ABSTRACT
In recent years, numerous over-the-counter (OTC) tooth whitening products have become available online to meet the demand of consumers wanting a convenient way to whiten their smile. This study investigated whether websites selling OTC whitening products containing hydrogen peroxide to New Zealanders are complying with hazardous substance laws set by the New Zealand Environmental Protection Authority (EPA). The search engine ‘Google’ was used to identify websites selling and shipping OTC whitening products to New Zealand. Data were collected from these websites and analysed. A total of 24 New Zealand based (n = 16) and overseas (n = 8) websites were included. Of these, 12 (50%) provided an ingredients list, 1 (4%) mentioned all precautionary statements required by the EPA, and 21 (88%) met the EPA restrictions for supply and application of a hazardous substance. 11 (46%) warned of tooth sensitivity as a potential side-effect and 8 (33%) gave a warning for gingival irritation. Fewer than half (42%) recommended consulting a dental professional before using their product. Over-the-counter tooth whitening products being sold online to New Zealanders may be breaching conditions of the EPA and putting New Zealanders at risk. Legislative changes should be considered to ensure that companies’ websites are providing correct precautionary statements.
KEYWORDS: Teeth whitening, online marketing, hydrogen peroxide, side-effect, hazardous substance
Introduction
In the modern era, physical and cosmetic appearance plays an essential role in an individual’s self-esteem and social success (Klages et al. 2004). As a result, dentistry has evolved from not only providing oral health services for the relief of pain and treatment of oral diseases but to also providing elective aesthetic services, such as tooth whitening (Theobald et al. 2006).
Tooth whitening involves bleaching tooth surfaces using either hydrogen or carbamide peroxide (Carey 2014). At-home tooth whitening using 10% carbamide peroxide with custom trays is the most common bleaching procedure prescribed by dentists (Demarco et al. 2009). To meet the demand of patients wanting a fast, cheap and straightforward way to get a whiter smile, a large variety of over-the-counter (OTC) whitening products have become available on the market, predominantly via the internet (Castro et al. 2015). Most companies selling unsupervised OTC tooth whitening kits online market peroxide-containing gels along with universal mouth trays (Demarco et al. 2009).
Dentist-supervised tooth whitening has been reported to be a relatively safe procedure; however, potential side-effects can arise, in particular, tooth sensitivity and gingival irritation (Li and Greenwall 2013). These two side-effects have been found to occur in the majority of people, with reports stating that between one half and two-thirds of patients experience them to some degree (Haywood et al. 1994; Tam 1999; Jorgensen and Carroll 2002). However, when the product is used appropriately, these side-effects are usually only mild to moderate in severity and transient, persisting for 2–5 days (Tredwin et al. 2006; Sulieman 2008; Li and Greenwall 2013). There are some factors that put a patient at a higher risk of suffering adverse effects. They include both dental and non-dental characteristics (Leonard et al. 1997; Jorgensen and Carroll 2002). These are summarised in Table 1.
Table 1.
Factors that increase the risk of suffering adverse effects when undergoing tooth whitening procedures.
| Dental characteristics | Non-dental characteristics |
|---|---|
|
|
It is widely accepted that as part of a safe tooth whitening protocol, a comprehensive oral examination should be completed by a dentist (Sarrett 2002). This serves to not only assess the patient’s dental health and risk of adverse effects, but also enables the cause of the discolouration to be determined and an appropriate tooth whitening method to be used (Sarrett 2002). Table 2 outlines the contraindications of tooth whitening (Sulieman 2008). Whitening procedures using OTC kits purchased by consumers are typically performed without the supervision of a dentist. Thus, consumers are able to undergo the treatment without knowing whether it is safe or whether the product will work on their type of tooth discolouration.
Table 2.
Contraindications to undergoing tooth whitening procedures.
|
That there is a lack of professional supervision raises safety concerns, particularly about potential abuse, inappropriate application and purchasing of the products by young patients (Demarco et al. 2009; Li and Greenwall 2013). There is limited clinical evidence on the safety and efficacy of OTC whitening products. Higher levels of gingival irritation in patients undergoing unsupervised OTC bleaching than dentist-supervised bleaching have been observed (Auschill et al. 2005). A possible reason for this was that the universal trays provided in the kits adapted poorly to the patient's mouth, leading to tissue impingement and greater contact between the bleaching gel and the soft tissues. Some reports have also stated that over-use of OTC products may cause demineralisation of dental enamel, especially if the products are too acidic (Castro et al. 2015).
