Contemporary flowable bulk-fill resin-based composites: a systematic review.

Flowable bulk-fill resin-based composites (BF-RBCs) represent a new and interesting alternative for the bulk-fill restorative techniques in the posterior region. However, they comprise a heterogeneous group of materials, with important differences in composition and design. Therefore, the aim of the present systematic review was to compare the main properties of flowable BF-RBCs, including their composition, degree of monomer conversion (DC), polymerization shrinkage and shrinkage stress, as well as flexural strength. The search was conducted following PRISMA guidelines in the Medline (PubMed), Scopus and Web of Science databases. In vitro articles reporting on the DC, polymerization shrinkage/shrinkage stress, and flexural strength of flowable BF-RBCs strength were included. The QUIN risk-of-bias (RoB) tool was used for assessing the study quality. From initially 684 found articles, 53 were included. Values for DC ranged between 19.41 and 93.71%, whereas polymerization shrinkage varied between 1.26 and 10.45%. Polymerization shrinkage stresses reported by most studies ranged between 2 and 3 MPa. Flexural strength was above 80 MPa for most materials. A moderate RoB was observed in most studies. Flowable BF-RBCs meet the requirements to be indicated for bulk fill restoration technique in the posterior region. However, important variations among composition and properties hinder extrapolation of the results to materials different from those reported here. Clinical studies are urgently required to assess their performance under a real working scenario.

The effect of filling technique on the cuspal strain, polymerization shrinkage stress, enamel crack formation and depth of cure of restored molars.

OBJECTIVE: Evaluate the effect of different restorative filling techniques on the residual shrinkage stress (ShrS), cuspal strain (CS), depth of cure (DC), and enamel crack formation (Ec) in molars with MOD restorations. METHODS: Post-gel shrinkage, elastic modulus, compressive and diametral tensile strength of the Filtek One Bulk Fill composite were calculated. Sixty molars with MOD preparations were restored using four filling techniques: Bulk; Horizontal; Oblique; Natural enamel and dentin substitution (NEDS) technique. CS was measured using a strain gauge (n = 10). The DC (n = 5) was measured using Knoop hardness. Shrinkage stress/strain was analyzed using 3D finite element analysis. The Ec analysis was carried out by transillumination. Two-way ANOVA with repeated measures and Tukey's HSD test (α = 0.05) was performed for the CS data. Two-Way ANOVA and Tukey's HSD test was performed for the DC data (α = 0.05). RESULTS: CS was higher at the lingual cusp for the horizontal and NEDS technique. No statistical difference was found between the buccal and lingual CS values for the Bulk (p = 0.367) or Oblique techniques (p = 0.192). CS values were lower for the Bulk. More enamel cracks were found for the Bulk. DC was lower at 4 mm regardless the filling technique. The Horizontal showed the highest ShrS values. The Bulk generated the lower ShrS values. SIGNIFICANCE: A Bulk technique caused the lowest shrinkage stress/strain. An Oblique technique yielded the best balance between stress, strain and crack formation. NEDS technique is a good alternative to decrease the number of increments while maintaining the stress levels nearby the Oblique technique.

Knowledge about composite restorations repair vs replacement- a survey among a subpopulation of saudi dental students / Conhecimento sobre reparo e substituição de restaurações de resina - uma pesquisa entre uma subpopulação de estudantes sauditas de odontologia

Objective: The purpose of this study was to evaluate the knowledge among dental students at King Khalid University, Jazan University, and Najran University in the kingdom of Saudi Arabia about when to repair or replace defective direct composite restoration. Materials and Methods: A questionnaire-based survey was formulated, pursuing the information about management (repair/replacement) of defective composite restorations and distributed among 200 dental students of three universities in the southern region of the kingdom of Saudi Arabia. The data were collected with the help of an online questionnaire. Data entry and the analysis were done using the statistical software package SPSS version 20.0. It was presented using descriptive statistics in the form of frequencies and percentages for qualitative variables, and range means and standard deviations for age, quantitative variable. Analytic statistics were done using Chi-Square tests (χ2) to test the significant difference between categorical variables. The level of significance, the p-value was 0.01(p<0.01). Results: The decision to choose between composite repair or replacement was influenced by whether this topic was taught to them at various undergraduate levels during Bachelor of Dental Surgery. The reason associated with the decision to repair defective composite restorations, 76% reported as cost-effective followed by Increased longevity (71%), the permanent filling (70%), patient's preference for repair (65%), and least time consuming (50%). 67% participants preferred significantly (p<0.001) repair due to secondary caries in the previously restored tooth with composite, followed by the small surface defect in a composite restoration (65%), risk of pulpal damage significantly (p<0.001) in a defective composite restoration (62.5%) and more invasive and destructive treatment option (35%). More than half of respondents 123 (61.5%) reported that they were not taught about composite repair during the Bachelor of Dental Surgery. Conclusion: It is suggested with the help of our study that didactic and clinical training components regarding composite repair should be seriously included in the teaching curriculum of dental institutions as it is in the best interest of the patient. Dental students should be provided with clinical training on this topic so that they can follow proper decision-making protocols available during repair or replacement of defective resin composite restorations. Other researches in the future can be carried out for refining the guidelines and techniques utilized for composite repair. (AU)

