Effect of Energy on Shear Bond Strength of Bonding Agents

Objectives: This study evaluated the effect of delivering clinically relevant amounts of energy on the shear bond strengths of two adhesives to dentin.

Methods: The energy delivered by 71 dental students to the same posterior restoration using the same curing light was measured using the MARC–Patient Simulator (BlueLight, Halifax). When using the light for 5 seconds, the average of the 3 students delivering the least amount of energy was 3.3J/cm². When using the same light for 20 seconds, the average energy delivered was 22.3J/cm². These two different energy values were delivered to Optibond FL(Kerr) and Single Bond Plus(3M-ESPE) bonding systems using the SmartLite iQ2(Dentsply) and the MARC-RC. Shades A2 and A4 of Z100(3M-ESPE) resin composite were bonded to human dentin in a random order with each system using the Ultradent bonding jig. The specimens were stored for 24 hours in water at 37 °C before they were subjected to a shear bond test using the Ultradent notched blade in an Instron testing machine. Eleven specimens were made with each combination of energy, bonding system. The results were compared using ANOVA and Fischer's PLSD (α=0.01).

Results: Overall, 3-way ANOVA showed that delivering more energy resulted in a greater bond strength (by 10.1 MPa), the Optibond FL bonding system produced greater bond strengths (by 3.1 MPa), and the A2 shade produced a greater bond strength (by 3.5 MPa) with no interactions.

Effect of Energy, Bonding System and Shade on Shear Bond Strength
Bonding System, Energy Used, Shade	Mean Shear Bond Strength (MPa)	S.D.
Optibond, 22J/cm2, A2	49.1 a	3.32
Optibond, 22J/cm2, A4	48.3 a	6.46
SingleBond, 22J/cm2, A2	46.4 a	3.88
SingleBond, 22J/cm2, A4	42.4 b	3.16
Optibond, 3J/cm2, A2	40.9 b	4.34
SingleBond, 3J/cm2, A2	36.6 c	4.20
SingleBond, 3J/cm2, A4	34.6 c	6.66
Optibond, 3J/cm2, A4	33.9 c	3.58

Similar ^{superscript letters} indicate no significant difference (Fischer's PLSD p>0.01)

Conclusions: Delivering insufficient, but clinically relevant amounts of energy, i.e., 3J/cm² instead of 22J/cm², had a threefold greater effect on shear bond strength compared to the bonding agent or shade of composite used in this study. Adhesives should be tested using a range of clinically relevant amounts of energy.

This study was supported by Dalhousie University, OHSU and NSERC.