Regulations for dental products containing peroxides that are either imported into or manufactured in New Zealand are set by the Environmental Protection Authority (EPA). The EPA is a New Zealand government agency that operates under the Ministry for the Environment. It is responsible for evaluating, approving and putting controls in place for hazardous substances pursuant to section 96B of the Hazardous Substances and New Organisms Act 1996 (Environmental Protection Authority 2020). Hazardous substances of a similar nature, type or use are put into group standards, which outline the conditions that allow that group of substances to be managed safely. Since both hydrogen and carbamide peroxide are classed as hazardous substances, they are classified into group standards depending on their concentration in any given product (Environmental Protection Authority 2020).
There are currently no data on online companies advertising and selling peroxide-containing OTC whitening products to New Zealand consumers. There is also a lack of evidence on whether or not they are adhering to the legal requirements of the EPA. The purpose of this study was to investigate whether online companies selling OTC whitening products are breaching the conditions of the EPA, and to evaluate the potential health risk to the New Zealand public.
Methods
Using a similar approach to that of Gurram et al. (2019), online searches were conducted to identify websites marketing online sales of whitening products to New Zealand consumers. All searches were carried out during April 2020 using the web browser Safari. A private browsing window was used for all searches to minimise the effects of browser and search history on the results. The search engine Google was used for all searches.
In order to determine which specific key terms would be used in the searches, Google Trends was used to identify the five most popular search terms related to tooth-whitening used in New Zealand over the previous 12 months (from April 2019 to March 2020). Five terms were compared at a time, with the least popular terms being eliminated. The most popular search terms identified were ‘whitening kit’, ‘teeth whitening kit’, ‘dental whitening’, ‘tooth whitening’, and ‘teeth whitener’. Each of these was then used in a separate search, and the website addresses for the first 50 results were recorded. This gave a comprehensive list of 250 website addresses.
From this list, duplicates were removed. The content of each website was assessed, and the inclusion and exclusion criteria were applied. The inclusion criteria were: (1) Any New Zealand-based or international commercial website that sold and shipped at-home tooth whitening kits to New Zealand consumers, without professional supervision; (2) The active ingredient of the product was peroxide-based (either hydrogen or carbamide peroxide); and (3) the concentration of the active ingredient had to be given. Websites that met all of these criteria were included. Excluded were; (1) any website that was non-commercial such as an educational resource, scientific literature, product review or news article; (2) websites that did not ship their products to New Zealand; and (3) websites advertising in-office whitening treatment but did not sell any products online. An IP location tracker was used to geolocate the websites. A website was recorded as being located in New Zealand if it had an IP located in New Zealand or if it had a New Zealand URL. All other websites were recorded as overseas. The search strategy used for the websites is summarised in Figure 1.
Figure 1.
Search strategy for websites selling OTC whitening products.
After the selection process, the websites were examined. The highest concentration of hydrogen peroxide in any product sold from a website was recorded. For the purpose of this study, if a website’s product contained carbamide peroxide as its active ingredient, it’s concentration was converted into the equivalent concentration of hydrogen peroxide using the ratio of 3:1 (Cosmetic Products Group Standard 2006–2012). This allowed each website to be investigated based on which EPA group standard their products are controlled by. A summary of the relevant group standards and their restrictions is provided in supplemental file 1. Data were collected on information provided by the websites, based on the specific requirements of the EPA, including: a list of ingredients; whether they listed all of the necessary precautionary statements; warnings for children under 16 years old;, and whether they provided the specific warning ‘if irritation occurs, discontinue use’.
From this information, it was possible to determine whether any particular website was meeting the conditions of the EPA. The websites were assessed for compliance with the ‘labelling and advertising’ section and the ‘supply and application of tooth whitening products’ restrictions. Data were also collected on the following information not required by the EPA but of relevance to this study: breastfeeding and pregnancy warnings; whether websites cautioned against using the product in the presence of other dental conditions or dental appliances; sensitivity warnings; and gingival irritation warnings.
If a website sold more than one peroxide containing product, they were classified as complying with the relevant EPA Group Standard conditions only if the required information was provided for every product.
Results
Websites
Duplicates from the original list of 250 websites were removed and the content of 139 websites was assessed. After applying the inclusion and exclusion criteria, a final list of 24 websites was deemed eligible for this study. 16 (67%) websites were located within New Zealand, and 8 (33%) were based overseas.
