Showing papers by "Allyson Nogueira Moreira published in 2014"

Propolis - based chitosan varnish: drug delivery, controlled release and antimicrobial activity against oral pathogen bacteria

Abstract: Dental caries is the most prevalent oral disease in several Asian and Latin American countries. It is an infectious disease and different types of bacteria are involved in the process. Synthetic antimicrobials are used against this disease; however, many of these substances cause unwarranted undesirable effects like vomiting, diarrhea and tooth staining. Propolis, a resinous substance collected by honeybees, has been used to control the oral microbiota. So, the objective of this study was to develop and characterize sustained-release propolis-based chitosan varnish useful on dental cariogenic biofilm prevention, besides the in vitro antimicrobial activity. Three formulations of propolis - based chitosan varnish (PCV) containing different concentrations (5%, 10% and 15%) were produced by dissolution of propolis with chitosan on hydro-alcoholic vehicle. Bovine teeth were used for testing adhesion of coatings and to observe the controlled release of propolis associated with varnish. It was characterized by infrared spectroscopy, scanning electron microscopy, casting time, diffusion test in vitro antimicrobial activity and controlled release. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were tested for the main microorganisms involved in the cariogenic biofilm through the microdilution test in 96-well plates. The formulations presented a tooth surface adherence and were able to form films very fast on bovine tooth surface. Also, propolis-based chitosan varnishes have shown antimicrobial activity similar to or better than chlorhexidine varnish against all oral pathogen bacteria. All microorganisms were sensitive to propolis varnish and chitosan. MIC and MBC for microorganisms of cariogenic biofilme showed better results than chlorhexidine. Propolis active components were released for more than one week. All developed formulations turn them, 5%, 10% and 15% propolis content varnish, into products suitable for clinical application on dental caries prevention field, deserving clinical studies to confirm its in vivo activity.

Propolis Varnish: Antimicrobial Properties against Cariogenic Bacteria, Cytotoxicity, and Sustained-Release Profile

Abstract: Varnishes are preparations that differ in the polymeric matrix and therapeutical agents. In dentistry they are used to prevent caries. In this study we developed a propolis varnish, considering propolis properties against cariogenic bacteria. To a chitosan polymeric base (CHV) was added ethanolic propolis extract in different concentrations: PV1 (5%), PV2 (10%), and PV3 (15%). Antimicrobial activity was carried out against Streptococcus mutans (SM), Streptococcus sanguinis (SG), Streptococcus salivarius (SS), and Lactobacillus casei (LC) through agar diffusion method. The three propolis concentrations incorporated were effective in inhibiting the growth of all microorganisms, but without significant difference between the zones of inhibition observed. Cytotoxicity assay was done by MTT method. Data were analyzed by one-way ANOVA and Bonferroni test. None of the varnishes were cytotoxic, keeping 80% of viable cells, while CHV allowed cellular proliferation (120%). Sustained-release test was carried out by applying 40 μL of each varnish in the buccal surface of bovine teeth and kept in an ethanol/water solution removed in regular times. According to the “independent model approach,” the release profiles were distinct from each varnish and the most prolonged was PV3 (8 weeks). Varnish formulations had satisfactory antimicrobial activity against cariogenic bacteria and have a low cytotoxicity (<50%).

Biomechanical evaluation of screw- and cement-retained implant-supported prostheses: A nonlinear finite element analysis

Abstract: Statement of problem The mechanical stability of the prosthetic components in the implant-prosthesis complex is essential to the long-term success of the restorations. However, little is known about the differences in the biomechanical behavior of screw- and cement-retained prostheses. Purpose The purpose of this study was to compare the preload maintenance, stresses, and displacements of prosthetic components of screw- and cement-retained implant-supported prostheses by using the finite element method in a nonlinear analysis. Material and methods Two 3-dimensional models were constructed: implant-supported fixed partial prostheses with 3 elements retained either by screws (SFP) or cement (CFP). After the simulation of screw tightening, the preload was calculated for both prostheses. Then vertical and oblique loads (100 N) were applied on the models. The preload was identified, the maximum von Mises equivalent stresses (SEQV) were obtained on the screws, and the displacement among the abutment, the implant, and screw was identified by observing the penetration and gap in the contact interfaces. Results Under vertical load, there was a higher decrease in the preload and in the SEQV on the screw in the SFP. Under oblique load, the SEQV was 24% higher on the screw of the SFP. In the displacement analysis under vertical load, penetration was concentrated in the threads of the screw in the SFP and between the abutment and implant in the CFP. The gap was 118% greater for the SFP and was concentrated on the abutment extension. Under oblique load, the displacement pattern was similar for both prostheses, but with values 66% higher for penetration and 96% higher for gap for the SFP. Conclusions The SFP showed a higher biomechanical risk of failure than the CFP.

