Isabel Cristina Celerino de Moraes Porto

Mechanical and physical properties of silorane and methacrylate-based composites

OBJECTIVES This study measured the degree of conversion (DC), sorption, solubility and microhardness of methacrylate (Filtek Z250 and Filtek Z350XT) and silorane-based composites (Filtek P90). METHODS DC was measured using near infrared spectroscopy immediately and 24h after the photoactivation. Sorption and solubility measurements were performed after 24h, 4 weeks and 12 weeks of storage in water. Knoop microhardness was measured after 24h and after thermal cycling. The data were statistically analyzed using ANOVA followed by Tukeys, Tamhane or paired t-tests (α=0.05). RESULTS The DC for P90 (37.22±1.46) was significantly lower than the Z250 (71.44±1.66) and Z350 (71.76±2.84). Water sorption was highest in the Z250 and lowest in the P90. All the tested composites exhibited similar values after 24h of immersion, and no significant differences were observed. No significant differences were observed between the solubilities of the P90 composite (12 weeks) and the Z250 or Z350 composites (4 weeks). KHN values were less elevated for the P90 composite and similar for the Z250 and Z350 composites. An effect of thermal cycling on KHN values was observed for all the composites (p<0.001). CONCLUSIONS Silorane produced the lowest DC and KHN values and exhibited lower water sorption and solubility compared to methacrylate-based composites. These differences suggest that silorane composites exhibit better hydrolytic stability after 3 months of water immersion compared to conventional methacrylate-based composites. CLINICAL SIGNIFICANCE Silorane had higher hydrolytic stability after 3 months of water immersion than the methacrylate-based resins, despite the lower values of DC and KHN recorded.

In vitro potential cytotoxicity of an adhesive system to alveolar macrophages

The purpose of this study was to evaluate the potential cytotoxicity of Adper Single Bond 2 (SB) simplified etch-and-rinse adhesive system in alveolar macrophage cultures, as a function of the post-polymerization time and duration of immersion in the culture medium for preparation of extracts, by observing the levels of nitric oxide (NO) release and cell survival rate (MTT assay). Wistar rat alveolar macrophages were exposed to 200 microL of extracts obtained from 24- or 72-h immersion of adhesive samples in culture medium (RPMI), immediately or 24 h after polymerization. Fresh RPMI and E. coli lipopolysaccharides were used as negative and positive controls, respectively. The cells were placed in a humidified incubator for 24 h. The results were analyzed by the Students-t test (alpha=5%). The amount of NO produced and viable cells were significantly different (p<0.05) between the experimental and the control groups, showing that, irrespective of the post-polymerization time and duration of immersion in the culture medium, the adhesive system caused intense cytotoxicity to the macrophages. The cytotoxic effects were not statistically different (p<0.05) among the experimental groups. In conclusion, chemical components released from SB in aqueous environment were highly toxic to cell culture and thus an inflammatory pulpal response should be considered during the clinical application of dental adhesives.

Comparative radiopacity of six current adhesive systems.

Background: The radiopacity of contemporary adhesive systems has been mentioned as the indication for replacement of restorations due to misinterpretation of radiographic images. Aims: This study aimed to evaluate the radiopacity of contemporary bonding agents and to compare their radiodensities with those of enamel and dentin. Methods and Materials: To measure the radiopacity, eight specimens were fabricated from Clearfil SE Bond (CF), Xeno V (XE), Adper SE Bond (ASE), Magic Bond (MB), Single Bond 2 (SB), Scotchbond Multipurpose (SM), and gutta-percha (positive control). The optical densities of enamel, dentin, the bonding agents, gutta-percha, and an aluminium (Al) step wedge were obtained from radiographic images using image analysis software. Statistical Analysis: The radiographic density data were analyzed statistically by analysis of variance and Tukeys test (α =0.05). Results: Significant differences were found between ASE and all other groups tested and between XE and CF. No statistical difference was observed between the radiodensity of 1 mm of Al and 1 mm of dentin, between 2 mm of Al and enamel, and between 5 mm of Al and gutta-percha. Five of the six adhesive resins had radiopacity values that fell below the value for dentin, whereas the radiopacity of ASE adhesive was greater than that of dentin but below that of enamel. Conclusion: This investigation demonstrates that only ASE presented a radiopacity within the values of dentin and enamel. CF, XE, MB, SB, and SM adhesives are all radiolucent and require alterations to their composition to facilitate their detection by means of radiographic images.

