OBJECTIVE: To quantitatively evaluate the accuracy of data obtained from liquid-interference surfaces using an intraoral 3D scanner (IOS) integrated with a compressed airflow system, so as to provide clinical proof of accuracy for the application of the compressed airflow system-based scanning head in improving data quality on liquid-interference surfaces. METHODS: The study selected a standard model as the scanning object, adhering to the "YY/T 1818-2022 Dental Science Intraoral Digital Impression Scanner" guidelines, a standard that defined parameters for intraoral scanning. To establish a baseline for accuracy, the ATOS Q 12M scanner, known for its high precision, was used to generate true reference values. These true values served as the benchmark for evaluating the IOS performance. Building on the design of an existing scanner, a new scanning head was developed to integrate with a compressed airflow system. This new design aimed to help the IOS capture high-precision data on surfaces where liquid-interference, such as saliva, might otherwise degrade scanning accuracy. The traditional scanning method, without airflow assistance, was employed as a control group for comparison. The study included five groups in total, one control group and four experimental groups, to investigate the effects of scanning lens obstruction, airflow presence, liquid media, and the use of the new scanning head on scanning process and accuracy. Each group underwent 15 scans, generating ample data for a robust statistical comparison. By evaluating trueness and precision in each group, the study assessed the impact of the compressed airflow system on the accuracy of IOS data collected from liquid-interference surfaces. Additionally, we selected Elite and Primescan scanners as references for numerical accuracy values. RESULTS: The scanning accuracy on liquid-interference surfaces was significantly reduced in terms of both trueness and precision [Trueness: 18.5 (6.5) vs. 38.0 (6.7), P < 0.05; Precision: 19.1 (8.5) vs. 31.7 (15.0), P < 0.05]. The use of the new scanning head assisted by the compressed airflow system significantly improved the scanning accuracy [Trueness: 22.3(7.6) vs. 38.0 (6.7), P < 0.05; Precision: 25.8 (9.6) vs. 31.7 (15.0), P < 0.05]. CONCLUSION The scanning head based on the compressed airflow system can assist in improving the accuracy of data obtained from liquid-interference surfaces by the IOS.
Imaging, Three-Dimensional/methods* ; Humans ; Dental Impression Technique/instrumentation*

OBJECTIVES: This study aims to explore the effect of improving clinical efficiency by replacing traditional impression workflow with centralized digital impression workflow. METHODS: The department of prosthodontics in Center of Stomatology, Peking University Shenzhen Hospital has improved the clinical workflow by replacing the traditional impression made by doctors using impression materials for each patient with a centralized digital impression made by one technician for all patients in the department. This cross-sectional study recorded the chairside time required for impression taking in patients undergoing single posterior zirconia full crown restoration before clinical process improvement; the time required for centralized digital impression production; the comfort level of patients; and the adjacency relationship, occlusal contact relationship, and time required for prostheses adjusting (i.e., whether centralized digital impressions would compromise the quality of pro-stheses and increase the time of prostheses adjusting). RESULTS: The average time to make a traditional impression was (9.98±1.41) min, and the average time required for each patient to make a centralized digital impression was (5.98±1.49) min, which was shorter than that to used make a traditional impression (P<0.05). Centralized digital impression made patients feel more comfortable compared with traditional impression (P<0.05). The adjacency relationship of restorations by centralized digital impression was more appropriate (P<0.05), and no significant difference in occlusal relationship was found (P>0.05). The time required for adjusting prostheses also had no significant differences (P>0.05). CONCLUSIONS Centralized digital impression can improve clinical efficiency for patients undergoing single posterior zirconia crown restoration. The time for impression taking is shorter, and patients feel more comfortable without compromising the quality of the prostheses.
Humans ; Cross-Sectional Studies ; Dental Impression Technique ; Crowns ; Zirconium ; Workflow ; Computer-Aided Design ; Time Factors ; Dental Impression Materials

