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BACKGROUND: Digital impression technique or computer-aided impression (CAI) has been recently concluded as a clinically acceptable alternative to conventional impression method (CIM) in the fabrication of crowns, short fixed partial dentures (FPDs), and implant-supported crowns. OBJECTIVE: The purpose of this study was to investigate the patients' opinion and subjective perception of two different ways of impression - digital and conventional. METHODS: A total of 45 patients were treated with CAI and CIM for the fabrication of tooth or implant-supported crowns. They fulfilled a questionnaire including 11 questions regarding the treatment time, gag reflex, discomfort related to manipulation, and other aspects of treatment. RESULTS: CAI was considered the preferential method for future treatment in 53% of patients, whereas 28.9% of the respondents preferred CIM. The preference for the impression method was influenced by the total time spent with the procedure, discomfort during manipulation with the tray or scanning head, size of the tray or scanning head, maximal opening discomfort, and (the tendency towards) gag reflex. CONCLUSION: CAI was considered a more comfortable and preferential method. Discomfort or difficulties during CAI negatively affected the patients' attitude to CAI, whereas the difficulties associated with CIM did not have any influence on the preferred method.

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AIM: The aim of the present in vivo study was to compare the clinical trueness of primary mucostatic impressions obtained either by a classical alginate or an optical intraoral scanner technique in patients with a fully edentulous maxilla. MATERIALS AND METHODS: A total of 30 patients with a fully edentulous maxilla were included in the study and underwent both conventional impressions and intraoral optical impressions (Trios 3). The conventional impressions were casted and the resulting plaster casts were digitized using a desktop scanner (Imetric D104i). These digitized impressions were superimposed over the optical impressions to compare the differences between the two data sets. Statistical analyses were performed to identify relevant deviations. RESULTS: For the 30 intraoral impressions, 80.88% of the surface areas were below the tolerance threshold of 25 µm and were thus considered similar to the areas scanned with the desktop scanner from the reference plaster cast. Interestingly, the differences (19.12% of the surface areas) were localized in depressible areas such as the vestibule, soft palate, incisive papilla, and flabby ridges. These locations were consistent with the mean of positive differences of +22.8 µm, indicating deformation or less compression with the use of the intraoral scanner. CONCLUSIONS: The digital primary impression of the fully edentulous maxilla can be considered similar to the conventional alginate impression except in the depressible areas. Considering the mucostatic objective of such a primary impression, one may consider the optical impression to be more accurate than the conventional one.

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PURPOSE: To compare the accuracy of digitizing conventional impressions to intraoral surface scans for all-on-four treatment in the maxillary arch. MATERIALS AND METHODS: An edentulous maxillary arch model with four implants placed in an all-on-four design was fabricated. Intraoral surface scans (n = 10) were obtained using an intraoral scanner after scan body insertion. For conventional polyvinylsiloxane impressions of the model, implant copings were inserted into the implant fixation for implant level, opened tray impressions (n = 10). The model and conventional impressions were digitized to obtain digital files. A reference file was created using a laboratory-scanned conventional standard tessellation language (STL) file with analog to scan the body using exocad software. STL datasets from the two digital and conventional impression groups were superimposed with reference files to assess the 3D deviations. Two-way ANOVA and paired-samples t-test was performed to assess the difference in trueness and examine the effects of impression technique and implant angulation on the deviation amount. RESULTS: No significant differences were found between the conventional impression and intraoral surface scan groups F(1, 76) = 2.705, p = 0.104. No significant differences were found between conventional straight and digital straight implants and between conventional and digital tilted implants F(1, 76) = .041, p = 0.841. No significant differences were found between conventional straight and conventional tilted implants p = 0.07 and between digital straight and digital tilted implants p = 0.08. CONCLUSION: Digital scans were more accurate than conventional impressions. The digital straight implants were more accurate than the conventional straight implants, and the digital tilted implants were more accurate than the conventional tilted implants, with higher accuracy for digital straight implants.

