Drug-Smectite Clay Amorphous Solid Dispersions Processed by Hot Melt Extrusion.

The aim of this study was to introduce smectite clay matrices as a drug delivery carrier for the development of amorphous solid dispersions (ASD). Indomethacin (IND) was processed with two different smectite clays, magnesium aluminium and lithium magnesium sodium silicates, using hot melt extrusion (HME) to prepare solid dispersions. Scanning electron microscopy (SEM), powdered X-ray diffraction (PXRD), and differential scanning calorimetry (DSC) were used to examine the physical form of the drug. Energy-dispersive X-ray (EDX) spectroscopy was used to investigate the drug distribution, and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic analysis was done to detect any chemical interaction between these two kinds. Both PXRD and DSC analyses showed that drug-clay solid dispersion contained IND in amorphous form. EDX analysis showed a uniform IND dispersion in the extruded powders. ATR-FTIR data presented possible drug and clay interactions via hydrogen bonding. In vitro drug dissolution studies revealed a lag time of about 2 h in the acidic media and a rapid release of IND at pH 7.4. The work demonstrates that preparation of amorphous solid dispersion using inorganic smectite clay particles can effectively increase the dissolution rate of IND.

Mixed-Phase Ion-Exchangers from Waste Amber Container Glass.

This study investigated the one-pot hydrothermal synthesis of mixed-phase ion-exchangers from waste amber container glass and three different aluminium sources (Si/Al = 2) in 4.5 M NaOH(aq) at 100 °C. Reaction products were characterised by X-ray diffraction analysis, Fourier transform infrared spectroscopy, 27Al and 29Si magic angle spinning nuclear magnetic resonance spectroscopy and scanning electron microscopy at 24, 48 and 150 h. Nitrated forms of cancrinite and sodalite were the predominant products obtained with reagent grade aluminium nitrate (Al(NO3)3∙9H2O). Waste aluminium foil gave rise to sodalite, tobermorite and zeolite Na-P1 as major phases; and the principal products arising from amorphous aluminium hydroxide waste were sodalite, tobermorite and zeolite A. Minor proportions of the hydrogarnet, katoite, and calcite were also present in each sample. In each case, crystallisation was incomplete and products of 52, 65 and 49% crystallinity were obtained at 150 h for the samples prepared with aluminium nitrate (AN-150), aluminium foil (AF-150) and amorphous aluminium hydroxide waste (AH-150), respectively. Batch Pb2+-uptake (~100 mg g-1) was similar for all 150-h samples irrespective of the nature of the aluminium reagent and composition of the product. Batch Cd2+-uptakes of AF-150 (54 mg g-1) and AH-150 (48 mg g-1) were greater than that of AN-150 (36 mg g-1) indicating that the sodalite- and tobermorite-rich products exhibited a superior affinity for Cd2+ ions. The observed Pb2+- and Cd2+-uptake capacities of the mixed-product ion-exchangers compared favourably with those of other inorganic waste-derived sorbents reported in the literature.

Continuous Manufacture and Scale-Up of Theophylline-Nicotinamide Cocrystals.

The aim of the study was the manufacturing and scale-up of theophylline-nicotinamide (THL-NIC) pharmaceutical cocrystals processed by hot-melt extrusion (HME). The barrel temperature profile, feed rate and screw speed were found to be the critical processing parameters with a residence time of approximately 47 s for the scaled-up batches. Physicochemical characterization using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction of bulk and extruded materials revealed the formation of high purity cocrystals (98.6%). The quality of THL-NIC remained unchanged under accelerated stability conditions.

3D printed bilayer tablet with dual controlled drug release for tuberculosis treatment.

In this study Fusion Deposition Modelling (FDM) was employed to design and fabricate a bilayer tablet consisting of isoniazid (INZ) and rifampicin (RFC) for the treatment of tuberculosis. INZ was formulated in hydroxypropyl cellulose (HPC) matrix to allow drug release in the stomach (acidic conditions) and RFC was formulated in hypromellose acetate succinate (HPMC - AS) matrix to allow drug release in the upper intestine (alkaline conditions). This design may offer a better clinical efficacy by minimizing the degradation of RFC in the acidic condition and potentially avoid drug-drug interaction. The bilayer tablet was prepared by fabricating drug containing filaments using hot melt extrusion (HME) coupled with the 3D printing. The HME and 3D printing processes were optimised to avoid drug degradation and assure consistent deposition of drug-containing layers in the tablet. The in-vitro drug release rate was optimised by varying drug loading, infilling density, and covering layers. Greater than 80% of INZ was released in 45 mins at pH 1.2 and approximately 76% of RFC was releases in 45 mins after the dissolution medium was changed to pH 7.4. The work illustrated the potential application of FDM technology in the development of oral fixed dose combination for personalised clinical treatment.

