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Objectives: To evaluate the effects of three different scanning strategies on the trueness and precision of optical impressions obtained with four intraoral scanners (IOSs)., Methods: The reference maxillary dental arch model was fabricated using Telio CAD, and the reference digital reference cast was obtained using a computer numerical control machine and an optical scanner (E4, 3Shape, Copenhagen, Denmark). Test scans were performed with four different IOSs (TRIOS3, MEDIT i700, CS 3600, and iTero Element 5D) by an experienced operator and three different scanning strategies (S1: manufacturer-recommended, S2: optimal per previous literature, and S3: experimental). The scan duration was recorded for each scan. All scans were converted to standard tessellation language format and imported into Geomagic Control X. The accuracy was measured by absolute deviation/distance between aligned surfaces. Data of trueness and precision of each IOS and scan duration were statistically compared using analysis of variance for repeated measures and Bonferroni post-hoc test (p < .05)., Results: No significant differences in trueness were found among strategies (S1: 9.98 µm, S2: 11.93 µm, S3: 8.84 µm; p = .388) in Trios 3 and iTero Element 5D (S1: 12.24 µm, S2: 11.53 µm, S3: 10.71 µm; p = p = .279). Scanning strategy S3 with MEDIT i700 achieved greater trueness (7.33 µm) than S2 (16.33 µm, p < .05), while no significant difference was noted between S1 (10.44 µm) and S3 (p = .291). S3 showed the highest trueness (16.28 µm) compared to S2 (24.05 µm) and S1 (24.78 µm, p < .001) for CS 3600, with no difference between S1 and S2 (p = .457). Trios 3 had higher precision with S2 (22.46 µm) than S3 (31.69 µm, p < .05), and no significant differences between S1 (25.67 µm) and S2/S3 (p > .05). MEDIT i700 with S3 (29.52 µm) was more precise than both S1 (39.52 µm) and S2 (46.24 µm) (p < .001) with no difference between the last two (p = .302). S2 yielded the highest precision (44.93 µm) compared to S3 (61.81 µm) and S1 (76.53 µm) (p < .001) for CS 3600, with S3 more precise than S1 (p < .001). Similarly, iTero Element 5D showed S2 as the most precise (30.19 µm) compared to S3 (42.80 µm) and S1 (44.45 µm) (p < .05), with no difference between S1 and S3 (p = .472). Scan durations were shorter for S3 and S1 compared to S2 in Trios 3 (p < .001), and S3 was faster than S1 and S2 for MEDIT i700 (p < .001). CS 3600 scans with S1 were quicker than S2 and S3 (p < .001). For iTero Element 5D, no significant differences were found between S1 and S3 (p = .511), but S2 was slower than both (p < .001)., Conclusions: Scanning strategies significantly affect the accuracy and scan duration of optical impressions. Specifically, S3 provided the best trueness with both the MEDIT i700 and the CS 3600 while the S2 strategy demonstrated the highest precision for most scanners. Overall, the S1 and S3 strategies resulted faster than S2 among the devices evaluated., Clinical Significance: The results suggest that the experimental scan strategy may optimize the use of intraoral scanners in clinical practice, potentially leading to more accurate and time-efficient dental impressions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objective: To evaluate the effect of intraoral scanners (IOSs) and implant libraries (ILs) on the trueness of digital impressions for the fabrication of implant-supported full-arch (FA) prostheses., Methods: A stone cast of an edentulous maxilla with 6 implant analogues and cylindrical scanbodies (IPD ProCam®, Matarò, Barcelona, Spain) was probed using a coordinate measuring machine to capture a reference model (RM). The cast was mounted on a mannequin and scanned with 3 different IOSs (iTERO Element 5D Plus®, Align Technologies, San José, CA, USA; IS 3800®, Dexis, Quackertown, PN, USA; and i-700®, Medit, Seoul, South Korea). Ten scans were performed by an experienced operator using each IOS, first capturing only the occlusal surfaces, then the buccal and finally the palatal surfaces (less than 45 s per scan). In each scan, the meshes of the SBs were replaced by the corresponding IL file, with and without increment, to obtain the best correction for the mesh growth. The positions of the SBs in each file were compared with those in the RM, to evaluate the linear and cross distances between them. The final outcome was the trueness of the different IOSs, evaluating the effect of using different ILs on the quality of the impressions., Results: Significant differences were found between the different IOS scans and the RM, and among the different IOSs, in the different segments. The correction of the mesh growth through incremental ILs did not affect the final trueness of the IOS scans., Conclusions: Different levels of trueness were found among the IOSs evaluated, in the different scan segments, but with the cylindrical SBs used herein, the correction of the mesh growth with incremental ILs did not affect the final quality of the digital impressions., Statement of Clinical Relevance: There are still errors with IOS in the FA impressions. IOS have an effect on the quality of the digital impressions, and apparently the library has not, with purely cylindrical SBs: further studies are needed to confirm this aspect., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objectives: To assess the impact of including the palate and the number of images recorded during intraoral digital scanning procedure on the accuracy of complete arch scans., Methods: An experienced operator conducted 40 digital scans of a 3D printed maxillary model and divided them into two groups: 20 with inclusion of the palate (PAL) and 20 without (NPAL). Each set of scans was performed using an intraoral scanner (IOS) (Trios 5; 3Shape A/S; Copenhagen, Denmark). The resulting STL files were imported into the Geomagic Control X software (3D Systems, Rock Hill, SC, USA) for accuracy comparison. A reference STL file was created using a 3Shape E3 laboratory scanner (3Shape Scanlt Dental 2.2.1.0; Copenhagen, Denmark). The number of images captured was recorded during the scanning procedure., Results: In the case of the right side no statistically significant difference in trueness was detected (84 µm ± 45.6 for PAL and 80.4 ± 40.4 µm for NPAL). In the case of the left side no significant difference in trueness was observed (215.1 ± 70.2 µm for PAL and 233.9 ± 70.7 µm for NPAL). In the case of the arch distortion a statistically significant difference in trueness was seen between the two types of scans (135.3 ± 71.9 µm for PAL and 380.4 ± 255.1 µm for NPAL). The average number of images was 831.25, and 593.8 for PAL and NPAL, respectively., Conclusions: Scanning of the palatal area can significantly improve the accuracy of dental scans in cases of complete arches. In terms of the number of images, based on the current results, obvious conclusions could not be drawn, and further investigation is required., Clinical Significance: Scanning the palate may be beneficial for improving the accuracy of intraoral scans in dentate patients. Consequently, this should be linked to an appropriate scanning strategy that predicts palatal scanning., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Statement of Problem: Quantitative 3D clinical analysis of the selective pressure impression technique directly measuring tissue displacement during impression making for complete maxillary dentures is lacking., Purpose: The purpose of this clinical study was to digitally compare impressions made of the edentulous maxillary ridge by using the selective pressure impression technique with different amounts of relief incorporated into custom tray designs., Material and Methods: Nine participants receiving maxillary complete dentures were enrolled in the study. An initial custom tray was fabricated in urethane dimethacrylate by using the alternative border molding technique without relief and scanned to create a standard tessellation language (STL) file from which 3 groups of custom trays were designed and 3D printed with 0.0-mm (no relief), 1.0-mm, and 3.0-mm relief over the anterior ridge and median palatal suture. Definitive impressions using each of the 4 custom trays were made with a consistent volume of light-body polyvinyl siloxane impression material. The definitive impressions were scanned, and the STL files were superimposed to investigate the topographical differences among the groups, each with respect to the no relief, 3D-printed custom tray definitive impression. Mean volumetric differences for all 3 groups were measured in areas where relief was used and statistically analyzed with the Friedman test (α=.05)., Results: No significant difference was found among any of the 3 groups of superimposed impressions in areas of no relief, 1.0-mm, and 3.0-mm relief (P=.558). The mean difference ±standard deviation for each comparison in regions of the anterior ridge and median palatal suture were 0.07 ±0.06 mm for no relief, -0.03 ±0.07 mm for the 1.0-mm tray relief, and -0.04 ±0.09 mm for the 3.0-mm tray relief. The negative values in mean difference indicated less compression of underlying tissues compared with the reference border molded urethane dimethacrylate custom tray impression., Conclusions: Although results showed less compression when compared with that of the control group, custom tray relief of 1.0 mm and 3.0 mm over the anterior residual alveolar ridge and median palatal suture did not significantly impact the resulting impression topography when compared with no relief custom trays., (Copyright © 2021 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives: The purpose of this in vitro study was to evaluate the trueness of scanning the post space up to 20 mm with an intraoral scanner (IOS)., Methods: We captured 20-, 18-, 16-, 14-, 12-, and 10-mm length post space scans using an IOS (Primescan) eight times each by shortening the apical 2 mm end of the same mandibular canine tooth. The reference impressions of each length group were taken using a light-body polyvinyl siloxane impression material and were scanned with an extraoral scanner. The recorded standard tessellation language (STL) data of all impressions were uploaded to a 3D matching program for the trueness evaluation via the root mean square (RMS) calculation. For the statistical analysis, the Kruskal-Wallis and post-hoc Mann-Whitney U nonparametric tests were performed to compare the differences among the groups (α=0.05)., Results: The median RMS values increased in direct proportion to the length of the post space from 10 mm (357.1 µm) to 20 mm (897.5 µm). We noted a significant difference among groups (p< 0.001). In the pairwise comparisons, there were no significant differences between the 14 mm and 16 mm groups (p=0.431) or between the 18 mm and 20 mm groups (p=0.036), while other paired groups showed significant differences (p=0.001)., Conclusions: The scanned space depth affected the trueness of the IOS (Primescan). If the post depth was below 14 mm, and the minimum diameter was 2.2 mm, Primescan could be used for impressions of the post-core structure, simplifying the impression procedure., Clinical Significance: IOS seems to be a promising technology for taking digital impressions of post spaces, but cannot be recommended as a routine procedure at its present stage, as final results are highly dependent on the clinical situation. Further studies with different IOS systems are needed to gain sound evidence., Competing Interests: Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Statement of Problem: Although studies have evaluated the accuracy of data obtained by intraoral scanners (IOSs), studies on the precision of interocclusal registrations made with IOSs are lacking., Purpose: The purpose of this clinical study was to compare the precision of IOS interocclusal registration with that of conventional methods with a silicone impression material and a gypsum cast., Material and Methods: Eight participants with complete natural dentitions were enrolled. Images of their maxillary and mandibular quadrant arches and their interocclusal relationship were scanned with 2 IOSs: the 3M True Definition Scanner and the TRIOS Scanner 3. In the conventional method, impressions of complete-arch dentition and quadrant-arch dentition were made with a silicone impression material, and gypsum casts were fabricated, mounted on a dental articulator related with a silicone interocclusal record, and scanned with a 3D laboratory scanner. These procedures were repeated 4 times, and 4 sets of interocclusal registration data in standard tessellation language (STL) format were generated for each condition. Interocclusal registration precision was evaluated by determining the discrepancy of the STL data between repeated measurements by using the best-fit-algorithm method., Results: The average discrepancies for all participants were 25 ±12 μm for the True Definition, 31 ±7 μm for the TRIOS 3, 154 ±59 μm for the complete arch, and 128 ±33 μm for the quadrant arch. The Kruskal-Wallis test revealed that the effect of the impression methods on the discrepancy was statistically significant (P<.001). The Steel-Dwass test showed that both digital scan methods exhibited significantly smaller discrepancies than the 2 conventional methods (P=.005)., Conclusions: These results suggest that the intermaxillary relationship captured by the digital scan method by using IOSs had better precision than that obtained by the conventional method., (Copyright © 2021 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives: The purpose of this systematic review was to compare the accuracy of digital and conventional full-arch impressions in vivo., Materials and Methods: This systematic review was conducted according to the PRISMA and registered at the PROSPERO (CRD42021232736). Electronic and hand searches were performed to identify in vivo studies comparing the linear or 3D accuracy of digital and conventional impressions. The risk of bias (ROB) of included studies was assessed by QUADAS-2, and the overall quality of evidence was assessed by GRADE., Results: Twenty-two studies met the inclusion criteria, and 13 studies were included in the meta-analysis. There was no significant difference between digital and conventional impressions in the linear measurements of tooth width, anterior Bolton ratio, overall Bolton ratio, intercanine distance (ICD), and intermolar distance (IMD). The repeated measurement mean errors (RMEs) were less than 0.1 mm, the intra-examiner intraclass correlation coefficient (ICC) values were more than 0.9, and the inter-examiner ICC values were more than 0.87 for both impression techniques. The 3D deviation between digital and alginate impressions was 0.09 mm. The 3D precision of both impression techniques was less than 0.1 mm., Conclusions: The trueness of digital and alginate full-arch impressions was similar, and both impression techniques showed high precision. More research was needed to compare digital impressions and other conventional impression materials., Clinical Relevance: For patients with completely natural dentition, the digital impressions obtained directly from intraoral scanning can be considered a viable alternative to alginate impressions., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

