Abstract
This in vitro study was designed to investigate whether conventionally produced casts and printed casts for prosthodontic purposes show comparable full-arch accuracy; a ceramic reference cast with inlay and crown preparations was fabricated. Ten gypsum casts were fabricated from conventional silicone elastomeric impressions. Ten digital impressions [IOS] of the reference cast were obtained by an intraoral scanner to fabricate 3D-printed resin casts. The ceramic reference cast, the gypsum, and the printed casts were digitized by an industrial structured light scanner (ILS) and provided as stl files. To evaluate absolute mean trueness values, the digitized gypsum casts [CON], digitized printed casts [PRINT], and [IOS] were superimposed with the digitized ceramic reference cast [REF]. Additionally, each [IOS] scan was compared with its corresponding [PRINT]. The precision was calculated for [CON], [IOS], and [PRINT]. The Mann–Whitney U test for independent samples and the Wilcoxon test for connected samples were performed (p ≤ 0.05). As absolute mean deviation trueness values were obtained: 69 ± 24 µm for [REF]-[CON], 33 ± 4 µm for [REF]-[PRINT], and 19 ± 3 µm for [REF]-[IOS]. The superimposition [IOS]-[PRINT] revealed 38 ± 6 µm. The precision was 74 ± 22 µm for [CON], 32 ± 10 µm for [PRINT], and 15 ± 4 µm for [IOS]. With respect to the workflow, the trueness values of [REF]-[CON] and [REF]-[PRINT] differed significantly. Within the digital workflow, [REF]-[PRINT], [REF]-[IOS], and [IOS]-[PRINT], all values differed significantly. Within the limitations of the study, digital impression and printed cast fabrication were more accurate and reproducible than the conventional workflow.
Highlights
If comprehensive fixed prosthetic rehabilitations are manufactured based on intraoral optical impressions, there are several reasons for the necessity to produce real casts
This in vitro study was designed to investigate whether conventionally produced casts and printed casts for prosthodontic purposes show comparable full-arch accuracy; a ceramic reference cast with inlay and crown preparations was fabricated
Within the limits of this study, the following conclusions were drawn: The printed casts obtained from a digital light processing (DLP) printer revealed significantly better full-arch trueness and precision results compared to conventionally fabricated casts
Summary
If comprehensive fixed prosthetic rehabilitations are manufactured based on intraoral optical impressions, there are several reasons for the necessity to produce real casts. To produce real casts from a data set of an intraoral optical impression, subtractive or additive methods are applied. Whereas subtractive methods such as milling are of minor relevance, 3D printing technology is a common method to transfer virtual 3D information into reality. The following technologies can be distinguished: stereolithography (SLA), digital light processing (DLP), and continuous liquid interface production (CLIP) as vat polymerization technologies, fused filament fabrication (FFF) in material extrusion, material jetting (MJ), and binder jetting (BJ) technologies as well as powder bed fusion technologies such as selective laser sintering or melting (SLS/M) [2,3]. Material extrusion describes a technique in which thermoplastic materials are melted and extruded through a jet head forming objects by filament layering [7]. Selective laser sintering and melting work with a laser to sinter or melt and fuse powdered materials such as polymers, metal, ceramic, or glass, which are applied layer-by-layer via rollers [3,9]
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