Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), which are partially stabilized zirconia, have been used for fabricating dental implants. This study investigated the soft tissue attachment, the collagen fiber orientation to zirconia at different surface conditions, and the bone response using implantation experiments in animals. The zirconia implant surfaces were treated with ultraviolet irradiation (UV), a combination of large-grit sandblasting and hydrofluoric acid etching (blastedHF), and a combination of blastedHF and UV (blastedHF+UV). The surface treated with blastedHF and blastedHF+UV appeared rough and hydrophilic. The surface treated with blastedHF+UV appeared to be superhydrophilic. Subsequently, tapered cylindrical zirconia implants were placed in the alveolar sockets of the maxillary molars of rats. The bone-to-implant contact ratio of blastedHF and blastedHF+UV implants was significantly higher than that of the non-treated controls and UV-treated implants. The four different surface-treated zirconia implants demonstrated tight soft tissue attachments. Perpendicularly oriented collagen fibers towards zirconia implants were more prominent in blastedHF and blastedHF+UV implants compared to the controls and UV-treated implants. The area of the soft tissue attachment was the greatest with the perpendicularly oriented collagen fibers of blastedHF+UV-treated implants. In conclusion, blastedHF+UV treatment could be beneficial for ensuring greater soft-tissue attachment for zirconia implants.

Two type of partially stabilized zirconia, namely yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and ceria-stabilized tetragonal zirconia polycrystals including aluminum oxide nanocomposite (Ce-TZP), were irradiated by nanosecond-pulsed Nd:YAG laser and the regular structure with concave and convex of each 30 μm width and 30 μm depth were prepared on both surfaces. In the case of Ce-TZP, the surface was changed to be black after laser irradiation. EDX measurement revealed the reduction of more amounts of oxygen atoms on Ce-TZP compared to Y-TZP. Laser irradiated zirconia implants were inserted into the bone defects of rat femur during 4 weeks. As a control, large grid sandblasted and acid etching (blastedHF) implant was used. Laser treatment for Y-TZP provided greater degree of bone-implant contact ratio than blastedHF treated Y-TZP (p<0.05). In the case of Ce-TZP, however, laser treatment showed no clear effect on bone response.

Multi-directional forging (MDFing) of titanium drastically improved its mechanical properties due to the evolution of an ultrafine-grained structure. Forging strain was repeatedly applied while changing the forging axis during MDFing. Of note is the decreased elastic modulus of MDFed titanium (MDF-Ti) as compared to conventional coarse-grained pure Ti (Ti). In the present study, we evaluated bone’s response toward surface-treated MDF-Ti after implantation into the extraction sockets of rat maxillary molars. As surface treatments, acid (Acid, sulfuric acid at 120 °C for 75 s), alkali without post-heat (Alkali, NaOH at 60 °C for 24 h), and alkali with post-heat (Alkali-heat, subsequent heating at 600 °C for 1 h) treatments were employed. The presence of minute nanoscale dimples in the microscale dimples to form regular fractal structures on MDF-Ti surfaces was observed after Acid treatments. Structures of sponge-like porous networks after Alkali treatments and submicron fiber networks after Alkali-heat treatment were produced on the surfaces of both Ti and MDF-Ti. Surface-treated specimens were superhydrophilic. More crystal deposition was clearly observed on each surface-treated specimen after immersion in simulated body fluid for both Ti and MDF-Ti. The bone-to-implant contact (BIC) ratios of the Acid and Alkali-heat specimens were significantly higher than those of the untreated control (p < 0.05). Moreover, Acid and Alkali-heat treatment for MDF-Ti caused significantly greater BICs than that for Ti (p < 0.05). In conclusion, Acid or Alkali-heat treatment of MDF-Ti is useful for improving bone response.

The purposes of this study were to evaluate the shear bond strength and perform the computational analysis for silane coupling treatments on the adhesion between CAD/CAM composite resin and resin cement. As silane coupling agents, γ-methacryloyloxy propyltrimethoxysilane, 8-methacryloyloxyoctyl trimethoxysilane, and 3-methacryloyloxypropyl trichlorosilane were used. The shear bond strengths were influenced by the silane coupling agent used, its application method, and acid addition. There was no correlation between the contact angle and shear bond strengths. The steric energy difference between a silane coupling agent and its corresponding hydrolyzed trisilanol compound, ∆E, was calculated by the molecular mechanics method. There was a moderate or strong linear correlation between ∆E and shear bond strengths in treatment without acid addition and a weak correlation between them in treatment with acid addition. Computational analysis could suggest the different path of silane coupling treatments of CAD/CAM composite resin in the presence or absence of acid.

The osseointegration of zirconia (ZrO₂) implants is still controversial. In this study, we aimed to make clear the influence of surface chemical composition, Ti or ZrO₂, to osseointegration. First, a roughened Ti surface was prepared with a combination of large-grit sandblasting and acid treatment. Then, we applied molecular precursor solution containing Zr complex onto roughened Ti surface and can deposit thin ZrO₂ film onto roughened Ti surface. We can change surface chemical composition from Ti to ZrO₂ without changing the surface structure and roughness of roughened Ti. The tetragonal Zr was uniformly present on the ZrO₂-coated Ti surface, and the surface of the ZrO₂-coated Ti showed a higher apparent zeta potential than Ti. Ti and ZrO₂-coated Ti rectangular plate implant was placed into the femur bone defect. After 2 and 4 weeks of implantation, histomorphometric observation revealed that the bone-to-implant contact ratio and the bone mass values for ZrO₂-coated Ti implants inserted into the femur bone defects of the rats at 2 weeks were significantly higher than those for Ti implants (p < 0.05). It revealed that ZrO₂ with a similar surface structure and roughness as that of roughened Ti promoted osteogenesis equivalent to or better than that of Ti in the early bone formation stage.