A mechanical evaluation of TiO2-gritblasted and Ca-P magnetron sputter coated implants placed into the trabecular bone of the goat: Part 1.

The influence of Ca-P magnetron sputter coated implants on the mechanical anchorage was evaluated in a goat model. Therefore, uncoated and coated screw designed commercially pure titanium TiO2-blasted implants were inserted into the trabecular bone of the femoral condyles of 12 goats. The thicknesses of the coatings were 0.1 micron (CaP-0.1), 1.0 micron (CaP-1) and 4.0 microns (CaP-4). In addition, uncoated TiO2-blasted implants (Ti) were used as control. Evaluation of the interface strength and appearance, using torque test and scanning electron microscopy, was done at implantation periods of 6 and 12 weeks. Although, especially at 6 weeks of implantation, the Ca-P coated implants showed higher failure torque values than the TiO2 blasted implants, the observed differences for type of implant and evaluation period were not significant (P > 0.1). SEM evaluation showed that all implants with failure values of more than 100 N conducted bone growth into their screw threads. In addition, we observed that the fracture plane for the CaP-4 implants was situated at the coating-implant interface or inside the coating. For the CaP-1 and CaP-0.1 the fracture line could not be determined definitely. For the Ti implants, the fracture torque testing resulted in failure at the bone-implant interface. Therefore, we conclude that all implants resulted in a good bonding strength with the surrounding bone. The sputtered Ca-P coatings seemed to improve the initial fixation of the TiO2 blasted implants.

A histological evaluation of TiO2-gritblasted and Ca-P magnetron sputter coated implants placed into the trabecular bone of the goat: Part 2.

The aim of this study was to investigate the synergetic influence of surface topography and chemical composition of oral implant materials on bone response. For the experiment screw designed implants were used. The implants were grit-blasted with TiO2 particles. The implants were left uncoated (Ti) or provided with three different amorphous/crystalline Ca-P magnetron sputter coatings, resp. 0.1 micron (CaP-0.1), 1 micron (CaP-1) and 4 microns (CaP-4), in thickness. The implants were inserted in the medial femoral condyles of 12 goats. Each femur received 2 implants. After implantation periods of 6 and 12 weeks the implants were retrieved and prepared for histological and histomorphometrical evaluation (bone contact and bone mass). The light microscopy revealed that bone response to CaP-4 and CaP-1 implants was similar. For example, after 12 weeks, screw threads were almost completely covered with bone. In contrast to CaP-0.1 and Ti implants, where bone apposition was less pronounced. Histomorphometry demonstrated that the bone-to-implant contact for the CaP-1 and CaP-4 implants was significantly higher (P < 0.05) than for the CaP-0.1 and Ti implants. This difference existed already after 6 weeks and was even enhanced after 12 weeks. The bone mass measurements revealed that only at 12 weeks CaP-4 implants had significantly more bone contact inside the screw threads than non-coated Ti-implants (P < 0.05). Supported by our findings, we conclude that the additional application of a 1-4 microns thick Ca-P magnetron sputter coating can further improve the healing response to surface roughened oral implants placed into trabecular bone.

Bone healing capacity of titanium plasma-sprayed and hydroxylapatite-coated oral implants.

The influence of surface quality, in particular surface topography and implant material, was evaluated by inserting titanium- and hydroxylapatite plasma-sprayed coated implants into the maxilla of 10 goats. Three types of plasma-spray coatings were applied to tapered, screw shaped implants; titanium plasma-spray coating (TPS), titanium plasma-spray coating with additional acid passivation (TPSA) and a bilayered coating (TPS/HA) consisting of titanium plasma-spray coating (TPS) and a hydroxylapatite part (HA). In addition, as-machined implants (TiM) were used as control. A total of 40 implants were inserted according a balanced split plot design. At the end of a 3-month healing period, it appeared that 5 implants (2 TPS, 1 TPSA, 1 TPS/HA and 1 TiM) were lost. Histological examination revealed a stronger bone response to TPS/HA coated implants. Even the TPS/HA coated implants induced bone formation on the part of the implant inserted into the sinus. No signs of delamination of the TPS coatings were visible. The HA part of the dual coating showed signs of degradation. Histomorphometrical analysis confirmed these findings. A significant difference in bone contact (P < 0.05) was measured between the TPS/HA coated implants and the other types of implants. Linear regression (r = 0.27) showed no correlation between the inscrew values at the base line and the bone contact measurements 3 months after healing. On the basis of these results, we can conclude that the chemical composition of the HA coating has a positive influence on the bone reaction. The influence of roughness is less evident.

