In vitro evaluation of the potential of CO2 laser associated or not to fluorides in inhibiting human enamel erosion

Considerando a eficácia limitada do flúor na proteção dos tecidos duros dentais contra a erosão, o objetivo do presente estudo foi investigar o potencial do laser de gás carbônico (CO2) (10,6 m), associado ou não a produtos fluoretados, na inibição da erosão de esmalte dental. Amostras de esmalte dental humano foram obtidas e divididas aleatoriamente em 8 grupos (n = 11): G1: controle (sem tratamento), G2: gel de Flúor Fosfato Acidulado (FFA), G3: gel de fluoreto de sódio (AmF/NaF), G4: solução de fluoreto estanhoso (AmF/SnF2), G5: laser de CO2 (0,3 J/cm2, 15 s, 226 Hz), G6: laser de CO2 + gel de FFA, G7: laser de CO2 + gel de AmF/NaF e G8: laser de CO2 + solução de AmF/SnF2. Após os tratamentos de superfície, as amostras foram imersas em ácido cítrico a 1% (pH 4,0, 3 minutos). Antes dos tratamentos de superfície e após o desafio ácido, a microdureza de superfície foi mensurada (0,49 N, 20 segundos) e os dados foram analisados estatisticamente através do teste ANOVA com subseqüentes comparações entre pares (p < 0,05). Os resultados mostraram que o grupo G3 (403,5 ± 25,0) apresentou a maior média de microdureza Knoop após o desafio ácido, seguido pelos grupos G2 (396,6 ± 45,0) e G6 (392,8 ± 24,9), sem diferença estatística entre eles. Dentre os grupos tratados com produtos fluoretados, o grupo G4 (305,5 ± 17,7) resultou em microdureza significativamente mais baixa que o G3 (403,5 ± 25,0) e o G2 (396,6 ± 45,0), os quais foram estatisticamente semelhantes entre si. Dentre os grupos tratados com laser, os grupos G5 (341,1 ± 23,8), G7 (374,9 ± 42,1) e G8 (328,6 ± 26,9) apresentaram valores de dureza estatisticamente semelhantes entre si. Dentro dos limites do presente estudo in vitro, pôde-se concluir que o tratamento com gel de AmF/NaF e gel de FFA (com ou sem irradiação prévia com o laser de CO2) mostrou potencial para controlar a progressão da erosão no esmalte dental humano.Considering the limited effectiveness of fluoride in protecting dental hard tissues against erosion, the aim of the present study was to investigate the potential of the CO2 laser (10.6 m) associated to fluoride agents in inhibiting human enamel erosion. Human enamel samples were obtained and randomly divided into 8 groups (n = 11): G1: control (no treatment), G2: APF gel, G3: AmF/NaF gel, G4: AmF/SnF2 solution, G5: CO2 laser (0.3 J/cm2, 15 s, 226 Hz), G6: CO2 laser + APF gel, G7: CO2 laser + AmF/NaF gel and G8: CO2 laser + AmF/SnF2 solution. After surface treatment, samples were immersed in 1% citric acid (pH 4.0, 3 min). Knoop Surface microhardness (SMH) (0.49 N, 20 s) was measured before surface treatments and after surface softening. The data were statistically analyzed by ANOVA model with subsequent pairwise comparisons (p < 0,05). Group G3 (403.5 ± 25.0) presented the highest SMH means after softening, followed by Groups G2 (396.6 ± 45.0) and G6 (392.8 ± 24.9) with no statistically significant difference between them. Between the fluoride-treated groups, G4 (305.5 ± 17.7) resulted in significantly low SMH mean than G3 (403.5 ± 25.0) and G2 (396.6 ± 45.0), which were statistically similar to each other. Between the laser-treated groups, G5 (341.1 ± 23.8), G7 (374.9 ± 42.1) and G8 (328.6 ± 26.9) presented SMH means statistically similar to each other. Within the limits of the present in vitro study, AmF/NaF and APF application (with or without previous CO2 laser irradiation) have shown a potential to control erosion progression in human dental enamel

In situ assessment of the potential of AmF/NaF/SnCl2 solution, associated or not to CO2 laser irradiation, on preventing dental enamel erosion

