Effect of Nano-Tricalcium Phosphate and Nanohydroxyapatite on the Staining Susceptibility of Bleached Enamel

Abstract

Objective
. This study was designed to evaluate the effect of nano-tricalcium phosphate (n-TCP) and nanohydroxyapatite (n-HAP) on prevention of restaining of enamel after dental bleaching.
Methods
. Forty bovine incisors were bleached with 20% carbamide peroxide for two weeks. Afterward, they were divided into five groups based on remineralization solution: no treatment (control), 10% n-TCP, 5% n-TCP, 10% n-HAP, and 5% n-HAP. Each group was daily immersed for 10 minutes in the restaining solution (tea) and for 3 minutes in the remineralization agent, respectively. This protocol was repeated for five days. Subsequently, three digital photographs (baseline, after bleaching, and after restaining) were analyzed by Adobe Photoshop software. The obtained

L

∗

,

a

∗

,

b

∗

, and

Δ
E

parameters were compared using ANOVA and Wilcoxon and Bonferroni tests.
Results
. After bleaching, there were significant changes in tooth colors (

P
<
0.001

) while, after restaining and immersion in remineralization solutions, there were no significant differences in

L

∗

,

a

∗

, and

b

∗

values of different groups (

P
>
0.05

). However,

Δ
E

of 10% TCP was significantly lower than the control (

P
=
0.02

) while there were no significant differences between the other groups (

P
>
0.05

).
Conclusion
. 10% n-TCP could significantly maintain the resultant color and reconstruct the enamel structure after bleaching.

Full text

Research Article
Effect of Nano-Tricalcium Phosphate and Nanohydroxyapatite
on the Staining Susceptibility of Bleached Enamel
Mohammad Bagher Rezvani,1,2 Mohammad Atai,3Mohammad Reza Rouhollahi,1,2
Kosar Malekhoseini,2Hamideh Rezai,2and Faeze Hamze2,4
1Operative Department, Shahed Dental School, Shahed University, Tehran, Iran
2Dental Research Center, Shahed Dental School, Shahed University, Tehran, Iran
3Iran Polymer and Petrochemical Institute (IPPI), Tehran, Iran
4Oral and Dental Diseases Research Center, Kerman University of Medical Sciences, Kerman, Iran
Correspondence should be addressed to Faeze Hamze; f hamzeh@kmu.ac.ir
Received  March ; Revised  April ; Accepted  May 
Academic Editor: Qingling Feng
Copyright ©  Mohammad Bagher Rezvani et al. is is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
Objective. is study was designed to evaluate the eect of nano-tricalcium phosphate (n-TCP) and nanohydroxyapatite (n-HAP)
on prevention of restaining of enamel aer dental bleaching. Methods. Forty bovine incisors were bleached with % carbamide
peroxide for two weeks. Aerward, they were divided into ve groups based on remineralization solution: no treatment (control),
% n-TCP, % n-TCP, % n-HAP, and % n-HAP. Each group was daily immersed for  minutes in the restaining solution (tea)
and for  minutes in the remineralization agent, respectively. is protocol was repeated for ve days. Subsequently, three digital
photographs (baseline, aer bleaching, and aer restaining) were analyzed by Adobe Photoshop soware. e obtained ∗,∗,
∗,and parameters were compared using ANOVA and Wilcoxon and Bonferroni tests. Results. Aer bleaching, there were
signicant changes in tooth colors ( < 0.001) while, aer restaining and immersion in remineralization solutions, there were no
signicant dierences in ∗,∗,and∗values of dierent groups ( > 0.05). However,  of % TCP was signicantly lower than
the control ( = 0.02) while there were no signicant dierences between the other groups ( > 0.05). Conclusion. % n-TCP
could signicantly maintain the resultant color and reconstruct the enamel structure aer bleaching.
1. Introduction
Home bleaching technique has been a popular treatment
for discolored teeth [].istechniqueoersaneective
treatment which is rather easy, safe, and cost-eective [,].
However, it has some possible side eects []suchashyper-
sensitivity, so tissue burning sensation [], and recurrent
staining of tooth surface in short term []. e employed
concentrations of carbamide peroxide in home bleaching
do not appear to cause any macroscopic changes in sur-
face enamel []. However, microscopic alterations such as
increased surface roughness and formation of shallow ero-
sions have been reported [,]. ese changes in the surface
topography are associated with sacricing the color and
glossy appearance of the enamel []. e defects mentioned
above are the result of a shi in the composition of bleached
enamel [] leading to reduction of calcium, phosphate,
and uoride contents []. Since this damage leads to more
staining susceptibility aer vital bleaching [,], it might be
possible to compensate for this problem by employing min-
eralizing agents []. Accordingly, it has been documented
that if the enamel surface is recovered with uoride, casein
phosphopeptide-amorphous calcium phosphate (CPP-ACP),
or hydroxyapatite (HAP) aer bleaching, the microstructural
defects might be repaired []. erefore, the bleaching eect
would last longer and staining would be prevented [–].
Furthermore, it has been discovered that, by reducing the
particle size down to nanorange, the remineralization process
wouldbeamplied[]. Indeed, due to the increased surface
to volume ratio and proportion of atomicity, the interaction
Hindawi Publishing Corporation
International Scholarly Research Notices
Volume 2015, Article ID 935264, 7 pages
http://dx.doi.org/10.1155/2015/935264

