Tooth Structure

Abrasion

Evidence: Medium Tooth Structure Reading time: approx. 5 min. Reviewed: 06.08.2026 · KEERN Editorial Team

Abrasion is the mechanical loss of tooth hard tissue caused by repeated mechanical friction, most often from toothbrushing rather than any disease process. How much substance is lost depends on the combination of brushing pressure, bristle stiffness, and toothpaste abrasivity, not on any single factor alone. The result is typically a wedge-shaped defect at the tooth neck, a pattern dentists group under the term non-carious cervical lesion.

Related terms:EnamelDental erosionCariesFluorideBruxismAttrition

Definition

Abrasion is the mechanical loss of tooth hard tissue caused by repeated mechanical friction. The most common cause is not disease but everyday mechanical stress, above all toothbrushing. Less often, habits such as nail-biting or holding objects between the teeth contribute.

This sets abrasion apart from erosion, chemical acid attack without friction, and from attrition, tooth-to-tooth contact such as grinding.

The typical presentation is a wedge-shaped defect at the tooth neck, often accompanied by heightened sensitivity to cold and heat once dentin becomes exposed. Not every wedge-shaped defect results from abrasion alone. Several processes often act together, such as abrasion combined with erosion or with abfraction, microfractures at the tooth neck triggered by chewing forces. Dentists group these combined presentations under the term non-carious cervical lesion.

What determines how much wear occurs

How much abrasion occurs does not depend on a single factor. It depends on the combination of brushing pressure, bristle stiffness, and toothpaste abrasivity. Only when excessive pressure, hard bristles, and a strongly abrasive toothpaste combine does substance loss reliably increase.

Common misconception

A low RDA value is often equated with a generally gentle toothpaste. That is too simple. RDA measures abrasivity against dentin only. Enamel is assessed separately through the REA value, and the two do not necessarily move together. Research has found toothpastes with a very low RDA but a very high REA, and the reverse. A low RDA value alone does not guarantee low wear on enamel. Choosing a toothpaste solely because it has a low RDA can therefore be misleading.

Risk factors

  • Excessive pressure while brushing, considered one of the most influential factors
  • Horizontal, scrubbing motion instead of a gentler circular or vertical technique
  • Hard or medium bristles, especially combined with high pressure
  • Highly abrasive toothpastes, such as certain whitening products
  • Brushing shortly after acidic food or drinks, when enamel is temporarily softened and more vulnerable to mechanical wear
  • Habits unrelated to brushing, such as nail-biting, thread-biting, or holding objects between the teeth

What helps

  • Use soft bristles and consciously reduce brushing pressure
  • Learn a gentle, non-scrubbing technique; a demonstration at the dental practice can help
  • Choose a toothpaste with a moderate RDA value, especially where defects are already visible
  • Consider an electric toothbrush with pressure sensing, which can automatically limit excessive force
  • See a dentist if defects are visible, to limit further loss early

Key takeaways

  • Abrasion results from repeated mechanical friction, most often toothbrushing, unlike erosion (chemical) or attrition (tooth-to-tooth contact)
  • Brushing pressure, bristle stiffness, and toothpaste abrasivity act together, not any single factor alone
  • A low RDA value does not automatically mean a gentle toothpaste overall; the REA value for enamel can be high independently
  • The typical presentation is a wedge-shaped defect at the tooth neck, often with more than one contributing cause
  • Soft bristles, moderate pressure, and an adjusted brushing technique are the most effective protective measures

Frequently Asked Questions

How do I recognize abrasion on my teeth?

Typical signs are wedge-shaped notches or smooth, flattened areas at the tooth neck, often together with sensitivity to cold or heat.

Are hard toothbrushes the cause on their own?

Not on their own. Research shows that at moderate brushing pressure, soft and medium bristles remove a similar amount of substance; a clear difference only appears at higher pressure. Pressure and bristle stiffness act together.

Does a low RDA value mean a gentle toothpaste?

Not necessarily. RDA applies to dentin only; enamel is measured separately through the REA value. The two can differ substantially, so a low RDA value alone is no guarantee of enamel-friendly wear.

Can electric toothbrushes cause abrasion?

Modern electric toothbrushes do not appear to increase abrasion when used correctly. Many models even reduce excessive brushing force through pressure sensors that alert or slow the brush when pressure gets too high.

Does abrasion need to be treated?

The substance loss itself is not acutely dangerous, but it can cause sensitivity and weaken tooth structure over time. Adjusting brushing technique, pressure, and toothpaste early usually prevents further progression without requiring formal treatment. Pronounced defects still warrant a dental assessment.

Can abrasion reverse itself?

No, lost tooth structure does not grow back. Adjusting brushing technique, pressure, and toothpaste can, however, effectively slow further progression.

Can abrasion be prevented completely?

Not entirely, since some mechanical wear from a lifetime of brushing is normal. The realistic goal is keeping wear within a harmless range through soft bristles, moderate pressure, and a gentle technique, not eliminating brushing-related wear altogether.

