Introduction – Including Materials Used

Everyone wants to have whiter teeth. Does that mean that we can provide tooth whitening treatments for every patient? Well, yes almost everyone!

One of the most common reasons patients seek dental care is discoloured front teeth. It is a common aesthetic concern with a profound effect on patient’s self-esteem, interaction with others and employability. We now have tooth whitening techniques that are simple and more predictable. (Note: this article uses the term “whitening “and “bleaching” interchangeably).

Tooth discolouration varies in aetiology, appearance, localization, severity, and adhesion to tooth structure. It can be defined as being:

• Extrinsic – factor from environment; that is, colouration from food, drinks or smoking,
• Intrinsic – factor from within oral cavity; that is accumulation of pigmented substance within the tooth structure upon tooth development or in non-vital tooth,
• A combination of both

Frequently used for the dental bleaching process are the following substances:

• Hydrogen peroxide
• Carbamide peroxide
• Sodium perborate

What Is Tooth Whitening?

“Tooth whitening” is to make a darker shade of teeth looks lighter.

• There are a number of different techniques available for tooth whitening; technique depends on various causes of discolouration.
• No matter which whitening technique or the bleaching substance that is being used, the mode of action is the same, which it involves  an oxidation reaction, resulting in the release of oxygen molecules.
• It is the oxygen molecules that penetrate the tooth and liberates the pigment molecules causing the tooth to whiten.

Non-Vital Tooth

A tooth becomes non-vital when the pulp or nerve of the tooth becomes necrotic, or dead, due to

• a filling being placed too close to the pulp
• decay penetrating the nerve chamber of the tooth or
• due to trauma

A non-vital tooth loses blood and water supply, making it slightly fragile and subject to darkening over time. A root canal treatment can be done to save the tooth, but will not to preserve the colour.

Why Non-Vital Teeth Darken?  

• When a tooth undergoes trauma and the pulp begins to become necrotic, blood is released as part of the inflammatory process.
• This blood becomes trapped in the dentinal tubules and breaks down.
• Breakdown products from blood penetrate dentinal tubules causing stains thus darken the tooth.

Ideal Treatment for Non-Vital Teeth

• Back teeth are often crowned in order to protect the weaken tooth structure, so that this discolouration is not important.
• Often discoloured teeth are crowned or veneered to make them match adjacent teeth. However for front teeth that have intact tooth structure are often not crowned. The treatment of choice is non-vital tooth whitening. Bleaching of root treated teeth that present with colour alteration is a conservative alternative to a more invasive aesthetic treatment such as placement of crowns or veneers. When metal-free restorations are planned, bleaching of the discoloured tooth can be useful in improving the final aesthetic results of the metal free restorations.

How Is It Done?

There are basically three different options for whitening non-vital teeth:

1. Walking bleach
2. Inside/outside bleaching
3. In-office bleaching

Different Methods and Procedures?

1.    Walking Bleach Techniques

• The least invasive method of internal bleaching of non-vital teeth.
• The name “walking” bleach technique is used because the procedure is like taking a walk, step by step through the teeth.
• Another reason for calling “walking bleach” is because the patient could “bring” the bleaching material “inside” the tooth home, they do not have to stay in the clinic for the treatment.
• This technique was first described by Spasser (Spasser, 1961) where sodium perborate is mixed with water into a paste form and then inserted into the access cavity of the tooth.
• Later, the technique was modified by mixing sodium perborate with hydrogen peroxide and inserting this into the access cavity of the tooth (Nutting & Poe, 1967).

Treatment procedure

1. The tooth colour of the patient’s teeth should be registered and documented.
2. Radiographic examination – to assess the quality of the root canal treatment and to ensure the surrounding bone is in healthy state.
3. Preparation of the access cavity – Root filling material (Gutta Percha) is removed to a level 2mm below the gum margin.
4. Cervical seal – Top of the root canal filling is sealed with cement to prevent the diffusion of bleaching agent from the pulp chamber into the canal space. This cement will act as a barrier.
5. Application of bleaching agent – Sodium perborate powder is mixed with water into paste form. Then, it is applied to the empty pulp chamber, cover with cotton pellet and seal with temporary restoration. The sodium perborate paste should be changed weekly to achieve the best bleaching status. This may need to be repeated a number of times to achieve the desired shade.
6. Permanent restoration – Once the desired colour change has been achieved, a permanent tooth-coloured restoration is placed.

2.    Inside/outside bleaching

• This technique was first described by Settembrini et al. (Settembrini et al, 1997) and later was modified (Liebenberg, 1997).
•  As the name implies, the idea is to apply bleaching agent both on the external and internal surfaces of the tooth.
• One advantage of this technique is that a low concentration of bleaching agent is sufficient to obtain the desired effect.