International Scholarly Research Notices
as well as the adhesion of nanoparticles with tooth structure
wouldbeimproved[,]. On this ground, in recent appli-
cations of HAP for biomimetic repair of damaged enamel, it
has been conrmed that the nano-HAP (n-HAP) would lead
to a considerably superior remineralization [,].
On the other hand, tricalcium phosphate (TCP) is a tran-
sitional phase in hydroxyapatite conversion. is complex
consists of some structural sites that can be activated by vari-
ous organic molecules, leading to very good remineralization
[,]. TCP has a specic form that overcomes the limited
bioavailability of other insoluble calcium phosphates for the
remineralization process [].
Application of bioactive glass or n-HAP in conjunction
with carbamide peroxide bleaching has been investigated in
very few recent studies [,]. Some of them reported that
these complexes do not aect tooth whitening ecacy []
while others concluded that it would prevent restaining aer
dental bleaching []. It should be noted, however, that the
available literature on this object especially comparing the
eect of nanoparticles on tooth color stability is extremely
scarce. erefore the aim of this study was to evaluate the
eect of nano-TCP (n-TCP) and n-HAP to prevent restaining
of enamel surface aer dental bleaching.
2. Materials and Methods
2.1. Materials. Rod-like hydroxyapatite particles (diameter <
 nm, aspect ratio -) were purchased from Nanoshel Co.
(Panchkula, India). Meanwhile, plate-like -TCP nanopar ti-
cles (diameter ∼ nm) were synthesized in a previous study
[].
2.2. Methods
2.2.1. Sample Preparation. Forty caries-free bovine incisors
were selected and aer cleaning with aqueous slurry of
pumice,theywerestoredin%thymolsolution.eroots
of the teeth were embedded in arch form silicon blocks. Sub-
sequently, a plastic cover was fabricated for the crowns of the
teeth using a vacuum forming machine. Finally, a digital pho-
tograph was taken in a standard method for determining the
color of each tooth.
2.2.2. Photography. All the digital photographs were taken
under a standard condition in a complete dark chamber while
the distance of the camera (Canon EOS D) was xed. In
order to work in a constant environment, the background
was black while the samples were put in a silicon box. For
exposure metering, a circular punch of the gray card with a
reectance value of % was put near each sample and the
samemanualexposuremodewasselectedforthewhole
samples [].
2.2.3. Tooth Bleaching. Carbamide peroxide % gel (Opales-
cence, Ultradent, USA) was inserted in each plastic cover
andthecrownsoftheteethwereexposedtoonedaily
application of the bleaching agents for two hours for fourteen
consecutive days. Finally, another digital photograph was
taken for recording the color. In order to mimic the oral
condition during bleaching, the specimens were stored in
% relative humidity at ∘C. Aer each daily treatment, the
specimens were thoroughly rinsed with air/water spray and
stored in distilled water until the next day.
2.2.4. Experimental Treatment and Restaining Solution. Fol-
lowing the bleaching process, all the specimens were ran-
domly divided into ve groups containing eight teeth.
Five  × mm glass boxes were prepared and the
specimens were immersed in the boxes as follows.
() e control group specimens (the rst group) were
daily immersed for  minutes in a standard tea
solution (boiling  gr of tea in  mL of water for 
minutes and then passing the solution through gauze
in order to remove the tea leaves), []xedinair
for another  minutes, and rinsed, respectively. en
they were stored in distilled water until the next day.
() e second group specimens were daily immersed in
% TCP for  minutes prior to receiving the treat-
ments similar to the control group.
() e third group specimens were daily immersed
in % TCP for  minutes prior to receiving the
treatments similar to the control group.
() e fourth group specimens were daily immersed in
% HAP for  minutes prior to receiving the treat-
ments similar to the control group.
() ehgroupspecimensweredailyimmersedin%
HAP prior to receiving the treatments similar to the
control group.
All these treatments were repeated for ve days and nally a
new photograph was taken for recording the color. Aerward,
the photographs were analyzed.
2.2.5. Analysis of Digital Photographs. e Adobe Photoshop
soware(CS)wasusedtoanalyzethephotographs.First,the
global color cast of the images was eliminated according to
the piece of gray card in the pictures. In order to compare
the color, we incorporated the Commission Internationale de
l’Eclairage(CIE)systemintheformof∗,∗,and∗obtained
by the soware. In the CIE system, “∗” characterizes the
lightnessandcanrangefrom(dark)to(light).evalue
of “∗” represents the red (+) green (−)spectrumand“∗”
represents the yellow (+) blue (−)spectrum.Subsequently,,
,andvalues of the selected area were metered and the his-
togram information was obtained. e Photoshop ,,and
values were transformed into the CIE ∗,∗,and∗values
using the following formulas []:
∗=(×100)
250 ,
∗=((−128)×240)
250 ,
∗=((−128)×240)
250 .
()

