Comparative Study of the Influence of Heat Treatment on Fracture Resistance of Different Ceramic Materials Used for CAD/CAM Systems.

The aim of this study was to compare the influence of heat treatment on fracture resistance (FR) of different ceramic materials used for CAD/CAM systems. METHODS: Eighty monolithic restorations were designed using the same parameters and milled with a CAD/CAM system (CEREC SW 5.0, PrimeMill, Dentsply-Sirona™, Bensheim, Germany), forming five study groups: Group 1 (n = 10), CEREC Tessera (Dentsply-Sirona™, Bensheim, Germany) crystallized (CCT), Group 2 (n = 10), CEREC Tessera uncrystallized (UCT), Group 3 (n = 20), Emax-CAD (Ivoclar Vivadent, Schaan, Liechtenstein) (CEC), Group 4 (n = 20), Vita Suprinity (Vita Zahnfabrik, Bad Säckingen, Germany) (CVS), and Group 5 (n = 20) Cameo (Aidite, Qinhuangdao, China) (CC). RESULTS: The average FR was similar for CCT, CC, and CEC at above 400 N, while CVS and UCT had the lowest values at 389,677 N and 343,212 N, respectively. CONCLUSION: Among the three ceramic materials that exhibited an FR above 400 N, CCT was considered the first recommended choice for CAD/CAM systems. This material not only demonstrated the highest FR but also exhibited outstanding consistency in the related measurements without the presence of outliers. Although the CC material showed high FR, its high dispersion revealed inconsistencies in the repetitions, suggesting caution in its use.

Comparative Analysis of the Structural Weights of Fixed Prostheses of Zirconium Dioxide, Metal Ceramic, PMMA and 3DPP Printing Resin-Mechanical Implications.

The aim of this study was to determine the mechanical implications of four-unit fixed dental prostheses (FDPs) made of (1) monolithic zirconium dioxide (ZR O2), (2) polymethylmethacrylate (PMMA), (3) metal ceramic (PFM) and (4) impression resin (3DPP). METHODS: Four groups were studied with eight samples for each material (n: 32). Each structure was weighed, subjected to compressive tests and analyzed using 3D FEA. RESULTS: PMMA presented the lowest structural weight (1.33 g), followed by 3DPP (1.98 g), ZR O2 (6.34 g) and PFM (6.44 g). In fracture tests, PMMA presented a compressive strength of 2104.73 N and a tension of 351.752 MPa; followed by PFM, with a strength of 1361.48 N and a tension of 227.521 MPa; ZR O2, with a strength of 1107.63 N and a tension of 185.098 MPa; and 3DPP, with a strength of 1000.88 N and a tension of 143.916 MPa. According to 3D FEA, 3DPP presented the lowest degree of deformation (0.001 mm), followed by PFM (0.011 mm), ZR O2 (0.168 mm) and PMMA (1.035 mm). CONCLUSIONS: The weights of the materials did not have a direct influence on the mean values obtained for strength, stress or strain. Since the performance was related to the tension and forces supported by the structures in critical zones, the importance of considering design factors is clear. In vitro and 3D FEA assays allowed us to simulate different scenarios for the mechanical properties of certain materials before evaluating them clinically. Thus, they can generate predictions that would allow for the design of a better research methodology in future clinical trials.

Comparative Analysis between Conventional Acrylic, CAD/CAM Milled, and 3D CAD/CAM Printed Occlusal Splints.

