Impression Materials and Laboratory Materials and Procedures Flashcards

Question

Polyvinyl siloxane material

Answer 1

for dimensional stability, Polyvinyl siloxane is the best impression material pouring of the model can be delayed as long as 7 to 10 days. stiffness of the material makes removal of the tray difficult, the material is dispensed with the use of an auto of an auto-maxing unit and mixing tips. The chemical makeup of Polyvinyl siloxane impression material is listed: 1. filler: silica 2. catalyst: chloroplatinic acid 3. base: silicone polymer

Answer 2

Bite Registration provide a reproduction of occlusal relationship between the maxillary and mandibular teeth. they provide an accurate registration of the patient's centric relationship between the maxillary and mandibular arches. Bite Registration are taken by the dentiist or dental assistant. Occlusal registration is an accurate registration of the normal centric relationship of the maxillary and mandibular arches. It also commonly referred to as the Bite Registration.

Answer 3

silicon impression materials are used for complete denture impression and fabrication of crown and bridge. They come in light, medium and heavy bodies; and a very high viscosity putty material. The chemicals make up the silicone impression materoal is listed: -Base: polydimethylsiloxane - Crosslinking agent: alkI orthosilicate or organo hydrogen siloxane - catalysts: organo tin compounds - fillers: sillica

Answer 4

one type of Types of occlusal registration is the wax bit, which is useful when the diagnose casts are trimmed. The most common technique involves the use of the softened baseplate wax. other type of occlusal registration include polysiloxane bite-registration and zinc oxide-eugenol (ZOE) bite-registration paste. -Polysiloxane: *supplied both as a paste system and also cartridges *Fast-setting * No resistance to biting force * No odor or taste for the patient *Gains dimensional stability over time * convenient to use - Zinc oxide: * offers litter or no resistance to bite closure and is a facst-setting material. * Is supplied in a paste system and dispensed onto a paper pad, mixed, and placed on a gauze tray for the ptient to bite into.

Answer 5

Dental Models: also known as study casts, they are three dimensional reproductions of the teeth and the surrounding soft tissue of a patient's maxillary and mandibular arches. Dental models are the following for the following tasks: - Diagnosis for a fixed or removable - Diagnosis for orthodontic treatment - visual presentation of dental treatment - makeing of custom trays - making of orthodontic appliances - making of provisional coverage - making of mouth guards.

Answer 6

Gypsum: a very soft mineral used in plaster castings. A products are used extensively in dentistry to make dental models. Gypsum is a mineral that is mined from the earth, Unrefined, gypsum is dihydeate form of calcium sulfate. A dihydrate is a substance made up of two parts water to one part calcium sulfate, It is converted into plaster of paris and artificial stone using a process called calcination (by heating the gypsum). This converts the calcium sulfate dihydrate crystals determine the water- to power rations for all three types of gypsum. There are three types of gypsum: - Model plaster: also referred ti a plaster of paris, it is used primarily for creation of preliminary impressions and the construction of diagnostic model. - Dental stone: For use as a working model when a more durable diagnostic cast is required; example include making custom trays and orthodontic appliances. - High-strength stone: Also known as dentist or improved dental stone, it is ideal because of its strength, hardness, and dimensional accuracy. IT is used for the creation of the dies used in the production of crown, bridges, and indirect restorations.

Answer 7

The recommended power to water rations for gypsum products vary by type as follows: -Model plaster (100g) to 45 to 50 ml of water - Dental stone (100g) to 30 to 32 mL of water - High strength stone (100g) to 19 to 24 of water.

Answer 8

Pouring dental models involves two pats: the anatomic portion and the art portion. The anatomic portion is created from the alginate impression, The art portion forms the base of the model. There are pour methods for creating the base of the cast. Those methods are listed here -Double pour method: The anatomic portion of the model is pouring first, then a second mmix of plaster or stone is used to prepare the art potion. - Box and pour method: Impression is surrounded with a box made o wax and poured as on unit. - one large batch of plaster or stone is mixed, and potions of the model are pouring in a single step. Inverted pour method: - begin pouring in small increments at the posterior of impression while holding the handle of the tray so that the impression rests on the vibrator to release air pockets. -once the impression is filled, but not overfilled, set the impression aside. take the rest of the plaster, thicken it if need be with additional powder, and create a base. Shape the sides. invert the impression onto the plaster base you just created, and smooth and contour the side of the base. Do not bury the sides of the impression tray in plaster because you might not be alble to remove the tray later.

Answer 9

To Trim mandibular dental models: 1. Trim the posterior potion of the mandibular model until it is even with the maxillary model. 2. trim the base 3. Trim the lateral cuts to cuts to match the maxillary lateral cuts. 4. Trim the back and heel cuts. 5. trim from canine to canine in a rounded form.

Answer 10

when Trimming and finishing dental model, first prepare the model should by soaking it in water for 5 min. makings on the model should me made in pencil. To trim the maxillary model 1. trim the base 2. trim the posterior area 3. trim the sides 4. trim the heel cuts 5. trim the angled portion from the canine to canine

Answer 11

to finish model: 1. mix slurry of gypsum and sill in any voids. 2. polish a plaster model 3. soak the model in a soapy solutions for 24 hr. 4. Dry the model and then polish it with a soft cloth.

