Impact of storage conditions on the fracture reliability and physical properties of a dental resin-based composite.

This study investigated the impact of 'storage condition' and 'period of storage' on selected physico-mechanical properties and fracture reliability of a resin-based composite (RBC). Specimens, prepared from a nanofilled RBC (Filtek Z350 XT; 3M ESPE), underwent tests for degree of conversion (DC), flexural strength (σ), flexural modulus (E), and hardness. The specimens were initially grouped into dry storage at 37°C or wet storage in distilled water at 37°C. Subsequently, they were further divided into four subgroups based on the period of storage: 6, 24, 72, or 168 hours. Specimens tested immediately after preparation served as control. Data analysis employed two-way ANOVA and Weibull analysis (α = 5%). Compared to the control, an increase in DC was observed only after 72 hours of dry storage; σ showed higher values after both dry and wet storage, regardless of the storage period (except for the group wet-stored for 168 hours); E increased with dry storage for at least 24 hours or wet storage for 72 hours; and hardness increased after dry storage for at least 24 hours or wet storage for up to 72 hours. The Weibull modulus remained unchanged under any of the distinct storage conditions. Dry storage resulted in greater characteristic strength than the control, whereas wet storage contributed to higher strength values only at shorter periods (up to 24 hours). Overall, the inherent properties of RBCs with a similar composition to that tested in this study may change with varying storage conditions and periods.

Impact of storage conditions on the fracture reliability and physical properties of a dental resin-based composite

Abstract This study investigated the impact of 'storage condition' and 'period of storage' on selected physico-mechanical properties and fracture reliability of a resin-based composite (RBC). Specimens, prepared from a nanofilled RBC (Filtek Z350 XT; 3M ESPE), underwent tests for degree of conversion (DC), flexural strength (σ), flexural modulus (E), and hardness. The specimens were initially grouped into dry storage at 37°C or wet storage in distilled water at 37°C. Subsequently, they were further divided into four subgroups based on the period of storage: 6, 24, 72, or 168 hours. Specimens tested immediately after preparation served as control. Data analysis employed two-way ANOVA and Weibull analysis (α = 5%). Compared to the control, an increase in DC was observed only after 72 hours of dry storage; σ showed higher values after both dry and wet storage, regardless of the storage period (except for the group wet-stored for 168 hours); E increased with dry storage for at least 24 hours or wet storage for 72 hours; and hardness increased after dry storage for at least 24 hours or wet storage for up to 72 hours. The Weibull modulus remained unchanged under any of the distinct storage conditions. Dry storage resulted in greater characteristic strength than the control, whereas wet storage contributed to higher strength values only at shorter periods (up to 24 hours). Overall, the inherent properties of RBCs with a similar composition to that tested in this study may change with varying storage conditions and periods.

Full analysis of the effects of modeler liquids on the properties of direct resin-based composites: a meta-analysis review of in vitro studies.

OBJECTIVES: This study systematically revised the literature to answer the following question: do modeler liquids (MLs) affect the properties of direct resin-based composites (RBCs)? MATERIALS AND METHODS: The review followed the PRISMA statement, and the search was conducted in PubMed, Scopus, Web of Science, Embase, and Lilacs databases. Studies were included if they investigated the properties of RBCs prepared using the restorative dental modeling insertion technique (RDMIT). The risk of bias was performed with the RoBDEMAT tool. Statistical analyses were conducted using Review Manager, and heterogeneity was assessed with the Cochran Q test and I2 statistics. RESULTS: From 309 studies identified, 25 met the eligibility criteria, and 23 were meta-analyzed. In total, 27 MLs and 23 RBCs were evaluated. Modeled and non-modeled RBCs showed similar results in terms of cohesive strength, flexural strength, load-to-fracture, modulus of elasticity, work of fracture, degree of conversion, solubility, weight change, microhardness, and color change. Sorption and roughness benefited from the use of MLs, whereas translucency and whitening index were more adequate in the non-modeled RBCs. Aging affected similarly the modeled and non-modeled RBCs. Most studies showed a moderate risk of bias. CONCLUSIONS: Modeled and non-modeled RBCs performed similarly in most of the properties, and the use of non-solvated lubricants offered beneficial effects in some cases. CLINICAL RELEVANCE: When a balance has to be made between the RDMIT and the conventional technique, our review supports the safe application of modeler liquids for the handling of composite increments during the sculpting fabrication of direct resin-based restorations.

New material perspective for endocrown restorations: effects on mechanical performance and fracture behavior.

