Assessing the osseointegration potential of a strontium releasing nanostructured titanium oxide surface: A biomechanical study in the rabbit tibia plateau model

OBJECTIVES

To investigate the impact of a Ti-Sr-O technology, applied to either a turned surface or an SLA surface, on the mechanical robustness of osseointegration, benchmarked against the SLActive surface.

MATERIAL AND METHODS

Ti discs (6.25-mm-diameter and 2-mm-thick) with three different surfaces were inserted on the proximal-anterior part of the tibial plateau of adult Swedish loop rabbits: (I) turned surface modified with Ti-Sr-O (turned + Ti-Sr-O), (II) SLA surface modified with Ti-Sr-O (SLA + Ti-Sr-O), and (III) SLActive surface (SLActive). Following a healing period of 2 weeks and 4 weeks, the pull-out (PO) force needed to detach the discs from the bone was assessed, as a surrogate of osseointegration.

RESULTS

The SLActive surface exhibited statistically significant higher median PO forces, compared with the SLA + Ti-Sr-O surfaces at both 2- and 4 weeks post-op (p > .05). In this study, no single turned + Ti-Sr-O surface disk was integrated.

CONCLUSIONS

The tested Ti-Sr-O technology failed to enhance osseointegration; however, this finding may be related to the inappropriateness of the rabbit tibia plateau model for assessing third-generation implant surface technologies, due to the limited diffusion and clearance at the disk-bone interface.

Determining primary stability for adhesively stabilized dental implants

OBJECTIVES

To examine factors influencing the primary stability of dental implants when stabilized in over-sized osteotomies using a calcium phosphate-based adhesive cement was the objective.

METHODS

Using implant removal torque measurements as a surrogate for primary stability, we examined the influence of implant design features (diameter, surface area, and thread design), along with cement gap size and curing time, on the resulting primary implant stability.

RESULTS

Removal torque values scaled with implant surface area and increasing implant diameters. Cement gap size did not alter the median removal torque values; however, larger gaps were associated with an increased spread of the measured values. Among the removal torque values measured, all were found to be above 32 Ncm which is an insertion torque threshold value commonly recommended for immediate loading protocols.

CONCLUSION

The adhesive cement show potential for offering primary implant stability for different dental implant designs. In this study, the primary parameters influencing the measured removal torque values were the implant surface area and diameter. As the liquid cement prevents the use of insertion torque, considering the relationship between insertion and removal torque, removal torque can be considered a reliable surrogate for primary implant stability for bench and pre-clinical settings.

CLINICAL RELEVANCE

At present, the primary stability of dental implants is linked to the quality of the host bone, the drill protocol, and the specific implant design. The adhesive cement might find applications in future clinical settings for enhancing primary stability of implants under circumstances where this cannot be achieved conventionally.

Local Release of Strontium from Sputter-Deposited Coatings at Implants Increases the Strontium-to-Calcium Ratio in Peri-implant Bone

It is well known that strontium (Sr) has a significant effect on peri-implant bone healing when administered systemically. Due to the risk of adverse effects of such treatments, new routes focusing on the local, sustained release of Sr from bone-implant contact surfaces have been explored, with success in in vivo experiments. However, the increase of Sr concentrations in the peri-implant bone has not been described in depth yet. Here, we show that a local, sustained Sr release from Ti-Sr-O physical vapor deposition (PVD) coatings by magnetron sputter coating increases the Sr/Ca ratio close to the implant in a rabbit model and that the Sr/Ca background level is reached approximately 500 μm from the implant.

Bone regenerating effect of surface-functionalized titanium implants with sustained-release characteristics of strontium in ovariectomized rats

Since strontium (Sr) is known for its anabolic and anticatabolic effect on bone, research has been focused on its potential impact on osseointegration. The objective of this study was to investigate the performance of nanotopographic implants with a Sr-functionalized titanium (Ti) coating (Ti–Sr–O) with respect to osseointegration in osteoporotic bone. The trial was designed to examine the effect of sustained-release characteristics of Sr in poor-quality bone. Three Ti–Sr–O groups, which differed from each other in coating thickness, Sr contents, and Sr release, were examined. These were prepared by a magnetron sputtering process and compared to uncoated grade 4 Ti. Composition, morphology, and mechanical stability of the coatings were analyzed, and Sr release data were gained from in vitro washout experiments. In vivo investigation was carried out in an osteoporotic rat model and analyzed histologically, 6 weeks and 12 weeks after implantation. Median values of bone-to-implant contact and new bone formation after 6 weeks were found to be 84.7% and 54.9% (best performing Sr group) as compared to 65.2% and 23.8% (grade 4 Ti reference), respectively. The 12-week observation period revealed 84.3% and 56.5% (best performing Sr group) and 81.3% and 39.4% (grade 4 Ti reference), respectively, for the same measurements. The increase in new bone formation was found to correlate with the amount of Sr released in vitro. The results indicate that sputtered nanostructured Ti–Sr–O coatings showed sustained release of Sr and accelerate osseointegration even in poor-quality bone, and thus, may have impact on practical applications for medical implants.

Enhanced osseointegration of endosseous implants by predictable sustained release properties of strontium

Studies have shown that strontium (Sr) incorporated into surfaces may enhance osseointegration. Thus, we suggested that a sustained Sr release from implant surfaces could improve bone healing. This study verifies and further investigates the effect of a novel Ti-Sr-O functionalized implant surface prepared from a magnetron co-sputtering platform with a continuous release of Sr.

MATERIALS AND METHODS

Four experimental Ti-Sr-O groups, which differed from each other in Sr contents and pre-wash procedures, were tested. Implants were prepared with a Ti-Sr-O coating by means of magnetron co-sputtering and compared to Grade 4 titanium. Composition, morphology and mechanical stability were analyzed; Sr-release data were gained from in vitro washout experiments. In vivo investigations were carried out in a rat model and analyzed histologically regarding bone-to-implant contact and new bone formation 30 days after implantation.

RESULTS

Structural differences were detected between the two basis Ti-Sr-O coatings with 6.7 at.% and 8.9 at.% Sr, respectively. Different release profiles were observed with 8.9 at.% Sr coating exhibiting the highest long-term release of Sr. Median values of new bone formation and bone-to-implant contact was found to be 60.1% and 91.6%, respectively, for the best group compared to 16.6% and 70.6% for the Grade 4 titanium reference. The increase in new bone formation was found to correlate with the amount of Sr released in vitro.

CONCLUSION

The results show that sputtered Ti-Sr-O coatings with sustained release of Sr may improve osseointegration, and could thus have impact on practical applications for medical implants.

PH-dependent self-assembly of the short Surfactant-like peptide KA6

Self-assembly of amphiphilic peptides designed during the last ten years by different research groups lead to a large variety of 3D-structures that already found applications in e.g., for stabilization of large protein complexes, cell culturing systems etc. We present synthesis and characterization of a novel amphiphilic peptide KA6 that exhibits clear charge separation controllable by the pH of the environment. The self-assembly in this system is largely governed by electrostatic interaction, thus a change in pH will not only lead to a change in critical micellar concentration (CMC) of the peptide but also to the changes in micellar structure as revealed by atomic force microscopy (AFM) and circular dichroism (CD) study. At basic pH the micellar structure inverts exposing the opposite end of the peptide chain to the solution. This interesting phenomenon could provide basis for novel pH sensitive materials including drug delivery and controlled release systems.