Cobalt-chromium Frameworks Research Articles

Peri-implant stress distribution in maxillary All-on-4 prosthesis fabricated on multi-unit angled abutment with cobalt chromium framework versus those with titanium framework: A 3D Finite Element Analysis

Peri-implant stress distribution in maxillary All-on-4 prosthesis fabricated on multi-unit angled abutment with cobalt chromium framework versus those with titanium framework: A 3D Finite Element Analysis

Peri-implant stress distribution in mandibular All-on-4 prostheses fabricated on multi-unit abutments with cobalt chromium framework versus those with zirconia framework: A 3D Finite Element Analysis

Peri-implant stress distribution in mandibular All-on-4 prostheses fabricated on multi-unit abutments with cobalt chromium framework versus those with zirconia framework: A 3D Finite Element Analysis

Non-metal framework for removable partial dentures – A 2-year follow-up clinical report

Traditional removable partial dentures (RPDs) with cobalt-chromium frameworks have been used for several decades, restoring the masticatory function. However, these frameworks have been documented as aesthetically unacceptable due to the display of metal clasps. The patients' increased demands regarding the aesthetic aspects of rehabilitation treatment led to the introduction of new, more aesthetic materials in clinical practice. One of the main materials is polyetheretherketone (PEEK). This clinical report presents PEEK as an alternative material for fabricating RPD frameworks for a Class III Kennedy partial edentulous mandible. The framework was constructed using CAD/CAM manufacturing, and the process combined laboratory scanning, digital framework design, resin try-in milling, and PEEK framework milling. The framework showed good adaptation to the abutment teeth and surrounding tissues. The patient was followed for 2 years without complaints and was grateful for the aesthetics. During this period, there were no signs of degradation in the framework, and the clasps were still as retentive as they were at the initial appointment, with only some pigmentation of the structure being observed.

Radiographic Estimation for the Effect of Using Karadent versus Cobalt Chromium Framework on the Supporting Structures in Bilateral Distally Extended Partial Denture Cases

Radiographic Estimation for the Effect of Using Karadent versus Cobalt Chromium Framework on the Supporting Structures in Bilateral Distally Extended Partial Denture Cases

Evaluation of Periodontal Health of The Abutment Teeth in Partial Dentures Made of Injection Molded PEEK Framework Versus Cobalt Chromium Framework in Mandibular Kennedy Class I Free End Saddle Edentulous Cases: A Randomized Clinical Trial

Evaluation of Periodontal Health of The Abutment Teeth in Partial Dentures Made of Injection Molded PEEK Framework Versus Cobalt Chromium Framework in Mandibular Kennedy Class I Free End Saddle Edentulous Cases: A Randomized Clinical Trial

Evaluation and comparison of retention and patient satisfaction with milled polyetheretherketone versus metal maxillary obturators

Statement of problemMetal and polyetheretherketone (PEEK) have been used to rehabilitate maxillary defects with obturators, each having advantages and disadvantages. However, patient satisfaction with the obturator retention of each material is unclear. PurposeThe purpose of this crossover clinical study was to compare retention and patient satisfaction between a milled cobalt chromium and a milled PEEK framework, each with a hollow bulb extension in polymethyl methacrylate (PMMA). Material and methodsTwenty patients who had received unilateral total maxillectomy and were treated in the prosthodontic department's maxillofacial clinic were enrolled in this crossover study. Each participant wore 2 different types of obturators for 6 months after insertion. Type CoCr received a milled cobalt chromium framework with a hollow bulb extension in PMMA first, and type Pk received a milled modified PEEK (BioHPP) framework with a hollow bulb extension in PMMA first. Patient satisfaction and retention force were measured immediately, at 3 months, and at 6 months after obturator insertions. The Fischer exact, chi-squared, and Monte Carlo tests were used to compare qualitative data. One-way ANOVA with the post hoc Tukey test was used for pair-wise comparison, and repeated measures ANOVA was used to compare before and after treatment at 3 and 6 months. ResultsNo significant difference was found between types in obturator insertion (P>.999), appearance of the upper lip (P>.999), mouth feeling (P=.301), pronunciation of words (P=.217), and talking in public (P=.589). A significant difference between types was found in speech after 6 months of obturator insertion (P=.016), swallowing liquids and food (P=.04), masticating foods (P=.007), appearance of clasps on anterior teeth (P=.002), satisfaction with appearance (P=.005), or avoidance of family events (P=.014) after 6 months of insertion. Types of obturators showed a statistically significant decrease in retention force with time (P<.001). ConclusionsAlthough the retention force was less with PEEK than with Co-Cr clasps engaging the same undercuts, this retention force was adequate for retaining removable partial dentures. Co-Cr clasps can be considered better than PEEK clasps because they engage the same undercuts regarding loss of retention with time. Quality of life in patients after maxillary resection could be improved by using maxillary obturators. Type Pk was better than type CoCr in terms of esthetics, but the retention of the PEEK obturator after 6 months decreased because of wear, leading to difficulty swallowing food or liquids, mastication, and speech.

