Effect of several repair techniques on the bond strength between composite resin and degraded Y-TZP ceramic

Wandscher, Vinícius Felipe; Brondani, Luana; Pereira, Gabriel Kalil Rocha; Melo, Renata Marques de

Objective:

To evaluate the bond strength of different repair treatments for composite resin to aged Y-TZP ceramics. Material and

Methods:

Zirconia blocks were cut into smaller specimens, sintered according to manufacturer's recommendations (final dimensions of 4×4×3 mm), and randomly allocated into nine groups (n=15) according to the surface treatment and presence/ absence of aging of the substrate (subjected to lowtemperature degradation - LTD), as follows without LTD (Control without treatment; TBS tribochemical silica coating + silane + adhesive); with LTD (Control-LTD without treatment; TBS-LTD TBS with hydrothermal degradation; MoS-LTD Monobond S + adhesive; MoPLTD Monobond Plus + adhesive; MZP-LTD Metal/ Zirconia Primer + adhesive; USB-LTD Single Bond Universal; AP-LTD Alloy primer + adhesive). LTD was simulated in an autoclave (134 °C, 2 bar, 5 h). The ceramic blocks were embedded in PVC cylinders with a self-curing acrylic resin; each surface treatment protocol was performed; a composite resin cylinder ( 3.25 mm and height 3 mm) was then build-up using split metallic matrices. All the specimens were aged (thermocycling + storage in water for 90 days) and subjected to the shear bond strength test using a universal testing machine (1 mm/min). The failure mode was classified into four types adhesive, composite resin cohesive fracture, ceramic cohesive fracture, and mixed. The bond strength values were subjected to MannWhitney test.

Results:

Only air-abraded samples (TBS and TBSLTD) survived thermocycling. More than 80% of the samples of the other groups presented pre-test failures. TBS groups presented higher values of bond strength (3.94) compared to TBSLTD (0.96). The predominant type of failure for the surviving samples were adhesive.

Conclusion:

Air particle abrasion is mandatory to improve the bond strength of the Y-TZP substrate; an aged substrate presents an even more unfavorable scenario for adhesion. (AU)

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