Impressed System Research Articles

Comparative analysis of 3D data accuracy of single tooth and multiple teeth captured by different intra oral digital impression systems

Comparative analysis of 3D data accuracy of single tooth and multiple teeth captured by different intra oral digital impression systems

DIGITAL RESTORATIVE PROCEDURES IN DENTISTRY

ABSTRACT The integration of digital technologies in restorative dentistry has significantly transformed clinical workflows, enhancing precision, efficiency, and patient outcomes. This article explores the pivotal role of various digital procedures in modern dental practices. Digital imaging techniques have revolutionized diagnostic capabilities, providing high-resolution, detailed visualizations essential for accurate treatment planning. Digital cone beam computed tomography (CBCT) has further refined diagnostic accuracy, enabling three-dimensional assessment of dental structures, which is crucial for implantology and complex restorative cases. Digital caries detection methods offer enhanced early detection of carious lesions, improving preventative care and treatment outcomes. The advent of digital impression systems has streamlined the process of capturing accurate dental impressions, reducing patient discomfort and enhancing the precision of prosthetic restorations. Additionally, digital design-manufacturing (CAD/CAM) systems have facilitated the rapid production of high-quality dental restorations, allowing for same-day procedures and greater customization. Collectively, these digital advancements are reshaping the landscape of restorative dentistry, offering unprecedented opportunities for improving the accuracy, efficiency, and overall success of dental restorations. This review aims to provide an in-depth understanding of the current state of digital restorative procedures in dentistry, with a focus on the latest technological advancements and their clinical implications. Keywords: Dentistry, digital technology, CAD/CAM, CBCT.

Sustainable freshwater/energy supply through geothermal-centered layout tailored with humidification-dehumidification desalination unit; Optimized by regression machine learning techniques

The application of regression machine learning techniques is crucial for the analysis and optimization of energy systems based on geothermal energy to produce freshwater, power, and heating. This study applied regression machine learning techniques to investigate and optimize a geothermal tri-generation energy system that combines double-flash geothermal energy, humidification-dehumidification desalination, and transcritical carbon dioxide Rankine cycle. The goal was to produce freshwater, power, and heating. The algorithms performed remarkably well, with R-squared values surpassing 96 %. It is worth mentioning that for specific parameters like freshwater production, heating capacity, and efficiency, the R-squared values exceeded an impressive 99 %. The optimum conditions include maintaining a Rankine pressure ratio of 3, a mass flow rate of 30 kg/s, a geothermal temperature of 220 °C, and a turbine pressure ratio of 2.2. By following these ideal parameters, it is possible to achieve the highest level of system performance. This will lead to the production of 7.88 kg/s of freshwater, the generation of 1283 kW of power, a heating capacity of 30.8 kg/s, and an impressive system efficiency of 24.98 %. The findings reveal that the integration of regression machine learning algorithms in geothermal energy systems for freshwater, power, and heating production holds great promise for a sustainable and efficient future.

Evaluation of the accuracy of different digital scanning systems and intraoral scanning strategies: An in vitro study

Abstract Introduction: Differentiating between the various available digital impression systems in terms of accuracy could help in determining the most appropriate system to be used. Aim: The purpose of this in vitro study was to evaluate the accuracy of four different intraoral scanners, along with different intraoral scanning strategies (IOSs), and using the conventional impression method. Materials and Methods: A model with prepared teeth was scanned with a laboratory scanner. Following that, the model was scanned using the following four intraoral scanners (IOSs): TRIOS, CEREC AC Omnicam, Medit i700, and iTero Element 2. Three scanning strategies were used with each scanner during the intraoral scanning (C-motion, zig-zag, and wiggling strategies). Each strategy was repeated eight times resulting in 96 scans, along with eight conventional impressions. All three-dimensional test models were compared with the master model using Geomagic Control X. The master model was trimmed to isolate the teeth and was superimposed with all 104 test models. The data was statistically analyzed using the nonparametrical Kruskal–Wallis test. Results: Statistically significant differences were found when comparing all groups (the four IOSs and the conventional impression method) in terms of trueness and precision (P < 0.001). For trueness, the i700 was the highest ranked IOS (35.68 ± 1.18 μm), excelling in all groups regardless of the strategy used. For precision results, the best IOS was the i700 (46.14 ± 1.43 μm) regardless of the strategy used. Conclusion: Medit’s i700 scanner exhibited better accuracy compared to the other three scanners. Meanwhile, the zig-zag strategy may provide the best scanning accuracy when used with the majority of the scanners.

