Impressed System Research Articles

INTRAORAL SCANNERS: A NARRATIVE REVIEW

Objectives: Accurate impressions are essential in fabricating dental restorations and fixed dental prostheses. During the last decade, digital impression systems have improved substantially. The objective of this narrative review is to discuss the recent research on intraoral scanners with regards to it’s technology, accuracy and applications for fabrication of dental restorations and fixed dental prostheses. Materials and methods: A search strategy was performed in MEDLINE/PubMed, Scopus and Google Scholar with keywords - intraoral scanners, accuracy, applications, dentistry. Results: 395 articles were retrieved. After hand search a total of 415 articles were identified. Ultimately, 30 articles were selected and summarized and discussed as they met the selection criteria. Conclusion: Within the scope of this review, reported literature showed that digital intra-oral impressions have presented an achievement in the dental market as they reduce time required and simplify the clinical procedures with better communication with the technician and the patient. The current intraoral scanners (IOS) are sufficiently accurate for capturing impressions for fabrication of prosthetic restorations (inlays/onlays, copings and frameworks, single crowns and fixed partial dentures) on both natural teeth and implants; in addition, they can be used for smile design, and to fabricate posts and cores, removable partial prostheses, obturators, orthodontic aligners and custom made devices. The use of IOS in long-span restorations with natural teeth or implants is still a challenge.

3D Digital Impression Systems Compared with Traditional Techniques in Dentistry: A Recent Data Systematic Review.

The advent of new technologies in the field of medicine and dentistry is giving improvements that lead the clinicians to have materials and procedures able to improve patients’ quality of life. In dentistry, the last digital techniques offer a fully digital computerized workflow that does not include the standard multiple traditional phases. The purpose of this study is to evaluate all clinical trials and clinical randomized trials related to the digital or dental impression technique in prosthetic dentistry trying to give the readers global information about advantages and disadvantages of each procedure. Data collection was conducted in the main scientific search engines, including articles from the last 10 years, in order to obtain results that do not concern obsolete impression techniques. Elsevier, Pubmed and Embase have been screened as sources for performing the research. The results data demonstrated how the working time appears to be improved with digital workflow, but without a significant result (P = 0.72596). The papers have been selected following the Population Intervention Comparison Outcome (PICO) question, which is related to the progress on dental impression materials and technique. The comparison between dentists or practitioners with respect to classic impression procedures, and students open to new device and digital techniques seem to be the key factor on the final impression technique choice. Surely, digital techniques will end up supplanting the analogical ones altogether, improving the quality of oral rehabilitations, the economics of dental practice and also the perception by our patients.

Accuracy of Intraoral Digital Impression Systems in Restorative Dentistry: A Review of the Literature

Digital impresión allows the dentist to directly obtain the data of the dental pieces that neet to be rehabilitated, giving it greater precisión and thus eliminating the impression and manufacturing of the dental model, error-sensitive aspects of the clinical phase. The aim of this review is to identify the most accurate intraoral digital impression system and identifiy the factors that affect the accuracy in the restorative dentistry. Through a bibliographic review with search in PubMed and Embase databases, 153 articles were obtained, after qualitative evaluation they were included in the revisión 14 that met the inclusion and exclusion criteria. It was determined that the experience of the dentist, the convergence in the dental preparation and the cervical termination are decisive at the accuracy of the digital impression, however, the use or not of dust is not relevant. The Lava C.O.S., iTero and True definition are the most accurate always depending on the type of rehabilitation to be performed.

Do Type and Shape of Scan Bodies Affect Accuracy and Time of Digital Implant Impressions?

