3D method for the volumetric evaluation and visualisation of dental biofilms

Background and objective: Traditional and planimetric plaque indices rely on plaque-disclosing agents and cannot quantify three-dimensional (3D) structures of dental biofilms. We introduce a novel computer-assisted method for evaluating and visualising plaque volume using intraoral scans (IOSs). Materials and methods: This was a 4-day, non-brushing, plaque-regrowth study (n = 15). All plaque was removed at baseline (T0). IOSs at T0 and after 4 days (T4) were used for volumetric plaque assessment in six steps: model acquisition, model superimposition, computer-aided determination of tooth-surface margins, tooth-surface superimposition, visualisation and volumetric evaluation of biofilms. Plaque formation at T4 was additionally assessed with the Turesky Modification of the Quigley-Hein Plaque Index (TMQHPlI). We used Pearson's correlation coefficients and multilevel models to investigate the relationships between TMQHPlI, volumetric plaque index (VPI) and the adjusted volumetric plaque index (AVPI, plaque volume/area). Results: VPI and AVPI positively correlated with the TMQHPlI, showing higher variability at lower TMQHPlI scores. VPI had a lower threshold for plaque detection and higher sensitivity than the TMQHPlI. VPI and TMQHPlI were highest on vestibular, maxillary and molar surfaces. Conclusion: VPI quantifies biofilm deposits, is a more precise measure for plaque detection than the TMQHPlI and can be visualised using colour-coded maps displaying areas of equal plaque thickness.