Effects of bleaching using 10% carbamide peroxide with calcium or amorphous calcium phosphate on enamel mineral content and hardness / Asociación entre la severidad de Hipomineralización Incisivo-Molar (HIM) y lesiones cavitadas de caries en escolares

ABSTRACT This study evaluated enamel mineral content and surface microhardness before and after bleaching treatment using 10% carbamide peroxide (CP) containing calcium (Ca) or amorphous calcium phosphate (ACP). Thirty-six bovine slabs were randomly allocated into 3 groups (n = 12) according to bleaching treatment: G1 - Opalescence PF 10% (CP), G2 -NiteWhite ACP (CP+ACP), and G3 - Opalescence PF (10%) with calcium (CP+CA). The bleaching agent was applied on enamel surface for 6 h/day over a period of 21 days. Enamel surface was evaluated by Knoop microhardness (KNH) and micro energy-dispersive X-ray fluorescence spectrometry (p-EDXRF) at baseline and at after bleaching treatment. Data were statistically analyzed by repeated measures ANOVA and Tukey's test (a = 0.05). There was a significant decrease in microhardness after bleaching treatments for all study groups, but no difference between bleaching gels. There was no difference in the Ca/P ratio measured by p-EDXRF for all groups at the study times, but the mean value was lower in group CP+CA than in group CP+ACP. Group CP was similar to both CP+ACP and CP+CA. It can be concluded that enamel microhardness decreased after the bleaching process, regardless of the presence of calcium or ACP, but there was no significant change in the Ca/P ratio of enamel after bleaching for each tested gel. This indicates that the bleaching gels have erosive potential, causing softening of enamel without promoting surface loss, regardless of the presence of calcium of ACP ions.

RESUMO Este estudo avaliou o conteúdo mineral do esmalte e a microdureza superficial antes e após o tratamento clareador, utilizando peróxido de carbamida 10% (PC) contendo cálcio (Ca) ou fosfato de cálcio amorfo (ACP) em sua composigao. Trinta e seis espécimes de esmalte bovino foram alocados aleatoriamente em 3 grupos (n = 12) de acordo com os tratamentos clareadores: G1 - Opalescence PF 10% (CP), G2 -NiteWhite (CP+ACP); e G3 - Opalescence PF (10%) com cálcio (CP + CA). O agente clareador foi aplicado na superficie do esmalte por 6 h/dia por um periodo de 21 dias. A superficie do esmalte foi avaliada por microdureza Knoop (KNH) e espectrometria de fluorescencia de raios X micro-dispersiva (p-EDXRF) no inicio e após o tratamento clareador. Os dados foram analisados estatisticamente pelo teste ANOVA de medidas repetidas e Tukey (a = 0,05). Houve uma diminuigao significativa da microdureza após os tratamentos clareadores para todos os grupos estudados, mas nao houve diferenga entre os diferentes géis. Nao houve diferenga da relagao Ca/P mensurada por p-EDXRF para todos os grupos nos tempos estudados; no entanto, o grupo CP+CA apresentou menor valor comparado ao grupo CP+ACP. O grupo CP foi similar aos grupos CP+ACP e CP+CA. Portanto, pode-se concluir que houve redugao significativa da microdureza do esmalte após o clareamento, independente da presenga de cálcio ou APC na composigao dos géis, embora nao tenha havido alteragao significando na relagao Ca/P do esmalte após o clareamento. Isto indica um potencial erosivo dos géis clareadores, causando o amolecimento sem perda da estrutura do esmalte, independente da presenga dos íons cálcio e ACP.

Efficacy of a bioactive material and nanostructured desensitizing on dentin hypersensitivity treatment / Eficácia de um material bioativo e dessensibilizante nanoestruturado no tratamento da hipersensibilidade dentinária

Introduction: Dentin hypersensitivity is a frequent occurrence in dental practice. It is clinically characterized by acute, short, and temporary pain in response to mechanical, chemical, thermal, or osmotic stimuli resulting from dentin exposure. Objective: To compare in vivo the effect of an experimental crystalline bioactive material and nanostructured desensitizing on the pain assessment among patients with cervical dentin hypersensitivity. Material and method: Thirty patients were selected for this study, who were randomly assigned to two groups (n=15) in a split-mouth design. Each patient received two treatments: group 1 (fluoride gel and bioactive material) and group 2 (fluoride gel and nanostructured desensitizing). Pain analyses were performed using a visual analogue scale, ranging 0-10. Baseline pain measurement was performed prior to initial treatment (T0) and new measurements were carried out weekly for 3 weeks (T1, T2, and T3) before materials were reapplied. Final pain analysis was performed 3 months after initial treatment (T4). Degree of pain reduction was calculated using the formula T0 - Tperiod after treatment. The data of the pain measurements were analyzed using 2-way repeated measure ANOVA and Tukey’s test (α=0.05). Result: Regardless of evaluation period, there was no statistical difference on pain reduction between the treatments (p>0.05). The degree of pain was reduced significantly in each evaluated period for all tested treatments (p<0.05), by approximately three degrees after 3 months. Conclusion: The tested desensitizing materials were effective on dentin hypersensitivity reduction.

