Effectiveness of Experimental Whitening Toothpastes Containing Colorants on the Optical Properties of Enamel.

Objective: This in vitro study investigated the whitening potential of experimental toothpastes containing optical colorants in their formulations in comparison with commercial products. The chemical and physical characteristics of the toothpastes, the morphology, and elemental analysis of the enamel surface after treatment were also analyzed. Materials and Methods: One hundred twenty-five bovine incisor teeth were randomly divided into five groups according to the treatment: (i) experimental PHTALOX dental gel (PHT); (ii) experimental blue silica dental gel (SDG); (iii) Sensodyne Whitening Repair & Protect (WRP); (iv) Sensodyne True White (STW); (v) Snow White Toothpaste (SWS). The whiteness index differences (ΔWI D ) and color alteration (CIELab-ΔE, CIEDE2000-ΔE 00) were calculated after color change analysis using a spectrophotometer before and after the enamel treatment (n = 25). The surface and cross-sectional micromorphology were assessed using scanning electron microscopy. The elemental analyses were determined with energy-dispersive X-ray spectroscopy (EDS). The pH, particle size, zeta potential, and polydispersity index of toothpaste were evaluated. Data was statistically analyzed (ANOVA/Tukey, 5%). Results: Whitening toothpastes containing optical colorants were effective for whitening the enamel, as whiter teeth were observed following treatment (higher means of ΔWI D ). In addition, when the parameters ΔE ab and ΔE 00 were evaluated, these toothpastes were graded as very good effectiveness (grade 4). Other toothpastes were graded as 3 (good effectiveness). PHT had a neutral pH and a larger mean particle size (412.8 nm). Elemental analysis demonstrated enamel with a silicon-enriched mineral layer on the enamel surface treated with SDG. The Ca/P ratio after enamel treatment varied from 1.74 (SWS) to 2.04 (SDG and WRP). Conclusions: Experimental whitening toothpastes containing optical colorants are effective at bleaching the enamel. The synergism among the different parameters analyzed seems to positively affect the color change after brushing with whitening toothpastes containing optical colorants.

Enamel remineralization and surface roughness after treatment with herbal-containing toothpastes.

BACKGROUND: Oral care products containing bioactive agents obtained from extracts of plant drugs were launched. This in vitro study investigated the effects of herbal-containing toothpastes associated or not with fluoride to remineralize the enamel after cariogenic challenge with pH cycling. The chemical and physical factors of toothpastes and the enamel surface roughness after brushing were also analyzed. MATERIAL AND METHODS: Sixty bovine enamel blocks were obtained and divided into 3 thirds: intact (untreated), demineralized (artificial caries lesion), and treated (caries lesion, pH cycling, and brushing with toothpastes). Toothpastes containing herbal compounds contained no fluoride [Galla chinensis (GCH)], low-F concentration [D'Or (DOR); Herbal Bliss (HBL)], or a different fluoride type [Elmex Anticaries (EAC)]. The results were compared to NaF-containing toothpastes: 1450 and 5000 ppm. Enamel blocks were brushed with the toothpastes using a pH-cycling model (7 days). The Knoop hardness (25g/10s) of the surface and the longitudinal sections were then evaluated. The percentage of surface hardness recovery (%SHR) was calculated. The enamel surface roughness, pH, particle size, zeta potential, and polydispersity index of toothpaste slurries were also evaluated. Data were statistically analyzed (α=5%). RESULTS: No significance was observed when %SHR was compared (p>0.05). DOR, GCH, and HBL were more effective in remineralizing the enamel subsurface. Significantly higher surface roughness was observed when treated with EAC and GCH (p<0.05). CONCLUSIONS: All toothpastes were able to remineralize the enamel, especially the subsurface, with results equal or better than that of standard toothpastes. Key words:Enamel, hardness, roughness, toothpaste, tooth remineralization.

Effects of age condition on the distribution and integrity of inorganic fillers in dental resin composites.

