Fernando Freitas Portella

Discrepancies in degree of conversion measurements by FTIR

The IADR mission highlights the importance of advancing research and broadening knowledge to improve oral health worldwide, by opening avenues of communication and oral health support programs, especially in less developed regions, and by strengthening partnerships with other social stakeholders, whether institutional or communitybased. Different organizations have designed strategic plans to achieve these goals. With this in mind, it is important to outline the theoretical and methodological framework that will facilitate this process and strengthen the results. This framework should involve:The purpose of this study was to evaluate the influence of the internal standard peak on the measured degree of conversion (DC) for methacrylate-based resins analyzed by Fourier-transform infrared spectroscopy (FTIR). The influence of different baseline measurement methods was also determined. Different blends were prepared, mixing BisGMA/BisEMA and BisGMA/TEGDMA at proportions of 0% to 100%, in weight. Camphoroquinone and ethyl-4-dimethylamino-benzoate were used to permit the light activation of blends. Degree of conversion was evaluated using FTIR equipped with an attenuated total reflectance (ATR) device. Samples were dispensed onto ATR crystal and light activated for 40 s. The DC was calculated by relating the height of the peak 1637 cm-1 to the intensity of different internal standard peaks (1715, 1608, or 1582 cm-1), measured using two different baseline methods, before and after polymerization. Data were compared by ANOVA at 5% significance. The relationship between DC and monomer ratio was obtained by regression analysis. Double-bond conversion ranged from 32.75% to 78.50% for BisGMA/BisEMA blends, and from 32.75% to 76.22% for BisGMA/TEGDMA blends. For the BisGMA/BisEMA blends, the DC showed a linear association with the composition of the comonomer blends, independent of the internal standard peak and baseline method used. In contrast, the trends in DC for BisGMA/TEGDMA blends were different for each method of measurement. The internal standard peaks and measurement baseline should be taken into account when using FTIR to calculate the DC of methacrylate-based resins, especially comonomer blends containing a high degree of monomers that lack aromatic rings.

Influence of chlorhexidine application on longitudinal adhesive bond strength in deciduous teeth

The aim of this study was to evaluate the influence of applying 2% chlorhexidine for 30 seconds after phosphoric acid conditioning of dentin on the immediate and long-term bond strengths in deciduous teeth. The occlusal enamel was removed from 40 human sound deciduous molars, which were exfoliated by natural means, and the dentin was conditioned with 37% phosphoric acid for 15 seconds and washed with running water. The specimens were divided into two groups of 20 teeth. The test group received an application of 2% chlorhexidine for 30 seconds prior to a three-step etch-and-rinse adhesive system, whereas the control group received only the adhesive system. Three cylindrical restorations were made with a composite resin for each tooth. Ten teeth in each group were submitted to a microshear bond strength test after 24 hours, while the remaining teeth were stored in distilled water at 37 °C for 6 months before testing the microshear bond strength. The test group had a higher bond strength than did the control group after 6 months of storage. No statistical differences were found when groups with the same dentin treatment were compared at different times. Short applications of chlorhexidine at low concentrations prevent hybrid layer degradation and positively affect bond strength over time.

Oral hygiene caregivers' educational programme improves oral health conditions in institutionalised independent and functional elderly.

OBJECTIVE The goal of this study was to determine the impact of an oral hygiene education programme for caregivers on the oral health of institutionalised elderly and to examine the effect of disability and low muscle strength on programme outcomes. MATERIALS AND METHODS The subjects of this study were geriatric patients (n = 80) from a nursing home. Katz Index for activities of daily living, handgrip strength and mucosal-plaque score (MPS) was evaluated at baseline and 1 year after intervention. The intervention consisted of an educational programme and specific guidelines for caregivers (to perform oral hygiene for dependent elderly and to supervise the independent elderly during oral hygiene practices). Differences on MPS were evaluated using a paired-sample t-test. A stratified analysis was carried out to identify differences in response to the programme according to the Katz Index and handgrip strength of elderly. RESULTS The MPS was significantly reduced (p = 0.001) at follow-up; however, a separate analysis showed that only the independent elderly (p = 0.002) and those with normal muscle strength (p = 0.006) showed a reduction in MPS during the follow-up examination. CONCLUSION The oral hygiene education programme for caregivers resulted in a positive impact on oral hygiene of the independent and functional elderly.

Influence of radiopaque fillers on physicochemical properties of a model epoxy resin-based root canal sealer

Objective To verify the influence of radiopaque fillers on an epoxy resin-based sealer. Material and Methods Experimental sealers were formulated by adding 20%, 40%, 60%, 80%, 100% and 120% of calcium tungstate, ytterbium trifluoride or barium sulphate by weight to an epoxy-resin-base. Setting time, flow, film thickness, radiopacity, sorption, solubility, pH and push-out bond strength were evaluated. Results The setting time ranged from 373 to 612.66 min, the flow varied from 13.81±0.49 to 22.49±0.37 mm, and the film thickness ranged from 16.67±5.77 to 33.33±11.54 µm. The lowest pH was 5.47±0.53, and the highest was 6.99±0.03. Radiopacity varied from 0.38±0.04 to 2.57±0.21 mmAl and increased with the amount of filler. Calcium tungstate sealers had a higher sorption and solubility than other sealers. There was no significant difference in the push-out bond strength among the fillers at the 120% concentration. Conclusion The inorganic fillers evaluated and their concentrations affect the physicochemical properties of an epoxy resin-based root canal sealer.

