Colour stability of temporary restorations with different thicknesses submitted to artificial accelerated aging.

This study evaluated the colour stability of temporary prosthetic restorations with different thicknesses submitted to artificial accelerated aging. The occlusal surfaces of 40 molars were grinded to obtain flat enamel surfaces. Twenty acrylic resin specimens [Polymethyl methacrylate (Duralay) and Bis-methyl acrylate (Luxatemp)] were made with two different thicknesses, 0.5 mm and 1.0 mm. Temporary restorations were fixed on enamel and CIE L*a*b* colour parameters of each specimen were assessed before and after artificial accelerated aging. All groups showed colour alterations above the clinically acceptable limit. Luxatemp showed the lowest colour alteration regardless its thickness and Duralay showed the greatest alteration with 0.5 mm.

The effect of a novel crystallised bioactive glass-ceramic powder on dentine hypersensitivity: a long-term clinical study.

The aim of this comparative clinical study was to evaluate a novel bioactive glass-ceramic (Biosilicate® 1-20 µm particles) to treat dentine hypersensitivity (DH). Volunteers (n = 120 patients/ 230 teeth) received the following treatments: G1-Sensodyne® , G2-SensiKill®, G3-Biosilicate® incorporated in a 1% water-free-gel and G4-Biosilicate® mixed with distilled water at 1:10 ratio. G1 and G3 were applied at home, daily for 30 days; G2 and G4 were applied once a week by a dentist (four applications). A visual analogue scale (VAS) was employed to evaluate pain for each quadrant in one sensitive tooth at baseline, weekly during treatment and during a 6-month follow-up period. Dentine hypersensitivity values (G1/n= 52), (G2/n =62), (G3/n = 59) and (G4/n = 59) were analysed with Kruskal-Wallis/Dunn tests. All the products were efficient in reducing DH after 4 weeks. Among the four materials tested, G4 demonstrated the best clinical performance and provided the fastest treatment to reduce DH pain. Distilled water proved to be an adequate vehicle to disperse Biosilicate®. Low DH scores were maintained during the 6-month follow-up period. The hypothesis that the novel bioactive glass-ceramic may be an efficient treatment for DH was confirmed.

Shear-bond strength between a new format of intra-buccal acrylic bioadhesive drug delivery system and adhesive systems.

AIM: An intra-buccal acrylic bioadhesive device designated for drug programmed release that can stay adhered to dental enamel, and also on removable prosthetic restorations, with preventive and/or therapeutic purpose for a large clinical applications based on polymethyl methacrylate/methyl methacrylate/2 hydroxyethyl methacrylate (PMMA/MMA/HEMA) was developed, using the sodium fluoride as an active principle. This bioadhesive was evaluated for its shear bond strength when bonded with different adhesive systems. METHODS: Two substrates (recently extracted human teeth and acrylic prosthesis basis) were used to obtain the 96 test-specimens. Four adhesive systems (Cyanoacrylate ester, 3M Concise Enamel Bond Resin with or without previous enamel etching, MMA/HEMA or PMMA/MMA/ HEMA) were chosen for the fixation of the bioadhesives to substrate. Artificial saliva or distilled water was used as medium for maintaining the specimens until test. RESULTS: Statistical analysis showed that the interaction bioadhesives/acrylic prosthesis basis/cyanoacrylate ester adhesive was the most resistant to the physical removal by shearing. CONCLUSION: The newly rounded semi-convex format of acrylic device developed in this study presented satisfactory shear bond strength and might contribute to the comfort of intra-buccal use.

Optical transmittance of reflecting wedges.

This study quantified the light intensity transmitted by the reflecting wedges perpendicularly to the growth axis. The results demonstrated that the cervical wedges did reflect the light of 180 degrees and original light intensity diminished by 83.9%. The maximal light intensity transmitted to the resin by the wedge was less than 8% of that receiving direct exposure to the curing wand. Differential measurements made on points closely spaced along the sides of the wedge indicated a maximal intensity at approximately 2 mm from the base of the wedge.