OBJECTIVES: The aim of this study is to evaluate the distribution of the filler size along with the zeta potential, and the integrity of silane-bonded filler surface in different types of restorative dental composites as a function of the material age condition. MATERIALS AND METHODS: Filtek P60 (hybrid composite), Filtek Z250 (small-particle filled composite), Filtek Z350XT (nanofilled composite), and Filtek Silorane (silorane composite) (3M ESPE) were tested at different stage condition (i.e., fresh/new, aged, and expired). Composites were submitted to an accelerated aging protocol (Arrhenius model). Specimens were obtained by first diluting each composite specimen in ethanol and then dispersed in potassium chloride solution (0.001 mol%). Composite fillers were characterized for their zeta potential, mean particle size, size distribution, via poly-dispersion dynamic light scattering. The integrity of the silane-bonded surface of the fillers was characterized by FTIR. RESULTS: The material age influenced significantly the outcomes; Zeta potential, filler characteristics, and silane integrity varied both after aging and expiration. Silorane presented the broadest filler distribution and lowest zeta potential. Nanofilled and silorane composites exhibited decreased peak intensities in the FTIR analysis, indicating a deficiency of the silane integrity after aging or expiry time. CONCLUSION: Regardless to the material condition, the hybrid and the small-particle-filled composites were more stable overtime as no significant alteration in filler size distribution, diameter, and zeta potential occurred. A deficiency in the silane integrity in the nanofilled and silorane composites seems to be affected by the material stage condition. CLINICAL SIGNIFICANCE: The materials conditions tested in this study influenced the filler size distribution, the zeta potential, and integrity of the silane adsorbed on fillers in the nanofilled and silorane composites. Thus, this may result in a decrease of the clinical performance of aforementioned composites, in particular, if these are used after inappropriate storage conditions.

Polymerization kinetics and polymerization stress in resin composites after accelerated aging as a function of the expiration date.

OBJECTIVES: To determine the effect of material condition (new, aged, and expired) on the polymerization kinetics and polymerization stress of different classifications of dental composites. MATERIALS AND METHODS: Specimens were obtained according to the following factors: Composites: (3M ESPE) Filtek P60, Filtek Z250, Filtek Z350XT, and Filtek Silorane; and Material conditions: new, aged, and expired. The syringe composites underwent an accelerated aging protocol (Arrhenius model) representing approximately 9 months of aging. Infrared (IR) spectra were obtained kinetically and were analyzed for: maximum conversion rate (%/s), time into exposure when maximum rate occurred (s), conversion at maximum rate (%), and total conversion (%) at 90 s by comparison of absorption IR peak ratios before and after polymerization. Polymerization was evaluated at the bottom surface of 2.0 mm-thick specimens. Polymerization stress was determined in a tensilometer, inserting the composite between acrylic rods fixed to clamps in a universal test machine and dividing the maximum load recorded by the rods cross-sectional area. Polymerization stress (MPa) was calculated at 300 s. Data were statistically analyzed by two-way ANOVA and Tukey's post hoc test (α=0.05). RESULTS: The majority of the polymerization kinetic parameters were not influenced by the material condition. Silorane composite presented significantly lower conversion rate and lower conversion at the maximum rate when expired (p<0.05). The nanofilled composite (Filtek Z350XT) presented a significantly higher total conversion when aged and expired compared to the new one (p>0.05). In all conditions, Filtek Z350XT and Filtek Silorane presented significantly lower conversion rates (p < 0.05). Filtek Silorane also exhibited the lowest stress, irrespective of the material condition (p<0.05). The polymerization stress was not influenced by the material condition (p>0.05). CONCLUSIONS: Most of the kinetic parameters are not influenced by the material condition. Filtek P60 and Filtek Z250 are more stable as both composites present similar polymerization kinetic results, irrespective of the material condition. Silorane composite presents lower stress values among the tested materials in all conditions. Aging does not affect stress development in restorative composites.

