Development of novel strontium containing bioactive glass based calcium phosphate cement.

OBJECTIVE: The aim of this study was to investigate the effect on properties of increasing strontium substitution for calcium in bioactive glasses used as precursors for novel calcium phosphate cements. METHODS: Glasses were produced by progressively substituting strontium for calcium. Cements were prepared by mixing the glass powder with Ca(H2PO4)2 powder with a 2.5% solution of Na2HPO4. Setting times and compressive strength were measured after 1h, 1 day, 7 days and 28 days immersion in Tris buffer solution. X-ray diffraction (XRD), Fourier transform infrared spectroscopy and radiopacity were measured and crystal morphology was assessed using scanning electron microscopy. RESULTS: A correlation between the phases formed, morphology of the crystallites, setting time and compressive strength were analyzed. Setting time increased proportionally with strontium substitution in the glass up to 25%, whereas for higher substitutions it decreased. Compressive strength showed a maximum value of 12.5MPa and was strongly influenced by the interlocking of the crystals and their morphology. XRD showed that the presence of strontium influenced the crystal phases formed. Octacalcium phosphate (Ca8H2(PO4)6·5H2O, OCP) was the main phase present after 1h and 1 day whereas after 28 days OCP was completely transformed to strontium-containing hydroxyapatite (SrxCa(10-x)(PO4)6(OH)2, SrHA). Radiopacity increased proportionally to strontium substitution in the glass. SIGNIFICANCE: A novel method to develop a bone substitute forming in vitro SrHA as a final product by using a bioactive glass as a precursor was shown. These novel injectable bioactive glass cements are promising materials for dental and orthopedic applications. Further in vivo characterizations are being conducted.

A double-blind, crossover study of Biotène Oralbalance and BioXtra systems as salivary substitutes in patients with post-radiotherapy xerostomia.

This study assessed the efficacy of the Bioxtra (BX) and Biotène Oralbalance (OB) systems in the treatment of post-radiotherapy xerostomia. In a double-blind, crossover study, 20 patients with post-radiotherapy xerostomia were randomly allocated to receive either OB then BX, or vice versa, each product for 2 weeks, with a 1 week wash-out period in between. Subject-based dry mouth scores derived from 100-mm visual analogue scales were recorded at days 0 and 14 of each 2-week period, together with subjective perception of changes in dry mouth symptoms. Both treatments were effective, resulting in reduction of visual analogue scale scores from day 0-14. Between-groups comparisons identified that BX achieved significantly better improvements compared with OB for the perception of dry mouth and improvements in speech and was also rated as more pleasant to use than OB (P < 0.05). In conclusion, both treatments were effective in alleviating the symptoms of post-radiotherapy xerostomia, although BX achieved superiority in some of the outcomes assessed compared with OB.

Bond strength of repaired anterior composite resins: an in vitro study.

The objectives of this study were to investigate the repair potential of two commercially available composite resins in terms of bond strength, and the effectiveness of two commercially available adhesive systems used as intermediary materials in the repaired specimens. The repair strength of Helio Progress (HP) and Herculite XRV (XRV) was tested using two bonding agents: DenTASTIC (DT) and All Bond 2 (AB2). The effect of surface abrasion of specimens and the effect of time on repair strength were also investigated. Surface abrasion significantly improved the bond strength (P < 0.001) and the use of bonding agents further enhanced bond strength but not significantly. Use of bonding agents alone improved the repair bond strength significantly (P < 0.001). Repair of HP with HP after surface abrasion and application of DT produced the highest repair bond strength which was 99% of the cohesive strength of the control (unrepaired) specimens. Although there were some differences in the bond strength over the time period of the study (one month) none of these was statistically significant. It is concluded that surface abrasion coupled with the application of bonding agent produces the highest repair strength. It seems likely that clinically acceptable bond strengths are possible after repair of anterior composite resins.