Objectives: The quality of CAD/CAM produced restorations highly depends on the accuracy of the CAD/CAM process. This accuracy is clinically expressed in the marginal fit. On the other hand there is a strong demand for high productivity of such systems with the scanning time as key factor.
The aim of this study was to determine the marginal fit of Lava™ Zirconia (LZ) frameworks processed with the LAVA system (LS, 3M ESPE) based on digitized data acquired by a new scanning device (NS). With the NS the scanning time was reduced by 50 %.
Methods: Frameworks of 4 different clinical situations of 4 splinted crowns and 3-unit bridges were manufactured out of Zirconia by means of the LS and scanned with NS. After manufacturing the copings were cemented on the scanned dies and embedded into acrylic. Specimens were sectioned faciolingually and mesiodistally. A stereomicroscope and a special analyzing software (analysis, Soft Imaging -System GmbH) were used for the determination of marginal opening (MO) and absolute marginal opening (AMO) of the cross-sections for each abutment. The means and standard deviations of all data (n=36) were determined.
Results:
K = abutment, B = pontic MO (µm) AMO (µm)
KKKK 24+/-10 56+/-29
KBK 20+/-5 55+/-35
The data show values comparable and better, respectively, than the literature (Tinschert et. al 2001, Boenig et. Al. 2000, May et. al 1998, Beuer et. al 2003). The 4 splinted crowns and the 3-unit bridges showed no significant difference in MO and AMO (2 sample t-test; p>0,05) and no difference compared to the old scanning device (Lava Scan) were determined (IADR 2005, #1764).
Conclusions: The NS showed an excellent marginal fit for 4- and 3- unit bridges. The faster scanning time of the NS also increases the productivity of the CAD/CAM system.