A new technique for incorporation of TiO2 nanotubes on a pre-sintered Y-TZP and its effect on bond strength as compared to conventional air-borne particle abrasion and silicatization TiO2 nanotubes application on pre-sintered Y-TZP

Abstract

Objective: This study evaluated the microshear bond strength of a resin cement to Y-TZP after different methods of TiO₂ nanotubes (nTiO₂) incorporation on pre-sintered Y-TZP surfaces.

Methods: nTiO₂ were synthesized and incorporated on Y-TZP slices as follows (n = 15): 1) nTiO₂ mixed with isopropyl alcohol/manual application (MAl); 2) nTiO₂ mixed with acetone/manual application (MAc); 3) nTiO₂ mixed with isopropyl alcohol/high-pressure vacuum application (HPVAl); 4) nTiO₂ mixed with acetone/high-pressure vacuum application (HPVAc). As controls, surfaces were sandblasted with Al₂O₃ (OX) or Rocatec silicatization (ROC). All ceramics were sintered after nTiO₂ incorporation. Surface treatments of OX and ROC were made after sintering. Surfaces were characterized by confocal laser microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Resin composite cylinders (1.40 mm diameter and 1 mm height) were cemented with a resin cement, stored in water at 37 °C for 24 h and thermocycled for 10 000 cycles before microshear bond strength evaluation. Data were analyzed with one-way ANOVA and Games-Howell (α = 0.05), and fracture analysis was performed using a stereomicroscope.

Results: EDS confirmed the presence of TiO₂ on treated Y-TZP. The confocal analysis showed higher roughness for HPVAc and OX. There were significant differences between surface treatments (p < 0.001). HPVAl (22.96 ± 10.3), OX (34.16 ± 7.9) and ROC (27.71 ± 9.4) showed higher microshear bond strengths and were statistically similar (p > 0.05). MAC showed intermediary values, and HPVAc and MAl presented decreased bond strength, with a high percentage of premature debonding.

Conclusion: High-pressure vacuum application of nTiO₂ mixed with isopropyl alcohol was able to produce bond strength values compared to conventional air abrasion and Rocatec silicatization.

Significance: The infiltration of TiO₂ nanostructures on the pre-sintered Y-TZP is an interesting approach that can improve bond strength without the need of sandblasting methods.

Keywords: Dental ceramics; Nanotechnology; Shear bond strength; Zirconia.