OBJECTIVES: This study aimed to investigate the influence of the dimensional stability of 3D printed resin master model on the replication accuracy of implant replicas. METHODS: Ten digital impressions of patients undergoing continuous crowns or fixed bridge restoration supported by two implants were obtained, and resin models with implant replicas were 3D printed. Scanning rods were fixed on the replicas 3, 7, and 14 days after printing. The 3D, linear, and angular deviations of the scanning rods at different times were analyzed through Geomagic Wrap 2021 software. RESULTS: The position of the replicas shifted mesiolingually, in the same direction as the shrinkage of the model. From day 7 onward, the 3D, distance linear, and angular deviations of the replicas (scanning rod) significantly increased compared with those on the 3rd day (P<0.05). On the 14th day, the changes were even more pronounced, with the above deviations showing statistical significance (P<0.05) compared with those for the 3-day and 7-day groups. No statistical difference in height linear deviation was observed among the groups. CONCLUSIONS The insufficient dimensional stability of 3D printed resin models can lead to changes in the relative position and angle of the replicas, thereby affecting the accuracy of the replicas in recreating the implant's position. Complete manufacturing of prosthesis is recommended within 7 days after the model is printed.
Printing, Three-Dimensional ; Humans ; Dental Implants ; Models, Dental ; Dental Impression Technique ; Crowns

OBJECTIVES: To evaluate the accuracy of a self-developed extraoral scanning system based on four-camera stereophotogrammetric technology in the acquisition of three-dimensional positional information on dental implants and conduct a comparative study involving an intraoral scanning system. METHODS: With the use of an in vitro edentulous jaw model with implants, extraoral (experimental group) and intraoral (control group) scanning systems were employed to obtain STL (Standard Tessellation Language) datasets containing three-dimensional morphological and positional information on scan bodies. In addition, a dental model scanner was used to obtain reference data. The three-dimensional morphological, linear, and angular deviations between groups and reference data were analyzed using Geomagic Wrap 2021 software to compare trueness and precision. RESULTS: The extraoral scanning system demonstrated superior trueness in three-dimensional morphological, linear, and angular deviations compared with the intraoral scanning system, with statistically significant differences (P<0.001). The extraoral scanning system also showed a higher precision in three-dimensional morphological deviation (P<0.001). As the number of implants increased, the extraoral scanning system exhibited increased three-dimensional morphological and linear deviations (P<0.001) but maintained a stable angular deviation. The intraoral scanning system displayed significant increases in three-dimensional morphological, linear, and angular deviations with the increase in the number of implants (P<0.05). CONCLUSIONS The stereophotogrammetry-based extraoral scanning system outperforms intraoral scanning system in terms of the accuracy for multi-unit implant positioning and provides a novel approach for attaining a fully digital workflow for implant rehabilitation in edentulous jaws.
Jaw, Edentulous ; Humans ; Dental Impression Technique ; Dental Implants ; Imaging, Three-Dimensional/methods* ; Photogrammetry/methods* ; Models, Dental

Objective: To explore the effect of scanning methods on finish line trueness of the full crown preparation. Methods: The standard full crown preparation model of the right maxillary first molars was prepared by using the maxillary standard resin dentition model. The standard preparation was scanned by imetric scanner and data were used as the true value. CEREC Omnicam and 3Shape TRIOS were used to scan the standard preparation. According to the scanning methods, they were divided into parallel scanning group, occlusal wave scanning group and buccolingual wave scanning group. Each group was scanned repeatedly 6 times. The data were imported into Geomagic Studio 2013 software, and the local finish line image data of the mesial, distal, buccal and lingual regions of the full crown preparation were extracted respectively. Three-dimensional deviation analysis was performed with the reference true value, and the root- mean-square error (RMSE) was the evaluation index of scanning trueness. The statistical method was one-way ANOVA. Results: Parallel scanning group: in general, the RMSE value of complete finish lines of scanner B [(35±6) μm] was significantly lower than that of scanner A [(44±7) μm](P<0.05). After scanner A occlusal wave scanning, the RMSE values of the mesial and distal finish lines [(33±5) and (50±12) μm] were significantly lower than those of parallel scanning group (P<0.05). After buccal and lingual wave scanning, the RMSE values of local finish lines in the mesial, distal, buccal and lingual regions [(37±3), (50±6), (28±6) and (29±8) μm] were significantly lower than those in parallel scanning group [(45±9), (63±7), (38±3) and (40±3) μm] (P<0.05). No significant difference was found in the RMSE values of the mesial, distal, buccal and lingual regions of scanner B between parallel scanning group, occlusal wave scanning group and buccolingual scanning group (P>0.05). Conclusions: The scanning trueness of the full crown preparation finish line obtained by the active triangulation scanning equipment can be improved by changing the scanning method to wave scanning.
Humans ; Imaging, Three-Dimensional ; Dental Impression Technique ; Computer-Aided Design ; Dental Care ; Crowns

