What is a sprue former in dentistry?

What is a sprue former in dentistry?

Sprue former is a wax, plastic or metal pattern used to form the channel or channels allowing molten metal to flow into a mould to make a castin. [2] The sprue also acts as a reservoir from where the casting may draw molten alloy during solidification, thus avoiding porosity due to shrinkage.

Where is the sprue former placed on the wax pattern?

Location of the sprue former The sprue former should be attached to the bulkiest portion of the wax pattern to minimize the distortion of the wax pattern because the sprue is away from the fine margins.

What is crucible former in dentistry?

The stand or base usually made of metal or resin onto which a sprued wax pattern is placed. The shape of the base permits the smooth passage of molten metal during the casting procedure. From: crucible former in A Dictionary of Dentistry » Subjects: Medicine and health — Dentistry.

What is the purpose of Spruing?

WHAT IS SPRUING? The process of attaching a sprue former or sprue pin to the wax pattern is called as spruing. The purpose is to provide a channel through which molten alloy can reach the mold in an invested ring after the wax has been eliminated.

What is casting sprue?

In casting, a sprue is the passage through which a molten material is introduced into a mold, and the term also refers to the excess material which solidifies in the sprue passage.

What is the shape of the sprue?

Cylindrical shape of sprue is advocated in books and used most commonly. Some manufacturers recommend different shapes of sprues, which have not been advocated in textbooks.

What is sprue wax?

Home / Foundry Supplies / Wax Sprues. These are wax lengths for bronze casting that come cored or solid, and red (standard) or green (harder). For creating the gating system to use with the los wax method.

What is casting ring in dental?

Casting rings or formers are used when casting dental parts using the lost wax technique. These rings or other-shaped formers hold the investment in place around the wax-up in order for the lab to properly prep the investment material for casting.

What is the meaning of sprue hole?

1 : the waste piece on a casting (as of metal or plastic) left by the hole through which the mold was filled. 2 : the hole in which a sprue forms.

What is sprue loss?

The material loss due to this portion of the metal used as a contact is called sprue loss. The sprue must be heavy enough to permit lifting the workpiece out of the impression. die without bending. The sprue loss is generally 7.5 per cent of the net weight.

What is sprue bush?

The sprue bush is the connecting member between the machine nozzle and the mold face, and provides suitable aperture through which the material can travel on its way to the mould cavity or the start of the runner system in multi-impression molds.

What are the advantages of hollow metallic sprue?

The hollow metallic sprue increase contact surface area and strengthen the attachment between the sprue and pattern. They are removed from the investment at the same time as the crucible former. c) Plastic – For smaller restorations Plastic is used for castings of alloys which use 2 stage burnout with phosphate-bonded investment.

What are the causes of porosity in steel sprues?

Cause: Porosity created at the connecting point of the cast restoration and the sprue, due to their solidification at the same time. Hence, compensation for the shrinkage is done from the connecting area. Avoiding too narrow or too long sprues. 6. Surface Porosity Gives a rough surface appearance. – Overheating of Alloy / Investment.

What is the difference between narrow sprue and large sprue?

A narrow sprue may be useful in air pressure casting procedure where the metal is melted in a conical depression formed by crucible former. Narrow sprue prevents premature metal flow into mold. Large diameter sprue: improves the flow of molten metal into the mold.

What are the investment materials used in the dental industry?

This investment material is used in construction of high melting temperature dental alloys e.g. soldering and porcelain veneering. For casting of inlays crowns and other restorations especially for alloys like gold, platinum, palladium, cobalt chromium and nickel chromium.