EPIDEMIOLOGY OF PERIODONTAL DISEASE

1. Epidemiology of Periodontal
Diseases
DR SINDHURA
READER,
DEPT. OF PERIODONTICS
NAVODAYA DENTAL COLLEGE AND HOSPITAL
1

2. INTRODUCTION
2

3. DEFINITION
Epidemiology is defined as ‘the study of the
distribution of disease or a physiologic
condition in human populations and of the
factors that influence this distribution’
(Lilienfeld, 1978).
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4. AIMS OF EPIDEMIOLOGY
 To describe the distribution & magnitude of
health & disease problems in human
populations.
 To identify aetiological factors in the
pathogenesis of disease.
 To provide the data essential to the planning,
implementation & evaluation of services for
the prevention, control & treatment of
disease.
4

5. INCIDENCE
The number of new cases of a specific
disease occurring in a defined population
during a specified period of time.
Incidence = New cases X 1000
Population at risk
Uses of incidence rate:
To control disease
For research into etiology &
pathogenesis, distribution of disease &
efficacy of preventive & therapeutic
measures
(WHO, 1981)
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6. 6

7. PREVALENCE
Indicates all current cases (old & new) of a
particular disease existing in a given
population at a given point in time, or over a
period of time.
 POINT PREVALENCE:
Total no. of cases at a given point in time X 100
Estimated total population
 PERIOD PREVALENCE:
Total no of cases during a given time interval X100
Estimated mid-interval population at risk
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8. Relation between incidence
& prevalence
Prevalence = Incidence X Duration
8

9. Uses of prevalence
To estimate the magnitude of health/disease
problems in the community & identify
potential high risk populations
For administrative & planning purposes eg
manpower needs, rehabilitation facilities etc.
9

10. EPIDEMIOLOGICAL METHODS
OBSERVATIONAL STUDIES EXPERIMENTAL
STUDIES /
INTERVENTION
STUDIES
DESCRIPTIVE
STUDIES
ANALYTICAL
STUDIES
CASE CONTROL STUDIES
COHORT STUDIES
RANDOMIZED
CONTROL
TRIALS
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11. DESCRIPTIVE EPIDEMIOLOGY
1) Defining the population
2) Defining the disease
3) Describing disease in terms of :
- Time, Place, Person
4) Measurement of disease
5) Comparing with known indices
6) Formulating of etiological hypothesis
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12. analytical studies
Two types :
Case control study
Cohort study
From each of these study one can determine :
(a) Whether or not a statistical association exists
between a disease and a suspected factor; and
(b) If one exists the strength of the Association.
12

13. CASE CONTROL STUDY
Retrospective study
First approach to test causal hypothesis
Has three distinct features :
Both exposure and outcome (disease) have
occurred before the start of the study.
The study proceeds backwards from effect to
cause
It uses a control or comparison group to
support or refute an inference.
13

14. ADVANTAGES
Relatively easy to carry out
Rapid and inexpensive
Require comparatively few subjects
Particularly suitable to investigate rare diseases
No risk to subjects
Allows the study of several different aetiological
factors
Risk factors can be identified. Rational
prevention and control programmes can be
established
No attrition problems, because case control
studies do not require follow-up of individuals in
the future.
Ethical problems minimal
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15. DISADVANTAGES
Problems of bias
Selection of an appropriate control group may
be difficult
We cannot measure incidence, and can only
estimate the relative risk
Do not distinguish between causes and
associated factors
Not suited to the evaluation of therapy or
prophylaxis of disease
Another major concern is the
representativeness of cases and controls.
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16. COHORT STUDY
Distinguishing features:
Cohorts are identified prior to the
appearance of the disease under
investigation
Study groups are observed over a period of
time to determine the frequency of disease
among them
Study proceeds forward from cause to
effect.
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17. Indications
When there is good evidence of an
association between exposure and disease
When exposure is rare, but the incidence of
disease is high among exposed
When attrition of study population can be
minimized and
When ample funds are available.
17

