Dental protectives and dressings are used as protective linings for cavities in order to prevent staining or chemical irritation of the dentine . They are also used as varnishes over synthetic fillings to protect them from secretions until setting is complete. Another important use of Dental protectives and dressings is to help in pulp healing.
In the dental operative procedures, following dental protectives and dressings are employed:
1. Zinc oxide: It is a tasteless, odourless, white powder which is insoluble in water. It is important to keep the bottle of zinc oxide well stoppered because it gradually absorbs carbon dioxide from air. It is a weak antiseptic and is used as basis for ointments and cements.
• In combination with carbolised resin, it is used as a sedative dressing in cavities for the treatment of bleeding sockets following extraction and also for the treatment of dry sockets.
• It acts as basis of different zinc cements, e.g. oxyphosphate of zinc cement.
• In combination with eugenol, it is used as an obtundent dressing. Such dressing is required in sensitive teeth and unfinished cavity preparation. For a copper amalgam filling in a deciduous tooth, zinc oxide and eugenol may be cut down to a lining after setting. After setting, they may be cut down to prelining in a permanent tooth.
• Zinc oxide and eugenol combination is available as zonalin. It is employed in deep deciduous cavities to have a lining with sedative qualities and to complete the filling at the same time.
• As a Dental protectives and dressings.
2. Resin: It is a fine crystalline powder which is obtained as residue left after distilling oil of turpentine. It is available as carbolised resin and cavity varnish.
i. Carbolic resin consists of chloroform (three parts), carbolic acid (four parts) and resin (four parts). It is used as an obtundent dressing. Carbolic acid is responsible for its obtundent properties and also causes some degree of anaesthesia in nerve endings. It is used in combination with zinc oxide as:
• An obtundent dressings in cavities
• A haemostatic to plug bleeding sockets
• A soothing and antiseptic dressing in the treatment of dry socket.
ii. Cavity varnish: It is prepared by dissolving resin in a volatile solvent (ether, chloroform or acetone). It is applied to silicate filling to protect the gel formation from moisture during the primary setting period. In this procedure, resin is left as a covering for the filling due to evaporation of volatile solvent.
3. Calcium hydroxide: It is a commonly used in Dental protectives and dressings . It exists as odourless, tasteless white powder. For dental use, only sterile powder is employed. So its sterility must be maintained. It is available as bland pulp capping material. For capping pulp material, calcium hydroxide is used in the form of a paste with sterile water. It has advantages over other pulp capping materials because:
• It is alkaline in reaction and
• Also stimulates odontoblastic activity Capping with calcium hydroxide leads to complete pulp healing in suitable cases. With its use as capping, no sign of inflammation is seen in pulp tissue and dentine bridge is formed beneath the calcium hydroxide which closes the exposure completely.
4. Glycerine: It is a clear, colourless, odourless and sweet liquid. It is obtained by decomposition of vegetable or animal fats. It is of a thick syrupy consistency and oily to the touch.
• Used as a solvent for drugs, e.g. borax (one part) and glycerine (6½ parts) which is applied to the oral tissues for the treatment of thrush. Since glycerine is readily absorbed into the tissues, it carries the dissolved borax with it.
• Used as a vehicle:
— With pumice for polishing teeth and filling
— To manufacture toothpastes.
• Applied to carbolic acid burns in the mouth following the application of alcohol to remove the caustic effect of carbolic acid.
• Applied to cracked or dry lips before carrying out dental operations.
5. Petroleum (vaseline): It exists as a white or yellow viscous substance which readily liquefies a few degrees above body temperature.
Uses of Dental protectives and dressings:
• Applied to cracked or dry lips during dental surgery to avoid pain to the patient.
• Used on discs or strips to protect silicate and cement fillings while polishing them.
• After the cavity has been filled with the silicate cement, a celluloid matrix strip covered with vaseline is placed in position.
• For applying to a matrix band before inserting a cement filling.
• To prevent rusting, vaseline is applied on instruments kept in storage.
• Put vaseline on instruments before placing a carbolised resin dressing.
• Apply vaseline around the puncture hole before placing rubber dam over the tooth to prevent its tearing.
6. Gutta-percha: It is a coagulated milky juice. It is obtained from certain types of rubber trees. Purified gutta-percha is a white, tasteless, odourless inert mass. It hardens on cooling and softens on heating. It is dissolved in oil of eucalyptus and chloroform. It is used:
• As a cavity dressings for completed or lined cavities, both deciduous and permanent.
• To maintain space between approximating teeth.
TO REMEMBER about Dental protectives and dressings
1. Dental protectives and dressings are used:
• As protective linings for cavities
• As varnishes over synthetic filling
• To help in pulp healing.
2. Zinc oxide is a weak antiseptic and is used as basis for ointment and cements.
3. Resin is available as carbolic resin and cavity varnish. Former is used as an obtundent dressing and later is employed to protect the gel formation from moisture during the primary setting period.
4 Calcium hydroxide is available as bland pulp-capping material, which leads to complete pulp healing in suitable cases.
5. Glycerine is used:
• As a solvent for drugs
• As vehicle with pumice for polishing teeth and filling
• To remove the caustic effect of carbolic acid
• To apply to cracked or dry lips
6. Petrolatum (vaseline) is used:
• For application on dry and cracked lips
• To protect silicate and cement fillings
• For applying to matrix band before inserting a cement filling
• To prevent rusting of surgical instruments.
7. Gutta-percha is used: a As a cavity dressing
• To maintain space between approximating teeth.