The Effect of Light-curing Access and Different Resin Cements on Apical Bond Strength of Fiber Posts

Abstract: Clinical Relevance Cementation of fiber glass posts with self-adhesive cement (RelyX U100) is more predictable than cementation with resin cement using a three-step etch-and-rinse adhesive system (RelyX ARC/SBMP) as its bond strength to apical dentin was not influenced by the level of light-curing access.

Degree of Conversion and Hardness of a Silorane-Based Composite Resin: Effect of Light-Curing Unit and Depth

Abstract: Clinical Relevance Forty seconds of light exposure in increments up to 3 mm of a novel silorane-based composite resin produced higher degree of conversion and hardness than thicker increments, using halogen or LED units.

Qualitative Evaluation of Scanning Electron Microscopy Methods in a Study of the Resin Cement/Dentine Adhesive Interface

Abstract: Sample preparation and imaging techniques for scanning electron microscopy (SEM) of dehydrated dental samples can hinder the structural analyses. This study qualitatively evaluated images obtained with two different protocols of SEM preparation and analysis to assess the dentine adhesive interface. The crown and root dentine of 12 bovine incisors were subjected to cementation with the resin cement RelyX U100 or RelyX ARC/SBMP (n = 6). After storage for 7 days in a moist environment at 37 ± 1°C, the dentine samples were dehydrated in an ascending alcohol series, and three specimens from each group were coated with gold or carbon and examined in a high-vacuum (JEOL JSM-6360LV, 10 kV) or low-vacuum (FEI Quanta 200F, 15-30 kV) microscope. Images were obtained at magnifications between 50 and 2,000×, but with different working distances. The use of high vacuum for carbon and gold coating and SEM visualization led to cracks in the samples. A small number of cracks can be described in the specimens subjected to the low-vacuum technique. The protocol for SEM imaging in low vacuum was considered more appropriate for preservation of the integrity of the evaluated structures.

Two-year clinical performance of dimethacrylatebased composite restorations repaired with a silorane-based composite.

Abstract: PURPOSE To investigate the clinical performance of a silorane-based composite resin used for repairing dimethacrylate- based composite restorations. MATERIALS AND METHODS One operator repaired defective dimethacrylate-based resin restorations that were randomly assigned to one of two treatment groups: control (n=50), repaired with Adper SE Plus and Filtek P60 Posterior Restorative (3M ESPE); or test (n=50), repaired with P90 System Adhesive Self-Etch Primer and Bond and Filtek P90 Low Shrink Posterior Restorative (3M ESPE). After 1 week, restorations were finished and polished. Two calibrated examiners (weighted Kappa≥0.78) evaluated the repaired restorations, blindly and independently, at baseline, after 6 months, 1 and 2 years. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries. The restorations were classified as Alfa, Bravo, or Charlie, according to modified US Public Health Service criteria. Variation in the levels of clinical parameters over time was evaluated by Friedman's ANOVA (α=0.05). The Mann-Whitney test assessed the differences between the materials for all clinical criteria at baseline, 6-month, 1- and 2-year recalls (α=0.05). The Wilcoxon test compared each composite resin for all clinical criteria at the same recalls (α=0.05). RESULTS After two years, 79 repaired restorations were re-examined. No statistically significant differences were found between the materials at baseline or at the 2-year recall (p>0.05). Comparing baseline and 2-year recall, there was a statistically significant difference for marginal discoloration (p=0.029) in silorane-based composite restorations. CONCLUSION After two years, the clinical performance of the silorane-based composite was similar to that of the dimethacrylate-based composite when used to make repairs.

Analysis of stresses during the polymerization shrinkage of self-curing resin cement in indirect restorations: a finite-element study.

Abstract: Background: Adhesive cementation is essential for the longevity of indirect esthetic restorations. However, polymerization shrinkage of resin cement generates stress, which may cause failures in the tooth-restoration interface. So, understanding of the biomechanics of resin cement is important for predicting the clinical behavior of an esthetic indirect restoration. Aims: To analyze the stresses generated during polymerization shrinkage of self-curing resin cement in ceramic and in indirect resin (IR) restorations, using the finite-element method (FEM). Settings and Design: Numerical study using the finite-element analysis. Materials and Methods: A three-dimensional (3D) model of a second molar restored with ceramic or IR onlay restoration was designed. The polymerization shrinkage of self-curing resin cement was simulated in FEM software using an analogy between the thermal stress and the resulting contraction of the resin cement. The localization and values of tensile stresses in the dental structure, cement, and adhesive layer were identified. Results: The location and value of the tensile stresses were similar for the two restorative materials. High tensile stresses were identified in the axiopulpal wall and angles of the tooth preparation, with the major stresses found in the cement located in the axiopulpal wall. Conclusions: The high stresses values and their concentration in the angles of the prepared tooth emphasize the importance of round angles and the use of cements with lower rates of shrinkage.