Apesar de vários estudos terem demonstrado resultados promissores do uso da solução de AmF/NaF/SnCl2 no controle da erosão do esmalte dental, não existem relatos da sua associação com a irradiação do substrato com o laser de CO2, de comprimento de onda de 9,6 ?m. Desta forma, o presente estudo teve como objetivo avaliar o potencial da solução de AmF/NaF/SnCl2, associada ou não ao laser de CO2 (4,5 J/cm2, 20 Hz, 20 ?s), em controlar a erosão em esmalte dental bovino. Treze voluntários participaram desse estudo in situ, de delineamento cruzado, em 02 fases (04 dias cada), onde 04 tratamentos foram testados utilizando réplicas (n = 13): GC - nenhum tratamento (controle negativo); GF - solução de AmF/NaF/SnCl2 (controle positivo); GL - irradiação com laser de CO2 (9,6 ?m); GLF - laser de CO2 associado à solução de AmF/NaF/SnCl2. Os voluntários usaram dispositivos intra-bucais removíveis contendo 08 amostras de esmalte bovino. Na primeira fase, 07 voluntários utilizaram dispositivos intra-bucais contendo amostras dos grupos GC e GL, e outros 06 voluntários utilizaram dispositivos contendo amostras dos grupos GF e GLF. Na segunda fase, os voluntários foram cruzados, permitindo que todos os grupos experimentais fossem avaliados no meio bucal dos 13 voluntários da pesquisa. Os dispositivos intra-bucais foram removidos da boca para ciclagem erosiva ex-situ em ácido cítrico 0,65%, pH 3,6, durante 4 minutos, 2x/dia, em horários pré-determinados. As amostras foram avaliadas em perfilômetro óptico de não-contato (n = 13) para análise da perda de tecido mineral após o desafio erosivo, e um ensaio de ultramicrodureza transversal (n = 13) foi realizado com o objetivo de determinar a profundidade da área de desmineralização abaixo da superfície do esmalte erodido. A análise morfológica foi realizada utilizando microscopia eletrônica de varredura (MEV) (n = 3). Os dados foram analisados estatisticamente por meio do modelo ANOVA 2 fatores para medidas repetidas, com subsequente comparação entre os diferentes tratamentos (? = 0,05). A ciclagem ácida realizada no presente estudo provocou perda de esmalte significativamente maior (p < 0,001) nos grupos GC (4,8 ± 1,4A ?m) e GL (4,4 ± 2,0A ?m). Não houve diferença estatística entre a perda de superfície nos grupos GF (1,9 ± 0,9B ?m) e GLF (1,7 ± 0,9B ?m). Os resultados de ultramicrodureza transversal mostraram que as amostras tratadas com a solução fluoretada (grupo GF) apresentaram uma zona parcialmente desmineralizada com média de dureza semelhante às amostras do grupo que não recebeu qualquer tipo de tratamento (grupo GC), com ambos os grupos apresentando média de dureza significativamente maior que os grupos que foram irradiados com o laser de CO2 (GL e GLF) (p < 0,001). As micrografias mostraram que as características morfológicas superficiais do esmalte nos grupos irradiados com laser de CO2 apresentaram-se semelhantes nos grupos GL e GLF, verificando-se a presença de áreas sugestivas de derretimento, resolidificação, microporos e microtrincas, sem evidências de precipitados fluoretados no grupo GFL. Uma camada amorfa pôde ser observada nas superfícies de esmalte tratadas apenas com a solução fluoretada contendo estanho. Pode-se concluir que o uso do enxaguatório bucal fluoretado contendo estanho (500 ppm F-, 800 ppm Sn2+, pH = 4,5) mostrou potencial de prevenção da erosão de esmalte dental. A irradiação do esmalte dental com o laser associado à solução fluoretada mostrou-se eficaz, mas seu efeito não foi sinérgico. O laser de CO2 (9,6 ?m), nos parâmetros utilizados, não foi capaz de prevenir a erosão em esmalte causada por ácido cítrico.Although several studies have shown promising results using the AmF/NaF/SnCl2 solution in preventing the erosion of dental enamel, there are no reports of their association with the irradiation of the substrate with the CO2 laser, working at 9.6 ?m. Thus, this study aimed to evaluate the potential of AmF/NaF/SnCl2 solution, associated or not to CO2 laser irradiation (4.5 J/cm2, 20 Hz, 20 ?s), to prevent erosion on dental enamel. Thirteen volunteers participated in this 2-phase (4 days each), crossover study, where 04 treatments were tested using replicas (n = 13): GC - no treatment (negative control); GF - AmF/NaF/SnCl2 solution (positive control); GL - CO2 laser irradiation (9.6 ?m); GLF - CO2 laser irradiation associated with AmF/NaF/SnCl2 solution. The volunteers wore removable intra-buccal appliances containing eight bovine enamel samples. In the first phase, seven volunteers used intra-oral appliances containing samples of groups GC and GL and 6 volunteers, appliances containing samples of groups GF and GLF. In the second phase volunteers were crossed over, allowing all experimental groups were evaluated in the buccal environment of the 13 volunteers. Intra-buccal appliances were removed from the mouth and were exposed to a daily ex-situ erosive cycling (0.65% citric acid, pH 3.6, for 4 minutes, 2x/day) at pre-determined times. Samples were evaluated for surface loss using an optical non-contact profilometer (n = 13) for analysis of loss of mineral after the erosive challenge and a cross-sectional nanohardness test (n = 13) was carried out in order to determine the depth of demineralized area below the erosive lesion. Morphological analysis was carried out using scanning electron microscopy (SEM) (n = 3). The data were statistically analyzed by two-way ANOVA repeated measures with subsequent pairwise comparison test (? = 0.05). Erosive challenge significantly increased enamel wear (p < 0.001) in GC (4.8 ± 1.4A ?m) and GL (4.4 ± 2.0A ?m) groups. There was no significant difference between the surface loss in GF (1.9 ± 0.9B ?m) and GLF (1.7 ±0.9B ?m) groups. Data from cross-sectional nanohardness showed that samples treated with stannous fluoride solution (GF group) showed a partially demineralized zone with average hardness similar to samples in the group that did not receive any treatment (GC group), both groups had significantly higher average nanohardness than the irradiated samples (GL and GLF group) (p < 0.001). Morphologically, all CO2 laser irradiated samples resulted in similar changes, showing the presence of areas suggestive of melting, resolidification and some microcracks. No fluoride precipitates were observed in GFL groups. An amorphous layer could be observed on the surface of enamel treated with tin-containing solution alone. Within the limits of this in situ study, it can be concluded that the AmF/NaF/SnCl2 solution (500 ppm F, 800 ppm Sn2+, pH = 4.5) showed potential for prevention of dental enamel erosion. The enamel irradiation with the CO2 laser associated with the fluoride solution was effective, but its effect was not synergistic. The CO2 laser (9.6 ?m), with the parameters considered in this study, was not able to prevent the enamel erosion caused by citric acid

