Enamel subsurface caries-like lesions induced in human teeth by different solutions: a TMR analysis

Abstract This study assessed the effectiveness of models for developing subsurface caries lesions in vitro and verified mineral changes by transverse microradiography (TMR). Enamel blocks from permanent (n=5) and deciduous teeth (n=5) were submitted to lesion induction by immersion in demineralizing solutions during 96 h, followed by pH cycles of demineralization (de) and remineralization (re) for 10 days. Two de-/re solutions were tested. Demineralizing solution "A" was composed by 2.2 mM CaCl2, 2.2 mM KH2PO4, 0.05 M acetic acid, with pH 4.4 adjusted by 1 M KOH. Demineralizing solution "B" was composed by 2.2 mM CaCl2, 2.2 mM NaH2PO4, 0.05 M acetic acid and 0.25 ppmF, with pH 4.5 adjusted by 1M KOH. Solution "A" produced cavitated lesions in permanent teeth, whereas solution "B" led to subsurface lesions in deciduous teeth. Solution "B" was then tested in enamel blocks from permanent teeth (n=5) and subsurface lesions were obtained, so that solution "B" was employed for both substrates, and the blocks were treated with slurries of a fluoride dentifrice (1450 ppm F, as NaF, n=5) or a fluoride-free dentifrice (n=5). Solution "B" produced subsurface lesions in permanent and primary teeth of an average (±SD) depth of 88.4µm (±14.3) and 89.3µm (±15.8), respectively. TMR analysis demonstrated that lesions treated with fluoride-free dentifrice had significantly greater mineral loss. This study concluded that solution "B" developed subsurface lesions after pH cycling, and that mineral changes were successfully assessed by TMR.

Resumo Este estudo avaliou a efetividade de modelos para o desenvolvimento de lesões de cárie subsuperficiais in vitro e verificou alterações minerais por microradiografia transversal (TMR). Blocos de esmalte de dentes permanentes (n = 5) e decíduos (n = 5) foram submetidos à indução de lesão por imersão em soluções desmineralizadoras durante 96h, seguido de ciclos de pH de desmineralização e remineralização por 10 dias. Duas soluções des-/re foram testadas. A solução desmineralizadora "A" foi composta por 2,2 mM de CaCl2, 2,2 mM de KH2PO4, 0,05 M de ácido acético, com pH de 4,4 ajustado por 1 M de KOH. A solução desmineralizadora "B" foi composta por 2,2 mM de CaCl2, 2,2 mM de NaH2PO4, 0,05 M de ácido acético e 0,25 ppmF, com pH de 4,5 ajustado por 1 M de KOH. A solução "A" produziu lesões cavitadas em dentes permanentes, enquanto a solução "B" apresentou lesões subsuperficiais em dentes decíduos. Portanto, a solução "B" foi posteriormente usada em blocos de esmalte de dentes permanentes (n = 5) e lesões subsuperficiais foram obtidas. Portanto, a solução "B" foi empregada para ambos os substratos, sendo metade deles tratada com dentifrício fluoretado e a outra metade com dentifrício livre de flúor. A solução "B" produziu lesões subsuperficiais de cárie com profundidade de 88.4µm (14.3) em dentes permanentes e com 89.3 µm (15.8) em dentes decíduos e TMR demonstrou que lesões tratadas com dentifrício sem flúor tiveram maior perda mineral. Este estudo concluiu que a solução "B" desenvolveu lesões subsuperficiais após o ciclo de pH e as alterações minerais foram avaliadas com sucesso por TMR.

