ABSTRACT
Abstract This study evaluated the effect of fluoride varnishes containing micrometric or nanosized sodium trimetaphosphate (TMP) on dentin erosive wear in vitro. Bovine root dentin blocks were selected by surface hardness and randomly divided into five experimental groups/varnishes (n = 20/group): placebo, 5% sodium fluoride (NaF); 5% NaF+5% micrometric TMP; 5% NaF+2.5% nanosized TMP; and 5% NaF+5% nanosized TMP. Half of the surface of all blocks received a single application of the assigned varnish, with subsequent immersion in artificial saliva for 6 h. Varnishes were then removed and the blocks were immersed in citric acid (90 s, 4×/day, 5 days). After each erosive cycle, ten blocks of each group were immersed in a placebo dentifrice for 15 s (ERO), while the other ten blocks were subjected to abrasion by brushing (ERO+ABR). Dentin erosive wear was assessed by profilometry. Data were submitted to 2-way ANOVA and to the Holm-Sidak test (p<0.05). Dentin erosive wear was significantly higher for ERO+ABR than for ERO for all varnishes. TMP-containing varnishes promoted superior effects against dentin erosive wear compared with 5% NaF alone; and 5% nanosized TMP led to the lowest wear among all varnishes. In conclusion, the addition of TMP to conventional fluoride varnish (i.e., varnish containing only NaF) enhanced its protective effects against bovine root dentin erosion and erosion+abrasion. Additionally, the use of 5% nanosized TMP led to superior effects in comparison to 5% micrometric TMP, both for erosion and erosion+abrasion in vitro.
ABSTRACT
O presente estudo avaliou o efeito de vernizes fluoretados suplementados com nanopartículas de Trimetafosfato de Sódio (TMP) sobre o desgaste erosivo do esmalte dental bovino, em protocolos in vitro e in situ. Para a 1ª fase, blocos de esmalte dental bovino (n=100) foram selecionados por meio de dureza de superfície (DS) e aleatoriamente divididos em 5 grupos experimentais (n=20/grupo), de acordo com os vernizes testados: (a) Placebo (Pla - sem F ou TMP), (b) 5% NaF, (c) 5% NaF + 5% TMP microparticulado (5% Micro), (d) 5% NaF + 2,5% TMP nanoparticulado (2,5% Nano), (e) 5% NaF + 5% TMP nanoparticulado (5% Nano). Os blocos receberam uma única aplicação dos vernizes e foram imersos em saliva artificial por 6 h. Em seguida, os vernizes foram removidos e todos os blocos, submetidos a 4 desafios erosivos diários durante 5 dias (ERO, imersão em ácido cítrico 0,05 M, pH 3,2, 90 s/ciclo, sob agitação). Após ERO, metade dos blocos foi submetida a abrasão por escovação (15 s/ciclo) com dentifrício placebo (ERO+ABR). Os blocos foram analisados por perfilometria, dureza de superfície (DS) e dureza em secção longitudinal (ΔKHN). Os dados foram submetidos a ANOVA a dois critérios e Teste de Fisher LSD (p< 0,05). O desgaste do esmalte foi significativamente menor para ERO comparado a ERO+ABR para todos os vernizes testados (p< 0,001), seguindo o padrão 5% Nano < 5% Micro < 5% NaF < 2,5% Nano < Pla (ERO e ERO+ABR). A maior perda de DS foi observada para o Pla e a menor para 5% NaF (ERO) e 2,5% Nano (ERO+ABR), sem diferenças significativas entre 2,5% Nano, 5% NaF e 5% Micro. Os maiores valores de ΔKHN foram observados para 5% Micro e 5% Nano a 5-30 µm, com diferenças menos acentuadas entre os grupos a 30-70 µm (ERO e ERO+ABR). Para a 2ª fase, blocos de esmalte bovino (n=224) foram selecionados por DS e distribuídos aleatoriamente entre os grupos: (a) Placebo (Pla - sem F ou TMP), (b) 5% NaF, (c) 5% NaF + 5% TMP microparticulado (5% Micro), e (d) 5% NaF + 5% TMP nanoparticulado (5% Nano). Os blocos foram inseridos em dispositivos acrílicos palatinos (n=4/dispositivo), e tratados com os vernizes uma única vez, permanecendo na cavidade bucal dos voluntários (n=14) por 6 h. Em seguida, os vernizes foram removidos e os blocos, submetidos à ERO (imersão ex vivo em ácido cítrico 0,05 M, pH 3,2, 90 s, 4x/dia), enquanto dois blocos foram adicionalmente submetidos a abrasão por escovação com dentifrício fluoretado (ERO+ABR), totalizando 5 dias em cada etapa experimental, seguindo