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A method is described for the verification and correction of a digital scan of a complete-arch implant-supported prosthesis for a completely edentulous patient. The technique provides an efficient way to integrate a highly accurate and precise scan of an implant index cast with a digital intraoral implant scan by using a computer-aided design and computer-aided manufacturing (CAD-CAM) software program. This method allows dental professionals to validate and, if necessary, correct the implant positions in the scan without the need for a conventional impression.

Photogrammetry technology has been used for the digitalization of multiple dental implants, but its trueness and precision remain uncertain.The purpose of this in vitro investigation was to compare the accuracy (trueness and precision) of multisite implant recordings between the conventional method and a photogrammetry dental system.A definitive cast of an edentulous maxilla with 6 implant abutment replicas was tested. Two different recording methods were compared, the conventional technique and a photogrammetry digital scan (n=10). For the conventional group, the impression copings were splinted to an additively manufactured cobalt-chromium metal with autopolymerizing acrylic resin, followed by recording the maxillary edentulous arch with an elastomeric impression using an additively manufactured open custom tray. For the photogrammetry group, a scan body was placed on each implant abutment replica, followed by the photogrammetry digital scan. A coordinate-measuring machine was selected to assess the linear, angular, and 3-dimensional discrepancies between the implant abutment replica positions of the reference cast and the specimens by using a computer-aided design program. The Shapiro-Wilk test showed that the data were not normally distributed. The Mann-Whitney U test was used to analyze the data (α=.05).The conventional group obtained an overall accuracy (trueness ±precision) value of 18.40 ±6.81 μm, whereas the photogrammetry group showed an overall scanning accuracy value of 20.15 ±25.41 μm. Significant differences on the discrepancies on the x axis (U=1380.00, P=.027), z axis (U=601.00, P.001), XZ angle (U=869.00, P.001), and YZ angle (U=788.00, P.001) were observed when the measurements of the 2 groups were compared. Furthermore, significant 3-dimensional discrepancy for implant 1 (U=0.00, P.001), implant 2 (U=0.00, P.001), implant 3 (U=6.00, P.001), and implant 6 (U=9.00, P.001) were computed between the groups.The conventional method obtained statistically significant higher overall accuracy values compared with the photogrammetry system tested, with a trueness difference of 3 μm and a precision difference of 18 μm between the systems. The conventional method transferred the implant abutment positions with a uniform 3-dimensional discrepancy, but the photogrammetry system obtained an uneven overall discrepancy among the implant abutment positions.

The digital fabrication of a maxillary obturator with a 3D-printed polyetheretherketone (PEEK) framework is described. Digital oral data were scanned for the computer-aided design (CAD) of the framework and the 3D printing of a preliminary resin cast. The framework was accurately printed from a PEEK filament material. A secondary impression was made to fabricate the definitive cast. The PEEK framework exhibited precise fit, excellent retention, and reduced weight compared with a typical metal framework.

Evidence comparing the marginal and internal fit of single metal copings fabricated via selective laser sintering and conventional lost-wax casting is inadequate.The purpose of this systematic review was to compare the fit of single metal copings fabricated via selective laser sintering and lost-wax casting. Moreover, the effects of different variables on fit accuracy were determined.Google Scholar, ScienceDirect, SpringerLink, and Wiley databases were searched electronically as well as manually. The mean absolute marginal gap, marginal gap, internal gap, axial gap, and occlusal gap values of single metal copings fabricated via selective laser sintering and lost-wax casting were statistically analyzed to determine and evaluate the factors affecting the fit accuracy (α=.05).Single metal copings fabricated via selective laser sintering had mean absolute marginal gaps and occlusal gaps similar to those of copings fabricated via lost-wax casting, based on a subgroup meta-analysis of gaps evaluated using stereomicroscopy (P.05). The fit of single metal copings was not affected by the type of tooth (P.05). The conventional impression, the indirect digital scan, and the direct digital scan led to similar values of mean axial gap, internal gap, and marginal gap for the copings fabricated via lost-wax casting (P.05). The indirect and direct digital scans led to similar values of mean axial gap, internal gap, and marginal gap for the copings fabricated via selective laser sintering (P.05). Printed wax patterns provided significantly smaller mean axial gap values than milled plastic or milled wax patterns for the copings fabricated via lost-wax casting (P.05). Printed, milled, and conventional wax patterns had similar mean marginal gaps and internal gaps for the copings fabricated via lost-wax casting (P.05). For single copings fabricated via lost-wax casting, Ni-Cr and Co-Cr had similar mean internal gaps (P.05).No statistically significant differences were found between single metal copings fabricated via selective laser sintering and lost-wax casting. Selective laser sintering can satisfy the clinical requirement for single metal copings.

Intraoral scanning has benefits over conventional impression making, but whether scanning is sufficiently accurate for multiple implants is unclear.The purpose of this in vitro study was to compare the trueness of digital scans acquired by using intraoral scanners from a small range to a complete arch with the conventional impression technique and to determine the influence of 2 different evaluation methods (best-fit algorithm versus absolute linear deviation) on the outcomes of accuracy assessment.A mandibular model with 8 implants (A-H) around an edentulous arch was used as the master model. Open-format standard tessellation language (STL) data sets (1 reference file from a highly accurate dental laboratory scanner, 10 files from an intraoral scanner, and 10 files from digitized conventional impressions at room temperature) were imported to a metrology software program, and 5 groups of scanning ranges (AB, FGH, CDEF, BCDEFG, and ABCDEFGH) were identified simulating different clinical situations. Two evaluation methods-root mean square values calculated from the best-fit algorithm and average value of linear discrepancies from absolute linear deviation-were used to describe the trueness values. The impacts of different scanning or impression methods, ranges, and evaluation methods were tested by using a 3-way ANOVA. The effect of the scanning range on accuracy was further identified with 1-way ANOVA. The paired-sample t test was used to determine the differences of trueness values between the 2 methods in different groups.The trueness values of the implant impressions were significantly affected by different scanning or impression methods (P.001), evaluation methods (P.001), and scanning ranges (P.001) as independent variables. With use of the best-fit algorithm, deviations from the digital scans were significantly greater than those from the conventional impressions in cross-arch situations (groups CDEF, BCDEFG, and ABCDEFGH). With use of the absolute linear deviation method, statistically significant lower accuracy was found when larger areas were encountered (groups BCDEFG and ABCDEFGH). Use of the absolute linear deviation method resulted in a higher mean score of inaccuracy than that from the best-fit algorithm method in most situations.Scanning or impression methods, ranges, and evaluation methods affected the dimensional accuracy (trueness) of scans or impressions with multiple implants. Digital scans had worse trueness values compared with those made with the conventional splinting open-tray technique when cross-arch implant impressions were acquired.

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.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.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.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).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.