Reports concerning the accuracy of intraoral digital impression systems are limited. This study aimed to assess the effects of scan body types and shapes on digital impression accuracy and scanning time in all-on-four restorations. This in vitro study was conducted with two acrylic maxillary models. Two implant systems with different connection types (internal trilobe and external hexagon connection) were inserted according to the all-on-four design. Scanning was performed using Doowon, NT-Trading, and DESS scan bodies. Changes in implants' positions (ΔR) and angulation (ΔA), and the implants' distance from the reference pin (ΔD) compared with the actual model were determined. Scanning times were also measured and compared. The effects of implant connections and scan bodies on ΔR and ΔA were significant (p ⟨0.05). Implant angulation could also affect ΔA (p=0.019). ΔD was only affected by scan body (p ⟨0.001). The three scan bodies were significantly different in terms of scanning time (p=0.001). The results showed that scan body type and shape, and implant connection and angulation could affect digital impression accuracy in all-on-four restorations. For both internal and external connections, the NT-Trading and DESS scan bodies had the shortest and longest scanning times, respectively.

Computerized optical impression making of edentulous jaws – An in vivo feasibility study

PurposeWithin the specialty of prosthodontics, oral impressions are ubiquitous tools utilized to transfer intraoral characteristics such as teeth, implants, and soft tissue into a physical state (stone cast) that is processable in a laboratory setting for the fabrication of dental restorations. In recent years, optical impression systems have become ubiquitous in clinical practice replacing the conventional method of impression making. The purpose of the present study was to evaluate the feasibility and accuracy of computerized optical impression making of edentulous jaws in an in vivo setting. Methods29 edentulous patients (27 maxillae and five mandibles) underwent conventional impressions as well as computerized optical impressions. The conventional impressions and the resulting stone casts were digitized and superimposed over the computerized/digitized optical impressions in order to obtain information on differences between the two datasets. Statistical analyses were performed to identify relevant deviations. ResultsThe overall mean difference between the stone cast, digital scans and the computerized optical scans were 336.7 ± 105.0 µm (n = 32), 363.7 ± 143.1 µm (n = 24), and 272.1 ± 168.5 µm (n = 29), respectively. The visual evaluations revealed highest deviations (≥ 500 µm) in the areas of the soft palate, the sublingual areas, and the vestibule (peripheral seal zone). ConclusionsWithin the limitations of the present study, the investigated scanners were not able currently to fully replace a conventional impression for the fabrication of a complete denture.

Evaluation of the effect of different digital impression systems on the impression accuracy of dental implant

Evaluation of the effect of different digital impression systems on the impression accuracy of dental implant

Electronic Device for Cathodic Protection and Measure of Corrosion in Situ

In this paper research was on the simulation of a prototype for corrosion control by means of cathodic protection with a current impressed system (CPCI) was carried out, whose electric supply is by a solar panel, and programmed in Arduino, for the electronic circuit LM324 operational amplifiers were used to measure the potential and the corrosion rate by the apply of the polarization resistance technique. Before developing the physical circuit, the elements in the Proteus 8 simulator were tested. For electrochemical analysis, seawater was used as electrolyte, Ag/AgCl electrode was used as reference electrode (RE), the working electrode (WE) was a 1018 steel plate, for the measurement of open circuit potential the Arduino Mega 2560 plate was used, using its digital outputs to sense the voltage of the 1018 steel plate and its PWM outputs to program the ramp signal. These values were made based on the ASTM G-59 standard.

Dimensional Accuracy of Polyvinyl Siloxane Impression Materials Considering Impression Techniques– A Literature Review

Objectives Impression accuracy is the main determinant of the fit, form and function of prosthetic restorations. Polyvinyl siloxane (PVS) is the material of choice in most clinical situations. The purpose of this paper is to provide an up-to-date review of scientific articles which discuss the dimensional accuracy of PVS impression material using various impression techniques, tray types and spacers. Besides, the procedure, advantages and disadvantages of commonly used impression techniques, technique modifications and innovations are also reviewed.Method An electronic search of scientific papers from 1990 to 2018 was carried out using MEDLINE and Google Scholar databases using the search terms “accuracy and polyvinyl siloxane and impression technique” and “accuracy and addition silicone and impression technique”.Results Searching the key words yielded a total of 312 articles. By application of inclusion and exclusion criteria, the obtained results were further reduced to 35 citations.Conclusion Impression technique is a critical variable in the accuracy of PVS impressions. Dual-phase 2-step technique with 1 to 2 mm space for the light body is proven to be highly accurate and is still considered as the standard technique. The use of 2-step technique without providing a space for the wash material is rejected by the literature. Triple-phase 2-step techniques including “matrix impression system” have also functioned well and even superior to traditional dual-phase 2-step technique. Papers suggest that custom trays do not significantly improve the accuracy of impressions and rigid stock trays are suitable alternatives

