CAD/CAM systems available for the fabrication of crown and bridge restorations

Comparison of clinical fit of three-unit zirconia fixed prostheses fabricated using chairside and labside CAD/CAM systems

The purpose of this study was to assess the clinical fit provided by EZIS system, the newly commercialized chairside CAD/CAM system. Prostheses were fabricated with the chairside CAD/CAM system (CS) and labside CAD/CAM system (LS) and marginal, axial, and occlusal fit of the prostheses were compared and analyzed by using replica technique. CS group presented significantly lower fit in all the three fits compared to LS group. Differences in marginal fit, axial fit, and occlusal fit were 12.57 μm (P < 0.001), 3.32 μm (P < 0.05), and 17.20 μm (P < 0.05), respectively. Newly commercialized EZIS system yielded clinically feasible fit; however, further researches covering its biomechanical, physiological, stability aspects are required to promote active clinical use.

Application Solid Laser-Sintered or Machined Ti6Al4V Alloy in Manufacturing of Dental Implants and Dental Prosthetic Restorations According to Dentistry 4.0 Concept

This paper presents a comparison of the impact of milling technology in the computer numerically controlled (CNC) machining centre and selective laser sintering (SLS) and on the structure and properties of solid Ti6Al4V alloy. It has been shown that even small changes in technological conditions in the SLS manufacturing variant significantly affect changes from two to nearly two and a half times in tensile and bending strengths. Both the tensile and bending strength obtained in the most favourable manufacturing variant by the SLS method is over 25% higher than in the case of cast materials subsequently processed by milling. Plug-and-play SLS conditions provide about 60% of the possibilities. Structural, tribological and electrochemical tests were carried out. In vitro biological tests using osteoblasts confirm the good tendency for the proliferation of live cells on the substrate manufactured under the most favourable SLS conditions. The use of SLS additive technology for the manufacturing of dental implants and abutments made of Ti6Al4V alloy in combination with the digitisation of dental diagnostics and computer-aided design and manufacture of computer-aided design/manufacturing (CAD/CAM) following the idea of Dentistry 4.0 is the best choice of technology for manufacturing of prosthetic and implant devices used in dentistry.

Effect of storage conditions on mechanical properties of resin composite blanks for CAD/CAM crowns

The objective of this study was to examine the effects of storage conditions on the flexural strengths of resin composite materials for CAD/CAM restorations. Seven commercially available resin composite CAD/CAM blanks were examined. Rectangular specimens (4.0×1.2×4.0 mm) of each material were trimmed from the blanks and subjected to thermal cycling between 5°C and 55°C in deionized water at 10,000 cycles or stored in 37°C deionized water for one week or air for one day (n=10 for each condition). The difference in storage condition between water immersion and thermal cycling did not affect the flexural strengths of resin composite materials for CAD/CAM examined in this study. The resin composite block CS300 made from Bis-MEPP and UDMA showed the greatest flexural strength under all storage conditions and less deterioration of strength by thermal cycling and water immersion among the resin composite blocks tested.

Dentistry 4.0 Concept in the Design and Manufacturing of Prosthetic Dental Restorations

The paper is a comprehensive but compact review of the literature on the state of illnesses of the human stomatognathic system, related consequences in the form of dental deficiencies, and the resulting need for prosthetic treatment. Types of prosthetic restorations, including implants, as well as new classes of implantable devices called implant-scaffolds with a porous part integrated with a solid core, as well as biological engineering materials with the use of living cells, have been characterized. A review of works on current trends in the technical development of dental prosthetics aiding, called Dentistry 4.0, analogous to the concept of the highest stage of Industry 4.0 of the industrial revolution, has been presented. Authors’ own augmented holistic model of Industry 4.0 has been developed and presented. The studies on the significance of cone-beam computed tomography (CBCT) in planning prosthetic treatment, as well as in the design and manufacture of prosthetic restorations, have been described. The presented and fully digital approach is a radical turnaround in both clinical procedures and the technologies of implant preparation using computer-aided design and manufacturing methods (CAD/CAM) and additive manufacturing (AM) technologies, including selective laser sintering (SLS). The authors’ research illustrates the practical application of the Dentistry 4.0 approach for several types of prosthetic restorations. The development process of the modern approach is being observed all over the world. The use of the principles of the augmented holistic model of Industry 4.0 in advanced dental engineering indicates a change in the traditional relationship between a dentist and a dental engineer. The overall conclusion demonstrates that it is inevitable and extremely beneficial to implement the idea of Dentistry 4.0 following the assumptions of the authors’ own, holistic Industry 4.0 model.

Clinical efficiency and patient preference of digital and conventional workflow for single implant crowns using immediate and regular digital impression: A meta-analysis

OBJECTIVE

To assess whether digital workflow gives better results than the conventional one in the single implant crowns, when analyzing the impression time, patient preference, time efficiency, and adjustment time.

MATERIAL AND METHODS

MEDLINE, Embase, and Cochrane were searched and supplemented via hand search up to June 19, 2019. Only clinical trials assessing conventional versus digital workflows for single implant crowns were included. Impression time was evaluated using random effects meta-analysis, while patient preference, adjustment time, and time efficiency were reported descriptively.

RESULTS

Among 1,334 publications identified, ten studies were included. The random effects models revealed statistically significant reduction in time in the digital impression group when compared to the conventional group by the mean meta-analysis (MD: 8.22 [95% CI: 5.48, 10.96]). Analysis from immediate digital impression versus conventional (MD: 3.84 [95% CI: 3.30, 4.39]) and regular digital impression versus conventional (MD:10.67 [95% CI: 5.70, 15.65]) showed statistically significant reduction in time on using the digital impression. Impression time in the digital process ranged between 6 min 39 s and 20 min, whereas for conventional, it was between 11.7 and 28.47 min. Patients showed greater preference for digital impression. Adjustment time in the digital process ranged between 1.96 and 14 min, whereas for conventional, it was between 3.02 and 12 min. Time efficiency in the digital process ranged between 36.8 and 185.4 min, whereas for conventional, it was between 55.6 and 332 min.

CONCLUSION

The digital workflow has demonstrated better clinical efficiency considering impression time, patient preference, and time efficiency. According to the adjustment time, different results were presented.

