Benzoyl germanium derivatives as novel visible light photoinitiators for dental materials.
OBJECTIVE
The objective of this study was to investigate the use of benzoyl germanium derivatives as a novel visible light photoinitiator of resin-based dental composites. Selected mechanical properties, such as flexural strength and flexural modulus, setting time, storage stability, and UV light stability, of the composites based on the novel photoinitiators benzoyltrimethylgermane (BTMGe) or dibenzoyldiethylgermane (DBDEGe) were investigated and compared to the properties of materials that are cured with a mixture of camphorquinone (CQ) and ethyl 4-(N,N-dimethylamino)benzoate (EMBO).


METHODS
The flexural strength and flexural modulus of elasticity were determined according to ISO 4049. For this purpose, test specimens (2 mm x 2 mm x 25 mm) of the composites investigated were prepared in stainless steel moulds and light-cured (150 mW/cm2, 2 s x 180 s). The flexural strength and flexural modulus of elasticity were measured after immersing the cured specimens in water for 24h at 37 degrees C and in certain cases, after they had been boiled for 24h in water. In addition, the setting time, curing depth, storage and UV stability of selected composites were determined.


RESULTS
The novel photoinitiators BTMGe or DBDEGe can be used to substitute the binary photoinitiator CQ/EMBO in visible light-cured restorative composites. Especially, DBDEGe showed a significantly higher photocuring activity in composites with a filler load of about 60 wt. % in comparison to that of CQ/EMBO. In addition, composites based on BTMGe or DBDEGe showed an improved UV stability and a storage stability comparable to that of CQ/EMBO-based composites.
D010129:4-Aminobenzoic Acid / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003116:Color; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D004548:Elasticity; D005857:Germanium / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D063065:Organophosphonates / Q000737:chemistry; D010777:Photochemistry; D018583:Pliability; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D012995:Solubility; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013729:Terpenes / Q000737:chemistry; D013997:Time Factors; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry; D062366:para-Aminobenzoates
C515802:1,6-bis(methacroyloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D009942:Organometallic Compounds; D063065:Organophosphonates; D011109:Polymethacrylic Acids; D013729:Terpenes; C531966:benzoyltrimethylgermane; C531967:dibenzoyldiethylgermane; C523330:ethyl 4-N,N-dimethylaminobenzoate; D062366:para-Aminobenzoates; D005857:Germanium; D014867:Water; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C048339:camphoroquinone; D010129:4-Aminobenzoic Acid