This document discusses methods for studying the prevalence, incidence, and etiology of periodontal diseases. It defines key terms like prevalence, incidence, and describes methods for measuring periodontal disease severity. The document also outlines different study designs used in periodontal research including descriptive, analytical, experimental and observational studies. It provides examples of different epidemiological study designs like case-control and cohort studies that are used to determine risk factors and causal relationships between exposures and periodontal outcomes.

4.  To describe the destribution and magnitude
of periodontal diseases
 To identify etiological factors and
pathogenesis of disease
 To study prognosis of the disease
 To provide data essential for prevention and
treatment of disease

5.  Prevalance is the proportion of persons in a
population who have the disease at a given
point in a period of time
PREVALANCE=NO OF PERSON WITH DISEASE
TOTAL NO OF PERSON IN POPULATION

6.  It is average percentage of unaffected person
who will develop the disease of interest
during a given period of time
Incidence = no of new cases
no of person at risk in population

7.  Probing depth
 Bleeding on probing
 Gingival recession
 Mobility of teeth
 Presence of furcation involvement
 Clinical attachment levels
 Microbiological measures
 Gingival crevicular fluid

12.  188 sites in patient that may or may not
bleed
1 bleeding site or 5 bleeding site regardless of
no of teeth
 ESI (extent and severity index)
 Consider the site where attachment loss is
more than 1mm
 E.g ESI(20,5.0)
 20% site examined has disease
 Attachment loss 5mm

13.  True endpoint:
Tangible outcomes that directly measure how
patient feel,function,or survive
e.g painful periodontal abcess
 Surrogate endpoint:
changes that are intangible to patient
e.g anatomic measures…probing depth
measure of inflammation
Microbiological measures
Immunological measures

14.  Continuous changes in type of surrogate data
collected
 Diversity of measurement
 Paucity of information
e.g probing depth from no of teeth present
leads to bias

15. STUDY DESIGN
EXPERIMENTAL OBSERVATION
ANAL
YTICA
L
ANALTI
CAL
DESCRI
PTIVE
•COMMUNITY
INTERVENTION TRIALS
•RANDOMIZED CLINICAL
TRIALS
•FIELD TRIALS
•CASE CONTROL
•COHORT
•CROSSSECTIONAL
•ECOLOGICAL

16.  DESCRIBITIVE STUDIES..observing the
destribution of disease
 ANALYTICAL STUDIES… to determine etiology
Establish casual relationship between factor
and disease

17.  Provide a probabilistic basis for making
causal inference between intervention and
outcome
Scaling and
rootplaning in
preganent
women
Biphasic calicum
phosphate
cermics
Infant low birth
weight
Clinical
attachment
level
823
137
treatment outcome
Sample
size

18.  Exposure based study design
 Subjects are classifed with respect to
exposure i.e smoking,diabetes
Exposure ……outcome
Periodontal disease+tooth loss …coronary heart disease
Gingivitis…. Tooth loss

19.  Outcome based study design
 Compare between case(person with
condition of interest) and control(person
without condition of interest)
 Case:
Person in population or study group having
particular disease,health disorder and
condition
Incident cases(date of diagnosis is after date of
study initiation)
Prevalent cases(date of diagnosis preceed)
Decedent cases(who died before date of study)

20.  Case
 control

21.  Sufficient cause: set of causes that initiate a
chronic disease
smoking,delay neutrophils apoptosis,IL-1 gene
defect
 Component cause:
The element of sufficent cause are component
cause
 Necessary cause:
A component cause which is an element of all
sufficient causes for a given disease

22.  Fermentable carbohydrates necessary cause
of dental caries
 Smoking is not necessary cause of lung
cancer