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Purpose: The purpose of this study was to evaluate the impression accuracy of two implants placed in different orientations and compare the impression accuracy obtained with the dual-arch impression technique using hybrid impression copings and the conventional open-tray impression technique. Materials and Methods: Five mandibular dentiform models were prepared by placing implants in the second premolar and second molar regions in the following different orientations: parallel to each other; 15-degree mesiodistal angulation; 30-degree mesiodistal angulation; 15-degree buccolingual angulation; and 30-degree buccolingual angulation. After making 10 impressions for each model with the open-tray impression technique and dual-arch impression technique with hybrid impression copings, cast models were fabricated for each impression (n = 10). Scan bodies were mounted on the five dentiform models and the fabricated 100 cast models were scanned using a desktop scanner. The three-dimensional deviation of the scan bodies on the cast models was calculated and compared to the reference data from the dentiform models. A two-way analysis of variance was conducted (α = .05). Results: The root mean square deviation values obtained from the implants placed with 30-degree mesiodistal angulation were 93.05 ± 6.21 µm with the open-tray impression technique and 104.01 ± 8.89 µm with the dual-arch impression technique, which were the largest deviation values for both techniques (P < .001). Compared to the open-tray impression technique, the dual-arch impression technique with the hybrid impression copings showed significantly lower accuracy when the angulation between the implants was 15 degrees mesiodistally (P < .001), 30 degrees mesiodistally (P = .016), or 30 degrees buccolingually (P < .001). However, there was no significant difference between the accuracy of the two impression techniques for parallel implants (P = .74). Conclusion: When the two implants were inclined 30 degrees mesiodistally, both implant impression techniques showed the largest deviation and the dual-arch impression technique showed lower accuracy compared to the conventional open-tray impression technique. Parallel placement of implants may improve impression accuracy and enable use of the dual-arch impression technique. [ABSTRACT FROM AUTHOR]

Günümüzde dental implantlar doğal dişlerin yerine geçebilecek en iyi seçenektir. İmplant destekli protetik restorasyonlarda pasif uyum tedavinin başarısı için en önemli faktördür. Pasif uyumlu implant destekli restorasyonlar, doğru ölçü tekniği ve uygun ölçü materyali kullanılarak doğru ölçü alınması, dişlerin komşu yapılarla ilişkilerinin doğru belirlenmesi ve ağız içi yapıların modele doğru aktarılması ile sağlanabilir. Ölçünün doğruluğu, ölçü materyalinden, kullanılan ölçü yönteminden, implantın pozisyonu, açısı ve derinliğinden, kullanılan alçının boyutsal stabilitesinden, kullanılan day sisteminden ve ölçü kopinglerinin uzunluğundan etkilenir. İmplant üstü ölçü yöntemleri geleneksel ve dijital olarak ikiye ayrılabilir. Bu derlemede implant üstü ölçü yöntemlerinin implant sayısı, ölçü materyalleri, splint materyali, koping tasarımı, implant açısı ve implant-abutment bağlantı şekli yönleriyle karşılaştırmalı olarak değerlendirilmesi amaçlanmıştır.

Copyright of Selcuk Dental Journal is the property of Selcuk Dental Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: A high transfer accuracy of the intraoral implant position to a model is required, to manufacture implant-supported restorations. However, clinically relevant deviations persist between the intraoral implant position and the model obtained, even for the benchmark conventional custom implant impressions with polyether. Thus, new approaches using 3-D printed impression trays may increase the transfer accuracy of implant impressions. The ability to adjust parameters such as the thickness of the layers and the influence of the openings in the impression tray could potentially affect accuracy. Methods: Four different types of impression trays (n = 10 for each group) for the conventional impression technique were investigated: conventional custom impression tray, customized foil tray, chairside 3-D printed impression tray with the SHERA system, and the Primeprint system using an implant master model with four implants in the posterior region and a reference cube. After plaster model casting, all models were measured using a coordinate measuring machine, and the deviation from the reference dataset was determined. A statistical ANOVA analysis was performed (p < 0.05). Results: Chairside 3-D printed impression trays showed the best results, followed by conventional custom impression trays. Implant impressions obtained using a customized foil tray exhibited the lowest accuracy. Statistically significant differences were observed between 3-D printed impression trays and conventional custom impression and customized foil trays (p < 0.05). Whereas, the implant position did not have any significant influence on accuracy (p > 0.05). Conclusions: Chairside 3-D printed impression trays significantly increase the transfer accuracy for implant impression taking. [ABSTRACT FROM AUTHOR]

Objective: The aim of this systematic review was to evaluate the influence of the characteristics of intraoral scan bodies (ISBs) on the accuracy of intraoral scanning. Materials and Methods: An electronic search was conducted through PubMed (MEDLINE), Scopus and Cochrane Library, up to March 2023. The literature search intended to retrieve all relevant clinical and in vitro studies about the effect that the various properties of ISBs may have on the accuracy (trueness and precision) of intraoral scanning. Only publications in English language were selected with animal studies, case reports, case series, technique presentation articles and expert opinions being excluded. Results: A total of 28 studies met the inclusion criteria and were included in this systematic review. They were published between 2019 and 2023 and were all in vitro studies. Among the parameters described, the scan body material, position, geometry, height, diameter, and fixation torque were evaluated. The most common materials used for ISBs were polyetheretherketone (PEEK) and titanium alloys. The diameter and position of ISBs seemed to affect the trueness of implant impressions. Subgingival implant position and decreased ISB height affected negatively the trueness of scanning. Geometrical characteristics of ISBs also affect the implant impression accuracy, especially the bevel location and the types of designing modifications. Conclusions: The characteristics of the currently used ISBs vary widely and the available scientific evidence is not yet conclusive about the optimal design of ISB. The implant impression accuracy achieved by any of the studied parameters is encouraging. Clinical studies are however necessary for more concrete conclusions. Clinical Significance: ISBs play a vital role in the digital workflow and influence significantly the accuracy and fit of implant restorations. More clinical trials are needed in order to conclude to the optimal characteristics of ISBs which would further enhance the success of the restorations. [ABSTRACT FROM AUTHOR]