A digital technique is described for designing and fabricating segmental individual tooth trays that can be used to make an impression of multiple preparations with high accuracy and efficiency. A digital model of prepared dentition was acquired. The segmental individual tooth trays with retention attachments and tissue stops were designed and 3D printed with light-polymerizing resin. The segmental impression of each section of the prepared dentition was made with the corresponding individual tooth tray loaded with the impression material. A final overall impression was made to pick up the segmental individual tooth trays with a full arch tray., (© 2021 by the American College of Prosthodontists.)

In recent years digital technology has transformed the practice of modern dentistry, with intraoral scanners (IOSs) being among the most significant materializations of this digital boom. IOSs eliminate the need for traditional impression materials and allow for the immediate digital capture of a 3-dimentional (3D) object being scanned.4 When assessing the "most ideal" IOS for a dental practice, key considerations include the types of procedures being performed, practice demands, and patient demographics. Only after an initial practice assessment has been made can advantages and disadvantages of various IOSs be compared against practice needs.

Statement of Problem: Elastomeric impression materials have been marketed for optimizing direct digital acquisition without requiring a stone cast. The trueness and precision of the digitization of these new elastomeric impression materials are unclear., Purpose: The purpose of this in vitro study was to compare the trueness and precision of digital dental casts obtained from the direct digitization of 2 types of vinylsiloxanether (VSXE) impression materials by using a laboratory laser scanner., Material and Methods: Thirty-eight elastomeric impressions were made of a master die with a similar morphology to a premolar crown preparation. The impression materials were Identium (IDE) and Identium Scan (SCAN), designed for direct digitalization. Each impression was digitalized by using an optical scanner to create digital casts. A computer-aided design (CAD) reference model of trueness (CRM) was created and aligned to each digital cast for digital 3-dimensional discrepancy analysis., Results: The mean ±standard deviation global trueness of IDE was 53 ±16 μm and that of SCAN was 46 ±3 μm. SCAN digital casts showed higher precision (58 ±5 μm) than IDE (69 ±18 μm) (P<.05). At the margin of the preparation and at the axial surfaces, SCAN models showed higher trueness (3 ±6 μm and 1 ±5 μm) than IDE (15 ±10 μm and 2 ±37 μm), respectively., Conclusions: Scannable impressions could be digitalized with higher global precision than conventional elastomeric materials. Higher trueness could be achieved in specific impression locations such as gingival areas or axial walls of preparations, where the light emitted by the scanner was not blocked., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Oral scanners allow dental impressions to be taken in a short time without the use of an impression material. However, it has been noted that high impression accuracy cannot be obtained in cases where the abutment is inclined or in cases where the span is long. Consequently, in daily clinical practice, impressions are often created using silicone impression material. When taking an impression using silicone impression material, the curing time or the removal time of the impression material are often based on the intuition of the dental staff. This study investigated the effects of impression holding time and impression tray removal speed on the dimensional accuracy of impressions. A specimen with an abutment inclined 30° to the removal direction of an impression was prepared. Four types of silicone rubber impression materials were used. Impressions were taken with two levels of holding time and two levels of removal speed using an autograph. The diameter of stone models was measured at 3, 6, and 9 mm from the baseline of each. The height of the inclined and opposite sides was also measured. Two-way analysis of variance was used to analyze data regarding the assessment of the effects of holding time and tray removal speed. The reproducibility of the impressions was affected by the volume of undercut caused by the inclined abutment. For a large undercut, longer holding times and faster tray removal speeds are recommended to reduce the deformation of silicone rubber impressions.