Objetivo: O objetivo deste estudo foi avaliar o conhecimento entre estudantes de odontologia da King Khalid University, Jazan University e Najran University, no reino da Arábia Saudita, sobre quando reparar ou substituir restaurações de resina composta direta defeituosas. Material e Métodos: Foi formulada uma pesquisa baseada em questionário, buscando informações sobre o manejo (reparo / substituição) de restaurações de resina composta e distribuída entre 200 estudantes de odontologia de três universidades da região sul do reino da Arábia Saudita. Os dados foram coletados com o auxílio de um questionário online. A entrada e análise dos dados foram feitas com o software estatístico SPSS versão 20.0. Foi apresentado por meio de estatística descritiva na forma de frequências e percentuais para as variáveis qualitativas, e amplitude de médias e desvios-padrão para a idade, variável quantitativa. A estatística analítica foi feita usando testes de qui-quadrado (χ2) para testar a diferença significativa entre as variáveis categóricas. Ao nível de significância, o valor de p foi de 0,01 (p <0,01). Resultados: A decisão de escolher entre o reparo ou substituição do compósito foi influenciada pelo fato de este tópico ter sido ensinado a eles em vários níveis de graduação durante o Bacharelado em Odontologia. O motivo associado à decisão de reparar restaurações de resina composta defeituosas, 76% relataram como custo-benefício seguido por maior longevidade (71%), restauração definitva (70%), preferência do paciente para reparo (65%) e menos demorado ( 50%). Sessenta e sete por cento dos participantes preferiram o reparo significativamente (p <0,001) devido a cárie secundária no dente previamente restaurado com resina composta, seguido pelo pequeno defeito de superfície em uma restauração composta (65%), risco de dano pulpar significativamente (p <0,001) em um restauração de resina composta com defeito (62,5%) e opção de tratamento mais invasiva e destrutiva (35%). Mais da metade dos entrevistados, 123 (61,5%) relataram que não foram ensinados sobre reparo de resina composta durante o Bacharelado em Odonotlogia. Conclusão: É sugerido com a ajuda de nosso estudo que os componentes do treinamento didático e clínico sobre reparo de resina composta devem ser seriamente incluídos no currículo de ensino de instituições odontológicas, pois é do interesse do paciente. Os estudantes de odontologia devem receber treinamento clínico sobre este tópico para que possam seguir os protocolos de tomada de decisão adequados disponíveis durante o reparo ou substituição de restaurações de resina composta com defeito. Outras pesquisas no futuro podem ser realizadas para refinar as diretrizes e técnicas utilizadas para reparo de resina (AU)

Bulk Fill flow resin contraction using 3D finite element model and calibration by Fiber Bragg Grating measurement.

Contraction due to polymerization of dental resin can cause failure on the adhesive interfaces, can lead to problems such as the appearance of gaps in the interfaces, postoperative sensitivity, pulp damage and the return of the caries. The objective of this work is the study of stresses on the dental adhesive that are generated by the process shrinkage of resin associated with biting forces. A laboratory experiment measured the strains and temperature inside the FiltekTM Bulk Fill Flow resin during the process of polymerization using Fiber Bragg Grating sensors in an ex vivo tooth. From tomographic images a three-dimensional geometric model of the tooth was reconstructed. A pre-tension was calibrated to simulate the residual contraction on the resin 3 D model. Finally, an Finite Element Method analysis was performed to access the adhesive stresses at the interface enamel/dentin with the adhesive, considering as loading the residual polymerization contraction of the dental resin and also biting loads. The model was able to represented the strain obtained in the laboratory experiment. The results of the stress analysis shows that the outer regions of adhesive are more prone to failure, as veried by dental surgeons in clinical practice.

Microleakage in posterior teeth with different materials and different types of cavities.

BACKGROUND: The purpose of this study was to investigate the behavior of a resin-based 2,2-bis (p-[2'-hydroxy-3'-methacryloxypropoxy] phenylene) propane and a composite resin modified with oxirane, regarding the ability of marginal sealing, both with direct restorations and indirect restorations. MATERIALS AND METHODS: To achieve this, mesio- and disto-occlusal cavities were made on the same tooth, totalling 100 cavities. These cavities were restored with two materials, Filtek P90 (3M ESPE) and Opallis (FGM). Then, they were divided into two groups: Fifty direct restorations, each sample restored with the two materials, following the manufacturer's protocol and fifty indirect restorations, and then cemented with a paste obtained by diluting the resin in its adhesive. The templates were thermally cycled, 30 s at 5°C and 30 s at 55°C for 500 cycles and then were immersed in methylene blue for 24 h. Afterward, they were trimmed using a plaster trimmer from occlusal toward a gingival direction. These samples were analyzed with stereomicroscope (×3) by two blinded observers. Then, a system which considers the average number of surrounding walls that have suffered infiltration on a scale of 0-3 was used. RESULTS: Data were subjected to statistical analysis (Mann-Whitney and Kruskal-Wallis tests) with a significance level of 5% maximum. CONCLUSION: It was concluded that the indirect restorations showed the greatest number of restorations with score 0 and 1 (34) and lowest score 2 and 3 (16). This suggests that indirect restorations regardless of the material used behaved more effectively regarding the marginal sealing of restorations.

