Kinetic analysis of monomer conversion in auto- and dual-polymerizing modes of commercial resin luting cements.
BACKGROUND
Lack of knowledge regarding the kinetics of the setting reaction of dual- and autopolymerizing resin luting agents (RLA) leads the clinician to underestimate the care required during occlusal adjustments of indirect restorations.


OBJECTIVE
The purpose of this study was to evaluate the degree of conversion (DC), maximum rate of polymerization (R(p)(max)), and potential of cure (ratio of conversions in autopolymerized relative to dual-polymerized modes; PC(A/D)) of 5 dual-polymerizable RLAs at 5 and 10 minutes, after mixing RLA components using infrared (IR) spectroscopy.


METHODS
The RLAs evaluated included Calibra, Duo-Link, Lute-It, Nexus 2, and RelyX ARC. The RLAs were manipulated and applied to the horizontal diamond element in the optical bench of an IR spectrometer. The materials were either light activated for 40 seconds (dual-polymerizing mode) or were allowed to autopolymerize (autopolymerizing mode). The DC, R(p)(max), and PC(A/D) were calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios before and after polymerization. Data (n=5) were analyzed by 2-way repeated measures ANOVA and Tukey's post hoc test (alpha=.05).


RESULTS
All autopolymerizing groups exhibited lower DC and R(p)(max) values than the dual-polymerizing groups (P<.001), and higher DC values at 10 minutes than at 5 minutes, only in the autopolymerizing mode. Duo-Link exhibited the highest R(p)(max) values among dual-polymerizing groups, while Lute-It and Calibra showed the lowest R(p)(max) values and the highest PC(A/D) values. Within autopolymerizing groups, Nexus 2 and Lute-It exhibited the highest R(p)(max) values, while RelyX ARC demonstrated the lowest R(p)(max) as well as the lowest PC(A/D) values.


CONCLUSIONS
The DC values of all autopolymerized groups of RLAs were lower than those of the dual-polymerized RLAs, but the differences in R(p)(max) and PC(A/D) were product dependent. The DC of all products was higher at the 10-minute interval than at the 5-minute interval, only in the autopolymerizing mode.
Arrais
Cesar A G
CA
Department of Operative Dentistry, School of Dentistry, University of Guarulhos, Guarulhos, São Paulo, Brazil. cesararrais@yahoo.com.br
Giannini
Marcelo
M
Rueggeberg
Frederick A
FA
D000704:Analysis of Variance; D006244:Hardness; D007700:Kinetics; D055115:Light-Curing of Dental Adhesives; D008689:Methacrylates / Q000737:chemistry; D044367:Phase Transition; D019279:Resin Cements / Q000737:chemistry*; D055116:Self-Curing of Dental Resins; D017550:Spectroscopy, Fourier Transform Infrared
D008689:Methacrylates; D019279:Resin Cements