Recent Trends and Future Direction of Dental Research in the Digital Era

The digital transformation in dental medicine, based on electronic health data information, is recognized as one of the major game-changers of the 21st century to tackle present and upcoming challenges in dental and oral healthcare. This opinion letter focuses on the estimated top five trends and innovations of this new digital era, with potential to decisively influence the direction of dental research: (1) rapid prototyping (RP), (2) augmented and virtual reality (AR/VR), (3) artificial intelligence (AI) and machine learning (ML), (4) personalized (dental) medicine, and (5) tele-healthcare. Digital dentistry requires managing expectations pragmatically and ensuring transparency for all stakeholders: patients, healthcare providers, university and research institutions, the medtech industry, insurance, public media, and state policy. It should not be claimed or implied that digital smart data technologies will replace humans providing dental expertise and the capacity for patient empathy. The dental team that controls digital applications remains the key and will continue to play the central role in treating patients. In this context, the latest trend word is created: augmented intelligence, e.g., the meaningful combination of digital applications paired with human qualities and abilities in order to achieve improved dental and oral healthcare, ensuring quality of life.

Trueness of CAD/CAM digitization with a desktop scanner - an in vitro study

BACKGROUND

Desktop scanners are devices for digitization of conventional impressions or gypsum casts by indirect Computer-Aided Design/Computer-Assisted Manufacturing (CAD/CAM) in dentistry. The purpose of this in vitro study was: 1, to investigate whether virtual models produced by the extraoral scanner have the same trueness as sectioned casts; and 2, to assess if digitization with an extraoral scanner influences the surface information.

METHODS

A polimethyl-methacrilic acid (PMMA) cast and a reference scanner (TwoCam 3D, SCAN technology A/S, Ringsted, Denmark; field of view 200 mm, resolution 0.1 mm ± 0.025 mm) were used to create the reference data in standard tessellation format (STL). According to the extraoral CAD/CAM digitization steps, impressions, mastercasts, and sectioned casts were made, and STL files were generated with the reference scanner. The pivotal point of the study was to digitalize these sectioned casts with the extraoral scanner (Straumann CARES Scan CS2 Visual 8.0 software, InstitutStraumann AG, Basel, Switzerland) and STL files were exported. Virtual caliper measurements were performed. Absolute deviations were compared using multilevel mixed-effects linear regression. Relative distortions were calculated with mean absolute errors and reference values.

RESULTS

Differences were observed in measurements of tooth sizes. All four prepared teeth were affected. No relationship was observed in relative deviations. Absolute differences between all the indirect digitization steps considering arch distances were: impressions, - 0.004 mm; mastercasts, 0.136 mm; sectioned casts, - 0.028 mm; and extraoral scanner, - 0.089 mm. Prepared dies on the virtual casts (extraoral scanner) were closer to each other than those on the sectioned gypsum casts. Relative deviation calculations revealed no relationship with the position of the dies in the arch.

CONCLUSION

The trueness of the virtual models generated by the extraoral scanner system used in this study was different from the dimensions of the sectioned casts. The digitization of gypsum casts changes both the dimensions of dies and the distances between the dies. The virtual casts had smaller distances than any distances measured at previous steps. Either bigger dies or longer distances did not result in greater distortions. We cannot, however, generalize our results to all scanners available on the market, because they might give different results.

Evaluating Fracture Resistance And Failure Modes Of Root Filled Teeth Restored With CAD/CAM-Fabricated Post And Core

Objective

The aim of this study was to measure the fracture resistance and failure modes of root-filled teeth restored with three different computer-aided design/computer-aided manufacturing (CAD/CAM)-fabricated post and core assemblies.

Methods

Thirty extracted intact maxillary central incisors were used in the study, and the teeth were endodontically treated and sectioned to a root length of 16 mm. The samples were divided into three groups (n = 10) according to the mean of the dimensions at the cervical portion of the root. The posts and cores were fabricated with CAD/CAM technology using metal, zirconia, and polymer-infiltrated ceramic network (PICN) material. The posts were luted using resin cement, and then, metal crowns were fabricated, cemented, and then subjected to a compression to determine the fracture resistance force. Fracture of the post and core or fracture of the root above the level of the acrylic resin was considered as a favorable fracture, while nonfavorable fractures were those where the root fracture occurred below the level of the acrylic resin. Statistical analysis was carried out using SPSS software, and one-way analysis of variance was used to analyze root fracture resistance in Newton. The number of failure modes, post–core fractures and/or root fractures was calculated. The differences between study groups were revealed using the chi-square test.

Results

The results of ANOVA revealed a nonsignificant difference in the resistance to fracture among the study groups (P = 0.114). The failure modes were nonfavorable for all metal and zirconia samples and seven PICN samples. However, three PICN samples exhibited a favorable represented by core fracture without root fracture.

Conclusion

There was no significant difference between metal and zirconia samples in terms of nonfavorable fracture, while few PICN samples exhibited a favorable fracture. PICN material can be used in the fabrication of post and core assemblies using CAD/CAM.

Digital versus conventional impressions for full-coverage restorations: A systematic review and meta-analysis

BACKGROUND

The primary objective of this systematic review was to investigate the survival of full-coverage restorations fabricated by using digital impressions (DIs) versus that of those fabricated by using conventional impressions. The authors also compared secondary outcomes of marginal and internal fit and occlusal and interproximal contacts.

TYPES OF STUDIES REVIEWED

The authors conducted a systematic literature search in multiple databases to identify clinical trials with no restrictions by publication type, date, or language. The authors assessed study-level risk of bias and outcome-level strength of evidence. The authors performed a meta-analysis by using a random-effects model.

RESULTS

Ten studies met the inclusion criteria. The authors identified no studies in which the investigators compared the impression techniques with respect to survival of full-coverage restorations. Mean differences for marginal gap and internal gap were -9.0 micrometers (95% confidence interval, -18.9 to 0.9) and -15.6 μm (95% confidence interval, -42.6 to 11.4), respectively. Studies assessing internal gap were substantially heterogeneous (I² = 72%; P = .003).

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Research is lacking to draw robust conclusions about the relative benefits of DIs in terms of restoration survival. Low-quality evidence for marginal fit and internal fit suggested similar performance for both techniques. Evidence quality for interproximal contact and occlusal contact was very low and insufficient to draw any conclusions regarding how the impression techniques compared. Given the uncertainty of the evidence, results should be interpreted with caution. With increasing popularity and adoption of digital scanners by dentists, pragmatic practice-based trials involving standardized, patient-centered outcomes may improve confidence in the comparative effectiveness of DIs.

