Nanofilled RMGI: Fracture Toughness, Surface Roughness and Gloss Testing

Objectives: Fracture toughness, roughness and gloss were compared in a nano-ionomer (NGI), two conventional glass ionomers (CGI), a resin-modified glass ionomer (RMGI), a compomer (CMP) and a microhybrid composite (MHy).  Methods: Compared were:  1) Ketac Nano (KN); 2) Esthet-X (EX); 3) Geristore (GS); 4) Photac Fil (PF); 5) Ketac Fil Plus (KF); and Fuji IX (F9).  A three-point bending test (MTS Sintech Renew) was used to test fracture toughness.  Gloss units (GU) were measured; (Gloss Checker, Model IG 331, Horiba).  Roughness (Ra; µm) was measured (Taylor Hobson Surtronic 3+).   Ra and GU specimens were measured three times.  Results: For fracture toughness (MPa-m^1/2) results were:  EX = 2.1; GS = 1.4; KN = 1.1; PF = 0.9;  KF = 0.5; and F9 = 0.5.  Results of statistical testing, from highest to lowest were:  EX > GS > KN > PF > KF = F9 (ANOVA; p < 0.001; except KF vs. F9; p = 0.30).  GU results were:  EX = 8.3; GS = 3.8; KN = 5.9; PF = 1.3; KF = 0.0; and F9 = 1.4.  Statistically, highest to lowest:  EX > KN > GS > PF = F9 > KF (p < 0.001; except PF vs. F9; p = 0.36).  Ra (µm):  EX = 0.09; GS  = 0.38; KN = 0.24; PF = 0.74;  KF = 1.58; and F9 = 0.66.  Statistically, lowest to highest:  EX < KN < GS < F9 < PF < KF (p < 0.001; except PF vs. F9; p = 0.35.  Ra & GU, Mixed model ANOVA).  Conclusions: Within the limitation of this in vitro experiment, it may be concluded that:  Relative to the two CGIs and the RMGI, the addition of nanofillers appears to result in higher fracture toughness, higher gloss and lower surface roughness.