Statement of problem The accuracy of impressions for implant-supported prostheses is essential to ensure a passive fit of the definitive prosthesis. Intraoral scanners (IOSs) have been developed as an alternative to complete-arch implant-supported restorations; however, whether they are sufficiently accurate when more than 3 nonaligned implants are involved is unclear. Purpose The purpose of this pilot clinical study was to determine whether the fit of complete-arch zirconia implant-supported frameworks processed on a cast obtained with an IOS and adjusted with an auxiliary device is equivalent to a prosthesis obtained from an elastomeric impression. Material and methods Twelve consecutive participants who were ready for complete-arch restorations on already osseointegrated implants were enrolled. Two records were made, one open-tray with polyether and splinted impression copings and the second with an IOS. A verification gypsum device was used for the elastomeric impression, and a prefabricated auxiliary device was used to adjust the intraoral scans. Two zirconia frameworks with the same design were processed and evaluated intraorally by 2 independent calibrated observers. Results In 11 of the 12 participants, the digitally processed prosthesis was preferred over the conventionally processed prosthesis. The clinical fit of the prostheses obtained with the completely digital workflow was better than that of those obtained with the conventional workflow. Conclusions The use of a prefabricated auxiliary device after intraoral scanning allowed delivery of complete-arch implant-supported monolithic zirconia prostheses with a fit better than those fabricated from conventional impressions.

Statement of problem Studies evaluating the accuracy of edentulous arch impressions encompassing conventional and digital methods are lacking. Purpose The purpose of this in vitro study was to evaluate 8 impression-making methods for edentulous arches and to determine the effects of using a 3-dimensionally printed polyetheretherketone (PEEK) scanning aid on the accuracy of intraoral scanners. Material and methods Three sets of edentulous arch typodonts were scanned with an industrial scanner as a reference. Subsequently, a scanning aid for the edentulous arch was individually designed on each reference scan dataset by using a 3-dimensional modeling software program and fabricated in PEEK with a 3-dimensional printer. Each typodont was scanned with 2 intraoral scanners 12 times, with and without the assistance of a scanning aid for the edentulous arch. Impressions were made with 4 different conventional impression materials (irreversible hydrocolloid, polysulfide, polyether, and polyvinyl siloxane)—12 times for each typodont—the casts were poured and digitized with a tabletop scanner. Each scan data set was superimposed over the corresponding scan data set, and the original and absolute distance values from the paired surface points were obtained to measure the trueness and precision. These were expressed by using the mean, median, root mean square, and (90 percentile-10 percentile)/2 of the absolute distance value (NMT) concepts, based on the raw data extraction protocol. A repeated-measures ANOVA followed by a post hoc Bonferroni test was conducted (α=.05). Results The impression-making methods did not show statistically significant differences (P>.05) for either trueness or precision, particularly when the median values of the original and absolute distance values from the paired surface points were chosen as the standard values. One of the intraoral scanners used exhibited significantly superior outcomes to conventional impression materials when scanned with the scanning aid for the edentulous arch for both trueness and precision when the mean, root mean square, and NMT concepts were applied (P Conclusions Intraoral scanners demonstrated accuracy comparable with that of conventional impression materials for making edentulous arch impressions, regardless of the concepts used to express the trueness and precision. The PEEK-based scanning aid for the edentulous arch did not improve the accuracy of the intraoral scanners; however, its application resulted in higher accuracy compared with that of conventional impression materials.

Statement of problem Three-dimensionally printed custom open trays have become a popular option in clinical implant dentistry because of advantages such as individualization, efficiency, and effectiveness. However, clinical evidence on their accuracy and feasibility is lacking. Purpose The purpose of this clinical study was to evaluate the accuracy and feasibility for impressions of multiple implants by using 3D-printed custom open trays versus conventional custom open trays. Material and methods Twenty-two partially edentulous individuals needing impression making for restorations supported by multiple implants were enrolled. Two types of custom open trays were made for each participant, a 3D-printed tray (test) and a conventional tray (control). With a splinted technique, silicone definitive impressions were obtained with the 2 custom open trays and poured with Type IV dental stone. Impression accuracy (primary outcome) was evaluated by measuring linear distances and the marginal gaps between the implant replicas and verification devices on the test and control casts. Clinical tray fit, impression quality, and cast quality were rated by an independent technician through a visual analog scale (VAS). The fabrication time and cost of the 2 types of custom open trays were recorded. The feasibility of 3D-printed trays was determined from these outcomes. The paired Student t test and Wilcoxon rank-sum tests were used for statistical analysis (α=.05). Results For impression accuracy, no statistically significant difference was found between test and control groups (P>.05). In terms of clinical tray fit, impression quality, and cast quality, no statistically significant difference was found (all P>.05). Regarding fabrication time and cost, the test group (57.65 ±6.49 minutes, 0.37 ±0.07 United States dollars [USD]) exhibited superiority over the control group (101.96 ±2.92 minutes, 4.41 ±0.37 USD) (both P Conclusions Within the limitations of this study, the 3D-printed custom open trays were clinically accurate, efficient, and cost-effective for impressions of multiple implants.

The impact of discrepancies between casts produced from digital scans and conventional impressions on the clinical performance of definitive restorations has not been fully investigated.The purpose of this crossover clinical trial was to evaluate the clinical performance of single implant-supported restorations fabricated with the digital scanning technique and computer-aided design and computer-aided manufacturing (CAD-CAM) casts compared with the conventional impression technique and gypsum casts in terms of efficiency, accuracy, and participant preference.Thirty participants underwent conventional impressions and digital scans of a single implant-supported restoration. Two crowns were fabricated for the same implant with each technique. The time taken for each procedure was recorded. After the accuracy and efficiency analysis of both crowns, the better crown was delivered. A questionnaire was used to assess participant preference and comfort with the techniques. The Wilcoxon signed-rank test was used to compare the time measurements, and multiple comparisons were performed using the Bonferroni method. The chi-square test was used to compare the implant locations of delivered crowns (α=.05).The total time for the conventional impression technique was 14.16 minutes, while that for the digital scanning technique was significantly less at 11.28 minutes (P.001). Remake times were 0.56 minutes for conventional impressions and 2.27 for digital scans, also significantly different (P.001). The adjustment time taken in delivering the crowns was 4.35 minutes for conventional impressions and 3.78 minutes for conventional impressions, which was not statistically significant (P=.940). Of the crowns chosen for delivery, 46.7% were from conventional impressions and 53.3% from digital scans. Participants preferred the digital scanning technique (89%) to the conventional impression technique (11%).The digital scanning technique was more efficient than the conventional impression technique for single implant-supported restorations. Digital scans and CAD-CAM implant casts had accuracy comparable with that of conventional impressions and gypsum casts. Most participants preferred digital scans to conventional impressions.

This article describes a dental implant impression technique using custom impression copings. The implant impression coping was designed by using a dental computer-aided design software program and manufactured by using additive methods. The impression copings were cemented to stock abutments, and the assemblies were used to make the definitive pick-up impression.

