Comparison of Conventional and Novel Dual-surface Pretreatment-method for Titanium

Abstract

Objectives: This laboratory study compared and contrasted effects of conventional grit-blasting+acid-etching treatment and novel dual-surface-treatment (acid-etching+silica-coating). Surface chemistry of titanium, surface roughness(Ra), topography and enclosed-mold-micro-shear bond strength(EM-µSBS) were assessed. Methods: Planar polished-c.p grade-2 Ti-specimens(n=168),10.0mmx10.0mmx1.0mm were randomly assigned to sub-groups. Polished-only-titanium was control(n=12). 96 were acid-etched with 9%HF or 12%HF, blends of 35%HCl-85%H3PO4 and 69%HNO3-35%HCl (60°C, 2min), and 48 of them were further silica-coated (Rocatec™Plus;110µm-silica-coated-alumina powder). 60 original Ti-specimens were silica-coated, followed by 48 acid-etched with acids/blends used. SEM,AFM,EDX,XPS and Ra analyses were conducted. All Ti-specimens were silanized with experimental-silane-primer 1.0vol%-3-acryloxypropyltrimethoxysilane(ACPS)+0.3vol%-1,2-bis-(triethoxysilyl)ethane(BTSE). For EM-µSBS testing 6 resin-cement (Multilink™ Automix) stubs were prepared and light-cured on Ti-specimens and tested after storage in water: 1 day, 1,4 and 8 weeks. One-way-ANOVA was used for mean Ra and EM-µSBS, and two-way-ANOVA to EM-µSBS. Bonferroni post-hoc multiple-comparisons were applied to mean values of Ra and EM-µSBS. Statistics software SPSS™ Version 24.0 was used for statistical analysis with value of significance p=0.05. Results: EDX indicated highest [Si] and [Al] after silanization and highest EM-µSBS values for Ti-specimens acid-etched plus silica-coated. EDX analysis found [Si]=10.86%–22.06%, [Al]=7.60%–15.21%. EM-µSBS on day-1 was from 23.4MPa±0.0MPa-to-37.8MPa±0.0MPa, week-8 from 12.4MPa±0.2MPa-to-27.4MPa±0.2MPa. Gradual decrease in EM-µSBS values was observed after water storage with adhesive failure. Ra was highest for all HF acid-etched specimens, from Ra=1.5µm±0.1µm to 3.1µm±0.1µm. SEM and AFM imaging supported Ra values. XPS analysis showed different chemical shifts for surface modifications. After HF-etching Ti4+,Ti3+,Ti2+,Tio,Si4+,Si3+ and Si2+ were identified. Conclusions: Novel dual-surface modification (acid-etching+silica-coating) increases [Si] on Ti-surface, and after silanization enables chemical bond with resin-cement. HF etching creates a variety of Ti and Si species on silica-coated Ti. This novel method might provide durable adhesion.