um protocolo duplo-cego e cruzado. As análises dos blocos e dos dados foram idênticas às da 1ª fase. Os valores do desgaste seguiram um padrão similar em ambas as condições experimentais (ERO ou ERO+ABR), com 5% Nano < 5% Micro < 5% NaF < Pla. Um padrão similar foi observado para dureza em secção longitudinal (ΔKHN), apesar de não serem verificadas diferenças significativas entre 5% Micro×5% Nano (5-30 µm). Quanto à perda de DS, o maior valor foi observado para Pla e o menor para 5% Nano (ERO ou ERO+ABR), sem diferenças significativas entre Pla×5% NaF (ERO), 5% NaF×5% Micro (ERO+ABR), e 5% Micro×5% Nano (ERO+ABR). Diante dos resultados, conclui-se que a adição de TMP a vernizes fluoretados melhorou significativamente a proteção contra o desgaste erosivo do esmalte in vitro e in situ. O uso de 5% de TMP em escala nanométrica aumentou ainda mais esses efeitos(AU)
The present study evaluated the effect of fluoride (F) varnishes supplemented with sodium trimetaphosphate (TMP) nanoparticles on erosive tooth wear, using in vitro and in situ protocols. For the first phase, bovine enamel blocks (n=100) were selected by surface hardness (SH) and randomly divided into 5 experimental groups (n=20/group), according to the varnishes tested: (a) Placebo (Pla - without F or TMP), (b) 5% NaF, (c) 5% NaF + 5% micrometric TMP (5% Micro), (d) 5% NaF + 2.5% nano-sized TMP (2.5% Nano), (e) 5% NaF + 5% nano-sized TMP (5% Nano). Blocks received a single varnish application, and were immersed in artificial saliva for 6 h. Varnishes were then removed and all blocks, subjected to 4 daily erosive challenges during for 5 days (ERO, immersion in 0.05 M citric acid, pH 3.2, 90 s/cycle, under agitation). After ERO, half of the blocks were subjected to abrasion by brushing (15 s/cycle) with placebo dentifrice (ERO+ABR). Blocks were analyzed by profilometry, surface hardness (SH) and cross-sectional hardness (ΔKHN). The data were submitted to 2-way ANOVA and Fisher's LSD test (p< 0.05). Enamel wear was significantly lower for ERO compared to ERO+ABR for all varnishes tested (p< 0.001), following the pattern 5% Nano < 5% Micro < 5% NaF < 2.5% Nano < Pla (ERO and ERO+ABR). The highest SH loss was observed for Pla, and the lowest for 5% NaF (ERO) and 2.5% Nano (ERO+ABR), without significant differences between 2.5% Nano, 5% NaF and 5% Micro. The highest values of ΔKHN were observed for 5% Micro and 5% Nano at 5-30 µm, with less marked differences between the groups at 30-70 µm (ERO and ERO+ABR). In the second phase, bovine enamel blocks (n=224) were selected by SH and randomly distributed among the groups: (a) Placebo (Pla - without F or TMP), (b) 5% NaF, (c) 5% NaF + 5% micrometric TMP (5% Micro), and (d) 5% NaF + 5% nano-sized TMP (5% Nano). The blocks were inserted in acrylic palatal devices (n=4/device), and treated with the varnishes only once, remaining in the oral cavity of the volunteers (n=14) for 6 h. Then, the varnishes were removed and the blocks, subjected to ERO (ex vivo immersion in 0.05 M citric acid, pH 3.2, 90 s, 4x/ day), while two blocks were additionally subjected to abrasion by brushing with fluoride dentifrice (ERO+ABR), totaling 5 days in each experimental stage, following a double-blind, crossover protocol. The blocks and the data were analyzed as described for the first phase. The wear values followed a similar pattern under both experimental conditions (ERO or ERO+ABR), with 5% Nano < 5% Micro < 5% NaF < Pla. A similar pattern was observed for hardness in depth (ΔKHN), although no significant differences were found between 5% Micro×5% Nano (5-30 µm). As for SH loss, the highest value was observed for Pla, and the lowest for 5% Nano (ERO or ERO+ABR), without significant differences between Pla×5% NaF (ERO), 5% NaF×5% Micro (ERO+ABR), and 5% Micro×5% Nano (ERO + ABR). In view of the results, it was concluded that the addition of TMP to fluoride varnishes significantly improved protection against erosive enamel wear in vitro and in situ. The use of 5% nano-sized TMP further increased these effects(AU)