The Influence of an Ultrasonic Cleaning Protocol for CAD/CAM Abutment Surfaces on Cell Viability and Inflammatory ResponseIn Vitro

Abstract

Background/Aim: To evaluate the effect of an ultrasonic cleaning and disinfection method for CAD/CAM abutment surfaces on cell viability and inflammatory response in vitro. Materials and Methods: Untreated and manually polished surfaces of CAD/CAM generated titanium and zirconia disks were randomly assigned, either to a 3-step ultrasonic cleaning and disinfection process (test: TiUF, TiPF, ZrUF, ZrPF) or to 30 sec steam cleaning (control: TiUS, TiPS, ZrUS, ZrPS). Pre-cleaning surface analyses using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and surface profilometry were performed. Human gingival fibroblasts (HGFs) were cultured on test and control specimens and subsequently examined for cell viability and inflammatory response. Expression of acute inflammatory cytokine interleukin (IL)-6 and vascular endothelial growth factor A (VEGFA) were assessed by means of RT-qPCR. Results: Cells on all specimens exhibited a satisfactory viability, indicating firm attachment. Cells on polished zirconia samples, cleaned by means of sonication (ZrPF), exhibited significantly higher viability than cells on the same material cleaned by steam (ZrPS), p=0.019. For all other three material/ surface treatment combinations (TiU, TiP, ZrU), no such difference was observed between the cleaning methods. The messenger ribonucleic acid (mRNA) levels of IL-6 and VEGFA were between 50 and 105% of that of the control cells on the non-toxic control surface. mRNA levels of IL-6 and VEGFA correlated well with each other. Conclusion: Except for higher viability of cells cultured on polished zirconia specimens, no universally applicable advantage could be found for the ultrasonic cleaning procedure for zirconia and titanium abutment surfaces regarding cell viability, IL-6 expression or VEGFA expression. The cleaning procedures did not have any negative effect either. Soft tissue adhesion to the transmucosal part of an implant abutment is essential, as it provides a protective seal which prevents bacterial invasion and subsequent inflammation (1, 2). Peri-implant mucosa is composed of well-keratinized oral, sulcular, and junctional epithelium, as well as underlying connective tissue (3). Human gingival fibroblasts (HGFs) are precursors of cells in the connective tissue of the mucosal seal and are involved in the homeostasis of collagen fibers around implant abutments (4, 5). Surface characteristics of the abutment determine to a large extent the quality of mucosal attachment (6). Surface topography, wettability and free energy determine cell reactions (7, 8), whereas contaminants and chemical debris could adversely 689 This article is freely accessible online.

Qualitative and Semi-Quantitative Assessment of Processing-Related Surface Contamination of One- and Two-Piece CAD/CAM Abutments before and after Ultrasonic Cleaning

“…In vitro results confirm a generally good cell viability on titanium samples [29]. Enhanced cell attachment and reduced inflammatory response of human gingival fibroblasts (HGFs) have been shown to zirconia surfaces for this cleaning and disinfecting method [30].…”

“…After the CAD/CAM-supported fabrication of corresponding zirconia or lithium disilicate copings, these ceramic copings are bonded to prefabricated titanium bases and then polished manually by the dental technician using silicone polishers of decreasing roughness. This polishing procedure reduces the surface roughness [30] and thus appears to make a decisive contribution to cleanliness and purity in the fabrication of hybrid abutments. In contrast, the tested monotype abutments were completely produced in a central production facility of an implant manufacturer, where typically no surface treatment such as polishing is performed.…”

“…All hybrid abutments were luted with a dimethacrylate/hydroxyethylmethacrylate-based cement (DMA/HEMA) (Multilink Implant, Ivoclar Vivadent, Schaan, Liechtenstein) according to the manufacturer's recommendations. Finally, removal of the bonding excess was performed as well as polishing of the bonding joint with silicone polishers and polishing paste according to a previously documented protocol [30].…”

“…In accordance with current health regulations, the abutment samples were cleaned three times in an ultrasonic bath (Finevo Cleaning System, Bredent GmbH & Co. KG, Senden, Germany) at 30 • C for 5 min each, as previously described by the authors [28,30]. The first bath contained an antibacterial cleansing solution, the second bath contained 80% ethyl alcohol, and the third bath contained medically pure water (aqua dest.).…”

“…In addition to overdue controlled clinical trials, efforts to ascertain the actual amount and extent of debris on customized abutments could be an important parameter to determine clinical relevance. Although the qualitative presence of organic and inorganic contaminants on CAD/CAM generated surfaces has been verified by microscopic and chemical analyzes [28,30], data on the quantity and scale of such contaminants are missing. Thus, the aim of the present study was to evaluate the quantity of processing-related surface contamination of CAD/CAM abutments before and after ultrasonic cleaning by means of scanning electron microscopy (SEM) and computer-aided planimetric measurement (CAPM).…”