ABSTRACT

Introduction: Fluid flow has a prominent influence on the metabolism of surface-attached biofilms. Dental biofilms are covered by a thin saliva film that flows at different rates in different locations under stimulated and unstimulated conditions.

Methods:The present study employed pH ratiometry to study the impact of different flow velocities, saliva film thicknesses and saliva concentrations on microscale pH developments in Streptococcus mutans biofilms of different age.

Results:While saliva flow at a velocity of 0.8 mm/min (unstimulated flow) had little impact on biofilm pH, stimulated flow (8 mm/min; 80 mm/min) affected vertical pH gradients in the biofilms and raised the average pH in 48-h biofilms, but not in 72-h and 168-h biofilms. The saliva film thickness had a strong impact on biofilm pH under both static and dynamic conditions. pH drops were significantly higher in biofilms exposed to a thin saliva film (≤ 50 µm) than a thick saliva film (> 50 µm). pH drops in the biofilms were also strongly dependent on the saliva concentration and thus the buffer capacity of the salivary medium. For 48-h and 72-h biofilms, but not for 168-h biofilms, pH drops in distinct microenvironments were more pronounced when the local biofilm thickness was high.

 抽象的

简介：流体流动对表面附着的生物膜的代谢具有显着影响。牙齿生物膜覆盖着一层薄薄的唾液膜，在刺激和未刺激条件下，唾液膜在不同位置以不同的速率流动。

方法：本研究采用pH比率测定法研究不同流速、唾液膜厚度和唾液浓度对不同龄期变形链球菌生物膜微尺度pH变化的影响。

结果：虽然唾液流速为 0.8 毫米/分钟（未刺激流）对生物膜 pH 值几乎没有影响，但刺激流（8 毫米/分钟；80 毫米/分钟）会影响生物膜中的垂直 pH 梯度，并提高生物膜中的平均 pH 值。 48 小时生物膜，但 72 小时和 168 小时生物膜则不然。在静态和动态条件下，唾液膜厚度对生物膜 pH 值都有很大影响。暴露于薄唾液膜（≤ 50 µm）的生物膜中 pH 值下降明显高于厚唾液膜（> 50 µm）。生物膜中的 pH 值下降也强烈依赖于唾液浓度，因此也依赖于唾液介质的缓冲能力。对于 48 小时和 72 小时的生物膜，但对于 168 小时的生物膜而言，当局部生物膜厚度较高时，不同微环境中的 pH 值下降更为明显。