Micro-sized erosions in a nanofilled composite after repeated acidic beverage exposures: consequences of clusters dislodgments

Objective: To evaluate the hardness (KHN), color stability (DE), and superficial micromorphology of two categories of composites after immersion in either distilled water or grape juice for up to 45 days. MATERIAL AND METHODS: Cylindrical specimens (6 mm diameter x 2 mm thick) were obtained according to the factors: composite [Opallis (FGM) and Filtek Z350XT (3M ESPE)]; immersion solution (distilled water and grape juice); and evaluation time: 24 h and 7, 14, 21, 28, and 45 days. After photoactivation, the specimens were stored at 37ºC for 24 h. KHN (50 g/15 s) and ΔE were then repeatedly assessed according to the immersion solutions. Data were analyzed (three-way ANOVA/Tukey's test). Scanning electron microscopy (SEM) topographic analysis was also performed. RESULTS: In general, KHN of both composites reduced after 24 h, irrespective of the immersion solution and time. A significantly lower KHN was noted for Opallis compared with Filtek Z350XT in all parameters. An increase in ΔE over time was noted for both composites, irrespective of the immersion solution. Significantly higher ΔE was noted for Filtek Z350XT immersed in grape juice compared with Opallis, regardless of the evaluation time. The grape juice caused significantly higher DE compared with water in all periods. SEM analysis showed eroded areas for Filtek Z350XT but not for Opallis. CONCLUSIONS: The compositions and immersion solutions influence the composite hardness and the color stability. In spite of the higher hardness, the nanofilled composite is more susceptible to color change than the microhybrid when immersed in an acidic dyed solution. .

Micro-sized erosions in a nanofilled composite after repeated acidic beverage exposures: consequences of clusters dislodgments.

OBJECTIVE: To evaluate the hardness (KHN), color stability (DE), and superficial micromorphology of two categories of composites after immersion in either distilled water or grape juice for up to 45 days. MATERIAL AND METHODS: Cylindrical specimens (6 mm diameter x 2 mm thick) were obtained according to the factors: composite [Opallis (FGM) and Filtek Z350XT (3M ESPE)]; immersion solution (distilled water and grape juice); and evaluation time: 24 h and 7, 14, 21, 28, and 45 days. After photoactivation, the specimens were stored at 37 ºC for 24 h. KHN (50 g/15 s) and ΔE were then repeatedly assessed according to the immersion solutions. Data were analyzed (three-way ANOVA/Tukey's test). Scanning electron microscopy (SEM) topographic analysis was also performed. RESULTS: In general, KHN of both composites reduced after 24 h, irrespective of the immersion solution and time. A significantly lower KHN was noted for Opallis compared with Filtek Z350XT in all parameters. An increase in ΔE over time was noted for both composites, irrespective of the immersion solution. Significantly higher ΔE was noted for Filtek Z350XT immersed in grape juice compared with Opallis, regardless of the evaluation time. The grape juice caused significantly higher DE compared with water in all periods. SEM analysis showed eroded areas for Filtek Z350XT but not for Opallis. CONCLUSIONS: The compositions and immersion solutions influence the composite hardness and the color stability. In spite of the higher hardness, the nanofilled composite is more susceptible to color change than the microhybrid when immersed in an acidic dyed solution.

Effects of curing protocols on fluid kinetics and hardness of resin cements.

The effects of polymerization protocols on water sorption/solubility, the diffusion coefficient (D), the flux (J), and the hardness (KH) of two resin cements were evaluated. The materials were manipulated and divided into three groups (n=6) according to the curing protocol: PA=photoactivation (40 s); DP=delayed photoactivation (10 min self-curing plus 40 s photoactivated); CA=chemical activation. After desiccation, the specimens were weighed, stored in water (37ºC), evaluated over 28-days, and hardness recorded. Chemical activation resulted in lower net water uptake, D, and J for RelyX ARC (RX). For Variolink II (VL), CA yielded equivalent D and lower J; however, photoactivation resulted in lower net water uptake. Hardness of VL was less affected by the water storage, irrespective of the polymerization protocol. Considering the water diffusion parameters, VL demonstrated immediate photoactivation dependence; for RX, a chemical activation. Different polymerization protocols affect the fluid kinetics and the hardness of the resin cements tested.