International audience; Statement of problem: Intraoral scanners have significantly improved over the last decade. Nevertheless, data comparing intraoral digital scans with conventional impressions are sparse.Purpose: The purpose of this systematic review and meta-analysis was to determine the impact of impression technique (digital scans versus conventional impressions) on the clinical time, patient comfort, and marginal fit of tooth-supported prostheses.Material and methods: The authors conducted a literature search based on the Population, Intervention, Comparison, and Outcome (PICO) framework in 3 databases to identify clinical trials with no language or date restrictions. The mean clinical time, patient comfort, and marginal fit values of each study were independently extracted by 2 review authors and categorized according to the scanning or impression method. The authors assessed the study-level risk of bias.Results: A total of 16 clinical studies met the inclusion criteria. The mean clinical time was statistically similar for digital scan procedures (784 ±252 seconds) and for conventional impression methods (1125 ±159 seconds) (P>.05). The digital scan techniques were more comfortable for patients than conventional impressions; the mean visual analog scale score was 67.8 ±21.7 for digital scans and 39.6 ±9.3 for conventional impressions (P.05).Conclusions: Digital scan techniques are comparable with conventional impressions in terms of clinical time and marginal fit but are more comfortable for patients than conventional impression techniques.

Statement of problem: New polyvinyl siloxane (PVS) materials with enhanced properties have been developed to improve and facilitate implant impression techniques. However, studies on their accuracy are lacking. Purpose: The purpose of this in vitro study was to determine the accuracy and precision of implant impressions made with some recently introduced materials on a simulated patient requiring an all-on-4 implant-supported prosthesis. Well-established polyether materials were also evaluated as a comparison. The variables considered were material type, consistency, splinting or not splinting techniques, and implant angulation. Material and methods: A reference master model was made by inserting 4 implants at angles of 0, 5, and 10 degrees. Eighty impressions were made at 37 °C in wet conditions by using a standardized technique. Eight groups (n=10) were created using monophasic, single-viscosity materials (Hydrorise Implant Medium, HIM-ns; Hydrorise Implant Medium, HIM; Honigum Mono, HM; Impregum, IMP), and 2-viscosity materials (Hydrorise Implant Heavy+Light-ns, HIH+L-ns; Hydrorise Implant Heavy+Light, HIH+L; Honigum Heavy+Light, HH+L; and Permadyne and Garant [Heavy+Light, PeH+L]). Hydrorise materials were used with splinting and not splinting (ns) techniques. The reference points located on the connecting platforms of the transfer copings (TCP) were compared with the same points on the implant connecting platforms (ICP) located in the reference model. The accuracy and precision of the impressions were determined as linear 3D errors and standard deviation between each TCP-ICP couple by using an optical coordinate measuring machine (OCMM). Results: PVS materials were generally better than polyether materials, with Hydrorise materials (HIM and HIH+L) showing significantly better accuracy and precision (30.9 ±14.4 μm and 28.7 ±15.5 μm, respectively) than IMP and PeH+L polyethers (44.2 ±16 μm and 43.8 ±17.6 μm, respectively; P

Statement of problem The triple-scan method for assessing the 3D adaptation of dental restorations has been introduced and reported to be reliable. However, the suitability of using a dental laboratory scanner in the triple-scan method has not been evaluated. Purpose The purpose of this in vitro study was to evaluate the suitability of the triple-scan method using a dental laboratory scanner to assess the 3D adaptation zirconia crowns. Material and methods A zirconia abutment and a zirconia crown were fabricated, and the abutment was fixed in a custom-made base. The crown was seated onto the abutment with the interposition of light-body silicone impression material between them. The triple-scan method was performed by using a dental laboratory scanner, and the mean cement-gap thickness was calculated. The seating and digitalization process was repeated 10 times, and after each digitalization, the light-body silicone layer was stabilized by applying heavy-body silicone impression material over it. Cement-gap thickness was measured on cross-sections of the aligned scan data sets and of the physical silicone replica. The results were assessed by using the paired t test and the Bland-Altman method (α=.05). Results Mean 3D cement-gap thickness assessed by the triple-scan method reported small dispersion with a coefficient of variation of 5.6% for the occlusal area, 1.9% for the axial area, and 6.4% for the margin area. Cement gap thickness measured at corresponding locations in the aligned scan data sets and in the physical silicone replica reported no significant difference (P=.326) and good agreement. Conclusions The cement gap was accurately duplicated in scan data sets. The triple-scan method by using a dental laboratory scanner is suitable for assessing the 3D adaptation of zirconia crowns.

Although intraoral scanners have gained in popularity, the traditional impression technique with a custom tray is still useful, particularly when making a definitive impression of multiple abutment teeth. A custom tray can be fabricated with a dental software program, avoiding the disadvantages of the manual laboratory procedures. However, additional module purchasing is necessary. This article presents a digital workflow for designing a custom tray by using an open-source software program.

Conventional implant impressions by using elastomeric impression material have been reported as a more reliable technique for a complete-arch implant record compared with intraoral scanner procedures. Photogrammetry technology may provide a reliable alternative to digital scanning or a conventional impression; however, its accuracy remains unclear.The purpose of this in vitro study was to measure and compare the implant abutment replica positions of the definitive cast with the implant abutment replica positions obtained by the conventional technique, photogrammetry, and 2 intraoral scanners.An edentulous maxillary cast with 6 implant abutment replicas (RC analog for screw-retained abutment straight) was prepared. Three impression techniques were performed: the conventional impression technique (CNV group) by using a custom tray elastomeric impression procedure after splinting the impression copings at room temperature (23°C), photogrammetry (PG group) technology (Icam4D), digital scans by using 2 different IOSs following the manufacturer's recommended scanning protocol, namely IOS-1 (iTero Element) and IOS-2 (TRIOS 3) groups (n=10). A coordinate measuring machine (CMM Contura G2 10/16/06 RDS) was used to measure the implant abutment replica positions of the definitive casts and to compare the linear discrepancies at the x-, y-, and z-axes and the angular distortion of each implant abutment replica position by using a computer aided-design software program (Geomagic) and the best fit technique. The 3D linear gap discrepancy was calculated. Measurements were repeated 3 times. The Shapiro-Wilk test revealed that the data were not normally distributed; therefore, the Kruskal-Wallis test was used to analyze the data, followed by pairwise Mann-Whitney U tests (α=.05).Significant y-axis linear and XY and YZ angular discrepancies were found among the CNV, PG, IOS-1, and IOS-2 groups (P.05). The PG group obtained a significantly higher distortion on the y-axis and 3D gap compared with all the remaining groups (P=.004). The 3D discrepancy of the CNV group was 11.7 μm, of the IOS-1 group was 18.4 μm, of the IOS-2 was 21.1 μm, and of the PG group was 77.6 μm. In all groups, the interquartile range was higher than the median errors from the discrepancies measured from the definitive cast, indicating that the relative precision was low.The conventional technique reported the lowest 3D discrepancy for the implant abutment position translation capabilities of all the implant techniques evaluated. The intraoral scanners tested provided no significant differences in linear distortion compared with the conventional method. However, the photogrammetry system tested provided the least accurate values, with the highest 3D discrepancy for the implant abutment positions among all the groups.

