Marginal fit of porcelain crowns with galvanized frames

Twenty extracted premolars were prepared for artificial crowns with a beveled shoulder. Ten porcelain-fused-to-galvanized-gold (PFGG) and ten porcelain-fused-to-metal (PFM) crowns were made according to the manufacturer's instructions by independent experienced dental technicians. Six sites per crown were selected for analysis. Photographs of these regions were projected on a screen for a total magnification of x 120. After cementation, the crowns were sectioned in the mesio-distal direction. The polished sections were analyzed for marginal accuracy and thickness of the cement. Measurements were recorded using the procedures described above. Before cementation, PFGG crowns exhibited primarily overextended margins, while 80% of the PFM crowns revealed short margins. The PFM crowns depicted a significantly smaller marginal gap (36 microns) than the PFGG crowns (53.7 microns). After cementation, the difference in the marginal gap was not statistically significant. The assessment of the thickness of the cement resulted in a significantly thinner cemental layer for the PFM crowns (PFM 40.2 microns, PFGG 48.5 microns). Although the results of this study demonstrated a diminished marginal gap and cement line for PFM crowns, this difference is too minimal to be clinically significant.