Incorporation of chlorhexidine gluconate or diacetate into a glass-ionomer cement: porosity, surface roughness, and anti-biofilm activity

To evaluate the porosity, surface roughness and anti-biofilm activity of a glass-ionomer cement (GIC) after incorporation of different concentrations of chlorhexidine (CHX) gluconate or diacetate. Methods: For the porosity and surface roughness tests, 10 test specimens were fabricated of the GIC Ketac Molar Easy Mix (KM) and divided into the following groups: Control, GIC and 0.5% CHX diacetate; GIC and 1.0% CHX diacetate; GIC and 2.0% CHX diacetate; GIC and 0.5% CHX gluconate; GIC and 1.0% CHX gluconate; GIC and 2.0% CHX gluconate. To evaluate porosity, the test specimens were fractured. The fragments were photographed by scanning electron microscopy (SEM), and the images analyzed with the aid of the software program Image J. The surface roughness (Ra) was obtained by the mean value of three readouts performed on the surface of each specimen, always through the center. To analyze the anti-biofilm activity, strains of S. mutans ATCC 35688 were used, and the groups control and GIC +CHX diacetate 1% were divided as follows: GIC (1 day); GIC (7 days), GIC (14 days), GIC (21 days); GIC+CHX (1 day), GIC+CHX (7 days), GIC+CHX (14 days), GIC+CHX (21 days); GIC+ CHX (1 day), GIC+ CHX (7 days), GIC+ CHX (14 days) and GIC+ CHX (21 days) using 10 test specimens per group. For biofilm growth, the specimens were placed in a vertical position in 24-well plates and incubated overnight 10 times. The culture medium was renewed every 24 hours. The suspension was diluted and seeded on BHI agar for quantification of the bacteria present. For evaluation of all the tests the two-way ANOVA was used, and if necessary, the Tukey test was applied, with a level of significance of 5%. Results: Regarding GIC porosity, the ANOVA showed that the presence of CHX increased the porosity (P< 0.001) proportionally to the increase in concentrations (P= 0.001), without however, presenting interaction between material and concentration (P= 0.705). Regarding the number of pores, a significant increase in pores was observed with the increase in CHX concentration (P= 0.003). The surface roughness test demonstrated no statistically significant effect as to increase or reduction in roughness at any of the CHX concentrations used (P> 0.05). Anti-biofilm activity analysis pointed out a significant effect of the factors material (P= 0.006) and time (P< 0.001), with CHX diacetate CHX presenting greater effectiveness in reducing microorganisms.

Color alteration, hydrogen peroxide diffusion, and cytotoxicity caused by in-office bleaching protocols

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

Dynamics of biofilm formation and the interaction between candida albicans and methicillin-susceptible (MSSA) and -resistant staphylococcus aureus (MRSA)

Coordenação de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)

Effect of surface and heat treatments on the biaxial flexural strength and phase transformation of a Y-TZP ceramic

To evaluate the effect of grinding and airborne-particle abrasion on the biaxial flexural strength (BFS) and phase transformation of a Y-TZP ceramic, and examine whether sintering the veneering porcelain renders the previous heat treatment recommended by the manufacturer unnecessary. Materials and Methods: Lava zirconia specimens (N = 108) were obtained with the following dimensions: 14.0 mm diameter × 1.3 mm thickness (n = 36) and 14.0 mm × 1.6 mm (n = 72). The thicker specimens were ground with diamond burs under irrigation and received (heat-treated groups) or not (non-heat-treated groups) a heat treatment (1000°C for 30 min) prior to the four firing cycles applied to simulate the sintering of the veneering porcelain. All specimens were air abraded as follows (n = 12): 1) 30-μm silica-modified Al2O3 particles (Rocatec Soft); 2) 110-μm silica-modified Al2O3 particles (Rocatec Plus); and 3) 120-μm Al2O3 particles, followed by Rocatec Plus. Three specimens of each group were analyzed by x-ray diffraction (XRD) to assess the monoclinic phase content (%). The BFS test was performed in a mechanical testing machine (Instron 8874). Data (MPa) were analyzed by two-way ANOVA (grinding × airborne-particle abrasion and heat treatment × airborne-particle abrasion) and Tukey's post-hoc test (α = 0.05). The strength reliability was analyzed using the Weibull distribution. Results: Grinding significantly decreased the BFS of the non-heat-treated groups (p < 0.01). Within the ground groups, the previous heat treatment did not influence the BFS (p > 0.05). Air abrasion only influenced the BFS of the ground/heat-treated groups (p < 0.01). For the non-heat-treated groups, the grinding did not decrease the Weibull modulus (m), but it did decrease the characteristic strength (σ0). For Rocatec Soft and 120-μm Al2O3 particles + Rocatec Plus, the heat-treated groups presented lower m and higher σ0 than the ground/non-heat-treated groups. The independent variables did not seem to influence phase transformation. Air-abraded surfaces presented higher monoclinic zirconia content than the as-sintered and ground surfaces, which exhibited similar content. Conclusion: Even under irrigation, grinding compromised the Y-TZP ceramic strength. The sintering of the veneering porcelain rendered the previous heat treatment recommended by the manufacturer unnecessary. Airborneparticle abrasion influenced the strength of heat-treated zirconia.

