Bioactive characteristics of an implant surface coated with a pH buffering agent: an in vitro study

Abstract

PurposeThe purpose of this study was to evaluate the effectiveness of conventional sandblasted, large-grit, acid-etched (SLA) surface coated with a pH buffering solution based on surface wettability, blood protein adhesion, osteoblast affinity, and platelet adhesion and activation.MethodsTitanium discs and implants with conventional SLA surface (SA), SLA surface in an aqueous calcium chloride solution (CA), and SLA surface with a pH buffering agent (SOI) were prepared. The wetting velocity was measured by the number of threads wetted by blood over an interval of time. Serum albumin adsorption was tested using the bicinchoninic acid assay and by measuring fluorescence intensity. Osteoblast activity assays (osteoblast adhesion, proliferation, differentiation, mineralization, and migration) were also performed, and platelet adhesion and activation assays were conducted.ResultsIn both the wetting velocity test and the serum albumin adsorption assay, the SOI surface displayed a significantly higher wetting velocity than the SA surface (P=0.000 and P=0.000, respectively). In the osteoblast adhesion, proliferation, differentiation, and mineralization tests, the mean values for SOI were all higher than those for SA and CA. On the osteoblast migration, platelet adhesion, and activation tests, SOI also showed significantly higher values than SA (P=0.040, P=0.000, and P=0.000, respectively).ConclusionsSOI exhibited higher hydrophilicity and affinity for proteins, cells, and platelets than SA. Within the limits of this study, it may be concluded that coating an implant with a pH buffering agent can induce the attachment of platelets, proteins, and cells to the implant surface. Further studies should be conducted to directly compare SOI with other conventional surfaces with regard to its safety and effectiveness in clinical settings.

Coating of a Sand-Blasted and Acid-Etched Implant Surface with a pH-Buffering Agent after Vacuum-UV Photofunctionalization

“…SA implant surfaces have demonstrated predictable clinical results and are regarded as standard implant surface [10,[26][27][28][29]. The superhydrophilicity of SA + VUV + BS, which was previously found on the flat surface of disks [15], was confirmed in our test of static surface wettability. As the ability to attract blood near to the top of the implant fixture (approximately 4 mm above the horizontal plate in our study) is what most clinicians ultimately prefer to check in a clinical setting, we added a new dynamic test of surface wettability to compare the wetting velocities of SA + VUV and SA + VUV + BS in more detail.…”

“…UV-C is capable of removing hydrocarbon from a TiO 2 layer of titanium by direct photodecomposition, which is more effective than photocatalysis by UV-A [18]. In our study, all implant fixtures were photofunctionalized by UV-C and VUV (100-200 nm), and the radical removal of hydrocarbon from TiO 2 layer of titanium could provide more superhydrophilicity [15,19]. VUV is rapidly absorbed by water in the atmosphere and is therefore capable of generating various reactive oxygen species by breaking hydrogen bonds in water molecules via hydrolysis [19].…”

“…During implant drilling in the bone, which produces a weakly acidic condition, a pH buffer may help keep the pH constant [38]. As a coating material, the pH-buffering agent appears to control the release of the inflammatory mediators [9] and enhance the conditions for osteoblast activity [15] by keeping the pH constant or at least preventing significant changes. The activity of platelets in blood clotting and both the activity of osteoblasts and the level of ALP for bone making are also inhibited by extracellular acidosis [11].…”

“…Implant fixtures of commercially pure titanium (grade IV) were prepared as SA, SA + VUV (TS III SA, Osstem, Seoul, Korea), and SA + VUV + BS (TS III SOI, Osstem) for use in this study. As shown in Figure 1a,b, the surface roughness of the implant fixtures were measured to be 2.5 ± 0.5 µm of R a value [15], and VUV treatment for photofunctionalization was achieved by exposing an implant fixture to low-pressure mercury-arc lamps emitting UV-C and VUV in UV ozone cleaner for 1 h. Coating the implant surface with a pH-buffering agent, comprising both of positively and negatively charged ionic groups, with 7.31 of pKa value at 37 • C [15,16], was supplemented for better superhydrophilicity (Figure 1c).…”

“…In our previous study, a novel SA surface coated with a pH-buffering agent after vacuum-UV (VUV) treatment was introduced [15,16]. This surface was closely associated with greater affinity for proteins, cells, and platelets, which promoted rapid and stable blood clotting, thrombogenesis, and osseointegration.…”