The aim of this in vitro study was to evaluate the accuracy of impressions made using two different silicones and corresponding stone casts in full-arch implant rehabilitation, using two laboratory scanners. A master model with six dental implants was created, scanned with a 12-megapixel scanner and used as digital master model. Ten implant impressions were obtained via two silicone impressions systems—Coltene® and Zhermack®—using the open-tray technique and poured gypsum. Two extraoral scanning systems (S600 ARTI Zirkonzhan® and Identica T500 Medit®) were used to scan the impressions and stone casts. Best-fit superimpositions were conducted between the master model and the virtual models obtained. A significance level of p < 0.05 was considered. The accuracy of the Medit® scanner was 82.26 [53.18; 111.34] µm for Coltene® silicone and 87.43 [72.00; 102.86] µm for Zhermack® silicone, and the accuracy of the Zirkonzhan® scanner was 69.90 [62.37; 77.43] µm for Coltene® silicone and 80.67 [65.77; 95.57] µm for Zhermack® silicone, without significant differences between scanners. When comparing the two silicones, no significant differences were found for the Medit® (p = 0.112) or Zirkonzhan® scanners (p = 0.162). The Zhermack® scanner showed better accuracy than the corresponding stone casts in the two scanners, Medit® (p = 0.019) and Zirkonzahn® (p = 0.002). The extraoral digitalization of impressions in edentulous dental arches with six implants proves to be a valid technique. [ABSTRACT FROM AUTHOR]

Purpose: There are currently no clear guidelines on the reuse of metal implant impression copings and scanbodies in implant dentistry. Manufacturers generally recommend single use, which has cost and ecologic implications. The objectives of this study were to examine the effect of multiple use of implant impression copings and scanbodies on the accuracy of partially dentate implant casts. Materials and Methods: Ten direct polyether impressions were made of a partially dentate mandibular acrylic resin master model fitted with two internal connection implants (Straumann RC bone level) in the positions of right first premolar and molar, to produce 10 dental stone casts. A single set of impression copings was utilized for the 10 impressions. The sample casts and the master model were digitized using a laboratory scanner. Ten digital scans were then performed on an implant stone cast with two bone-level internal connection implant analogs using one set of scanbodies to produce scans 1 to 10. Measurements were made on all the digitized casts using computer software and discrepancies calculated in the x-, y-, and z-axes, and in the overall three-dimensional position (R). Data were statistically analyzed using paired t tests (α = .05), and P values were adjusted using Holm- Bonferroni sequential correction. Results: The outcomes were mixed, in that no significant differences were found between the casts or scans produced by reusing impression copings (P > .05) and scanbodies (P > .005), respectively, in all dimensions, for most repetition cycles; however, significant differences were noted in the y-axis for cast 6, and in relation to R, for casts 2, 4 (P < .05), and 8 (P < .005), and the scanbody reuse elicited significant differences in 3D(R) with scan 2 alone (P < .005). Conclusion: Reuse of impression copings and scanbodies up to 10 times did not seem to consistently affect the accuracy of partially dentate multi-implant dental casts and digital models. [ABSTRACT FROM AUTHOR]

Objective: To study the influence of implant depth and scanning rod lengths on the accuracy of digital impression for single-tooth implant restoration of the mandibular posterior teeth., Methods: Five standard dental cast models with missing right mandibular first molar (46) were prepared with the subgingival implant depths of 0, 1, 3, 5 and 7 mm. ITI RC and ITI RC H11 scanning rods were connected to the replacement body and placed into the seating tract for scanning. The reference data were obtained using a 3D dental scanner, and the experimental data were obtained by 10 scans of each model using a digitized intraoral scanner. Geomagic Wrap 2021 was used to analyze the model data to test the trueness and precision of the models., Results: The trueness did not differ significantly among the groups ( P > 0.05). The implant depth of 1 mm achieved the highest impression precision (66.81±2.45 μm), and the depth of 0 mm resulted in a significantly lower precision (95.60±3.04 μm) than the depth of 1 and 3 mm. Starting from the subgingival depth of 1 mm, the precision of the scan decreased progressively with the increase of the implant depth. At the subgingival implant depth of 5 or 7 mm, the use of an extended rod significantly improved the scan precision., Conclusion: For single-tooth implant restoration of the mandibular posterior teeth, the implant depth can substantially affect the accuracy of digital impression, which decreases as the implant depth increases. For a deep implant, the use of a longer scanning rod can improve the scanning accuracy.

Purpose: To determine the influence of using 3D-printed scan aids in varying colors on the trueness of digital scans., Materials and Methods: A master cast with five multi-unit analogues was scanned. The acquired dataset was exported to standard tessellation language (STL) file format to serve as the reference STL. 3D printing of the prototype in five distinct colors (beige [SA BEIGE ], grey [SA GREY ], white [SA WHITE ], red [SA RED ], and blue [SA BLUE ]) of polylactic acid filament was executed. The experimental STLs of each color group were aligned to the reference STL. RMS values were solely computed for the scan bodies. Based on the centers of the created best-fit and offset planes, scan bodies were converted into virtual cylinders. Cartesian coordinates of each cylinder were acquired. Subsequently, angular (AD) and linear deviation (LD) values were calculated. LD was further examined separately along the x, y, and z axes. Data were statistically analyzed., Results: According to the results of one-way ANOVAs, significant differences were detected among color groups on AD, LD, RMS estimate error, ∆x, ∆y, and ∆z data. The lowest AD and LD values were exhibited by the SA GREY group in all implant sites. The SA GREY group was followed by the SA BEIGE , SA WHITE , SA RED , and SA BLUE groups., Conclusions: The SA GREY outperformed the other groups in terms of trueness. Although the LD values of all color groups were below the threshold value (<100 µm), only the AD values of the SA GREY , SA BEIGE , and SA WHITE groups were clinically acceptable (<0.5°)., (© 2024 The Author(s). Journal of Prosthodontics published by Wiley Periodicals LLC on behalf of American College of Prosthodontists.)