Effect of surface and heat treatments on the biaxial flexural strength and phase transformation of a y-tzp ceramic

To evaluate the effect of grinding and airborne-particle abrasion on the biaxial flexural strength (BFS) and phase transformation of a Y-TZP ceramic, and examine whether sintering the veneering porcelain renders the previous heat treatment recommended by the manufacturer unnecessary. Materials and Methods: Lava zirconia specimens (N = 108) were obtained with the following dimensions: 14.0 mm diameter × 1.3 mm thickness (n = 36) and 14.0 mm × 1.6 mm (n = 72). The thicker specimens were ground with diamond burs under irrigation and received (heat-treated groups) or not (non-heat-treated groups) a heat treatment (1000°C for 30 min) prior to the four firing cycles applied to simulate the sintering of the veneering porcelain. All specimens were air abraded as follows (n = 12): 1) 30-μm silica-modified Al2O3 particles (Rocatec Soft); 2) 110-μm silica-modified Al2O3 particles (Rocatec Plus); and 3) 120-μm Al2O3 particles, followed by Rocatec Plus. Three specimens of each group were analyzed by x-ray diffraction (XRD) to assess the monoclinic phase content (%). The BFS test was performed in a mechanical testing machine (Instron 8874). Data (MPa) were analyzed by two-way ANOVA (grinding × airborne-particle abrasion and heat treatment × airborne-particle abrasion) and Tukey's post-hoc test (α = 0.05). The strength reliability was analyzed using the Weibull distribution. Results: Grinding significantly decreased the BFS of the non-heat-treated groups (p < 0.01). Within the ground groups, the previous heat treatment did not influence the BFS (p > 0.05). Air abrasion only influenced the BFS of the ground/heat-treated groups (p < 0.01). For the non-heat-treated groups, the grinding did not decrease the Weibull modulus (m), but it did decrease the characteristic strength (σ0). For Rocatec Soft and 120-μm Al2O3 particles + Rocatec Plus, the heat-treated groups presented lower m and higher σ0 than the ground/non-heat-treated groups. The independent variables did not seem to influence phase transformation. Air-abraded surfaces presented higher monoclinic zirconia content than the as-sintered and ground surfaces, which exhibited similar content. Conclusion: Even under irrigation, grinding compromised the Y-TZP ceramic strength. The sintering of the veneering porcelain rendered the previous heat treatment recommended by the manufacturer unnecessary. Airborneparticle abrasion influenced the strength of heat-treated zirconia.

Description of a rat palatal acrylic plate that can be relined

Purpose: The objective of this article is to describe a method to construct an intraoralacrylic device that permits a reline material to be added to the inner surface of thepalatal plate.Materials and Methods: Fifteen 60-day-old adult female rats (Rattus NorvegicusAlbinus Wistar), weighing 150 to 250 g were used for this study and allocated to threegroups (n = 5): G1, animals wearing a heat-polymerized acrylic resin palatal plate(Lucitone 550) for 14 days; G2, animals wearing a heat-polymerized acrylic resinpalatal plate (Lucitone 550) relined with Tokuyama Rebase II for 14 days; and G3,animals maintained under the same conditions as the experimental groups, withoutwearing palatal plates for 14 days. The manipulation of the animals followed theguidelines of the Brazilian College of Animal Experimentation, under the approval ofthe animal ethics committee of the State University of Ponta Grossa. The palatal platescovered the whole palate, were fixed in the molar region with light-cured resin, andwere kept there for 14 days. The animals received a paste diet and water ad libitum.Before and after the trial period, the rats were weighed individually on a precisionscale. Statistical analysis was performed using a two-way analysis of variance (α =0.05) test for comparison of the animals’ weight (g) at time 0 and after 14 days ofusing the palatal plate.Results: No statistical differences were observed regarding the weight of the animalsamong the experimental groups in the study.Conclusions: The individual master impressions, the molar teeth coverage, and themethod of cementation with nonadhesive composite resin provided good stability forthe palatal plate showed in this study, not disturbing the eating habits and nutritionof the animals. This model seems reproducible, offering adequate histopathologicalevaluation. Differences in tissue morphology exist between the animals that used thepalatal plate and the animals that did not use this device. Use of these palatal platescould clarify how prostheses bring changes in the palatal mucosa of users.