Review of follow-up of clinical success of implant-supported complete dental prostheses

Abstract: OBJECTIVE: The aim of this study was to assess the clinical success rate of implant-supported complete dental prostheses, which are being used as a feasible alternative in planning of oral rehabilitation. Over the years, the two-stage surgical protocol has increasingly been replaced by immediate loading procedures, especially in the mandibular anterior region in cases of rehabilitation of completely edentulous patients. This procedure has become feasible due to the high success rate of the technique with very satisfactory results.METHODS: By means of a literature review focused on published articles with clinical follow-up between 8 and 15 years.RESULTS: Implants placed in the mandible had higher success rates than those inserted in the maxilla. Cases with longer follow-up periods, 15 years, showed higher success rates in comparison with follow-up periods of 8 and 10 years.CONCLUSION: Success rates of implant-supported complete dental prostheses are very high.

Silorane-based composite as repair material: a six-month randomized clinical trial / Resina composta à base de silorano como material de reparo: estudo clínico randomizado de seis meses

Abstract: Objective This study investigated the clinical performance of a silorane-based composite resin when used for repairing conventional composite restorations. Methods Defective dimethacrylate-based composite resin restorations were randomly assigned to one of two treatment groups: Control group - Adper SE Plus + Filtek P60 (3M/ESPE, St. Paul, EUA) and Test Group - P90 Adhesive System + Filtek P90 (3M/ESPE, St. Paul, EUA). All repaired restorations were evaluated at baseline, and at six-month recall. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, post-operative sensitivity and secondary caries. The restorations were classified according to modified USPHS criteria. Mann-Whitney and Wilcoxon tests were used to compare the groups. Results Of the 100 restorations repaired in this study, 93 were reexamined at baseline and 91 at 6-month recall. Drop-out was about 9%. No statistically significant differences were found between the materials for all clinical criteria, at baseline and at 6-month recall (p > 0.05). No statistically significant differences were registered (p > 0.05) for each material when compared for all clinical criteria, at baseline and at 6-month recall. The hypothesis tested in this randomized controlled clinical trial was accepted. Conclusion After the six-month evaluations, silorane-based composite exhibit a similar performance compared to dimethacrylate-based composite when used as repair material. Indexing terms : Composite resins. Corrective maintenance. Dental restoration repair. Silorane resins. RESUMO Objetivo Investigar o desempenho clinico de uma resina de baixa contracao a base de silorano quando utilizada para reparar restauracoes convencionais de resina composta. Metodos Restauracoes defeituosas de resina composta a base de dimetacrilato foram aleatoriamente reparadas por um de dois grupos de tratamento: Grupo Controle - Adper SE Plus + Filtek P60 (3M/ESPE, St. Paul, EUA) e Grupo Teste - Sistema adesivo P90 + Filtek P90 (3M/ESPE, St. Paul, EUA). Todas as restauracoes reparadas foram avaliadas em baseline e ao longo de 6 meses. Os parâmetros analisados foram a adaptacao marginal, forma anatomica, rugosidade superficial, descoloracao marginal, sensibilidade pos-operatoria e lesoes de carie. As restauracoes foram classificadas de acordo com os criterios do Servico de Saude Publico dos Estados Unidos modificados. Os testes de Mann-Whitney e Wilcoxon foram utilizados para comparar os grupos. Resultados Das 100 restauracoes reparadas neste estudo, 93 foram examinadas uma semana apos terem sido reparadas - baseline e 91 apos 6 meses. A perda foi de aproximadamente 9%. Nenhuma diferenca estatisticamente significativa foi encontrada entre os materiais para todos os criterios clinicos, em baseline e ao longo de 6 meses (p> 0,05). Conclusao A hipotese testada neste ensaio clinico controlado randomizado foi aceita. Apos 6 meses de avaliacoes, resinas compostas a base de silorano apresentaram desempenho clinico semelhante as resinas compostas a base de dimetacrilato quando utilizadas para reparar restauracoes de resina composta a base de dimetacrilato. Termo de indexacao : Resinas compostas. Manutencao corretiva. Reparacao de restauracao dentaria. Resinas de silorano.