Effect of different concentrations of fluoride in dentifrices on dentin erosion subjected or not to abrasion in situ/ex vivo

This in situ/ex vivo study assessed the effect of different concentrations of fluoride in dentifrices on dentin subjected to erosion or to erosion plus abrasion. Ten volunteers took part in this crossover and double-blind study performed in 3 phases (7 days). They wore acrylic palatal appliances containing 4 bovine dentin blocks divided in two rows: erosion and erosion plus abrasion. The blocks were subjected to erosion by immersion ex vivo in a cola drink (60 s, pH 2.6) 4 times daily. During this step, the volunteers brushed their teeth with one of three dentifrices D (5,000 ppm F, NaF, silica); C (1,100 ppm F, NaF, silica) and placebo (22 ppm F, silica). Then, the respective dentifrice slurry (1: 3) was dripped on dentin surfaces. While no further treatment was performed in one row, the other row was brushed using an electric toothbrush for 30 s ex vivo. The appliances were replaced in the mouth and the volunteers rinsed with water. Dentin loss was determined by profilometry and analyzed by 2-way ANOVA/Bonferroni test (alpha = 0.05). Dentin loss after erosive-abrasive wear was significantly greater than after erosion alone. Wear was significantly higher for the placebo than for the D and C dentifrices, which were not significantly different from each other. It can be concluded that the presence of fluoride concentrations around 1,100 ppm in dentifrices is important to reduce dentin wear by erosion and erosion + abrasion, but the protective effect does not increase with fluoride concentration. Copyright (C) 2008 S. Karger AG, Basel.

Effects of Erosive, Cariogenic or Combined Erosive/Cariogenic Challenges on Human Enamel An in situ/ex vivo Study

Individuals with cariogenic diet can also consume erosive beverages. Thus, it seems necessary to investigate a possible caries/erosion interaction. To test in situ/ex vivo a combination of these challenges, 11 subjects wore intraoral appliances containing four enamel blocks randomly assigned. In the first 2-week phase, the appliances were immersed in a cola drink 3 times/day. Two blocks were free of plaque (erosion only: EO) and two blocks were covered with plaque (erosion + plaque: EP). In the second 2-week phase, four new blocks were all covered with plaque and subjected to a sucrose solution 8 times/day. Among the four new blocks, two were also subjected to the cola drink 3 times/day (erosion + caries: EC) while the other two were not (caries only: CO). Thus, in EO, the specimens were fixed at the intraoral appliance level. In EP, EC and CO they were fixed 1.0 mm under the appliance level and covered with plastic meshes for dental plaque accumulation. Changes in wear and hardness were measured. Data were tested using ANOVA and Tukey`s test (p < 0.05). Mean values of wear (mu m) and change in hardness (kp/mm(2)) were: EO 4.82/310; EP 0.14/48; EC 0.34/245; CO 0.42/309. With respect to surface softening, EP and EC differed significantly from each other and from EO and CO, which did not differ significantly. EO presented significantly higher wear than the other groups. The data suggest that the presence of dental plaque can decrease the acid attack of an erosive drink and the association of erosive and cariogenic challenges showed less enamel alterations when compared to erosive or cariogenic challenges only. Copyright (C) 2008 S. Karger AG, Basel

Short-term in situ/ex vivo study of the anticariogenic potential of a resin-modified glass-ionomer cement associated with adhesive systems

Objective: As resin-modified glass-ionomer cement (RMGIC) is an adhesive material, its association to dentin bonding agents (DBAs) was previously proposed. This study investigated the adjunctive behavior of an RMGIC with etch-and-rinse bonding systems under in situ/ex vivo cariogenic challenge. Method and Materials: Bovine enamel blocks (3 3 2 mm) were randomly assigned to group VP, Vitremer + its own primer (3M ESPE); group VSB, Vitremer + Single Bond (3M ESPE); and group VPB, Vitremer + Prime & Bond 2.1 (Dentsply). Two blocks of each group were randomly placed in an acrylic palatal appliance, so each appliance included six blocks. Volunteers (n = 10) wore these appliances according to given instructions to promote a sucrose challenge eight times/day for 15 days. After this period, the blocks were removed from the devices and cleaned, and demineralization was assessed through longitudinal microhardness analysis (Knoop indenter, 25 g/5 s). Data were submitted to three-way ANOVA and Tukey test (P < .05). Results: No treatment was able to completely avoid demineralization. All materials showed a statistically significant difference in mineral loss when the microhardness on the outer enamel was compared with deeper regions (P < .05). Conclusion: Association of the tested RMGICs with etch-and-rinse DBAs did not seem to be more beneficial against caries than the conventional treatment with RMGIC. (Quintessence Int 2010; 41: e192-e199)