Introdução: A hipersensibilidade dentinária é uma ocorrência frequente na prática clínica; clinicamente caracterizada por dor aguda, curta e temporária, em resposta ao estímulo mecânico, químico, térmico ou osmótico causada pela exposição dentinária. Objetivo: Comparar in vivo o efeito de um material bioativo cristalino experimental e um dessensibilizante nanoestruturado na avaliação da dor de pacientes com hipersensibilidade dentinária cervical. Material e método: Trinta pacientes foram selecionados para este estudo, que foram randomicamente divididos em dois grupos (n=15) em um desenho experimental de boca dividida. Cada paciente recebeu dois tratamentos: grupo 1 (flúor gel e material bioativo) e grupo 2 (flúor gel e dessensibilizante nanoestruturado). As análises de dor foram realizadas usando uma escala visual analógica, variando de 0-10. A mensuração da dor inicial foi realizada previamente ao tratamento inicial (T0) e novas análises foram realizadas semanalmente durante 3 semanas (T1, T2 e T3) antes da reaplicação dos materiais. A análise final da dor foi realizada 3 meses após o início do tratamento (T4). O grau de redução de dor foi mensurado pela fórmula: T0 - Tperíodo após tratamento. Os dados das mensurações de dor foram analisados pela ANOVA para medidas repetidas 2 critérios e teste de Tukey (α=0,05). Resultado: Independente do período de avaliação, não houve diferença estatística entre todos os tratamentos na redução da dor (p>0,05). O grau de dor reduziu significativamente em cada período avaliado para todos os tratamentos testados (p<0,05), aproximadamente três graus após 3 meses. Conclusão: Os materiais dessensibilizantes testados foram efetivos na redução da hipersensibilidade dentinária.

Effect of pre- heating on hardness of methacrylate- and silorane- based composites

AIM: To evaluate the effect of composite pre-heating on the microhardness of different monomer resin-based. MATERIALS AND METHOD: Circular specimens of methacrylate- and silorane-based composite resins pre-heated at 23, 39, and 55˚ C were carried out, and cured using a halogen light-curing unit at 650 mW/cm². After 24 h, the specimens were polished and Knoop hardness number (KHN) was measured using a microhardness tester with 50-g load for 15 s. The data were analyzed with ANOVA and Tukey's tests (α = 0.05). RESULTS: Top surface presented higher KHN than bottom, methacrylate-based composite showed higher KHN compared to silorane, and pre-heating increased the KHN of the composites tested. CONCLUSION: Pre-heating can be used to improve the microhardness of methracrylate- and silorane-based composites.

Radiant exposure effects on physical properties of methacrylate - and silorane-composites

AIM: To evaluate the effect of different radiant exposures on the degree of conversion (DC), Knoop hardness number (KHN), plasticization (P), water sorption (WS), and solubility (S) of different monomer resin-based composites. METHODS: Circular specimens (5 x 2 mm) were manufactured from methacrylate and silorane composite resins, and light-cured at 19.8, 27.8, 39.6, and 55.6 J/cm2, using second-generation LED at 1,390 mW/cm2. After 24 h, DC was obtained using a FT-Raman spectrometer equipped with a Nd:YAG laser, KHN was measured with 50-g load for 15 s, and P was evaluated on the top and bottom surfaces by the percentage of hardness reduction after 24 h immersed in absolute alcohol. WS and S were determined according to ISO 4049. Data were subjected to statistical analysis (α=0.05). RESULTS: Methacrylate material presented higher DC, KHN, P, and WS than silorane (p<0.05). There was no difference in the S values (p>0.05). The increased radiant exposures improved only the KHN (p<0.05). In general, top surfaces showed higher DC and KHN than bottom, for both materials (p<0.05). The increase of the radiant exposure did not improve most physical properties of the composites and were monomer-base dependent. CONCLUSIONS: Chemical composition of the composite resins resulted in different physical properties behavior and could affect the clinical longevity of dental restorations, but overall these properties were not influenced by the different radiant exposures evaluated in the study...

