Influence of Different Enamel Substrates on Microtensile Bond Strength of Sealants After Cariogenic Challenge

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Purpose: To evaluate the microtensile bond strength (mu TBS) of resin sealer on enamel substrates after cariogenic challenge. Materials and Methods: Enamel blocks were obtained from human third molars and randomly divided into 6 groups (n = 10) according to enamel substrates (S: sound, CL: caries-like lesion, or CLTF: caries-like lesion + topical fluoride application) and sealant material (F: FluroShield, or H: Helioseal Clear Chroma). Sealants were placed on enamel surfaces, stored in 100% humidity (24 h, 37 degrees C), and longitudinally sectioned into hourglass shapes. According to the groups, pH cycling was applied and the mu TBS test was performed. The fracture patterns were assessed by SEM. Results: Regarding substrates, the highest mu TBS values in MPa were observed for CLTF enamel (26.0 +/- 7.6), followed by S (22.0 +/- 7.4) and CL (15,5 +/- 4.9). A significant interaction was found between material and pH cycling (p = 0.0395). F (23.9 +/- 7.6) showed higher mu TBS values than H (18.3 +/- 7.5) when submitted to pH cycling. The majority of samples presented mixed failure. Conclusions: Enamel substrate significantly affected mu TBS, with the highest values for remineralized caries-like enamel lesions. Furthermore, mu TBS values were dependent on both materials and pH cycling.132131137Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [05/60595-1

Marginal adaptation of composite restorations photoactivated by LED, plasma arc, and QTH light using low-modulus resin liners

Purpose: The aim of this study was to evaluate the influence of resin liners on the marginal adaptation to dentin of resin composite restorations photoactivated by a conventional quartz-tungsten halogen lamp (QTH), light emitting diodes (LED), and a plasma arc light (PAC). Materials and Methods: The buccal surfaces of 120 bovine incisors were ground until a flat dentin area was obtained. A circular cavity (4 mm in diameter x 1.5 mm in depth) was prepared in this area. Scotchbond Multi Purpose was applied in the cavities following the manufacturer's instructions. The specimens were randomly assigned into 4 groups according to the lining technique: (1) control (1 adhesive layer); (2) three adhesive layers; (3) Filtek Flow; (4) Protect Liner F. Each group was further divided into 3 subgroups according to the light-curing method: (A) QTH; (B) LED; (C) PAC. All cavities were then restored with a single increment of Filtek Z250 restorative composite and polished. Caries Detector was applied to each specimen for 5 s. Images of dye-stained gaps were observed under a stereomicroscope and transferred to a computer measurement program. Gap values were obtained by dividing the dyed margin length by the total cavity length, then multiplying by 100. Data were analyzed using ANOVA and Tukey's test (p<0.05). Results: All the tested lining techniques significantly decreased marginal gap formation when compared with the control group only for the QTH light groups. There was no significant difference among the light-curing methods. Conclusion: The use of resin liners can effectively reduce the gap formation along dentin margins, but only when QTH light is used.8422322

Changes in the masticatory cycle after treatment of posterior crossbite in children aged 4 to 5 years

Introduction: The aim of this study was to analyze the dynamics of the masticatory cycle after occlusal adjustment through coronoplasty on deciduous teeth (selective grinding) and composite resin occlusal guidance for posterior crossbite correction. Methods: Nineteen children, aged 4 to 5 years, with functional posterior crossbites diagnosed at their clinical examinations, were selected. Analyses of masticatory cycles, including lateral excursive movements, were performed before and after treatment by using kinesiographic examinations in the 3 reference planes (frontal, horizontal, and sagittal). The examinations were done during bubble-gum chewing. The data were submitted to sign, Mann-Whitney, and paired t tests concerning the variables: left maximum lateral movement, right maximum lateral movement, total lateral movement (LM), vertical movement (VM), anteroposterior maximum movement, maximum lateral movement (MLM), and total maximum lateral movement (TMLM). Results: The treatment produced increased TMLM, a significant increase of the MLM opposite the crossbite, no statistically significant difference of the crossbite side, and a significant decrease of LM. Left crossbite children showed significant decreases in the LM after treatment; right crossbite children showed significant increases in VM after treatment. Conclusions: Functional crossbite treatment with selective adjustment and occlusal guiding changed masticatory cycle patterns, producing larger horizontal and vertical planes. The cycles became more symmetric in the frontal plane, increasing the tendency of bilateral alternate mastication.131446447

Effect of hydrofluoric acid concentration and etching time on bond strength to lithium disilicate glass ceramic

The aim of this study was to evaluate the influence of different concentrations of hydrofluoric acid (HF) associated with varied etching times on the microshear bond strength (μSBS) of a resin cement to a lithium disilicate glass ceramic. Two hundred seventy-five ceramic blocks (IPS e.max Press [EMX], Ivoclar Vivadent), measuring 8 mm × 3 mm thickness, were randomly distributed into five groups according to the HF concentrations (n=50): 1%, 2.5%, 5%, 7.5%, and 10%. Further random distribution into subgroups was performed according to the following etching times (n=10): 20, 40, 60, 120, and 20 + 20 seconds. After etching, all blocks were treated with a silane coupling agent followed by a thin layer of an unfilled resin. Three resin cement cylinders (∅︀=1 mm) were made on each EMX surface, which was then stored in deionized water at 37°C for 24 hours before testing. The μSBS was in a universal testing machine at a crosshead speed of 1 mm/min until failure. Data were submitted to two-way analysis of variance, and multiple comparisons were performed using the Tukey post hoc test (α=0.05). One representative EMX sample was etched according to the description of each subgroup and evaluated using scanning electron microscopy for surface characterization. The HF concentrations of 5%, 7.5%, and 10% provided significantly higher μSBS values than 1% and 2.5% (p0.05). The effect of re-etching was more evident for 1% and 2.5% HF (p<0.05). Different HF concentrations/etching times directly influenced the bond strength and surface morphology of EMX426606615CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES304493/2014-7Sem informaçã