Prevalence of enamel defects in permanent teeth of patients with complete cleft lip and palate.

Objective : To evaluate the prevalence, types, location, and characteristics of enamel defects in anterior permanent teeth of patients with complete unilateral and bilateral cleft lip and palate, as well as the relation with the cleft. Setting : Hospital for Rehabilitation of Craniofacial Anomalies, Bauru, São Paulo, Brazil. Participants : Eighty patients of both genders, 12 years and older, with unilateral or bilateral cleft lip and palate. Methods : A single examiner carried out clinical examination under artificial light with a dental probe and mirror after drying teeth according to the modified DDE index. Results : Seventy-four of 80 patients presented with at least one tooth affected by enamel defects: 165 of 325 evaluated teeth (50.8%) presented enamel defects, with hypoplasia being the most prevalent (50.7%), followed by diffuse opacity (23.1%) and demarcated opacity (18.4%). The most affected tooth was 21 (36.5%), followed by 11 (34%), located at the middle (40%) and incisal (33%) thirds. Most defects occur at the buccal surface (47.7%), followed by the distal (22.7%), the mesial (19%), and the palatal (10.6%) surfaces. A significant relationship was found between the cleft side and enamel defects. Conclusion : Upper anterior teeth of patients with complete cleft lip and palate present a high prevalence of enamel defects; the highest percentage on the cleft side suggests that the cleft does influence the occurrence of enamel defects in permanent teeth.

Solvent retention of contemporary commercial dentin bonding agents in a demineralized dentin matrix.

OBJECTIVES: Solvents are ingredients in dentin-bonding agents (DBAs) that are essential to obtain efficient adhesion to dentin under wet-technique bonding protocol. However, an excess of solvents can compromise bonding durability. This study aimed to assess the retention of solvents present in different DBAs after their application to a demineralized dentin matrix. METHODS: Thirty-six specimens of bovine dentin were demineralized for 7 days in 0.5M EDTA and divided into six groups n=6 (Scotchbond primer, Adper Single Bond 2, Excite, AdheSE primer, Prime & Bond NT and Xeno III). These specimens were individually saturated by the systems for 5 min and then kept in vials protected against light exposure. Each specimen was measured using a digital balance and then measured at the following intervals 10, 20, 30 sec, 1, 2 and 5 min thereafter. Data were analyzed by two-way ANOVA and Tukey tests (alfa=.05). RESULTS: There were significant differences evident in Excite, Prime & Bond NT at 2 and 5 min, respectively. There was no significant interaction between materials and time in all experimented time evaluated. The amount of solvent spontaneously evaporated was limited even in acetone-based specimens. CONCLUSIONS: After DBAs are applied, professionals may facilitate their evaporation, since spontaneous evaporation is limited.

Os princípios gerais dos preparos cavitários para restaurações diretas podem ser considerados após 100 anos? / Do biomechanical principles of cavity preparation to direct restorations should be considered atfer 100 years?

O avanço da Odontologia rumo à ciência foi iniciado por Black³ que, há mais de 100 anos, desenvolveu e classificou os preparos cavitários de forma compatível com as lesões cariosas e com os materiais restauradores existentes na época. Naquele período, o amálgama predominava como material restaurador, o que exigia um maior envolvimento da estrutura dentária sadia e a confecção de preparos cavitários retentivos para a adaptação desse material. Com o conhecimento do mecanismo de ação do flúor no processo de remineralização das lesões cariosas e o advento dos materiais adesivos, os preparos cavitários passaram a ser mais conservadores, preservando a estrutura dentária hígida. Contudo, esse novo conceito da Dentística Contemporânea ainda requer a obediência de uma série de princípios biológicos e mecânicos durante a confecção dos preparos cavitários, tornando-se necessário adequá-los às condições atuais

