Physico-mechanical properties and Streptococcus mutans biofilm formation of bio‑based flexible crowns versus stainless steel and zirconia crowns for pediatric full-coverage restorations

Authors

• Tzu-Yu Peng, School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan
• Szu-Yu Lai, School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan.
• Yan-An Wu, School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan
• Ya-Ting Yang, Department of Oral Medicine, Taipei Medical University Shuang Ho Hospital, New Taipei City, Taiwan
• Yuichi Mine, Project Research Center for Integrating Digital Dentistry, Hiroshima University, Hiroshima, Japan.
• Huei-Yu Huang, School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei, TaiwanFollow

Abstract

Background/purpose: Bio‑based flexible (BFX) have recently emerged as a potential alternative to conventional pediatric full‑coverage restorations, but evidence regarding their properties and microbial behavior remains limited. Thus, this study aimed to evaluate the physico-mechanical properties and microbial behavior of BFX crown compared with stainless steel crowns (SSC) and zirconia crowns (ZRC) for pediatric full-coverage restorations.

Materials and methods: Mandibular primary molar crowns from BFX, SSC, and ZRC were assessed. Weight was measured using an electronic balance, and surface roughness and topography were evaluated using a stylus profilometer and atomic force microscopy. The arithmetic mean roughness (Ra) and root mean square roughness (Rq) were determined. Compressive strength was assessed using a universal testing machine, and deformation was quantified as the root mean square (RMS) deviation from three-dimensional scans. Streptococcus mutans (S. mutans) biofilm formation was quantified using crystal violet staining, with optical density measured at 490 nm (OD490) at 24 and 48 h. Data were analyzed using one-way analysis of variance with Tukey's post hoc test (α = 0.05).

Results: BFX crowns had the lowest mean weight (0.15 g) and the highest surface roughness parameters Ra (0.162 µm) and Rq (0.121 µm) among the tested systems (P < 0.05); they also exhibited a more irregular and undulating surface, as indicated by three-dimensional surface topography analysis. Furthermore, BFX exhibited the highest maximum compressive load (1306.5 N) and a significantly greater RMS deformation, suggesting a more compliant mechanical behavior (P < 0.05). Over time, S. mutans biofilm accumulation was consistently greater on BFX than on SSC and ZRC surfaces (P < 0.05).

Conclusion: BFX crowns combine low weight, high load-bearing capacity, and mechanical compliance, offering a potential alternative for pediatric full-coverage restorations. However, their greater surface roughness and biofilm formation may increase bacterial adhesion, warranting cautious use in pediatric population with high caries risk.

Recommended Citation

Peng, Tzu-Yu; Lai, Szu-Yu; Wu, Yan-An; Yang, Ya-Ting; Mine, Yuichi; and Huang, Huei-Yu (2026) "Physico-mechanical properties and Streptococcus mutans biofilm formation of bio‑based flexible crowns versus stainless steel and zirconia crowns for pediatric full-coverage restorations," Journal of Dental Sciences: Vol. 21: Iss. 4, Article 20.
Available at: https://jds.ads.org.tw/journal/vol21/iss4/20

Publication Date

2026

Received Date

June 13 2026

Accepted Date

June 24 2026

Final Revision Date

June 24 2026