| Objective:Through the two chairside scan systems Cerec Bluecam and Cerec Omnicam to made digital models, and to produce stereolithographic models with a three-dimensional printer, and then compare the scanning accuracy of the two systems, which was aimed to provide guidance and experimental basis for the clinical application of the two systems.Methods:1 Stereolithographic models preparationMaster model making: With reference to the shape and size of the standard maxillary dentition to manufactured a metal model by precision instrument,of which the thickness of the model base was 10 mm.There were four cylindrical metal preparations on the base, respectively to simulate the maxillary canine preparations and the first molar preparations, and the right canine and the right first molar respectively expressed in A and B,and the left canine and the left first molar respectively expressed in C, D.The hight of the four simulated preparations were 6 mm, and the diameter of simulation preparations A,C and B,D were 6.005 mm and 7.960 mm respectively.The distance AB, CD was 26.830 mm, distance AC was 44.032 mm, distance BD was 56.970 mm. Polish the metal model until it has no sharp edge. A device which was similar to removable partial denture was produced,and fixed it on the metal model, as the master model of the experiment.Using the Cerec Bluecam to make digital impressions:A thin layer of optical imaging powder was sprayed on the master model before scanning. A stable fulcrum must be choosen when the scanning began, the front of camera support touches the master model slightly, or keeps a small gap with the master model. Scanning start from the distal end of the first right molar preparation gradually to the left first molar preparation along the dental arch.Checking the 3-dimensional digital model on the screen, and store the digital impression until the master model images were clear and complete. According to this method to scan the master model 10 times and get 10 digital impressions data,as the Cerec Bluecam group(hereinafter referred to as Bluecam group).Using the Cerec Omnicam to make digital impressions: The camera preheating 15 ~ 20 minutes and the master model needed to be clean and dry befor be scanned. There was a distance of about 5 mm between the camera and preparation. Move the camera at a constant speed from the first right molar simulation preparation to the left first molar simulation preparationat along the dental arch. Check the 3-dimensional digital model on the screen, and store the digital impression until the master model images were clear and complete. According to this method to scan the master model 10 times and get 10 digital impressions data,as the Cerec Omnicam group(hereinafter referred to as Omnicam group).Data processing and stereolithographic models making: using Cerec in Lab software(Sirona Connect) to process the data of digital models, and the processed data of digital models was exported in STL data format.Using the files to produce with a 3-dimensional printer, after removing excess wax, cleaning and dring the stereolithographic models regularly, we got two experiments stereolithographic models. All of the above are operated by one skilled physician.2 Measurements:Using coordinate measuring machine to measure the master model and two groups of stereolithographic models,including the distance AB, AC, BD, and diameter of the right canine teeth simulation preparation(d). All the measurements were performed by one worker in the same conditions,and all measurements were repeated 3 times,and we took the average.3 Statistical analysis:The experimental data were analyzed with SPSS 13.0 software. Test normality and homogeneity of variance. If the result was normal distribution, used mean and standard deviation to describe the results, and the results should be recorded in the form of X ±s. One Way-ANOVA and LSD-t test were chosen if the data were normal and the variances were equal. Ranking test was chosen if the data were not normal or the variances were not equal. Inspecting standard a=0.05.Results:1 The measurement results of master model and different groups were as follows:master model:AB(26.830±0.0015)mm,AC(44.032±0.0037)mm, BD(56.970±0.0015)mm,d(6.005±0.0051)mm;Cerec Bluecam:AB(26.711±0.0023) mm,AC(43.707±0.0042)mm,BD(56.625±0.0177)mm,d(5.992±0.0091)mm; Cerec Omnicam : AB(26.835±0.0079)mm, AC(44.142±0.0055)mm, BD(56.876±0.0234)mm, d(6.025±0.0068)mm.2 Statistical analysis results showed that:The distance AB,AC,BD and diameter(d) were diffierent between the Bluecam group and master model, the differences respectively were as follow:-0.119 mm,-0.325 mm,-0.345 mm, and- 0.013 mm. The difference of the distance AB, AC, BD was statistically significant(P<0.05), the differences of diameter(d)has no statistical significance(P>0.05); The distance AB, AC, BD and diameter(d) were diffierent between the Bluecam group and master model,the differences respectively were as follow:0.005 mm,0.110 mm,-0.094 mm,0.020 mm, among them, the difference of the distance AC, BD was statistically significant(P< 0.05), the differences of the distance AB and diameter(d)has no statistical significance(P>0.05); Bluecam group and Omnicam group had differences in all the distances and diameter(d), and the differences were statistically significant(P<0.05).Conclusions:1 The scanning accuracy of Cerec Bluecam is highest on a single preparation scanning.With the increase of scanning area, the scanning accuracy of Cerec Bluecam is significantly decreased,which can not be used when scanning across the arch clinically.2 The scanning accuracy of Cerec Bluecam is highest on a single preparation scanning.With the increase of scanning area, the scanning accuracy of Cerec Omnicam is decreased,which meets the requirements of clinical application.3 The scanning accuracy of Cerec Bluecam is higher than Cerec Omnicam on a single preparation scanning. And the difference between Cerec Bluecam and Cerec Omnicam was statistically significant. |
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