Application of Plasma-Sprayed Zirconia Coating in Dental Implants: Study in Implants
The aim was to investigate the osseointegration of a novel coating—plasma-sprayed nanostructured zirconia (NSZ)—for dental implants. Nanostructured zirconia coating on non-thread titanium implant was prepared by plasma spraying, and the implant surface morphology, surface roughness, and wettability were measured. In vivo, nanostructured zirconia-coated implants were inserted in rabbit tibia, and the animals were sacrificed at 2, 4, 8, and 12 weeks after implantation. The bond strength between implant and bone was measured with the removal torque (RTQ) test. Osseointegration was observed by scanning electron microscopy (SEM), microcomputerized tomography (micro CT), and histological analyses. Quantified parameters were calculated, including removal torque, bone volume to tissue volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation/spacing (Tb.Sp), and bone-implant contact (BIC) percentage. The statistical differences were detected with a two-tail Mann-Whitney U test (SPSS 20.0). The surface roughness (1.58 μm) and wettability (54.61°) of a nanostructured zirconia-coated implant was more suitable than the titanium implant (0.598 μm, 74.38°) for osseointegration and hierarchical surface morphology seen on the zirconia coating. The histological analyses showed that a zirconia-coated implant induced earlier and had more condensed bone formation than did the titanium implant at 2 and 4 weeks. Quantified parameters showed the significant differences between these 2 groups at an early healing period, but the differences between the 2 groups decreased with an increased healing period. All these results demonstrated that plasma-sprayed zirconia coated implants induced better bone formation than did titanium implants at an early stage.
Implants used for surface analyses and in vivo osseointegration study. (a) Nonthreaded dental implants were produced from medical grade titanium bars. (b) The implants were coated by nanostructured zirconia with a thickness of 400 μm.
Surface analyses of nanostructured zirconia (NSZ)-coated dental implants. (a) The average surface roughness of NSZ coating layer was 1.58 ± 0.21 μm, which was significantly higher than that of titanium (Ti) implants (0.598 ± 0.11 μm). (b) The contact angle of NSZ coating surface was significantly lower than that measured for mechanically processed Ti surface (NSZ: 54.61 ± 1.80°, Ti: 74.38 ± 3.61°). (c) Scanning electronic microscope analysis of NSZ coating surface (panels c1 and c2: magnification, ×200, panels c3 and c4: magnification, ×1000). *P < .05. NSZ+Ti indicates NSZ-coated titanium implant.
Assessment of osseointegration induced by nanostructured zirconia (NSZ)-coated implants. (a) Statistically significant differences in RTQ were detected between NSZ+Ti and Ti groups at 4 w, 8 w, and 12 w. (b) SEM analysis of bone-implant interface at 2 w, 4 w, and 8 w (magnification, ×1000). (c) Micocomputerized tomography (micro CT) analysis of bone-implant interface at 2 w, 4 w, and 8 w. Bone-like structures are labeled in green. (d, e, f, i) BV/TV (%), Tb.Th (mm), Tb.N (1/mm), and BIC (%) in NSZ+Ti group were significantly higher than those in Ti group at 2 w, 4 w, 8 w, and 12 w of the healing period. (g) Significant differences in Tb.Sp (mm) between 2 groups were only detected at 2 w, 4 w, and 8 w. (h) Histological analysis of bone-implant interface during the healing period. *P < .05. RTQ indicates removal torque; Ti, titanium; NSZ+Ti, NSZ-coated titanium implant; Imp, implant; BV/TV, bone volume to tissue volume; Tb.Th, trabecular thickness; Tb.N, trabecular number; Tb.Sp, trabecular separation/spacing; BIC, bone-implant contact.
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