The Current State of Chairside Digital Dentistry and Materials

This article describes and illustrates the current state of chairside computer-aided design computer-aided manufacturing technologies and materials. It provides a historical background and discusses the different components of the chairside digital workflow: intraoral scanners, design software, milling machines, and sinter furnaces. The material range available for chairside digital dentistry is broad and includes polymethyl methacrylates, composite resins, and a large variety of ceramics. Clinical applications and success rates of the different material groups are summarized and discussed based on the current scientific evidence.

Ti(C, N) as Barrier Coatings

Metals and their alloys are materials that have long been used in stomatological prosthetics and orthodontics. The side effects of their application include reactions of the body such as allergies. Their source can be corrosion products as well as metal ions released in the corrosion process, which penetrate the surrounding tissue. In order to prevent the harming effect of metal alloys, intensive research has been performed to purify metal prosthetic restorations by way of modifying their surface. The study presents the investigation results of Ti(C, N)-type coatings applied to alloy Ni–Cr by means of the magnetronic method. Five coatings differing in the nitrogen and carbon content were investigated. The studies included the determination of the coatings’ chemical composition, construction, as well as the amount of ions released into the environment: distilled water, 0.9% NaCl and artificial saliva. The performed investigations showed that, in reference to an alloy without a coating, each coating constitutes a barrier reducing the amount of ions transferred into the examined solutions. So, Ti(C, N)-type coatings can be considered for biomedical applications as protective coatings of non-precious metal alloys.

Additive manufacturing of ceramics for dental applications: A review

OBJECTIVE

The main goal of this review is to provide a detailed and comprehensive description of the published work from the past decade regarding AM of ceramic materials with possible applications in dentistry. The main printable materials and most common technologies are also addressed, underlining their advantages and main drawbacks.

METHODS

Online databases (Web of knowledge, Science Direct, PubMed) were consulted on this topic. Published work from 2008 to 2018 was collected, analyzed and the relevant papers were selected for inclusion on this review.

RESULTS

Ceramic materials are broadly used in dentistry to restore/replace damaged or missing teeth, due to their biocompatibility, chemical stability and mechanical and aesthetic properties. However, there are several unmet challenges regarding their processing and performance. Due to their brittleness nature, a very tight control of the manufacturing process is needed to obtain dental pieces with adequate mechanical properties. Additive manufacturing (AM) is an emerging technology that constitutes an interesting and viable manufacturing alternative to the conventional subtractive methods. AM enables the production of customized complex 3D parts in a more sustainable and less expensive way. AM of ceramics can be achieved with an extensive variety of methods.

SIGNIFICANCE

There is no perfect technology for all materials/applications, capable alone of fulfilling all the specificities and necessities of every patient. Although very promising, AM of ceramic dental materials remains understudied and further work is required to make it a widespread technology in dentistry.

In vitro Comparative Study of Fibroblastic Behaviour on Polymethacrylate (PMMA) and Lithium Disilicate Polymer Surfaces

Polymethyl methacrylate (PMMA) and lithium disilicate are widely used materials in the dental field. PMMA is mainly used for the manufacture of removable prostheses; however, with the incorporation of CAD-CAM technology, new applications have been introduced for this material, including as a provisional implant attachment. Lithium disilicate is considered the gold standard for definitive attachment material. On the other hand, PMMA has begun to be used in clinics as a provisional attachment until the placement of a definitive one occurs. Although there are clinical studies regarding its use, there are few studies on cell reorganization around this type of material. This is why we carried out an in vitro comparative study using discs of both materials in which human gingival fibroblasts (HGFs) were cultured. After processing them, we analyzed various cellular parameters (cell count, cytoskeleton length, core size and coverage area). We analyzed the surface of the discs together with their composition. The results obtained were mostly not statistically significant, which shows that the qualities of PMMA make it a suitable material as an implant attachment.

Current status and applications of additive manufacturing in dentistry: A literature-based review

Objective

To study the current status and applications of additive manufacturing (AM) in dentistry along with various technologies, benefits and future scope.

Methods

A significant number of relevant research papers on the additive manufacturing application in dentistry are identified through Scopus and studied using bibliometric analysis that shows an increasing trend of research in this field. This paper briefly describes various types of AM technologies with their accuracy, pros and cons along with different dental materials. Paper also discusses various benefits of AM in dentistry and steps used to create 3D printed dental model using this technology. Further, ten major AM applications in dentistry are identified along with primary references and objectives.

Results

Additive manufacturing is an innovative technique moving towards the customised production of dental implants and other dental tools using computer-aided design (CAD) data. This technology is used to manufacture elaborate dental crowns, bridges, orthodontic braces and can also various other models, devices and instruments with lesser time and cost. With the help of this disruptive innovation, dental implants are fabricated accurately as per patient data captured by the dental 3D scanner. The application of this technology is also being explored for the precise manufacturing of removal prosthetics, aligners, surgical templates for implants and produce models that for the planning of treatment and preoperative positioning of the jaws.

How 'smart' is smart dentistry?

Background: Latest advances in information and health technologies enabled dentistry to follow the paradigm shift occurring in medicine - the transition to so called smart medicine. Consequently, the aim of this paper is to assess how 'smart' is smart dentistry as of the end of 2018. Methods: We analysed the state of the art in smart dentistry, performing bibliometric mapping on a corpus of smart dentistry papers found in the Scopus bibliographical database. Results: The search resulted in a corpus of 3451 papers, revealing that smart dentistry research is following the progress in smart medicine; however, there are some gaps in some specific areas like gamification and use of holistic smart dentistry systems. Conclusions: Smart dentistry is smart; however, it must become smarter.

How 'smart' is smart dentistry?

Background: Latest advances in information and health technologies enabled dentistry to follow the paradigm shift occurring in medicine - the transition to so called smart medicine. Consequently, the aim of this paper is to assess how 'smart' is smart dentistry as of the end of 2018. Methods: We analysed the state of the art in smart dentistry, performing bibliometric mapping on a corpus of smart dentistry papers found in the Scopus bibliographical database. Results: The search resulted in a corpus of 3451 papers, revealing that smart dentistry research is following the progress in smart medicine; however, there are some gaps in some specific areas like gamification and use of holistic smart dentistry systems. Conclusions: Smart dentistry is smart; however, it must become smarter.