Comparison of the Polymerization Shrinkage of Eclipse Resin for Prostheses with Conventional Acrylic Resins / Comparación de la Contracción de Polimerización de la Resina Eclipse para Prótesis con Resinas Acrílicas Convencionales

ABSTRACT: The objective of this study was to compare the polymerization shrinkage of Eclipse photopolymerization resin for prosthesis based on urethane dimethacrylate (UDMA) with that of three heat-cured acrylic resins based on polymethyl methacrylate (PMMA) after the polymerization process and immersion in water. A total of 40 prostheses were fabricated on a standard metallic upper edentulous model: group 1, Eclipse; group 2, Triplex hot; group 3, Veracril; and group 4, Lucitone 199. Subsequently, the polymerization contraction was tested using a microscope in which measurements were made in micrometres at 3 points located in the middle parts of the right and left sides and the middle part of the palate at three time points once the prosthesis was completed, after 30 days of immersion in water for 8 hours a day at a temperature of 37 °C, and after cutting the prosthesis at the level of the second premolar. ANOVA revealed that the contraction of the polymerization no statistically significant differences between the groups, (P> 0.05). The type of resin and its interaction with the processing method behaves similarly for all test resins. The Veracril heat-cured resin obtained the lowest contraction value in the three measurements (mm) and the highest value was obtained with the Eclipse photopolymerization resin. The Eclipse resin exhibited no lower polymerization shrinkage compared to conventional acrylic resins based on polymethyl methacrylate (PMMA), however it was not significantly affected by immersion in water.

RESUMEN: El objetivo de este estudio fue comparar la contracción de polimerización de la resina de fotopolimerización Eclipse para prótesis basadas en dimetacrilato de uretano (UDMA) con la de tres resinas acrílicas curadas con calor a base de polimetacrilato de metilo (PMMA) después del proceso de polimerización e inmersión en agua. Se fabricaron un total de 40 prótesis en un modelo edéntulo superior metálico estándar: grupo 1, Eclipse; grupo 2, triplex caliente; grupo 3, veracril; y grupo 4, Lucitone 199. Posteriormente, la contracción de la polimerización se probó utilizando un microscopio en el que se realizaron mediciones en micrometros en 3 puntos ubicados en las partes medias de los lados derecho e izquierdo y la parte media del paladar en tres puntos de tiempo una vez la prótesis se completó, después de 30 días de inmersión en agua durante 8 horas al día a una temperatura de 37 °C, y después de cortar la prótesis a nivel del segundo premolar. ANOVA reveló que la contracción de la polimerización no presenta diferencias estadísticamente significativas entre los grupos, (P> 0,05). El tipo de resina y su interacción con el método de procesamiento se comportan de manera similar para todas las resinas de prueba. La resina curada con calor Veracril obtuvo el valor de contracción más bajo en las tres mediciones (mm) y el valor más alto se obtuvo con la resina de fotopolimerización Eclipse. La resina Eclipse no mostró una contracción de polimerización menor en comparación con las resinas acrílicas convencionales basadas en polimetilmetacrilato (PMMA), sin embargo, no se vio afectada significativamente por la inmersión en agua.

Polymerization Shrinkage Evaluation of Restorative Resin-Based Composites Using Fiber Bragg Grating Sensors.

The purpose of this study was to compare the linear polymerization shrinkage of different restorative resin-based composites (RBCs) using fiber Bragg grating (FBG) sensors. Five RBCs were evaluated: Zirconfill® (ZFL); Aura Bulk-Fill (ABF); Tetric® N-Ceram Bulk-Fill (TBF); FiltekTM Bulk-Fill (FBF); and Admira Fusion-Ormocer® (ADF). Ten samples per resin were produced in standardized custom-made half-gutter silicone molds. Two optical FBG sensors were used to assess temperature and polymerization shrinkage. Light curing was performed for 40 s and polymerization shrinkage was evaluated at 5, 10, 40, 60, 150, and 300 s. Statistical analysis was accomplished for normal distribution (Shapiro-Wilk, p > 0.05). Two-way repeated measures ANOVA with Greenhouse-Geisser correction followed by Bonferroni's post-hoc test was used to analyze the linear shrinkage data (p < 0.05). ZFL showed the highest linear shrinkage and ADF the lowest. Shrinkage increased for all RBCs until 300 s, where significant differences were found between ADF and all other resins (p < 0.05). Among bulk-fill RBCs, TBF showed the lowest shrinkage value, but not statistically different from FBF. The ADF presented lower linear shrinkage than all other RBCs, and restorative bulk-fill composites exhibited an intermediate behavior.

Linear polymerization shrinkage of Bulk Fill resins

Objective: the objective of the present study was to analyzethe polymerization shrinkage gap of different compositeresins. Methods: four commercial brands (n=5)were tested: Z350 (3M/ESPE); Filtek Bulk Fill (3M/ESPE);Surefill (Dentsply); Xtra Base (Voco). Increments of compositeresins were inserted into a circular metal matrixof 7 mm internal diameter and 4 mm high and pressedby two glass plates supported on polyester strips. Afterphotoactivation with a Optilight Plus device (Gnatus),with light intensity of 1000 ± 10mW/cm2, the test sampleswere polished and 24h later, taken to the scanningelectron microscope for analysis of the polymerizationshrinkage gap, measured at 4 points in the sample (3, 6,9, and 12 o'clock). The data were analyzed by analysisof variance (Anova one-way). Results: the highest meanof polymerization shrinkage gap was observed for FiltekZ350 (3M/ESPE), while the lowest mean of gap wasfound for Xtra Base (Voco) brand, with significant differencesbetween the groups. Conclusion: the inorganicfiller content and different associations in the organicmatrices interfered expressively in the polymerizationshrinkage gap.

