Experimetelle Untersuchungen über den Einfluss von Eugenol auf die Mikrozugfestigkeit eines Vier-Schritt- Etch-and-rinse Systems bei Klasse-I-Kavitäten

Aim of this study The main aim of this in vitro study was to evaluate the effect of a eugenol-based temporary restorative material on the shear bond strength of a four-step total-etching composite to dentin after standardized cleaning procedures. Material and methods Forty-five previously impacted, caries-free third molars were prepared with a class I cavity and then randomly divided into two main groups later filled with either cement-based eugenol-containing temporary cement (Temp-Bond®, Kerr Corporation, Orange, CA, USA) or cement-based eugenol-free temporary cement (Temp-Bond® NE™, Kerr Corporation, Orange, CA, USA). All specimens were incubated for 7 days in physiological saline solution, and the temporary cement remnants were then removed by using three different procedures: Scaler/Excavator, aluminium oxide (RONDOflex Plus Powder, KaVo Dental GmbH, Biberach/Riß, Germany) and glycine powder (Clinpro™ Prophy Powder®, 3M™ ESPE™ AG, Seefeld, Germany). In all experimental series, the dentin surfaces were pretreated with a dentine-bonding agent (Syntac®, Ivoclar Vivadent AG, Ellwangen, Germany) and all groups were filled with a nanohybrid resin composite (Venus® Diamond, Heraeus, Hanau, Germany) utilizing a variety of incremental composite layering techniques. The specimens were then sectioned to obtain beams of 0.7 mm² each for measuring microtensile bond strength (µTBS) with a steady feed speed of 1 mm/min. Surfaces and resin-dentine interfaces were observed by scanning electron microscopy. Results and observations A significant influence of eugenol on the adhesion on dentin could not be found between the main groups (p > 0.05). An evaluation of the microtensile bond strength showed only marginal differences between the groups even in comparison to the control group. The mean values of the bond strength varied from 7.1 MPa to 18.4 MPa. In this study, significant differences were obtained between the groups which had been pretreated after temporary cement application (subgroup 2,3,6 and 7) and those which had been cleaned with scaler and excavator (subgroup 1,4,5 und 8) (p < 0.05). Subgroup 1 and 5 (8.2; 7.1 MPa) yielded low shear bond strength values, followed by subgroup 4 and 8 (14.9; 15.4 MPa). Pretreatment of the dentin with aluminum oxide resulted in the strongest microtensile measurements within its group (16.4 MPa und 18.4 MPa). In contrast, the previous airpolishing with glycine powder caused only insignificantly lower values of adhesion strength (15.2 MPa und 17.6 MPa). Practical Conclusions The prior use of temporary cements, independent of eugenol, does not affect bond strength of a nanohybrid composite to dentin unless having been removed by sandblasting. The present study shows that a manual cleansing procedure by using a scaler and excavator should be avoided when dentin-bonded restaurations are being planned. In the process, aluminium oxide air polishing represents an ideal method; glycine powder is a good alternative. Moreover, an effective surface cleansing is critical to achieve a successful adhesion strength from dentin to composite.