For dental impression of a prepared tooth, the goal is a void-free negative representation from which an accurate cast of a tooth and its surrounding tissue can be reproduced. This in-vitro study assessed and compared the reproduction accuracies of surface detail obtained with three different dental elastomeric impression materials: vinyl polysiloxane (VPS), vinyl polyether silicone (VPES), and polyether (PE). A stainless-steel model with two abutments was used, with impressions taken 10 times for each material, for 20 abutment impressions per group, using a two-phase, one-step technique (heavy body/light body). The impressions were removed and assessed for numbers of enclosed voids and open voids visible on the surface. The defect frequency was 95% for impressions with the VPS and VPES materials, and 30% for the PE material. No significant differences were seen for number of impressions with defects for VPS versus VPES. Significant differences were seen for VPS and VPES versus the PE material (P <.05). No significant differences were seen for the defect type distributions across these three impression materials. The PE impression material showed better accuracy for reproduction of surface detail of these dental impressions compared to the VPS and VPES impression materials.

Statement of Problem: The dimensional stability of alginate dental impressions is a key factor for the reliability of delayed gypsum pouring and digital scanning. However, studies of the dimensional stability of alginates with conventional methods that consider the dimensional variations of large impressions are lacking., Purpose: The purpose of this in vitro study was to investigate and compare 2 digital methods for the analysis of dimensional stability of large impressions made with 5 different extended-pour alginates and to assess dimensional stability up to 5 days., Material and Methods: Impressions of a simplified master maxillary model were made with Alginoplast, Blueprint, Hydrogum 5, Orthoprint, and Phase Plus and then analyzed at different time points. Digital scans of the alginate impression surfaces were obtained with a desktop scanner and analyzed by evaluating the linear measurements between reference points and by using a novel method that consists of the analysis of the entire scanned surface to evaluate the expansion and contraction of the impressions., Results: The first method revealed that the dimensional changes did not exceed 0.5%, with the exception of Phase Plus at day 3 (-0.6 ±0.7%), and the average dimensional variation was always lower than or equal to 0.2 mm. Blueprint was the most stable material (-0.2 ±0.6%). The second method revealed dimensional variations always lower than 0.03 mm and confirmed Blueprint as the best performing material (0.001 ±0.006 mm) and Phase Plus the worst (-0.019 ±0.006 mm)., Conclusions: Both the methods used to evaluate alginate stability showed that the analyzed materials remain stable over time; the dimensional variations showed a similar trend, with differences in the absolute values depending on the applied method. Linear measurements are affected by the operator and choice of reference points; however, by evaluating the average variations of the entire structure surfaces, local variations should be minimized. The evaluation of the average variations with the second method offers the advantage of a rapid visual representation of these variations., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

The aim of this study was to evaluate the precision and accuracy of molds made with four commercial brands of alginate scanned at different times using digital model analysis. Eighty molds of a standard Typodont were made using 4 types of alginate (CCC: Cavex Color Change; IA: Identic Alginate; HY5: Hydrogum 5 and JP: Jeltrate Plus). The molds were scanned at four times: immediately (T1), 24h (T2), 72h (T3) and 120h (T4) after molding. Measurements were taken in three dimensions: anteroposterior, transverse and vertical. Significant differences in dimensional changes were noted between the materials over time (p <0.05). Anteroposterior dimensional variation was noted between times, especially for IA and JP. For transverse and vertical variables, a difference was found between the groups, especially at 24 h, 72 h and 120 h. CCC presented significant dimensional shrinkage only at T120 (transverse). IA and JP presented larger dimensional distortions in the vertical measurements. The molding materials used were not dimensionally stable when evaluated after 120 hours of molding. However, such evidence suggests that alginates with longer storage time, such as Cavex Color Change, are more accurate than conventional alginates., Competing Interests: none, (Sociedad Argentina de Investigación Odontológica.)

Purpose: This study investigates the accuracy of abutment transfer with current impression materials and provides a concise overview, including other relevant factors, in order to enable clinicians to make an informed decision about the optimal impression for this treatment procedure., Methods: In all, 96 impressions of a cadaver head with two orthodontic miniscrews in place were taken with four common impression materials by two observers and using two methods of application. After pouring with a standard type IV stone and abutment transfer, all models and the upper jaw (which had been separated from the head) were scanned in a standard model scanner (Zirkonzahn® [Zirkohnzahn GmbH, Gais, Italy] S600 ARTI) and evaluated using a computer-aided design (CAD) program (GOM-Inspect [Gesellschaft für optische Messtechnik m.b.H., Braunschweig, Germany]). The deviations were measured at six points per screw and statistically evaluated with SPSS® (IBM, Chicago, IL, USA)., Results: Optimal values were obtained with biphasic polyvinylsiloxane, while monophasic polyvinylsiloxane, alginate and polyether also resulted in acceptable accuracy. Observer experience showed no effect and the method of application had only a minor effect on accuracy., Conclusions: Within the limitations of this study, it seems that all impression materials are suitable for miniscrew abutment transfer, provided that methods of intraoral adaptation of the orthodontic appliance can be employed. If higher accuracy is needed or for clinicians with less experienced, a biphasic polyvinylsiloxane impression with the putty-wash technique should be used as this combination reduces setting time. The most cost-effective version, alginate, can be used if the consequences of greater deviations can be handled. Caution is advised with polyether if undercuts are present.

Purpose: To evaluate the dimensional accuracy of impressions made using a new fast-setting polyether material., Materials and Methods: A metallic reference model with two crown preparations, one inlay preparation, and three stainless steel precision balls was digitized to create a digital reference model. Sixteen one-step impressions were made for each of the four study groups, differing in impression material (regular-setting polyether [RSP] vs fast-setting polyether [FSP]) and technique (monophase vs dualphase), for a total of 64 specimens. Plaster casts fabricated from these impressions were digitized using 3D scans. Global accuracy was studied by evaluating distance and angle deviations between the replica and the reference model. Local accuracy was described in terms of trueness and precision of the aligned individual abutment tooth surfaces., Results: For all impression materials and techniques, the local accuracy at the abutment tooth level was excellent. For surfaces prepared for crowns, mean trueness was < 10 μm, and mean precision < 12 μm. Inlay surfaces were associated with higher inaccuracies (mean trueness < 21 μm and mean precision < 37 μm). The greatest global inaccuracies were generally measured for the cross-arch span, with mean distance changes between -55 μm and -94 μm. For all aspects of studied accuracy, impressions with FSP were at least comparable to those fabricated with RSP., Conclusion: Within the limitations of this study, all tested polyether materials would allow for clinically acceptable impression making. The new fast-setting material could be an alternative to regular-setting polyether materials, especially for single crowns and small fixed partial dentures.

Purpose: The digitization of the dental field has been vigorously promoted in recent years. An impression using an intraoral scanner is considered to significantly change future dental treatment. The purpose of this review is to evaluate accuracy and practicality of various intraoral scanners and verification method of intraoral scanners., Study Selection: This review was based on articles searched through the MEDLINE and PubMed databases. The main keywords that were employed during the search were "Oral Scanner, Intraoral Scanners, Desktop Scanner, and Digital Impression"., Result: It was reported that illuminance and color temperature affected trueness and precision of intraoral scanners. The repeatability of intraoral scanners indicated the possibility of producing fixed prostheses within the range of being partially edentulous. It is considered difficult to use intraoral scanners in fabricating cross-arch fixed prostheses. However, with intraoral scanners, it may be considered possible to fabricate mouth guards and dentures equivalent to those of desktop scanners. Current intraoral scanner scans are considered more comfortable than traditional impressions that use irreversible hydrocolloid and elastomeric impression materials., Conclusion: Since the intraoral scanner is an evolving device, further improvement in accuracy is expected in the future. In addition, verification of the accuracy of intraoral scanners must be conducted accordingly., (Copyright © 2019 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

Purpose: To determine the accuracy of direct digital impressions in vivo and compare it to that of conventional impressions in order to assess whether intraoral scanners could be a legitimate alternative for the manufacturing of fixed prosthodontics., Materials and Methods: An electronic systematic search was conducted in the PubMed, Web of Science, Embase, and Cochrane Library databases using query terms such as digital impression; intraoral digital impression; intraoral scanner; intraoral digital scanner; conventional impression; analogue impression; and accuracy. The outcomes were the trueness and precision of digital impressions in comparison to those of high-precision conventional impressions in vivo., Results: Six studies matched the inclusion criteria. Four studies investigated the precision of digital impressions, while two studies focused on their trueness. Even if all the authors agreed that conventional impressions were more accurate than digital impressions in vivo, they gave different opinions on using intraoral scanners in a clinical context without causing misfit of the final restoration., Conclusion: According to the results of the present review, conventional impressions performed using high-precision impression materials showed greater accuracy than digital impressions. However, additional studies assessing the accuracy of digital impressions in a wider variety of clinical situations are highly recommended.

