Objectives: CAD/CAM fabricated zirconia frameworks are known to be a basis for clinically successful restorations. To guarantee good fit a high accuracy of the optical scanning device typically used within the CAD/CAM process is essential. Accuracy and the scanlength are often contradictory parameters with such devices. In this study the accuracy of a new 3M ESPE LAVA scanner (ST, scanlength=51mm) was investigated with respect to its predecessor (LS, scanlength=38mm). Methods: 5 different stone models for bridge cases of a spanwidth >40mm have been investigated. With all cases stumps not only at the ends of the bridges but also somewhere in-between were present. This allowed scanning first the cases with LS in two successive steps with a lateral shift of the models in-between in order to capture the full situation and matching secondly the two data sets together at the central stump, which has been captured by both scans. The resulting data were then overlaid by best-fit algorithms to a single scan obtained from ST, which did capture the full case due to the enlarged scanlength in one step. The distances of 10 arbitrarily selected spots on each distal surface of the outer stumps at the LS surface to the surface obtained with ST were computed. The mean distances (MD) for each case were compared to the MD from a reference test, which was obtained from overlaing LS and ST data from a single stump scanned in the center of the scanwindows of both scanners. The MD were compared using ANOVA (p<0.01). Results: The distal MD for the investigated cases were (µm): 6.1+/-2.6, 5.5+/-2.0, 4.7+/-3.1, 6.2+/-3.3, 4.2+/-3.2. None of them was statistically significant different from the reference (4.1+/-2.0). Conclusions: With the larger scanlength of ST no significant effect on the accuracy as compared to LS was found.

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