Spectral fluorescence of direct anterior restorative materials.

The fluorescent characteristics of silicate cements, acrylic resins, and composite resins and all anterior restorative materials have been compared with the natural teeth when specimens were submitted to ultra-violet radiation. The effect of glazes on composite resins and of discolouration from ultra-violet radiation on composites and acrylic resins is to reduce the amount of fluorescence of the former and to change the quality of the fluorescence.

Comparative study of the direct-lift and platinum foil techniques in the marginal discrepancy of collarless metal ceramic restorations.

This study was carried out to evaluate the marginal discrepancy of collarless metal ceramic restorations, using a combination of three different techniques to manufacture the porcelain butt margin with two brands of body porcelain. Statistical analysis showed no significant difference between the techniques or brands of body porcelain used in this study.

Capacity of denture plaque/biofilm removal and antimicrobial action of a new denture paste.

The efficacy of a paste for complete dentures was analyzed in terms of denture plaque/biofilm removal and antimicrobial action against specific microorganisms by determination of colony forming units of mutans group streptococci and yeast from 120 full denture wearers with a healthy palatine mucosa. The patients were given a questionnaire to evaluate the experimental product in terms of important characteristics. The paste was widely accepted by the patients, and effective in denture plaque removal and antimicrobial action. The species of yeasts most frequently isolated were C. albicans, C. tropicalis and C. glabrata. We conclude that it is possible for complete denture wearers to keep their dentures clean with the regular use of a paste-like hygienic product.

[In vitro assessment of antibacterial activity of ozonized water against Staphylococcus aureus]. / Avaliação in vitro da atividade antibacteriana da água ozonizada frente ao Staphylococcus aureus.

Staphylococcus aureus belongs to the normal flora of the skin, mucosa and nasopharynx of several animal species, including man, but it is also associated to illnesses such as abscesses, bacteremia, endocarditis and osteomyelitis, besides showing resistance to multiple drugs. The purpose of this paper was to evaluate the disinfecting ability of ozone when dissolved in water. Suspensions of Staphylococcus aureus with concentrations varying from 10(6) to 10(16) microorganisms/ml were prepared. One milliliter of each recently prepared suspension was added to 99 ml of distilled water (with or without previous ozonization) contained in a crystal reactor. Aliquots of 0.1 ml of this new suspension were taken at various time intervals and, then, serially diluted and inoculated on plaques. The data indicated that there was difference in the disinfecting effect when distilled water was used with and without previous ozonization.

Tensile bond strength of a polymeric intra-buccal bioadhesive: the mucin role.

The intra-bucal polymeric bioadhesive systems that can stay adhered to the oral soft tissues for drug programmed release, with the preventive and/or therapeutic purpose have been employed for large clinical situations. A system based on hydroxypropyl methyl cellulose/Carbopol 934TM/magnesium stearate (HPMC/Cp/StMg), was developed with the sodium fluoride as an active principle. This kind of system was evaluated according to its resistance to the removal by means of physical test of tensile strength. Swine buccal mucosa extracted immediately after animals' sacrifice was employed as a substrate for the physical trials to obtain 16 test bodies. Artificial saliva with or without mucin was used to involve the substrate/bioadhesive system sets during the trials. Artificial salivas viscosity were determined by means of Brookfield viscometer, and they showed 10.0 cP artificial saliva with mucin, and 7.5 cP artificial saliva without mucin. The tensile strength assays showed the following averages: 12.89 Pa for the group "artificial saliva with mucin", and 12.35 Pa for the group "without mucin". Statistical analysis showed no significant difference between the assays for both artificial salivas, and we can conclude that the variable mucin did not interfere with the bioadhesion process for the polymeric devices.

Effect of cigarette smoke on color stability and surface roughness of dental composites.

