SEMINAR

1. WHITE SPOT LESIONS IN ORTHODONTICS
DR SHEHNAZ JAHANGIR
FINAL YEAR MDS
DEPT. OF ORTHODONTICS &
DENTOFACIAL ORTHOPAEDICS

2. CONTENTS
 Introduction
 Definition
 Incidence
 Formation of white spot lesions
 Classification
 Prevalence
 Diagnosis
 Prevention of WSLs
 Effects of fluoride
 Remineralisation
 Conclusion
 References

3. Introduction
 Esthetics is a very important reason for which patients
seek orthodontic treatment.
 The introduction of fixed appliances has proved to be a
boon for the orthodontists as well as orthodontic
patients with several advantages such as shorter
treatment time, precise and more controlled tooth
movement etc.
 However the advent of bonded multibracket fixed
appliances in 1970s brought enamel white spot lesions.

4.  Decalcification of the enamel surface adjacent to fixed
orthodontic appliances is an important and prevalent
iatrogenic effect of orthodontic therapy.
 The banding and bonding of orthodontic appliances to
teeth increases the plaque retention sites and as a
result, oral hygiene becomes more difficult.
 The low pH of plaque adjacent to orthodontic brackets
hinders the remineralisation process and
decalcification of enamel can occur.

5.  As enamel translucency is directly related to the
degree of mineralization, initial enamel
demineralization usually manifests itself as “white
spot lesion.”

6. Definition:
Subsurface enamel porosity from carious
demineralization that presents itself as “milky white
opacity when located on smooth surfaces”

7. Incidence
 In general, orthodontic patients have significantly
more WSLs than non-orthodontic patients,
 and these WSLs may present aesthetic problems years
after treatment.
 One study found that the prevalence of at least one
WSL in patients who underwent treatment with fixed
orthodontic appliances was 49.6%; this compares to
only 24% in an untreated control group.

8. This was recently confirmed in a prospective study
from the nothern part of norway . About 50% of the
patient receiving orthodontic treatment developed
one or more WSLs during treatment and 5.7% of the
teeth were affected.
This compared with a matched group of non
orthodontic patients in whom 11% developed WSLs on
the labial surface in the same period of time and 0.4%
of the teeth were affected.

9. • Using more advanced detection techniques like
quantitative light-induced fluorescence , Boersma and
coworkers observed that 97% of all subjects and on
average 30% on the buccal surfaces in the person were
affected.
• On average, 40%of the surfaces in male and 22%in
females showed white spot lesions.

10.  Formation of white spot lesions:
fixed orthodontic appliances
rapid increase in the volume of dental plaque
low pH
increased cariogenic risk, rapid shift in
the composition of bacterial flora S. mutans ↑
acid by-products, ↓ pH
carious decalcification
Fermentable carbohydrates→

11.  The first clinical evidence of this demineralization is
visualized as white spot lesion.
 Such lesion have been clinically induced in a span of 4
weeks, which is typically within the time period
between one orthodontic appointment and the next.
 In the highly cariogenic environment adjacent to
orthodontic appliances or under loose bands, these
lesion can rapidly progress.
 If left untreated they may produce carious cavitation
that will need an appropriate restoration.

12. Classification
 According to Gorelick and coworkers
Small lesion
Severe lesion
Cavitation.

13.  Clinical examination for the presence of white spots was made
on the labial surface of individual teeth and, as shown in Fig. ,
the lesions were scored as follows:
 In the group that had worn bonded metal orthodontic
brackets, all teeth were examined immediately after debonding
at the termination of orthodontic treatment.
Leonard Gorelick,* Arnold M. Geiger,** and A. John Gwinnett***

14. PREVALENCE
The greatest prevalence of WSLs was found on the first
molars, the canines and the premolars in the
orthodontic group .
Of the anterior teeth, the lateral incisors were more
affected than the central incisors.
The most likely reason for this observation is that the
brackets are placed closer to the gingival margin
because of the anatomic shape of these tooth groups.
In the untreated group, the greatest prevalence was
observed on the first molars and lower premolars.

15. DIAGNOSIS

16. Evaluation of white spot lesions on teeth
with orthodontic brackets
 Evaluation of demineralized white spot lesions during
orthodontic treatment is important for both clinicians
and researchers.
 Clinicians must discover enamel lesions early so that
they can advice patients regarding changes in oral
hygiene and diet as well as implement suitable
preventive measures.
 There are macroscopic and microscopic methods used
in the detection and measurement of demineralized
white lesions.

