No abstract

This study evaluated the effects on human enamel after two bleaching procedures: with a fluoridated bleaching agent and with topical fluoride application postbleaching. It used 43 enamel blocks (3 mm(2) ) that were ground flat (600-2,000 grit) and polished with polishing paste (one and one-fourth). Specimens were randomly divided into three groups according to the bleaching procedure: (1) control group, (2) hydrogen peroxide 35% (HPF) and topical application of fluoride 1.23%, and (3) HP 38% (OP) with fluoride in its composition. Bleaching agents were used according to the manufacturer's instructions. Three methodologies were used: nanoindentation, to observe surface hardness and elastic modulus; atomic force microscopy, to observe surface roughness (R(a) - R(z)); and scanning electron microscopy, to observe the enamel surface effects. Group OP had a decrease in the elastic modulus after bleaching, which was recovered at 14 days. An increased roughness (R(a); 32%) was observed on group HPF and had an increased erosion on enamel surface (67%). It was concluded that topical application of fluoride, after using the nonfluoridated whitening agent, increased the roughness values and erosion of enamel.

The objective of this study was to evaluate the effect of passive or active phosphoric acid (PA) application after hydrofluoric acid (HA) treatment on the microshear bond strength of lithium disilicate. Thirty ceramic discs were made with IPS Emax 2 (10 mm thick and 10 mm diameter). The specimens were divided into 3 groups, A: 9.6% HA application; AF: 9.6% HA application + cleaning with 37% PA in passive mode and AFF: 9.6% HA application + cleaning with 37% PA in active mode. For the microshear test, four tygons (0.9 mm diameter and 0.2 mm high) were filled with resin cement (RelyX Ultimate) and placed on the ceramic disks. After testing, the fracture modes were examined under scanning electron microscopy. Data were analyzed by one-way ANOVA and Tukey's post test (α=0.05). The bond strength values were significantly higher in Group AFF (11.0±2.5 MPa) compared with group A (8.1±2.6 MPa) (p<0.002). AF group was not statistically different (9.4±2.5 MPa) from Group A. It was concluded that the active application of 37% PA after 9.6% HA increases the microshear bond strength values between the resin cement and lithium disilicate ceramic.

The aim of this study was to evaluate different conditioning protocols and sonic/ ultrasonic application of an infiltrant resin (IR) in artificial white spot lesions (AWSL). the V/L surfaces of 48 molars were induced to an AWSL and divided in 6 groups, according to the conditioning protocols and application technique: 15% hydrochloric acid (HA) + manual application of the IR; HA + 37% phosphoric acid (PA) + manual application of the IR; HA + ultrasonic application (U) of the IR; HA + sonic application (S) of the IR; PA+HA+S; and PA+HA+U. For the Penetration Depth (PD), the crowns were etched with HA for 120s. The IR Icon® (DMG) was applied according to the manufacturer`s instructions. The crowns were dye penetrated (0.1% red fluorophore rhodamine B isothiocyanate for 12h) and bleached with 30% hydrogen peroxide for 12 h. The discs were immersed in a 50% ethanol solution, containing 100 µM of sodium fluorescein. The PD (in µm) was measured using confocal laser scanning microscopy (20x). The bond strength (BS) was performed by michoshear test (0.5 mm/min). Data were submitted to 2-way ANOVA and Tukey (α=0.05). For BS, the interaction was not significant (p>0.05). For PD, the main factors were significant (application -p<0.001; conditioning technique -p=0.003). The ultrasonic application showed the highest PD values. PA+HA presented higher results than HA. The sonic/ultrasonic applications and the use of phosphoric acid prior to hydrochloric acid improved PD of the infiltrant resin. Conditioning protocols or application techniques did not influence BS values.

<p>The longevity of resin, depends on its binding between the margin of restorations and the polymer, and one factor that influences this aspect is the shrinkage stress, so the working group makes the following systematic review which looks at the influence of the composite resin composition of the shrinkage stress.</p>

Objetivo:evaluar la microdureza y el grado de conversión después de diferentes técnicas poscurado en dos tipos de resinas compuestas. Materiales y métodos: se realizaron 36 cuerpos de prueba con 12 mm de diámetro y 4 mm de altura, con dos resinas: Filtek z350 y Ena Miscerium. Después de la confec-ción, los cuerpos de prueba se llevaron al microduremetro y a espectroscopia de infrarrojo, y fueron sometidos a cuatro procesos de pospolimerización: agua en ebullición, microonda, calor seco, autoclave y horno gradia. Resultados: se hizo análisis estadístico por medio de Anova de dos factores con postest Tukey por resina evaluada, se presentan media y desviación estándar, los valores de grado de conversión muestran un gran aumento en la resina Ena comparado con el grupo control (63,81%), cuando es realizado pospolimerización con calor seco (89,02%) y una gran disminución cuando es realizado con agua en ebullición (36,41%). Con-clusiones: el proceso de curado posterior por microondas y autoclave aumenta los valores de microdureza y grado de conversión, y el agua destilada a temperaturas altas disminuye la microdureza de la superficie de las resinas compuestas

Conical implant–abutment connections are popular for their stability; however, in other conditions, such as excessive force, implants and abutments can absorb all the stress. Some connections with three points of support can resist more than conical connections. In recent years, different studies has shown that the design of a connection affects its stability. The aim of this study was to analyze and compare the stresses in finite elements (FEs) in a newly proposed conical triangular connection in implants with hexagonal and conical connections. A nonlinear 3D FE parametric model was developed using SOLIDWORKS 2017®. All the connections, i.e., external and internal hexagons, morse taper, conical connection, and the new conical triangular proposal were compared when axial forces of 150, 250, and 350 N were applied to the occlusal. The maximum stress was found in the external hexagon. The maximum stress was concentrated at the level of the neck of the abutment, implant, and bone, except for the morse taper; at the level of the crown and abutment, the lowest stress occurred in the new proposal. Conclusions: The new conical triangular (CT) connection and the conical connection (CC) generate similar stress in the implant, abutment, and crown. However, the CT connection improves the CC by reducing stress at the bone level, adding an advantage to having three retention points.

<p><strong>Objetive:</strong> The purpose of this study is was to evaluate the influence of sandblasting ceramic and enamel structure on bond strength, changing  distance.</p><p><strong>Material and methods:</strong> 60 third molars , were selected, enamel surfaces were ground flat with wet 600 - 2000 grit aluminum oxide abrasive papers  and polished with three, one, and one-fourth micrometer-grit diamond pastes. Obtained 120 lithium disilicate-based core ceramic discs ( 2 mm diameter;1 mm thickness), divided into 7 groups  [Group C, don’t sandblasting, Group SB-E(5-10) enamel sandblasting 5 and 10 mm, Group SB-C(5-10)  ceramic sandblasting 5 mm and 10 mm, Group SB-EC(5-10)  enamel and ceramic sandblasting 5 mm and 10 mm]   after was performed microshear and Atomic Force Microscopy (AFM), Statistic Teste of normality , after one-way ANOVA and Tukey test (α: 0.05).</p><p><strong>Results:</strong> The group C present bond strength (59.2±12.5), the group SB-E 5 mm (21.7±08.8) (p&lt;0.005), the group SB-E10 (53.6±14.3).</p><p><strong>Conclusion:</strong> The use of sandblasting treatment of the enamel surface a 5 mm by 20 seconds decreases the bonding strength to microshear.</p>