Abstract Background With the development of intraoral scanners, their trueness and precision have been evaluated in various studies. Through these studies, the amount of accuracy that can be expected from intraoral scanners has gradually been disclosed, at the same time, it was difficult to integrate the results of individual studies due to differences in evaluation methods between studies. The purpose of this article was to review the currently available evidence, summarise what is currently known about IOS, analyse the evaluation methods of each study, and list points to note when interpreting the results. Main text Most of the studies were conducted in vitro. The accuracy is evaluated in situations such as single missing teeth, partially edentulous ridges with multiple missing teeth, and fully edentulous jaws. To evaluate the accuracy, direct measurement of distance or angle by coordinate measuring machines and calculation of surface deviation by superimposing surface data were predominantly performed. The influence of parameters such as the number of implants, distance between implants, angle between implants, and experience of the operator was evaluated. Many studies have shown that trueness tends to decrease as the distance between the implants and the scan range increases. It was agreed that the implant angle did not affect either trueness or precision. Regarding other factors, the results varied among studies. Therefore, the effects of these parameters are not clear. Conclusions Heterogeneity in the research methodology was prevalent among the studies considered in this review. Therefore, we cannot make a decisive statement regarding the trueness and precision of digital implant impressions by IOSs. So far, the comparison of the numerical values of error between studies has yet to elucidate any clear answers, despite small methodological differences.

Impression accuracy is fundamental to achieve a passive fit between implants and the superstructure. Three transfer types were tested to evaluate the differences in impression accuracy and their efficiency in case of different implant angles. A master model with four implant analogues placed at 0°, 15° and 35° was used. 27 impressions were taken with three different types of impression coping: closed tray technique coping (CT), open tray technique coping (COT) and telescopic open tray coping (TOT). The impressions were poured. Analogues were matched with scan bodies to be scanned and exported in STL. An implant bar was designed from each STL and another one from the master model. A comparison between these bars was obtained. Linear and angular measurements for every type of coping were calculated for different angulations. The collected data were analyzed with ANOVA test (95% of confidence). Student's t test showed a significative discrepancy (p ≤ 0.001) on linear and angular measurements on Δx, Δy, Δz with different transfer types as well as diverse implant positioning angles (p ≤ 0.001). Within the limitations of this study, it can be concluded that the coping type and the implants divergence may be significant parameters influencing the impression accuracy. [ABSTRACT FROM AUTHOR]

Abstract Background The outcome of the evaluation of impression techniques accuracy may improve the selection criteria for an ideal technique. The aim was to evaluate the accuracy of the open and closed tray techniques for implant impressions, in a partially edentulous maxilla, replaced with a three-unit fixed partial denture, as well as to assess the effect of implants parallelism on accuracy. Material and methods This is an experimental in vitro study to evaluate impressions accuracy of a simulated area restored with an implant retained FPD, using the open and closed tray implant impression techniques. The effect of implant position angulation, parallelism, and implant systems (Straumann, SIC Invent, Osstem) was also evaluated. Three custom-made acrylic resin test models were prepared with two parallel and two non-parallel implants, on either side of a maxillary arch. One hundred and ninety-two impressions were made using monophase VPS impression material. Their master casts were obtained and evaluated for the horizontal and vertical discrepancy. The casts were scanned using a model scanner. The distances between the two reference points were measured. Results The Straumann and SIC Invent implants showed no statistically significant differences (Mann-Whitney U test), regarding accuracy for both the open and closed tray impression techniques (P = 0.667 and P = 0.472). There were no significant differences for the parallel and non-parallel implants (P = 0.323 and P = 0.814), respectively, while the Osstem system showed statistically significant differences for both the open and closed tray impression techniques (P = 0.035) and between the parallel and non-parallel implants (P = 0.045). For the vertical discrepancies, significant differences were detected (chi-square test) between the open and closed tray impression techniques (P = 0.037). Conclusions Within the limitations of this study, there were generally no significant differences between open and closed, although better results were obtained for the open tray techniques. On the use of the non-parallel implants, the open tray technique provided a better result than the closed tray technique.

Background: With the development of intraoral scanners, their trueness and precision have been evaluated in various studies. Through these studies, the amount of accuracy that can be expected from intraoral scanners has gradually been disclosed, at the same time, it was difficult to integrate the results of individual studies due to differences in evaluation methods between studies. The purpose of this article was to review the currently available evidence, summarise what is currently known about IOS, analyse the evaluation methods of each study, and list points to note when interpreting the results. Main text: Most of the studies were conducted in vitro. The accuracy is evaluated in situations such as single missing teeth, partially edentulous ridges with multiple missing teeth, and fully edentulous jaws. To evaluate the accuracy, direct measurement of distance or angle by coordinate measuring machines and calculation of surface deviation by superimposing surface data were predominantly performed. The influence of parameters such as the number of implants, distance between implants, angle between implants, and experience of the operator was evaluated. Many studies have shown that trueness tends to decrease as the distance between the implants and the scan range increases. It was agreed that the implant angle did not affect either trueness or precision. Regarding other factors, the results varied among studies. Therefore, the effects of these parameters are not clear. Conclusions: Heterogeneity in the research methodology was prevalent among the studies considered in this review. Therefore, we cannot make a decisive statement regarding the trueness and precision of digital implant impressions by IOSs. So far, the comparison of the numerical values of error between studies has yet to elucidate any clear answers, despite small methodological differences. [ABSTRACT FROM AUTHOR]

