Master Model Research Articles

An In-Vitro Evaluation of Articulation Accuracy for Digitally Milled Models vs. Conventional Gypsum Casts.

With the advent of a digital workflow in dentistry, the inter-occlusal articulation of digital models is now possible through various means. The Cadent iTero intraoral scanner uses a buccal scan in maximum intercuspation to record the maxillomandibular relationship. This in-vitro study compares the occlusion derived from conventionally articulated stone casts versus that of digitally articulated quadrant milled models. Thirty sets of stone casts poured from full arch polyvinyl siloxane impressions (Group A) and thirty sets of polyurethane quadrant models milled from digital impressions (Group B) were used for this study. The full arch stone casts were hand-articulated and mounted on semi-adjustable articulators, while the digitally derived models were pre-mounted from the milling center based on the data obtained from the buccal scanning procedure. A T-scan sensor was used to obtain a bite registration from each set of models in both groups. The T-scan data derived from groups A and B were compared to that from the master model to evaluate the reproducibility of the occlusion in the two groups. A statistically significant difference of the contact region surface area was found on #11 of the digitally articulated models compared to the master. An analysis of the force distribution also showed a tendency for a heavier distribution on the more anterior #11 tooth for the digitally articulated models. Within the limitations of this study, the use of a digitally articulated quadrant model system may result in a loss of accuracy, in terms of occlusion, the further anteriorly the tooth to be restored is located. Care must be taken to consider the sources of inaccuracies in the digital workflow to minimize them for a more efficient and effective restorative process.

Does the geometry of scan bodies affect the alignment accuracy of computer-aided design in implant digital workflow: An in vitro study?

To compare 2 implant scan bodies with different geometry on the accuracy of the virtual alignment process in the digital workflow. A master model of the edentulous maxilla with 6 implants and multiunit abutments (MUA) inserted was fabricated. Six dome-shaped and cuboidal scan bodies were mounted on the MUAs, respectively, and consecutively scanned by a laboratory scanner 10 times. The original scans were imported to a dental-specific CAD software and virtually aligned with the default CAD model in the implant library. Thus, 10 aligned models were created. Both the original scans and the aligned models were evaluated by an inspection software for deviation of the scan body surfaces, the centroids of scan body and MUA, the scan body center-axis, and the inter-MUA distances/angles. The two-sample T-test/Mann-Whitney U test were used to analyze the data with the level of significance set at 0.05. The cuboidal group showed significant greater deviations of the model surface (13.9µm vs. 10.7µm) and the MUA centroids (31.7µm vs. 22.8µm) but smaller deviation of the inter-MUA angle (0.047° vs. 0.070°) than those of the dome-shaped group (p<.05). No significant differences in the deviation of scan body centroids, center-axis, and the inter-MUA distances between the 2groups were found. Virtual alignment of implant scan body affected the accuracy of the digital workflow for complete-arch implant-supported prostheses (up to ~30µm/0.09°). Different geometries of the implant scan body could also influence the transfer accuracy in the CAD process.

Comparison of retentive force and wear pattern of Locator® and ADD-TOC attachments combined with CAD-CAM milled bar.

PURPOSEThe purpose of this study was to investigate changes in retention and wear pattern of Locator® and ADD-TOC attachments on a digital milled bar by performing chewing simulation and repeated insertion/removal of prostheses in fully edentulous models.MATERIALS AND METHODSLocator (Locator®; Zest Anchors Inc., Escondido, CA, USA) was selected as the control group and ADD-TOC (ADD-TOC; PNUAdd Co., Ltd., Busan, Republic of Korea) as the experimental group. A CAD-CAM milled bar was mounted on a master model and 3 threaded holes for connecting a bar attachment was formed using a tap. Locator and ADD-TOC attachments were then attached to the milled bar. Simulated mastication and repeated insertion/removal were performed over 400,000 cyclic loadings and 1,080 insertions/removals, respectively. Wear patterns on deformed attachment were investigated by field emission scanning electron microscopy.RESULTSFor the ADD-TOC attachments, chewing simulation and repeated insertion/removal resulted in a mean initial retentive force of 24.43 ± 4.89 N, which were significantly lower than that of the Locator attachment, 34.33 ± 8.25 N (P < .05). Amounts of retention loss relative to baseline for the Locator and ADD-TOC attachments were 21.74 ± 7.07 and 8.98 ± 5.76 N (P < .05).CONCLUSIONCAD-CAM milled bar with the ADD-TOC attachment had a lower initial retentive force than the Locator attachment. However, the ADD-TOC attachment might be suitable for long-term use as it showed less deformation and had a higher retentive force after simulated mastication and insertion/removal repetitions.