Aplicabilidade clínica dos avanços da tecnologia CAD-CAM em Odontologia

O avanço tecnológico tem se mostrado um grande aliado em diversas áreas, assim como na odontologia. O surgimento da tecnológica CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) na década de 1950 trouxe outra realidade para a prática clínica diária. Previamente todo o processo laboratorial de trabalhos protéticos era demorado e puramente físico, atualmente a fabricação das peças protéticas demanda um menor tempo devido a utilização do meio digital, o que consequentemente diminui as consultas aos Cirurgiões-Dentistas. A adição de ferramentas digitais no planejamento e na execução dos tratamentos odontológicos alterou completamente o workflow, fazendo com que a busca para um aperfeiçoamento seja constante visando sempre o melhor atendimento e qualidade dos tratamentos realizados. Dessa forma este trabalho tem o objetivo de realizar uma revisão crítica da literatura sobre a aplicabilidade clínica da tecnologia CAD-CAM em Odontologia.

Attitudes of the Students from the School of Dental Medicine in Zagreb towards CAD/CAM

Aim

Due to fast and continuing advances in digital dental technology it is important to provide appropriate CAD/CAM education of preclinical (PS) and clinical (CS) dental students. Therefore, the aim of this study was to determine the knowledge and attitudes on CAD/CAM technology of PS and CS at the School of Dental Medicine, University of Zagreb since the obtained results can show the level of students’ knowledge and possibly a need for additional education.

Materials and methods

This study included 216 undergraduate dental students from the School of Dental Medicine in Zagreb: 77 (35.6%) of preclinical students (PS) and 139 (64.4%) of clinical students (CS). All participants filled out the questionnaire specially designed for this study. The obtained data were statistically analyzed with a significance level of p<0.05.

Results

Most of the students (182, 84.23%) heard about CAD/CAM technology at regular lectures held at the School (p<0.05). Regardless of their level of education, most of the students (204, 94.4%) did not attend any CAD/CAM course which were not held within regular lectures at the School (p<0.05). Most of PS (72, 33.3%) and most of CS (133, 61.6%) participants believe that they are not sufficiently informed about CAD/CAM technology (p<0.05).

Conclusion

Although most of the students (PS and CS) heard about CAD/CAM technology, it could be concluded that they are not sufficiently informed and that additional education on CAD/CAM technology is required. Also, CS students do not posses greater knowledge about CAD/CAM technology than PS students.

Four-year outcomes of full-arch fixed dental prostheses using CAD/CAM frameworks: A retrospective review of 15 cases

The aim of this report is to analyze the clinical performance of 20 full-arch implant-supported titanium frameworks using CAD/CAM (Computer-Aided Design and Computer-Aided Manufacturing) technology. One hundred and four implants were placed in 15 patients using a one-stage protocol. After planning the location of all implants via 3-dimensional software (NobleClinician), 4-8 implants were placed in each edentulous arch based on anatomical measurements. Twenty edentulous arches were treated with full arch implant-supported fixed dental prostheses utilizing CAD/CAM milled titanium frameworks . All patients were followed up for 48±4 months. Clinical performance of the implants and restorations were evaluated for implant/prosthesis survival, framework fit, marginal bone levels, and maintenance requirements. One implant was lost during the follow up period, giving an implant survival rate of 99.1%. The average distance from the implant platform to first bone-implant contact was 1.1±0.2 mm from the time of metal-framework try-in to the time of the last recall appointment. None of the prostheses needed a replacement, indicating the prosthesis success rate was 100%. Sixteen occlusal adjustments and 5 broken denture teeth were repaired chairside during the study period. The results of this retrospective clinical report suggest that CAD/CAM milled titanium frameworks using the software and scanner presented in this study fit accurately and can be a viable treatment option to restore edentulous arches.

Key words:CAD/CAM, framework, implant, mandible, titanium.

Laboratory workflow to obtain long-term injected resin composite interim restorations from an additive manufactured esthetic diagnostic template

OBJECTIVE

An analogue and digital workflow for the fabrication of a diagnostic 3D printed polymer template and its duplication for long-term injected composite resin interim restorations is described, because of the lack of scientific evidence in 3-dimensional (3D) printing applied to dentistry in terms of printer technology, printer parameters, postpolymerization processes, and material characteristics. In addition, in the case of 3D printed temporary resins, they cannot be relined successfully and its mechanical properties in the mouth have not been tested yet.

CONCLUSIONS

The main benefits of this approach relate to the improvement of clinical and laboratory procedures, as conventional waxing is eliminated, conventional master casts are not needed and the process is entirely automatized, improving the workflow, with minimal intervention of the laboratory technician.

CLINICAL SIGNIFICANCE

The additive manufactured diagnostic template represents the materialization of the digital diagnostic waxing and provides a powerful tool to visualize the digital diagnostic waxing in the patient's mouth and face. Furthermore, the diagnostic 3D printed template can be used for multiple applications including interim restorations, radiographical, or surgical guide fabrication. The duplication technique described provides a predictable workflow to obtain long-term injected resin composite restorations from an additive manufactured esthetic diagnostic template, improving the laboratory and chairside procedures.

Internal Adaptation of Implant-Supported, Polymer-Infused Ceramic Crowns Fabricated by Two CAD/CAM Systems

PURPOSE

The aim of this in vitro study was to compare the internal 3D adaptation of polymer-infused ceramic crowns fabricated using two CAD/CAM systems: CEREC inLab MC XL and Ceramill Motion 2 (5X).

MATERIALS AND METHODS

Twenty-five implant-supported metal-ceramic crowns were fabricated conventionally using the lost-wax technique, and the outer contour was scanned to serve as a guide for designing the polymer-infused ceramic CAD/CAM crowns. Twenty-five crowns were fabricated using CEREC, and 25 crowns were fabricated using Ceramill. The cement space was set to 20 μm. The Zeiss Accura Microsystem Coordinate Measuring Machine (CMM), Calypso, and Geomagic software were used to measure the 3D accuracy of fit of all crowns to their respective implant abutments. To test for the statistical significance between groups in terms of 3D total distortion, a one-way ANOVA was conducted. The Kolmogorov-Smirnov test was used to investigate the differences in the x, y, and z coordinates. A p-value of 0.05 or less was considered statistically significant at an alpha level of 0.05.

