, higher μTBS, adequate durability, and comparable resin tag development to controls.

Influence of Hydroxyapatite Nanospheres in Dentin Adhesive on the Dentin Bond Integrity and Degree of Conversion: A Scanning Electron Microscopy (SEM), Raman, Fourier Transform-Infrared (FTIR), and Microtensile Study

An experimental adhesive incorporated with different nano-hydroxyapatite (n-HA) particle concentrations was synthesized and analyzed for dentin interaction, micro-tensile bond strength (μTBS), and degree of conversion (DC). n-HA powder (5 wt % and 10 wt %) were added in adhesive to yield three groups; gp-1: control experimental adhesive (CEA, 0 wt % HA), gp-2: 5 wt % n-HA (HAA-5%), and gp-3: 10 wt % n-HA (HAA-10%). The morphology of n-HA spheres was evaluated using Scanning Electron Microscopy (SEM). Their interaction in the adhesives was identified with SEM, Energy-Dispersive X-ray (EDX), and Micro-Raman spectroscopy. Teeth were sectioned, divided in study groups, and assessed for μTBS and failure mode. Employing Fourier Transform-Infrared (FTIR) spectroscopy, the DC of the adhesives was assessed. EDX mapping revealed the occurrence of oxygen, calcium, and phosphorus in the HAA-5% and HAA-10% groups. HAA-5% had the greatest μTBS values followed by HAA-10%. The presence of apatite was shown by FTIR spectra and Micro-Raman demonstrated phosphate and carbonate groups for n-HA spheres. The highest DC was observed for the CEA group followed by HAA-5%. n-HA spheres exhibited dentin interaction and formed a hybrid layer with resin tags. HAA-5% demonstrated superior μTBS compared with HAA-10% and control adhesive. The DC for HAA-5% was comparable to control adhesive.

Repair bond strength and surface topography of resin-ceramic and ceramic restorative blocks treated by laser and conventional surface treatments

This study intended to compare the repair bond strength of computer-aided design/computer-aided manufacturing (CAD/CAM) blocks consisting of resin and feldspathic ceramics following different surface treatments using the microtensile bond strength (μTBS) test. Ten specimens were prepared with 4 mm height for Vita Enamic (VE), Lava Ultimate (LU), Vita Mark II (VM), and thermocycled (10,000 cycle, 5-55°C). Each material was categorized into one of five subgroups according to following surface treatments: (a) bur grinding (BG), (b) hydrofluoric acid etching (HF), (c) neodymium-doped yttrium aluminum garnet (Nd:YAG or NY), (d) erbium-doped yttrium aluminum garnet (Er:YAG or EY), and (e) erbium, chromium-doped yttrium, scandium, gallium, and garnet (Er,Cr:YSGG or ECY) laser conditioning. After surface treatment procedures, specimens were properly restored to 4 mm high with a micro-hybrid composite resin. Bar specimens (1 × 1 × 8 mm) were obtained using a low-speed cutting machine and then thermocycled (10,000 cycle, 5-55°C). The μTBS was tested at 1 mm/min crosshead speed, and failure modes were evaluated. Data were analyzed with two-way ANOVA and post hoc Tukey tests. LU-BG showed significantly higher μTBS (32.94 ± 5.80 MPa) compared to LU-laser groups (p < .05). VE-BG showed significantly higher μTBS (22.06 ± 4.26 MPa) compared to other VE groups (p < .05). Among the laser groups, the NY laser produced the lowest (p < .05) μTBS for LU (13.42 ± 3.44 MPa) and VE (2.27 ± 0.85 MPa), while EY showed the highest (p < .05). Laser-treated VM groups were all prefailured. VM-HF produced a higher μTBS (18.73 ± 3.75 MPa) than VM-BG (5.05 ± 1.76 MPa) (p < .05).

Evaluation of the effect of natural versus synthetic matrix metalloproteinase silencers in preservation of dentin collagen and long-term bond strength of total etch adhesive

Aim

This study investigated the effect of various synthetic (galardin [Gal] and benzalkonium chloride [BAC]) and natural agents (hesperidin [HES] and epigallocatechin gallate) on the stability of dentin collagen matrix to resist collagenase degradation and improve long-term microtensile bond strength.

Materials and Methods

Ten sound-impacted third molars were collected and manual removal of pulp, periodontal ligament, cementum, and enamel was done. Remaining dentin fragments were pulverized under liquid nitrogen to obtain dentin powder. 2 mg aliquot of dentin powder was allocated to each of the test solutions and subjected to hydroxyproline assay. Another 60 sound human third molars were collected and occlusal enamel was ground flat to reach dentinoenamel junction. Class I cavities were prepared in dentin, followed by etching using 37% phosphoric acid for 15 s. Samples were then subjected to surface treatment with different agents for 60 s, followed by application of Optibond S and restoration with P 60 composite resin. Samples of all groups except control were subject to thermocycling. Samples were sectioned to 1 mm thick slabs which were subject to universal testing machine to determine ultimate tensile strength. One-way analysis of variance and Bonferroni post hoc test with a significance level of P < 0.05 were used to analyze data.

