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Assessment Of Residual Coronal Tooth Structure Post-Endodontic Cavity Preparation Using Intra-oral Digital Scanner and Micro-CT Nassr Al-Nuaimi, Rupert Austin, Shanon Patel, Federico Foschi, Francesco Mannocci Department of Conservative Dentistry, King’s College London Dental Institute, UK Introduction The longevity of root canal treated teeth is significantly affected by the reduction in the amount of remaining coronal tooth structure 1,2 due to the combination of dental caries, restorations, endodontic treatment and fractures. 3 Establishing a reliable method to quantify the amount of remaining coronal hard tooth structure may assist in predicting the survival of endodontically treated teeth and aid in future treatment planning. The purpose of this in vitro study was to evaluate the volumetric scanning accuracy and reliability of digital impressions for 3D measurement of residual coronal tooth structure post-endodontic cavity preparation, with reference to high-resolution micro-computed tomography (μCT). Materials & Methods References Prior to scanning, quantification of the accuracy and precision of the intra- oral digital scanner was performed using metrology gauge block and a profilometric tooth calibration model. Non-invasive access cavities were cut in 34 human extracted molar teeth. All teeth were scanned with an intra-oral digital scanner (Test Scanner: 3M™True Definition scanner) in high-resolution mode and μCT (Reference scanner: GE Locus SP μCT scanner) in high (REF 1) and low (REF 2) resolution modes (Fig. 1). Figure 1 Representative samples for a) tooth, b) intra-oral digital scanner, c) REF 1 and d) REF 2 μCT models before 3D superimposition Alignment was made by superimposing the intra-oral digital scanner datasets on both μCT (REF1 & REF 2) datasets using best-fit alignment (Geomagic ® Control™). Volume measurements and 3D deviations were performed separately and recorded for each scan modality. 3D deviations between test and reference scanners were expressed as mean (+/-) and maximum (+/-) values (µm) and displayed in a colour-coded image using the Geomagic software (Fig.2). Figure 2 Colour-coded difference images presenting for positive and negative deviations analysis between intra-oral digital model and a) REF 1 model, b) REF 2 model 1. Nagasiri R, Chitmongkolsuk S. Long-term survival of endodontically treated molars without crown coverage: a retrospective cohort study. J Prosthet Dent 2005;93:164-70. 2. Ferrari M, Vichi A, Fadda GM, Cagidiaco MC, Tay FR, Breschi L et al. A randomized controlled trial of endodontically treated and restored premolars. J Dent Res 2012;91:72S-8S. 3. Caplan DJ, Weintraub JA. Factors related to loss of root canal filled teeth. J Public Health Dent 1997;57:31-9. The intra-oral digital scanner accuracy was 2 µm, the repeatability was 14.4 µm and the reproducibility was 16.6 µm. Data analysis showed no statistically significant difference in the volumetric measurements obtained from intra-oral scanner, REF 1 and REF 2 μCT scans (P>0.05). (Fig.3) Figure 3 Mean, standard deviations and volume differences of intra-oral digital and μCT scans The mean and maximum +ve deviation values between intra-oral digital scanner and both μCT datasets were significantly different (P<0.001). (Fig. 4 a & b) a) b) * Significant difference (P<0.001) Figure 4 a) Mean, b) Maximum +ve & -ve deviations (mm) and SD resulted from superimposition of 34 μCT (REF) datasets with intra-oral scanner (Test) datasets. Conclusion Results Volumetric scanning using digital impressions of endodontically accessed teeth was not statistically different to the μCT scanner (P>0.05). Intra-oral digital scanner is able to accurately quantify the amount of residual coronal tooth structure following access cavity cutting. From an endodontic point of view, the volumetric accuracy of the True Definition scanner is adequate to be used to create accurate virtual models that reproduce the residual coronal tooth structure. 435.491 441.397 438.44 0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 Digital scanner REF 1 REF 2 -0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04 Digital scanner vs. REF 1 Digital scanner vs. REF 2 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 Digital scanner vs. REF 1 Digital scanner vs. REF 2 Clinical Relevance Scanning the intra-coronal aspect of the endodontically accessed tooth for reliable assessment of the loss of tooth structure during endodontic treatment can be used to make inferences about the prognosis of the endodontic and restorative treatment, leading to improvement in treatment planning process. * * A A a d b c a b
