Conventional Impression Research Articles

Comparison of digital scanning and conventional impression taking for implant-supported prostheses

The effect of discrepancies between digital scans and conventional impressions on the clinical performance of a permanent restoration has not been fully understood.Thirty patients received conventional impressions and digital scans of a single implant restoration. Two crowns were made for the same implant using both methods. The time taken for each procedure was recorded. After analyzing the accuracy and effectiveness of both crowns, the best one was placed. A questionnaire was conducted to assess the preferences and comfort when using crowns made by one method or another.The total time for the traditional impression technique was 15 minutes, while the time for the digital scanning technique was significantly less – 10 minutes.The preparation time, including the disinfection of the silicone impressions, their transportation to the laboratory, the casting of the impressions, the hardening of the plaster, as well as the preparation of the model by the technician, was 4 hours for conventional impressions.The timing for sending the STL file and modeling the structure was less than 2 hours for the digital scan method. The production time of crowns takes 3 hours for both conventional impressions and digital ones.Of all crowns selected for placement, 46.7% were made from conventional impressions and 53.3% from digital scans. Participants preferred the digital scanning technique (89%) over the traditional impression-taking technique (11%).The data from this study suggest that digital scanning and CAD/CAM technology may be more effective and better accepted by study par-ticipants for a single implant restoration than conventional impressions and plaster casts.

Comparison of digital and silicone impressions for single-tooth implants and two- and three-unit implants for a free-end edentulous saddle

BackgroundThe use of intraoral scanners (IOS) has facilitated the use of digital workflows for the fabrication of implant-supported prostheses not only for single missing teeth, but also for multiple missing teeth. However, the clinical application of IOS and computer-aided design/manufacturing (CAD/CAM) in implant-supported prosthodontics remains unclear. This study aimed to compare the accuracy of digital and silicone impressions for single-tooth implants for bounded edentulous spaces and two-unit and three-unit implant-supported fixed dental prostheses for free-end edentulous spaces.MethodsThis study enrolled 30 patients (n = 10 for each of the three groups) with an average age of 61.9 years. Conventional silicone-based and digital IOS-based impressions were made for all patients, and the implant superstructures were fabricated. We measured the scan-body misfit and compared the accuracy of the impressions for single-unit, two-unit, and three-unit implant prostheses with a bounded edentulous space by superimposing the standard triangulated language (STL) data obtained from IOS over the STL data of the plaster model used for final prosthesis fabrication. The scan bodies of the superimposed single-molar implant, two-unit implant prosthesis without teeth on the mesial side, two-unit implant prosthesis without teeth on the distal side, three-unit implant prosthesis without teeth on the mesial side, and three-unit implant prosthesis without teeth on the distal side were designated as A, B1, B2, C1, and C2, respectively. The misfit for each scan body was calculated and the accuracies were compared using the Tukey–Kramer method.ResultsThe average scan-body misfit for conditions A, B1, B2, C1, and C2 was 40.5 ± 18.9, 45.4 ± 13.4, 56.5 ± 9.6, 50.7 ± 14.9, and 80.3 ± 12.4 μm, respectively. Significant differences were observed between the accuracies of A and B2, A and C2, and C1 and C2 (P < 0.001).ConclusionsIOS and CAD/CAM can find clinical applications for implant-supported prostheses of up to three units for a bounded edentulous saddle. The use of IOS could render implant treatment easier, benefiting both the surgeons and patients. Prosthesis maladjustment may lead to peri-implantitis and prosthetic fracture. Therefore, further validation of the accuracy of IOS impressions is required in patients with multiple missing teeth in long-span implant prostheses.

Intraoral scanning of neonates and infants with craniofacial disorders: feasibility, scanning duration, and clinical experience.