Copyright of Implantologie is the property of Quintessenz Verlags GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: This in vitro study evaluated the accuracy of multiple-unit dental implant casts obtained from splinted or nonsplinted direct impression techniques using various splinting materials by comparing the casts to the reference models. The effect of two different impression materials on the accuracy of the implant casts was also evaluated for abutment-level impressions. Materials and Methods: A reference model with six internal-connection implant replicas placed in the completely edentulous mandibular arch and connected to multi-base abutments was fabricated from heat-curing acrylic resin. Forty impressions of the reference model were made, 20 each with polyether (PE) and polyvinylsiloxane (PVS) impression materials using the open tray technique. The PE and PVS groups were further subdivided into four subgroups of five each on the bases of splinting type: no splinting, bite registration PE, bite registration addition silicone, or autopolymerizing acrylic resin. The positional accuracy of the implant replica heads was measured on the poured casts using a coordinate measuring machine to assess linear differences in interimplant distances in all three axes. The collected data (linear and three-dimensional [3D] displacement values) were compared with the measurements calculated on the reference resin model and analyzed with nonparametric tests (Kruskal-Wallis and Mann- Whitney). Results: No significant differences were found between the various splinting groups for both PE and PVS impression materials in terms of linear and 3D distortions. However, small but significant differences were found between the two impression materials (PVS, 91 μm; PE, 103 μm) in terms of 3D discrepancies, irrespective of the splinting technique employed. Conclusions: Casts obtained from both impression materials exhibited differences from the reference model. The impression material influenced impression inaccuracy more than the splinting material for multiple-unit abutment-level impressions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A precise impression is mandatory to obtain passive fit in implant-supported prostheses. The aim of this study was to evaluate the effect of impression material and implant angulation on the impression accuracy of external-connection implants. Four customized epoxy resin master models, with twoimplant analogs placed parallel or with different degrees of divergence (10, 20 and 30 degrees), were fabricated with their corresponding passively fitted reference frameworks. Ten impressions were taken, for each model, with vinyl polysiloxane (VPS) and polyether (PE) using custom open tray impression technique. Impressions were poured with type IV dental stone and vertical discrepancies between the reference frameworks and the platforms of the implant replicas were evaluated, with a stereo video microscope, applying the one-screw test. The data were analyzed using two-way ANOVA, Sidak, and one-sample t-test at p = 0.05. No significant differences were found between PE and VPS at various angulations (p > 0.05). However, all groups showed a significant difference (p < 0.05) when compared to their true values. Within the limitations of this study, impression material and implant angulation had no significant effect on impression accuracy of external connection implants. [ABSTRACT FROM AUTHOR]

Purpose: The effects of implant angulation, impression material, and variation in width of the arch curvature on transfer models were evaluated. Materials and Methods: Three edentulous maxillary epoxy resin models were fabricated, and six internal-connection implant analogs were placed in different locations and different angulations in each model. In the first model, implants were positioned in the canine, first premolar, and first molar regions, and all analogs were positioned parallel to each other and perpendicular to the horizontal crestal plane (parallel model). In the second model, analogs were positioned in same regions (canine, first premolar, and first molar), but three of them were positioned with 10-degree buccal angulations (versus the horizontal crestal plane) (angular model). In the third model, analogs were inserted in the lateral incisor, canine, and second molar regions and parallel to each other (wide-arch model). Eighteen impressions of each model were made with each of the three materials--condensation silicone, polyvinyl siloxane, and polyether--and impressions were poured and kept at room temperature for 24 hours. They were then observed under a toolmaker's microscope, with epoxy resin models of each group used as references. Distance deformations between implants in each model in the x- and y-axes were recorded separately. Implant angulation deformations were recorded in the x-z plane. Statistical evaluations were performed with analysis of variance and the least significant difference post hoc test. Results: Angular model measurements showed the greatest deformation values (P < .05). All impression materials showed deformation, and the polyether impression models showed statistically significantly less deformation in angular measurements (P < .05). Conclusions: The models with implants placed parallel to each other exhibited greater accuracy than a model with implants placed at angles to each other. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this in vitro study was to investigate the effect of impression technique and implant angulation on the impression accuracy of external- and internal-connection implants using a novel experimental device. Materials and Methods: An experimental device was designed and fabricated to make in vitro impressions by means of open- and closed-tray techniques. Impressions of eight implants with two different connections (four external-hex and four internal-hex) at three angulations (0, 15, and 25 degrees) were made using a medium-consistency polyether material. Evaluation of implant impression accuracy was carried out by directly measuring the difference in coordinate values between the implant body/impression coping positioned on the base and the impression coping/laboratory analog positioned in the impression using a touch-probe coordinate measuring machine. Experimental data were analyzed by two-way analysis of variance. The significance level of all hypothesis testing procedures was set at P < .05. Results: The results showed that: (1) for implants with external connections, impression accuracy is not significantly affected by the impression technique, implant angulation, or their interaction; and (2) for implants with internal connections, impression accuracy is significantly affected only by implant angulation: Impression inaccuracy was greater at the 25-degree implant angulation. Conclusions: Within the limitations of this in vitro study, the open- and closed-tray techniques had no effect on the accuracy of multiple implant impressions. The interaction between impression technique and implant angulation was also not significant. However, implant angulation significantly affected the impression accuracy when implants with internal connections were used. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to determine the accuracies of implant-level impressions for internal-connection dental implants with various angles of divergence. Materials and Methods: Five groups were created according to the angles of divergence (0, 5, 10, 15, and 20 degrees) between two implant analogs in a master model. A master stone model for each group was fabricated. The divergent angle in each master model was verified with a profilometer. Study models (n = 10) from each master model were constructed through the implant-level impression technique. The divergent angle in each study model was verified with the profilometer. The splinted metal framework with passive fit was cast with base metal and cast-on abutments in each master model. The metal framework was tried in the study models and the fit of each framework was evaluated. One-way analysis of variance and the Tukey Honestly Significant Difference test were used for statistical analysis. Results: Statistically significant deformations of the impressions were found in the study models with divergently placed implant analogs. A larger divergence angle resulted in a larger gap between the framework and the implant analogs. The gap in the 20-degree divergence group differed significantly from that measured in the master model (P < .01). Conclusions: Internal-connection implants were accurate when the divergence angle was less than 15 degrees. Inaccuracy of impressions increased as the divergence angle increased. The inaccuracy was significantly greater for the 20-degree-divergent implants than the other groups. [ABSTRACT FROM AUTHOR]

Purpose: This study evaluated the accuracy of four implant-level impression techniques with optical microscopy on two angulated conical internal-connection implants. Materials and Methods: A master cast with two internal-connection implant analogs angulated 10 degrees from each other and a master framework were fabricated. Four impression techniques were examined: octagonal transfer impression coping, nonoctagonal transfer impression coping, nonoctagonal pickup impression coping, and nonoctagonal pickup impression copings joined together with autopolymerizing acrylic resin. Experimental casts were fabricated from 40 polyether impressions divided into four groups. After the master framework was seated on each of the casts, one abutment screw was tightened and marginal gap measurements between analog and abutment were recorded on the other side with an optical microscope. Results: The casts produced from nonoctagonal pickup impression techniques were more accurate than those produced using transfer impression techniques (P < .05). However, there was no statistically significant difference in the accuracy between the unsplinted and splinted methods in pickup impression techniques (P > .05) or between the use of octagonal coping and nonoctagonal coping in transfer impression techniques (P > .05). Conclusion: The casts produced from nonoctagonal pickup impression techniques were more accurate than those produced by transfer impression techniques, regardless of whether they were splinted, for angulated conical internal-connection implants. [ABSTRACT FROM AUTHOR]

