Dissolution Improvement of Progesterone and Testosterone via Impregnation on Mesoporous Silica Using Supercritical Carbon Dioxide.

Progesterone (PRG) and testosterone (TST) were impregnated on mesoporous silica (ExP) particles via supercritical carbon dioxide (scCO2) processing at various pressures (10-18 MPa), temperatures (308.2-328.2 K), and time (30-360 min). The impact of a co-solvent on the impregnation was also studied at the best determined pressure and temperature. The properties of the drug embedded in silica particles were analysed via gas chromatography (GC), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and nitrogen adsorption. An impregnation of 1 to 82 mg/g for PRG and 0.1 to 16 mg/g for TST was obtained depending on the processing parameters. There was a significant effect of pressure, time, and co-solvent on the impregnation efficiency. Generally, an increase in time and pressure plus the use of co-solvent led to an improvement in drug adsorption. Conversely, a rise in temperature resulted in lower impregnation of both TST and PRG on ExP. There was a substantial increase in the dissolution rate (> 90% drug release within the first 2 min) of both TST and PRG impregnated in silica particles when compared to the unprocessed drugs. This dissolution enhancement was attributed to the amorphisation of both drugs due to their adsorption on mesoporous silica.

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.

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.

Bioprinting and Preliminary Testing of Highly Reproducible Novel Bioink for Potential Skin Regeneration.

Three-dimensional (3D) bioprinting is considered as a novel approach in biofabricating cell-laden constructs that could potentially be used to promote skin regeneration following injury. In this study, a novel crosslinked chitosan (CH)-genipin (GE) bioink laden with keratinocyte and human dermal fibroblast cells was developed and printed successfully using an extruder-based bioprinter. By altering the composition and degree of CH-GE crosslinking, bioink printability was further assessed and compared with a commercial bioink. Rheological analysis showed that the viscosity of the optimised bioink was in a suitable range that facilitated reproducible and reliable printing by applying low pressures ranging from 20-40 kPa. The application of low printing pressures proved vital for viability of cells loaded within the bioinks. Further characterisation using MTT assay showed that cells were still viable within the printed construct at 93% despite the crosslinking, processing and after subjecting to physiological conditions for seven days. The morphological study of the printed cells showed that they were mobile within the bioink. Furthermore, the multi-layered 3D printed constructs demonstrated excellent self-supportive structures in a consistent manner.

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.

Synthesis of mesoporous triple-metal nanosorbent from layered double hydroxide as an efficient new sorbent for removal of dye from water and wastewater.

In this study, co-precipitation synthesis of the mesoporous triple-metal nanosorbent from Fe, Cu, Ni layered double hydroxide (FeCuNi-LDH), on the basis of the data obtained from the TG analysis was carried out. The FTIR spectroscopy and XRD results confirm the formation of CuO, NiO and Fe2O3 nanoparticles, while the EDX analysis does not show significant variations on the surface in elemental composition. BET analysis shows that FeCuNi-280 (FeCuNi-LDH calcinated at 280 °C) with mesoporous structure, has larger surface area compared to FeCuNi-LDH and FeCuNi-550 (FeCuNi-LDH calcinated at 550 °C). The value of pHPZC of FeCuNi-280 is found to be 8.66. Obtained FeCuNi-280 material showed the ability for efficient removal of dye Reactive Blue 19 (RB19) from water, with a very high sorption capacity of 480.79 mg/g at optimal conditions: the sorbent dose of 0.6 g/dm3, stirring speed of 280 rpm and pH 2. The kinetics results of the sorption process were well fitted by pseudo-second order and Chrastil model, and the sorption isotherm was well described by Sips, Langmuir and Brouers-Sotolongo model. FeCuNi-280 was easily regenerated with aqueous solution of NaOH, and reutilization was successfully done in five sorption cycles. The present study show that easy-to-prepare, relatively inexpensive nanosorbent FeCuNi-280 is among the best sorbents for the removal of RB19 dye from water solution and wastewater from textile industry in wide range of pH.

Release of antimicrobial compounds from a zinc oxide-chelate cement.

This study examined the release of cetylpyridinium chloride and benzalkonium chloride from fatty acid chelate temporary dental cement and their antimicrobial effects. The cement was Cavex Temporary, and either cetylpyridinium chloride or benzalkonium chloride was added (1% or 5% by mass), incorporating into the base paste. Release of the additives was determined by reverse-phase high-performance liquid chromatography. Possible chemical interactions between the cement components and additives were examined by Fourier transform infrared (FTIR) spectroscopy. Antimicrobial effects were assessed by measuring the zone of inhibition around sample discs after 24 h in a Streptococcus mutans culture. FTIR spectroscopy showed no interaction with cement components. For both additives, release was by diffusion for approximately the first 6 hours, with equilibration after about 2 weeks. Diffusion coefficients were 1.76 m2 s½ to 8.05 × 10-12 m2 s½ and total release was 10.3 to 44.7% of additive loading. Zones of inhibition with additive were significantly larger than those for control discs. In conclusion, the antimicrobial properties of Cavex temporary cement are improved by the addition of the antimicrobial compounds cetylpyridium chloride and benzalkonium chloride, which are released by a diffusion process.

