To investigate morphological surface features of different composite resins after 30,000 sliding wear cycles under two- and three-body wear action.

The morphology of worn surfaces of four nanofiller containing composite resins, Filtek Supreme XT (FIL), MI Flow (MFL), Venus Diamond (VED) and Venus Pearl (VEP) were investigated and compared with three conventional composites as references, microfilled Durafill VS (DUR), microhybrid Filtek Z250 (Z250) and hybrid-type Clearfil AP-X (APX). Plane surfaces of the polymerized and water-saturated materials (n = 5) were tested in a custom-built pin-on-disk wear machine fitted with a zirconia ball, 4 mm in diameter, serving as the antagonist ‘cusp’ and loading the specimen at 15° angulation for 3.7 mm long sliding paths (50 N load, 1.2 Hz, 30,000 cycles) either in water, simulating two-body wear, or in slurries of PMMA beads or poppy seed, simulating three-body wear. Random samples of each material were selected and sputter-coated with gold for inspection of the wear patterns using scanning electron microscopy.

Under two-body wear action all materials showed cracking as indicator of fatigue. MFL and VEP with prepolymer particles were least affected. Similarly, surfaces after three-body wearing with PMMA bead slurry revealed crack formation for five of the composites tested. The micro-hybrid Z250 and the nanofilled FIL displayed compressed and shallow delaminated areas. With poppy seed slurry as the third-body medium DUR was deeply destructed. Also the nanohybrid VED with a small fraction of up to 20 ƒÝm large ground glass fillers revealed deep cracks, whereas small delamination areas characterized the hybrid composite APX. Z250 as well as FIL, MFL and VEP were smoothly abraded without showing signs of cracking or delamination.

Composite resin surfaces, worn under two-body sliding showed mainly crack formation as an expression of fatigue. Similarly, three-body abrasion with a PMMA bead slurry revealed surface cracks to various extent and delamination, which is also an expression of fatigue related damage. With fine-ground poppy seed slurry only the microfilled composite with large prepolymer particles showed catastrophic failure. In all other cases the small poppy seed fragments in the slurry abraded the surfaces, removing polymer or fine particle loaded matrix uniformly. Supposedly, poppy seed slurry is a suitable third-body medium, simulating occlusal wear produced by food, rich in fibers or grain.

Koottathape N, Takahashi H, Iwasaki N, Kanehira M, Finger WJ. Morphological Features of Composite Resin Surfaces after Two- and Three-Body Wear Simulation. World J Dent 2012;3(3):221-228.