Laser Structured Dental Zirconium for Soft Tissue Cell Occupation—Importance of Wettability Modulation

Abstract

Various approaches are being pursued to physico-chemically modify the zirconia neck region of dental implants to improve the integration into the surrounding soft tissue. In this study, polished zirconia discs were laser microstructured with periodic cavities and convex waves. These zirconia samples were additionally activated by argon plasma using the kINPen®09. The surface topography was characterized by scanning electron microscopy and the surface wettability by water contact angle. The in vitro study with human gingival fibroblasts (HGF-1) was focused on cell spreading, morphology, and actin cytoskeleton organization within the first 24 h. The laser-induced microstructures were originally hydrophobic (e.g., 60 µm cavities 138.4°), but after argon plasma activation, the surfaces switched to the hydrophilic state (60 µm cavities 13.7°). HGF-1 cells adhered flatly on the polished zirconia. Spreading is hampered on cavity structures, and cells avoid the holes. However, cells on laser-induced waves spread well. Interestingly, argon plasma activation for only 1 min promoted adhesion and spreading of HGF-1 cells even after 2 h cultivation. The cells crawl and grow into the depth of the cavities. Thus, a combination of both laser microstructuring and argon plasma activation of zirconia seems to be optimal for a strong gingival cell attachment.

Pulsed Electrical Stimulation Affects Osteoblast Adhesion and Calcium Ion Signaling

“…For example, Khatib et al [ 68 ] described an increase in intracellular Ca 2+ concentration in human osteoblasts after 20 min of DC stimulation at 2 V/cm due to an influx of extracellular Ca 2+ through stretch-activated cation channels (SACC), a release from intracellular stores, as well as activation of phospholipase C (PLC). We primarily suspect an enhanced release of Ca 2+ from intracellular stores, as we observe a strong response of cells by the addition of ATP, which activates the PLC pathway via G-protein coupled receptor, and finally releases Ca 2+ from the ER [ 30 ]. Extracellular Ca 2+ influx via ion channels is of secondary importance in our short 10 min stimulation, as analyses without extracellular Ca 2+ sources from the HEPES buffer [ 36 ], also demonstrated an increased basal Ca 2+ level in MG-63s in all ES parameters (data not shown).…”

“…The membrane-permeable calcium indicator fluo-3/AM (Life Technologies Corporation, Eugene, OR, USA) was used [ 30 ], to detect if AC mobilizes calcium ions (Ca 2+ ) in the cytosol. Fluo-3/AM consists of molecules with two free binding sites that display an increase in fluorescence in the presence of free Ca 2+ .…”

Biomimetic Implant Surfaces and Their Role in Biological Integration—A Concise Review

“…Most of them found that better bone cell behavior was associated with an increase in surface roughness [ 67 , 69 , 70 ]. Some studies on soft tissue response show somewhat contradictory results, with greater proliferation and spread of fibroblast cells on smooth surfaces [ 65 , 68 , 71 ]. A literature review of in vitro studies on this subject concluded that regardless of the implant surface distinctions that should be made, titanium or zirconia surfaces with micro rough topography resulted in increased osteoblastic differentiation, collagen type I production, bone matrix protein expression, and cell-matrix layer mineralization [ 72 ].…”

Optimized Gingiva Cell Behavior on Dental Zirconia as a Result of Atmospheric Argon Plasma Activation

“…The integration of soft but also hard tissue in modern dental implants is mainly determined by the topographical, biological, and chemical surface conditions [ 1 , 16 , 17 ]. In recent years, modifications of surface topography [ 18 , 19 , 20 ] and chemistry have been introduced to optimize oral implants to increase bioactivity [ 21 , 22 ].…”

“…In previous studies, we have shown that a topographical modification of ZrO 2 with innovative sinusoidal structures positively affected cellular adhesion [ 20 ]. However, very rough surfaces or deep cavities hindered cellular attachment and the spreading of gingival fibroblasts [ 20 , 22 ]. We discovered that zirconia surfaces developed hydrophobic surface characteristics after laser-induced micro-roughening, which reduced cell spreading [ 22 ].…”