Effect of restorative technique and thermal/mechanical treatment on marginal adaptation and compressive strength of esthetic restorations

This study evaluated the compressive strength and marginal adaptation of composite onlays using indirect and direct techniques after thermal and mechanical cycling. Onlay standardized cavities were prepared in 50 permanent molars and restored with Z-250 resin composite using indirect (IRT) or direct (DRT) restorative techniques. The restorations were either submitted or not submitted to thermal (500 cycles, 5 degrees to 55 degrees C) and mechanical cycling (50,000 cycles, 50N). The teeth were distributed to five groups (n=10): G1-IRT/cycling; G2-IRT/no cycling; G3-DRT/ cycling; G4-DRT/no cycling and G5 (control group)-sound teeth. All prepared teeth were stored in 100% relative humidity at 37 degrees C for 24 hours, followed by finishing with Sof-Lex discs. A caries detector solution was applied on the tooth-restoration interface of all teeth for five seconds, followed by washing and drying. Four digital photographs were taken of each tooth surface. The extent of gaps was measured using standard software (Image Tool 3.0). All groups were submitted to compression testing in a universal testing machine (INSTRON) at a crosshead speed of 1 mm/minute until failure. The compressive strength (CS) and marginal adaptation data were submitted to ANOVA and Takey test (p < 0.05). For both evaluation criteria (compressive strength and marginal adaptation), there were no statistically significant differences among the restorative techniques. Deterioration over time was observed for both types of restorations. However, the prevalence of catastrophic fractures increased among direct restorations. The application of thermal/mechanical cycling only influenced marginal adaptation.33443444

Effect of sodium hypochlorite on primary dentin - A scanning electron microscopy (SEM) evaluation

Objective: The aim of this study was to evaluate the alterations of etched deciduous dentin when submitted to different time and concentrations of sodium hypochlorite (NaOCl), using scanning electron microscopy (SEM). Material and methods: Forty deciduous anterior teeth were selected, cleaned and ground until expose a flat dentin area on the buccal surface. The specimens were randomly distributed into eight groups (n = 5), according to dentin surface treatment (35% phosphoric acid etching for 7 s-AE and/or NaOCl application), NaOCl solution concentration (5% or 10%), and time of application (0, 30, 60, and 120 s), as follows: G1: control (without AE and NaOCl); G2: only AE; G3, G4, and G5: AE + 5% NaOCl for 30, 60, and 120 s, respectively; G6, G7, and G8: AE + 10% NaOCl for 30, 60, and 120 s, respectively. All specimens were prepared for SEM analysis and the photomicrographs (three for each specimen) were classified according to a score as follow: 0: presence of smear layer (SL); 1: absence of SL + non-altered collagen fibrils; 2: absence of SL + collagen fibrils slightly altered; 3: absence of SL + collagen fibrils severely altered; and 4: absence of SL and absence of collagen fibrils. Data were submitted to Kruskal-Wallis and Mann-Whitney tests (p < 0.05). Results: All groups treated with NaOCl solution were significant different from G1 and G2, and showed alterations on the collagen fibrils network. Collagen complete removal was only observed when a 5% NaOCI solution was applied for 120 s and 10% NaOCI solution for 30, 60, and 120 s. Conclusions: The NaOCl action produced significant changes in the etched deciduous dentin. The higher NaOCl concentration, the lower the time required to completely removing the collagen fibrils network in deciduous dentin. (c) 2005 Published by Elsevier Ltd.34745445

Effects of Chemical Agents on Physical Properties and Structure of Primary Pulp Chamber Dentin

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)This study evaluated the effects of chemical agents on the physical properties and structure of primary pulp chamber dentin using surface roughness, microhardness tests, and scanning electron microscopy (SEM). Twenty-five primary teeth were sectioned exposing the pulp chamber and were divided into five groups (n=5): NT, no treatment; SH1, 1% sodium hypochlorite (NaOCl); SH1U, 1% NaOCl+Endo-PTC (R); SH1E, 1% NaOCl+17% EDTA; and E, 17% EDTA. After dentin treatment, the specimens were submitted to roughness, microhardness testing, and SEM analysis. Roughness and microhardness data were submitted to one-way ANOVA and Tukey's test (P0.05). Microhardness values could not be obtained in the EDTA groups (SH1E and E). The presence of intertubular dentin with opened dentin tubules was observed in the NT, SH1, and SH1U groups. SH1E showed eroded and disorganized dentin with few opened tubules and the intertubular/peritubular dentin was partially removed. Considering the physical and structural approaches and the chemical agents studied, it can be concluded that NaOCl and NaOCl associated with Endo-PTC (R) were the agents that promoted the smallest changes in surface roughness, microhardness, and structure of the pulp chamber dentin of primary teeth. Microsc. Res. Tech. 77:52-56, 2014. (c) 2013 Wiley Periodicals, Inc.7715256Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [05/58561-1