Effects of Eugenol Concentration in ZOE Provisionals on Bond Strength

Objectives: The literature is contradictory regarding effects of eugenol on dentin bonding.  This study evaluated effects of eugenol concentration in ZOE provisionals on dentin bond strength of composite(part 1), and assessed dentists opinion of potential ZOE effects before and after seeing study results(part 2).

Methods: Part 1-Eighteen molars divided into six groups had occlusal enamel removed exposing dentin.  A layer of ZOE(IRM/Caulk) was applied to dentin at the manufacturers P:L ratio 6:1 by weight, or with greater eugenol amounts(P:L of 6:1.5, 6:2, 6:2.5 and 6:3).  The control group had no ZOE. After storing in 100% humidity at 37°C for 7d, ZOE was removed by hand instrument and water-pumice slurry(10s). Optibond FL(Kerr) dentin adhesive was applied, and resin composite(Premise) was built up in 2x2mm increments.  Teeth were stored overnight, then cut into 1x1mm sticks for microtensile testing(1mm/min).  Results were analyzed using ANOVA/Tukey's(p=0.05). Part 2-A web-based survey assessed members of the PROH practice-based research network regarding their use of ZOE products and knowledge of potential effects on dentin bonding before and after presenting our results.

Results: Groups with the same letter were not different.

Powder:Liquid(P:L)	Mean±s.d.	N
6:1.0	28.93±9.65    a,b	18
6:1.5	23.17±10.66    b	29
6:2.0	23.16±4.60      b	29
6:2.5	31.63±10.19    a	25
6:3.0	25.43±7.69    a,b	28
Control	28.78±6.15    a,b	26

In general, bond strength was not affected by prior exposure of dentin to ZOE, even when eugenol concentration was 3X recommended.   93% of dentists(n=30) pre-surveyed were aware of potential adverse effects of eugenol on bonding and 83% expected this study to support that.  After seeing the results and being presented with a supporting literature review, 82% said they would be less concerned about using eugenol prior to dentin bonding.

Conclusion:  Contrary to surveyed dentists expectations, exposure to ZOE had little effect on adhesive bond strength to dentin.  Supported by OHSU-OSLER funds.