Purpose: Passive fit is difficult to achieve in implant-supported restorations with existing superstructure fabrication techniques. The aim of the study presented was to investigate whether computer-generated fixed partial dentures (FPDs) based on optical impressions lead to less strain development than conventionally fabricated FPDs. Materials and Methods: A measurement model with 2 implants was set up and strain gauges were attached to the model material mesially and distally adjacent to the implants. Two groups of conventional cementable restorations based on repositioning and pick-up impressions, respectively, and 1 group of CAD/CAM-generated FPDs based on optical impressions were fabricated (n = 10). Strain development during FPD fixation was recorded. In order to compare the different FPD groups with one another, a multivariate analysis of variance (MANOVA) was performed at a level of significance of α = .05. Results: The mean strain development at the different strain gauge locations ranged from 80.38 μm/m to 437.11 μm/m. The 2 groups of conventionally fabricated FPDs showed no significant difference in terms of strain development (P = .07). The CAD/CAMfabricated FPDs revealed a significantly lower strain development than those made from pick-up technique impressions (P = .01). No significant difference could be detected between the FPDs manufactured from repositioning technique impressions and the CAD/CAM-generated restorations (P = .19). Conclusion: Within the limitations of the study presented, it can be concluded that restorations fabricated on the basis of optical impressions demonstrate a level of fit which is at least as passive as that of conventional FPDs. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the influence of intraoral scanning coverage (IOSC) on digital implant impression accuracy in various partially edentulous situations and predict the optimal IOSC., Methods: Five types of resin models were fabricated, each simulating single or multiple tooth loss scenarios with inserted implants and scan bodies. IOSC was subgrouped to cover two, four, six, eight, ten, and twelve teeth, as well as full arch. Each group underwent ten scans. A desktop scanner served as the reference. Accuracy was evaluated by measuring the Root mean square error (RMSE) values of scan bodies. A convolutional neural network (CNN) was trained to predict the optimal IOSC with different edentulous situations. Statistical analysis was performed using one-way ANOVA and Tukey's test., Results: For single-tooth-missing situations, in anterior sites, significantly better accuracy was observed in groups with IOSC ranging from four teeth to full arch (p < 0.05). In premolar sites, IOSC spanning four to six teeth were more accurate (p < 0.05), while in molar sites, groups with IOSC encompassing two to eight teeth exhibited better accuracy (p < 0.05). For multiple-teeth-missing situations, IOSC covering four, six, and eight teeth, as well as full arch showed better accuracy in anterior gaps (p < 0.05). In posterior gaps, IOSC of two, four, six or eight teeth were more accurate (p < 0.05). The CNN predicted distinct optimal IOSC for different edentulous scenarios., Conclusions: Implant impression accuracy can be significantly impacted by IOSC in different partially edentulous situations. The selection of IOSC should be customized to the specific dentition defect condition., Clinical Significance: The number of teeth scanned can significantly affect digital implant impression accuracy. For missing single or four anterior teeth, scan at least four or six neighboring teeth is acceptable. In lateral cases, two neighboring teeth may suffice, but extending over ten teeth, including contralateral side, might deteriorate the scan., 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 Elsevier Ltd. All rights reserved.)

PURPOSE. The newest technologies for digital implant impression (DII) taking are developing rapidly and showing acceptable clinical results. However, scientific literature is lacking data from clinical studies about the accuracy of DII. The aim of this study was to compare digital and conventional dental implant impressions (CII) in a clinical environment. MATERIALS AND METHODS. Twenty-four fixed zirconia restorations supported by 2 implants were fabricated using conventional open-tray impression technique with splinted transfers (CII group) and scan with Trios 3 IOS (3Shape) (DII group). After multiple verification procedures, master models were scanned using laboratory scanner D800 (3Shape). 3D models from conventional and digital workflow were imported to reverse engineering software and superimposed with high resolution 3D CAD models of scan bodies. Distance between center points, angulation, rotation, vertical shift, and surface mismatch of the scan bodies were measured and compared between conventional and digital impressions. RESULTS. Statistically significant differences were found for: a) inter-implant distance, b) rotation, c) vertical shift, and d) surface mismatch differences, comparing DII and CII groups for mesial and dist al implant scan bodies (P≤.05). CONCLUSION. Recorded linear differences between digital and conventional impressions were of limited clinical significance with two implant-supported restorations. [ABSTRACT FROM AUTHOR]

The accuracy of definitive impressions has a significant impact on the quality of the final prosthesis. Elastic impression materials are commonly used in the traditional approach to replicate anatomical structures while indirectly fabricating prostheses. Digital impression has gained increasing popularity due to its various advantages, including three-dimensional previsualization, cost-effectiveness, and reduced time consumption. The objective of this study is to evaluate existing studies to provide an overview of the comparative advantages of digital impression techniques over conventional techniques. The review will focus on evaluating the accuracy, patient acceptability, operator preference, and time effectiveness of digital impression techniques in comparison to conventional techniques. The Population, Intervention, Comparison, and Outcome framework served as the basis for this study's search strategy. We conducted a comprehensive literature review by electronically searching articles published between 2000 and 2023 in PubMed, Medline, Cochrane, and the Web of Science. Furthermore, additional manual searches were conducted. The study examined the differences between optical impressions and traditional impressions in terms of accuracy, patient outcomes, and operator outcomes. It included both clinical and preclinical studies as well as randomized controlled trials. In conclusion, this review provides a short summary indicating that digital impressions exhibit comparable accuracy to conventional impressions without any statistically significant difference. This conclusion is based on an evaluation of accuracy, patient preference, and operator preference., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2024, Ahmed et al.)