Impression-making is a necessary part of providing restorative and rehabilitative dentistry to patients. The use of physical impression trays and materials dates back to at least the 19th century, which included the development of corrective and functional impression techniques.1 This method of acquiring and conveying information remained largely unchanged throughout the 20th century, although the development and subsequent improvement of elastomeric impression materials greatly enhanced the quality and predictability of impression results. Now with the digitization of the dental profession, the introduction and advancement of digital impressions represents the latest step forward in impression-making. This article reviews the current state of physical impression-making and the.

Objective: To compare patient experience, chairside time, dental arch distances, and costs of dental models derived from intraoral scans and alginate impressions in pre-orthodontic children and young adolescents., Materials and Methods: Fifty-nine children and young adolescents (9-15 years, mean: 12.70 years) had an intraoral scan and an alginate impression prior to orthodontic treatment. During the procedures, chairside time was registered in minutes and patient experience was assessed by a Visual Analogue Scale questionnaire. Four maxillary dental arch distances were measured on digital models, on plaster casts, and directly in the mouth (intraoral). The cost of each procedure was presented graphically. Differences between the two procedures were tested by paired t -test and general linear model., Results: Patient experience was statistically better during intraoral scan compared with alginate impression regarding comfort, gag reflex, breathing, smell/sound, taste/vibration, and all statements concerning anxiety ( P < .05). No significant difference in chairside time between the two procedures was found. No statistically significant differences in dental arch distances between digital models and plaster casts were found, but dental arch distances measured intraorally differed significantly from both digital models and plaster casts ( P < .05). Cost calculation showed that the digital procedure was 10.7 times more expensive than the conventional procedure initially and, that after 3.6 years, the two procedures were equal in cost., Conclusions: Children preferred intraoral scan rather than alginate impression. Chairside time was equal for the two procedures as were the measurements of maxillary dental arch distances. The two procedures were equal in cost at 3.6 years.

Aim: The aim of this study is to check the dimensional precision of stone models made by two different brands of polyvinyl siloxane impression materials using the monophase, one-step, and two-step putty/light-body impression techniques., Materials and Methods: A metal model, having two crown preparations, was fabricated. With each technique, 40 impressions were made using two types of polyvinyl siloxane impression materials (Aquasil and Virtual). A total of 240 impressions were made with both the polyvinyl siloxane impression materials. Monophase impressions were made with a medium body using an acrylic custom tray. By simultaneous usage of putty and light-body, one-step impressions were made with a perforated metal stock tray. For two-step impressions, a 25-40 microns thick cellophane sheet spacer was used. The stone casts were obtained from the impressions of the stainless steel model. Three different dimensions (height, diameter, and inter-abutment distance) on these resultant stone casts were compared with the standard die. The accuracy of two different brands of impression materials was also compared. The results were then statistically analyzed., Results: The resultant casts obtained from the different impression techniques had significantly larger dimensions in height and diameter, but smaller dimensions were observed for the inter-abutment distance. Larger deviation in resultant casts was observed in the monophase than one-step impression technique and the least deviation was observed in the two-step impression technique., Conclusion: The two-step impression technique produced the most accurate results in terms of the resultant casts. Out of the two different brands, Aquasil produced more fare results., Clinical Significance: Adequate marginal adaptation, proper fit and least distortion of the castings, and the final prosthesis can be achieved by using the adequate impression technique and impression material.

Purpose: Intraoral scanners (IOSs), which create digital "impressions" of dental arches, have become popular for prosthetic and orthodontic applications. Adoption in oral and maxillofacial surgery (OMS) practices has been slower, likely because of high implementation costs and low-volume use. The purpose of this study was to evaluate costs for introduction of an IOS into an OMS practice. The authors hypothesized that digital impressions would be more efficient in time and cost compared with conventional impressions and that implementation costs would be offset within 1 year., Materials and Methods: This was a prospective study that included patients who had digital impressions during the first year after introduction of an IOS to the practice. Conventional alginate impressions obtained at the same visit were included for comparison. Variables included time for each step in each impression process, IOS experience of the operator obtaining the impression, and associated costs. Per-arch costs for each technique were calculated using time-driven activity-based costing methodology., Results: Sixty-three digital impressions and 31 conventional impressions were included. Mean total times for digital and conventional impressions were 14.1 ± 1.3 and 19.4 ± 4.0 minutes per arch, respectively. On a per-patient basis (2 arches for digital impressions and 4 arches for conventional impressions because of the inability to create duplicate stone models from each alginate impression), total impression times were 24.8 ± 2.7 minutes for digital and 67.2 ± 14.8 minutes for conventional impressions. Total calculated costs for digital and conventional impressions were $21.42 and $29.40 per arch and $37.66 and $102.10 per patient, respectively. In a practice with 2 patients for impressions per working day (500 per year), it would take 1.04 years to offset the purchase of the IOS; with 5 sets of impressions per day (1,250 per year), it would take 5 months., Conclusion: Digital impressions are more efficient and cost effective than standard impressions, and implementation costs can be offset within the first year., (Copyright © 2019 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to assess the precision of 3D-printed splints generated from different dental model offsets., Methods: Ten maxillary models were offset by given distances (0.05 mm, 0.1 mm, and 0.2 mm). Digital splints were created by means of the boolean operation. The physical splints were fabricated by means of digital light-processing (DLP) rapid prototyping technologies. A layer of impression material, which could be weighed by means of an electronic analytical balance, was placed in the airspace between the splint and the teeth. We also calculated the shell-to-shell deviations by measuring the 3-dimensional (3D) euclidean distances between the surface points of the scanned splints and the original digital splint and evaluating the results with color-mapping methods., Results: There was a statistically significant difference in the amounts of impression material remaining in the airspace between the 0.0-mm group and the 0.05-mm, 0.1-mm, and 0.2-mm groups (P < 0.05), between the 0.05-mm and the 0.1-mm and 0.2-mm groups (P < 0.05), and between the 0.0-mm group and the 0.05-mm, 0.1-mm, and 0.2-mm groups (P < 0.05). There was a statistically significant difference in shell-to-shell deviations between the 0.05-mm and the 0.1-mm and 0.2-mm groups (P < 0.05)., Conclusions: 3D-printed splints generated from offset dental models (offset 0.05 mm, 0.1 mm, and 0.2 mm) can fit better on the teeth than splints from no-offset dental models. An offset of 0.1 mm is the best choice of parameter for generating the splint., (Copyright © 2019 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Purpose: To compare the effect of 3 tray designs and 3 commonly used impression materials on the displacement of flabby tissue during maxillary edentulous impression by superimposition of 3D digital models., Materials and Methods: Fifteen maxillary edentulous casts with simulated flabby tissue were fabricated by modifying a standard maxillary edentulous acrylic resin cast. Three types of impression trays were fabricated: trays with conventional relief, trays with additional relief, and trays with an open window. Three impression materials were tested: light-body polysulfide, light-body vinylpolysiloxane, and zinc oxide eugenol paste. For the analysis of tissue displacement during impression making, the test and control stone casts were scanned using a 3D laser scanner, and the 3D digital models were superimposed using metrology software. Statistical analyses were performed with an α = 0.05., Results: Negative deviations were recorded at the areas of the alveolar crest, posterior part of flabby tissue, and middle of the palate. On the other hand, a positive deviation was recorded at the area of the anterior part of flabby tissue. A significant difference in the displacement of flabby tissue was found when using different tray designs (p < 0.0001). The tray with the open window showed significantly low tissue displacement at the flabby tissue region. Depending on sites, the amount of flabby tissue displacement showed different significances by the different impression materials used (anterior part: p < 0.0001; alveolar crest: p = 0.097; posterior part: p < 0.0001). Conventionally relieved trays showed significantly higher values of displacement at the anterior part of flabby tissue (p < 0.0001), while trays with open windows showed similar values of displacement at all measuring points, and no significant differences among different impression materials were found (p = 0.104)., Conclusions: There were significant differences in the displacement of flabby tissue with different tray designs, especially with displacement occurring at the anterior and posterior parts of flabby tissue. Tray designs should be considered in order to make proper impressions when flabby tissue is present., (© 2019 by the American College of Prosthodontists.)

