Novel glass ionomer cements for biomedical applications.

Since their invention in the late 1960's, glass ionomer cements (GICs) have been used extensively in dentistry but recently they have also been utilised as bone cements in ear nose and throat (ENT) surgery. Unfortunately, AI3+, a component of conventional ionomer glasses, has been linked to poor bone mineralisation and neurotoxicity. Consequently, the aim of the research was to modify the glass composition in GIC bone cements to reduce the amount of AI3+ present and therefore its potential release during clinical usage. Fe2O3 was therefore substituted for AI2O3 in the glass formulations and the resulting cements compared with conventional GIC's Glasses with molar compositions of 4.5SiO2∙XM2O3∙YP2O5∙3CaO∙2CaF2 (M = AI or Fe, X = 3 or 1.5 Y = 0 – 1.5)were fabricated using a conventional glass-processing route. Cements were prepared using a standard ratio; 1 g of glass powder: 0.2 g of dried polyacrylic acid: 0.3 g of 10% tartaric acid solution, and their setting times, mechanical properties, and in-vitro biocompatibility evaluated. AI2O3-based glasses were amorphous when cast into water but crystallised to apatite and mullite when heat treated at 750°C and 950°C, respectively. In contrast, Fe2O3-based glasses devitrified to magnetite and apatite on cooling irrespective of the quench rate. Cements could be fabricated from all glasses and glass ceramics. GIC's based on Fe2O3 containing glasses gave similar mechanical properties to conventional AI2O3 based GIC's and several compositions were identified whose setting times were appropriate for clinical usage. Good in vitro biocompatibility was observed for all Fe2O3 - based cements and for those formed from AI2O3-based ionomer glasses crystallised at 750°C to form apatite

Therapeutic ion-releasing bioactive glass ionomer cements with improved mechanical strength and radiopacity

Bioactive glasses (BG) are used to regenerate bone, as they degrade and release therapeutic ions. Glass ionomer cements (GIC) are used in dentistry, can be delivered by injection and set in situ by a reaction between an acid-degradable glass and a polymeric acid. Our aim was to combine the advantages of BG and GIC, and we investigated the use of alkali-free BG (SiO2-CaO-CaF2-MgO) with 0 to 50% of calcium replaced by strontium, as the beneficial effects of strontium on bone formation are well documented. When mixing BG and poly(vinyl phosphonic-co-acrylic acid), ions were released fast (up to 90% within 15 minutes at pH 1), which resulted in GIC setting, as followed by infrared spectroscopy. GIC mixed well and set to hard cements (compressive strength up to 35 MPa), staying hard when in contact with aqueous solution. This is in contrast to GIC prepared with poly(acrylic acid), which were shown previously to become soft in contact with water. Strontium release from GIC increased linearly with strontium for calcium substitution, allowing for tailoring of strontium release depending on clinical requirements. Furthermore, strontium substitution increased GIC radiopacity. GIC passed ISO10993 cytotoxicity test, making them promising candidates for use as injectable bone cements

Effect of reduced exposure times on the cytotoxicity of resin luting cements cured by high-power led

OBJECTIVE: Applications of resin luting agents and high-power light-emitting diodes (LED) light-curing units (LCUs) have increased considerably over the last few years. However, it is not clear whether the effect of reduced exposure time on cytotoxicity of such products have adequate biocompatibility to meet clinical success. This study aimed at assessing the effect of reduced curing time of five resin luting cements (RLCs) polymerized by high-power LED curing unit on the viability of a cell of L-929 fibroblast cells. MATERIAL AND METHODS: Disc-shaped samples were prepared in polytetrafluoroethylene moulds with cylindrical cavities. The samples were irradiated from the top through the ceramic discs and acetate strips using LED LCU for 20 s (50% of the manufacturer's recommended exposure time) and 40 s (100% exposure time). After curing, the samples were transferred into a culture medium for 24 h. The eluates were obtained and pipetted onto L-929 fibroblast cultures (3x10(4) per well) and incubated for evaluating after 24 h. Measurements were performed by dimethylthiazol diphenyltetrazolium assay. Statistical significance was determined by two-way ANOVA and two independent samples were compared by t-test. RESULTS: Results showed that eluates of most of the materials polymerized for 20 s (except Rely X Unicem and Illusion) reduced to a higher extent cell viability compared to samples of the same materials polymerized for 40 s. Illusion exhibited the least cytotoxicity for 20 s exposure time compared to the control (culture without samples) followed by Rely X Unicem and Rely X ARC (90.81%, 88.90%, and 83.11%, respectively). For Rely X ARC, Duolink and Lute-It 40 s exposure time was better (t=-1.262 p=0,276; t=-9.399 p=0.001; and t=-20.418 p<0.001, respectively). CONCLUSION: The results of this study suggest that reduction of curing time significantly enhances the cytotoxicity of the studied resin cement materials, therefore compromising their clinical performance