Removing saliva contamination from porcelain veneers before bonding.

STATEMENT OF PROBLEM: Contamination of the fitting surfaces of porcelain veneers with saliva at the try-in stage is almost inevitable.
PURPOSE: This study used bond strength tests to examine the effect of salivary contamination on Scotchbond adhesive/composite luting material bond to porcelain and evaluated the effectiveness of various procedures used (acetone, phosphoric acid) to overcome such contamination.
MATERIAL AND METHODS: Bond strength test specimens were prepared with porcelain adherends. Surfaces of the adherends were cut flat, sandblasted, and divided into 12 groups, each of which received a different surface treatment. After bonding and storage for 24 hours, tensile bond strength values were measured on an Instron machine. Fracture modes were determined with a scanning electron microscope.
RESULTS: Salivary contamination of porcelain surfaces significantly reduced the resin cement-to-porcelain bond from 29.2 +/- 4.5 MPa to 10.3 +/- 4.5 MPa (P <.05). Silane applied to the porcelain, a few days before contamination, resulted in increasing the bond strength from 10.3 +/- 4.5 MPa to 29.9 +/- 8.1 MPa (P <.001). The most effective method of dealing with salivary contamination was by applying silane before the try-in stage and, after the try-in, the porcelain was treated with phosphoric acid for 60 seconds and a fresh layer of silane applied. The bond strength value achieved after this method was 45.0 +/- 9.0 MPa.
CONCLUSION: Contamination of porcelain surfaces with saliva is detrimental to the resin cement-to-porcelain bond. Of the many procedures investigated to overcome this contamination, the use of phosphoric acid to clean the contaminated surface was the most beneficial.