Recycling selective laser melting alloy powder on cobalt chromium-to-ceramic bond strength

Statement of problemReusing the powder in selective laser melting machines after multiple cycles is a cost-effective procedure for dental laboratories. However, information on the metal-ceramic bond strength of the framework fabricated by using recycled powder is lacking. PurposeThe purpose of this in vitro study was to investigate how the bonding agent and repeated alloy powder reuse affected the metal-ceramic bond strength of cobalt chromium frameworks fabricated by using selective laser melting. Material and methodsFour square and 40-bar-shaped cobalt chromium frameworks were fabricated by selective laser melting. Half were produced by using virgin alloy powder (Group V; nsquare=2, nbar=20), and half with 30-times reused powder (Group R; nsquare=2, nbar=20). The particle size of each powder was measured by using scanning electron microscopy, and its phase composition was characterized by using radiograph diffraction. Each group was divided into 2 subgroups (Group W [Wash Opaque] and Group N [NP-Bond]) according to the brand of bonding agent used. After ceramic application, the metal-ceramic bond strengths were evaluated by using 3-point bend tests. The bonding agents’ chemical composition was analyzed by using radiograph fluorescence. Bond strength data were analyzed by using a 2-way analysis of variance (α=.05). ResultsMean ±standard deviation bond strengths did not differ significantly (P>.05) between Groups V (31.25 ±4.65) and R (30.88 ±4.78). Group W (35.34 ±1.78) had significantly higher bond strength than Group N (26.80 ±1.74; P<.001). Radiograph diffraction analysis found that the phase composition of all powders was similar. The bonding agent in Group W contained cerium, whereas, that in Group N did not. ConclusionsMetal-ceramic bond strength was unaffected by alloy powder reuse. However, the bonding agent brand may affect the bond strength of cobalt chromium frameworks fabricated by using selective laser melting.

Fabrication of a removable partial denture of injectable poly (ether-ether-ketone) (PEEK) made partially by a digital workflow: case report

The introduction of computer-aided design and computer-aided manufacturing in rehabilitation with removable partial denture, enabled the emergence of new methods of fabrication of the framework and materials. In view of this, polyether-ether-ketone appears as an alternative to Cobalt-Chromium, due to its aesthetic properties, high resistance and for being non-allergic. In this sense, the present study aimed to report a clinical case where the framework of a removable partial denture was manufactured from a digital workflow, using polyether-ether-ketone as the material of choice, compared to a removable partial denture made with a cobalt-chromium framework. In this case, it was possible to perceive that the use of computer-aided design and computer-aided manufacturing technology for the construction of a removable partial denture framework of polyether-ether-ketone resulted in a denture with adequate adaptation and good aesthetics. Patient satisfaction, comfort, retention, number of follow-up sessions, masticatory performance and quality of life were evaluated. Compared with the conventional denture, the polyether-ether-ketone framework denture provided better satisfaction and comfort. Both prostheses showed similar results in terms of masticatory performance and in terms of quality of life, however the polyether-ether-ketone framework denture showed better results. In conclusion, polyether-ether-ketone proved to be a viable material for making removable partial denture framework. However, controlled and randomized clinical trials are needed to demonstrate the benefits of this treatment as an alternative in relation to the conventional denture.

