Igor Studart Medeiros | Universidade de São Paulo (original) (raw)

Papers by Igor Studart Medeiros

Evaluation of the mechanical properties of acetic-cure silicone with

Brazilian Dental Science, 2019

Objective: Despite the increase of all-ceramic prosthesis in dental practice there is no evidence... more Objective: Despite the increase of all-ceramic prosthesis in dental practice there is no evidence of the possibility of welding these structures if necessary. The objective of this study was to use CO2 laser (?=10.6µm) as a welding agent to fuse dental polycrystalline alumina ceramic. Methods: Ceramic blocks of pre-sintered alumina were sectioned into 20 bars (10.0 x 1.5 x 1.5mm) and sintered to the final cross?section dimension of 1.2 x 1.2mm. The bars were adapted to an LHPG (Laser Heated Pedestal Growth) system device where the bars could be fixed in pairs and have their ends irradiated with CO2 laser to fusion. The ring-shaped laser beam (300 µm thickness) was directed with the aid of mirrors to reach samples’ ends. The laser was continuously applied (40W nominal power, 5 seconds). After welding, the samples were analyzed in stereomicroscope and SEM. A diffraction analysis was carried out with one sample. Results: The ceramic bars were successfully fused, but some of them showed...

Clinical and Laboratorial Research in Dentistry, 2020

Secondary caries is the primary cause of restoration failure. Thus, the development of adhesives ... more Secondary caries is the primary cause of restoration failure. Thus, the development of adhesives with antimicrobial action is an advantageous option for their inhibition. However, this effect must be proven, as well as that the additional benefit does not interfere with material mechanical properties or biocompatibility. We analyzed adhesives with antimicrobial action by microbiological tests, bond strength, degree of conversion, and cytotoxicity. We analyzed 32 studies with commercially available antimicrobial adhesives (Clearfil™ SE Protect Bond/ MDPB, Gluma 2Bond/ glutaraldehyde, Peak Universal Bond/chlorhexidine), and experimental materials or commercial adhesives modified with antimicrobial agents, including materials with quaternary ammonium methacrylate (QAM) [dimethylaminododecyl methacrylate (DMADDM) and dimethylaminohexadecyl methacrylate (DMAHDM)], nanoparticles [silver (NAg), titanium dioxide (TiO2), zinc oxide (ZnO)], silver or zinc doped bioactive active glass (BAG), t...

Progress in Biomaterials, 2019

In vitro effect of 1% theobromine addition on the physical and chemical properties of conventiona... more In vitro effect of 1% theobromine addition on the physical and chemical properties of conventional glass ionomer (GIC) cement was investigated. Conventional GIC (GIC-C) and 1% theobromine added to GIC (GIC-THEO) specimens were compared regarding the microhardness (n = 10), sorption (n = 5), solubility (n = 5), color change (n = 10), fluoride release in saliva (n = 10) and the amount of biofilm deposition (n = 20). Compared against conventional GIC, adding 1% theobromine increased microhardness (p < 0.05), while its sorption, solubility, color and fluoride release to saliva (p > 0.05) remained unchanged. On the other hand, Streptococcus mutans biofilm amount deposited on its surface decreased statistically when theobromine was added to GIC (p < 0.05). Based on the results, it could be concluded that 1% theobromine addition to GIC can be a good strategy as it keeps some of its properties and improves microhardness and biofilm deposits strengthening its role in the preventive approach of dentistry.

Surface and Coatings Technology, 2018

The aim of this study was to develop and characterize wettability, morphology, chemical compositi... more The aim of this study was to develop and characterize wettability, morphology, chemical composition and color of plasma-deposited thin films on the surface of dental materials. A porcelain (VM9, VITA (PC)) and two indirect composite discs (Enamic, VITA (EN) and Lava Ultimate, 3M ESPE (LU)) were used. Different methodologies of film deposition were established: plasma-enhanced chemical vapor deposition (PECVD) with HMDSO/Ar (PAr); PECVD with HMDSO/O 2 (PO 2); plasma immersion ion implantation and deposition using HMDSO/Ar (PII). Surface roughness and film thickness were determined by profilometry. Contact angles were measured with a goniometer. Morphological analysis was evaluated using SEM and chemical composition was investigated by FTIR and XPS. Color differences (ΔE) were verified by a spectrophotometer. The films' thicknesses were 620 nm (PAr), 540 nm (PO 2) and 70 nm (PII). Surface roughness was not changed for most of the groups. An increase in contact angles for all film groups was detected, except for LU-PII group. In PO 2 films, granular structures covered the entire surface and their presence decreased in PAr and PII. Color differences maintained below 3.0. PO 2 showed a silica-like and PII silicon oxycarbide-like structure and PAr presented an organic behavior. Plasmadeposited thin films were developed and altered surface characteristics of restorative materials, maintaining the materials color and adequate surface roughness potentially working as a protective barrier.