Objectives: The objective of this study was to evaluate the accuracy of different impression techniques on multiple implants.Material and methods: A master cast simulating a jaw with four implants was used.Eight impression techniques were tested: open tray-polyether#1, open tray plus splint of impression copings with acrylic resin-polyether#1, closed tray-polyether#1, open tray-polyether#2, open tray-splint-polyether#2, closed tray-polyether#2, open tray-impression plaster, and digital impression (DI).Five impressions of the master cast were taken with each traditional impression (TI) technique, pouring 35 sample casts. Three different clinicians took 5 DI each (n = 15).A three-dimensional coordinate measurement machine (CMM) was used to measure implant angulation and inter-implant distances on TI casts. TI data and DI Standard Tessellation Language datasets were compared with the master cast.The best and the worst impressions made with TI and DI were selected to fabricate four milled titanium frameworks. Passive fit was evaluated through Sheffield test, screwing each framework on the master cast. Gaps between framework-implant analogs were measured through a stereomicroscope (×40 magnification).Results: Statistically significant differences in accuracy were found comparing the different impression techniques by CMM (p < 0.01). DI performed the best, while TI techniques revealed a greater variability in the results.Sheffield test revealed a mean gap of 0.022 ± 0.023 mm (the best TI), 0.063 ± 0.059 mm (the worst TI), 0.015 ± 0.011 mm (the best DI), and 0.019 ± 0.015 mm (the worst DI).Conclusions: Within the limits of this in vitro study, the digital impression showed better accuracy compared to conventional impressioning.Clinical relevance: The digital impression might offer a viable alternative to traditional impressions for fabrication of full-arch implant-supported prostheses with satisfactory passive fit. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: To conduct a systematic review to evaluate the evidence of possible benefits and accuracy of digital impression techniques vs. conventional impression techniques. Materials and Methods: Reports of digital impression techniques versus conventional impression techniques were systematically searched for in the following databases: Cochrane Central Register of Controlled Trials, PubMed, and Web of Science. A combination of controlled vocabulary, free‐text words, and well‐defined inclusion and exclusion criteria guided the search. Results: Digital impression accuracy is at the same level as conventional impression methods in fabrication of crowns and short fixed dental prostheses (FDPs). For fabrication of implant‐supported crowns and FDPs, digital impression accuracy is clinically acceptable. In full‐arch impressions, conventional impression methods resulted in better accuracy compared to digital impressions. Conclusions: Digital impression techniques are a clinically acceptable alternative to conventional impression methods in fabrication of crowns and short FDPs. For fabrication of implant‐supported crowns and FDPs, digital impression systems also result in clinically acceptable fit. Digital impression techniques are faster and can shorten the operation time. Based on this study, the conventional impression technique is still recommended for full‐arch impressions. [ABSTRACT FROM AUTHOR]

Introduction: One of the most important factors in long-term success of implant supported restorations is an accurate transfer of implant position by means of impression techniques. This study was designed to evaluate the effect of Implant Abutment Connection (IAC) on the accuracy of impression with different implant angulations and two different impression materials.Materials and Methods: A stainless steel model containing 10 implants (5 with external and 5 with internal connection) was fabricated with 0, 15, 30 and 40 degrees angulations. An open-tray impression technique was performed, using a custom tray and polyether (n = 30)/monophase polyvinyl siloxane (n = 30). The impressions were poured by stone type IV. The orientation of implants on the master models and the samples was evaluated by coordinating measuring machine (CMM) with 1 µm precision. Two-way analysis of variance and t-student test were used for statistical analysis via SPSS software. (α = 0.05)Results: No statistical differences were found between the two impression materials. There was also no significant difference between connection types in implants with 15˚and 30˚ angulations. However, 40˚ angulations showed higher degrees of error, using internal IAC.Conclusion: Types of connection along with implant angulations seem to have great impacts on impression precision. As observed, 40˚ implants with internal connection reduced impression precision. Key words: Impression accuracy, Implant angulation, Connection

Background: The objectives of this study were to determine the attitude of the dental practitioners practicing dental implants in Saudi Arabia toward the restorative phase of implant dentistry. In particular, this study investigated the most accepted impression materials and techniques used to make impressions for dental implants among these practitioners and their opinions regarding the clinical factors that may influence the decision-making process for the selection of impression materials and techniques. Materials and Methods: An email questionnaire, of a closed response format, was sent to dental practitioners across Saudi Arabia. Returned responses were subjected to qualitative and quantitative analysis. Results: A total of 315 dental implant practitioners responded to this survey. The majority (about 85%) of the respondents preferred using additional silicone and polyether as an impression material, and 70% of them used the open-tray technique. About two-thirds of the respondents agreed that the presence of angulated implants and sub-gingival implant depth adversely affect the impression's accuracy. About 63% of the respondents preferred splinting the copings before taking the impression for multiple implants whereas 71% confirmed the seating of the copings with radiographs. Only 45% of the respondents used the verification jig while taking the impression. Significant relationships between the choice of the impression technique and some of the demographic characteristics of the respondents were noted. The open-tray technique was more used by non-Saudi practitioners (P = 0.008) and those respondents who had an implant degree (P = 0.036). Conclusions: It can be concluded from the current study survey that, most of the dentists with postgraduate diploma or board qualification in dental implant followed the well-documented technique and proven materials. [ABSTRACT FROM AUTHOR]

Background Several studies link the seamless fit of implant-supported prosthesis with the accuracy of the dental impression technique obtained during acquisition. In addition, factors such as implant angulation and coping shape contribute to implant misfit. Purpose The aim of this study was to identify the most accurate impression technique and factors affecting the impression accuracy. Material and Methods A systematic review of peer-reviewed literature was conducted analyzing articles published between 2009 and 2013. The following search terms were used: implant impression, impression accuracy, and implant misfit. A total of 417 articles were identified; 32 were selected for review. Results All 32 selected studies refer to in vitro studies. Fourteen articles compare open and closed impression technique, 8 advocate the open technique, and 6 report similar results. Other 14 articles evaluate splinted and non-splinted techniques; all advocating the splinted technique. Polyether material usage was reported in nine; six studies tested vinyl polysiloxane and one study used irreversible hydrocolloid. Eight studies evaluated different copings designs. Intraoral optical devices were compared in four studies. Conclusions The most accurate results were achieved with two configurations: (1) the optical intraoral system with powder and (2) the open technique with splinted squared transfer copings, using polyether as impression material. [ABSTRACT FROM AUTHOR]