Effect of cariogenic challenge on the degradation of adhesive-dentin interfaces

Abstract The aim was to evaluate, in vitro, the influence of pH cycling on microtensile bond strength (µTBS) and percentage of nanoleakage (%NL) in the dentin-adhesive interface. Flat dentin surfaces were obtained in 56 extracted third molars. The teeth were randomly divided into four groups (n=14): G1- Single Bond Universal (etch-and-rinse mode); G2- Single Bond Universal (self-etch mode); G3- Scotchbond Multi-Purpose; G4- Clearfil SE Bond. A block of composite was built on the adhesive area. Eight tooth/resin sets were cut parallel to the tooth's long axis to obtain 48 beams (0.8 mm2) for each group. Half of the beams were submitted to four cycles of pH cycling (demineralizing solution for 6 h and remineralizing solution for 18 h). The samples were submitted to µTBS test in a universal testing machine. Six tooth/resin sets were cut parallel to the tooth's long axis to obtain three slices of the central region (1.0 mm thickness). Half of the slices were submitted to pH cycling. The nanoleakage methodology was applied to obtain the %NL at the adhesive interfaces. According to two-way ANOVA, the interaction between factors (adhesive system x storage) was significant (p=0.0001) for µTBS and %NL. After pH cycling, there was a significant decrease in µTBS and a significant increase in %NL for all adhesives. The adhesives applied in the self-etch mode obtained lower %NL, differing significantly from the etch-and-rinse adhesives. It was concluded that the pH cycling negatively influenced the µTBS and %NL for all adhesives evaluated. However, self-etch adhesives allowed less %NL.

Resumo O objetivo foi avaliar, in vitro, a influência da ciclagem de pH na resistência de união à microtração (RUµT) e na porcentagem de nanoinfiltração (%NI) na interface dentina-adesivo. Superfícies planas em dentina foram obtidas em 56 terceiros molares. Os dentes foram aleatoriamente divididos em quatro grupos (n=14): G1- Single Bond Universal (condicionamento ácido prévio); G2- Single Bond Universal (autocondicionante); G3- Scotchbond Multi-Purpose; G4- Clearfil SE Bond. Bloco de resina composta foi construído sobre o adesivo. Oito conjuntos dente/resina foram cortados paralelamente ao longo eixo do dente para obter 48 palitos (0,8 mm2) para cada grupo. Metade dos palitos foi submetida a quatro ciclos de ciclagem de pH (solução desmineralizadora por 6 h e solução remineralizadora por 18 h). As amostras foram submetidas ao teste de RUµT em máquina de ensaio universal. Seis conjuntos dente/resina foram cortados paralelamente ao longo eixo para obter três fatias da região central (1,0 mm de espessura). Metade das fatias foi submetida à ciclagem de pH. A metodologia de nanoinfitração foi aplicada para obter a %NI nas interfaces. De acordo com ANOVA de duas vias, interação entre os fatores (adesivo x armazenamento) foi significativa (p=0.0001) para for RUµT e %NI. Após ciclagem de pH, houve redução significativa na RUµT e aumento significativo na %NI para todos adesivos. Os adesivos aplicados na técnica autocondicionante obtiveram menor %NI, diferindo significativamente dos adesivos com condicionamento ácido prévio. Concluiu-se que a ciclagem de pH influenciou negativamente a RUµT e a %NI para todos adesivos. Contudo, adesivos autocondicionantes permitiram menor %NI.

Dentin Bond Strength of a Fluoride-Releasing Adhesive System Submitted to pH-Cycling

To evaluate the microtensile bond strength (µTBS) of a fluoride-containing adhesive system submitted to a pH-cycling and storage time regimen for primary outcomes. As secondary outcomes the fluoride released amount was evaluated. Twelve dentin surfaces from sound third molar were divided into 2 groups according to adhesive systems: Clearfil SE Protect (PB) and Clearfil SE Bond (SE). Sticks obtained (1.0 mm2) from teeth were randomly divided into 3 subgroups according to storage regimen model: immediate (24h); 5-month deionized water (W); and pH-cycling model (C). All sticks were tested for µTBS in a universal testing machine. Fluoride concentration was obtained from 1-4 days and 30-day in W and 1-4 days in demineralization (DE)/remineralization (RE) solutions from C, using a fluoride-specific electrode. µTBS and fluoride released data were, respectively, submitted to ANOVA in a split plot design and Tukey, and Friedman' tests (a=0.05). There was no significant interaction between adhesive system and storage regimen for µTBS. W showed the lowest µTBS values. There was no significant difference between 24 h and C models for µTBS. There was no significant difference between adhesive systems. Failure mode was predominantly cohesive within composite for the 24 h and W, for the C group it was mixed for SE and cohesive within composite for PB adhesive system. Fluoride concentrations in the DE/RE solutions were less than 0.03125 ppm and not detected in W. In conclusion, the fluoride-containing adhesive system performed similarly to the regular one. Hydrolytic degradation is the main problem with both adhesive systems, regardless of fluoride contents.

