Abrasivity of dentrifices: An update

Abstract

Tooth abrasion is a leading dental problem in common population. The main culprit of this is toothpaste abrasives. Hence, measurement and standardization of toothpaste is required. Various recommended methods were described previously. However, radioactive dentin abrasion (RDA) is the mostly followed method. In this article, we presented the basic need of toothpaste abrasivity testing, brief description of the recommended methods, different etiologies of tooth wasting other than caries, and RDA values of different tooth pastes.

Full text

© 2016 SRM Journal of Research in Dental Sciences | Published by Wolters Kluwer - Medknow
96
Abrasivity of dentrifices: An update
Sunil Kumar Rath, Vipul Sharma1, C. B. Pratap, T. P. Chaturvedi
Department of Orthodoncs and Dento Facial Orthopedics, Faculty of Dental Sciences, BHU, 1Department of Orthodoncs and Dento
Facial Orthopedics, Faculty of Dental Sciences, IMS‑BHU, Varanasi, Uar Pradesh, India
INTRODUCTION
Abrasion can be defined as the removal of material from the
bulk of the substrate, during relative movement of the abrasive
and substrate and as such the term can be used to include the
removal of tooth surface films, such as pellicle.[1] Soft microbial
layers in the oral cavity can be removed by brushing alone.
That may be plaque, debris, which is adhered to tooth surface
by chemical and physical attachment. Dentifrices have been
used for many years and have been proven to be an important
tool for improving both oral health and esthetics. The primary
purpose of brushing the teeth with a dentifrice (dens-tooth,
fricare-to rub) is to clean the accessible tooth surfaces of
immature dental plaque which, if not removed, matures in
24 h. Besides chemically active agents, abrasives are essential
compound of dentifrices as the major cleaning effects of
toothpastes are still due to mechanical action (abrasivity).[1,2]
Various wasting disorders can be seen externally such as
toothpaste abrasion, erosion, attrition as shown in Chart 1.
Typical formulation of toothpaste is abrasive 10–40%,
humectants 20–70%, water 5–30%, binder 1–2%, detergent
1–3%, flavor 1–2%, preservative 0.05–0.5%, and therapeutic
agent 0.1–0.5%. There are various types of abrasive materials
used in toothpaste. These may include the use of one or more
of, for example, hydrated silica, calcium carbonate, dicalcium
phosphate dihydrate, calcium pyrophosphate, alumina, Perlite,
and sodium bicarbonate.[3] Various key parameters that have
been demonstrated to influence the abrasion process along
with material used and its properties which include particle
hardness, shape, size, size distribution, and concentration.
Various methods for measuring abrasivity of toothpaste has
been described in this article and along with that diagnosis
of wasting disorder has briefly discussed. Aim of this article
can be considered to be spreading knowledge of abrasivity of
toothpaste; so that dental surgeon will well aware about when
and why to prescribe different formulation of dentrifice.
METHODE OF SELECTION OF ARTICLES
We searched in Google scholar, PubMed, IndMED with the
phrase “abrasivity of toothpaste” and found 112 article of
ABSTRACT
Tooth abrasion is a leading dental problem in common population. The main culprit of this is
toothpaste abrasives. Hence, measurement and standardization of toothpaste is required.
Various recommended methods were described previously. However, radioactive dentin
abrasion (RDA) is the mostly followed method. In this article, we presented the basic need
of toothpaste abrasivity testing, brief description of the recommended methods, different
etiologies of tooth wasting other than caries, and RDA values of different tooth pastes.
Key words: Radioactive dentin abrasion, tooth abrasion, tooth paste
Address for correspondence:
Dr. Vipul Sharma,
Orthodontics and Dento Facial Orthopaedics, Faculty of Dental
Sciences, IMS-BHU, Varanasi - 221 005, Uttar Pradesh, India.
E-mail: Dr.vipul2010@gmail.com
How to cite this article: Rath SK, Sharma V, Pratap CB,
Chaturvedi TP. Abrasivity of dentrices: An update. SRM J Res Dent
Sci 2016;7:96-100.
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Rath, et al.: Abrasivity of dentrifices
SRM Journal of Research in Dental Sciences | Vol. 7 | Issue 2 | April-June 2016 97
choice. After the 1st step of scrutiny, we selected 21 articles
on the method of abrasivity measurement and 2 articles of
dental wasting disorder and a review of those article and
information gathered were presented in this following way.
VARIOUS METHODS TO TEST ABRASIVITY OF
DENTIFRICES
Various qualitative and quantitative methods are used to
measure toothpaste abrasivity. Quantitative methods are
radioactive dentin abrasion (RDA) method, weight, and
volume loss. Qualitative methods are profilometry, light
reflection techniques, microscopy, etc.
Different methods to test abrasivity are as follows in
chronological order:

Miller described the wasting of tooth tissue as abrasion,
chemical abrasion, denudation.[3]

Scratch tests for particulates:
• 1937–Glassscratchtest[4]
• 1942–Silverscratchtest.