RESULTS

Comparing the 3D misfit of metal-ceramic crowns to those of CAD/CAM crowns fabricated using CEREC revealed no significant difference (88.20 ± 36.59 μm vs. 102.45 ± 36.58 μm, p = 0.161). Similarly, no significant difference in 3D total distortion was identified between metal-ceramic crowns and crowns fabricated using Ceramill (88.20 ± 36.59 μm vs. 78.40 ± 31.03 μm, p = 0.336); however, the 3D total distortion of polymer-infused crowns made by Ceramill was significantly reduced compared to that of crowns fabricated by CEREC (78.3 ± 31.0 μm vs. 102.4 ± 36.5 μm, p = 0.019).

CONCLUSIONS

Polymer-infused ceramic crowns fabricated using CEREC exhibited the least accurate 3D fit. All misfit values of the tested groups were within clinically acceptable levels.

A study on the machining accuracy of dental digital method focusing on dental inlay

PURPOSE

The purpose of this study was to compare the cutting method and the lamination method to investigate whether the CAD data of the proposed inlay shape are machined correctly.

MATERIALS AND METHODS

The Mesial-Occlusal shape of the inlay was modeled by changing the stereolithography (STL). Each group used SLS (metal powder) or SLA (photocurable resin) in the additive method, and wax or zirconia in the subtractive method (n=10 per group, total n=40). Three-dimensional (3D) analysis program (Geomagic Control X inspection software; 3D systems) was used for the alignment and analysis. The root mean square (RMS) in the 2D plane state was measured within 50 µm radius of eight comparison measuring points (CMP). Differences were analyzed using one-way analysis of variance and post-hoc Tukey's test were used (α=.05).

RESULTS

There was a significant difference in RMS only in SLA and SLS of 2D section (P<.05). In CMP mean, CMP 4 (−5.3±46.7 µm) had a value closest to 0, while CMP 6 (20.1±42.4 µm) and CMP 1 (−89.2±61.4 µm) had the greatest positive value and the greatest negative value, respectively.

CONCLUSION

Since the errors obtained from the study do not exceed the clinically acceptable values, the lamination method and the cutting method can be used clinically.

Vertical and Horizontal Misfit Analysis of 3-unit FDP Fabricated with Different Techniques and CAD/CAM Systems

The aim of this is was evaluate the vertical and horizontal marginal adaptation of 3-unit fixed partial denture frameworks fabricated using different techniques and CAD/CAM systems. A total of 40 framework specimens were fabricated and divided into four groups as follows: lost-wax casting (G1); lost-wax casting with welding (G2); extraoral optical scanning of models (3S/DWOS) (G3); intraoral optical scanning (Cerec Bluecam/Sirona) (G4). A reference model was used to simulate a fixed partial denture with three elements (with a central pontic). The frameworks of G1 and G2 were cast in nickel-chromium (NiCr) alloy, whereas those of G3 and G4 were milled in zirconia. In all groups, vertical and horizontal marginal adaptation (over-contour and under-contour) was evaluated using a three-dimensional optical microscope (Quick Scope, Mitutoyo). The results showed higher vertical marginal misfit in G1 than in the other groups (p<0.001). Regarding horizontal marginal misfit, higher over-contour values occurred in G3 than in the other groups (p<0.001). G3 did not show under-contour at all, whereas the other groups did not differ from each other in this regard (p>0.05). Within the limitations of this study, it can be concluded that lost-wax casting with welding is a viable alternative to the use of CAD/CAM systems to fabricate frameworks of three-unit FPDs, since the techniques yielded similar vertical misfit values. Extra-oral CAD/CAM systems showed the highest horizontal misfit (over-contour) compared to other groups.

Wear of resin composites: Current insights into underlying mechanisms, evaluation methods and influential factors

The application of resin composites in dentistry has become increasingly widespread due to the increased aesthetic demands of patients, improvements in the formulation of resin composites, and the ability of these materials to bond to tooth structures, together with concerns about dental amalgam fillings. As resistance to wear is an important factor in determining the clinical success of resin composite restoratives, this review article defines what constitutes wear and describes the major underlying phenomena involved in this process. Insights are further included on both in vivo and in vitro tests used to determine the wear resistance of resin composite and the relationships between these tests. The discussion focuses on factors that contribute to the wear of resin composite. Finally, future perspectives are included on both clinical and laboratory tests and on the development of resin composite restorations.

Implementing a new curriculum for computer-assisted restorations in prosthetic dentistry

INTRODUCTION

Computer-aided design/computer-aided manufacturing (CAD/CAM) of fixed prosthetic restorations has gained popularity in the last decade. However, this field of dentistry has not been integrated in the dental curriculum at most universities.

MATERIAL AND METHODS

According to the method of Kern, a curriculum was designed and established on a voluntary basis in the prosthetic education of a German dental school. The success of the implementation was measured by evaluation carried out by the participants on a visual analogue scale. Furthermore, the clinical performance of the fabricated restorations was evaluated.

RESULTS

Ninety-four percent of all students participated in the CAD/CAM curriculum indicating considerable interest. Nearly half of all students used the acquired knowledge to design crowns for their patients. All restorations fabricated by participants of the new CAD/CAM programme showed good clinical performance.

DISCUSSION

By phasing-in the CAD/CAM training programme, independent CAD/CAM-based fabrication of all-ceramic crowns increased student's self-confidence in tooth preparation. A tendency was found that students using CAD/CAM technology prepared more teeth than their fellow students who did not use CAD/CAM technology. Further studies are required to investigate the influence of independent CAD/CAM-based single-crown fabrication on the quality of the preparation.

Bonding to new CAD/CAM resin composites: influence of air abrasion and conditioning agents as pretreatment strategy

OBJECTIVES

Because of their industrially standardized process of manufacturing, CAD/CAM resin composites show a high degree of conversion, making a reliable bond difficult to achieve.

PURPOSE

The purpose of this experiment was to investigate the tensile bond strength (TBS) of luting composite to CAD/CAM resin composite materials as influenced by air abrasion and pretreatment strategies.

