Influence of scanner precision

Introduction: Three dimensional scans are increasingly used to quantify biological topographical changes and clinical health outcomes. Traditionally, this has been limited to specialised centres due to the necessity for expensive scanning equipment and complex analysis software. Within dentistry, improving technology has made cheaper, more accessible methods of data capture and analysis available, potentially facilitating a primary care system to quantify disease progression. However, this system has yet to be compared with previous high precision methods in university hospital settings. The aim of this study was to compare a dental primary care method of data capture (intraoral scanners) with a precision hospital-based method of data capture (laser profilometer) in addition to comparing open source and commercial softwares available to analyse data. Methods: Longitudinal dental wear data from 30 patients were analysed using a two-factor factorial experimental design. At the same appointment, bimaxillary intraoral digital scans (TrueDefinition, 3M, UK) and conventional silicone impressions, poured in type 4 dental stone, were made at baseline and follow up appointments (36 months±10.9). Stone models were scanned using precision laser profilometry (Taicaan, Southampton UK). 3D changes in both forms of digital scans of the first molars (n=76) were quantitatively analysed in engineering software Geomagic Control (3DSystems, Germany) and freeware WearCompare (LeedsDigitalDentistry, UK). Volume change (mm3) was the primary measurement outcome. The maximum point loss (m) and the average profile loss (m) were also recorded. Data, analysed in SPSSv25 (IBM, USA), were paired and skewed. Wilcoxon signed rank tests with Bonferroni correction were used. Results: The median volume change (IQR) for Geomagic using profilometry was -0.37mm3 (IQR-3.75,2.30) and for the intraoral scan +0.51mm3 (IQR -2.17,4.26), p<0.001. In WearCompare, the median volume change for profilometry was -1.21mm3 (IQR -3.48,0.56) and -0.39 mm3 (IQR -3.96,2.76) for intraoral scanning (p=0.039). WearCompare detected significantly greater volume loss than Geomagic regardless of scanner type. No differences were observed between groups when maximum point loss or average profile loss was analysed. Discussion: As expected, the method of data capture, software used, and measurement metric all significantly influenced the measurement outcome. However, when appropriate analysis was used, the primary care system was able to quantify a degree of change and can be recommended depending on the accuracy needed to diagnose a condition. Lower resolution scanners may underestimate complex changes when measuring at a micron level