Influence of light-curing procedures and photo-initiator/co-initiator composition on the degree of conversion of light-curing resins.
OBJECTIVE
The hypothesis that the degree and rate of conversion can be modified favourably by using different light-curing procedures and different photo initiator/co-initiator combinations was tested.


METHODS
A photo-initiator (0.02 mM/g resin); either camphorquinone (CQ) or 1-phenyl-1,2-propanedione (PPD), was mixed with bisGMA:TEGDMA (50:50 by weight). In addition, a co-initiator (0.04 mM/g resin); either N,N-dimethyl-p-aminobenzoic acid ethylester (DABE), N,N-cyanoethylmethylaniline (CEMA), or 2-dimethylaminoethyl methacrylate (DMAEMA), was added. These six combinations were subjected to three curing conditions (standard curing, soft-start curing or LED curing). The conversion levels (DC) were determined with differential scanning calorimetry (DSC). The DSC results were analysed using a general linear model (GLM) and Duncan's multiple range test and regular t-test.


RESULTS
The fastest conversion initially was obtained by standard curing, followed by LED curing and soft-start curing. After 40 s of curing, conventional curing and soft-start curing produced a higher DC than LED curing. However, strong interactions occurred between the different variables (curing method, initiator and co-initiator). Initially, CQ was more efficient than PPD, but after 40 s, this difference was insignificant.


CONCLUSIONS
By using soft-start curing and an appropriate photo initiator/co-initiator combination it is possible to achieve slow curing and a high DC at within a curing time of 40 s.
Emami
N
N
Division of Polymer Engineering, Luleå University of Technology, S-971 87, Luleå, Sweden. nazanin.emami@sirius.luth.se
Söderholm
K-J M
KJ
D000180:Acrylic Resins / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D000465:Algorithms; D002152:Calorimetry, Differential Scanning / Q000379:methods*; D002484:Cementation / Q000379:methods*; D003188:Composite Resins / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006244:Hardness / Q000528:radiation effects; D008422:Materials Testing / Q000379:methods; D010777:Photochemistry / Q000379:methods*; D011140:Polyurethanes / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D011829:Radiation Dosage
D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011140:Polyurethanes