Effects of chelating agent and acids on Biodentine.

BACKGROUND: To evaluate the effect of distilled water, ethylenediaminetetraacetic acid (EDTA), phosphoric acid and maleic acid on Biodentine regarding surface topography, microhardness and push-out bond strength (POBS). METHODS: Fifty-two cylindrical shaped Biodentine specimens were divided into groups: control (distilled water); EDTA (17% EDTA); PA (37% phosphoric acid); and MA (7% maleic acid). Surfaces were evaluated by topographic analysis and Vickers microhardness test. Topographic changes were evaluated qualitatively and microhardness was statistically analyzed by Kruskal-Wallis test. Forty mandibular molars were used to simulate clinical conditions. The crowns were removed and a perforation was created at the furcal floor. The Biodentine was packed into the root perforations and the roots were divided into four groups (DW, EDTA, PA, MA). Samples were stored and subjected to interfacial analysis. POBS data were analyzed by Kruskal-Wallis and Dunn tests. RESULTS: Ethylenediaminetetraacetic acid, MA and PA changed the morphology of the Biodentine surface. PA showed microhardness similar to distilled water (P > 0.05), while MA and EDTA demonstrated reduced values when compared with PA (P < 0.05). PA improved the POBS of Biodentine in comparison with the control. CONCLUSIONS: Changes in the topography, microhardness and POBS of Biodentine are associated with irrigant agent used.

Resistance to vertical root fracture of root filled teeth using different conceptual approaches to canal preparation.

AIM: To evaluate the resistance to vertical root fracture of root filled teeth using different root canal preparation concepts: apical stop and continuously tapering preparation, with different foraminal enlargement. In addition, the effect of filling associated with these different concepts was assessed. METHODOLOGY: Ninety single-rooted premolars were used. The crowns were removed to standardize the root length at 11 mm. Ten roots were not instrumented and not filled (control group). The other roots were divided into four groups (n = 20): apical stop to finishing file size 25, 0.08 taper; apical stop to finishing file size 45, 0.02 taper; continuously tapering preparation to finishing file size 25, 0.08 taper; and continuously tapering preparation to finishing file size 45, 0.02 taper. Afterwards, 10 roots of each group were root filled using Gutta-percha and AH Plus. A continuous wave of condensation was used as the filling technique. The roots were evaluated as regards resistance to vertical fracture using a universal testing machine. The data were evaluated using the Kruskal-Wallis and Mann-Whitney tests. RESULTS: No significant difference in performance was observed between continuously tapering preparation size 25, 0.08 taper and apical stop size 45, 0.02 taper groups. Lower resistance values were found in continuously tapering preparation size 45, 0.02 taper group and the highest in apical stop size 25, 0.08 taper group. After filling, a significant increase in resistance values was observed in all groups. In addition, the continuously tapering preparation size 45, 0.02 taper group had values comparable with those of the control. CONCLUSION: The different canal preparation techniques reduced resistance to fracture when compared with the control group; however, after root filling, there was a significant increase in resistance.

Adhesion of resin-based sealers to dentine: an atomic force microscopy study.

AIM: To evaluate the effect of several final irrigants on the adhesion force (Fad) between dentine and resin-based sealers by means of atomic force microscopy (AFM). METHODOLOGY: Twelve distal roots of mandibular molars were used. The roots were smoothened and cut to obtain 36 specimens. During chemomechanical preparation of the root canals, 5.25% NaOCl was used as the irrigant. The specimens were then divided into six groups according to the final irrigant used: control group - immersed in distilled water (DW) for 1 min; chlorhexidine (CHX) group - in 2% CHX for 1 min; NaOCl group - in 5.25% NaOCl for 1 min; EDTA group - in 17% EDTA for 5 min, EDTA/CHX group - in EDTA, followed by intermediate flushing with DW and then immersed in CHX; EDTA/NaOCl group - in EDTA, followed by intermediate flushing with DW and then immersed in NaOCl. After the treatments, all groups were washed with DW to remove all traces of the irrigants. Afterwards, the samples were dried and attached to a glass base. AFM tips containing AH Plus and Real Seal SE sealers were used to obtain force-distance curves with regard to dentine-treated surfaces. Data were analysed statistically using nonparametric tests with the significance level set at P < 0.05. RESULTS: In the groups with smear layer, a final flush with CHX and NaOCl resulted in significantly higher Fad values than the control group for both sealers (P < 0.001). When smear layer was removed, the highest Fad values associated with AH Plus occurred with a final flush of NaOCl, whilst in Real Seal SE, the highest values were found with a final flush of CHX (all results significant at P < 0.001). CONCLUSION: Irrigants had a positive effect on the adhesion of the resin-based sealers, AH Plus and Real Seal SE, to dentine.

Mechanical properties of asphalt binders evaluated by atomic force microscopy.

Atomic Force Microscopy was employed in order to relate the features observed on the surface of a 50/70 asphalt binder according to its local stiffness and elastic recovery. Indentations were performed in different points of the surface and a significant variation of elasticity was observed between the points on the so-called bee structure and the matrix. Also, indentations varying the maximum force were performed on similar white spots in the bee structure and the recovery was followed up to 1 h after indentation. It was observed that the elastic recovery is very much dependent on the colloidal structure of the bee. The final surface state of the binder, close to the bee for usual bees is not the same as the initial one indicating severe plastic deformation. Also, permanent phase change could be observed for bright spots presented in not well-structured bee arrangements. A surface hardening was observed in the bee region.

High temperature AFM study of CAP 30/45 pen grade bitumen.

Bitumen is a complex mixture of hydrocarbons for which microstructural understanding is incomplete. In an effort to detail this microstructure, a asphalt cement sample (CAP 30/45) was analysed by thermal phase detection atomic force microscopy. Phase contrast and topography images showed that sample morphology is highly dependent on temperature. The 'bee structure' changed considerably at temperatures between 50 degrees C and 56 degrees C. A decrease of the oscillation amplitude was observed upon heating and the 'bees' completely disappeared at temperatures above 57 degrees C. When the temperature was decreased after melting at 170 degrees C, the 'bees' began to nucleate gradually at temperatures of 57 degrees C and its evolution with time was followed. Changes in morphology were compared to thermal analysis results and a model for the 'bee' structure was proposed.

Further studies on the structural analysis of the cuticle of Litomosoides chagasfilhoi (Nematoda: Filarioidea).

In order to obtain further information on the structural organization of the cuticle of nematodes, this structure was isolated from adult forms of the filariid Litomosoides chagasfilhoi. The purity of the fraction was determined by light and transmission electron microscopy, deep-etching, high resolution scanning electron microscopy, atomic force microscopy, immunocytochemistry, gel electrophoresis (SDS-PAGE) and Western blot. The epicuticle presented a rugous surface with parallel rows and several globular particles that could be involved in the absorption of nutrients and secretion of products. Analysis by SDS-PAGE of purified cuticles revealed five major polypeptides corresponding to 151, 41, 28, 13 and 11 kDa. A polyclonal antibody against a synthetic 18 amino-acid peptide that corresponds to the sequence of domain E of the Haemonchus contortus3A3 collagen gene recognized several protein bands on the Western blot of purified cuticle, and labeled all cuticular layers, as shown by immunocytochemistry.