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Abrasiveness evaluation of silica and calcium carbonate used in the production of dentifrices

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Abstract

Our purpose was to apply a radiometric method to an abrasiveness evaluation in samples of silica and calcium carbonate used as an abrasive in a dentifrice, to help in a prudent selection of materials by dentifrice producers. The results of RDA (radioactive dentin abrasion) abrasiveness indices obtained for these compounds varied from 136 to 19. The relative standard deviations of these RDA results varied from 5.9% to 11.8%, showing a good precision in the method. Also, the results obtained indicated that the abrasiveness indices increase with the particle size of the material. A comparison between different abrasives with similar particle sizes showed that silica presents higher RDA values than calcium carbonate.
Cosmet. Sd., 52, 163-167 (May/June 2001)
Abrasiveness evaluation of silica and calcium carbonate
used in the production of dentifrices
I. M. C. CAMARGO, M. SAIKI, M. B. A. VASCONCELLOS, and
D. M. ]tVILA, Instituto de Pesquisas Energdticas e Nucleares, Centro de
Qu/mica e Meio Ambiente, IPEN/CNEN-SP, Caixa Postal 11049, ZIP
05422-970, S•o Paulo, SP, Brazil.
Accepted for publication March 15, 2001.
Synopsis
Our purpose was to apply a radiometric method to an abrasivehess evaluation in samples of silica and
calcium carbonate used as an abrasive in a dentifrice, to help in a prudent selection of materials by dentifrice
producers. The results of RDA (radioactive dentin abrasion) abrasivehess indices obtained for these com-
pounds varied from 136 to 19. The relative standard deviations of these RDA results varied from 5.9% to
11.8%, showing a good precision in the method. Also, the results obtained indicated that the abrasivehess
indices increase with the particle size of the material. A comparison between different abrasives with similar
particle sizes showed that silica presents higher RDA values than calcium carbonate.
INTRODUCTION
Dentifrices are cosmetics used with toothbrushes to clean tooth surfaces to prevent the
accumulation of stains and plaques. Therefore, they should present an appropriate abra-
siveness to clean the teeth, but without causing wear. Consequently, knowledge of the
characteristics of the abrasive agents used for dentifrice manufacturing is of interest to
industries in order to obtain appropriate products for perfect oral hygiene without
causing wear to the teeth or restorative materials. The abrasives commonly utilized in
the dentifrices produced in Brazil are silica and calcium carbonate, and their quantities
in dentifrices vary from 30% to 48% in mass (1,2).
Among several articles related to the use of abrasives in the dentifrices, one by Boer et
al. (3) evaluated the wear caused by abrasives through the method of surface profilometry
and verified the correlation between abrasivehess and the particle size of abrasives. Also,
these authors obtained different abrasivehess values for distinct abrasives presenting
similar particle sizes, that is, the abrasive AI(OH) 3 of 7-1•m particle size showed greater
abrasivehess than that presented by CaCO 3 with 8-1•m particle size. This difference in
abrasivehess may be attributed to the distinct particle hardness of these two agents.
Address all correspondence to M. Saiki.
163
164 JOURNAL OF COSMETIC SCIENCE
Kinoshita et al. (4) examined several dentifrices by the methods of surface analyzer and
scanning electron microscopy. Among the several abrasives (CaHPO 4 ß 2H20, a mix of
CaHPO 4 ß 2H20 + CaHPO4, and CaSiO3) , CaSiO 3 appeared to be more abrasive than
the other two. Also, Panzeri et al., (5) examined by scanning electron microscopy the
particles of abrasives used in 17 dentifrices and concluded that the majority of their
particles present irregular forms and heterogeneous arrangements of the particles.
In this work, the abrasiveness of the samples of silica and calcium carbonate was
evaluated by radiometric method. This method consisted of brushing the irradiated teeth
(dentine) with an abrasive agent and reference material slurties, one at each time. The
beta radioactivity of 3•p transferred from the dentine to slurties was measured using a
plastic scintillatot detector. The abrasiveness index or RDA (radioactive dentine abra-
sion) is the ratio of 3•p counting rates obtained for abrasive and reference material
slurties (6).