Effect of coded healing abutment height and position on the trueness of digital intraoral implant scans

Statement of problemInformation regarding the effect of the height and position of a coded healing abutment (CHA) on the trueness of intraoral digital scans is lacking. PurposeThe purpose of this in vitro study was to investigate the effect of the height and position of a scannable CHA on the trueness (distance and angular deviations) of intraoral digital scans. Material and methodsScannable CHAs (BellaTek Encode Impression system; Zimmer Biomet Dental) were used in 2 different height pairs (3 mm and 8 mm) on 2 implants at mandibular left second and first molar positions. Each pair was scanned 10 times by using 1 intraoral scanner (TRIOS; 3Shape) by 1 operator to generate a total of 20 intraoral scan files. Master standard tessellation language (STL) files were created for both 3-mm and 8-mm CHA pairs by using a structured blue light scanner (COMET L3D 8M 150 Precision Structured Blue Light Scanner; ZEISS). These master STL files were imported into a software program (PolyWorks Inspector) and were used as the reference for the inspection. Scans obtained by using the intraoral scanner were aligned to the reference scan by using a best-fit alignment to measure the distance and angular deviations. Two-way repeated-measures ANOVA was used to analyze the data, and the Tukey-Kramer test was used to determine significant differences among groups (α=.05). ResultsThe CHA position had a significant effect on distance deviation (P<.001). However, no significant effect of CHA height on distance deviation was found. The interaction between CHA height and position had a significant effect on the angular deviation (P=.041). The 3-mm posterior CHA (P=.026) and 8-mm anterior CHA (P=.039) had significantly lower angular deviations than the 8-mm posterior CHA. ConclusionsThe distance deviation of CHA was significantly influenced by position. CHAs in the anterior had lower distance deviations for both 3 mm and 8 mm. The effect of CHA height on distance deviation was found to be small and was affected by the location of the CHA. Height affected angular deviation depending on the position of the CHA. Both 3-mm posterior and 8-mm anterior CHAs showed lower angular deviations than the 8-mm posterior CHA.

Simulation of Linear Anode-Pipe Cathodic Protection System: Primary and Secondary Current and Potential Distribution Analysis

Nowadays, the use of a linear anode in an impressed current cathodic protection system is one of the most interesting technical solutions to guarantee the corrosion protection of short pipe in comm...

Hermann Cohen w drodze ku „Religii rozumu ze źródeł judaizmu”. Przystanek Breslau

Hermann Cohen on the Way to „Religion of Reason: Out of the Sources of Judaism” Breslau Stop On the way leading Hermann Cohen from his family Coswig to Marburg and — later — to Berlin, from a Jewish province to a multicultural metropolis, Breslau is a special point. The future philosopher came here in 1857, hoping for the future of fice of the rabbi, to begin studies at the newly established Jewish Theological Seminary. Here too, four years later, he enrolled at the university, opening up the prospect of an academic career. A special point, which allowed him to create in the next years an “impressive system” which is a bold attempt to present German and Judaism as identical or connected. Jewish and religious content was a permanent and constant component of Cohen’s works, and Religion of Reason and System of Philosophy form a whole. Already before the creation of works devoted to Kant, some features of Cohen’s philosophy of religion are revealed, which originated in his studies at Breslau, one of the most important Haskalah centers in the middle of the 19th century. Cohen found there an atmosphere conduciveto the later shaping of the science of the universal religion of reason. After many years, Cohen assessed the Jewish Theological Seminary as “the most important educational institution [of his] youth.”

