Effect of different metal surface treatments and thermocycling on shear bond strength of heat cure and light cure at CoCr and NiCr interface

الملخص EN

Background Optimum bond strength at the metal–resin interface of prosthesis is essential for the success of that prosthesis.

The junction between metal alloy and acrylic resin is an area of clinical concern .Failure of a R.P.D.

may be linked to this interface.

The main objective of this study were to determine the effect of different metal surface treatment and thermo cycling on the shear bond strength of Co / Cr alloy and Ni / Cr alloy to heat cure acrylic resin and light cure acrylic resin.

Materials and methods : 120 metal samples were prepared, 60 Co / Cr samples and 60 Ni / Cr of square flat plate (30 mm x 30mm x 2 mm) that incorporated a central area (8mmx 12mm) of a large retentive mesh to simulate denture framework.

The samples were cleaned, finished and electro polished.

Sixty samples of each type of metals were divided into two groups according to the type of acrylic resin received each one 30 samples (A and group C) for heat cure, B and group D for light cure) which were fatherly subdivided according to the type of surface treatment into 3 subgroups each one 10 samples(A1 ,B1, C1and D1) for no surface treatment, no thermocycling as a control group (A2, B2 ,C2 and D2) for Metal Prime II application with thermocycling (A3, B3, C3 and D3) for combination of Air Abrasion and Metal Primer II application with thermocycling.

The acrylic block were then prepared as a rectangular block(12mm length, 8 mm width, 6 mm high) that was placed on a central area of metal plates, the acrylic was fabricated in the same conventional way of denture construction.

All the sample were mounted on specially test fixture that would hold them rigid at a 90-degree angle from the horizontal plane of the crosshead of the Intron machine .A tangent shear force was created by applying vertical load to the specimen.

All of the specimen were tested with Instron machine using stainless steel chisel shaped road at a constant crosshead speed of 5 mm min until failure of the bond occurred The specimen were stressed to failure.

The force of bond failure was recorded in Newton, which was dividing by the surface of the bonded area (96 mm2) to obtain the shear bond strength calculated in Map.

Result : the results showed that the subgroup that received no surface treatment and without thermo cycling for both two type of resins heat cure and light cure (A1, B1, C1and D1) had the highest shear bond values, followed by subgroups that received Air Abrasion + Metal Primer II surface treatments and thermo cycling (A3, B3, C3, D3).Subgroups that received Metal Primer II alone (A2, B2, C2 and D2) showed the least shear bond value than the other subgroups.

Conclusion : all metal samples of Co / Cr and Ni / Cr with heat cure acrylic resin showed higher SBS mean values than that light cure resin whether with surface treatment and thermo cycling or without thermo cycling concluded higher binding of heat cure acrylic resin with the metal surface.