MATERIALS AND METHODS
MATERIAL SAMPLE
The materials silica and calcium carbonate were provided from industries.
PROCEDURE
The radiometric method applied was based on a paper by Hefferren (6). The experi-
mental conditions were established in order to use the available facilities. This experi-
mental procedure consisted of the following steps:
Selection of the teeth. The substracts to be abraded were roots from extracted permanent
human teeth. After extraction, the teeth were stored in 4% formaldehyde solution. They
were cleaned by stirring in a domestic detergent solution and then were washed with
water and cut, separating the crown from the root.
Irradiation of roots of the teeth. The roots of the teeth immersed in formaldehyde solution
were irradiated in plastic vials during a one-hour period under a thermal neutron flux of
10 •2 n/cm-2/s -• at the IEA-R1 nuclear research reactor and in a position where the
temperature was lower than 40øC. After irradiation, the tooth samples were removed
from the core of the reactor to avoid damage from gamma radiation. During the
irradiation a part of 3•p present in the hydroxyapatite of teeth was converted to radio-
active 32p.
Brushing operation of the teeth. After about one week of decay time, these irradiated teeth
were fixed in a mold made by dental methacrylate resin that was fitted in a sample
holder (reservoir for slurry) of a brushing machine. The brushing machine was manu-
factured at IPEN/CNEN-SP and was equipped with two toothbrushes made of nylon
bristles of medium hardness and a stroke counter with 125 strokes/min. A pressure
corresponding to 150 g could be applied on each toothbrush. Before the first brushing,
the irradiated dentins were brushed with a slurry containing reference material of
calcium pyrophosphate for 6000 strokes in order to reduce irregular patterns of abrasion
on the surfaces of the newly mounted teeth. The number of strokes applied to each
toothbrushing operation was 1000.
EVALUATION OF DENTAL ABRASIVES 165
The slurries of reference material calcium pyrophosphate supplied by Monsanto Co. (St.
Louis, MO) or of abrasives were prepared using a mass of 10 g of the material and 50
ml of diluent. In the case of thickeners, the slurries were prepared using a mass of 5 g
of the material and 50 ml of diluent because of the large volume of the thickener. The
diluent was prepared by adding 5 g of carboxymethylcellulose in 50 ml of glycerin
heated to 60øC while stirring to obtain a homogenous mixture. Another 50 ml of heated
glycerin was added to the mixture, and then 900 ml of distilled water was added. The
stirring was continued at room temperature to obtain a clean solution of diluent.
Each radioactive slurry was stirred, and three aliquots of 3 ml were pipetted onto
separated planchets. These slurries were dried in an oven with air circulation, at 60øC,
carefully to avoid cracking in the dried samples. The beta radiation of 1.71 MeV 3•p
(with a half life of 14.3 days) of the dried samples was measured using a plastic
scintillator detector.
Calculation of abrasivehess indices. To calculate the abrasiveness indices, known as RDA,
the 32p counting rate obtained for abrasive material was compared to that obtained for
the reference material. A score of 100 for calcium pyrophosphate RDA was considered
according to an ADA (American Dental Association) committee (6). Correction factors
were also applied in this calculation because different abrasives may present distinct
self-absorption and backscatterring radiation characteristics.
Particle size and microscopy analysis of abrasives. The particle size of the silica and calcium
carbonate samples was determined by sedigraphic method and their particle forms were
examined using scanning electron microscopy at the Metallurgy Department of the
IPEN/CNEN-SP.
RESULTS AND DISCUSSION
Table I shows RDA values obtained for six samples of silica and three samples of calcium
carbonate, together with their particle sizes determined by sedigraphic method.
