Accuracy of three digital workflows for implant abutment and crown fabrication using a digital measuring technique

The accuracy of a full digital workflow using an Atlantis abutment and a milled zirconia crown; a full digital workflow with a 3Shape split-file workflow using a zirconia abutment and crown; and an interrupted digital workflow using an Atlantis abutment and a milled zirconia crown is unclear.

The purpose of this in vitro study was to compare 2 full digital workflows relative to an interrupted workflow for restoring an implant with a custom abutment and crown. The secondary purpose of this study was to validate a digital means of measuring internal fit and marginal discrepancy using engineering software programs.

Three workflows were evaluated. The first group, interrupted digital Atlantis (IDA) workflow, included a customized Atlantis abutment that was designed, received, and then rescanned for the definitive crown design. The second group, full digital Atlantis (FDA) workflow, included a customized Atlantis abutment and its corresponding standard tessellation language (STL) file, the Atlantis Core File, which was immediately imported into design software and used for crown design and milling. The third group, full digital split-file (FDSF) workflow, used 3Shape's full digital workflow for abutment and crown design called the split-file workflow, in which the crown and abutment were designed and milled simultaneously. All restorations were evaluated with standardized measurements using a scanning electron microscope (SEM) for 2D measurements, followed by standardized measurements using Geomagic Control, an engineering software program, which facilitated 3D evaluations of the specimens.

The 2 Atlantis workflows, IDA and FDA, had statistically smaller marginal openings (P=.002) than the FDSF when measured using 2D SEM. The FDA had a statistically smaller 2D SEM marginal gap than the other 2 groups, IDA (P=.002) and FDSF (P=.002). The FDA had a statistically smaller 3D Geomagic marginal gap than the other 2 groups, IDA (P=.004) and FDSF (P=.006). The FDSF had a statistically smaller 3D Geomagic internal fit than the other 2 groups, FDA and IDA (both P=.006).

All 3 workflows evaluated in this study showed clinically acceptable results in terms of mean marginal gap below 120 μm. The SEM evaluation of mean marginal opening revealed that IDA and FDA mean marginal openings were statistically smaller than the FDSF mean marginal opening. SEM and Geomagic measurements revealed that the FDA mean marginal gap was significantly smaller than IDA and FDSF mean marginal gaps. Geomagic evaluation of mean internal fit revealed that the FDSF was significantly smaller than IDA and FDA. The use of Geomagic to measure and evaluate mean marginal gap and mean internal fit as defined in this study proved to be an acceptable form of measurement with statistical validation.