Influence of a hydroxyapatite suspension on 48-h dental biofilm formation in-situ.

The aim of the present in-situ study was to investigate anti-adherent properties of mouthrinses containing hydroxyapatite (HAP) nanoparticles on oral biofilm formation. Biofilm was formed for 48 h on bovine enamel or dentine specimens that were fixed to maxillary splints and worn intraoral by six volunteers. During biofilm formation, rinsing was performed with sterile water, HAP (5%) or chlorhexidine (0.2%) according to two different rinsing protocols in order to assess substantivity. Scanning electron microscopy was used to investigate biofilm coverage of specimens, biofilm thickness and morphology. In addition, saliva samples were collected and analysed with transmission electron microscopy. Rinsing with sterile water or HAP resulted in 2.1 or 2.3 µm thick biofilms, respectively, covering more than half of specimen' surfaces. Despite single deposits of nanoparticles in saliva and biofilm, HAP did not inhibit biofilm formation. Chlorhexidine on the other hand significantly reduced biofilm thickness and coverage. Mouthrinses containing HAP nanoparticles showed no anti-adherent effects during 48 h of biofilm formation in-situ. • Hydroxyapatite has no anti-adherent effect during 48-h of biofilm formation. • Nanoparticles adhere to proteins in saliva and are integrated in the biofilm. • Photomerged images of specimens are very representative. [ABSTRACT FROM AUTHOR]