9. • 'Caries' is Latin for 'rot' or 'rotten'.
• Dental caries means rotten teeth.
• Caries is the noun which names the disease
• Carious is the adjective, not 'a caries‘,
• 'a carious area' or 'an area of caries'.
10. Dental caries can be defined as
• Chronic progressive deconstructive
disease of hard dental tissues
• Bacterial infected diseases caused by
specific bacteria
• a reversible multifactorial process of
tooth demineralization and
remineralization.
11. Dental caries
• Dental caries, a bacterial infection, may be
define as a posteruptive pathological
process of external origin, involving the
softening of the hard dental tissue and
proceeding to cavity formation. This is
distinct from the dissolution of the hard
dental tissues of an unerupted tooth which
is not dental caries but tooth resorption.
12. The carious process
a pathological process of localized destruction of calcified
tooth tissues by acids produced by organisms. Etiologically
caries is considered a multi-factorial disease, which
involves interplay between the host (saliva and teeth) micro
organisms (streptococcus mutans), and the substrate
(dietary carbohydrate sucrose), with the production of
Lactic acid. Dental plaque (Bio-film) serves as the medium
for caries development.
13. Basic pathological changes
• demineralization of inorganic tissues of
tooth
• Disintegration of the organic tissues of
tooth
• involves enamel, dentin, cementum
15. Measuring caries activity
Prevalence rate （患病率）：
is the proportion of a population affected by a
disease of a condition at one point time.
Incidence （发病率）：
is a mesurement of the rate at which a disease
progresses the increase or decrease in the
number of new cases occurring in a population
within the same time period
16. DMF index
• D the mean number of decayed teeth with untreated
carious lesions
• M the mean number of teeth which have been
extracted and are therefore missing
• F the mean number of filled teeth
• DMF(T) to denote decayed,missing, and filled teeth
• DMF(S) to denote decayed,missing, and filled surfaces
in permanent teeth
• dmf(t) dmf(s) similar indices for the primary dentition
19. distribution of dental caries
according to tooth surface
• Occlusal > interproximal >buccal
20. Caries is world wide in its distribution
1. The prevalence of dental caries increases with the
development of economy
2. High DMF before 1970 in the industrialized country
To decrease after 1970 in the industrialized country
4. More prevalence in industrialized than in the third word
country
5. Caries experience tends to increase in the developing
country and decline in many western countries.
6. Caries experience is higher in urban than in rural
communities in developing countries.
21. • Prevalence of dental caries
(1995) ， special for 12-18Y age groupsis
increased significantly （ 20-40% ）
• In recent 10 years, prevalence of dental
caries in primary dentition is increased
significantly than the permanent
22. Why has caries prevalence decreased
in modern population?
The is possibly attributable to
2. The fluoridation of drinking water, use of
fluoride toothpastes and improved oral
health
3. A changing pattern of sugar consumption
4. A decrease in virulence( 毒力 ) of the
organsims
24. The organic deposits on the enamel surface
原发性釉护膜 (primary enamel cuticle)
残余釉上皮 （ reduced enamel epithelium)
获得性膜 （ acquired pellicle ）
食物碎片 （ food debris, material alba ）
牙菌斑（ dental plaque ）
牙结石（ calculus, tartar ）
25. four factors is essential for the
initiation of dental caries, namely:
1.Micro-organism
b.mutans streptococci
c.Lactobacilli
d.Actinomyces
26. 1. Substrate
• Refined carbohydrates( 精制碳水化合物 ) such
as sucrose 蔗糖 provide a suitable substrate on
which the cariogenic micro-organisms act to
produce the acids that lead to dissolution of the
hard dental tissues
• Caries experience is influenced by the quantity,
quality and especially frequency of consumption
of the refined carbohydrate
27. 1. Susceptible teeth 易感牙
• The ingestion of fluorides during tooth
mineralization leads to the formation of fluor-
apatite in enamel. Its presence in enamel makes
the tooth less susceptible to dental caries because
it is less soluble in acid than the
hydroxyapatite( 羟磷灰石 ) which is normally
present in the hard dental tissues
28. 1. Time
• All the factors should be present for
sufficiently long time for the caries
process to be initiated.
31. STRUCTURE OF DENTAL PLAQUE
Plaque on smooth surface
Plaque-dental surface
Middle layer---- condensed microbial layer
body of plaque
The surface layer of plaque
Plaque in pit and fissure
32. Composition of Dental plaque
• bacteria which form 50-70% of dental plaque
a small number of epithelial cells
Leukocytes
Macrophages
• glycoproteins which, together with extracellular polysaccharides, form
the plaque matrix
• mucopolysaccharides ( 粘多糖 ) such as glucans and fructans( 右旋糖
)
• Inorganic components
calcium
phosphorus
fluorides
.
33.
34. MECHANISMS OF PLAQUE FORMATION
The attachment, growth, removal and
reattachment of bacteria to the tooth surface
is a continuous and dynamic process.
35. Several distinct processes can be recognized
Absorption of salivary proteins and
glycoproteins, together with some bacterial
molecules, to the tooth surface to form a
conditioning film (the acquired pellicle).—— 获
得性膜的形成
non-specific interaction of microbial cell surfaces
with the acquired pellicle via van der Walls
attractive forces.
36. • Irreversible adhesion can occur if specific
inter-molecular interactions take place
between adhesions on the cell surface and
receptors in the acquired pellicle.
37. • Secondary or late-colonizers attach to
primary colonizers (coaggregation 共集 ),
also by specific inter-molecular
interactions.