Objective: To investigate the trueness of 4 three-dimensional (3D) facial scanners and to evaluate the applicability of their clinical use. Methods: An art head model was used as the scanning object, and it was scanned by Handyscan 3D scanner in an enclosed environment with a fixed light source to obtain the reference digital model. Three fixed 3D facial scanners (A: 3dMDface; B: Facego Pro; C: RDS Facescan) and a portable hand-held 3D facial scanner (D: Revopoint POP 2) were used to scan the art head model 10 times, and 10 models of each scan group were obtained. The face of the reference model was divided into 16 regions according to anatomy and muscle distributions in the Geomagic Wrap software with saved boundary curves of whole face and each region. The test models were also divided into 16 regions through the curves above after registered with the reference model through "Best fit" function. The root-mean-square error (RMS) of the complete test models and their segmented regions compared with the reference model and its corresponding regions were calculated by 3D comparison function. The smaller the RMS, the higher the accuracy. One-way ANOVA and SNK post-test were used for statistical analysis. Results: RMS of complete test models scanned by A, B, C, D scanners were (0.295±0.005), (0.216±0.053), (0.059±0.012) and (0.103±0.026) mm (F=123.81, P<0.001), respectively. There was significant difference between any two groups (P<0.05). For each facial region, the group D had the best trueness in nasal region, lip region, left orbital region and right orbital region [RMS were (0.079±0.032), (0.061±0.019), (0.058±0.021), (0.081±0.032) mm, respectively], while the group C had the best trueness in frontal region, left buccal region, right buccal region, left zygomatic region, right zygomatic region, left parotideomasseteric region, right parotideomasseteric region, left temporofacial region, right temporofacial region, mental region, left infraorbital region and right infraorbital region [RMS were (0.039±0.011), (0.034±0.007), (0.033±0.007), (0.066±0.023), (0.038±0.022), (0.070±0.030), (0.067±0.024), (0.063±0.029), (0.045±0.023), (0.063±0.006), (0.039±0.010), (0.046±0.008) mm, respectively]. Conclusions: On the basis of art head model scanning, although the overall average deviation between the scanning model and the reference models obtained by the four kinds of 3D facial scanners were small, the portable handheld 3D facial scanner (D) has better accuracy than the fixed 3D facial scanners (A, B, C) in the orbital area, nasal area, lip area and areas with rich features.
Computer-Aided Design ; Imaging, Three-Dimensional ; Software ; Dental Impression Technique

OBJECTIVE: To compare the operation complexity and accuracy of traditional splint impression technique and impression technique with prefabricated rigid connecting bar system for full-arch implants-supported fixed protheses in vitro. METHODS: Standard mandibular edentulous model with six implant analogs was prepared. The implants were placed at the bone level and multiunit abutments screwed into the implants. Two impression techniques were performed: the traditional splint impression technique was used in the control group, and the rigid connecting bar system was used in the test group. In the control group, impression copings were screwed into the multiunit abutments and connected with autopolymerizing acrylic resin. Open tray impression was fabricated with custom tray and polyether. In the test group, cylinders were screwed into the multiunit abutments. Prefabricated rigid bars with suitable length were selected and connected to the cylinders with small amount of autopolymerizing acrylic resin, and open tray impression was obtained. Impression procedures were repeated 6 times in each group. The working time of the two impression methods were recorded and compared. Analogs were screws into the impressions and gypsum casts were poured. The gypsum casts and the standard model were transferred to stereolithography (STL) files with model scanner. Comparative analysis of the STL files of the gypsum casts and the standard model was carried out and the root mean square (RMS) error value of the gypsum casts of the control and test groups compared with the standard model was recorded. The trueness of the two impression techniques was compared. RESULTS: The work time in the test group was significantly lower than that in the control group and the difference was statistically significant [(984.5±63.3) s vs. (1 478.3±156.2) s, P < 0.05]. Compared with the standard model, the RMS error value of the implant abutments in the test group was (16.9±5.5) μm. The RMS value in the control group was (20.2±8.0) μm. The difference between the two groups was not significant (P>0.05). CONCLUSION The prefabricated rigid connecting bar can save the chair-side work time in implants immediate loading of edentulous jaw and simplify the impression process. The impression accuracy is not significantly different from the traditional impression technology. The impression technique with prefabricated rigid connecting bar system is worthy of clinical application.
Acrylic Resins ; Calcium Sulfate ; Dental Implants ; Dental Impression Materials ; Dental Impression Technique ; Humans ; Jaw, Edentulous ; Models, Dental ; Mouth, Edentulous

