Calcium phosphates and silicon: exploring methods of incorporation

Background: Bioinorganics have been explored as additives to ceramic bone graft substitutes with the aim to improve their performance in repair and regeneration of large bone defects. Silicon (Si), an essential trace element involved in the processes related to bone formation and remodeling, was shown not only to enhance osteoblasts proliferation but also to stimulate the differentiation of mesenchymal stem cells (MSCs) and preosteoblasts into the osteogenic lineage. In this study, the added value of Si to calcium phosphate (CaP) coatings was evaluated. Methods: Tissue culture plastic well plates were coated with a thin CaP layer to which traces amounts of Si were added, either by adsorption or by incorporation through coprecipitation. The physicochemical and structural properties of the coatings were characterized and the dissolution behavior was evaluated. The adsorption/incorporation of Si was successfully achieved and incorporated ions were released from the CaP coatings. Human MSCs were cultured on the coatings to examine the effects of Si on cell proliferation and osteogenic differentiation. For the statistical analysis, a one-way ANOVA with Bonferroni post-hoc test was performed. Results: The results showed that human MSCs (hMSCs) responded to the presence of Si in the CaP coatings, in a dosedependent manner. An increase in the expression of markers of osteogenic differentiation by human MSCs was observed as a result of the increase in Si concentration. Conclusions: The incorporation/adsorption of Si into CaP coatings was successfully achieved and hMSCs responded with an increase in osteogenic genes expression with the increase of Si concentration. Furthermore, hMSCs cultured on CaP-I coatings expressed higher levels of ALP and OP, indicating that this may be the preferred method of incorporation of bioinorganics into CaPsPortuguese Foundation for Science and Technology (FCT) for providing Ana I. Rodrigues her PhD scholarship (Grant No. SFRH/BD/69962/2010). This work was partially supported by national funds through the FCT under the scope of the project OSTEOSYNTHESIS project (PTDC/CTM-BIO/0814/2012) and by the European Regional Development Fund (FEDER) through the “COMPETE” - Operational Programme for Competitiveness factors (FCOMP-01-0124-FEDER-028491).info:eu-repo/semantics/publishedVersio

Variation in the dispersions of powder liquid ratios in hand-mix glass ionomers

BACKGROUND: The Powder/Liquid Ratio (PLR) influence, and the literature regarding the handling and physical properties of Glass Ionomer restorative materials (GIC) were investigated. OBJECTIVE: The objective of the study was to compare the PLR variability and magnitude in hand-mix GICs, as dispensed for clinical use. From the recorded individual powder and liquid weights, additional comparisons could be made by pairing the various “extreme” outer observations in relation to the manufacturer’s PLR. STUDY DESIGN: The materials assessed were Ketac Universal Hand-mix (KUH), Riva Self Cure Hand-mix (RSCH) and Fuji IX GP Hand-mix (FIXH). Twenty scoops of powder were paired with twenty drops of liquid, as would be the case in the clinical scenario. Statistical analysis was completed with the Kruskal Wallis H test, Intraclass Correlation (ICC) and straight line regressions with One-way ANOVA and the post-hoc Tukey HSD Test (p<0.05 was considered significant). RESULTS: The powder and liquid observations indicate a lack of consistency in both the powder and liquid dispersions. The volume remained “one drop” but the weights were much lower than the manufacturer’s recommended drop weight for some observations, due to air in the liquid drop. The Kruskal-Wallis H test indicated significant differences (p=0.0001) between the three materials for the paired PLRs. The One-way ANOVA and post-hoc Tukey HSD Test were used to compare the recommended PLR to the results and the significant differences (p<0.01). CONCLUSION: The recommended manufacturers’ powder and liquid weights were KUH 0.150/0.05g; RSC 0.165/0.035; FIXH 0.18/0.05, respectively. KUH, FIXH and RSCH liquid had powder and liquid dispersions above the manufacturer’s recommendations. FIXH had the most paired PLR observations within the ±10% range followed by KUH. Extreme powder and liquid combinations could occur in the clinical scenario and these combinations were considered

Heat treatment following surface silanization in rebonded tribochemical silica-coated ceramic brackets: shear bond strength analysis

OBJECTIVE: This study aimed to evaluate the effects of heat treatment on the tribochemical silica coating and silane surface conditioning and the bond strength of rebonded alumina monocrystalline brackets. MATERIAL AND METHODS: Sixty alumina monocrystalline brackets were randomly divided according to adhesive base surface treatments (n=20): Gc, no treatment (control); Gt, tribochemical silica coating + silane application; Gh, as per Gt + post-heat treatment (air flux at 100ºC for 60 s). Brackets were bonded to the enamel premolars surface with a light-polymerized resin and stored in distilled water at 37ºC for 100 days. Additionally, half the specimens of each group were thermocycled (6,000 cycles between 5-55ºC) (TC). The specimens were submitted to the shear bond strength (SBS) test using a universal testing machine (1 mm/min). Failure mode was assessed using optical and scanning electron microscopy (SEM), together with the surface roughness (Ra) of the resin cement in the bracket using interference microscopy (IM). 2-way ANOVA and the Tukey test were used to compare the data (p>0.05). RESULTS: The strategies used to treat the bracket surface had an effect on the SBS results (p=0.0), but thermocycling did not (p=0.6974). Considering the SBS results (MPa), Gh-TC and Gc showed the highest values (27.59±6.4 and 27.18±2.9) and Gt-TC showed the lowest (8.45±6.7). For the Ra parameter, ANOVA revealed that the aging method had an effect (p=0.0157) but the surface treatments did not (p=0.458). For the thermocycled and non-thermocycled groups, Ra (µm) was 0.69±0.16 and 1.12±0.52, respectively. The most frequent failure mode exhibited was mixed failure involving the enamel-resin-bracket interfaces. CONCLUSION: Regardless of the aging method, Gh promoted similar SBS results to Gc, suggesting that rebonded ceramic brackets are a more effective strategy

Réactions radicalaires dans un monocristal de diphosphène irradié : étude par résonance paramagnétique électronique

L’étude RPE d’un monocristal de ArP = PAr irradié aux rayons X permet d’identifier plusieurs radicaux de type phosphinyl. Ceux-ci résultent d’une cyclisation de la molécule qui incorpore un atome de phosphore dans un cycle pentagonal ou de l’addition d’un H’ sur l’un des deux atomes de phosphore. Une augmentation de la température rompt la liaison P-P présente dans ces radicaux et conduit à de nouvelles espèces phosphinyles