DISCOLORATION is a challenge that many dentists face, and internal bleaching
is a practical treatment option. Internal bleaching is used to lighten
a discolored tooth that has had root canal therapy. It involves placing
a chemical oxidizing agent within the coronal portion of a tooth to remove
discoloration. The etiology of tooth discoloration can be intrinsic,
extrinsic, or both; it can involve dentin, enamel, or pulp; it may be brought
on by diet, age, or habits; it may be local or systemic; and in some cases
it may be iatrogenic. Discoloration can be caused by endodontic filling
materials or medications that the patient is taking. Discoloration
associated with pulpal involvement can be caused by intrapulpal hemorrhage
(in which case it is pink or brown), necrotic pulpal tissue, secondary
dentin formation (in which case it is yellowish), and internal resorption
(in which case it is a pink spot).
Most bleaching agents are oxidizers that act on
organic structures of the hard tissues and degrade them into smaller molecules
that are lighter in color, such as C02, 02 and H20.
Indications for internal bleaching are discoloration
of pulpal origin, dentin stains, and stains not amenable to extra-coronal
bleaching. Contraindications to internal bleaching are superficial enamel
stains, defective enamel formation, severe dentin loss, presence of caries,
and discolored composites.
There are two techniques for internal bleaching:
the chairside technique and the “walking bleach” technique. The chairside
technique uses Superoxyl in 30 to 35 percent concentration, H202, and heat.
This technique is highly effective, but the oxiding agent is strong and
can burn. There is a six-to-eight percent chance of cervical resorption,
increasing to 18 to 25 percent when the technique is used in conjunction
with heat. The “walking bleach” technique uses a mixture of sodium
perborate and water and may be utilized if the chairside results are inadequate
or if you prefer to avoid the possibility of a higher chance of cervical
root resorption. The sodium perborate when fresh is 95 percent perborate
giving off 9.9 percent of available oxygen. This material is more easily
controlled and safer than Superoxyl; therefore, it is the material of choice.
The radiograph in Figure 1 shows a tooth that had
root canal treatment and internal bleaching ten years earlier. The patient
presented to our office with sensitivity in the gingiva in the area around
the tooth. The patient presented with a complete history clearly indicating
that he had received internal bleaching via the chairside technique.
Internal resorption usually occurs at six months
after internal bleaching, and after two years the tooth is usually not
restorable, so recall accordingly.
FIGURE 1: Illustrating cervical
resorption, number 11, etiology internal bleaching.