Novel bioactive and biodegradable glass ceramics with high mechanical strength in the CaOSiO₂B₂O₃ system

Abstract

Novel bioactive and biodegradable glass ceramics with high mechanical strength in the (50-x/2)CaO ⅐ SiO 2 OxB 2 O 3 (4.2 Յ x Յ 17.2) system were investigated. The systems consisted of three phases: monoclinic wollastonite, calcium metaborate, and amorphous borosilicate matrix. The glass ceramics containing 4.2 mol% and 8.4 mol% B 2 O 3 showed high bulk density and a dense microstructure. Mechanical strengths of the glass ceramics were higher than those of other bioactive ceramics: high compressive strength (2813 MPa), bending strength of 212 MPa, and fracture toughness of 3.12 MPa ⅐ m 1/2 . The glass-ceramic formed apatite layer on their surface in the simulated body fluid and showed significant biodegradation. The degree of apatite formation in the glass ceramics depended on the calcium metaborate content and borosilicate glassy matrix. Additional calcium metaborate and borosilicate glassy matrix increased the apatite formation rate on the surface. It might be likely that calcium metaborate causes supersaturation of Ca ions, for its high solubility in SBF and the water-reactive borosilicate glassy matrix formed SiOOH groups on the surface to provide nucleation sites for apatite formation. Also, through in vitro test for the biocompatibility of the CaOOSiO 2 OB 2 O 3 glass ceramics, no cytotoxicity of the glass ceramics were found. The results on bioactivity and noncytotoxicity indicated that glass ceramics in the (50-x/ 2)CaO ⅐ SiO 2 OxB 2 O 3 (4.2 Յ x Յ 17.2) system could be useful as a biodegradable bone replacement material.

Glass-frit size dependence of densification behavior and mechanical properties of zinc aluminum calcium borosilicate glass-ceramics

“…The porosity and grain size of the ZAeCBSÀ1.2 sample are the lowest (3.9%) and the smallest (1.5 mm) ones, respectively, and significantly contribute to its highest flexural strength. The flexural strength of the ZAeCBSÀ1.2 sample sintered at 900 C (116 MPa) is comparable with the previously reported value for a calcium borosilicate glass system [18]; meanwhile, the ZAeCBSÀ2.9 and ZAeCBSÀ4.8 samples are characterized by much lower flexural strength values indicating that smaller sizes and lower size distributions of glass frits are important for achieving maximal flexural strength, especially at lower temperatures.…”

“…In particular, pores of sintered samples significantly affect their mechanical properties since they often originate crack propagation. From the experimental point, ceramic strength decreases almost exponentially with increasing porosity, which is consistent with the formula suggested by Ryschkewitsch [18,28]. The porosity and grain size of the ZAeCBSÀ1.2 sample are the lowest (3.9%) and the smallest (1.5 mm) ones, respectively, and significantly contribute to its highest flexural strength.…”

“…For example, bioactive and biodegradable properties of CBS glass systems were reported by C. Ohtsuki et al [17]; however, they exhibited poor mechanical properties. Ryu et al reported that CBS glass can be crystallized (leading to glass-ceramic formation) by heat treatment and controlling its chemical composition, thus demonstrating improved mechanical properties (such as bending strength and fracture toughness) of the material [18]. However, the number of reported studies on this topic is limited, and the related mechanical properties of glass-ceramics should be further enhanced in order to become suitable for more advanced applications [7].…”

Incorporation of B2O3 in CaO-SiO2-P2O5 bioactive glass system for improving strength of low-temperature co-fired porous glass ceramics

“…Saranti et al reported that the boron in the glass network of CaO-B 2 O 3 -P 2 O 5 system has a catalytic effect at favoring bioactivity of the other calcium phosphate glasses [22]. Recently, Lee et al found that this ternary CBS system was bioactive, and may be favorable as orthopaedic implants due to its low chemical durability in physiological fluids [23,24]. More recently, they have developed a high-phosphorus, low-boron CaO-SiO 2 -P 2 O 5 -B 2 O 3 BGC melted at 1550°C (with composition (wt.%): CaO 41.8, SiO 2 35.8, P 2 O 5 13.9, B 2 O 3 0.5, CaF 2 2.0 and MgO 6.0).…”

Control of the thermal properties of slow bioresorbable glasses by boron addition

“…Different oxide systems have been studied to understand the effect of changes in the glass composition on the bioactivity [8][9][10][11], glass structure [12], crystallization [11,13], and working range [7]. If the glasses are used as thin fibers (10-20 μm), their composition should be adjusted to prevent too rapid a dissolution in body fluids.…”