Polymerization kinetics and reactivity of alternative initiators systems for use in light-activated dental resins.
OBJECTIVE
The purpose of this study was to evaluate the reactivity and polymerization kinetics behavior of a model dental adhesive resin with water-soluble initiator systems.


METHODS
A monomer blend based on Bis-GMA, TEGDMA and HEMA was used as a model dental adhesive resin, which was polymerized using a thioxanthone type (QTX) as a photoinitiator. Binary and ternary photoinitiator systems were formulated using 1mol% of each initiator. The co-initiators used in this study were ethyl 4-dimethylaminobenzoate (EDAB), diphenyliodonium hexafluorophosphate (DPIHFP), 1,3-diethyl-2-thiobarbituric acid (BARB), p-toluenesulfinic acid and sodium salt hydrate (SULF). Absorption spectra of the initiators were measured using a UV-Vis spectrophotometer, and the photon absorption energy (PAE) was calculated. The binary system camphorquinone (CQ)/amine was used as a reference group (control). Twelve groups were tested in triplicate. Fourier-transform infrared spectroscopy (FTIR) was used to investigate the polymerization reaction during the photoactivation period to obtain the degree of conversion (DC) and maximum polymerization rate (R(p)(max)) profile of the model resin.


RESULTS
In the analyzed absorption profiles, the absorption spectrum of QTX is almost entirely localized in the UV region, whereas that of CQ is in the visible range. With respect to binary systems, CQ+EDAB exhibited higher DC and R(p)(max) values. In formulations that contained ternary initiator systems, the group CQ+QTX+EDAB was the only one of the investigated experimental groups that exhibited an R(p)(max) value greater than that of CQ+EDAB. The groups QTX+EDAB+DPIHFP and QTX+DPIHFP+SULF exhibited values similar to those of CQ+EDAB with respect to the final DC; however, they also exhibited lower reactivity.


CONCLUSIONS
Water-soluble initiator systems should be considered as alternatives to the widely used CQ/amine system in dentin adhesive formulations.
Biomaterials Development and Control Center, Federal University of Pelotas, Pelotas, RS, Brazil.
Caroline
C
Ely
Luis Felipe J
LF
Schneider
Fabrício A
FA
Ogliari
Carla C
CC
Schmitt
Ivo C
IC
Corrêa
Giana da S
Gda S
Lima
Susana M W
SM
Samuel
Evandro
E
Piva
D015502:Absorptiometry, Photon; D001713:Biphenyl Compounds / Q000737:chemistry / Q000528:radiation effects; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D002164:Camphor / Q000031:analogs & derivatives / Q000737:chemistry / Q000528:radiation effects; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D009861:Onium Compounds / Q000737:chemistry / Q000528:radiation effects; D058567:Photoinitiators, Dental / Q000737:chemistry* / Q000528:radiation effects; D011092:Polyethylene Glycols / Q000737:chemistry / Q000528:radiation effects; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry / Q000528:radiation effects; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013858:Thiobarbiturates / Q000737:chemistry / Q000528:radiation effects; D013892:Thioxanthenes / Q000737:chemistry / Q000528:radiation effects; D014050:Toluene / Q000031:analogs & derivatives / Q000737:chemistry / Q000528:radiation effects; D014867:Water / Q000737:chemistry; D044004:Xanthones / Q000737:chemistry / Q000528:radiation effects; D062366:para-Aminobenzoates / Q000737:chemistry / Q000528:radiation effects
D001713:Biphenyl Compounds; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D009861:Onium Compounds; D058567:Photoinitiators, Dental; D011109:Polymethacrylic Acids; D013858:Thiobarbiturates; D013892:Thioxanthenes; D044004:Xanthones; D062366:para-Aminobenzoates; D014867:Water; C031291:diphenyliodonium; C020946:triethylene glycol dimethacrylate; D014050:Toluene; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C005044:hydroxyethyl methacrylate; D002164:Camphor; C030747:ethyl 4-dimethylaminobenzoate; C046058:1,3-diethyl-2-thiobarbituric acid; C484911:thioxanthone; C065428:4-toluenesulfinic acid; C553149:camphorquinone