Transcript Summary of Lecture # 2 October 3, 2007 Abdullah S. Al-Swuailem BDS, MS, MPH, Dr PH.

Summary of Lecture # 2
October 3, 2007
Abdullah S. Al-Swuailem BDS, MS, MPH, Dr PH
Bacterial Plaque
-
Biolfim bacteria behave differently from
Planktonic (liquid-phase) cells. Bacteria growing in
biofilm are more resistant to host defence
mechanisms and exogenous antimicrobial agents.
Thus mechanical removal of bacterial biofilm is
needed to have effective antimicrobial therapy
- subsurface pellicle vs. acquired pellicle
Bacterial Plaque

1.
2.
3.
4.
Factors influencing the build-up of dental
plaque:
Mechanical displacement (chewing, tongue
movement, oral hygiene aids)
Stagnation (colonization in sheltered
environments, e.g. inter-proximal area)
Availability of nutrients
Interactions between the microbes and the
host’s inflammatory immune system
Bacterial Plaque

-
-
-
-
Plaque formation:
Within 2 hours, initial plaque formation begins as a
series of isolated bacterial colonies confined to tooth
surface irregularities
In about 2 days, the plaque double in mass and
bacterial colonies coalesce
In the first 4-5 days of plaque formation, the number
of bacteria increase significantly
After approximately 21 days, bacterial replication
slows so that plaque accumulation becomes relatively
stable. Bacteria in the deeper portion of the
developing plaque are either facultative or obligate
anaerobes
Bacterial Plaque

-
-
-
Dental calculus:
Supra-gingival calculus:
located coronal to gingival margin and frequently
develops opposite to duct orifices of major salivary glands.
30% mineralized. Yellow to white chalky mass
Sub-gingival calculus:
Located below the gingival margin and derived its
minerals from crevicular fluids within the gingival sulcus.
It is thinner and harder (60% mineralized) than supragingival calculus. Gray to black in color.
Calculus formation can be inhibited by using agents
containing pyrophosphate or metal ions such as zinc
Dental Caries
Learning objectives:
-
-
Be able to define the dental caries and know the
different types of dental caries and the process of
disease initiation and progression
Know the risk factors associated with root caries
Explain how Stephan’s curve is plotted and its
significance
Recognize methods to prevent dental caries
Know the difference between gingivitis and
periodontitis
Understand how periodontal disease can be
prevented
Dental Caries


-
-
Definition of tooth cavitation: localized , posteruptive pathological process involving bacterial
acid demineralization of hard tooth tissue resulting
in the formation of a cavity.
Theories of caries:
Worm theory
Vital theory (1700s)
Chemo-parasitic theory (W.D Miller 1890)
Dental Caries

1.
2.
3.
4.
Types of caries lesions:
Pit and fissure caries
Smooth surface caries
Root surface caries
Secondary (recurrent) caries
Dental Caries


Mature enamel is composed of 95% inorganic
(minerals) and 5% organic material and water
(Fig 3-5).
Enamel of a newly erupted tooth is not fully
mineralized. Therefore, newly erupted teeth are
more susceptible for caries than teeth that have
been present in the mouth for some time.
Dental Caries

1.
2.
3.

Stages of dental caries:
Incipient lesion
Lesion extending to or beyond DE junction
Frank lesion with cavitation
In theory, caries extending to dentin with intact
enamel surface can be slowly be remineralized
(ten Cate, 2001)
Dental Caries

-
-
Incipient lesion
Characterized by white spot on the enamel
surface.
In fissure caries, usually occurs bilaterally on the
two surfaces at the orifice of the fissure and
eventually coalesces at the base
The surface enamel is usually intact and lesion is
located subsurface
Dental Caries

1.
2.
3.
4.

Progression of caries depends on
Ions concentration
pH
Salivary flow
Buffering action
Plaque acids dissolve first the magnesium and
carbonate ions and followed later by less soluble
ions such as calcium and phosphate ions.
Dental Caries



For caries to develop, acidogenic bacteria must
be present and a means must exist to prevent the
acid from being washed away.
Germ-free animals do not develop caries even
when fed cariogenic diet (Orland et al 1954)
Mutans streptococci and lactobacilli are the two
major acidogenic bacteria
Dental Caries

1.
2.
3.
4.
5.

