Assessment Of The Accuracy Of Tooth Morphological Measurement Using Different Methods

Method of measuring tooth morphology can be divided into two kinds of direct measurement and indirect measurement, direct measurement refers to the extracted teeth with vernier caliper for manual measurement, indirect measurement, including dental imaging method for measuring and plaster model of the measurement. Imaging methods is the use of Micro CT, CBCT, spiral CT and panoramic photography and other equipment scanning and measuring the teeth or dental arch. To find an accurate, fast, simple and low cost imaging method to measure the teeth, this study set extracted teeth manual measurement as the control group, the simulated tooth dentition was scaned and measured with MicroCT, CBCT, spiral CT and panoramic photography, respectively. Comparaing accuracy of various methods and screening out an accurate and feasible technique to measure the teeth in vivo.Measuring plaster models by hand is the traditional method of obtaining the teeth size date. But because of the physical properties of gypsum making plaster casts have weakness in the storage, management, transportation, and repeated caliper measurements affect the accuracy. The purpose of this study were to evaluate the feasibility of replacing dental crown shape measurements taken with calipers on plaster dental casts by those from computed tomography scans of the dentition with MicroCT.Contents and methods1. Direct measurement of extracted teeth Cleaning and disinfecting the extracted teeth, and then measuring it with digital caliper, which including tooth length, crown width, thickness and height. Obtaining the date of extracted teeth from averaging three measurements for each item.2. The accuracy analysis of four kinds of imaging methods to measure the teeth shape Using MicroCT, CBCT, spiral CT, and panoramic photography scaned and measured simulated teeth dentition, the length of the teeth, the mesiodistal width and the buccolingual width of the teeth crown was measured. Each item measured three times and repeated after three weeks. The average of three times mesurements as the final results. The results compared with hand-held extracted teeth. Comparing accuracy of four imaging methods by reliability and validity of statistical methods.3. Accuracy of crown measurements with MicroCT and caliper The plaster modals were scanned and reconstructed by MicroCT,and then the digital models were measured by software and the plaster models were measured by manual with digital caliper. Each item measured three times and repeated after three weeks. The average of three times mesurements as the final results. The results compared with hand-held extracted teeth.Results1. The date of tooth length, crown width, thickness and height of extracted teeth within the scope of the Chinese dental database measured by Professor Wang Huiyun, which proved the extracted teeth was from normal dentition. The date was truthful and reliable, which can be the gold standard for follow-up experiments.2. Four kinds of imaging methods measured the simulated dentition between the two measurements are highly correlated(r≥0.964), which proved the reliability of the methods is better. Comparing to the standerd date, the accuracy of MicroCT was highest, its errors ranged from -0.50mm to +0.50mm, but it could not measure the dentition in vivo. Similarity with the MicroCT, the accuracy of CBCT was -0.51~0.51mm, it could be a good method for measuring dentition in vivo. Spiral CT followed CBCT, is -0.62 ~ 0.62mm, its operation was complicated and cost was higher. Panoramic photography measurement error is -1.48 ~ +1.48mm, it could not be used for measuring tooth size for its image was distortion3. The digital model was obtained from scanning the plaster model by MicroCT. The results showed there were close correlations and no significant differences between different groups(r≈1,p<0.001). Comparing to the standerd date, the errors of MicroCT ranged from–0.338mm to +0.338mm, which were less than the errors of plaster cast, -0.408~0.408mm. MicroCT is a better method for measuring crown of plaster model than manual measurements.Conclusions1. Considering the measurement accuracy, operability, applicability and cost, etc., we believe that the CBCT is more suitable for dental dentition morphological measurements in vivo.2. The MicroCT can generate high precision digital dental models which enables operator to measure dental crown shape more freely and precisely in comparison with the plaster models.