Accuracy of Conventional and 3D-Printed Casts for Partial Fixed Prostheses.

To evaluate and compare the accuracy of conventional and 3D-printed casts using five different 3D printers. In the control group (CG group, n = 5), five conventional impressions using light- and heavy-body polyvinyl siloxane were obtained from the master model, resulting in five stone models. In the test groups, five different scans were performed by a well-trained and experienced clinician using a TRIOS intraoral scanner. All data were exported in STL file format, processed, and sent to five 3D printers. Five casts were manufactured in each printer group: SG (CARES P20, Straumann); FG (Form 2, Formlabs); WG (Duplicator 7, Wanhao); ZG (Zenith D, Zenith); and MG (Moonray S100, Moonray). Measurements of the accuracy (trueness and precision) of the casts obtained from conventional elastomeric impressions and 3D-printing methods were accomplished using a 3D analysis software (Geomagic Control). The FG group showed the lowest values for trueness (indicating a value closer to real dimensions), which were similar to the SG group only (P > .05). MG, WG, and ZG groups presented higher values and were similar compared to each other. Data on precision demonstrated that all 3D-printed groups showed lower values for precision (smaller deviation) when compared to the CG. The trueness depends on the chosen 3D printer. All of the tested 3D printers were more precise than cast models obtained from conventional elastomeric impressions.

42 - Fatigue Resistance of CAD/CAM and 3D-Printing Provisional Restorations

3D-printed provisional restorations can be fabricated using additive manufacturing (AM) technologies. However, little information about their performance is available. The aim of this study was to compare the fatigue resistance of 3-teeth provisional resin restorations obtained by 3D printing with those made from polymethylmethacrylate (PMMA) blocks using a CAD/CAM system. A titanium master model for 3-teeth fixed dental prostheses (FDPs) (abutment teeth 45 and 47) was prepared. The master model was scanned and 14 provisional FDPs were produced using respectively: group 1 (N=7): CAD/CAM + BreCAM HIPC-Bredent (BH); group 2 (N=7): 3D printing + NextDent (ND). The FDPs were cemented on the titanium master model with a provisional cement (Temp Bond, Kerr) and submitted to a 5-step incremental cyclic isometric loading: step 1: 5.000 cycles at 10 Hz with 200 N compressive load; steps 2 to 5: 30.000 cycles at 3 Hz with a compressive load respectively of 400 N, 600 N, 800 N and 950 N. Group 1 and 2 were compared using the life table survival analysis and t-test. In group 1 (BH), only 5 specimens endured the entire fatigue process, while 2 specimens failed at 950 N. In group 2 (ND), 1 specimen failed at 400 N, 5 specimens (ND) failed at 600 N) and 1 specimen failed at 800 N. PMMA CAD/CAM provisional FDPs showed higher fatigue resistance when compared to the ones made via 3D printing.

Accuracy of Different Complete-Arch Digital Scanning Techniques with a Combined Healing Abutment-Scan Body System.

