Influence of Different Surface Treatments on the Bond Strength of Yttria-Stabilized Tetragonal Zirconia Ceramic.

Objective: This in vitro study evaluates the shear bond strength (SBS) of yttria-stabilized tetragonal zirconia (Y-TZP) and resin cement after different surface treatments. Materials and methods: Forty-eight ceramic cubes were divided into four groups (n = 12): G1 (control) sandblasting with Al2O3; G2-sandblasting with silica-coated Al2O3 (Rocatec); G3-Rocatec + CO2 laser; and G4-CO2 laser + Rocatec. A metallic primer was applied to the pretreated ceramic. A rubber ring was adapted on the central area, and then, the resin cement was inserted into the matrix and photoactivated. The samples were evaluated regarding surface roughness (Ra), SBS, failure type, and qualitatively with scanning electron microscopy (SEM). The data were analyzed by one-way analysis of variance followed by Tukey's test (p < 0.05). Results: The mean values of Ra (µm) were as follows: G1-4.52a, G2-4.24a,b, G3-4.10a,b, and G4-2.90b and the mean values of SBS (MPa) were as follows: G1-7.84a , G2-4.41b , G3-4.61b and G4-6.14a,b. SEM analyses showed superficial irregularities for all groups, being more prominent for G1. The presence of silica deposits was observed for G2, G3, and G4, but in the last two groups there were some linear areas, promoted by the fusion of silica, due to the thermomechanical action of the CO2 laser. Conclusions: The surface treatment with CO2 laser + Rocatec, using one MDP-based cement, can be an alternative protocol for the adhesion cementation of Y-TZP ceramic since it was as effective as the conventional pretreatment with aluminum oxide sandblasting.

Longitudinal, Randomized, and Parallel Clinical Trial Comparing a Violet Light-Emitting Diodes System and In-Office Dental Bleaching: 6-Month Follow-Up.

Objective: This in vivo study compared two bleaching techniques with regard to the degree of tooth sensitivity (TS), color change, and treatment stability for a 6-month follow-up period. Materials and methods: Sixty volunteers were selected according to inclusion and exclusion criteria and submitted to in-office bleaching. For group 1, we performed one bleaching session with a 35% hydrogen peroxide gel and a second bleaching session after 7 days; for group 2, we performed two bleaching sessions with two applications per session, each session with a 7-day interval, using a light-emitting diodes (LEDs) device emitting violet light (405-410 nm) without employing peroxide-containing bleaching gel. TS was recorded immediately before and immediately after each bleaching session using the Variance Analogic Scale. The color of upper central incisors and upper canines at baseline was recorded immediately after each bleaching session, after 15, 30, and 180 days, with a value-oriented shade guide used by two well-trained observers. Results: The two whitening protocols results were similar regarding the immediate effectiveness and 6-month stability of tooth whitening. Dental bleaching with violet LED did not promote postoperative pain sensitivity at any of the evaluated times. However, dental bleaching performed with 35% hydrogen peroxide promoted higher postoperative pain sensitivity. Conclusions: The violet light alone provided dental bleaching and had the clinical advantage of promoting less immediate postoperative sensitivity; however, an unwanted repigmentation occurred after dental bleaching with light alone.

Influence of Abutment Surface Treatments on Screw Loosening of Morse Taper Implants.

PURPOSE: To evaluate the effect of blasting and bonding on abutment surface to prevent screw loosening in Morse taper connections. MATERIAL AND METHODS: Twenty-eight Morse taper connection implants were divided into 4 groups: no treatment (G1), blasting (G2), bonding (G3), and blasting + bonding (G4). In groups G2 and G4, the abutments were blasted with aluminum oxide granules; in groups G3 and G4, the conical abutment region was covered with a thin layer of bond thread lock agent. In all implants, the abutment-implant joint was tightened at a torque of 35 Ncm. The specimens were submitted to the mechanical cycling, under an oblique load for 1.0 × 10 cycles. The torque was measured with a digital torque meter. Data were analyzed by the t test, one-way analysis of variance, and Tukey tests (95%). RESULTS: The loosening strength was significantly higher in group G4 (35.83 ± 3.02 Ncm). There was no significant difference among groups G1 (25.86 ± 1.96 Ncm), G2 (25.86 ± 3.29 Ncm), and G3 (26.14 ± 2.12 Ncm). CONCLUSION: The association of blasting and bonding on abutment surface can be used to prevent screw loosening in Morse taper implants.

Potential of CO2 lasers (10.6 µm) associated with fluorides in inhibiting human enamel erosion.

