EPIDEMIOLOGYEPIDEMIOLOGY

Is defined as the study of health Is defined as the study of health and disease in populations and of and disease in populations and of how these states are influenced how these states are influenced by hereditary, biology, physical by hereditary, biology, physical environment, social environment environment, social environment and ways of living.and ways of living.

TYPES OF TYPES OF EPIDEMIOLOGICAL EPIDEMIOLOGICAL STUDIESSTUDIES DESCRIPTIVE STUDIESDESCRIPTIVE STUDIES (observational (observational

epi). Surveys records the prevalence of epi). Surveys records the prevalence of various conditions various conditions ““meaningmeaning”” The word The word prevalence serve to indicate per age prevalence serve to indicate per age group, group, the proportion of the population the proportion of the population affected,affected, with a given degree of with a given degree of severity of periodontal disease, as their severity of periodontal disease, as their highest score, and is given in percent of highest score, and is given in percent of the population examined. (Age, sex, the population examined. (Age, sex, and geographic location).and geographic location).

ANALYTICAL STUDIES:ANALYTICAL STUDIES: Attempts to Attempts to determine associations between disease determine associations between disease and possible risk factors determinants, and possible risk factors determinants, and quantify the degree of risk.and quantify the degree of risk.

RISK:RISK: Is the probability that a specified Is the probability that a specified event will occur e.g. that an individual event will occur e.g. that an individual will become ill or die within a stated will become ill or die within a stated period of time or particular age. Then period of time or particular age. Then trying to remove or modify the risk trying to remove or modify the risk factor e.g. smoking, sugar, etcfactor e.g. smoking, sugar, etc……

Analytical studies, frequently require at Analytical studies, frequently require at least least TWOTWO sets of measurements among sets of measurements among the same people at different times to the same people at different times to determine the progress of the condition.determine the progress of the condition.

INCIDENCE STUDIES:INCIDENCE STUDIES: It is defined as It is defined as the change in prevalence of a condition the change in prevalence of a condition over a given period of time. In another over a given period of time. In another word, it is the rate at which new cases of word, it is the rate at which new cases of the disease appear in a population.the disease appear in a population.

CROSS-SECTIONAL STUDIES:CROSS-SECTIONAL STUDIES: A comparison A comparison of the prevalence of dental caries in TODAYS of the prevalence of dental caries in TODAYS sixth-grades with that of ten years ago, must sixth-grades with that of ten years ago, must be cross-sectional study, though it is obvious be cross-sectional study, though it is obvious that different persons are studied each time.that different persons are studied each time.

LONGITUDINAL STUDIES:LONGITUDINAL STUDIES: If all the children If all the children originally in first grade in a school system are originally in first grade in a school system are studied periodically until they finish sixth studied periodically until they finish sixth grade, the study would be longitudinal grade, the study would be longitudinal because same children would be seen on because same children would be seen on several occasions.several occasions.

EXPERIMENTAL STUDIES:EXPERIMENTAL STUDIES: ““Clinical trialsClinical trials””. . Is a controlled study of group comparison Is a controlled study of group comparison based on epidemiological principles and based on epidemiological principles and designs to test the hypothesis that a designs to test the hypothesis that a particular agent or procedure favorably particular agent or procedure favorably alters the natural history of a disease. The alters the natural history of a disease. The group receiving the agent is the group receiving the agent is the test test groupgroup, and the comparable group not , and the comparable group not subjected to the agent is the subjected to the agent is the control control groupgroup. (Age, sex, race and socioeconomic . (Age, sex, race and socioeconomic status are similar, and most importantly status are similar, and most importantly Disease ExperienceDisease Experience).).

INDICES USED TO EVALUATE INDICES USED TO EVALUATE SIGNS, SYPTOMS AND SIGNS, SYPTOMS AND ETIOLOGICAL FACTORS ETIOLOGICAL FACTORS ASSOCIATED WITH THE ASSOCIATED WITH THE

DISEASE OF THE DISEASE OF THE PERIODONTIUMPERIODONTIUM..