Accuracy of Silicone Impressions and Stone Models Using Two Laboratory Scanners: A 3D Evaluation.

To evaluate the in vitro accuracy of impressions obtained with two silicone and corresponding stone models using two laboratory scanners. A master model with synthetic resin teeth with two single-unit crown preparations was created and scanned using a 12-megapixel scanner. Five conventional impressions of the physical model were prepared with different silicone impression systems (Zhermack and Coltene) using the double-mix technique and poured with gypsum. The impressions and stone models obtained were scanned using two extraoral scanning systems (Identica T500, Medit; S600 ARTI, Zirkonzahn). All best-fit superimpositions of the teeth areas were conducted between the master model and the scans of the impressions and models obtained with the two scanners. A P < .05 level was considered significant. The Identica T500 Medit scanner showed an accuracy of 102.34 (89.67, 115.01) μm for Coltene silicone and 79.51 (67.82, 91.21) μm for Zhermack silicone, while the S600 ARTI Zirkonzhan scanner presented 110.79 (98.24, 123.33) μm and 91.91 (81.29, 102.54) μm, respectively, with significant differences between scanners for Zhermack silicone (P = .008) and for the corresponding stone models (P = .002). Zhermack silicone presented overall discrepancies lower than Coltene silicone, with statistically significant differences in both scanners analyzed (P < .001; P = .017). However, the discrepancies found were within clinically acceptable values. With the Zirkonzahn scanner, discrepancies found in the Zhermack impressions were lower than in the corresponding stone models (P < .001). The direct digitization of silicone impressions with laboratory scanners presented comparable results to conventional techniques with stone models.

Порівняльна клінічна характеристика застосування цифрових і аналогових відбитків на якість непрямих реставрацій у пацієнтів із дефектами твердих тканин жувальних зубів у різні терміни спостереження

Introduction. Diseases of the hard tissues of the teeth are recognized as one of the most common dental diseases. These are mainly dental caries, congenital defects, fractures, fluorosis or acid erosion. Production of indirect restorations, which require taking impressions of the jaws, is one of the most common methods of restoring the hard tissues of the tooth when they are significantly destroyed. In today’s era of growing interest in digital dentistry, researchers are still undecided as to whether a digital impression provides the same accuracy as a conventional impression for making indirect restorations. Goal. To conduct a comparative characterization of the use of digital and analog impressions on the quality of indirect restorations in patients with defects of the hard tissues of chewing teeth at different follow-up periods. Research material and methods. The research involved 58 patients aged 25-60 years who applied to the Department of Stomatology of the P. L. Shupyk National Healthcare University of Ukraine for the purpose of orthopedic treatment of 79 defects of the hard tissues of the lateral teeth with destruction of 50-60% of their occlusal surface. In the course of orthopedic rehabilitation, patients were made indirect restorations - ceramic inlays using E. MAX Press material (Ivoclar Vivadent, Liechtenstein, Germany). The research group was further divided into 2 subgroups depending on the method of obtaining the impression. Subgroup A included patients who underwent digital scanning of a one-stage two-phase silicone impression, and subgroup B included patients who underwent impression removal using an intraoral digital impression system (TRIOS®, 3shape). The degree of destruction of the occlusal surface of chewing teeth and the choice of indirect restoration was carried out using the index of destruction of the occlusal surface of chewing teeth for I and II class according to Black (IROPZ). The clinical quality of indirect restorations was evaluated 1 week after the installation of the restoration and at long-term periods (12, 24, 36 months) using visual-instrumental control and according to the recommendations of the revised FDI criteria for the evaluation of direct and indirect dental restorations (2023). The presence of inflammatory changes in periodontal tissues was determined using the gingivitis index, the presence of dental plaque was determined using the OHI-S index (Green-Vermillion, 1964), the gingival sulcus bleeding index (SVI) was determined according to the Miihlemann and Son method before indirect restorations, during 1 week, 12 month and 24 month visits after cementation. Conclusion. Dental restorations made using digital impressions showed similar marginal discrepancy as restorations made using traditional impression methods (P&gt;0.05). Lateral masticatory restorations fabricated by intraoral scanning using CAD/ CAM technology have acceptable results in terms of periodontal tissue condition, color, contour, marginal adaptation, and occlusion. Although both direct and indirect digitization have been shown to be equally effective, digital impressions have shown advantages in patient acceptance of the procedure. They take less time for both the doctor and the patient and facilitate the digital workflow. No significant difference was found between conventional and digital displays in the accuracy of the 3D data sets. Key words: defects of hard dental tissues, indirect restorations, digital and traditional impression, inflammatory changes in periodontal tissues, marginal adaptation.

