Effect of thermo-mechanical cycling on the shear bond strength of porcelain to milled and cast cobalt-chromium alloys

Abstract

Statement of problem: Most of the failures in metal-ceramic restorations occurs at the interface between the two materials. For long term clinical performance, these restorations should have adequate bond strength between metal and ceramic. Few data is available in regards to the metal-ceramic bond strength of Cobalt Chromium (Co-Cr) alloys fabricated by computer aided designing design/computer aided manufacturing CAD/CAM technology. Purpose of the study: The purpose of this in vitro study was to explore the influence of Co-Cr fabrication techniques on shear bond strength of porcelain to milled and cast Co-Cr alloys and to evaluate failure mode with & without thermo-mechanical cycling. Materials & Methods: A total of 20 disc samples (10 mm diameter x 4 mm thickness) were fabricated of Co-Cr alloy and divided into two groups (10 discs each) according to their fabrication technique: Group I: fabricated by CAD/CAM milling and Group II: fabricated by conventional casting. Then porcelain build up for all discs (10 mm diameter x 2mm thickness) was done using feldspathic porcelain. Each group was subdivided according to discs' exposure to thermomechanical cycling into two subgroups (5 discs each). Subgroup A : without thermo-mechanical cycling and Subgroup B: with thermo-mechanical cycling. All the disc samples were subjected to the shear bond strength (SBS) test and the failure mode was investigated under digital microscope at 40 X. Data were statistically analyzed using Independent sample t-test and Two-way ANOVA test (P ≤ 0.05). Results: The results showed that the fabrication techniques were statistically insignificantly affecting the SBS of both CAD/CAM milled and conventional casting groups. Regarding the thermo-mechanical cycling, the CAD/CAM milled and conventional casting groups without thermo-mechanical cycling showed a statistically significantly higher SBS than those with thermomechanical cycling. Failure mode was mixed type for all disc samples. Conclusions: Fabrication technique of Co-Cr alloy had no significant effect on SBS. Thermomechanical cycling of milled and cast Co-Cr samples significantly affecting SBS with the superiority of the non-thermo-mechanical cycled samples. All the tested samples showed SBS values within the clinically acceptable levels. CAD/ CAM fabricated Co-Cr may be considered a promising alternative to conventional cast Co-Cr for metal ceramic prosthesis in terms of SBS.

The resin bond to high‐translucent zirconia—A systematic review

“…To date, there is little consensus about the specific aging parameters. However, a combination of thermal and mechanical load cycling may best simulate intra‐oral conditions 171 . The mechanical loading mimics chewing forces while thermocycling subjects the test specimens to sudden changes in temperature, which causes repetitive contraction‐expansion stresses to resin cements 172,173 .…”

“…However, a combination of thermal and mechanical load cycling may best simulate intra-oral conditions. 171 The mechanical loading mimics chewing forces while thermocycling subjects the test specimens to sudden changes in temperature, which causes repetitive contraction-expansion stresses to resin cements. 172,173 And lastly, exposure in a wet environment subjects the applied materials to hydrolysis.…”

Bond Strength of Porcelain Fused to Casting and Selective Laser Base Metal Alloy with a Bonding Agent

“…In this study, a total of 40 disc samples (10 mm diameter x 4 mm thickness with ring base (12 mm diameter x 1 mm thickness) [5]were fabricated of Co-Cr alloy for casting (Adentatec, Germany) and for SLM (Mediloy ® S-Co BEGO , Germany) then divided into two groups (20 discs for each group) according to their fabrication technique and addition of vita bonding agent as follows:…”

“…Group A (n =10): There was no use of bonding material. Then, porcelain build-up for all discs (10 mm diameter x 2 mm thickness) was done using feldspathic porcelain [5], Fig. 1.…”

“…The specimen mounting, as well as the one-of-a-kind testing device, which consists of the lower part stationary and upper part sliding stainless steel pieces, are shown in Fig . 4, 0.5 mm/min cross-head speed, the upper part of the device slides down the grooves of the stationary part, loading the PFM interface until fracture done [5]. The values of the SBS were kept track of.…”