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AIM: To introduce an objective method to evaluate the accuracy of implant position assessment in partially edentulous patients by comparing different techniques (conventional impression, intraoral scan, CBCT) to a reference 3D model obtained with an industrial scanner, the latter mimicking the clinical situation. MATERIALS AND METHODS: Twenty-nine implants were placed in four human cadaver heads using a fully guided flapless protocol. Implant position was assessed using (a) a conventional impression, (b) an intraoral scan, and (c) CBCT and compared to an industrial scan. Three-dimensional models of intraoral scan body and implant were registered to the arch models and the deviation at implant shoulder, apex, and the angle of deviation were compared to each other as well as to the reference model. RESULTS: The three assessment techniques showed statistically significant deviations (p < .01) from the industrial scan, for all measurements, with no difference between the techniques. The maximum deviation at the implant shoulder was 0.16 mm. At the implant apex this increased to 0.38 mm. The intraoral scan deviated significantly more than the CBCT (0.12 mm, p < .01) and the conventional impression (0.10 mm, p = .02). The maximum implant angle deviation was 1.0°. The intraoral scan deviated more than the conventional impression (0.3°, p = .02). CONCLUSION: All assessment techniques deviated from the reference industrial scan, but the differences were relatively small. Intraoral scans were slightly less accurate than both conventional impressions and CBCT. Depending on the application, however, this inaccuracy may not be clinically relevant.

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OBJECTIVES: The study aimed to compare the trueness and precision of five intraoral scanners (Emerald S, iTero Element 5D, Medit i700, Primescan, and Trios 4) and two indirect digitization techniques for both teeth and soft tissues on fresh mandibular and maxillary cadaver jaws. METHODS: The maxilla and mandible of a fully dentate cadaver were scanned by the ATOS industrial scanner to create a master model. Then, the specimens were scanned eight times by each intraoral scanner (IOS). In addition, 8 polyvinylsiloxane (PVS) impressions were made and digitized with a Medit T710 desktop scanner. Stone models were then poured and again scanned with the desktop scanner. All IOS, PVS, and stone models were compared to the master model to calculate the mean absolute surface deviation for mandibular teeth, maxillary teeth, and palate. RESULTS: For mandibular teeth, the PVS trueness was only significantly better than the Medit i700 (p < 0.001) and Primescan (p < 0.05). In maxillary teeth, the PVS trueness was significantly better than all IOSs (p < 0.05-0.001); the stone trueness was significantly better than Emerald S (p < 0.01), Medit i700 (p < 0.001) and Primescan (p < 0.01). In the palate, PVS and stone trueness were significantly lower than the iTero Element 5D (p < 0.01) and Trios 4 (p < p < 0.01). Stone trueness was significantly lower than the Medit i700 (p < 0.05). The precision in the palate was significantly lower for PVS and stone than for Emerald S (p < 0.01, p < 0.05), iTero Element 5D (p < 0.01, p < 0.01), Primescan (p < 0.001, p < 0.001), and Trios 4 (p < 0.001, p < 0.01). Significant differences in trueness between the IOSs were observed only in the mandibular teeth. The Medit i700 performed worse than Emerald S (p < 0.01) and iTero Element 5D (p < 0.01). For mandibular teeth, the Medit i700 was significantly more precise than Primescan (p < 0.01) and the Emerald S (p < 0.05). The Trios 4 was significantly less precise than Emerald S (p < 0.05). The precision of Medit i700 was significantly worse than iTero Element 5D (p < 0.01) for maxillary teeth, as well as the Primescan (p < 0.01) and Trios 4 (p < 0.05) for the palate. CONCLUSIONS: In general, indirectly digitized models from PVS impressions had higher trueness than IOS for maxillary teeth; precision between the two methods was similar. IOS was more accurate for palatal tissues. The differences in trueness and precision for mandibular teeth between the various techniques were negligible. CLINICAL SIGNIFICANCE: All investigated IOSs and indirect digitization could be used for complete arch scanning in mandibular and maxillary dentate arches. However, direct optical digitization is preferable for the palate due to the low accuracy of physical impression techniques for soft tissues.