The aim of this study was to investigate the mechanical performance and the fracture behavior of endocrown restorations prepared using distinct restorative materials. A total of 42 sound molars with similar crown size and shape were cut at 2 mm above the cementoenamel junction and endodontically treated. They were categorized according to the restorative material used to fabricate endocrown restorations (n=7), namely, conventional composite (Filtek™ Z350 XT), bulk fill composite (Filtek™ Bulk Fill), conventional composite modeled using resin adhesives (SBMP: Scotchbond™ Multipurpose Adhesive; or SBU: Scotchbond™ Universal Adhesive), and IPS e.max lithium disilicate (Ivoclar Vivadent; positive control). Unprepared sound teeth were used as negative control. All endocrowns were bonded using a self-adhesive cement (Rely-X™ U200). The teeth were submitted to fatigue (Byocycle) and fracture (EMIC DL500) testing. Load-to-fracture (in N) and work-of-fracture (Wf, in J/m2) values were analyzed by ANOVA (p < 0.05). The endocrowns did not fracture or de-bond upon fatigue, showing similar load-to-fracture and work-of-fracture values, regardless of the restorative material (p > 0.05). The endocrowns fabricated by combining Z350 and SBMP had the least harsh fractures, in contrast to endocrowns prepared using Z350 only, which exhibited an equilibrium between repairable and irrepairable fractures. The e.max endocrowns exhibited more aggressive failures (root fracture) than other groups, resulting in higher rates of irrepairable fractures. In conclusion, dental practitioners may satisfactorily restore severely damaged nonvital teeth using the endocrown technique. Composite endocrowns prepared using resin adhesive as modeler liquid or using bulk fill material may result in less aggressive failures, thus providing a new material perspective for endocrown restorations.

New material perspective for endocrown restorations: effects on mechanical performance and fracture behavior

Abstract The aim of this study was to investigate the mechanical performance and the fracture behavior of endocrown restorations prepared using distinct restorative materials. A total of 42 sound molars with similar crown size and shape were cut at 2 mm above the cementoenamel junction and endodontically treated. They were categorized according to the restorative material used to fabricate endocrown restorations (n=7), namely, conventional composite (Filtek™ Z350 XT), bulk fill composite (Filtek™ Bulk Fill), conventional composite modeled using resin adhesives (SBMP: Scotchbond™ Multipurpose Adhesive; or SBU: Scotchbond™ Universal Adhesive), and IPS e.max lithium disilicate (Ivoclar Vivadent; positive control). Unprepared sound teeth were used as negative control. All endocrowns were bonded using a self-adhesive cement (Rely-X™ U200). The teeth were submitted to fatigue (Byocycle) and fracture (EMIC DL500) testing. Load-to-fracture (in N) and work-of-fracture (Wf, in J/m2) values were analyzed by ANOVA (p < 0.05). The endocrowns did not fracture or de-bond upon fatigue, showing similar load-to-fracture and work-of-fracture values, regardless of the restorative material (p > 0.05). The endocrowns fabricated by combining Z350 and SBMP had the least harsh fractures, in contrast to endocrowns prepared using Z350 only, which exhibited an equilibrium between repairable and irrepairable fractures. The e.max endocrowns exhibited more aggressive failures (root fracture) than other groups, resulting in higher rates of irrepairable fractures. In conclusion, dental practitioners may satisfactorily restore severely damaged nonvital teeth using the endocrown technique. Composite endocrowns prepared using resin adhesive as modeler liquid or using bulk fill material may result in less aggressive failures, thus providing a new material perspective for endocrown restorations.

Bleaching and enamel surface interactions resulting from the use of highly-concentrated bleaching gels.

Tooth bleaching is considered a non-invasive treatment, although the use of highly-concentrated products may provoke increased surface roughness and enamel demineralization, as well as postoperative sensitivity. Thus, the aim of this study was to investigate whether hydrogen peroxide (H2O2) concentration would affect tooth bleaching effectiveness and the enamel surface properties. Enamel/dentin bovine specimens (6 × 4 mm) were immersed in coffee solution for 7 days and evaluated with a spectrophotometer (Easyshade; baseline), using the CIEL*a*b* color parameters. Hardness was measured using a hardness tester. The specimens were randomly assigned into four groups: one negative control, in which the specimens were not bleached, but they were irradiated with a laser-light source (Whitening Lase II, DMC Equipments); and three groups using distinct H2O2 concentration, namely LP15% (15% Lase Peroxide Lite), LP25% (25% Lase Peroxide Sensy), and LP35% (35% Lase Peroxide Sensy), all products from DMC. The bleached specimens were also irradiated with the laser-light source. After bleaching, all specimens were evaluated using scanning electron microscopy (SEM). pH kinetics and rate was monitored during bleaching. The data were analyzed using ANOVA and Tukey's test (p < 0.05). All bleaching gels produced similar color change (p > 0.05). Concerning hardness, only the LP25% and LP35% significantly reduced hardness after bleaching; also, there was a progressive tendency for a greater percentage reduction in hardness with increased H2O2 concentration of the gel (R2 = 0.9973, p < 0.001). SEM showed that LP25% and LP35% produced an etching pattern on enamel with prism rods exposure. In conclusion, H2O2 concentration above the 15% level does not increase bleaching effectiveness, and may increase the possibility for alteration of enamel hardness, surface morphology, and acidity of the medium. When using H2O2-based bleaching agents, dental practitioners should choose for less concentrated gels, e.g., around the 15% level.

