Daniel Galafassi

Influence of sodium hypochlorite and edta on the microtensile bond strength of a self-etching adhesive system

Chemical substances used during biomechanical preparation of root canals can alter the composition of dentin surface and affect the interaction with restorative materials. Objective The purpose of this study was to evaluate the microtensile bond strength (µTBS) of a self-etching adhesive system to dentin irrigated with sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (eDTA). Material and Methods Thirty human third molars were sectioned 3 mm below the occlusal surface, polished with 600- to 1200-grit silicon carbide papers, and randomly divided into 3 groups: G1 (control): no irrigating solution; G2: 1% NaOCl; and G3: 1% NaOCl followed by the application of 17% eDTA. The specimens received the self-etching adhesive system (XeNO III - Dentsply), restored with microhybrid composite resin (Z250 - 3M ESPE), sectioned and trimmed to create 4 hourglass-shaped slabs of each tooth. The slabs were tested in microtensile strength in a universal testing machine (emic DL 2000) at a crosshead speed of 0.5 mm/min until fracture. The results were analyzed statistically by ANOVA and Newman-Keuls test. Results Mean µTBS values and standard deviations in MPa were: G1 = 11.89 ± 4.22; G2 = 19.41 ± 5.32; G3 = 11.34 ± 4.73. 1% NaOCl increased the adhesive resistance significantly (p<0.001/ F=22.5763). The application of 1% NaOCl/17% eDTA resulted in statistically similar µTBS to the control group. Conclusions None of the irrigants affected negatively the µTBS of XeNO III to dentin. The use of 1% NaOCl alone resulted in higher bond strength than the other treatments. The combination of 1% NaOCl and 17% eDTA produced similar bond strength to that of untreated dentin.

In Vitro Erosive Effect of Pediatric Medicines on Deciduous Tooth Enamel

This study evaluated, in vitro, the erosive potential of pediatric liquid medicines in primary tooth enamel, depending on the exposure time. Sixty deciduous incisors were randomly assigned to 4 groups (n=15), according to the immersion solutions: guaifenesin; ferrous sulfate; salbutamol sulfate and artificial saliva. The immersion cycles in the medicines were undertaken under a 1-min agitation, which wasperformed three times daily, during 28 days. Surface microhardness was measured at 7,14, 21 and 28 days. The titratable acidity and buffering capacity of the immersion media were determined. Data were analyzed by Analysis of Variance and Tukeys test (α=0.05). Salbutamol sulfate caused a gradual loss in enamel microhardness deciduous, observed at all times (p<0.005). Exposure to guaifenesin or ferrous sulfate resulted in significant decrease of enamel microhardness only after 28 days (p<0.005). In the control group (artificial saliva), microhardness did not changed (p>0.005) at any of the studied times. Scanning Electron Microscopy (SEM) images revealed that after 28 days the surfaces clearly exhibited structural loss, which was unlike those immersed in artificial saliva. Erosion of deciduous enamel was dependent on the type of medicine and exposure time.

Calcium hypochlorite as a dentin deproteinization agent: Microleakage, scanning electron microscopy and elemental analysis

Purpose: This study investigated the influence of collagen removal with calcium hypochlorite on the surface morphology of acid‐etched dentin and on the microleakage of composite restorations. In addition, the elemental composition (EC) of dentin after removal of the collagen fibrils was analyzed. Materials and Methods: Forty third molars received two cavities and were divided into four groups according to dentin treatment: CTRL—no pre‐treatment; Na10—10% NaOCl for 30 s; Ca10—10% CaOCl for 30 s, and Ca15—15% CaOCl for 30 s. The cavities were filled using an acetone‐based adhesive system and a resin composite; they were then subjected to thermal cycling for 5,000 cycles, immersed in methylene blue for 4 h and sectioned into 1‐mm thick slabs. Two examiners evaluated two slices per tooth using a stereomicroscope and assigned the degree of infiltration (scores 0–3). The data were analyzed using the Kruskal–Wallis (α = 0.05). Four teeth received surface treatment according to the groups and were submitted to SEM and EDS to carry at the EC. Results: There was no significant difference between the experimental groups (P = 0.533). CaOCl alters the morphology and surface composition of the dentin, resulting in an increase in the amount of calcium in the interface. Conclusions: When used prior to an acetone‐based adhesive system, CaOCl did not produce any differences in microleakage when compared to the CTRL group or to the Na10 group. Microsc. Res. Tech. 78:676–681, 2015.

Hardness and modulus of elasticity of primary and permanent teeth after wear against different dental materials

Objectives: The purpose of this study was to determine the Youngs modulus and the hardness of deciduous and permanent teeth following wear challenges using different dental materials. Materials and Methods: Wear challenges were performed against four dental materials: A resin-based fissure sealant (Fluoroshield®), a glass ionomer based fissure sealant (Vitremer®), and two microhybrid composite resins (Filtek Z250 and P90®). Using the pin-on-plate design, a deciduous or a permanent tooth was made into a pin (4 mm × 4 mm × 2 mm) working at a 3 N vertical load, 1 Hz frequency, and 900 cycles (15 min) with Fusayama artificial saliva as a lubricant. Before and after the tribological tests, the hardness and elasticity modulus of the tooth samples were measured by creating a nanoindentation at load forces up to 50 mN and 150 mN. All of the results were statistically analyzed using ANOVA and post-hoc Duncans tests (P < 0.05). Results: No difference in hardness was encountered between deciduous and permanent teeth (P < 0.05) or modulus of elasticity (P < 0.05) before or after the wear challenges for all of the dental materials tested. Conclusions: Wear challenges against the studied dental materials did not alter the properties of permanent or deciduous teeth after the application of a 3 N load.

Long-term chlorhexidine effect on bond strength to Er:YAG laser irradiated-dentin.