The concentration of hydrogen peroxide
The highest concentration of hydrogen peroxide in any product advertised based on location is summarised in Table 3. A total of 20 websites were subject to the labelling and advertising conditions of the Dental Products (Subsidiary Hazard) Group Standard. However, these products were not subject to any supply or application restrictions set by the EPA. Two websites were subject to both labelling and advertising conditions and supply and application restrictions under the EPA Dental Products (Subsidiary Hazard) Group Standard. Two websites were subject to restrictions under the EPA Dental Products (Oxidising 5.1.1C) Group Standard. Three websites (one New Zealand based and two based overseas) did not give the concentrations of hydrogen peroxide in their products. Because of this, they were unable to be assigned to any EPA group standard and were therefore excluded from further data collection and investigation.
Table 3.
Websites categorised according to location and the highest concentration of hydrogen peroxide in any product sold.
| Highest concentration of hydrogen peroxide | New Zealand (n = 17) | Overseas (n = 10) | Total (n = 27) |
|---|---|---|---|
| Containing or releasing less than 7% | 14 (82%) | 6 (60%) | 20 (74%) |
| Containing or releasing between 7 and 8% | 2 (12%) | 0 (0%) | 2 (7%) |
| Containing or releasing greater than 8% | 0 (0%) | 2 (20%) | 2 (7%) |
| No concentration given | 1 (6%) | 2 (20%) | 3 (11%) |
Epa required precautionary information
Table 4 outlines the proportion of websites providing information required by both of the EPA group standards that cover tooth whitening products containing less than and greater than 8% hydrogen peroxide under Schedule 1 Part 1 ‘Labelling and Advertising’. Only half of the websites located from both within New Zealand and overseas provided a complete list of ingredients for their products. Six websites gave at least one of the required precautionary statements (or equivalents of) but not all. No New Zealand websites provided all of the necessary precautionary statements. The only website that listed all of the statements was located overseas. Only 25% of all websites advised against the use of their products in children aged under 16 years old. No New Zealand-based website (and only two from overseas) stated the specific irritation warning ‘if irritation occurs, discontinue use’.
Table 4.
Proportion of websites providing the information required by the EPA ‘Labelling and Advertising’ conditions.
| Information required | New Zealand (n = 16) | Overseas (n = 8) | Total (n = 24) |
|---|---|---|---|
| Ingredients list given | 8 (50%) | 4 (50%) | 12 (50%) |
| All precautionary statements | 0 (0%) | 1 (13%) | 1 (4%) |
| Irritation warning | 0 (0%) | 2 (25%) | 2 (8%) |
Compliance with EPA conditions
The single New Zealand based website that did not comply was a website not run by either registered oral health practitioners or non-registered whitening technicians and was selling a product containing 7.5% hydrogen peroxide. 75% of the overseas-based websites adhered to the supply and application restrictions of both EPA group standards. The two that did not comply were selling products with hydrogen peroxide concentrations of up to 15% and were not run by registered oral health practitioners or non-registered whitening technicians. Only one (4%) of all websites complied with the labelling and advertising requirements of the group standard they were covered by. This particular overseas website also met the EPA supply and application restrictions, making it the only investigated website that met all required conditions.
Other precautionary labels
Half of New Zealand and three-quarters of overseas-based websites recommended against the use of their products in breastfeeding or pregnant women. Less than half of all websites cautioned against use if a consumer had dental conditions such as periodontal disease, damaged enamel, caries or exposed roots. 42% of all websites recommended consulting a dental practitioner before treatment. Fewer than half of all websites gave a warning of possible sensitivity and a third mentioned gingival irritation as a potential side effect. The percentage of New Zealand websites providing extra information and warnings about side effects or seeking professional help was consistently lower than the overseas websites. In all websites, most of the information on health and safety was located under either the ‘frequently asked questions’ or terms and conditions sections.
Discussion
Online marketing of OTC whitening products has recently become more popular as dentistry has evolved to provide more elective cosmetic procedures. This study has shown that all but one website may have breached the EPA regulations, which brings into question the safety of the New Zealand public.
A significant strength of this research is that there is no other similar study that has looked into online marketing of OTC whitening products in New Zealand. When a customer purchases a whitening product online, they are not able to physically see the label of the product unless a photo of it is provided on the website. In this study, an online vendor was reported as having this information if it was found anywhere on the website, as opposed to on the label. Therefore, any website that was reported as not having provided the necessary information may actually have it on the labels of their products, just not on their website. This is a possible weakness of this study. However, consumers should be provided with all necessary information at the time of purchase. The general public are unlikely to know that whitening products contain a controlled hazardous substance. Additionally, they are also unlikely to have the scientific or medical knowledge required to know what potential risks are associated with this substance. This leaves them vulnerable.