17. Macroscopic methods
 Rely mainly on the change in the optical properties of
enamel with demineralization.
 A demineralized lesion in enamel is white is due to an
increase in the backscatter of light.
1. Clinical examination
• Clinicians are trained to use clinical examinations to
assess the presence of demineralization .
• Advantages:
 Simple and inexpensive
 Clinically valid.

18.  Disadvantage
Validity – it is often difficult clinically to distinguish
white spots caused by demineralization and those that
are due to other causes such as developmental
hypoplasia or fluorosis.
Fluoride opacities
White spot lesions

19. 2. Photographic examination
• Advantages
 This method can be standardized so that the clinical
variability of diagnostic conditions may be
minimized.
 Provides a permanent record and can therefore be
examined during one assessment session and re-
examined at different time to determine
reproducibility.

20. It is easy to mask the patient details so they can be
examined in random order to reduce the potential for
bias.
More versatile than a visual examination . They can
also be digitized and using computer to measure the
severity of the lesion in terms of area or change in
whiteness or gray levels.

21.  Disadvantages
Might record details differently than the naked eye.
Tend to overestimate the incidence of opacities, partly
due to the reflection of the flash from the tooth
surface.
Standardization of the procedures may be difficult
particularly with respect to wetness of the tooth.

22. 3. Optical Non-fluoroscent methods
Light scattering
Demineralization leads to more scattering of the light
entering the enamel.
The scattering results in sidewards displacement of the
light which can be measured using the Optical Caries
Monitor.
Use a 100w white light as light source and measure
backscatter with densitometer.
Show good correlation between OCM readings and
other more direct but destructive methods of measuring
mineral loss.

23.  Advantages
It enables a convenient and non-destructive
quantification of enamel demineralization.
• Disadvantages
Technique sensitive and results can vary with the
degree of wetness or drying of the tooth.

24.  4.Optical Fluoroscent Methods:
Fluoroscent dye uptake:
Mainly used for detection and removal of carious
dentin.
The disadvantage is that slight procedural variations
can result in widely different degrees of dye uptake.

25. Ultraviolet
Early studies used ultraviolet light for detection of
carious lesion on the smooth surface.
Special precautions has to be taken to protect the
patient and the operator because UV radiation which
has a shorter wavelength than visible light is harmul
to eyes and skin.

26. Laser
Bjelkhagen and coworkers used an argon laser to show
differences in luminescence from intact and carious
enamel in the laboratory.
De Josselin de Jong and coworkers developed the
technique of quantitative laser fluorescence for use in
the mouth.
The equipment was calibrated to calculate the
difference in fluroscence between the demineralized
area and the surrounding sound enameland therby
quantify mineral loss and lesion size.

27.  DIAGNOdent:
Does not produce a picture of the tooth, but produces
a reading, which is thought to be an indication of
bacterial activity, rather than mineral loss.

28. Quantitative Light- Induced Fluorescence Or QLF
Most promising fluorescent method of measuring
demineralization in use today.
Not only does early detection of demineralized lesions,
but also detects changes in the mineral loss and size
overtime.

29. Microscopic Methods

30. 1. Caries models
 Microhardness testing
 Polarized light microscopy
 Microradiography
 Allows direct measurement of mineral loss or lesion
depth in enamel.
• Disadvantage
 Include lack of availability of teeth and only patients
requiring extractions can participate.
 There is less control over lesion reproducibility and
restrictions regarding lesion location.
 The patient cannot commence orthodontic treatment
until tooth is extracted

31.  The In Situ Caries Model
• Advantages :
 Reproduces the natural caries process without causing
irreversible damage to the volunteer.
 Specimen of the same tooth may be kept as a control,
allowing a more accurate determination of the changes
that occur.
 It is possible to induce an artificial subsurface lesion in
the specimen, so that remineralization as well as further
demineralization can be studied.
 It will not effect the orthodontic treatment

32.  Disadvantage
Very time consuming particularly in laboratory and
analysis time.

33. Prevention of WSLs
 Perhaps the most important prophylactic measure to
prevent the occurrence of WSLs in orthodontic
patients is implementing a good oral hygiene regimen
including proper tooth brushing with fluoridated
dentifrice.
 Dentifrices typically contain either sodium fluoride,
monofluorophosphate, stannous flouride, amine
fluoride or a combination .
 As orthodontic patients are at an increased caries risk,
a fluoride concentration below 0.1% in dentifrices is
not recommended.