An intrusion detection system based on convolution neural network.

With the rapid extensive development of the Internet, users not only enjoy great convenience but also face numerous serious security problems. The increasing frequency of data breaches has made it clear that the network security situation is becoming increasingly urgent. In the realm of cybersecurity, intrusion detection plays a pivotal role in monitoring network attacks. However, the efficacy of existing solutions in detecting such intrusions remains suboptimal, perpetuating the security crisis. To address this challenge, we propose a sparse autoencoder-Bayesian optimization-convolutional neural network (SA-BO-CNN) system based on convolutional neural network (CNN). Firstly, to tackle the issue of data imbalance, we employ the SMOTE resampling function during system construction. Secondly, we enhance the system's feature extraction capabilities by incorporating SA. Finally, we leverage BO in conjunction with CNN to enhance system accuracy. Additionally, a multi-round iteration approach is adopted to further refine detection accuracy. Experimental findings demonstrate an impressive system accuracy of 98.36%. Comparative analyses underscore the superior detection rate of the SA-BO-CNN system.

Systematic Review of In Vitro Studies on Distortion Generated by Intraoral Scanning Systems for Oral Rehabilitations with More Than Three Implants

(1) Background: This systematic review intends to answer the following Patient–Intervention–Comparison–Outcome (PICO) question: Do digital impression systems generate significant errors during scanning in extensive implant restorative treatments? (2) Methods: Following the PRISMA protocol and according to predefined inclusion criteria, two trained investigators searched for relevant articles in the PubMed database and related sources using a standard keyword sequence. The investigators were responsible for selecting studies and performing quality analysis. (3) Results: From 78 titles, only 9 studies were selected. An analysis of registration distortion variations was conducted for each potential influencing factor in terms of accuracy: interimplant distance, implant angulation, scanner type, and scanning body type. The results showed repeatable differences in accuracy between types of scanning technologies and techniques, and a positive correlation between interimplant distance and the amplitude of deviations detected in comparative analysis, with the highest error levels in total edentulous arch recording. There was no consensus on the error level owing to implant angulation, and statistically significant differences were found between the types of scan bodies used. (4) Conclusions: Digital impression systems generate significant errors during scanning in extensive implant restorative treatments, influenced by scanning technology, interimplant distance, and scanning body type.

Investigation of single and multiple MPPT structures of solar PV-system under partial shading conditions considering direct duty-cycle controller

Partial shading of solar panels diminishes their operating efficiency and energy synthesized as it disrupts the uniform absorption of sunlight. To tackle the issue of partial shading in photovoltaic (PV) systems, this article puts forward a comprehensive control strategy that takes into account a range of contributing factors. The proposed control approach is based on using multi-string PV system configuration in place of a central-type PV inverter for all PV modules with a single DC-DC converter. This adaptation enhances overall efficiency across varying radiation levels. Also, the proposed technique minimizes the overall system cost by reducing the required sensors number by utilizing a radiation estimation strategy. The converter switching strategy is synthesized considering direct duty-cycle control method to establish the maximum power point (MPP) location on the P–V curve. The direct duty-cycle tracking approach simplifies the control system and improves the system’s response during sudden partial shading restrictions. To validate the effectiveness of the suggested MPPT method, two system configurations were constructed using MATLAB/SIMULINK software and assessed under various partial shading scenarios. Additionally, a multi-string system was subjected to real irradiance conditions. The sensor-less MPPT algorithm proposed achieved an impressive system efficiency of 99.81% with a peak-to-peak ripple voltage of 1.3V. This solution offers clear advantages over alternative approaches by reducing tracking time and enhancing system efficiency. The system findings undoubtedly support the theoretical scrutiny of the intended technique.

