Mechanical properties of one-step adhesive-polymers in dry vs. wet

Objectives: To evaluate the mechanical properties of five one-step self-etch adhesive polymers measured in dry vs. wet.

Methods: Five commercial one-step self-etch adhesives, Xeno IV (Dentsply Caulk), Bond Force (Tokuyama Corp.), One-Up Bond F Plus (Tokuyama Corp), S3 Bond (Kuraray Medical Inc.) and G Bond (GC co.) were used. Ten "I"-shaped polymers of each adhesive were used to obtain the modulus of elasticity (E) by three-point flexural test and the ultimate tensile strength (UTS) in micro-tensile testing. E and UTS were measured both in dry polymers and after immersion in water for 24 h. Ten resin disks (1.5 mm thick, 8.0 mm diameter) of each adhesive were dehydrated for 24 h and weighed to constant dry mass (micro-gram) (M1), using a modification of the ISO 4049 standard. They were placed in water and weighed as well; until maximum wet mass (micro-gram) (M2) was obtained. The water sorption (WS) was calculated using the following equation: WS (micro-gram/mm3)= (M2- M1) / V, where V is the specimen volume in mm3. Correlation analyses were used to determine the correlations between E vs. UTS, and water sorption of these five polymers vs. changes in UTS or E.

Results: In dry, E of five adhesive polymers were from 948 to 1531 MPa, and UTS were from 24.4 to 61.5 MPa. Those same specimens tested after soaking in water for 24 h gave much lower E (from 584 to 1072 MPa) and UTS (from 16.5 to 35.0 MPa). WS varied from 32.13 (G Bond) to 105.82 micro-gram/mm3 (One-Up Bond F Plus).

Conclusion: There were significant correlations between E and UTS of five adhesives under dry or wet condition. Both E and UTS fell significantly when the specimens were immersed in water. The percent change of UTS was significantly correlated with the water sorption.