The Application of 29Si NMR Spectroscopy to the Analysis of Calcium Silicate-Based Cement using Biodentine™ as an Example.

Biodentine is one of the most successful and widely studied among the second generation of calcium silicate-based endodontic cements. Despite its popularity, the setting reactions of this cement system are not currently well understood. In particular, very little is known about the formation and structure of the major calcium silicate hydrate (C-S-H) gel phase, as it is difficult to obtain information on this poorly crystalline material by the traditional techniques of powder X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR). In this study, the hydration reactions of Biodentine are monitored by XRD, FTIR, isothermal conduction calorimetry and, for the first time, 29Si magic angle spinning nuclear magnetic resonance spectroscopy (29Si MAS NMR) is used to investigate the structures of the anhydrous calcium silicate phases and the early C-S-H gel product. XRD analysis indicated that the anhydrous powder comprises 73.8 wt% triclinic tricalcium silicate, 4.45 wt% monoclinic ß-dicalcium silicate, 16.6 wt% calcite and 5.15 wt% zirconium oxide. Calorimetry confirmed that the induction period for hydration is short, and that the setting reactions are rapid with a maximum heat evolution of 28.4 mW g-1 at 42 min. A progressive shift in the FTIR peak maximum from 905 to 995 cm-1 for the O-Si-O stretching vibrations accompanies the formation of the C-S-H gel during 1 week. The extent of hydration was determined by 29Si MAS NMR to be 87.0%, 88.8% and 93.7% at 6 h, 1 day and 1 week, respectively, which is significantly higher than that of MTA. The mean silicate chain length (MCL) of the C-S-H gel was also estimated by this technique to be 3.7 at 6 h and 1 day, and to have increased to 4.1 after 1 week. The rapid hydration kinetics of Biodentine, arising from the predominance of the tricalcium silicate phase, small particle size, and 'filler effect' of calcite and zirconium oxide, is a favorable characteristic of an endodontic cement, and the high values of MCL are thought to promote the durability of the cement matrix.

Effect of Calcium Precursor on the Bioactivity and Biocompatibility of Sol-Gel-Derived Glasses.

This study investigated the impact of different calcium reagents on the morphology, composition, bioactivity and biocompatibility of two-component (CaO-SiO2) glasses produced by the Stöber process with respect to their potential application in guided tissue regeneration (GTR) membranes for periodontal repair. The properties of the binary glasses were compared with those of pure silica Stöber particles. The direct addition of calcium chloride (CC), calcium nitrate (CN), calcium methoxide (CM) or calcium ethoxide (CE) at 5 mol % with respect to tetraethyl orthosilicate in the reagent mixture gave rise to textured, micron-sized aggregates rather than monodispersed ~500 nm spheres obtained from the pure silica Stöber synthesis. The broadening of the Si-O-Si band at ~1100 cm-1 in the infrared spectra of the calcium-doped glasses indicated that the silicate network was depolymerised by the incorporation of Ca2+ ions and energy dispersive X-ray analysis revealed that, in all cases, the Ca:Si ratios were significantly lower than the nominal value of 0.05. The distribution of Ca2+ ions was also found to be highly inhomogeneous in the methoxide-derived glass. All samples released soluble silica species on exposure to simulated body fluid, although only calcium-doped glasses exhibited in vitro bioactivity via the formation of hydroxyapatite. The biocompatibilities of model chitosan-glass GTR membranes were assessed using human MG63 osteosarcoma cells and were found to be of the order: CN < pure silica ≈ CC << CM ≈ CE. Calcium nitrate is the most commonly reported precursor for the sol-gel synthesis of bioactive glasses; however, the incomplete removal of nitrate ions during washing compromised the cytocompatibility of the resulting glass. The superior bioactivity and biocompatibility of the alkoxide-derived glasses is attributed to their ease of dissolution and lack of residual toxic anions. Overall, calcium ethoxide was found to be the preferred precursor with respect to extent of calcium-incorporation, homogeneity, bioactivity and biocompatibility.

The antibacterial activity and release of quaternary ammonium compounds in an orthodontic primer.

