Effect of ozone gas application on the mechanical properties of dental adhesives bonded to dentin

Objectives To assess the effect of ozone gas on the mechanical properties of different classes of dental adhesives. Methods Extracted molars were sectioned perpendicularly to their long axis for obtaining dentin slices to be bonded with one of the following adhesives: Prime&Bond NT (Dentsply), Excite (Ivoclar-Vivadent), Syntac/Heliobond (Ivoclar-Vivadent) and Silorane System Adhesive (3 M-ESPE). Prior to bonding, the slices were sectioned in two halves: one was treated with ozone gas for 120 s (4.2 g/m3; HealOzone, KaVo) and the other served as control. The Vickerʹs hardness (VH), elastic modulus (E), elastic work (We/Wtot) and the creep (Cr) of the materials were measured with an automatic micro hardness indenter (Fischer) 30 min and 24 h after bonding procedure. Data were analyzed with the multivariate ANOVA followed by the Tukeyʹs test and partial eta-squared statistics. Results The adhesive and the time of testing were significant factors affecting the investigated parameters (p < 0.001; image). Dentin treatment, though significant, exerted a minimal effect on mechanical properties (image). Ozone did not consistently affect the mechanical properties at both, 30 min and 24 h measurements, as all variations were below 10%. Small differences between ozone and control resulted only in the Cr and We/Wtot of Excite and in the VH of the Silorane System Adhesive at the 30 min measurement; and in the We/Wtot, Cr and VH of the Syntac/Heliobond system after 24 h. Significance Ozone gas did not compromise the mechanical properities of the tested adhesives. Thus, its application on dentin prior to bonding procedures is possible, without impairing the performance of the final restoration.