Polymerization shrinkage stress of resin-based dental materials: A systematic review and meta-analyses of composition strategies.

PURPOSE: A systematic review was conducted to determine whether there were composition strategies available to reduce and control polymerization shrinkage stress development in resin-based restorative dental materials. DATA SOURCES: This report was reported in accordance with the PRISMA Statement. Two reviewers performed a literature search up to December 2016, without restriction of the year of publication, in seven databases: PubMed, Web of Science, Scopus, SciELO, LILACS, IBECS, and BBO. STUDY SELECTION: Only laboratory studies that evaluated polymerization shrinkage stress by direct testing were included. Pilot studies, reviews and in vitro studies that evaluated polymerization shrinkage stress by indirect methods (e.g., microleakage or cuspal deflection measurements), finite elemental analysis, or theoretical and mathematical models were excluded. Of the 6113 eligible articles, 62 studies were included in the qualitative analysis, and the meta-analysis was performed with 58 studies. The composition strategy was subdivided according to the modified part of the material: filler phase, coupling agent, or resin matrix. A global comparison was performed with random-effects models (α = 0.05). The only subgroup that did not show a statistical difference between the alternative strategy and the control was 'the use of alternative photo-initiators' (p = 0.29). CONCLUSION: Modification of the resin matrix made the largest contribution to minimizing stress development. The technology used for decreasing stress in the formulation of low-shrinkage and bulk-fill materials was shown to be a promising application for reducing and controlling stress development.

Polymerization shrinkage stress of resin-based dental materials: A systematic review and meta-analyses of technique protocol and photo-activation strategies.

PURPOSE: A systematic review was conducted to determine whether there were any alternative technique or additional step strategies available to reduce and control polymerization shrinkage stress development in dental resin-based restorative materials. DATA SOURCES: This report followed the PRISMA Statement. A total of 36 studies were included in this review. Two reviewers performed a literature search up to December 2016, without restriction of the year of publication, in seven databases: PubMed, Web of Science, Scopus, SciELO, LILACS, IBECS, and BBO. STUDY SELECTION: Only in vitro studies that evaluated polymerization shrinkage stress by direct testing were included. Pilot studies, reviews and in vitro studies that evaluated polymerization shrinkage stress by indirect methods (e.g., microleakage or cuspal deflection measurements), finite elemental analysis or mathematical models were excluded. Of the 6.113 eligible articles, 36 studies were included in the qualitative analysis, and the meta-analysis was performed with 25 studies. A global comparison was performed with random-effects models (α = 0.05). The strategies were subdivided as follows: the use of an alternative technique protocol of placing the material inside the tooth cavity; the modification of the irradiation intensity or total energy delivered to the material; the use of an alternative light-curing source; or the use of an alternative photo-activation mode. All alternative strategies showed statistically significant differences when compared with their respective controls (p < 0.05). CONCLUSION: The use of alternative light-curing sources contributed more to minimizing stress development than placing the material by means of an alternative technique protocol or by modifying the irradiant intensity or total energy delivered to the material during photo-activation. Moreover, the use of an alternative photo-activation mode (intermittent light, exponential, soft-start or pulse delay modes) was shown to be an effective strategy for reducing and controlling stress development in resin-based dental materials.

Effect of the photoinitiator system on the properties of a dental material based on a hybrid polymer / Efeito do sistema fotoiniciador sobre as propriedades de um material dentário baseado em um polímero híbrido

Objetivo: Nesse estudo, foram avaliados os efeitos de dois diferentes protocolos de cura sobre as propriedades de um compósito usando um polímero híbrido como resina dentária. Material e Métodos: Dois compósitos diferentes foram preparados, um contendo uma mistura de TEGDMA/Bis-GMA (50:50) e, outro contendo uma mistura de TEGDMA/p-MEMO (50:50), [p-MEMO: precursor oligomérico inorgânico]. Ambos compósitos foram reticulados com lucirin e canforoquinona. Os compósitos foram preparados com 70% em massa de carga inorgânica. Resistência flexural foi avaliada com uma máquina de testes universal e o grau de conversão calculado por espectroscopia na região do infravermelho. Um picnômetro a gás hélio foi usado para obter os dados de contração de polimerização. Testes de sorção foram feitos e microscopia eletrônica de varredura foi usada para avaliar efeitos deletérios sobre as superfícies das resinas. Resultados: A amostra constituída com TEGDMA/p-MEMO reticulada com lucirin (L-T/p) apresentou os melhores valores das propriedades monitoradas. Conclusão: Lucirin é o sistema fotoiniciador mais adequado para compostos dentários contendo polímeros híbridos.

Objective: In this study, the effects of two different cure protocols upon the properties of composites using a hybrid-polymer as dental resin were evaluated. Material and Methods: Two distinct dental composites were prepared, one containing a mixture of TEGDMA/bis-GMA (50:50) and, another containing a mixture of TEGDMA/p MEMO (50:50), [p-MEMO: oligomeric inorganic precursor]. Both composites were polymerized with lucirin and canphorquinone as photoinitiators. The composites were made with a 70 % wt of inorganic filler. Flexural strength was evaluated with a universal test machine and the degree of conversion was measured by infrared spectroscopy. A helium pycnometer was used to obtain polymer shrinkage data. Sorption tests were performed and SEM microscopy was used to show deleterious effects upon the resins’ surfaces. Results: The sample based on TEGDMA/p-MEMO polymerized with lucirin (L-T/p) showed the best values of the monitored properties. Conclusion: Lucirin is the most suitable photoinitiator for dental composites containing hybrid polymers.

