In vivo model for frontal sinus and calvarial bone defect obliteration with bioactive glass S53P4 and hydroxyapatite.

An in vivo model was developed to investigate the usability of a frontal sinus and a calvarial bone defect obliteration with bioactive glass S53P4 (BG) and hydroxyapatite (HA) granules. Roofs of 21 Elco rabbit frontal sinuses were drilled open from 4 separate holes using a standard method, and the sinuses, located in pairs, in frontal bone were filled with BG on one side and with HA on the other side. Two parallel posterior defects were covered with a pedicled periosteum flap, and 2 anterior defects with a free flap. The stability of materials, new bone, and connective tissue formation were observed with histomorphometry, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), and X-ray pictures at 1, 3, 6, and 12 months postoperatively. The results showed more rapid resorption of filling material (p = 0.019) and new bone formation (p = 0.0001) in the defects filled with BG than in the corresponding HA-filled defects studied by histomorphometry throughout the study. New bone formation and resorption of materials were faster in defects covered by a pedicled flap than by a free periosteum flap. The results were supported by SEM histomorphometric and radiologic analysis. Both bioactive materials studied were well tolerated in frontal sinuses and in calvarial bone defects. The experimental model showed the influence of early periosteum vascularization on accurate frontal sinus filling and the healing process in rabbit frontal sinuses.

Clinical follow-up method for frontal sinus obliteration with bioactive glass S53P4.

A clinical follow-up method was developed to investigate the behavior of a massive amount of bioactive glass S53P4 (BG) clinically used in frontal sinus obliteration. Two sizes of granules (0.63-0.8 mm or 0.8-1.0 mm) in 16 separate BG amounts, weight 25 g, were tested both in simulated body fluid (SBF) and in a buffer containing tris-hydroxymethyl aminomethane citric acid (TRIS-c.a) in standard conditions. The dissolution of silicon (Si) and phosphate (P) was detected with direct current plasma atom emission spectroscopy (DCP-AES) monthly up to 6 months. The BG masses were scanned both wet in the solutions and dried by computer tomography (CT), and the scans were analyzed by Region of Interest (ROI) technique. Calcium phosphate (CaP)- and silica (Si)-gel-layers were studied by scanning electron microscopy (SEM) at 1, 3, and 6 months. Cumulative loss of Si and P was stronger in TRIS-c.a than in SBF (p < 0.0001), and it was higher with smaller than with larger granules in both solutions (p < 0.0001). This was shown correspondingly by the decrease of Hounsfield units (HUs) in ROI analysis (p < 0.0001). The level of HUs was lower with dried than with wet BG (p < 0.0001). The results were compared for clinical ROI analysis of patients with obliterated frontal sinuses up to 48 months and they were parallel. The follow-up method seems to indirectly reveal the behavior of BG and the healing process in the obliterated cavity.

In vitro model for frontal sinus obliteration with bioactive glass S53P4.

An in vitro model was used to investigate the behavior of a massive frontal sinus obliteration with bioactive glass S53P4 (BG) for clinical purposes. Two sizes of granules (0.63-0.8 mm or 0.8-1.0 mm) in 16 separate BG amounts, weight 25 g, were tested both in simulated body fluid (SBF) and a buffer containing trishydroxymethyl aminomethane citric acid (TRIS-c.a) in standard conditions. The dissolution of silicon (Si) and phosphate (P) was detected with direct current plasma atom emission spectroscopy (DCP-AES) monthly up to 6 months. The BG masses were scanned by computer tomography (CT) and the scans analyzed by Region of Interest (ROI) technique. Calcium phosphate (CaP)- and silica (Si)-gel-layers were studied by scanning electron microscopy (SEM) at 1, 3, and 6 months. Cumulative loss of Si and P was stronger in TRIS -c.a than in SBF (p < 0.0001), and it was higher with smaller than with larger granules in both solutions (p < 0.0001). This was shown correspondingly by the decrease in Hounsfield units (HU) by ROI analysis (p < 0.0001). In SBF-soaked BG masses, the CaP-layer occurred on the uppermost granules, and in TRIS-c.a at 3-6 months, on the granules in the center and lower parts. The decrease of HU seems to reveal indirectly the resorption of BG.