Autonomous university of City

Juárez

Types of Plasters

Mario Chávez Viguería

Alfredo Nevárez Rascón

Student

Teacher

Dental plasters

The plaster is a mineral that is exploited in several parts of the world. And it is one of the materials more used in the odontolgy, Due to the fact that the manufacturer, by means of technologies, can change easily his properties and uses.

FIG.1

The plaster is a mineral, normally of white color, because pigmenta This is a sulfate of di-hydrated calcium CaSO4*2H2O (Two masses of sulfate relate to two water masses).

Fig.2

Fig.3

Fig.4

The principal applications

• Material for impressions (in disuse).• Model construction and stumps.• Assembly of the models on the articulates.• Preparation of the muffles or masks.• Cementing agent for some types of

coatings mergers, weld, etc.

Classification of the plasters

PLASTER THREAD: He is the white plaster or better acquaintance as " white snow " It is the least costly but it is that of scantier resistanceIt is used for bottled, mounted and model base.

PLASTER ALPHA 1 : Also they call him plaster rock, It possesses a major hardness and more dimensional accuracy , This makes it more desirable for the confection of certain restorations. It is in use for running models of work, models of study and of diagnosis. PLASTER ALPHA 2: Also called VELMIX or DENCITA, It is in use for works that demand a maximum precision and resistance. The VELMIX is in use for the models of work for prothesis and The DENCITA for models for treatment of orthodontics.

Type I: Plaster for impressions. Type II: Plaster for models of study. Type III: Hard plaster for models. Type IV: Hard plaster for stumps of

high hardness and low expansion. Type V: Hard plaster of high hardness

and high expansion.

Classification according to the Dental American

Association

Type l They serve for the relief of the impressions

And the principal constituent one is the sulfate of calcium Semi-hydrated β With the incorporation of additives. It is in the habit of being made of white color.

Fig.5

For the model construction of study preparation of the muffles in the construction of the total protheses.

Type ll

Fig.6

It serves for the model construction, which they must present high resistance to the compression and to the graze. This plasters they are used for models antagonists or for mobile protheses.

Type lll (Plaster Rock)

Fig.7

For the model construction, The resistance from which to the compression And to the graze it is particularly high. Minimal quantity of H2O, they are the resistant mas and the dense mas of all.

Type IV

Fig.8

There are extra hard of high hardness for stumps, But with an expansion mas raised still. And also for metallic protheses.

Tipo V

Fig.9

Differences between Plasters.

All the plasters have the same chemical formula his difference:

It takes root principally in his physical properties.

In the Stucco they are comparatively irregular and porous.

In others they are denser and of more regular form.

This difference allows to have the same consistency with less water in the cements stone and of great resistance, That in the stucco.

Relation Powder / water

Advantages Disadvantages

They do not need sophisticated equipment for his manipulation.

They need a place fresh air to be stored and without dampness.

Handling them adequately, there can be achieved a complete, smooth model and without bubbles.

The properties are critical to obtain the physical results of agreement with the type.

It is an economic product that one finds easily in the dental warehouse.

A vibrated excessive or inadequate mechanic favors that the plaster catches bubbles.

It is compatible with all the materials of impression of odontologic use.

Material and equipment to realize the manual mixture of the plaster

Fig.10 Fig.11 Fig.12 Fig.13

Manometer Cup Spatula

Plaster

To place in the container the necessary water, according to the quantity of mixture that is needed to prepare, remembering that to minor quantity of water for a certain quantity of powder, major hardness of the plaster as soon as it has set.

To beat energetically 1 min manually or 20-30 seconds with food-mixer to the emptiness of plasters, the components without adding not even any more powder any more does not even water down, since this would cause weakness in the plotted material.

Steps for the obtaining mixture

To avoid the incorporation of air bubbles during the mixture, to prevent the porosity, which he carries to the appearance of weak points and superficial irregularities.

Not to change the relation plaster waters down once begun the mixture, because a disorder takes place in the crystals. If one adds water later they affect the cores of crystallization, since different stages of hardening take place and since not the whole mass crystallizes at the same time, tensions are generated.

After finished the espatulado, places the material before frague in the place where there is claimed that it hardens, once fact this has to be kept the immobility of the same one, since any movement during the work of plotted causes faults and weak zones.

It is suitable to hope that the plaster has set completely before submitting it to any manipulation.

To the 48 hrs of plotted it is considered that the plaster has acquired his maximum hardness and resistance, being variable the time according to the relative dampness of the environment. Nevertheless for common uses one can work on the plaster an hour after this one has set, remembering that the resistance is increasing in agreement with the step of the following hours.

Commercial brands

Barceló Santana, Federico Humberto (Materiales Dentales)

http://protesistadental.blogspot.com/2006/11/clasificacin-de-yesos_116395478531374938.html

http://www.monografias.com/trabajos88/yesos-dentales-utilizados-odontologia/yesos-dentales-utilizados-odontologia.shtml

http://html.rincondelvago.com/materiales-odontologicos.html

http://www.slideshare.net/DavidAizencop/clases-yesos-presentation

http://frixdental.blogspot.com/2011/03/yesos-dentales.html

Bibliography