Influence of loading types on the shear strength of the dentin-resin interface bonding

Small differences in the shear bond test can make critical differences in t he bonding strength values. The purpose of this study was to compare the in fluence of the orthodontic-looped wire, stainless steel tape and chisel sys tems used in shear bonding tests to verify the resistance in the dentin-res in interface. Forty-eight human teeth were used and divided in three groups . The teeth were ground until a flat smooth surface was achieved, that was delimited with an adhesive tape containing a hole of 4 mm diameter. After, the dentine surface was treated with Scotchbond Multi Purpose and the compo site Z-100 was applied in layers, through a stainless steel mold. The sampl es were stored at 37 degreesC and 100% of relative humidity for 24 h and, t hen, submitted to 500 thermal cycles. After, they were taken to an universa l test machine (Otto Wolpert) with crosshead speed of 6 mm/min. The results were statistically analyzed using a Tukey's test (p\lt 0.05). The orthodon tic-looped wire determined the highest values of shear bond (13.33 MPa), fo llowing by chisel (7.81 MPa) and stainless steel tape (4.87 MPa). The debon ding values depend on a complex stress combination produced during the load ing of the samples. Small variations in test methodologies give statistical ly different values for shear bond strength. Different shear strength metho ds in vitro make the comparative clinical performance of the resin filling materials difficult. (C) 2001 Kluwer Academic Publishers.