Tooth-whitening update: The crux of the matter

The impact on the entire area of tooth whitening is manifold and far-reaching. The crux of the matter is the new 6.0% limit of hydrogen peroxide in tooth-whitening products. Even the sale of products containing more than 0.1% and up to 6.0% hydrogen peroxide is restricted to dentists, who are only permitted to administer these products to patients after advising patients in detail about the product and its usage. The directive will also put an end to the online sale of tooth-whitening products, which has generally been associated with adverse side-effects.

The new regulation has been interpreted differently in each European country. Some countries, such as the Netherlands and the UK, regard it as the maximum upper limit and restrict the use of tooth-whitening gels with a higher concentration of hydrogen peroxide. In these countries, even registered self-employed dental hygienists are not permitted to perform tooth-whitening procedures without the supervision of a dentist―an impractical state of affairs. This is also due to the new directive, which requires that a dental examination be conducted before commencing tooth whitening.

Advantages
Owing to these extreme interpretations of the directive, certain leading tooth-whitening products are no longer available or have been taken off the market in these countries. Germany has taken a much more pragmatic and practice-oriented approach: in general, tooth whitening is performed by dental professionals, but can be conducted under the supervision of a dentist. Even before the directive, the Supreme Court had restricted cosmetic whitening treatments performed by non-dental professionals to a maximum hydrogen peroxide concentration of 6.0%. The new EU directive is very much to the advantage of the dentist, as it no longer allows non-dental professionals to perform cosmetic whitening procedures. It also establishes legal certainty that dentists can still use products with a hydrogen peroxide concentration higher than 6.0% for medical whitening in order to treat discolouration due to tetracycline, trauma, or the use of medication or prolonged use of discolouring substances, genetically determined extensive discolouration, or highly discoloured teeth with devitalised roots, among others.

These treatments are therefore classified as medical indications and do not lie in the area of cosmetic indications.

Expertise
In my opinion, high-quality whitening procedures should only be performed by dentists or highly qualified dental nurses, hygienists or therapists. The incidence of side-effects, especially with products that contain a high concentration of hydrogen peroxide, is simply too high and irritation of the gingiva and hypersensitivity can only be avoided with substantial knowledge of the products and experience in their use.

Revolutionary
The implementation of the new directive requires substantial changes in dental practices, but also offers benefits in everyday tooth-whitening procedures by preserving tooth structure and rendering treatment more pleasant for the patient through new technologies. Long before the new directive came into effect, a number of forward-looking companies were already seeking not just a simple tooth-whitening alternative but a revolutionary new technology with novel treatment benefits.

The new PrevDent CrWR tooth-whitening system, for example, illustrates this new development clearly. For many years, PrevDent had distributed the BriteSmile in-office whitening system in many European countries, but this product falls outside of the hydrogen peroxide limit set by the new EU directive in some of those countries. After intensive research and a paradigm shift, PrevDent’s development engineers developed an ideal combination based on the concurrent development in the field of surface protection with nanotechnology. The result is a combination of a 6.0% low-level hydrogen peroxide gel and nano-hydroxyapatite (nHAp). The potential of this interesting and pioneering invention can only be grasped after an in-depth analysis of current studies on the topic of nanotechnology.

Ground-breaking
Current research in all areas of application of nHAp has provided ground-breaking results regarding the protection and long-term preservation of the tooth structure. Remineralisation of the enamel surface, detected with an electron microscope, has been observed, as well as extensive antibacterial effects on the tooth surface that appear to protect against caries and periodontitis. Comparative studies at the University of Pisa have shown that nHAp has a similar antibacterial effect to chlorhexidine, which is considered the gold standard in the field of periodontology. Nano-hydroxyapatite technology has also found its way into the field of filling materials. Researchers at the University of Maryland have already been using filling materials with nHAp for some time and the preliminary results are promising.