Effect of Er:YAG laser and diamond drill on hybrid layer morphology obtained with self-etch adhesive: analysis by SEM and confocal laser scanning microscopy (CLSM)

This study aimed to evaluate the effect of Er:YAG (L) and diamond drills (DD) on: 1) the microshear bond strength (MPa); 2) the adhesive interface of two-step (TS) – Adper Scotchbond Multipurpose and one-step (OS) adhesives – Adper EasyOne, both from 3M ESPE. Material and methods: According to the preparation condition and adhesives, the samples were divided into four groups: DD_TS (control); DD_OS; L_TS and L_OS. 60 bovine incisors were randomly divided into experimental and groups: 40 for microshear bond strength (n = 10) and 20 for the adhesive interface morphology [6 to measure the thickness of the hybrid layer (HL) and length of tags (t) by CLSM (n = 3); 12 to the adhesive interface morphology by SEM (n = 3) and 2 to illustrate the effect of the instruments on dentine by SEM (n = 1)]. To conduct the microshear bond strength test, four cylinders (0.7 mm in diameter and 1 mm in height with area of adhesion of 0.38 mm) were constructed with resin composite (Filtek Z350 XT – 3M ESPE) on each dentin surface treated by either L or DD and after adhesives application. Microshear bond strength was performed in universal testing machine (EMIC 2000) with load cell of 500 kgf and a crosshead speed of 0.5 mm / min. Adhesive interface was characterized by thickness of hybrid layer (HL) and length of tags (t) in nm, with the aid of UTHSCSA ImageTool software. Results: Microshear bond strength values were: L_TS 34.10 ± 19.07, DD_TS 24.26 ± 9.35, L_OS 33.18 ± 12.46, DD_OS 21.24 ± 13.96. Two-way ANOVA resulted in statistically significant differences only for instruments (p = 0.047). Mann-Whitney identified the instruments which determined significant differences for HL thickness and tag length (t). Concerning to the adhesive types, these differences were only observed for (t). Conclusion: It can be concluded that 1) laser Er:YAG results in higher microshear bond strength values regardless of the adhesive system (TS and OS); 2) the tags did not significant affect the microshear bond strength; 3) the adhesive interface was affected by both the instruments for cavity preparation and the type of adhesive system used.

Cuspal movement related to different polymerization protocols

Objective: The aim of this study to investigate the effects of different polymerization protocols on the cuspal movement in class II composite restorations. Materials and methods: Human premolar teeth were prepared with class II cavities and then restored with composite and three-step and two-step etch-and-rinse adhesive systems under different curing techniques (n = 10). It was used a lightemittingdiode curing unit and the mode of polymerization were: standard (exposure for 40 seconds at 700 mW/cm2), pulse-delay (initial exposure for 6 seconds at 350 mW/cm2 followed by a resting period of 3 minutes and a final exposure of 37 seconds at 700 mW/cm2) and soft-start curing (exposure 10 seconds at 350 mW/cm2 and 35 seconds at 700 mW/cm2). The cuspal distance (µm) was measured before and after the restorative procedure and the difference was recorded as cuspal movement. The data were submitted to two-way ANOVA and Bonferroni test (p < 0.05). Results: The type of adhesive system did not influenced the cuspal movement for all the curing methods. Standard protocol showed the highest values of cuspal movement and was statistically different from the pulse-delay and soft-start curing modes. Conclusion: Although the cuspal displacement was not completely avoided, alternative methods of photocuring should be considered to minimize the clinical consequences of composites contraction stress.

Influence of light source and immersion media in surface roughness and hardness of a nanofilled composite resin

The study evaluated the influence of light curing units and immersion media on superficial roughness and microhardness of the nanofilled composite resin Supreme XT (3M/ESPE). Light curing units used were: XL 3000 (3M/ESPE), Jet Lite 4000 Plus (JMorita) and Ultralume Led 5 (Ultradent) and immersion media were artificial saliva, Coke®, tea and coffee, totaling 12 experimental groups. Specimens (10mm x 2mm) were immersed in each respective solution for 5 seconds, three times a day, during 60 days and so, were submitted to measure of superficial roughness (Ra) and Vickers hardness. Data were subjected to two-way ANOVA test (p<0.05). Results showed that only the light source factor showed statistically difference for hardness. It was observed that the hardness of the composite resin Filtek Supreme XT (3M/ESPE) was influenced by the light source (p<0.01) independently of the immersion media (p= 0.35) and the Jet Lite 4000 Plus (JMorita) was the light curing unit that presented lower values. In relation to surface roughness, it was noted no-significant statistical difference for light source (p=0.84), when specimens were immersed in different beverages (p=0.35).

