Effects of filler composition and surface treatment on the characteristicsof opaque resin composites

The effects of filler composition and surface treatment of titanium dioxide (TiO2) on the shear bond strength to noble metal and mechanical properties of opaque dental resin composites were assessed. A series of fillers for r esin composites were prepared with untreated TiO2 or treated silica/alumina -coated TiO2 with silane coupling agent; these fillers were replaced with s ilanized SiO2 in increasing amounts. Each of various powder compositions we re mixed with the liquid and applied to the surface of a silver-palladium-c opper-gold (Ag-Pd-Cu-Au) alloy and light cured. A light-activated resin-ven eering composite material was placed on top with the use of a brass ring mo ld and light cured. Specimens were stored at 37 degreesC in water for a per iod of 24 h. Additionally some specimens were thermocycled at 4 degreesC an d 60 degreesC in water baths for 1 min each for 5000 cycles before shear mo de testing was performed. Light-activated opaque resin composites containin g filler with specific filler compositions of 50 wt% of untreated TiO2-50 w t% of silanized SiO2. (untreated TiO(2)50) and 40 wt% of untreated TiO2-60 wt% of silanized SiO2 (untreated TiO(2)40) showed higher shear bond strengt hs to the Ag-Pd-Cu-Au alloy than any other specific compositions when no th ermocycling was involved. Surface treatment of TiO2 filler and TiO(2)50- an d TiO(2)40-opaque resin composites prepared thereof showed significantly hi gher shear bond strengths than untreated TiO(2)50- and TiO(2)40-opaque resi n composites when subjected to thermocycling. Surface-treated opaque resin composite had significantly higher compressive and flexural strength than u ntreated opaque resin composite after immersion in water for 1 month. Scann ing electron microscopy of the fractured opaque resin composite surface sho wed an interface failure between TiO2, and the matrix resin for untreated c omposite, and cohesive failure within the resin for surface-treated composi te. Surface-treated TiO(2)50 and TiO(2)40, may be clinically useful as the filler for light-activated opaque dental resin composites. (C) 2001 John Wi ley & Sons, Inc.