Patients missing multiple teeth are often treated with dentures to address masticatory, articulatory, and swallowing dysfunction. Soft relining material is indicated in clinical dentistry when the mucosa at the site of denture use is associated with abnormalities of the mucosa due to denture use. However, soft relining material is difficult to clean, and dentures are prone to becoming unclean. Growth of Candida albicans can be a problem for poor denture cleaning. In the present study, C. albicans was cultured on the surface of the soft relining material and then cleaned with an enzyme-based denture cleanser. Cleaning effect was observed from the morphology of C. albicans and surface structure of the soft relining material was observed from the surface roughness and cross-sectional curves. It was inferred that C. albicans was reduced and didn’t cause nano-sized damage to surface microstructure due to the properties of the enzyme component in the enzyme-based detergent.

Tooth-surface-polishing agents are a material for tooth surface polishing for dental hygienists to use after removing plaque, exogenous deposit, and tartar that cannot be removed by patient self-care. We performed cytotoxicity tests of 5 products among clinically available products. As a result, when a tooth-cleaning agent was mixed with the assay medium as a 1/5-concentration sample, cell viability reduced in proportion to sample addition. As there were marked differences in cell viability among the products used in this experiment, dental hygienists should understand the characteristics of a tooth-cleaning agent before use. They are routinely used in current dental clinical practice, but few studies have reported their biological influence.

Chinese-hamster-derived V79 cells and Dulbecco's Modified Eagle's Medium (DMEM) containing 10% fetal bovine serum as an assay medium were used. Cell viability was investigated using the three-dimensional culture method with collagen and MTT assay. The results showed marked differences in cell viability among the samples after cell exposure to each tooth-surface-polishing agents at a 1/5 concentration. It is necessary to understand the characteristics of various tooth-surface-polishing agents and select the most appropriate one for each purpose.

Bone marrow cells from the rat femur, which contain mesenchymal stem cells (MSCs), have frequently been used for bone and tooth regeneration both in vivo and in vitro. However, since a low number of MSCs are present in dental pulp cells (DPCs), hard tissue regeneration in vitro requires a long period of time. Therefore, bioactive substances are needed to promote the proliferation and differentiation of these cells. DPCs from rats (rDPCs) treated with a subcutaneous injection of an immunosuppressant formed significantly more mineralized nodule aggregates in subcultures with dexamethasone (Dex). The effects of vitamin B₁₂ (VB₁₂) on the formation of mineralized nodules in subcultures of rDPCs have also been investigated. VB₁₂ was confirmed to be effective for the proliferation and differentiation of MSCs in a subculture with Dex. Therefore, we herein investigated the effects of VB₁₂ on MSC proliferation, differentiation, and osteogenesis in DPCs from immunosuppressant-injected rats. VB₁₂ effectively enhanced the formation of mineralized nodule aggregates in a subculture of rDPCs.

The Vitrigel-Eye Irritancy Test (EIT) method is an in vitro assay that determines the presence or absence of eye irritation potential of chemicals with high sensitivity. The Vitrigel-EIT method with the applicability domain excluding acidic chemicals showing pH ≤ 5 in the test chemical preparation and all solids was registered as the OECD test guideline No.494 in 2019. In this study, we aimed to revise the test method as it is available for not only liquids but also solids by performing a pretest to exclude the test chemical preparations showing pH ≤ 5 and/or rapid phase-separation within 3 min of testing time. We examined total 158 chemicals (94 liquids, 64 solids), and consequently 51 test chemical preparations (12 showing pH≤ 5, 39 showing rapid phase-separation) were excluded in the pretest. The sensitivity, specificity and accuracy for the 107 applicable test chemicals were 96% (51/53), 67% (36/54) and 81% (87/107), respectively. Meanwhile, the number of chemicals applicable to the Vitrigel-EIT method with the applicability domain in the above TG494 was 89 out of 158, and the sensitivity, specificity and accuracy of the 89 applicable test chemicals were 95% (38/40), 67% (33/49) and 80% (71/89), respectively. These data demonstrated that not only the number of applicable chemicals but also the predictability was improved by the revised Vitrigel-EIT method with the pretest.

This study investigates the cellular uptake and antibacterial properties of metal nanoparticles (MNPs). MNPs, such as AgNPs, PtNPs, and ZnONPs, are known for their enhanced physicochemical properties due to their large surface area. AgNPs possess broad-spectrum antibacterial properties, while PtNPs are used for their catalytic and antioxidant properties. ZnONPs are utilized in various industries for their antibacterial and UV absorption properties. The study aimed to improve the effects of AgNPs and ZnONPs by mixing them with PtNPs. TEM observations confirmed the uptake of MNPs into lysosomes. Pt-AgNPs significantly reduced biofilm formation, while Pt-ZnONPs did not show sufficient efficacy. Future research should focus on optimizing the mixing ratio and particle size to balance antimicrobial efficacy and safety.

Fusobacterium nucleatum (Fn) is a bacterium that plays a significant role in oral biofilm formation, and four subspecies have been identified: Fn animalis (Fna), Fn nucleatum (Fnn), Fn polymorphum (Fnp), and Fn vincentii (Fnv). The present study aimed to isolate Fn strains from interdental plaque samples collected from 40 healthy adults, as a preliminary step in evaluating the differences in biofilm-forming abilities among the subspecies. High-resolution phylogenetic analysis was conducted using the 16S rRNA and rpoB gene sequences. Among the 80 isolates analyzed, 55 strains were classified as Fn, 35 as Fnp, 14 as Fna, and six as Fnv, whereas no Fnn strains were isolated. In addition, strains belonging to other species of the genera Fusobacterium and Leptotrichia were identified. The findings of this study provide a foundation for understanding the role of each Fn subspecies in biofilm formation. The methods established in this study can serve as valuable tools for future research on Fn and oral microbiota.