Influence of light curing units and fluoride mouthrinse on morphological surface and color stability of a nanofilled composite resin

Composite resin is a dental material susceptible to color change over time which limits the longevity of restorations made with this material. The influence of light curing units and different fluoride mouthrinses on superficial morphology and color stability of a nanofilled composite resin was evaluated. Specimens (N = 150) were prepared and polished. The experimental groups were divided according to the type of light source (halogen and LED) and immersion media (artificial saliva, 0.05% sodium fluoride solution-manipulated, Fluordent Reach, Oral B, Fluorgard). Specimens remained in artificial saliva for 24-h baseline. For 60 days, they were immersed in solutions for 1 min. Color readout was taken at baseline and after 60 days of immersion. Surface morphology was analyzed by Scanning Electron Microscopy (SEM) after 60 days of immersion. Color change data were submitted to two-way Analysis of Variance and Tukey tests (α = 0.05). Surface morphology was qualitatively analyzed. The factor light source presented no significant variability (P = 0.281), the immersion media, significant variability (P < 0.001) and interaction between factors, no significant variability (P = 0.050). According to SEM observations, no difference was noted in the surface of the specimens polymerized by different light sources, irrespective of the immersion medium. It was concluded that the light source did not influence the color stability of composite, irrespective of the immersion media, and among the fluoride solutions analyzed, Fluorgard was the one that promoted the greatest color change, however, this was not clinically perceptible. The immersion media did not influence the morphology of the studied resin. Microsc. Res. Tech. 77:941–946, 2014. © 2014 Wiley Periodicals, Inc.

Colour stability of acrylic resin denture teeth after immersion in different beverages

The colour stability of acrylic resin denture teeth in beverages was investigated. A spectrophotometer measured the colour (CIE-L*a*b* system) of all specimens after storage in distilled water for 24 h at 37°C (T0). Specimens were then immersed in various beverages. After 15 days (T1) and 30 days (T2), for each material, the mean ∆E values were calculated and compared by two-way ANOVA and Tukey intervals (α=0.05). In the ∆T0T1 period, specimens stored in red wine were significantly discoloured, compared to distilled water (P=0.003). There was no difference between immersion solutions in ∆ET0T2 (P=0.772) and in ∆ET1T2 (P=0.058), and no difference between materials in all immersion periods.

Spectrophotometric evaluation of dental bleaching under orthodontic bracket in enamel and dentin

Aware of the diffusion capacity of bleaching in the dental tissues, many orthodontists are subjecting their patients to dental bleaching during orthodontic treatment for esthetic purposes or to anticipate the exchange of esthetic restorations after the orthodontic treatment. For this purpose specific products have been developed in pre-loaded whitening trays designed to fit over and around brackets and wires, with clinical efficacy proven. Objective: The objective of this study was to evaluate, through spectrophotometric reflectance, the effectiveness of dental bleaching under orthodontic bracket. Material and Methods: Thirty-two bovine incisors crown blocks of 8 mm x 8 mm height lengths were used. Staining of tooth blocks with black tea was performed for six days. They were distributed randomly into 4 groups (1-home bleaching with bracket, 2- home bleaching without bracket, 3- office bleaching with bracket, 4 office bleaching without bracket). The color evaluation was performed (CIE L * a * b *) using color reflectance spectrophotometer. Metal brackets were bonded in groups 1 and 3. The groups 1 and 2 samples were subjected to the carbamide peroxide at 15%, 4 hours daily for 21 days. Groups 3 and 4 were subjected to 3 in-office bleaching treatment sessions, hydrogen peroxide 38%. After removal of the brackets, the second color evaluation was performed in tooth block, difference between the area under the bracket and around it, and after 7 days to verified color stability. Data analysis was performed using the paired t-test and two-way variance analysis and Tukey’s. Results: The home bleaching technique proved to be more effective compared to the office bleaching. There was a significant difference between the margin and center color values of the specimens that were subjected to bracket bonding. Conclusions: The bracket bond presence affected the effectiveness of both the home and office bleaching treatments.

Surface roughness and hardness of yttria stabilized zirconia (Y-TZP) after 10 years of simulated brushing

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Mineral Loss and Morphological Changes in Dental Enamel Induced by a 16% Carbamide Peroxide Bleaching Gel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Push-out bond strength of fiber posts to root dentin using glass ionomer and resin modified glass ionomer cements

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)