The aim of this study was to evaluate intraoral scanning (IOS) in infants, neonates, and small children with craniofacial anomalies for its feasibility, scanning duration, and success rate. Impression taking in vulnerable patients can be potentially life-threatening, with the risk of airway obstruction and aspiration of impression material. The advantage of increasingly digitalized dentistry is demonstrated. IOS was captured with the Trios 3® (3Shape, Copenhagen, Denmark) intraoral scanner. The underlying disorders were divided into cleft lip and palate (CLP), Trisomy 21 (T21), Robin Sequence (RS), Treacher Collins syndrome (TC), and isolated mandibular retrognathia (MR). Scan data were analysed by scanning duration, number of images, possible correlations of these factors with the different craniofacial disorders, patient age, and relationship between first and subsequent scans. Clinical experiences with the repeated digital impressions are described. Patient data of 141 scans in 83 patients were analysed within an 11-month period. Patients had a median age of 137 days. Median scanning duration was 138 seconds, resulting in a median of 352 images. There was a statistically significant difference in scanning duration (P = 0.001) between infants and neonates. IOS took longest in patients with CLP (537 seconds) and shortest in T21 patients (21 seconds), although there was no statistically significant difference between aetiologies. There was no statistically significant difference between first and subsequent scans in scanning duration. In four cases the IOS had to be repeated, and one patient ultimately required conventional impression taking (all CLP patients; success rate 94%). No severe adverse events occurred. IOS is a fast, safe, and feasible procedure for neonates, small children, and infants with craniofacial malformations. One special challenge for both technician and user was identified in patients with CLP, though implementing this new approach of digital impression taking was otherwise found to be highly successful in everyday clinical routine.

Time-efficiency and cost-analysis comparing three digital workflows for treatment with monolithic zirconia implant fixed dental prostheses: A double-blinded RCT

ObjectivesThis double-blinded randomized controlled trial investigated economic performance indicators (EPI) in terms of time-efficiency and production costs of 3-unit monolithic zirconium-dioxide (ZrO2) implant fixed dental prostheses (iFDP) in three different workflows. MethodsTwenty patients with two Straumann Tissue-Level-Implants received three iFDPs; two were fabricated in proprietary complete digital workflows with intraoral optical scanning and model-free fabrication with company-related CAD/CAM lab-software while one iFDP was manufactured on digitized casts from conventional impressions. The sequence of impression-taking for the three workflows (TRIOS 3/3Shape [Test-1]; Virtuo Vivo/Dental Wings [Test-2]; Impregum/3M Espe [Control]) was randomly allocated. Sixty iFDPs bonded to ti-base abutments were analyzed. Clinical and technical worksteps for Test-1/Test-2/Control were recorded and evaluated for time-efficiency including cost-analysis (CHF=Swiss Francs) using ANOVA-Tests (significance level α=0.05). ResultsMean total work time, as the sum of clinical plus technical steps, was 97.5 min (SD ± 23.6) for Test-1, 193.1 min (SD ± 25.2) for Test-2, and 172.6 min (SD ± 27.4) for Control. Times were significantly different between Test-1/Test-2 (p < 0.00001), Test-1/Control (p < 0.00001), and Test-2/Control (p < 0.03610). Technical costs were 566 CHF (SD ± 49.3) for Test-1, 711 CHF (SD ± 78.8) for Test-2, 812 CHF (SD ± 89.6) for Control, and were also significantly different for all comparisons (p < 0.00001). ConclusionsTest-1 demonstrated the best performance for time-efficiency, Test-2 revealed the worst result. This indicates that digital workflows are not the same and not necessarily superior to analog workflows of monolithic ZrO2 iFDPs. Complexity decreases by reducing the number of steps following complete digital workflows, resulting in lower production costs compared to the mixed analog-digital workflow with conventional impressions. Clinical significanceComplete digital workflows comprising intraoral optical scanning without physical models for treatment with monolithic ZrO2 iFDPs is an efficient alternative to mixed analog-digital workflows with conventional impressions and labside digitization of dental casts.