18. Types of Cohort studies
Prospective cohort studies In which the disease has
not yet occurred at the time the investigation begins
Retrospective cohort studies In which the outcome have
all occurred before the start of the investigation
Combination of retrospective and prospective cohort
studies Cohort is identified from past records & is
followed up for future assessment of outcome
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19. Advantages
Incidence can be calculated
Several possible outcomes related to
exposure can be studied simultaneously
Provide a direct estimate of relative risk
Dose-response ratio can also be calculated
Since comparison groups are formed before
disease develops, certain forms of bias can
be minimized like misclassification of
individuals into exposed & unexposed
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20. Disadvantages
Involve a large number of people.
Takes a long time to complete the study and
obtain results
It is not unusual to lose a substantial
proportion of the original cohort—they may
migrate, lose interest in the study or simply
refuse to provide any required information.
There may be changes in the standard
methods or diagnostic criteria of the disease
over prolonged follow-up.
Expensive.
20

21. Case Control study
 Proceeds from "effect to
cause".
 Starts with the diseases
 Tests whether the suspected
cause occurs more
frequently in those with the
disease than among those
without the disease.
 Usually the first approach
to the testing of a
hypothesis, but also useful
for exploratory studies.
Cohort study
•Proceeds from "cause to
effect".
•Starts with people exposed to
risk factor or suspected cause.
•Tests whether disease occurs
more frequently in those
exposed, than in those not
similarly exposed.
•Reserved for testing of
precisely formulated
hypothesis.

22.  Involves fewer number of
subjects
 Yields relatively quick results
 Suitable for the study of rare
diseases
 Generally yields only estimate
of RR (odds ratio)
 Cannot yield information about
diseases other than that selected
for study
 Relatively inexpensive
•Involves larger number of
subjects
•Long follow-up period needed,
involving delayed results.
•Inappropriate when the disease or
exposure under investigation is
rare.
•Yield Incidence rates
•Can yield information about more
than one diseases outcome.
•Expensive

23. EXPERIMENTAL EPIDEMIOLOGY
AIMS:
To provide scientific proof of aetiological or
risk factors which may permit the modification
or control of those diseases
To provide a method of measuring the
effectiveness & efficiency of health services
for the prevention, control & treatment of
disease & improve the health of the
community
2 types
Randomized control trials
Non randomized or non experimental trials
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24. Randomized control trials
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Select suitable population
(Refrence or target population)
Select suitable sample
(Experimental or study population)
Make necessary exclusions
Randomize
Experimental group Control group
Manipulation & follow up
Assessment
Not eligible
Do not give
consent

25. METHODS OF MEASURING
ORAL DISEASES
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26. 26
INDEX- Numerical value describing the
relative status of a population on a
graduated scale with definite upper and
lower limits, which is designed to permit
and facilitate comparison with other
populations classified by the same criteria
and methods.
(Russel A.L. , 1969)

27. IDEAL REQUISITES OF AN
INDEX
 Clarity, Simplicity and objectivity.
 Validity.
 Reliability.
 Quantifiability.
 Sensitivity.
 Specificity.
 Acceptability.
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28. PURPOSES AND USES OF AN
INDEX
For individual patients
Provide individual assessment to help a patient
recognise an oral problem.
Reveal the degree of effectiveness of present
oral hygiene practices.
Motivate the person in preventive and
professional care for the elimination and control
of oral disease.
Evaluate the success of individual and
professional treatment over a period of time by
comparing index scores.
Provide a means for personal assessment by the
dental hygienist of abilities to educate and
motivate individual patient.
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29. In Research
 Determine baseline data before experimental
factors are introduced.
 Measure the effectiveness of specific agents for
the prevention, control or treatment of oral
conditions.
 Measure the effectiveness of mechanical devices
for personal care, such as Toothbrushes,
Interdental cleaning devices etc.
In community Health
 Show the prevalence and trends of incidence of a
particular condition occurring within a given
population.
 Provide baseline data to show existing dental
health practices.
 Assess the needs of a community.
 Compare the effects of a community program and
evaluate the results.
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30. CLASSIFICATION OF INDICES
 Irreversible Index
 Reversible Index
 Full Mouth Indices
 Simplified Indices
37

