Department of Oral Medicine and Stomatology, Tsurumi University School of Dental Medicine, Tsurumi, Tsurumi-ku, Yokohama, Kanagawa, Japan.
Department of Removable Partial Prosthodontics, Graduate School, Tokyo Medical and Dental University (TMDU), Yushima, Bunkyo-ku, Tokyo, Japan.
PLoS One. 2019 May 28;14(5):e0217496. doi: 10.1371/journal.pone.0217496. eCollection 2019.
This study aimed to investigate the cleansing effects of grapefruit seed extract (GSE) on biofilms of Candida albicans (C. albicans) formed on denture-base resin and the influence of GSE on the mechanical and surface characteristics of the resin. GSE solution diluted with distilled water to 0.1% (0.1% GSE) and 1% (1% GSE) and solutions with Polident® denture cleansing tablet dissolved in distilled water (Polident) or in 0.1% GSE solution (0.1% G+P) were prepared as cleansing solutions. Discs of acrylic resin were prepared, and the biofilm of C. albicans was formed on the discs. The discs with the biofilm were treated with each solution for 5 min at 25°C. After the treatment, the biofilm on the discs was analyzed using a colony forming unit (CFU) assay, fluorescence microscopy, and scanning electron microscopy (SEM). In order to assess the persistent cleansing effect, the discs treated with each solution for 5 min were aerobically incubated in Yeast Nitrogen Base medium for another 24 h. After incubation, the persistent effect was assessed by CFU assay. Some specimens of acrylic resin were immersed in each solution for 7 days, and changes in surface roughness (Ra), Vickers hardness (VH), flexural strength (FS), and flexural modulus (FM) were evaluated. As a result, the treatment with 1% GSE for 5 min almost completely eliminated the biofilm formed on the resin; whereas, the treatment with 0.1% GSE, Polident, and 0.1% G+P for 5 min showed a statistically significant inhibitory effect on biofilms. In addition, 0.1% GSE and 0.1% G+P exerted a persistent inhibitory effect on biofilms. Fluorescence microscopy indicated that Polident mainly induced the death of yeast, while the cleansing solutions containing at least 0.1% GSE induced the death of hyphae as well as yeast. SEM also revealed that Polident caused wrinkles, shrinkage, and some deep craters predominantly on the cell surfaces of yeast, while the solutions containing at least 0.1% GSE induced wrinkles, shrinkage, and some damage on cell surfaces of not only yeasts but also hyphae. No significant changes in Ra, VH, FS, or FM were observed after immersion in any of the solutions. Taken together, GSE solution is capable of cleansing C. albicans biofilms on denture-base resin and has a persistent inhibitory effect on biofilm development, without any deteriorations of resin surface.
本研究旨在探讨柚籽提取物（GSE）对义齿基托树脂上形成的白色念珠菌（C. albicans）生物膜的清洁效果，以及 GSE 对树脂的机械和表面特性的影响。将 GSE 溶液用蒸馏水稀释至 0.1%（0.1% GSE）和 1%（1% GSE），并制备溶解在蒸馏水（Polident）中的 Polident®义齿清洁片溶液或溶解在 0.1% GSE 溶液中的溶液（0.1% G+P）作为清洁溶液。制备丙烯酸树脂圆盘，并在圆盘上形成白色念珠菌的生物膜。将带有生物膜的圆盘用每种溶液在 25°C 下处理 5 分钟。处理后，通过集落形成单位（CFU）测定、荧光显微镜和扫描电子显微镜（SEM）分析圆盘上的生物膜。为了评估持续的清洁效果，将用每种溶液处理 5 分钟的圆盘在酵母氮基培养基中好氧孵育 24 小时。孵育后，通过 CFU 测定评估持续效果。将一些丙烯酸树脂标本浸入每种溶液中 7 天，评估表面粗糙度（Ra）、维氏硬度（VH）、弯曲强度（FS）和弯曲模量（FM）的变化。结果，用 1% GSE 处理 5 分钟几乎完全消除了树脂上形成的生物膜；而用 0.1% GSE、Polident 和 0.1% G+P 处理 5 分钟对生物膜具有统计学上显著的抑制作用。此外，0.1% GSE 和 0.1% G+P 对生物膜具有持续的抑制作用。荧光显微镜表明，Polident 主要诱导酵母死亡，而至少含有 0.1% GSE 的清洁溶液诱导菌丝和酵母死亡。SEM 还显示，Polident 导致酵母细胞表面主要出现皱纹、收缩和一些深凹坑，而至少含有 0.1% GSE 的溶液不仅诱导酵母细胞表面出现皱纹、收缩和一些损伤，还诱导菌丝细胞表面出现损伤。浸入任何溶液后，Ra、VH、FS 或 FM 均无明显变化。综上所述，GSE 溶液能够清洁义齿基托树脂上的白色念珠菌生物膜，并对生物膜的形成具有持续的抑制作用，而不会对树脂表面造成任何恶化。