Influence of Dental Plaque on Human Enamel Erosion: In Situ/Ex Vivo Study

Purpose: The objective of the present in situ study was to evaluate the influence of dental plaque on human enamel erosion. Materials and Methods: Thirteen volunteers wore acrylic palatal devices with four enamel specimens that were prepared from freshly extracted impacted human third permanent molars (4 x 4 mm), randomly selected and distributed into two vertical rows, corresponding to the following groups: GI, erosion of dental plaque-free samples, and GII, erosion of dental plaque-covered samples. For the formation of dental plaque, the specimens were placed 1 mm below the level of the appliance and covered with a plastic mesh to allow the accumulation of dental plaque. The palatal device was continuously worn by the volunteers for 14 consecutive days and then immersed in a soft drink (Coca-Cola (R), 150 ml) for 5 min, three times a day. Half of the surfaces of specimens were coated with nail varnish for profilometry tests. The study variables included the depth of enamel surface wear (profilometer, vertical ranges in pm) and the percentage of superficial microhardness change (%SMHC). Data were analysed using the t test (P < 0.05). Results: The %SMHC and depth of enamel surface wear were significantly higher for GI (-87.82% +/- 3.66 and 4.70 mu m +/- 1.65) than for GII (-13.79% +/- 4.22 and 0.14 mu m +/- 0.03). Conclusions: It was concluded that the dental plaque formed in situ was able to protect the enamel surface against erosion by a cola soft drink, thus reducing the depth of enamel surface wear and the %SMHC.

Light cola drink is less erosive than the regular one: An in situ/ex vivo study

Objective: This in situ/ex vivo study assessed the erosive potential of a light cola drink when compared to a regular one. Methods: During 2 experimental 14-days crossover phases, eight volunteers wore palatal devices with 2 human enamel blocks. The groups under study were: group light, erosive challenge with light cola drink and group regular, erosive challenge with regular cola drink. During 14 days, erosive challenges were performed extraorally 3X/day. In each challenge, the device was immersed in 150 ml of light cola (group light) or regular cola (group regular) for 5 min. Erosion was analysed by surface profilometry (mu m) and surface microhardness change (%SMH). The data were statistically analyzed using paired t test (p<0.05). Results: Group light (0.6 +/- 0.2 mu m) showed significantly lesser wear than group regular (3.1 +/- 1.0 mu m). There was no significant difference between the groups for the %SMH (group light -63.9 +/- 13.9 and group regular -78.5 +/- 12.7). Conclusions: The data suggest that the light cola drink is less erosive than the regular one. (C) 2008 Elsevier Ltd. All rights reserved.

In situ effect of an erosive challenge on different restorative materials and on enamel adjacent to these materials

Objectives: This in situ study evaluated the effect of an erosive challenge on different restorative materials and on enamel restored with these materials, as well as the ability of these materials to protect the adjacent enamel against erosion. Methods: Ten volunteers wore palatal devices with eight bovine enamel blocks, randomly selected and distributed into two vertical rows, corresponding to the following groups: GI/GV, resin-modified glass ionomer; GII/GVI, conventional glass ionomer; GIII/GVII, composite resin; GIV/GVIII, amalgam. one row (corresponding to groups I-IV) was immersed in a cola drink and the other row (corresponding to groups V-VIII) was subjected to saliva only. The palatal device was continuously worn for 7 days and only half of the appliance (groups I-IV) was immersed in the soft drink (Coca-Cola (R), 150 mL) for 5 min, three times a day. The study variables comprised the wear (profilometry, mu m) and the percentage of surface microhardness change (%SMHC). Data were tested for significant differences by two-way ANOVA and Tukey`s tests (p < 0.05). Results: Considering the restorative materials, for %SMHC and wear, there were no differences among the materials and between the saliva and the erosive challenge. For enamel analyses, the erosive challenge promoted a higher wear and %SMHC of the enamel than did the saliva. There were no significant differences in wear and %SMHC of the enamel adjacent to the different restorative materials. Conclusion: This research data suggest that there is little %SMHC and wear of the studied restorative materials and none of them had a preventive effect against erosion on adjacent enamel, which showed a pronounced wear. (c) 2007 Elsevier Ltd. All rights reserved.

