Acta Biomedica Scientia

EFFECT OF METAL PRIMER ON THE SHEAR BOND STRENGTH OF POLY METHYL METHACRYLATE HEAT CURED DENTURE BASE RESIN TO CAST TITANIUM AND COBALT-CHROMIUM ALLOYS: AN IN-VITRO STUDY

Mahendirakumar Nagarajan*, Narendran Sangili, Vijitha D

nmk.mds@gmail.com

Cobalt-chromium alloy, Denture base resin, Shear strength, Titatnium alloy

Background: Poor chemical bonding of acrylic resins to metal alloys can result in microleakage and failure of the bond. Metal primer has been shown to be effective in improving the bond strength of acrylic resins to metal alloys. However, there is insufficient information about their effect on bonding to different types of metals.Aim and Objective: The purpose of this study was to evaluate the effect of metal primer on the shear bond strength of PMMA heat cured denture base acrylic resins to cast Titanium and Cobalt-Chromium alloys. Material and methods:A total of 40 disk-shaped wax patterns (10 mm in diameter and 3 mm thick) were cast in Titanium (Tritan) and Cobalt-Chromium alloy, (Remanium G 800). After casting, the disk surfaces were finished till 600 grit abrasive paper under water.The specimens were numbered and then divided into 4 groups (n=10). Samples were subjected to airborne particle abrasion with aluminum oxide 250 µm at 4.5 kgf/cm2 pressure. The distance between the nozzle tip and the specimen surfaces was maintained at 5 mm, and sandblasted for 5 seconds and then ultrasonically cleaned in ultrasonic cleaner for 10 min in acetone and air dried to ensure the removal of all residual particles and surface contaminants. The specimens were divided into 2 Groups for each metal (n=10) which were air abraded with 250 µm aluminum oxide and the other 2 groups for each metal (n=10) which were air abraded with 250 µm aluminum oxide and then received the Alloy Primer. The specimens were flasked and Lucitone 199 PMMA denture base resin was used to make the resin tags.The specimens were tested in a universal testing machine at a crosshead speed of 0.5 mm/min in shear mode till the resin fractured from the metal surface. Stereo zoom macroscope was used to study the mode of failure between the metal and resin. Data (MPa) were analyzed using Paired t- test with significance level (p=0.05). Results: The paired t- test indicated that shear bond strength (SBS) values varied according to the surface preparations used (P<0.001). The SBS between Titanium and heat-polymerized resin (Group II) with sandblasted and Alloy Primer applied was the highest (2.73 MPa), and the SBS between Cobalt-Chromium and acrylic resin (Group III) which was only air abraded, was the lowest (1.93 MPa). The SBS values between sandblaste (Group I & III) and sandblasted and primed specimens of Titanium and Cobalt-Chromium alloys, (Group III & IV) respectively showed significant difference (p<0.001). When comparing the bond strength of sandblasted and Primed Titanium (Group II) with sandblasted and primed Cobalt-Chromium (Group IV), Titanium (Group II) showed the highest bond strength. Adhesive type of bond failure was noted with air abraded specimens where in, mixed type of bond failure was noted with air abraded and primed specimens. Conclusion: The metal primer was associated with an increase in the adhesive bonding of acrylic resins to irrespective of the metal alloys. The shear bond strength of heat cured acrylic resin to the Titanium alloy was significantly higher than to that of Cobalt-Chromium alloy.