PULP PROTECTION during Cavity Preparation


Pulp is the life of the tooth . So during any kind of  conservative procedure .. protection or conservation of pulp is one of the most essential steps. Pulpal injury is one of the main reason for the failure of  conservative treatment.

How can a pulpal injury happen ?

Galvanic currents ( due to the contact between dissimilar metal restorations that in the oral cavity fluid acts like a circuit)

Chemical from the restorative materials ( Constant seeping chemicals from the overlying  restorative material can cause necrosis of pulp)

Restorative material with good thermal conductivity. ( certain restorative  materials are not good thermal insulators)

Heat generated by injudicious cutting( necrosis due to heat generated by excessive cutting and improper drilling instruments)

The two most common agents used in pulp protection are Liners and Bases.

Liners are volatile or aqueous suspensions or dispersion of zinc oxide or calcium hydroxide that can be applied to the cavity surface in a relatively thin film.

Bases are those cements, which are applied, in thicker dimensions beneath permanent restorations to provide for mechanical, chemical and thermal protection of the pulp.

Mostdentists use some type of cavity liner or base in almostall  cavity  preparations.    They  are  used  primarily  toprotect the pulp and to aid the pulp in recoveringfrom  irritation  resulting  from  cavity  preparation.Liners  and  bases  are  placed  when  the  cavitypreparation  is  completed,  just  before  insertion of restorative material .

Glass ionomer cements and dentin bonding agentsare  used  primarily  to  seal  the  dentin  and  protect  thepulp from bacterial invasion. Calcium hydroxide canbe  used  in  extremely  deep  areas  as  an  antibacterialagent and/or as a pulp capping material.

Most  bases  are  applied  best  when  the  assistant wipes   the   instrument   clean   between   each   small application.The dentist   will  hold  a  gauze  sponge  in  thetransfer  zone  and  quickly  wipe  the  end  of  theinstrument as the dentist moves toward the base mix. Ifthe dentist inadvertently gets the base on the enamelwalls   of   the   cavity   preparation,   you   will   pass   aninstrument for removal of the material.

Cavity varnish/ Bases

is a liner used to seal the dentinaltubules to help prevent microleakage and is placed in acavity to receive amalgam alloy after any bases havebeen placed.

Cavity varnish is being used less and less with amalgam restorations, and dentin bonding agentsare  replacing  cavity  varnish  as  the  liner  of  choice.

Cavity  varnish  has  an  organic  solvent  of  ether  orchloroform that quickly evaporates, leaving the resinas a thin film over the preparation.

This varnish shouldbe slightly thicker than water. If it becomes very thick,discard it.

Cavity varnish is not used with compositessince  the  varnish  retards  the  set  of  composites  andinterferes with the bonding of composites

A  small  cotton  pellet  held  by  cotton  forceps  isdipped into the varnish just enough to wet the pellet

The cavity varnish is applied to the pulpal area, wallsof  the  cavity  preparation,  and  onto  the  edge  of  themargins of the preparation.

Any excess varnish can beremoved from the enamel with a fresh cotton pellet.

A second application of cavity varnish is placed over the first to thoroughly coat the surfaces of the dentin and fill  any  voids  from  bubbles  created  when  the  firstapplication  dries.  After  liners  and  bases  are  placed  intothe cavity preparation, the tooth may be restored withmaterials, such as amalgam, composite resin, or GIC.

Pulp ProtectionPreparation of cavity liners

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