An in situ/ex vivo comparison of the ability of regular and light colas to induce enamel wear when erosion is combined with abrasion

Objective: To evaluate whether the type of cola drink (regular or diet) could influence the wear of enamel subjected to erosion followed by brushing abrasion, Method and !Materials: Ten volunteers wore intraoral devices that each had eight bovine enamel blocks divided into four groups; ER, erosion with regular cola; EAR, erosion with regular cola plus abrasion; EL, erosion with light cola; and EAL, erosion with light cola plus abrasion, Each day for 1 week, half of each device was immersed in regular cola for 5 minutes, Then, two blocks were brushed using a fluoridated toothpaste and electric toothbrush for 30 seconds four times daily, Immediately after, the other half of the device was subjected to the same procedure using a light cola, The pH, calcium, phosphorus, and fluoride concentrations of the colas were analyzed using standard procedures, Enamel alterations were measured by profilometry. Data were tested using two-way ANOVA and Bonferroni test (P < .05), Results: Regarding chemical characteristics, light cola presented pH 3.0, 13.7 mg Ca/L, 15.5 mg P/L, and 0.31 mg F/L, while regular cola had pH 2.6, 32.1 mg Ca/L, 1:8.1 mg P/L, and 0.26 mg F/L, The light cola promoted less enamel loss (EL, 0.36 pm; EAL, 0.39 pm) than its regular counterpart (ER, 0.72 pm; EAR, 0.95 pm) for both conditions, There was not a significant difference (P > .05) between erosion and erosion plus abrasion for light cola, However, for regular cola, erosion plus abrasion resulted in higher enamel loss than erosion alone,.nclusion: The data suggest that light cola promoted less enamel wear even when erosion was followed by brushing abrasion, (Quintessence Int 2011;42:xxx-xx)()

Effect of a 10% carbamide peroxide on wear resistance of enamel and dentine: In situ study

Objectives: This triple-blind, 2 x 2 crossover in situ study, was undertaken to verify whether the wear resistance of enamel and root dentine would be affected by bleaching with a 10% carbamide peroxide agent and a placebo agent. Methods: Thirty slabs of each. substrate (2 mm x 3 mm x 2 mm) were selected for each phase, after flattening and polishing procedures and microhardness test. After a 7-day lead-in period, one specimen of each substrate was randomly bonded on the facial surface of each one of 30 subject`s upper second premolars. The volunteers received instructions on how to perform toothbrushing and application of gel in the tray. Fifteen volunteers bleached their maxillary arch with a 10% carbamide peroxide bleaching agent for a 2-week period, while the remainders used a placebo agent. After a 1-week washout period, a new set of enamel and root dentine slabs were bonded to the premolars and volunteers were crossed over to the alternate agent for 14 days. The resistance of enamel and root dentine to wear following bleaching, toothbrushing and intraoral exposure was measured with a profilometer, using reference areas. Results: For enamel, ANOVA did not demonstrate significant difference between wear provided by placebo and bleaching agent (p = 0.3713), but higher wear depth was observed for bleached root dentine (p = 0.0346). Conclusions: While overnight bleaching caused no alteration in wear resistance of enamel, root dentine showed increased tissue loss. (C) 2008 Elsevier Ltd. All rights reserved.

Potential effect of sodium bicarbonate-containing dentifrice in controlling enamel erosion in situ

Purpose: To assess, by a crossover 2 x 2 in situ study, the speculated protective role of a sodium bicarbonate-containing toothpaste in controlling erosive lesions. Methods: Bovine enamel slabs were sterilized, and submitted to baseline Knoop microhardness measurements. After a 3-day lead-in period, 14 volunteers wore palatal acrylic appliances containing six enamel slabs (three on each side), for 4 consecutive days. On the first day, appliances with contained specimens were placed in the oral cavity to allow salivary pellicle formation. On the subsequent days, half of the enamel slabs were immersed extraorally in a lemonade-like soft drink for 90 seconds, twice daily. On both of these occasions, the appliance was dipped in toothpaste slurry of either a sodium bicarbonate-containing toothpaste or a regular counterpart for 60 seconds. Following a 3-day washout period, a new set of enamel slabs were mounted and the volunteers started the second period using the alternate dentifrice. Results: ANOVA (alpha = 0.05) showed no statistically significant difference between enamel treated with regular and sodium bicarbonate-based dentifrices, regardless of whether specimens were eroded or not (P=0.8430). Acid-challenged specimens revealed lower microhardness values than uneroded samples. (Am J Dent 2008;21:300-302).