Erasure conversion in a high-fidelity Rydberg quantum simulator

Minimizing and understanding errors is critical for quantum science, both in noisy intermediate scale quantum (NISQ) devices1 and for the quest towards fault-tolerant quantum computation2,3. Rydberg arrays have emerged as a prominent platform in this context4 with impressive system sizes5,6 and proposals suggesting how error-correction thresholds could be significantly improved by detecting leakage errors with single-atom resolution7,8, a form of erasure error conversion9–12. However, two-qubit entanglement fidelities in Rydberg atom arrays13,14 have lagged behind competitors15,16 and this type of erasure conversion is yet to be realized for matter-based qubits in general. Here we demonstrate both erasure conversion and high-fidelity Bell state generation using a Rydberg quantum simulator5,6,17,18. When excising data with erasure errors observed via fast imaging of alkaline-earth atoms19–22, we achieve a Bell state fidelity of ge 0.997{1}_{-13}^{+10}, which improves to ge 0.998{5}_{-12}^{+7} when correcting for remaining state-preparation errors. We further apply erasure conversion in a quantum simulation experiment for quasi-adiabatic preparation of long-range order across a quantum phase transition, and reveal the otherwise hidden impact of these errors on the simulation outcome. Our work demonstrates the capability for Rydberg-based entanglement to reach fidelities in the 0.999 regime, with higher fidelities a question of technical improvements, and shows how erasure conversion can be utilized in NISQ devices. These techniques could be translated directly to quantum-error-correction codes with the addition of long-lived qubits7,22–24.

Effect of substrate adjacent to the scan region on the trueness of four intraoral scanners: An in vitro study

ObjectivesThe purpose of this in vitro study was to evaluate the trueness of four commercially available intraoral scanners (IOSs) on scanning different substrates that existed in the adjacent proximal contact area. MethodsFour IOSs (TRIOS 4, TRIOS 3, Primescan, Omnicam) were used for scanning the intact enamel surface of a molar tooth, and six restorative materials (zirconia, lithium disilicate glass-ceramic, composite resin, hybrid ceramic, feldspathic ceramic, metal) that were located at the adjacent proximal contact area of the same tooth. Reference scans were obtained using an extraoral scanner (inEos X5). A 3-dimensional analyzing software (Geomagic Control X) was used to compare the reference and tested scans. The two-way analysis of variance (ANOVA) followed by Bonferroni correction was performed for statistical analyses (α=0.05). ResultsTRIOS 3 and TRIOS 4 showed higher trueness than Primescan, and Primescan showed higher trueness than Omnicam (p<0.001), while there were no differences between TRIOS 3 and TRIOS 4. Metal showed significantly higher Root Mean Square values (0.273 ± 0.24 mm) than other substrates. No difference was found between the scanners’ zirconia, lithium disilicate glass-ceramic, composite, and feldspathic ceramic scans (p > 0.05). For the metal, TRIOS 3 and TRIOS 4 showed higher trueness than Primescan and Omnicam, while Omnicam showed lower trueness among all scanners. For the hybrid ceramic, TRIOS 3 showed higher trueness than Omnicam (p<0.001). For the enamel, TRIOS 3 showed higher trueness than Primescan and Omnicam (p<0.001). ConclusionsThe trueness of IOSs can be affected by the substrates that exist in the proximal contact area. Amongst all, the metal substrate affected most the trueness of the IOSs. Clinical SignificanceThe clinician should decide on the impression system, taking into account that the IOS and the surfaces to be scanned affect the trueness of the digital data. The deviation of the digital impression would be high in the presence of a metal restoration on the adjacent proximal surface.

Randomized Clinical Trial for Evaluation of Efficacy of a Tissue-displacing Impression System in Comparison with Conventionally Used Gingival Displacement Materials in Young Adult Population

Randomized Clinical Trial for Evaluation of Efficacy of a Tissue-displacing Impression System in Comparison with Conventionally Used Gingival Displacement Materials in Young Adult Population

Curated Decay

Nova Scotians understand economic hardships at both the personal and community levels. This is especially true for the residents of Pictou County. With the eclipse of coal, steel, and heavy manufacturing, successive governments looked to tourism to augment an eroding economic base and to commemorate the working lives of Nova Scotians. This article offers an analysis of the initial decision to construct and maintain the Museum of Industry in a region of the province subjected to sequential phases of deindustrialization. The venture, officially opened to regular attendance in 1995, is the largest facility in the province’s impressive system of 28 regional museums. The creation of the museum, however, was fraught with uncertainty and narrowly avoided financial collapse and plans to disperse the collection of artifacts. The project was subsequently left straddling an uneasy divide between celebrating industrial heritage and tempering controversies of economic and environmental development. Despite Nova Scotia’s proud heritage of worker resistance and union activism, visitors may exit the museum with the ambiguous message that while working lives are often harsh and riven with uncertainty, optimism for the future must prevail. The implication is that the appropriate response is selective anodyne forms of nostalgia, even resignation, but not resentment of the human and environmental costs of deindustrialization.