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Scanning edentulous arches during complete denture fabrication is a crucial step; however, the quality of the resulting digital scan is still questionable. The purpose of this study is to systematically review studies (both clinical and in vitro) and determine whether intraoral scanners have clinically acceptable accuracy when recording completely edentulous arches for the fabrication of removable complete dentures. An electronic search in medical databases like PubMed, Scopus, and Web of Science (WOS), using a combination of relevant keywords, retrieved 334 articles. After full-text evaluation, twelve articles fulfilled the inclusion criteria for this review (eight clinical studies and four in vitro studies). A quality analysis of the included studies was carried out using the QUADAS-2 tool. The accuracy values varied between different intraoral scanners. Different regions of the edentulous arches showed differences in trueness and precision values in both in vitro and clinical studies. Peripheral borders, the inner seal, and poorly traceable structures like the soft palate showed maximum discrepancies. The accuracy of intraoral scanners in recording clear anatomic landmarks like hard tissues with attached mucosa was comparable to conventional edentulous arch impressions. However, higher discrepancies were recorded when digitizing mobile and poorly traceable structures. Intraoral scanners can be used to digitize denture-bearing areas, but the interpretation of the peripheral border and the soft palate should be carefully carried out.

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An accurate impression is vital during prosthodontic rehabilitation. Digital scanning has become an alternative to conventional impressions. This study compares conventional preliminary impression techniques with digital scanning, evaluating the efficiency, treatment comfort, and trueness. Impressions of 28 patients were taken using conventional and digital techniques. The efficiency of both impression techniques was evaluated by measuring the mean working time. A visual analog scale questionnaire (1-10) was used to appreciate the participants' perceptions of discomfort. Morphometric measurements, which were carried out to determine the differences between the casts, were made on the buccolingual cross sections of teeth 11 and 31 and the distolingual and mesiobuccal cusp tips of each first molar. The total treatment time was 75.5 min for conventional and 12 min for digital impressions. The patients scored a mean discomfort assessment of 6.66 for conventional and 9.03 for digital scanning. No significant differences existed between the examined areas (p < 0.05, Wilcoxon and Mann-Whitney tests) of the digital casts obtained by both techniques. The intraoral scan can be considered as an alternative to conventional preliminary impressions for performing study model analysis during orthodontic treatment planning. The digital impression is more comfortable and accepted by the patients than the conventional impression and has a shorter working time.

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ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Bandiaky ON, Le Bars P, Gaudin A, Hardouin JB, Cheraud-Carpentier M, Mbodj EB, Soueidan A. Comparative assessment of complete-coverage, fixed tooth-supported prostheses fabricated from digital scans or conventional impressions: A systematic review and meta-analysis. J Prosthet Dent. 2022 Jan;127(1):71-79. doi: 10.1016/j.prosdent.2020.09.017. Epub 2020 Nov 2. PMID: 33,143,901. SOURCE OF FUNDING: Information not available TYPE OF STUDY/DESIGN: Systematic review with meta-analysis of data.

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The use of computerized optical impression making (COIM) for the fabrication of removable dentures for partially edentulous jaws is a rising trend in dental prosthetics. However, the accuracy of this method compared with that of traditional impression-making techniques remains uncertain. We therefore decided to evaluate the accuracy of COIM in the context of partially edentulous jaws in an in vivo setting. Twelve partially edentulous patients with different Kennedy classes underwent both a conventional impression (CI) and a computerized optical impression (COI) procedure. The CI was then digitized and compared with the COI data using 3D analysis software. Four different comparison situations were assessed: Whole Jaw (WJ), Mucosa with Residual Teeth (M_RT), Isolated Mucosa (IM), and Isolated Abutment Teeth (AT). Statistical analyses were conducted to evaluate group differences by quantifying the deviation values between the CIs and COIs. The mean deviations between the COIs and CIs varied significantly across the different comparison situations, with mucosal areas showing higher deviations than dental hard tissue. However, no statistically significant difference was found between the maxilla and mandible. Although COIM offers a no-pressure impression method that captures surfaces without irritation, it was found to capture mucosa less accurately than dental hard tissue. This discrepancy can likely be attributed to software algorithms that automatically filter out mobile tissues. Clinically, these findings suggest that caution is required when using COIM for prosthetics involving mucosal tissues as deviations could compromise the fit and longevity of the prosthetic appliance. Further research is warranted to assess the clinical relevance of these deviations.