Shear bond strength of resin composite to enamel treated with Er: YAG laser and phosphoric acid

The purpose of this work was to evaluate the shear bond strength of resin composite to enamel treated with Er:YAGlaser. It was used 33 human third molars. After the dental crowns cutting, the mesial and distal surfaces were embeddedperpendicularly to the PVC cylinders long axis. Enamel was ground and the samples were randomly divided into 6 groups:G1- phosphoric acid (control), G2- Er:YAG laser (60mJ/10Hz), G3- Er:YAG (100mJ/10Hz), G4- Er:YAG (60mJ/10Hz+ acid), G5- Er:YAG (100mJ/ 10Hz + acid), G6- Er:YAG (80mJ/2Hz). In all groups, Single Bond was used and resincomposite cylinders (Z100) were prepared. The samples were stored in distilled water at 37oC for 24 hours and submittedto shearing test. G1 presented bond strength values significantly higher than G2, G3 and G6. The groups irradiated onlywith Er:YAG laser, in different intensities and frequencies, were equivalent as for the bond strength values. The groupstreated with laser + acid presented strength values statistically equal to those of the control group. The enamel treatmentwith phosphoric acid, or its association with laser, is important to obtain good bond. The use of Er: YAG laser alone isnot recommended, considering the conditions tested in this study.

Objetivou-se avaliar a resistência adesiva da resina composta ao esmalte condicionado com Er:YAG laser, através do teste de cisalhamento. Foram utilizados 33 terceiros molares humanos. Após o seccionamento das coroas dentárias, as faces mesial e distal foram incluídas perpendiculares ao longo eixo de cilindros de PVC. O esmalte foi planificado com lixa 600 e os espécimes aleatoriamente divididos em 6 grupos: G1- ácido fosfórico (controle), G2- Er:YAG laser(60mJ/10Hz), G3- Er:YAG (100mJ/10Hz), G4- Er:YAG (60mJ/10Hz + ácido), G5- Er:YAG (100mJ/ 10Hz + ácido), G6-Er:YAG (80mJ/2Hz). Em todos os grupos, o sistema adesivo Single Bond foi aplicado e os cilindros de resina composta (Z100) confeccionados. Os espécimes foram armazenados em água destilada a 37°C por 24h e submetidos ao teste de cisalhamento. O G1 apresentou valores de resistência adesiva significantemente superiores aos grupos G2, G3 e G6.Os grupos irradiados apenas com Er: YAG laser, nas diferentes intensidades e freqüências, equivaleram-se quanto aos valores de resistência adesiva. Os grupos tratados com laser + ácido apresentaram valores de resistência estatisticamente iguais ao grupo controle. O tratamento do esmalte com ácido fosfórico, ou a sua associação com laser, é importante para a obtenção de uma boa adesão. A utilização somente do Er: YAG laser não é recomendada, considerando-se as condições testadas neste estudo.

Influence of light-curing sources on polymerization reaction kinetics of a restorative system.

PURPOSE: To determine the effect of using a variety of commercial light-curing units on polymerization of a dentin-bonding agent (Adper Single Bond) and of a resin composite (Filtek Z250). METHODS: Infrared (IR) spectra were obtained kinetically at one scan/second at 2 cm(-1) resolution for a period of 5 minutes and were analyzed for: maximum conversion rate (%/s), time into exposure when maximum rate occurred (seconds), conversion at maximum rate (%), and total conversion (%) at 300 seconds by comparison of aliphatic-to-aromatic absorption IR peak ratios, before and after polymerization. Light units used were: QTH 540 mW/cm2 (XL3000); LED 750 mW/cm2 (Elipar FreeLight 2); PAC 2,130 mW/cm2 (ARC II). Exposure followed manufacturers' recommendations: dentin bonding agent for 10 seconds, RC for 20 seconds (QTH), and 10 seconds (LED and PAC). Polymerization kinetics was evaluated at the bottom surface (2.5 mm thick) for the resin composite and as a thin film for the dentin bonding agent on the diamond surface of an attenuated total reflectance accessory in the IR spectrometer. Values (n = 5) were compared using ANOVA and Tukey's pairwise post-hoc test: pre-set alpha 0.05. RESULTS: PAC produced the highest total conversion and conversion rate for the resin composite (P < 0.05). Total conversion was lower for dentin bonding adhesive using PAC than with LED or QTH (P < 0.05). LED provided the highest proportion of conversion at the maximum rate with respect to conversion at 300 seconds for both materials. QTH demonstrated the lowest maximum rate value that occurred at a longer time into exposure (P < 0.05). Polymerization kinetic parameters varied greatly between the restorative materials as well as among light-curing unit types when compared to values observed when using a QTH light as control.