MATERIAL AND METHODS

The treatment factors of the present study were (1) brand of the CAD/CAM resin composite (Brilliant Crios [Coltene/Whaledent], Cerasmart [GC Europe], Shofu Block HC [Shofu], and Lava Ultimate [3M]); (2) air abrasion vs. no air abrasion; and (3) pretreatment using a silane primer (Clearfil Ceramic Primer, Kuraray) vs. a resin primer (One Coat 7 Universal, Coltene/Whaledent). Subsequently, luting composite (DuoCem, Coltene/Whaledent) was polymerized onto the substrate surface using a mold. For each combination of the levels of the three treatment factors (4 (materials) × 2 (air abrasion vs. no air abrasion; resin) × 2 (primer vs. silane primer)), n = 15, specimens were prepared. After 24 h of water storage at 37 °C and 5000 thermo-cycles (5/55 °C), TBS was measured and failure types were examined. The resulting data was analyzed using Kaplan-Meier estimates of the cumulative failure distribution function with Breslow-Gehan tests and non-parametric ANOVA (Kruskal-Wallis test) followed by the multiple pairwise Mann-Whitney U test with α-error adjustment using the Benjamini-Hochberg procedure and chi-square test (p < 0.05).

RESULTS

The additional air abrasion step increased TBS values and lowered failure rates. Specimens pretreated using a resin primer showed significantly higher TBS and lower failure rates than those pretreated using a silane primer. The highest failure rates were observed for groups pretreated with a silane primer. Within the Shofu Block HC group, all specimens without air abrasion and pretreatment with a silane primer debonded during the aging procedure.

CONCLUSIONS

Before fixation of CAD/CAM resin composites, the restorations should be air abraded and pretreated using a resin primer containing methyl-methacrylate to successfully bond to the luting composite. The pretreatment of the CAD/CAM resin composite using merely a silane primer results in deficient adhesion.

CLINICAL RELEVANCE

For a reliable bond of CAD/CAM resin composites to the luting composite, air abrasion and a special pretreatment strategy are necessary in order to achieve promising long-term results.

Marginal Adaptation of CAD/CAM All-Ceramic Crowns Made by Different Impression Methods: A Literature Review

All-ceramic crowns for teeth are widely used for restoring teeth. Stone casts have been made from conventional impression methods; however, newer techniques have made this process easier and faster for both the patient and the practitioner. Laboratory CAD/CAM technology mainly involves scanning the die stone, while other systems permit impression or intraoral scanning; however, one major concern remaining is the marginal fit of the restorations made using different methods for recording the prepared teeth. This study aims to review studies evaluating the marginal fit of all-ceramic crowns manufactured by CAD/CAM systems using different extra- and intra-oral scanners compared to conventional impressions.

In vitro Evaluation of the Marginal Fit and Internal Adaptation of Zirconia and Lithium Disilicate Single Crowns: Micro-CT Comparison Between Different Manufacturing Procedures

Background:

Prosthetic precision can be affected by several variables, such as restorative materials, manufacturing procedures, framework design, cementation techniques and aging. Marginal adaptation is critical for long-term longevity and clinical success of dental restorations. Marginal misfit may lead to cement exposure to oral fluids, resulting in microleakage and cement dissolution. As a consequence, marginal discrepancies enhance percolation of bacteria, food and oral debris, potentially causing secondary caries, endodontic inflammation and periodontal disease.

Objective:

The aim of the present in vitro study was to evaluate the marginal and internal adaptation of zirconia and lithium disilicate single crowns, produced with different manufacturing procedures.

Methods:

Forty-five intact human maxillary premolars were prepared for single crowns by means of standardized preparations. All-ceramic crowns were fabricated with either CAD-CAM or heat-pressing procedures (CAD-CAM zirconia, CAD-CAM lithium disilicate, heat-pressed lithium disilicate) and cemented onto the teeth with a universal resin cement. Non-destructive micro-CT scanning was used to achieve the marginal and internal gaps in the coronal and sagittal planes; then, precision of fit measurements were calculated in a dedicated software and the results were statistically analyzed.

Results:

The heat-pressed lithium disilicate crowns were significantly less accurate at the prosthetic margins (p<0.05) while they performed better at the occlusal surface (p<0.05). No significant differences were noticed between CAD-CAM zirconia and lithium disilicate crowns (p>0.05); nevertheless CAD-CAM zirconia copings presented the best marginal fit among the experimental groups. As to the thickness of the cement layer, reduced amounts of luting agent were noticed at the finishing line, whereas a thicker layer was reported at the occlusal level.

Conclusion:

Within the limitations of the present in vitro investigation, the following conclusions can be drawn: the recorded marginal gaps were within the clinical acceptability irrespective of both the restorative material and the manufacturing procedures; the CAD-CAM processing techniques for both zirconia and lithium disilicate produced more consistent marginal gaps than the heat-pressing procedures; the tested universal resin cement can be safely used with both restorative materials.

Influence of different surface treatments on bond strength of novel CAD/CAM restorative materials to resin cement

PURPOSE

To evaluate the effects of different surface treatments on the bond strength of novel CAD/CAM restorative materials to resin cement by four point bending test.

MATERIALS AND METHODS

The CAD/CAM materials under investigation were e.max CAD, Mark II, Lava Ultimate, and Enamic. A total of 400 bar specimens (4×1.2×12 mm) (n=10) milled from the CAD/CAM blocks underwent various pretreatments (no pretreatment (C), hydrofluoric acid (A), hydrofluoric acid + universal adhesive (Scotchbond) (AS), sandblasting (Sb), and sandblasting + universal adhesive (SbS)). The bars were luted end-to-end on the prepared surfaces with a dual curing adhesive resin cement (Variolink N, Ivoclar Vivadent) on the custom-made stainless steel mold. Ten test specimens for each treatment and material combination were performed with four point bending test method. Data were analyzed using ANOVA and Tukey's test.

RESULTS

The surface treatment and type of CAD/CAM restorative material showed a significant effect on the four point bending strength (FPBS) (P<.001). For LDC, AS surface treatment showed the highest FPBS results (100.31 ± 10.7 MPa) and the lowest values were obtained in RNC (23.63 ± 9.0 MPa) for control group. SEM analyses showed that the surface topography of CAD/CAM restorative materials was modified after treatments.

CONCLUSION

The surface treatment of sandblasting or HF acid etching in combination with a universal adhesive containing MDP can be suggested for the adhesive cementation of the novel CAD/CAM restorative materials.