From this study, we have found that no New Zealand based websites advertising OTC whitening products comply with the EPA labelling and advertising conditions. We need to question whether customers purchasing these products without being given the appropriate precautions is ethical. The principle of informed consent should be considered. A significant part of the informed consent process is ensuring the patient is aware of all potential risks and side effects of treatment. As mentioned previously, the majority of patients undergoing tooth whitening will experience tooth sensitivity and gingival irritation. However, only 46% of websites mentioned tooth sensitivity and 33% mentioned gingival irritation. Since these warnings are not required under any EPA group standard for dental products, likely, they are also not provided on any labels. Therefore, it can be assumed that New Zealanders are undergoing whitening procedures, possibly with products containing more than the legal concentration of hydrogen peroxide and experiencing these side effects without being informed of them. The advertising of these products may also be in breach of section 30(1) of the Fair Trading Act 1986 which states that goods must not be advertised or supplied unless product safety standards are complied with (Fair Trading Act 1986–2022).
The supply and application conditions of the EPA group standards ensure the safety of the public by only allowing low concentrations of hydrogen peroxide to be available commercially. We have observed that three websites breached their group standard conditions by selling whitening products containing greater than 7% hydrogen peroxide. One of these even sold products containing 15% hydrogen peroxide, more than twice the legal limit (Dental Products (Subsidiary Hazard) Group Standard 2017b). Furthermore, two websites did not disclose the concentration of peroxide in their products at all, posing a huge safety risk. Application of higher concentrations of hydrogen peroxide is restricted to dental professionals and tooth- whitening practitioners because of the risk of adverse effects such as severe soft tissue burns (Walsh 2000). Tthe unsupervised use of whitening products of this concentration may allow potential adverse effects to be either more likely or more severe with the accidental or intentional abuse or inappropriate application of these products.
The lack of professional dental supervision also means that the New Zealand public is likely to be undergoing whitening when they have oral conditions that contraindicate such a procedure, particularly given the low reported rates of dental attendance in New Zealand (Ministry of Health 2019). Despite this, less than half of the websites included in this study recommend consulting a dental professional before using their products. Consequently, customers could be unknowingly subjecting themselves to exacerbations of current conditions or more severe adverse effects. Consumers are also unlikely to know if the product they are purchasing and using will even be effective on their type of tooth discolouration.
As the core regulatory body for hazardous substances, the EPA is primarily responsible for protecting the public from danger when it comes to peroxide-containing products. Their current group standards fail to take into consideration that with the increase of online shopping, OTC products are becoming more widely available over the internet. Unless the website gives the appropriate information and warnings, there is no way a consumer can read a safety label without already purchasing the product and having it physically in front of them. Therefore, the EPA should consider making amendments to these group standards so that they include that online vendors must freely provide an ingredients list and all necessary precautionary statements on their website in addition to on the product labels. They should also include that websites need to recommend that consumers consult a dental professional before using their products and have warnings of the potential adverse effects.
Both the Dental Council of New Zealand and the New Zealand Dental Association advocate for dental bleaching to be a restricted activity, only able to be performed by dental professionals. Dentists need to be aware that their patients could be using OTC whitening products containing greater than the legal concentration of hydrogen peroxide. Dentists should advise patients who are considering tooth whitening against purchasing products online unless they have undergone a comprehensive dental examination. It is also recommended that there be more public information available to patients and consumers on the risks of tooth whitening so that anyone who is considering purchasing OTC products can know what to look for and make a more informed decision.
Conclusion
Over-the-counter tooth whitening products being sold online to New Zealanders may be breaching the conditions of the Environmental Protection Authority. This is potentially putting the health and safety of the New Zealand public at risk. Therefore, legislative changes should be considered to ensure companies that use websites are being held accountable and are providing the correct precautionary statements, warnings for potential adverse effects and recommending that consumers consult a dentist before using their products. Dentists should be working to raise patients’ awareness on the possible risks of using such products.
Supplementary Material
Disclosure statement
No potential conflict of interest was reported by the author(s).
References
- Annual Data Explorer 2017/2018: New Zealand Health Survey . 2019. Ministry of Health; [accessed 2020 Oct 7]. https://www.health.govt.nz/publication/annual-update-key-results-2017-18-new-zealand-health-survey.