Objective: To evaluate the effect of adding a geometric feature on the accuracy of digital impressions obtained by intraoral scanners for implant restoration of edentulous jaw quantitatively. Methods: A dentiform model of the maxilla of completely edentulous arch with 6 implant analogs+scan bodies (No. 1-6) was selected as the reference model. Without geometric feature, the dentiform model was scanned by dental model scanner and repeated for 5 times as true value group. Before and after adding the geometric feature, the same operator used intraoral scanner A (Trios 3) and B (Aoralscan 2) to scan the dentiform model with the same scanning path. Each type of intraoral scanner scanned 10 times and ".stl " datas were obtained. The results were imported into reverse engineering software (Geomagic Studio 2015). The linear distances of center point of upper plane between sacn body 1 to 6 was calculated, denoted as D12, D13, D14, D15 and D16. Trueness was the absolute value subtracted from the measured value of the intraoral scanner groups and true value; precision was the absolute value of pairwise subtraction of the measured values in the intraoral scanner groups.The smaller the value, the better the accuracy or precision.With or without the feature, all scan data were statistically analyzed, and the effect of adding geometric feature on the trueness and precision of the two intraoral scanners were evaluated. Results: As for intraoral scanner A, with the feature in place, significant differences were found in D14, D15, D16 for tureness(t=2.66, 2.75, 2.95, P<0.05); the trueness for D16 decreased from (101.9±47.1) μm to (49.6±30.3) μm. On the other hand, with features on the edentulous area, the precision was significantly increased in D15 and D16 (U=378.00, 672.00, P<0.05); the precision for D15 decreased from 40.8 (45.1) μm to 13.1 (17.0) μm. As for intraoral scanner B, the trueness of D12, D13 and D14 after adding geometric features was significantly better than before (t=3.02, 2.66, U=22.00, P<0.05). With feature on the edentulous area, the trueness for D13 decreased from (116.6±41.2) μm to (70.8±35.5) μm. There was no statistical significance in the trueness of D15 and D16 with or without geometric feature (P>0.05), however, the precision of D15 and D16 after adding geometric feature was significantly better than before (U=702.00, 489.00,P<0.05). The precision of D16 decreased from 112.5 (124.7) μm to 35.9 (85.8) μm. Conclusions: The use of geometric feature in edentulous space improves the trueness and precision of the different principle intraoral scanners tested.
Computer-Aided Design ; Dental Implants ; Dental Impression Technique ; Imaging, Three-Dimensional ; Models, Dental

Objective: To compare the accuracy of photogrammetry and conventional impression techniques for complete-arch implant rehabilitation. Methods: An edentulous maxillary stone cast containing 8 screw-retained implant abutment replicas was derived from a 74-year-old male patient who visited the Department of Dental Implant Center, Capital Medical University School of Stomatology in September 2019. The stone cast was copied through the open-tray splinted impression, and the copied cast was used as the master cast for this study. The abutment-level impressions of master cast were made by photogrammetry (PG) and the conventional impression technique (CNV) by one attending doctor. Group PG: after which scan bodies were connected to each implant replica, a photogrammetry system was used to obtain digital impressions of the master cast (n=10); Group CNV: conventional open-tray splinted impression technique was performed to fabricate conventional definitive casts (n=10). After connecting the scan bodies onto each implant replicas, the master cast and the 10 definitive casts from group CNV were digitized with a laboratory reference scanner. All data of group PG, group CNV and mater cast were saved as ".stl" files. For all test scans and reference scan, the three-dimensional information of scan bodies were converted to implant abutment replicas using a computer aided design software (Exocad). The data of the group PG and the group CNV were respectively registered with the reference data (trueness analysis) and pairwise within group (precision analysis) for accuracy evaluation in a three-dimensional analysis software (Geomagic Control X). Results: The trueness and precision of group PG [(17.33±0.34) and (2.50±0.79) μm ] were significantly statistically better than those of group CNV [(24.30±4.16) and (26.12±4.54) μm] respectively (t=-5.29 and -34.35, P<0.001). Conclusions: For complete-arch implant abutment-level impression, photogrammetry produces significantly better accuracy than conventional impression technique.
Aged ; Computer-Aided Design ; Dental Implants ; Dental Impression Materials ; Dental Impression Technique ; Humans ; Models, Dental ; Photogrammetry

