Silanation Enhancement for High Strength Dental Ceramics

Objective: To develop a practical method to chemically modify the surface of high strength dental ceramics (alumina and zirconia) to facilitate viable, robust adhesive bonding using commercially available silanes and resin cements.

Methods: Initial investigations focused on functionalizing alumina and zirconia surfaces with an ultra-thin Si-based layer (1-10 nm thick) allowing for silane treatments to tether hydro-carbons.  These hydro-carbon groups are a common reactant with arcylate-based resins allowing for strong covalent bonding between a dental prosthesis and the underlying structure (dentin/enamel, implant abutment).  As a proof of concept, several planar test structures, consisting of dental porcelain, alumina, and zirconia, were prepared, treated, and analyzed, before and after Si-O modification, using x-ray photoelectron spectroscopy (XPS).

Results: Preliminary investigations show that surface pretreatments can chemically modify the surface of high strength ceramics (alumina and zirconia), suggesting a promising pretreatment for silanation.  XPS investigations detailed that the pretreatment process deposited a monolayer of Si on the surface.  A commercially available organo-silane coupling agent (monobond^TM (MB)) was then applied to the treated surface.  High resolution core scans of the C(1s) and Si(2p) supports the successful chemical bonding of the organo-silane to the Si-O-treated surface.  Chemical concentration data from XPS relative intensity analysis is summarized in Table 1, below. 

Zirconia	O	C	Si	Zr
Si-O pretreatment	54.28	8.00	7.94	29.78
Pretreatment /MB	40.65	35.61	8.11	15.63
Alumina				Al
Si-O pretreatment	56.67	7.40	6.11	29392
Pretreatment /MB	40.00	38381	6.15	15.05

Table 1 - Elemental atomic percentages as calculated

Conclusions: Preliminary data support the chemical attachment of an ultra-thin, 1-10 monolayer, Si-O film on both zirconia and alumina substrates.  Further analysis will included mechanical properties analyses to assess the quality of the intermediate bonding pretreatment layer. Research was supported by NIH/NIDCR grant DE13511-04. Materials contributed by Ivoclar Vivadent.