International Scholarly Research Notices 
0
20
40
60
80
∗∗
∗
∗
L before
bleaching
L aer
bleaching
A before
bleaching
A aer
bleaching
B before
bleaching
B aer
bleaching
F : e absolute mean values ±standard deviations of color
parametersof the teeth before and aer bleaching. ∗(lightness) was
signicantly increased while the absolute amounts of ∗and ∗(red-
green and yellow-blue spectrum, resp.) were signicantly decreased.
ese changes conrm ecient bleaching.
Ultimately, ∗that represents the total color dierence in
CIE system was calculated as
∗=∗2∗2∗21/2.()
2.2.6. Surface Morphology Observation. One sample of each
group was observed to evaluate the changes in the surface
morphology aer ve days of treatment. e samples were
mounted on the aluminum stub using carbon-coated double
sided adhesive tape and then coated with gold using a sputter
coater. Subsequently, the supercial microstructure of the
specimens was analyzed using scanning electron microscopy
(SEM) (TESCAN, VEGAII, XMU, Czech Republic).
2.3. Statistical Analysis. Aer exploring the normal distribu-
tion, Wilcoxon test was used to compare the baseline color
parameters with the results of aer bleaching. Meanwhile,
the data regarding the specimens receiving mineralizing
agents were analyzed using one-way ANOVA and post hoc
Bonferroni test. Statistical signicance was dened at =
0.05.
3. Results
3.1. e Eect of Bleaching Protocol. Color parameters of the
teeth before and aer bleaching (∗,∗,and∗values) are
demonstrated in Figure .ebaseline∗,∗,and∗values
underwent signicant changes aer bleaching ( < 0.001).
erefore, it was revealed that the bleaching process had
signicantly improved the enamel color of the examined
teeth.
3.2. Color Changes Subsequent to Restaining. As it is sum-
marized in Table , aer ve days of restaining regimens,
there were no signicant dierences between ∗,∗,and∗
values of dierent groups ( > 0.05). However,  of %
TCP was signicantly lower than the control group (=
0.02) while there were no signicant dierences between the
other groups, indicating that immersing in % TCP solution
signicantly compensated for the demineralization eect of
bleaching process and leading to longer stability of tooth
color. Moreover the representative images of experimental
and control groups are demonstrated in Figure .
3.3. Changes in Surface Microstructure. As Figure  illus-
trates, numerous porosities were observed on the surface
of the control and the % HAP groups. In contrast, all the
samples treated by other remineralizing agents (% TCP,
% TCP, and % HAP) had considerably smoother surfaces
compared to the control. It could be concluded that applica-
tion of all the studied remineralizing agents, except for the
% HAP solution, led to an observable remineralization and
smoothening of the enamel surface.
4. Discussion
e results of the current study showed that application of
n-HAP or n-TCP on tooth surface aer bleaching protocol
woulddecreasetherestainingofenamel.However,onlythe
% n-TCP had a signicant eect.
e results of the present study are consistent with
previous reports incorporating other agents such as uoride,
nanocarbonate apatite, or CCP-ACP aer bleaching [,
]. is eect is attributed to their mineralizing ability.
Accordingly, it has been documented that n-HAP []and
nanocarbonate apatite [] penetrate into the intercrystalline
spaces and rod sheaths [,]. erefore, these nanoparti-
cles enhance the supercial enamel smoothness and block up
surface defects [].
Resembling our study, Pedreira de Freitas et al. compared
the eect of % neutral sodium uoride and nano-HAP
aer bleaching treatment and reported that the surface gloss
increased only in the nano-HAP group []. Since the scat-
tering or reection of the light strongly depends on the
surfacetexture[], their investigation could suggest that n-
HAP noticeably recovered the surface irregularities caused
by bleaching which consequently prevented restaining. eir
nding is also in agreement with Singh et al. who reported
that the restaining of bleached teeth would be prevented by
applying uoride or CPP-ACP aer bleaching [].
One of the most interesting outcomes of the current
research was the stronger eect of n-TCP compared to n-
HAP.isndingisinagreementwithresearcherswhostud-
ied the soluble compound of calcium and phosphate (amor-
phous ACP) []. ey reported that amorphous ACP is more
soluble and is more similar to bone or tooth structure com-
pared to crystalline HAP []. erefore, ACP dissolves read-
ily in the oral cavity and redeposits on the damaged enamel
[]. Similar to ACP, the water solubility of TCP is higher than
HAPwhichisquiteeectiveforremineralization[]. For