Color stability of silorane-based composites submitted to accelerated artificial ageing-An in situ study

Objectives: To assess the in situ color stability, surface and the tooth/restoration interface degradation of a silorane-based composite (P90, 3M ESPE) after accelerated artificial ageing (AAA), in comparison with other dimethacrylate monomer-based composites (Z250/Z350, 3M ESPE and Esthet-X, Dentsply). Methods: Class V cavities (25 mm(2) x 2 mmdeep) were prepared in 48 bovine incisors, which were randomly allocated into 4 groups of 12 specimens each, according to the type of restorative material used. After polishing, 10 specimens were submitted to initial color readings (Easyshade, Vita) and 2 to analysis by scanning electronic microscopy (SEM). Afterwards, the teeth were submitted to AAA for 384 h, which corresponds to 1 year of clinical use, after which new color readings and microscopic images were obtained. The values obtained for the color analysis were submitted to statistical analysis (1-way ANOVA, Tukey, p < 0.05). Results: With regard to color stability, it was verified that all the composites showed color alteration above the clinically acceptable levels (Delta E >= 3.3), and that the silorane-based composite showed higher Delta E (18.6), with a statistically significant difference in comparison with the other composites (p < 0.05). The SEM images showed small alterations for the dimethacrylate-based composites after AAA and extensive degradation for the silorane-based composite with a rupture at the interface between the matrix/particle. Conclusion: It may be concluded that the silorane-based composite underwent greater alteration with regard to color stability and greater surface and tooth/restoration interface degradation after AAA. (C) 2011 Elsevier Ltd. All rights reserved.

Assessing the diurnal evolution of surface radiation balance over the western region of Tropical Atlantic Ocean using in situ measurements carried out during the FluTuA balance Project

In this work, the diurnal evolution of the radiation balance components over the tropical Atlantic Ocean is described and analysed. The analysis is based on measurements carried Out on board a Brazilian Navy ship during the observational campaign of the FluTuA Project (`Fluxos Turbulentos sobre o Atlantico`), from 15 to 23 May 2002. The observations indicated that the albedo responds its expected to atmospheric attenuation effects with a diurnal evolution similar to the Fresnel albedo. In general, the observed longwave radiation values agreed better with the estimated values obtained without longwave reflection. In agreement with the literature, the average surface emissivity was around 0.97. The net radiation, estimated from published equations for albedo, atmospheric transmissivity and surface emissivity, agreed with the observations, indicating that these parameters are representative of the radiometric properties of the air-sea interface in the region between Natal (6 degrees S, 35.2 degrees W) and the Sao Pedro and Sao Paulo Archipelago (1 degrees N, 29.3 degrees W). Copyright (C) 2008 Royal Meteorological Society

Strong quenching of chlorophyll fluorescence in the desiccated state in three poikilohydric and homoiochlorophyllous moss species indicates photo-oxidative protection on highly light-exposed rocks of a tropical inselberg

The three poikilophydric and homoiochlorophyllous moss species Campylopus savannarum (C. Muell.) Mitt., Racocarpus fontinaloides (C. Muell.) Par. and Ptychomitrium vaginatum Besch. grow on sun-exposed rocks of a tropical inselberg in Brazil subject to regular drying and wetting cycles. Effective photo-oxidative protection in the light-adapted desiccated state in all three species is achieved by a reduction of ground chlorophyll fluorescence, F, to almost zero. Upon rewatering, the kinetics of the recovery of F in air dry cushions to higher values is very fast in the first 5min, but more than 80min are needed until an equilibrium is reached gradually. The kinetics were not different between the three species. The three moss species, have a distinct niche occupation and form a characteristic zonation around soil vegetation islands on the rock outcrops, where C. savannarum and R. fontinaloides form an inner and outer belt, respectively, around vegetation islands and P vaginatum occurs as small isolated cushions on bare rock. However, they were not distinguished by the reduction of F in the dry state and the rewetting recovery kinetics and only slightly different in their photosynthetic capacity. Stable isotope ratios (delta C-13, delta N-15) indicate that liquid films of water limiting diffusion of CO2 are important in determining carbon acquisition and suggest that limitation of CO2 fixation by water films must be more pronounced over time in P vaginatum than in the latter species. This is determined by both the micro site occupied and the form of the moss cushions. (c) 2007 Elsevier GmbH. All rights reserved.