Marginal Fit Comparison of CAD/CAM Crowns Milled from Two Different Materials

PURPOSE

To evaluate the marginal fit of CAD/CAM copings milled from hybrid ceramic (Vita Enamic) blocks and lithium disilicate (IPS e.max CAD) blocks, and to evaluate the effect of crystallization firing on the marginal fit of lithium disilicate copings.

MATERIALS AND METHODS

A standardized metal die with a 1-mm-wide shoulder finish line was imaged using the CEREC AC Bluecam. The coping was designed using CEREC 3 software. The design was used to fabricate 15 lithium disilicate and 15 hybrid ceramic copings. Design and milling were accomplished by one operator. The copings were seated on the metal die using a pressure clamp with a uniform pressure of 5.5 lbs. A Macroview Microscope (14×) was used for direct viewing of the marginal gap. Four areas were imaged on each coping (buccal, distal, lingual, mesial). Image analysis software was used to measure the marginal gaps in μm at 15 randomly selected points on each of the four surfaces. A total of 60 measurements were made per specimen. For lithium disilicate copings the measurements for marginal gap were made before and after crystallization firing. Data were analyzed using paired t-test and Kruskal-Wallis test.

RESULTS

The overall mean difference in marginal gap between the hybrid ceramic and crystallized lithium disilicate copings was statistically significant (p < 0.01). Greater mean marginal gaps were measured for crystallized lithium disilicate copings. The overall mean difference in marginal gap before and after firing (precrystallized and crystallized lithium disilicate copings) showed an average of 62 μm increase in marginal gap after firing. This difference was also significant (p < 0.01).

CONCLUSIONS

A significant difference exists in the marginal gap discrepancy when comparing hybrid ceramic and lithium disilicate CAD/CAM crowns. Also crystallization firing can result in a significant increase in the marginal gap of lithium disilicate CAD/CAM crowns.

The complete digital workflow in fixed prosthodontics: a systematic review

BACKGROUND

The continuous development in dental processing ensures new opportunities in the field of fixed prosthodontics in a complete virtual environment without any physical model situations. The aim was to compare fully digitalized workflows to conventional and/or mixed analog-digital workflows for the treatment with tooth-borne or implant-supported fixed reconstructions.

METHODS

A PICO strategy was executed using an electronic (MEDLINE, EMBASE, Google Scholar) plus manual search up to 2016-09-16 focusing on RCTs investigating complete digital workflows in fixed prosthodontics with regard to economics or esthetics or patient-centered outcomes with or without follow-up or survival/success rate analysis as well as complication assessment of at least 1 year under function. The search strategy was assembled from MeSH-Terms and unspecific free-text words: {(("Dental Prosthesis" [MeSH]) OR ("Crowns" [MeSH]) OR ("Dental Prosthesis, Implant-Supported" [MeSH])) OR ((crown) OR (fixed dental prosthesis) OR (fixed reconstruction) OR (dental bridge) OR (implant crown) OR (implant prosthesis) OR (implant restoration) OR (implant reconstruction))} AND {("Computer-Aided Design" [MeSH]) OR ((digital workflow) OR (digital technology) OR (computerized dentistry) OR (intraoral scan) OR (digital impression) OR (scanbody) OR (virtual design) OR (digital design) OR (cad/cam) OR (rapid prototyping) OR (monolithic) OR (full-contour))} AND {("Dental Technology" [MeSH) OR ((conventional workflow) OR (lost-wax-technique) OR (porcelain-fused-to-metal) OR (PFM) OR (implant impression) OR (hand-layering) OR (veneering) OR (framework))} AND {(("Study, Feasibility" [MeSH]) OR ("Survival" [MeSH]) OR ("Success" [MeSH]) OR ("Economics" [MeSH]) OR ("Costs, Cost Analysis" [MeSH]) OR ("Esthetics, Dental" [MeSH]) OR ("Patient Satisfaction" [MeSH])) OR ((feasibility) OR (efficiency) OR (patient-centered outcome))}. Assessment of risk of bias in selected studies was done at a 'trial level' including random sequence generation, allocation concealment, blinding, completeness of outcome data, selective reporting, and other bias using the Cochrane Collaboration tool. A judgment of risk of bias was assigned if one or more key domains had a high or unclear risk of bias. An official registration of the systematic review was not performed.

RESULTS

The systematic search identified 67 titles, 32 abstracts thereof were screened, and subsequently, three full-texts included for data extraction. Analysed RCTs were heterogeneous without follow-up. One study demonstrated that fully digitally produced dental crowns revealed the feasibility of the process itself; however, the marginal precision was lower for lithium disilicate (LS2) restorations (113.8 μm) compared to conventional metal-ceramic (92.4 μm) and zirconium dioxide (ZrO2) crowns (68.5 μm) (p < 0.05). Another study showed that leucite-reinforced glass ceramic crowns were esthetically favoured by the patients (8/2 crowns) and clinicians (7/3 crowns) (p < 0.05). The third study investigated implant crowns. The complete digital workflow was more than twofold faster (75.3 min) in comparison to the mixed analog-digital workflow (156.6 min) (p < 0.05). No RCTs could be found investigating multi-unit fixed dental prostheses (FDP).

CONCLUSIONS

The number of RCTs testing complete digital workflows in fixed prosthodontics is low. Scientifically proven recommendations for clinical routine cannot be given at this time. Research with high-quality trials seems to be slower than the industrial progress of available digital applications. Future research with well-designed RCTs including follow-up observation is compellingly necessary in the field of complete digital processing.

Selective Laser Melting Technique of Co-Cr Dental Alloys: A Review of Structure and Properties and Comparative Analysis with Other Available Techniques

PURPOSE

The aim of this study was to review the effect of selective laser melting (SLM) procedure on the properties of dental structures made of Co-Cr alloys and to evaluate its quality and compare it to those produced by conventional casting and milling fabrication techniques.

MATERIALS AND METHODS

A computerized database search using PubMed and Scopus was conducted for peer-reviewed scientific research studies regarding the use of SLM in Co-Cr dental alloys with no restrictions for publication years. The search engines provided hundreds of results, and only 48 scientific research papers, case studies, or literature reviews were considered relevant for this review.

RESULTS

The innovative manufacturing concept of SLM offers many advantages compared with casting and milling fabrication techniques. SLM provides different microstructure from casting and milling with minimal internal porosity and internal fitting, marginal adaptation, and comparable bond strength to porcelain. Mechanical and electrochemical properties of SLM structures are enhanced compared to cast, while clinical longevity of single-metal ceramic crowns is comparable to Au-Pt dental alloy.

