Rodivan Braz

Evaluation of crack propagation in dental composites by optical coherence tomography

OBJECTIVES The purpose of this study was to image the sites of fracture initiation and slow crack propagation in a fiber reinforced composite, using the optical coherence tomography (OCT) technique. METHODS Bar specimens (2mm x 3mm x 25mm) of fiber reinforced composite were mechanically and thermally cycled to emulate oral conditions. The interior of these samples was analyzed prior to and after loading, using OCT. The device used was a home-built Fourier domain OCT setup working at 800 nm with 6 microm spatial resolution. RESULTS Intact specimens after load cycling were analyzed. It was clearly seen that OCT images provide an insight into crack propagation, which is not seen by the naked eye. SIGNIFICANCE By using OCT the possibility of analyzing the fracture propagation quantitatively, and in depth, was added, opening up possibilities to quantitative studies.

Arrest of non-cavitated dentinal occlusal caries by sealing pits and fissures: a 36-month, randomised controlled clinical trial

OBJECTIVE This study aimed to evaluate the progression of sealed non-cavitated dentinal occlusal caries in a randomised controlled clinical trial. MATERIALS AND METHODS Sixty teeth with non-cavitated dentinal occlusal caries were selected in patients with a high risk for caries. Patients were randomly divided into two groups so that each group included 30 teeth. Patients in the experiment group were given oral hygiene instructions and a fissure sealant. Patients in the control group were given oral hygiene instructions only. Caries progression and sealant loss were monitored over a period of 36 months by clinical and radiographic examinations. RESULTS Clinical and radiographic progression of caries was significantly more frequent in the control group than in the experiment group. Three teeth lost their sealant and showed caries progression, but this was apparent only at the 12-month follow-up. At the 24- and 36-month recall appointments, neither sealant loss nor caries progression were observed. CONCLUSION The pit and fissure sealant utilised in this study was shown to be effective in arresting carious lesions at 36 months.

Deproteinized dentin: a favorable substrate to self-bonding resin cements?

The adhesive performance on deproteinized dentin of different self-adhesive resin cements was evaluated through microtensile bond strength (μTBS) analysis and scanning electron microscopy (SEM). Occlusal dentin of human molars were distributed into different groups, according to the categories: adhesive cementation with two-step bonding systems-control Groups (Adper Single Bond 2 + RelyX ARC/3M ESPE; One Step Plus + Duolink/Bisco; Excite + Variolink I/Ivoclar Vivadent) and self-adhesive cementation-experimental groups (Rely X Unicem/3M ESPE; Biscem/Bisco; MultiLink Sprint/Ivoclar Vivadent). Each group was subdivided according to the dentin approach to: α, maintenance of collagen fibers and β, deproteinization. The mean values were obtained, and submitted to ANOVA and Tukey test. Statistical differences were obtained to the RelyX Unicem groups (α = 13.59 MPa; β = 30.19 MPa). All the BIS Group specimens failed before the mechanical tests. Dentinal deproteinization provided an improved bond performance for the self-adhesive cement Rely X Unicem, and had no negative effect on the other cementing systems studied.

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

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

In vitro biological response to a self-adhesive resin cement under different curing strategies

Self-adhesive resin cements represents a new approach in indirect restorative dentistry, although little is known about its biological properties. The influence of the curing strategy on the biological response of a self-adhesive resin cement (Rely-X Unicem/3M ESPE) was evaluated through methyltetrazolium (MTT) and nitric oxide (NOx) assays. Cylindrical specimens (n = 48) were prepared and cured according to the following strategies: photoactivation with halogen light-curing unit (LCU) Demetron/Kerr, LED LCU Radii/SDI, and chemical activation. A control group with culture medium and a group with lipopolysaccharide, employed for cells stimulation, were used for comparisons (n = 8). After 24 h of direct contact between specimens and rat alveolar macrophages, the biological response was evaluated. Statistical evaluation of the data was performed with Kruskal-Wallis and Dunns test (p = 0.05). The MTT test showed that the specimens cured by halogen light and chemical activation provided higher alterations on cell metabolism. For LED-cured specimens, cell viability was compatible to the results observed in the control group. For the NOx assay, all curing methods were cytotoxic to rat macrophages. Rely-X Unicem demonstrated different cytotoxic effects according to the curing strategy employed.