The Journal of Prosthetic Dentistry, 2019

Rehabilitation with maxillofacial prostheses restores esthetics and function, protects remaining ... more Rehabilitation with maxillofacial prostheses restores esthetics and function, protects remaining tissues, and improves the quality of life of wearers. 1-3 Maxillofacial prostheses are fabricated from room temperature or heat-polymerized elastomers. These materials are translucent, easy to manipulate and pigment, 4-6 promote excellent esthetics, 7 and have a lifetime of 6 months to 3 years 8-10 The optical properties of maxillofacial elastomers determine the quantity and quality of transmitted, reflected, and absorbed light and are therefore essential for color perception. 11,12 Transmittance is a measure of the fraction of incident light at a specified wavelength, and spectral reflectance is a fraction of incident light that is reflected at an interface

Brazilian Dental Journal, 2017

The aim of this study was to evaluate the influence of an extended use of desensitizing toothpast... more The aim of this study was to evaluate the influence of an extended use of desensitizing toothpastes (DTs) on dentin bonding, microhardness and roughness. One hundred and twenty bovine incisor teeth were randomly divided into four groups: G1, distilled water (WATER); G2, Colgate Total 12 (CT12); G3, Colgate Sensitive Pro-Relief (CSPR); and G4, Sensodyne Repair ?αμπ; Protect (SRP). Dentin surfaces were etched with 17% EDTA and 2 years of simulated tooth brushing (20,000 cycles) was performed on their surfaces. Knoop microhardness, surface roughness and scanning electron microscopy (SEM) were performed before and after the simulated tooth brushing. For microshear bonding test, a 2-step self-etching adhesive system (Clearfil SE Bond) was used and 0.8 mm diameter composite resin (Filtek Z350 XT) cylinders were built. Microshear test was performed with an orthodontic wire and with a crosshead speed of 0.5 mm/min. The data were analyzed for: 1) bond strength (one-way ANOVA), 2) microhardne...

Journal of Research in Dentistry, 2013

When immersed in oral fluids, water absorption by the restorative resin composite material can oc... more When immersed in oral fluids, water absorption by the restorative resin composite material can occur, which is identified by some researchers as one of the causes of loss of aesthetic features and reduction of mechanical properties over time. On the other hand, some authors have suggested that the fluids sorption may contribute to the reduction of shrinkage stress generated at the adhesive interface and reduce the width of gaps. The aim of this study was verifying if the storage time in water of restorations carried out with different filling techniques could influence on the integrity of tooth-restoration adhesive interface. Eighteen cavities were built in bovine incisors and they were divided into 3 groups after the adhesive procedure: group B (“Bulk”) received one single increment of light-cured resin composite; group I (“Increments”) received the same composite in three oblique increments; and the group B+S (“Bulk + Self-cured resin composite”). The last one firstly received a f...

Brazilian dental journal

The aim of this study was to characterize a conventional and a pressed porcelain for zirconia cor... more The aim of this study was to characterize a conventional and a pressed porcelain for zirconia core as to biaxial flexural strength (BFS), apparent fracture toughness (FT) and microstructure composition, and to investigate the effect of glaze cooling rate on the BFS of the zirconia/porcelain bilayers. Monolayers of conventional porcelain Vita VM9 and pressed porcelain Vita PM9 (n=15) (12 mm diameter x 1.2 mm thick) were prepared for the BFS test (MPa). Apparent fracture toughness (MPa.m1/2) was measured by indentation technique (n=15). t-Student test was performed for statistical analysis. Scanning electron microscopy and x-ray diffraction were used to analyze the porcelain's microstructure. For the BFS of bilayers, zirconia discs (12 mm diameter x 1 mm thick) (Vita In-Ceram YZ) were veneered with the two porcelains (1 mm thick). After the glaze firing simulation, the specimens were submitted to fast or slow cooling (n=15). Apparent fracture toughness (MPa.m1/2) was measured on t...