Definition of an Index:Definition of an Index: As defined As defined by Russell 1966. Is a numerical value by Russell 1966. Is a numerical value describing the relative status of a describing the relative status of a population on a graduated scale with population on a graduated scale with definite upper and lower limits, which definite upper and lower limits, which is designed to permit and facilitate is designed to permit and facilitate comparisons with other populations comparisons with other populations classified by the same criteria and classified by the same criteria and methods.methods.

Ideally an Index, including its scoring Ideally an Index, including its scoring criteria should posses the following criteria should posses the following properties:properties:

Clarity, Simplicity and Objectivity.Clarity, Simplicity and Objectivity.

The examiner should be able to The examiner should be able to memorize the criteria, and the Index memorize the criteria, and the Index should be reasonably easy to apply so should be reasonably easy to apply so as not to lose time in field as not to lose time in field examination.examination.

Acceptability.Acceptability.

The use of an Index should not be The use of an Index should not be painful or demeaning to the subject.painful or demeaning to the subject.

Validity.Validity. The Index must measure what it is The Index must measure what it is

intended to measure, it should correspond intended to measure, it should correspond with clinical stages of the disease under with clinical stages of the disease under study at each point (reflects the true study at each point (reflects the true disease situation).disease situation).

Quantifiability.Quantifiability. Should be amenable to statistical analysis. Should be amenable to statistical analysis.

So as the status of a group can be So as the status of a group can be expressed by a distribution, expressed by a distribution, MEANMEAN and and MEDIANMEDIAN, or other statistical measures., or other statistical measures.

Reliability.Reliability. The Index should be able to measure The Index should be able to measure

consistently at different times and under consistently at different times and under variety of conditions (Reproducibility).variety of conditions (Reproducibility).– Inter-examiner-variability.Inter-examiner-variability.– Intra-examiner-variability.Intra-examiner-variability.

Sensitivity.Sensitivity. The Index should be able to detect The Index should be able to detect

reasonably small shifts in either reasonably small shifts in either direction.direction.

Classification and Classification and Characteristics:Characteristics:

INDICES TO MEASURE INDICES TO MEASURE GINGIVITISGINGIVITIS

Gingival Index: Gingival Index: ““Loe and Silness 1963Loe and Silness 1963””

The first index to evaluate every The first index to evaluate every single tooth surface.single tooth surface.

A blunt probe A blunt probe ““Instrument is usually Instrument is usually usedused””..

Gingival tissue is divided into four Gingival tissue is divided into four scoring units.scoring units.

Buccal Buccal –– Mesial Mesial –– Lingual and Distal. Lingual and Distal. Scores from 0 Scores from 0 –– 3. 3. GI for single surface.GI for single surface. GI for a tooth GI for a tooth ““4 surface4 surface”” TotalTotal = GI tooth. = GI tooth. 44 GI for individuals GI for individuals == Total GI/per toothTotal GI/per tooth Number of teethNumber of teeth Can be used for a group of teeth GI for Can be used for a group of teeth GI for

e.g. 6 teeth.e.g. 6 teeth.

Converting numerical scores into subjective Converting numerical scores into subjective or varying degrees of clinical gingivitis as or varying degrees of clinical gingivitis as follows:follows:

Gingival ScoresGingival Scores ConditionCondition

0.1 0.1 –– 1.0 1.0 Mild Gingivitis Mild Gingivitis

1.1 1.1 –– 2.0 2.0 Moderate GingivitisModerate Gingivitis

2.1 2.1 –– 3.0 3.0 Severe GingivitisSevere Gingivitis

0 = Normal gingiva.0 = Normal gingiva. 1 = Mild inflammation, slight change in color, 1 = Mild inflammation, slight change in color,

slight edema. No bleeding on probing.slight edema. No bleeding on probing. 2 = Moderate inflammation, redness, edema 2 = Moderate inflammation, redness, edema

and glazing. Bleeding on probing.and glazing. Bleeding on probing. 3 = Severe inflammation, marked redness and 3 = Severe inflammation, marked redness and

edema, ulceration and tendency to edema, ulceration and tendency to spontaneous bleedingspontaneous bleeding..

