| Background: Oral implants have been used for decades to treat patients with partial or complete missing teeth using implant-supported fixed restorations（IFDP）with some clinical success.Passive fit of IFDP is a prerequisite for maintaining the health of the implant-bone interface and is essential for long-term stabilization of their prognosis and improving success rates.Although absolute passive fit has not been achieved at this stage,a large number of clinical and laboratory studies have shown that providing optimal passive fit is the basis for the prevention of biological and mechanical complications,including screw loosening and breakage,implant breakage,and prosthetic component strain and breakage.However,the accuracy of the final prosthetic cast depends heavily on the impression technique and the accuracy of the material.With the development of digital technology,the digital impression obtained by intraoral optical scanner（IOS）has gradually become an alternative to traditional impression technology.To date,there have been only a few clinical studies on the digital workflow of implant-supported restorations,most of which have reported good results with intraoral optical scanners in single-implant restorations,but it seems less clear that impressions obtained for the design and fabrication of long-span restorations are due to different characteristics（acquisition methods and reconstruction algorithms）as the variety of IOS on the market continues to increase.When selecting IOS in clinical practice,it is important not only to consider its operating characteristics — such as the size of the tip of the scanning head,the speed of image acquisition,or the convenience of operation — but most importantly to consider its accuracy.Therefore,the precision and correctness of IOS must be closely considered in order for digital impressions to obtain the correct implant position.Purpose: This study mainly compared the accuracy of digital impressions made by four intraoral optical scanners in simulating different edentulous conditions.Materials and methods: Four standard maxillary resin models were printed using highprecision light-cured 3D tooth mold resin representing six different edentulous conditions:（1）single anterior tooth loss（SAT）: 11 missing teeth;（2）single posterior tooth loss（SPT）:26 missing teeth;（3）free end posterior tooth continuous loss（APCF）: 15,16,and 17 missing teeth;（4）non-free end posterior tooth continuous loss（APCNF）: 25 and 26 missing teeth;（5）anterior tooth continuous loss（CAT）: 11,12,21,and 22 missing teeth;and（6）edentulous jaw（TEM）: 12,14,16,22,24,and 26 missing teeth.Models were acquired using a desktop scanner（D900;3Shape）as reference groups（RMs）and four IOSs(CS 3600 ?,I500 ?,Trios3 ?,Trios4 ?)scanned 10 times each deletion type as test groups for a total of 240 digital models.Data obtained from all IOSs were imported into reverse engineering software(Geomagic Qualify 2013 ?)and sequentially superimposed on the corresponding RM to assess correctness;precision was assessed by superimposing each other within groups.Final data were statistically analyzed using multivariate analysis of variance and Tukey multiple comparisons.Results: In terms of accuracy: in the SAT group,Trios4 ?（17.1 ± 1.6 μm）had the best results,followed by CS 3600 ?（17.3 ± 1.0 μm）,I500 ?（17.5 ± 0.7 μm）,and Trios3 ?（17.8 ± 0.6 μm）;in the SPT group,the accuracy was Trios4 ?（17.7 ± 0.5 μm）,CS 3600?（17.9 ± 0.5 μm）,Trios3 ?（18.6 ± 0.3 μm）,and I500 ?（20.4 ± 0.3 μm）;in the APCNF group,CS 3600 ?（24.5 ± 1.8 μm）had the best accuracy,followed by I500 ?（26.4 ± 3.7μm）,Trios4 ?（27.9 ± 0.9 μm）,and Trios3 ?（29.5 ± 2.1 μm）;in the APCF group,Trios3?（39.1 ± 3.1 μm）had the best results,This was followed by I500 ?（40.4 ± 1.4 μm）,Trios4 ?（42.4 ± 2.5 μm）,and CS 3600 ?（43.5 ± 3.4 μm）;the results of the CAT group showed that CS 3600 ?（26.1 ± 2.3 μm）had the best accuracy,i.e.This was followed by I500 ?（30.4 ± 0.8 μm）,Trios4 ?（33.1 ± 1.8 μm）,and Trios3 ?（34.5 ± 2.2 μm）;CS3600 ?（45.9 ± 6.4 μm）showed the best accuracy results in the TEM group,followed by Trios4 ?（46.8 ± 8.6 μm）,Trios3 ?（47.1 ± 4.3 μm）,and I500 ?（49.1 ± 1.3 μm）.Statistical analysis revealed that:（1）there was a significant statistical difference in accuracy between IOS under the same deletion type（P < 0.05）;（2）there was also a significant difference between different deletion types when the same IOS was used（P < 0.05）.In terms of precision: In the SAT group,I500 ?（6.3 ± 0.7 μm）had the best precision,followed by Trios4 ?（9.5 ± 1.0 μm）,Trios3 ?（9.8 ± 0.8 μm）,and CS 3600 ?（10.7 ±1.1 μm）;in the SPT group,I500 ?（6.6 ± 0.5 μm）had the best results,followed by Trios4?（8.4 ± 0.9 μm）,Trios3 ?（8.8 ± 1.7 μm）,and CS 3600 ?（10.9 ± 1.3 μm）;in the APCNF group,Trios4 ?（14.1 ± 1.3 μm）had the best precision,followed by CS 3600 ? 16.3 ±1.2 μm),Trios3 ?（16.7 ± 0.9 μm）,and I500 ?（20.0 ± 1.5 μm）;and in the APCF group,I500 ?（15.3 ± 1.6 μm）had the best precision.The others were Trios3 ?（20.9 ± 1.6 μm）,Trios4 ?（22.4 ± 1.5 μm）,and CS 3600 ?（24.7 ± 1.5 μm）;in the CAT group,the best results were obtained with I500 ?（8.8 ± 0.9 μm）,i.e.This was followed by CS 3600 ?（17.2 ± 2.6 μm）,Trios4 ?（19.2 ± 2.5 μm）,and Trios3 ?（19.6 ± 2.5 μm）;in the TEM group,precision results were as follows: Trios4 ?（31.8 ± 2.7 μm）,CS 3600 ?（33.7 ±3.9 μm）,I500 ?（34.0 ± 3.8 μm）,and Trios3 ?（38.5 ± 2.5 μm）.And in statistical analysis:（1）CS 3600 ? was not found to be statistically different between SAT and SPT groups and CAT and APCNF groups（P > 0.05）;（2）Trios3 ? and Trios4 ? were not statistically different between SAT and SPT groups and CAT and APCF groups（P > 0.05）;（3）any IOS in the experiment was statistically significantly different between different deletion types（P < 0.05）.Conclusion: Within the scope of this experimental study,the following conclusions can be drawn: 1.IOSs included in this experiment can be collected at the time of single tooth loss;2.CS 3600 ? performs better in both CAT and APCNF;3.Trios3 ? and I500 ? are more suitable as collection tools in APCF;4.Trios4 ? has better accuracy in TEM. |
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