Pesquisa Brasileira em Odontopediatria e Clínica Integrada, 2015

Objective: To evaluate the shear bond strength of a recent adhesive system used in the cementatio... more Objective: To evaluate the shear bond strength of a recent adhesive system used in the cementation of zirconia. Material and Methods: Overall, 72 zirconia specimens (Zirconzhan) were divided and randomized into 3 groups according to the type of surface treatment: G1 no treatment + adhesive system; G2 blasted with aluminum oxide + adhesive system and G3 tribochemical treatment (Rocatec Plus) + adhesive system. Half of each group (n = 12) had bond strength evaluated on two occasions: 24 hours after cementation, kept stored in distilled water at 37 ° C without thermal cycling, and after thermal cycling (5000 cycles, 5°C-55°C). Data were analyzed by ANOVA with Tukey's post-test (α≤0.05). Results: At first moment, G1 and G3 showed higher bond strength (8.64 ± 3.43 MPa and 6.55 ± 2.27 MPa) compared to G2, with no statistically significant difference between them. After thermal cycling, G3 showed higher bond strength (7.70 ± 1.82 MPa). Conclusion: Initially, only the adhesive system promoted higher bond strength, but after thermal cycling,bond strength decreased. The best treatment to promote high bond strength to zirconia is to associate tribochemical treatment with the adhesive system; most failures observed after thermal cycling were mixed and cohesive, showing a mechanical imbrication of the adhesive system, suggesting that there is no chemical bond; and the surface of the group with greater bond strength after thermal cycling showed more surface irregularities compared to the other groups.

Análise da influência da variação da composição e sentido de puxamento na microestrutura e no mód... more Análise da influência da variação da composição e sentido de puxamento na microestrutura e no módulo de ruptura (MOR) de compostos de

Disposit ivos LED para polimerização de resinas compost as dent ais: comparação com out ras f ont... more Disposit ivos LED para polimerização de resinas compost as dent ais: comparação com out ras f ont es de luz. Capítulo I: Introdução e Objetivos Dispositivos LED para polimerização de resinas compostas dentais comparação com outras fontes de luz. Capítulo I: Introdução e Objetivos

Clinical Oral Investigations, 2015

This study aims to correlate patient-reported reactions with in vitro analyses of the pH, abrasiv... more This study aims to correlate patient-reported reactions with in vitro analyses of the pH, abrasive quality, and cytotoxicity of four toothpastes. One hundred twenty-one patients received non-identified samples of toothpaste to be used for 6 days and answered a questionnaire about their sensations. In vitro analysis: the pH of toothpastes was measured with a pH meter. The abrasivity of toothpastes was evaluated against composite resin specimens (n = 10). A toothbrushing machine was used to simulate wear, which was indirectly measured by mass loss using a scale. Cell culture media conditioned with toothpaste were used to assess the cytotoxicity. Confluent cells were kept in contact with the conditioned media or control for 24 h. The cell viability was measured using the 3-(bromide, 4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium (MTT)-reduction assay. The obtained data on the pH, weight loss, and cell viability were compared by ANOVA/Tukey&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s tests (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). With the exception of the bleaching effect paste, the Oral B® paste produced the highest frequencies of irritation reports, tooth sensitivity, taste discomfort, and texture discomfort in the clinical study; patients also reported rougher teeth, soft tissue peeling, dry mouth, thrush, tingling, and taste changes in response to this paste. The in vitro analysis demonstrated that Oral B® had the lowest pH, the highest abrasivity, and produced the lowest cell viability (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). Results suggest that low pH toothpastes that are highly abrasive and cytotoxic may cause undesirable reactions in patients. Toothpaste&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s properties should be well known for indication to patient therefore minimizing discomfort reports.

Acta Scientiarum. Health Sciences, 2015

Current study evaluates the mechanical properties (tensile and tear strength) of an acetic-cure s... more Current study evaluates the mechanical properties (tensile and tear strength) of an acetic-cure silicone with the addition of 10 or 20% vol. magnesium silicate. Magnesium silicate was added to the silicone at concentrations of 10 (MS-10) and 20% (MS-20) volume, followed by the analysis of tensile strength, maximal elongation during tensile and tear strength. Results were compared to control group of silicone without additives (CG). Mean rates were determined and compared by analysis of variance and Tukey's test (p < 0.05). Control group had the greatest elongation when subjected to tensile strength (650%), whereas the MS-10 group statistically showed a better tensile strength (8.8 MPa) when compared to CG (7.5 MPa) and MS-20 (7.5 MPa) groups. Both magnesium silicate groups exhibited statistically similar tear strength, whereas MS-20 group demonstrated statistically greater tear strength. The addition of 10% magnesium silicate increased tensile strength, but tear strength and elongation were similar to control. The addition of 20% magnesium silicate did not affect tensile but increased tear strength.