This Index can be used also as simplified form.This Index can be used also as simplified form. 6 2 46 2 4 4 2 64 2 6

Criteria for Gingival IndexCriteria for Gingival Index

INDICES TO MEASURE INDICES TO MEASURE PLAQUEPLAQUE Plaque Indices: Plaque Indices: ““Silness and Loe 1964Silness and Loe 1964”” Epidemiological studies: It provides a Epidemiological studies: It provides a

quick and representative picture of the quick and representative picture of the level of oral hygiene in a population.level of oral hygiene in a population.

In private practice: Is not intended to In private practice: Is not intended to determine the average plaque determine the average plaque accumulation but to record the accumulation but to record the distribution of plaque in the oral cavity distribution of plaque in the oral cavity i.e. to determine the i.e. to determine the ““Plaque Plaque PicturePicture”” of an individual patient. of an individual patient.

Some areas of the patientSome areas of the patient’’s dentition s dentition may be cleaned quite effectively, while may be cleaned quite effectively, while others e.g. the lingual surfaces of others e.g. the lingual surfaces of mandibular molars remain routinely mandibular molars remain routinely uncleaned.uncleaned.

1.1. The most important consideration in the The most important consideration in the plaque index is the thickness of plaque plaque index is the thickness of plaque along the gingival margin. along the gingival margin.

2.2. It involves the same scoring units of the It involves the same scoring units of the tooth of the Gingival Index. tooth of the Gingival Index. ““Loe and Loe and Silness 1963Silness 1963””..

3.3. A mouth mirror and dental explorer are A mouth mirror and dental explorer are used.used.

4.4. To visualize plaque, it is important that To visualize plaque, it is important that compressed air be used to dry the tooth compressed air be used to dry the tooth surfaces prior to the evaluation of the surfaces prior to the evaluation of the unstained plaque deposits.unstained plaque deposits.

PLAQUE IS NOT STAINED.PLAQUE IS NOT STAINED.

5.5. It does not exclude or substitute for teeth It does not exclude or substitute for teeth with gingival restorations, or crowns, or with gingival restorations, or crowns, or ““missing teethmissing teeth”” if partial scoring is used. if partial scoring is used.

PERIODONTAL SCREENING PERIODONTAL SCREENING AND RECORDING IndexAND RECORDING Index

Principles of the P.S.RPrinciples of the P.S.R..

In this system, the dentition is In this system, the dentition is divided into six sextants:divided into six sextants:

Premolars & Molars Canines & Incisors Premolars & Premolars & Molars Canines & Incisors Premolars & MolarsMolars

R.R. Ant. Ant. L.L.Premolars & Molars Canines & Incisors Premolars & Premolars & Molars Canines & Incisors Premolars &

MolarsMolars

THE PROBETHE PROBE

The tip is 0.5 mm spherical ball.The tip is 0.5 mm spherical ball.

Calibration of its use.Calibration of its use.

Force 20-25 grams.Force 20-25 grams.

Path of insertion.Path of insertion.

Prepared by: Dr. Nicola Barghout

P.S.R. CODINGP.S.R. CODING

0 0 –– The black band remains fully visible. The black band remains fully visible.

1 1 – – As code 0 As code 0 –– except bleeding on probing. except bleeding on probing.

2 2 –– As code 1 As code 1 –– except the probe detects except the probe detects supra and subgingival calculus, overhangs. supra and subgingival calculus, overhangs.

3 3 –– The black band disappears partly into The black band disappears partly into the gingival crevice. the gingival crevice.

4 4 –– The black band disappears into the The black band disappears into the gingival crevice. gingival crevice.

P.S.R. SCORING P.S.R. SCORING EXAMPLEEXAMPLE

4*13

20X