Evaluation Of The Accuracy Of Three Intraoral Scanners With Models Containing Different Numbers Of Crown Prepared Abutments

Background:Computer-aided design&computer-aided manufacture has been rapidly developed and popularized in the past 30 years.Among them,the data collection of oral related organization are the precondition and foundation,and the accuracy of data is the key to the success of digital restoration.The digital impression technology has excellent advantages,but its actual accuracy often falls short of the accuracy provided by the manufacturer and requires more data support.In recent years,the superposition of 3D images has been widely used in scanner accuracy studies,and the three-dimensional difference between two surface data can be analyzed by using an appropriate software overlay.Purposes:This study aimed to evaluate the accuracy of three intraoral scanners,TRIOS(3 Shape,Denmark),iTero(Align Technology,USA),CEREC Omnicam(Sirona,Germany)neglecting the effect of the oral environment.for the resin models containing different number abutments.It provides references for relevant research and clinical application.Methods:Using a high-precision resin printer(perfactory-ddp4,envision TEC,Germany)prints 6 resin models containing different numbers of crown prepared abutments(upper jaw):(1)single prepared maxillary right central incisor,(2)single prepared maxillary left second molar,(3)prepared maxillary right first premolar and first molar with the second premolar absent,(4)prepared abutments from right upper canine to left canine,(5)half of upper right arch with 7 prepared teeth,(6)entire upper arch with 14 prepared teeth.6 reference models were digitally scanned,10 times per group,through a dental model scanner(reference scanner)and three three-dimensional scanners(TRIOS,iTero Element,CEREC Omnicam).The obtained data is loaded into the 3D software Geomagic Studio2014(Raindrop Geomagic,USA),and the 3D deviation between the same model data obtained from the reference scanner and different scanner is calculated by comparing the best fitting alignment.The proximity between the test data and the reference data is used as the trueness,and the precision is expressed by the standard deviation of the test result.The one-way variance analysis method was used to compare the differences between groups.(Test level a=0.05)Results:1.The trueness of the three scanners are different for the same scanned object:In Model 1,the trueness of the scanner from high to low:CEREC Omnicam(13.12?m),TRIOS(14.77?m),iTero(18.92p?m);Model 2,TRIOS scanner(12.82?m)and iTero scanner(13.79?m)are superior to CEREC Omnicam(16.01 ?m);In Model 3,the trueness of the CEREC Omnicam scanner(9.52 ?m)is better than those of TRIOS(13.10 ?m)and iTero(12.06 ?m);Model 4,iTero(13.16?m)and CEREC Omnicam(11.63?m)are better than TRIOS(18.79?m);In model 5,CEREC Omnicam trueness(15.65?m)is better than TRIOS(23.20?m)and iTero((23.23?m);In Model 6,the trueness from high to low:CEREC Omnicam(26.07 ?m),iTero(40.87?m),TRIOS(64.94 ?m).2.The trueness of different models scanned by the same scanner are different:The scan trueness of TRIOS and iTero scanners for model 4,model 5 and model 6 are significantly lower than model 1,model 2 and model 3;Trueness of CEREC Omnicam for scanner model 6 is significantly lower than those of other model scans;trueness of model 3 is better than model 1,model 2 and model 5;for model 4 is better than model 2 and model 53.For the same scanned object,the precision of the three scanners are not the same:Model 1,the scanner precision from high to low are:TRIOS,CEREC Omnicam,iTero;Model 2,precision from high to low:TRIOS,iTero,CEREC Omnicam;Model 3,precision from high to low:iTero,CEREC Omnicam,TRIOS;Model 4,iTero and CEREC Omnicam scanners are superior to TRIOS;Model 5,CEREC Omnicam scanner precision is better than TRIOS and iTero;Model 6,iTero and CEREC Omnicam scanners are superior to TRIOS in precision.4.Precision comparison results of scanning different models for the same scanner:For TRIOS scanner,the precision of model 6 is significantly lower than those of other models.For iTero scanner,the scanning precision of model 6 is significantly lower than those of other models,and the scanning precision of model 2 is better than those of model 1 and model 5.For CEREC Omnicam scanner,the scanning precision of model 6 is significantly lower than those of other models,and the precision of model 4 and model 1 are significantly better than those of other groups.5.For the visual analysis of 3D deviation plots of superimposed data,the three scanners exhibit a certain bias pattern:For model 1,three scanners have deviations at the shoulder and incisal edge;In model 4,the TRIOS scanner showed large deviations on the axial surfaces of both cuspids.The iTero scanner was located at the incisal edge of the incisor and the distal approximal surface of the cuspid.The deviation of the CEREC Omnicam appeared in the distal approximal surface of the two cuspids and buccal surface of the right cuspid.For the model 5,all three scanners show large deviations in approximal shoulders of the middle incisor and the distal approximal surface of the second molar.The iTero also shows a large deviation in the incisal edge of anterior teeth and the posterior teeth cusps.For model 6,all three scanners showed deviations in the posterior area.TRIOS and CEREC Omnicam scanners exhibited horizontal contraction in the premolar and molar areas.The CEREC Omnicam scanner also had large deviations in the anterior teeth.iTero's data deviation is vertical distortion.Conclusions:1.CEREC Omnicam show a high trueness than TRIOS and iTero except for the second molar single prepared abutments model.2.TRIOS and iTero scanners have low trueness in scanning long arches(anterior,half arch,full dentition)and decrease in trueness as the range of the arch scan increases;CEREC Omnicam scanner have a a high degree of trueness,for the three-unit fixed bridge and anterior areas scanning with long dental arch range.All three scanners have the lowest trueness in scanning the full arch model.but all are within a clinically acceptable range.3.TRIOS has the highest precision for single-abutment model scans,with the increase of scanning arch range,iTero and CEREC Omnicam are superior to TRIOS in precision.All three scanners exhibited the worst precision when scanning the full arch.4.There are specific deviation patterns.A large deformation exists in the incisal edge of the anterior teeth and end of scanning area.