REDM 104

Glass Ionomer Materials

Glass ionomer is a versatile material with chemical properties allowing it to be used as a restorative material, liner, bonding agent, and permanent cement.

 Commercial examples of these are Vitrebond and Fuji LC.

Indications for using Glass Ionomers

• Primary teeth
• Final restorations in nonstress areas
• Intermediate restorations
• Core material for a buildup
• Long-term temporary restorations 

In the restoration of a deep cavity preparation, CaOH (Dycal) may be placed in the deepest portion over the pulp as a liner, followed by glass ionomer (Vitrebond), which must be light-cured.

The remaining preparation is then etched, bonded, and restored with the use of composite resin.

Glass ionomer alone may also be placed on dentin in a slightly deep area of a preparation.

Qualities of Glass Ionomers

• The ability to chemically bind to the teeth
• No need to prepare the tooth structure as extensively as one does for an amalgam or composite resin 
• The release of fluoride after its final setting 

Note that etching and other pretreatments are not necessary, so the smear layer remains.

The components may be light-sensitive.

The material is biocompatible.

Composition of Glass Ionomers

• Glass
  • Ceramic particles
  • Glassy matrix
• Acrylic acid
• Tartaric acid
• Maleic acid 
• Metal-reinforced glass ionomer
  • Silver-tin alloy + glass ionomer

Ionomers in the name “glass ionomers” refer to which ion-crosslinked polymers? (acrylic, tartaric, and maleic acids)

Supply of Glass Ionomers

• Powder and liquid: manually mixed together on a treated paper pad
• Light-protected tubes: dispensed onto a treated paper pad
• Paste/paste system: mixed for application
• Premeasured capsule: triturated for application

Preparation tip: With powder and liquid components, such as Vitrebond, the powder is fluffed to loosen the components before being dispensed.

Place with the use of a ball applicator (only on dentin).

Half a millimeter or less should be placed first and cured, after which a second layer of as much as 2 mm may be placed.

Components should be mixed in 10 to 15 seconds to allow ample working time (about 2 minutes). The mixture should then be light-cured for a minimum of 30 seconds.

Remember, a higher room temperature will increase the setting time.

Temporary Restorative Materials

Temporary restorative materials are designed to maintain or restore function to a tooth or teeth and keep the patient comfortable until permanent restorations can be placed.

These materials may also be used in emergency patients when insufficient time is allotted for definitive restoration.

Eugenol, or oil of clove, provides a sedative effect.

Placement of intermediate restorative material (IRM) in a molar. 

This slide displays a molar isolated with the use of a rubber dam and surrounded by a matrix and matrix holder (bottom of photo), with and a wedge (blue) at the distal edge.

 The bright-white material, IRM, is being placed with the use of the instrument shown in the image.

 Newly mixed IRM has a puttylike consistency and must remain dry until it is completely set.

Indications for using IRM

• Reducing sensitivity and discomfort of a tooth to make a diagnosis 
• Maintaining the function and esthetics of a tooth until a permanent restoration can be placed 
• Protecting the margins of a prepared tooth that will receive a permanent casting at a later time
• Preventing shifting of the adjacent or opposing teeth because of open space 

 Describe clinical situations in which IRM may be placed:

A patient presents with a very sensitive posterior tooth. Caries removal extends deep toward the pulp and extensively throughout the tooth to the point that a crown is indicated. 

IRM may be placed for 4 to 8 weeks to see whether symptoms decrease before final restoration (direct, indirect, or both). The necessity for a root canal can be evaluated before the final restoration.

IRM placement is also usefule in situations in which the diagnosis, the prognosis of the tooth, or both are unclear and under circumstances in which time is limited, such as in emergency treatment.)

Composition of IRM

• Zinc oxide gives strength and durability.
• Eugenol has a sedative effect.
• IRM is supplied in two forms:
  • Powder/liquid
  • Premeasured capsules

 Is IRM compatible with composite resin? (No.) 

 If IRM is dispensed as a powder and a liquid, what is the ratio? (One drop to one scoop, mixed with the use of a metal spatula.)

 If IRM is dispensed in premeasured capsules, they are mixed by means of trituration, like amalgam capsules, in an amalgamator.

Both of these methods may require the addition of more powder to improve manipulation.

Provisional Restorative Materials (Temporary Crowns)

Provisional restorative materials cover the major portion, if not the entire clinical portion, of a tooth or several teeth for a period of time.

 You will need to be comfortable with dispensing and mixing this material if you assist in indirect restorative procedures.

 Knowledge of this material will also be important if you are asked to fabricate provisional restorations as an expanded-duty assistant.

Examples of provisional coverage materials. 

Acrylic resin is supplied as liquid/powder, tubes, and auto-mix cartridges.
(From Hatrick CD, Eakle WS, Bird WF: Dental materials: clinical applications  for dental assistants and dental hygienists, St Louis, 2003, Saunders.)

At the bottom left are a liquid (dark bottle) and a powder (white bottle). The dropper is used to measure liquid into a dappen dish, to which the powder is gradually added to achieve the desired consistency.

This photo displays a few of the dispensing methods for these materials, including an auto-mixing tip attached to a cartridge with two separate barrels, which is attached to a dispensing gun.

Process of Application

• Material is mixed and placed in either an alginate impression or a vacuum-formed tray. 
• It is then seated over the prepared tooth and allowed to cure. 
• The occlusion and margins are adjusted.
• The material is cemented in place with the use of temporary cement.  

Vacuum-formed tray: plastic stent formed over model of the tooth or teeth before preparation for an indirect restoration. 

Caution: Some materials set in an exothermic reaction (giving off heat) . Therefore the necessary precautions, such as rinsing the tooth with cool water during setting, should be taken.

 Some provisional materials must be polished to a final luster.