O objetivo principal desse estudo foi avaliar a resistência de união à microtração de dois sistemas adesivos (com e sem flúor) após a ciclagem de pH e armazenagem em água deionizada. A quantidade de flúor liberada foi avaliada secundariamente. Doze terceiros molares hígidos foram separados em 2 grupos de acordo com o sistema adesivo: Clearfil SE Protect - com flúor (PB) e Clearfil SE Bond - sem flúor (SE). Os palitos (1 mm2) obtidos do mesmo dente foram aleatoriamente divididos em 3 subgrupos de acordo com o meio de armazenagem: em água deionizada por 24h ou 5 meses e ciclagem de pH. Os palitos foram tracionados em uma máquina de ensaio universal a 0,5 mm/min. A concentração de flúor foi analisada em água deionizada (1-4 dias e 30 dias) e na solução remineralizadora e desmineralizadora (1-4 dias) usando um eletrodo específico. Os dados de resistência de união e liberação de flúor foram, respectivamente, submetidos à Análise de Variância em esquema de parcela subdividida e ao teste de Friedman (a=0,05). Não houve nenhuma interação significativa na resistência de união entre os sistemas adesivos e os meios de armazenagem. Os menores valores de resistência de união à microtração foram encontrados para os palitos armazenados em água deionizada. Não houve nenhuma diferença significativa nos valores de resistência de união após 24h e ciclagem de pH. Nenhuma diferença significativa na resistência de união foi observada entre os 2 sistemas adesivos. O modo de falha foi predominantemente coesivo em compósito para os grupos armazenados em água por 24h ou 5 meses para ambos os sistemas adesivos. No grupo submetido à ciclagem, a falha foi mista para o SE e coesiva em compósito para o PB. A concentração de flúor nas soluções DE/RE foi menor que 0,03125 ppm e não detectada em água deionizada. Concluindo, o sistema adesivo com flúor (PB) apresentou performance similar ao sistema adesivo sem flúor (SE). A degradação hidrolítica foi o principal fator para ambos os sistemas adesivos, independente da adição de flúor.

The influence of storage time and pH variation on water sorption by different composite resins.

Objective: The objective of this work was to assess the influence of storage time and pH cycling on water sorption by different composite resins. Materials and Methods: Nine resin brands were selected and divided into groups: G1-ROK (SDI), G2-ICE (SDI), G3-GLACIER (SDI), G4-Z350 (3M/ESPE), G5-Z250 (3M/ESPE), G6-TPH 3 (DENTSPLY), G7-ESTHET X (DENTSPLY), G8-SUPRAFILL (SSWHITE), and G9-MASTERFILL (BIODINΒMICS). Ninety specimens, ten per group, were obtained using an aluminum matrix. Specimens measured 10 mm diameter × 2 mm width. The groups were divided into subgroups according to the immersion solution: A - control (n = 05) stored in artificial saliva pH = 7.0 and B-test (n = 05) submitted to seven consecutive days of pH cycling (cariogenic challenger) that consisted of immersion in a pH° = 4.3 solution for 6 h followed by immersion in a pH¹ =7.0 solution for 18 h and stored in artificial saliva pH = 7.0 until the end of the experiment. The specimens were weighed on six occasions: T 0 (after fabrication), T 1 (24 h), T 2 (7 days), T 3 (15 days), T 4 (30 days), T 5 (60 days), and then analyzed. The water sorption was determined by the weight difference between the specimens at the time intervals. Results: The mean weight gain was exactly the same for both the subgroups within group G4. The highest means for the control subgroup were found in groups: G1, G5, G7, G8, and G9. For the pH cycling subgroup, the highest means were found in G2, G3, and G6; however, significant differences between the subgroups compared to the mean-weight gain were found for G1, G5, and G7. Conclusion: The water sorption of composite resins is dependent upon their storage time. The pH cycling created a significant impact on resins G1, G5, and G7. The sorption and solubility of composite resins vary according to their chemical composition.

