Dental Waxes

Chapter 18

IntroductionMany different waxes are used in

dentistry.The composition, form, and color of

each wax are designed to facilitate its use and to produce the best possible results.

PropertiesDental waxes are composed of a

mixture of components from natural and synthetic sources.

Natural waxes are produced from plants (used in carnauba wax), insects (used in beeswax), and minerals (used in paraffin wax).

These natural waxes contribute properties to the wax but are rarely used in their pure form.

MeltingDental waxes have a melting range, that is,

a range of temperatures at which each component of the wax will start to soften and then flow.

Components with lower melting points will soften first; then, as the temperature is increased, more components soften and the wax will eventually flow.

Flow is the movement of wax as molecules slip over each other.

As the temperature of the wax increases, the viscosity of the wax decreases until the wax becomes a liquid.

Inlay WaxGeneral

Inlay wax is used to prepare patterns. These patterns are reproduced in gold or

other material in the fabrication of inlays, crowns, and fixed and removable partial dentures.

Inlay wax is sometimes called casting wax.

Dimensional Change

Waxes expand when heated and contract when cooled; the thermal expansion and contraction of waxes are greater than those of any other dental material. This property is especially important for

pattern waxes.If a wax is heated too far above the

melting range or is heated unevenly, expansion above acceptable standards will result.

Classifications of WaxesWaxes are grouped into three

classifications: Pattern waxes Processing waxes Impression waxes

Manufacturers produce these waxes in several forms: Sticks, sheets, blocks, and tins are used.

Pattern Waxes

Inlay Wax

Properties For success in these procedures, the wax

must have properties that will enable very close adaptation to prepared portions of the tooth to be restored, must provide freedom from distortion, must permit detailed carving without flaking or chipping, and must not leave excessive residue when it is removed from a mold by burning.

Inlay Wax (cont’d)The wax should harden at body

temperature but soften at a temperature low enough to permit it to be manipulated in a plastic state in the mouth without injury to pulp or oral tissues.

Its color should contrast with the colors of teeth and oral tissues to facilitate carving.

Casting WaxesCasting waxes are used to construct

the metal framework of partial and complete dentures.

Casting waxes are provided in sheets and in pre-formed shapes.

The physical properties of casting waxes are similar to those of inlay waxes, with the exception of melting range.

Baseplate WaxGeneral

Baseplate wax is used mainly to make occlusion rims and to hold artificial teeth to baseplates during the fabrication of dentures.

Baseplate Wax (cont’d)

Baseplate wax is used mainly for making occlusion rims and for holding artificial teeth to baseplates during the fabrication of dentures.

Properties Baseplate wax is composed mainly of

beeswax, paraffin, and coloring matter, which are mixed together, cast into blocks, and rolled into sheets.

Processing Waxes

Boxing WaxBoxing wax is used to form a box

around impressions of the mouth when a cast is made.

Boxing limits the flow of stone gypsum material.

Boxing wax usually is issued in red strips measuring 1 1/2 inches wide, 12 inches long, and 1/8 inch thick.

Boxing wax is soft and pliable enough at room temperature to be formed into a desired shape without heating.

Utility WaxUtility wax is used to provide rim locks

and otherwise to adapt impression trays for individual impressions, to build up post-dam areas on impressions, and to form a bead or border on preliminary and final impressions.

Utility wax is pliable enough at room temperature to be used without heating.

Utility wax normally is issued in stick form and usually is red.

Sticky WaxProperties

Sticky wax becomes sticky when melted and has the property of adhering to the surfaces of various materials.

Sticky wax is composed of beeswax, paraffin, and resins.

Sticky wax usually is supplied as hexagonal sticks of various colors, often orange or purple.

Sticky wax is brittle at room temperature and assumes a thick liquid consistency when heated.

Impression Waxes

Corrective Impression Wax

Corrective impression wax is used in conjunction with other impression materials in the process of taking edentulous impressions.

This wax flows at mouth temperatures and is used to correct undercuts.

Bite Registration Wax

Bite registration wax is used to produce wax bite registrations for articulation of models.

Pre-formed horseshoe shapes often are reinforced with metal particles to provide stability.

Manipulation

Wax should be softened evenly in dry heat, with warm hands, or by flame.

Melted wax should be added in layers onto an object.

If distortion of waxes is to be avoided, they should be stored at or slightly below room temperature.

Lost Wax Technique

The lost wax technique has been used for centuries to construct everything from jewelry to dental crowns.

This technique was developed as a way to cast gold.

The lost wax technique basically involves buildup of the unit in wax to an exact replication of the desired crown or substructure.

Summary

The dental assistant and the hygienist may have occasion to use dental waxes in a variety of clinical and laboratory procedures.

Although waxes have inherent disadvantages in dimensional stability and control of flow, they may be used successfully.