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This study aimed to examine the effect of inter-dental abutment distance on the accuracy of digital and conventional impression methods. Five maxillary and mandibular models were prepared with different inter-dental abutment distances. Digital scans were obtained using an extraoral laboratory scanner as reference data. Each group was scanned 8 times using the intra-oral scanner for the digital method. For the conventional impression method, 8 additional silicone impression material was used to generate the stone casts from each group. Then casts were scanned. In the next step, stereolithography (STL) data was exported from the scans. The STL files were super-imposed on the reference scans using 3shape dental designer software to make the measurement. Kolmogorov-Smirnoff was used to determine if the data were normally distributed. In the digital impression method, as the abutment distance increased, the accuracy decreased. Various inter-dental abutment distances in digital groups showed significant differences (p=0.016) in impression accuracy, while the difference among conventional groups was not statistically significant (p=0.822). In the digital method, the mean inter-dental abutment between the 4-5 and 3-7 groups, 4-6 and 3-7 groups had a significant difference (p<0.05). However, the conventional method revealed no significant differences (p>0.05) between groups. In conclusion, when the inter-dental abutment distance exists and is surrounded by soft tissue, the possibility of error in the digital impression method is higher than in the conventional impression method.

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PURPOSE: To compare conventional and digital workflows in terms of accuracy in partially edentulous cases restored with implant-supported restorations. METHODS: An electronic search in the databases PubMed, Scopus, Web Of Science, and CENTRAL was conducted to identify relevant publications, comparing digital and conventional workflows in partially edentulous cases restored with implant-supported prostheses. RESULTS: 18 articles were included in the systematic review. Ten of the studies were in-vitro, and eight were clinical. Sample sizes varied considerably from 20 to 100. In three studies, three implants were investigated, whereas, in all other instances, accuracy was evaluated on two implants. Substantial heterogeneity in the methodology of the selected studies is evident, which prevents summarising the accuracy outcomes. CONCLUSIONS: Digital impressions showed similar results in terms of accuracy compared to the conventional approach. There is a lack of uniform criteria for the tolerable misfit, which hampers the ability to transfer in-vitro results to clinical situations. A need for a standardised approach in the evaluation of impression and workflow accuracy is warranted to enable the systematisation and analysis of results from different studies.

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Both conventional and digital impressions aim to record the spatial position of implants in the dental arches. However, there is still a lack of data to justify the use of intraoral scanning over conventional impressions for full-arch implant-supported prostheses. The objective of the in vitro study was to compare the trueness and precision of conventional and digital impressions obtained with four intra-oral scanners: Trios 4 from 3Shape®, Primescan from Dentsply Sirona®, CS3600 from Carestream® and i500 from Medit®. This study focused on the impression of an edentulous maxilla in which five implants were placed for implant-supported complete prosthesis. The digital models were superimposed on a digital reference model using dimensional control and metrology software. Angular and distance deviations from the digital reference model were calculated to assess trueness. Dispersion of the values around their mean for each impression was also calculated for precision. The mean distance deviation in absolute value and the direction of the distance deviation were smaller for conventional impressions (p-value < 0.001). The I-500 had the best results regarding angular measurements, followed by Trios 4 and CS3600 (p < 0.001). The conventional and I-500 digital impressions showed the lowest dispersion of values around the mean (p-value < 0.001). Within the limitations of our study, our results revealed that the conventional impression was more accurate than the digital impression, but further clinical studies are needed to confirm these findings.

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In the present era when interest in digital dentistry is increasing, the published literature is still confusing about whether digital impression provides similar accuracy as provided by a conventional impression for the fabrication of a single-unit ceramic crown. The aim of the study was to systematically review the in vivo studies comparing marginal, axial, and occlusal fit of single-unit ceramic crowns fabricated after digital impressions with the ones fabricated after conventional impressions. The PubMed, Scopus, and Cochrane online databases were searched for studies comparing the digital impression technique with the conventional technique for single-unit ceramic crowns. Data extraction was done for the year of publication, type of study, country, number of patients, impression system (intraoral scanner [IOS] or conventional impression), marginal fit, axial fit, and occlusal fit. Ten studies were included for meta-analysis regarding the discrepancy in marginal fit, axial fit, and occlusal fit. The digital impression proved to be better than the conventional impression. The mean difference for marginal fit was 6.54 µm (heterogeneity P < 0.00001, I2 = 93%), for axial fit 24.69 µm (heterogeneity P = 0.34, I2 = 11%), and for occlusal fit 6.99 µm (heterogeneity P = 0.03, I2 = 59%). The results of meta-analyses suggest that there is no significant difference between the impression systems (marginally favoring digital impression). The digital impression technique provided better marginal and internal fit of single-unit ceramic crowns than the conventional impression technique. The digital workflow using IOS provided a clinically acceptable marginal fit for single-unit crowns.