Evaluation of polymerization shrinkage of dental composites by an optical method.

This study proposes an alternative methodology for evaluating polymerization shrinkage of dental composites using an advanced video extensometer (AVE) system. This equipment measures the displacement between two points drawn on a tooth's wall without requiring physical contact with the tooth. By doing so, the polymerization process was monitored by the cusp deflection. This technique was used in human and bovine teeth, where the cavities were prepared under controlled conditions so that the volume of the composite used was the same in both types of teeth. After the cavity preparation, the specimens were acid etched, washed and dried, and then the adhesive was applied and polymerized. The composite was then inserted into the cavity. Polymerization was performed with two different light polymerizing units (LD Max and Optilight Max - Gnatus do Brasil), and the displacement curve of the tooth cusp was recorded for a period of 400 s. After a statistical analysis, it was concluded that the technique was capable of evaluating shrinkage by the deflection from the cusps and that the human and bovine teeth do not react in a similar manner towards the polymerization shrinkage of composites.

A urethane-based multimethacrylate mixture and its use in dental composites with combined high-performance properties.

OBJECTIVES: To synthesize and characterize different molar weight urethane multimethacrylates with a single stage (one-pot) procedure. To prepare and characterize the properties of related composites. METHODS: Two methacrylate precursors were initially synthesized. Then, these precursors and the multimethacrylate system formed by their coupling were characterized by FTIR and (1)H NMR. The final product was used as a matrix (with TEGDMA and SiO2 silanized microparticles) in the preparation of composites and their physical and mechanical properties were compared to those of a bis-GMA-based resin. Water sorption and solubility measurements of the composites were also performed. RESULTS: FTIR and NMR suggested that the proposed synthesis route yields a mixture of mainly urethane-di, -tri, and tetramethacrylates. The composites presented low polymerization shrinkage (e.g. 1.88±0.08% for a resin with 70% of SiO2) and high flexural strength (e.g. 124.74±9.68 MPa for a resin with 65% of SiO2) when compared to the bis-GMA based resin and other composites found to date. Water sorption and solubility results show that the composites were deemed compliant with ISO 4049 requirements. SIGNIFICANCE: The mixture containing different molar weight of urethane multimethacrylates showed to be an excellent substitute for bis-GMA, achieving an equilibrium of properties (unlike reports elsewhere which show the enhancement of some parameters in detriment to others) and composites with low polymerization shrinkage, suitable microhardness and degree of conversion, and up to standard water sorption/solubility and flexural strength.

Síntese e análise de compósitos experimentais para uso odontológico reforçados com nanoargila / Synthesis and analysis of experimental composites for dentistry use reinforced with nanoclay

O objetivo do presente estudo foi de avaliar os efeitos de diferentes frações de partículas de nanoargila modificadas do tipo montmorilonita Cloisite® 20A em propriedades físicas, mecânicas e biológicas de resinas experimentais do tipo nanohíbrida. Compósitos dentais foram preparados através da mistura de 30% de matriz resinosa (BisGMA/TEGDMA) em 70% de partículas de carga (vidro de bário silicato silanizado ­VB, dióxido de silício ­ SD, partículas de nanoargila MMT). Quatro grupos de compósitos experimentais foram formados, variando o percentual de nanoargila empregada (0%, 5%, 7,5%, 10%). O processamento foi realizado em uma máquina de dupla mistura (SpeedMixer DAC, Germany, 3500 rpm). A citotoxicidade in vitro do material foi avaliada baseada nas normas ISO 10993- 5-2009 e comparado com compósito comercial. Ensaios mecânicos para cálculo de Resistência à Flexão e Módulo de Elasticidade foram realizados em máquina de ensaios universal EMIC. O aparelho Acuvol® foi utilizado para o ensaio de contração de polimerização. A sorção e solubilidade dos compósitos foram calculadas baseadas nas normas ISO 4049. Os dados foram analisados estatisticamente, utilizando-se a tabela ANOVA e o Teste de Tukey para comparação dos grupos de dois em dois. O nível de significância utilizado foi de 95% (p< 0,05). Por meio do exame dos resultados, concluiu-se que foi possível esfoliar 5 e 7,5% de partículas de MMT satisfatoriamente na matriz BisGMA/TEGDMA, porém, o inserção de 10% de MMT na matriz orgânica não trouxe vantagens ao compósito, certamente por não permitir a total exfoliação de suas partículas. A inserção de 5 e 7,5% de nanoargila ao compósito dental experimental possibilitou uma diminuição da contração de polimerização do material em 22,13 e 17,4%, respectivamente. Além disso, esses dois grupos permaneceram com suas propriedades mecânicas e de absorção e solubilidade satisfatórias, além de apresentar ausência de citotoxicidade para as células fibroblasticas L929 testadas