Impact of light-curing time and aging on dentin bond strength of methacrylate- and silorane-based restorative systems

AIM: To evaluate the impact of different light-curing times on dentin microtensile bond strength of two restorative systems after 24 h and 6 months of water storage. METHODS: Standardized Class II preparations were performed in 56 freshly-extracted human molars (n = 7), restored with methacrylate- or silorane-based restorative systems, and light-cured using a light-emitting diode at 1390 mW/cm2 by the recommended manufacturers' time or double this time. After storage for 24 h at 37 oC, the teeth were sectioned to yield a series of 0.8-mm thick slices. Each slab was trimmed into an hourglass shape of approximately 0.64 mm2 area at the gingival dentin-resin interface. Specimens were tested using universal testing machine at crosshead speed of 0.5 mm/min until failure, after 24 h and 6 months of storage. Data were statistically analyzed by three-way ANOVA and Tukey's test (α = 0.05). RESULTS: The highest bond strength values were recorded for the groups restored with methacrylate system (p<0.001) as well as for extended light-curing time (p = 0.0034). There was no statistically significant difference between 24 h and 6 months storage on bond strength (p>0.05). CONCLUSIONS: Bond strength was influenced by the material and light-curing time, but the 6-month storage did not affect the bond strength of restorations...

Physicochemical properties of enamel after microabrasion technique

AIM: This study aimed to evaluate the enamel microhardness, surface roughness, and chemical composition after microabrasion technique, followed by polishing and different immersion times in artificial saliva. Materials and methods: Ninety enamel blocks (25mm2) from bovine incisors were divided into two groups (G1 and G2), and then subdivided in five subgroups (n = 9) according to their microabrasion treatment and polishing with a diamond paste: 35% phosphoric acid and pumice (H3PO4+Pum) and polishing; just H3PO4+Pum; 6.6% hydrochloric acid and silica (HCl+Sil) and polishing; just HCl+Sil; and control (no treatment). For G1, roughness and microhardness analyses were performed before (L1) and after (L2) microabrasion. After 15 (L3) and 30 (L4) days of immersion in artificial saliva, microhardness analysis was also performed. After (L4) analysis, the specimens were subjected to SEM analysis. G2 was used for the chemical analysis using energy dispersion testing (EDS). The data was subjected to statistical analysis (α = 5%). For roughness, L2 presented higher values than L1, except for the polished groups. For microhardness, L2 presented higher values than L1, except for unpolished groups. The L3 and L4 did not differ and were higher than L1. RESULTS: No changes were observed in the phosphorus concentrations of the microabrasioned enamel. However, the specimens treated with HCl+Sil were observed as having decreased calcium and increased chlorine and silica on the EDS test. Conclusion: Microabrasion followed by polishing and immersion in artificial saliva for 15 days is enough to increase the microhardness of microabrasioned enamel surfaces, although the microabrasion procedure can alter the mineral content of the enamel.

Erosão dental e suas implicações sobre a saúde bucal / Dental erosion and its implications on the oral health

Os conceitos de promoção de saúde bucal e o aumento da expectativa de vida têm contribuído para a maior manutenção dos elementos dentais. Assim, com os novos hábitos alimentares e comportamentais, a perda irreversível de tecido dental duro de origem não cariosa tem aumentado substancialmente, sendo dividida em atrição, erosão e abrasão. A erosão dental é uma enfermidade crônica, definida como a perda superficial de tecido dental duro como resultado de um processo químico sem envolvimento de bactérias, causada porácidos, que podem ter origem intrínseca, extrínseca ou idiopática, provocando a perda irreversível de tecido mineralizado e hipersensibilidade dentinária. O presente trabalho tem por objetivo apresentar uma revisão da literatura sobre os principais fatores que podem ocasionar as lesões de erosão, reunindo os diferentes aspectos relacionados à sua etiologia, classificação, diagnóstico, prevenção e tratamento.

Erosão dental e suas implicações sobre saúde bucal / Dental erosion and its implication on the oral health

Os conceitos de promoção de saude bucal e o aumento da espectativa de vida tem contribuído para a maior manutenção dos elementos dentais. Assim, com os novos hábitos alimentares e comportamentais, a perda irreversível de tecido dental duro de origem não cariosa tem aumentado substancialmente, sendo dividida em atrição, erosão e abrasão. A erosão dental é uma enfermidade crônica, definida como a perda superficial de tecido dental duro como resultado de um processo químico sem envolvimento de bactérias, causada por ácidos, que podem ter origem intrínseca, extrínseca ou idiopática, provocando a perda irreversível de tecido mineralizado e hipersensibilidade dentinária. O presente trabalho tem por objetivo apresentar uma revisão da literatura sobre os principais fatores que podem ocasionar as lesões de erosão, reunindo os diferentes aspectos relacionados à sua etiologia, classificação, diagnóstico, prevenção e tratamento