OBJECTIVE: To evaluate the color stability and surface roughness of 3 dental composites subjected to cigarette smoke and brushing. METHODS: Twenty specimens were prepared for each type of restorative material used: nanohybrid (Tetric N-Ceram); hybrid (Z250-3M ESPE) and silorane-based microhybrid (Filtek P90-3M ESPE), which were divided into 2 groups (n=10), according to the type of finishing/polishing received: Group 1 - papers with decreasing abrasive grit and Group 2 - polyester matrix (without polishing). After initial readouts of color (Easy Shade-VITA) and surface roughness (SJ-201P Mitutoyo), specimens were subjected to action of smoke from 20 cigarettes, (Marlboro Red-Philip Morris). After each cigarette, the samples were submitted to brushing in a standardised device. After this, final readouts were taken to calculate change in color (ΔE and ΔL) and roughness (ΔRa), which were statistically analysed (2-way ANOVA, Bonferroni, and Student's-t tests respectively, p<0.05). RESULTS: Tetric N-Ceram presented color change at clinically unacceptable levels (ΔE>3.3) when the polyester strip was used for finishing, a result differing (p<0.05) from those of the other composites, which presented no difference between them (p>0.05). Unpolished composites presented higher Ra values than those that were polished (p<0.05), with exception of the silorane based composite. CONCLUSION: Absence of polishing increases cigarette capacity to stain composites and surface roughness of composites, with exception of the silorane based type.

Evaluación de una resina epóxica experimental como material alternativo para obtención de modelos odontológicos / Evaluation of an experimental epoxy resin as an alternative material for dental casts

El objetivo de este estudio fue comparar la fidelidad de copia y estabilidad dimensional entre modelos de resina epóxica y modelos de yeso (Fuji Rock EP - GC Europe; Implant Stone - Polidental). Fue realizada la impresión de una matriz de acero para obtener 30 especímenes (n=10). La matriz simulaba dos piezas dentarias talladas para recibir coronas totales, sobre éstas fueron adaptados dos copings metálicos con aletas horizontales. Se evaluó al microscopio (Microscopio Measurescope, Nikon) la distancia entre el coping y la línea de terminación de las piezas talladas (en adelante, "desadaptación vertical") y la distancia entre las aletas horizontales de los copings (en adelante, "desadaptación horizontal"), las medidas obtenidas entre la matriz de acero y copings metálicos fueron consideradas como grupo control. Los copings metálicos fueron después adaptados sobre los modelos de yeso y sobre la resina experimental y fue realizada la evaluación al microscopio del mismo modo que el descrito anteriormente. Fueron realizadas 3 mediciones en dos tiempos (24 y 48 horas). Respecto a la desadaptación horizontal, el yeso FujiRock presentó una mejor estabilidad dimensional después de 24 horas, ya que la desadaptación fue similar estadísticamente a la desadaptación de la matriz (control) (p>0,05). Después de 48 horas, todos los grupos presentaron valores similares a la matriz (p>0,05). Respecto a la desadaptación vertical, todos los materiales presentaron diferencia estadísticamente significante en relación a la matriz (p?0,05), sin embargo, no hubo diferencia entre los materiales evaluados (p>0,05). La resina epóxica experimental puede ser una alternativa viable para la obtención de modelos odontológicos...

The aim of this study was to compare the accuracy of surface detail reproduction and dimensional stability of casts made from an experimental epoxy resin and gypsum (Fuji Rock EP - GC Europe; Implant Stone - Polidental). A steel matrix was molded to obtain 30 cast samples (n=10). The matrix simulated two teeth prepared to receive total crowns on which two metal copings with horizontal flaps were adapted. Three readings were performed (Measurescope microscope, Nikon) in order to measure the vertical and horizontal misfit and those readings were used as control. Metal copings were adapted over the gypsum and epoxy resin casts and three measurements were made in two periods (24 and 48 hours). Regarding the horizontal misfit, Fujirock had better dimensional stability after 24 hours, being statistically similar to the matrix (p> 0.05). After 48 hours, all groups had statistically similar values to the matrix (p> 0.05). Regarding the vertical misfit, all materials were statistically different in relation to the matrix (p ? 0.05). However, there was no statistically significant difference between the materials evaluated (p> 0.05). The experimental epoxy resin could be a suitable alternative to obtain dental casts...