The aim of this study was to evaluate the impact of 10 wt% benzalkonium chloride (TB-BAC) or 10 wt% cetylpyridinium chloride (TB-CPC) on the antimicrobial properties of the orthodontic adhesive primer, Transbond XTT (TB). Antimicrobial activity was assessed using a zone of inhibition diffusion test and the release of the antimicrobial compounds was monitored by high performance liquid chromatography (HPLC). Shear bond strength (SBS) was tested using bovine enamel. Control, TB, specimens failed to demonstrate intrinsic antibacterial activity at 1, 7 and 14 days; whereas, TB-BAC and TB-CPC showed antibacterial effects at all times. HPLC analysis indicated no significant differences in the release behaviour of TB-BAC and TB-CPC (t-test, p > 0.05), except for the 7-day release which was higher for TB-BAC (p < 0.05). By 14 days the extents of release were 27 ± 2% and 25 ± 5% of the total initial loading for TB-BAC and TB-CPC, respectively. The incorporation of 10 wt% BAC or CPC in Transbond XTT adhesive primer also resulted in superior shear bond strength at 7 and 14 days (Fisher s LSD, p < 0.05) with no significant change in the mode ofbracket failure under shear stress (Pearson's chi-squared, p > 0.05).

El objetivo de este estudio fue evaluar el impacto del cloruro de benzalconio al 10% en peso del peso (TB-BAC) o de cloruro de cetilpiridinio al 10% del peso (TB-CPC) con propiedades antimicrobianas presentes en el adhesivo acondicionador ortodóncico, Transbond XT T (TB). La actividad antimicrobiana se evaluó usando una zona de prueba de difusión de inhibición y la liberación de los compuestos antimicrobianos se controló mediante cromatografía líquida de alta resolución (HPLC). La resistencia de adhesión al corte (SBS) se probó usando esmalte bovino. Las muestras control, TB no lograron demostrar actividad antibacteriana intrínseca a 1, 7 y 14 días; mientras que TB-BAC y TB-CPC mostraron efectos antibacterianos en todo momento. El análisis por HPLC no indicó diferencias significativas en el comportamiento de liberación de TB-BAC y TB-CPC (prueba t, p> 0,05), excepto en la liberación a los 7 días que fue más alta para TB-BAC (p <0,05). A los 14 días, los grados de liberación fueron de 27 ± 2% y de 25 ± 5% de la carga inicial total para TB-BAC y TB-CPC, respectivamente. La incorporación de 10% en peso de BAC o CPC en el imprimador adhesivo Transbond XT T también dio como resultado una resistencia superior corte a los 7 y 14 días (Fisher's LSD, p <0.05) sin cambios significativos en el modo de falla del bracket bajo tensión de corte (Pearson's chi-cuadrado, p> 0.05).

Characterisation and microleakage of a new hydrophilic fissure sealant - UltraSeal XT® hydro™.

OBJECTIVES: The aim of this study was to characterise the new hydrophilic fissure sealant, UltraSeal XT® hydro™ (Ultradent Products, USA), and to investigate its in vitro resistance to microleakage after placement on conventionally acid etched and sequentially lased and acid etched molars. MATERIAL AND METHODS: The sealant was characterised by Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and Vickers indentation test. Occlusal surfaces of extracted human molars were either conventionally acid etched (n=10), or sequentially acid etched and laser irradiated (n=10). UltraSeal XT® hydro™ was applied to both groups of teeth which were then subjected to 2,500 thermocycles between 5 and 55°C prior to microleakage assessment by fuchsin dye penetration. RESULTS: UltraSeal XT® hydro™ is an acrylate-based sealant that achieved a degree of conversion of 50.6±2.2% and a Vickers microhardness of 24.2±1.5 under standard light curing (1,000 mWcm-2 for 20 s). Fluoride ion release is negligible within a 14-day period. SEM and EDX analyses indicated that the sealant comprises irregular submicron and nano-sized silicon-, barium-, and aluminium-bearing filler phases embedded in a ductile matrix. Laser preconditioning was found to significantly reduce microleakage (Mann-Whitney U test, p<0.001). The lased teeth presented enhanced surface roughness on a 50 to 100 µm scale that caused the segregation and concentration of the filler particles at the enamel-sealant interface. CONCLUSION: Laser preconditioning significantly decreased microleakage and increased enamel surface roughness, which caused zoning of the filler particles at the enamel-sealant interface.