Synthesis and characterization of a glycerol salicylate resin for bioactive root canal sealers.

AIM To develop and characterize a salicylate resin with potential use in bioactive endodontic sealers. METHODOLOGY Methyl salicylate, glycerol and titanium isopropoxide were added in a closed system for the transesterification reaction. The resin obtained was characterized by proton nuclear magnetic resonance spectroscopy (1H NMR) and size exclusion chromatography (SEC). To verify the applicability of the resin to the development of endodontic sealers, experimental cements were prepared by mixing glycerol salicylate resin, calcium hydroxide and methyl salicylate in the ratios of 2 : 1 : 1, 1 : 2 : 1, 1 : 1 : 2, 1 : 1 : 1, 4 : 1 : 1, 1 : 4 : 1 and 1 : 1 : 4. Setting times were measured according to ISO 6876. Features of the hardening reaction were described by micro-RAMAN spectroscopy. RESULTS The transesterification reaction had a 72% efficiency. The (1) H NMR analysis revealed the presence of the expected functional groups (hydroxyls and aromatic rings), and the SEC confirmed the molar mass of the resin produced. The setting times of experimental sealers ranged from 70 min (ratio 1 : 1 : 1) to 490 min (ratio 1 : 1 : 4). The conversion of the salicylic groups (1 613 cm(-1) ) to salicylate salt (1 543 cm(-1) ) and the reduction in calcium hydroxide peaks (1084 and 682 cm(-1) ) were confirmed by micro-RAMAN spectroscopy, which showed the calcium chelation by the resin. CONCLUSION The new glycerol salicylate resin was successfully synthesized and revealed a potential application in the development of endodontic sealers.

Glycerol salicylate-based containing α-tricalcium phosphate as a bioactive root canal sealer

The use of bioactive materials instead of inert materials to fill the root canal space could be an effective approach to achieve a hermetic seal and stimulate the healing of periapical tissues. The purpose of this study was to develop and characterize an endodontic sealer based on a glycerol salicylate resin and α-tricalcium phosphate (αTCP) at physical and chemical properties. Different sealers were formulated using 70% of a glycerol salicylate resin and 30% of a mixture of calcium hydroxide and αTCP (0, 5, 10, or 15%, in weight). Sealers formulated were characterized based on setting time, in vitro degradation over time, pH, cytotoxicity, and mineral deposition. Sealers presented setting time ranging from 240 to 405 min, and basic pH over 8.21 after 28 days. Higher αTCP concentration leads to sealers with low solubility. Cell viability after 48 h in direct contact with sealers was similar to a commercial sealer used as reference. The 10% and 15% αTCP sealers exhibited a calcium-phosphate layer on the surface after immersion in water and SBF for 7 days. Glycerol salicylate sealers with 10% and 15% α-tricalcium phosphate showed reliable physical-chemical properties and apatite-forming ability.

Glycerol Salicylate-based Pulp-Capping Material Containing Portland Cement

The purpose of this study was to evaluate the water sorption, solubility, pH and ability to diffuse into dentin of a glycerol salicylate-based, pulp-capping cement in comparison to a conventional calcium hydroxide-based pulp capping material (Hydcal). An experimental cement was developed containing 60% glycerol salicylate resin, 10% methyl salicylate, 25% calcium hydroxide and 5% Portland cement. Water sorption and solubility were determined based on mass changes in the samples before and after the immersion in distilled water for 7 days. Material discs were stored in distilled water for 24 h, 7 days and 28 days, and a digital pHmeter was used to measure the pH of water. The cements ability to diffuse into bovine dentin was assessed by Raman spectroscopy. The glycerol salicylate-based cement presented higher water sorption and lower solubility than Hydcal. The pH of water used to store the samples increased for both cements, reaching 12.59 ± 0.06 and 12.54 ± 0.05 after 7 days, for Hydcal and glycerol salicylate-based cements, respectively. Both cements were able to turn alkaline the medium at 24 h and sustain its alkalinity after 28 days. Hydcal exhibited an intense diffusion into dentin up to 40 µm deep, and the glycerol salicylate-based cement penetrated 20 µm. The experimental glycerol salicylate-based cement presents good sorption, solubility, ability to alkalize the surrounding tissues and diffusion into dentin to be used as pulp capping material.

Methacrylate‐based root canal sealer containing chlorexidine and α‐tricalcium phosphate

The aim of this study was to develop and to characterize a methacrylate-based root canal sealer containing chlorhexidine (CHX) and α-tricalcium phosphate (α-TCP). Experimental dual cure methacrylate-based sealer was produced containing 0, 2.5, or 5 wt% of CHX and 0, 25, or 50 wt% of α-TCP. Experimental sealers were evaluated based on flow, film thickness, radiopacity, degree of conversion (DC), degradation in water, pH and antibacterial activity. Flow ranged from 15.09 ± 0.11 to 17.47 ± 0.42 mm. All groups presented mean film thickness lower than 50 µm and had radiopacity equivalent to 3 mmAl. DC was higher than 60% for all compositions. The weight loss (WL) ranged 0.12-3.47%. The groups containing 5% of CHX presented the highest WL and the lower pH values after 28 days of water immersion. All chlorexidine-compositions exhibited antibacterial efficacy against Enterococcus faecalis on direct contact and agar diffusion tests. CHX and α-TCP addition at an experimental methacrylate-based root canal sealer influenced the physicochemical properties and provided antibacterial properties. The incorporation of CHX and α-TCP could be an alternative to antibacterial sealers with potential to improve periapical healing in endodontic treatments.