Evaluation of the trueness and precision of complete arch digital impressions on a human maxilla using seven different intraoral digital impression systems and a laboratory scanner.

An impression accuracy study using a cadaver maxilla was performed using both prepared and intact teeth as well as palatal tissue. Three crown preparations were performed on a cadaver maxilla. Seven different digital impression systems along with polyvinylsiloxane impressions were used to create digital models of the maxilla. Three-dimensional (3D) files of the experimental models were compared to a master model. The 3D files were overlaid and analyzed using a comparison software to create color coded figures that were measured for deviations between the master and experimental models. For scanning tooth structure, only the Planscan was significantly less accurate than the rest of impression techniques. No significant differences in accuracy were found between models created using digital impressions and those created from traditional vinyl polysiloxane impressions with cross arch deviations ranging from 18 to 39 μm for each. Impressions taken using all digital impression systems, save for the Planscan, were able to accurately replicate the tissues of a complete arch human maxilla. Studies examining accuracy of digital impression systems have generally been performed on materials other than dental tissues. Optically, materials such as plastic and metal have properties different from enamel and dentin. This study evaluates accuracy of digital impression systems on human dentin, enamel, and soft tissues.

Effect of scan substrates on accuracy of 7 intraoral digital impression systems using human maxilla model.

This study aimed to determine how the accuracy of digital impressions was affected by four common dental substrates using seven prevalent IOS systems to scan the complete arch of a human maxilla. The Department of Oral Rehabilitation at the Medical University of South Carolina. A single cadaver maxilla. Seven digital intraoral impression systems were used to scan a freshly harvested human maxilla. The maxilla contained several teeth restored with amalgam and composite, as well as unrestored teeth characterized by enamel. Also, three teeth were prepared for full coverage restorations to expose natural dentin. An industrial grade metrology software program that allowed 3D overlay and dimensional computation compared deviations of the complete arch and its substrates on the test model from the reference model. Substrates were significantly different from each other when considering scan data as a whole, as well as when comparing IOS devices individually. Only PlanScan failed to reveal trueness differences between the different substrates, while only Emerald revealed precision differences between the substrates. Substrate type does impact the overall accuracy of intraoral scans with dentin being the most accurate and enamel being the least accurate. The four substrates scanned impacted the trueness of all IOS devices.

Learning like a human

Neuroscience The deep network systems underlying artificial intelligence (AI) reflect a highly simplified version of our current understanding of human brain circuitry and the hierarchy of cellular connections. This has allowed the generation of impressive AI systems, but a major challenge remains for human-like learning and perception. In a Perspective, Ullman discusses whether more lessons can be applied from our understanding of how the brain works to improve AI. Science , this issue p. [692][1] [1]: /lookup/doi/10.1126/science.aau6595

An Efficient One‐Pot Synthesis of 7,7‐Dimethyl‐2‐(2‐oxo‐2H‐chromen‐3‐yl)‐4‐aryl‐7,8‐dihydroquinolin‐5(6H)‐one Derivatives Using Chitosan–SO3H as Biodegradable Organocatalyst

Chitosan sulfonic acid (CS–SO3H), a biodegradable green catalyst, was found to be an impressive system for one‐pot four‐component reaction of different aromatic aldehydes, 3‐acetylcoumarin, dimedone, and ammonium acetate leading to 7,7‐dimethyl‐2‐(2‐oxo‐2H‐chromen‐3‐yl)‐4‐aryl‐7,8‐dihydroquinolin‐5(6H)‐one under solvent‐free condition. This methodology produces diverse superiorities such as operational simplicity, short reaction time, and high yield. Further, the catalyst can be reused for four times without any noticeable decrease in the catalytic activity.

Monitoring and testing corrosion and responsive behaviour in galvanic systems.

