KU Leuven BIOMAT, Department of Oral Health Sciences, University of Leuven & Dentistry University Hospitals Leuven, Kapucijnenvoer 7, 3000 Leuven, Belgium.
Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200d, 3001 Heverlee, Belgium.
J Dent. 2017 Aug;63:36-43. doi: 10.1016/j.jdent.2017.05.015. Epub 2017 May 26.
Composites may undergo biodegradation in the oral cavity. The objective was to investigate the effect of single- and multi-species biofilms on the surface roughness and topography of two composites.
Disk-shaped specimens of a paste-like, Bis-GMA-free (Gradia Direct Anterior, GC), and a flowable, Bis-GMA-based composite (Tetric EvoFlow, Ivoclar-Vivadent) were prepared. After ethylene-oxide sterilization (38°C), specimens (n=3) were incubated with Streptococcus mutans or mixed bacterial culture (Streptococcus mutans, Streptococcus sanguinis, Actinomyces naeslundii and Fusobacterium nucleatum). As negative controls, unexposed specimens and specimens exposed to sterile medium (BHI) were used. Specimens exposed to acidified BHI medium (pH=5) and enzymatic solution of cholesterol esterase served as positive control. Following 6-week incubation, the attached biofilms were collected for real-time PCR assessment, after which the surface roughness and topography of the specimens were analyzed with atomic force microscopy. Surface hydrophilicity/hydrophobicity was determined by contact angle measurements. Biofilm structure was analyzed with scanning electron microscopy.
Even though multi-species biofilms were thicker, with more cells attached, they did not significantly affect the surface roughness of the composites. On the other hand, S. mutans alone significantly increased the roughness of Tetric by 40.3%, while its effect on Gradia was lower (12%). The total amount of attached bacteria, however, did not differ between the composites.
S. mutans can increase the surface roughness of composites, depending on their composition. This ability of S. mutans is, however, mitigated in co-culture with other species. In particular, bacterial esterases seem to be responsible for the increased composite surface roughness upon biofilms exposure.
Cariogenic bacteria can degrade composites, thereby increasing the surface roughness. Increased roughness and subsequent improved bacterial accumulation may facilitate the development of secondary caries around composites, which is the most common reason for the restoration failure.
复合材料在口腔中可能会发生生物降解。本研究旨在探讨单一和多物种生物膜对两种复合材料表面粗糙度和形貌的影响。
制备块状的糊剂型 Bis-GMA 自由型（Gradia Direct Anterior，GC）和流动性 Bis-GMA 基复合材料（Tetric EvoFlow，Ivoclar-Vivadent）试件。经环氧乙烷灭菌（38°C）后，将试件（n=3）与变形链球菌或混合细菌培养物（变形链球菌、血链球菌、奈瑟氏放线菌和中间普氏菌）孵育。作为阴性对照，使用未暴露的试件和暴露于无菌培养基（BHI）的试件。将暴露于酸化 BHI 培养基（pH=5）和胆固醇酯酶酶解溶液的试件作为阳性对照。孵育 6 周后，收集附着的生物膜进行实时 PCR 评估，然后用原子力显微镜分析试件的表面粗糙度和形貌。通过接触角测量确定表面润湿性/疏水性。用扫描电子显微镜分析生物膜结构。
尽管多物种生物膜更厚，附着的细胞更多，但它们并没有显著影响复合材料的表面粗糙度。另一方面，单独的变形链球菌显著增加了 Tetric 的粗糙度 40.3%，而对 Gradia 的影响较低（12%）。然而，两种复合材料的附着细菌总量没有差异。
变形链球菌可根据其成分增加复合材料的表面粗糙度。然而，在与其他物种共培养时，变形链球菌的这种能力会降低。特别是，细菌酯酶似乎是生物膜暴露后复合材料表面粗糙度增加的原因。
致龋细菌可降解复合材料，从而增加表面粗糙度。增加的粗糙度和随后的细菌积累增加可能会促进复合树脂周围继发龋的发展，这是修复失败的最常见原因。