Background and purpose It is crucial to keep the misfit of the abutment-fixture unit at the lowest possible rate. There are a few controversial studies on the accuracy of impression making of angulated implants, and much fewer (and controversial) studies on the abutment-level impression technique, which is a convenient and clinically favorable method. Besides, there are no studies on comparison of sectional vs. full-arch trays. We aimed to assess these. Methods A trapezoidal model with four angulated implants installed at 20° and 30° buccal tilts was fabricated. Forty impressions were taken from this model, with two groups of full-arch and sectional custom trays ( n = 2 × 20), each divided into two subgroups of implant-level and abutment-level techniques ( n = 2 × 2 × 10 in four subgroups). Absolute and non-absolute linear and angular impression errors were estimated by comparing the fabricated casts with the model, using a coordinate measuring machine. The effects of sectional/full-arch trays and abutment-level and fixture-level techniques on impression accuracies were analyzed using one- and two-way analyses of variance ( ANOVA), Tukey, Mann- Whitney, and one-sample t-tests (α = 0.05, Mann- Whitney's α using the Bonferroni Bonferroni method). Results No significant differences between the absolute linear errors of the two trays ( P = 0.100 [ ANOVA]) and the two levels ( P = 0.400 [ ANOVA]) were observed. The assessment of absolute angular errors showed no significant differences (all P values ≥ 0.4 [ ANOVA]). The difference between the linear errors in the full-arch vs. sectional trays was not significant in the fixture-level group ( P = 0.290). However, in the abutment-level group, the linear error was significantly greater in the sectional tray compared to full-arch tray ( P = 0.013, α = 0.025 [ Mann- Whitney]). Conclusions Using sectional trays might not be advantageous over full-arch trays. Sectional trays are not recommended for taking abutment-level impressions. The abutment-level impression technique is as accurate as the studied fixture-level technique. Increasing the angle of implants' divergence from 40° to 60° might not usually lead to a significant increase in the errors, particularly when using abutment-level impressions. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the accuracy of impressions on changing the implant component (coping and abutment replica) between Brânemark and BIOMET 3i and between Straumann and Allfit. Materials and Methods: Two master casts were constructed, one containing pair of Brânemark selftap Mk II fixtures (Nobel Biocare) labeled Master cast I and the other containing pair of Straumann Standard plus implant, SLA fixtures (Straumann) labeled Master cast II. Ten impressions of each master cast were made by open tray technique using polyether impression material. Five out of 10 impressions made from master cast I contained Brânemark pair of coping and replica and the other 5 contained 3i (Implant Innovations). Five out of 10 impressions made from master cast II contained Straumann pair of copings and replica and the remaining 5 contained Allfit implants (Ihde Dental). Duplicated casts were prepared, and distances between copings were measured using traveling microscope and compared the distance in master casts. Result: No significant difference was observed in mean value between 2 master casts and their duplicates. Conclusion: The interchangeability of coping and abutment replica between Brânemark and BIOMET 3i and between Straumann and Allfit was found to be possible without compromising the quality of impressions. [ABSTRACT FROM AUTHOR]

We examined older and younger adults' accuracy judging the health and competence of faces. Accuracy differed significantly from chance and varied with face age but not rater age. Health ratings were more accurate for older than younger faces, with the reverse for competence ratings. Accuracy was greater for low attractive younger faces, but not for low attractive older faces. Greater accuracy judging older faces' health was paralleled by greater validity of attractiveness and looking older as predictors of their health. Greater accuracy judging younger faces' competence was paralleled by greater validity of attractiveness and a positive expression as predictors of their competence. Although the ability to recognize variations in health and cognitive ability is preserved in older adulthood, the effects of face age on accuracy and the different effects of attractiveness across face age may alter social interactions across the life span. [ABSTRACT FROM AUTHOR]

The article refutes several myths related to dentistry. It presents various digital technologies that can be used effectively to get desired results in the field of cosmetic dentistry. The myths discredited in the article include one related to the scanning of all the teeth, and another one related to the need for tissue retraction and management.

Abstract: One critical and to date understudied social psychological construct with significant implications for technology-mediated distributed work is impression formation. Forming useful impressions of each other is crucial for coworkers to avoid mistrust, misattribution, and conflict, and thereby, work effectively and productively. In this theoretical review paper I systematically outline how elements of distributed and virtual work – geographic dispersion, electronic dependence, heterogeneity, and dynamic structures – shape coworkers’ impression of each other by influencing information and motivation, the main moderators of impression formation. I develop a model of how the impression formation process acts in technology-mediated distributed work settings, draw propositions, and identify ways to mitigate the breakdown in impression formation among distributed coworkers. Finally, I conceptualize impression accuracy in terms of descriptive, predictive, and explanatory knowledge about others and discuss how it can be increased with positive outcomes for trust, attribution, knowledge sharing, and conflict resolution. [Copyright &y& Elsevier]

Background: The aim of this study was to compare the accuracy of different direct implant impression techniques for edentulous arches with multiple implants. Methods: Five experimental groups (n = 5) were assembled. Experimental models were created by a direct splinted technique (EG2 to EG5) and a non-splinted technique (EG1). In EG2 and EG3 synOcta impression copings were splinted with an acrylic resin bar, and in EG4 and EG5 with a light-curing composite resin bar. In EG3 and EG5 the resin bars were sectioned, while the other experimental groups were not. Three-dimensional discrepancies were measured by a computerized coordinate measuring machine. Distortion values among the groups were analysed using one-way repeated measures ANOVA. The post hoc Tukey's test was then performed for multiple comparisons. Results: The highest accuracy was obtained in EG2 (mean deviation: 12.70 μm). The acrylic bars demonstrated less deviation (12.70 μm and 22.71 μm) from the master model than the light-curing composite resin groups and the non-splinted group (41.09 μm). The post hoc Tukey's test showed no significant difference among the groups when the effect of splint design on accuracy was investigated. Conclusions: For situations where impressions of multiple implants are to be made, splinting impression copings with acrylic resin demonstrate superior results than the non-splinted technique and splinting with light-curing composite. [ABSTRACT FROM AUTHOR]