1. Using rotating plate application of abrasive to
substrate
1933 – Silver as substrate.[5]
2. Using tooth brushing machine:
1942 – Antimony and brass as substrates
1942 – Electrolytic copper as substrate
1971 – In vivo method with acrylic substrate on
veneer crowns[6]
1982 – Acrylic as a substrate for abrasion of power
toothbrushes.[7,8]

• Radiotracermeasuringmethodandprotocols
• Profilometrycollaborative studycomparing
radioactive dentin and profilometry methods
• International collaborative study of abrasion
methods.

• 1937– USGovernment toothpastepurchasing
guidelines that included glass scratch test for grit
as a qualitative abrasion test method[4]
• 1976–AmericanDiabetesAssociation(ADA)used
RDA method for tooth paste
• 1981–BritishStandardsInstitute(BSI)Toothpaste
Specification BS 5137 that included radiotracer and
profilometry abrasion measuring methods
• 1995–ISOtoothpastespecification11,609includes
radioactive dentin abrasivity and profilometry
methods
• 1995–Chinesespecificationincludesglassscratch
test.


In 1933, Hodge and McKay[5] reported in the on the
rotating plate method for tooth brushing. The method
used silver metal as the brushing substrate that was
abraded with a mixture of abrasive, glycerin, and water.
Silver was chosen because of its comparable hardness to
human enamel based on 2.7 Mohr and 96 Bierbahm units,
two methods using the relative ability to scratch a surface
as a hardness measurement value. Other metals have also
been used as abrasion substrates with the rotating plate
concept. Peerless used antimony and silver with hardness
of 231 and 200 Bierbahn units, respectively. The silver
used by Peerless was thus twice as hard as the silver of
Hodge and McKay. Antimony and brass were also used as
abrasion substrates.[6]
Wear
Others
Facial surface
of
lower canine
and premolar
severe
Anatomic
detail faded
by sand
blasting
Posterior
greater than
anterior
Anterior
greater than
posterior
Wear facets
match up
Linguals of upper
anteriors worn smoothly
from gingiva
Cusping of
cratering
present
Bruxism Regurgitation
Lower 1st
molar most
severe
Even
posterior
wear upper
and lower
Coke swishing Fruit mulling
Toothpste
MisceIlaneous
Chart 1: Dental wasting disorders
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SRM Journal of Research in Dental Sciences | Vol. 7 | Issue 2 | April-June 2016
98
In 1942, Monsanto used of electrolytic copper (2.6–2.8
Mohr’s scale, 74 Bierbahn units) as an abrasion substrate
which was comparable in hardness to silver in Mohr’s scale,
and <96 Bierbahn units of the silver used by Monsanto and
McKay.[7]
In 1982, Harrington et al. at general electric used acrylic
strips as abrasion substrates for power toothbrushes and
toothpastes.[8]

In 1972, Ashmore et al.[9] described an abrasion method
using profilometry.

At least six enamel and six dentine specimens should be
allocated to each product and the reference dentifrice. Prior
to the abrasion test; each specimen should be taped with two
pieces of PVC adhesive tape, placed parallel to each other
to expose a window of enamel or dentine approximately
2 mm wide. After dentifrice slurry brushing, remove the
tape from specimens and re-measure using the operating
method for the particular profilometer. For two-dimensional
contact profilometer, the profile should be taken from just
inside the previously taped zone of the specimen across
the exposed zone and just into the opposite previously
taped zone. For three-dimensional contact and noncontact
profilometer, a length in the x-axis of the exposed window,
such as 1 mm, can be taken and the instrument provides
scans at several microns along this zone, again from the edge
of the previously taped zone across the treated zone to the
edge of the other previously taped zone. Depending on the
number of specimens of enamel and dentine allocated to
each reference and test dentifrice, a mean abrasive depth
across the respective specimen group is calculated.

