RESUMEN
Objective@#To isolate the cariogenic Streptococcus mutans (Sm) strains and study the therapeutical effect of egg yolk antibody (IgY) of the Sm on dental caries development.@*Methods@#Sm strains were isolated from the children's dental plaque samples. Morphological, biochemical and molecular biological methods were applied to identify the serotype, acid producing and adhesion abilities of isolated Sm strains. After inactivation one of the Sm strains was used as antigen to immune laying hens to collect and extract the specific anti-Sm IgY. The rats were infected with Sm (serotype e). After 16 weeks of infection, all the rats were found developing dental caries. The rats were then randomly divided into two groups. The rats in experimental group were supplied with diet containing anti-Sm IgY while the rats in control group with normal IgY. All rats were sacrificed after another 8 weeks' observation. The degree of caries for each rat was assessed using Keyes' method.@*Results@#We isolated 7 Sm strains from the children's dental plaque samples in the present study. The numbers of serotype c, e, f, k were 3, 2, 0 and 2, respectively. All strains showed similar morphological and biochemical characters as standard UA159 Sm strain, and possessed strong capabilities of acid production and adherence. Interestingly, even the same serotypec strains, such as No.3 and No.7 strains, demonstrated significant difference on acid producing and adherence capabilities. After 16 weeks infection with serotype e strain, the rats' mandibular teeth were apparently decayed, and treatment with specific anti-Sm IgY obviously attenuated the development of caries in the experiment group rats (16.4±2.0) compared with that in the control group rats (30.2±9.3) (P<0.05) determined by Keyes' method.@*Conclusions@#Seven cariogenic Sm strains of different serotypes were isolated, which possesses similar morphology and biochemical characters. Although belonging to the same serotype strains they always show significant difference in acid-producing and adherencec apabilities. Further experiment provides evidences that the serotype e strain could obviously induce caries independently, and employment of specific anti-Sm IgY as passive immunotherapy additive might effectively inhibit the further development of dental caries.
RESUMEN
Objetivo: Este estudo in vitro utilizou ensaio de microdureza para avaliar a desmineralização do esmalte pela indução de lesões artificiais de cárie adjacentes a materiais restauradores. Metodologia: Foram utilizados dois cimentos de ionômero de vidro convencionais (MAXXION R® e VIDRION R®), um cimento de ionômero de vidro modificado por resina (VITREMER®) e uma resina composta sem flúor (Z-250®). Cavidades padronizadas foram confeccionadas em 160 blocos de esmalte bovino, divididos aleatoriamente em 4 grupos experimentais (n=40) de acordo com o material utilizado. Após ser realizado o ensaio de microdureza inicial, os blocos de esmalte foram restaurados e submetidos à ciclagem térmica e de pH, simulando o desafio cariogênico. Os blocos foram então submetidos a novos ensaios de microdureza. A partir dos dados obtidos, foi calculada a perda de dureza superficial (PDS) do esmalte, a qual foi comparada através da análise de variância e teste de Tukey (α=0,05). Resultados: A ordem decrescente de perda de dureza superficial do esmalte adjacente foi: Z-250 = VITREMER > VIDRION R > MAXXION R. Conclusão: A desmineralização foi menor no esmalte adjacente aos cimentos de ionômero de vidro convencionais do que no esmalte adjacente aos materiais resinosos.
Purpose: This in vitro study used microhardness testing to assess the enamel demineralization induced by artificial caries lesions adjacent to restorative materials. Methods: Two conventional (MAXXION R® and VIDRION R®) and one resin-modified (VITREMER®) glass ionomer cements and one non-fluoridated composite resin (Z-250®) were tested. Standard cavities were prepared in 160 bovine enamel blocks. The enamel blocks were randomly divided into 4 experimental groups (n=40) according to the material used. After the initial microhardness measurement, the enamel blocks were restored and subjected to thermal and pH cycling, simulating cariogenic challenge. Microhardness measurements were performed on the enamel blocks to calculate the loss of enamel surface hardness. Data were analyzed by analysis of variance and Tukey test (α<0.05). Results: The descending sequence of loss of enamel surface hardness adjacent to the restoration was: Z-250 = VITREMER > VIDRION R > MAXXION R. Conclusion: The enamel adjacent to the conventional glass ionomer cements showed less demineralization than the enamel adjacent to resin-modified materials.