Wear at the implant-framework interface between titanium implant platform and the additively manufactured titanium and cobalt-chromium frameworks.

To measure the wear at the implant interface between the Grade 4 titanium (Ti) of the implant and frameworks fabricated using two additively manufactured alloys (Ti alloy and cobalt-chromium [Co-Cr]) pre- and post-artificial aging. Three-unit frameworks supported by two implants were additively manufactured (Atlantis; Dentsply Sirona) using Ti and Co-Cr dental alloys. Two implants (OsseoSpeed EV, Astra Tech; Dentsply Sirona) were torqued on each non-engaging framework. The assembled implant-frameworks were secured into polyurethane foam blocks. Groups were created based on the material and surface assessed: framework (Ti-framework and Co-Cr-framework groups) and implant (Ti-implant group). Two subgroups were created depending on the location: premolar (PM) and molar (M). Computed tomography images were obtained pre- (as manufactured) and post-simulated mastication procedures. The pre- and post-simulated mastication files of each specimen were aligned using the best-fit algorithm using a metrology program. Wear was measured by calculating the volumetric discrepancies at the implant interface on 64 measurement points per area analyzed. Three-way ANOVA and Tukey tests were used to analyze the data (α=0.05). The mean volumetric discrepancy values ranged from 0.8 to 3.1µm among all the subgroups tested. The group (framework vs. implant) (p<0.001) and tooth location (p<0.001) were significant factors of the mean volumetric discrepancy values obtained. The framework group presented with significantly lower volumetric discrepancy mean values (1µm) compared with the implant group (3µm), whereas the premolar area obtained significantly lower mean volumetric discrepancy values (1.9µm) compared with the molar location (2.3µm). Volumetric discrepancies were found at the implant-framework interface tested between the pre- and post-artificial aging measurements ranging from 1 to 3µm after 1,200,000 cyclic loading that simulated approximately 12 months of function.

Accuracy of digital impressions for implant-supported complete-arch prosthesis when using an auxiliary geometry device

Background/purposeDigital impressions using intraoral scanners have recently gained popularity. The aim of the present study was to evaluate the fit of full-arch screw-retained cobalt-chromium frameworks fabricated via two different digital impression methods. Materials and methodsAn edentulous resin master model with four dental implants was fabricated. Forty cobalt-chromium superstructures were fabricated and evaluated according to four groups. In Group 1, the superstructures were evaluated using an intraoral scanner to generate digital impressions. Group 2 relied on the help of an auxiliary geometric appliance in generation of digital impressions via intraoral scanner. The traditional method of splinted open-tray conventional impressions was designated for Group 3. Finally, the control group (Group 4) relied on scanning of the master model directly with a laboratory scanner. Vertical marginal discrepancy was evaluated, and data obtained were statistically analyzed. ResultsThe highest mean vertical marginal gap value (80.86 ± 50.06 μm) was observed for Group 1 and statistically higher than Group 2, 3, and 4 (P < 0.05). The lowest mean vertical marginal gap value (41.98 ± 26.33 μm) was measured from Group 4 and statistically similar to Group 2 and 3 (P > 0.05). ConclusionIt has been suggested that the use of auxiliary geometric appliances yields increased scanning accuracy. Frameworks fabricated using the traditional splinted open-tray technique were more reliable compared to those frameworks from digital impressions.