There are numerous successful applications of nHAp, including the following:

1. protection against caries by preventing Streptococcus mutans adhering to the tooth surface;[1]
2. use in atraumatic restorative treatment as non-invasive caries therapy in countries with insufficient dental health care infrastructure;[2]
3. addition of nHAp to composite materials for longer durability of fillings;[2]
4. remineralisation of early carious lesions;[3]
5. remineralisation of erosive enamel lesions;[4]
6. regeneration and repair of enamel structures;[5]
7. sealing of dentinal tubules and formation of a protective dentine layer;[6]
8. formation of a protective coating against acid and subsequent reduction in hypersensitivity.[7]

Prevention
In the field of tooth whitening, the newest application concerns the prevention of hypersensitivity. The University of Indianapolis has been very active in this area of research. Browning et al. have demonstrated that the use of nHAp reduces hypersensitivity substantially during whitening.[8] Moreover, Deschepper et al.—also from Indianapolis—have demonstrated a reduction in surface roughness when nHAp was used, as well as simultaneous sealing of the surfaces.[9] These findings correspond with that of Kawamata et al., who established that the application of nHAp after whitening resulted in the restoration of the enamel structure.[10] Additionally, Takikawa et al., already early on, indicated the positive effects of the use of an nHAp-containing conditioner that is applied after tooth whitening.[11] To date, patients with hypersensitive teeth, who had to be pretreated with amorphous calcium phosphate, fluoride or other desensitisers, with simultaneous use of analgesics in order to avoid severe side-effects, have been the greatest challenge for us. Owing to the nanotechnology, we no longer need to be concerned about these side-effects and can perform whitening without any specific pretreatments.

No side-effects
Once nHAp comes into contact with the tooth surface, the nano-components seal the sensitive structure effectively and the whitening procedure can be performed without any side-effects. No hypersensitivity occurs during or after the tooth whitening. The tooth-whitening cycles are shorter: instead of three cycles of 20 minutes each, six cycles of 10 minutes each are recommended. This is also due to the low hydrogen peroxide concentration and has proven to be very successful. Owing to the more frequent and shorter cycles, freshly activated low-level hydrogen peroxide is applied to the surfaces. Furthermore, PrevDent responded quickly in the development of post-treatment products and introduced a toothpaste that contains nHAp. Studies at the University of Pisa have already demonstrated the toothpaste’s desensitising effect. In addition, brushing one’s teeth with the PrevDent nHAp toothpaste alone has a rewhitening effect, as the continuously remineralised surface reflects light better.

Bio-whitening
In addition to the positive effects of the use of nHAp described above, it has to be stated that the tooth-whitening effect of the PrevDent CrWR system is very good, even though the teeth do not appear to be quite as white directly after treatment. They have the same colour one would normally expect a day after conventional whitening with a higher-concentration gel. This is mainly because the teeth are not as heavily dehydrated. One day after whitening, however, the colour of the teeth is identical to that of teeth whitened conventionally, but without the painful side-effects. In the truest sense of the word, the procedure can be described as a bio-whitening.

The new technology extends the range of indications of tooth-whitening treatment. Furthermore, patients with highly discoloured teeth and fear of the side-effects can be treated earlier. Frequent whitening can be performed in shorter intervals completely free of side-effects. In my opinion, there are no longer any contra-indications to whitening treatments owing to the introduction of nHAp. In the future, treatment with nHAp is likely therefore to increase exponentially.

No more hypersensitivity
While further research is necessary, it has been determined that whitening with nHAp improves and seals the tooth structure and has made once-dreaded hypersensitivity a thing of the past. It remains to be seen how the market will react in the near future. Most certainly, more tooth-whitening products will be developed. Many manufacturers will seek to introduce similar nHAp-containing products to the market. In any event, this is a result of the new EU directive. It has given new impetus to the whitening market.
 

Editorial note: This is a translated version of the article titled “Aktuelles Bleaching-Update nach der EU-Richtlinie 2011/84/EU—Die Zukunft gehört dem Nanohydroxyapatite (nHAp)”, which was published in the 02/2013 issue of the German edition of the cosmetic dentistry magazine.

A complete list of references is available from the publisher.