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  • Photoelastic evaluation of the effect of composite formulation on polymerization shrinkage stress.

Photoelastic evaluation of the effect of composite formulation on polymerization shrinkage stress.

Brazilian oral research (2012-05-30)
Karla Mychellyne Costa Oliveira, Simonides Consani, Luciano Souza Gonçalves, William Cunha Brandt, Renzo Alberto Ccahuana-Vásquez
ABSTRACT

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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Camphor, 96%
Sigma-Aldrich
(±)-Camphor, meets analytical specification of Ph. Eur., BP, racemic, ≥95% (GC)
Sigma-Aldrich
(±)-Camphor, purum, synthetic, ≥95.0% (GC)
Supelco
(−)-Camphor, analytical standard
Sigma-Aldrich
(1R)-(+)-Camphor, 98%
Sigma-Aldrich
(±)-Camphor, ≥95.5%
Sigma-Aldrich
(1S)-(+)-Camphorquinone, 99%
Sigma-Aldrich
(±)-Camphor, SAJ first grade, ≥96.0%
Camphor (dl), primary reference standard
Camphor (racemic), European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
D-Camphor, ≥97%, FG
Supelco
D-Camphor, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
(1S)-(−)-Camphor, 95%