For the retention and stability of removable complete dentures, the denture base should be fabricated with appropriate borders and polished surfaces. A technique for transferring the contour of a functional impression for digitally fabricated removable complete dentures is described.

Retrofitting a new crown to an existing removable partial denture (RPD) is a challenging procedure. Recently, intraoral scanners (IOSs) have been successfully used to solve this issue. However, purchase of IOSs is necessary, and most clinicians still use the conventional impression technique. This article describes a combined conventional and digital approach to fabricating a new crown under an RPD without an IOS.

Evis, Zafer/0000-0002-7518-8162 WOS:000545315200013 PubMed: 31672424 Statement of problem. Recent commercial extended-pour irreversible hydrocolloid impression materials (EPIHIMs) claim to maintain dimensional stability up to 120 hours. However, data regarding their mechanical properties and performance after 120 hours of storage are lacking. Purpose. The purpose of this in vitro study was to test the elastic recovery, strain in compression, and tear strength properties of 5 commercially available EPIHIMs, immediately after preparation and after 120 hours of storage under specific storage conditions. Material and methods. A total of 150 specimens were prepared in accordance with the ISO 21563:2013 standard from 5 commercially available EPIHIMs (Blueprint Xcreme, Kromopan, Alginmax, Hydrogum 5, and Alginelle). The specimens were subjected to elastic recovery, strain in compression, and tear strength tests immediately after specimen preparation (n=5) and after 120 hours of storage inside clear plastic zipper bags held at 23 degrees C (n=5). Data were analyzed with a multivariate analysis of variance (MANOVA) test for brand and duration parameters. Normality of data was analyzed with the Shapiro-Wilk test. The Duncan test or Games-Howell test was used for multiple comparisons (alpha=.05). Results. Elastic recovery and strain in compression values of the EPIHIMs tested were affected by brand and duration parameters (P.05). Data distribution was normal except for Alginmax in terms of the elastic recovery values and Blueprint Xcreme in terms of the strain in compression values (P.05). However, 120 hours of storage led both to a statistically significant decrease in mean strain in compression values of the tested EPIHIMs (P.05) and a statistically significant difference among mean strain in compression values of the tested EPIHIM brands (P.05). However, statistically significant differences were present among mean tear strength values of the tested EPIHIM brands tested immediately after preparation (P

Trying to capture all the details of multiple teeth preparation in one impression is challenging. Techniques have been suggested to extend the working time of an impression material. This article describes a segmental impression technique to accurately capture all the preparation margins while allowing additional impression-making time.

As residual excess cement in peri-implant tissues is a problem that can lead to implant failure, great care must be taken when delivering cement-retained crowns. Cement selection, prosthetic design, and cementation techniques can reduce the chances of having excess cement in peri-implant tissues. Multiple techniques have been described, but, in many, the cement space has been reproduced by unreliable means. The dual-space technique allows the clinician to fabricate an implant crown delivery device in which the cement space has been replicated in a predictable and straightforward manner. In this technique, light-body impression material is used to create the luting space before the fabrication of the device with bis-acryl resin.

Intraoral digital scanning of edentulous arches has provided the dental profession with the ability to obtain genuinely mucostatic impressions. The drawback, because of the omission of border molding procedures, has been underextended flanges which might affect the retention and stability of the definitive prosthesis. A technique for combining the concept of registering the polished surfaces with a functional impression material and the intraoral digital mucostatic scanning workflow is described.

The best-fit method is frequently used to evaluate the accuracy of different implant impression techniques. However, the method includes inherent superimposition errors, which may accumulate and become more exaggerated in complete-arch impressions.The purpose of this in vitro study was to evaluate and compare the trueness and precision of conventional open-tray impressions and intraoral digital scans at the implant level in an edentulous maxillary model with 6 implant replicas without superimposition.A master model was fabricated using epoxy resin by duplicating a maxillary edentulous cast that had 6 implant replicas in the right first molar, right first premolar, right lateral incisor, left lateral incisor, left first premolar, and left first molar positions. The conventional open-tray, splinted-coping impression technique was used to fabricate 10 definitive casts (group CI). Intraoral digital scans were performed, after which scan bodies were connected to each implant replica to fabricate 10 digital models (group IOS). For the master model and group CI, a computerized coordinate-measuring machine was used to determine the 3D spatial orientation of the implant replicas. For group IOS, the scan bodies were converted to implant replicas using a digital library, and an inspection software program was used to measure the implant replicas. To compare the accuracies of different impression techniques, a 3D part coordinate system was set to compute the centroid and projection angles of each implant replica. The changes in the centroid coordinates (linear displacement: Δx, Δy, Δz, and ΔD; ΔD=ΔxGroup CI gave more accurate trueness values than group IOS for overall Δx (P.001), Δy (P =.029), Δz (P.001), and ΔD (P.001). Furthermore, group CI had more accurate precision values for Δx, Δy, and Δz. Group IOS exhibited a statistically greater angular displacement in the ZX plane (P=.002), but the difference was only 0.24 degrees. No differences were found between the 2 groups for the angular displacement in the XY plane (P=.529).Conventional open-tray impressions produced significantly smaller linear displacements than the digital scan obtained using an intraoral scanner at the implant level in a complete-arch model.

Patients who have undergone a bilateral maxillectomy are particularly difficult to rehabilitate prosthetically by using a conventional obturator prosthesis, mainly because of the extensive loss of tissues for retention and support. In these situations, adapting to existing undercuts within the defect is essential. Traditional impression techniques capture certain anatomic landmarks but may fall short of the needed sinus undercuts. This article describes an alternative impression technique for capturing 3 opposing undercuts to help retain, support, and stabilize a hollow 1-piece obturator prosthesis for a patient who underwent a total maxillectomy.

Selective laser melting (SLM) is a novel 3-dimensional (3D) printing technology that can directly form the metal frameworks of removable partial dentures. The adaptation of SLM frameworks has not been thoroughly evaluated.The purpose of this in vitro study was to evaluate the tissue surface adaptation of removable partial denture frameworks fabricated by an SLM technique.Four types of maxillary partial edentulous resin models were custom made: bilateral second premolars and molars missing, bilateral premolars and first molars missing, all teeth missing except 2 canines, and 2 central incisors missing. According to these dentition-defect patterns, 4 types (I, II, III, and IV) of virtual removable partial denture frameworks were designed, and an SLM printer was used for 3D printing using cobalt-chromium (Co-Cr) alloys (repeated 3 times). As a control, refractory casts duplicated from the resin models were used to fabricate denture frameworks by the lost-wax casting technique. Average gaps and maximum gaps between frameworks and models were measured using the silicone impression material. Two-way ANOVA was used to determine the influence of production methods and design types on the gaps (α=.05).The 2-way ANOVA showed that average gaps were significantly influenced by the production methods and design types, as well as their interactions (P.001). With design Types I and II, the average gaps of the SLM-printed frameworks were larger than those of the cast ones (P.001). However, no such differences were found for design Type III, P=.325, or IV, P=.862.SLM-printed frameworks achieved an acceptable adaptation. However, among frameworks with a large span and relatively more retainers and clasps, the adaptation of those made by the precision casting technique was slightly better than that of those printed by the SLM technique.

