Determination of Excess Removability of Self-adhesive Resin Cements

Objectives: While seating a restoration, such as a crown, excess resin cement is formed around the margin. Many manufacturers of self-adhesive resin cements (SARCs) state easy excess removal. We aim to determine the force required to remove a defined amount of SARCs excess from a (pretreated) dentin surface after tack curing.
Methods: Bovine teeth (n=5) were ground flat to expose dentin, polished (grit 320 sandpaper), distilled water rinsed, and gently air-dried. With the aid of a drilling template fixed with superglue (Sekundenkleber, Renfert GmbH), 1 to 3 cylindrical cavities (4.5±0.1mm diameter x 2.0±0.1mm depth) were drilled. Superglue was mechanically removed after drilling. Resin cement weighing 30mg was placed in the cavity and pushed through with a stainless-steel rod (4.0±0.05mm diameter x 2.0±0.1mm height), so that all of the excess cement was pushed out onto one side of the cavity to form a half moon. Excess cement was cured for a defined time of 5 seconds, from a defined distance (2mm spacer) from the tooth surface using an Elipar^TM S10 light curing device (3M ESPE). Excess cement was sheared off using a jig (Zwick Z010, n=5; speed= 0.75mm/min). Maximum force (N) to shear off the excess cement was recorded.
Results: See data in table 1.
Conclusions: A method was developed to quantify force needed to remove cement excess. Under standardized conditions, different levels of removal force were identified. PAN, CU and EXP require a significantly lower force for excess removal. SCP and MAX require an intermediate force. RXU2 and TC require a significantly higher force to achieve excess removal. Excess removal force can be lowered by reducing irradiation time as shown with RXU2a and RXU2b.