Properties of silorane-based dental resins and composites containing a stress-reducing monomer.
OBJECTIVE
To evaluate properties of silorane-based resins and composites containing a stress reducing monomer.


METHODS
Resin mixtures and composites were formulated containing (a) a developmental stress reducing monomer [TOSU; Midwest Research Institute]; (b) Sil-Mix (3M-ESPE); (c) photo cationic initiator system. Standard BISGMA/TEGDMA resin (B/T) and composite (Filtek Z250) were used as controls. Polymerization volume change was measured using a NIST mercury dilatometer and polymerization stress using an Enduratec mechanical testing machine. Three point bend tests determined flexural elastic modulus, work of fracture, and ultimate strength (ADA 27; ISO 4049). Fracture toughness was measured using ASTM E399-90. Four groups of resins and composites were tested: Sil-Mix, methacrylate standard, and Sil-Mix with two addition levels of TOSU. An ANOVA was used and significant differences ranked using Student-Newman-Keuls test (alpha=0.05).


RESULTS
Polymerization stress values for resins containing TOSU were significantly less than the other materials. Polymerization shrinkage values for Sil-Mix formulations were significantly less than for B/T, but were not different from each other. TOSU-containing formulations generally had somewhat lower mechanical properties values than Sil-Mix or B/T. Polymerization stress values for Sil-Mix-based composites were significantly less as compared to Z250. The 1wt.% TOSU composite had the lowest stress. No difference between composite groups was noted for fracture toughness or work of fracture. For ultimate strength, the 5wt.% TOSU formulation differed significantly from Z250. All Sil-Mix formulations had elastic modulus values significantly different from Z250.


CONCLUSIONS
The ability of TOSU to reduce polymerization stress without a proportional reduction in mechanical properties provides a basis for improvement of silorane-based composites.
Eick
J David
JD
Department of Oral Biology, University of Missouri-Kansas City, Kansas City, MO, USA. eickj@umkc.edu
Kotha
Shiva P
SP
Chappelow
Cecil C
CC
Kilway
Kathleen V
KV
Giese
Gregory J
GJ
Glaros
Alan G
AG
Pinzino
Charles S
CS
D000473:Alkanes / Q000737:chemistry; D000704:Analysis of Variance; D003188:Composite Resins / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects; D018772:Dental Marginal Adaptation; D003799:Dental Stress Analysis; D004548:Elasticity; D004852:Epoxy Compounds / Q000737:chemistry; D006244:Hardness; D008027:Light; D008422:Materials Testing; D044367:Phase Transition; D018583:Pliability; D017655:Silicon Compounds / Q000737:chemistry*; D013141:Spiro Compounds / Q000737:chemistry*; D014297:Trimethylsilyl Compounds
C523292:3,9-diethyl-3,9-bis(trimethylsilylpropyloxymethyl)-1,5,7,11-tetraoxaspiro(5.5)undecane; D000473:Alkanes; D003188:Composite Resins; D004852:Epoxy Compounds; C523293:Sil-Mix; D017655:Silicon Compounds; D013141:Spiro Compounds; D014297:Trimethylsilyl Compounds