Mutans streptococci:
Ability to adhere to tooth surfaces
Production of abundant insoluble extracellular
polysaccharides (glucan)
Production of intracellular polysaccharides
Rapid production of lactic acid
Acid tolerance
Damage observed in carious lesion is due to lactic
acid, although other acids are present within the
plaque
Dental Caries

-
-
Lactobacilli:
LB does not play a major role in carious lesion
initiation, but important in the progression of
lesion
With established low pH, the number of LB
increases and the number of MS decreases.
Dental Caries

-
-
Ecology of dental caries:
Before teeth eruption the number of MS is very
low
The source of infection of infant by MS is from
caregiver (usually the mother) by mouth-tomouth transmission via kissing or sharing spoon
during feeding
Dental Caries

-
-
-
Root Caries:
Individuals are living longer and therefore
retained teeth may develop root caries associated
with gingival recession
Most seniors are consuming medications known
to reduce the salivary flow and therefore increase
the risk of root caries
Prevention of root caries can be achieved by
preventing periodontal disease
Dental Caries

-
Stephan Curve:
Named after Dr. Robert Stephan
Showed the effect of eating or drinking different
foods and beverages on plaque pH (Fig 3-9)
Dental Caries

Demineralization and remineralization:
-
Long term exposure of teeth to low concentration of fluoride
(as in fluoridated water) results in gradual incorporation of
fluoride into existing hydroxyapatite (HAP) crystals to form
fluorhydroxyapatite (FHA) that is more resistant to acid
damage. This form is known to be firmly bound fluoride
Topical application of higher concentration of fluoride to the
tooth surface results in the formation of surface globules of
calcium fluoride that is subsequently covered with phosphate
and proteins from saliva rendering these globules more
insoluble. This form is known to be loosely bound fluoride
-
Dental Caries

Demineralization and remineralization:
-
Following an attack by the plaque acids, the CaF2 dissolve
first followed by HAP and finally FHA.
With the increase of ions concentration, the crystals
dissolution slows.
New HAP and FHA reform to fill the defect with most of
fluoride ions coming from CaF2 and newly adsorb CaF2
-
-
Dental Caries

Demineralization and remineralization:
-
Use of fluoride varnish:
Some studies have shown that biannual application of fluoride
varnish may stop the activity of 81% of active enamel caries
on primary teeth
Periodontal Disease

Definition: periodontal disease is a
dental plaque-induced disease
affecting the supporting tissue of
the tooth (periodontium). It ranges
from mild reversible form
(gingivitis) to a more severe and
irreversible form (periodontitis).
Periodontal Disease

Structures of periodontium
Periodontal Disease

Gingivitis: An inflammation process of the
gingiva in which the junctional epithelium,
although altered by the disease, remains
attached to the tooth at its original level.

Periodontitis: An inflammation condition of the
gingival tissues, characterized by loss of
attachment of the periodontal ligament and the
bony support of the tooth
Periodontal Disease

Factors affecting the PD:
1.
Bacterial plaque
Patient’s medical conditions
Patient’s environmental factors
Patient’s genetic background
2.
3.
4.
Periodontal Disease

Development of gingivitis
-
Gingivitis can be observed 9-21 days after cessation
of oral hygiene measures in a healthy mouth
-
The degree of gingival inflammation depends on the
amount of plaque accumulation
Periodontal Disease

Development of gingivitis
-
Damaged caused by gingivitis can be reversed by
practicing removing the cause of disease, i.e., dental
plaque and calculus
Systemic conditions such as pregnancy or hormonal
imbalance may exaggerate gingival tissue response
to bacterial presence in the dental plaque
Similar reactions maybe also seen with certain
drugs
-
-
Periodontal Disease

Development of gingivitis
-
Clinical changes observed with gingivitis:
Alterations in color (pink
red)
Knife-edge margin of free gingiva
rolled
Gingiva firm consistency
Spongy consistency
Bleeding maybe observed
1.
2.
3.
4.
Periodontal Disease

Periodontal Microflora
-
Periodontal disease process is
understood in the frame of two
Hypotheses:
Non-specific plaque Hypothesis
Specific plaque Hypothesis
1.
2.
Periodontal Disease


All periodontitis is preceded by gingivitis
progresses, but not all untreated gingivitis
progresses to periodontitis
The development of periodontal pocket
(pathological) implies that there is apical
migration of junctional epithelium
Periodontal Disease

1.
2.
-
3.
Prevention of periodontal disease
Mechanical plaque control:
Regular toothbrushing
Routine use of dental floss
Chemical plaque control:
Use of mouth rinses such as chlorhexidine
Topical fluoride maybe used to prevent root caries
Removal of local factors such as calculus (via
scaling) or restorations with defective margin (i.e.
new restorations)
Tooth-Brushes and
Tooth Brushing Methods