Accuracy of the Provisional Prosthesis Scanning Techniqueversus a Conventional Impression Technique on Completely Edentulous Arches

Purpose: In this study, we aimed to compare the marginal fit of fixed dental restorations fabricated with the provisional prosthesis scanning technique versus a conventional impression technique and to determine the effect of both variables on the accuracy outcome. Materials and Methods: Twelve identical polyurethane edentulous maxillary models were equally divided into two groups: control (conventional impression group) and test (provisional prosthesis scanning group). After obtaining the impression using the above-mentioned methods and further preparing the final prosthesis, the passivity of the metal framework prosthesis was checked using a single screw test, i.e., only one screw was fixed on the terminal right abutment, and all others were empty. The marginal fit of the final prosthetic frameworks screwed onto the implants on the terminal left abutment was measured at the terminal right sight by periapical radiographs obtained immediately after metal framework placements in both groups. The medians derived from the two groups were compared using the Mann–Whitney test. In all tests, a p-value &lt; 0.05 indicated statistical significance. Results: In the provisional prosthesis scanning group, the median marginal fit discrepancy was 170 µm (range 120–190). In the conventional impression group, the median marginal fit discrepancy was 1080 µm (range 1040–1100). There was a significant difference in the implant-framework marginal gap fit discrepancy between these two groups. Conclusion: Prostheses fabricated with the provisional prosthesis scanning technique are significantly more accurate than those fabricated with conventional impression techniques.

The Influence of Hard- and Software Improvement of Intraoral Scanners on the Implant Transfer Accuracy from 2012 to 2021: An In Vitro Study

This study aimed to investigate the transfer accuracy (trueness and precision) of three different intraoral scanning families using different hardware and software versions over the last decade from 2012 to 2021, compared to a conventional impression. Therefore, an implant master model with a reference cube was digitized and served as a reference dataset. Digital impressions of all three scanning families (True definition, TRIOS, CEREC) were recorded (n = 10 per group), and conventional implant impressions were taken (n = 10). The conventional models were digitized, and all models (conventional and digital) were measured. Therefore, it was possible to obtain the deviations between the master model and the scans or conventional models in terms of absolute three-dimensional (3D) deviations, deviations in rotation, and angulation. The results for deviations between the older and newer scanning systems were analyzed using pairwise comparisons (p &lt; 0.05; SPSS 26). The absolute 3D deviations increased with increasing scan path length, particularly for the older hardware and software versions (old vs. new (MW ± SD) True Definition: 355 ± 62 µm vs. 483 ± 110 µm; TRIOS: 574 ± 274 µm vs. 258 ± 100 µm; and CEREC: 1356 ± 1023 µm vs. 110 ± 49 µm). This was also true for deviations in rotation and angulation. The conventional impression showed an advantage only regarding the absolute 3D deviation compared to the older systems. Based on the data of the present study, the accuracy of intraoral scanners is decisively related to hardware and software; though, newer systems or software do not necessarily warrant improvement. Nevertheless, to achieve high transfer accuracy, regular updating of digital systems is recommended. The challenge of increasing errors with increasing scan paths is overcome in the most recent systems. The combination of two different scanning principles in a single device seems to be beneficial.

Clinical performance of posterior monolithic zirconia implant-supported fixed dental prostheses with angulated screw channels: A 3-year prospective cohort study

