Effect of a 45S5 Bioactive Glass–Containing Gel on the Remineralization of Artificial Caries- Like Lesions in Primary Teeth: An in Vitro Study

Background This in vitro study investigated the remineralization of artificial caries-like lesions in primary teeth using a multimodal microscopy approach. Micro- and nano-sized 45S5 bioactive glass (BAG) gels were compared with fluoride varnish in terms of surface morphology and volumetric mineral density changes. Methods Enamel–dentin blocks prepared from extracted human primary molars and incisors were demineralized and randomly assigned to three treatment groups (n = 10): fluoride varnish, micro-sized BAG gel, and nano-sized BAG gel. Following treatment, all specimens were subjected to a 6-day pH-cycling protocol. Surface characteristics and elemental composition were analyzed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS), while three-dimensional mineral density (MD) distributions were quantified using micro-computed tomography (µCT). Results SEM/EDS analysis demonstrated that both BAG gels produced relatively uniform surface deposits compared to fluoride varnish. However, µCT measurements revealed significantly higher mineral density in the fluoride-treated specimens (1.39 ± 0.10 g/cm ³ ) than in the micro-sized (1.09 ± 0.21 g/cm ³ ) and nano-sized BAG groups (0.98 ± 0.16 g/cm ³ ) (p < 0.05). Conclusions The combined findings highlight a discrepancy between surface-level observations and subsurface mineral recovery, emphasizing the importance of volumetric µCT analysis when assessing remineralization efficacy. Fluoride achieved higher volumetric mineral density than bioactive glass gels. This study demonstrates the value of integrating surface and volumetric microscopy techniques for the accurate evaluation of mineralized dental tissues.