Investigate the effects of three different complete-arch digital implant scanning techniques used with a combined healing abutment-scan body (CHA-SB) system on the accuracy (trueness and precision) and scan time. A poly(methyl methacrylate) master model simulating an edentulous maxilla was fabricated with four parallelly inserted dental implants. A CHA-SB system was attached to each implant. The model surface was scanned using a structured blue light industrial extraoral scanner to achieve a reference model standard tessellation language file (MRM-STL). Three different scanning techniques-(1) conventional technique with unmodified master model, (2) scan body splinting technique using orthodontic elastic ligatures and plastic splint materials, and (3) land-marking technique using pyramid-shaped glass-ceramic markers-were performed. Fourteen consecutive digital scans were made by using an intraoral scanner (IOS) for each technique, converted to an STL file, and superimposed on the MRM-STL. Trueness and precision were calculated for each technique. The scan time was also recorded. The data were analyzed with one-way analysis of variance (ANOVA) and Tukey honest significant difference (HSD) tests (α = .05). Effects of different scanning techniques on the trueness (distance and angular deviations; P < .001) and scan time (P = .002) were statistically significant. For precision, different scanning techniques had only a significant effect on the distance deviation (P < .001). Regarding trueness and precision, none of the scanning techniques was superior to others. The scan body splinting technique led to significantly less scan time.

Accuracy of different materials used in impressions for fixed partial dentures

Background: There are several elastic impression materials available for dental use. The present study evaluated accuracy of different materials used in impressions for fixed partial dentures.Materials & Methods: A master model of partially edentulous mandibular left hemi-arch segment was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were taken using alginate and elastomeric materials and stone casts were formed. For the silicones, impression techniques were compared. Results: The mean discrepancies between the prepared tooth edges in the master model and in the stone casts in group I was 0.38 mm, in group II was 0.20 mm, in group III was 0.15 mm and in group IV was 0.34 mm. The difference was significant (P

ВЫСШЕЕ МЕДИЦИНСКОЕ ОБРАЗОВАНИЕ С ПОЗИЦИИ АНДРАГОГИЧЕСКОГО ПОДХОДА

The requirements for medical university graduates in modern conditions imply a broad mastery of professional competencies, including not only theoretical knowledge, but also practical medical skills. The rapid development of medical science and practice doesn`t allow us to limit ourselves to the traditional «academic» approach to learning, the basis of which is the memorization of large amounts of information, but dictates the necessity to teach students the skills of self­education and self­improvement throughout their lives. Andragogical approach, which requires the introduction of other methods and principles into the educational process, corresponds to the achievement of this goal. An important component of modern learning technology is the motivation of a student to master a future profession, the acquisition of skills in the analysis and synthesis of information, the principles of a scientific approach, the formation of an individual trajectory of the educational process. In this regard, we need to discuss possible ways to increase the motivation of not only the student, but also the teacher to master and implement andragogical models and principles. A graduate of a medical university, starting an independent medical activity, should have the skill of teamwork, quick decision­making, which can be formed only if the principle of joint training of a teacher and a student is observed.

Didactic model of masters of philology training for cultural and educational activities under distance learning conditions

Didactic model of masters of philology training for cultural and educational activities under distance learning conditions

Improvement of laser hardening technology with oscillating beam using multiphysics simulation

A simulation approach was used to improve the results of the laser hardening process of a thin-walled medium manganese steel specimen using oscillating beam technology. During the analysis of the material hardness results, it was found that the hardened zone had an irregular shape, which was the result of different thermal cycles varying with the process progress and heating of the sample. A simulation model of the laser hardening process was built to determine the proper power values to compensate for the effect of thermal inertia of the cool part. The simulation approach, in addition to the development of the master model, included the definition of the proper beam power distribution and the virtual determination of the necessary oscillation frequency that allows the equivalent linear beam distribution to be used in the calculations. The main model considered the dependence of the material properties on the phase composition of the material and was calibrated based on the results of experimental thermocouple measurements. This enabled the determination of the required power course. Using the simulation-calculated beam power, a hardening process was carried out, the results of which confirmed the successful modification of the shape of the hardened zone.