Statement of problemThe choice of retention type of an implant-supported fixed dental prosthesis (FDP) becomes critical when the dental implant is not placed in a prosthetically ideal location. In recent years, computer-aided design and computer-aided manufacturing (CAD-CAM) technology has enabled the correction of the location of screw access hole depending on the clinical needs of the patient. However, how FPDs with angulated screw channels (ASCs) perform clinically is unclear. PurposeThe purpose of this prospective clinical study was to evaluate the mechanical complications and crestal bone loss (CBL) when posterior monolithic zirconia implant-supported FDPs with an ASC are used. Material and methodsParticipants (N=37) with a missing single posterior tooth or multiple teeth, sufficient bone height, and an implant site without infection were included. Each participant received parallel-walled implants (Nobel Parallel CC) of 7-, 8.5-, or 10-mm length by using a 1-stage approach. After 4 months of healing, a conventional impression was made, and a digital workflow was followed. Monolithic zirconia restorations (Katana ML) were milled, stained, and mechanically attached to a titanium base (NobelProcera ASC abutment). CBL was measured from radiographs at 6, 12, 24, and 36 months after the placement of the prosthesis. Implant and prosthetic characteristics including implant diameter, implant length, screw channel angle (angle≤15 degrees versus angle>16 degrees), prosthetic type (single crown versus multiple-unit FDP), and antagonist dentition (natural versus prosthesis) were also recorded. A generalized linear mixed model with a log link was estimated to assess the independent predictors of CBL among the angles of ASC-retained definitive restorations and the clinically relevant variables (α=.05). ResultsThirty-seven participants received 51 implants, and the median follow-up period was 30 months (interquartile range: 22-36). Two single-crown implants failed within the first 12 months of delivery. The implant and restoration survival rate was 96% at 36 months. Screw loosening was recorded in 2 study participants. After a follow-up of 36 months, the mean ±standard deviation CBL value was 0.15 ±0.14 mm with an increase over time (P<.001). The effect of the angle of ASC, implant diameter, implant length, prosthetic type, and antagonist on the CBL was not statistically significant (P>.05). ConclusionsCBL was not associated with the angle of ASC, implant diameter, implant length, prosthetic type, or antagonist when posterior monolithic zirconia implant-supported FDPs with ASCs were used. Screw loosening in 2 situations was the only mechanical complication during the first 3 years of service.

Accuracy of digital impressions versus conventional impressions for 2 implants: an in vitro study evaluating the effect of implant angulation

BackgroundAccurate implant impression is an essential requirement for the fabrication of implant prosthesis. This in vitro study evaluated the accuracy of digital impressions by intraoral scanner (IOS) systems in comparison to conventional impressions for recording the position of 2 parallel implants and 2 divergent implants.Materials and methodsIn vitro 3-unit prosthesis master models with 2 tissue level implants were fabricated; one model had parallel implants, and the other model had one 15° tilted implant. The conventional open-tray impressions were obtained with non-splinted (NSP) and splinted (SP) impression copings. Trios 4 (TS), Medit i500 (MT), and True Definition (TD) were used to make digital impressions with scan bodies. A total of 10 impressions were obtained with every technique. The virtual test images of the conventional and digital impressions were converted to 2 virtual implant images. For each group, trueness, precision, inter-implant distance deviation, and angle deviation were measured.ResultsThere was a general tendency for digital impressions to provide a more accurate outcome for trueness, precision, and angle deviation. The 2 conventional impressions showed similar accuracy, except for the angle deviation, where the NSP was significantly inferior than SP (p < 0.01) for the divergent implants model. The TD was generally the least accurate among all the IOS systems, especially for the inter-implant distance deviation (p < 0.05).ConclusionsWithin the limitations of the laboratory set-up of the present study and the limited clinical resemblance, the digital impressions appeared to have sufficient accuracy for 2 implants and were least affected by the presence of angle between implants. The most inferior outcome was observed for the NSP technique.

Comparison of marginal and internal fit of 5-unit zirconia fixed dental prostheses fabricated with CAD/CAM technology using direct and indirect digital scans

Background/purposeAdvancements in digital dentistry and the development of intraoral scanners (IOS) have provided clinicians with an accurate and efficient alternative to analog impressions. The aim of this study was to assess the accuracy of the marginal and internal fit of 5-unit monolithic zirconia fixed dental prostheses (FDPs) fabricated with CAD/CAM technology using direct and indirect digitalization methods.Material and methodsThree teeth in a maxillary typodont model were prepared to receive a 5-unit zirconia FDP. Six different groups were created according to the type of scanner (intraoral and extraoral) and the type of workflow. For direct workflow, the typodont was scanned with two different IOS (3Shape Trios 3 [3S-IOS] and Cerec Omnicam [C-IOS]). For indirect workflow, after conventional impressions were obtained, the impressions (IMP) were scanned with two different laboratory scanners (3S-IMP and C-IMP). After the impressions were poured, the stone (STN) casts were scanned with the same laboratory scanners (3S-STN and C-STN). Sixty 5-unit monolithic zirconia FDPs (10 in each group) were designed and milled. The marginal and internal fit was assessed.ResultsThe mean marginal gap values were 78.2±9 μm in the IOS group, 82.6± 9 μm in the IMP group, and 82.6±9 μm in the STN group, indicating no statistically significant differences among groups (p > 0.05). The mean axial gap values were 77.7 ± 10 μm in IOS group, 83.61 ± 15 μm in the IMP group, and 84.5±9 μm in the STN group, indicating no statistically significant differences among groups (p > 0.05).ConclusionThe marginal and internal fit of 5-unit monolithic zirconia FDPs fabricated with direct and indirect digital scans were similar. The smallest gap values were observed at the marginal region while the greatest gap values were detected at the occlusal region.

