Degradation of trans-polyisoprene after root filling with thermoplasticized techniques.

AIM: To evaluate ex vivo degradation of gutta-percha following six thermoplastic obturation techniques. METHODOLOGY: Ninety human-extracted mandibular premolars were selected and divided randomly into nine groups for filling. Group 1: thermomechanical compaction for 3 s with Konne gutta-percha points (Konne Ind. e Com. de Mat. Odontol., Belo Horizonte, MG, Brazil); Group 2: thermomechanical compaction for 3 s with Dentsply TP gutta-percha points (Dentsply Indústria e Comércio Ltda, Petrópolis, R.J. Brazil); Group 3: thermomechanical compaction for 10 s with Konne; Group 4: thermomechanical compaction for 10 s with Dentsply TP; Group 5: warm vertical condensation using System B (EIE/Analytic, Richmond, WA, USA) with Konne; Group 6: warm vertical condensation using System B with Dentsply TP; Group 7: vertical condensation with Konne; Group 8: vertical condensation with Dentsply TP; Group 9: Microseal cone (Analytic Endodontics, Glendora, CA, USA). A further four groups were assessed without using teeth, Group 10: Microseal microflow (Analytic Endodontics); Group 11: Obtura (Obtura Corporation, Penton, MO, USA); Group 12: Obtura flow (Obtura Corporation); Group 13: Thermafil (Dentsply Maillefer, Tulsa, OK, USA). The filling material was removed from the root canal and trans-1,4-polyisoprene isolated by solubilization of the root filling remnants in chloroform followed by filtration and centrifugation. By gel permeation chromatography and infrared spectroscopy, the occurrence and degree of degradation were assessed. The results were analysed statistically using the Kruskal-Wallis test. With differential scanning calorimetry, the thermal behaviour of the gutta-percha was determined. RESULTS: A significant decrease in polymer molar mass and the production of carboxyl and hydroxyl groups in the polymer were observed with thermomechanical compaction used for 10 s and vertical condensation filling techniques (P = 0.0001 and P = 0.0005, respectively). Other techniques caused no polymer degradation. CONCLUSION: Polyisoprene degrades with high temperature. Thermomechanical compaction for 10 s and vertical condensation were associated with the greatest degradative process.

Pickering emulsion stabilized by cashew gum- poly-l-lactide copolymer nanoparticles: Synthesis, characterization and amphotericin B encapsulation.

In this work, we provide proof-of-concept of formation, physical characteristics and potential use as a drug delivery formulation of Pickering emulsions (PE) obtained by a novel method that combines nanoprecipitation with subsequent spontaneous emulsification process. To this end, pre-formed ultra-small (d.∼10 nm) nanoprecipitated nanoparticles of hydrophobic derivatives of cashew tree gum grafted with polylactide (CGPLAP), were conceived to stabilize Pickering emulsions obtained by spontaneous emulsification. These were also loaded with Amphotericin B (AmB), a drug of low oral bioavailability used in the therapy of neglected diseases such as leishmaniasis. The graft reaction was performed in two CG/PLA molar ratio conditions (1:1 and 1:10). Emulsions were prepared by adding the organic phase (Miglyol 812®) in the aqueous phase (nanoprecipitated CGPLAP), resulting the immediate emulsion formation. The isolation by centrifugation does not destabilize or separate the nanoparticles from oil droplets of the PE emulsion. Emulsions with CGPLAP 1:1 presented unimodal distributions at different CGPLA concentration, lower values in size and PDI and the best stability over time. The AmB was incorporated in the emulsions with a process efficiency of 21-47%, as determined by UV-vis. AmB in CGPLAP emulsions is in less aggregated state than observed in commercial AmB formulation.

Chemically sulfated galactomannan from Dimorphandra gardneriana seed: characterization and toxicity evaluation.

Dimorphandra gardneriana galactomannan (DG) was sulfated in pyridine:formamide using chlorosulfonic acid as the sulfation agent. The degree of substitution was 0.32, determined from the sulfur percentage. Confirmation of sulfation was obtained by FTIR spectroscopy through the presence of an asymmetrical SO stretching vibration at 1,259 cm(-1). NMR data showed that the sulfation occurred on primary hydroxyl groups. NMR and GPC data indicate degradation during reaction with elimination of galactose. At the maximum tested concentration of 1,000 µg/mL, unmodified DG polysaccharide did not show a statistically significant cytotoxicity in Vero cells by the MTT method. Therefore, the CC50>1,000 µg/mL obtained for the sulfated polysaccharides from D. gardneriana in Vero cells point to its lower cytotoxicity than the sulfated galactomannan from Mimosa scabrella.

Contribution of the cashew gum (Anacardium occidentale L.) for development of layer-by-layer films with potential application in nanobiomedical devices.

The search for bioactive molecules to be employed as recognition elements in biosensors has stimulated researchers to pore over the rich Brazilian biodiversity. In this sense, we introduce the use of natural cashew gum (Anacardium occidentale L.) as an active biomaterial to be used in the form of layer-by-layer films, in conjunction with phthalocyanines, which were tested as electrochemical sensors for dopamine detection. We investigated the effects of chemical composition of cashew gum from two different regions of Brazil (Piauí and Ceará states) on the physico-chemical characteristics of these nanostructures. The morphology of the nanostructures containing cashew gum was studied by atomic force microscopy which indicates that smooth films punctuated by globular features were formed that showed low roughness values. The results indicate that, independent of the origin, cashew gum stands out as an excellent film forming material with potential application in nanobiomedical devices as electrochemical sensors.

Degradation of trans-polyisoprene over time following the analysis of root fillings removed during conventional retreatment.

AIM: To evaluate in vivo degradation of root filling materials over time. METHODOLOGY: Thirty-six root filled teeth with or without periapical lesions were selected. Teeth with poor coronal restoration were not included. The teeth had been root filled 3-30 years previous and were scheduled for conventional retreatment. The association of root canal treatment, age, periapical lesion and root filling degradation was investigated. The filling material was removed from the root canal using files and no solvent. Trans-1,4-polyisoprene was isolated through solubilization of root filling remnants in chloroform followed by filtration and centrifugation. Gel permeation chromatography (GPC) and infrared spectroscopy (FT-IR) were utilized to study the occurrence and degree of degradation. The GPC and FT-IR data were collected for each sample and analysed statistically using the Kruskal-Wallis test. RESULTS: Degradation of trans-1,4-polyisoprene was a slow process. The process was identified as an oxidation reaction through the production of carboxyl and hydroxyl groups. Compared with the control group, significant molar mass decrease was noted after 15 years (P = 0.0146) in teeth with no periapical lesions. However, in teeth associated with periapical lesions the number of years for significant degradation was reduced to 5 (P = 0.0009). CONCLUSION: Polyisoprene degrades inside root canals as an oxidative process. The presence of periapical lesions was associated with a more rapid onset of degradation.