34.  In addition to the anti-caries activity, stannous
flouride may have plaque inhibiting effect by
interfering with the adsorption of plaque bacteria to
the enamel surface.
 Tin atoms-block the passage of sucrose into bacterial
cells thus inhibiting acid production.
 It is observed that the use of fluoridated antiplaque
dentifrice may reduce enamel demineralization
around brackets more than the use of flouridated
dentifrice.

35. For less compliant patients
 Fluoridated dentifrice alone- ineffective
 Supplemental sources of fluoride are often suggested
 Fluoridated mouth rinse containing 0.05%
sodium fluoride used daily have been shown to
significantly reduce lesion formation beneath the
bands.
 While proper use of these products provide with
increased caries protection , patient compliance is
required and such co-operation can be difficult to
obtain in some patients.

36.  The in-office application of a high concentration of
fluoride in the form of varnish may be beneficial and
should be considered by the clinician.
 These products offer the combined benefit of delivering
high concentration of fluoride during regular orthodontic
visit while eliminating the need for patient co-operation.
 Limitation of frequency of exposures that the patient will
receive. Increase cost and chair side time.
 One disadvantage is the temporary discoloration of the
teeth and gingival tissue, with the use of most available
products.
 However it has been reported that the application of a
fluoride varnish resulted in 44.3% reduction in enamel
demineralization in orthodontic patients.

37.  Recent advances in fluoride prevention
Titanium tetrafluoride solutions inhibit lesion
development in association with fixed orthodontic
appliances markedly & more efficiently than
conventional preparations.
The cariostatic mechanism of titanium tetrafluoride is
probably due to retentive, titanium rich, glaze like
surface coating formed on the treated enamel surfaces.
At low pH, titanium binds with an oxygen atom of a
phosphate group that is densely distributed on enamel
surfaces.

38. Following the application of aqueous solutions of
titanium tetrafluoride,-Ti-O-Ti-O chains are formed
on the tooth surfaces and covalently bond titanium
covers the tooth surface. A strong complex formed is
thus formed between the titanium compounds and the
hydroxyapatite.
This surface coating has been found to resist
challenges even under extreme alkaline and acidic
conditions.

40. Fluoride and the
cariostatic effect

41.  Fluoride with no doubt the most important caries
preventive agent.
 For many years it was thought that fluoride should be
incorporated into the tooth structure to achieve preventive
effect on tooth mineral solubility.
 Research has shown that the effect is overestimated and
that the mechanism is related to fluoride being present in
the fluid phase of the caries process.
 The fluoride ions then execute an inhibiting effect on
tooth demineralization and an enhanching effect on
tooth remineralization.

42.  When topical fluoride is applied , a calcium fluoride-
like material builds up in plaque, on the tooth surface
or the incipient lesions.
 The CaF2 acts as a reservoir of the fluoride ions for
release when pH is lowered during caries attack.
 The dissolution rate of CaF2 at different pH is
controlled by phosphate and proteins.

44.  Importance of pH on the fluoride effect:
Arneberg and coworkers studied pH in plaque of
orthodontic patients following a sucrose challenge.
The lowest pH during resting and fermenting
conditions was observed in the plaque of the bonded
upper incisors. In these sites, pH could fall to as low as
4.
Low pH- any reservoir of fluoride is rapidly lost.
The limit of fluoride effect is reached when pH drops
so low that even the solubility product of pure
fluoroapatite is exceeded.(<4.5).

45.  At this low pH the liquid phase of the plaque will be
undersaturated with respect to both hydroxyapatite
and fluoroapatite and no redeposition of lost mineral
occur.

46.  Sealants, primers and adhesives:
Duration of orthodontic treatment ↑ caries risk.
As a result a continuous fluoride release from the
bonding system around the bracket base would be
extremely beneficial.
Thus fluoride containing sealants and adhesives to
bond brackets has been attempted.

47.  GIC were initially introduced as orthodontic bonding
adhesives to take advantage of some of their deisrable
characteristics, namely their ability to chemically
bond to the tooth structure, in addition to their
sustained fluoride release following bonding.

48.  Lower bond strength- use for bonding orthodontic
brackets fairly limited.
 In an attempt to increase the bond strength of the
GICs, resin particles were added to their formulation
to create RMGI bonding systems.
 Release fluoride like conventional GICs and have
high bond strength.
 Although earlier studies indicate that RMGIs have
lower shear bond strength compared with composites
resins, particularly within the first half hour after
bonding, more recently these products were found to
have an increased shear bond strength .

