Accuracy Of Impression And Implant Digital Surgical Guides For Partially Edentulous And Edentulous Arches Using Intraoral Scanning Technique

Objectives:The study aimed to evaluate the accuracy of impression and implant digital surgical guides for partially edentulous,mainly free-end dentition,and edentulous arches using intraoral scanning(IOS)technique.Methods:The first part of this article assessed the accurary of IOS for partially edentulous and edentulous arches.An in-vitro study was carried out to measure the accuracy of IOS for partially edentulous models.Six pair of free-end dentition and nonfree-end dentition models were scanned with laboratory scanner(inEOS X5;Dentsply Sirona,Germany)and the result was set as reference.After IOS(Trios 3,3shape,Denmark),the general trueness and precision deviation were calculated in Geomagic Control(Geomagic INC,USA).Then,we evaluated the accuracy of IOS for edentulous maxilla and mandible models with and without resin markers.The edentulous models with resin markers and without resin markers were scanned with intraoral scanner(Trios 2,3shape,Denmark)respectively,the result of laboratory scanner(inEOS X5;Dentsply Sirona,Germany)was set as reference.The general trueness and precision deviation was calculated in software.The scanning time and number of images were recorded to evaluate scanning efficiency.The next in-vivo experiment evaluated the accuracy of IOS for edentulous arches and the influence of different trimming methods on it.Sixteen edentulous maxillas and 10 edentulous mandibles were scanned with intraoral scanner(Trios 3,3shape,Denmark).The conventional impression was taken with impression compound and alginate impression material,the stone casts were scanned with laboratory scanner and used as reference.In software,the deviation between the IOS and conventional impression was calculated.The digital impression was trimmed with two methods and the deviation value for different trimming methods were compared.The second part of this article is a preliminary study of fabricating implant surgical guides for free-end dentition and edentulous arch with IOS technique.Firstly,a self controlled clinical trial was carried out to compare the accuracy of implant suigical guides fabricated with IOS and convention impression technique for free-end dentition.Six bilateral free-end dentition arches were included and 12 implants were analyzed.On one side of the arch,the implant surgical guide was fabricated basing on IOS data while on the other side basing on conventional impression data.The implant deviation was compared pairly.Next,we made preliminary exploration on the feasibility and accuracy of implant surgical guides for edentulous arches using IOS technique.Two clinical cases were performed and 5 implants were analyzed.Results:The result of the first part of this article showed:the trueness and percision deviation of IOS for free-end dentition models was 72.4-108.3?m and 66.8-97.3?m,that for nonfree-end dentition models was 60.9-81.9?m and 45.2-92.8?m.The trueness deviation of free-end dentition was significantly higher than the nonfree-end group(p<0.01),but no statistical difference was found in precision deviation.The loss of anterior teeth would influence the accuracy.The trueness deviation of the IOS for edentulous model was 126.30135.50 ?m in maxilla and 156.60-161.10?m in mandible.Resin markers placed on the hard palate of edentulous maxilla could improve the precision of the IOS and improve scanning efficiency.However,they did not affect the trueness of the IOS for edentulous maxillae or mandibles.The IOS accuracy of edentulous arches was(904.6±122.2)?m in maxilla and(1395.8±173.7)?m in mandible.After the movable mucosa and vestibule area was trimmed,the deviation was(263.5±75.6)?m in maxilla and(344.2±77.1)?m in mandible.The accuracy of the two trimming methods was siginificantly different.The result of the second part of this article showed:in the IOS group,the general platform deviation was(1.09±0.41)mm,the general apex deviation was(1.49±0.3 8)mm and the angle deviation was(5.83±4.19)degrees.Higher platform deviation and coronal-apical apex deviation was observed in IOS group comparing to conventional impression group(P<0.05).The accuracy of implant surgical guides for edentulous arches basing on IOS technique was:general platform deviation(1.90±0.85)mm,general apex deviation(2.18±0.74)mm and angle deviation(5.40±4.73)degrees.Conclusions:The result of our research indicated that1.The result of in-vitro experiments showed the trueness and precision deviation of IOS for free-end models and edentulous models were clinically acceptable.Setting resin markers on the hard palate of maxilla could improve intraoral scanning accuracy.2.In actual clinical practice,the deviation between IOS impression and conventional impression for edentulous jaw was large,the deviation was mainly caused by the movable mucosa in vestibule and mouth floor area.After movable mucosa was trimmed off,the accuracy of IOS for edentulous jaw improved significantly.3.The full digital workflow of fabricating implant surgical guides for free-end dentition is clinically available,and the general accuracy was acceptable.4.Several factors could influence the accuracy of implant surgical guides fabricatied with IOS impression for edentulous arches.Furthur exploration should be make to evaluate the feasibility of fabricating implant surgical guide in full digital workflow.