Substantial in-vitro and emerging clinical evidence supporting immediate dentin sealing.

The application of resin adhesive to freshly cut dentin after teeth preparation, the so-called immediate dentin sealing (IDS) has been suggested as an alternative to the delayed dentin sealing (DDS), a technique in which resin adhesive is applied just before final bonding of indirect restorations.The aim of this review is to demonstrate the evidence of the claimed advantages made by the proponents of IDS technique.The results of this review revealed substantial in-vitro evidence supporting the IDS benefits including improved bond strength, reduced dentin permeability, improved restorations’ adaptation, and increased fracture strength of the restorations. Clinical studies have shown that IDS improves survival of ceramic laminate veneers bonded to prepared teeth with increased exposure of dentin. Moreover, it has been shown that IDS reduces post-cementation hypersensitivity in full coverage restorations, which is characterized by exposure of a large number of dentinal tubules. The selection of filled resin adhesive that is capable of producing thick adhesive layer appears to contribute to the success of the technique. Furthermore, careful management of the oxygen inhibition layer before conventional impression making and proper cleaning of the residual temporary cement used with provisional restorations appears to affect the outcome of the restorations.

Digital verification and correction of digital intraoral scans for fixed implant rehabilitation of edentulous arches: A dental technique

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.

Use of aluminum foil to facilitate open-tray implant impressions

When the conventional impression technique is selected over digital optical scanning for multiple implants, the open tray impression technique has been recommended over the closed tray or transfer technique in situations where 4 or more implants are present.1,2 The open tray technique incorporates a large opening in the impression tray that accommodates the complete-arch impression copings.3 While loading the impression material into the tray, preventing the material from escaping through the opening is often difficult.

Flabby tissue– revisited: Case report

The success of complete denture is enhanced by achieving the objectives of impression making, that is preservation of underlying tissue, retention, stability, support and esthetics. Flabby tissue is a common clinical finding affecting the alveolar ridges of both mandibular or maxillary arches. The use of conventional impression techniques for recording flabby tissues can lead to unstable and unsatisfactory denture. But some modification in the impression techniques can record the flabby tissues in an undistorted form and thus help to fabricate a stable denture. The problem with conventional denture is rigidity of material which comes in contact with tissue surface, leading to uneven distribution of load. A liquid supported denture allows uniform stress distribution due to its flexible tissue surface and provides improved patient’s acceptance.

Randomized Clinical Trial comparing clinical adjustment times of CAD/CAM screw-retained posterior crowns on ti-base abutments created with digital or conventional impressions. One-year follow-up.