Physicomechanical characterization and biological evaluation of bulk-fill composite resin

The aim of this study was to evaluate the cytotoxic effect, degree of conversion (% DC), Vickers hardness (VH), and surface morphology of composite resins. Eleven resins, nine bulk-fill resins, and two conventional resins were evaluated. Each material was sampled to evaluate DC (using FTIR), VH, cytotoxicity (using MTT and Neutral Red - NR test), surface morphology (using SEM and AFM), and organic filler (using EDS). All statistical tests were performed with SPSS and the level of significance was set at 0.05. MTT revealed that the materials presented low or no cytotoxic potential in relation to the control. Opus was the resin with the lowest cell viability at a 1:2 concentration at 72 h (32%) and at 7 days (43%), but that significantly increased when the NR test was applied at a 1:2 concentration after 7 days. Thickness and surface subjected to polymerization had no influence on DC, and differences were observed only between the materials. In the microhardness test, statistical differences were observed between the evaluated thicknesses. The bulk-fill resins analyzed in this study exhibited low and/or no cytotoxicity to L929 cells, except for Opus, which showed moderate cytotoxicity according to the MTT assay. When the NR test was used, results were not satisfactory for all composites, indicating the need for different methodologies to evaluate the properties of these materials. The assessed resins demonstrated acceptable physicomechanical properties.

Marginal microleakage in Bulk Fill resins

Introduction Despite advances and innovations in restorative dentistry, microleakage remains one of the main problems in this area. Objective To evaluate in vitro marginal microleakage of Bulk Fill resins in class II cavities, with cervical termination in the dentin. Material and method Cavities, standardized on the mesial and distal surfaces, were prepared in forty top molars and randomly assigned to four groups (n = 10), according to the resin used. G1 (control): Filtek Z350 (3M/ESPE); G2: Filtek Bulk Fill flow (3M/ESPE); G3: Surefill SDR (Dentsply); G4: X-tra (Voco). These were further subdivided into subgroups according to the strategy used to apply the adhesive (self-etch technique and conventional). After storage for 24 hours in an oven (37 °C), the samples were submitted to the thermocycling test (500 cycles: 5 °C/55 °C). They were later waterproofed, immersed in Basic Fuchsin (0.5%) and sectioned in the mesial-distal direction for evaluation using a stereo magnifying glass at 40X (Coleman) Scores from 0 to 3 were assigned according to the microinfiltration observed. The Mann-Whitney and Kruskal-Wallis tests, with a significance level of 5%, were used for statistical analysis. Result There was no statistically significant difference between the Bulk Fill resins when the total acid-etching technique was used. Only the Filtek Bulk fill flow resin presented statistically significant results when the application of the adhesive system strategy was considered, with worse results, in relation to other groups, when it the self-etching strategy was considered. Conclusion The degree of leakage of the bulk fill resins studied, in class II cavities, was not influenced by the method of application of the adhesive system (conventional or two-step self-etching bonding agent), except for the Filtek Bulk fill flow.