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BACKGROUND: The accuracy of impression techniques determines the marginal fit of fixed prostheses. Marginal accuracy plays a main role in the success and failure of treatments. This in-vivo study evaluated the marginal fit of anterior three-unit monolithic zirconia fixed partial dentures (FPDs) using conventional and scannable polyvinyl siloxane impression materials. METHODS: Ten patients were selected to replace the lateral teeth with a three-unit monolithic zirconia bridge. For each patient, in the first group, an impression was made with a two-step putty-wash technique using scannable polyvinyl siloxane material (BONASCAN; DMP, Greece). In the identical session, as the second group, an impression of conventional putty-wash polyvinyl siloxane was taken (BONASIL A+ Putty; DMP, Greece). The marginal discrepancy was measured through the replicas, which were cut perpendicularly within the buccolingual and mesiodistal directions. An Independent t-test was employed for data analyses (P < 0.05). RESULTS: The marginal discrepancy in a conventional method for central abutment in mid-buccal, mid-lingual, mid-mesial, and mid-distal was higher than in the scannable method but it was not significant (P > 0.05). Also, the marginal discrepancy for canine abutment in the conventional method was higher than in the scannable method, but it was not significant, either (P > 0.05). CONCLUSIONS: FPDs fabricated from both scannable and conventional impression materials were not superior to each other in marginal fit for both central and canine abutments by evaluation using the replica technique.

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AIM: This study aimed to evaluate the effect of different definitive impression techniques for the resorbed mandibular ridge on the retention of lower complete dentures. MATERIALS AND METHODS: Ten completely edentulous male patients with severe atrophic mandibular ridge were selected from the Prosthodontic Department's outpatient clinic, Faculty of Dentistry, Sinai University (Kantara branch). Each patient received four dentures. Dentures were divided into four groups according to the type of final impression, Group I: Conventional impression techniques (open mouth technique), Group II: Cocktail impression techniques, Group III: Modified functional impression technique, and Group IV: Wire impression technique. Each denture was used for one month and at the end of the month the retention test was carried out and the results were tabulated and statistically analyzed. RESULTS: There is a statistically significant difference between the groups. The results also showed that the highest mean value was in group IV, whereas the lowest mean value of retention was in group I. CONCLUSION: Wire impressions produce lower dentures with higher retention, whereas conventional impressions produce lower dentures with the lowest retention, so it is considered to be more advantageous. CLINICAL SIGNIFICANCE: The wire impression technique is superior in the management of resorbed ridges as compared with other techniques.

