Effect of electroplated coating with copper or tin and oxidation of metal surface on the strength of metal to ceramic bond

The bond strength between the porcelain and the underlying alloy is influenced by the meticulous surface preparation. In this study Wiron 77 alloy was used for the casting of 20 rod shape and 12 plate form metallic samples. The samples were divided into four groups, each comprised 5 rods and 3 plates. Samples of the 1st group was porcelainized directly, while those of the 2nd group were porcelainized after metal surface oxidation. Samples of the 3rd group were porcelainized after coating the surface with copper, while those of the 4th group were porcelainized after coating the surface with tin. The rod shape samples were used for testing the shear bond strength, while plate shape samples were used for metallographic examination. From this study, it can be concluded that Wiron 77 dental alloy is highly sensitive to form an oxide layer. A thick layer of oxides formed on the metal surface before porcelainization, causes a decrease in the bond strength. Coating the alloy with copper or tin increases the shear strength at the ceramo-metallic system

Effect of some variables on inner and outer surface topography of castings

Two different commercial alloys used in crown and fixed prosthodontics and two phosphate bonded investments were evaluated for the surface roughness from the outer and inner surface of castings, as well as the surface indentation at the point of sprue attachment. The surface roughness and /or surface indentation affected seating of cast restoration on the prepared abutment. A two sprue thickness and two angles of attachment of sprue to the wax pattern were evaluated. The results revealed that, not all commercial phosphate bonded investments available for casting base metal alloys are the same as regards their effect on surface topography of castings. The surface roughness and /or indentation were more from the inner surface than that from the outer surface. Statistically the difference was significant. The indentation and /or surface roughness were decreased with increasing the thickness of sprue from 1.5 to 3 mm and decreasing angle of sprue attachment to the wax pattern from 90 to 45 degrees. The effect of the type of investment, sprue thickness and angle of sprue attachment was statistically significant

Evaluation of tissue response to two dental alloys and two veneering materials by subcutaneous implantation

The aim of this study was to evaluate the effect of polishing on the tissue response to two dental alloys and two veneering materials, using a st and ardized subcutaneous implantation technique. Ten pellet shape samples [5 polished and 5 unpolished] were prepared for each material, cleaned, disinfected, and implanted in 5 adult albino rats, and 2 pellets [polished and unpolished], subcutaneously in each animal. Thirty days after the implantation, animals were sacrificed, and specimens were prepared and examined under light microscopy. From this study, it can be concluded that the polished gold alloy surface supported more tissue compatibility than polished non-precious alloy surface. Moreover, the glazed porcelain surface supported more tissue compatibility than polished composite resin surface. Also, there was a direct correlation between surface smoothness and nature of tissue reaction

Dimensional accuracy of combined hydrocolloid system compared with two elastic impression materials

Recently, combined reversible irreversible impression system became available aiming to produce the accuracy of the impression and the easy manipulation. The aim of this investigation was to compare the dimensional accuracy of two commonly used elastic impression materials [Impregum F and Reprosil] and the newly introduced combined hydrocolloid system [Cavex Comblloid, Vericol Anoma and CA 37]. This study was planned to investigate the linear dimensional accuracy by using a measuring microscope. It can be concluded that the addition of cured silicone produces less inter abutment discrepancy than combined agar/alginate system. Also, the single unit preparation can be recorded accurately using the combined agar/alginate system. Moreover, for three-unit bridge, the combined agar/alginate system is not accurate, when compared with the addition cured silicone and polyether

Effect of reheating rubber base impressions on the accuracy of poured dies

The axial discrepancy [Um] of stone dies, which were poured in three different types of rubber impressions, was measured using the dial gauge. Dies were poured from impressions under the following conditions: Cooling to room temperature for 15 minutes, cooling to room temperature for 15 minutes and preheating water and stone to 37C, and cooling to room temperature for 15 minutes and reheating to 37C for 30 minutes and preheating water and stone to 37C. Results showed that the least axial discrepancy was measured in case of dies poured from impressions which were cooled at room temperature for 15 minutes and then reheated to 37C for 30 minutes and the water and stone preheated to 37C

Bond strength of two porcelain repair systems after three months

The aim of this study was to evaluate the effect of aging on the bond strength of two porcelain repair systems. The materials tested were Silanit and Cover Up II. Silanit bond strength depends on coupling agent, while in Cover Up II it depends on porcelain etching agent, in addition to the coupling agent. From this study, it can be concluded that Cover Up II might be suitable as a porcelain repair material over a long period of time. Besides, Silanit as a repairing material might not be suitable over a long period of time

Stress attenuating function of split shaft post system

The aim of this study was to compare the reduction in the insertion stress factor by using solid and split shaft post systems in an experimental determination of the stress level. From the results of this study, it was detected that the undesirable stress concentration at solid post-model interface have been reduced 50%, by using split shaft one. This is due to collapsing ability of split shaft during the insertion into the post space. It can be concluded that split shaft post have provided a stress breaking function, so it is recommended for restoration of endodontically treated teeth

effect of incorporating metronidazole and teracyline on the surface roughness and water sorption of visible light cure resin and acrylic resins

The usage of drugs for the topical treatment of diseases of teeth, periodontium and oral mucosa, has been attempted by many methods. The aim of this study was to discuss the surface roughness and water sorption of some acrylic resins and visible light cure resins, incorporated by metronidazole and tetracycline. From this study, it was concluded that incorporation of drugs to temporary restorations as partial denture or acrylic crowns or bridges may be useful for treatment of oral diseases, for certain periods of time