31. ASSEMENT OF ETIOLOGIC
AGENTS & THE RESULT OF
ORAL HYGINE PRACTICES
 Oral hygiene index- Greene & vermillion 1960, 1964
 Plaque index- Ramfjord 1959,1967
 Plaque index- Quigley & Hein, 1962
 Plaque index- Silness & Loe, 1964
 Plaque control record- O’Leary, Drake & Naylor 1972
 Patient hygiene performance index- Podshadley & Haley, 1968
38

32. SIMPLIFIED ORAL HYGIENE
INDEX (OHI-S)
John C. Greene and Jack R. Vermillion. (1964)
SURFACES AND TEETH TO BE EXAMINED
16- Buccal
11- Labial
26- Buccal
36- Lingual
31- Labial
46- Lingual
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33. DEBRIS INDEX - SIMPLIFIED (DI-S)
SCORE CRITERIA
0 No debris or stain present
1 Soft debris covering ≤ 1/3rd of the tooth
surface, And/or presence of extrinsic
stains without debris regardless of
surface area covered
2 Soft debris covering >1/3rd, but ≤2/3rd of
the exposed tooth surface.
3 Soft debris covering >2/3rd of the
exposed tooth surface 40
"Oral Debris" : soft foreign matter loosely attached
to the teeth. It consists of mucin, bacteria and food.

34. CALCULUS INDEX -
SIMPLIFIED (CI-S)
 "Oral Calculus" : Deposit of inoranganic salts
composed primarily of calcium carbonate and
phosphate mixed with food debris, bacteria and
desquamated epithelial cells.
 Supragingival Calculus- Deposits, usually white to
yellowish brown in colour
 Subgingival Calculus- Deposits, usually are light
brown to black in colour.
41

35. CALULUS INDEX (CI)
SCORE CRITERIA
0 No calculus present
1 Supragingival calculus covering ≤ 1/3rd of the
exposed tooth surface.
2 Supragingival calculus covering >1/3rd, but ≤
2/3rd of the exposed tooth surface and/or the
presence of individual flecks of subgingival
calculus around the cervical portion of the
tooth.
3 Supragingival calculus covering >2/3rd of the
exposed tooth surface and/or a continuous
heavy band of subgingival calculus around
the cervical portion of the tooth.
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36. CALCULATION OF INDEX
DI-S and CI-S values range from 0 to 3
 Good - 0.0 to 0.6
 Fair - 0.7 to 1.8
 Poor - 1.9 to 3.0
OHI-S value ranges from 0 to 6
 Good - 0.0 to 1.2
 Fair - 1.3 to 3.0
 Poor - 3.1 to 6.0
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OHI-S = DI-S + CI-S

37. PLAQUE
Highly variable specific entity resulting from the
colonization and growth of microorganisms on
the tooth surfaces, restorations, soft, tissues and
oral appliances.
“Schluger, Yodelis and Page” (1977)
44

38. PLAQUE COMPONENT OF THE
PERIODONTAL DISEASE
INDEX
S P. Ramfjord (1959)
INDEX TEETH
16 21 24 36 41 44
SURFACES SCORED
Facial
Lingual
Mesial
Distal
METHOD
Bismark brown solution
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39. SCORING CRITERIA
SCORE CRITERIA
0 No Plaque present
1 Plaque present on some but not on all
interproximal, buccal and lingual
surface of the tooth.
2 Plaque present on all interproximal,
buccal and lingual surfaces, but
covering < ½ of these surfaces.
3 Plaque extending over all
interproximal, buccal and lingual
surface, and covering > ½ of these
surfaces.
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40. Only fully erupted teeth should be
scored.
Missing teeth should be substituted.
CALCULATION:
Plaque Score of an Individual =
Total Score
No. of teeth examined.
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41. SHICK & ASH MODIFICATION OF PLAQUE
CRITERIA 1961.
SCORING SYSTEM
SCORE CRITERIA
0 Absence of dental plaque
1 Dental plaque in the interproximal areas or at
the gingival margin covering < 1/3rd of the
gingival half of the facial or lingual surface of
the tooth.
2 Dental plaque covering > I/3rd but < 2/3rd of the
gingival half of the facial or lingual surface of
the tooth
3 Dental plaque covering ≥ 2/3 rd of the gingival
half of the facial or lingual surface of the
tooth. 48