RDA method is currently recommended by ADA. ISO
standardization number 11609 also recommends this
method. The method is based on the methodology described
by Grabenstetter, et al.[10] and Hefferren.[11]
ISO recommendation for toothpaste should not have more
than 250 RDA, i.e., 2.5 times more than dentine.[12]


The most common dentifrice abrasives are calcium
phosphates. Calcium or phosphate analysis of the toothpaste
slurry used to brush the teeth is not possible (for one could
not differentiate between the calcium and phosphate in the
brushing slurry coming from the loss of tooth structure, and
that coming from the toothpaste abrasive system).
This situation led to the use of irradiated teeth and the
measurement of the isotopic forms of the elements coming
from the tooth. The amount of calcium and phosphate
coming from irradiated teeth was variable between teeth and
between sequential layers of the same tooth. This measure
is RDA.
A specific lot of calcium pyrophosphate was set aside by
the Monsanto Company (St. Louis, MO, USA) as the first
abrasive method reference for the dental research community
the abrasivity of this lot was assigned an RDA value of 250,
and later changed to an AI (Abrasivity Index) of 100. Various
toothpaste described having RDA values [Table 1].
INTERNATIONAL COLLABORATION
In 1984, an international collaborative study compared
the ADA RDA and the BSI radioactive and profilometry
methods.[9,13-15]
Five laboratories used the ADA method, two laboratories
used the profilometry method, three laboratories used the
BSI modified RDA method,[15] with sequential dilution of
the toothpaste slurry to mimic the salivary dilution occurring
when brushing in the mouth.
The test toothpaste included two calcium phosphate and two
chalk blends to achieve lower and higher dentin abrasivity.
The ADA method had a somewhat narrower range for both
the phosphate and chalk pastes. The BSI profilometry
method was somewhat more variable and tended to rank
some abrasives differently than the radiotracer methods.
SODIUM BICARBONATE AS A CLEANSING AGENT
Sodium bicarbonate in various crystalline sizes has very
low dentin abrasivity. Mean abrasivity of seven grades of
sodium bicarbonate particles was one-ninth that of the
abrasivity reference, calcium pyrophosphate. The mean ratio
of abrasion to cleaning power (abrasion cleaning power) for
the seven grades of sodium bicarbonate was 10.2, compared
to 1.7 for calcium pyrophosphate. The cleaning function
of sodium bicarbonate is achieved by a combination of
mechanical and chemical cleaning; thus sodium bicarbonate
cleans with less abrasion.[16-18]
Clinical implication
Tooth abrasion during brushing, have multi-factorial etiology.
This also includes physical properties of the toothpaste and
toothbrush used with patient-related factors such as tooth
brushing frequency and force of brushing. Tooth brushing
abrasion is mainly related to the abrasivity of the toothpaste,
while the toothbrush acts as a carrier, with addendum effects
of the toothpaste. Acid impacted tooth has more material
loss in enamel as compared to dentin.
All these factors should be considered when a patient
confirmed with tooth brushing erosion comes to dental
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SRM Journal of Research in Dental Sciences | Vol. 7 | Issue 2 | April-June 2016 99
Table 1: Contd...
Toothpaste name RDA
Aquafresh Whitening 113
Crest Extra Whitening 118
Crest Multicare Whitening 118
Colgate Total Whitening 120-150
Crest Plus Scope Whitening (paste) 125
Crest Tartar Protection 125
SENSODYNE Extra Whitening 125±15%
SENSODYNE Full Protection Plus Whitening 125±15%
SENSODYNE Tartar Control Plus Whitening 125±15%
Crest Sensitivity Protection 126
Crest Whitening Expressions (paste) 132
Ultra Brite 133
Crest Pro-health night 140
Ultra brite Advanced Whitening formula 145
Pepsodent 150
Crest Pro-Health 160-180
Colgate Total Gum Defense 165-185
Colgate Tartar Control 165
Arm and Hammer Dental Care PM Fresh Mint 178
Colgate Total Advanced Whitening 180-200
Crest Vivid White 187
FDA recommended upper limit 200
ADA recommended upper limit 250
ADA: American Dental Association, FDA: Food and Drug Administration
Contd...
clinics. The brand name of the patient’s dentrifice should
be asked and the RDA value should be checked.
In general, dentin loses more material so if already abraded
enamel condition came, the doctor should go for the pH
test of morning and random saliva. Then, the toothpaste
with minimum RDA value can be prescribed along with a
soft bristle brush.[19]
On the contrary, if no abrasion of enamel noted then the
acidity to be controlled with importance, to protect the un
eroded enamel. There are not many publication regarding the
molecule ‘Novamin’, which considered as the remineralizing
property. However, some article compared the sensitivity
testing and proved good molecule.[20,21]
The chart shown in this article can be regarded as the
clinical diagnostic flow chart and helps you to get arrive at
a conclusion.