Endo‑perio lesion: A dilemma from 19 th until 21 st century

The interrelationship between endodontic and periodontal diseases has been a subject of speculation, confusion and controversy for many years. Pulpal and periodontal problems are responsible for more than 50% of tooth mortality today. An endo-perio lesion can have a varied pathogenesis which ranges from quite simple to relatively complex one. These lesions often present challenges to the clinician as far as diagnosis and prognosis of the involved teeth are concerned. It is very essential to make a correct diagnosis so that the appropriate treatment can be provided. To make a correct diagnosis the clinician should have a thorough understanding and scientific knowledge of these lesions and may need to perform restorative, endoontic or periodontal therapy, either singly or in combination to treat them. Therefore, this presentation will highlight the diagnostic, clinical guidelines and decision-making in the treatment of these lesions from an Endodontists point of view to achieve the best outcome. Clinical Relevance to Interdisciplinary Dentistry Perio-endo lesions are very complex in nature and can have a varied pathogenesis. Treatment decision-making and prognosis depend primarily on the diagnosis of the specific endodontic and/or periodontal diseases. To have the best prognosis, clinician should refer the case to various areas of specialization, to perform restorative, endodontic or periodontal therapy, either singly or in combination. Therefore, to achieve the best outcome for these lesions, a multi-disciplinary approach should be involved.

Effect of dentin pretreatment with potassium oxalate: Analysis of microtensile bond strengths and morphologic aspects

An effective and stable bond is the most desirable characteristic of contemporary adhesive systems. The aim of this study was to evaluate the effect of potassium oxalate on dentin/resin bond strength. Dentin on the occlusal surface of human premolars was exposed and etched with 35% phosphoric acid, to receive 3% monohydrated potassium oxalate and the following adhesive systems: Scotchbond Multipurpose (SMO; 3M/ESPE) and Prime & Bond NT (PBO; Dentsply), followed by the application of resin composite (Z250; 3M/ESPE). The control groups (SM and PB) did not receive potassium oxalate application. The prepared teeth were kept in distilled water at 37°C for 24 h and 12 months. They were then cut longitudinally into sticks with a bond area of ∼0.8 mm2 for submission to the microtensile bond strength test. The data were analyzed by two‐factor ANOVA, Tamhanes paired comparisons, and the Student t‐test (α = 0.05). The hybrid layer formed was observed by scanning electron microscopy (SEM). SEM analysis of the surfaces treated with PB revealed shorter resin tags associated with the application of potassium oxalate, whereas SM showed tags similar to those without potassium oxalate. A significant difference was shown between the two storage times for each of the protocols. There was a significant difference among SMO, SM, and PBO (24 h), as well as among SM, SMO, and PBO, and between PB and PBO (12 months). The application of potassium oxalate before conventional adhesive systems may result in alteration of the bond strength between dentin and resin composite, depending on the material. Microsc. Res. Tech. 2011.

