Particle release from implantoplasty of dental implants and impact on cells

Abstract: Background: With increasing numbers of dental implants placed annually, complications such as peri-implantitis and the subsequent periprosthetic osteolysis are becoming a major concern. Implantoplasty, a commonly used treatment of peri-implantitis, aims to remove plaque from exposed implants and reduce future microbial adhesion and colonisation by mechanically modifying the implant surface topography, delaying re-infection/colonisation of the site. This in vitro study aims to investigate the release of particles from dental implants and their effects on human gingival fibroblasts (HGFs), following an in vitro mock implantoplasty procedure with a diamond burr. Materials and methods: Commercially available implants made from grade 4 (commercially pure, CP) titanium (G4) and grade 5 Ti-6Al-4 V titanium (G5) alloy implants were investigated. Implant particle compositions were quantified by inductively coupled plasma optical emission spectrometer (ICP-OES) following acid digestion. HGFs were cultured in presence of implant particles, and viability was determined using a metabolic activity assay. Results: Microparticles and nanoparticles were released from both G4 and G5 implants following the mock implantoplasty procedure. A small amount of vanadium ions were released from G5 particles following immersion in both simulated body fluid and cell culture medium, resulting in significantly reduced viability of HGFs after 10 days of culture. Conclusion: There is a need for careful evaluation of the materials used in dental implants and the potential risks of the individual constituents of any alloy. The potential cytotoxicity of G5 titanium alloy particles should be considered when choosing a device for dental implants. Additionally, regardless of implant material, the implantoplasty procedure can release nanometre-sized particles, the full systemic effect of which is not fully understood. As such, authors do not recommend implantoplasty for the treatment of peri-implantitis

Lithium-silicate sol-gel bioactive glass and the effect of lithium precursor on structure-property relationships

This work reports the synthesis of lithium-silicate glass, containing 10 mol% of Li 22 O by the sol–gel process, intended for the regeneration of cartilage. Lithium citrate and lithium nitrate were selected as lithium precursors. The effects of the lithium precursor on the sol–gel process, and the resulting glass structure, morphology, dissolution behaviour, chondrocyte viability and proliferation, were investigated. When lithium citrate was used, mesoporous glass containing lithium as a network modifier was obtained, whereas the use of lithium nitrate produced relatively dense glass-ceramic with the presence of lithium metasilicate, as shown by X-ray diffraction, 2929 Si and 77 Li MAS NMR and nitrogen sorption data. Nitrate has a better affinity for lithium than citrate, leading to heterogeneous crystallisation from the mesopores, where lithium salts precipitated during drying. Citrate decomposed at a lower temperature, where the crystallisation of lithium-silicate crystal is not thermodynamically favourable. Upon decomposition of the citrate, a solid-state salt metathesis reaction between citrate and silanol occurred, followed by the diffusion of lithium within the structure of the glass. Both glass and glass-ceramic released silica and lithium ions in culture media, but release rate was lower for the glass-ceramic. Both samples did not affect chondrocyte viability and proliferation

Sol-gel derived lithium-releasing glass for cartilage regeneration

Wnt - signalling cascade is one of the crucial pathways involved in the development and homeostasis of cartilage . I nfluencing this pathway can potentially contribute to improved cartilage repair or regeneration. One key molecular regulator of the Wnt pathway is the glycogen synthase kinase - 3 (GSK - 3) enzyme, the inhibition of which allows initiation of the signalling pathway. This study aims to utilise a binary SiO 2 - Li 2 O sol - gel derived glass for controlled delivery of lithium, a known GSK - 3 antagonist . The effect of the dissolution products of the glass on chondrogenic differentiation in an in vitro 3 - D pellet culture model is reported . D issolution products that contained 5 mM lithium and 3.5 mM silicon, were capable of inducing chondrogenic differentiation and hyaline cartilaginous matrix formation without the presence of growth factors such as TGF - β3. The results suggest that sol - gel derived glass has the potential to be used as a delivery vehicle for therapeutic lithium ions in cartilage regeneration applications

Tailoring the delivery of therapeutic ions from bioactive scaffolds while inhibiting their apatite nucleation: a coaxial electrospinning strategy for soft tissue regeneration

The delivery of therapeutic ions, as a key element for the regeneration of soft tissue, represents a viable alternative to conventional drugs. Primarily designed for the regeneration of hard tissue, degradable bioactive inorganic matrices are a carrier of choice for the delivery of ionic chemical cues. However, they nucleate calcium-phosphate crystal on their surface, which could be undesired for most soft tissue regeneration. Here, a coaxial electrospinning process was engineered, generating core–shell fibres with inorganic particles enclosed within a bio-inert polymeric shell. Silicon doped vaterite (SiV) dispersed in poly(L-lactic acid) was selected as an inorganic composite core and poly(D,L-lactide-co-glycolide) (PLGA) as a shell. By careful selection of the electrospinning parameters, fibres of constant diameter (≈10 μm) with controllable shell thickness (from 1.3 to 4.2 μm) were obtained. The release of calcium and silica followed the Weibull model, showing a purely diffusive release after hydration of the PLGA layer. The rate of release could be controlled with the shell thickness. The nucleation of calcium-phosphate crystals was inhibited. In addition, with the presence of a PLGA shell layer, the mechanical properties of the fibermats were greatly improved with, for instance, an increase of the Young's modulus up to 536% as compared to original composite. These non-woven porous materials are an affordable investigation platform to study the effect of local ionic release onto the surrounding cell metabolism

A unified in vitro evaluation for apatite-forming ability of bioactive glasses and their variants

The aim of this study was to propose and validate a new unified method for testing dissolution rates of bioactive glasses and their variants, and the formation of calcium phosphate layer formation on their surface, which is an indicator of bioactivity. At present, comparison in the literature is difficult as many groups use different testing protocols. An ISO standard covers the use of simulated body fluid on standard shape materials but it does not take into account that bioactive glasses can have very different specific surface areas, as for glass powders. Validation of the proposed modified test was through round robin testing and comparison to the ISO standard where appropriate. The proposed test uses fixed mass per solution volume ratio and agitated solution. The round robin study showed differences in hydroxyapatite nucleation on glasses of different composition and between glasses of the same composition but different particle size. The results were reproducible between research facilities. Researchers should use this method when testing new glasses, or their variants, to enable comparison between the literature in the future