Experimental follow-up model for clinical frontal sinus obliteration with bioactive glass (S53P4)

Bioactive glass S53P4 (BG) is an osteoconductive allograft material. Since 1990, BG has been used in the obliteration of Frontal sinuses in more than 30 consecutive patients. The patients have been monitored regularly with cl inical examinations, computer tomography (CT) scans, laboratory tests and, in a few cases, biopsies have also been obtained. The material has been wel l tolerated and no loss of volume of obliteration material has been seen in the obliterated sinuses. However, in repeated CT monitoring and with Regio n of Interest (ROI) analysis, a decrease in the density of the obliteration material inside the frontal sinuses has been seen. In the present study, t he clinical conditions after an obliteration operation were simulated and t he behaviour of the BG in the obliterated area was observed. The aim was to study whether it is possible indirectly to estimate the resorption of a ma ssive amount of BG with ROI analysis for monitoring the clinical success of the treatment. Thus two sizes of granules (0.63-0.8 mm and 0.8-1.0 mm) in eight separate BG amounts, weight 25 g, were tested in simulated body fluid (SBF) in standard conditions. The dissolution of silicon (Si) and phosphat e (P) was detected with direct plasma atom emission spectroscopy (DCP-AES) monthly up to 6 months. The BG amounts were scanned with CT and the slices analysed using the ROI technique at 1, 3 and 6 months. The cumulative loss of Si and P in SBF was significant during the study (p < 0.0001) and it was stronger with smaller than with larger granules (p < 0.0001). This was sho wn correspondingly by the decrease of Hounsfield units (p < 0.0001) in ROI analysis. The method seems reliably to reveal the resorption of BCT for cli nical purposes.