The RDA results for raw materials used as abrasive agents (silica 1 and calcium car-
bonate) presented in Table I varied from 136 to 19. The relative standard deviations of
these RDA results, in general, varied from 5.9% to 11.8%, showing a good precision in
Table I
RDA and Particle Size Obtained for Raw Materials, Silica and Calcium Carbonate
Silica 1 (abrasive)
Silica 2 (thickener)
Calcium carbonate
Samples A B C D E F G H I
RDA_+ s 136 + 8 94-+ 6 85 -+ 10 7 _+ 1 6.6_+ 1.0 5.5 -+ 2.1 54 + 4 24_+ 2 19-+ 2
s r (%) (5.9) (6.4) (11.8) (14.3) (15.2) (38.2) (7.4) (8.3) (10.5)
n 7 8 8 8 5 6 8 8 8
Mean diameter
(t•m) 4.26 3.21 2.54 1.20 0.31 0.32 3.13 1.77 1.49
RDA _+ s: RDA arithmetic mean values and standard deviation.
st: relative standard deviations of the RDA values.
n: number of determinations.
166 JOURNAL OF COSMETIC SCIENCE
the method. The silica 2 substances used as agent thickener presented less satisfactory
results, with relative standard deviations varying from 14.3% to 38.2% (Table I). The
precision of the thickener results was not so good, probably due to the difficulty in
obtaining a homogeneous slurry of thickener during the toothbrushing.
Table I indicates that there may be a relationship between the RDA results and particle
size of each type of raw material, that is, the abrasivity indices of CaCO_• and SiO 2 used
as abrasive agents increase with the particle size of the material. However, different types
of abrasives with similar particle size presented distinct RDA values. As can be seen in
the case of the sample, silica B with a particle size of 3.21 pm presented an RDA value
about two times higher than that presented by calcium carbonate G with a 3.13 ]am size.
This result is in agreement with those presented by Boer et al. (3).
Figure 1 shows the shapes of particles of silica and calcium carbonate obtained by
scanning electron microscopy. It can be observed that the particle shapes of the two
abrasives are not uniform and that the CaCO 3 appears to have more agglomerated
particles than SiO 2. According to Navarre (7), the materials constituted of particles with
heterogeneous arrangements and irregular forms are more abrasive than those formed
with homogeneous arrangements and regular forms.
RDA values for calcium carbonate were also evaluated using different masses of the
abrasives in the preparation of slurry with 50 ml of diluent. For 5, 10, 15 and 30 g of
CaCO3, the RDA values obtained were 52, 74, 71 and 73, respectively. This preliminary
study indicated the increase in RDA values with the mass of CaCO_• until about 10 g.
For quantities of CaCO3 higher than 10 g, the RDA values were very close.
According to Roa (1), the quantity of CaCO• generally used in dentifrice manufacturing
corresponds to about 20 g of CaCO3 in the slurry (50 ml) used in our RDA evaluation.
CONCLUSIONS
The determination of RDA values of the abrasives can be utilized for prudent selection
of raw materials by dentifrice producers. The radiometric method presented here is
simple and fast because it does not require long periods for toothbrushing. Also, the
RDA results obtained indicated that the abrasiveness of calcium carbonate and silica
compounds increased with the particle sizes of the materials. However, it is important
Figure 1. A: SiO 2 particles (502x magnification). B: CaCO• particles (447x magnification).
EVALUATION OF DENTAL ABRASIVES 167
to consider that others factors, such as particle hardness, shape, and distribution, can also
affect the abrasiveness of the raw materials.
ACKNOWLEDGMENTS
We acknowledge Colgate Palmolive Ltd. for supplying the raw materials; the Monsanto
Company for supplying calcium pyrophosphate reference material; the Dentistry School
and Faculty of Pharmaceutical Sciences of Ribeirgo Preto, University of Sgo Paulo, for
tooth samples; Dr. J.J. Hefferren from Kansas State University for advice; and CNPq
and FAPESP for financial support for this project.
REFERENCES
(1) W. E. P. Roa, Aplicagio e composigio de dentifrfcios, Aerosol Cosmet., 5, 5-14 (1983).