This in vitro study aimed to investigate the potential of CO2 lasers associated with different fluoride agents in inhibiting enamel erosion. Human enamel samples were randomly divided into 9 groups (n = 12): G1-eroded enamel; G2-APF gel; G3-AmF/NaF gel; G4-AmF/SnF2 solution; G5-CO2 laser (λ = 10.6 µm)+APF gel; G6-CO2 laser+AmF/NaF gel; G7-CO2laser+AmF/SnF2solution; G8-CO2 laser; and G9-sound enamel. The CO2 laser parameters were: 0.45 J/cm2; 6 µs; and 128 Hz. After surface treatment, the samples (except from G9) were immersed in 1% citric acid (pH 4.0, 3 min). Surface microhardness was measured at baseline and after surface softening. The data were statistically analyzed by one-way ANOVA and Tukey's tests (p < 0.05). G2 (407.6 ± 37.3) presented the highest mean SMH after softening, followed by G3 (407.5 ± 29.8) and G5 (399.7 ± 32.9). Within the fluoride-treated groups, G4 (309.0 ± 24.4) had a significantly lower mean SMH than G3 and G2, which were statistically similar to each other. AmF/NaF and APF application showed potential to protect and control erosion progression in dental enamel, and CO2 laser irradiation at 0.45J/cm2 did not influence its efficacy. CO2 laser irradiation alone under the same conditions could also significantly decrease enamel erosive mineral loss, although at lower levels.

Accuracy of a self-perforating impression tray for dental implants.

STATEMENT OF PROBLEM: Difficulties are involved in impression making with conventional open impression trays. PURPOSE: The purpose of this study was to evaluate the accuracy of transferring implant impressions with a self-perforating impression tray. MATERIAL AND METHODS: A reference model of a mandible was fabricated, and 4 implants were placed in the regions of the first premolars and lateral incisors (implants 1, 2, 3, 4). Ten impressions of the reference model with polyvinyl siloxane were made for each group; control (conventional open impression tray) and test (self-perforating impression tray; Miratray Implant). A metal bar was screw-retained on implant 1, and the gaps generated at the vestibular face of implants 3 and 4 were measured by optical microcopy. The 2-way ANOVA and least square difference post hoc test were used (α=.05). RESULTS: Higher mean (±SD) values were obtained for the test group than for the control group for both implants: implant 3: 150 ±84 µm for the test group, 73 ±63 µm for the control group (P=.019); implant 4: 129 ±65 µm for the test group, 62 ±61 µm for the control group (P=.04). CONCLUSION: The self-perforating impression tray provided less accuracy than the conventional open tray.

Effect of CO2 laser on root caries inhibition around composite restorations: an in vitro study.

The aim of the present study was to investigate the in vitro effect of CO2 laser on the inhibition of root surface demineralization around composite resin restorations. For this purpose, 30 blocks obtained from human molar roots were divided into three groups: group 1 (negative control), cavity prepared with cylindrical diamond bur + acid etching + adhesive + composite resin restoration; group 2, cavity prepared with cylindrical diamond bur + CO2 laser (5.0 J/cm(2)) + acid etching + adhesive + composite resin; and group 3, cavity prepared with cylindrical diamond bur + CO2 laser (6.0 J/cm(2)) + acid etching + adhesive + composite resin. After this procedure, the blocks were submitted to thermal and pH cycling. Root surface demineralization around the restorations was measured by microhardness analysis. The hardness results of the longitudinally sectioned root surface were converted into percentage of mineral volume, which was used to calculate the mineral loss delta Z (ΔZ). The percentage of mineral volume, ΔZ, and the percentage of demineralization inhibition of the groups were statistically analyzed by using analysis of variance and Tukey-Kramer test. The percentage of mineral volume was higher in the irradiated groups up to 80 µm deep. The ΔZ was significantly lower in the irradiated groups than in the control group. The percentage of reduction in demineralization ranged from 19.73 to 29.21 in position 1 (50 µm), and from 24.76 to 26.73 in position 2 (100 µm), when using 6 and 5 J/cm(2), respectively. The CO2 laser was effective in inhibiting root demineralization around composite resin restorations.

Interaction between staining and degradation of a composite resin in contact with colored foods.

Composite resins might be susceptible to degradation and staining when in contact with some foods and drinks. This study evaluated color alteration and changes in microhardness of a microhybrid composite after immersion in different colored foods and determined whether there was a correlation between these two variables. Eighty composite disks were randomly divided into 8 experimental groups (n = 10): kept dry; deionized water; orange juice; passion fruit juice; grape juice; ketchup; mustard and soy sauce. The disks were individually immersed in their respective test substance at 37 ºC, for a period of 28 days. Superficial analysis of the disk specimens was performed by taking microhardness measurements (Vickers, 50 g load for 45 seconds) and color alterations were determined with a spectrophotometer (CINTRA 10- using a CIEL*a*b* system, 400-700 nm wavelength, illuminant d65 and standard observer of 2º) at the following times: baseline (before immersion), 1, 7, 14, 21 and 28 days. Results were analyzed by ANOVA and Tukey's test (p < 0.05). Both variables were also submitted to Pearson's correlation test (p < 0.05). The passion fruit group underwent the greatest microhardness change, while the mustard group suffered the greatest color alteration. Significant positive correlation was found between the two variables for the groups deionized water, grape juice, soy sauce and ketchup. Not all color alteration could be associated with surface degradation.

