Marginal and internal discrepancies of zirconia copings: Effects of milling system and finish line design.
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Date
2015-01
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Abstract
Context: Discrepancies at the abutment/crown interface can affect the longevity of zirconia
restorations.
Aim: The aim was to evaluate the marginal and internal discrepancies (MD and ID) of zirconia
copings manufactured by two milling systems with different finish lines.
Materials and Methods: Three aluminum‑master‑dies (h = 5.5 mm; Ø =7.5 mm; 6°), with
different finish lines (large chamfer [LC]; tilted chamfer [TC]; rounded shoulder [RS]) were
fabricated. Twenty impressions were made from each master die and poured. Sixty zirconia
copings were manufactured and divided according to the factors “finish line” and “milling
system” (n = 10): CADLC = Computer‑aided design/computer‑aided manufacturing (CAD/
CAM) + LC; CADTC = CAD/CAM + TC; CADRS = CAD/CAM + RS; MADLC = manually aided
design/manually aided manufacturing (MAD/MAM) + LC; MADTC = MAD/MAM + TC; and
MADRS = MAD/MAM + RS. For MD analysis, each coping was fixed, and the distance between the
external edges of the coping and the edge of the cervical preparation was measured (50 points).
Using the same copings, the ID of each coping was evaluated, by the replica technique, at
12 points equally distributed among the regions (n = 10): Ray (R), axial (A), and occlusal (Occl).
The measurements were performed by optical microscopy (×250). The data (μm) were subjected
to parametric and non‑parametric statistical analyses.
Results: For the MAD/MAM system, the “finish line” (P = 0.0001) affected significantly
the MD median values (μm): LC = 251.80a, RS = 68.40a and TC = 8.10b (Dunn’s test). For
the CAD/CAM system, the median MD values (μm) were not affected by the factor “finish
line” (P = 0.4037): LC = 0.82a, RS = 0.52a, and TC = 0.89a. For the ID, it was observed interaction
between the finish line types and the region (P = 0.0001) and between region and milling
system (P = 0.0031) (RM‑ANOVA).
Conclusions: The CAD/CAM system presented lower MD values, regardless the finish line.
However, the MAD/MAM system showed ID values smaller than those of CAD/CAM.
Description
Keywords
Computer‑aided design/computer‑aided manufacturing system, internal discrepancy, manually aided design/manually aided manufacturing system, marginal discrepancy, replica technique
Citation
Ribeiro Isabella Lima Arrais, Campos Fernanda, Sousa Rafael Santiago, Alves Maria Luiza Lima, Rodrigues Dalton Matos, Souza Rodrigo Othavio Assunção, Bottino Marco Antonio. Marginal and internal discrepancies of zirconia copings: Effects of milling system and finish line design. Indian Journal of Dental Research. 2015 Jan-Feb; 26(1): 15-20.