Investigation of thiol-ene and thiol-ene-methacrylate based resins as dental restorative materials.
OBJECTIVE
The objective of this work was to evaluate thiol-norbornene and thiol-ene-methacrylate systems as the resin phase of dental restorative materials and demonstrate their superior performance as compared to dimethacrylate materials.


METHODS
Polymerization kinetics and overall functional group conversions were determined by Fourier transform infrared spectroscopy (FTIR). Flexural strength and modulus were determined with a 3-point flexural test. Polymerization-induced shrinkage stress was measured with a tensometer.


RESULTS
Thiol-ene polymer systems were demonstrated to exhibit advantageous properties for dental restorative materials in regards to rapid curing kinetics, high conversion, and low shrinkage and stress. However, both the thiol-norbornene and thiol-allyl ether systems studied here exhibit significant reductions in flexural strength and modulus relative to BisGMA/TEGDMA. By utilizing the thiol-ene component as the reactive diluent in dimethacrylate systems, high flexural modulus and strength are achieved while dramatically reducing the polymerization shrinkage stress. The methacrylate-thiol-allyl ether and methacrylate-thiol-norbornene systems both exhibited equivalent flexural modulus (2.1+/-0.1 GPa) and slightly reduced flexural strength (95+/-1 and 101+/-3 MPa, respectively) relative to BisGMA/TEGDMA (flexural modulus; 2.2+0.1 GPa and flexural strength; 112+/-3 MPa). Both the methacrylate-thiol-allyl ether and methacrylate-thiol-norbornene systems exhibited dramatic reductions in shrinkage stress (1.1+/-0.1 and 1.1+/-0.2 MPa, respectively) relative to BisGMA/TEGDMA (2.6+/-0.2 MPa).


CONCLUSIONS
The improved polymerization kinetics and overall functional group conversion, coupled with reductions in shrinkage stress while maintaining equivalent flexural modulus, result in a superior overall dental restorative material as compared to traditional bulk dimethacrylate resins.
Cramer
Neil B
NB
Department of Chemical & Biological Engineering, University of Colorado, Boulder, CO 80309, USA.
Couch
Charles L
CL
Schreck
Kathleen M
KM
Carioscia
Jacquelyn A
JA
Boulden
Jordan E
JE
Stansbury
Jeffrey W
JW
Bowman
Christopher N
CN
D015097:3-Mercaptopropionic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D000498:Allyl Compounds / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D001643:Bridged Bicyclo Compounds / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D055119:Elastic Modulus; D006536:Heptanes / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D009636:Norbornanes / Q000737:chemistry*; D018583:Pliability; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011409:Propylene Glycols / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties; D014227:Triazines / Q000737:chemistry
C504926:(2.2.1)bicyclohept-2-ene; D000498:Allyl Compounds; D001643:Bridged Bicyclo Compounds; D003188:Composite Resins; D003764:Dental Materials; D006536:Heptanes; D008689:Methacrylates; D009636:Norbornanes; D011108:Polymers; D011109:Polymethacrylic Acids; D011409:Propylene Glycols; D013438:Sulfhydryl Compounds; D014227:Triazines; C501435:pentaerythritol tetra(3-mercaptopropionate); C507611:triallyl-1,3,5-triazine-2,4,6-trione; C018163:trimethylolpropane; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; C074277:ethoxylated bis-phenol A dimethacrylate; D017438:Bisphenol A-Glycidyl Methacrylate; D015097:3-Mercaptopropionic Acid