Purpose: This study compared the three-dimensional (3D) accuracy of conventional impressions with digital impression systems (intraoral scanners and dental laboratory scanners) for two different interimplant distances in maxillary edentulous arches., Materials and Methods: Six impression systems comprising one conventional impression material(Impregum), two intraoral scanners (TRIOS and True Definition), and three dental laboratory scanners (Ceramill Map400, inEos X5, and D900) were evaluated on two completely edentulous maxillary arch master models (A and B) with six and eight implants, respectively. Centroid positions at the implant platform level were derived using either physical or virtual probe hits with a coordinate measuring machine. Comparison of centroid positions between master and test models (n = 5) defined linear distortions (d x , d y , d z ), global linear distortions (d R ), and 3D reference distance distortions between implants (ΔR). The two-dimensional (2D) angles between the central axis of each implant to the x- or y-axes were compared to derive absolute angular distortions (Absdθ x , Absdθ y )., Results: Model A mean d R ranged from 8.7 ± 8.3 μm to 731.7 ± 62.3 μm. Model B mean d R ranged from 16.3 ± 9 μm to 620.2 ± 63.2 μm. Model A mean Absdθ x ranged from 0.021 ± 0.205 degrees to -2.349 ± 0.166 degrees, and mean Absdθ y ranged from -0.002 ± 0.160 degrees to -0.932 ± 0.290 degrees. Model B mean Absdθ x ranged from -0.007 ± 0.076 degrees to -0.688 ± 0.574 degrees, and mean Absdθ y ranged from -0.018 ± 0.048 degrees to -1.052 ± 0.297 degrees. One-way analysis of variance (ANOVA) by Impression system revealed significant differences among test groups for d R and ΔR in both models, with True Definition exhibiting the poorest accuracy. Independent samples t tests for d R , between homologous implant location pairs in Model A versus B, revealed the presence of two to four significant pairings (out of seven possible) for the intraoral scanner systems, in which instances d R was larger in Model A by 110 to 150 μm., Conclusion: Reducing interimplant distance may decrease global linear distortions (d R ) for intraoral scanner systems, but had no effect on Impregum and the dental laboratory scanner systems. Impregum consistently exhibited the best or second-best accuracy at all implant locations, while True Definition exhibited the poorest accuracy for all linear distortions in both Models A and B. Impression systems could not be consistently ranked for absolute angular distortions.

Introduction: The purpose of this study was to investigate differences in orthodontists' treatment plans based on digital models compared with plaster models. Additionally, we assessed whether digital or plaster models influence the reliability of orthodontists' treatment plans, as well as the amount of time required to arrive at the plan., Methods: Sixteen orthodontists planned treatment for 20 patients at 2 time points using either the same or different model formats (digital or plaster). The treatment plan decisions and time spent making the plans were recorded. The permutation test and a random effects model were used to analyze the data., Results: The treatment plans arrived at with digital and plaster models were similar. With respect to extractions, the mean difference between digital and plaster formats was 11.9% (95% CI, 7.5%-16.3%). For surgery, the mean difference was 9.4% (95% CI, 5.0%-13.8%). There was no significant difference in the agreement rate between those who viewed models in different formats compared with those who viewed models twice in the same format (P >0.05). The time spent to plan treatment with plaster models was not significantly different from the time spent with digital models (P = 0.87)., Conclusions: Based on this study, digital models can be substituted for plaster models with no significant differences in the final plans, the reliability of the plans, and the time required to create the plan., (Copyright © 2018 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Aim: Deformation of the mandible presents a major challenge for many dentists, both in conventional prosthetic supraconstructions and in complex implant restorations. This study aimed to evaluate the three-dimensional (3D) deformation of the mandible in vivo with scannable impression material and an industrial optical scanner., Materials and Methods: In the present study, 20 female and 20 male subjects were examined. In each case, two impressions were made with polyvinylsiloxane: one with the mouth slightly open, and a second with the mouth wide open. The impressions were digitized with an industrial optical scanner and transformed into a virtual model. The two corresponding models were digitally superimposed over all the teeth. Then, an individual local coordinate system was assigned to each individual tooth. Subsequently, a best-fit procedure was performed for each individual tooth. Finally, the open- and closed-mouth models were compared by calculating the differences and rotations in the individual axes. This procedure was performed individually for each tooth., Results: The mean deviations in the x-, y-, and z-coordinates ranged from 0.011 mm at the canines to 0.232 mm at the molars. Larger discrepancies were observed in the female subjects than in the male subjects; however, these differences were not statistically significant., Conclusion: The results demonstrated that the posterior region of the mandible deformed when the mouth was maintained in a wide-open position. Therefore, this position should be avoided when performing dental impressions. Moreover, potential negative consequences of this mandibular deformation should be taken into consideration when planning wide-span fixed dental restorations.

Introduction: A rapidly advancing digital technology in orthodontics is 3-dimensional (3D) modeling and printing, prompting a transition from a more traditional clinical workflow toward an almost exclusively digital format. There is limited literature on the accuracy of the 3D printed dental models. The aim of this study was to assess the accuracy of 2 types of 3D printing techniques., Methods: Digital and alginate impressions of the oral environment were collected from 30 patients. Subsequently, digital impressions were used to print 3D models using digital light processing (DLP) and polyjet printing techniques, and alginate impressions were poured up in stone. Measurements for the 3 model types (digital, DLP, and polyjet) were compared with the stone models. Tooth measurements (first molar to first molar) included mesiodistal (crown width) and incisal/occlusal-gingival (crown height). Arch measurements included arch depth and intercanine and intermolar widths. Intraobserver reliability of the repeated measurement error was assessed using intraclass correlation coefficients., Results: The intraclass correlation coefficients were high for all recorded measurements, indicating that all measurements on all model types were highly reproducible. There were high degrees of agreement between all sets of models and all measurements, with the exception of the crown height measurements between the stone and DLP models, where the mean difference was statistically significant., Conclusions: Both the DLP and polyjet printers produced clinically acceptable models and should be considered viable options for clinical application., (Published by Elsevier Inc.)

Purpose: The aim of the current study is to develop a novel method to investigate the accuracy of 3D scanners and digital articulation systems., Materials and Methods: An upper and a lower poured stone model were created by taking impression of fully dentate male (fifty years old) participant. Titanium spheres were added to the models to allow for an easily recognisable geometric shape for measurement after scanning and digital articulation. Measurements were obtained using a Coordinate Measuring Machine to record volumetric error, articulation error and clinical effect error. Three scanners were compared, including the Imetric 3D iScan d104i, Shining 3D AutoScan-DS100 and 3Shape D800, as well as their respective digital articulation software packages. Stoneglass Industries PDC digital articulation system was also applied to the Imetric scans for comparison with the CMM measurements., Results: All the scans displayed low volumetric error (p⟩0.05), indicating that the scanners themselves had a minor contribution to the articulation and clinical effect errors. The PDC digital articulation system was found to deliver the lowest average errors, with good repeatability of results., Conclusion: The new measuring technique in the current study was able to assess the scanning and articulation accuracy of the four systems investigated. The PDC digital articulation system using Imetric scans was recommended as it displayed the lowest articulation error and clinical effect error with good repeatability. The low errors from the PDC system may have been due to its use of a 3D axis for alignment rather than the use of a best fit., (Copyright© 2018 Dennis Barber Ltd.)