International Scholarly Research Notices
T : Bleached and nal (aer treatment by experimental solutions) values of ∗,∗,and∗for each group and .
Groups  

Baseline Bleached Final Baseline Bleached Final Baseline Bleached Final
No treatment . ±. . ±. . ±. −. ±. −. ±. −. ±. −. ±. −. ±. −. ±. . ±.a
n-TCP % . ±. . ±. . ±. −. ±. −. ±. −. ±. −. ±. −. ±. −. ±. . ±.b,c
n-TCP % . ±. . ±. . ±. −. ±. −. ±. −. ±. −.   ±. −. ±. −. ±. . ±.a,c
n-HAP % . ±. . ±. . ±. −. ±. −. ±. −. ±. −. ±. −. ±. −. ±. . ±.a,c
n-HAP % . ±. . ±. . ±. −. ±. −. ±. −. ±. −.   ±. −. ±. −.  ±. . ±.a,c
Valu e s w e re me a n ±standard deviation. Δ𝐸 of n-TCP %was signicantly lower than the control group. erefore, signicant prevention of restaining was achieved in n-TCP %group. However, there was no
signicant dierence among other groups.
a,b,cSame letters were not signicant by Bonferroni multiple comparison of P<.. n-TCP indicated nano-tricalcium phosphate. n-HAP indicated nanohydroxyapatite.