Preparation and antimicrobial activity of gelatin microparticles containing propolis against oral pathogens.

Gelatin microparticles containing propolis ethanolic extractive solution were prepared by spray-drying technique. Particles with regular morphology, mean diameter ranging of 2.27 microm to 2.48 microm, and good entrapment efficiency for propolis were obtained. The in vitro antimicrobial activity of microparticles was evaluated against microorganisms of oral importance (Enterococcus faecalis, Streptococcus salivarius, Streptococcus sanguinis, Streptococcus mitis, Streptococcus mutans, Streptococcus sobrinus, Candida albicans, and Lactobacillus casei). The utilized techniques were diffusion in agar and determination of minimum inhibitory concentration. The choice of the method to evaluate the antimicrobial activity of microparticles showed be very important. The microparticles displayed activity against all tested strains of similar way to the propolis, showing greater activity against the strains of E. salivarius, S. sanguinis, S. mitis, and C. albicans.

[Quantitative evaluation of reflectance of some acrylic resins mixed with powdered enamel and/or natural quartz]. / Avaliação quantitativa da refletância de algumas resinas acrílicas misturadas com esmalte e/ou quartzo natural em pós.

Autopolymerizing acrylic resins for temporary prothesis and crown veneering have been mixed with dental enamel and/or quartz in powder form in different percentages, to simulate optical properties of the tooth. The analysis of our measurements of apparent reflectance of those mixings show that is possible to approximate several of those values to the ones corresponding to natural tooth; being sufficient to follow the formulation given++ in this paper.

[Resistance and deformation of acrylic resin reinforced with cut and ground fiberglass. 1. Rupture tension]. / Medidas de resistência e deformação de resina acrílica reforçada com fibras de vidro picadas e moídas: Parte I--Tensão e ruptura.

Traction trials were carried out on acrylic resin test bodies for denture frames reinforced with cut and ground fiberglass, to determine rupture tension. The results demonstrated that: 1--Cut fibers tend to increase the resistance of acrylic to traction forces, and the increase in load percentage of these fibers also increase resistance. 2--This increase was more marked when treatment with SILANE A 174 was combined with the use of cut fibers, at all concentrations tested.

[Resistance and deformation of acrylic resin reinforced with cut and ground fiberglass. 2. Rupture lengthening]. / Medidas de resistência e deformação de resina acrílica reforçada com fibras de vidro picadas e moídas: Parte II--Alongamento de ruptura.

The rupture lengthening test demonstrated the addition of fiberglass to acrylic resin tends to make the test bodies more rigid, making them fracture with a shorter lengthening than unloaded resin. The greatest rigidity was observed with a 20% load.

[Resistance and deformation of acrylic resin reinforced with cut and ground fiberglass. 3. Modus of elasticity]. / Medidas de resistência e deformaaão de resina acrílica reforçada com fibras de vidro picadas moídas: Parte III - Modulo de elasticidade.

With respect to the elasticity module, it was observed that the incorporation of fiberglass to acrylic resin makes the test bodies more rigid, decreasing their rupture lengthening. The presence of fibers confers on the material a greater capacity of elastic recovery.

[Emission microspectrometric study of the amalgam restoration-tooth interface]. / Estudo da interface dente-restauração a amálgama por microespectrometria de emissão.

Optical Emission Microspectroscopy was used to identify the corrosion products in the amalgam tooth interface with and without cavity varnish use in different times. The factor time determined new chemical elements in the older specimens. A major mercury concentration was found in the restoration interface which used cavity varnish, at the initial twenty-four hours. The first corrosion product had the tin in its composition, possibly from the degradation of 2 phase.