Comparative photoelastic stress analysis between all-on-four implant-supported cobalt-chromium framework and carbon fiber reinforced framework with varying cantilever lengths - An in vitro study

CONTEXT: In implant prosthodontics, metal frameworks are used to rigidly spilt the implants together to provide rigidity and stiffness to the prosthesis. However, due to the limitations associated with the metal framework fabrication, the recent advances have made it possible to fabricate metal-free implant-supported prostheses using fiber-reinforced composite frameworks.AIM: This study aimed to evaluate and compare photoelastic stresses between all-on-four implant-supported cobalt-chromium (Co-Cr) framework and the carbon fiber-reinforced composite (CFRC) framework at varying cantilever lengths.MATERIALS AND METHODS: Two photoelastic models of an edentulous mandible were fabricated according to the all-on-four concept. Following this, frameworks with a bilateral cantilever extension of 20 mm, one with CFRC and the other with Co-Cr, were fabricated and were subjected to a progressive load of 120–180 N with an interval of 20 N. The principal stresses (σ) were calculated using the mean maximum fringe order.STATISTICAL ANALYSIS: The quantitative analysis was performed using the Kruskal–Wallis test and Mann–Whitney U-test, P ≤ 0.05.RESULTS: The CFRC framework showed mean principal stress values significantly lower than the Co-Cr framework under all loading conditions; however, deformation of the framework was observed at the cantilever lengths of 15 mm and 20 mm.CONCLUSION: The study and its findings have indicated that the CFRC framework appears suitable for the fabrication of a framework for an “All-on-four” prosthesis. Within the confines of this study, the use of 10 mm as an arbitrary cantilever length recommendation for the CFRC framework and 15 mm for the Co-Cr framework seems reasonable.

Effect of Palatal Vault Depth on the Trueness of Metal Laser-Sintered and Cast Cobalt-Chromium Removable Partial Denture Frameworks.

This in vitro study compared the trueness of removable partial denture cobalt-chromium (Co-Cr) frameworks fabricated by 3D-printed pattern casting and those fabricated by selective laser sintering (SLS) with different palate vault depths. A partially edentulous Kennedy class II mod.1 maxillary model with a deep palatal vault was used, which was modified and duplicated to produce another model with medium palatal vault depth. After model scanning, the partial denture framework was designed using CAD software to fabricate 20 removable partial denture (RPD) frameworks. For each model, two types of frameworks were fabricated. For the 1st type, the 3D-printed resin patterns were formed using a 3D printer, and then casting was performed (AM-cast framework). For the 2nd type, a direct metal laser sintering machine was used for the RPD frameworks fabrication (SLS framework). 3D scanning of fabricated frameworks was performed, and the standard tessellation language (STL) file was superimposed over the STL file from the original design, and the average deviation was recorded. Data were statistically analyzed. Two-way ANOVA test was used, followed by the least significant difference (LSD) for pair-wise comparisons to estimate any significant differences between groups. The RPD frameworks with high palatal vault depth represent larger discrepancies mean value than that with the medium palatal vault depth with a highly significant statistical difference. SLS shows less deviation than AM-cast CO-Cr frameworks with highly significant statistical differences whatever palatal vault depth. RPD metal frameworks fabricated with SLS have better accuracy compared to those fabricated by AM-cast, regardless of the depth of the palatal vault.

In vitro comparison between some mechanical properties of CAD/CAM polyetheretherketone and conventional cobalt chromium frameworks in removable partial denture

In vitro comparison between some mechanical properties of CAD/CAM polyetheretherketone and conventional cobalt chromium frameworks in removable partial denture

Fit of removable partial denture frameworks fabricated from 3D printed patterns versus the conventional method: An in vitro comparison