A ação de gorduras alimentares na microdureza de uma resina composta fotopolimerizável / Effect of alimentary fats on microhardness of composite restoratives

Introdução - Este estudo in vitro teve como objetivo verificar se alguns alimentos gordurosos alteram a microdureza superficial de uma resina composta (Filtek Z250-3M Espe). Materia e Métodos - Vinte e cinco corpos de prova (4 mm de diâmetro x 2 mm de espessura) foram confeccionados e mantidos por 30 dias, em estufa, a 37°C e a seguir divididos aleatoriamente, em 5 grupos (n = 5). De acordo com os meios de imersão em que foram mantidos, por 21 dias a 37°C, os grupos foram definidos como: G1 - água deionizada (controle); G2 - maionese (Hellmans); G3 - banha (Sadia), G4 - óleo de soja (Soya); G5 - margarina (Doriana). A microdureza Vickers (HMW 2000 - Shimadzu) da superfície de cada corpo de prova foi avaliada, uma vez antes e a cada 7 dias após a imersão, usando 50 g de carga e 45 s de tempo. Os dados foram submetidos à análise estatística (ANOVA) e Tukey (p<0,05). Resultados - O resultados da ANOVA dois fatores (meios de imersão x tempos) para Delta Vickers mostraram que houve diferença estatisticamente significante para o fator meio de imersão (p = 0,02%), sendo que não há significância para o fator (p= 13,6%), bem como não há significância na interação deses fatores (p = 44,2%). Os valores de Delta Vickers para o fator meio de imersão encontrados foram: G1 (6,79a), G2 (18,31b), G3 (8,10a), G4 (8,70a), G5 (12,43ab). Conclusão - Todas as gorduras testadas alteraram significativamente a resina composta. Os grupos G2 e G5 apresentaram maior degradação. Não houve variação significativa para tempos

Influence of the distance of the curing light source and composite shade on hardness of two composites.

This study evaluated the influence of curing tip distance, shade and filler particle size on Vickers microhardness (VHN) of composite resins. Two composites were tested: Filtek Z250 microhybrid (3M ESPE; shades A1 and A3.5) and Filtek Supreme nanofilled (3M ESPE; shades A1B and A3.5B). For each resin, 42 specimens (5 mm in diameter and 2 mm height) were prepared being 21 for each shade. The specimens were exposed using a 20-second exposure to a quartz-tungsten-halogen light source with an irradiance of approximately 560 mW/cm(2), at the following distances: 0 mm (surface contact), 6 mm and 12 mm from composite surface. Effectiveness of cure of different resins, shades and curing distances was determined by measuring the top and bottom hardness (VHN) of specimens using a digital microhardness tester (load: 50 g; dwell time: 45 seconds) 24 hours following curing. The hardness ratio was calculated by dividing VHN of the bottom surface by VHN of top surface. Three-way ANOVA and Tukey's post-hoc test (p<0.05) revealed statistically significant differences for all analyzed factors. As for top hardness, as microhardness ratio (bottom/top), the factors shade, distance and composite filler particle size exerted influence on resin curing. Lighter shade composites (A1 and A1B) showed higher hardness values. At 6 and 12 mm curing tip distances, hardness was lower when compared to 0 mm. The microhybrid composite resin presented higher hardness, being its microhardness ratio satisfactory only at 0 mm for both shades and at 6 mm for the lighter shade. The nanofilled composite resin did not present satisfactory microhardness at the bottom while the microhybrid composite resin had higher hardness than the nanofilled. Composite's curing tip distance and shade can influence hardness.

A importância da Dentística na identificaçäo pelos dentes, no arco dental / The importance of operative dentistry in body identification through the teeth in dental arch

O autor descreve em seu trabalho um método alternativo na identificaçäo de corpos calcinados, o que, de algum modo, vem facilitar a composiçäo da ficha odontológica destes corpos para futura identificaçäo. Em se sabendo em que condiçöes se apresentariam os diferentes materiais restauradores expostos à temperaturas elevadas de 400º a 600ºC, torna-se razoavelmente mais fácil o conhecimento de um odontograma de um corpo calcinado. Na opiniäo do autor requer-se, com fundamental importância, que todos os profissionais preencham com devido cuidado a ficha odontológica de seus pacientes, com especial atençäo aos tipos de materias e características técnicas das restauraçöes, para que numa eventualidade de seus pacientes sofrerem um acidente com calcinaçäo uma vez publicada pelo perito a ficha odontológica dos corpos carbonizados, possa o profissional de pronto dar a identificaçäo de seu paciente envolvido neste acidente. A opiniäo do autor é de que todos os profissionais tenham sempre em mente os detalhes que envolvem a odontologia forense (legal) para que possam dirigir os seus trabalhos em seus pacientes nos seus consultórios, sempre tendo em mente a possibilidade de um deles vir a sofrer um acidente com carbonizaçäo