Evaluation of Diverse Digital Impression Systems on the Three-Dimensional (3D) Fit of All-Ceram CAD/CAM Crowns

Aim: This in vitro study's objective is to assess the Three-Dimensional (3D) internal and marginal fit of all-ceramic CAD/CAD crowns produced by various digital impression systems. Materials and Methods: Three different intraoral scanners: CEREC Primescan (Dentsply Sirona), Trios 4 (3Shape), and CS 3700 (Carestream Dental) were used to digitally scan an experimental model based on ISO 12836:2015. The CAD/CAM processes suggested by each system (CEREC Primescan, Trios 4 and CS 3700; N = 15) were used to create ceramic crowns. A 3D inspection program (Geomagic control X) was used to measure The Three-Dimensional (3D) marginal and internal fit of each ceramic crown. By using the Kruskal-Wallis test, differences between the systems and various measurements were assessed. Pairwise comparisons were used to validate statistically significant differences (= 0.05). Results: Occlusal gaps in the CEREC Primescan, Trios 4 and CS 3700 groups were 113.0, 161.3, and 438.2 µm, respectively (p&lt;0.001). The axial gaps were 83.4, 78.0, and 107.9 µm, respectively. While the marginal gaps were 77.8, 99.3, and 60.6 µm, respectively, finally the whole gaps were 85.9, 107.3, and 214.0 µm, respectively. The marginal gap sizes with the Trios 4 system were considerably different from those with the other two systems. The CEREC Primescan system proved no distinctive variations between the four measured regions. However, the Trios 4 and CS 3700 systems did show a statistically significant difference (p&lt;0.05). Conclusion: The marginal gap, which is the most essential aspect in the marginal and internal fit of fixed prostheses, was recorded to be below 100 µm in all three systems, leading to the conclusion that all three systems are capable of producing clinically acceptable prostheses.

DIGITAL IMPRESSIONS- PAVING PATH TOWARDS GREEN DENTISTRY: A REVIEW

The concept of making an impression has undergone a paradigm shift as a result of the development of highly accurate and novel impression systems based on new technologies.1 Digital intraoral imaging represents a cutting-edge technique that allows the dentist to create a virtual computer-generated replica of the hard and soft tissues. Digital impression-making techniques are highly accurate, and they will undoubtedly lessen the need for traditional techniques in the near future. The information is stored in specialized software to be utilized in the manufacture of appliances, positive replicas, or other restorations. Additionally, this makes it possible to access data at any moment for further research and follow-ups. The future of digital dentistry is bright, but there is still work to be done to make sure that the technology delivers significant benefits to practitioners and patients in terms of therapeutic outcomes, regardless of how beautiful the process itself maybe. At the same time, it must be kept affordable and investments should yield a solid return.1

Optical Impression Accuracy of Preparations for Fixed Prosthodontics: A Systematic Review.

This systematic review aimed to evaluate the accuracy of different optical impressions of tooth preparations. An electronic search in PubMed, Web of Science, Scopus, Medline Complete, and ScienceDirect was performed to identify articles comparing the accuracy of different optical impressions (OI) published up to the 1st of March 2022. The inclusion criteria enclosed the accuracy of optical impressions acquired for tooth-supported fixed prosthodontics. Exclusion criteria were defined as studies focused on orthodontic impressions and implant-supported restorations. This review was registered to Prospero; CRD42021287758. Eleven included studies had in vitro design and a low risk of bias. Considering scanned objects, 5 studies evaluated the accuracy based on a single preparation, 2 studies evaluated the accuracy of OIs based on fixed partial denture (FPD) restoration, 3 studies included both single preparation and preparations to receive FPD restorations, and 1 article included a fullarch scan. Mean values of the trueness and precision of OI systems varied according to methodological differences. Optical impression has certain advantages. However, stating a particular optical impression system as the most accurate or superior to conventional impression is not feasible because of the heterogeneity of the accuracy results presented in this systematic review.

Comparison of Milled Full-Arch Implant-Supported Frameworks Realised with a Full Digital Workflow or from Conventional Impression: A Clinical Study.

