{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,19]],"date-time":"2026-03-19T15:14:17Z","timestamp":1773933257010,"version":"3.50.1"},"reference-count":19,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,3,19]],"date-time":"2026-03-19T00:00:00Z","timestamp":1773878400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>This study evaluated the potential protective effect of a synthesized self-antibacterial nano-hydroxyapatite (nano-HA) toothpaste against erosive changes in the enamel surface induced by a cola-based soft drink, based on a qualitative scanning electron microscopy (SEM) study, in comparison with conventional fluoride toothpaste. Thirty extracted human premolars were sectioned to obtain enamel specimens and randomly assigned into a control group and experimental groups in which fluoride or synthesized nano-HA toothpaste was applied either before or after cola exposure (n = 5 per group). Enamel surface morphology was qualitatively assessed using SEM, and surface roughness (Ra) was estimated using a semi-quantitative approach based on SEM image analysis using ImageJ software. Antibacterial activity was evaluated using the agar diffusion method to explore the potential additional benefits of the synthesized self-antibacterial nano-HA formulation. SEM observations showed that, after cola exposure, specimens treated with nano-HA exhibited less surface erosion than fluoride-treated groups. Post-treatment with nano-HA results in a denser and more uniform surface layer with fewer structural defects. Similarly, enamel treated with nano-HA after cola exposure showed a statistically significant reduction in surface roughness compared with the fluoride group (p &lt; 0.05). These findings suggest that nano-HA provides greater protective effects against acid-induced enamel surface erosion. Furthermore, nano-HA indicated potential antibacterial activity against S. aureus and E. coli. Overall, nano-HA toothpaste provided enhanced protection against acid-induced enamel erosion with additional antibacterial effects.<\/jats:p>","DOI":"10.3390\/ijms27062796","type":"journal-article","created":{"date-parts":[[2026,3,19]],"date-time":"2026-03-19T12:49:24Z","timestamp":1773924564000},"page":"2796","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["A Qualitative In Vitro SEM Study on the Protective Effects of a Self-Antibacterial Nano-Hydroxyapatite Toothpaste Against Acid-Induced Enamel Surface Erosion"],"prefix":"10.3390","volume":"27","author":[{"given":"Chamnan","family":"Randorn","sequence":"first","affiliation":[{"name":"Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"},{"name":"Center of Excellence in Materials Science and Technology, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pongpen","family":"Kaewdee","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"},{"name":"Office of Research Administration, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gobwute","family":"Rujijanagul","sequence":"additional","affiliation":[{"name":"Center of Excellence in Materials Science and Technology, Chiang Mai University, Chiang Mai 50200, Thailand"},{"name":"Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"},{"name":"Multidisciplinary Research Institute, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sujitra","family":"Tandorn","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"},{"name":"Office of Research Administration, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"401","DOI":"10.1002\/sca.21132","article-title":"Preventive Effect of Different Toothpastes on Enamel Erosion: AFM and SEM Studies","volume":"36","author":"Lombardini","year":"2014","journal-title":"Scanning"},{"key":"ref_2","first-page":"e861","article-title":"Remineralizing Effect of a Zinc-Hydroxyapatite Toothpaste on Enamel Erosion Caused by Soft Drinks: Ultrastructural Analysis","volume":"9","author":"Colombo","year":"2017","journal-title":"J. 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