Background: This in vivo study evaluated the difference of two well-known intraoral scanners used in dentistry, namely iTero (Align Technology) and TRIOS (3Shape)., Methods: Thirty-two participants underwent intraoral scans with TRIOS and iTero scanners, as well as conventional alginate impressions. The scans obtained with the two intraoral scanners were compared with each other and were also compared with the corresponding model scans by means of three-dimensional surface analysis. The average differences between the two intraoral scans on the surfaces were evaluated by color-mapping. The average differences in the three-dimensional direction between each intraoral scans and its corresponding model scan were calculated at all points on the surfaces., Results: The average differences between the two intraoral scanners were 0.057 mm at the maxilla and 0.069 mm at the mandible. Color histograms showed that local deviations between the two scanners occurred in the posterior area. As for difference in the three-dimensional direction, there was no statistically significant difference between two scanners., Conclusions: Although there were some deviations in visible inspection, there was no statistical significance between the two intraoral scanners.

Purpose: To compare the dimensional accuracy of dies generated from digital intraoral scans with dies generated from conventional polyvinyl siloxane (PVS) impression material., Materials and Methods: A machined metal die was impressed 10 times using PVS, and scanned 10 times using the iTero Cadent system and 10 times using the LAVA C.O.S. system. Dies generated from each system were imaged in a standardized holder using a microscope and measured with analytical software at three sites and compared with the dimensions of the master die., Results: The dimensional differences between the master die and both the PVS and iTero groups were approximately 60 μm in all three dimensions but the Lava C.O.S. die dimensions measured close to 100 μm at two of the three sites., Conclusion: PVS/Die and iTero groups offered superior reproduction of the master die in terms of dimensional accuracy, but these differences are likely of little clinical significance., (© 2016 by the American College of Prosthodontists.)

Introduction: Replacing impression by intraoral camera is a paradigm shift. However no in vivo independent studies have compared the accuracy of analog impressions with three systems of digital impression. Are digital recordings precise enough for our orthodontic practices?, Materials and Methods: Five impressions of the maxillary and mandibular arch of the same subject were conducted in vinylpolysiloxane, cast in plaster type IV then scanned by a laboratory scanner (VPS group). A model (maxilla and mandible) is the reference. Five scans of the maxillary and mandibular arch of the plaster model reference (group EXO) and the subject in intra-oral (INTRA group) were performed successively by the Lythos™ cameras (Ormco) version 1, iTero ® (AlignTech) version 1 and TRIOS ® (3shape) version 2. Numerical models of each group were cut and stacked Best Fit technique references models., Results: The images of the INTRA group have a lack of accuracy of 18 microns (p = 3.88 10 -08 ) compared to images of EXO and VPS group. The maxillary arch has greater fidelity of 6 microns with respect to the mandibular arch in the three systems (p = 0.002). The fingerprinting technique (analog or digital) and the camera model - despite a difference on the number of points recorded - has no statistically significant effect on accuracy., Conclusion: Carried out under ideal conditions, the accuracy of the cameras is certainly less than conventional impressions VPS but is clinically sufficient. The reduction of acquisition time may affect the accuracy, smooth out errors and get the arches contracted., (© EDP Sciences, SFODF, 2017.)

Objectives: Direct and indirect digitalization offer two options for computer-aided design (CAD)/ computer-aided manufacturing (CAM)-generated restorations. The aim of this study was to evaluate the accuracy of different intraoral scanners and compare them to the process of indirect digitalization., Material and Method: A titanium testing model was directly digitized 12 times with each intraoral scanner: (1) CS 3500 (CS), (2) Zfx Intrascan (ZFX), (3) CEREC AC Bluecam (BLU), (4) CEREC AC Omnicam (OC) and (5) True Definition (TD). As control, 12 polyether impressions were taken and the referring plaster casts were digitized indirectly with the D-810 laboratory scanner (CON). The accuracy (trueness/precision) of the datasets was evaluated by an analysing software (Geomagic Qualify 12.1) using a "best fit alignment" of the datasets with a highly accurate reference dataset of the testing model, received from industrial computed tomography., Results: Direct digitalization using the TD showed the significant highest overall "trueness", followed by CS. Both performed better than CON. BLU, ZFX and OC showed higher differences from the reference dataset than CON. Regarding the overall "precision", the CS 3500 intraoral scanner and the True Definition showed the best performance. CON, BLU and OC resulted in significantly higher precision than ZFX did., Conclusions: Within the limitations of this in vitro study, the accuracy of the ascertained datasets was dependent on the scanning system. The direct digitalization was not superior to indirect digitalization for all tested systems., Clinical Relevance: Regarding the accuracy, all tested intraoral scanning technologies seem to be able to reproduce a single quadrant within clinical acceptable accuracy. However, differences were detected between the tested systems.

This clinical technique provides a key procedure for successful prosthetic treatment in patients with an anatomical compromise after a maxillectomy. When making a preliminary impression, the clinician must keep the handle of the stock tray parallel to the patient's interpupillary line extraorally to maintain the correct position of the tray and to make a record of the inclination of the occlusal plane. This simple consideration during this first step of making a preliminary impression can be an important guide for both dentists and dental technicians. Information about the correct positioning of the tray and the inclination of the occlusal plane obtained by using a stock tray handle will greatly reduce the stress experienced by dentists, dental technicians, and patients during the fabrication of the prosthesis and will ultimately lead to successful prosthetic treatment in patients with anatomic compromise resulting from a maxillectomy., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Little peer-reviewed information is available regarding the accuracy and precision of the occlusal contact reproduction of digitally mounted stereolithographic casts., Purpose: The purpose of this in vitro study was to evaluate the accuracy and precision of occlusal contacts among stereolithographic casts mounted by digital occlusal registrations., Material and Methods: Four complete anatomic dentoforms were arbitrarily mounted on a semi-adjustable articulator in maximal intercuspal position and served as the 4 different simulated patients (SP). A total of 60 digital impressions and digital interocclusal registrations were made with a digital intraoral scanner to fabricate 15 sets of mounted stereolithographic (SLA) definitive casts for each dentoform. After receiving a total of 60 SLA casts, polyvinyl siloxane (PVS) interocclusal records were made for each set. The occlusal contacts for each set of SLA casts were measured by recording the amount of light transmitted through the interocclusal records. To evaluate the accuracy between the SP and their respective SLA casts, the areas of actual contact (AC) and near contact (NC) were calculated. For precision analysis, the coefficient of variation (CoV) was used. The data was analyzed with t tests for accuracy and the McKay and Vangel test for precision (α=.05)., Results: The accuracy analysis showed a statistically significant difference between the SP and the SLA cast of each dentoform (P<.05). For the AC in all dentoforms, a significant increase was found in the areas of actual contact of SLA casts compared with the contacts present in the SP (P<.05). Conversely, for the NC in all dentoforms, a significant decrease was found in the occlusal contact areas of the SLA casts compared with the contacts in the SP (P<.05). The precision analysis demonstrated the different CoV values between AC (5.8 to 8.8%) and NC (21.4 to 44.6%) of digitally mounted SLA casts, indicating that the overall precision of the SLA cast was low., Conclusions: For the accuracy evaluation, statistically significant differences were found between the occlusal contacts of all digitally mounted SLA casts groups, with an increase in AC values and a decrease in NC values. For the precision assessment, the CoV values of the AC and NC showed the digitally articulated cast's inability to reproduce the uniform occlusal contacts., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives: Little information is available on the impact of different scan strategies on the accuracy of full-arch scans with intraoral scanners. The aim of this in-vitro study was to investigate the trueness and precision of full-arch maxillary digital impressions comparing three scan strategies., Method and Materials: Three scan strategies (A, B, and C) were applied each five times on one single model (A, first buccal surfaces, return from occlusal-palatal; B, first occlusal-palatal, return buccal; C, S-type one-way). The TRIOS Pod scanner (3shape, Copenhagen, Denmark) with a color detector was used for these digital impressions. A cast of a maxillary dentate jaw was fabricated and scanned with an industrial reference scanner. This full-arch data record was digitally superimposed with the test scans (trueness) and within-group comparison was performed for each group (precision). The values within the 90/10 percentiles from the digital superimposition were used for calculation and group comparisons with nonparametric tests (ANOVA, post-hoc Bonferroni)., Results: The trueness (mean ± standard deviation) was 17.9 ± 16.4 μm for scan strategy A, 17.1 ± 13.7 μm for B, and 26.8 ± 14.7 μm for C without statistically significant difference. The precision was lowest for scan strategy A (35.0 ± 51.1 μm) and significantly different to B (7.9 ± 5.6 μm) and C (8.5 ± 6.3 μm)., Conclusions: Scan strategy B may be recommended as it provides the highest trueness and precision in full-arch scans and therefore minimizes inaccuracies in the final reconstruction.