The aim of the present study was to investigate the accuracy of a new digital impression system, comparing it to the plaster impression technique in the realization of full-arch implant-supported metal frameworks. We took 11 scans (8 of the upper maxilla and 3 of the lower jaw) on a sample of nine patients previously rehabilitated with fixed full-arch screw-retained prostheses following the Columbus Bridge Protocol (CBP) with four to six implants (total: 51) since at least 4 months. Two impressions were taken for each dental arch: one analogic plaster impression using pick-up copings and an open tray technique and a second one using an intra-oral scanner. Two milled metal substructures were realised. The precision and passivity of the substructures were clinically analysed through the Sheffield test and endo-oral radiographs. Laboratory scans of the plaster casts obtained from an intra-oral scanner (IOS) and of the plaster casts obtained from traditional impression were compared with the intraoral scans following Hausdorff's method and an industrial digital method of optical detection to measure discrepancies. A Mann-Whitney test was performed in order to investigate average distances between surfaces after the superposition. The Sheffield test demonstrated an excellent passivity of the frameworks obtained through both the digital and the analogic method. In 81.81% of cases (n = 9) both substructures were found to have a perfect fit with excellent passivity, while in 18.18% (n = 2) of cases the substructures were found to have a very slight discrepancy. From the radiographic examination, no gaps between the frameworks and the implant heads or multiunit abutments were observed, with 100% accuracy. By superimposing digital files of scans according to Hausdorff's method, a statistically significant discrepancy (p = 0.006) was found between the digital scans and the digital models obtained from plaster impressions. Three-dimensional optical detection found a mean discrepancy of 0.11 mm between the analogic cast and the cast derived from the digital impression. The present study clinically demonstrates that milled implant-supported full-arch frameworks obtained through a digital scan and the herein described technique have an accuracy comparable to those obtained with traditional plaster impression.

COVID-19 infection rates and mitigation strategies in orthodontic practices

BackgroundCOVID-19 has impacted and increased risks for all populations, including orthodontic patients and providers. It also changes the practice management and infection control landscape in the practices. This study aimed to investigate the COVID-19 infection and vaccination status of orthodontic providers and mitigation approaches in orthodontic practices in the United States during 2021.MethodsA validated 50-question research electronic data capture (REDCap) browser-based questionnaire was distributed to 12,393 orthodontists and pediatric dentists who reported actively providing orthodontic treatment. Questions were designed to collect demographic data of respondents, evaluate the COVID-19 mitigation approaches, and evaluate the history of COVID-19 infection and vaccination status of the orthodontic providers. Associations of demographic and the COVID-19 mitigation approaches were assessed using chi-square tests at the significance level of 0.05.ResultsFour hundred fifty-seven returned the survey (response rate 3.69%) for analysis. Most respondents were vaccinated, and increased infection control measures in response to the pandemic. Half of the respondents practiced teledentistry and switched to digital impression systems. Two-thirds reported difficulties in attaining PPEs due to the increased cost and scarcity of PPEs. About 6% of respondents reported a history of COVID-19 infection, and 68.9% of their staff had COVID-19 infection. Statistically significant associations were found between increased practice experience with difficulties in acquiring PPE (p = .010). There were no significant associations between races of respondents, geographic location, and years of practicing when cross-tabulated with vaccination status or COVID-19 infection rate (p > .05).ConclusionIncreased infection control strategies were employed in almost all orthodontic practices in addition to existing universal precaution. Most of the orthodontic providers and their staff members were vaccinated. While staff’s infection rates were an issue, doctors’ infection rates remained low.

Accuracy of single-unit ceramic crown fabrication after digital versus conventional impressions: A systematic review and meta-analysis.

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

Effect of different impression techniques on marginal fit of restoration - An In Vitro study.

Impression making is one such important clinical step, which is critical in the accurate fitting of resulting prostheses. Impression making itself depends on the type of material and the impression technique used to record the details. Various combinations of material and the technique have been described in the literature. To evaluate the effect of three different impression techniques on the marginal fit of computer-aided designed/computer-aided manufactured (CAD/CAM) single unit composite fixed dental prostheses (FDP), different consistencies of addition silicone impression material and different tray design were utilized. Impression of prepared tooth on typodont was made using Matrix impression system, two-step putty wash technique, and individual tooth tray technique. Prosthesis was fabricated using CAD/CAM technology and marginal accuracy was evaluated using scanning electron microscopy (SEM). In the present study, the matrix impression system resulted in less microgap in both mid-buccal and mid-mesial region, whereas putty wash technique showed very high standard deviation in the interproximal region. Matrix impression system had the best results at both mid-buccal and mid-mesial position with least marginal discrepancy. The findings of this study could be used by clinicians to help them choose the viscosity of polyvinylsiloxane material and impression techniques for FDP that will result in high-accuracy impressions and well-fitting prostheses.