OBJECTIVE: To provide a reference for using intraoral scanners for making clinical diagnostic dentures of edentulous jaws by comparing the accuracy of three intraoral scanners for primary impression and jaw relation record of edentulous jaws. METHODS: This study contained 6 primary impressions of the edentulous patients. Each of the impressions consisted of the maxillary primary impression, the mandibular primary impression and the jaw relation record. For each of them, a dental cast scanner (Dentscan Y500) was used to obtain stereolithography (STL) data as reference scan, and then three intraoral scanners including i500, Trios 3 and CEREC Primescan were used for three times to obtain STL data as experiment groups. In Geomagic Studio 2013 software, trueness was obtained by comparing experiment groups with the reference scan, and the precision was obtained from intragroup comparisons. Registered maxillary data of the intraoral scan with reference scan, the morphological error of jaw relation record was obtained by comparing jaw relation record of the intraoral scan with the reference scan. Registered mandibular data with jaw relation record of intraoral scan and the displacement of the jaw position were evaluated. Independent samples t test and Mann-Whitney U test in the SPSS 20.0 statistical software were used to statistically analyze the trueness, precision and morphological error of jaw relation record of three intraoral scanners. The Bland-Altman diagram was used to evaluate the consistency of the jaw relationship measured by the three intraoral scanners. RESULTS: The trueness of i500, Trios 3 and CEREC Primescan scanners was (182.34±101.21) μm, (145.21±71.73) μm, and (78.34±34.79) μm for maxilla; (106.42±21.63) μm, and 95.08 (63.08) μm, (78.45±42.77) μm for mandible. There was no significant difference in trueness of the three scanners when scanning the maxilla and mandible(P>0.05). The precision of the three scanners was 147.65 (156.30) μm, (147.54±83.33) μm, and 40.30 (32.80) μm for maxilla; (90.96±30.77) μm, (53.73±23.56) μm, and 37.60 (93.93) μm for mandible. The precision of CEREC Primescan scanner was significantly better than that of the other two scanners for maxilla (P<0.05). Trios 3 and CEREC Primescan scanners were significantly better than i500 scanner for mandible (P<0.05). The precision of the i500 and Trios 3 scanners for mandible was superior to maxilla (P<0.05). The upper limit of 95% confidence intervals of trueness and precision of three scanners for both maxilla and mandible were within ±300 μm which was clinically accepted. The morphological error of jaw relation record of the three scanners was (337.68±128.54) μm, (342.89±195.41) μm, and (168.62±88.35) μm. The 95% confidence intervals of i500 and Trios 3 scanners were over 300 μm. CEREC Primescan scanner was significantly superior to i500 scanner(P<0.05).The displacement of the jaw position of the three scanners was (0.83±0.56) mm, (0.80±0.45) mm, and (0.91±0.75) mm for vertical dimension; (0.79±0.58) mm, (0.62±0.18) mm, and (0.53±0.53) mm for anterior and posterior directions; (0.95±0.59) mm, (0.69±0.45) mm, and (0.60±0.22) mm for left and right directions. The displacement of the jaw position of the three scanners in vertical dimension, anterior and posterior directions and the left and right directions were within the 95% consistency limit. CONCLUSION Three intraoral scanners showed good trueness and precision. The i500 and Trios 3 scanners had more errors in jaw relation record, but they were used as primary jaw relation record. It is suggested that three intraoral scanners can be used for obtaining digital data to make diagnostic dentures and individual trays, reducing possible deforming or crack when sending impressions from clinic to laboratory.
Computer-Aided Design ; Dental Impression Technique ; Humans ; Imaging, Three-Dimensional ; Jaw, Edentulous ; Models, Dental