Effect of post-rinsing time on the mechanical strength and cytotoxicity of a 3D printed orthodontic splint material.

Affiliation

Xu Y(1), Xepapadeas AB(2), Koos B(2), Geis-Gerstorfer J(3), Li P(4), Spintzyk S(3).
Author information:
(1)State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, Sichuan, China; Department of Oral Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, Sichuan, China; University Hospital Tübingen, Section Medical Materials Science and Technology, Osianderstrasse 2-8, Tübingen 72076, Germany.
(2)Department of Orthodontics, University Hospital Tübingen, Osianderstrasse 2-8, Tübingen 72076, Germany.
(3)University Hospital Tübingen, Section Medical Materials Science and Technology, Osianderstrasse 2-8, Tübingen 72076, Germany.
(4)University Hospital Tübingen, Section Medical Materials Science and Technology, Osianderstrasse 2-8, Tübingen 72076, Germany. Electronic address: [Email]

Abstract

OBJECTIVE: Since the post-rinsing time is inconsistently recommended, this study aims to investigate the effect of post-rinsing time on the flexural strength and cytotoxicity of an stereolithographically (SLA) printed orthodontic splint material. METHODS: SLA-printed specimens were ultrasonically rinsed with isopropanol (IPA) for 5 min, 12 min, 20 min, 30 min, 1 h, and 12 h, respectively. Surface characterization was conducted by scanning electron microscopy and roughness measurements. Flexural strength was evaluated using a three-point bending test. Cytotoxicity was determined by direct contact test and extract test. For both tests, cell viability (live/dead staining) and cell metabolic activity (CCK-8 assay) were evaluated. Additionally, water sorption and water solubility were tested to analyze the mass loss from immersion. RESULTS: No apparent surface alterations could be detected on the samples post-rinsed for less than 1 h. In contrast, when the post-rinsing time was prolonged to 12 h, surface fissures could be observed. Flexural strength linearly decreased with increasing post-rinsing time. All post-processed specimens did not show an obvious cytotoxic effect. SIGNIFICANCE: The removal of cytotoxic methacrylate monomers by post-rinsing with IPA could be achieved in 5 min. Extending post-rinsing time could not improve the cytocompatibility of the SLA-printed orthodontic splint material, and may result in a decrease in flexural strength.