- Auschill TM, Hellwig E, Schmidale S, Sculean A, Arweiler NB.. 2005. Efficacy, side-effects, and patients acceptance of different bleaching techniques (OTC, in-office, at-home). Operative Dentistry 30:156–163. [PubMed] [Google Scholar]
- Carey CM. 2014. Tooth whitening: what we now know. Journal of Evidence Based Dental Practice. 14:70–76. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Castro J, Godinho J, Mata JM, Pessanha S.. 2015. Study of the effects of unsupervised over- the-counter whitening products on dental enamel using u-Raman and u-EDXRF spectroscopies. Journal of Raman Spectroscopy. 47:444–448. [Google Scholar]
- Cosmetic Products Group Standard 2006 as amended July 2012 . 2006–2012. Environmental Protection Authority; [accessed 2020 March 7]. http://epa1.cwp.govt.nz/assets/Uploads/Documents/Hazardous-Substances/Old-Group-Standards/e1f83f48f0/Previous-Cosmetic-Products-Group-Standard-HSR002552.pdf.
- Demarco FF, Meireles SS, Masotti AS.. 2009. Over-the-counter whitening agents: a concise review. Brazilian Oral Research. 23:64–70. [DOI] [PubMed] [Google Scholar]
- Dental Products (Subsidiary Hazard) Group Standard 2017 – HSR002558 . 2017b. Environmental Protection Authority; [accessed 2020 March 6]. https://www.epa.govt.nz/assets/Uploads/Documents/Hazardous-Substances/2017-Group- Standards/fe90667bdb/Dental-Products-Subsidiary-Hazard-Group-Standard-2017-HSR002558.pdf.
- Fair Trading Act 1986 . 1986–2022. New Zealand Legislation; [accessed 2022 June 20]. https://www.legislation.govt.nz/act/public/1986/0121/latest/whole.html.
- Gurram N, Thomson G, Wilson N, Hoek J.. 2019. Electronic cigarette online marketing by New Zealand vendors. The New Zealand Medical Journal. 132:20–33. [PubMed] [Google Scholar]
- Haywood VB, Leonard RH, Nelson CF.. 1994. Effectiveness, side effects and long-term status of nightguard vital bleaching. Journal of the American Dental Association. 125:1219–1226. [DOI] [PubMed] [Google Scholar]
- Hazardous substances and the EPA . 2020. Environmental Protection Authority; [accessed 2020 March 6]. https://www.epa.govt.nz/industry-areas/hazardous-substances/what-are-hazardous-substances/.
- Jorgensen MG, Carroll WB.. 2002. Incidence of tooth sensitivity after home whitening treatment. Journal of the American Dental Association. 133:1076–1082. [DOI] [PubMed] [Google Scholar]
- Klages U, Bruckner A, Zenter A.. 2004. Dental aesthetics, self-awareness, and oral health-related quality of life in young adults. The European Journal of Orthodontics. 26:507–514. [DOI] [PubMed] [Google Scholar]
- Leonard RH Jr, Haywood VB, Phillips C.. 1997. Risk factors for developing tooth sensitivity and gingival irritation associated with nightguard vital bleaching. Quintessence Int. 28(8):527–534. [PubMed] [Google Scholar]
- Li Y, Greenwall L.. 2013. Safety issues of tooth whitening using peroxide-based materials. British Dental Journal. 215:29–34. [DOI] [PubMed] [Google Scholar]
- Sarrett DC. 2002. Tooth whitening today. Journal of the American Dental Association. 133:1535–1538. [DOI] [PubMed] [Google Scholar]
- Sulieman M. 2008. An overview of tooth-bleaching techniques: chemistry, safety and efficacy. Periodontol 2000. 48:148–169. [DOI] [PubMed] [Google Scholar]
- Tam L. 1999. A clinical trial of three 10% carbamide peroxide bleaching products. Journal of the Canadian Dental Association. 65:201–205. [PubMed] [Google Scholar]
- Theobald AH, Wong BKJ, Quick AN, Thomson WM.. 2006. The Impact of the popular media on cosmetic dentistry. New Zealand Dental Journal. 102:58–63. [PubMed] [Google Scholar]
- Tredwin CJ, Naik S, Lewis NJ, Scully C.. 2006. Hydrogen peroxide tooth-whitening (bleaching) products: review of adverse effects and safety issues. British Dental Journal. 200:371–376. [DOI] [PubMed] [Google Scholar]
- Walsh LJ. 2000. Safety issues relating to the use of hydrogen peroxide in dentistry. Australian Dental Journal. 45:257–269. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.