Influence of Curing Rate of Resin Composite on the Bond Strength to Dentin

Abstract

SUMMARYThis study determined whether the strength with which resin composite bonds to dentin is influenced by variations in the curing rate of resin composites. Resin composites were bonded to the dentin of extracted human molars. Adhesive (AdheSE, Ivoclar Vivadent) was applied and cured (10 seconds @ 1000 mW/cm 2 ) for all groups. A split Teflon mold was clamped to the treated dentin surface and filled with resin composite. The rate of cure was varied, using one of four LED-curing units of different power densities. The rate of cure was also varied using the continuous or pulse-delay mode. In continuous curing mode, in order to give an energy density totaling 16 J/cm 2 , the power densities (1000, 720, 550, 200 mW/cm 2 ) emitted by the various curing units were compensated for by the light curing period (16, 22, 29 or 80 seconds). In the pulsedelay curing mode, two seconds of light curing at one of the four power densities was followed by a one-minute interval, after which light cure was completed (14, 29, 27 or 78 seconds), likewise, giving a total energy density of 16 J/cm 2 . The specimens produced for each of the eight curing protocols and two resin composites (Tetric EvoCeram, Ivoclar Vivadent; Filtek Supreme XT, 3M ESPE) were stored in water at 37°C for seven days. The specimens were then either immediately subjected to shear bond strength testing or subjected to artificial aging (6,000 cycles between 5°C and 55°C baths) prior to testing. Failure modes were also assessed. The shear bond strengths were submitted to factorial analysis of variance, and the failure modes were submitted to a Chi-square test (α=0.05). All but power densi- When deciding on a specific curing protocol, dental professionals should be aware of the advantages and limitations of each curing mode.

Effect of Light Energy Density on Conversion Degree and Hardness of Dual-cured Resin Cement

“…20 Rapid polymerization may also result in the formation of high cross-linked short polymer chains. 21 The results of the current study show that all light energy densities achieve high CD and KHN values. Additionally, the light curing unit tip was directly in contact with the resin cement.…”

Influence of light intensity on surface-free energy and dentin bond strength of single-step self-etch adhesives

“…When the distance between the curing light tip and cavity wall increases, light intensity reaching the adhesive surface decreases 9) . It has been demonstrated that reduced light intensity causes lower bond strengths between self-etch adhesives and dentin 10) . In addition, after the light irradiation of adhesives at a reduced light intensity, the top surface of the adhesive is covered with a relatively thick, uncured adhesive layer due to the oxygen inhibition 11) .…”

Effect of light intensity for adhesives on shear bond strength to dentin

“…It is noteworthy that in light-cured resin composites, the photoinitiator used requires a certain amount of light energy to produce a certain number of free radicals 15) . To overcome this problem, an extension of irradiation time or use of high-light-intensity curing units might be effective in increasing the degree of polymerization of adhesive resins 11) . However, an extension of irradiation time is tantamount to prolonged operation time, and that irradiation with high light intensity elevates the temperature during adhesive polymerization 16,17) .…”

“…Our previous study suggested that airblowing suitable for self-etching one-step (all-in-one adhesive) systems depended upon the type of solvent contained in the system 8) . Further on factors that influence bond strength, there are several studies which reported on the effect of light intensity for filled resin composites on their bond strengths to tooth substrates [9][10][11] . Benetti et al 11) investigated the influence of variations in the curing rate of resin composites on the bond strength of resin composites to dentin, and concluded that only power density -but not curing mode, resin composite material, nor mode of aging -significantly affected shear bond strength.…”

“…Further on factors that influence bond strength, there are several studies which reported on the effect of light intensity for filled resin composites on their bond strengths to tooth substrates [9][10][11] . Benetti et al 11) investigated the influence of variations in the curing rate of resin composites on the bond strength of resin composites to dentin, and concluded that only power density -but not curing mode, resin composite material, nor mode of aging -significantly affected shear bond strength. There are also several studies which reported on the effect of light curing of the bonding agents prior to the placement of resin composites on the shear bond strength to tooth substrates 12,13) .…”