Purpose: The purpose of this study is to compare the pressure dynamics in the trays caused by differences in the various impression materials and in the thickness of the relief provided for the trays., Methods: In this study, two types of polyvinylsiloxane elastomers, one type of polyether elastomer and one type of alginate impression material were used. Pressure sensors were embedded at eight locations in a model of an edentulous maxilla, and used a simulation model covered with a pseudomucosa. For each impression material, the measurement was performed five times for each of the three types of trays, and the mean values were determined. Statistical analysis was carried out using one-way analysis of variance and the Tukey's HDS method, and the various pressure sensor values for each of the impression materials were compared 10s and 20s after the start of the measurement. Additionally, we compared differences among the three types of trays after 20s., Results: The pressure values for sensors placed in the relief region tended to become uniform. Furthermore, we saw a tendency for the pressure to increase at the alveolar crests of the first molars on the left and right and at the posterior border of the palate, all of which support the denture, when relief was provided., Conclusions: The above results suggest that making the final impression for the denture using the selective pressure technique, with consideration given to the pressure dynamic, may lead to a good outcome in terms of preservation of the alveolar ridge., (Copyright © 2015 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

Statement of Problem: Digital impression systems have undergone significant development in recent years, but few studies have investigated the accuracy of the technique in vivo, particularly compared with conventional impression techniques., Purpose: The purpose of this in vivo study was to investigate the precision of conventional and digital methods for complete-arch impressions., Material and Methods: Complete-arch impressions were obtained using 5 conventional (polyether, POE; vinylsiloxanether, VSE; direct scannable vinylsiloxanether, VSES; digitized scannable vinylsiloxanether, VSES-D; and irreversible hydrocolloid, ALG) and 7 digital (CEREC Bluecam, CER; CEREC Omnicam, OC; Cadent iTero, ITE; Lava COS, LAV; Lava True Definition Scanner, T-Def; 3Shape Trios, TRI; and 3Shape Trios Color, TRC) techniques. Impressions were made 3 times each in 5 participants (N=15). The impressions were then compared within and between the test groups. The cast surfaces were measured point-to-point using the signed nearest neighbor method. Precision was calculated from the (90%-10%)/2 percentile value., Results: The precision ranged from 12.3 μm (VSE) to 167.2 μm (ALG), with the highest precision in the VSE and VSES groups. The deviation pattern varied distinctly according to the impression method. Conventional impressions showed the highest accuracy across the complete dental arch in all groups, except for the ALG group., Conclusions: Conventional and digital impression methods differ significantly in the complete-arch accuracy. Digital impression systems had higher local deviations within the complete arch cast; however, they achieve equal and higher precision than some conventional impression materials., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives: This study examines accuracy of dental impressions and following plaster models taken during treatment with fixed appliances., Materials and Methods: A maxillary typodont was provided with brackets. Three examiners took impressions three times each of the variants: brackets only, archwire fixed by alastics, ligatures or Kobayashi-hooks, and brackets and archwire covered completely or just on the gingival side by protection or impression wax. Casts were scanned using Activity102(®). Virtual models were compared to the scan of the typodont using Comparison(®). Differences were measured and descriptively analyzed. Estimated means with 95% confidence intervals were computed. Significance was assessed using linear mixed models., Results: While pyramidal reference blocks had a mean difference of 0.019 mm (95% CI = 0.017-0.021 mm) to the master model, teeth without attachments showed 0.097 mm (95% CI = 0.082-0.111 mm), and teeth with brackets 0.169 mm (95% CI = 0.156-0.182 mm) (p < 0.001). Smallest mean was found when using protection wax only on the gingival bracket side (0.152 mm (95% CI = 0.113-0.192 mm)). Incisors deviated most (0.258 mm (95 % CI = 0.239-0.277 mm))., Conclusions: Teeth with brackets make impressions more inaccurate because of undercuts. Removing the archwire before taking the impression or covering the brackets on the gingival side shows tendencies toward better precision., Clinical Relevance: Taking impressions during treatment with fixed appliances, some inaccuracy has to be taken into account.

Objective: The splint technique of implant-supported restorations is a popular impression method; however, in-vivo studies showing the advantage of this method are scarce. The objective was to compare radiographic fit of the metal frameworks fabricated according to splinted or nonsplinted impression techniques. The null hypothesis was that splinting techniques would result in more accurate impressions., Method and Materials: A retrospective analysis was performed on 71 patients who had undergone multi-implant-supported rehabilitation in the years of 2012 to 2013. The treatment was carried out by three senior dentists or by residents in the department of Oral Rehabilitation at the Hebrew University Hadassah Medical Center. Each senior and the residents under his guidance treated patients consistently by only one different impression method: (1) no splint; (2) splinted transfers with pattern resin over dental floss scaffold; (3) splinting of transfers to impression tray with pattern resin. Orthoradial radiographs were used to determine if the metal framework fit the implant abutments., Results: In total, 81 impressions and 285 implants were included in the study; 56 impressions were done by seniors and 25 by residents. There was no difference in success between the three methods when done by seniors (P = .76). The fixation to tray method was found to be significantly unsuccessful in the hands of residents (P = .01)., Conclusion: Because the splint methods were not found to be more accurate, splinting the transfers might be an unnecessary step. Splinting of transfers to the impression tray is not recommended for inexperienced dentists.

Neutral electrolyzed water was developed with new concepts of long-term good durability and minimum corrosiveness to metal in addition to its excellent bactericidal activities similar to acid type of electrolyzed waters. The present study examined the bactericidal effects of the neutral electrolyzed water on disinfection of the alginate impression of a dental arch model contaminated by bacteria. Only 1-min immersion in neutral electrolyzed water could sufficiently disinfect the alginate impression including the metallic tray under ultrasonic with no significant differences from acid electrolyzed waters. No bactericidal effects were found in any electrolyzed water when used as mixing water. Considering the advantages and disadvantages of each electrolyzed water in a comprehensive way, it was suggested that neutral electrolyzed water may be the most appropriate for the disinfection of alginate impression.

Dual arch impressions have been in use for many years. Five in-office techniques for fabrication of the tray have been suggested, in case the manufactured (stock) tray is not available to the clinician. The design consists of two parts of the tray (the plastic frame and lattice). Five types of materials for the lattice have been described. The indications, advantages, and disadvantages of the techniques together with an appraisal of the five different lattice materials have been described. Overall the techniques are simple and require materials that are easily available. It does not take much time and can be used to attain efficient results in case the stock tray is not available in the operatory.

This study proposes a method of superimposing a physical palatal profile, extracted from a speaker's maxillary impression, onto real-time mid-sagittal articulatory data. A palatal/dental profile is first obtained by three-dimensional-scanning the maxillary impression of the speaker. Then a high resolution mid-sagittal palatal line, extracted from the profile, is sub-divided into articulatory zones and superimposed, by Iterative Closest Point algorithm, onto reconstructed palatal traces in electromagnetic articulometric (EMA) data. Evaluations were carried out by comparing consonant targets elicited by EMA with the proposed method and by static palatography. The proposed method yields accurate results, as supported by palatography.

