Dr. Alfredo Nevárez RascónPolyethers and polysulfides
To make individual impressions for the procedures of prosthetic restorations Printing for fixed In total impressions partial prints bridgework (totally or partially edentulous patients)For highaccuracyand fidelityof detail In preparation of single or multiple deposit
•foundation Low molecular weight (4,000 approx.)polysulfide Presence of reactive groups SH mercaptans in the polymer chain •To give consistency. Fill best known is titanium dioxide, zinc sulfideFILLING and silica in proportion 12 to 50% Lithopone is a white pigment mixture consisting of zinc sulfide and barium sulfate Using 3 types of accelerators: Dioxide or lead peroxide (T rapidly reactivates and environmentTHROTTLE curing reaction is maintained for a longer than others. Shortening occurs lead peroxide in the polymer chain by oxidation of the terminal groups SH. Hidroxiperóxido colorless organic t-butyl or amine activator, with In order to remove the brown color of lead dioxide. These compounds have little dimensional stability and contract by the Evaporation of the volatile constituent of hidroxiperóxido. Another type is the Cu hydroxide gives a blue-green is better dimensional stability but may be more toxic than the PbO2 and its product end is unstable.
To facilitate the polymerization of the poly sulfides, sulfur is added as an advocate SULFUR Which facilitates the chemical reaction and stearic acid to assist the polymerization.DIBUTYLPHTHALATE Is used as a plasticizer
Is made between the mercaptan or paste and lead dioxide or accelerator To give a polysulfidepolysulfide Lead Dioxide polysulfide+ lead sulfide+ water (base) (acelerador) (material totalmente polimerizado)
Good dimensional stability to make an impression. Finish line is clearly visible. No special equipment. DISADVANTAGES Single cell is required. Not tolerate water in the furrows. unpleasant odor
It is approx. Like 5-7 minutes hydrocolloidsWORKING TIME based on agar-agar and alginates than The curing time is 8-13 minutes. It can be modified by several methods: Higher temperature accelerates the polymerizationCURING TIME Base-rate accelerator: less time basis accelerates. Adding a drop of water accelerates the polymerization mixture, but it is more difficult to mix and monitor their effect. Adding a drop of oleic acid slows time polymerization
In these materials, the base polymer is acyclic ether in terminal groups, imino groups(triangles are similar to epoxy but withnitrogen instead of oxygen in a vertex)
▫Polyether based etilenoamina ring terminals. ▫ silica filler. ▫ A plasticizer ftalatode filled with glycol ether. • Accelerator or catalyst or trigger: ▫ Thinner: Element to provide proper consistency to the material. Is octyl phthalate and 5% methyl cellulose.
–Flexibility of 3.3% -Elastic Recovery 99% -Contraction from 0 .2% 0.3% at 24 hrs Special Considerations. -Hydrophilic
The two pastes are colors that contrast each other, which facilitates efficient mixing. It is important that the print is placed in position and kept still to avoid tensions that can lead to distortion. The polymerization is completed in 5 minutes.
▫It comes in a single consistency. ▫ low acceptance is coming in a single consistency. ▫ Its use should only cover up to 4 teeth and these must not have periodontal disease and being too rigid cause discomfort to the withdrawal. This aimed at elaboration of fixed prosthetics (crowns and bridges).
▫Excellent dimensional stability. ▫ High level of fidelity. ▫ Tear strength
▫Smell and taste unpleasant. ▫ Difficult handling. ▫ hard rigid material removal from mouth
•PHILLIPS , CIENCIA DE LOS MATERIALES DENTALES•http://www.uaeh.edu.mx/docencia/P_Presentaciones/icsa/asignatura/M_D_6.pdf
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