Cytogenetic characterization of Metynnis maculatus (Teleostei; Characiformes): the description in Serrasalminae of a small B chromosome bearing inactive NOR-like sequences

Mitotic chromosomes of Metynnis maculatus (KNER 1860) (Teleostei, Characiformes), a fish species that occurs in the Amazon and Parana-Paraguay river basins, were analyzed for the first time by Giemsa and Ag-NOR staining, C-banding and fluorescence in situ hybridization (FISH) with 18S and 5S rDNA sequences. The basic chromosome number of the species is 2n=62 (32M+22SM+4ST+4A) and, in addition to the 62 regular chromosomes, one small acrocentric supernumerary B chromosome was found in part of the specimens analyzed. Four active NORs were present, and constitutive heterochromatin blocks were found in the pericentromeric region of several chromosomes. A heterochromatic block was also present in the interstitial portion of the submetacentric NOR-bearing pair and the B chromosome was entirely heterochromatic. FISH using an 18S rDNA probe confirmed the results obtained with AgNO(3) staining, and an additional signal was also present on the B chromosomes. 5S rDNA sequences mapped only to the largest acrocentric pair. This is the first description of supernumerary B chromosomes in Serrasalminae, and this karyotype characterization may be useful in further studies about chromosome evolution in this fish group.

High frequency of immature dendritic cells and altered in situ production of interleukin-4 and tumor necrosis factor-alpha in lung cancer

Introduction Antigen-presenting cells, like dendritic cells (DCs) and macrophages, play a significant role in the induction of an immune response and an imbalance in the proportion of macrophages, immature and mature DCs within the tumor could affect significantly the immune response to cancer. DCs and macrophages can differentiate from monocytes, depending on the milieu, where cytokines, like interleukin (IL)-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF) induce DC differentiation and tumor necrosis factor (TNF)-alpha induce DC maturation. Thus, the aim of this work was to analyze by immunohistochemistry the presence of DCs (S100+ or CD1a+), macrophages (CD68+), IL-4 and TNF-alpha within the microenvironment of primary lung carcinomas. Results Higher frequencies of both immature DCs and macrophages were detected in the tumor-affected lung, when compared to the non-affected lung. Also, TNF-alpha-positive cells were more frequent, while IL-4-positive cells were less frequent in neoplastic tissues. This decreased frequency of mature DCs within the tumor was further confirmed by the lower frequency of CD14-CD80+ cells in cell suspensions obtained from the same lung tissues analyzed by flow cytometry. Conclusion These data are discussed and interpreted as the result of an environment that does not oppose monocyte differentiation into DCs, but that could impair DC maturation, thus affecting the induction of effective immune responses against the tumor.

In situ X-ray diffraction studies of phase transition in Pb1-x La x Zr0.40Ti0.60O3 ferroelectric ceramics

The temperature dependence of the crystalline structure and the lattice parameters of Pb1-xLaxZr0.40Ti0.60O3 ferroelectric ceramic system with 0.00 x 0.21 was determined. The samples with x 0.11 show a cubic-to-tetragonal phase transition at the maximum dielectric permittivity, Tmax. Above this amount and especially for the x = 0.12 sample, a spontaneous phase transition from a relaxor ferroelectric state (cubic phase) to a ferroelectric state (tetragonal phase) is observed upon cooling below the Tmax. Unlike what has been reported in other studies, the x = 0.13, 0.14, and 0.15 samples, which present a more pronounced relaxor behavior, also presents a spontaneous normal-to-relaxor transition, indicated by a cubic to tetragonal symmetry below the Tmax. The origin of this anomaly has been associated with an increase in the degree of tetragonality, confirmed by the measurements of the X-ray diffraction patterns. The differential thermal analysis (DSC) measurements also confirm the existence of these phase transitions.