The bioactive glass known as Bioglass or Perioglass (USB) (US Biomaterials, Alachua, FL) has proven to be an effective graft material owing to the apatite layer which forms on the surface of the glass, promoting bone formation. USB particles range in size from 90 to 710 microns in diameter, as determined by optical microscopy. A similar bioactive material, BioGran (OV) (Orthovita, Malvern, PA), was developed to limit the particle size of 4555 to the range between 300 and 360 microns, as determined by sieving. The objective of this study was to histologically and biomechanically compare the 4555 bioactive glass, produced by US Biomaterials, in a wide particle range (USB) to the narrower particle range glass produced by Orthovita (OV) The grafted defects will then be compared to normal cancellous bone (NORM) of the distal femur in rabbits. Histologically, more bone was quantified at both 4 and 12 weeks within the defects filled with USB and NORM when compared to the limbs filled with OV (p< 0.05). The OV particles had greater particle axes and larger particle areas on average than the USB particles (p < 0.05). However, the particle axis and area of the two materials decreased with time at a similar rate. Biomechanically, the USB- and OV-grafted defects had comparable peak compressive load, compressive stiffness, and compressive modulus which were equivalent to normal bone.

Bioactive glasses form a surface apatite layer in vivo that enhances the formation and attachment of bone. Sol-gel Bioglass graft material provides greater nanoscale porosity than bioactive glass (on the order of 50-200 A), greater particle surface area, and improved resorbability, while maintaining bioactivity. This study histologically and biomechanically evaluated, in a rabbit model, bone formed within critical-sized distal femoral cancellous bone defects filled with 45S5 Bioglass particulates, 77S sol-gel Bioglass, or 58S sol-gel Bioglass and compared the bone in these defects with normal, intact, untreated cancellous bone and with unfilled defects at 4, 8, and 12 weeks. All grafted defects had more bone within the area than did unfilled controls (p < 0.05). The percentage of bone within the defect was significantly greater for the 45S5 material than for the 58S or 77S material at 4 and 8 weeks (p < 0.05), yet by 12 weeks equivalent amounts of bone were observed for all materials. By 12 weeks, all grafted defects were equivalent to the normal untreated bone. The resorption of 77S and 58S particles was significantly greater than that of 45S5 particles (p < 0.05). Mechanically, the grafted defects had compressive stiffness equivalent to that of normal bone at 4 and 8 weeks. At 12 weeks, 45S5-grafted defects had significantly greater stiffness (p < 0.05). At 8 and 12 weeks, all grafted defects had significantly greater stiffness than unfilled control defects (p < 0.05). In general, the 45S5-filled defects exhibited greater early bone ingrowth than did those filled with 58S or 77S. However, by 12 weeks, the bone ingrowth in each defect was equivalent to each other and to normal bone. The 58S and 77S materials resorbed faster than the 45S5 materials. Mechanically, the compressive characteristics of all grafted defects were equivalent or greater than those of normal bone at all time points.

Bioactive glasses form a surface apatite layer in uivo that enhances the formation and attachment of bone. Sol-gel Bioglass graft material provides greater nanoscale porosity than bioactive glass (on the order of 50-200 A), greater particle surface area, and improved resorbability. while maintaining bioactivity. This study histologically and biomechanically evaluated, in a rabbit model. bone formed within critical-sized distal femoral cancellous bone defects filled with 4SS5 Bioglass particulates, 77s sol-gel Bioglass. or 58s sol-gel Bioglass and compared the bone in these defects with normal. intact, untreated cancellous bone and with unfilled defects at 4, 8. and 12 weeks. All grafted defects had more bone within the area than did unfilled controls (p < 0.05). The percentage of bone within the defect was significantly greater for the 4585 material than for the 58s or 77s material at 4 and 8 weeks (p < 0.05), yet by 12 weeks equivalent amounts of bone were observed for all materials. By 12 weeks, all grafted defects were equivalent to the normal untreated bone. The resorption of 77s and 58s particles was significantly greater than that of 4585 particles (p < 0.05). Mechanically, the grafted defects had compressive stiffness equivalent to that of normal bone at 4 and 8 weeks. At 12 weeks, 45SS-grafted defects had significantly greater stiffness (p < 0.05). At 8 and 12 weeks, all grafted defects had significantly greater stiffness than unfilled control defects (p < 0.05). In general, the 45S5filled defects exhibited greater early bone ingrowth than did those filled with 585 or 77s. However, by 12 weeks, the bone ingrowth in each defect was equivalent to each other and to normal bone. The 58s and 77s materials resorbed faster than the 45S5 materials. Mechanically, the compressive characteristics of all grafted defects were equivalent or greater than those of normal bone at all time points.

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Summary:Bioactive glasses form a surface apatite layer in uivo that enhances the formation and attachment of bone. Sol-gel Bioglass graft material provides greater nanoscale porosity than bioactive glass (on the order of 50-200 A), greater particle surface area, and improved resorbability. while maintaining bioactivity. This study histologically and biomechanically evaluated, in a rabbit model. bone formed within critical-sized distal femoral cancellous bone defects filled with 4SS5 Bioglass particulates, 77s sol-gel Bioglass. or 58s sol-gel Bioglass and compared the bone in these defects with normal. intact, untreated cancellous bone and with unfilled defects at 4, 8. and 12 weeks. All grafted defects had more bone within the area than did unfilled controls (p < 0.05). The percentage of bone within the defect was significantly greater for the 4585 material than for the 58s or 77s material at 4 and 8 weeks (p < 0.05), yet by 12 weeks equivalent amounts of bone were observed for all materials. By 12 weeks, all grafted defects were equivalent to the normal untreated bone. The resorption of 77s and 58s particles was significantly greater than that of 4585 particles (p < 0.05). Mechanically, the grafted defects had compressive stiffness equivalent to that of normal bone at 4 and 8 weeks. At 12 weeks, 45SS-grafted defects had significantly greater stiffness (p < 0.05). At 8 and 12 weeks, all grafted defects had significantly greater stiffness than unfilled control defects (p < 0.05). In general, the 45S5-filled defects exhibited greater early bone ingrowth than did those filled with 585 or 77s. However, by 12 weeks, the bone ingrowth in each defect was equivalent to each other and to normal bone. The 58s and 77s materials resorbed faster than the 45S5 materials. Mechanically, the compressive characteristics of all grafted defects were equivalent or greater than those of normal bone at all time points.Some osseous defects and fractures may require supplementation to support and promote healing. An assortment of animal models has been used to investigate many biomaterials as potential bone grafts, with varying success.Autograft is clearly the gold standard; however, the limited graft supply and postoperative donor site morbidity are problematic (15,39). Allografts and freshfrozen and demineralized bone matrix have proved effective (9,15,30,35) yet carry the theoretical risk of disease transmission (1,37). Many synthetic materials have been investigated for the regeperation of skeletal tissue, including hydroxyapatite (3,4,18,26), tricalcium phosphates (4,18,26), calcium sulfate (2,24), polymers (14,20,27), bioactive glass (12,28,31,38,40), and collagen sponges impregnated with growth factors (6,44). Each graft material has been shown to have advantages and disadvantages.Bioactive glasses are of particular interest due to their unique capacity to form a thick apatite gel layer on the particle surfaces that attracts osteoprogenitor cells and osteoblasts (19). A very strong bond is formed between the bone tissue and the gl...