Objectives: The aim of this study was to evaluate the effect of Cholesterol Esterase enzyme (CE) on long term in vitro bond strength of two self etching primer systems (SEP).

Methods: Non-traumatized, non-carious 24 extracted human molar teeth were used. Standart Class I cavities were prepared and the teeth were randomly divided into 2 groups according to the SEP system used ( SE Bond and Protect Bond, Kuraray Co, Japan) (n=12), restored  with a resin composite (Clearfil AP-X, Kuraray Co, Japan). The restored teeth were then divided into 2 subgroups according to the storage conditions (artificial saliva with or without CE) (n=6) and 3 subgroups according to the time period (24 hours, 6 months and 1 year) (n=2). At the end of storing period, using the “nontrimming” technique, multiple beams were prepared and the specimens were operated in tension at 1mm/min until failure for microtensile test. The data was expressed in MPa and was analyzed using a one-way ANOVA and Tukey HSD tests.

Results:

Values with same letter on same column are not statistically different (p>0.05).

ABF Bond showed more stable bond strength in artificial saliva even after one year while SE Bond's  performance was less consistent in artificial saliva with or without CE. CE decreased bond strength of ABF Bond (p<0,0005).

Conclusions: CE had a negative effect on bond strength of fluoride containing ABF Bond in in vitro conditions (p<0.05)