Comparison of Marginal Fit of Zirconia Copyings Milled with 4-Axis and 5-Axis Milling Machines

Purpose: To compare the marginal fit accuracy of zirconia crown copings milled with 4-axis and 5-axis milling machines. Materials and Methods: Ten zirconia crown copings were milled on 4-axis milling machine and 5-axis milling machine by taking a single die. The crown copings were seated on the master die and high resolution photographs were made of the marginal area of crown copings by using GOM INSPECT V8. The marginal openings were then measured using a calibrated digital software program. Results: The marginal gap was 4-axis milled crown copings: 0.05-0.10mm; 5-axis milled crown copings: 0.06-0.09mm. There was a statistically significant difference between the 4-axis milled crown copings and 5-axis milled crown copings. Conclusions: There was negligible difference between the crown copings manufactured by the same type of milling machine. The external marginal fit is nearly same for both type of crown copings. Achievement: From comparison of marginal fit of crown copings milled on 4-axis and 5-axis milling machine, it was observed that the marginal gap for both 4-axis and 5-axis milled crown copings demonstrated within acceptable discrepancy range but the 5-axis milled crown copings resulted in smaller vertical marginal gaps than 4-axis milled crown copings.