Objectives: Inherently porous, bioactive 58S sol-gel glass tissue engineering scaffolds are considered suitable as osteoproductive human bone allografts, having superior resorbtion profiles compared to the original, impermeable, melt derived 45S5 Bioglass®. Providing tissue fluid ingress routes and becoming saturated within minutes, the pore network's distribution and interconnectivity requires investigation. Porosity defined during manufacture, regulates bioactivity by controlling surface area dependent reaction stages. Conceivably, post-implantation, the pores enlarge, ultimately becoming sites for accelerated osteogenesis. Methods: Five complimentary methods resolving distinct pore sizes, were applied to twenty 58S sol-gel monoliths. Nitrogen porosimetry (BET analysis) resolved micro (<20Å) and smaller mesopores (20-500Å), supplemented by helium ultra-pycnometry. Mercury intrusion (0-33 Kpsi) best characterised meso-macropores (>500Å), while SEM and confocal reflection microscopy of residual mercury, identified macropores. Confocal fluorescence microscopy demonstrated rhodamine labelled ethanol and command set dentine bonding polymers (2HEMA,Bis-methacrylate), permeating networks. Results: Both porosimetry techniques yielded surface area data, pore volumes, skeletal density values and identified overlapping micro, meso & macropore distributions (1-1000Å diameter). However, mercury porosimetry defined larger populations especially above discernable nitrogen adsorption size ranges. Confocal reflection microscopy of intruded specimens, demonstrated mercury within pores up to 20microns diameter. After fracture, SEM identified meso and macropores within 58S monoliths but provided no proof of network patency under standard conditions. Confocal fluorescence microscopy demonstrated fluorochrome labelled bonding resin infiltration proportionate to the square root of time, indicating a genuinely patent network, refuting suggestions that porosimetry intrusion pressures had forced systems open. Rhodamine labelled ethanol rapidly occupied the pore network, homogeneously staining it, suggesting a uniform distribution, contiguous with the solid silicate network. Conclusions: The patency, uniform distribution and isotropy of the interconnecting pores ranging from 5Å to 20 microns diameter, was clearly demonstrated. This enhances the potential of 58S glass as a regulatable bioactive human bone allograft. Large molecule infiltration further supports potential additional drug depot and biosensor roles.

Back to the Dental Materials: VIII - Others-Non-metallic Program
Back to the IADR/AADR/CADR 80th General Session (March 6-9, 2002)

Top Level Search