Abstract
This study determinates the persistence of retention force in Akers-clasps for removable partial dentures made from Co-Cr alloy. Therefore, standardized computer-aided designed (CAD) clasp #1 specimens were made by direct metal laser melting (DMLM, n = 10) and by lost-wax dental casting (DC) of computer-aided manufactured (CAM) replicas (n = 10, DC) from two comparable Co-Cr alloys. The retention force was tested after manufacturing for 9000 cycles of setting and removal from a molar tooth crown analog made from zirconia; simulating in-vitro a duration of six years in service. The first and last 360 cycles (T0 and T1, 3 months each) of all specimens were selected for comparison of retention forces between the materials. A constant decrease of 6% from the initial retention force (T0 = 4.86 N, SD = 0.077; T1 = 4.57 N, SD = 0.037) was detected at the DC specimens, and an increase of 4% in DMLM specimens (T0 = 5.69 N, SD = 0.078; T1 = 5.92 N, SD = 0.077); all differences were statistically significant (p < 0.0001). Even if these deviations are not of clinical relevance, further studies and applications should investigate the fatigue behavior of laser melted Co-Cr-alloys for dental application.
Highlights
According to the standard DIN EN ISO 17296, generative manufacturing, known as “3D printing” or “additive manufacturing” (AM), is subdivided into deposition and binding approaches.The “deposition approach” means a thermosensitive material is heated or even melted and laid out in defined paths
Direct Metal Laser Melting (DMLM) is performed in a chamber containing a heatable building platform that can be moved in vertical direction to allow the layering
For dentistry or rather dental technology, DMLM of alloys allows us to overcome conventional lost-wax casting of metals as well as computer-aided design/ computer-aided manufacturing (CAD/computer-aided manufactured (CAM))-based subtractive fabrication of fixed or removable partial dentures, especially when it comes to complex designs such as combined solutions with patrices and matrices or even one-piece casted clasp-retained removable partial dentures (RPDs)
Summary
According to the standard DIN EN ISO 17296, generative manufacturing, known as “3D printing” or “additive manufacturing” (AM), is subdivided into deposition and binding approaches. DMLM is performed in a chamber containing a heatable building platform that can be moved in vertical direction to allow the layering. For dentistry or rather dental technology, DMLM of alloys allows us to overcome conventional lost-wax casting of metals as well as computer-aided design/ computer-aided manufacturing (CAD/CAM)-based subtractive fabrication of fixed or removable partial dentures, especially when it comes to complex designs such as combined solutions with patrices and matrices (such as telescopic crowns) or even one-piece casted clasp-retained removable partial dentures (RPDs). The present study was conducted in order to compare a DMLM procedure based on a digital workflow with a conventional dental casting of clasps, both from a non-precious cobalt-chromium alloy for RPDs. the study addresses the retention forces of clasps delivered from both fabrication methods, before and after a simulated wearing period of six years. There is no statistically significant difference in the retention force before and after a simulated wearing period of six years for the DMLM-fabricated and cast clasps
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