Post-curing conversion kinetics as functions of the irradiation time and increment thickness

Abstract

Objective:This study evaluated the variation of conversion degree (DC) in the 12 hours following initial photoactivation of a low-shrinkage composite resin (Venus Diamond).Material and Methods:The conversion degree was monitored for 12 hours using Attenuated Total Reflection (ATR) F-TIR Spectroscopy. The composite was placed in 1 or 2 mm rings and cured for 10 or 20 seconds with a LED lamp. ATR spectra were acquired from the bottom surface of each sample immediately after the initial photoactivation (P=0), 30 minutes (P=0.5) and 12 hours after photoactivation (P=12) in order to obtain the DC progression during the post-curing period. Interactions between thickness (T), irradiation time (I) and post-curing (P) on the DC were calculated through ANOVA testing.Results:All the first order interactions were statistically significant, with the exception of the T-P interaction. Furthermore, the shift from P=0 to P=0.5 had a statistically higher influence than the shift from P=0.5 to P=12. The post-curing period played a fundamental role in reaching higher DC values with the low-shrinkage composite resin tested in this study. Moreover, both the irradiation time and the composite thickness strongly influenced the DC.Conclusions:Increased irradiation time may be useful in obtaining a high conversion degree (DC) with a low-shrinkage nano-hybrid composite resin, particularly with 2 mm composite layers.

Evaluation of Microhardness and Microleakage of Class II Silorane-Based Composite Restorations Post-Photoactivation Silorane-Based Composite Restorations Post-Photoactivation Techniques Technique

“…15 In an earlier study, Nicola et al concluded that an increased irradiation time produced higher DC at the bottom surface of the restorations. 16 In addition, Gritsch et al explained that a longer exposure time with lower intensities improved the polymerization of the composite in depth. The authors found that this was caused by a delay in the rigid network formation.…”

Bonding system choice and practices among senior dental students

“…In addition, suboptimal polymerization of resin composites may promote bacterial colonization at its surface. [ 30 31 32 33 ]…”

The effect of UDMA and Bis-GMA irradiation period on residual monomers in resin packable composite

“…4 For process efficiency and maximum restoration results, more beam-activated composite resins are employed. 5 Currently, quartz tungsten-halogens (QTH) and lightemitting diodes (LED) constitute the light sources most frequently used for hardening composite resin as the photon suppliers which activate photon-initiators. Composite polymerization is initiated by exposure to light produced by a light curing unit (LCU).…”

“…8 The DC constitutes an important parameter in determining the final properties of active composite resin irradiation including: physical, mechanical and biological properties the light wavelength and depth employed, ray tip size, photo activation method, distribution, number of inorganic fillers, composite resin color, and the exposure period which is directly affected by an increase in the irradiation period. 5 A low degree of conversion causes decreasing resin properties and the number of non-reactive (trapped or free) residual monomers. One strategy to maximize DC and minimize monomer elution as a means of providing sufficient energy to the material is that of prolonging the hardening time.…”