Compositional dependence of the formation of calcium phosphate films on bioglass

Abstract

Bioglass, which has a composition of sodium carbonate, calcium carbonate, phosphorous pentoxide and silica, has been shown to bond to living bone. This ability is dependent on controlled surface reactions. Investigators with 45S5 bioglass have demonstrated that the formation of a SiO2-rich layer and a calcium phosphate film on its surface in an aqueous environment is associated with the film bonding the bioglass to bone. The objects of this research were: 1. To study SiO2 dependence on the formation of a silica-rich layer and calcium phosphate films on a bioglass surface in a simulated physiological solution, and 2. To establish a correlation between in vitro surface reactions and in vivo bonding ability. It was discovered that three types of reactions occur in a simulated physiological solution depending on bioglass composition: 1. A calcium phosphate film and SiO2-rich layer form simultaneously and the reaction rate is fast for bioglasses which have a lower content of SiO2 (approximately 46 mol% SiO2). 2. A SiO2-rich layer forms first and a calcium phosphate film develops later between the aqueous environment and the SiO2-rich layer for bioglasses whose SiO2 content is between 46--55 mol %. 3. A calcium phosphate film does not form for glasses whose SiO2 content is more than 60 mol %.

Structural models of bioactive glasses from molecular dynamics simulations

“…The overall thickness of the bonding HA layer is approximately 100-200 mm in bioactive compositions (Hench & Andersson 1993); this layer creates a strong bridge between the natural tissues and the artificial implanted material, thus promoting the integration of the bioactive implant; at the same time, it passivates the glass surface against further degradation, which would otherwise extend to the rest of the glass. This crucial double role of the HA film explains the close correlation observed between the rate of HA formation and the bone-bonding ability of a glass composition: an exceedingly slow rate of HA formation will, in fact, result in no bonding to tissue (Ogino et al 1980). On the other hand, the most bioactive composition of this class, the 45S5 Bioglass, containing 45 wt% SiO 2 , crystallizes HA in few hours after implant, and achieves bonding to both hard and soft tissues in approximately a week (Hench & Andersson 1993;Hench 1998).…”

Biomaterials in orthopaedics

“…Owing to their poor mechanical properties, low tensile strength and very low fracture toughness, BGs are not suitable for loadbearing applications. Conversely, BGs were successfully used in low load-bearing material applications for bone repair in dental and orthopaedic surgery (Ogino et al 1980;Schepers et al 1991;Stanley et al 1997). BG surfaces have also been modified to enhance their bioactivity by coating them with adhesive proteins such as fibronectin to promote cell adhesion (García et al 1998).…”

In vitro apatite formation on organic polymers modified with a silane coupling reagent

“…The decrement of static contact angle can be explained by considering the fact that, since PA has -NH and CaO groups and are easily attacked by g-MPS oligomer radicals, the amount of g-MPS grafted on PA increased. The grafting introduced silanol groups as confirmed by the FT-IR and XPS spectra in figures 2 and 4, which should stimulate the formation of apatite when the grafted samples are soaked in SBF or 1.5 SBF (Ogino et al 1980;Kokubo et al 1990a;Tanahashi et al 1995;Oyane et al 1999Oyane et al , 2003Kim et al 2001). Indeed, PA (PA1, PA2, PA3) and HDPE3 samples deposited apatite in SBF.…”

“…When placed in a body environment, several glasses and ceramics (Ogino et al 1980;Kokubo et al 1990a) spontaneously deposit an apatite layer. Such ability is denoted as in vivo bioactivity, while it is in vitro bioactivity when such apatite deposition is achieved in a simulated body fluid (SBF) of the Kokubo recipe.…”