An Experimental Thermally Deposited Coating for Improved Bonding to Glass-fiber Posts

To determine whether an experimental thermally deposited siloxane-methacrylate coating for use in industrial scale applications would improve the bond strength of resin-based materials to glass fiber posts (GFPs) without affecting their mechanical properties.

An experimental 5% (w/v) solution of methacryloxypropyltrimethoxysilane was prepared. Two types of GFPs (Exacto, Angelus; White Post DC, FGM) were divided into the following groups: S: silane; SA: silane and adhesive; HS: 35% H₂O₂ and silane; HSA: 35% H₂O₂, silane and adhesive; Exp: siloxane-methacrylate coating (Si-O) via post immersion in experimental solution followed by heating; Exp-S: silane after Si-O treatment; Exp-A: adhesive after Si-O treatment; and Exp-SA: silane and adhesive after Si-O treatment. The posts were positioned in a mold to allow insertion of a dual-curing resin core, serially sectioned into beams, and subjected to microtensile bond strength (μTSB) testing. The three-point bending test and SEM/EDX analysis were used to assess the mechanical and surface properties of untreated GFPs that were etched with H₂O₂ or treated with Si-O.

Surface treatments affected the μTSB only for the Exacto GFPs. The highest μTBS (MPa) was observed in Exp-S and Exp-SA groups, whereas H₂O₂ etching resulted in intermediate values. The mechanical properties were not affected by surface treatments. Exacto GFPs had significantly higher flexural strength (σf) and flexural modulus (Ef) than did the White Post DC GFPs, but the latter were significantly stiffer (S) than Exacto, regardless of the surface treatment tested. H₂O₂ promoted morphological changes in post surfaces. The experimental treatment promoted deposition of Si onto the post surface, improving bond strengths of Exacto posts.

The proposed novel coating technique is a viable procedure for fiber post manufacturers to improve the μTSB of resin-based materials.