Results

HES resulted in maximum resistance to collagen degradation, followed by epigallocatechin gallate (EGCG), Gal, and BAC with a significant difference among the groups. Samples of Gal group showed the highest microtensile bond strength values, followed by HES, EGCG, BAC with a significant difference between the groups except HES and EGCG where the difference was nonsignificant.

Conclusion

The use of matrix metalloproteinase silencers could improve the mechanical properties of collagen and resist enzymatic degradation, leading to an improved long-term intimate restoration.

Effect of Over-Etching and Prolonged Application Time of a Universal Adhesive on Dentin Bond Strength

This study investigated the effect of over-etching and prolonged application time of a universal adhesive on dentin bond strength. Ninety extracted human molars were ground to dentin and randomly allocated into nine groups (G1-9; n = 10 per group), according to the following acid etching and adhesive application times. In the control group (G1), phosphoric acid etching was performed for 15 s followed by application of the universal adhesive Scotchbond Universal (3M) for 20 s, as per manufacturer's instructions. In groups G2-5, both the etching and adhesive application times were either halved, doubled, quadrupled, or increased eightfold. In groups G6-9, etching times remained the same as in G2-5 (7.5 s, 30 s, 60 s, and 120 s, respectively), but the adhesive application time was set at 20 s as in the control group (G1). Specimens were then restored with a nanofilled composite material and subjected to microtensile bond strength testing. Bond strength data were statistically analyzed by ANOVA and Tukey's post-hoc tests (α = 0.05). The relationship of bond strength with etching and adhesive application time was examined using linear regression analysis. Treatment of dentin with halved phosphoric acid etching and adhesive application times (G2) resulted in a significant bond strength decrease compared to the control group (G1) and all other test groups, including the group with halved acid etching, but 20 s of adhesive application time (G6). No significant differences in bond strength were found for groups with multiplied etching times and an adhesive application time of 20 s or more, when compared to the control group (G1). In conclusion, a universal adhesive application time of at least 20 s is recommended when bonding to over-etched dentin.

Bonding Performance of a Hydrophilic Amide Monomer Containing Adhesive to Occlusal and Cervical Dentin

This study aimed to evaluate the bonding performance of a new one-step self-etching adhesive system containing a novel hydrophilic amide monomer. Clearfil Universal Bond Quick (CUB) and Clearfil Megabond 2 (CMB) were used as the one-step and two-step adhesive systems, respectively. Flat dentin surfaces of human premolars were exposed using #600 SiC (silicon carbide) and bonded with the respective adhesives of each system. The teeth were sectioned to obtain beams (1 mm × 1 mm) after 24 h of water storage. The mean bond strength and standard deviations (MPa) on an occlusal surface were as follows: CUB: 45.9 ± 19.7 and CMB: 67.9 ± 25.3. The values for cervical ones were CUB: 56.0 ± 20.3 and CMB: 67.6 ± 16.0, respectively. In both conditions, the microtensile bond strength (μTBS) value was lower than that of CMB. As seen during the microscopic observation, no adhesive failure was observed after μTBS testing because CUB formed a firm and tight adhesive interface.

Effect of matrix metalloproteinase inhibitors on microtensile bond strength of dental composite restorations to dentin in use of an etch-and-rinse adhesive system

Aim

This study assesses the effect of matrix metalloproteinases on microtensile bond strength (μTBS) of an etch‐and‐rinse adhesive system.

Methods

This in vitro study evaluated 88 extracted premolars. The teeth were sectioned to expose dentin and were then randomly divided into four groups (n = 22). In group 1 (control), dentin surface was etched, and Adper Single Bond 2 was applied. In groups 2–4, dentin surface was etched and chlorhexidine (CHX), 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide (EDC), and dimethyl sulfoxide (DMSO) were applied on the surfaces, respectively, and blotted dry. Next, Adper Single Bond 2 was applied and all teeth were built up with Z350 composite. In each group, half the samples immediately and the other half after 10,000 thermal cycles underwent μTBS test. Data were analyzed using ANOVA and Tukey's test (α = .05).

Results

In thermocycled samples, maximum μTBS was noted in CHX group followed by DMSO, EDC, and control group (p < .001). The thermocycled μTBS of composite to dentin was significantly higher in CHX group compared with EDC, DMSO, and control groups (p < .001) but was not significantly different in EDC and DMSO groups (p = .498).

Conclusion

The thermocycled μTBS obtained by the application of CHX, EDC, and DMSO was significantly higher compared with the value to the control group.