Testing methods for corrosion prevention in structures have, historically, been based on the steel polarising from the protective current. Modern galvanic systems aim to protect the steel by restoring the protective alkaline environment, rather than through polarisation. Since 2012 standard guidelines allow for alternative testing to be used [1]. Scientific testing of galvanic systems will be discussed looking at the nature of constant potential galvanic systems and comparing them to the traditional constant current impressed systems, looking in particular at unique anode behaviours such as low median current during times of low corrosion risk and responsive behaviour during corrosion hazards. This work lays out a protocol for the evaluation and testing of existing galvanic corrosion protection (CP) systems in reinforced concrete through the lens of various real-world studies. Data taken from over a decade of monitored systems are used to support the protocol. Modern testing strategies such as 2-dimensional relative potential mapping and corrosion rate monitoring will measure the steel's corrosion. Galvanic currents rise and fall with corrosion risk providing protection while ensuring a long life to the design.

The Ecology of Travel on the Great Lakes Frontier: Native Knowledge, European Dependence, and the Environmental Specifics of Contact

The Michigan Historical Review 45:1 (Spring 2019): 1-26©2019 Central Michigan University. ISSN 0890-1686 All Rights Reserved 2018 Graduate Student Essay Prize Winner The Ecology of Travel on the Great Lakes Frontier: Native Knowledge, European Dependence, and the Environmental Specifics of Contact By John William Nelson Returning from what the French called le Pays d’en Haut, the upper country of the Great Lakes watershed, Antoine de la Mothe, Sieur de Cadillac reflected on his time stationed near Michilimackinac. Cadillac served as the commander of Fort du Baude from 1694 to 1696 and, as he laid plans for his own colony at Detroit, he wrote to stress the geographic potential of the Great Lakes. He proclaimed the region “the finest lands ever seen,” since they were “broken by an infinitude of large and beautiful rivers which replenish the lakes.”1 Cadillac made sure to emphasize the distinctiveness of the Great Lakes themselves. They were no ordinary bodies of water, and he even pondered “why the name lakes has been given to these watery deeps of such vast extent.”2 Such expanses of open water were nothing like Europeans had ever seen, and they remain unique in world geography. Cadillac described the waterborne potential that such distinct geography might hold. He observed the region’s native peoples plying the waters of the lakes as flotillas of Potawatomi, Odawa, and Ojibwe canoes passed along the Straits of Michilimackinac. Witnessing such waterborne mobility, he reported that “nothing is easier than to find a communication between the two seas [the Gulf of Saint Lawrence and the Gulf of Mexico] by way of the lakes and rivers traversing the backcountry for 1200 or 1500 leagues.”3 Cadillac dreamed of an interior maritime network connecting French interests 1 Lamothe Cadillac, “The Memoir of Lamothe Cadillac,” in Milo Milton Quaife, ed., The Western Country in the 17th Century: The Memoirs of Lamothe Cadillac and Pierre Liette (Chicago: Lakeside Press, 1947), 77. 2 Ibid., 5. 3 Ibid., 74. 2 The Michigan Historical Review from the Saint Lawrence Valley to the lower Mississippi and French Caribbean, all linked by the freshwaters of the Great Lakes.4 While Cadillac recognized the geopolitical significance of these inland waterways, he underplayed the complicated methods for navigating them. Cadillac alluded to the two overland connections necessary to link the Great Lakes with the Saint Lawrence and Mississippi River valleys at Niagara and Chicago, but failed to mention the many portage paths, created and used by American Indians in the centuries before European contact, that served to knit the interior maritime region together. Europeans venturing into the Great Lakes necessarily relied on indigenous geographic knowledge to navigate between waterways over these portages. Likewise, newcomers adopted indigenous birchbark canoes, constructed from materials of the surrounding woodlands, as the best vessels for traversing the lakes and rivers. Cadillac gives little mention of such particulars, let alone how French fur traders or missionaries journeying through the region might feed themselves and survive the seasonal variations of the Great Lakes climate. European travelers, if they were to navigate the Great Lakes successfully, had to master such specific environmental and geographic knowledge, or rely on those who already possessed it: the region’s native peoples. In the distinct freshwater ecosystems of the Great Lakes, indigenous peoples had crafted an effective method of waterborne travel that relied on the marine geography and local ecology. This worked, as one modern Huron scholar has put it, as an interlinked “chain of relationships” wherein native peoples of the region orchestrated the cultivation and use of an array of wild plant and animal species for their own benefit. This multi-species web of relationships—an ecology crafted by Native Americans in the precontact era—allowed for an impressive system of 4 The Laurentian Great Lakes Basin is indeed distinct, both in terms of scale—the lakes span 95,160 square miles of open water—but also in potability—the watershed holds roughly 21% of the world’s freshwater drinking supply. Gales on the lakes produce winds nearing hurricane speed and waves topping 38 feet. Thus, the lakes offer both the benefits of interior freshwater access and sustenance while also posing the...