International Scholarly Research Notices 
(a) (b) (c) (d)
F : Although the experimental and control samples had quite similar color immediately aer bleaching (a and b), the experimental
sample that was treated by % nano-tricalcium phosphate and restained by tea solution (c) showed more color stability than the control
sample (d) that was restained by tea solution without receiving any treatment.
bone regeneration, the highly crystalline HAP particles are
classied as nonresorbable materials while TCP is resorbable
[]. It has been shown that the degradation of biomaterials
strongly depends on their solubility []. erefore, the
higher solubility of n-TCP could be the reason for its stronger
eect compared to n-HAP. is hypothesis has been con-
rmed by previous publication in which the calcium com-
ponent of resorbable calcium phosphate materials was intro-
duced as a major factor for local mineralization and also the
surrounding calcium pool [].
However, our results demonstrated a dose-dependent
eect for n-TCP because it was not meaningfully eective at
% but a signicant restaining inhibition occurred at %.
Similarly, in published literatures, dose dependency has been
reported frequently for remineralizing agents [,]. It has
been documented that, as the calcium content in treatment
solution increase, the remineralization would increase too
[,].
Moreover, the SEM micrographs showed noticeably
smoother surface in the groups receiving remineralizing
treatment (except for n-HAP %) compared to the con-
trol. Accordingly, it has been reported that n-HAP may
be deposited onto the enamel surface [,]. Our SEM
micrographs demonstrated that many surface defects were
produced on the enamel surface as a result of bleaching pro-
cess,whilethenanoparticlesreconstructedthesurfacetopog-
raphy. In a similar study, Gjorgievska and Nicholson applied
toothpaste containing bioactive glass on the bleached enamel
surface. eir SEM micrographs also represented changes in
enamel surface morphology aer the bleaching procedure,
whereas, by incorporation of the toothpaste, the irregularities
were repaired [].
Although our SEM micrograph showed signs of reminer-
alization in n-HAP groups, our color analysis did not demon-
strate signicant restaining prevention for n-HAP groups.
isndingisconsistentwithsomeinvestigatorswhileitis
against some other ones [,]. Pedreira et al. surveyed
bleached enamel and claimed signicant increase in surface
gloss aer polishing with n-HAP []. is controversy in
ndings would be attributed to the dierent methods. e
results of this study revealed that restaining by tea solution
was strongly prevented by % n-TCP. Although in previous
researches dierent solutions were used for restaining, it has
been indicated that, compared to coee or chlorhexidine,
teeth have higher susceptibility to staining by tea [].
Overwhelmingly,asitisshowninTa b l e  ,theresultsof
this study showed that all the treatment solutions decreased
the color change compared to the control. However, only
% n-TCP was signicantly eective. erefore, it can be
concluded that some of nanoparticle which has a tooth-like
structure would be benecial for longer ecacy of the
bleaching protocol.
5. Conclusion
Aer bleaching, all the experimental solutions prevented the
restaining of enamel to some extent. However, only the %
n-TCP could signicantly maintain the resultant color com-
pared to the control, indicating the recovery of the damaged
enamel surface by the calcium phosphate compound.
Conflict of Interests
e authors declare that there is no conict of interests
regarding the publication of this paper.
Acknowledgment
e authors acknowledge with gratitude the Dental Research
Center of Shahed Dental School, Tehran, Iran, for nancial
support of the study.

International Scholarly Research Notices
(a) (b)
(c) (d)
(e)
F : SEM micrographs of the enamel surfaces in dierent groups (×). (a) Control, (b) % n-TCP (nano-tricalcium phosphate),
(c) % n-TCP, (d) % n-HAP (nanohydroxyl apatite), and (e) % n-HAP. All the experimental group showed smoother surface compared to
the control except for the % n-HAP.
References
[] A. V. Ritter, R. H. Leonard Jr., A. J. S. Georges, D. J. Caplan,
and V. B. Haywood, “Safety and stability of nightguard vital
bleaching:  to  years post-treatment,” Journal of Esthetic and
Restorative Dentistry,vol.,no.,pp.–,.
[] V.B.HaywoodandH.O.Heymann,“Nightguardvitalbleach-
ing:howsafeisit?”Quintessence International,vol.,no.,pp.
–, .
[] W.R.Howard,“Patient-appliedtoothwhiteners,”e Journal of
the American Dental Association,vol.,no.,pp.–,.

