Bond strength to radicular dentin of two experimental luting cements

Aim The aim of this study was to test two different of experimental cements based on two types of polymerization techniques comparing them with one already well known in the market.

Materials and methods  Thirty intact central incisors, extracted for periodontal reasons, were selected and endodontically treated, then were randomly divided into 3 groups of 10 samples: Group 1, light cured composite experimental material with self-etch adhesive and dual polymerization activator; Group 2, dual experimental core build-up with self-etch adhesive and dual-polymer activator; Group 3 (control group), dual cement with self-etch adhesive and dual polymerization activator. One fiber post was luted into the root canal strictly following manufacturer€™s instructions. Each sample was cut in slices in order to perform the push-out bond strength test with a testing machine. To express the bond strength in MegaPascals (MPa), the breaking load recorded in Newton (N) was divided by the area of the bonded interface (A) in mm². The area of the bond interface was calculated as the area of the surface of a truncated cone using the formula: A = Ï€ (R + r) [h2 + (Rr) 2] 1/2, where R represents the major radius of the coronal post, r represents the minor radius of the apical post and h is the thickness of the slice in millimeters. The diameters and thickness of the slice were measured individually using a digital caliper with 0.01 mm precision. After the test, each slide was observed to detect the type of failure and classified as adhesive between cement and dentin (AD); adhesive between the cement and the post (AP); fracture of the sample, cohesive inside the post and dentin (FR); cohesive in cement (CC); mixed (M).

Results  Group 2 recorded the highest values of adhesion strength,  group 1 the lowest. There were no statistically significant differences among groups 1 and 2 and controls. The most common failure mode was the mixed one and the less frequent was the adhesive type between the post and the cement.

Conclusions  Within the limitations of this study, it can be concluded that the bond strength of experimental resin cements is comparable to that of a cement marketed by the same manufacturer, used here as a control and well known in the market.