Analysis of the erosive effects of children's beverages using a pH-cycling model / 대한구강보건학회지

OBJECTIVES: The aims of this in vitro study were (1) to assess the erosive potential of several children's beverages in comparison to cola and orange juice, by using an in vitro pH-cycling model, and (2) to investigate the factors related to dental erosion caused by the beverages. METHODS: Eight different children's beverages (Chorongi, Capri-sun, Grateful nature wisdom, I-kicker, Koal-koal koala, My friend pororo, Qoo, and Strong zzanggu), Cola, and an orange juice, which are available in the Korean market, were used. To characterize each test beverage, the pH, titratable acidity to pH 7.0, concentration of calcium and phosphorus, and degree of saturation with respect to hydroxyapatite (DS(HAP)) were analyzed. Erosive potential of the test beverages was assessed by the depth of enamel loss observed in specimens subjected to pH cycling for 8 days. This cycle consisted of exposure to each beverage for 20 min, thrice daily, and to a remineralizing solution every day. The correlation between the depth of the enamel loss and the chemical properties of the beverages was assessed by Spearman's rank correlation coefficients and multiple linear regression tests (P<0.05). RESULTS: The depth of enamel loss caused by the beverages was found to vary from 0.11 to 105.47 microm. Enamel loss with all the children's beverages tested was lesser compared to that with Cola (P<0.05) but was similar or greater than that with orange juice, except in one beverage. The pH, concentration of calcium, and DS(HAP) were significantly correlated with the depth of enamel loss (rho=-0.842, rho=-0.796, and rho=-0.867, respectively; P<0.01). Multiple regression analysis showed that pH and concentration of calcium were impact variables for the erosive potential of test beverages (P<0.05). CONCLUSIONS: The children's beverages tested had lower erosive potential than Coca Cola, but five (I-kiker, Grateful nature wisdom, Qoo, Capri-sun, and Chorongi) of them had higher erosive potential than orange juice. Moreover, among the chemical properties of beverages, significant factors affecting enamel loss were pH value and concentration of calcium.

The remineralization effect of topical fluoride agents on artificial enamel caries / 대한구강보건학회지

OBJECTIVES: The aim of this study was to compare the remineralization effect of the topical fluoride agents on artificial enamel caries, under the chemical pH cycling model, using surface microhardness. METHODS: Bovine enamel specimens, embedded in acrylic resin with the labial surfaces exposed, were developed artificial enamel caries. Thereafter, this study used 56 samples on VHN 25-45. The experimental groups were divided into 4 groups: control, 2% NaF solution, 1.23% APF gel, 5% NaF varnish. Samples, except in the control group, were applied to each topical fluoride agent for 4 minutes. All groups were exposed to a pH cycling model, which consisted of demineralization (4 hours) and remineralization (20 hours) for 17 days. The Vickers surface microhardness number (VHN) was measured, using the microhardness tester. The results were analyzed, using a repeated measures analysis of variance of a general linear model, and compared the baseline, each day, using a contrast analysis (simple) about within a subject factor at a significance level of 0.05. RESULTS: Result of a repeated measures analysis regarding the surface microhardness of topical fluoride agents, there were significant differences at P-values of within and between the subject factor (P0.05). CONCLUSIONS: In this study, although there were significant differences at P-values of within and between the subject factor, there were no significant differences between the experiment groups on chemical pH cycling model in vitro, and it was limited to utilize this result in a clinical situation of the fluoride application.

Análise in vitro da influência da aplicação tópica de fluoreto nas propriedades mecânicas de uma resina ortodôntica sob ciclagem de pH / In vitro influence of topical fluoride application on the mechanical properties of an orthodontic resin under pH cycling