RDA-profilometry equivalent is an up graded method
that checks the depth through contact profilometry had a
guideline for testing abrasivity of dentrifices.[22] In a clinical
study, some paste produce tooth sensitivity, taste discomfort,
and texture discomfort; patients also reported rougher
teeth, soft tissue peeling, dry mouth, thrush, tingling,
and taste changes in response the paste with lower pH.
Hence, toothpaste’s properties should be well known for
the indication to patient therefore minimizing discomfort
reports.[23] The flexibility (soft, medium, hard) of bristles
considered secondary to abrasion process and abrasivity of
dentifrice is more important in abrading tooth.[24]
Table 1: Updated values of common toothpaste
Toothpaste name RDA
Toothbrush with plain water 4
Plain baking soda 7
Arm and Hammer Dental Care Tooth Powder 8
Weleda Salt Toothpaste 15
Elmex Sensitive Plus 30
Weleda Plant Tooth Gel 30
Sensodyne ProNamel - Isoactive - Daily Protection 32±15%
Sensodyne ProNamel - Mint Essence 37±15%
Sensodyne ProNamel - Fresh Wave 37±15%
Weleda Children’s Tooth Gel 40
ARM and Hammer PeroxiCare Toothpaste 42
Arm and Hammer Advance White Baking Soda and Peroxide 42
Sensodyne Iso-active - Multi Action 44±15%
Squiggle Enamel Saver 45-55
Weleda Calendula Toothpaste 45
Weleda Pink Toothpaste with Ratanhia 45
Oxyfresh 45
Arm and Hammer Dental Care Advanced Cleaning Toothpaste 49
Tom’s of Maine Sensitive 49-100
Crest Plus Scope Flavor (green gel) 51
Sensodyne Cool Gel-Fresh 51±15%
Sensodyne Fresh Impact 51±15%
Sensodyne Fresh Mint 51±15%
Rembrandt Original 53
Arm and Hammer Dental Care Icy Mint Whitening
Toothpaste
55
Tom’s of Maine Childrens 57-100
Mentadent Advanced Whitening 60
Supersmile 62
Rembrandt Mint 63
Arm and Hammer Complete Care Enamel Strengthening 65
Crest plus Scope Flavor Whitening (white gel) 68
Colgate Regular 68
Colgate Total 70
Arm and Hammer Advance White for Sensitive Teeth 70
Colgate 2-in-1 Fresh Mint 70
Sensodyne Isoactive - Whitening 75±15%
Tooth Builder - Squigle 70-80
Biotene 78 Pepsodent® Complete Care Original Flavor 80
Close-Up 80
Arm and Hammer Complete Care Extra Whitening 81
Under the Gum 82
Colgate Sensitive Max Strength 83
Arm and Hammer Complete Care Intense Freshening 83
Sensodyne ProNamel - Gentle Whitening Alpine Breeze 83±15%
Nature’s Gate 87
Mentadent Advanced Breath Freshening 88
Aquafresh Sensitive 91
Tom’s of Maine 93-100
Rembrandt Plus 94
Oxyfresh with Fluoride 95
Aim Cavity Protection Toothpaste 96
Oxyfresh Powder 97
Arm and Hammer Advanced White Brilliant Sparkle Gel 100
Close-Up Cinnamon Red Gel with Mouthwash 100
Natural White 101
SENSODYNE ProNamel Iso-active Gentle Whitening 100±15%
Crest Whitening Expressions (liquid gel) 105
Colgate Platinum 106
Crest Baking Soda and Peroxide Whitening 107
Crest Kid’s 108
Crest Cavity Protection 108
Crest Advanced Cleaning 109
Colgate Herbal 110
Amway Glister 110
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CONCLUSION
Wasting of tooth material is a common disease regarding
to-days population. Various causes may cause abrasion; one
of these is abrasivity of toothpaste. Proper clinical diagnosis
can help us to recommend various treatment and preventive
measures. Preventive measure includes the testing of any
marketed toothpaste before clinical trials. Various methods
were described and RDA is most frequently followed and
recommended by ADA and Foreign Direct Investment
authorities. Mechanical along with chemical method should
be employed for cleaning of tooth. It is difficult to distinguish
the effect of the toothbrush on the abrasivity from that of the
toothpaste and it is probably dependent on the interaction
between the two elements.
A secondary problem from the abrasiveness of the paste is
notching of the tooth at the gum line causing a structural
compromise. Often, a filling is necessary to protect the future
integrity of the tooth. Again, selecting a paste with a low RDA
can prevent both sensitivity and structural compromises
that can cause the need for future restorative dentistry. The
importance of in vivo study must be taken into concern and
abrasibility (roughness value) of that material must be tested.
Financial support and sponsorship
Nil.

There are no conflicts of interest.
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