BIOMAT, Department of Oral Health Sciences, University of Leuven and Dentistry University Hospitals Leuven, Kapucijnenvoer 7, 3000, Leuven, Belgium.
Center for Innovative Clinical Medicine, Okayama University Hospital, 2-5-1 Shikata-cho, Okayama, Kita-ku, 700-8558,, Japan.
Clin Oral Investig. 2017 Jun;21(5):1861-1869. doi: 10.1007/s00784-016-1972-3. Epub 2016 Oct 20.
In spite of contradicting results, the high susceptibility of composites for secondary caries is still often associated with the bacterial growth-stimulating effect of released methacrylate monomers. However, most studies that showed this effect were performed with techniques having inherent limitations (spectrophotometry).
Therefore, our objective was to determine the effect of four methacrylate monomers (2-Hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA), ethylene glycol dimethacrylate (EGDMA), diethylene glycol dimethacrylate (DEGDMA)) on the growth of two caries-associated bacteria, Streptococcus mutans and sobrinus, and one non-cariogenic species, Streptococcus sanguinis, using TaqMan quantitative polymerase chain reaction (qPCR) to quantify bacterial DNA.
Cultures were exposed to monomer solutions selected after spectrophotometric growth measurements. At baseline and predetermined time intervals, bacterial DNA was extracted and quantified with TaqMan qPCR. Biofilms grown in the presence of monomers were analyzed with scanning electron microscopy (SEM).
Spectrophotometry indeed showed increased growth rates of all three strains with 5 mM TEGDMA, EGDMA, and DEGDMA and increased total biomass of S. sanguinis with 5 mM TEGDMA. However, qPCR failed to show any growth-stimulating effect of these monomers on S. mutans and S. sobrinus. In contrast, some monomers exhibited a growth-inhibiting effect on S. sanguinis. SEM revealed extracellular matter in S. sobrinus and S. sanguinis biofilms, which might be attributed to polymer formation.
Techniques which quantify bacterial DNA are more appropriate to evaluate bacterial growth in the presence of monomers than spectrophotometry.
Even though methacrylate monomers did not affect the growth of cariogenic species, growth inhibition of S. sanguinis, a non-cariogenic antagonistic species, may lead to ecological shifts towards higher cariogenicity.
尽管结果相互矛盾，但复合材料易于发生继发龋仍是普遍认为与释放的甲基丙烯酸盐单体的细菌生长刺激作用有关。然而，大多数显示这种作用的研究都是用具有固有局限性的技术（分光光度法）进行的。
因此，我们的目的是使用 TaqMan 定量聚合酶链反应（qPCR）来定量细菌 DNA，以确定四种甲基丙烯酸盐单体（2-羟乙基甲基丙烯酸酯（HEMA）、三乙二醇二甲基丙烯酸酯（TEGDMA）、乙二醇二甲基丙烯酸酯（EGDMA）、二乙二醇二甲基丙烯酸酯（DEGDMA））对两种致龋菌（变形链球菌和远缘链球菌）和一种非致龋菌（血链球菌）生长的影响。
在分光光度生长测量后选择单体溶液对培养物进行暴露。在基线和预定的时间间隔，用 TaqMan qPCR 提取和定量细菌 DNA。用扫描电子显微镜（SEM）分析在单体存在下生长的生物膜。
分光光度法确实显示，所有三种菌株在 5mM TEGDMA、EGDMA 和 DEGDMA 存在下的生长率增加，并且 S. sanguinis 的总生物量增加在 5mM TEGDMA 存在下增加。然而，qPCR 未能显示这些单体对 S. mutans 和 S. sobrinus 有任何生长刺激作用。相比之下，一些单体对 S. sanguinis 表现出生长抑制作用。SEM 显示变形链球菌和血链球菌生物膜中存在细胞外物质，这可能归因于聚合物的形成。
与分光光度法相比，定量细菌 DNA 的技术更适合评估单体存在下细菌的生长。
尽管甲基丙烯酸盐单体不会影响致龋菌的生长，但非致龋拮抗物种血链球菌的生长抑制可能导致生态系统向更高的致龋性转变。
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