Statement of problem A nonpassive fit of implant-supported restorations can jeopardize the biological and mechanical success of the treatment. Data regarding the fit of different impression techniques for the all-on-4 protocol are limited. Purpose The purpose of this in vitro study was to digitally evaluate 4 different impression techniques used with the all-on-4 protocol, with distal multiunit analogs positioned in 4 different angulations. Material and methods Four maxillary definitive cast models with 4 multiunit analogs (T0 32202; NucleOSS) were fabricated according to the all-on-4 treatment protocol. In the anterior region, the analogs were positioned in a parallel direction, whereas in the posterior region, they were positioned in different angulations (0, 10, 20, and 30 degrees). One hundred and sixty models were obtained by using 4 different impression techniques (closed tray without plastic cap, closed tray with plastic cap, splinted open tray, sectioned resplinted open tray) (n=10) and polyvinyl siloxane impression material. Definitive casts and definitive duplicate casts were scanned using a modified laser scanner (Activity 880; Smart Optics Sensortechnik GmbH), and data were transferred to a software program (VRMesh Studio; Virtual Grid Inc). The definitive casts and definitive duplicate cast scans were digitally aligned. Angular and linear deviations in all axes (x, y, and z) of the analogs between definitive and duplicate casts were calculated and subjected to statistical analyses (α=.05). Results Mean angular deviations were in the range of 0.03 to 0.16 degrees, and linear deviations were in the range of 0.10 to 0.75 mm. The increased angulation between impression copings caused higher linear and angular deviations when closed-tray impression techniques were used (P Conclusions Reduced linear and angular displacements were obtained from the open-tray impression techniques compared with the closed-tray impression techniques in the angulated groups. Angular and linear deviations increased with the increase in the angulation of the posterior analog.

The technique described allowed an implant custom tray to be fabricated referencing the location of connected impression copings. The technique uses dental computer-aided design (CAD) software and 3D printing technology. The method controls the thickness of the impression material around the impression copings, improving the impression-making process.

This article presents an impression technique involving transfer of the position of implants and the emergence profile of splinted interim prostheses fabricated on nonindexed interim abutments to definitive single crowns fabricated on indexed abutments.

STATEMENT OF PROBLEM Clinical trials are needed to evaluate digital and conventional technologies for providing fixed partial dentures. PURPOSE The purpose of the first part of this clinical study was to test whether complete-arch digital scans were similar to or better than complete-arch conventional impressions regarding time efficiency and participant and clinician perceptions. MATERIAL AND METHODS Ten participants in need of a posterior tooth-supported 3-unit fixed partial denture were included. Three intraoral digital scanners and subsequent workflows (Lava C.O.S.; 3M [Lava], iTero; Align Technology Inc [iTero], Cerec Bluecam; Dentsply Sirona [Cerec]) were compared with the conventional impression method using polyether (Permadyne; 3M) and the conventional workflow. A computer-generated randomization list was used to determine the sequence of the tested impression procedures for each participant. The time needed for the impression procedures, including the occlusal registration, was assessed. In addition, the participant and clinician perceptions of the comfort and difficulty of the impression were rated by means of visual analog scales. Data were analyzed with the nonparametric paired Wilcoxon test together with an appropriate Bonferroni correction to detect differences among the impression systems (α=.05). RESULTS The total time for the complete-arch impressions, including the preparation (powdering) and the occlusal registration, was shorter for the conventional impression than for the digital scans (Lava 1091 ±523 seconds, iTero 1313 ±418 seconds, Cerec 1702 ±558 seconds, conventional 658 ±181 seconds). The difference was statistically significant for 2 of the 3 digital scanners (iTero P=.001, Cerec P

Available studies comparing fit accuracy of zirconia fixed partial dentures (FPDs) fabricated from conventional impressions and digital scans provide contradictory results. In addition, studies have been heterogeneous and of a limited number to provide conclusive evidence.The purpose of this systematic review and meta-analysis was to compare the marginal and intaglio fit of tooth-supported zirconia FPDs fabricated from conventional impressions and digital scans and to investigate the effect of different variables on the fit results.An electronic search was performed on the National Library of Medicine (NLM), Cochrane Central Register of Controlled Trials, and Scopus databases. In addition, a manual search was carried out. Studies comparing the fit of tooth-supported zirconia FPDs fabricated from conventional impressions and digital scans and reporting sufficient data for qualitative and quantitative analysis were included. Standard mean differences (SMDs) and 95% confidence intervals (CI) were calculated for meta-analysis. Subgroup analysis was performed to study the effect of variables including restoration form (monolithic or framework), units number, intraoral scanner (IOS) type, conventional impression material, spacer thickness, and abutments region.The initial search resulted in a total of 608 articles. Nine articles were included in the analysis (1 clinical and 8 in vitro) evaluating 118 restorations. Digital scan displayed significantly better marginal fit (P.001; SMD: -0.68; 95% CI: -0.92, -0.09) and intaglio fit (P=.020; SMD: -0.51; 95% CI: -0.94, -0.42). Test for subgroup difference showed a significant influence of only impression material type (P=.008) and units number (P=.030) on marginal fit. Digital scan showed significantly better marginal accuracy for 3-unit FPDs than 4-unit FPDs (P.001; SMD: -1.02; 95% CI: -1.41, -0.63). In addition, digital scanning had significantly better marginal fit with polyvinyl siloxane than polyether (P.001; SMD: -0.98; 95% CI: -1.32, -0.64). A cement spacer ≤50 μm improved both marginal and intaglio fit in the digital group. The TRIOS scanner resulted in the best performance in the digital group for marginal fit.Digital scanning provides significantly better marginal and intaglio fit than conventional impression making for fabricating zirconia FPDs up to 4 units, either in monolithic form or frameworks and at any region of the arch. However, further clinical studies are recommended to obtain more substantial results.