A comparative effect of various surface chemical treatments on the resin composite-composite repair bond strength

Aim: The aim of this in vitro study was an attempt to investigate the effect of different surface treatments on the bond strength between pre-existing composite and repair composite resin. Materials and Methods: Forty acrylic blocks were prepared in a cuboidal mould. In each block, a well of 5 mm diameter and 5 mm depth was prepared to retain the composite resin (Filtek™ Z350, 3M/ESPE). Aging of the composite discs was achieved by storing them in water at 37°C for 1 week, and after that were divided into 5 groups (n = 8) according to surface treatment: Group I- 37% phosphoric acid, Group II-10% hydrofluoric acid, Group III-30% citric acid, Group IV-7% maleic acid and Group V- Adhesive (no etchant). The etched surfaces were rinsed and dried followed by application of bonding agent (Adper™ Single Bond 2. 3M/ESPE). The repair composite was placed on aged composite, light-cured for 40 seconds and stored in water at 37°C for 1 week. Shear bond strength between the aged and the new composite resin was determined with a universal testing machine (crosshead speed of 0.5 mm/min). Statistical Analysis: The compressive shear strengths were compared for differences using ANOVA test followed by Tamhane′s T2 post hoc analysis. Results: The surface treatment with 10% hydrofluoric acid showed the maximum bond strength followed by 30% citric acid, 7% maleic acid and 37% phosphoric acid in decreasing order. Conclusion: The use of 10% hydrofluoric acid can be a good alternative for surface treatment in repair of composite resin restoration as compared to commonly used 37% orthophosphoric acid.

Effect of in-office bleaching with 35% hydrogen peroxide with and without addition of calcium on the enamel surface

This study aimed to evaluate effectiveness and effects of bleaching with 35% hydrogen peroxide with and without calcium on color, micromorphology, and the replacement of calcium and phosphate on the enamel surface. Thirty bovine enamel blocks (5.0 × 5.0 mm) were placed into the following groups: G1: artificial saliva (control); G2: 35% hydrogen peroxide gel without calcium (Whiteness HP Maxx–FGM); and G3: 35% hydrogen peroxide gel with calcium (Whiteness HP Blue–FGM). Three color measurements were performed with a spectrophotometer: untreated (baseline), after performing staining, and after application of bleaching agents. Calcium deposition on the enamel was evaluated before and after the application of bleaching agents using energy‐dispersive X‐ray spectrometry. The enamel surface micromorphology was observed under scanning electron microscopy. The pH of each product was measured. The data were subjected to one‐factor analysis of variance (ANOVA), and any differences were analyzed using Tukeys test (P < 0.05). G3 showed greater variation in total color after the experiment than G2 and G1; there was no significant difference in calcium or phosphorus concentration before and after the experimental procedures; morphological changes were observed only in G2 and G3; and the pH values of the Whiteness HP Maxx and Whiteness HP Blue bleaching agents were 5.77 and 7.79, respectively. The 35% hydrogen peroxide with calcium showed greater bleaching potential, but the addition of calcium had no effect in terms of reducing morphological changes or increasing the calcium concentration on the enamel surface. Microsc. Res. Tech. 78:975–981, 2015.

Effect of cross infection control barriers used on the light-curing device tips on the cure depth of a resin composite

Background: Among the advice on prevent cross-infection was included usage of mechanical barriers on tips of photoactivation units. However, questions about the use of protective barriers placed on the light-curing units tips and the possibility of interference with the ability of guaranteeing an effective polymerization of composite resins need to be clarified. Aims: The aim of this study was to evaluate the effect of cross infection control barriers used on the light-curing device tips on the cure depth of composite resin. Materials and Methods: Power density measurements from the light-cure unit were recorded with a radiometer on ten separate occasions with different types and placement modes of each barrier (low-density polyethylene and polyvinyl chloride (PVC) film – smooth and folds) and no-barrier (control). Cure depth of TPH™ Spectrum™ resin, A2-A4, was evaluated by the scraping test. Statistical Analysis: The data were analyzed using Students t-test or ANOVA one-way with Tukeys test (α =0.05). Results: Same type of barrier and different shades (A2, A4) of composite exhibited significant difference in the cure depth among all groups (P < 0.05). Both low-density polyethylene and PVC film folded barriers produced a significant reduction in the light intensity (P < 0.05). Conclusions: Regarding the resin shade, there was a significant reduction in the cure depth of A4 composite resin (dark shade) but this reduction is not enough to cause any adverse effect on the materials clinical performance. Therefore, disposable barriers can be recommended for use over the end of the light guide.