42. SEXTANTS
17-14 13-23 24-27
47- 44 43-33 34-37
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INDEX TEETH:
Age >20yrs.:-
17 16 11 26 27 47 46 31 36 37
PROBE:
WHO Periodontal examination probe
CPITN Probe
TRS 621-1978

43. CODES AND CRITERIA :
“
CODE X" : When 1 or no teeth are present in a sextant
(3rd molars are excluded unless they function in place
of 2nd molars)
"CODE 0" : Healthy Tissue : No signs of disease.
"CODE 1" : Bleeding observed during or after probing.
"CODE 2" : Calculus or other plaque retentive factors
such as ill-fitting crown or poorly adapted edges of
restorations are either seen or felt during probing.
"
50

44. CODE 3" : Pathological pocket of 4 mm or 5 mm
present, i.e. when the gingival margin is on the
black area of the probe.
"CODE 4" : Pathological pocket of ≥ 6 mm
present i.e. the black area of CPTIN probe is
not visible.
51

45. 52

46. TN - 0 A recording of code 0 (Healthy) or code
X (missing) for all six sextants indicates
that there is no need for treatment.
TN - 1 A code of I or higher indicates need for
improving the personal oral hygiene of
that individual
TN - 2 A code of 2 & 3 or higher indicates need
for professional cleaning of teeth and
removal of plaque retentive factors +
oral hygiene instructions
TN- 3 A code of 4 indicates need for ‘complex
treatment’ which involves deep scaling,
root planning, & more complex surgical
procedures
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CLASSIFICATION OF TREATMENT NEEDS

47. CALCULATION OF CPITN
Step I : Count the number of charts with different codes
and add up the codes individually (i.e. codes
0,1,2,3,4).
Step II : To obtain the prevalence (parentage) of
subjects with codes 0,1,2,3,4 as their score, divide
the counts of codes respectively, by the total
number of dentate subjects examined and multiply
by 100.
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48. ASSESSMENT OF VARIOUS
ADDITIONAL CONDITIONS
Retention index- Loe 1967
Mobility index- Ramjford 1967
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49. RETENTION INDEX
Loe 1967
SCORING CRITERIA
SCORE CRITERIA
0 No caries, no calculus, no imperfect margin
of dental restoration in a gingival location
1 Supragingival cavity, calculus or imperfect
margin of dental restoration
2 Subgingical cavity, calculus or imperfect
margin of dental restoration
3 Large cavity, abundance of calculus or
grossly insufficient marginal fit of dental
restoration in a supra- &/or subgingival
location
56

50. MOBILITY INDEX
Ramfjord 1967
SCORE CRITERIA
0 Physiologic mobility, firm tooth
1 Slightly increased mobility
2 Definite to considerable increase
in mobility, but no impairment of
function
3 Extreme mobility, a “loose” tooth
that cannot be used for normal
function
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SCORING CRITERIA

51. Prevalence of periodontal
diseases:
Prevalence Periodontitis in adults
58
Two samples : 1.565 Norwegian student.
2. 480 Sri Lankan tea laborers
.
Löe et al. (1978)
Norway/Sri Lanka
Norwegian group: excellent oral hygiene.
attachment loss; mean AL at the age of 30 < 1 mm.
Sri Lankan group: poor oral hygiene, abundant
plaque and calculus,
and AL at the mesial and facial aspects of all
attachment loss present at the age of 16, increasing
with age;
teeth mean AL at the age of 30 ≈ 3 mm,
a substantial number of
teeth with AL of > 10 mm
Norwegian group: excellent oral hygiene.
1

52. thank you