Microshear Bond Strength of Different Adhesive Systems to Dentin

The effect of dentin surface pretreatment using dimethyl sulfoxide on the bond strength of a universal bonding agent to dentin

BACKGROUND

This study aimed to evaluate the effect of dentin pretreatment by Dimethyl Sulfoxide (DMSO) on the bond strength and microleakage of a universal bonding agent to dentin.

METHODS

Fifty-six dentinal discs (thickness = 2 mm) were obtained from the crowns of the human third molars. The disks were assigned into 4 groups and treated as follows; self-etch-control group: G-Premio universal adhesive was used in self-etch mode, total-etch-control: G-Premio universal adhesive was used in total-etch mode, self-etch-DMSO: Water-based DMSO (50% volume) was applied on the samples for 60 s followed by application of G-Premio universal adhesive in self-etch mode, and Total-etch-DMSO: The samples were etched, and then, water-based DMSO was applied on them for 60 s followed by the application of G-Premio universal adhesive in total-etch mode. Afterward, resin composite was placed on all samples and light-cured. The samples were kept in distilled water and subjected to 5000 thermal cycles. Microshear bond strength was measured using the universal testing machine and failure modes were analyzed using a stereomicroscope. Forty-eight human third molars were used for microleakage evaluation and a standardized class five cavity was prepared on the buccal surface of each tooth. The teeth were assigned into 4 groups and received aforementioned surface treatment and the cavities were filled with resin composite. After storing in water for 24 h, the samples were subjected to 5000 cycles of thermocycling and the microleakage level of the samples was evaluated using silver nitrate uptake at the bonded interface. Two-way ANOVA test was used to analyze the effect of bonding technique (self-etch/ total-etch) and DMSO pretreatment on the microshear bond strength and microleakage of G-Premio adhesive to dentin.

RESULTS

Bonding technique had no effect on the bond strength values (p = 0.17) while DMSO pretreatment significantly decreased the microshear bond strength of the samples (p = 0.001). DMSO application increased microleakage significantly in total-etch (P-value = 0.02) while it had no effect in self-etch mode (P-value = 0.44).

CONCLUSIONS

Pretreatment of dentin using 50% DMSO significantly reduced the bond strength of G-Premio Bond in both self-etch and total-etch modes. DMSO effect on microleakage depended on the etching technique; DMSO increased the microleakage level when the adhesive was used in total-etch mode while did not affect the microleakage in self-etch mode.

[Evaluation of the adhesive resistance of a composite resin to dentin treated with chlorhexidine and photodynamic therapy. in vitro study]

Introduction

Photodynamic therapy consists of the application of a light with an adequate wavelength on the cavities prior to the application of a photosensitizing agent, with the purpose of eliminating remnants of microorganisms remaining after instrumentation.

Objective

Evaluate the adhesive resistance to dentin treated with 2% chlorhexidine and photodynamic therapy with a 660nm diode prior to the insertion of composite resin.

Materials an Methods

In this in vitro experimental study, 60 bovine mandibular incisors were collected, After dentin wear, the samples were divided into 3 groups, with 20 samples per group: control group (no therapy was applied), 2% chlorhexidine, and 660nm diode laser (photosensitizer: methylene blue). Adhesive strength test was measured by shear test compared to kruskall-wallis test and post-hoc pairwise comparison.

Results

The average values from highest to lowest result with the CHX (14.82 ± 3.14), followed by the 660nm diode laser (14.77 ± 4.02) and the control group (9.25 ± 1.16). Similar groups of 660 nm diode laser and 2% CHX changed values (P>0.05), but significantly higher than the control group (P<0.001). Conclusion: Photodynamic therapy increased adhesive resistance as well as chlorhexidine, both therapies presented an increase in adhesive resistance compared to the control group.

Micro-shear bond strength of composite to deep dentin by using mild and ultra-mild universal adhesives

Background

Considering the increasing demand for tooth-colored restorations, this study sought to assess the micro-shear bond strength (μSBS) of composite to deep dentin by using mild and ultra-mild universal adhesives.

Materials and Methods

This in vitro, experimental study evaluated 75 sound third molar teeth randomized into five groups (n = 15) of Clearfil self-etch (SE) Bond (control), Tokuyama Universal Bond (TUB), and All-Bond Universal (ABU) in etch and rinse (E and R) and SE modes. The occlusal surfaces of the teeth were trimmed to expose deep dentin at 0.5 mm distance from the pulp chamber. Adhesives were applied on the dentin surface according to the manufacturers' instructions, and Z350XT composite cylinders were bonded to dentin using Tygon tubes (0.9 mm internal diameter, 2 mm height). After incubation at 37°C and 100% humidity for 24 h, the teeth underwent μSBS test in a universal testing machine. The mode of failure was also determined under a stereomicroscope. Analysis of variance, Bonferroni test, and Fisher's exact test were applied for data analysis (alpha = 0.05).

Results

TUB in E and R mode (13.78 MPa) and ABU in SE mode (7.85 MPa) yielded the maximum and minimum μSBS values, respectively. No significant difference was noted in μSBS of tested universal adhesives in E and R and SE modes to deep dentin (P > 0.05). TUB yielded significantly higher μSBS than ABU (P < 0.05). No significant difference was noted in mode of failure of the groups (P > 0.05).

Conclusion

Type of adhesive affected the μSBS but etching mode of universal adhesives had no significant effect on their μSBS to deep dentin.