KEERN Perspective

Abrasion shows that oral care cannot be reduced to a single number on a label.

Only the interplay of toothpaste, brushing technique, pressure, and individual circumstances determines how gentle daily cleaning actually is.

Visible defects at the tooth neck deserve a dental assessment, not just a change of toothpaste brand. Understanding the true cause matters more than chasing a lower RDA number.

Gentle cleaning is not weaker cleaning. It is often the more effective long-term strategy.

Professional perspective

Clinical relevance

  • Differential diagnosis against erosion, attrition, and abfraction
  • History-taking on brushing behavior, toothbrush choice, and toothpaste selection
  • Individualized recommendations on bristle stiffness, brushing technique, and toothpaste abrasivity
  • Management of exposed dentin in cases of pronounced sensitivity

Clinical implications

The presence of a cervical lesion does not automatically identify its cause. Non-carious cervical lesions rarely result from a single mechanism. Abrasion, erosion, and abfraction frequently act together, and identifying the dominant contributor guides which preventive measures are most likely to help.

Patients presenting with cervical dentin hypersensitivity should be assessed for the underlying wear pattern before symptomatic treatment, since addressing the cause reduces the likelihood of continued progression.

Mechanism: multifactorial

Abrasive loss of dentin and enamel results from the interaction of brushing pressure, bristle characteristics (stiffness, filament count, tip geometry), and the abrasivity of the toothpaste used. No single factor reliably explains the extent of substance loss; the combination is what matters.

Bristle stiffness and brushing pressure

Hamza et al. (2021) examined the combined effect of bristle stiffness (soft versus medium) and brushing force (1 to 4 N) on 160 bovine dentin specimens. At 1 to 3 N, there was no statistically significant difference in abrasive dentin loss between soft and medium bristles. Only at 4 N did medium bristles cause significantly more wear than soft ones. With soft bristles, wear increased significantly from 1 to 2 N but then remained largely stable; with medium bristles, wear increased continuously up to 3 N. The interaction between bristle stiffness and applied pressure appears more relevant than bristle stiffness considered on its own.

RDA and REA: two independent measures

Dobler et al. (2023) compared four toothpastes with markedly different REA and RDA values, including one with REA 1 and RDA 42 and another with REA 244 and RDA 12, for their actual enamel and dentin wear. The toothpaste with the highest REA value caused the greatest enamel wear despite having the lowest RDA value. The authors concluded that both REA and RDA values should be disclosed, since a low RDA value permits no conclusions about a toothpaste's enamel compatibility.

Under ISO 11609:2017, a toothpaste is generally considered safe for lifelong daily use up to an RDA of 250 and an REA of 40. These thresholds describe the toothpaste itself under standardized test conditions; they do not account for how an individual actually brushes, which is why pressure and technique remain independently important.

Evidence summary

What current evidence supports

  • Brushing pressure and bristle stiffness interact, and pressure appears to be the more influential factor
  • A low RDA value does not guarantee low wear on enamel, since RDA and REA are measured separately and can vary independently
  • ISO 11609 sets accepted safety thresholds, RDA 250 or below and REA 40 or below, for daily-use toothpaste
  • Non-carious cervical lesions are typically multifactorial, involving abrasion alongside erosion or abfraction

What remains uncertain

  • How well in-vitro findings on bovine specimens translate to long-term clinical outcomes in humans
  • The relative contribution of each mechanism, abrasion, erosion, and abfraction, when they occur together in an individual patient
  • Whether a universally accepted REA safety limit will be formally adopted with the same regulatory status as the RDA threshold under ISO 11609

Hamza et al. (2021), in the International Journal of Dental Hygiene, tested the interaction of bristle stiffness and brushing force on bovine dentin, establishing that pressure can be the more decisive factor.

Dobler et al. (2023), in Oral Health & Preventive Dentistry, demonstrated the lack of correlation between REA and RDA values across four commercial toothpastes.

Sources

📚 Hamza B, Tanner M, Körner P, Attin T, Wegehaupt FJ (2021): Effect of toothbrush bristle stiffness and toothbrushing force on the abrasive dentine wear. International Journal of Dental Hygiene, 19(4), 355-359.
📚 Dobler L, Hamza B, Attin T, Wegehaupt FJ (2023): Abrasive Enamel and Dentin Wear Resulting from Brushing with Toothpastes with Highly Discrepant Relative Enamel Abrasivity (REA) and Relative Dentin Abrasivity (RDA) Values. Oral Health & Preventive Dentistry.
📋 International Organization for Standardization: ISO 11609:2017, Dentistry: Dentifrices: Requirements, test methods and marking.

For a deeper understanding, we also recommend

← All terms starting with A← Back to the KEERN Lexicon

The KEERN Lexicon provides evidence-based educational information about oral health. It is intended to support, not replace, individual advice from a dentist, physician, or pharmacist. Diagnosis and treatment decisions should always be based on a personal clinical assessment.