Application of resin adhesive on the surface of a silanized glass fiber-reinforced post and its effect on the retention to root dentin.

INTRODUCTION: In this study, the effect of different post surface treatments on the retention of glass fiber-reinforced post to root dentin was evaluated. The hypotheses tested were (1) post silanization would not improve its retention and (2) the application of silane plus resin adhesive on the post would enhance its retention. METHODS: After root canal preparation, 4 different protocols (n = 5) of post surface treatment were evaluated, combined with or without silane (Silane coupling agent) and adhesive (Scotchbond Multipurpose): silane + adhesive (S/A), only silane, only adhesive, or no treatment (control). RelyX ARC was used for post cementation. Next, specimens were subjected to push-out bond strength testing, and data were analyzed by two-way analysis of variance and Tukey test (P < .05). RESULTS: S/A showed higher bond strength than other protocols in the middle and coronal root regions (P < .001). Only silane did not enhance post retention compared with control (P > .05). The root dentin region influenced bond strength results only in the S/A group. CONCLUSIONS: Whereas silanization as the only post surface treatment did not improve retention, the combination of silane plus resin adhesive enhanced post retention to dentin in the middle and coronal root regions.

Prevotella intermedia: uma breve revisão / Prevotella intermedia: A brief review

Prevotella intermedia é um microrganismo anaeróbio Gram negativo, considerado um dos agentes etiológicos de doenças periodontais. Tendo em vista que o biofilme subgengival é um dos seus principais habitats, qualquer quebra na homeostase do meio pode favorecer seu desenvolvimento e consequente dano aos tecidos atingidos. Diversas pesquisas vêm sendo realizadas a fim de identificar o papel deste microrganismo nas doenças periodontais. Assim, este trabalho teve por objetivo revisar a literatura para coletar informações sobre as características e efeitos de Prevotella intermedia no contexto saúde-doença periodontal. A busca foi realizada nas bases de dados PubMed e Lilacs, bem como através de uma busca aleatória. De um total de 47 artigos incluídos, alguns principais resultados puderam ser destacados: Prevotella intermedia está fortemente associada ao quadro de doenças periodontais e suas características favorecem o acometimento e intensificação de doenças diversas. Além disso, este microrganismo é capaz de produzir pigmentos e uma variedade de enzimas as quais favorecem danos aos tecidos periodontais. Existem várias características que aumentam a patogenicidade e virulência deste microrganismo, como por exemplos a sua cápsula polissacarídica, a presença de enzimas protetoras contra o oxigênio, a presença e produção de proteases, além da estimulação de fatores de crescimento no hospedeiro. Não há consenso na literatura acerca da relação de causa-efeito entre presença de Prevotella intermedia e diabetes. Contudo, este microrganismo parece estar envolvido no quadro de pacientes HIV positivo. Por fim, é importante salientar que Prevotella intermedia pode adquirir resistência a alguns tipos de antibióticos, e, por isso, o seu controle é um desafio à clínica atual...

Prevotella intermedia is a Gram negative anaerobic microorganism, considered one of the etiologic agents of periodontal diseases. Taking into account that the subgingival biofilm is its major habitat, any break of the environment homeostasis may lead to the development of the microorganism and consequent damage to the surrounding tissues. Several researches have been conducted in order to identify the role of this microorganism in the periodontal diseases. Thus, this study aimed to review the literature in an attempt to collect information about the characteristics and effects of Prevotella intermedia in the periodontal healthdisease context. The search was performed in the PubMed and Lilacs databases, as well as under a random search. From a total of 47 included articles, some major results could be drawn: Prevotella intermedia is strongly related to the occurrence of periodontal diseases, and its characteristics lead to the incidence of several diseases. Moreover, this microorganism is able to produce pigments and a variety of enzymes, which potentiate the damage of periodontal tissues. There are several characteristics that increase the pathogenicity and virulence of this microorganism, including the polyssacharidic capsule, the presence of protective enzymes against oxygen, the presence and production of proteases, as well as the stimulation of grow factors in the host. There is no consensus in the literature regarding the cause-effect relationship between the presence of Prevotella intermedia and diabetes. However, this microorganism seems to be involved in the occurrence of HIV-positive people. Lastly, it is worth to mention that Prevotella intermedia may acquire strength to some antibiotic types, and, therefore, its control is a challenge to the current clinic...

