Periodontology
Lec. 5
‫سهى محمد سامي حسن‬.‫د‬
‫ – جراحة الفم والوجه والفكين‬-‫ماجستير‬
Dental calculus :
1. Definition
2. Types of calculus
3. Sub gingival calculus
4. Supra gingival calculus
5. Theories of calculus formation
6. Mode of attachment of calculus
calculus formation .
Calculus formation is preceded by the plaque formation ,
the plaque formation serve as an organic matrix for the
subsequent mineralization of the deposit .
Initially some crystals are seen in the inter microbial matrix
frequently in close apposition to the external aspect of
bacteria , gradually the matrix between the microorganism
becomes entirely calcified and eventually the bacteria also
become mineralized .
while the deposition of crystals within preformed plaque is
the usual mode of calculus formation , minerals may also be
deposited at the surface of supra gingival plaque
accumulation , in such foci the crystals are rod shaped and
these crystal are calcium phosphate precipitated as
Brushite .
The time required for supra gingival calculus
formation is about two weeks , the first evidence of
calcification may occur after few days however the
development of a deposit with crystal composition
characteristic of old calculus requires months or
years .
Attachment of calculus to the teeth .
Calculus often adhere firmly to teeth and sub gingival
calculus may be difficult to remove ,one reason for
its firm attachment to the tooth may be that the
pellicle beneath the plaque also calcifies so that
calculus crystals come into intimate contact with the
enamel , cementum or dentin crystals .
also calculus may be introduced inside the surface
irregularity ,so that calculus is virtually locked to
the tooth .
In case of periodontal disease small pieces of
cementum may be lost as a result of wear when the
periodontal ligament was still attached ,under such
conditions it becomes impossible to remove all
calculus without the loss of some of the tissues of
the teeth .
Theories of calculus formation:
Calculus has puzzled , there are two important
aspects must be explain it :
A. The nucleation of the crystallite .
B. Their growth .
1.Mineralization theory .
The saliva is super saturated with respect to the salts
and thus it is able to support crystal growth , but
that spontaneous precipitation does not occur unless
the solution is seeded crystals for this nucleation
process are present in the tooth surface but since
they are covered by a pellicle they can not be used
for this function .
2. Carbon dioxide theory .
It claims that freshly secreted saliva leaving the opening of
the salivary ducts has a CO2 tension of about of 60 mm Hg ,
expired air is lower than that it is about 29 mm Hg ,
the atmosphere is 0.3 mm Hg , this discrepancy will result in
the escape of CO2 from saliva , the PH will rise , when the
PH of saliva increase , less Ca and phosphorous can be
accommodated in the ionized form and consequently
spontaneous precipitation may occur , once crystallites are
present the physiological super saturation accounts for this
growth.
This theory explain the formation of calculus near the orifice
of the major salivary gland in copious amount.
it can not explain the formation of sub gingival calculus ,
which may be formed from the salts in the gingival exudates
.
3. Ammonia theory .
Ammonia is a break down product from urea and
might result in a local PH increase in plaque , the
PH of plaque is actually frequently above that of
saliva , this is attributed to proteolytic activity
which may result in the formation of amines , urea
and ammonia . proteolytic enzymes are present in
plaque , and a positive correlation has been found
between their proteolytic activity and calculus
formation .
It is thought that the organic matrix of plaque could
act as a seeding agent , when crystallization is
nucleated by a compound of different chemical
composition the phenomenon is termed epitaxis
.Although epitaxis has been claimed for the last 25
years to occur in biological mineralization including
calculus , the compound responsible has still not
been identified .
It is reasonable to assign bacteria a key role in a
possible mechanism for the mineralization
process .
this does not mean that they a lone are responsible
for producing nucleating compounds .
Effect of calculus on periodontal tissues :
Calculus by itself is harmless to the periodontal tissues except probably
the mechanical irritation of its structure to the periodontal tissues.
Also the presence of dental plaque always on the porous surface of
dental calculus make the calculus very harmful to the periodontal
tissues because here it will affect the periodontal tissues both
mechanically and chemically and can produce inflammatory
changes ,also calculus may interfere with the proper brushing
techniques .
so from those reasons calculus should be removed to prevent the
inflammation of the periodontal tissues .
Calculus should be removed also to keep the mechanical method s of
teeth brush more easy , since Calculus is considered to be one of the
major factors for plaque retention .