38. FORMATION AND DEVELOPMENT OF DENTAL PLAQUE
• Formation of acquired pellicle and
primary aggregation
• Bacteria growth and development
• The mature of dental plaque
39. Development
Pellicle formation
– Microorganisms do not attach thermselves
directly to the mineralized tooth surface
and the teeth are always covered by an a
cellular proteinaceous film, the pellicle
– Forms on the “naked” tooth surface within
minutes to hours
40. Major constituents of Pellicle
• Salivary glycoproterns
• Carbohydrates
• Lipid
• a lesser extent components from
the gingival crevicular fluid( 龈
沟液 )
41. Function of Pellicle
• Because of its selective nature restrict
transportation of irons in and out of the
dental hard tissue. It may play an important
modifying role in caries
• Provide further protection against
demineralization of the enamel
• Modify the number of potential adsorption
sites for different bacterial species
• As the substrate for the microorganisms
42. microbial colonization
Initial microbial colonization
• streptococcus mutans( 变形链球菌 )
accounting for 56% of the total initial microflora
• Actinomyces spp( 放线菌 )
a minor proportion
• gram-negative bacteria(G-)
43.
44. Microbial succession
• The initial establishment of a streptococcal
flora appears to be a necessary antecedent
for the subsequent proliferation of other
organisms
• The most striking changed is shift from
streptococcus-dominated plaque to plaque
dominated by Actinomyces.
45.
46. MICROBIAL AETIOLOGY OF CARIES
• animal studies
micro-organisms are involved in the
aetiology of dental caries
48. Cariogenic properties
( 致龋菌的特性 )
• they are able to produce acid rapidly from
fermentable carbohydrates (acidogenic).
• They thrive under acid conditions
(aciduric)
• able to adhere to the tooth surface because
of their ability to synthesize sticky
extracelluar polysaccharides from dietary
sugars
49. Micro-organism and caries
• Advanced lesions often have a high proportion of
lactobacilli
• dentinal lesions have a diverse micro flora with many
Gram positive Gram negative bacteria.
• Root surface caries was originally associated with
Actinomyces spp. but recent studies suggest a similar
aetiology to enamel caries
• Rampant caries can occur in xerostomic patients and in
infants fed with high levels of sugar in pacifiers (nursing
bottle caries). The plaque contains high levels of mutans
streptococci and lactobacilli.
51. 1. Chemico-parasitic theory
( 化学细菌学说 )
• This postulates that oral bacteria act on
sugar to produce acid which demineralizes
the inorganic component of enamel,
resulting in the development of a carious
lesion.
52. 1. Proteolytic theory( 蛋白溶解学说 )
• It is thought that the organic component of
enamel is first broken down by proteolytic
enzymes, opening up path-ways for bacteria
to attack the enamel by other processes such
as by acid or by chelation.
53. 1. Chelation theory( 螯合学说 )
• This postulates that enamel is
demineralized by chelating agents at neutral
pH.
• Protein breakdown products as well as
lactic acid are some chelating agents known
to exist in nature.
54. 1. Auto-immunity theory
• In this theory, it is suggested that 'forbidden
clones' of lymphocytes attack target cells
(odontoblasts) rendering the tooth
vulnerable to caries attack.
55. • Four foctors theories
microorganisms
The four circle diagrammatically
represent the parameters
Host involved in the carious process.
& caries substrate
All four factors must be acting
tooth
concurrently (overlapping of the
circles) for caries to occur.
time
56. The role of dietary carbohydrate
• Nutrition ------
systemic dietary effects
• Diet ------
local dietary effects
57. epidemiological studies
Caries prevalence is low in populations
adhering to a primitive way of living and
a diet of local products with little sugar
A drastic increase in caries is invariably
seen when these population
“improve”their standard of living and
adopt a modern “civilized”diet with high
sugar content
A strong correlation between caries
development and sugar consumption
58. Sucrose( 蔗糖 )------called the arch-criminal in
dental caries
Monosaccharides ,disaccharides and of the
polysaccharide starch can be fermented to acid
by the plaque bacteria
Sorbitol （山梨糖） xylitol ( 木糖醇 )
-----sugar substitutes used in sugar-free
chewing-gums
Dietary habits and caries prevalence
59. Host & tooth (susceptible teeth)
• It was a clinical experience that not all
individuals with poor oral hygiene and
frequent sugar consumption develop caries
• In the laboratory, extracted teeth exposed
to the same acidic buffer challenge
certainly do not develop artificatial caries-
like lesions to the same degree within a
short period of time
60. Host & tooth
• Tooth morphology: susceptible sites
• Environment of the tooth:
» Saliva
» fluoride
61. • Tooth morphology bacterial plaque is an essential precursor
of caries , sites on the tooth surface which favour palque
retention and stagnation are particularly prone to decay
• Saliva under normal conditions, the tooth is continually
bathed in saliva. It is capable of remineralizing the early
carious lesion because it is supersaturated with Ca and P.
when salivary buffering capacity has been lost, a low Ph
environment is encouraged and persists longer
• Fluoride particular interest was the discovery of the
association between fluoride concentration in water supplies
and prevalence of dental caries in children
62. Time
1. It is evident that the mere existence of the
three factors operating together does not
result in instantaneous mineral loss
2. therefore a fourth circle is often added to
stress the time dimension taken for dental
caries to develop
63. Other factors
•Age
•Sex
•Geography
•Race
•Economics status
•Nutrition
•Health status