Intraoral scanning has been reported to be preferred by patients over conventional impression making. Nevertheless, information regarding patient-related outcomes for conventional impression making and digital scanning is sparse.The purpose of this systematic review and meta-analysis was to analyze patient-related outcomes of intraoral scanning and conventional impression methods. The primary outcomes evaluated were patient preference and satisfaction, and the secondary outcomes discomfort, nausea, unpleasant taste, breathing difficulty, pain, and anxiety.Electronic and manual searches were performed for clinical trials that evaluated patient-related outcomes for intraoral scanning and conventional impression making for prosthetic rehabilitation. The Cochrane Collaboration risk of bias tool and Newcastle-Ottawa scale were used to assess the quality of the studies. Random-effects models using mean difference were used for meta-analyses. Heterogeneity was assessed using the Cochran Q test and IThe search strategy identified 1626 articles, and 11 studies were included in the meta-analyses. Patients preferred intraoral scanning to conventional impression making. The mean difference for patient preference was 15.02 (95% confidence interval of 8.33 - 21.73; P.001). Discomfort, absence of nausea, absence of unpleasant taste, and absence of breathing difficulty were also significantly different (P.05).Intraoral scanning is a suitable alternative to conventional impression procedures, promoting less discomfort for patients sensitive to taste, nausea, and breathing difficulty than when conventional impression making techniques are used.

Statement of problem Making impressions of 2-piece implants is typically associated with the repeated disassembly and reassembly of superstructures and related to soft-tissue trauma. Intraoral scanning of 1-piece zirconia implants is problematic because scan bodies are not readily available. Whether using virtual hybrid casts generated by merging intraoral scan data with the known surface geometry of abutments can solve these difficulties is not clear because data on accuracy of the workflow are sparse. Purpose The purpose of this in vitro study was to evaluate the accuracy of virtual hybrid casts with respect to the impact of different gingival situations. The workflow was designed to render pointless the use of impression posts and scan bodies and avoid any displacement of the gingiva. Material and methods The mandibular right first molar in a typodont was replaced with a 2-piece titanium implant with a custom abutment and then a 1-piece zirconia implant. Three situations representing different gingival heights covering the abutments were simulated. Twelve intraoral scans were made for each situation to capture the recordable parts of the abutments, and virtual hybrid casts were constructed by superimposing and merging the intraoral scan data with the original laboratory scan data of the abutments. Hybrid casts were compared with reference data by using the root mean square error. Scan body–related and cast scan–related protocols were performed representing conventional digital workflows. Statistical analysis with the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests with the Bonferroni correction was conducted with a statistical software program (α=.05). Results Deviation was low in the hybrid casts of the custom abutment when the entire abutment was recorded (6.5 μm; IQR: 3.0 μm), when the preparation margin was disguised (7.0 μm; IQR: 1.0 μm), and when half of the abutment was covered (8.0 μm; IQR: 4.0 μm). The accuracy in the 1-piece zirconia implant was 10.0 μm (IQR: 4.0 μm) when the whole surface of the abutment was visible and 12.5 μm (IQR: 6.0 μm) when the preparation margin was covered. When only half of the abutment was captured, a larger deviation of 22.0 μm (IQR: 7.0 μm) was observed. The hybrid cast concept demonstrated superior accuracy compared with protocols using scan body scans (76.0 μm; IQR: 27.0 μm) and cast scans (23.0 μm; IQR: 15.0 μm). Conclusions Digital intraoral scanning and the generation of virtual hybrid casts provide high accuracy and are suitable for the fabrication of single-implant-supported restorations. The atraumatic procedure avoids tissue manipulation and reduces clinical effort.

Statement of problem Conventional impressions and digital intraoral scanning for implant-supported fixed complete-arch prostheses still have many problems that influence accuracy. Although stereophotogrammetry may offer a reliable alternative to other techniques, it has seldom been investigated. Purpose The purpose of this in vitro study was to measure and compare the intraoral scan body deviations of the reference cast with the intraoral scan body distortions obtained by conventional, digital, and stereophotogrammetric techniques. Materials and methods An edentulous maxillary “all-on-four” cast was prepared with 2 straight and two 17-degree angled screw-retained abutments screwed on the implant. Three capture techniques were compared: the conventional impression technique (CI group) using impression plaster (IP), the digital intraoral scanning (DIS group) technique, and the stereophotogrammetry (SPG group) technique. A calibrated extraoral scanner was used to digitize the definitive cast to compare its intraoral scan body positions with those of the other techniques in terms of global angular distortion and 3D deviations of the whole scan body and flat angled surface alone by using an inspection and metrology software program and the best fit alignment technique. The Kolmogorov-Smirnov and Shapiro-Wilk tests showed normal distribution of the quantitative variables. Thus, the repeated measures analyses of variance followed by univariate analysis and Bonferroni multiple comparison tests were performed to analyze the data (α=.05). Results Significant global angular discrepancies and 3D deviations of the whole scan body and flat angled surface were found among the CI, DI, and SPG groups for both trueness (P Conclusions The stereophotogrammetry capture technique reported the highest accuracy in terms of trueness and precision for the intraoral scan bodies of all the techniques evaluated. However, at the flat angled surface region of the scan body, higher trueness was detected with the digital technique. Conventional impressions showed better trueness results than the digital ones, but the opposite was true of precision.

The accuracy of digital scanning for complete dental arch and implant-supported complete-arch restorations has been reported. However, research addressing the accuracy of digital scanning methods for complete-arch tooth preparation is lacking.The purpose of this in vitro study was to compare the accuracy of intraoral scanning, impression scanning, and cast scanning for complete-arch preparation.Maxillary and mandibular jaw typodonts with 28 teeth prepared for complete crowns were used as reference casts and digitized as reference data sets with a desktop scanner. Three digital scanning methods were applied. First, the reference casts were each scanned 10 times with an intraoral scanner to generate the intraoral scanning group data sets. Second, the reference casts were each captured 10 times by using polyvinyl siloxane impression material, and the impressions were scanned with a desktop scanner to generate the impression scanning group data sets. Third, the impressions obtained in the impression scanning group were used to make gypsum casts which were then digitized with a desktop scanner to generate the cast scanning group data sets. Accuracy was determined by trueness and precision. Three-dimensional deviations of the prepared arches and anterior and posterior segments were measured from root mean square values and depicted on color-difference maps. Differences among test groups were analyzed by using a 1-way ANOVA and the post hoc Bonferroni test for normally distributed data or the Kruskal-Wallis test with Bonferroni correction for non-normally distributed data (α=.05).The trueness of the maxillary arch was significantly higher in the impression scanning group than in the cast scanning and intraoral scanning groups (P.05), but no significant differences were found among the 3 groups of the mandibular arch (P.05). The precision of both arches was significantly higher in the impression scanning and intraoral scanning groups than in the cast scanning group (P.05). Color maps showed horizontal symmetrical displacement in the intraoral scanning group relative to the reference data sets and within-group unilateral distal-end distortion. Irregular arch deformations were noted in the impression scanning group, and buccal and occlusal expansion occurred in the anterior-posterior direction in the cast scanning group. Pooled data for anterior teeth indicated that the trueness was lowest in the intraoral scanning group; however, that for the maxillary anterior teeth did not differ, while that for the mandibular anterior teeth differed significantly among groups (P.05). For the posterior teeth, deviation was the lowest in the impression scanning group, and significant differences were noted in both arches among the 3 groups (P.05).Of the methods tested, impression scanning was the most accurate for the creation of a digital cast of a complete prepared arch.