(2) H. Panzeri, Personal communication (Dentistry School of Ribeirio Preto, SP, Brazil, 2001).
(3) R. Boer, A. S. H. Duinkerke, and J. Arends, Influence of tooth paste particle size and tooth brush
stiffness on dentine abrasion in vitro, Caries Res., 19, 232-239 (1985).
(4) S. Kinoshita, T. Arai, and R. Uraguchi, Abrasive properties of commonly ua_d dentifrices, Bull. Tokyo
Med. Dent. Univ., 26, 225-242 (1979).
(5) H. Panzeri, E. H. G. Lara, F. Siessere, and R. M. Marchetti, Availagio de dentifrfcios. 2 a parte: Forma
a distribuigio de partfculas abrasivas, Odontd/ogo Moderno, VI, 13-25 (1979).
(6) J.j. Hefferren, A laboratory method for assessment of dentifrice abrasivity,J. Dent. Res., 55,563-573
(1976).
(7) M. G. Navarre, The Chemistry and Manuj•kcture of Cosmetics (Continental Press, Orlando, Florida, 1975),
Vol. III, pp. 445-470.
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Aim: The aim of this in vitro study was to evaluate the effect of whitening dentifrices on the color change of two different glass ionomer restorative materials. Materials and Method: In this study; ChemFil Rock, Glass Hybrid Dentsply, Germany and Fuji II LC, Resin Modified Glass Ionomer GC Dental and Japan materials are used. 50 discs of 2 mm height, 10 mm diameter were prepared from each 2 materials. After the prepared discs were kept at 370C for 24 hours, the initial color measurements of the samples were made. Average values of L0*, a0* and b0* were calculated. Then, while the samples were kept in the stove for 6 days and the coloring was imitated for 6 months. After coloring with coffee, values of L1*, a1* ve b1* were recorded by measurements. After the samples contain activated carbon (Colgate Optical White Activated Charcoal), carbamide peroxide content (Yotuel All in One Snowmint), abrasive particle content (Opalescence), fluoride content (Sensodyne Promine) pastes and control (artificial saliva), (n = 10) brushed with a 6 months period imitated, L2*, a2* ve b2* values were recorded. Initial, coffee hold and brushing values of all samples were calculated with the CIE2000 system. The data obtained were analyzed by one-factor repeated three-way analysis of variance and Tukey test. Results: After holding in coffee, the most color change has been observed in Chemfil material in the all toothpaste groups. When we compared the groups applied whitening toothpaste among themselves, there was no statistically significant difference (p>0.05). For both materials; the amount of color change was significant, holding in coffee and after brushing (p<0,001). Conclusion: According to the results of this study; For both glass ionomer restorative materials, it has been exceeded for clinically acceptable threshold in all toothpaste groups after holding in coffee and brushing. Keywords: glass ionomer, color change, CIE2000, whitening toothpastes Beyazlatıcı Diş Macunlarının Cam İyonomer Simanların Renk Değişimine Etkisi ÖZET: Amaç: Bu in vitro karşılaştırmalı çalışmanın amacı farklı içerikli beyazlatıcı diş macunlarının, iki farklı cam iyonomer restoratif materyalin renk değişikliğine etkisini değerlendirmektir. Gereç ve Yöntem: Çalışmada ChemFil Rock, (Dentsply, Almanya) ve Fuji II LC Rezin Modifiye Cam İyonomer (GC Dental, Japonya) kullanılmıştır. Her 2 materyalden 2 mm yüksekliğinde 10 mm çapında 50’şer disk hazırlanmıştır. Hazırlanan diskler 370C de 24 saat bekletildikten sonra örneklerin