Pulpal temperature increase with high-speed handpiece, ER : YAG laser and ultrasound tips

The aim of this study was to compare intrapulpal temperature increase produced by high-speed handpiece, Er:YAG laser and CVDentus ultrasound tips during cavity preparation. Thirty bovine mandibular incisors with an enamel/dentin thickness of 4 mm at buccal surface had their roots amputated and were allocated to the following groups (n=10): Group I- high-speed handpiece; Group II- noncontact Er:YAG laser (250 mJ/4Hz); and Group III- CVDentus ultrasouns tips. All devices were used with water cooling. Class V cavities were prepared to a depth of 3.5 mm, measured with a periodontal probe. A type T thermocouple was placed inside the pulp chamber to determine the temperature increase (degrees C), which was recorded by a data acquisition system ADS 2000 IP (Lynx Technology) linked to a notebook computer. Data were analyzed statistically by oneway ANOVA and Tukey's test (p=0.05). The mean temperature rises were: 1.10 degrees C ( 0.56) for Group 1, 0.84 degrees C (0.55) for Group II, and 3.00 degrees C (1.34) for Group III. There were no statistically significant differences (p > 0.05) between Groups I and II, but both of them differed significantly from Group III (p < 0.05). In conclusion, the use of Er:YAG laser and high-speed handpiece for cavity preparation resulted in similar temperature increase. Although ultrasound tips generated significantly higher intrapulpal temperature increase, it remained below the critical value of 5.5 degrees C and may be considered safe for use.

Bonding Efficacy of New Self-etching, Self-adhesive Dual-curing Resin Cements to Dental Enamel

Purpose: This study evaluated the efficacy of the union between two new self-etching self-adhesive resin cements and enamel using the microtensile bond strength test.Materials and Methods: Buccal enamel of 80 bovine teeth was submitted to finishing and polishing with metallographic paper to a refinement of #600, in order to obtain a 5-mm(2) flat area. Blocks (2 x 4 x 4 mm) of laboratory composite resin were cemented to enamel according to different protocols: (1) untreated enamel + RelyX Unicem cement (RX group); (2) untreated enamel + Bifix SE cement (BF group); (3) enamel acid etching and application of resin adhesive Single Bond + RelyX Unicem (RXA group); (4) enamel acid etching and application of resin adhesive Solobond M + Bifix SE (BFA group). After 7 days of storage in distillated water at 37 degrees C, the blocks were sectioned for obtaining microbar specimens with an adhesive area of 1 mm(2) (n = 120). Specimens were submitted to the microtensile bond strength test at a crosshead speed of 0.5 mm/min. The results (in MPa) were analyzed statistically by ANOVA and Tu key's test.Results: Enamel pre-treatment with phosphoric acid and resin adhesive (27.9 and 30.3 for RXA and BFA groups) significantly improved (p <= 0.05) the adhesion of both cements to enamel compared to the union achieved with as-polished enamel (9.9 and 6.0 for RX and BF).Conclusion: Enamel pre-treatment with acid etching and the application of resin adhesive significantly improved the bond efficacy of both luting agents compared to the union achieved with as-polished enamel.

The effect of porcelain thickness and surface liner application on the fracture behavior of a ceramic system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The Disk-Specimen Thickness Does Not Influence the Push-Out Bond Strength Results Between Fiber Post and Root Dentin

This study evaluated the effect of different thickness of disk-shaped specimens on the push-out bond strength test. Eighteen lower bovine teeth were sectioned (20mm) and prepared (15mm) with the same post system drill (Light Post (R) #1, Schaumburg, IL, Bisco, USA). The apical third of each specimen was embedded in a plastic matrix filled with an acrylic resin (Dencrilay (TM), Dencril, São Paulo, Brazil). The posts were cleaned with alcohol, silanated (ProSil (R), FGM, Joenville, SC, Brazil) and cemented with the RelyX (TM) U100 (3M ESPE, St. Paul, MN, USA). Each specimen was sectioned into three pieces of differing thicknesses (1, 2, and 4 mm). These disk-samples were allocated into 3 groups (n=18) and subjected to push-out testing. One-way ANOVA showed no influence of the specimen thickness on the results (p=0.842). No correlation was observed between thickness and push-out bond strength (Pearson Correlation, r(2)=0.0688; P=0.6209). The push-out bond strength test was not affected by the thickness of the disk-specimens.

