Protein adsorption onto titanium (Ti) or zirconia (ZrO₂) was evaluated using a 27 MHz quartz crystal microbalance (QCM). As proteins, fibronectin (Fn), a cell adhesive protein, and albumin (Alb), a cell adhesion-inhibiting protein, were evaluated. The Ti and ZrO₂sensors for QCM were characterized by atomic force microscopy and electron probe microanalysis observation, measurement of contact angle against water, and surface roughness. The amounts of Fn and Alb adsorbed onto the Ti and ZrO₂sensors and apparent reaction rate were obtained using QCM measurements. Ti sensor showed greater adsorption of Fn and Alb than the ZrO₂sensor. In addition, amount of Fn adsorbed onto the Ti or ZrO₂sensors was higher than that of Alb. The surface roughness and hydrophilicity of Ti or ZrO₂may influence the adsorption of Fn or Alb. With regard to the adsorption rate, Alb adsorbed more rapidly than Fn onto Ti. Comparing Ti and ZrO₂, Alb adsorption rate to Ti was faster than that to ZrO₂. Fn adsorption will be effective for cell activities, but Alb adsorption will not. QCM method could simulatein vivoFn and Alb adsorption to Ti or ZrO₂.

The bone-bonding ability of a material is evaluated by examining apatite formation on its surface in simulated body fluid (SBF). Partially stabilized zirconia (ZrO2) is currently attractive as an alternative to titanium (Ti) implants; however, no quantitative analysis of apatite formation between Ti and ZrO2 in SBF has been reported. In the present study, we quantitatively evaluated apatite formation onto Ti or ZrO2 in SBF using the 27 MHz quartz crystal microbalance method (QCM). In the QCM measurements, apatite formation was detected as a frequency decrease in the Ti or ZrO2 sensor. Frequency decreases were observed at around 1 hour for Ti and at around 2 hours for the ZrO2 sensor after the injection of SBF. This revealed that the Ti sensor showed faster apatite formation than ZrO2. There was no significant difference in the amounts of apatite formation between the Ti and ZrO2 sensors after 24 hours of apatite formation in SBF. In conclusion, the present quantitative study using QCM revealed that apatite formation on the Ti surface in the SBF was obviously faster than that on the ZrO2 surface. Faster apatite formation may predict faster initiation of bone formation on Ti compared with ZrO2.

It is postulated that biofilm formation in the oral cavity causes some oral diseases. Lactoferrin is an antibacterial protein in saliva and an important defense factor against biofilm development. We analyzed the adsorbed amount of lactoferrin and the dissociation constant (K_d) of lactoferrin to the surface of different dental materials using an equilibrium analysis technique in a 27 MHz quartz crystal microbalance (QCM) measurement. Four different materials, titanium (Ti), stainless steel (SUS), zirconia (ZrO₂) and polymethyl methacrylate (PMMA), were evaluated. These materials were coated onto QCM sensors and the surfaces characterized by atomic force microscopic observation, measurements of surface roughness, contact angles of water, and zeta potential. QCM measurements revealed that Ti and SUS showed a greater amount of lactoferrin adsorption than ZrO₂and PMMA. Surface roughness and zeta potential influenced the lactoferrin adsorption. On the contrary, theK_dvalue analysis indicated that the adsorbed lactoferrin bound less tightly to the Ti and SUS surfaces than to the ZrO₂and PMMA surfaces. The hydrophobic interaction between lactoferrin and ZrO₂and PMMA is presumed to participate in better binding of lactoferrin to ZrO₂and PMMA surfaces. It was revealed that lactoferrin adsorption behavior was influenced by the characteristics of the material surface.

Dental titanium implants and their surface modifications markedly improve implant biocompatibility. However, studies evaluating the mechanical biocompatibility of implants are scarce. In particular, the analysis of mechanical biocompatibility deficiencies leading to stress shield-induced bone resorption. Recently, we focused on using PEEK as a dental material. This study explored the hypothesis that PEEK implants improve the stress shielding of titanium. In this study, artificial bone surfaces were examined to measure strains on the artificial bone surface under compressive loading with the implants in place. Additionally, 3D image analysis of the fracture state inside the bone tissue was performed using micro-CT (µCT). This hypothesis was supported by µCT imaging analysis of bone tissue changes under stress, which revealed that PEEK implants transfer greater loads than titanium implants. µCT imaging and statistical analysis showed that bone porosity had little effect on stress shielding.