The antibacterial activity and release of quaternary ammonium compounds in an orthodontic primer

The aim of this study was to evaluate the impact of 10 wt% benzalkonium chloride (TBBAC) or 10 wt% cetylpyridinium chloride (TBCPC) on the antimicrobial properties of the orthodontic adhesive primer, Transbond XT™ (TB). Antimicrobial activity was assessed using a zone of inhibition diffusion test and the release of the antimicrobial compounds was monitored by high performance liquid chromatography (HPLC). Shear bond strength (SBS) was tested using bovine enamel. Control, TB, specimens failed to demonstrate intrinsic antibacterial activity at 1, 7 and 14 days; whereas, TBBAC and TBCPC showed antibacterial effects at all times. HPLC analysis indicated no significant differences in the release behaviour of TBBAC and TBCPC (ttest, p > 0.05), except for the 7day release which was higher for TBBAC (p < 0.05). By 14 days the extents of release were 27 ± 2% and 25 ± 5% of the total initial loading for TBBAC and TBCPC, respectively. The incorporation of 10 wt% BAC or CPC in Transbond XT™ adhesive primer also resulted in superior shear bond strength at 7 and 14 days (Fisher's LSD, p < 0.05) with no significant change in the mode of bracket failure under shear stress (Pearson's chisquared, p > 0.05) (AU)

El objetivo de este estudio fue evaluar el impacto del cloruro de benzalconio al 10% en peso del peso (TBBAC) o de cloruro de cetilpiridinio al 10% del peso (TBCPC) con propiedades antimicrobianas presentes en el adhesivo acondicionador ortodóncico, Transbond XT ™ (TB). La actividad antimi crobiana se evaluó usando una zona de prueba de difusión de inhibición y la liberación de los compuestos antimicrobianos se controló mediante cromatografía líquida de alta resolución (HPLC). La resistencia de adhesión al corte (SBS) se probó usando esmalte bovino. Las muestras control, TB no lograron demostrar actividad antibacteriana intrínseca a 1, 7 y 14 días; mientras que TBBAC y TBCPC mostraron efectos antibac terianos en todo momento. El análisis por HPLC no indicó diferencias significativas en el comportamiento de liberación de TBBAC y TBCPC (prueba t, p> 0,05), excepto en la liberación a los 7 días que fue más alta para TBBAC (p <0,05). A los 14 días, los grados de liberación fueron de 27 ± 2% y de 25 ± 5% de la carga inicial total para TBBAC y TBCPC, respectivamente. La incorpora ción de 10% en peso de BAC o CPC en el imprimador adhesivo Transbond XT ™ también dio como resultado una resistencia superior corte a los 7 y 14 días (Fisher's LSD, p <0.05) sin cambios significativos en el modo de falla del bracket bajo tensión de corte (Pearson's chicuadrado, p> 0.05) (AU)

Characterisation and microleakage of a new hydrophilic fissure sealant - UltraSeal XT® hydro

ABSTRACT Objectives The aim of this study was to characterise the new hydrophilic fissure sealant, UltraSeal XT® hydro™ (Ultradent Products, USA), and to investigate its in vitro resistance to microleakage after placement on conventionally acid etched and sequentially lased and acid etched molars. Material and Methods The sealant was characterised by Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and Vickers indentation test. Occlusal surfaces of extracted human molars were either conventionally acid etched (n=10), or sequentially acid etched and laser irradiated (n=10). UltraSeal XT® hydro™ was applied to both groups of teeth which were then subjected to 2,500 thermocycles between 5 and 55°C prior to microleakage assessment by fuchsin dye penetration. Results UltraSeal XT® hydro™ is an acrylate-based sealant that achieved a degree of conversion of 50.6±2.2% and a Vickers microhardness of 24.2±1.5 under standard light curing (1,000 mWcm-2 for 20 s). Fluoride ion release is negligible within a 14-day period. SEM and EDX analyses indicated that the sealant comprises irregular submicron and nano-sized silicon-, barium-, and aluminium-bearing filler phases embedded in a ductile matrix. Laser preconditioning was found to significantly reduce microleakage (Mann-Whitney U test, p<0.001). The lased teeth presented enhanced surface roughness on a 50 to 100 μm scale that caused the segregation and concentration of the filler particles at the enamel-sealant interface. Conclusion Laser preconditioning significantly decreased microleakage and increased enamel surface roughness, which caused zoning of the filler particles at the enamel-sealant interface.