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Objectives To systematically investigate the biological interface of Bio-Oss by analysing dissolution–precipitation behaviour and osteogenic responses using in vitro experimental systems.

Material and methods Different concentrations (1–100 mg/ml) of Bio-Oss were incubated in cell culture medium for 24 h before elemental concentrations for calcium, phosphorus and silicon in the medium were analysed with inductive coupled plasma-optical emission spectroscopy. Radioactive calcium-45 isotope labelling technique was used to study possible precipitation of calcium on the Bio-Oss particle. Biological interface of Bio-Oss was studied in osteogenic experiments using mineralization medium and three different sources of cells (primary mouse bone marrow stromal cells, primary rat calvarial cells and MC3T3-E1 mouse pre-osteoblast cell line). Cells were fixed and stained with Toulidine blue, von Kossa or Alizarin Red staining for confirmation of extracellular matrix mineralization.

Results Elemental analysis of the cell culture medium demonstrated a significant decrease of calcium and phosphorus and a dose-dependent release of silicon to the medium after incubation with Bio-Oss. A significant decrease of calcium and phosphorus in the medium occurred even at low concentrations of Bio-Oss. Uptake of calcium on the Bio-Oss particle was confirmed with radioactive calcium-45 isotope labelling technique. In osteogenic experiments with Bio-Oss (<1 mg/ml), matrix mineralization around the Bio-Oss particles were demonstrated in all three cell types with von Kossa and Alizarin Red staining.

Conclusion Dissolution–precipitation reactions occur at the surface of Bio-Oss, and osteogenic responses are seen at the biological interface. The concentration of Bio-Oss is a key factor for the experimental in vitro results, and may also have implications for the clinic.

Biomaterials are widely used in clinical practice as bone graft substitutes for treating patients with bone defects. A molecular level understanding of the chemical processes at the interface between the biomaterial and the biological environment is crucial to succeed in tissue regeneration and to predict the treatment outcome. In this study, we used three different bone graft substitute materials (BioGlass 45S5—synthetic, Bio-Oss—bovine derived and Algipore—derived from algae) which were incubated in an α-minimum essential medium (α-MEM) during 1, 3 and 7 days. Initial surface composition of the biomaterials and the chemistry of their solid–solution interface were monitored by XPS with a fast-frozen samples technique. The XPS analysis showed that the equilibrium at the solid-solution interface is reached within 24 h. The Na/Cl atomic ratio at equilibrium indicates a negatively charged surface for Bio-Oss. In contrast, the other two materials gained a positive surface charge, which resulted in pronounced adsorption of amino acids at the interface from the medium. The surface chemical reconstruction and charge generation mechanism responsible for this effect are discussed with regard to bulk composition of the materials and possible proliferation and differentiation cell patterns that could be expected at the interface. Copyright © 2010 John Wiley & Sons, Ltd.

Pathological processes in the alveolar and facial bones can lead to bone loss that may not heal with complete regeneration. Biomaterials can be used to facilitate the healing process and/or as a bone substitute, but the mechanisms are not fully understood. Persistent leakage of bacteria/bacterial toxins, after root canal treatment, may lead to a residual bone defect. The healing is dependent on a placed dental biomaterial providing a tight seal. The composition of the filling material may also influence the healing process.

The general aim of this study is to investigate surface properties and biological interactions of biomaterials used in dento-alveolar surgery. A dental biomaterial, a bonded compomer (DAP) containing a corroding glass filler, was used as a root end filling material, promoting a new operation technique. The healing (assessed according to Molven´s x-ray criteria) demonstrates a significant improvement in healing results for the compomer group, compared to a commonly used technique. The surface properties and biological interactions of DAP were analyzed. ICP-OES of DAP cell culture medium extract demonstrated a significant release of Sr, Si and F from the dental biomaterial. Human periodontal ligament (PDL) cells grew on and around DAP specimens without any sign of toxic reactions. DAP extract stimulated proliferation of PDL cells, but caused an inhibition of osteoblastic gene expression in mouse bone marrow cells. The surface properties of the glass containing compomer may contribute to improved healing of the periapical lesions.