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BACKGROUND: Facial mutilation and deformities can be caused by cancer, tumours, injuries, infections, and inherited or acquired deformities and has the potential to degrade one's quality of life by interfering with fundamental tasks like communication, breathing, feeding, and aesthetics. Depending on the type of defect, producing maxillofacial prostheses for the rehabilitation of patients with various defects can be challenging and complex. The prosthesis is used to replace missing or damaged parts of the cranium and face, like the nose, auricle, orbit, and surrounding tissues, as well as missing areas of soft and hard tissue, with the primary goal of increasing the patient's quality of life by rehabilitating oral functions such as speech, swallowing, and mastication. Traditional maxillofacial prosthesis impression and fabrication processes include a number of complicated steps that are costly, time-consuming, and uncomfortable for the patient. These rely on the knowledge of the maxillofacial team, dental clinicians, and maxillofacial technician. The foundation of the impression is the keystone for creating a prosthesis. However, this is the most time-consuming and difficult chair-side operation in maxillofacial prosthesis manufacturing since it requires prolonged interaction with the patient. The field of prosthesis fabrication is being transformed by the digital revolution. Digital technology allows for more accurate impression data to be gathered in less time (3 to 5 min) than traditional methods, lowering patient anxiety. Digital impressions eliminate the need for messy impression materials and provide patients with a more pleasant experience. This method bypasses the procedure of traditional gypsum model fabrication. This eliminates the disparity caused by a dimensional distortion of the impression material and gypsum setting expansion. Traditional dental impression processes leave enough room for errors, such as voids or flaws, air bubbles, or deformities, while current technology for prosthesis planning has emerged as an alternative means to improve patient acceptability and pleasure, not only because the end result is a precisely fitted restoration but also because the chair-side adjustments required are reduced. The most frequent approaches for creating 3D virtual models are the following. To begin, 3D scanning is employed, in which the subjects are scanned in three dimensions, and the point cloud data is used to create a virtual digital model. METHODS: It will be a hospital-based randomised control trial, carried out at the Department of Prosthodontics, Sharad Pawar Dental College, Sawangi (Meghe), Wardha, a part of Datta Meghe Institute of Medical Sciences (Deemed University). A total of 45 patients will be selected from the outpatient department (OPD) of the Department of Prosthodontics. All the patients will be provided written consent before their participation in the study. METHODOLOGY: 1. Patient screening will be done, and the patient will be allocated to three techniques that are the conventional manual method, photogrammetry method, and 3D scanning in a randomised manner 2. The impression of the defect will be recorded by conventional manual method, photogrammetry method, and 3D scanning 3. The defect will be modelled in three ways: first is as per the manual dimension taken on the patient, second is the organisation of photographic image taken with lab standards and third is plotting of point cloud data to generate the virtual 3D model 4. For photogrammetric prosthesis design, finite photos/images will be taken at multiple angles to model the 3D virtual design. With the use of minimum photographs, the 3D modelling can be performed by using freeware, and a mould is obtained 5. The CAD software was used to design the prosthesis, and the final negative mould can be printed using additive manufacturing 6. The mould fabricated by all three methods will be analysed by a software using reverse engineering technology Study design: Randomised control trial Duration: 2 years Sample size: 45 patients DISCUSSION: Rodrigo Salazar-Gamarra1, Rosemary Seelaus, and Jorge Vicente Lopes da Silva et al., in the year 2016, discussed, as part of a method for manufacturing face prostheses utilising a mobile device, free software, and a photo capture protocol, that 2D captures of the anatomy of a patient with a facial defect were converted into a 3D model using monoscopic photogrammetry and a mobile device. The visual and technical integrity of the resulting digital models was assessed. The technological approach and models that resulted were thoroughly explained and evaluated for technical and clinical value. Marta Revilla-León, Wael Att, and Dr Med Dent et al. (2020) used a coordinate measuring equipment which was used to assess the accuracy of complete arch implant impression processes utilising conventional, photogrammetry, and intraoral scanning. Corina Marilena Cristache and Ioana Tudor Liliana Moraru et al. in the year 2021 provided an update on defect data acquisition, editing, and design using open-source and commercially available software in digital workflow in maxillofacial prosthodontics. This research looked at randomised clinical trials, case reports, case series, technical comments, letters to the editor, and reviews involving humans that were written in English and included detailed information on data acquisition, data processing software, and maxillofacial prosthetic part design. TRIAL REGISTRATION: CTRI/2022/08/044524. Registered on September 16, 2022.

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Introduction The current gold standard is a conventional impression made with various impression materials and trays and results in a gypsum cast. With the development of milling and printing materials in dentistry, especially zirconia, a digital model has become increasingly important. Objectives To compare the accuracy of the conventional impression scan (CIS), gypsum cast scan (GCS), and digital impression scan (DIS) to obtain a full-arch digital model. Materials and methods A resin reference cast was fabricated. It was scanned by an extra-oral scanner to measure its accuracy as a reference scanner. Eight conventional impressions of the reference cast were taken by polyvinyl siloxane and scanned. After that, they were poured with type IV dental stones and scanned too. The reference cast was scanned by an intraoral scanner eight separate times. Digital models within each group were superimposed individually to measure precision. In addition, each model from each group was superimposed on one model from the reference scanner precision group to measure trueness. Results The reference scanner showed the highest accuracy among groups with a precision of 1.5±0.8 µm and a trueness of 5.5±1.9 µm (P<0.006), while precision values of gypsum cast were 8.1±1.7 µm and trueness values were 9.3±2.6 µm (P<0.012). Conventional impressions showed a precision of 14.06±2.01 µm and a trueness of 16.15±2.07 µm (P<0.012). Digital impressions were the least accurate among the groups, as precision values were 38.22±15.23 µm and trueness values were 35.19±8.7 µm (P<0.006). Conclusion The gypsum cast scans showed the highest accuracy, followed by the conventional impression scans, and finally the digital impression scans, with no clinical significance.

