Dental cements: Zinc oxide, Copper, EBA, Glass-ionomer and More

Uses of Dental cements

  1. Temporary or semi-permanent fillings
  2. To cement in position crowns, inlays, and bridges.
  3. To line cavities in order to prevent thermal or chemical damage to the pulp.
  4. Support of remaining weak tooth structure.

The main Dental cements used are :

  1. Zinc oxide and eugenol
  2. Accelerated zinc oxide eugenol.
  3. Specific zinc oxide eugenol products.
  4. EBA cements.
  5. Zinc polycarboxylates.
  6. Zinc and copper phosphates.
  7. Glass-ionomer cements.

Zinc oxide and eugenol

Uses of zinc oxide and eugenol

  1. Protective cavity sub-linings (over which an oxyphosphate lining is placed for resistance to packing and biting pressure).
  2. Sedative or obtundent (soothing) dressings(eugenol relieves painful hyperemia of the pulp).
  3. Temporary fillings.
  4. Pulp caps.
  5. Root canal fillings.
  6. Periodontal packs.

Properties of zinc oxide and eugenol

  1. Consists of a liquid and powder:-powder consists of zinc oxide, magnesium oxide, and zinc acetate (an accelerator ). liquid contains eugenol, olive oil, and acetic acid as an accelerator.
  2. Sedative action on pulp.
  3. Prevent conduction of heat to the pulp.
  4. Very soluble in water.
  5. Very weak.
  6. Bacteriostatic.
Dental cements

Technique

  Four parts of powder are mixed with I of liquid until a putty-like consistency is obtained . This set slowly in the present of moisture, including saliva. If kept reasonably dry in a container (with a dehydrating agent such as calcium chloride), it will remain ready for use throughout the day. This saves mixing some each time it is required.
For more information: Properties and uses of dental fillings

  Accelerated zinc oxide-eugenol

   Quick-setting mixtures contain a resin you speed up the setting time from the normal twelve hours to five minutes. They are prepared and used in the same ways as normal zinc oxide mixtures. However, they are not displaced if amalgam is condensed directly on to it, so no other lining needs to be placed between the two materials.

Special zinc oxide-eugenol products

  Some contain antibiotics such as tetracyclines, plus steroids. They are used for root canal therapy and pulp capping.

EBA Dental cements

Properties
EBA (ortho-ethoxy benzoic acid) consists of a powder and liquid:
The powder contains zinc oxide, fused quartz, and hydrogenated rosin.
Liquid consists of eugenol and O-ethoxy benzoic acid.
Technique
  As much as seven parts of powder are added to one of liquid in order to improve the mechanical properties.
Zinc polycarboxylates

Uses of polycarboxylates

  1. Cementation of fixed orthodontic appliances.
  2. Cavity linings.

Properties of zinc polycarboxylates

  1. They originally consisted of :

a. Powdered zinc oxide with small quantities of magnesium oxide.

  b. A liquid of approximately 40 percent aqueous solution of polyacrylic acid.
Recent materials have included:
  a. Products with two liquids of different viscosities; a thinner liquid for cementing and a vicious one for cavity lining.
  b. Two products with polyacrylic acid in the powder. The liquids for these contain 95 percent water. One product is encapsulated for mechanical mixing.
  c. Encapsulated material with about 43 per cent alumina on the powder.
  d. One product with a polymer slightly different to polyacrylic acid.
  e. One cement contains stannous fluoride.
  2. Very adhesive to clean dry enamel.
  3. Saliva considerably reduces the adhesive strength.
  4. Adheres better to a smooth surface than to a rough one (in contrast to zinc phosphates).
  5. Adhesion to dentine is not as good as to enamel.
  6. Does not adhere well to gold or porcelain.
  7. Adheres to stainless steel.
  8. Little irritant effect on the pulp.
  9. More soluble than zinc phosphate materials.
 10. Good thermal insulation properties.
Technique
       The liquid and powder must be thoroughly mixed as quickly as possible, as the cement will not stick to tooth substance once set has begun. This can be a little difficult as the liquid is somewhat thicker than in Most cements. Once ‘cobwebbing’ occurs the mix must not be used.

      Zinc Oxyphosphate

     Uses
 1. Cavity lining.
 2. Cementing crown, bridges,and inlays
    Properties
 1.consists of a powder and a liquid:-
     Powder is mainly zinc oxide, plus magnesium oxide,and other oxides.
  Liquid is mostly an aqueous solution of phosphoric acid.
  2. Highly acidic, so deep cavities require a sub-lining to protect the pulp.
  3. Stronger than zinc oxide-eugenol.
  4. Good thermal insulator.
  5. Does not adhere well to enamel or dentine.
       Technique
     The required amount of liquid and powder are mixed with a stainless steel spatula on a clean, cool glass slab. The quantity  of powder incorporated varies according  to the purpose for which it is required:
a. As a lining, thick mix for strength and lessened risk of pulpal damage as there is a lower proportion of acid.
b. As a cement, slightly thinner to provide a reduced thickness of cement between crown and tooth.
Powder is added slowly, using a little at a time from three or four heaps, to slow the setting rate. Each heap is mixed in thoroughly before the next is added. The spatula is rapidly moved in circles around the slab ensuring that no unmixed particles of powder are left. Speculation must cease by the time setting begins or mix will be weakened.
One minute is the usual time for speculation.
As with all materials, the correct quantities of liquid and powder should have been placed on the slab. This assessment of amounts gets easier with practice. Under no circumstances should any be returned to the bottle as it will be contaminated, and so will affect subsequent mixes.
After use, the slab should be placed in warm water to facilitate cleaning. The glass should not be scratched or later mixes of cement will tend to stick to it.
Stoppers must be replaced immediately on bottles, as water is lost or absorbed according to atmospheric humidity. Absorption leads to speedier setting times; evaporation slows it down. If sufficient evaporation has occurred for crystals to appear in the bottle the liquid must be discarded.
Copper Cements

Uses of copper dental cements

  1. To cement splints to the teeth of patients with fractured jaws.

Properties of copper dental cements

  1. It is similar to zinc phosphate cement, but the powder contains a copper compound in addition to zinc oxide. The color varies according to the type of copper oxide:-

Red if cuprous oxide.

    Black if cupric oxide.
  2. Black cement is bactericidal.
  3. Black cement has a worse effect on pulp that has the unmodified zinc oxyphosphate.
  Technique
Similar to oxyphosphate

Glass-ionomer (ASPA) dental cements.

  ASPA relates to both silicates and polycarboxylates. It combines certain properties of both. The name is derived from aluminosilicate polyacrylic acid.

Uses of Glass-ionomer dental Cement

  1. Erosion cavities.
  2. Deciduous restorations.
  3. Cementation of porcelain crowns.
  4. Fissures sealants.

Properties

  1. Consists of a powder and liquid.

Powder relates to silicates, consisting of fused quartz and alumina.

      Liquid consists of a 50 per cent solution of polyacrylic acid, stabilized to prevent gelling and thickening.
  2. Has adhesive properties similar to zinc polycarboxylate cement.
  3. As strong and translucent as silicates, I.e. superior to zinc oxide-based materials.
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