OBJECTIVETo evaluate the potential corrosive effect of topical fluoride agents used for professional treatments at dental prophylaxis on the polished surfaces of five composite resins.

METHODSA total of 125 specimens were fabricated from micro hybrid composite, nano-combined composite, nanocomposite, compomer and ormocer in a phi 6 mm x 3 mm cavity with 25 specimens for each composite group. The flat surfaces of the specimens were smoothed and polished, then applied respectively with four topical fluoride agents and distilled water, and stored at 37 degrees C 100% relative humidity for 30 min. The changes in morphologic features of the surfaces were assessed by scanning electron microscopy (SEM). The disintegrated surface was further analysed under a confocal laser scanning microscope (CLSM).

RESULTSAll fluorides showed reaction to all composites except nanocomposite. The aggressiveness of the fluorides arranged sequentially as F (Elmex fluid) > G (Elmex gelée) > D (Duraphat) > B (Bifluorid 12). The treated surfaces were generally rough. F and G caused the overall surface corrosion, whereas etching on the surface by D and B was sporadic confined. The destructive effects demonstrated a large number of craters on the surface somewhat like an atoll owing to filler dissolution. Crack formation resulted in destruction of the filler-matrix interface was observed. Ormocer was severely affected after F and G treatment. Instead of crater glass filler protruding from the bumpy surface indicated the excessively disintegrated matrix of ormocer. Topography under CLSM exhibited the roughening of the composite surface, roughness parameters for profile (Sa, Sz, Smax) increased when the surface was treated. Surface change in nanocomposite specimens was neither visually nor numerically discerned.

CONCLUSIONSTopical application of highly concentrated fluoride prophylactic agents leaded to surface degradation and porosity of composite, nanocomposite was, however, chemically resistant. Isolation of the composite surface should be considered in clinical application of topical fluoride.