WITHDRAWN: Comparative evaluation of internal and marginal fit of interim crowns fabricated by CAD/CAM milling and two different 3D printing systems - An in vitro study

The aim of the present study is to compare and evaluate the internal and marginal fit of interim crowns fabricated by CAD/CAM milling and two different 3D printing systems. Fabrication of the metal master model was done by Selective Laser Melting Unit after preparing and scanning a typhodont tooth. A designing software was used to design crowns onto the metal master model after scanning it. The STL (Stereolithography) file of designed crowns is then sent to CAD/CAM milling machine and two different 3D printing systems namely Stereolithography (SLA) and digital light processing (DLP) for fabrication of 15 crowns each. Internal and marginal fit was measured with the help of silicon replica technique and obtained data was analysed with one way ANOVA which was followed by Tukey’s post-hoc analysis test for verifying the statistical significance. The smallest discrepancy of 96.7 μm was observed in DLP 3D Printing group followed by 131.1 μm in SLA 3D printing group and lastly CAD/CAM group stood with the discrepancy of 179.6 μm. A significant difference was seen for discrepancy values of the 3 groups and it was observed that DLP 3D Printing was able to manufacture crowns with better marginal and internal fit than SLA 3D Printing and SLA 3D Printing was better than CAD/CAM Milling group.

Do digital impressions have a greater accuracy for full-arch implant-supported reconstructions compared to conventional impressions? An in vitro study.

The purpose of this study was to compare the accuracy of conventional implant impressions with digital impression techniques made using two different intraoral scanners. In-Vitro study. A scan of master cast containing four implants was made using two intraoral scanners: CEREC Primescan (Dentsply Sirona, USA) and 3Shape Trios (Copenhagen, Denmark) with PEEK scan bodies attached to the implants. Model was scanned ten times using different scanners. The accuracy of the chairside scanners was compared with highly accurate laboratory scanner. The scans were transferred into the software (Geomagic Control X 20, 3D Systems, Rock Hill, SC, USA) for analysis. The linear deviations and the angular deviations between the scans (scan of each model made using high-definition scanner and the master model scan) were calculated to determine the accuracy. Trueness was used as a parameter to compare the accuracy of different scanners (comparing test and reference). Analysis of variance was performed with Bonferroni's post hoc test for multiple group comparisons. Distribution of the mean overall absolute linear deviation was significantly lower in the conventional impression group compared to the CEREC Primescan scanner group and 3Shape Trios group (P < 0.05 for both). Distribution of the mean overall absolute linear deviation was significantly lower in the CEREC Primescan scanner group compared to the 3Shape Trios group (P < 0.05). Distribution of the mean overall absolute angular deviation did not differ between the three groups (P > 0.05 for all). Conventional impressions showed significantly greater accuracy compared to the digital impressions made with both the above intraoral scanners for implant-supported restoration of an edentulous arch. In addition, the digital impressions with the CEREC Primescan scanner showed greater accuracy as compared to the 3Shape Trios scanner.

Investigation of the marginal fit of a 3D-printed three-unit resin prosthesis with different build orientations and layer thicknesses.

PURPOSEThe purpose of this study was to analyze the marginal fit of three-unit resin prostheses printed with the stereolithography (SLA) method in two build orientations (45°, 60°) and two layer thicknesses (50 µm, 100 µm).MATERIALS AND METHODSA master model for a three-unit resin prosthesis was designed with two implant abutments. Forty specimens were printed using an SLA 3D printer. The specimens were printed with two build orientations (45°, 60°), and each orientation was printed with two layer thicknesses (50 µm, 100 µm). The marginal fit was measured as the marginal gap (MG) and absolute marginal discrepancy (AMD), and MG and AMD measurements were performed at 8 points per abutment, for 16 points per specimen. All statistical analyses were performed using SPSS software. Two-way analysis of variance (ANOVA) was separately performed on the MG and AMD values of the build orientations and layer thicknesses. Moreover, one-way ANOVA was performed for each point within each group.RESULTSThe margins of the area adjacent to the pontic showed significantly high values, and the values were smaller when the build orientation was 45° than when it was 60°. However, the margin did not differ significantly according to the layer thicknesses.CONCLUSIONThe marginal fit of the three-unit resin prosthesis fabricated by the SLA 3D method was affected by the pontic. Moreover, the marginal fit was affected by the build orientation. The 45° build orientation is recommended.