Conservative dentistry: non-beveled esthetic restorations in anterior teeth / Odontologia conservadora: restaurações estéticas sem bisel em dentes anteriores

The pursuit of esthetic excellence in dentistry today requires dental practitioners to enhance their knowledge and technique in restorations of the anterior teeth. Due to the high incidence and prevalence of fractures in this dental area, mimicking the optical properties and characteristics of the dental structure in young patients (aged 6 to 15 years) is a major challenge. This case report describes the minimally invasive, non-beveled restoration of two fractured anterior teeth (class IV). After diagnosing fractures of teeth 11 and 21 in a 10-year-old patient, a composite mock-up was performed, followed by a diagnostic wax-up. With the aid of a silicon guide, the restorations were prepared without beveling the enamel surface. We performed color stratification by using different types of composite resins. Finally, finishing and polishing procedures were carried out.

A busca da excelência estética na odontologia atual exige, por parte do cirurgião-dentista, o aprimoramento de seus conhecimentos e técnicas para a confecção de restaurações em dentes anteriores. Em razão da alta incidência e prevalência de fraturas nesta região dentária, o desafio de mimetizar as propriedades e características ópticas da estrutura dental em pacientes jovens (entre 6 e 15 anos) torna-se um desafio. O presente caso clínico relata a restauração minimamente invasiva, sem utilização de bisel, na superfície dentária de duas classes IV. Após a constatação de fratura nos elementos 11 e 21 do paciente com 10 anos, realizou-se o ensaio restaurador do mesmo, com posterior moldagem e enceramento diagnóstico. A partir da confecção do guia de silicone, confeccionaram-se as restaurações através da técnica da muralha e posteriormente foi realizada a estratificação de cores mediante o uso de diferentes tipos de resina composta. Finalmente, realizaram-se os procedimentos de acabamento e polimento.

Influence of surface moisture condition on the bond strength to dentin of etch-and-rinse adhesive systems

AIM: To evaluate the immediate microtensile bond strength (µTBS) of three two-step etch-and-rinse adhesive systems applied under different dentin surface moisture conditions. METHODS: Class V cavities were prepared in seventy-two bovine incisors. Each tooth was randomly allocated into three groups, according to the adhesive system used: Single Bond 2 (SB), Prime & Bond 2.1 (PB) and XP Bond (XPB). Each group was divided in three subgroups, according to the dentin moisture condition: over-wet, moist and dry (n=8). For the moist subgroups the adhesive was applied as to the manufacturer's instructions; for the over-wet ones, without drying the cavity after the rinsing procedure; and for the dry subgroups, drying the surface for 20 s. The teeth were restored with Filtek Z-250 and stored in distilled water (24 h); next, each restoration was sectioned in beam-shaped specimens which were stored for 24 h at 37 °C. Each specimen was submitted to µTBS test (EMIC), and data were analyzed using two-way ANOVA and Tukey test (p<0.05). RESULTS: There was a statistically significant interaction between the adhesive system type and the dentin surface moisture condition (p=0.003). SB and XPB presented higher bond strength in the moist dentin condition, and PB showed high µTBS values in the dry substrate. CONCLUSIONS: The moisture condition influenced the bond strength between the adhesives and dentin. SB performed better in the moist condition, whereas PB and XPB showed satisfactory bond strength in the moist and in the dry substrates. The over-wet dentin condition only impaired bond strength to SB and XPB...

The effect of time between handling and photoactivation on self-adhesive resin cement properties.

PURPOSE: To evaluate the degree of conversion, absorption, and solubility in water of self-adhesive resin cements subjected to different time intervals between material preparation and the photoactivation procedure. MATERIALS AND METHODS: Two dual self-adhesive resin cements were tested: RelyX Unicem and SmartCem2. The degree of conversion as a function of time was evaluated by Fourier-transformed infrared spectroscopy using the attenuated total reflectance technique. Three time intervals between handling and photoactivation were applied: Group 1 = immediately; Group 2 = a 1-minute interval; Group 3 = a 4-minute interval. All specimens were irradiated with a light-emitting diode source for 40 seconds. Thirty discs of each cement (1 mm thick × 6 mm diameter, n = 10) were prepared for the absorption and solubility tests. These specimens were stored in distilled water at 37°C for 90 days. The results were subjected to ANOVA with two factors (material and activation time intervals) and Tukey's test (95% significance). RESULTS: The 4-minute interval significantly reduced the degree of conversion of SmartCem2 (30.6% ± 8.3%). No other significant changes were observed for the degree of conversion; however, the time intervals before photoactivation interfered significantly in the water absorption of the RelyX Unicem specimens but not the SmartCem2 specimens. The time intervals did not affect the solubility of either cement. In all cases, SmartCem2 had higher solubility than RelyX Unicem. CONCLUSION: The time interval between handling and photoactivation significantly influenced the degree of conversion and water sorption of the resin-based cements. In general, one can say that the self-adhesive resin cements should be photoactivated as soon as possible after the material handling process.