Brazilian Dental Science, 2013

Aim: This work evaluated dental porcelain sintering by CO2 laser irradiation. Methods: Two commer... more Aim: This work evaluated dental porcelain sintering by CO2 laser irradiation. Methods: Two commercial veneering porcelains were used: VM7 and VM9 (VITA Zahnfabrik). Porcelain disks (0.35 mm dia. x 2.0 mm) were sintered by a continuous CO2 laser (Coherent, USA – 35 W e ?= 10.6 ?m) in two irradiances (20 and 23 W/cm2) and exposure times: 5 and 10 min. A control group was sintered in a conventional oven following manufacturer’s instructions. After sintering, one of the disks surfaces was mirror polished. Superficial pores (%) were assessed by images obtained in an optical microscope (100x) submitted to the software Image J analysis. Apparent density was measured by Archimedean’s method. Microhardness and fracture toughness (Indentation Fracture - IF) were determined with a Vickers indenter (Shimadzu). Results: Porosity ranged between 4.0 and 5.9% for irradiated specimens; control group had 6.0 and 4.7% of porosity for porcelain VM7 and VM9 respectively. Density of porcelain VM7 irradi...

Clinical and Laboratorial Research in Dentistry, 2014

This study evaluated the infl uence of 20% sodium ascorbate (SA) and 10% ascorbic acid (AA) hydro... more This study evaluated the infl uence of 20% sodium ascorbate (SA) and 10% ascorbic acid (AA) hydrogels on the microleakage of class V composite restorations after an offi ce bleaching protocol (B). Methods: Sixty bovine incisors were sectioned at one point extending 8 mm from the amelodentinal junction toward the incisal edge, and at a second point extending 2 mm from the amelodentinal junction toward the root apex. Root canals were sealed with a composite and the teeth were divided into 5 groups. In Group C (control group), the teeth were prepared (P; 4 × 3 mm depth × diameter; diamond bur 3131, KG Sorensen), etched, rinsed (ER), submitted to an adhesive system protocol (Ambar, FGM), and restored (R) with a microhybrid composite (Opallis, FGM); In Group IR, the teeth were bleached (B; 2 sessions, 1 week interval, 35% hydrogen peroxide, Whitness HP Blue, FGM) + P + ER + R; In Group SA, teeth were B + P + SA (20%/15 minutes) + ER + R; In Group AA, teeth were B + P + AA (10%/15 minutes) + ER + R; and in Group MR, the teeth were B + stored in water (37°C/14 days) + P + ER + R. Specimens were submitted to an aging process by thermocycling (5 × 10 4 cycles of 5°C and 55°C with a dwelling time of 30 s), varnish-sealed, immersed in basic fuchsin (3 h), washed and sectioned with a diamond disc. Microleakage was measured with the aid of ImageTool  software. ANOVA and Tukey's post hoc test (p < 0.05) were applied. Results: Microleakage (mm) and standard deviations per group were as follows: C, 0.29 (0.06) A ; IR, 1.86 (0.15) C ; SA, 1.08 (0.09) B ; AA, 1.07 (0.10) B ; MR, 1.02 (0.12) B. Conclusions: Bleached teeth submitted to superfi cial treatment with 20% SA and 10% AA applied for 15 minutes prior to restoration presented reduced microleakage, as compared to immediately restored bleached teeth. Use of these antioxidants led to a microleakage comparable to that observed after a waiting period of 14 days prior to restoration. Dental Materials; Dental Leakage; Tooth Bleaching.

