B Daleprane C Nemesio de Barros Pereira RL Oréfice AC Bueno RR Vaz AN Moreira CS Magalhã es Clinical RelevanceCementation of fiber glass posts with self-adhesive cement (RelyX U100) is more predictable than cementation with resin cement using a three-step etch-and-rinse adhesive system (RelyX ARC/SBMP) as its bond strength to apical dentin was not influenced by the level of light-curing access. SUMMARYPurpose: This study evaluated the effect of light-curing access on the bond strength of fiber glass posts to the apical area of bovine roots using self-adhesive cement or dual-cured cement with an etch-and-rinse adhesive system.Materials and Methods: The root canals of 60 bovine teeth were endodontically treated and filled. A 15-mm-length post space was prepared and roots were randomly divided into three groups, simulating the levels of light-curing access: coronal (C), with 15-mm post space; middle (M), in which the coronal thirds of roots were cut out, leaving a 10-mm post space; and apical (A), in which the coronal and middle thirds of roots were cut out, leaving a 5-mm post space. Fiber glass posts (Reforpost # 3, Angelus) were cemented with RelyX U100 (3M ESPE) or RelyX ARC/Scotchbond Multi Purpose Plus (SBMP) (3M ESPE) (n=10) and lightcured. After 24 hours, the apical thirds of roots were sectioned perpendicularly to the long axis and submitted to a push-out test (0.5 mm/

Sample preparation and imaging techniques for scanning electron microscopy (SEM) of dehydrated dental samples can hinder the structural analyses. This study qualitatively evaluated images obtained with two different protocols of SEM preparation and analysis to assess the dentine adhesive interface. The crown and root dentine of 12 bovine incisors were subjected to cementation with the resin cement RelyX U100 or RelyX ARC/SBMP (n = 6). After storage for 7 days in a moist environment at 37 ± 1°C, the dentine samples were dehydrated in an ascending alcohol series, and three specimens from each group were coated with gold or carbon and examined in a high-vacuum (JEOL JSM-6360LV, 10 kV) or low-vacuum (FEI Quanta 200F, 15-30 kV) microscope. Images were obtained at magnifications between 50 and 2,000×, but with different working distances. The use of high vacuum for carbon and gold coating and SEM visualization led to cracks in the samples. A small number of cracks can be described in the specimens subjected to the low-vacuum technique. The protocol for SEM imaging in low vacuum was considered more appropriate for preservation of the integrity of the evaluated structures.

The effect of thickness, shade and translucency of CAD/CAM lithium disilicate glass-ceramic on light transmission of light-emitting diode (LED) and quartz-tungsten-halogen units (QTH) were evaluated. Ceramic IPS e.max CAD shades A1, A2, A3, A3.5, high (HT) and low (LT) translucency were cut (1, 2, 3, 4 and 5 mm). Light sources emission spectra were determined. Light intensity incident and transmitted through each ceramic sample was measured to determine light transmission percentage (TP). Statistical analysis used a linear regression model. There was significant interaction between light source and ceramic translucency (p=0.008) and strong negative correlation (R=-0.845, p<0.001) between ceramic thickness and TP. Increasing one unit in thickness led to 3.17 reduction in TP. There was no significant difference in TP (p=0.124) between shades A1 (ß1=0) and A2 (ß1=-0.45) but significant reduction occurred for A3 (ß1=-0.83) and A3.5 (ß1=-2.18). The interaction QTH/HT provided higher TP (ß1=0) than LED/HT (ß1=-2.92), QTH/LT (ß1=-3.75) and LED/LT (ß1=-5.58). Light transmission was more effective using halogen source and high-translucency ceramics, decreased as the ceramic thickness increased and was higher for the lighter shades, A1 and A2. From the regression model (R2=0.85), an equation was obtained to estimate TP value using each variable ß1 found. A maximum TP of 25% for QTH and 20% for LED was found, suggesting that ceramic light attenuation could compromise light cured and dual cure resin cements polymerization.

Introduction Convencional resin cements can be used in combination with a total-etch system in a conventional mode or as self-adhesive resin cements. The latter are less technique sensitive and able to bond to dental tissues without previous treatment or adhesive layer and requires only a single step to be applied to dental structures. Objective To compare qualitatively the adhesive interfaces of two self-adhesive resin cements and one conventional resin cement after different tooth surface treatments under scanning electron microscopy. Material and method 42 crowns of bovine incisors were sectioned and flattened exposing enamel (E) or dentine (D) substrate. Subgroups were defined according to conditioning type and time: E1—no treatment, E2—37% phosphoric acid for 15 seconds, E3—37% phosphoric acid for 30 seconds; D1—no treatment, D2—37% phosphoric acid for 5 seconds; D3—11.5% polyacrylic acid for 15 seconds. A resin block was bonded to each substrate using the self-adhesive resin cements RelyX U100 (3M ESPE) and RelyX U200 (3M ESPE). As a reference hybrid layer, six resin blocks were luted with RelyX ARC and Scotchbond Multi-Purpose adhesive system (3M ESPE) (enamel—EA; dentine—DA). After aging for 7 days in a moist environment at 37±1°C, samples were prepared for microscopy analysis. Result and Discussion In the ARC specimens, there was hybrid layer formation in both EA and DA. U100 E1 showed gaps at the adhesive interface, while E2 and E3 showed interaction for both self-adhesive cements. There was superficial interaction with bothU100 and U200 in D1, while in D2 and D3, resin tags were only observed in the case of U100. Conclusion It was concluded that substrate conditioning may enhance the interaction between self-adhesive resin cements and dental tissues, although this is not the case for RelyX U200 and dentine.

Silane treatment enhanced bond strength in all conditions evaluated, showing best results with HF etching.

Aim: Little is known about the biomechanical behavior of disocclusion patterns in implantsupported prostheses. Thus, the aim of the present study was to analyze the stresses generated at bone-implant interface during different patterns of disocclusion in an implant-supported lower complete denture without free distal ends using the three-dimensional (3-D) finite element method.

Objective: To evaluate the effect of two insertion techniques of self-adhesive dual resin cement on the bond strength of fiberglass posts in different portions of the root. The homogeneity of the cement layer along the root canal was also evaluated. Material and Methods: The root canals of 28 bovine teeth were instrumented, filled, and 14mm-space was prepared for luting fiberglass posts (Reforpost #3, Angelus), maintaining 4mm of apical sealing. The roots were randomly allocated into two groups according to the cement insertion technique (n=14): Lentulo Drill (Dentsply/Maillefer) or Centrix syringe (Dentsply). The posts were fixed with self-adhesive resin cement (RelyX U200, 3M ESPE). After 7 days, the roots were cross-sectioned to obtain three 1.0-mm-thick samples of each third of the space prepared for the post. Two samples of each third were subjected to push-out test (0.5 mm/min; 200N) and the third specimen was used for the analysis of cementation layer homogeneity. Images of specimens (40x magnification) were assessed and classified by two calibrated examiners (Kappa = 0.87) according to the presence or absence of voids and misfit. Data were analyzed by two-way ANOVA and Pearson Chi-Square test. Results: There was no statistically significant effect of insertion technique (p=0.278) or post-space thirds (p = 0.521) on bond strength of fiberglass posts. Chi-Square test showed that cement insertion with the Lentulo drill produced more cement voids than Centrix syringe (p = 0.023). Conclusion: The cement insertion technique did not influence bond strength of fiberglass posts in bovine root dentin. The use of Centrix syringe for cement insertion is preferred since it produced more homogenous cement layer.

No abstract