The development of digital technologies has allowed for the fabrication of new materials; however, it makes it difficult to choose the best methods to obtain occlusal splints with optimal properties, so it is essential to evaluate the effectiveness of these materials. The aim of the study is to compare the fracture resistance of occlusal splints made of different materials after thermo-mechanical aging. METHODS: A total of 32 samples were made from 4 materials (two 3D printed polymeric materials, a PMMA disc for CAD/CAM, and a conventional heat-cured acrylic resin); subsequently, the fracture test was performed using the load compression mode applied occlusally on the splint surface. STATISTICAL ANALYSIS: Four statistical tests were used (Shapiro-Wilk, Levene's test, ANOVA, and Tukey's HSD test). RESULTS: The following study showed that there are differences in fracture strength among the four materials investigated, where the highest strength was observed in the milled splint, with a mean of 3051.2 N (newton) compared to the strength of the flexible splint with 1943.4 N, the printed splint with 1489.9 N, and the conventional acrylic splint with 1303.9 N. CONCLUSIONS: The milled splints were the most resistant to fracture. Of the printed splints, the splint made with flexural rigid resin withstood the applied forces in acceptable ranges, so its clinical indication may be viable. Although the results of this research indicated differences in the mechanical properties between the CAD/CAM and conventional fabrication methods, the selection may also be influenced by processing time and cost, since with a CAD/CAM system there is a significant reduction in the production time of the splint material.

Fracture Resistance Comparative Analysis of Milled-Derived vs. 3D-Printed CAD/CAM Materials for Single-Unit Restorations.

The aim of this study was to evaluate and compare the fracture resistance of a single-unit fixed prosthesis, using a CAD/CAM PMMA material and two printed materials (3DPPa and 3DPPb). A typodont with a specific preparation for a full crown was used; a digital impression was made with a state-of-the-art scanner (PrimeScanTM, Dentsply-SironaTM, New York, NY, USA), and a full coverage restoration was designed using a biogeneric design proposal by means of specific software (InLAB 22.1, Dentsply-Sirona, NY, USA). Sixty crowns were prepared, divided into three groups according to the material: 3DPPa (n = 20), 3DPPb (n = 20), both 3D-printed from the .STL file with a resolution of 50 µm, and PMMA (n = 20) milled-derived, which were subjected to a thermocycling process. A universal testing machine (Universal/Tensile Testing Machine, Autograph AGS-X Series) with integrated software (TRAPEZIUM LITE X) equipped with a 20 kN load cell was used to determine the fracture resistance. Significant differences were found by Kruskal-Wallis test and multiple comparisons (p < 0.05) in fracture resistance between materials. The fracture resistance for the PMMA material was higher, and the standard deviation was lower (x = 1427.9; sd = 36.9 N) compared to the 3DPPa (x = 1231; sd = 380.1 N) and 3DPPb (x = 1029.9; sd = 166.46 N) prints. The restorations from the milled-derived group showed higher average fracture resistance than the provisional restorations obtained from the printed groups. However, the results demonstrated that all three materials analyzed in single-unit restorations are capable of withstanding the average masticatory forces.

Comparative Analysis between 3D-Printed Models Designed with Generic and Dental-Specific Software.

With the great demand in the market for new dental software, the need has been seen to carry out a precision study for applications in digital dentistry, for which there is no comparative study, and there is a general ignorance regarding their applications. The purpose of this study was to investigate the accuracy differences between digital impressions obtained using generic G-CAD (general CAD) and D-CAD (CAD dental) software. Today, there is a difference between the design software used in dentistry and these in common use. Thus, it is necessary to make a comparison of precision software for specific and generic dental use. We hypothesized that there is no significant difference between the software for specific and general dental use. METHODS: A typodont was digitized with an intraoral scanner and the models obtained were exported in STL format to four different softwares (Autodesk MeshMixer 3.5, Exocad Dental, Blender for dental, and InLAB). The STL files obtained by each software were materialized using a 3D printer. The printed models were scanned and exported in STL files, with which six pairs of groups were formed. The groups were compared using analysis software (3D Geomagic Control X) by superimposing them in the initial alignment order and using the best fit method. RESULTS: There were no significant differences between the four analyzed software types; however, group 4, composed of the combination of D-CAD (Blender-InLAB), obtained the highest average (-0.0324 SD = 0.0456), with a higher accuracy compared to the group with the lowest average (group 5, composed of the combination of the Meshmixer and Blender models), a generic software and a specific software (0.1024 SD = 0.0819). CONCLUSION: Although no evidence of significant difference was found regarding the accuracy of 3D models produced by G-CAD and D-CAD, combinations of groups where specific dental design software was present showed higher accuracy (precision and trueness). The comparison of the 3D graphics obtained with the superimposition of the digital meshes of the printed models performed with the help of the analysis software using the best fit method, replicating the same five reference points for the six groups formed, evidenced a greater tolerance in the groups using D-CAD.

