Improved osseointegration and interlocking capacity with dual acid-treated implants: a rabbit study

Early bone healing to implants with different surface characteristics. A pre-clinical in vivo study

AIM

To examine early bone healing around implants with non-modified and modified surfaces.

MATERIAL & METHODS

Four implants with 4 different surface characteristics were installed in one side of the mandible following tooth extraction in 6 dogs. Implants in group A had a non-modified, turned surface, while implants in group B had a surface modification consisting of TiO-blasting and sequential acid-etching in oxalic and hydrofluoric acid. The surface modification of implants in group C was confined to sequential acid-etching in oxalic and hydrofluoric acid and Group D implants had a surface modification of TiO-blasting and acid-etching in hydrofluoric acid. The implant installation procedures were repeated in the opposite side of the mandible 4 weeks later. Biopsies were obtained and prepared for histological analysis 2 weeks later.

RESULTS

B and C implants had a higher degree of bone-to-implant contact (BIC%) than A and D implants at 2 weeks of healing. At 6 weeks of healing, the BIC% was higher at B than at A, C and D implants, and higher at C implants than at A implants. The amount of newly formed bone in contact with the implant within the defect area at 2 weeks was higher at implants with modified surfaces (groups B, C and D) than at implants with a non-modified surface (group A). Corresponding results at 6 weeks were superior at B implants.

CONCLUSION

It is suggested that an implant surface modification with acid-etching in oxalic and hydrofluoric acid promotes early formation of bone-to-implant contact.

Effects of surface sub-micrometer topography following oxalic acid treatment on bone quantity and quality around dental implants in rabbit tibiae

Background

To explore the effects of topographical modification of titanium substrates at submicron level by oxalic acid treatment on bone quality and quantity around dental implants in rabbit tibiae.

Methods

A total of 60 blasted CP-grade IV titanium dental implants were used. Twenty-eight control implant surfaces were treated with a mixture of HCl/H₂SO₄, whereas 28 other test implant surfaces were treated with oxalic acid following HCl/H₂SO₄ treatment. Two randomly selected sets of control or test implants were placed in randomly selected proximal tibiae of 14 female Japanese white rabbits. Euthanasia was performed 4 and 8 weeks post-implant placement. Bone to implant contact (BIC), bone area fraction (BAF), ratios of mature and immature bone to total bone, and the amount and types of collagen fibers were evaluated quantitatively. Two control and two test implants were used to analyze surface characteristics.

Results

Treatment by oxalic acid significantly decreased Sa and increased Ra of test implant surfaces. BIC in test implants was increased without alteration of BAF and collagen contents at 4 and 8 weeks after implant placement when compared with control implants. The ratios of immature and mature bone to total bone differed significantly between groups at 4 weeks post-implantation. Treatment by oxalic acid increased type I collagen and decreased type III collagen in bone matrices around test implants when compared with control implants at 8 weeks after implant placement. The effects of topographical changes of implant surfaces induced by oxalic acid on BAF, mature bone, collagen contents, and type I collagen were significantly promoted with decreased immature bone formation and type III collagen in the later 4 weeks post-implantation.

Conclusions

Treatment of implant surfaces with oxalic acid rapidly increases osseointegration from the early stages after implantation. Moreover, submicron topographical changes of dental implants induced by oxalic acid improve bone quality based on bone maturation and increased production of type I collagen surrounding dental implants in the late stage after implant placement.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40729-020-00275-x.

Low dose effect of bisphosphonates on hMSCs osteogenic response to titanium surface in vitro

Since the 1980s, titanium (Ti) implants have been routinely used to replace missing teeth. This success is mainly due to the good biocompatibility of Ti and the phenomenon of osseointegration, with very early events at implant placement being important in determining good osseointegration. However, enhancing implant performance with coatings such as hydroxyapatite (HA) and calcium phosphate has proved largely unsuccessful. Human mesenchymal stem cells (hMSCs) are the first osteogenic cells to colonise implant surfaces and offer a target for enhancing osseointegration. We previously reported that small doses of bisphosphonate (BP) may play an integral role in enhancing hMSC proliferation and osteogenic differentiation. The aim of this study is to investigate whether small doses of bisphosphonates enhance proliferation and osteogenic differentiation of hMSCs on Ti surfaces, to enhance bone osseointegration and to accelerate wound healing around the implant surface. Our data suggests that treating cells with small doses of BP (100 nM & 10 nM) induces significant hMSC stimulation of osteogenic markers including calcium, collagen type I and ALP compared to control group on titanium surfaces (P < 0.05). In addition, cell proliferation and migration were significantly enhanced on titanium surfaces (P < 0.05).

Simulation of the mechanical interlocking capacity of a rough bone implant surface during healing

Background

When an implant is inserted in the bone the healing process starts to osseointegrate the implant by creating new bone that interlocks with the implant. Biomechanical interlocking capacity is commonly evaluated in in vivo experiments. It would be beneficial to find a numerical method to evaluate the interlocking capacity of different surface structures with bone. In the present study, the theoretical interlocking capacity of three different surfaces after different healing times was evaluated by the means of explicit finite element analysis.

Methods

The surface topographies of the three surfaces were measured with interferometry and were used to construct a 3D bone-implant model. The implant was subjected to a displacement until failure of the bone-to-implant interface and the maximum force represents the interlocking capacity.

Results

The simulated ratios (test/control) seem to agree with the in vivo ratios of Halldin et al. for longer healing times. However the absolute removal torque values are underestimated and do not reach the biomechanical performance found in the study by Halldin et al. which might be a result of unknown mechanical properties of the interface.

Conclusion

Finite element analysis is a promising method that might be used prior to an in vivo study to compare the load bearing capacity of the bone-to-implant interface of two surface topographies at longer healing times.