Comparative evaluation of three gingival displacement materials for efficacy in tissue management and dimensional accuracy.

Aim:Displacement of gingiva is essential for obtaining accurate impressions for the fabrication of fixed prostheses, particularly when the finish line is at or within the gingival sulcus. Various newer impression materials have been introduced to achieve gingival displacement while recording the impressions. A comparative evaluation of these new gingival displacement materials was deemed necessary for efficacy in tissue management and dimensional accuracy.Materials and Methods:Ten individuals were selected according to the inclusion and exclusion criteria for gingival displacement using retraction cord impregnated with aluminum chloride and two polyvinyl siloxane impression materials (Aquasil and NoCord VPS impression system) according to Latin block design. Intraoral scanner and Vernier caliper were used to study and compare the dimensional accuracy of each die obtained following which the dies were sectioned and evaluated under optical microscope with image analyzer to measure the amount of gingival retraction.Results and Conclusion:Statistical analysis showed that the amount of gingival retraction obtained by using retraction cord impregnated with aluminum chloride as gingival retraction agent was maximum as compared to NoCord followed by Aquasil. All three gingival displacement techniques could produce gingival displacement >0.2 mm which is the optimum amount of retraction required for impression making. All the three materials are found to be dimensionally accurate.

The Ecology of Travel on the Great Lakes Frontier: Native Knowledge, European Dependence, and the Environmental Specifics of Contact