Fracture Resistance Analysis of CAD/CAM Interim Fixed Prosthodontic Materials: PMMA, Graphene, Acetal Resin and Polysulfone.

The aim of this study was to evaluate and compare the fracture resistance of temporary restorations made of polymethylmethacrylate (PMMA), graphene-modified PMMA (GRA), acetal resin (AR) and polysulfone (PS) obtained by a subtractive technique (milling) using a computer-aided design and manufacturing (CAD/CAM) system of a three-unit fixed dental prosthesis (FDP). METHODS: Four groups of ten samples were fabricated for each material. Each specimen was characterized by a compression test on a universal testing machine, all specimens were loaded to fracture and the value in Newtons (N) was recorded by software connected to the testing machine. The fracture mode was evaluated on all samples using a stereomicroscope. RESULTS: There were statistically significant differences (p value < 0.005) between PMMA and the other three materials (PMMA: 1302.71 N; GRA: 1990.02 N; RA: 1796.20 N; PS: 2234.97). PMMA presented a significantly lower value than the other materials, and PS showed the highest value. GRA and RA presented a similar range of values but they were still higher than those of PMMA. CONCLUSIONS: GRA, RA and PS are presented as valid options within the range of interim milled restorative materials and as alternatives to PMMA.

Clinical outcomes of the biologically oriented preparation technique (BOPT) in fixed dental prostheses: A systematic review.

STATEMENT OF PROBLEM: The biologically oriented preparation technique is a concept with a vertical tooth preparation, gingitage, an immediate interim restoration preserving the clot, and a specific laboratory technique aiming to adapt the marginal periodontal tissue to a remodeled emergence profile of the crown. However, the published scientific evidence on this subject is limited. PURPOSE: The purpose of this systematic review was to analyze whether using the biologically oriented preparation technique leads to improved clinical outcomes in terms of probing depth, gingival inflammation index, gingival marginal stability, and fewer mechanical and biological complications. MATERIAL AND METHODS: Recommendations from the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were used in this systematic review. An electronic search of the MEDLINE/PubMed, EMBASE, Science Direct, Wiley Online Library, Cochrane, and ProQuest databases was made for articles published between March 2010 and July 2021 using keywords. Three reviewers selected and analyzed all articles that mentioned the biologically oriented preparation technique and met the inclusion criteria. RESULTS: A total of 6 articles met the inclusion criteria: 1 prospective randomized clinical study, 1 randomized clinical study, 1 prospective clinical study, and 3 case series. According to these studies, of all the teeth treated with the biologically oriented preparation technique, probing depth (greater than 3 mm) increased in only 2.3%, gingival inflammation was present in 22.8%, gingival recession occurred in 1.7% (decreased gingival stability), and mechanical and biological failures occurred in 4.4% of the teeth. CONCLUSIONS: Fixed dental prosthesis treatments performed following the concept of the biologically oriented preparation technique did not increase probing depth and showed a moderate rate of gingival inflammation, lower recession rates, and lower mechanical and biological failures at the 5-year follow-up. The biologically oriented preparation technique appears to be a viable alternative technique for obtaining satisfactory and stable clinical results up to 5 years. Long-term randomized clinical trials are recommended to reach more conclusions about this protocol.

Digital Volumetric Analysis of CAD/CAM Polymeric Materials after Tooth Brushing.

