Post-thermocycling shear bond strength of a gingiva-colored indirect composite layering material to three implant framework materials

Fatigue behavior and damage modes of high performance poly-ether-ketone-ketone PEKK bilayered crowns

OBJECTIVES

To evaluate and compare the fatigue behavior (fatigue limit and fatigue life) and damage modes of high-performance poly-ether-ketone-ketone (PEKK), zirconia and alloy bilayered crowns.

MATERIALS AND METHODS

A total of 110 crowns (n = 50 for fatigue limit and n = 60 for fatigue life) were fabricated and used in this study. Pekkton® ivory discs, yttrium stabilized zirconia blanks and NiCr casting alloy were used to produce the respective PEKK, zirconia and alloy copings for crown fabrication. The prepared crowns were veneered with composite resin and subjected to fatigue tests. The fatigue limit was evaluated using the staircase method and the fatigue life of the samples was evaluated by subjecting the crowns to a load lower than the fatigue limit of that particular group, and also with an intermediate load of 522 N. A graphical plot was generated from the shape parameter (β) and life parameter (α) values obtained through the Weibull analysis method. Kruskal-Wallis and Mann-Whitney tests were applied to determine the significance differences in the recorded fracture mode between the study groups. The damage modes of the samples were assessed using Burke's classification.

RESULTS

The recorded fatigue limits of the groups were 442.8 ± 42.1 N, 608.7 ± 7.6 N, and 790.4 ± 29.2 N for zirconia, NiCr and PEKK, respectively. A significant difference in the fatigue limit of the groups was observed (p < 0.05). PEKK samples demonstrated the highest survival cycles of 1,170,000 and the lowest survival cycles was observed with zirconia samples at 100,000 under 522 N loading. The fracture modes in PEKK samples were largely distributed between code 1 and 2 whereas the fracture modes in NiCr group was distributed between code 1 and 4 and YZ crowns exhibited more of code 5 fractures. The difference in fracture modes among the groups was statistically significant (p < 0.05).

CONCLUSION

The PEKK group demonstrated better results compared to zirconia and NiCr based crowns. The PEKK group demonstrated high fatigue limit and survived the highest fatigue life cycles among the tested groups.

Effects of Different Surface Treatments on Bond Strength of Resin Cement to Machined Pure Titanium

PURPOSE

To investigate the effects of grit blasting, acidic or alkaline/heat treatments, and metal primer application on the shear bond strength (SBS) of resin cement to machined commercially pure titanium (CP-Ti).

MATERIALS AND METHODS

Titanium plates were machined and received one of the following treatments: grit-blasting (GB), or grit-blasting followed by either acidic treatment (GB/AC) or alkaline/heat treatment (GB/AH). The specimens were randomly divided into 4 groups and treated with Rely X Ceramic Primer (RCP), Z Prime Plus (ZPP), and Alloy Primer (ALP), or without primer as the control. The pairs of titanium plates were cemented together with the Rely X Unicem cement. SBS was measured before and after thermocycling between 5°C and 55°C for 5000 cycles.

RESULTS

SEM observation showed that honeycomb-shaped pores formed on the surface of machined CP-Ti after GB/AC treatment, whereas a uniform net-like pattern formed after GB/AH treatment. In descending order, the surface roughness was GB, GB/AC, and GB/AH. The GB/AH group showed the highest SBS among all the treatments. As for primers, ALP group showed the highest SBS, while the RCP group showed the lowest. GB followed by ALP presented the highest SBS.

CONCLUSION

A fine, uniform network structure was formed on the surface of CP-Ti following GB/AH treatment, providing an effective micromechanical interlocking mechanism for resin bonding. At the same time, after AH treatment, the -OH formed on the surface of the machined CP-Ti triggered a chemical reaction with the acid monomers in the resin adhesives, creating a chemical bond. As a result, GB/AH treatment significantly improved the bond strength relative to GB/AC treatment. In addition, ALP treatment facilitated the formation of hydrogen bonds, which further improved the chemical bond strength. Finally, the combination of the effects mentioned above resulted in the most robust bond between machined CP-Ti and the resin adhesives.