Introduction
No one is able to go through their lives without attaining stains on their teeth. Between the foods that we eat and the things that we drink, teeth lose their whiteness as each of us grows older. One of the ways to combat this problem and whiten teeth is by using whitening toothpaste.
There are many whitening toothpastes on the market these days. It seems a little too easy to think that toothpaste can whiten teeth while you brush. If it were that easy, then why isn't everyone using this method? The truth is that many people do not know if whitening toothpastes really work.
Toothpastes are used to clean teeth and prevent dental problems. When a whitening effect is added, it has to be added to the ingredients that are already working to help your teeth stay clean. This automatically means that the active ingredients for the whitening of teeth are going to be of less concentrate in the toothpaste in spite of specific whitening treatments performed by the dentist. This can give the illusion that whitening toothpastes do not work.
The truth is that most whitening toothpastes on the market are effective (Abrasion, polishing, and stain removal characteristics of various commercial dentifrices in vitro, 2011). No matter what toothpaste you choose, the effectiveness of the whitening will vary depending on many things, first, there are always directions to brushing your teeth. You have to make sure that you are brushing your teeth after every meal and brushing them for at least three minutes. Without brushing your teeth as often or as long as directed, you can automatically decrease the effectiveness of the whitening in toothpastes.
What stains teeth?
The most important lose of teeth whitness happens in people who smoke (Randomized controlled trial to evaluate tooth stain reduction with nicotine replacement gum during a smoking cessation program, 2012) or drink dark colas or coffee, but the truth is that everyone has some stains on their teeth.
However the yellow decoloration in our teeth is natural and inevitable. These stains inside the tooth are called intrinsic stains. As we age, the innermost layer of our tooth, the dentin, changes yellow in color. So we can say that discoloration results from the aging process. As teeth age, more secondary dentin is formed and the more translucent enamel layer thins. Furthermore, it is proven that exposure to too much fluoride (see also Fluorosis) also causes the inner dentin layer to change color. However, each tooth can become discolored on the outer layer as well. The enamel is made up of pores that can hold stains; this is why products such as coffee, red wine, iron salts, certain medications, and tobacco stain our teeth to a greater degree than most other foods. Not only does the enamel hold stains, but there is also a sticky coating on the outside of your tooth that picks up stains. Since tooth whitening toothpaste is most effective on surface stains, its result is temporary and it does not penetrate the discoloration of the inner-most layer of the tooth.
Substances commonly used in a whitening toothpaste
Whitening toothpastes use hydrogen peroxide (H202) or carbamide peroxide (agenti sbiancanti) which is similar to the hydrogen peroxide, but more manageable and stable because it splits in contact with saliva. The hydrogen peroxide acts more rapidly but must be handled with greater attention. The carbamide peroxide is more stable, easier to handle but requires a longer application. The enamel and dentine are permeable to these peroxides, then bleaching occurs in the interior of the tooth and can eliminate the endogenous stains that can not be removed just by cleaning the outside of the tooth and even good oral hygiene to the dentist.
Other substances really common to find in a whitening toothpaste are:
- ABRASIVE: These can include alumina, silica, calcium carbonate and dicalcium phosphate which help break up the stains off the surfaces of the teeth. However dentist's opinion is that of using toothpaste with low index of abrasivness in order to avoid enamel damages. The mildly abrasive nature of these particulate substances incorporated into the formulation a whitening toothpaste when combined with the scrubbing action of a toothbrush can often remove surface staining.
- DETERGENTS (sodium lauryl sulfate): This chemical is basically like soap which foams and cleans the outer layer of the teeth.
- POLYVINILPORROLYDONE (PVP): This is a protective ingredient that keeps stains away from the tooth surface.
- OTHERS: These include enzymes such as papain, triclosan, citric acid, sodium tripolyphosphate.
The scrubbing motion of the bristles of a toothbrush in combination with the presence of these small particles creates an action that can have an effect where it scours debris off the surface of teeth. So, as opposed to peroxide-based teeth whiteners where the whitening effect is produced by a chemical change that occurs within a tooth, whitening toothpastes produce a whitening effect solely by way of removing accumulated debris off a tooth's external surface. For this reason, teeth whitening toothpastes are sometimes referred to as "nonbleaching" whitening products.
Adverse effects of whitening toothpastes
Unlike the specific whitening treatments, which is known to cause the onset of hypersensitivity and decreased enamel hardness, it has been shown by a study vitro that the same is not true for whitening toothpastes. (Comparison of the Effects of Two Whitening Toothpastes on Microhardness of the Enamel and a Microhybride Composite Resin: An in Vitro Study, 2010)
According to this study that tests the possible side effects of two whitening toothpastes on the market, there is no damage to the enamel layer . However it has been shown that the use of these toothpastes can go to reduce the hardness of the dental restorative materials and therefore reduce its strength.
However, another in vitro study (In vitro study on tooth enamel lesions related to whitening dentifrice, 2011) still investigating the possible contraindications of these toothpastes has observed a change in the morphology of the enamel. These observations were carried out using an electron microscope and identified lesions of varying severity on the enamel, minor injury after the use of toothpaste containing carbamide peroxide, more severe after using toothpaste containing sodium bicarbonate (abrasive substance).
Electron micrographs of the enamel surface darkened in the laboratory and treated with dentifrice without whitening agent. Magnitude: ×540
Electron micrographs of the enamel surface darkened in the laboratory and treated with dentifrice containing hydrogen peroxide. Magnitude: ×500
On the basis of these studies it can be stated that the hardness of the enamel is not changed but small changes were observed on the surface of the enamel. However, that which has not yet been made clear is whether these microscopic lesions in enamel or no clinical relevance.
Conclusions
It’s important to note that there are a few whitening toothpastes which have a sole purpose to only whiten teeth; most whitening toothpastes are meant to clean teeth, prevent cavities, and whiten. Hence, most whitening toothpastes only contain a small concentration of the whitening chemical because they also contain protective tooth decay ingredients such as fluoride. On a comparative basis, teeth whitening toothpastes typically are not considered to be the most effective type of tooth whitening products available, primarily because their effect is only one of removing superficial debris as opposed to creating a true internal color change as is the case with peroxide-based whiteners. However, there can be circumstances when a whitening toothpaste is the best choice.
Some people may find that they are, for the most part, perfectly content with the color of their teeth. With time however, typically beginning some weeks or months after their most recent professional dental cleaning, they will notice that their teeth have begun to take on a stained appearance. In most cases the stain is only found on a few teeth or just a grouping of teeth. Often the staining will be dark and quite noticeable in some areas and almost unnoticeable in other regions. This type of tooth discoloration is surface staining. And this is precisely the type of staining that a tooth whitening toothpaste is intended to address.
Luca Tallone, Andrea Brondino
CdL in Odontoiatria e Protesi Dentaria