Effects of cement thickness and bonding on the failure loads of CAD/CAM ceramic crowns: Multi-physics FEA modeling and monotonic testing

Objective. To determine the influence of cement thickness and ceramic/cement bonding on stresses and failure of CAD/CAM crowns, using both multi-physics finite element analysis and monotonic testing.Methods. Axially symmetric FEA models were created for stress analysis of a stylized monolithic crown having resin cement thicknesses from 50 to 500 mu m under occlusal loading. Ceramic-cement interface was modeled as bonded or not-bonded (cement-dentin as bonded). Cement polymerization shrinkage was simulated as a thermal contraction. Loads necessary to reach stresses for radial cracking from the intaglio surface were calculated by FEA. Experimentally, feldspathic CAD/CAM crowns based on the FEA model were machined having different occlusal cementation spaces, etched and cemented to dentin analogs. Non-bonding of etched ceramic was achieved using a thin layer of poly(dimethylsiloxane). Crowns were loaded to failure at 5 N/s, with radial cracks detected acoustically.Results. Failure loads depended on the bonding condition and the cement thickness for both FEA and physical testing. Average fracture loads for bonded crowns were: 673.5 N at 50 mu m cement and 300.6 N at 500 mu m. FEA stresses due to polymerization shrinkage increased with the cement thickness overwhelming the protective effect of bonding, as was also seen experimentally. At 50 mu m cement thickness, bonded crowns withstood at least twice the load before failure than non-bonded crowns.Significance. Occlusal "fit" can have structural implications for CAD/CAM crowns; pre-cementation spaces around 50-100 mu m being recommended from this study. Bonding benefits were lost at thickness approaching 450-500 mu m due to polymerization shrinkage stresses. (C) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Influence of Potentially Remineralizing Agents on Bleached Enamel Microhardness

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Strength of a feldspar ceramic according to the thickness and polymerization mode of the resin cement coating

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

In vitro study of the Nd : YAG laser effect on human dental enamel: Optical and scanning electron microscope analysis

Objective: the Nd:YAG laser irradiation of dental enamel was evaluated in enamel demineralization experiments in a Streptococcus mutans culture media. Summary Background Data: Previous studies had shown that a continuous wave Nd:YAG laser at an energy of approximately 67 mJ may induce an increased acid resistance in human dental enamel when exposed to severe demineralization conditions. Methods: Enamel windows of 3 x 4 cm in the buccal surface were irradiated with a continuous wave Nd:YAG laser at a wavelength of 1,064 Ecm using energy densities of from 83.75 to 187.50 J/cm(2), Enamel windows of 3 x 4 cm on the lingual surface served as control (without the laser irradiation). The enamel windows were then exposed to a Streptococcus mutans culture media at a temperature of 37 degrees C for 15 and 21 days. The laser effects and demineralization were examined both by optical microscopy and scanning electron microscopy (SEM), Results: A comparison between the lased and the unlased windows of enamel showed fusion and recrystalization of the enamel and increased acid-resistance in all groups irradiated with the Nd:YAG laser, on the other hand, the 3 x 4 delimited enamel surfaces from the control group (not irradiated with the Nd:YAG laser) showed 100% deminerization, Conclusions: These findings are consistent with the finding that laser irradiation of dental results in significant reduction of the effective solubility of enamel mineral.

