Marginal Fit of Milled Copings Utilizing Digital Scanners

Objectives: To evaluate marginal fit of copings with different finish line designs fabricated with various digital scanners and milling systems and to investigate the scanner ability to read varying depths accurately.

Methods: Three model teeth were prepared with three finish line designs: Design 1: Chamfer; Design 2: chamfer with shallow depression in one aspect of finish line; Design 3: chamfer with a deep depression.

"Master" dies were replicated using elastomeric impressions and type IV stone generating 10 dies per design. Dies were scanned and copings were milled utilizing three digital scanners and CAD-CAM systems: System-1: InEos Red (Sirona) & Vitablocks Mark II (VITA) copings milled by Cerec-inLab (Sirona); System-2: Cerec BlueCam (Sirona) & Vitablocks Mark II (VITA) copings milled by Cerec-inLab (Sirona); system-3: NobleProcera Optical Scanner & Procera zirconia copings milled by Noble Procera milling machine. Copings were seated on their respective "master dies" clamped with uniform force. Eight measurements per coping were performed (Zeiss Metallurgical microscope, 200X magnification) at pre-established points, including depressions in designs 2 and 3.

Results: Mean marginal gaps (microns) are displayed in histograms below. Data were subjected to one-way ANOVA (α=0.05).

Conclusions: Significant difference was found among the three systems for marginal fit (p<0.0001) with System-3 exhibiting significantly smaller marginal gaps. There was a significant difference in fit between design 2 and 3 preparations for all systems. However, marginal gaps for all systems tested were clinically acceptable.