The aim of the present study was to evaluate the effect of different weight fractions of modified montmorillonite nanoclay fillers Cloisite ® 20A on mechanical, physical and biological properties of nanohybrid experimental resins. Dental composites were prepared by mixing 30% of resin matrix (BisGMA / TEGDMA) to 70% of particulate fillers (Silanized barium silicate particles - BS, silicone dioxide - SD, montmorillonite nanoclay cloisite 20AMMT). Four groups of experimental composite were formed with various fractions of the nanoclay fillers (0%; 5%; 7,5%; 10% ). Processing was performed using a dual high speed mixing machine (SpeedMixer DAC, Germany, 3500 rpm). In vitro citotoxicity of the material was calculated based on standards ISO 10993-5-2009 and compared to a comercial composite. Tensile strenght and elastic modulus were performed using an universal test machine EMIC. The volumetric shrinkage was calculated by Acuvol® machine. Water sorption and solubility were measured based on International Standard ISO 4049. Data were statistically analyzed by ANOVA and Tukey Test for multiple comparisons. The significance level utilized was 95% (p < 0,05). By the results, it was concluded that it is possible to exfoliate nicely 5 and 7.5% of MMT particles inside Bis-GMA/TEGDMA matrix. However, insertion of 10% of MMT did not improve composite, certainly, because the total exfoliation of particles did not occured. Insertion of 5 and 7.5% of nanoclay in dental composite diminished polymerization shrinkage in 22,13% and 17,4% , respectively. Furthermore, these two groups maintained their mechanical properties, satisfactory sorption and solubility and also presented no citotoxicity for L929 fibroblastic cells

Influence of different flask systems on tooth displacement and framework misfit in mandibular fixed implant-supported complete dentures.

PURPOSE: To evaluate the influence of different metallic flask systems for acrylic resin denture processing on tooth displacement and framework misfit of mandibular fixed implant-supported complete dentures. METHODS: Standard mandibular implant-supported complete dentures in five implants were waxed and randomly assigned to three groups: G1 - conventional flask, G2 - double flask, and G3 - occlusion flask. Framework misfit in all the implants and the linear distances between teeth (I-I - incisor-to-incisor; P-P - premolar-to-premolar; M-M - molar-to-molar; RI-RM - right-incisor-to-right-molar; and LI-LM - left-incisor-to-left-molar) were measured before and after denture processing using an optical microscope. Dentures were processed by hot water curing cycle (9h/74°C). Collected data were analyzed by paired Student's t-test and one-way ANOVA (α=0.05). RESULTS: All the measured distances presented changes in tooth displacement after denture processing. However, the M-M distance for G1 (p=0.003) and the P-P (p=0.042) and LI-LM (p=0.044) distances for G3 showed statistically significant differences. Differences between the flask systems were not statistically significant. Statistically significant differences in the framework misfit due to denture processing were found for all the implants and groups, with the exception of right median implant for G2 and right distal implant for G3. A comparison of the flask systems found statistically significant differences in which G1 presented an increase in the misfit values and G2 and G3 a decrease. CONCLUSIONS: Different flask systems did not cause significant changes in tooth displacement. Frameworks misfit values were influenced by the different flask systems. The conventional flask presented an increase in the framework misfit, while the experimental flasks showed a decrease.

Efeito do fator cavitário na resistência adesiva à dentina de um sistema restaurador à base de silorano / C factor effect on bond strength of a restorative system based on silorane

O objetivo deste estudo foi avaliar o efeito do fator C na resistência adesiva à dentina humana de um compósito à base de silorano, comparando-o com um compósito à base de metacrilato. Foram utilizados 40 molares humanos hígidos. Em metade da amostra foi realizado um preparo do tipo Classe I, com dimensões de 4x4 mm e 2 mm de profundidade, enquanto na outra metade foi realizado um preparo virtual (flat) com auxílio de uma matriz de teflon branco, com as mesmas dimensões da cavidade (4x4x2 mm), apoiada na superfície de dentina exposta. Cada grupo foi divido em dois, de acordo com o sistema restaurador: Sistema Adesivo P90 e resina Filtek P90; Adper Scotchbond Multiuso e resina Filtek Z350 XT (3M ESPE). Após a aplicação do sistema adesivo segundo as especificações do fabricante, as cavidades (real e virtual) foram preenchidas com as resinas (Z350 XT e P90) em dois incrementos. Foi realizada a fotoativação de cada incremento durante 25s. Após uma semana, as coroas foram seccionadas, obtendo-se espécimes constituídos de resina/dente na forma de um paralelepípedo (palitos). Estes palitos foram utilizados para o teste de microtração (Emic), onde a resistência adesiva na unidade MPa foi calculada. Os resultados foram avaliados estatisticamente pelo teste de análise de variância ANOVA One-Way (p = 0,05), e pelo teste de múltiplas comparações Student Newman Keuls. Foi observada uma diferença estatística entre a resina P90 (flat= 16,13±7,7 MPa e Cavidade= 16,75±9,0 MPa) e a Z350 XT (flat= 25,82±11,6 MPa e Cavidade=24,47±13,5 MPa), independentemente do tipo de cavidade restaurada. E não foi possível observar diferença estatística entre os tipos de cavidades (real ou virtual) restauradas com a mesma resina. Através dos testes realizados, foi possível concluir que: o fator C não afetou a resistência adesiva dos dois sistemas restauradores utilizados, e o tipo de sistema restaurador afeta a resistência adesiva, sendo que o sistema à base de silorano apresenta ...