CONCLUSION

The SLM technique provides dental prosthetic restorations more quickly and less expensively without compromising their quality compared with restorations prepared by casting and milling techniques.

CLINICAL SIGNIFICANCE

The current SLM devices provide metallic restorations made of Co-Cr alloys for removable and fixed partial dentures without compromising the alloy or restoration properties at a fraction of the time and cost, showing great potential to replace the aforementioned fabrication techniques in the long term; however, further clinical studies are essential to increase the acceptance of this technology by the worldwide dental community.

Integration of Digital Dentistry into a Predoctoral Implant Program: Program Description, Rationale, and Utilization Trends

A recently revised predoctoral implant curriculum at the University of Illinois at Chicago College of Dentistry integrated digital dentistry into both the preclinical dental implant course and clinical activities. Traditionally, competence in the didactic and clinical parts of predoctoral education in single tooth implant restorations has emphasized the analog impression technique and subsequent mounting of soft tissue working casts. However, computer-aided design/computer-aided manufacturing (CAD/CAM) implant restorations can play a significant role in predoctoral dental education utilizing digital technologies. The goal of the curriculum expansion is to transition from analog to partially digital and, finally, complete digital workflow. The aim of this article is to describe the specific components, implementation, and rationale for the new digitally integrated implant curriculum and present short-term clinical utilization trends.

Anterosuperior rehabilitation with metal-free fixed prosthesis based on zirconia

The loss of upper front dental elements causes functional and psychosocial problems to the affected individuals. In this case report, the treatment planning considered hard and soft tissue loss for a complex fixed partial denture (FPD) rehabilitation. The six-element, all-ceramic FPD was manufactured using a computer-aided design/computer-aided manufacturing system with zirconia framework, veneered with leucite-reinforced ceramic. Ceramic artificial gum was also produced to guarantee tooth-facial proportions as well as lip support, promoting both esthetics and phonetics. The material's mechanical properties allowed for the coupling of the esthetic and mechanical requirements, proving an alternative to the well-established metal-ceramic technology, optimizing biomimetic. One of the endodontic-treated abutment teeth required a radicular retainer with cast metal post, but because of the opacity of zirconia, the esthetics of the prosthesis was not compromised. The low silica content of high resistance ceramics such as zirconia hampers the adhesive cementation, with numerous studies advocating for different cementation protocols, with no clear scientific consensus so far. In the present case, the internal surface of the FPD was initially blasted with aluminum oxide, followed by the application of a universal adhesive system containing 10-methacryloyloxydecyl dihydrogen phosphate. Finally, cementation to the dental structure was conducted with dual-cure self-adhesive resin cement.

Influence of Teeth Preparation Finishing on the Adaptation of Lithium Disilicate Crowns

The polishing step of teeth preparations for crowns is a step often performed, so that there is an increased time during the clinical procedure. The aim of this study is to evaluate the marginal and internal adaptation of all-ceramic CAD/CAM lithium disilicate crowns in polished preparations for crown and nonpolished preparations for crowns. For this purpose, 20 first molars were selected, which were divided into two groups (n = 10) G1, teeth that received surface roughening similar to preparation without polishing, and G2 (control), polished preparations. After the preparations were completed the teeth were scanned (Cerec Bluecam, Sirona, Bensheim, Germany), and the crowns were designed and machined using CAD/CAM technology (Sirona, Bensheim, Germany). The adaptation of the pieces was evaluated using polyvinyl siloxane replicas and stereomicroscope photographs with 70x magnifications. The normality test indicated a nonnormal result, so a Man-Whitney nonparametric test was performed. One out of the 24 measured regions showed a statistically significant difference (p = 0.0494). With this study it can be concluded that crowns fabricated by CAD/CAM technology performed on unpolished preparations are not influenced by the internal marginal adaptation and the ceramic part and are different from polished preparations.

Effect of air-particle pressures on the surface topography and bond strengths of resin cement to the hybrid ceramics

This study aimed to determine the appropriate pressure for airborne-abrasion by comparing the shear bond strength values for different hybrid ceramic surfaces. Two materials were used to produce hybrid ceramic specimens: Lava Ultimate and MAZIC Duro. The group of specimens whose surfaces were not subjected to airborne-abrasion was set as the control group. In the experimental group, airborne-abrasion was performed at pressures of 0.1, 0.2, and 0.3 MPa. After the adhesive and resin cement was applied, an SBS test was performed. For the MAZIC Duro block, the SBS increased monotonically with the airborne-abrasion pressure increased, peaking at 0.3 MPa. For the Lava Ultimate block, the SBS increased as the airborne-abrasion pressure increased to 0.2 MPa, and then decreased in the 0.3-MPa group, thereby peaking at 0.2 MPa. This study has confirmed that the bonding strength varies with the material used even when applying the same surface treatment.

CAD/CAM machining Vs pre-sintering in-lab fabrication techniques of Y-TZP ceramic specimens: Effects on their mechanical fatigue behavior

This study evaluated the effects of different pre-sintering fabrication processing techniques of Y-TZP ceramic (CAD/CAM Vs. in-lab), considering surface characteristics and mechanical performance outcomes. Pre-sintered discs of Y-TZP ceramic (IPS e.max ZirCAD, Ivoclar Vivadent) were produced using different pre-sintering fabrication processing techniques: Machined- milling with a CAD/CAM system; Polished- fabrication using a cutting device followed by polishing (600 and 1200 SiC papers); Xfine- fabrication using a cutting machine followed by grinding with extra-fine diamond bur (grit size 30 μm); Fine- fabrication using a cutting machine followed by grinding with fine diamond bur (grit size 46 μm); SiC- fabrication using a cutting machine followed by grinding with 220 SiC paper. Afterwards, the discs were sintered and submitted to roughness (n=35), surface topography (n=2), phase transformation (n=2), biaxial flexural strength (n=20), and biaxial flexural fatigue strength (fatigue limit) (n=15) analyses. No monoclinic-phase content was observed in all processing techniques. It can be observed that obtaining a surface with similar characteristics to CAD/CAM milling is essential for the observation of similar mechanical performance. On this sense, grinding with fine diamond bur before sintering (Fine group) was the best mimic protocol in comparison to the CAD/CAM milling.