[The service life of Cerec abrasive disks]

The aim of this study was to evaluate the efficiency of Cerec CAD-CAM grinding discs coated with a standard (StD) and experimental (FeD) diamond pattern using 126 microns and 91 microns diamond grain sizes on each coating. The four types of grinding discs (StD126/91, FeD126/91) were used to mill the same standard mod inlays from blocoff+ (10 x 12 x 15 mm) of feldspathic porcelain (Vita) vs. Dicor MGC glass ceramic (Dentsply). The millings were performed on 12 Cerec units (Siemens) simultaneously for each combination of type of disc and type of material. Using porcelain, the discs milled the following median numbers of inlays: StD126: 6.3, StD91: 3.5 (p less than 0.01) and FeD126: 9.5, FeD91: 8.4. The milling efficiency of FeD91 was significantly (p less than 0.001) higher than that of StD126. Damaging effects on inlay margins were observed; degree 0: StD126 = 35% and FeD126 = 25%; degree 2: StD126 = 10% and FeD126 = 25%. Using Dicor MGC glass ceramic the median number of milled inlays was generally low (StD126: 4.0, StD91: 1.0, FeD126: 3.0, FeD91: 2.0). Damaging degree 3 occurred as follows; StD126 = 2.1%; FeD126 = 4.3%; FeD91 = 0.8%. Concluding from the observed milling efficiency and damaging effects, the standard disc StD126 was judged to offer the best compromise for milling both glass ceramic and porcelain material.