While leaving carious dentin in the last 0.5 mm from the pulp improves the prognosis of a tooth compared to exposing the pulp, occasionally pulp exposures will happen. When this occurs, treatment options are extraction, endodontic therapy, or placing a direct pulp cap.
Most restorative materials have been tried out as direct pulp capping materials, but most have failed to consistently provide a favorable outcome: an asymptomatic vital pulp with deposition of sound reparative dentin at the exposed site.
Calcium hydroxide products were the best available before the development of mineral trioxide aggregate. MTA can have a very high success rate when placed correctly; it is technique sensitive. The bioactive cement BioDentine has recently been studied as a substitute for MTA and has shown good results while being easier to use. The bioactive cement Activa has been suggested as a useful material for direct pulp caps, but studies are lacking. Note that Activa has a resin component that has, in other products, shown to be unfavorable to the development of dentin bridges in teeth with direct pulp exposures.
Mineral trioxide aggregate (MTA)
MTA was initially developed as a repair material for endodontic perforation repair and apexification procedures. It also works as a direct pulp capping material. When set, it has good physical properties and a good seal. Unfortunately, it has a multi-hour setting reaction, so it must be placed wet, then covered with some other material which protects it from being disturbed during setting. In clinical situations involving a vital tooth with a bleeding pulpal exposure, a direct pulp cap utilizing MTA covered with a bioactive cement such as Activa or a resin modified glass ionomer should be considered. If the tooth in question will receive a crown or be utilized as an abutment for a partial denture, endodontic therapy should be initiated.
Uses of MTA include:
- Direct pulp caps
- Endodontic perforation repair and apexification procedures
MTA should not be used as a liner or as an indirect pulp cap. It has several uses in endodontics, but within restorative dentistry it should only be used as a direct pulp capping material. Note that direct pulp caps are biologically fraught procedures: once insulted, pulps tend to die. Strict adherence to protocol is critical.
All of the following steps need to be followed:
- All softened dentin in the area of the exposure needs to be aggressively removed. Caries indicator may be helpful in detecting demineralized/infected dentin. All cariogenic bacteria must be removed or killed. This will result in an enlargement of the exposure. A large clean wound is preferable to a small dirty one.
- A cotton pellet with sodium hypochlorite should be placed over the exposure for one minute. This will stop bleeding and disinfect the area. This should be dried with cotton pellet (drying with air or water may reintroduce cariogenic bacteria).
- A small amount of MTA powder is mixed in a Dappen dish with distilled water. Local anesthetic is generally accepted as a source of sterile water, but there is no current evidence supporting or discouraging this substitution.
- The MTA slurry is placed over the wound. The exposure needs to be completely covered by MTA; the pulp will not survive contact with other restorative materials. It may be blotted with a cotton pellet to make the mass firmer, but it will not set in a clinically useful time frame.
- The mass of MTA should be completely covered with an RMGI or bioactive material. Activa is the product of choice at Pacific. Light cure for 20 seconds.
- Place a final (not provisional) direct restoration. The tooth and restoration should not be revisited unless absolutely necessary.