Background: With regard to implant-supported prostheses, to date no technique has been proven to guarantee a completely passive fit of prosthetic frameworks. Several clinical variables may affect the precision of impressions, particularly in the presence of implants. Purpose: To compare the accuracy of implant impressions made with different materials, lengths of impression coping connections, and not parallel position of the implants. Materials and Methods: A calibrated testing device allowing reproducible standardized positions was used. Two control groups of master models and eight experimental groups with predetermined undercuts were used to make addition silicon and polyether implant impressions by means of the open-tray pick-up technique. Four reference distances were evaluated on each study cast by using a profile projector and a standardized measurement protocol. The data were statistically analyzed by means of three-factor analysis of variance. Results: The impressions made in the presence of angulated implants were significantly less accurate than the ones made with parallel implants. The tested addition silicon resulted advantageous in presence of nonparallel implants whereas the polyether achieved the best results with parallel implants and standard impression copings. Conclusions: The angulation of the implants may cause strains of impressions, probably because of the higher forces required for the impression removal. Moreover, undercuts negatively affected the impression accuracy. More accurate casts were obtained using the tested addition silicon in the presence of nonparallel implants and using a standard length connection of the copings in the presence of parallel implants, respectively. [ABSTRACT FROM AUTHOR]

The bad genes and anomalous face overgeneralization accounts of facial preferences were tested by examining cue validity, cue utilization, and accuracy in judging health and intelligence from faces in the upper and lower halves of the distributions of attractiveness and its components: averageness, symmetry, and masculinity. Consistent with the bad genes hypothesis, facial attractiveness, averageness, symmetry, and male face masculinity each provided valid cues to intelligence and/or health for faces in the lower but not the upper halves of the distributions of these facial qualities. Consistent with the anomalous face overgeneralization hypothesis, attractiveness and its components were utilized as cues not only for faces in the lower halves of the distributions, but also for those in the upper halves. Intelligence and health were judged accurately for faces in the lower but not the upper half of the attractiveness distribution, and attractiveness mediated this accuracy at all ages except adolescence. Since adolescence is the prime mating age, the latter finding raises questions about the utility of attractiveness as an evolved mechanism to ensure the selection of high quality mates. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effects of arch size and implant angulation on the accuracy of implant impressions., Materials and Methods: Four different resin models (small and large) of edentulous maxilla were fabricated and four implants were inserted (Blossom®, ø 4.75 × 10 mm) in each model. Implants were either parallel or angled 25° buccally. Forty working casts (small parallel, small angled, large parallel, and large angled) were fabricated in dental stone (n=10). For each implant, linear and angular displacements were measured using a coordinate-measuring machine (CMM) and mean values were analyzed by univariate analysis (α = 0.05)., Results: Arch size did not affect the linear or angular displacement (P ⟩ .05). However, the implant angulation had a marked influence on the linear displacement (P ⟨ .05). The largest linear displacement occurred in implant no. 4 of angled small groups., Conclusion: Regardless of arch size, linear and angular accuracy of implant impression varied with the implant angulation., (Copyright© 2021 Dennis Barber Ltd.)

Background: The outcome of the evaluation of impression techniques accuracy may improve the selection criteria for an ideal technique. The aim was to evaluate the accuracy of the open and closed tray techniques for implant impressions, in a partially edentulous maxilla, replaced with a three-unit fixed partial denture, as well as to assess the effect of implants parallelism on accuracy.Material and methods: This is an experimental in vitro study to evaluate impressions accuracy of a simulated area restored with an implant retained FPD, using the open and closed tray implant impression techniques. The effect of implant position angulation, parallelism, and implant systems (Straumann, SIC Invent, Osstem) was also evaluated. Three custom-made acrylic resin test models were prepared with two parallel and two non-parallel implants, on either side of a maxillary arch. One hundred and ninety-two impressions were made using monophase VPS impression material. Their master casts were obtained and evaluated for the horizontal and vertical discrepancy. The casts were scanned using a model scanner. The distances between the two reference points were measured.Results: The Straumann and SIC Invent implants showed no statistically significant differences (Mann-Whitney U test), regarding accuracy for both the open and closed tray impression techniques (P = 0.667 and P = 0.472). There were no significant differences for the parallel and non-parallel implants (P = 0.323 and P = 0.814), respectively, while the Osstem system showed statistically significant differences for both the open and closed tray impression techniques (P = 0.035) and between the parallel and non-parallel implants (P = 0.045). For the vertical discrepancies, significant differences were detected (chi-square test) between the open and closed tray impression techniques (P = 0.037).Conclusions: Within the limitations of this study, there were generally no significant differences between open and closed, although better results were obtained for the open tray techniques. On the use of the non-parallel implants, the open tray technique provided a better result than the closed tray technique. [ABSTRACT FROM AUTHOR]

Aims: The aim of this study was to compare the dimensional accuracy of four different implant impression techniques of a mandibular edentulous model with five parallel implants., Materials and Methods: Five dental implants were placed in an edentulous mandibular model in parallel. A total of forty impressions were obtained using four different impression techniques. In Group 1 (G1) and Group 2 (G2), closed tray impressions with and without plastic caps, respectively, were used. In Group 3 (G3) and Group 4 (G4), open tray impressions with a direct splinted technique and an improved direct splinted technique, respectively, were used. All the impressions were poured with Type IV dental stone. Master model and study casts were scanned with a laser optical scanner and aligned by observing the superpositions of the anatomical landmarks using a software program., Statistical Analysis Used: Fifty measurements of the apical, coronal, and angular discrepancies of the master and study casts were obtained (n = 50) and statistically analyzed using a one-way analysis of variance and post hoc (least significant difference ) and Friedman's tests., Results: The lowest accuracy was obtained from G2 when the angular (1.48°), coronal (0.32 μm), and apical (0.14 μm) deviations were tested (P < 0.05), whereas no statistically significant differences were found among the other groups (P < 0.05)., Conclusions: In cases with five parallel mandibular implants, improved accuracy was achieved using the direct splinted technique, the improved direct splinted technique, or the closed tray impression technique with snap on plastic caps., Competing Interests: There are no conflicts of interest