Statement of problem The technology behind optical scanners has greatly improved recently, making their dental application advantageous. While their accuracy is now comparable with that of conventional impression materials, whether these techniques have other advantages is unclear. Purpose The purpose of this systematic review and meta-analysis was to determine whether digital scanning for implant-supported restorations is more time-efficient and convenient for the patient. Material and methods The study was conducted on September 23, 2020 using 4 different databases (Medline, Cochrane, Web of Science, Scopus) searching for clinical studies that compared the time needed and/or patient perceptions between those who had undergone the digital scanning procedure and those who had undergone conventional impression making. Results Twelve studies met the inclusion criteria for qualitative and quantitative analysis. Outcome variables were measured as standard mean differences (SMDs) by following a fixed-effects model or random-effects model (in the case of high heterogeneity). Digital scanning was more time-efficient and was preferred by patients for all 4 analyzed outcomes (comfort, anxiety, nausea, time perception). Conclusions Digital scanning was found to be more time-efficient and convenient than conventional impression making for implant-supported restorations. Additional randomized controlled trials are needed to confirm the findings of this review.

This report describes a digital workflow for the fabrication of a complete maxillary denture opposing an implant-retained overdenture. This procedure provides a predictable and accurate 3-visit technique to digitally scan and articulate edentulous ridges, avoiding the discomfort associated with analog impression making. Wax rims were applied to intraorally relined plastic edentulous stock trays. The occlusal relationship was registered at the appropriate vertical dimension of occlusion by using these tray and rim assemblies. The digital laboratory scanning of the relined tray and rim assemblies resulted in accurate virtual articulation of the digital edentulous intraoral scans. The removable restorations were digitally designed, milled, and delivered, and the clinical and laboratory steps are described.

Made available in DSpace on 2021-06-25T10:49:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Statement of problem: Redesigned mixing tips, promising less impression material waste, have been marketed. However, whether their use adversely affects the dimensional stability and detail reproduction of the impression material is unclear. Purpose: The purpose of this in vitro study was to evaluate the dimensional stability, detail reproduction, and material waste of different polyvinyl siloxane impression materials (regular and light-body) mixed with 2 different mixing tips (MIXPAC T-Mixer mixing tip and MIXPAC helical mixing tip). Material and methods: Six different polyvinyl siloxane impression materials were used in 2 different consistencies: Virtual Monophase and Virtual Light Body (Ivoclar Vivadent AG), Express XT Regular and Express XT Light Body (3M ESPE), and Panasil initial contact Regular and Panasil initial contact Light (Kettenbach). The polyvinyl siloxane impression materials were mixed with 2 different mixing tips: conventional helical and T-Mixer (n=10). The specimens were prepared in a metal matrix as per specification #19 of the American National Standards Institute/American Dental Association (ANSI/ADA) and International Organization for Standardization (ISO) 4823:2015. The materials were mixed with both mixing tips as per the manufacturer's instructions, inserted into a perforated custom tray on the matrix, and allowed to polymerize completely. The dimensional stability was calculated based on the measurement of the reproduction of lines engraved in the metal matrix. Detail reproduction was evaluated through analysis of continuity and reproducibility of those lines, immediately, 7 days, and 14 days after polymerization. Material waste was assessed by the difference between the initial (before mixing) and final weight (after complete polymerization) of both mixing tips. The data on dimensional stability and detail reproduction among the materials were submitted to the Kruskal-Wallis test, followed by the Student-Newman-Keuls test (α=.05). Comparison between the mixing tips was carried out with the Mann-Whitney test (α=.05), while the comparison among the periods of analysis (immediate, 7 days, and 14 days) was carried out with the Friedman test (α=.05). The data on material waste between the mixing tips were submitted to 1-way ANOVA, followed by the Tukey honestly significant difference tests (α=.05). Results: The T-Mixer mixing tip resulted in reduced material waste. For dimensional stability, Virtual Light mixed with T-Mixer resulted in lower dimensional change (0.53 ±0.58%) compared with the helical mixing tip (1.09 ±0.43%). Among the materials, Panasil Light presented higher values of dimensional change at immediate and 7-day analysis when mixed with T-Mixer tip with a statistical difference compared with Express Light, Virtual Light, and Panasil Regular (P.05) for qualitative analysis of detail reproduction. Conclusions: The T-Mixer tip resulted in less material waste compared with the helical mixing tip. In general, light-body materials showed higher dimensional stability when the T-Mixer tip was used compared with the conventional tip. In general, reduced detail reproduction was observed after periods longer than 7 days after impression making. Postgraduate student Department of Dental Materials and Prosthodontics Araçatuba School of Dentistry São Paulo State University UNESP Professor Western Parana State University UNIOESTE Associate Professor Department of Restorative Dentistry Araçatuba School of Dentistry São Paulo State University UNESP Professor Division of Dentistry Dental Press Associate Professor Department of Dental Materials and Prosthodontics Araçatuba School of Dentistry São Paulo State University UNESP Postgraduate student Department of Dental Materials and Prosthodontics Araçatuba School of Dentistry São Paulo State University UNESP Associate Professor Department of Restorative Dentistry Araçatuba School of Dentistry São Paulo State University UNESP Associate Professor Department of Dental Materials and Prosthodontics Araçatuba School of Dentistry São Paulo State University UNESP

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.

Single-use plastics in dentistry are significant contributors to biomedical waste. Various plastic tubes and mixing cartridges with different plastic mixing tips are widely used for elastomeric impression materials. To minimize the dental plastic footprint, a technique is described for making reusable plastic mixing tips for elastomeric impression materials.

A clinical and laboratory workflow for fabricating and retrofitting a monolithic ceramic crown to an existing removable partial denture (RPD) is described. A conventional polyvinyl siloxane impression was made of the prepared tooth with the RPD in place. A stone cast was poured and, after die sectioning, scanned with a tabletop scanner. The ceramic crown was designed and fabricated by using a digital workflow to fit the RPD clasp assembly, providing an adequate undercut for the clasp. The crown was then delivered and the RPD evaluated for adequate fit.

This article describes a step-by-step digital protocol for the design and fabrication, through additive manufacturing, of a splinted framework and a custom tray for the impression of a complete-arch prosthesis supported by multiple implants. The protocol presented uses open source software to control the thicknesses of the custom tray, splinting material, and impression material during the procedure, reducing laboratory and chairside time and costs.