Effect of Caries Infiltration Technique and Fluoride Therapy on Microhardness of Enamel Carious Lesions

Enamel white spot subsurface lesions compromise esthetics and precede cavitation; therefore, they must be halted. The aim of this study was to evaluate the effect of a caries infiltration technique and fluoride therapy on the microhardness of enamel carious lesions. Subsurface carious lesions were produced in 60 bovine specimens with polished enamel surfaces. The specimens were divided into four groups (n=15), according to the treatment used: CON, control immersion in artificial saliva; DF, daily 0.05% fluoride solution; WF, weekly 2% fluoride gel; and IC, resin infiltration (Icon). The specimens were kept in artificial saliva and evaluated for microhardness at five points: baseline, after caries production, after four and eight weeks of treatment, and a final evaluation after being submitted to a new acid challenge. The repeated-measures analysis of variance showed significant differences according to the type of treatment (TREAT; p=0.001) and time of evaluation (EV; p=0.001). The results of the Tukey test were TREAT: CON = 45.18 (+/- 29.17)a, DF = 107.75 (+/- 67.38)b, WF = 83.25 (+/- 51.17)c, and IC = 160.83 (+/- 91.11)d. Analysis of correlation between the TREAT and EV factors showed no significant differences for DF (138.63 +/- 38.94) and IC (160.99 +/- 46.13) after the new acid challenge. The microhardness results in decreasing order after eight weeks were IC > DF > WF > CON. It was concluded that the microhardness of carious lesions increased with the infiltration of resin, while the final microhardness after a new acid challenge was similar for DF and IC.

Effect of antioxidant agents on bond strength of composite to bleached enamel with 38% hydrogen peroxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of dental surface treatment with Nd:YAG and Er:YAG lasers on bond strength of resin composite to recently bleached enamel

The aim of this work is to evaluate the effect of surface treatment with Er:YAG and Nd:YAG lasers on resin composite bond strength to recently bleached enamel. In this study, 120 bovine incisors were distributed into two groups: group C: without bleaching treatment; group B: bleached with 35% hydrogen peroxide. Each group was divided into three subgroups: subgroup N: without laser treatment; subgroup Nd: irradiation with Nd:YAG laser; subgroup Er: irradiation with Er:YAG laser. The adhesive system (Adper Single Bond 2) was then applied and composite buildups were constructed with Filtek Supreme composite. The teeth were sectioned to obtain enamel-resin sticks (1 x 1 mm) and submitted to microtensile bond testing. The data were statistically analyzed by the ANOVA and Tukey tests. The bond strength values in the bleached control group (5.57 MPa) presented a significant difference in comparison to the group bleached and irradiated with Er:YAG laser (13.18 MPa) or Nd:YAG (25.67 MPa). The non-bleached control group presented mean values of 30.92 MPa, with statistical difference of all the others groups. The use of Nd:YAG and Er:YAG lasers on bleached specimens was able to improve the bond strengths of them.

Microtensile bond strengths and scanning electron microscopic evaluation of self-adhesive and self-etch resin cements to intact and etched enamel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Surface roughness of enamel and four resin composites

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influence of Methods of Application of Self-etching Adhesive Systems on Adhesive Bond Strength to Enamel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Microhardness change of enamel due to bleaching with in-office bleaching gels of different acidity

Objective. The aim of this study was to assess the enamel microhardness treated with three in-office bleaching agents, containing 35% hydrogen peroxide with different acidity. Materials and methods. Bovine incisors were divided into three groups that received the following bleaching agents: Whiteness HP, Total Bleach and Opalescence Xtra. Three gel applications/10-min each, totaling 30-min of bleaching treatment, were made on the teeth and activated with a blue LED (1000 mW/470 nm) combined to a LASER (120 mW/795 nm) device (Easy Bleach-Clean Line). Vickers hardness (VH) was evaluated at baseline and after the bleaching procedure. The values of Hardness loss [HNL] (% reduction) were calculated. The two-sample t-test was used for comparison of the HNL of the three bleaching products (5% level of significance). Results. The Opalescence Xtra, which had the lowest pH value (pH = 4.30), showed a significant increase of HNL when compared with Total Bleach bleaching agent, which had the highest pH value (pH = 6.62). Conclusions. The 35% hydrogen peroxide bleaching agents resulted in a reduction in surface enamel microhardness and bleaching with the most acid agent resulted in a significant enamel hardness loss compared to the less acid agent (4.30 vs 6.62). Strategies proposed to reduce the enamel loss after bleaching treatment may include the use of daily fluoride therapy, mouth rinsing (fluoride, milk and sodium bicarbonate solution), fluoride/bicarbonate dentifrices without abrasives, do not toothbrush immediately after bleaching, fluorides and calcium add to bleaching agents.