Fluoroalkylethyl silane coating as a moisture barrier for dental ceramics

The performance of dental ceramics is reduced in wet environments due to stress-corrosion limiting restoration lifetime. As analysis suggests that fracture is typically initiated from the internal surface, placement of a thin coating before a restoration is cemented to place may prevent fracture if it acts as a moisture barrier. Of coatings we tested, a fluoroalkylethyl silane (du Pont MPD-7680) showed promise. This study aimed to test a range of concentrations on glass and to determine any strength improvement on dental ceramics. Glass slides (n = 8-9) were indented (29-N load) stored 24 h, etched, coated with 100, 50, and 25% fluorosilane in isopropyl alcohol, and air-cured for 24 h. The slides were fractured on a biaxial fixture in water at 0.5 mm/min and maximum stresses calculated. Uncoated controls were tested in water and liquid N2 to determine the inert strength without stress-corrosion. Results showed increasing mean strength from uncoated (53.6 MPa) to 100% (68.0 MPa) which compared to the 80.4 MPa inert strength. ANOVA showed P < .05. Subsequently the experiment was repeated on discs of three dental ceramics (n = 7-10): feldspathic (Ceramco), glass-ceramic (Dicor MGC), high-leucite (Optec) with the 100% solution only. Mean strength was significantly (P < .01) enhanced in the feldspathic (56.2 MPa, untreated, 70.7 MPa, treated) but not the high-leucite (83.1, 83.0) or the glass-ceramic (283.9, 271.4). Fluoroalkylethyl silane coating reduced stress-corrosion in glass and feldspathic porcelain. It may be a practical approach to reducing fracture of ceramic restorations.