başlangıç renk ölçümleri yapıldı, L0*, a0* ve b0*ortalama değerleri hesaplandı. Ardından örnekler 6 gün süre ile etüvde kahvede bekletilerek, 6 aylık süre ile renklendirme taklit edildi. Kahve ile renklendirme sonrası ölçümler yapılarak L1*, a1* ve b1* değerleri kaydedildi. Ardından örnekler aktif karbon içerikli (Colgate Optik Beyaz Aktif Kömür), karbamid peroksit içerikli (Yotuel All in One Snowmint), aşındırıcı partikül içerikli (Opalescence), florür içerikli (Sensodyne Promine) macunlar ve kontrol (yapay tükürük), (n=10) ile fırçalanarak 6 aylık süre taklit edildi, L2*, a2* ve b2* değerleri kaydedildi. Tüm numunelerin başlangıç, kahvede bekletme ve fırçalama sonrası renk değimim değerleri CIE2000 sistemi ile hesaplanmış, elde edilen veriler tek faktör tekrarlı üç yönlü varyans analizi ve Tukey testi ile analiz edilmiştir. Bulgular: Kahvede bekletme sonrası en fazla renk değişim değerleri tüm diş macunu gruplarında Chemfil materyalinde gözlenmiştir. Beyazlatıcı diş macunu uygulanan grupları kendi arasında karşılaştırdığımızda istatistiksel açıdan anlamlı bir farklılık bulunmamıştır. (p>0.05) Her iki materyal için renk değişim miktarı kahvede bekletme ve fırçalama sonrası anlamlı bulunmuştur (p<0,001). Sonuç: Bu çalışmanın sonuçlarına göre; her iki cam iyonomer restoratif materyali için de kahvede bekletme ve fırçalama sonrası tüm diş macunu gruplarında klinik olarak kabul edilebilir eşik değerleri aşılmıştır. Anahtar Kelimeler: cam iyonomer, renk değişikliği, CIE2000, beyazlatıcı diş macunları
... According to Hunter et al, 32 while calcium carbonate and hydrated silica is chemically similar, different cleaning/abrasion characteristics can be produced. Other studies 33,34 are in agreement with this study and observed that calcium carbonate toothpaste showed lower abrasivity when compared against toothpaste containing hydrated silica. ...
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Objectives This study aimed to evaluate nanosized eggshell–titanium dioxide (EB@TiO2) abrasiveness in comparison with calcium carbonate and hydrated silica-containing toothpaste. Material and Methods Thirty-five bovine tooth enamels were prepared, and specimens randomly assigned to a sample group of five (n = 7), namely, Colgate regular, Colgate pro-relief, Sensodyne rapid relief, Sensodyne repair, and EB@TiO2. Half of the enamel surface was brushed with each respective sample group, while the other half was covered with a tap. Statistical Analysis The mean roughness value (Ra) of the brushed and covered halves were measured using an atomic force microscope (AFM). To assess the surface morphology and changes, a scanning electron microscope (SEM) was performed. Using pair sample test and ANOVA, the Ra for the entire specimens were analyzed. A Bonferroni correction was used to identify the mean differences among the five groups (α=.05). Results The findings from this analysis show that all the tested toothpaste abraded the enamel significantly (p < 0.05). The abrasive value contained in toothpaste comprising calcium carbonate was lower than the silica toothpaste hydrated. Conclusion Overall, Colgate regular had the lowest toothpaste abrasivity, followed by EB@TiO2, while Sensodyne rapid relief had the most enamel wear. The prominent feature of this study suggests that EB@TiO2 is suitable for oral use, as its abrasivity is comparable with calcium carbonate-containing toothpaste.