Effect of dentin pretreatment with potassium oxalate: A 6-year follow-up: PORTO et al.

Oxalate‐based products are effective against dentine sensitivity and have been studied as an option to improve long‐term adhesive bonding strength. Our aim was to evaluate the effect of potassium oxalate on the microtensile bond strength (µTBS) of the dentin/resin interface after 24 h, 1, and 6 years. Dentin on the occlusal surface of 16 human premolars was exposed and etched with 35% phosphoric acid. The teeth were divided into four groups. Two groups received 3% monohydrated potassium oxalate and the following adhesive systems and composites: Adper Scotchbond Multipurpose + FiltekZ350 (3M/ESPE) and Prime & Bond NT + Esthet‐X (Dentsply). Two control groups did not receive potassium oxalate. Teeth were cut into sticks and kept in distilled water at 37°C for 24 h, 1, and 6 years. The sticks underwent µTBS testing after storage. ANOVA, Tukeys post hoc test, and paired t test were used to compare storage times (α = 0.05). The fracture mode of the specimens was classified under a stereomicroscope (40×). Morphology of the hybrid layer and the fracture pattern were observed with scanning electronic microscopy (SEM). Mean µTBS was high at 24 h and decreased after 1 and 6 years. After 6 years, the mean µTBS values were similar with no statistically significant difference between the groups (p = .121). SEM images showed proper dentin hybridization. Dentin pretreatment with potassium oxalate did not affect hybrid layer formation, but bond strength decreased over time after 24 h. Therefore, the clinical use of potassium oxalate to increase dentin bond durability is not indicated.

Polymeric nanoparticle systems loaded with red propolis extract: a comparative study of the encapsulating systems, PCL-Pluronic versus Eudragit®E100-Pluronic

The aim of the present study was to compare two nanoparticle composition loaded with Brazilian red propolis extract regarding its physicochemical characteristics and its antioxidant and antileishmanial activities. The red propolis nanoparticles in an aqueous medium and in solid-state presented particle size in a nanometric scale with an apparent size of 100–288 nm for the NEPE and 175–380 nm for the NPPE. ATR-FTIR and thermal analysis revealed an encapsulation of flavonoids from the red propolis extract in polymeric matrices for the multidrug delivery system. UPLC-DAD identified red propolis markers (flavonoids) in EPE, NEPE and NPPE. The efficiency of encapsulation (28.0–55.0% for NEPE and 61.2–81.0% for NPPE) were determined and calculated using UPLC-DAD. DPPH method showed the antioxidant activity of both EPE and nanoparticle compositions of red propolis. These polymeric matrices systems were able to encapsulate flavonoids from red propolis extract with specific characteristics of solubility and polarity. EPE and nanoparticles loaded with red propolis extract in the multi-constituent co-delivery system presented leishmanicidal activity and a good correlation was established between IC50 and efficiency of encapsulation. Red propolis nanoparticles exhibited leishmanicidal activity but NEPE presented a lower leishmanicidal effect in relation to NPPE, which showed similar activity compared to EPE. The nanopolymeric matrices choice should be established in propolis nanoparticle compositions to avoid lack of efficacy of bioproducts. Red propolis nanoparticles were shown to be a potential final bulk product for the preparation of various pharmaceutical and cosmetics compositions in therapy against diseases such as leishmaniasis. Scanning Electron Microscopy of red propolis nanoparticles (NEPE 30) (A). ATR-FTIR spectra of NPPE 30 and NPPE placebo (B). Chromatogram of the NPPE 30 (C). Determination of IC using leishmanicidal assay against Leishmania braziliensis for EPE, NEPE and NPPE (D).