A new technique for assessing hybrid layer interfacial micromorphology and integrity: two-photon laser microscopy.

PURPOSE: This study describes a two-photon laser fluorescence microscopy technique developed to evaluate the interfacial micromorphology of the hybrid layer in bonded restorations. MATERIALS AND METHODS: Micropermeability of the hybrid layer was characterized by means of simultaneously contrasting a dye-containing adhesive with a differently colored dye placed into the pulp chamber and allowed to diffuse toward the different-colored hybrid layer. A fluorescent red dye (rhodamine B) was incorporated into a commercial dentin bonding agent. Class I preparations (margins in enamel) were made on extracted human third molars. The teeth were restored using conventional methods: bonding agent, composite, finishing, and polishing. An aqueous solution of a yellow/green dye (fluorescein) was then placed into the pulp chamber for 3 h, allowing time to diffuse toward the different-colored bonded interface. The teeth were then embedded, sectioned, and microscopically analyzed using two-photon laser microscopy at 40X magnification. RESULTS: Subsurface fluorescent imaging using this technique enabled interfacial micromorphology to be characterized at submicrometer resolution and provided high-contrast images. The quality of surrounding structures and potential presence of gaps were also precisely assessed. CONCLUSION: Two-photon laser microscopy provided high quality, high-resolution images of the bonded interface and surrounding areas, allowing accurate qualitative and quantitative analysis of the structure and integrity of the hybrid layer.

Factors affecting use of fluorescent agents in identification of resin-based polymers.

PURPOSE: The present study is a compilation of methodologies developed in order to evaluate the effects of addition of a fluorescent agent, rhodamine B, to resin-based materials. The intent of the work was to develop a systematic methodology that accounts for variables not shown to be of concern in past testing, but may significantly affect interpretation of the resulting images and material properties. MATERIALS AND METHODS: Different methodologies were specifically developed to evaluate factors affecting the use of the fluorescent agent rhodamine B in the identification of resin-based materials. The influence of dye concentration was evaluated with respect to adhesive polymerization reaction kinetics and bond strength of the resin into which the dye is added. The pH of the dye-solvent solution was also considered. Additionally, the mass and percentage of rhodamine B leached into different media over time was determined. RESULTS: It was demonstrated that a specific dye must be used with caution, and the concentration of a fluorescent agent is important with respect to both the conversion and bond strength of the resin to which the dye is added. An alcohol-based dye solution also produced an extremely high amount of dye leaching from polymerized specimens. The adhesive pH was not altered. CONCLUSION: The standardized methodology developed here to analyze restoration interfaces using a fluorescent dye can lessen the impact of variables when interpreting results.

Bond strength of resin-based restorations polymerized with different light-curing sources.