International Scholarly Research Notices 
[] B. Azrak, A. Callaway, P. Kurth, and B. Willershausen, “Inu-
ence of bleaching agents on surface roughness of sound or
eroded dental enamel specimens,” Journal of Esthetic and
Restorative Dentistry,vol.,no.,pp.–,.
[] M. A. M. Sulieman, “An overview of tooth-bleaching tech-
niques: chemistry, safety and ecacy,” Periodontology 2000,vol.
,no.,pp.–,.
[]A.G.GamaCunha,A.A.MeiradeVasconcelos,B.C.
Dutra Borges et al., “Ecacy of in-oce bleaching techniques
combined with the application of a casein phosphopeptide-
amorphous calcium phosphate paste at dierent moments and
its inuence on enamel surface properties,” Microscopy Research
and Technique,vol.,no.,pp.–,.
[] A.C.PedreiradeFreitas,S.B.Botta,F.deS
´
a Teixeira, M. C.
B. S. Salvadori, and N. Garone-Netto, “Eects of uoride or
nanohydroxiapatite on roughness and gloss of bleached teeth,”
Microscopy Research and Technique,vol.,no.,pp.–
, .
[] A. Wandera, R. J. Feigal, W. H. Douglas, and M. R. Pintado,
“Home-use tooth bleaching agents: an in vitro study on quan-
titative eects on enamel, dentin, and cementum,” Quintessence
International,vol.,no.,pp.–,.
[] I. Potoˇ
cnik, L. Kosec, and D. Gaspersic, “Eect of % car-
bamide peroxide bleaching gel on enamel microhardness,
microstructure, and mineral content,” Journal of Endodontics,
vol. , no. , pp. –, .
[] Y. S. Kim, H. K. Kwon, and B. I. Kim, “Eect of nano-carbonate
apatite to prevent re-stain aer dental bleaching in vitro,”
Journal of Dentistry,vol.,no.,pp.–,.
[] A. Watts and M. Addy, “Tooth discolouration and staining: a
review of the literature,” British Dental Journal,vol.,no.,
pp.–,.
[] E. Gjorgievska and J. W. Nicholson, “Prevention of enamel
demineralization aer tooth bleaching by bioactive glass incor-
poratedintotoothpaste,”Australian Dental Journal,vol.,no.
, pp. –, .
[] T. Attin, A. M. Kielbassa, M. Schwanenberg, and E. Hellwig,
“Eect of uoride treatment on remineralization of bleached
enamel,” JournalofOralRehabilitation,vol.,no.,pp.–
, .
[] S.Bayrak,E.S.Tunc,I.S.Sonmez,T.Egilmez,andB.Ozmen,
“Eects of casein phosphopeptide-amorphous calcium phos-
phate (CPP-ACP) application on enamel microhardness aer
bleaching,” American Journal ofD entistry,vol.,no.,pp.–
, .
[] R.D.Singh,S.M.Ram,O.Shetty,P.Chand,andR.Yadav,“E-
cacy of casein phosphopeptide-amorphous calcium phosphate
to prevent stain absorption on freshly bleached enamel: an in
vitro study,” Journal of Conservative Dentistry,vol.,no.,pp.
–, .
[] A.Generosi,J.V.Rau,V.RossiAlbertini,andB.Paci,“Crys-
tallization process of carbonate substituted hydroxyapatite
nanoparticles in toothpastes upon physiological conditions:
an in situ time-resolved X-ray diraction study,” Journal of
Materials Science: Materials in Medicine,vol.,no.,pp.–
, .
[] T. J. Webster, C. Ergun, R. H. Doremus, R. W. Siegel, and R.
Bizios, “Specic proteins mediate enhanced osteoblast adhe-
sion on nanophase ceramics,” JournalofBiomedicalMaterials
Research,vol.,no.,pp.–,.
[] R.L.Karlinse,A.C.Mackey,G.K.Stookey,andA.M.Pfarrer,
“In vitro assessments of experimental NaF dentifrices contain-