The purpose of this study is to evaluate the effect of the C factor in the bond strength of a composite based on silorane to human dentin, comparing its results with a methacrylate-based composite. A total of 40 human molars were used. In half of this sample was used a Class I standard preparation method, comprising the dimensions of 4x4 mm and 2 mm deep, while with the other half was used a virtual preparation method (flat), being applied a white Teflon matrix, respecting the same dimensions cavity (4x4x2 mm), supported on the surface of exposed dentin. Each group was divided into two parts, in accordance with the 2 different restorative systems: P90 Adhesive System and Filtek P90; Filtek Z350 XT and Adper Scotchbond Multipurpose (3 ESPE). Based on manufacturer's specifications the adhesive system was applied , the cavities (real and virtual) were filled with the resins (Z350 XT and P90) in two increments. Polymerization was performed for each increment during 25 seconds. After one week, the crowns were sectioned, obtaining specimens made of resin / tooth in the form of a parallelepiped (stick-shaped). These sticks were used in a microtensile test (Emic), where the bond strength was calculated in Mpa unit . It was used the analysis of variance One-Way ANOVA (p = 0.05) and also, the Student Newman Keuls test for multiple comparisons to evaluate the results statistically. It was observed a statistical difference between the P90 resin (flat = 16.13±7.7 MPa and cavity = 16.75±9.0 MPa) and Z350 XT (flat = 25.82±11.6 MPa and cavity = 24.47±13.5 MPa), regardless of the cavity restored. And it was not possible to observe a statistical difference between the types of cavities (real or flat) restored with the same composite. The conclusion of the tests is: the C factor did not affect the bond strength of two restorative systems applied, and the type of restorative system affects the bond strength, and the system based on silorano presents ...

Efeito da base de cimento de ionômero de vidro convencional e modificado por resina na interface adesiva dente/resina composta após termociclagem / Effect of conventional and resin-modified glass ionomer cements base on tooth/composite resin adhesive interface after termocycling

Resinas compostas apresentam contração de polimerização e a tensão gerada durante essa polimerização compete com a força adesiva na interface dente/restauração. A técnica incremental e o uso de bases com alta resiliência e módulo de elasticidade próximo ao das estruturas dentárias são técnicas desenvolvidas para tentar diminuir a tensão originada pela contração de polimerização. O presente estudo teve como objetivo analisar a influência do uso de bases de cimento de ionômero de vidro convencional e modificado por resina na qualidade e adaptação marginal na interface dentina/resina composta, após a ciclagem térmica, usando testes de resistência adesiva e análise em microscopia confocal de varredura a laser. Foram confeccionadas cavidades na face oclusal (4,5mm x 3mm x 5mm) de 60 molares humanos extraídos divididos em 6 grupos: 1 e 4 - sistema adesivo (Adper^TM Single Bond; 3M ESPE) + resina composta (Filtek Z250; 3M ESPE); 2 e 5 - base de cimento de ionômero de vidro convencional (Ketac Molar Easymix; 3M ESPE) + sistema adesivo + resina composta; e 3 e 6 - base de cimento de ionômero de vidro modificado por resina (Vitrebond; 3M ESPE) + sistema adesivo + resina composta. Os grupos 4, 5 e 6 sofreram um processo de termociclagem com dois banhos (5ºC 55ºC) durante 30 segundos em 5.000 ciclos. Após 24 horas, os dentes foram seccionados em uma máquina de cortes com disco de diamante em espessura de 0,8mm. Uma fatia de cada dente foi separada aleatoriamente para análise em Microscópio Confocal para observação e mensuração de possíveis fendas marginais internas. As demais fatias foram seccionadas para a confecção de palitos (0,8mm X 0,8mm) que foram submetidos a testes de microtração em uma máquina de ensaios universal EMIC. Os resultados de resistência adesiva foram submetidos à análise de variância a um critério (ANOVA) e ao teste t-Student (p< 0,05).

A presença de fendas foi avaliada com o teste da razão de verossimilhança ou teste exato de Fisher e os valores de comprimento das fendas foram avaliados pelo teste não paramétrico de Kruskal-Wallis (p<0,05). Não foram observadas diferenças estatisticamente significantes na resistência adesiva em nenhum dos grupos sem termociclagem (G1 19,28 MPa; G2 16,29 MPa; e G3 15,95MPa) ou com termociclagem (G4 19,74 MPa; G5 16,58 MPa; e G6 16,01 MPa). A análise das medidas das fendas revelou não haver diferença estatisticamente significante entre os grupos G1 (1,4µm), G2 (2,88µm) e G3 (4,63µm) e entre os grupos G4 (4,2µm), G5 (12,5µm) e G6 (5,4µm). No entanto, a termociclagem determinou um aumento do tamanho médio das fendas no grupo com base de CIV convencional (G4 12,5µm). A análise da presença ou ausência de fendas mostrou um aumento na porcentagem do número de fendas quando os espécimes foram termociclados, para os grupos sem base e com base de CIV (G1 - 30%; G2 - 25% G3 25%; G4 - 53,33%; G5 70%; e G6 30%). Os resultados mostraram, ainda, não haver relação entre o comprimento e a formação das fendas com a resistência adesiva. Conclui-se, portanto, que o uso de base de cimento de ionômero de vidro modificado por resina mantém mais estável a qualidade da interface adesiva dentina/resina composta após envelhecimento artificial com termociclagem.