Brazilian Oral Research, 2009

The purpose of this study was to evaluate the flexural strength of a direct composite, for indire... more The purpose of this study was to evaluate the flexural strength of a direct composite, for indirect application, that received heat treatment, with or without investment. One indirect composite was used for comparison. For determination of the heat treatment temperature, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed, considering the initial weight loss temperature and glass transition temperature (T g). Then, after photoactivation (600 mW/cm²-40 s), the specimens (10 × 2 × 2 mm) were heat-treated following these conditions: 170ºC for 5, 10 or 15 min, embedded or not embedded in investment. Flexural strength was assessed as a means to evaluate the influence of different heat treatment periods and investment embedding on mechanical properties. The data were analyzed by ANO-VA and Tukey's test (α = 0.05). TGA showed an initial weight loss temperature of 180ºC and DSC showed a T g value of 157°C. Heat treatment was conducted in an oven (Flli Manfredi, Italy), after 37°C storage for 48 h. Flexural strength was evaluated after 120 h at 37°C storage. The results showed that different periods and investment embedding presented similar statistical values. Nevertheless, the direct composite resin with treatments presented higher values (178.7 MPa) compared to the indirect composite resin (146.0 MPa) and the same direct composite submitted to photoactivation only (151.7 MPa). Within the limitations of this study, it could be concluded that the heat treatment increased the flexural strength of the direct composite studied, leading to higher mechanical strength compared to the indirect composite.

Operative Dentistry, 2007

Clinical Relevance Lower depth of cure with the LED unit, compared to the QTH unit, is associated... more Clinical Relevance Lower depth of cure with the LED unit, compared to the QTH unit, is associated with different light scattering due to differences in spectral emission.

Lasers in Medical Science, 2013

This work tested continuous CO 2 laser as a surface treatment to dental porcelain and compared it... more This work tested continuous CO 2 laser as a surface treatment to dental porcelain and compared it to oven glaze (auto-glaze) by means of roughness and color parameters. Three commercial veneering porcelains with different crystalline content were tested: VM7, VM9, and VM13. Porcelain discs (3.5×2.0 mm, diameter × height) were sintered and had one side ground by a diamond bur (45 μm) simulating a chairside adjustment in a clinical office. Specimens (n=7) were divided into the following groups: C-control (no treatment), G-auto-glaze (oven), and L-surface continuous irradiation with CO 2 laser (Gem Laser, Coherent; λ=10.6 μm). Laser was tested in three exposure times (3, 4, or 5 min) and two irradiances (45 and 50 W/cm 2). Roughness parameters (Ra, Rz, and Rpm/Rz) were measured using a rugosimeter (Surftest 301, Mitutoyo). Color differences (ΔE) between the G and L groups were calculated (VITA Easyshade); ΔE values up to 3.3 were considered as not perceivable. A surface analysis was conducted by stereomicroscopy (Olympus SZ61) and SEM (Stereoscan 440, LEO). Crystalline content of specimens from groups C and L (50 W/cm 2 , 5 min) was assessed by X-ray diffraction and then compared. Surface roughness (Ra and Rz) observed for laser-irradiated groups was similar to G for all studied porcelains. Rpm/Rz ratios were near 1.0 for all groups that indicated a sharp ridge profile for all specimens. Only one laser condition studied (50 W/cm 2 , 3 min) from VM7 porcelain resulted in color difference (ΔE=3.5) to G. Specimens irradiated with 50 W/cm 2 for 5 min presented the smoother surface observed by SEM, comparable to G. X-ray diffraction data revealed an increase in leucite crystallite size for VM9 and VM13 porcelains after laser treatment. Regarding roughness, continuous CO 2 laser applied on porcelain surface was as effective as conventional oven auto-glaze.

Journal of the Mechanical Behavior of Biomedical Materials, 2009

The aim of this study was to test the hypothesis that the addition of continuous or milled GdAlO ... more The aim of this study was to test the hypothesis that the addition of continuous or milled GdAlO 3 /Al 2 O 3 fibers to a dental porcelain increases its mechanical properties. Porcelain bars without reinforcement (control) were compared to those reinforced with long fibers (30 vol%). Also, disk specimens reinforced with milled fibers were produced by adding 0 (control), 5 or 10 vol% of particles. The reinforcement with continuous fibers resulted in significant increase in the uniaxial flexural strength from 91.5 to 217.4 MPa. The addition of varied amounts of milled fibers to the porcelain did not significantly affect its biaxial flexural strength compared to the control group. SEM analysis showed that the interface between the continuous fiber and the porcelain was free of defects. On the other hand, it was possible to note the presence of cracks surrounding the milled fiber/porcelain interface. In conclusion, the reinforcement of the porcelain with continuous fibers resulted in an efficient mechanism to increase its mechanical properties; however the addition of milled fibers had no significant effect on the material because the porcelain was not able to wet the ceramic particles during the firing cycle.