This study evaluates the bond strength of dentin prepared with Er:YAG laser or bur, after rewetting with chlorhexidine on long‐term artificial saliva storage and thermocycling. One hundred and twenty human third molars were sectioned in order to expose the dentin surface (n = 10). The specimens were randomly divided in 12 groups according to treatment and aging: Er:YAG laser rewetting with deionized water (LW) and 24 h storage in artificial saliva (WC); LW and 6 months of artificial saliva storage + 12.000 thermocycling (6M), LW and 12 months of artificial saliva storage + 24.000 thermocycling (12M), Er:YAG laser rewetting with 2% chlorhexidine (LC) and WC, LC and 6M, LC and 12M, bur on high‐speed turbine rewetting with deionized water (TW) and WC, TW6M, TW12M, bur on high‐speed turbine + 2% chlorhexidine (TC) and WC, TC and 6M, TC and12M. The specimens were etched with 35% phosphoric acid, washed, and dried with air. Single Bond 2 adhesive was applied and the samples were restored with a composite. Each tooth was sectioned in order to obtain 4 sticks, which were submitted to microtensile bond strength test (µTBS). The two‐way ANOVA, showed no significant differences for the interaction between the factors and for the aging factor. Tukey 5% showed that the LC group had the lowest µTBS. The rewetting with chlorhexidine negatively influenced the bond strength of the preparation with the Er:YAG laser. The artificial saliva aging and thermocycling did not interfere with dentin bond strength. Microsc. Res. Tech. 77:37–43, 2014.

Effects of a potentially erosive antiasthmatic medicine on the enamel and dentin of primary teeth: An in situ study

This study evaluates, in situ, the effect of an anti‐asthmatic medicine on the enamel and dentin of primary teeth. Twenty‐eight specimens of enamel and dentin were prepared, selected, sterilized, and stored. Microhardness, microscopic morphology, and initial surface roughness were evaluated. Fourteen volunteers wore palatal devices containing two dentin specimens and two enamel specimens. Volunteers underwent surface treatment three times a day for 5 days, with the dripping of 5 ml of salbutamol sulfate for 1 min, only on specimens from one side of the device. At the end of the experiment the microscopic morphology, roughness, surface loss, and microhardness were ascertained. For enamel surfaces exposed to the medicine, erosion was observed in the microscopy images, along with a significant increase in roughness (p = .0325) and tissue loss (p = .03251) and a significant decrease in microhardness (p = .0325). For the dentin surfaces, erosion was observed in the microscopy images, but there was no significant increase in roughness (p = .593) or tissue loss (p = .285) nor any decrease in microhardness (p = .1088). In conclusion, the salbutamol sulfate had an in situ erosive effect on primary teeth enamel and this effect was observed morphologically on primary dentin.

Resistência à fratura de raízes bovinas usando dois tipos de pinos pré-fabricados

O objetivo deste trabalho foi avaliar a resistencia a fratura de raizes restauradas com protese unitaria e nucleo de preenchimento, comparando dois tipos de pinos pre-fabricados: metalico e de fibra de vidro. Foram selecionados vinte incisivos bovinos, seccionados a 17 mm do apice radicular, tratados endodonticamente e divididos em dois grupos experimentais: G1 – pino de fibra de vidro paralelo com termino apical conico (#3 Fibrekor-post System®, Jeneric Pentron); G2 – pino paralelo rosqueado metalico com termino apical conico (#3 Flexi-post®, EDS). Ambos os grupos foram restaurados com nucleos de preenchimento em resina composta e coroas metalicas unitarias. As amostras foram posicionadas a 135° em relacao a ponteira da maquina de ensaios EMIC, para realizacao do ensaio de compressao obliqua, a velocidade de 0,5 mm/min. Os dados foram submetidos a analise de variância, nao apresentando diferenca estatistica ao nivel de 5% de significância. O teste de contraste t student apresentou t = 2,542, nao significativo, e c.v. = 10,9215. Foi possivel concluir que nao houve diferenca entre pinos pre-fabricados metalicos ou de fibra de vidro, quando associados a nucleo de preenchimento de resina composta, na resistencia a fratura de raizes bovinas restauradas com proteses unitarias metalicas.

Influência da desproteinização e da umidade sobre o substrato dentinário na microinfiltração em restaurações de resina composta

O objetivo deste estudo foi verificar a influencia da desproteinizacao e da condicao do substrato dentinario (umido ou seco) na microinfiltracao marginal em restauracoes com resina composta. Oitenta cavidades classe V, preparadas em quarenta terceiros molares humanos (Banco de Dentes da FO-UPF), com margem gengival em dentina foram divididas aleatoriamente em quatro grupos: G1 (controle) – sistema adesivo (Prime & Bond 2.1®, Dentsply) aplicado a dentina umida; G2 – sistema adesivo aplicado a dentina seca; G3 – dentina desproteinizada com hipoclorito de sodio (NaOCl 10%, 60s) e o sistema adesivo aplicado a dentina umida; G4 –dentina desproteinizada e o sistema adesivo aplicado a dentina seca. Apos restaurados, os especimes foram termociclados, isolados, imersos em corante, incluidos em resina acrilica e seccionados. Para a analise das seccoes foi utilizado um microscopico optico e os escores, tabulados. Os dados foram submetidos a analise estatistica (Kruskal Wallis/1%; Ho = 0,69%), sendo que G3 e G4 apresentaram diferenca estatistica entre si. Os demais grupos nao apresentaram diferenca estatisticamente significativa quando correlacionados. Nas condicoes experimentais foi possivel concluir que a camada de colageno nao tem influencia na infiltracao marginal. Um indice de microinfiltracao significativamente menor foi encontrado apos a remocao do colageno para o substrato dentinario seco.