Objetivo: Avaliar a resistencia ao cisalhamento e o indice de remanescente adesivo de uma resina ortodontica apos submissao in vitro a ciclagem de pH e aplicação topica de fluor. Metodo: Br quetes edgewise foram colados com resina TransbondTM XT na superficie vestibular de 40 incisivos bovinos. Os dentes foram divididos em 4 grupos (n=10): G1: controle pré-ciclagem (cisalhamento imediato); G2: controle pós-ciclagem (ciclagem de pH na ausência de fluor); G3: experimental com aplicação tópica unica de gel fluoretado neutro (NaF 2%) antes da ciclagem de pH; G4: experimental com tres aplicações diarias de dentifricio fluoretado (MFP 1500 ppmF) durante a ciclagem de pH. Apos o periodo de 14 dias de ciclagem de pH, (saliva  cida em pH 4,5), avaliou-se a resistencia ao cisalhamento e o indice de remanescente adesivo (IRA). Foram aplicados a an lise de variancia (ANOVA) e o teste Tukey para avaliação da resistencia ao cisalhamento, bem como os testes Man-Witney e Kruskal-Wallis para analise do IRA, adotando-se o intervalo de confiança de 95% (p0,05). Na avaliação do IRA, 100% dos corpos de prova de G1, G2 e G4, assim como 60% de G3, apresentaram escore 1; enquanto 40% dos espacimes de G3 apresentaram escore 2. Foi encontrada diferença com significancia estatistica (p<0,05). Resultados: A an lise da resistencia ao cisalhamento não revelou diferença estatistica entre os grupos (p>0,05). Na avaliação do IRA, 100% dos corpos de prova de G1, G2 e G4, assim como 60% de G3, apresentaram escore 1; enquanto 40% dos especimes de G3 apresentaram escore 2. Foi encontrada diferença com significancia estatistica (p<0,029) entre G1 e G3; G2 e G3; G3 e G4. Conclusão: A aplicação tópica de fluoreto concomitante a ciclagem de pH não exerceu influencia na resistencia ao cisalhamento da resina Transbond TM XT; porem o uso de gel fluoretado neutro sugeriu redução dos riscos de fratura dentaria na descolagem de brackets ortodonticos, de acordo com as caracteristicas do indice de remanescente adesivo.

Objective: To evaluate the shear bond strength and the adhesive remnant index (ARI) of an orthodontic resin after in vitro pH cycling and topical fluoride application. Methods: Edgewise brackets were bonded with TransbondTM XT resin on the buccal of 40 bovine incisors. The teeth were divided in 4 groups (n=10): G1: pre cycling group (immediate shearing); G2: pos cycling group (pH cycling in the absence of fluoride); G3: experimental group with single topical application of neutral fluoride gel (2% NaF) before pH cycling; G4: experimental group with three daily applications of fluoride dentifrice (MFP 1500 ppmF) during pH cycling. Shear bond strength and ARI were evaluated after 14 days of pH cycling (acid saliva, pH 4.5). Shear bond strength data were analyzed by ANOVA and Tukey's test while the Man-Whitney and Kruskal-Wallis were used for analysis of ARI data using a 95% confidence interval (p<0.05). Results: There was no statistically significant difference (p>0.05) in the shear bond strength among the groups. For the ARI analysis, 100% of the specimens of G1, G2 and G4, and 60% of G3 were scored 1, while 40% of the specimens of G3 were scored 2. There was statistically significant difference (p=0.029) between G1 and G3; G2 and G3; G3 and G4. Conclusion: Topical fluoride application concomitant to pH cycling did not exert influence on the shear bond strength of TransbondTM XT resin, but the use of neutral fluoride gel indicated a reduction in the risks of tooth fracture on debonding of orthodontic brackets, according to the ARI characteristics.

Evaluation of commercial fluoride solutions on bovine enamel demineralization, using pH-cycling model / Avaliação de soluções fluoretadas comerciais na redução da perda mineral em esmalte bovino, utilizando modelo de ciclagem de pH