ObjectivesThe purpose of this randomized clinical trial was to compare the required time of potential clinical adjustments of posterior screw‐retained monolithic zirconia implant retained crowns based on intraoral optical scanning (IOS) or conventional impressions.Materials and methodsPatients with posterior tissue level implants (Straumann RN) replacing solitary teeth were recruited. Of all patients, impressions were taken with both an IOS (3M™ TDS) and a conventional (polyether) pick‐up impression. Randomization was performed after impression taking and patients were to receive either a crown based on the digital or the conventional impression. The time required for adjustments at placement was recorded. Additionally, restoration survival and mechanical complications with a follow‐up of one year were documented.ResultsThirty two patients with 45 implants were included: 23 restorations in the test (IOS) and 22 in the control (conventional) group. The average adjustment time was 3.35 min (SD ± 3.38, range: 0–11 min) for the digital versus 6.09 min (SD ± 4.63, range: 0–18 min) for the conventional impressions (p = .039). A proper fit (no adjustments required) was achieved 39,1% in the digital and 18,2% conventional group respectively. All 45 restorations could be placed within the two planned appointments and only two minor mechanical complications occurred during the first year of function.ConclusionsThe use of IOS resulted in shorter adjustment times at try‐in than conventional impressions for solitary CAD/CAM implant restorations. Screw‐retained solitary monolithic zirconia restorations on ti‐base abutments show low complication‐ and survival rates in the short term.

Influence of the Gingival Condition on the Performance of Different Gingival Displacement Methods—A Randomized Clinical Study

This randomized clinical study examined the influence of the gingival condition—healthy versus mild inflammation—on sulcus representation and possible gingival recession for two gingival displacement procedures prior to conventional impression making. The interventions double cord technique or a kaolin paste containing aluminum chloride were applied to 40 probands. The opposite quadrant served as intrapersonal reference (split-mouth design). Precision impressions were then made. Extraoral digitization of the plaster models resulting from the reference impression prior to gingival displacement, the intervention impression and control impressions were the basis for the computer-aided three-dimensional analysis. After six months, a mild artificial gingivitis was induced, and the contralateral quadrant (cross-over design) was examined for the intervention. The gingivitis deteriorated the sulcus representation for the double cord technique group but did not affect the paste technique group. The gingival condition had no influence on the marginal gingiva height changes. The minor extent of those changes, which were measured up to six months after intervention at the palatal study site, were not considered to be in the clinically relevant range for gingival recession. For healthy gingiva, the cord technique showed superior sulcus representation compared to the paste technique. This advantage was lost to a great extent under the conditions of mild gingivitis.

Comparison between stereophotogrammetric, digital, and conventional impression techniques in implant-supported fixed complete arch prostheses: An in vitro study

Statement of problemConventional 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. PurposeThe 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 methodsAn 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). ResultsSignificant 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<.001) and precision (P<.001). ConclusionsThe 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.

Patient-reported experiences and preferences with intraoral scanners: a systematic review.

Intraoral scanners have become an increasingly popular alternative to conventional impression methods. Although their accuracy and validity have been examined thoroughly, patient-reported information including experiences, preferences, and satisfaction has not yet been investigated in a systematic way. The objective of this systematic review is to investigate the available data and appraise the evidence on patient-reported experiences and preferences following impression taking with intraoral scanners. Unrestricted search of seven databases (Pubmed, CENTRAL, Cochrane reviews, Scopus, Web of Science, Clinical Trials, and ProQuest) and grey literature were conducted until October 2020. Detailed search strategies were developed for each database. Studies involving individuals of any gender or age, subjected to full arch impression taking with conventional and intraoral scanning methods were eligible for inclusion. Following the retrieval and selection of the studies, data extraction was performed. Risk of bias assessment was performed using the RoB 2 and ROBINS-I tools. From the initially identified records, nine studies [eight crossover (two of them randomized) and one parallel group] were eventually included in the present systematic review. Randomized studies were shown, overall, to have some concerns regarding bias, whereas the non-randomized studies were found to be at serious risk, mainly because of bias due to confounding. All studies demonstrated some benefit in favour of intraoral scanning compared with conventional techniques. More positive feelings were generally observed with the intraoral scanners regarding smell, taste, sound, vibration, nausea, and queasiness. Overall, comfort assessment mostly favoured digital methods. No differences were found concerning the level of anxiety between the two methods. Among the included studies, time perception was a parameter leading to contradictory results. These emerge due to the nature and characteristics of the information retrieved from the included studies. The validation of the instruments to capture patient-reported outcomes needs to be further elaborated. Intraoral scanners seem to be a promising new asset in the orthodontic office from the perspective of individuals' experiences and preferences. Nevertheless, to investigate patient-reported outcomes correctly, further high-quality studies are required in the future. Open Science Framework (https://osf.io/ayug2/).