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PURPOSE: The present study compared the accuracy between digital and conventional implant impressions. MATERIALS AND METHODS: The experimental models were divided into six groups depending on the implant location and the scanning span. Digital impressions were captured using the intraoral optical scanner TRIOS (3Shape, Copenhagen, Denmark). Conventional impressions were taken with the monophase impression material based on addition-cured silicones, Honigum-Mono (DMG, Hamburg, Germany). A high-precision laboratory scanner D900 (3Shape, Copenhagen, Denmark) was used to obtain digital data of resin models and stone casts. Surface tessellation language (STL) datasets from scanner were imported into the analysis software Geomagic Qualify 14 (3D Systems, Rock Hill, SC, USA), and scan body deviations were determined through two-dimensional and three-dimensional analyses. Each scan body was measured five times. The Sidak t test was used to analyze the experimental data. RESULTS: Implant position and scanning distance affected the impression accuracy. For a unilateral arch implant and the mandible models with two implants, no significant difference was observed in the accuracy between the digital and conventional implant impressions on scan bodies; however, the corresponding differences for trans-arch implants and mandible with six implants were extremely significant (P<.001). CONCLUSION: For short-span scanning, the accuracy of digital and conventional implant impressions did not differ significantly. For long-span scanning, the precision of digital impressions was significantly inferior to that of the traditional impressions.

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OBJECTIVES: This in vitro study compared the dimensional accuracy of conventional impressions (CI) with that of digital impressions (DI) in a partially edentulous maxilla. DIs were made by two intraoral scanners, Omnicam (OC) and Primescan (PS). MATERIALS AND METHODS: CI and both intraoral scanners were used to take 30 impressions of two identical reference models. CIs were poured with type 4 gypsum and the saw-cut models were digitized. The reference models simulated a maxilla with six prepared teeth that accommodated a cross-arch fixed partial denture. Center points of five precision balls and center points at the margin level of each prepared tooth were used to detect changes in dimensions and tooth axis between the reference model and the scans. RESULTS: For DI, the largest deviations (176 µm for OC and 122 µm for PS) occurred over the cross-arch. For CI, the largest deviation (118 µm) occurred over the anterior segment. For shorter distances up to a quadrant, DI was superior to CI. For longer scan distances, DI was comparable (2 sextant and anterior segment) or inferior (cross-arch) to CI. Vertical and tooth axis deviations were significantly smaller for CI than for DI (p < 0.001). CONCLUSIONS: The impression method affected the impression accuracy of a partially edentulous maxilla with prepared teeth. DI is recommended for scans up to a quadrant. Larger scan volumes are not yet suitable for fabricating a fixed partial denture because of the high scatter of accuracy values. CLINICAL RELEVANCE: In contrast to conventional impressions, digital impressions lead to comparable or better results concerning scans up to a quadrant. Consequently, for larger scan volumes, several smaller scans should be performed or, if restoration-related not possible, it is recommended to take conventional impressions.

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The aim of this systematic review was to evaluate the in vitro accuracy of dental implants impressions taken with intraoral scanner compared with impressions taken with conventional techniques. Two independent reviewers conducted a systematic electronic search in the PubMed, Web of Science and Scopus databases. Some of the employed key terms, combined with the help of Boolean operators, were: "dental implants", "impression accuracy", "digital impression" and "conventional impression". Publication dates ranged from the earliest article available until 31 July 2021. A total of 26 articles fulfilled the inclusion criteria: 14 studies simulated complete edentation (CE), nine partial edentation (PE) and only two simulated a single implant (SI); One study simulated both CE and SI. In cases of PE and SI, most of the studies analyzed found greater accuracy with conventional impression (CI), although digital impression (DI) was also considered adequate. For CE the findings were inconclusive as six studies found greater accuracy with DI, five found better accuracy with CI and four found no differences. According to the results of this systematic review, DI is a valid alternative to CI for implants in PE and SI, although CI appear to be more accurate. For CE the findings were inconclusive, so more studies are needed before DI can be recommended for all implant-supported restorations.

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