Polymerization shrinkage leads to a tension into dentin/resin composite interface that can cause marginal discoloration, poor marginal adaptation, secondary caries and post-operative sensitivity. The incremental restorative technique and the use of a resilient liner with a modulus of elasticity similar to dental structures are techniques used to decrease the shrinkage polymerization tension. The aim of this in vitro study was to analyze the effect of glass-ionomer cement as a liner on the adhesive interface dentin/resin of occlusal restorations after thermocycling aging. Occlusal cavities were prepared sixty human extracted molars, divided into six groups: 1 and 4 with no liner; 2 and 5 glass-ionomer cement (Ketac Molar Easymix); and 3 and 6 resin-modified glass-ionomer cement (Vitrebond). Resin composite (Filtek Z250) was placed after application of adhesive system Adper Single Bond 2. Adhesive system was mixed with fluorescent reagent (Rhodamine B) to allow confocal microscopy analysis. After that, the specimens of groups 4, 5, 6 were thermocycled into 2 baths (5ºC 55ºC) of 30s each in 5.000 cycles. After this period, teeth were sectioned in 0,8mm slices. One slice of each tooth was randomly selected for analysis in Confocal Microscopy. The other ones were sectioned in sticks, which were submitted to micro-tensile test. The results of adhesive strength were analyzed by one way ANOVA and t-Student tests. Gap formation were analysed by Fisher test and the gaps size were analyzed by Kruskal-Wallis test (p<0,05). No statistical difference on adhesive resistance was showed between groups.

Confocal Microscopy analysis showed gaps with a higher mean sizes for group 4 (12,5µm) and higger percentage of marginal gaps formation for the thermocycled groups (G1 - 30%; G2 - 25%; G4 - 53,33%; G5 70%). Groups 3 (25%) and 6 (30%) showed the lowest percentage of marginal gap formation. The results revealed that gap formation is not related to adhesive strength. It can be concluded, therefore, that the use of a resin-modified-glassionomer cement liner showed less gap formation on dentin/composite adhesive interface after artificial aging compared to conventional glass ionomer cement liner and restorations with no lining.

Effect of light-curing units and activation mode on polymerization shrinkage and shrinkage stress of composite resins

The aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a LED and a quartz tungsten halogen (QTH) light sources. The LED was used in a conventional mode (CM) and the QTH was used in both conventional and pulse-delay modes (PD). The composite resins used were Z100, A110, SureFil and Bisfil 2B (chemical-cured). Composite deformation upon polymerization was measured by the strain gauge method. The shrinkage stress was measured by photoelastic analysis. The polymerization shrinkage data were analyzed statistically using two-way ANOVA and Tukey test (p<0.05), and the stress data were analyzed by one-way ANOVA and Tukey's test (p<0.05). Shrinkage and stress means of Bisfil 2B were statistically significant lower than those of Z100, A110 and SureFil. In general, the PD mode reduced the contraction and the stress values when compared to CM. LED generated the same stress as QTH in conventional mode. Regardless of the activation mode, SureFil produced lower contraction and stress values than the other light-cured resins. Conversely, Z100 and A110 produced the greatest contraction and stress values. As expected, the chemically cured resin generated lower shrinkage and stress than the light-cured resins. In conclusion, The PD mode effectively decreased contraction stress for Z100 and A110. Development of stress in light-cured resins depended on the shrinkage value.

Volumetric polymerization shrinkage of contemporary composite resins

The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill Magic, Alert, and Solitaire) to determine whether there are differences among these materials. The tests were conducted with precision of 0.1 mg. The volumetric shrinkage was measured by hydrostatic weighing before and after polymerization and calculated by known mathematical equations. One-way ANOVA (ß=0.05) was used to determine statistically significant differences in volumetric shrinkage among the tested composite resins. Suprafill (1.87±0.01) and Definite (1.89±0.01) shrank significantly less than the other composite resins. SureFil (2.01±0.06), Filtek Z250 (1.99±0.03), and Fill Magic (2.02±0.02) presented intermediate levels of polymerization shrinkage. Alert and Solitaire presented the highest degree of polymerization shrinkage. Knowing the polymerization shrinkage rates of the commercially available composite resins, the dentist would be able to choose between using composite resins with lower polymerization shrinkage rates or adopting technical or operational procedures to minimize the adverse effects deriving from resin contraction during light-activation.

Analysis of gap formation at tooth-composite resin interface: effect of C-factor and light-curing protocol

OBJECTIVE: The aim of this study was to evaluate the effect of C-factor and light-curing protocol on gap formation in composite resin restorations. Material and METHODS: Cylindrical cavities with 5.0 mm diameter and three different depths (A=1.0, B=2.0 and C=3.0 mm) were prepared on the occlusal surface of 30 human molars and restored in a single increment with P 60. The composite resin was light-cured according to two protocols: standard - 850 mW/cm² / 20 s and gradual - 100 up to 1000 mW/cm² / 10 s + 1000 mW/cm² / 10 s. After storage in distilled water (37°C/7 days), the restorations were cut into three slices in a buccolingual direction and the gap widths were analyzed using a 3D-scanning system. The data were submitted to ANOVA and Student-Newman-Keuls test (alpha=0.05). RESULTS: ANOVA detected a significant influence for the C-factor and light-curing protocol as independent factors, and for the double interaction C-factor vs. light-curing protocol. Cavities with higher C-factor presented the highest gap formation. The gradual light-curing protocol led to smaller gap formation at cavity interfaces. CONCLUSIONS: The findings of this study suggest that the C-factor played an essential role in gap formation. The gradual light-curing protocol may allow relaxation of composite resin restoration during polymerization reaction.