CONVENTIONAL VS DIGITAL IMPRESSION TECHNIQUE FOR MANUFACTURING OF THREE-UNIT ZIRCONIA BRIDGES: CLINICAL TIME EFFICIENCY

Introduction: Taking an impression of the oral cavity, which accurately recreates the prosthetic field, the surrounding hard dental and soft tissues, is one of the main and most important stages in the process of making any fixed prosthetic restoration. In modern prosthetic dentistry, impressions taken with the help of polyether and vinyl polysiloxane impression materials are common. Digital impressions eliminate some of the steps of conventional impression techniques and save clinical time. Aim: The aim of this article is to compare the clinical time in digital and conventional impression techniques from a whole dental arch using a controlled clinical trial. Material and methods: The present study includes 36 patients from Varna who need prosthetic treatment with fixed 3-unit bridge construction. For all participants, the conventional impression technique was performed first and one week later - the digital one. All clinical manipulations related to the implementation of the two impression techniques were performed according to the instructions of the manufacturing companies by the same specialist dentist. Results: In all participants, the time required to perform the digital impression technique is significantly less than that of the conventional impression technique. Conclusion: The digital impression technique has proven to be more efficient in terms of clinical time required for its implementation than the conventional impression technique.

Clinical performance of intraoral digital impression for fixed prosthodontics: a Meta-analysis.

To analyze the clinical performance of the intraoral digital impression (IDI) in the fixed prosthodontics. Databases of Medline (Ovid), EMBASE, Cochrane Central Register of Controlled Trials, and CNKI were searched for randomized controlled trial (RCT) on the use of IDI in fixed prosthodontics until May 2020. Two reviewers independently screened literature, extracted data, and assessed the risk of bias of included studies. A Meta-analysis was conducted when available. Eleven RCTs involving 618 patients were included in this study. A total of 2 and 3 studies had low and high risks of bias, respectively, and other included studies had a medium risk of bias. Results illustrated that the IDI group could shorten the impression-taken time [SMD=-5.63, 95%CI (-11.25, -0.01), P=0.05] and improve the accuracy of the marginal fit [SMD=-0.53, 95%CI (-0.84, -0.22), P=0.000 7] compared with the conventional impression group. However, no significant difference was observed in the internal fit. Evidence indicated a good clinical performance of IDI for fixed prosthodontics. Notably, high-quality studies are expected to further support the conclusion.

Time Efficiency of Digitally and Conventionally Produced Single-Unit Restorations.

The purpose of this in vitro study was to compare the time efficiency of digital chairside and labside workflows with a conventional workflow for single-unit restorations. The time efficiency in this specific sense was defined as the time, which has to be spent in a dental office by a dental professional performing the relevant steps. A model with interchangeable teeth on position 36 was created. These teeth were differently prepared, responding to several clinical situations to perform single-unit restorations. Different manufacturing techniques were used: For the digital workflows, CEREC Omnicam (CER) and Trios 3 (TN/TI) were used. The conventional workflow, using a dual-arch tray impression technique, served as the control group. For the labside workflow (_L) and the conventional impression procedure (CO), the time necessary for the impressions and temporary restorations was recorded and served as operating time. The chairside workflow time was divided by the time for the entire workflow (_C) including scan, design, milling and finishing the milled restoration, and in the actual working time (_CW) leaving out the chairside milling of the restoration. Labside workflow time ranged from 9 min 27 s (CER_L) to 12 min 41 s (TI_L). Entire chairside time ranged from 43 min 35 s (CER_C) to 58 min 43 s (TI_C). Pure chairside working time ranged from 15 min 21 s (CER_CW) to 23 min 17 s (TI_CW). Conventional workflow time was 10 min 39 s (CO) on average. The digital labside workflow and the conventional workflow require a similar amount of time. The digital chairside workflow is more time consuming.