Objective: The accuracy of digital impressions greatly influences their clinical viability in implant restorations. The aim of this study was to compare the accuracy of gypsum models acquired from the conventional implant impression to digitally milled models created from direct digitalization by three-dimensional analysis., Materials and Methods: Thirty gypsum and 30 digitally milled models, impressed directly from a reference model, were prepared. The models and reference model were scanned by a laboratory scanner, and 30 surface tessellation language datasets from each group were imported to an inspection software program. The datasets were aligned to the reference dataset by a repeated best-fit algorithm, and 10 specified contact locations of interest were measured in mean volumetric deviations. The areas were pooled by cusps, fossae, interproximal contacts, horizontal and vertical axes of implant position and angulation. The pooled areas were statistically analysed by comparing each group to the reference model to investigate the mean volumetric deviations accounting for accuracy and standard deviations for precision., Results: Milled models from digital impressions had comparable accuracy to gypsum models from conventional impressions. However, differences in fossae and vertical displacement of the implant position from the gypsum and digitally milled models compared to the reference model exhibited statistical significance (P < 0.001, P = 0.020, respectively)., Conclusion: Milled models from digital impression are comparable to gypsum models from conventional impression., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

In this study, we evaluated the repeatability of scans of stone models and impressions of abutment teeth using a blue LED scanner and compared the findings between different abutment teeth types. For the stone models as well as impression of the canines, premolars, and molars, we generated 10 color-difference-maps and reports for each tooth type (n=10 per tooth type). One-way analysis of variance (ANOVA) and independent t-tests were performed to evaluate the repeatability of scans of the stone models and impressions obtained from a blue LED scanner. Our results indicate a high repeatability of scans of stone models and impressions of abutment teeth using the blue LED scanner and suggest a possible clinical advantage for scanning impressions of different abutment teeth types.

Background: There is a scarce knowledge on the accuracy of intraoral digital impression systems for dental implants., Purpose: The purpose of this study is to evaluate the accuracy of a digital impression system considering clinical parameters., Materials and Methods: A master model with six implants (27, 25, 22, 12, 15, 17) was fitted with polyether ether ketone scan bodies. Implant no. 25 was placed with 30° mesial angulation in relation to the vertical plane (y axis), and implant no. 15 was positioned with 30° distal angulation. Implant no. 22 was placed 2 mm and no. 12, 4 mm below the gingiva. Experienced (n = 2) and inexperienced operators (n = 2) performed scanning (Lava Chairside Oral Scanner; 3 M ESPE, St Paul, MN, USA) at standard and high accuracy mode. Measurements involved five distances (27-25, 27-22, 27-12, 27-15, 27-17). Measurements with high accuracy three-dimensional coordinated measuring machine (CMM) of the master model acted as the true values. The data obtained were subtracted from those of the CMM values., Results: Experience of the operator significantly influenced the results (p = .000). Angulation (p = .195) and depth of implant (p = .399) did not show significant deviation from the true values. The mean difference between standard and high accuracy mode was 90 μm., Conclusions: With the active wavefront sampling, technology-based digital impression system training seems to be compulsory. Impressions of angulated implants may diminish the accuracy of the impression, yet the results were not significant., (© 2013 Wiley Periodicals, Inc.)

Purpose: The purpose of this study was to compare the three-dimensional accuracy of indirect plastic impression copings and direct implant-level impression copings from three implant systems (Nobel Biocare [NB], Biomet 3i [3i], and Straumann [STR]) at three interimplant buccolingual angulations (0, 8, and 15 degrees)., Materials and Methods: Two-implant master models were used to simulate a three-unit implant fixed partial denture. Test models were made from Impregum impressions using direct implant-level impression copings (DR). Abutments were then connected to the master models for impressions using the plastic impression copings (INDR) at three different angulations for a total of 18 test groups (n = 5 in each group). A coordinate measuring machine was used to measure linear distortions, three-dimensional (3D) distortions, angular distortions, and absolute angular distortions between the master and test models., Results: Three-way analysis of variance showed that the implant system had a significant effect on 3D distortions and absolute angular distortions in the x- and y-axes. Interimplant angulation had a significant effect on 3D distortions and absolute angular distortions in the y-axis. Impression technique had a significant effect on absolute angular distortions in the y-axis. With DR, the NB and 3i systems were not significantly different. With INDR, 3i appeared to have less distortion than the other systems. Interimplant angulations did not significantly affect the accuracy of NBDR, 3iINDR, and STRINDR. The accuracy of INDR and DR was comparable at all interimplant angulations for 3i and STR. For NB, INDR was comparable to DR at 0 and 8 degrees but was less accurate at 15 degrees., Conclusions: Three-dimensional accuracy of implant impressions varied with implant system, interimplant angulation, and impression technique.

Purpose: To evaluate the dimensional accuracy of the resultant (duplicative) casts made from two different impression materials (polyvinyl siloxane and polyether) in parallel and angulated implants., Materials and Methods: Three definitive master casts (control groups) were fabricated in dental stone with three implants, placed at equi-distance. In first group (control), all three implants were placed parallel to each other and perpendicular to the plane of the cast. In the second and third group (control), all three implants were placed at 10° and 15 o angulation respectively to the long axis of the cast, tilting towards the centre. Impressions were made with polyvinyl siloxane and polyether impression materials in a special tray, using a open tray impression technique from the master casts. These impressions were poured to obtain test casts. Three reference distances were evaluated on each test cast by using a profile projector and compared with control groups to determine the effect of combined interaction of implant angulation and impression materials on the accuracy of implant resultant cast., Results: Statistical analysis revealed no significant difference in dimensional accuracy of the resultant casts made from two different impression materials (polyvinyl siloxane and polyether) by closed tray impression technique in parallel and angulated implants., Conclusion: On the basis of the results of this study, the use of both the impression materials i.e., polyether and polyvinyl siloxane impression is recommended for impression making in parallel as well as angulated implants.

Purpose: This in vitro study aimed to identify the effects of the implant system, impression technique, and impression material on the transfer accuracy of implant impressions. The null hypothesis tested was that, in vitro and within the parameters of the experiment, the spatial relationship of a working cast to the placement of implants is not related to (1) the implant system, (2) the impression technique, or (3) the impression material., Materials and Methods: A steel maxilla was used as a reference model. Six implants of two different implant systems (Standard Plus, Straumann; Semados, Bego) were fixed in the reference model. The target variables were: three-dimensional (3D) shift in all directions, implant axis direction, and rotation. The target variables were assessed using a 3D coordinate measuring machine, and the respective deviations of the plaster models from the nominal values of the reference model were calculated. Two different impression techniques (reposition/pickup) and four impression materials (Aquasil Ultra, Flexitime, Impregum Penta, P2 Magnum 360) were investigated. In all, 80 implant impressions for each implant system were taken. Statistical analysis was performed using multivariate analysis of variance., Results: The implant system significantly influenced the transfer accuracy for most spatial dimensions, including the overall 3D shift and implant axis direction. There was no significant difference between the two implant systems with regard to rotation. Multivariate analysis of variance showed a significant effect on transfer accuracy only for the implant system., Conclusions: Within the limits of the present study, it can be concluded that the transfer accuracy of the intraoral implant position on the working cast is far more dependent on the implant system than on the selection of a specific impression technique or material.

Objectives: The use of fast-setting impression materials with different viscosities for the one-stage impression technique demands precise working times when mixing. We examined the effect of varying working time on impression precision in a randomized clinical trial., Materials and Methods: Focusing on tooth 46, three impressions were made from each of 96 volunteers, using either a polyether (PE: Impregum Penta H/L DuoSoft Quick, 3 M ESPE) or an addition-curing silicone (AS: Aquasil Ultra LV, Dentsply/DeTrey), one with the manufacturer's recommended working time (used as a reference) and two with altered working times. All stages of the impression-taking were subject to randomization. The three-dimensional precision of the non-standard working time impressions was digitally analyzed compared to the reference impression. Statistical analysis was performed using multivariate models., Results: The mean difference in the position of the lower right first molar (vs. the reference impression) ranged from ±12 μm for PE to +19 and -14 μm for AS. Significantly higher mean values (+62 to -40 μm) were found for AS compared to PE (+21 to -26 μm) in the area of the distal adjacent tooth., Conclusions: Fast-set impression materials offer high precision when used for single tooth restorations as part of a one-stage impression technique, even when the working time (mixing plus application of the light- and heavy-body components) diverges significantly from the manufacturer's recommended protocol., Clinical Relevance: Best accuracy was achieved with machine-mixed heavy-body/light-body polyether. Both materials examined met the clinical requirements regarding precision when the teeth were completely syringed with light material.