The sectional and the single-step are techniques for border molding. Even though the sectional technique is routinely taught in dental schools in the United States, and is followed by a large number of general dental practitioners, it is not without disadvantages. Common problems associated with the sectional technique include its time-consuming nature and the difficulty in mastering it because of the short manipulation time of the impression compound modeling plastic. Single-step border molding, however, presents advantages; for example, fewer insertions of the tray for border molding are necessary, and development of all borders simultaneously avoids the propagation of error. This article presents a simplified technique for performing single-step border molding using visible light-polymerizing tray material.

Although computer-aided design and computer-aided manufacturing (CAD-CAM) complete removable dental prostheses (CRDPs) have gained popularity, conventional impressions are still common for CAD-CAM CRDP treatment. These need to be digitized and converted into virtual edentulous casts with a laboratory impression scan protocol during prosthesis fabrication. How this can best be accomplished is unclear.The purpose of this in vitro study was to compare the accuracy and reproducibility of virtual edentulous casts created by a dental laboratory laser scanner and a cone beam computed tomography (CBCT) scanner with a digitized master cast.A master cast was digitized as the virtual reference cast. Ten polyvinyl siloxane impressions were made on the master cast and scanned with the dental laboratory laser scanner and CBCT scanner. The impressions were sprayed with antiglare spray and rescanned. Four groups of virtual study casts (N=40) were created from the impression scans. All virtual study casts and the reference cast were registered with surface-matching software, and the root mean square (RMS) values (representation of overall accuracy) and percentage of measurement data points within 1 standard deviation (SD) of mean RMS values (%, representation of overall reproducibility) among the 4 study groups were measured. Additionally, 95 numeric distance differences (representation of accuracy at each region) were measured in 5 distinct regions: the apex of the denture border, 6 mm from denture border, crest of the ridge, palate, and posterior palatal seal. The repeated-measures ANOVA and post hoc test (t grouping) were used to determine statistical differences (α=.05).The laboratory scanner group had a significantly larger RMS value (4.0 ±0.3 μm, P.001) and smaller percentage of measurement data points within 1 SD of mean RMS value (77.5 ±1.0%, P.001). The RMS values between the CBCT scanner (1.2 ±0.3 μm) and CBCT scanner-spray (1.1 ±0.2 μm) groups were not significantly different (P=.968), and the percentage of measurement data points within 1 SD of mean RMS values (90.1 ±1.1% versus 89.5 ±0.8%) were also not significantly different (P=.662). The numeric distance differences across 5 regions were affected by the scanning protocols (P.001). The laboratory scanner and laboratory scanner-spray groups had significantly higher numeric distance differences at the apex of the denture border and crest of the ridge regions (P.001).The CBCT scanner created more accurate and reproducible virtual edentulous casts, and the antiglare spray only significantly improved the accuracy and reproducibility of virtual edentulous casts created by the dental laboratory laser scanner. The accuracy of the virtual edentulous casts was different across 5 regions and was affected by the scanning protocols.

Factors that may affect the marginal adaptation of computer-aided design and computer-aided manufacturing (CAD-CAM) restorations include preparation design, impression technique, and CAD-CAM system. The influence of impression technique and preparation design on CAD-CAM partial coverage restorations has not been fully addressed.The purpose of this in vitro study was to investigate the influence of direct and indirect digital scanning techniques and 2 preparation designs on the marginal adaptation of CAD-CAM onlays.Two mesio-occlusal buccal onlay preparations with reduction of the mesiobuccal cusp were made: conventional preparation (CP) with a 1.2-mm modified shoulder margin and modified preparation (MP) flat cuspal reduction without shoulder. Virtual models were generated from each preparation by using a digital scanner (BlueCam; Dentsply Sirona) from the plastic teeth (direct digital scan) or from the stone dies (indirect digital scan). Onlays were designed using a CAD-CAM system (CEREC 4.0; Dentsply Sirona), and nanoceramic resin blocks (Lava Ultimate Restorative; 3M ESPE) were milled using the CEREC MCX milling machine. Marginal discrepancy was evaluated using an optical stereomicroscope at ×25 magnification in 18 locations distributed along the margins of the preparation. The data were analyzed by using 3-way ANOVA followed by the Tukey HSD test (α=.05).CP presented a statistically significant reduced average marginal adaptation (59 ±50 μm) than did MP (69 ±58 μm) (P.001). The Tukey HSD test showed the presence of a significantly larger marginal discrepancy in the mesial and buccal locations of MP when compared with CP. Regarding impression techniques, the buccal location presented the smallest average marginal discrepancy in restorations fabricated with indirect impression when compared with direct impression (42 ±33 μm and 60 ±39 μm) (P.001).The results showed that conventional preparation with a modified shoulder margin presented improved marginal adaptation compared with modified preparation with flat cuspal reduction. Direct and indirect digital scanning techniques produced restorations within a clinically acceptable range; however, the indirect scanning technique resulted in the fabrication of restorations with superior marginal adaptation on the buccal location.

Statement of problem Intraoral scanners are effective for direct digital impression when dental restorations are fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM); however, if the abutment tooth cannot be dried completely or the prepared margin is placed subgingivally, accurate digital images cannot always be guaranteed. Purpose The purpose of this in vitro study was to compare the internal and marginal discrepancies of zirconia copings fabricated directly using an intraoral scanner with those fabricated indirectly with impression scanning. Material and methods Forty-five resin dies fabricated with a 3-dimensional (3D) printer were divided into 3 groups: direct scanning (DS), impression scanning (IMP), and lost-wax casting (LW). For the DS group, a resin die was scanned with an intraoral scanner (Trios; 3Shape), whereas for the IMP group, impressions made with polyether were scanned with a cast scanner (D700; 3Shape). The zirconia copings were fabricated in the same way in the DS and IMP groups. For the LW group, impressions were made in the same way as in the IMP group, and Ni-Cr alloy copings were fabricated using LW. The marginal and internal discrepancies of the copings were measured by cementing them onto resin dies, embedding them in acrylic resin, and sectioning them in a buccolingual direction. The cement layer was measured, and the Kruskal-Wallis test was used to detect significant differences (α=.05). A nonparametric Friedman test was also performed to compare the measurements of each group by location (α=.05). Results The mean marginal discrepancies in the DS, IMP, and LW groups were 18.1 ±9.8, 23.2 ±17.2, and 32.3 ±18.6 μm (mean ±standard deviation), respectively. The mean internal discrepancies of the DS, IMP, and LW groups in the axial area were 38.0 ±9.1, 47.0 ±16.3, and 36.5 ±15.8 μm, and those in the occlusal area were 36.7 ±16.9, 33.4 ±21.6, and 44.5 ±31.9 μm, respectively. No statistically significant differences were found in marginal or internal discrepancies among groups ( P >.05). Conclusions Within the limitations of this study, the zirconia copings fabricated with CAD-CAM using different digitization methods and Ni-Cr copings fabricated using the lost-wax technique and casting produced clinically acceptable marginal and internal discrepancies. No significant differences were found among the DS, IMP, and LW groups.