Purpose: The aim of this in vitro study was to evaluate the fluoride concentration in mouthrinses and their capacity to intervene with the caries process. Methods: The analysis of the fluoride concentration in the solutions was carried with ion specific electrode connected to an ion analyzer. Bovine incisors enamel blocks with previously known superficial microhardness were submitted to a pH cycling model and treated with fluoridated solutions, and later reanalyzed for microhardness and fluoride incorporation. Results: The fluoride concentration (ppm) found in the solutions SANiFill- Sanikids®, Colgate Plax Fresh Mint®, Oral B®, Sorriso Fresh® and Cepacol® (not fluoridated) were, respectively: 242.91±21.89; 248.42±3.55; 248.29±11.31; 257.61±17.57 and 35.37±10.64. The lowest loss of superficial microhardness was observed with the use Sorriso Fresh® (29.66%± 8.84), followed by Plax Fresh mint® (32.99%±14.09) and Oral B® (43.00%±18.34). Conclusion: The data suggest that fluoride solutions, in proper concentrations, are capable of intervening on the phenomena of demineralization and remineralization, promoting fluoride incorporation and, consequently, decreasing the loss of microhardness on dental enamel.

Objetivo: O objetivo deste estudo in vitro foi analisar a concentração de flúor em diferentes soluções fluoretadas para bochechos e sua capacidade de interferir no processo de cárie. Metodologia: A análise da concentração de flúor nas soluções para bochecho foi realizada com eletrodo específico para íon flúor acoplado a um analisador de íons Orion. Blocos de esmalte de dentes incisivos bovinos com a microdureza superficial conhecida foram submetidos à ciclagem de pH e uso de soluções fluoretadas, sendo, posteriormente, avaliados por uma nova análise de microdureza e também pela incorporação de flúor. Resultados: As concentrações de flúor (ppm) encontradas nas soluções SANiFill®, Colgate® Plax®, Oral B®, Sorriso® e Cepacol® (não fluoretada) foram, respectivamente: 245,94; 247,61; 251,50; 258,01 e 38,44. A menor perda de porcentagem de dureza superficial foi observada com o uso da solução fluoretada Sorriso® (29,7%±14,4), seguida por Colgate® Plax® (33%±14,1) e Oral B® (43%±18,3). Todas as soluções fluoretadas analisadas mostraram capacidade de incorporar flúor no esmalte dental. Conclusão: Os dados sugerem que as soluções fluoretadas foram capazes de interferir nos fenômenos de desmineralização e remineralização, promover incorporação de flúor e, conseqüentemente, diminuir a perda de dureza no esmalte dental.

Surface degradation of composite resins by acidic medicines and ph-cycling

This study evaluated the effects of acidic medicines (Dimetapp® and Claritin®), under pH-cycling conditions, on the surface degradation of four composite resins (microhybrid: TPH, Concept, Opallis and Nanofilled: Supreme). Thirty disc-shaped specimens (Ø = 5.0 mm / thickness = 2.0 mm) of each composite were randomly assigned to 3 groups (n = 10): a control and two experimental groups, according to the acidic medicines evaluated. The specimens were finished and polished with aluminum oxide discs, and the surface roughness was measured by using a profilometer. After the specimens were submitted to a pH-cycling regimen and immersion in acidic medicines for 12 days, the surface roughness was measured again. Two specimens for each material and group were analyzed by scanning electron microscopy (SEM) before and after pH-cycling. Data were analyzed by the Student's-t test, ANOVA, Duncan's multiple range test and paired t-test (α=0.05). Significant increase in roughness was found only for TPH in the control group and TPH and Supreme immersed in Claritin® (p<0.05). SEM analyses showed that the 4 composite resins underwent erosion and surface degradation after being subjected to the experimental conditions. In conclusion, although the roughness was slightly affected, the pH-cycling and acidic medicines caused surface degradation of the composite resins evaluated. Titratable acidity seemed to play a more crucial role on surface degradation of composite resins than pH.

Fluoride release of six restorative materials in water and pH-cycling solutions

The fluoride release of restorative materials in deionized water has been the subject of many studies, but the behavior of these materials under conditions of acid challenge that simulates the oral cavity, needs to be further explored. Therefore, the aim of this study was to evaluate the fluoride release of restorative materials in two storage protocols: deionized water and pH-cycling system (demineralizing solution-pH 4.3 and remineralizing solution-pH 7.0) for 15 days. Eight disks of each material (Vitremer™-positive control, Dyract AP, Ariston pHc, Definite®, Tetric®Ceram and Z100-negative control) were prepared (11.0 mm x 1.5 mm) and suspended individually in 4.0 mL of each solution, which were daily changed. Daily fluoride release was analyzed with an ion specific electrode (Orion 9609) by the direct method or after HMDS-facilitated diffusion, following 1, 7 and 15 days. The values obtained were converted into µgF/mm² and the data analyzed by ANOVA and Tukey's test (p< 0.05). The results showed that all materials released more fluoride in the pH-cycling system, except for Ariston pHc which maintained a constant release during the experiment. The highest fluoride release was presented by the positive control, Vitremer™ in pH-cycling and by Ariston pHc, in deionized water. The negative control Z100 and the resins Definite® and Tetric®Ceram did not present statistically significant differences.

