Salivary concentrations of urea released from a chewing gum containing urea and how these affect the urea content of gel-stabilized plaques and their pH after exposure to sucrose
Salivary concentrations of urea released from a chewing gum containing urea and how these affect the urea content of gel-stabilized plaques and their pH after exposure to sucrose
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DOI：
10.1159/000047473
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发表时间：
2001-09-01
期刊：
影响因子：
4.2
通讯作者：
Dibdin, GH
中科院分区：
文献类型：
--
作者：
Daws, C;Dibdin, GH
目标是：(1)测定咀嚼含有30毫克尿素的无糖口香糖20分钟内唾液中尿素的浓度；(2)测量尿素扩散到凝胶稳定菌斑的程度；(3)研究尿素对暴露在10%蔗糖中1分钟的pH值下降和随后上升的影响(斯蒂芬曲线)；(4)对测量2和3进行数学建模。第1点，12名受试者咀嚼口香糖前2min唾液尿素浓度最高为47 mmo1/L，15min内降至未刺激唾液中的3.4mmo1/L，平均回收率为81.5%。琼脂中1%的琼脂糖或67%的死亡细菌从唾液中积累尿素大致与预期的一样，而那些含有8%活的和59%死亡的前庭链球菌的菌斑显示出可以忽略不计的积累。计算机模拟显示，这种差异是由于活细菌的尿素酶在尿素进入斑块时迅速分解所致。在后一种菌斑中，对斯蒂芬曲线开始后咀嚼口香糖的影响的模拟显示，pH迅速上升，但随后在返回到非刺激条件时再次下降，这种下降在以前的研究中没有看到，对于口腔链球菌，也没有被计算机模拟预测。无论是实验模拟还是计算机模拟都表明，在接触蔗糖之前咀嚼含尿素的口香糖对随后的斯蒂芬曲线没有任何影响。因此，口香糖只有在摄入可发酵碳水化合物后咀嚼时才可能抑制龋齿，而不是在食用之前咀嚼。版权所有(C)2001 S.Karger AG，巴塞尔。
The objectives were to: (1) determine the salivary concentrations of urea during 20 min chewing of a sugar-free gum containing 30 mg of urea; (2) measure the degree to which this urea would diffuse into a gel-stabilized plaque; (3) study the effect of the urea on the fall and subsequent rise in pH (Stephan curve) on exposure to 10% sucrose for 1 min; (4) model the measurements 2 and 3 mathematically. In point 1, the salivary urea concentration of the 12 subjects peaked at 47 mmol/l in the first 2 min of gum chewing, failing within 15 min to the unstimulated salivary concentration of 3.4 mmol/l. Recovery of urea from the saliva averaged 81.5%. 'Plaques' of 1% agarose or 67% dead bacteria in agarose accumulated urea from the saliva roughly as expected, whereas those plaques containing 8% live and 59% dead Streptococcus vestibularis showed negligible accumulation. Computer modelling showed this difference to be due to urease of live bacteria breaking down the urea as rapidly as it entered the plaque. Simulation of the effect of gum chewing subsequent to initiation of a Stephan curve in the latter type of plaque showed a rapid rise in pH but then a fall again on return to unstimulated conditions, This fall had not been seen in previous studies, with Streptococcus oralis, nor was it predicted by the computer modelling. Neither experimental simulation nor computer modelling suggested that chewing urea-containing gum before exposure to sucrose would have any effect on a subsequent Stephan curve. Thus chewing gum is only likely to inhibit caries when it is chewed after consumption of fermentable carbohydrate, rather than before. Copyright (C) 2001 S. Karger AG, Basel.