Evaluation and comparison of vertical marginal fit of three different types of multiunit screw-retained framework fabricated for an implant-supported prosthesis - An in vitro study.

The present study aimed to evaluate on a comparative basis the vertical marginal fit between conventionally casted, direct metal laser sintered (DMLS), and milled computer-aided design/computer-aided manufacturing (CAD-CAM) one-piece metal framework supported by five implants using one-screw test and screw resistance test. This is an in vitro study. Five implants were placed parallel to one other in a Styrofoam master model. A total of 30 implant-supported screw-retained superstructures were manufactured using three techniques, i.e., conventionally casted, milled, and sintered. To evaluate the vertical marginal discrepancy, screw resistance test, and one-screw test were used, and measurements were made using a stereomicroscope. The data was analysed using two statistical tests, i.e., ANOVA and the post hoc Bonferroni test. On evaluating the frameworks using one-screw test, the mean vertical misfit value at the terminal implant for the control group was 292.58 ± 15.46μm, for conventionally casted framework 398.41 ± 21.13 μm, for DMLS 343.44 ± 24.73 μm, and for CAD-CAM was 304.03 ± 14.23 μm, whereas the average misfit values at four implants on applying screw resistance test were 1268.65 ± 84.24 (control), 1774.88 ± 67.70 (casted), 1508.02 ± 62.19 (DMLS), and 1367.29 ± 81.87 (CAD-CAM). The average misfit values on two implants using screw resistance test were 635.02 ± 57.33 for the control group; for conventionally casted, it was 879.75 ± 35.93; for (DMLS) framework, it was 761.51 ± 32.85; and for milled CAD-CAM framework, it was 687.07 ± 42.17 μm. The mean vertical marginal discrepancy, when compared with control, was least in milled CAD-CAM frameworks, followed by sintered DMLS and conventionally casted frameworks. Hence, according to the present study, CAD/CAM technique is recommended to achieve maximum marginal fit in full mouth screw-retained implant-supported FDPs.

Accuracy of Elastomeric Impression Made with Standard and Dual Arch Tray: An In-vitro Study

Introduction: The dual-arch impression techniques utilise special stock impression trays of various designs. These trays are made of plastic or metal with fabric or mesh material placed across the occlusal surfaces of the teeth connecting their buccal and lingual flanges. These special trays register the impression of the opposing segments of the dentition. The dual arch impression technique is used in dentistry effectively since many decades but there is very little evidence published regarding the effect of different tray design on the accuracy of impression. Aim: To evaluate the accuracy of inter-abutment distance in dies obtained from different dual-arch trays and with those obtained from stock metal trays. Materials and Methods: This in-vitro study was carried out in the Department of Prosthodontics, M.M. College Of Dental Sciences and Research, Mullana, Haryana, India between June 2016 to November 2017. A total of 70 elastomeric impression using heavy and light body addition silicone impression material were made, of the prepared typodont teeth of right mandibular first premolar and first molar for thee- unit fixed partial denture. impressions were grouped into four groups, based on the type of tray used i.e. Group A consisted of impressions obtained from plastic dual-arch trays (n=20), Group B- plastic reinforced with metal dual-arch trays (n=20), Group C- metal dual-arch trays (n=20) and Group D-full stock metal trays (n=10). Group A, B and C were further divided into Subgroup I (working side poured first) (n=10) and Subgroup II (non-working side poured first) (n=10) depending upon the sequence of pouring. The measurements were obtained using travelling microscope and statistical analysis was done using one-way Analysis of Variance (ANOVA) test which was then followed by a post-hoc test. Results: The inter-abutment distance showed a decreased value in all the groups when compared to the master model (p-value &gt;0.05). Percentage decrease in inter-abutment distance was between 0.006% - 0.48%. The results indicated statistical insignificant difference when full arch metal stock tray impression is compared to all dual arch trays impression. There was insignificant difference between the inter-abutment distance obtained using dual arch trays which were poured with working or non working side first. Conclusion: The impressions obtained with both dual arch trays and stock tray, produced dies with distortion in a clinically relevant range. Thus, dual arch trays can be recommended for making impressions of short span fixed partial dentures, and can be considered to be an alternative to the conventional method.

