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Managing Caries in Ename
l
Dr Raya Al-Naimi
lect.3
second term
Dental caries is a process which may take place on any tooth surface in
the oral cavity where a microbial biofilm (dental plaque) is allowed to
develop over a period of time.
Formation of the biofilm is a natural physiological process. It is important
to remember that the biofilm is not a haphazard collection of micro-
organisms, but a community with a collective physiology, which can
solve the specific physico-chemical problems posed by the environment
at the site. The bacteria in the biofilm are always metabolically active,
causing minute fluctuations in pH. These may cause a net loss of mineral
from the tooth when the pH is dropping. This is called demineralization.
Alternatively, there may be a net gain of mineral when the pH is
increasing. This is called remineralization. The cumulative result of these
de- and remineralization processes may be a net loss of mineral and a
carious lesion that can be seen. Alternatively, the changes may be so
slight that a carious lesion never becomes apparent.
The formation of the biofilm and its metabolic activity cannot be
prevented, but disease progression can be controlled so that a clinically
visible. enamel lesion never forms. management depends on appreciating
that the deand remineralization processes can be modified. For instance,
if the biofilm is partially or totally removed, mineral loss may be stopped
or even reversed towards mineral gain.
Keyes (1954) was the first to explain the interplay between local cariogenic
bacteria in plaque, fermentable carbohydrates, constitutional factors (related to
species and strains) and tooth structure. Dental caries was shown to be an
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infectious process of teeth with the interplay of three principal factors: the
host, microflora and diet. Even though knowledge of the biological
determinants and the interactions among the different factors has increased,
this model is still valid today.
Factors which influence the magnitude of the pH fluctuations
are also very important and many of these can be influenced
1- The composition and thickness of the microbial deposits,
2- The diet.
3-Fluoride ion concentration.
4- The salivary secretion.
These biological factors can in turn be influenced by various sociological
parameters such as a person’s behaviour, attitudes, their knowledge and
beliefs.
The carious process and the carious lesion
Carious lesions can form on any tooth surface exposed to the mouth; thus
they can form on enamel, cementum, or dentine. Principles of
management of the process are the same, irrespective of the tooth tissue
involved.
The term
“caries”
can be used to refer to both the caries process and the
caries lesion that forms as a result of that process.
The concept of activity
1-The caries process may or may not be progressive.
2- Lesions may be active.
3- Lesions may be arrested—by diet, oral hygiene, and use of fluorides.
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Caries risk assessment
Factors relevant to assessment of caries risk
High risk Low risk
1-Social history
Socially deprived middle class
High caries in siblings low caries in siblings
Low knowledge of disease Dentally aware
Irregular dental attendance regular dental attendance
Snacking very much No regular snacking
2-Medical history
Medically compromised No problem medically
Disabled No physical problem
Xerostomia Normal flow of saliva
Medicinal syrups for long period of time No long term medication
3-Dietary habit
Frequent intake of sugar Infrequent intake of sugar
4-Fluorides
Non fluoridated area Fluoridated area
No fluoride supplements Fluoridated supplements
No fluoridated toothpaste Fluoridated toothpaste
5-Plaque control
Infrequent,ineffective cleaning Frequent ,effective cleaning
Poor manual dexterity Good manual dexterity
6-Saliva
Low flow rate Normal flow rate
Low buffering capacity High buffering capacity
Increased counts of S mutans Low counts of Sterp. Mutans
Increased Lactobacillus counts Low counts of lactobacillus
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7-Clinical evidence
New lesions evident No new lesions
Premature extraction of primary No extractions of primary
Anterior caries or restorations No or very few restorations
Repeated restorations Restorationsinserted years ago
with no recurrent caries
No fissure sealants Fissure sealants present
Orthodontic appliances, No orthodontic ,fixed or
fixed or removable prosthesis Removable or fixed prosthesis
Site predilection for the caries process
1- Any surface where the microbial biofilm remains undisturbed.
2- Partially erupted teeth.
3-Depth of the fissure system.
4- Approximally, below the contact point.
Enamel reactions during eruption
Once the enamel erupts into the oral cavity, it is covered by the
metabolically active biofilm and is continually modified by the
alternating de- and remineralizations of the carious process.
Eruption is an important time. The tooth emerges gradually over a
number of months. The partly erupted tooth does not participate in
mastication and it is difficult to clean. For these reasons, microbial
accumulation is enhanced, and during this time there are many episodes
of de- and remineralization. This is the carious process at a sub-clinical
level.
The deeper parts of the fissure system are particularly protected from
removal of the biofilm and visible signs of caries may develop where
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bacterial deposits remain for the longest period of time. A similar
situation exists approximally because bacteria are protected beneath the
contact point and along the gingival margin, where plaque control may
also be poor.
Carious lesions occure in site where microbial deposits are likely to
remain undisturbed. These areas, although not unique chemically, may
well develop clinically visible lesions..
Ultra structural changes in enamel related to the biofilm
An elegant series of in vivo experiments followed the development of the
initial lesion formed under an undisturbed biofilm. The investigators
created these conditions by cementing bands onto teeth which were
subsequently extracted for orthodontic purposes. The bands prevented
mechanical disturbance of the plaque. After various periods of time, the
bands were removed and replicas of the surfaces taken for scanning
electron microscopy. The teeth were then left uncovered, and mechanical
plaque control was resumed, with further replicas showing how the surface
reacted to resumption of biofilm removal.
After one week of undisturbed biofilm formation, no changes in the
enamel were seen clinically, even after samples had been careful air-dried.
However, at the ultrastructural level, there were signs of direct dissolution
of the outer enamel surface. This was seen as an enlargement of the
intercrystalline spaces due to partial dissolution of the individual crystal
peripheries.
After two weeks with completely undisturbed plaque, the enamel changes
were visible clinically after samples were air-dried. The “white spot”
lesion was now visible. After three and four weeks, these changes could be
seen before samples were air-dried, the lesion being opaque with a matte
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surface. Ultrastructurally, there was: complete dissolution of the thin
perikymata
overlappings;
marked
dissolution
corresponding
to
developmental irregularities such as Tomes’ processes, pits, and focal
holes; and continued enlargement of the intercrystalline spaces.
Thus, the surface participates in the enamel reaction from the very
beginning of lesion formation by direct dissolution of the outermost
microsurface and enlargement of intercrystalline diffusion pathways. This
direct surface erosion is most likely partly responsible for the matte surface
of the active lesion.
When the orthodontic bands were removed, allowing for disturbance of
the biofilm, the white appearance diminished and the surface became hard
and shiny again. Ultrastructural studies showed wear of the external
microsurface. This led the authors to suggest that the return to a shiny, hard
surface was a result of abrasion or polishing of the partly dissolved surface
of the active lesion. This important series of experiments shows the precise
relationship of the lesion to the biofilm and shows that regular disturbance
of the biofilm will arrest the lesion.