Shear strength of dentin and dentin bonded composites.
OBJECTIVE
The objective of this study was to compare the shear strength of dentin with the shear strength of dentin bonded composites, and to determine how variables such as composite strength and blade width used during shear testing influence shear strength values.


METHODS
Dentin test samples (n = 36) were made by milling the anatomical molar crowns to a shape similar to a composite rod bonded to a flat dentin surface. Dentin bonding was accomplished by bonding composites to flat dentin surfaces (n = 72) using Scotchbond MP and Z100 (n = 36) or Silux Plus (n = 36) composites. Shear testing was conducted using a guillotine-like device with a flat blade embracing half the dentin or composite cylinders. The blade thickness was either 0.25, 0.5, 0.75, 1.0, 1.25, or 1.50 mm. Six samples per material and blade thickness were tested. In addition to the above study, the bond strength of Z100 (n = 6) and Silux (n = 6) bonded with Scotchbond MP and tested with an orthodontic edgewire loop were also tested and compared with the bond strength of the Z100 and Silux samples tested with the 0.5 thick blade. All shear testing was done at a load rate of 0.5 mm/min. The results were analyzed using ANOVA and Duncan's multiple range test.


RESULTS
The shear strength values when tested with the blades were: dentin = 39.7 +/- 13.0 MPa, Z100 = 29.3 +/- 7.2 MPa, and Silux = 21.1 +/- 4.9 MPa; each group had significantly different values (p < 0.05). The blade thickness had no significant effect on strength (p = 0.471). Comparing the 0.5-mm-wide blade with the edge wire (width = 0.45 mm) revealed a significant difference (p = 0.0014) favoring the blade. Z100 performed better than Silux (p = 0.0014).


CONCLUSIONS
The shear strength of the tested bonding agent is significantly lower than the shear strength of dentin. The shear strength depends on testing method (blade vs loop) and composite material.
Mondragon
E
E
Department of Dental Biomaterials, College of Dentistry, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610-0446, USA.
Söderholm
K J
KJ
D000704:Analysis of Variance; D003188:Composite Resins; D001840:Dental Bonding; D003799:Dental Stress Analysis; D003804:Dentin / Q000502:physiology*; D017220:Dentin-Bonding Agents; D006801:Humans; D008422:Materials Testing / Q000295:instrumentation; D008963:Molar; D019279:Resin Cements; D012822:Silicon Dioxide; D018709:Statistics, Nonparametric; D013718:Tensile Strength; D015040:Zirconium
D003188:Composite Resins; D017220:Dentin-Bonding Agents; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; C083568:Z100 composite resin; C074741:Silux Plus; D012822:Silicon Dioxide; D015040:Zirconium