Profilometry is established in erosion research. However, in the case of dentine, factors such as the demineralised organic matrix, desiccation effects, or type of measuring device may have an impact on the measurement results, which were investigated in the present study. Dentine specimens were eroded with citric acid (1%, pH 2.6) for 5, 10, 15, 20, 30, 60, 90, and 120 min (n = 15 each). For each specimen, tissue loss was determined under various conditions - before/after enzymatic matrix removal, under standardised wet and desiccated (2/10 min) conditions - with non-contact and contact profilometry. In the presence of matrix, under wet conditions, non-contact profilometry revealed almost no tissue loss. Values (mean ± SD) ranged between 0.3 ± 0.7 µm (5 min) and 3.4 ± 1.5 µm (120 min). Contact profilometry increased values significantly (range: 2.9 ± 1.1 to 30.6 ± 5.8 µm). Desiccation (2 min) significantly increased values, except for 5 min of demineralisation, for non-contact profilometry (range: 0.8 ± 1.3 to 22.1 ± 5.5 µm), and decreased values for contact profilometry up to 15 min and increased them as from 90 min (range: 0.9 ± 1.2 to 33.0 ± 5.5 µm); results after 10 min of desiccation were comparable. After the removal of matrix, under wet conditions, values were distinctly higher (non-contact: 3.5 ± 0.8-55.5 ± 7.4 µm; contact: 4.2 ± 1.3-57.8 ± 8.1 µm). Desiccation (10 min) lowered values by about 2-5 µm due to specimen deformation. Bland-Altman comparisons of various outcomes revealed distinct significant proportional and relative biases. Loss of mineralised tissue cannot be adequately quantified in the presence of matrix. Desiccation leads to matrix shrinkage and specimen deformation. Most importantly, tissue loss values obtained in the presence or absence of matrix are not proportional. Therefore, if mineral status is the target criterion, matrix removal and moisture control are prerequisites.

Detecting and monitoring dental plaque is an important issue in research and clinical practice. In this context, new digital imaging methods that permit permanent documentation of the clinical findings could be promising tools. The aim of the study was therefore to investigate whether disclosed plaque can be reliably visualised on 2D and 3D images captured with digital intraoral imaging devices. Clinical examination was the reference method. Twenty subjects (27.5±1.2 years) were included and plaque was measured at three different stages: habitual plaque (T1), after 72 h without oral hygiene (T2) and after a subsequent habitual brushing exercise (T3). At each time point, plaque was disclosed followed by the clinical examination and capturing the 2D and 3D images (intraoral-camera CS 1500 and intraoral-scanner CS 3600; Carestream Dental, Germany). Plaque amounts were recorded on oral and vestibular surfaces of the Ramfjord-teeth (16, 21, 24, 36, 41, 44) using the Rustogi-modified-Navy-Plaque-Index (RMNPI) and expressed as percentage of plaque-containing RMNPI areas of all RMNPI areas. At T1, percentages (mean±SD) obtained from the clinical examination, 2D and 3D images were 62.2±10.6, 65.1±10.0 and 64.4±10.6 resp. increasing to 76.9±8.0, 77.9±8.6 and 77.5±9.4 resp. at T2. After toothbrushing (T3), values decreased to 56.3±11.1, 58.2±12.1 and 61.2±10.8 resp. All methods were able to show statistically significant changes in plaque amounts at the different time points with in part statistically significant but minor differences between them. The Bland-Altmann analysis revealed a good agreement between values from both 2D and 3D images with the clinical examination. The agreement of the scores obtained with the both image-based methods for the single RMNPI areas with the clinical examination was mainly classified as substantial to almost perfect. Amounts of plaque can be reliably detected and monitored on 2D images from an intraoral camera and on 3D images from an intraoral scanner.

Planimetry is a reliable method for detecting and monitoring plaque. Until now, this method has mainly been applied to conventional-camera images, which is difficult and time-consuming in relation to the entire dentition. Today, 3D-intraoral-scans are well suited for imaging the entire dentition and are therefore an efficient and feasible alternative. 3D-intraoral-scans have already proven successful for the quantification of plaque based on a plaque index. Therefore, aim of this study was to investigate whether images from 3D-intraoral-scans are also suitable for valid planimetric plaque measurements and monitoring; intraoral-camera images served as a reference. Twenty subjects (27.5±1.2 years) were included. Plaque was disclosed at three different time points: habitual plaque (T1), after 72 h without oral hygiene (T2) and after subsequent tooth brushing (T3) and quantified using 3D-intraoral-scans and intraoral-camera images (intraoral-camera CS 1500, intraoral-scanner CS 3600; Carestream Dental, Germany). The percentage of the plaque-covered surface of the total surface area (P%) was determined with a software specially programmed for this purpose using images from 3D-intraoral-scans of the oral and vestibular surfaces of the Ramfjord teeth (16, 21, 24, 36, 41, and 44); the intraoral-camera images of the vestibular surfaces of 16 and 36 served as reference. P% from images of the 3D-intraoral-scan and the intraoral-camera revealed a very good correlation (r = 0.876; p ≤ 0.001); the Bland-Altmann analysis showed a good agreement with no proportional and a very minor systematic bias with slightly higher values from images of the 3D-intraoral-scan. Further, P% measurements of the images of the 3D-intraoral-scan were able to detect changes in plaque levels, showing a 47% (p ≤ 0.001) increase in P% from T1 to T2 and a 43% (p ≤ 0.001) decrease after toothbrushing (T3). Planimetry using images of the 3D-intraoral-scan seems to be a suitable tool for whole mouth planimetry to record and monitor dental plaque.

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