Treatment procedure

1. A vacuum-drawn splint is made with reservoir to the tooth to be bleached.
2. The access cavity is made as in the walking bleach technique.
3. The cavity access remains open during the treatment process.
4. The patient is instructed in the use of the splint.
5. Using a syringe, the access cavity and the corresponding location of the vacuum-drawn splint are filled with 10% carbamide peroxide (pea-sized amount of bleaching agent).
6. The splint is inserted and worn at night.
7. After a period of bleaching, the patient should clean the access cavity of the tooth.
8. Recall is recommended every two or three days to monitor the colour change.
9. When the desired colour has been attained, the access cavity is cleaned and then closed with a temporary restoration.
10. A week later, the definitive restoration can be placed.

3.    In-Office Bleaching

• This method is well known from bleaching vital teeth, but it can also be employed for non-vital teeth.

Treatment procedure

1. Preparation of the access cavity and sealing of the root canal is performed as in the walking bleach technique.
2. After the application of 30% hydrogen peroxide gel of 15-20 minutes per cycle, the gel is rinsed off and the procedure is repeated, if necessary.

What Are The Side Effects?

1. External cervical root resorption.
   • Cervical root resorption is a painless, inflammatory-mediated external resorption of the root, which can be seen after trauma and following internal bleaching. It is usually detected only through routine radiographs; however swelling on gum or tenderness to percussion can sometimes be observed.
   • It has proven that formulation using either 30% hydrogen peroxide alone, or in combination with sodium perborate, is more toxic for periodontal ligament cells than sodium perborate mixed with water (Harrington & Natkin, 1979).
2. Stability
   • The stability of bleaching is multifactorial and variable.
3. Effects on enamel
   • Enamel may become more susceptible to extrinsic discolouration after bleaching due to increased surface roughness.
4. Effect on restorations
   • Bleaching has little effect or no effect on most common restorative materials.
   • Bleaching may increase the solubility of glass ionomer or other cements and reduce the bond strength between enamel and resin composites. Because bleaching releases oxygen into the tooth, the oxygen released inhibits the polymerization of the resin (Titley et al, 1991).
   •  A delay of a week or more following the bleaching process is advised, prior to the placement of a new composite, to allow for this effect to be dissipated.
5. Toxity
   • Controversy still exists regarding tooth whitening procedures.

How Long Does The Whitening Take?

• The whitening effect is variable, as tooth discolouration has a multifactorial aetiology as a result of complex physiochemical reaction between chromogen and tooth substance.
• The correct diagnosis of the cause is of great importance as it has profound effect on treatment outcome.

What Are The Costs Involved?

• The price of bleaching of only one tooth (in case of non-vital tooth) is RM120 per tooth, while the price of bleaching on every tooth varies.
• The “at-home” bleaching costs approximately RM800 and above,
• The “in-office” type costs around RM1500 and above

(MDA Recommended Scale of Fees, 2010).

The price varies depending on each clinic and promotional campaigns.

Is tooth whitening subsidized by Malaysian Government?

The answer is “No”.

How Long Will My Tooth Stay White?

• “Tooth whitening” helps to make the tooth colour lighter up to certain level depending on the original colour.
• The tooth will not be whiter if the whiteness has reached its peak. This whiteness will stay for about 1 year or longer (about 3-5 years) depending on the behavioural and the post-operative care of each person.
• It is recommended that the patient has a “touch-up’ visit every year so that the result will last longer and remain more stable.

Conclusion

• Non-vital tooth whitening is a more conservative option compared to restoration with veneers or crowns.
• Proper diagnosis, selection of bleaching materials, placement technique, and an understanding of the biologic interaction with soft and hard tissues are all factors that determine not only immediate success but also long term success, safety, and patient satisfaction as well.

For more information, please consult your dentist at nearby government dental clinic.

References

1. Harrington, G.W., & Natkin, E. (1979). External root resorption associated with bleaching of pulpless teeth. Journal of Endodontic; 5: 344-48.
2. Liebenberg, W.H. (1997). Intracoronal lightening of discoloured pulpless teeth: A modified walking bleach technique. Quintessence Int; 28:771-777.
3. Malaysian Dental Association (MDA) Recommended Scale of Fees. (2010).
4. Nutting, E.B., & Poe, G.S. (1967). Chemical bleaching of discoloured, endodontically treated teeth. Dental Clinical North America; 11: 655-62.
5. Settembrini, L., Gultz, J., Kalm, J., & Scherer, W. (1997). A technique for bleaching non-vital teeth inside/outside bleaching. Journal of American Dental Association; 128(9): 1283-1284.
6. Spasser, H.F. (1961). A simple bleaching technique by using sodium perborate. New Jersey State Dental Journal; 17:365-68.
7. Titley, K.C., Torneck, C.D., Ruse, N.D., & Krmec, D. (1993). Adhesion of a resin composite to bleached and unbleached human enamel. Journal of Endodontic; 19: 112.