49.  Furthermore, it was also reported that no significant
differences in bracket failure rates between the RMGIs and
composite adhesives.
 A study showed the mean amount of daily fluoride released
by Fuji Ortho LC showed a rapid decrease from day 1 (57
mg/cm2) to day 3 (20.5 mg/cm2). Thereafter, the decrease
was significantly less, up to 4.4 mg/cm2 after the third
week.
 The total fluoride released by the adhesive Light Bond
during the first month was reported to be 8.73 mg/cm2. It
was characterized by an initial burst of fluoride during the
first day (5 mg/cm2),followed by gradual tapering down
(0.111 mg/cm2 after the third week).

50.  The fluoridated resin Light Bond, that has been used
with its fluoridated sealant, showed no statistical
differences in terms of demineralization compared
with the nonfluoride-containing composite groups in
which only the self-etching primer or the sealant was
responsible for the release of fluoride.
 Light Bond and Pro Seal showed significantly lower
Lds compared with a nonbonded control in a recent
investigation, whereas no differences were found
between the mean Lds of these 2 groups

51.  Effects of adding fluoride and other antibacterial
agents on shear bond strength of orthodontic
adhesives.
The application of fluoride containing sealants has
been shown to not affect the SBS of orthodontic
adhesives and they are able to produce a sustained
fluoride release.
However, it was determined that the conc. Of fluoride
ions released significantly decreased with time.
Therefore the important factors that need to be
considered by the clinicians using these materials
include the duration and conc of fluoride that is being
released as well as the ability of these sealants to be
recharged with fluoride ions.

52.  Recently, it was determined that fluoride releasing
sealant(ProSeal; reliance orthodontics) was capable of
releasing fluoride ions for 17 weeks.
 While the sealant initially released ions at
0.074ppm/wk/mm2 and this level dropped to
0.037ppm/wk/mm2 after the first 3 weeks and reached
a low of 0.01 by the end of 17 week.

53.  Antimicrobials have also been suggested as an
adjunct for those patients.
 Combining chlorhexidine with the bonding primer or
applying it after bonding is completed resulted in no
significant decrease in SBS. However other methods of
incorporating chlorhexidine into the bonding
procedure resulted in significantly weaker bond
strength.
 A recent report that evaluated the use of another
antimicrobial , cetylpyridinium chloride(CTC),
found no significant differences in tensile bond
strength between an adhesive impregnated with
2.5%cetylpyridinium chloride and a control.

54.  Moreover the adhesive containing 2.5% CTC was
shown to inhibit bacterial growth for 196 days.
 Additionally it was found that using a combination of
an anti-microbial selfetching primer and fluoride
releasing primer and a fluoride -releasing adhesive
had stronger SBS than conventional composite .
 In a recent study, a comparision between clearfil
protect bond and transbond plus showed that the
failure rate with Clearfil Protect Bond was significantly
higher than that with Transbond Plus.

55.  For patients with adequate oral hygiene, there was no
benefit with regard to plaque accumulation and prevention
of demineralization with Clearfil Protect Bond.
 Although the fluoride-releasing effect extends around the
bracket, the antibacterial activity of 12-
methacryloyloxydodecylpyridinium bromide(MDPB)
might not extend beyond the edges of the bracket; this is a
possible limitation of its antibacterial action.
 The immobilized agent is known to be effective when
bacteria contact the surface. This would be beneficial
against demineralization under orthodontic brackets from
microleakage that can occur after polymerization.

56.  Clinical effects of applying different varnishes.
An in vivo study found that the use of either fluoride
and chlorhexidine varnishes in combination or using a
fluoride varnish alone resulted in 30% reduction in
WSLs at the time of debonding when compared with a
control group that did not receive any varnish
applications during treatment.
The findings also indicate that on the maxillary
incisors, it was observed that only half of them
developed WSLs when both varnishes were applied
than when only fluoride varnish was used.

57.  According to a study by todd and coworkers mean
lesion depth in group that was treated with DFR
varnish was 50% smaller than the group that was
untreated.
 Schmit and co-workers studied the effect of fluoride
varnish DFR on human enamel demineralization
adjacent to brackets bonded with a RMGI cement.
 DFR+ RMGI= lesion depths 50%less
 Only RMGI= lesion depths 50%less
 Only DFR= 35% less.