Durability of the adhesive cementation to the dentin substract

Objective The aim of this study was to evaluate, in vitro, the union stability of resin cements to the dental substract through microtensile bond strength (µTBS) analysis and scanning electron microscopy (SEM). Methods Fifty-four third human molars, stored in water for a short (24 hours) and long period of time (1 year) presented a flat oclusal superficial dentin. The teeth were distributed in six different groups: G1- Panavia F2.0/Kuraray; G2- RelyXUnicem/3M ESPE; G3- G-Cem/GC; G4- Biscem/ Bisco; G5- Panavia F2.0/Kuraray without pre-treatment and G6- Multilink Sprint/Ivoclar-Vivadent which were adhered to its respective indirect resin composite restoration, (G1- Clearfil AP-X/Kuraray; G2- Filtek Z350/3M ESPE; G3- Gradia Direct X(tm)/GC; G4- Aelite(tm)/ Bisco; G5- Clearfil AP-X/Kuraray; G6- Tetric Ceram/ Ivoclar-Vivadent). The resin blocks were cemented and the sticks were obtained by tooth, with an area of adhesive interface of 0,8mm² (±0,2). Results The mean values, submitted to Mann-Whitney and Kruskal-Wallis tests (α = 5%) were in MPa after 24 hours: G1 = 9.66 (A), G2 = 13.37 (A); G3 = 15.89 (A); G5 = 4.18 (B); G6 = 11.01 (A) and after 1 year: G1 = 9.75 (A), G2 = 11.73 (A); G3 = 20.10 (B); G5 = 6.80 (A); G6 = 21.09 (B). All G4 group presented pretest failures. Conclusion During the one year period, with the exception of BisCem, the self-adhesive resin cements were a favorable alternative for the adhesive cementation, standing out among these, the G-Cem and Multilink Sprint.

Intracanal pain remission in child with amelogenesis imperfecta. Case report

BACKGROUND AND OBJECTIVES: Amelogenesis imperfecta is characterized by enamel structural defects, which may severely affect dental structure in both dentitions. When accompanied by severe decay, it may impair the pulp complex requiring endodontic treatment and in case of incomplete root formation treatment becomes more complex due to pulp volume and anatomic conditions. This study aimed at reporting a clinical case of patient with amelogenesis imperfecta and with multiple incomplete root formation as a consequence. CASE REPORT: Female patient, 12 years old, leucodermic, with painful symptoms, who has looked for dental assistance. At intraoral clinical evaluation teeth presented with shape and size changes, yellowish color, covered by a thin enamel layer with roughened surface and absent in some areas, with anterior vestibular sulcus fistula and without edema. At radiographic evaluation, both dentitions were affected by the abnormality with delayed chronology of permanent teeth eruption. At the end of all evaluations, patient was diagnosed with amelogenesis imperfecta, and periodontal treatment was started, followed by endodontic treatment. CONCLUSION: Amelogenesis treatment is complex, especially when in more advanced stages of dental structure destruction. However, it is possible to reestablish patient’s functionality and esthetics with good planning and multidisciplinary approach.

Bond strength to dentin of total-etch and self-etch adhesive systems

OBJECTIVE: To assess the bond strength to dentin of the Single Bond (3M ESPE) and XP Bond (Dentsply) total-etch and Adper SE Plus (3M ESPE) self-etch adhesive systems.METHODS: Fifteen healthy human third molars were randomly allocated across three different groups of five teeth each according to the adhesive system. The occlusal portion of each tooth was removed under refrigeration using a flexible diamond disc (EXTEC, Enfield, CT, USA) down to an area of dentin that did not reveal enamel, as confirmed under a 40X stereo microscope (Ramsor, Sao Paulo, Brazil). A standardized smear layer was created with #600 grit silicon-carbide paper. The adhesive systems were applied as per manufacturer recommendations, with the exception of the Adper SE Plus system, which was triple-polymerized. Composite resin blocks (5 mm) were placed on the dentin surface. The specimens were stored in distilled water for 24 hours at 37oC. Using a flexible diamond disc (EXTEC, Enfield, CT, USA), toothpick-like specimens with an adhesive area of less than 1 mm² were obtained. A microtensile bond test was then carried out using a universal testing machine (KRATOS) with a crosshead speed of 0.5 mm/min. Analysis of variance (ANOVA) and Tukeys test were used for comparisons.RESULTS: The bond strength values obtained with each adhesive system were as follows: XP Bond, 96.24 MPa; Adper Single Bond, 72.39 MPa; Adper SE Plus, 49.91 MPa.CONCLUSION: In terms of bond strength to dentin, conventional adhesives outperform self-etching systems.