Diffusion charging of aerosol nanoparticles with an excess of bipoloar ion

The equations of diffusion charging of aerosol particles in a bipolar ion environment have no analytical transient solution. Such a solution can, however, be obtained in the special but important case of a relatively high ion concentration and aerosols with a particle size of a few nanometres, for which the probability of multiple charging is vanishingly small. The analytical transient solution obtained has an application to nanoaerosol particle size distribution measurement by electric mobility analysis. It also allows determination of the mean aerosol residence time required to attain the stationary charge distribution as a function of the ion concentration and physical properties (mass, mobility), this result having a practical application to the design of charging devices for aerosol nanoparticlesPeer reviewe

Umversorgung von einem perkutanen auf ein transkutanes BAHA-System bei Gehörgangsatresie - zwei Fallberichte

This in vitro study aimed to investigate the potential of CO2 lasers associated with different fluoride agents in inhibiting enamel erosion. Human enamel samples were randomly divided into 9 groups (n = 12): G1-eroded enamel; G2-APF gel; G3-AmF/NaF gel; G4-AmF/SnF2 solution; G5-CO2 laser (λ = 10.6 µm)+APF gel; G6-CO2 laser+AmF/NaF gel; G7-CO2laser+AmF/SnF2solution; G8-CO2 laser; and G9-sound enamel. The CO2 laser parameters were: 0.45 J/cm2; 6 μs; and 128 Hz. After surface treatment, the samples (except from G9) were immersed in 1% citric acid (pH 4.0, 3 min). Surface microhardness was measured at baseline and after surface softening. The data were statistically analyzed by one-way ANOVA and Tukey’s tests (p < 0.05). G2 (407.6 ± 37.3) presented the highest mean SMH after softening, followed by G3 (407.5 ± 29.8) and G5 (399.7 ± 32.9). Within the fluoride-treated groups, G4 (309.0 ± 24.4) had a significantly lower mean SMH than G3 and G2, which were statistically similar to each other. AmF/NaF and APF application showed potential to protect and control erosion progression in dental enamel, and CO2 laser irradiation at 0.45J/cm2 did not influence its efficacy. CO2 laser irradiation alone under the same conditions could also significantly decrease enamel erosive mineral loss, although at lower levels

AmF/NaF/SnCl2 solution reduces in situ enamel erosion – profilometry and cross-sectional nanoindentation analysis

Abstract This in situ study aimed to investigate the effect of a tin-containing fluoride solution in preventing enamel erosion. Also, its effects on the partly demineralized zone were assessed for the first time. Thirteen volunteers participated in this 2-phase study, wearing removable intra-oral appliances containing four sterilized bovine enamel slabs, for 8 days, where 2 treatment protocols were tested using samples in replicas (n = 13): CO - no treatment (negative control) and FL - AmF/NaF/SnCl2 solution (500 ppm F-, 800 ppm Sn2+, pH = 4.5). Samples were daily exposed to an erosive challenge (0.65% citric acid, pH 3.6, 4 min, 2x/day). In the 2nd phase, volunteers switched to the other treatment protocol. Samples were evaluated for surface loss using a profilometer (n = 13) and a cross-sectional nanohardness (CSNH) test (n = 13) was carried out in order to determine how deep the partly demineralized zone reaches below the erosive lesion. The data were statistically analyzed by two-way ANOVA. Erosive challenges lead to smaller enamel surface loss (p < 0.001) in the FL group when compared to group CO. Data from CSNH showed that there was no significant difference in demineralized enamel zone underneath erosion lesions between the groups. An amorphous layer could be observed on the surface of enamel treated with tin-containing solution alone. Under the experimental conditions of this in situ study, it can be concluded that AmF/NaF/SnCl2 solution prevents enamel surface loss but does not change the hardness of the partly demineralized zone near-surface enamel