Effect of Er:YAG laser enamel conditioning and moisture on the microleakage of a hydrophilic sealant.

For a given sealant, successful pit and fissure sealing is principally governed by the enamel conditioning technique and the presence of moisture contamination. A new generation of hydrophilic resin sealants is reported to tolerate moisture. This study investigates the impact of Er:YAG laser pre-conditioning and moisture contamination on the microleakage of a recent hydrophilic sealant. Occlusal surfaces of extracted human molars were either acid etched (n = 30), or successively lased and acid etched (n = 30). Ten teeth from each group were either air-dried, water-contaminated, or saliva-contaminated prior to sealing with UltraSeal XT® hydro™. Samples were inspected for penetration of fuchsin dye following 3000 thermocycles between 5 and 50 °C, and the enamel-sealant interfaces were observed by scanning electron microscopy (SEM). Significant differences in microleakage were evaluated using the Mann-Whitney U test with Bonferroni adjustment (p = 0.05). Laser pre-conditioning significantly reduced dye penetration irrespective of whether the enamel surface was moist or dry. Microleakage of water-contaminated acid etched teeth was significantly greater than that of their air-dried or saliva-contaminated counterparts. SEM analysis demonstrated good adaptation in all groups with the exception of water-contaminated acid etched teeth which exhibited relatively wide gaps. In conclusion, this hydrophilic sealant tolerates the presence of saliva, although water was found to impair its sealing ability. Laser pre-conditioning significantly decreases microleakage in all cases.

Component Release and Mechanical Properties of Endodontic Sealers following Incorporation of Antimicrobial Agents.

Root canal sealers with antimicrobial activity are highly beneficial; therefore, their antimicrobial properties could be improved by incorporation of antimicrobial agents. In the present study, the release of the quaternary ammonium compounds from endodontic sealers admixed with either benzalkonium chloride (BC) or cetylpyridinium chloride (CPC) at loadings of 2% wt was monitored. The effect of these additives on the compressive strengths and their release from the sealers was determined after 1 and 4 weeks. All of the materials studied were found to be capable of releasing antimicrobial additive in useful quantities. The release of CPC occurred to a statistically significant greater extent than BC for all materials. The addition of both BC and CPC generally decreased the compressive strength of all the endodontic sealers, with the exception of CPC in AH Plus, where the compressive strength was significantly increased. This suggests that, for these endodontic sealers, the antimicrobial additives alter the setting chemistry. AH Plus is an epoxy-based material cured with an amine, and in this case the increase in compressive strength with CPC is attributed to an enhanced cure reaction with this system. In all other cases, the additive inhibited the cure reaction to a greater or lesser extent.

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).

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™.

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.

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.

Release of cetyl pyridinium chloride from fatty acid chelate temporary dental cement.

Objective To determine whether the antimicrobial nature of a fatty acid chelate temporary dental cement can be enhanced by the addition of 5% cetyl pyridinium chloride (CPC). Materials and methods The temporary cement, Cavex Temporary was employed, and additions of CPC were made to either the base or the catalyst paste prior to mixing the cement. Release of CPC from set cement specimens was followed using reverse-phase HPLC for a period of up to 2 weeks following specimen preparation. Potential interactions between Cavex and CPC were examined by Fourier transform infrared spectroscopy (FTIR) and antimicrobial effects were determined using zone of inhibition measurements after 24 h with disc-shaped specimens in cultured Streptococcus mutans. Results FTIR showed no interaction between CPC and the components of the cement. CPC release was found to follow a diffusion mechanism for the first 6 h or so, and to equilibrate after approximately 2 weeks, with no significant differences between release profiles when the additive was incorporated into the base or the catalyst paste. Diffusion was rapid, and had a diffusion coefficient of approximately 1 × 10-9 m2 s-1 in both cases. Total release was in the range 10-12% of the CPC loading. Zones of inhibition around discs containing CPC were significantly larger than those around the control discs of CPC-free cement. Conclusions The antimicrobial character of this temporary cement can be enhanced by the addition of CPC. Such enhancement is of potential clinical value, though further in vivo work is needed to confirm this.