An analytical descriptive study using microscopic magnification of nickel chromiumalloyetching with different acids after resin cementbonding and debonding (In-vitro study)

Abstract

Background and Aim of study:Bonding betweena resin cement and metal frameworkis a great challenge,which limits the use of fixed prosthodontics with minimal preparation.The aim of this study was to evaluate using microscopic magnificationthe patterns of resin cement failurewith the nickel-chromium alloy after the surface treatment with acid etching using multiple acid solutions with or without sandblasting. and studying the effect of acid onthe nickel-chromium alloy .

Materials and Methods:80 pairs of metal plates made of nickel-chromium alloy have been designed (one circular and one square).  Plates were divided into ten equal main groups according to the surface treatment (sandblasting, sandblasting plus acid etching, or acid etching alone). Initially,all specimen bonding surfaces were polished. Thengroup I Received no treatment, group II: test surfaces were sandblasted with 250 μm sized aluminium oxide particles, In groups (III,IV,V &VI), the test surfaces were treated by acid etching using four acid solutions (A: Aqua-regia, B: 37%HCl, C: HF+HNO3, D: H2SO4+HCl) respectively. In groups (VII,VIII,IX &X), the test surfaces were first treated by sandblasting followed by acid etching using four acid solutions (A,B,C&D) respectively. Every two plates have been bonded together using chemical resin cement, shear bond strength tests were applied upon the bonded plates until they were separated. the patterns of resin cement failure in each pair of samples were studied under the microscope. Resultswere analyzed using Chi-squared test at (α=0.05) significance level.

Results:Group (I& V,IX)showed primarily adhesive failure(100%), while the (VII &X) groups had anadhesive failure with very low percentage 12.5% ​​and the patternfailure is exhibited primarily cohesive failure, and groups (II &III)had also anadhesive failure at low precentage25%.In group (VIII), the rate of adhesive failure was37.5%, whilein group (IV & V) the adhesive failure rate were (62.5%, 75%) respectively.

Conclusions:The microscopeexamination showed that adhesive failure of resin cement to metal surfacewas uncommon whenthe last one was treated with sandblasting followed by etching with one of these acidic solution (Aqua-regia, HCl,H2SO4+HCl),more over the resin cement adhesive was acceptable when the metal surface was only sandblasted.