ing a prospective calcium phosphate technology,” American
Journal of Dentistry,vol.,no.,pp.–,.
[] R. L. Karlinsey, A. C. Mackey, E. R. Walker, and K. E. Frederick,
“Preparation, characterization and in vitro ecacy of an acid-
modied -TCP material for dental hard-tissue remineraliza-
tion,” Acta Biomaterialia,vol.,no.,pp.–,.
[] E. C. Reynolds, “Calcium phosphate-based remineralization
systems: scientic evidence?” Australian Dental Journal,vol.,
no.,pp.–,.
[] A.A.M.deVasconcelos,A.G.G.Cunha,B.C.D.Borges,C.
T. MacHado, and A. J. S. Dos Santos, “Tooth whitening with
hydrogen/carbamide peroxides in association with a CPP-ACP
paste at dierent proportions,” Australian Dental Journal,vol.
, no. , pp. –, .
[] R. Marefat Seyedlar, A. Nodehi, M. Atai, and M. Imani,
“Gelation behavior of in situ forming gels based on HPMC
and biphasic calcium phosphate nanoparticles,” Carbohydrate
Polymers,vol.,pp.–,.
[] W. M. Bengel, “Digital photography and the assessment of ther-
apeutic results aer bleaching procedures,” Journal of Esthetic
and Restorative Dentistry, vol. , supplement , pp. S–S,
.
[] A. Leard and M. Addy, “e propensity of dierent brands of
tea and coee to cause staining associated with chlorhexidine,”
Journal of Clinical Peri odontology,vol.,no.,pp.–,.
[]R.Tanaka,Y.Shibata,A.Manabe,andT.Miyazaki,“Micro-
structural integrity of dental enamel subjected to two tooth
whitening regimes,” Archives of Oral Biology,vol.,no.,pp.
–, .
[] K. Yamagishi, K. Onuma, T. Suzuki et al., “Materials chemistry:
a synthetic enamel for rapid tooth repair,” Nature,vol.,
article , .
[] W. Linhart, F. Peters, W.Lehmann et al., “Biologically and chem-
ically optimized composites of carbonated apatite and polyg-
lycolide as bone substitution materials,” Journal of Biomedical
Materials Research,vol.,no.,pp.–,.
[] R. A. Horowitz, Z. Mazor, C. Foitzik, H. Prasad, M. Rohrer, and
A. Palti, “-tricalcium phosphate as bone substitute material:
properties and clinical applications,” Jour nal of Osseointeg ration,
vol. , no. , pp. –, .
[]F.Cai,P.Shen,M.V.Morgan,andE.C.Reynolds,“Rem-
ineralization of enamel subsurface lesions in situ by sugar-
free lozenges containing casein phosphopeptide-amorphous
calcium phosphate,” Australian D ental Journal,vol.,no.,pp.
–, .
[] G. D. Walker, F. Cai, P. Shen et al., “Consumption of milk with
added casein phosphopeptide-amorphous calcium phosphate
remineralizes enamel subsurface lesions in situ,” Australian
Dental Journal,vol.,no.,pp.–,.
[] S. Huang, S. Gao, L. Cheng, and H. Yu, “Combined eects of
nano-hydroxyapatite and Galla chinensis on remineralisation
of initial enamel lesion in vitro,” Journal of Dentistry,vol.,
no.,pp.–,.
[] S. B. Huang, S. S. Gao, and H. Y. Yu, “Eect of nano-
hydroxyapatite concentration on remineralization of initial
enamel lesion in vitro,” Biomedical Materials,vol.,no.,
Article ID , .
[] W. D. Browning, S. D. Cho, and E. J. Deschepper, “E ect of a
nano-hydroxyapatite paste on bleaching-related tooth sensitiv-
ity,” Journal of Esthetic and Restorative Dentistry,vol.,no.,
pp. –, .