Metal-ceramic Prosthesis Research Articles

Intraoral repair in metal-ceram ic prostheses: a clinical report

Repairing fractured metal-ceramic prosthesis is a treatment alternative that can increase the restoration longevity, preserve dental structure, and/or the integrity of implant components, besides being a simple, low-cost technique. However, clinicians often see restoration repair as a challenge because of the many doubts regarding the procedures required to obtain satisfactory results. Therefore, the motivation to write this article is the need to provide instructions for clinicians dealing with a situation involving fractured porcelain, presenting an intraoral repair technique that can be used in cases of a fractured ceramic veneer of a fixed partial prosthesis. The technique consisted in treating the remaining ceramic surface and applying a microhybrid composite resin following the steps of a protocol that, according to scientific evidence, has promoted high bond strength to porcelain, in addition to being cost effective.

Technological features of metal-ceramic prosthesis frameworks manufactured from domestic alloys of precious and base metals.

The aim of the study was to examine changes in physical and mechanical properties of dental alloys depending of the initial composition at re-casting. Russianc precious alloys: Plagodent (AuPtPd) and Palladent (PdAu) and base alloys: Vitiriy-N (NiCrMo) and Vitiriy-C (CoCrMo) were used as study samples, which were divided in three groups: a primary casting from the granules; 50% of re-casting; 100% of re-casting. We investigated the yield strength in bending, coefficient of thermal expansion and hardness. Changing in the composition of the alloys has led to changes of all physical and mechanical properties.

Gingival pigmentation by Ni-Cr-based metal ceramic crowns: A clinical report

This clinical report describes treatment of a patient with gingival pigmentation after the restoration of the right maxillary canine and first premolar with Ni-Cr–based metal ceramic crowns and investigation of mechanisms of gingival discoloration. Histopathological observation and energy dispersive x-ray spectroscopy analysis of the retrieved pigmented gingiva revealed brown deposits both in the epithelial cells and along the basement membranes but no trace of Ni or Cr elements in the pigmented particles, indicating that the gingival pigmentation adjacent to the Ni-Cr–based metal ceramic prosthesis may not be caused by direct deposition of the released ions.

Reconstruction of maxillary ridge atrophy caused by dentoalveolar trauma, using autogenous block bone graft harvested from chin: a case report

Background Dentoalveolar trauma, especially when involving front teeth, negatively affect the patient’s life; in particular, tooth avulsion is a complex injury that affects multiple tissues, and no treatment option offers stable long-term outcomes. The aim of this study was to report a case of reconstruction of atrophic anterior alveolar ridge after tooth loss, performed with autograft harvested from the chin, and subsequent prosthetic rehabilitation with the use of an osseointegrated implant. Case report A 23-years-old Caucasian girl, presented an atrophic alveolar bone in the area of tooth 11, as a result of tooth resorption 10 years after a tooth reimplantation procedure. Reconstruction was performed with autogenous bone harvested from the chin. After 6-months healing period to allow autograft incorporation, a dental implant was inserted. After further 6- months, a screw-retained implant supported metal-ceramic prosthesis was fabricated. Results The prosthetic rehabilitation was successful, and after a follow-up period of 5 years, the achieved result was stable. Conclusion It can be concluded that the autogenous bone graft harvested from the chin, is a safe and effective option for alveolar ridge defects reconstruction, allowing a subsequent placement of a dental implant supporting a prosthetic restoration.

Heat Treatments Influence on Corrosion Behaviour of Some Metallic Biomaterials Potentially Used in Metal-Ceramic Prosthesis

The present paper put in evidence the influence of applying different heat treatments on some metallic materials such as cobalt and titanium alloys, usualy used for medical applications. The alloys were cobalt base alloy type CoCrMo (22%Cr, 6%Mo, rest Co), in nontreated state, quenching at 1100°C /1h/aer, quenching at 1100°C /1h/air+ sensiblizing at 550°/4h/ air, 600°/4h/air and/or 650°C/4h/air and titanium base alloys - alloy TiMo0.3Ni0,7 (0.23%Mo, 0.72%Ni, Ti rest), alloy TiAl5Fe2V2Mo1,5(1.52%Mo, 5.15%Al, 2.56%Fe, 2.35%V, Ti rest), each of them in non treated state, annealing at 1050°C/1h/air and annealing at 850°C/1h/air. Corrosion tests were made at potentiostat-galvanostat AUTOLAB, in Ringer solution (for both alloys) and NaCl infusion solution (only for cobalt base alloy) by drawing the polarization curves. Our conclusion is that by applying correct and proper heat treatments to both at cobalt alloys and in titanium alloys there is an improving of the corrosion resistance.