The effect of titanium plasma-sprayed implants on trabecular bone healing in the goat.

The bone response to different titanium plasma-sprayed implants was evaluated in a goat model. Therefore, beam-shaped implants were installed into the trabecular femoral condyles of 10 goats. These implants were provided with three different titanium plasma-sprayed coatings (Ti2, Ti3 and Ti4) with a Ra of 16.5, 21.4 and 37.9 microm, respectively. An Al2O3 grit-blasted implant (Ti-un) with a Ra of 4.7 microm was used as control. After an implantation period of 3 months, the implants were evaluated histologically and histomorphometrically. Only one implant (Ti3) was not recovered after the evaluation period. Light microscopy showed a limited amount of bone for the various implants. Most of the implants showed a different degree of fibrous tissue alternating with direct bone contact. Complete fibrous encapsulation of the implants was observed in some of the sections. No signs of delamination of the plasma-sprayed coating was visible. No significant difference in bone contact were measured between the different types of implants (P > 0.05). Histomorphometrical analysis revealed significantly higher bone mass close to the implant (0-500 microm) for the Ti3, Ti4 and Ti-un implants placed in the medial femoral condyle and the Ti4 implants placed in the lateral condyle. At distance (500-1500 microm), no difference in bone mass measurements between the different implants was observed (P > 0.05).

Histomorphometrical and mechanical evaluation of titanium plasma-spray-coated implants placed in the cortical bone of goats.

The aim of this study was to investigate the biological and mechanical response of bone to titanium plasma-sprayed implants of different roughnesses. Three types of titanium plasma-spray coating were applied to beam-shaped implants: Ti2, Ti3, and Ti4, with a Ra of 16.5, 21.4, and 37.9 microm, respectively. An Al2O3 grit-blasted implant (Ti-un) with a Ra of 4.7 microm was used as a control. In total, 72 implants were inserted in the tibial cortical bone of nine adult female goats. These implants were evaluated histologically and mechanically 3 months after implantation. At the end of the experiment, of the 72 inserted implants, two implants (one Ti2 and one Ti4) were lost. Histological evaluation of the other retrieved implants revealed a uniform bone reaction for all implants. The unloaded plasma-spray coatings showed no signs of delamination at the implant-coating interface. Occasionally, particles of the Ti4 coating broke free and were found near the implant. Histomorphometry revealed no difference in bone contact for the different implants (P > 0.05). Furthermore, the push-out test showed no significant difference (P > 0.05). Linear regression showed no interaction between the push-out values and the roughness values (r = 0.5). On the basis of these results, it may be concluded that the used surface roughnesses did not lead to differences in bone response or mechanical attachment strength in goat cortical bone.

The effect of Ca-P plasma-sprayed coatings on the initial bone healing of oral implants: an experimental study in the goat.

The response of bone of low density to uncoated, fluorapatite (FA), hydroxyapatite (HA), and hydroxyapatite heat treated (HAHT) plasma-sprayed coated implants was investigated 3 and 6 months after installation. Forty-eight threaded implants of commercially pure titanium were inserted into the maxilla of twelve goats according to a split-plot design. One goat died shortly after installation of the implants, five goats were sacrificed 3 months after installation, and the other six goats 6 months after installation. Histological evaluation revealed no difference in bone reaction between the 3- and 6-month implantation periods. In addition, probably due to the wide inter- and intra-animal variability, no significant difference between the 3- and the 6-month periods could be observed in the histomorphometrical measurements performed. Further, no significant differences were found in bone reaction among the various implant materials. Finally, qualitatively it appeared that all coatings showed reduction in coating thickness and that such reductions were most pronounced for the HA coatings.