PURPOSE: To evaluate the influence of different light-curing units on microtensile bond strength of resin composite restorations. MATERIALS AND METHODS: Standardized Class I preparations (6.0 x 4.5 mm, 2.5 mm deep) were made in extracted human third molars after abrading the cusps. Resin was inserted in bulk using a 3M ESPE restorative system [Adper Single Bond (DBA)/ Filtek Z250 (RC)]. Both materials were polymerized using different light-curing units: QTH at 540 mW/cm(2) (XL 3000, 3M ESPE); LED at 750 mW/cm(2) (Elipar FreeLight2, 3M ESPE); PAC at 2130 mW/cm(2) (Arc Light II, Air Techniques). Nine different light combinations were developed to polymerize both DBA and RC: QTH/QTH; QTH/LED; QTH/PAC; LED/LED; LED/QTH; LED/PAC; PAC/PAC; PAC/QTH; PAC/LED. Restored teeth were stored in distilled water for 24 h at 37 degrees C and then sectioned, yielding stick-shaped specimens with a bonded area of approximately 0.9 mm(2). Specimens were assessed in a testing machine at a crosshead speed of 1 mm/min. The results were analyzed using two-way ANOVA and Tukey's test at a pre-set alpha = 0.05. RESULTS: The combinations PAC/QTH and QTH/QTH presented the highest bond strength values, and LED/QTH the lowest (p < 0.05). Significantly lower values were observed in combinations when the LED light was used to polymerize DBA compared to QTH and PAC lights, irrespective of the light source used to polymerize RC (p < 0.05). Same light combinations presented similar bond strength values. CONCLUSIONS: Different light sources influence restoration bond strength. Bond strength is more dependent on the light source used for DBA than for curing RC.

Fotoativação: estágio atual LED: classificação e características / Photoactivation: an update LED: classification and characteristics

Os aparelhos fotoativadores com lâmpada halógena têm sido amplamente utilizados para polimerizar materiais resinosos. No final dos anos 90 surgiram aparelhos LED (1ª geração) que se mostraram pouco efetivos. Posteriormente surgiram os 2ª geração com alta densidade de potência (alguns em torno de 1.000 mW/cm2). Mas, apesar desta evolução, eram necessários aparelhos capazes de fotoativar materiais que contivessem diferentes fotoiniciadores, já que o espectro de irradiância destes primeiros aparelhos era estreito, embora coincidente com a absorvância da canforoquinona. Desta forma, a recém-lançada 3ª geração apresenta, além de LEDs que emitem luz azul, LEDs que emitem luz violeta. Os aparelhos a serem lançados devem ser mais efetivos na polimerização dos materiais restauradores, independente do fotoiniciador contido nos materiais.

Quartz-tungsten halogen lights have been used to polymerize resin materials. A new technology was developed to polymerize these materials, called first-generation LED lights. These lights were found to be less effective and a new generation came on the market (second-generation). These lights provided a very high power density (around 1.000mW/cm2). Despite this evolving technology, it was necessary to produce LED units able to polymerize all materials, irrespective of the photoiniciator, due to the narrow spectrum provided by these lights, similar to camphorquinone absorbance. Third-generation LED light was developed and included, not only blue LED’s, but also LED’s providing violet light, thus curing all materials. Light sources to be launched might be more effective to polymerize composites, regardless the photoiniciator molecule.

Evaluation of the effect of water-uptake on the impedance of dental resins.

UNLABELLED: Electrical impedance spectroscopy (EIS) offers a quantitative method of measuring the stability of resin films in aqueous solution over time. PURPOSE: The purpose of this study was to measure the EIS of five experimental dental adhesive films (ca. 17 microm thick) of increasing hydrophilicity (ranked by their Hoy's solubility parameters), and how much these values change over 3 weeks in aqueous buffer. METHODS: The resin films were placed in a U-shaped chamber and a pair of Ag-AgCl electrodes was used for EIS. The EIS results were confirmed by immersing the films in 50% AgNO3 for 24 h to trace the distribution of any water absorption into the resins by TEM observations. RESULTS: The resistance (Rr) of the resins 1-4 films increased most during the first day, and varied from 1x10(11) ohm for resin 1, to 40Omega for resin 5 at day 1. The day 1 Rr values of resins 1-4 were inversely proportional to their Hoy's solubility parameter for hydrogen bonding forces. Electrical impedance values of resins 1-3 and 5 varied widely but were relatively constant over time, while those of resin 4 decreased more than 99% from day 1 to 21 (p<0.05). Capacitance (Cr) of films of resins 1-4 all increased over the first day and then were relatively unchanged over the 20 days (except for resin 4 that continued to increase) and were between 0.01 and 1 nF. Silver uptake by TEM revealed the development of water-filled branching structures that formed in resins 4 and 5 over time.

