Research Of Digital Registration Method To Evaluate Accuracy Of Oral Implants And Its Applications

PurposeThe aim of the present study was to establish a new method to evaluate the three-dimensional accuracy of oral implant.The new digital registration method which was convenient,economical and non-radiographic was established.Meanwhile,the precision of the new method was verified and the method was used to investigate the accuracy of oral implants inserted by freehand and surgical guide.Materials and methods1.A new digital registration method to evaluate the three-dimensional accuracy of oral implant was established.Firstly,the postoperative plaster cast containing impression cylinder and implant replica was optically scanned.Secondly,the digital cast was aligned with registration models which consist of impression cylinder inserted on implant respectively to calculate the postoperative implant position.Finally,the new method was compared with the traditional radiographic method.(1)For the selected partially edentulous patients,a total of 32 implants from 19 patients with sufficient bone volume were enrolled in the study and all implant surgeries were conducted by one experienced practitioner.Before the surgery,a cone beam computerized tomography(CBCT)scan was made for each patient along with a diagnostic impression to design the ideal implant position using Simplant software.The digital registration method was compared to the traditional radiographic method to evaluate the accuracy of implants.The difference between them was calculated.(2)For fully edentulous dentition,a standard fully edentulous cast with 6implant holes and radiographic markers was designed with Geomagic Studio software.Then the designed digital data were 3D printed and the corresponding implants were inserted into the implant holes.Next the digital registration method and traditional radiographic method were used to measure the threedimensional accuracy of the 6 implants.Finally the difference between two groups was calculated.2.A number of 112 freehand placed implants from 75 patients were collected according to the inclusion and exclusion criteria.The digital registration method was used to evaluate the accuracy of freehand inserted implants.The mesiodistal and buccolingual deviations at implant entrance point and apical point were calculated.The accuracy and its influential factors were evaluated.3.The accuracy of computer aided design/computer aided manufacture(CAD/CAM)surgical template was evaluated.CAD/CAM surgical template group(24 cases)and freehand group(22 cases)were designed to evaluate the clinical effect of CAD/CAM surgical template.Each group contained 36 implants.Digital registration method was used to evaluate the accuracy of implants between two groups.Results1.The results showed that there were no significant differences in threedimensional accuracy of implants between the digital registration method and radiographic method even in partially edentulous patients and the new 3D printed model.2.The three-dimensional accuracy of freehand inserted implant was1.22±0.63 mm at entrance point and 1.91±1.17 mm at apical point.According to the result of multi-ANOVA,the presence of adjacent teeth had an effect on buccolingual and mesiodistal direction at the entrance point.The quadrant factor was vital to the buccolingual direction at the apical point.The edentulous number mainly affected the mesiodistal direction at the entrance point.3.The three-dimensional accuracy was 0.54±0.31 mm at entrance point,0.94±0.51 mm at apical point and 3.29±1.23° in angulation in CAD/CAM surgical template group.The three-dimensional accuracy was 1.01±0.70 mm at entrance point,1.28±0.86 mm at apical point and 4.71±1.98° in angulation in freehand group.Differences were found between the CAD/CAM group and freehand group.ConclusionThe new digital registration method was established which was convenient,economical and non-radiographic.Among the influential factors of freehand implant placement,the presence of adjacent teeth had an effect on buccolingual and mesiodistal direction at the entrance point.The quadrant factor was vital to the buccolingual direction at the apical point.The edentulous number mainly affected the mesiodistal direction at the entrance point.The three-dimensional accuracy of implants in CAD/CAM surgical template group was better than freehand group.