Comparison of Fit of 3-axis and 5-axis milled Zirconia Abutments

Objectives:

CAD/CAM manufactured zirconia abutments offer custom design for each individual patient and improved esthetics and have become an attractive solution for implant cases. Fully machined abutments increase the productivity because there are less manual steps necessary than using prefabricated abutments. In order to mill angulated abutments with a CAD/CAM-system, a 4- or 5-axis milling machine is necessary. Otherwise the abutments need manual finishing afterwards. However, due to higher requirements of kinematics and accuracy, 5-axis machining is more challenging as compared to 3-axis. The purpose of this study was to investigate, whether angulated abutments using 5-axis milling (ANG5X) can be manufactured by a dental CAD/CAM system with the same precision like straight abutments using 3-axis milling (STR3X).

Methods:

ANG5X and STR3X for titanium-bases Camlog_43 and Neoss_RP were milled 5 times on the Lava™CNC500 (3M ESPE). After manufacturing the fit on the titanium-bases was assessed by 2 dental technicians with a ranking scale from 1 (poor) to 5 (perfect fit) resulting in 20 data points each. In addition the inner diameter at the bottom side of the Neoss_RP-Abutments was measured using an Inductive Dial Comparator (Mahr GmbH).

Results:

The following table lists the means and standard deviations (in brackets) of the ranking and of the measured diameters:

There is no significant difference between the 3-axis and the 5-axis versions (Mann-Whitney Test, p>0.05).

Conclusions:

Customized angulated abutments produced with the Lava™-System with 5-axis milling have the same fit like straight abutments produced with 3 axis milling.