Statement of problemThe conventional method of fabricating removable partial denture (RPD) patterns is a time-consuming, expensive, and complex process, and the success of the treatment depends on the fit of the framework. Questions still remain as to whether the 3D-printing method is an acceptable procedure compared with the conventional method. PurposeThe purpose of this in vitro study was to compare the fit of RPDs cast from 3D printed frameworks and conventionally fabricated RPDs according to the gaps between the framework and the reference model. Material and methodsA metal reference model was made from a Kennedy class III modification 1 maxillary typodont. For the conventional group (n=9), impressions were made from the metal cast. Cobalt chromium frameworks were cast with the conventional method. For the digital group (n=9), the metal cast was scanned with a laboratory scanner, and the RPD was designed in the 3Shape platform. The standard tessellation language (STL) file of the design was downloaded to a 3D printer (Hunter DLP), and 9 resin frameworks were printed. These frameworks were invested and cast in the same dental laboratory as the first group. Gap measurement was assessed vertically with a superimposition software program (Geomagic Control X), and additional measurements were assessed under rests, reciprocal arms, and a 2.2-mm box under the major connector. The independent t test was used for determining the results and statistical analysis between groups. The paired t test was used for statistical analysis within groups (α=.05 for all tests). ResultsNo significant differences (P>.05) were observed in the mean ±standard deviation in overall fit according to the gaps in the conventional group (103 ±18 μm) and those in the digital group (109 ±21 μm). The biggest gap (poorest fit) was observed in the 2.2-mm box under the major connector (115 ±6 μm). ConclusionsBoth conventional and 3D-printing methods showed clinically acceptable fits. Further clinical studies with a larger sample size and long-term follow-up are needed.

Additive Manufacturing of a Removable Partial Prosthesis in Titanium Using Binder Jetting Technology: A Brief Research Report

Objective: The purpose of this study was to measure the surface roughness and compare the fit of a cobalt-chromium selective laser-melted removable partial denture framework and a titanium binder jetting removable partial denture framework.Materials and methods: A design for a removable partial prosthesis framework was made using 3Shape software, and thereafter, one framework was additively manufactured in cobalt-chromium with selective laser melting and one in titanium using binder jetting technology. The weight of the frameworks was measured, and the surface parameters Sa, Sds, and Sdr were measured by white light interferometry. The fit of the frameworks was analyzed using visual inspection and the pressing test.Results: The weight of the frameworks in their post-printed state was 15.66 g and 7.43 g for cobalt-chromium and titanium, respectively. After finishing and polishing, the cobalt-chromium framework’s outer surface showed a high shine and smooth surface, with lower values in the Sa and Sdr parameters. The visual inspection showed gaps in the titanium framework, and the pressing test detected movement greater than 0.5 mm for the same material.Conclusion: The Ti framework showed higher surface roughness and was left with a lackluster finish after polishing. Also, the fit of the Ti framework was not clinically acceptable. The additive manufacturing binder jetting technology for titanium needs improvement or an adjustment of the settings to be used for clinically removable partial dentures. The cobalt-chromium framework manufactured by selective laser melting showed an acceptable clinical fit and surface roughness.

Removable Partial Denture Frameworks in the Age of Digital Dentistry: A Review of the Literature

Alloys of cobalt chromium have been used for decades to create frameworks for removable partial dentures. While cobalt chromium has multiple advantages, such as strength and light weight, the casting process is laborious and requires special care to ensure that human error is minimized. Furthermore, the display of metal clasps in these frameworks may be considered a limitation at times, especially with esthetically demanding patients. The introduction of digital technology to manufacturing in dentistry has brought forward new methods of fabricating cobalt chromium frameworks, some of which eliminate the casting process. Moreover, the development of high-performance polymers for use as removable partial denture frameworks brings multiple advantages, but raises concerns over design guidelines and principles. This review examines alternatives to conventionally cast frameworks so that clinicians may make evidence-based decisions when choosing framework materials and fabrication methods in the rapidly advancing world of digital dentistry.

Retention Forces of Implant-Supported Single Crowns and Fixed Dental Prostheses after Cementation: An In-Vitro Study