Comparative evaluation of internal and marginal fit of interim crowns fabricated by CAD/CAM milling and two different 3D printing systems - An in vitro study

The aim of the present study is to compare and evaluate the internal and marginal fit of interim crowns fabricated by CAD/CAM milling and two different 3D printing systems. Fabrication of the metal master model was done by Selective Laser Melting Unit after preparing and scanning a typhodont tooth. A designing software was used to design crowns onto the metal master model after scanning it. The STL (Stereolithography) file of designed crowns is then sent to CAD/CAM milling machine and two different 3D printing systems namely Stereolithography (SLA) and digital light processing (DLP) for fabrication of 15 crowns each. Internal and marginal fit was measured with the help of silicon replica technique and obtained data was analysed with one way ANOVA which was followed by Tukey’s post-hoc analysis test for verifying the statistical significance. The smallest discrepancy of 96.7 μm was observed in DLP 3D Printing group followed by 131.1 μm in SLA 3D printing group and lastly CAD/CAM group stood with the discrepancy of 179.6 μm. A significant difference was seen for discrepancy values of the 3 groups and it was observed that DLP 3D Printing was able to manufacture crowns with better marginal and internal fit than SLA 3D Printing and SLA 3D Printing was better than CAD/CAM Milling group.

EVALUATION OF MARGINAL FIT AND INTERAL FIT OF METAL COPINGS FABRICATED BY THREE DIFFERENT TECHNIQUES- AN IN VITRO STUDY

Statement of problem: An optimal marginal and internal fit plays an important role in the longevity of a restoration. Increased marginal gaps can cause bacterial and biofilm adherence. Also, poor internal fit can lead to decreased retention and resistance form. There are various techniques available for the fabrication of restorations. All these techniques have their own pros and cons. In regards to these problems, the present study was conducted to find out whether the manufacturing technique has any influence on the marginal and internal fit of copings. Aim: The aim of this study was to evaluate and compare the internal and marginal fit of Co-Cr copings fabricated by three different techniques namely, conventional lost wax technique, 3D resin printing technique and CAD/CAM milling technique. Materials and methods: A stainless steel master model and a custom tray were fabricated. Totally 30 impressions were made and poured with die stone to obtain 30 die specimens. The specimens were grouped into three groups. Group 1- conventional lost wax technique, group 2- 3D resin printing technique and group 3- CAD/CAM milling technique. Co-Cr copings were fabricated using the respective technique. For evaluating the internal fit, weighing technique was followed. The cross-sectional technique was followed to assess the marginal fit. Results: There was statistically significant difference between the different groups in terms of internal and marginal fit. The CAD/CAM milling technique showed better marginal and internal fit compared to the other two techniques. The 3D resin printing technique showed better results than the conventional technique but was not statistically significant. Conclusion: Within the limitations of this present study, the results drawn suggests the use of CAD/ CAM milling technique and the 3D resin printing technique for fabricating restorations in routine dental practice.