Microhardness and fluoride release of restorative materials in different storage media

This study evaluated the surface microhardness and fluoride release of 5 restorative materials - Ketac-Fil Plus, Vitremer, Fuji II LC, Freedom and Fluorofil - in two storage media: distilled/deionized water and a pH-cycling (pH 4.6). Twelve specimens of each material, were fabricated and the initial surface microhardness (ISM) was determined in a Shimadzu HMV-2000 microhardness tester (static load Knoop). The specimens were submitted to 6- or 18-h cycles in the tested media. The solutions were refreshed at the end of each cycle. All solutions were stored for further analysis. After 15-day storage, the final surface microhardness (FSM) and fluoride release were measured. Fluoride dose was measured with a fluoride-specific electrode (Orion 9609-BN) and digital ion analyzer (Orion 720 A). The variables ISM, FSM and fluoride release were analyzed statistically by analysis of variance and Tukey's test (p<0.05). There was significant difference in FSM between the storage media for Vitremer (pH 4.6 = 40.2 ± 1.5; water = 42.6 ± 1.4), Ketac-Fil Plus (pH 4.6 = 73.4 ± 2.7; water = 58.2 ± 1.3) and Fluorofil (pH 4.6 = 44.3 ± 1.8; water = 38.4 ± 1.0). Ketac-Fil Plus (9.9 ± 18.0) and Fluorofil (4.4 ± 1.3) presented higher fluoride release in water, whereas Vitremer (7.4 ± 7.1), Fuji II LC (5.7 ± 4.7) and Freedom (2.1 ± 1.7) had higher fluoride release at pH 4.6. Microhardness and fluoride release of the tested restorative materials varied according to the storage medium.

Este estudo avaliou as propriedades de microdureza de superfície e liberação de flúor de 5 materiais restauradores (Ketac-Fil Plus, Vitremer, Fuji II LC, Freedom e Fluorofil) em dois meios de imersão: água destilada/deionizada e modelo de ciclagem de pH (4,6). Doze corpos-de-prova de cada material foram confeccionados e tiveram a microdureza de superfície inicial (MSI) determinada utilizando o microdurômetro Shimadzu HMV-2000 Micro Hardness Tester (carga estática Knoop). Os corpos-de-prova foram submetidos a ciclos de 6 e 18 h para os dois meios de imersão. A cada final de ciclo as soluções foram substituídas e armazenadas. Após 15 dias de imersão, a microdureza de superfície final (MSF) e a liberação de flúor foram determinadas. A dosagem de flúor foi feita com um eletrodo específico combinado para íon flúor (9609 BN - Orion) e analisador de íons digital (Orion 720 A). As variáveis MSI, MSF e liberação de flúor foram submetidas à análise de variância e teste de Tukey (p<0,05). Houve diferença estatisticamente significante na MSF entre os meios de imersão para o Vitremer (pH 4,6 = 40,2 ± 1,5; água = 42,6 ± 1,4), Ketac-Fil Plus (pH 4,6 = 73,4 ± 2,7; água = 58,2 ± 1,3) e Fluorofil (pH 4,6 = 44,3 ± 1,8; água = 38,4 ± 1,0). O Ketac-Fil Plus (9,9 ± 18,0) e o Fluorofil (4,4 ± 1,3) liberaram mais flúor na água; o Vitremer (7,4 ± 7,1), Fuji II LC (5,7 ± 4,7) e o Freedom (2,1 ± 1,7) no pH 4,6. A microdureza e liberação de flúor dos materiais restauradores estudados variaram de acordo com o meio de imersão.