A bovine inorganic bone graft substitute (BO) is commonly used as a treatment option in dento-alveolar surgery with new bone formation in immediate close contact with BO material. ICP-OES dissolution analysis of cell culture media, after incubation with BO particles, demonstrated a dosedependent release of Si and a decrease of Ca and P. An uptake of Ca from the medium to the BO particle was demonstrated with calcium-45 labeling. The Si dissolution varied between different batches, possibly reflecting a variation in food intake in the animals. Stimulated osteogenic response was seen in close contact to the BO particles in cell cultures. Furthermore, it was clearly demonstrated that the study design is a critical factor for correctly understanding biomaterials’ biological interactions.

The surface properties of three bone graft substitutes reported to have good results in dento-alveolar surgery were investigated, in order to establish whether or not dissolution-precipitation reactions could contribute to the bone healing. Dissolution-precipitation extracts of BO, bioactive glass 45S5 (BG) and a marine algae hydroxyl apatite (AP) in cell culture media were analyzed. Dissolution of Si at significant levels was detected for BO and 45S5 over time. Significant uptake levels of Ca and P from the culture were seen for both 45S5, BO and AP but at different times. Surface analysis of the biomaterials with SEM/EDAX, before and after immersion in cell culture media, revealed a smoothing of the surface morphology for 45S5 over time. No obvious alterations for BO and AP were detected. Ca/P ratio decreased significantly for 45S5, but no major changes were detected by XPS for BO or AP. XPS further demonstrated a surface charge for BO, changing from negatively to positively charged when exposed to serum. 45S5 and AP had positive surface charges, both in the absence and the presence of serum. These demonstrated surface changes in biomaterials could contribute to adherence of cells and subsequently affect bone healing.

Conclusion: Biomaterials used in dento-alveolar surgery interact with biological surroundings through surface and dissolution-precipitation reactions which may have implications for bone healing.

Objective. This study investigates the treatment outcome of a root-end filling technique that uses a light-cured compomer combined with a light-cured dental adhesive.

Study design. The study used 34 single-rooted teeth restored with post, core, and crowns. A shallow concave apical preparation was filled with a light-cured compomer with a light-cured dental adhesive. As a control, a chemically cured glass ionomer was used with a conventional root-end preparation. A follow-up clinical and radiographic evaluation of the treatment result was conducted after 1 year.

Results. A significantly higher success rate (P\.015) was observed in the treatment group that used a compomer (89% complete healing) compared to glass ionomer (44% complete healing).

Conclusions. When used as a retrograde root filling in a shallow concave preparation, a light-cured compomer and a dental adhesive improves healing regardless of the quality of the remaining root filling.

OBJECTIVES: The aim of this work was to investigate the release of inorganic ionic products from specimens of the polyacid-modified composite resin Dyract AP (DAP) and furthermore, to analyze the biological effect of DAP and the medium extract in human periodontal ligament (PDL) cells and mouse bone marrow cell (BMC) cultures.

METHODS: Ion release from DAP specimens immersed in cell culture medium was analyzed with inductively coupled plasma optical emission spectroscopy (ICP-OES). Cells were cultured with either DAP specimens or with DAP media extract and effects on cell proliferation, osteoblastic gene expression and mineralization capacity were analyzed with direct-contact tests, neutral red (NR) uptake, quantitative real-time PCR and a bone nodule formation assay.

RESULTS: ICP-OES analysis of DAP extract demonstrated a significant increase in fluoride, strontium and silica. PDL cells demonstrated normal growth pattern in the direct-contact tests with the material. DAP extracts produced a dose-dependent stimulation of cell proliferation and concomitant inhibition of osteoblast specific markers and nodule formation.

SIGNIFICANCE: The compomer may have possible bioactive properties due to ions leaching out from the filler component.