The aim of this in vitro study was to investigate three different cements for their suitability to provide semi-permanent cementation, and to compare the retention forces of implant-supported single crowns (SC) and three-unit fixed dental prostheses (FDP) luted with these cements. Twenty-four methacrylate models were supplied with three implants/abutments each to simulate the condition of SCs/FDPs. Cobalt-chromium frameworks were fabricated, sandblasted (Al2O3/50 µm/0.2 MPa) then cemented with glass-ionomer (KTC), polycarboxylate (DUR) or self-adhesive resin cement (RXU). Specimens were stored in a saline-solution (NaCl/37 °C/24 h) or subjected to thermocycling. A universal testing machine and a pull-off device were used to remove the copings. The multi-factor ANOVA showed that the retention force differed significantly among all cements for the SCs after NaCl storage (p &lt; 0.05). Mean retention forces (in Newtons) after NaCl storage were (SCs/FDPs): KTC 170/352, DUR 409/406, RXU 265/426, and after thermocycling (SCs/FDPs): KTC 156/262, DUR 306/380, RXU 494/508. FDPs showed higher retention values in comparison to SCs. For SCs, artificial aging with thermocycling resulted in a significant retention increase for RXU, whereas the retention of KTC and DUR was decreased. Glass ionomer can be used as a semi-permanent cement for both SCs and FDPs. Polycarboxylate cement is considered semi-permanent after one year of aging.

Phonetic Improvement with an Obturator of the Acquired Defect in a Case of Palatal Mucoepidermoid Carcinoma: A Case Report

Introduction: Following surgical resection of palatal mucoepidermoid carcinoma (MEC), the resulting defect is best corrected with surgical reconstruction and rehabilitation. However, the patient’s clinical course with ill-defined recurrence resulted in the fabrication of cobalt chromium obturator prosthesis as the best treatment option for reliable restoration. Case description: A 48 years old Chinese man was referred for construction of an obturator prosthesis after one year following a wide excision surgery for low grade mucoepidermoid carcinoma of the hard palate. Leaving him with a maxillary defect of Okay Class 1a classification with oronasal communication. He complained of difficulty in speaking, inability to properly chew food and fluid leakage into his nose due to looseness of the previous surgical obturator. An obturator with a cobalt chromium framework was fabricated and silicone material for direct relining is used to provide cushioning and path of insertion to the obturator. Discussion: The defect created post surgically had caused several problems such as deglutition and feeding difficulties and changing of the sounds of speech. Such a properly designed obturator prosthesis obtained its retention, support and stability from remaining teeth. Not only it distributed force equally to the remaining teeth and provided cover to the soft tissue defect and the created border between the oral and nasal cavity helping in the improvement of the patient’s sound of speech. The silicone substitution part provided a non-traumatic distribution of the pressure on tight insertion at areas of the defect and becomes successful in improving patients' speech during monitoring periods with a delay rehabilitation.

Comparative evaluation of stress distribution of zirconia, cobalt chromium, and polyetheretherketone (PEEK) framework material on an atrophic maxilla in all-on-six implant treatment concepts: A three-dimensional finite element analysis

Aims: This study aims to evaluate the effect of prosthetic framework material on the stress distribution patterns of the all-on-six implant support system under vertical and oblique loading. Materials and methods: The cone beam computed tomography (CBCT) images of the maxilla were converted to a stereo lithography file. HyperMesh software system was accustomed to convert three-dimensional pictures into numerical models. Geometric models of short implant and zirconia, cobalt chromium, and polyetheretherketone (PEEK) framework material were created using SOLID EDGE software and were then inserted in the bone model. A total of six models were constructed with three different types of framework materials with four implants in the anterior maxilla region and two distal short implants and mini-abutments. The prosthetic frameworks were made with 14 teeth (central incisors to the second molar bilaterally). The models were transferred through the solid works simulation program for finite element analysis and stress distribution investigation. An oblique load of 150 N with 30 inclination in the linguo-buccal direction and vertical loads parallel to the long axis of the tooth with 100 N magnitude were applied unilaterally on the posterior teeth of each framework. Results: Principal and Von misses stress in the PEEK framework were least when compared to stresses in the zirconia and cobalt chromium framework on vertical loading and oblique loading. Conclusion: PEEK as a framework material had the least stress for the all-on-six implant treatment concepts on vertical and oblique forces than zirconia and cobalt chromium framework.

Effect of different surface treatments on the bond strength between cobalt-chromium (Co-Cr) framework infrastructure and veneer resin or artificial tooth

Effect of different surface treatments on the bond strength between cobalt-chromium (Co-Cr) framework infrastructure and veneer resin or artificial tooth