Clinical Performance of Filled/Nanofilled Versus Nonfilled Adhesive Systems in Noncarious Cervical Lesions: A Systematic Review and Meta-analysis

Influence of Irradiance and Exposure Times on the Mechanical and Adhesive Properties of Universal Adhesives with Dentin

OBJECTIVES

This study evaluated the influence of irradiance/exposure time on the Knoop hardness (KHN) and polymer cross-linking density (PCLD), as well as microtensile bond strength (μTBS), nanoleakage (NL), and in situ degree of conversion (DC) of universal adhesives.

METHODS AND MATERIALS

Two universal adhesive systems, Clearfil Universal Bond Quick (CUQ) and Scotchbond Universal Adhesive (SBU), were light-cured using various irradiance/exposure times: 1400 mW/cm2 for 5 s (1400*5); 1400 mW/cm2 for 10 s (1400*10); 3200 mW/cm2 for 5 s (3200*5); and 3200 mW/cm2 for 10 s (3200*10). Adhesive disks from each group were used to measure PCLD by KHN. One hundred and twenty-eight human molars were randomly assigned to 16 groups according to the following variables: adhesive system vs adhesive strategies vs radiance/exposure times. After restoration, specimens were sectioned into resin-dentin sticks and tested for μTBS, NL, and DC. The data from PCLD (%), KHN, μTBS (MPa), NL (%), and DC (%) data were subjected to ANOVA and Tukey's test (α=0.05).

RESULTS

Significant reductions in KHN, μTBS, and DC (p=0.00001) values and an increase in NL and PCLD (p=0.00001) values were observed for 3200*10 when compared with other groups. Higher KHN, μTBS, and DC (p=0.000001) values were observed for 3200*5 in comparison with the other groups. The 1400*5 (7 J/cm2) and 1400*10 (14 J/cm2) groups showed intermediate values (p=0.000001).

CONCLUSION

Although similar results in terms of hardness, polymer cross-linking density and nanoleakage were observed when 5 seconds at 3200 mW/cm2 and 10 seconds at 1400 mW/cm2 groups were compared, the use of higher irradiance (3200 mW/cm2) for only 5 seconds showed better results in terms of bond strength and degree of conversion for both universal adhesives to dentin. The prolonged exposure time (10 seconds) at the higher irradiance (3200 mW/cm2) showed the worst results.

Nanofiller Particles and Bonding Durability, Water Sorption, and Solubility of Universal Adhesives

The aim of this study was to evaluate the influence of nanofiller particles in simplified universal adhesive on the long-term microtensile bond strength and silver nitrate up-take, as well as water sorption and solubility. Commercial adhesives Ambar Universal (FGM) in nanofilled-containing version (filled) and same lot without fillers (unfilled) were donated and applied by means of etch-and-rinse strategy. Microtensile bond strength was surveyed after 24-hours or 1-year water storage. Silver nitrate uptake was assayed using scanning electron microscopy (SEM). Water sorption and solubility experiments were performed based on ISO 4049:2009. Statistical analysis was performed using two-way ANOVA and Tukey test (p<0.05). The bond strength of both the adhesives were statistically similar at 24 hours (p>0.05), but the filled group attained significant bond strength reduction after aging when compared to initial bond strength (p<0.001). Conversely, unfilled adhesive presented stable adhesion after 1-year storage (p=0.262). Silver nitrate uptake was similar for both adhesives, with little silver impregnation at the hybrid and adhesive layers. Water sorption was higher with filled adhesive compared to the unfilled one (p=0.01). Conversely, solubility was higher in unfilled in comparison to filled one (p=0.008). The presence of nanofillers in universal adhesive achieves higher water sorption and dentin bond degradation, which did not occur in the unfilled adhesive.