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White Spot Lesions in Enamel
Dr Raya Al-Naimi
The white spot lesion
The same series of experiments also extracted teeth at varying times to
allow detailed examination of sections in polarized light. After only one
week of undisturbed biofilm formation, this examination showed a slight
increase in enamel porosity and the tissue beneath the porous outer
microsurface was more porous than the microsurface itself. This so-called
subsurface demineralization became more obvious at weeks two, three,
and four and the classical histological zones of the white spot lesion in
polarized light could be identified
1- The surface zone
2- body of the lesion, best seen after imbibition of sections in water
3- The dark zone
4- Primary translucent zone seen after imbibition of sections in
quinoline
The shape of the white spot lesion is determined by the distribution
of the biofilm and the direction of the enamel prisms.Thus, on an
approximal surface, the lesion formed beneath the biofilm is a kidney-
shaped area between the contact facet and the gingival margin. Within the
enamel, spread of dissolution takes place along the enamel prisms. In
section, the smooth surface lesion is conical. This conical shape is the
result of systematic variations in dissolution along the enamel prisms.
The oldest or most active part of the lesion is located along the central
traverse. The conically shaped lesion represents a range of increasing
stages of lesion progression beginning with dissolution at the
ultrastructural level at the edge of the lesion. Arrested lesions are
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characterized by multiple dark zones, when examined in quinoline
indicating re-deposition of mineral.
Using porosity in diagnosis
The porosity of the subsurface lesion can be turned to some advantage
by the clinician. First it explains why the white spot lesion looks white
and why a dentist, looking at a clean tooth surface can, using vision and a
three-in-one syringe, determine the depth of penetration of the lesion. The
lesion that is only visible on a dry tooth surface is probably in the outer
enamel; whereas, a lesion visible on a wet tooth surface has penetrated
most of the way through the enamel and maybe into the dentine. This
relates to the relative refractive indices of enamel, water, and air. Enamel
has a refractive index of 1.62. In the sub-surface lesion, the pores are
filled with a watery medium of refractive index 1.33.
The difference in refractive index between water and the enamel
affects the light scattering and makes the lesion look opaque. If the
surface is now dried, air, refractive index 1.0, replaces the water. The
difference in refractive index between the air and the enamel is now
greater than that between the water and the enamel. This means,
the
lesion becomes more obvious or an earlier lesion can be detected.
Porosity is the basis of many techniques that detect carious
lesions; for
instance, radiography, and two quantitative techniques,
quantitative light-
induced fluorescence and electrical
resistance. These techniques allow
quantitation of the degree of
porosity.
The dentist must be careful when using a sharp probe. It is very useful
to gently draw the point across the lesion to detect a matt surface
indicating an active lesion. It is, however, most unwise to jab the sharp
probe into the lesion to see whether it is ‘sticky’. The probe is likely to
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cause a cavity and this will encourage biofilm stagnation and lesion
progression.
Shape of the carious lesion
1- Determined by distribution of the biofilm.
2- Guided by the direction of enamel prisms.
3- On approximal surfaces; kidney shaped between contact facet and
gingival margin.
4- On occlusal surfaces: cone-shaped.
Caries management
Preventive treatment, and in cases in which cavities preclude plaque
control, operative treatment is also needed
Why the patient is a caries risk
The dentist needs to determine the relative importance of the various
caries-promoting factors for the individual patient. Unless the practitioner
and the patient can work together to find the cause of the problem
1-Plaque control: A disclosing agent should be used so that the patient
can see the relationship between plaque and carious lesions.
2-Diet: All patients designated as high risk should keep a diet sheet.
3- Fluoride history: The fluoride content of the water, toothpaste, and any
mouthwash the patient uses should be checked.
4- Salivary flow: Both stimulated and unstimulated salivary low should
be measured.
Some risk factors such as plaque control, diet, and fluoride use are
amenable to alteration by the patient. Other risk factors, such as a dry
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mouth, are less amenable to alteration. For instance, a patient with
Sjögren’s syndrome may always be at high risk and may always have to
make strenuous preventive efforts.
Mechanical Plaque Control
Regular disturbance of the biofilm with a toothpaste containing
fluoride will prevent the formation of visible lesions and will arrest
lesions that have already formed.
The dentist should check whether the patient’s toothpaste contains
fluoride. It is suggested that small children should use the adult, family
paste but a small pea-sized portion of toothpaste should be used. Small
children cannot spit and will, therefore, swallow the paste and this
precaution will avoid fluorosis.
The dentist should show the patient, and the parent in the case of a
child, the white spot lesions and then disclose the teeth. This will
demonstrate the relationship of the biofilm to the lesion.
Watching the patient in action with a toothbrush to remove the plaque,
helping improve technique where necessary.The patient should be
encouraged to feel the shiny, plaque-free surface with their tongue with
the aim of achieving this feel at home. The dentist should note whether
the patient can remove plaque. If the patient can but does not, the
problem is motivation not manual dexterity
With children, particular attention should be paid to the occlusal surface
of erupting teeth. The erupting tooth is below them line of the arch and
will be missed by the brush unless it is brought in at right angles to the
arch. It should be noted that an occlusal surface is most susceptible to
plaque stagnation.
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Use of fluoride
The dentist should check that the patient is using a fluoride toothpaste.
Some products formulated for sensitive teeth and some herbal toothpastes
do not contain fluoride. The paste should be used twice daily and cleared
from the mouth by spitting out only, rather than vigorously rinsing.
fluoride mouthrinse (0.05% sodium fluoride) used every day is a useful
fluoride supplement in a high-risk patient, althoughThese rinses should
not be used in children under 6 who cannot rinse and spit as there is a risk
of fluorosis if the solution is swallowed.
Application of fluoride varnish is a useful preventive measure, and
particularly valuable in those unlikely to comply with a daily mouthwash
regime.
Dietary advice
The sugar attacks have been highlighted, and the number of individual
attacks has been written at the top. This gives the dentist the opportunity
to explain the Stephen curve and the importance of decreasing the
frequency of sugar intake. The dentist should try to get the patient to
suggest changes.
Fissure sealing
An additional preventive tool to halt caries progression is fissure
sealing. If the patient or parent cannot totally prevent the establishment of
the biofilm in pits and fissures of the erupting or erupted teeth, then we
need to look at alternative means of protecting these vulnerable sites.
Occluding the pit or fissure mechanically is one such means.
Fissure sealants are materials that are chemico-mechanically retained
within the pit or fissure, and thus prevent the ingress of biofilm. Provided
the sealant material is retained in its entirety and that there is no marginal
leakage, such vulnerable sites remain free of caries
.