design/computer-aided manufacturing (CAD/CAM) is becoming increasingly
integrated into dental practice workflow at a pace that exceeds
scientific validation. The aim of this study is to evaluate a complete
digital split-file protocol relative to segmental digital and analog
techniques for restoring a single maxillary anterior edentulous space
with custom abutment and crown.
Materials and Methods
treatment workflows were assessed: complete digital (CD), segmental
digital (SD), milled wax (AM), and heat pressed and hand waxed (AH) and
heat pressed. The CD workflow “split” an abutment and crown into
separate files to fabricate a zirconia abutment and both
zirconia/lithium disilicate crown restorations. The SD workflow scanned
the existing abutment for design of segmental restorations in zirconia,
lithium disilicate, and milled wax (AM). The AH specimens were
conventionally hand waxed. Both the AM and AH specimens were heat
pressed with lithium disilicate. All restorations were evaluated with
standardized measurements using scanning electron microscopy (SEM) as
manufactured without internal adjustments and after manual adjustment.
The number of adjustments, adjustment time, and location of adjustments
were recorded. One-way ANOVA with repeated measures was used to report
geometric means with 95% confidence intervals.
mean marginal gap after adjustment of the CD group was 69 μm, with an
upper bound (UB) of 79 μm and a lower bound (LB) of 60 μm. SD group mean
was 26 μm with an UB of 31 μm and LB of 22 μm. The AM group mean was 32
μm, with an UB of 49 μm and a LB of 20 μm; AH group mean of 26 μm with
an UB of 34 μm and a LB of 20 μm. The SD, AM, and AH workflows were
statistically similar (p = 1.000), and the CD workflow was statistically greater than the other three (p < 0.001).
split-file (CD) protocol results in marginal gap size within clinical
standards after adjustment; however, 52 of the 60 digitally produced
restorations showed a horizontal marginal offset that required
adjustment for proper contours.