58.  Joziak and coworkers reported that DPT fluoride varnish
released significantly more fluoride ions into water and was
associated with significantly more fluoride uptake in enamel
when compared with DFR varnish.
 Juhlin compared the ability of fluoride varnishes DPT and FP
to inhibit enamel demineralization in teeth on which
brackets were bonded with composite resin . The mean
lesion depth of the FP group was significantly less than the
dept of DPT group .
 Much of the FP varnish remained on the enamel surface at
the end of the study, whereas 100% of the DPT varnish was
removed by the 9th day of the study.

59.  Loucks and coworkers compared the ability of FP
varnish, Delton (D) sealant and Pro Seal(PS) to resist
tooth abrasion and afterward, enamel demineralization
from a single 96-hour exposure to a cariogenic solution.
 FP -47% reduction in lesion depths
 D-72% reduction
 PS-92% reduction
 The lesion detected in the PS group were caused by
small air bubbles trapped in the sealant that were
exposed by toothbrush abrasion that, in turn, allowed
the cariogenic solution to reach the enamel surface.

60.  A randomized prospective clinical trial found that
varnish FP applied once every 3 months during
orthodontic treatment resulted in a 27% reduction in
the occurrence of white spot lesions.
 Repeated applicaton of varnish FP are recommended
during treatment, perhaps at each appointment.
 The most durable material was sealant PS that resisted
2 years of simulated toothbrush wear as well.

61. Remineralization and regression of
white spots
 Clearly the best approach during orthodontic treatment is to
prevent lesions from occuring.
 Once formed, however, many of these early lesions appear to be
surface demineralization rather than subsurface lesion with an
intact surface zone.
 Remineralization of these white lesions is a natural phenomenon
resulting in the partial reversal of what an early caries lesion is.
 The mineral of dental enamel is in equilibrium with its
environment and saliva contains all the necessary elements for
hydroxyapatite crystal growth.

62.  In natural state there is demineralization and
remineralization continously taking place.
 Remineralization varies considerably from subject to subject
and from site to site in the mouth.
 Studies have shown that an average remineraliztion takes
place about 20% to 30% over 2 weeks.
 Sometimes the amount of remineralization cannot totally
overcome the amount of demineralization even with an
effective agent present.
 Following removal of fixed orthodontic appliance, some
regression of postorthodontic lesions is known to occur
provided other etiological factors are favorable.

63.  Longitudinal measurements of the size of white spot
lesions have shown that there was a reduction in the
size of the white lesions with time.
 In a study performed using lesion size as the outcome
measure, the mean size at debond was 2.72mm2 . After
26 weeks the mean size was 1.30mm2 . In most cases
rapid size reduction occurred during the first 12 weeks
after appliance removal.
 Lesion size reduced on average by 1/3 after 12 weeks
and ½ by 26 weeks.

64.  Ogaard and coworkers warned against treating visible
white lesions on the labial surfaces with concentrated
fluoride agents, since this arrests both demineralization
and remineralization in the lesion by hypermineralization.
 Instead this workers advocated allowing remineralization
by saliva, as this results in greater repair and less visible
lesion.
 The use of high doses of fluoride completely arrests the
carious process, which is ideal for posterior carious lesions,
but the white spot lesion of orthodontic origin presents a
cosmetic challenge and regression is therapeutic goal.

65.  If high doses of fluoride are used locally the arrested
lesion stays as same size and frequently becomes
unsightly and stained with organic debris.

66.  Natural remineralization also produces greater resistance to
further dissolution due to the fact that during
remineralization, components are replaced with less soluble
substance that may have larger crystals.
 This has been reported as plugging of diffusion pathways of
enamel by hydroxyapatite crystals as hyper-remineralization.
 Workers in this field, however have recommended the
remineralization of small lesions with low fluoride
preparations. They have shown that lesions smaller than
60μm deep can be remineralized using these preparations.

68.  To avoid arresting the lesion and obtunding the surface
layer, several workers have recommended low-dose fluoride
applications to enhance subsurface remineralization.
 Lee linton showed that 50ppm of fluoride mouth rinse had
higher efficiency for remineralization than the control
solution or a regular mouth rinse containing 250ppm of
fluoride.
 For lesions on surfaces other than on the visible labial
surface, application of concentrated fluoride was suggested
to prevent further progression.
 It was suggested that acid etching of the fluoride treated
lesions could facilitate remineralization of the lesions by
oral fluid.

