Demineralised dentine matrix (DDM) contains a myriad of growth factors and matrix proteoglycans, the bioactivity of which can utilised in dental restorations and bone augmentations. This study aimed to develop a novel antimicrobial, bioactive dental cement to promote reparative dentinogenesis and prevent infections, improving the longevity of current dental restorations.

Nanocarriers containing DDM (extracted from non-carious dentine; 1–100 μg/mL), and triclosan (300 μg/mL) were made. Human dental pulp stem cells (hDPSCs) were treated with DDM nanocarriers (10 ng/mL-100 μg/mL) for 3, 9, 21 and 35 days. Cell proliferation and viability were assessed by cell counts, Caspase-Glo 3/7 (Promega) and MTT assays. qRT-PCR was used to examine the expression of osteogenic markers runx2 and osteocalcin at days 3, 9 and 21. A transwell chemotaxis/ migration assay was used to assess the ability of DDM nanoparticles to recruit hDPSC progenitors. Triclosan nanocarriers were tested using growth curves and zones of inhibitions for S. Anginosus and E. Faecalis. SEM and biomechanical testing was carried out on Vitremer (Henry Schein) dental cements containing loaded and empty nanocarriers.

DDM nanocarriers were able to significantly recruit hDPSCs and induce the expression of osteogenic markers in hDPSCs after 9 days. DDM Nanocarriers had no effect on cell proliferation or survival. Triclosan nanocarriers were able to inhibit the growth of S. Anginosus and E. Faecalis. Nanocarriers had limited effect on the biomechanical integrity of Vitremer cements.

Nanocarriers successfully delivered DDM to hDPSC, promoting their in vitro recruitment and osteogenic differentiation, and triclosan to endodontic bacteria inhibiting their growth. The nanocarriers were incorporated into cements with minimal physical artefacts, therefore a novel antimicrobial, bioactive dental cement was produced, which could be a useful tool for dental tissue engineering.

The most common mode of failure observed in cemented orthopaedic implants is aseptic loosening of the prosthesis over time. This occurs as a result of fatigue failure of the bone cement under different loading conditions. Although a great deal of research has been carried out on the fatigue crack development of poly(methyl methacrylate) (PMMA) bone cements, the effects of different loading frequencies at low and high stress intensities are not well understood. Therefore, the aims of this study are to determine the effects of loading PMMA bone cement at different stress intensities and loading frequencies, as seen in-vivo, and the effects of changing these parameters on fatigue crack propagation. To achieve these aims, disc compact tension (DCT) samples with chevron notches were made and Krak Gages (Russenberger Prufmaschinen, Neuhausen am Rheinfall, Switzerland) were attached to monitor crack growth. The bone cement used in this study was the Cemex System, which uses a cement gun to mix and apply the material into the cavity. From standard compression and bending tests it was found that the cement made using this system had an average compressive strength of 86.66±5.52MPa, an average bending modulus of 3696.06±121.13MPa and an average bending strength of 51.95±4.14MPa. These values are within the normal range of acrylic resin cements for implants and above the minimum requirements of the ISO5833:2002 standard. A program has been written that loads the DCT samples with a stress intensity of 0.2MPam^1/2, 0.6MPam^1/2 and 1.0MPam^1/2 at a frequency of 1Hz, 2Hz, 5Hz, 10Hz and 20Hz. The crack was allowed to grow 0.2mm at each frequency and the frequencies were increased (1Hz to 20Hz) then decreased in magnitude (20Hz to 1Hz) for each of the stress intensities.

This experimental design enables much more sensitive detection of small changes in crack growth rate than a conventional test where the crack grows through the entire range of δK at a single frequency. By repeatedly varying the loading within the same specimen the effects of variation between specimens can be removed, revealing significant differences in crack growth rate. The results provide important information on bone cement when loaded in conditions similar to those seen in-vivo and how frequency and stress intensities affect the fracture mechanics of PMMA.