Loosening torque of prosthetic screws in metal–ceramic or metal–acrylic resin implant-supported dentures with different misfit levels

The aim of this study was to evaluate the effect of the prosthesis material (metal–acrylic resin or metal–ceramic) on loosening torque of the prosthetic screws in an implant-supported mandibular denture under two levels of vertical misfit. Ten frameworks were fabricated with commercially pure titanium, and five of them received acrylic resin and acrylic artificial teeth as veneering material and the other five were veneered with porcelain. Two levels of vertical fit were also created by fabricating 20 cast models to obtain four experimental groups according to the prosthesis material and misfit: Group 1 (metal–acrylic resin prosthesis with a passive fit); Group 2 (metal–acrylic resin prosthesis with a non-passive fit); Group 3 (metal–ceramic prosthesis with a passive fit); and Group 4 (metal–ceramic prosthesis with a non-passive fit). Two hundred prosthetic titanium-alloy screws were divided in 40 sets (five screws per set, n=10). After 24h, the loosening torque of the screws was evaluated using a digital torque meter. The results were submitted to two-way ANOVA analysis of variance followed by a Tukey's test (α=0.05). The mean values and standard deviations for each group were G1=7.05 (1.64), G2=5.52 (0.90), G3=6.46 (1.34), and G4=4.35 (0.99). Overall, the prosthesis material and misfit factors showed a statistically significant influence on the loosening torque (p<0.05). Metal–ceramic prosthesis and misfits decreased the loosening of the torque of the prosthetic screws.

Alternate metal framework designs for the metal ceramic prosthesis to enhance the esthetics

PURPOSEThe objective of the present study was to evaluate the effect of five different metal framework designs on the fracture resistance of the metal-ceramic restorations.MATERIALS AND METHODSFor the purpose of this study, the central incisor tooth was prepared, and the metal analogue of it and a master die were fabricated. The counter die with the 0.5 mm clearance was used for fabricating the wax patterns for the metal copings. The metal copings with five different metal framework designs were designed from Group 1 to 5. Group 1 with the metal collar, Group 2, 3, 4 and 5 with 0 mm, 0.5 mm, 1 mm and 1.5 mm cervical metal reduction respectively were fabricated. Total of fifty metal ceramic crown samples were fabricated. The fracture resistance was evaluated with the Universal Testing Machine (Instron model No 1011, UK). The basic data was subjected to statistical analysis by ANOVA and Student's t-test.RESULTSResults revealed that the fracture resistance ranged from 651.2 to 993.6 N/m2. Group 1 showed the maximum and Group 5 showed the least value.CONCLUSIONThe maximum load required to fracture the test specimens even in the groups without the metal collar was found to be exceeding the occlusal forces. Therefore, the metal frameworks with 0.5 mm and 1 mm short of the finish line are recommended for anterior metal ceramic restoration having adequate fracture resistance.

Contact stomatitis due to palladium in dental alloys: A clinical report

A patient was treated with a maxillary gold-palladium alloy fixed partial denture (FPD). Shortly after placement, the patient contracted severe contact mucositis. Patch-testing revealed a positive reaction to palladium chloride (PdCl 2 , 1% petrolatum) but not to any other component of the prosthesis. After removal of the FPD and placement of a provisional acrylic resin restoration, all signs and symptoms disappeared. A definitive metal-ceramic (titanium-porcelain) prosthesis was placed, and no signs of lesions appeared. This clinical report demonstrates that titanium may be a satisfactory alternative for patients who require prostheses and are sensitive to other metals.