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Statement of problem. Although resin materials and additive manufacturing (AM)
technologies have been evolving rapidly, they still present limitations compared with
subtractive manufacturing (SM). These limitations become particularly relevant in
prefabricated abutments with detailed retentive geometries, where minor deviations
can compromise the fit and retention of the restoration.
Purpose. The aim of this in vitro study was to compare the accuracy (trueness and
precision) of the SM and 2 AM methods to produce single implant-supported crowns.
Material and methods. Implant-supported crowns with prefabricated abutments (RC
Variobase for Crown; Institute Straumann AG) simulating a mandibular first molar were
manufactured using 3 manufacturing methods: digital light projection (DLP),
stereolithography (SLA), and SM, with 15 specimens per group. The accuracy was
evaluated using an intraoral scanner to generate a standard tessellation language
(STL) file and a metrology software program to compare both STL files: the original
design with the manufactured crown. Root mean square (RMS) deviations and
color maps were generated to quantify deviations. Kruskal–Wallis with Bonferroni-
adjusted Mann–Whitney and Friedman with Bonferroni-adjusted Wilcoxon tests were
used to analyze the data (a=.05).
Results. The SM group demonstrated higher trueness and precision than SLA (P<.001
and P<.001 respectively) and higher trueness and precision than DLP (P<.001 and P<.001
respectively). The DLP group showed lower trueness at the margin region than SLA
(P<.001) and SM (P<.001). The DLP also had lower precision at the margin region
than SLA (P<.001) and SM (P<.001).
Conclusions. The SM group showed the highest accuracy, DLP the lowest, especially
at the margin region. All methods demonstrated intaglio accuracy values within ranges
previously associated with clinically acceptable internal fit.