The Michigan Historical Review 45:1 (Spring 2019): 1-26©2019 Central Michigan University. ISSN 0890-1686 All Rights Reserved 2018 Graduate Student Essay Prize Winner The Ecology of Travel on the Great Lakes Frontier: Native Knowledge, European Dependence, and the Environmental Specifics of Contact By John William Nelson Returning from what the French called le Pays d’en Haut, the upper country of the Great Lakes watershed, Antoine de la Mothe, Sieur de Cadillac reflected on his time stationed near Michilimackinac. Cadillac served as the commander of Fort du Baude from 1694 to 1696 and, as he laid plans for his own colony at Detroit, he wrote to stress the geographic potential of the Great Lakes. He proclaimed the region “the finest lands ever seen,” since they were “broken by an infinitude of large and beautiful rivers which replenish the lakes.”1 Cadillac made sure to emphasize the distinctiveness of the Great Lakes themselves. They were no ordinary bodies of water, and he even pondered “why the name lakes has been given to these watery deeps of such vast extent.”2 Such expanses of open water were nothing like Europeans had ever seen, and they remain unique in world geography. Cadillac described the waterborne potential that such distinct geography might hold. He observed the region’s native peoples plying the waters of the lakes as flotillas of Potawatomi, Odawa, and Ojibwe canoes passed along the Straits of Michilimackinac. Witnessing such waterborne mobility, he reported that “nothing is easier than to find a communication between the two seas [the Gulf of Saint Lawrence and the Gulf of Mexico] by way of the lakes and rivers traversing the backcountry for 1200 or 1500 leagues.”3 Cadillac dreamed of an interior maritime network connecting French interests 1 Lamothe Cadillac, “The Memoir of Lamothe Cadillac,” in Milo Milton Quaife, ed., The Western Country in the 17th Century: The Memoirs of Lamothe Cadillac and Pierre Liette (Chicago: Lakeside Press, 1947), 77. 2 Ibid., 5. 3 Ibid., 74. 2 The Michigan Historical Review from the Saint Lawrence Valley to the lower Mississippi and French Caribbean, all linked by the freshwaters of the Great Lakes.4 While Cadillac recognized the geopolitical significance of these inland waterways, he underplayed the complicated methods for navigating them. Cadillac alluded to the two overland connections necessary to link the Great Lakes with the Saint Lawrence and Mississippi River valleys at Niagara and Chicago, but failed to mention the many portage paths, created and used by American Indians in the centuries before European contact, that served to knit the interior maritime region together. Europeans venturing into the Great Lakes necessarily relied on indigenous geographic knowledge to navigate between waterways over these portages. Likewise, newcomers adopted indigenous birchbark canoes, constructed from materials of the surrounding woodlands, as the best vessels for traversing the lakes and rivers. Cadillac gives little mention of such particulars, let alone how French fur traders or missionaries journeying through the region might feed themselves and survive the seasonal variations of the Great Lakes climate. European travelers, if they were to navigate the Great Lakes successfully, had to master such specific environmental and geographic knowledge, or rely on those who already possessed it: the region’s native peoples. In the distinct freshwater ecosystems of the Great Lakes, indigenous peoples had crafted an effective method of waterborne travel that relied on the marine geography and local ecology. This worked, as one modern Huron scholar has put it, as an interlinked “chain of relationships” wherein native peoples of the region orchestrated the cultivation and use of an array of wild plant and animal species for their own benefit. This multi-species web of relationships—an ecology crafted by Native Americans in the precontact era—allowed for an impressive system of 4 The Laurentian Great Lakes Basin is indeed distinct, both in terms of scale—the lakes span 95,160 square miles of open water—but also in potability—the watershed holds roughly 21% of the world’s freshwater drinking supply. Gales on the lakes produce winds nearing hurricane speed and waves topping 38 feet. Thus, the lakes offer both the benefits of interior freshwater access and sustenance while also posing the...

Marginal accuracy and internal fit of copings by the digital impression and CAD‐CAM systems

Background Digital impression systems have been developed to overcome the disadvantages associated with conventional impression methods while, the computer-aided design computer-aided manufacturing (CAD CAM) technology in dentistry have been replaced error-prone manual laboratory steps with aligned industrial manufacturing processes. Therefore, the combination of them can be time-saving, comfortable, and cost-effective compared to conventional impression and casting technology. Aim/Hypothesis The purpose of this study was to compare the marginal fit and internal fit of metal and zirconia copings obtained with the use of an iTero digital impression and two different CAD-CAM systems in the anterior, premolar and molar teeth with chamfer or shoulder margin. Material and Methods A typodont model with prepared metal tooth was used as the master model. For the conventional impression group, base metal dies were replicated as stone dies by means of a conventional impression technique with polyvinyl siloxane material. For the digital impression, base metal dies were replicated as polyurethane dies with the iTero system. For the zirconia copings by Cercon® and Arum® CAD-CAM systems, stone and polyurethane dies were scanned and CAD-CAM milled. For gold and Empress copings, wax-up and casting procedures were performed based on the stone and polyurethane dies. The marginal gap and internal fit of each specimen were measured after manual refinement with a light microscope and silicone weight technique. One-way ANOVA and the Scheffe's test were used for statistical analysis (P < 0.05). Results There was no significant difference in the marginal gap among four different groups of copings between digital and conventional impression regardless of the tooth location and type of finish line (P > 0.05). However, statistically significant differences in the silicone weight for internal fit were found between the casting groups and CAD-CAM groups (P < 0.05). Conclusions and Clinical Implications The internal fit between the copings and definitive base metal die was greater in the groups that used the digital impression method and CAD-CAM systems in the group that used the conventional impression and casting method. However, the marginal discrepancies of all of the groups were no difference and clinically acceptable.