Photoelastic evaluation of the effect of composite formulation on polymerization shrinkage stress.
We compared polymerization stress in two commercial composites and three experimental composites made using camphorquinone (CQ) and/or phenylpropanedione (PPD) as photoinitiators. The internal surfaces of photoelastic resin discs with cylindrical cavities were roughened and treated with adhesive. Composites were divided into five groups: two commercial composites (Filtek Silorane and Filtek Z250) and three experimental composites with CQ/amine, CQ/PPD/amine, and PPD/amine. Composites were photopolymerized inside cavities, and subjected to photoelastic analysis immediately and at 24 hours and 7 days later using a plane polariscope. Stress created by Silorane (3.08 ± 0.09 MPa) was similar to that of Z250 (3.19 ± 0.13 MPa) immediately after photopolymerization (p > 0.05). After 24 hours and 7 days, Z250 (3.53 ± 0.15 and 3.69 ± 0.10 MPa, respectively) showed higher stress than Silorane (3.19 ± 0.10 and 3.16 ± 0.10 MPa, respectively). Qualitative analysis immediately after photopolymerization showed composite/CQ promoted higher stress than PPD, but stress levels at other evaluated times were statistically similar, varying between 3.45 ± 0.11 MPa and 3.92 ± 0.13 MPa. At 24 hours and 7 days, Silorane created the lowest stress. All photoinitiators created comparable tensions during polymerization.
Department of Dental Materials, Piracicaba Dental School, State University of Campinas, SP, Brazil. karlamychellyne@yahoo.com
Karla Mychellyne Costa
KM
Oliveira
Simonides
S
Consani
Luciano Souza
LS
Gonçalves
William Cunha
WC
Brandt
Renzo Alberto
RA
Ccahuana-Vásquez
D000704:Analysis of Variance; D002164:Camphor / Q000031:analogs & derivatives* / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D055119:Elastic Modulus; D006801:Humans; D008422:Materials Testing; D044367:Phase Transition; D058567:Photoinitiators, Dental / Q000737:chemistry*; D058105:Polymerization; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
D003188:Composite Resins; D058567:Photoinitiators, Dental; D002164:Camphor; C553149:camphorquinone