# Mapping dental biofilms: from plaque index through planimetry to volumetric analysis

## TL;DR

This study introduces a 3D method to measure dental plaque volume, offering a more accurate and objective way to assess plaque accumulation compared to traditional methods.

## Contribution

The paper presents a novel 3D volumetric analysis method for dental plaque using intraoral scans and machine learning.

## Key findings

- 3D volumetric analysis correlates with plaque surface area only for mature, purple-stained plaque.
- Early plaque growth is primarily lateral, while later growth is vertical thickening.
- The 3D method improves personalized oral hygiene assessment and clinical decision-making.

## Abstract

Conventional plaque assessment methods, such as clinical indices and planimetry, rely on plaque-disclosing agents and may overemphasize thin biofilm areas due to plaque thickness variations. This study introduces a digital 3D method to quantify and visualize dental plaque volume from consecutive intraoral scans (IOS) and compares it with the Turesky Modification of the Quigley-Hein Plaque Index (TMQHPlI) and planimetry.

After professional supragingival debridement at baseline (T0), fifteen participants refrained from oral hygiene for four days (T4). De novo plaque formation was assessed at T4 using TMQHPlI after application of a two-tone (pink/purple) plaque-disclosing agent. IOSs (3Shape TRIOS 4) were obtained at T0 and T4. Plaque accumulation was quantified using color-coded IOS comparisons with the Volumetric Plaque Index (VPI) and Adjusted VPI (AVPI). Machine learning (Trainable Weka Segmentation) was used to calculate the Planimetric Plaque Index (PPI).

A correlation between plaque surface area and volume was observed only for purple/mature plaque (p = 0.043). Early plaque growth was dominated by expansion of pink-stained, newly formed plaque. Once more than one-third of the surface was covered, further increases resulted mainly from vertical thickening rather than lateral spread.

3D volumetric analysis offers a comprehensive, objective, and clinician-friendly method for assessing dental biofilms.

The proposed 3D approach enables accurate monitoring of plaque accumulation and maturation, improving personalized oral hygiene assessment, patient education, and clinical decision-making.

The online version contains supplementary material available at 10.1007/s00784-025-06729-z.