RDA Value – Relative Dentin Abrasion

Toothpaste has many functions. Besides freshening breath and preventing tooth decay, it should above all, clean teeth thoroughly! To achieve this, toothpastes contain small particles that help remove plaque, food residue and bacteria.

In the process, the cleaning particles in the toothpaste – especially in the case of aggressive whitening toothpastes – can also remove a minimal amount of the tooth enamel. This process is called abrasion. The abrasiveness of a toothpaste is indicated by its RDA value. This stands for the so-called Relative Dentin Abrasion.

This article explains what you need to know about the RDA value and which values are good for which application purpose.  In addition, recommendations concerning which RDA value is specifically relevant for children and why the Kinder Karex Toothpaste cleans thoroughly while being gentle on a child’s teeth will be given.

1. What is the RDA value?
2. Table of RDA Values
3. Which RDA value is a good one?
4. Which RDA value is recommended for children?
5. RDA value of Kinder Karex Toothpaste

RDA is the short form for radioactive or relative dentin abrasion.  To be precise, this complicated sounding term tells us how much a tooth “abrades” dentin (i.e. the interior of teeth) under laboratory conditions. In other words, it refers to the abrasion of the tooth substance caused by a toothpaste. In a figurative sense, the brushing performance of a toothpaste can also be indirectly derived from this.

How is the RDA value measured?

In a laboratory, the cleaning performance of a toothpaste is tested under standardized conditions in comparison to a reference value. Therefore, the R often stands for relative dentin abrasion. At the same time, or alternatively, the term radioactive dentin abrasion is also commonly used, as the tooth structure is irradiated for the measurement. This examination takes place in vitro, i.e. not on living organisms.

Significance of the RDA value

Although the RDA value is probably the best-known unit of measurement for the abrasion of a toothpaste, it is not to be viewed entirely uncritically and is also not to be found on every toothpaste. There is no requirement to declare the RDA value. The declaration is voluntary and is handled differently by different manufacturers. 

However, the major criticism of the RDA value and alternative methods, such as the PCR value (Pellicle Cleaning Ratio) or REA (Radioactive Enamel Abrasion) is that the results from the laboratory cannot be directly transferred to daily use. Many other effects, such as the type of toothbrush or the pressure applied when brushing, also have an influence on abrasion¹. Furthermore, the RDA value is measured on dentin, which is not directly transferable to abrasion on enamel.

While all measurement methods provide indications of the cleaning performance of toothpastes, consumers should note that other, individual factors also play a role.

The higher the RDA value, the higher the abrasiveness of the toothpaste and thus the dentin abrasion. The RDA scale can be roughly divided into four levels:

• Below 30: Very low abrasiveness with low cleaning power
  • suitable for toothpastes for babies
• 30 to 50: Low abrasiveness with a good ratio between abrasion and cleaning effect
  • suitable for daily dental care of baby teeth
• 50 to 80: Medium abrasiveness with a good ratio of abrasion to cleaning efficiency
  • suitable for daily use for adults
• Over 100: Very abrasive, e.g. in toothpaste for white teeth
  • not at all suitable for permanent use

Attention! 
In Europe, toothpastes with a RDA value of up to 250 are permitted. A toothpaste with such a high abrasiveness would probably damage teeth after only a few uses. Therefore, most products available in Germany are much less abrasive.

In general, the value for a toothpaste for daily use in adults, should be between 30 and 80. For values below 30, the cleaning effect might be too weak for healthy teeth and plaque can hardly be sufficiently removed. For values above 80, the toothpaste is highly abrasive and might damage tooth enamel (or dentin) if used too frequently.

However, the RDA value alone does not necessarily determine whether tooth structure will be harmed or not. Which RDA value is actually good for you or your children also depends on a number of individual factors:

• Toothbrush: Depending on whether you use a toothbrush with soft or hard bristles, you should choose a toothpaste with an appropriate RDA value. A toothbrush with hard bristles also contributes to increased abrasion. Particularly with toothbrushes for children care should be taken to choose a soft one. Where electric toothbrushes are used, a toothpaste with a low to medium RDA value is usually sufficient.
• Tooth brushing technique: How the teeth are brushed can also influence whether additional enamel is removed. The teeth should be gently brushed, and horizontal movements should be avoided in order to protect the teeth and gums. Parents should pay attention and ensure their children use the correct tooth brushing technique.
• Condition of the teeth: Teeth with dentin hypersensitivity or exposed necks of teeth can be a sign that the enamel is already damaged. In this case, it is recommended that you use toothpastes with a lower dentin abrasion. Patients who grind their teeth (bruxism) also suffer damage to the tooth substance and should be particularly gentle when cleaning their teeth.
• Baby teeth: Baby teeth enamel is only half as thick as that of permanent teeth. Therefore, tooth for babies and toddlers should also have a rather low RDA value.
• Desired result: To remove tooth discolouration, special whitening toothpaste is often used to whiten teeth. These are often characterized by a particularly high abrasion value. For this reason, such toothpastes should only be used in consultation with your dentist and never on a long-term basis.

Discuss with your dentist or prophylaxis team which cleaning strength is best for your teeth and those of your children.

Sources:

1. Enax, J; Epple, M.: The characterization of cleaning agents in toothpastes; Deutsche Zahnärztliche Zeitschrift (German Dentist Magazine); 2018; 73 (2), p.100ff