Accuracy evaluation of metal copings fabricated by computer-aided milling and direct metal laser sintering systems.
OBJECTIVE
To assess the marginal and internal gaps of the copings fabricated by computer-aided milling and direct metal laser sintering (DMLS) systems in comparison to casting method.


METHODS
Ten metal copings were fabricated by casting, computer-aided milling, and DMLS. Seven mesiodistal and labiolingual positions were then measured, and each of these were divided into the categories; marginal gap (MG), cervical gap (CG), axial wall at internal gap (AG), and incisal edge at internal gap (IG). Evaluation was performed by a silicone replica technique. A digital microscope was used for measurement of silicone layer. Statistical analyses included one-way and repeated measure ANOVA to test the difference between the fabrication methods and categories of measured points (α=.05), respectively.


RESULTS
The mean gap differed significantly with fabrication methods (P<.001). Casting produced the narrowest gap in each of the four measured positions, whereas CG, AG, and IG proved narrower in computer-aided milling than in DMLS. Thus, with the exception of MG, all positions exhibited a significant difference between computer-aided milling and DMLS (P<.05).


CONCLUSIONS
Although the gap was found to vary with fabrication methods, the marginal and internal gaps of the copings fabricated by computer-aided milling and DMLS fell within the range of clinical acceptance (<120 µm). However, the statistically significant difference to conventional casting indicates that the gaps in computer-aided milling and DMLS fabricated restorations still need to be further reduced.
Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, Republic of Korea.
Jong-Kyoung
0000-0001-7508-7823
JK
Park
Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, Republic of Korea.
Wan-Sun
WS
Lee
Department of Public Health Science, Graduate School & BK21+ Program in Public Health Science, Korea University, Seoul, Republic of Korea.
Hae-Young
0000-0003-2043-2575
HY
Kim
Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, Republic of Korea.
Woong-Chul
WC
Kim
Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, Republic of Korea.
Ji-Hwan
0000-0003-3889-2289
JH
Kim
CAD/CAM system; Cobalt-chromium alloy; Computer-aided milling; Direct metal laser sintering; Marginal and internal fit