The objective of the study was to evaluate the volumetric wear of four composite materials for CAD/CAM (computer-aided design/computer-aided manufacturing) systems. The materials evaluated were: Cerasmart (CER), Shofu Block HC (SBH), Tetric CAD (TEC) and Brava (BRA). All the samples (n = 40) were subjected to simulated brushing (100,000 cycles). Wear was evaluated by superimposing pre-and post-brushing scans obtained with an intraoral optical scanner (CEREC Primescan; Dentsply Sirona, Germany), which were subsequently imported into the OraCheck software 5.0 (Dentsply Sirona, Germany). The data were analyzed by ANOVA test and Tukey's HSD test was used for multiple comparisons. Cerasmart showed the least wear after brushing. All the tested materials exhibited mass loss.

Fracture Resistance of Sintered Monolithic Zirconia Dioxide in Different Thermal Units.

The purpose of this study was to compare the fracture strength of monolithic zirconium dioxide subjected to a sintering process in two different furnaces: InFire HTC Speed and CEREC SpeedFire. METHODS: Forty restorations were designed and machined using a computer aided design / computer aidded machine (CAD/CAM) system. The restorations were randomly assigned to two groups of 20 samples each, Group 1 for the SpeedFire furnace (fast sintering) and Group 2 for the InFire furnace (slow sintering). Each of the crowns was subjected to a maximum compression load recorded in Newtons (N) and a displacement control with a speed of 1 mm/min. RESULTS: Group 1 presented an average of 1222.8 N and a standard deviation of 136.91 N. Group 2 obtained a mean of 1068.5 N and a standard deviation of 316.39 N. CONCLUSIONS: There were no significant differences between the two groups, and the mechanical strength of the material was not affected, which would imply a saving of clinical and laboratory time when performing rapid sintering on monolithic translucent zirconium dioxide restorations. However, rapidly sintered restorations have limited reliability.

Analysis of the mesh resolution of an .STL exported from an intraoral scanner file.

OBJECTIVES: This study aimed to provide information on the accuracy of exported digital files with the different resolutions available in the CEREC 4.6.2 software obtained by means of an intraoral scanner (IOS), in addition to establishing differences between materialized models with different exported resolutions, and how these different exported files can influence finite element analysis (FEA) simulations. MATERIALS AND METHODS: The upper complete arch of 10 patients was scanned through an IOS (CEREC Omnicam 1.0/Dentsply Sirona). Files of three resolution meshes digitalized by a CAD software (Cerec SW, 4.6.2) high, medium and low (IOSH, IOSM, and IOSL) were exported. Each file was evaluated by a software (NETFABB) about the number of triangles obtained and compared with the number announced by the manufacturer. Also, with a superimposition with a specialized software (GEOMAGIC X), the digital models were compared. The files of each resolution were printed (Sprintray 3D Printer), and the printed models were scanned with IOS (Omnicam 1.0) and compared with the control group (intraoral scanned high-resolution file, IOSH). FEA simulations were imported into COMSOL and analyzed under different loading conditions. RESULTS: The number of exported triangles coincided with that reported by the manufacturer. The digital models from files of different resolution did not show significant differences (less than 1.5 um) between each other. Models printed (H, M, L) from files of the same resolution mesh (H, M, L) did not show significant differences between them either in partial measures of the arch and neither in the complete arch. FEA showed significant differences in stress concentration between different exported models. CLINICAL SIGNIFICANCE: Digital models can be exported and printed in three resolutions of the mesh, without differences clinically significative. On the other hand, for future FEA applications further research should be performed in order to determine the optimal number of triangles.

The importance of esthetic integration through laboratory adaptation profiles in the biologically oriented preparation technique.

The biologically oriented preparation technique (BOPT) has revolutionized the execution of fixed prosthetic treatments, ensuring tissue stability and the integration of the gingival tissue with the prosthetic restorations. BOPT follows both a clinical and laboratory sequence; the two must be perfectly integrated and synchronized, with the phase of preparation and temporary restorations in the clinic correlating with a well-founded and protocolized execution of the laboratory steps. In turn, prosthetic work returned to the clinic must show perfect integration between the prosthesis, the preparation, and the periodontal tissue, with a balance between pink and white esthetics. The clinical case in the present article illustrates the close relationship between the clinical and laboratory steps, including the technical laboratory procedures, that make it possible to achieve these objectives. The aim of the article is to introduce the concept of the prosthetic adaptation profile of new restorations, establishing the definition, importance, and direct relationship of this profile with the success of the rehabilitation treatment.