Water sorption/solubility of dental adhesive resins.

OBJECTIVES: This study evaluated the water sorption, solubility and kinetics of water diffusion in commercial and experimental resins that are formulated to be used as dentin and enamel bonding agents. METHODS: Four commercial adhesives were selected along with their solvent-monomer combination: the bonding resins were of Adper Scotchbond Multi-Purpose (MP) and Clearfil SE Bond (SE) systems, and the "one-bottle" systems, Adper Single Bond (SB) and Excite (EX). Five experimental methacrylate-based resins of known hydrophilicities (R1, R2, R3, R4 and R5) were used as reference materials. Specimen disks were prepared by dispensing the uncured resin into a mould (5.8mm x 0.8mm). After desiccation, the cured specimens were weighed and then stored in distilled water for evaluation of the water diffusion kinetics over a 28-day period. RESULTS: Resin composition and hydrophilicity (ranked by their Hoy's solubility parameters) influenced water sorption, solubility and water diffusion in both commercial and experimental dental resins. The most hydrophilic experimental resin, R5, showed the highest water sorption, solubility and water diffusion coefficient. Among the commercial adhesives, the solvated systems, SB and EX, showed water sorption, solubility and water diffusion coefficients significantly greater than those observed for the non-solvated systems, MP and SE (p<0.05). In general, the extent and rate of water sorption increased with the hydrophilicity of the resin blends. SIGNIFICANCE: The extensive amount of water sorption in the current hydrophilic dental resins is a cause of concern. This may affect the mechanical stability of these resins and favor the rapid and catastrophic degradation of resin-dentin bonds.

Use of fluorescent compounds in assessing bonded resin-based restorations: a literature review.

OBJECTIVES: This work reviews fundamental concepts involved with fluorescent imaging in the dental materials field. DATA: Fluorescent dyes have been widely used: incorporated into adhesive system components, placed in the pulp chamber and allowed to diffuse toward the restorative interface, as well as used as a visible tracer in microleakage tests. CONCLUSIONS: Although use of fluorescent imaging has substantially contributed to the existing knowledge base, there is no standardized methodology used, and as a result, interpretation of study results as well as comparison of results among studies remains questionable.

Efficacy of composite surface sealers in sealing cavosurface marginal gaps.

OBJECTIVES: The ability of commercially available composite surface sealers to penetrate and seal a controlled gap formed in all-enamel margin, Class V in vitro resin composite restorations in human bicuspids was examined. METHODS: A fluorescent red dye (Rhodamine B) was incorporated to a variety of commercially available composite surface sealers. The teeth were restored using acid etching, a dentin bonding agent, and a photo-activated microfilled composite, finished, polished, and sealed. The teeth were thermocycled and then immersed in an aqueous solution of a green fluorescent dye (Dextran-Fluorescein) to evaluate the sealing ability and penetration of surface sealers into the controlled gaps formed at unbonded margins. Teeth were embedded, sectioned, and images recorded using confocal microscopy. RESULTS: All sealers leaked, and use of a dentin-bonding agent to seal the gap performed better than the commercial sealing products. CONCLUSIONS: Commercial surface sealers evaluated were not able to totally seal controlled-size cavosurface gaps, and sealer penetration into the controlled gap varied greatly. Composite restorative procedures should be performed to obtain ideal marginal sealing, minimizing the need for composite surface sealers, which were found to not totally seal an exposed cavosurface margin. Use of a dentin-bonding agent may provide better sealing than commercial products developed specifically for this purpose.