Answer 12

Custom impression trays must: - Be sufficiently rigid - fit and adapt well to edentulous - provide accurate adaptation to an edentulous or a partially edentulous arch - Maintain an even distribution of impression material. In addition, the maxillary tray must cover the teeth and hard palate, and extend slightly the gingival margin. The mandibular tray must cover the teeth and extend beyond the ginvival margin. Consider the following when outling the tray - The margins of the cast where the finished tray will be seated are outlined in pencil. -The outline designate the area to be covered by the tray - The outline extends over the attached gingiva to the mucogingival junction and 2 to 3 mm beyond the last tooth in the quadrant.

Answer 13

When creating custom impression tray, the first steps in cast preparation is to fill undercuts with wax or other molding material. Air bubbles in the cast, the shape of the arch and ridge, carious lesions, fractured teeth, and deep interproximal spaces and malposed teeth can cause undercuts. A spacer is placed on the cast to create room in the tray for the impression material. Baseplate wax, a folded moist paper towel, o a commercial nonstick molding material can be used for this purpose. To create the spacer, cut a length of wax, warm it, and place it on the cast over the area of the tray. A warmed plastic instrument is used to lute the wax to the cast.

Answer 14

The next step of creating a custom impression tray is to create a spacer stop. Triangular or round holes are cut out of the spacer with the use of a laboratory knife or wax spatula. These cutouts are placed to prevent the tray from being seated too deeply onto the arch or quadrant. Allow for an adequate quantity of impression material around the preparations. An edentulous tray requires a minimum of four stops, one each on the crest of the alveolar ridge in the area of the first or second molar. Additional stop can be placed on the crest of the ridge in the area of each canine. A tray used to take an impression of prepared natural teeth, as for a crown or bridge, has the stops placed near, but not on, the prepared teeth. The prepared cast, spacer, and immediate surrounding area are painted with a separating medium so that the completed tray can be readily separated from the cast. The next step of creating a custom impression tray is to form a handle. A handle adapted to the tray will allow easier placement into, and removal from, the patient's mouth. The handle should be placed at the anterior of the tray. It should be placed as close to the midline as possible, facing outward and parallel to the occlusal surfaces of the teeth. It can be formed from a piece of scrap acrylic that has been cut away from the tray. The end of the handle and the area where it will be attached to the tray are moistened with tray resin liquid. After the tray has been formed, the spacer is removed, and the tissue side of the tray is cleaned. A small stiff brush, such as a toothbrush, is used to remove most of the wax at this time. The remainder of the spacer is removed, and the interior of the tray is cleaned after it reaches its final set.

Answer 15

When finishing a custom impression tray, rough areas in the tissue side of the tray do not need to be removed removed; this surface will be covered with impression material. However, any rough outer edges of the tray should be smoothed so they do not injured the tissues of the patient's mouth. A laboratory knife can be used to smooth miner rough areas. An acrylic bur in a straight handpiece can be used to remove major rough areas. An alternative is use the laboratory lathe to smooth the edges. The tray should now be given a final rinse and disindected in accordance with the manufacture's instructions.

Answer 16

Dental Waxes are use for various procedures in dentistry. For example, they can be used to line the impression trays to make them larger. they are designed for different functions in the dental office and come in different colors to help differentiate their functions. Boxing wax: is soft, pliable wax a smooth, shiny appearance. It is supplied in long narrow strips measuring 1 to 1 1/2 inches wide and 12 to 18 inch long. It is ised to form a wall or box around a perliminary perliminary when pouring. Utillity wax: is supplies in various form depending on its composed of beeswax, , petroleum and and other soft waxes. Utillity wax is used to - Extend the borders of an impression tray - cover brackets in orthodontic treatment. - Sticky wax: is supplied in skicks or blocks. Its main ingredients are beeswax and rosin. It is quite brittle; but because very tacky when heated. Skicky wax is usedful for creating a wax pattern or joining acrylic resin. - Inclay casting wax: is a hard, britle wax made from paraffin wax, carnauba wax, resin, and beeswax. it is used to create a pattern of the indirect restoration on a model. It is classificed according to flow as follows: - type A: hard inlay wax - Type B: medium inlay wax -Type C: soft inlay wax

Answer 17

- casting wax: is made of paraffin, ceresin, beeswax, and resins. It is supplied in sheets of various thicknesses and it used for single tooth indirect restorations, fixed bridges, and casting of metal portional of partal denture. Baseplate wax: is made of paraffin or ceresin with beeswax and carnuba wax. It is hard and brittle at room temperature and supplied in sheets. there are three types of baseplate wax; *Type I: softer wax used for denture construction *Type II medium- hardness wax used in moderate climates * Type III: harder wax for use in tropical climates. - Bite registration waxes: are soft and very similar to casting waxes. Bite registration wax softens under warm water. The patient is instructed bite down, leaving an imprint of the teeth in the wax.