Testing rate and cementation seating load effects on resin-strengthening of a dental porcelain analogue

Objectives To determine the resin-strengthening dependence of a soda-lime-glass analogue for dental porcelain as a function of biaxial flexure strength (BFS), test crosshead rate and cementation seating load. Methods Disc-shaped soda-lime glass specimens were divided into twelve groups (n = 24), alumina particle air abraded and hydrofluoric acid-etched. Specimens (Groups A-D) were stored in a desiccator prior to testing at crosshead rates of 0.01, 0.1, 1 and 10 mm/min, respectively. The remaining specimens were silane treated, Rely-X Veneer resin-coated with a seating load of 5 N (Groups E-H) and 30 N (Groups I-L) prior to light irradiation at 480 ± 20 mW/cm², 24 h dry storage and BFS testing at 0.01, 0.1, 1 and 10 mm/min, respectively. A linear logarithmic regression curve was fit to the raw data to elucidate static fatigue effects of the soda-lime-glass. Analysis of group means was performed utilising a general linear model univariate analysis and post hoc all paired Tukey tests (P < 0.05). Results The linear logarithmic regression curve demonstrated the static fatigue effects of the soda-lime-glass analogue. Rely-X Veneer resin-coating (Groups E-L) resulted in significant increases in the mean BFS data for all crosshead rates examined (all P < 0.001). However, the pattern of rate dependence effects on resin-cementation deviated from the log relationship observed with the uncoated controls. Conclusion This study further highlights that when slow crack growth is simulated during testing, valuable insights into the significant modification of a hereto well described phenomenon such as resin-strengthening mediated by the resin-ceramic hybrid layer is provided. © 2013 Elsevier Ltd.