Neutral gum

CA (Table S1) and CS were purchased from Macklin Biological Co., Ltd. (Shanghai, China), the average molecular weight of CS is 3.0 × 10⁵ Da, and the degree of deacetylation is about 10%. Soy lecithin was purchased from Pengrui Biomedicine Co., Ltd. (Pizhou, China). Hematoxylin and eosin (HE) dye solution, neutral gum, and CCK-8 kit were purchased from BioSharp Co., Ltd. (Hefei, China). Miglyol 812N was purchased from Beijing Fengli Jingqiu Pharmaceutical Co., Ltd. (Beijing, China). Phosphate buffered solution (PBS) solution was prepared with NaCl, KCl, Na₂HPO₄, and KH₂PO₄. The pH value of PBS was adjusted with hydrochloric acid and sodium hydroxide to 7.4, and the concentration of PBS is 0.1 M. The model strain of S. mutans (UA159) was donated by the stomatology laboratory of Zunyi Medical University, and human oral epithelial cells (HOECs) were derived from the cell-sharing platform of Zunyi Medical University. Sprague-Dawley rats were purchased from Zhuhai BesTest Bio-Tech Co., Ltd. (Zhuhai, China).

Dendritic spine structure was observed by Golgi staining (He et al., 2020) using the FD Rapid Golgi Stain Kit (FD Neurotechnology, Inc., Columbia, MD, USA). All procedures were conducted in the dark. The brain tissues were immersed in a mixture of equal volumes of solutions A and B at room temperature for 2 weeks, after which the tissues were transferred to solution C for 72 hours. Next, 100-μm thick coronal sections were cut using a cryostat microtome at –22°C, and mounted on gelatin-coated microscope slides using solution C. A staining solution (one part solution D, one part solution E, and two parts DW) was used to stain the sections for 5 minutes. After the sections were dehydrated and cleared, coverslips were applied using neutral gum (Biosharp, Guangzhou, China). Golgi-stained sections were analyzed with an optical microscope (DFC425 C; Leica).