Comparative Analysis of Fracture Resistance between CAD/CAM Materials for Interim Fixed Prosthesis.

The aim of this study was to evaluate and compare the resistance to fracture of interim restorations obtained through additive techniques (3D impressions) and subtractive techniques (milling) using a computer-aided design and manufacture (CAD/CAM) system of a three-unit fixed dental prosthesis (FDP) to ascertain its clinical importance. (1) Materials and methods: In total, 40 samples were manufactured and divided into two groups (n = 20) using: (1) light-curing micro hybrid resin for temporary crowns and bridges (PriZma 3D Bio Prov, MarketechLabs, São Paulo, Brazil) for the rapid prototyping group (RP) and (2) a polymethylmethacrylate (PMMA) CAD/CAM disc (Vipiblock Trilux, VIPI, São Paulo, Brazil) for the computer-assisted milling (CC). The resistance to fracture was determined with a universal testing machine. (2) Results: The strength and the standard deviation for the computer-assisted milling group were higher (1663.57 ± 130.25 N) than the rapid prototyping (RP) group, which had lower values of (1437.74 ± 73.41 N). (3) Conclusions: The provisional restorations from the computer-assisted milling group showed a greater resistance to fracture than the provisional restorations obtained from the rapid prototyping group.

Resistance to Fracture of Lithium Disilicate Feldspathic Restorations Manufactured Using a CAD/CAM System and Crystallized with Different Thermal Units and Programs.

The aim of this study was to determine the resistance to fracture of feldspathic restorations with lithium disilicate and crystallized with different ovens and programs. METHODS: Sixty monolithic restorations (LD) (EMAX CAD™ LT, Ivoclar-Vivadent™) were designed with the same parameters and milled with a CAD/CAM system (CEREC SW 5.1, CEREC MCXL, Dentsply-Sirona™, Bensheim). Each restoration was randomly assigned by randomization software (RANDNUM) to one of the three groups: (a) (NF) Oven P310 (Ivoclar, Vivadent) normal crystallization program, (b) (FF) Ivoclar P310 oven (Ivoclar-Vivadent™) rapid crystallization program, or (c) (SF) SpeedFire oven (Dentsply-Sirona™). RESULTS: There were statistically significant differences between the groups (ANOVA, p < 0.05). The NF and FF groups showed the highest values of resistance to fracture, with statistically significant differences with the SF group. CONCLUSIONS: Using a furnace from the same dental company with predetermined programs from the material manufacturer, as well as using a predetermined program for rapid crystallization, has no effect on fracture resistance, and would save clinical time when performing ceramic restorations with lithium disilicate, while keeping their mechanical properties.

Adhesive Systems Used in Indirect Restorations Cementation: Review of the Literature.

New technologies are changing the therapeutical options to do indirect restorations and new adhesive systems are continuously introduced to be used by clinicians. Different interactions between restorations, adhesive systems components, enamel and dentin require having criteria based on the selection of the adhesive system, ensuring the longevity of the restorations and the preservation of the biological remnant. The adhesion force to the dental tissue is one of the indicatives of the behavior of the adhesive systems and influences the behavior of the treatments with direct and indirect restorations. The objective of this search was to find the adhesive systems with the best results in terms of the adhesion strength of indirect restorations on the dental tissues. The search was conducted in two MEDLINE digital databases (PubMed), and the Cochrane Library with a search strategy based on the combination of MeSH (Medical Subject Headings) keywords. This systematic review used the PRISMA guide (Preferred Reporting Items for Systematic Reviews and Meta-Analysis). According to this review, the 3-step adhesive systems were the best performing and still are the gold standard for the cementing of indirect restorations. In addition, it can be concluded that self-etched adhesive systems reduce the time spent in clinical practice, however at the interface level they behave as permeable membranes more susceptible to degradation.