69.  Use of casein phosphopeptitde amorphous
calcium phosphate(CPP-ACP).
 In 1980s Reynolds drew attention to the fact that casein
phosphopeptide amorphous calcium phosphate, which
is derived from milk casein was capable of absorbing
through the enamel surface and could affect the
carious process.
 CPP-ACP is a delivering system that allows freely
available calcium and phosphate ions to attach to
enamel and reform into calcium phosphate crystals.
 The free calcium and phosphate ions move out of the
CPP-ACP and into the enamel rods and free form as
apatite crystals.

70.  A number of different media have been produced to
deliver the CPP-ACP , including a water- base mousse, a
topical cream, chewing gum, mouth rinses, and sugar
free lozenges.
 The material is marketed under the trade name
“Recaldent.”

71.  At present no harmful effect of this material is
reported and there is good reason to believe from the
invitro reports that remineralization of enamel will
provide benefits for the patient suffering from the
postorthodontic white spot demineralization.

72.  Chewing gum to promote remineralization
 For sometime, the use of chewing gum has been recommended
to assist enamel demineralization.
 In non-orthodontic patients, a regimen using sorbitol-based
chewing gum chewed for 20 mins, 5 times daily for 3 weeks,
showed significant remineralization of demineralized enamel
when compared with controls without chewing gum.
 The use of xylitol as an alternative sweetner may be superior
when compared with sorbitol because of potential anticaries
properties.
 It is agreed that the beneficial remineralization effects seen is
attributable in large measure to salivary stimulation.

73.  Microabrasion :
 If undesirable whitened enamel is still present, the patient
parent and dentist need to decide if further esthetic
treatment is desired.
 Whitened enamel that is very apparent compared with the
remainder of natural tooth enamel can receive
microabrasion treatment.
 Microabrasion is merely the application of an acidic and
abrasive compound to the surface of the enamel.
 Research indicates that 1 minute application of commercially
available microabrasion compounds removes 12μm on the
first application and 26μm on subsequent applications.

74.  Removes small amount of surface enamel but leaves a highly
polished enamel surface.
 Abrades surface while compacting calcium and phosphate
into interprismatic spaces.
 Research has demonstrated that although microabrasion
removes small amount of enamel surface , the new polished
enamel is less suspectible to bacterial colonization and
demineralization than natural nonabraded enamel.
 Following a microabrasion technique, a 4 minute 2% sodium
fluoride treatment is recommended.
 If the microabrasion technique has not achieved optimal
esthetics and some whitened enamel is still apparent, vital
tooth bleaching can be considered.

76.  Vital tooth bleaching:
 Mild whitened enamel can often be camouflaged by
bleaching with standard tray based whitening systems
used over-night or with hydrogen peroxide
impregnated polyethylene strips.

77. Conclusion
 Prevention of enamel demineralization during orthodontic
treatment is of utmost importance.
 If enamel demineralization occurs, early diagnosis and
intervention is appropriate.
 Improved brushing with fluoridated dentifrice and over the
counter fluoride rinses would be the first recommended
intervention.
 If more aggressive intervention has to be considered due to the
extent of demineralized enamel or expected noncompliance with
oral hygiene by the patient, professionally applied and/or
prescribed fluorides are recommended.

78. Refrences
 Graber 5th edition
 Øgaard B. Prevalence of white spot lesions in 19-year-olds:
a study on untreated and orthodontically treated persons 5
years after treatment. Am J Orthod Dentofacial Orthop
1989;96:423-7.
 Basdra EK, Huber H, Komposch G. Fluoride released from
orthodontic bonding agents alters the enamel surface and
inhibits enamel demineralization in vitro. Am J Orthod
Dentofacial Orthop 1996;109:466-72.
 Cohen WJ, Wiltshire WA, Dawes C, Lavelle CL. Long-term
in vitro fluoride release and rerelease from orthodontic
bonding materials containing fluoride. Am J Orthod
Dentofacial Orthop 2003;124:571-6.

79.  Gorton J, Featherstone JD. In vivo inhibition of
demineralization around orthodontic brackets. Am J
Orthod Dentofacial Orthop 2003;123:10-4.
 Soliman MM, Bishara SE, Wefel J, Heilman J, Warren
JJ. Fluoride release rate from an orthodontic sealant
and its clinical implications. Angle Orthod
2006;76:282-8.
 Corry A, Millett DT, Creanor SL, Foye RH, Gilmour
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82. Thank you…..