Comparison of stresses in monoblock tilted implants and conventional angled multiunit abutment-implant connection systems in the all-on-four procedure

BackgroundThe All-on-four dental implant method is an implantology method designed to provide a comfortable prosthetic treatment option by avoiding advanced surgical procedures. This research aims to compare and evaluate the stress and tension values in conventional angled multiunit abutment-implant connection systems and monoblock dental implants used in the all-on-four procedure with finite element analysis.MethodsTwo master models were created by placing four implants connected to multiunit abutments (group A) in the interforaminal region of a completely edentulous mandible and four monoblock implants (group B) in the same region of another completely edentulous mandible. Group A implants were classified according to their diameter as follows: 3.5 mm (M1A), 4.0 mm (M2A), and 4.5 mm (M3A). Similarly, group B implants were classified as M1B, M2B, and M3B. In the six models rehabilitated with acrylic fixed prostheses, a 100 N force was applied to the anterior implant region, and a 250 N force was applied to the posterior cantilever in both axial and 30° oblique directions. Von Mises stresses were analyzed in the bone and implant regions of all models.ResultsM1A and M1B, M2A and M2B, and M3A and M3B were compared with each other under axial and oblique forces. The maximum Von Mises stresses in the bone around implants and the prosthesis screws, and the maximum and minimum principal stresses in the cortical and trabecular bone in group A models were significantly higher than those in group B models.ConclusionsIn monoblock implant systems under axial and oblique forces, higher stress is accumulated in the bone, prosthesis screw and implant compared to multiunit abutment-implant connection systems.

Main and Secondary Controller Assignment With Optimal Priority Policy Against Multiple Failures

This paper proposes a master and slave controller assignment model against multiple controller failures in software defined networks considering latency between switches and controllers. The survivability guarantee of each switch is satisfied by assigning a set of controllers, where one of them works as the master controller to control the switch. Given assigned controllers, we introduce a policy-based approach to automatically specify the master controllers in each failure pattern, which leads to a lightweight configuration on a switch. We define the average-case expected latency, the worst-case expected latency, and the expected number of switches within a latency bound, as three objectives to be optimized in three different problems. We prove that a low latency first policy achieves the optimal objective for each considered problem. We formulate the proposed controller assignment model with different goals as three mixed integer linear programming problems. We prove the NP-completeness for all the three problems. A greedy algorithm with polynomial time complexity is developed; we show that it provides a 1/2-approximation for the case without the survivability guarantee constraint. The numerical results observe that the proposed model obtains the optimal objective value with the computation time about 102 times shorter than that of a baseline that introduces decision variables to determine the master controllers.

Evaluation of physical properties of polyamide and methacrylate based denture base resins polymerized by different techniques.

This study aims to comparatively evaluate the flexural strength, internal adaptation, elastic modulus, and maximum deflection of a newly introduced, strengthened injection-molded semi-flexed polyamide resin (Deflex) and a conventional heat-cured resin containing cross-linking polymethyl methacrylate denture base polymers (QC-20). A vinyl polysiloxane film replicating the gap between the denture base and the metallic master model of an edentulous maxilla was weighed using an analytical balance with an accuracy of 0.0001 g for the measurement of internal adaptation. The measurements were performed immediately after surface finishing. Seven rectangular test samples measuring 65 × 10 × 3.3 mm3 were set up for flexural strength test. Flexural strength test (three-point bending test) was performed using a universal machine under axial load at a crosshead speed of 5 mm/min. One-way ANOVA (α = 0.05) following by t tests was utilized in statistical analysis. The difference between the flexural strength of the denture base resins of Deflex and QC-20 was found to be statistically significant. The injection-molded resin demonstrated better internal adaptation compared to the conventional heat-polymerized resin. Evaluation of the physical test results revealed that the polyamide samples were more flexible than polymethyl methacrylate and did not break during flexural strength tests. Some properties of denture base resins, such as resin types, internal adaptation, and mechanical strength, may play a significant role in clinical performance of complete dentures and removable partial prostheses. Because of the superior flexural strength properties and internal adaptation characteristics, Deflex may prove to be a useful alternative to conventional denture base resin.