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The objective of this study was to evaluate the effect of natural bleaching products on the color, whiteness, and superficial properties of dental enamel. Seventy fragments of bovine teeth were obtained (6mm x 6mm x 2mm). Initial surface roughness (Surfcorder SE1700, Kosakalab), microhardness (HMV-2, Shimadzu), color (EasyShade, VITA), and surface gloss (Micro-Gloss 45º BYK, Gardner) readings were done. Samples were separated into five groups (n=14) according to the treatments used: CT-conventional toothpaste (negative control); CH-charcoal; TU-turmeric; BP-banana peel, and CP16%-16% carbamide peroxide gel (positive control, 4 h/day for 14 days), and then brushed for 560 cycles (T1) and 1200 cycles (T2), equivalent to 14 and 30 days of brushing. New measurements were performed after T1 and T2. The whiteness index for dentistry change (∆WID) and Weight loss (Wl) were calculated. CP16% demonstrated the highest (p<.05) color change (ΔE00) and ∆WID (2-way ANOVA, Bonferroni, p<.05). Surface gloss alterations were lower for TU, CP16%, and BP. CT and CH increased surface roughness (p<.05). CP16% decreased enamel microhardness. CH presented medium abrasiveness, and CT and TU, low abrasiveness. The popular bleaching products were not efficient for tooth whitening. Furthermore, brushing with charcoal increased the enamel surface roughness, and CP16% decreased enamel microhardness over time.
This study was conducted to examine the effect of various dentifrices on the abrasion of acrylic resin and extracted human tooth. The influence of the difference in the hardness of the filament of the toothbrush on the abrasion was also studied, using three kinds of toothbrushes. The specimens (acrylic resin and extracted human tooth) were brushed 3,000 times by the back- and -forth stroke movement using a toothbrushing machine for two hours. The surface irregularities of the specimen were analyzed by the surface analyzer and observed by the scanning electron microscopy before and after the brushing procedure. Moreover, the weight loss of the test specimens of the acrylic resin materials was determined, weighing them by a microbalance before and after brushing. The abrasiveness of the dentifrices showed a wide range, but the abrasiveness of the toothbrush itself was not observed. All dentifrices except one which did not contain the abrasive materials had abrasive effects on both the acrylic resin and human tooth. There was a high correlation (r = 0.96) between the weight loss and the surface irregularities in the case of acrylic resin.
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This is the report of the Laboratory Abrasion Committee of the American Dental Association (ADA) Dentifrice Program relative to specific methods to measure the in vitro abrasivity of dentifrices. This method was used in two collaborative studies with six participating laboratories. These studies were designed by the ADA Dentifrice Program Statistical Committee and their interpretations form a basis for recommendations on the use of the method. This laboratory method is recommended for use in dentifrice development and may provide some basis for expectations in normal dentifrice use.
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The influence of particle size and tooth brush stiffness on abrasion of dentine was determined by means of a brushing machine, using 1,000, 2,000, 5,000, and 10,000 strokes and 200 g tooth brush load. Tooth pastes with two particle sizes were used: 7 and 15 μm diameter for the CaCO3 and 8 and 13 μm for Al(OH)3 abrasive systems. Abrasion was measured by a surface profilometer system and expressed in mean depth. The results show that (1) abrasion was always linearly correlated to the number of strokes; (2) nearly independent of the tooth paste system the abrasion is roughly 1.4 × more severe for the medium than for the soft brush; (3) the abrasion rates (average thickness removed per stroke) prooved to be significantly (p < 0.05) different for all four tooth paste systems, and (4) larger particles lead to higher abrasion rates for both abrasive systems.Copyright © 1985 S. Karger AG, Basel
Aplicagio e composigio de dentifrfcios
  • W E P Roa
W. E. P. Roa, Aplicagio e composigio de dentifrfcios, Aerosol Cosmet., 5, 5-14 (1983).
Personal communication (Dentistry School of Ribeirio Preto
  • H Panzeri
H. Panzeri, Personal communication (Dentistry School of Ribeirio Preto, SP, Brazil, 2001).
The Chemistry and Manuj@BULLETkcture of Cosmetics
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Availagio de dentifrfcios. 2 a parte: Forma a distribuigio de partfculas abrasivas
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H. Panzeri, E. H. G. Lara, F. Siessere, and R. M. Marchetti, Availagio de dentifrfcios. 2 a parte: Forma a distribuigio de partfculas abrasivas, Odontd/ogo Moderno, VI, 13-25 (1979).