Intracoronal bleaching or Internal Bleaching is the procedure where a discolored non-vital tooth is whitened using oxidizing agents inside the coronal portion of the non-vital tooth to decrease the discoloration. With Intracoronal bleaching we can decrease or completely eliminate discoloration and increase the degree of translucency. The result of Intra-coronal bleaching depends on the cause of non-vitality, proper diagnosis, case selection and following the steps in a proper manner.
Intracoronal bleaching is done in Non-vital teeth with discoloration, the other types of bleaching are done on Vital teeth mostly like – Walking bleaching or sealed bleaching, Office bleaching and photo or thermo bleaching.
Chemicals used in Non-Vital Bleaching:
Bleaching gels used in non-Vital bleaching are –
10% or 16% Carbamide peroxide
6% Hydrogen Peroxide with the bleaching tray technique applying it to the lingual or labial surfaces
Precautions to be taken before Intracoronal Nonvital Bleaching:
- Isolate tooth properly from surrounding soft tissue
- Gums and other soft tissue should be isolated properly using barriers
- Proper oburation should be done
- Acid etching should be avoided
- Concentrations of chemicals used should be checked
Bleaching Techniques for Non-Vital Teeth:
- Use 16% to 20% Carbamide peroxide – In this method, 16% carbmide peroxide is sealed in the coronal portion of the pulp chamber or Access cavity.
- Use of 35% CPS or 35% hydrogen Peroxide – In this method, 6% Hydrogen peroxide is sealed in the coronal portion of the pulp chamber or Access cavity.
- Use of Sodium Perborate
Combination of the above two methods:
A bleaching tray is used to place 10-16% carbamide peroxide into the bleaching tray, bleaching is done from lingual surface of the tooth.
Non-Vital or Intracoronal Bleaching Technique:
It is called as Walking Bleach procedure because bleaching happens between visits outside the clinic. The procedure is also called as sealed bleach technique as the chemical is placed inside the tooth making it safe to use and requiring less chair time.
Steps of Nonvital or Sealed Bleaching:
The Non-vital Discolored tooth needs to be Endodontically treated before going in for Bleaching. Access the periapical tissue status before starting the procedure.
Capture photographs of the tooth, the shade of the discolored tooth needs to be noted down to access the improvement and also for future reference.
Step 1: Tooth should be Isolated using a Dental Rubber Dam sealing off the tooth at the cervical region, this prevents the leakage of the bleaching materials from coming in contact with the soft tissues.
Step 2: Remove the Restorative material from the Access Opening (Gic or Composite) to expose the GP points (if a RCT tooth) in the coronal portion then expose and clean the pulp tissue thoroughly (Complete RCT in such tooth).
Step 3: Remove all the Restorative materials from the Coronal portion of the tooth up to the labial-gingival margin or cervical region. You can use a heated Instrument to remove the Sealed GP point or a RC solvent like Eucalyptus oil, Orange oil or Chloroform to properly remove the Root canal sealers.
Step 4: You need to Etch inside the access cavity using 37% phosphoric acid which is controversial as some suggest it is needed and some say it does not affect the prognosis.
Step 5: A barrier needs to be placed at the cervical region of the tooth, to prevent the bleaching materials from seeping into the root portion of the tooth. The materials used are mostly – Glass Ionomer Restorative material, polycarboxylate cement, zinc phosphate. The barrier should be at least 2mm in thickness.
According to Steiner and West 1994, the coronal height of the barrier should protect the dentin tubules and extend up to the external epithelial attachment.
Step 6: Using a nozzle, 16% carbamide peroxide gel is placed inside the access cavity. Use a plastic instrument to pack the pulp chamber with the paste. Use a cotton pellet to remove any excess liquid which might ooze out during packing.
Note: In Europe, sodium perborate is not allowed to be used in dentistry, hence carbamide peroxide gel or hydrogen peroxide gel are used at a strength of less that 6% for hydrogen peroxide.
Step 7: Excess bleaching paste has to be removed from undercuts in the pulp horns and gingival area. Now a temporary filling paste has to be filled having thick consistency, it should be atleast 3 mm in thickness to ensure good seal. In some cases to achieve good seal, polytetrafluoroethyene or PTFE or Teflon.
Step 8: You can remove the barriers and Rubber Dam placed in the patient and inform the patient about the Temporary Restoration and its limitations.
Step 9: It is important to inform the patient about the slow progress of the whitening process as many expect instant results. Make sure to inform the patient to return after 2 weeks for re-evaluation and repeat the placement of the chemicals if required.
Step 10: You can also use Walking Bleach technique as an option to make the whitening process faster. Sodium perborate with Hydrogen Peroxide 3-30% instead of Water can be used. This is generally not advised because of the ill effects of the bleaching agent of the cervical periodontium which can be damaging.
Note: Inform the patient about the time taken for Whitening to start and improve, it is also important to mention that it will take one or two appointments or the complete effect to be seen.
Sealed Bleaching + Thermo/Photo Bleaching procedure:
This is a process which is controversial due to the side effects such as External Root Resorption. The steps followed are the same as mentioned in the Sealed bleaching technique in addition, electric heating devices or light application is done using special lamps for specified intensity. There are studies showing damage to the cementum and periodontal ligament which is due to Hydrogen Peroxide + heat combination leading to Root Resorption
Complications of interacoronal Bleaching
There are many complications which have been reported caused due to either the chemicals or due to errors made in isolation during the procedure.
External Root Resorption: This complication has been seen when higher concentrations of Hydrogen Peroxide are used – more than 30-35%. The higher concentration of H2O2 tends to damage the Cementum and Periodontium leading to root External resorption. It is suspected that the chemical seeps through the unprotected dentinal tubules and cementum defects affecting the root on its external surface leading to necrosis of the cementum and inflammation of the periodontal ligament thus leading to root resorption. According to Cvek and Lindvall – the process is said to enhance in presence of heat on case of bacterial infection.
Chemical Burns: The chemical causing chemical burns is also Hydrogen Peroxide – 30-35%. When Hydrogen peroxide comes in contact with the gingiva it leads to chemical burns and sloughing of the gingiva. Placing a barrier on the Gingiva as isolating it from the chemicals is a very important aspect to prevent chemical burns due to bleaching agents.
Effect on Restorations: Teeth which have been exposed to Hydrogen peroxide affect the bonding of composite resins to dental hard tissues. It is observed that there is an interaction between residual hydrogen peroxide and composite resin leasing to inhibition of polymerization and increase in resin porosity.