Epidemiology

Epidemiology

Epidemiology is the science concerned with the factors and conditions that determine the occurrence and distribution of health, disease, defects, disability, and death among groups of individuals.

• A detailed description of the principles and practices in epidemiology are beyond the scope of this book, only a brief description of a few indices is dealt with in this chapter.

Classification Of Index Systems

Indices may be classified into five categories:

1. Indices for the inflammatory changes of the gingiva
2. Indices for the loss of periodontal tissues
3. Oral hygiene indices
4. Miscellaneous indices such as retention index, alveolar bone loss, and mobility index, and
5. Treatment needs indices.

Read And Learn More: Periodontology Important Question And Answers

Question 1: Describe the indices to assess inflammatory changes in the gingiva.
Answer:

Gingival Index

The most commonly used index for assessing the status of gingival health or inflammation is the gingival index (GI) proposed by Loe and Silness (1963).

• While all the indices published before 1963 were based on the single tooth as a unit, the GI was the first index to evaluate every single tooth surface.
• Each of the buccal, mesial, lingual, and distal surfaces of the gingival tissues is given a score of 0-3.

Gingival Index Score

• This then constitutes the GI for the area, and scores for the 4 areas of the tooth are added and divided by four to give the GI for the tooth. Scores for individual teeth may be grouped to designate the GI for that group of teeth such as incisors, premolars, and molars.
• The scores may be added and divided by the number of teeth examined to derive the GI for the individual. Usually, all tooth surfaces are included or designated and single tooth surfaces may be selected.
• The major difference between the gingival index and the sulcular bleeding index (Muhlemann and Son 1971) or the papillary bleeding index (Saxer and Muhlemann 1975) is that there is a score(1) for initial color and texture change in the tissues without the development of bleeding on gentle probing.
• The GI has gained wide acceptance as a simple, accurate, and reproducible method for the evaluation of gingival health or disease in epidemiological and clinical research.

Question 2: Describe the indices to assess periodontal tissue support.

The periodontal index (PI) was developed for epidemiological purposes and assumes that periodontal disease begins as gingivitis and progresses to the pocket formation and ultimately loss of attachment apparatus.

Periodontal Index

• A score ranging from 0 to 0.2 may be obtained for clinically normal gingival tissue. Persons with simple gingivitis usually register with a PI = 0.3 to 0.9.
• Subjects with significant gingivitis ranging upwards towards incipient destructive disease usually score in the range of PI = 0.7 to 1.9.
• These persons with established destructive periodontal disease should score approximately PI = 1.6 to 5.0, whereas those in the terminal stages of periodontal disease would present a score of PI = 3.8 to 8.0.

Question 3: Describe the indices to assess the presence of local factors.
Answer:

Assessment of Soft Plaque Deposits

Originally, the oral hygiene index (OHI) included a measurement of twelve tooth surfaces (Greene and Vermillion 1960). Subsequently, it was reduced to six tooth surfaces and it is now known as the“simplified oral hygiene index” or OHI-S (Greene and Vermillion 1964).

• The debris measured in the OHI-S is on the labial surfaces of teeth 11, 16, 26, and 31, and the lingual surfaces of 36 and 46. The index has two components, one describing the soft deposits and one the calcified deposits present.

Oral Hygiene Index

The DI-S score is the sum of debris scores for all teeth, divided by the number of surfaces scored. At least two of the possible six surfaces must have been included to calculate the score, and adjacent teeth may be substituted for the selected teeth if missing.

• The score is termed “good” if the DI-S score is between 0.3 and 0.6, “Fair” when it is between 0.7 and 1.8, and “poor” when between 1.9 and 3.0. This relatively simple assessment is fairly reproducible.

Plaque Index (Silness and Loe 1964)

The plaque index (PI) system introduced by Silness and Loe (1964) uses the same teeth and “scoring units” as the Gingival Index (GI) by Loe and Silness (1963) that is, the distal-facial, facial, mesialfacial, and lingual surfaces of each tooth.

• As opposed to most other plaque indices, this system evaluates the thickness of plaque growth at the gingival margin of the teeth. Occlusion extension of plaque is only incorporated in the evaluation indirectly.
• All or selected teeth may be used, and no disclosing solution is needed. The criteria for the PI range from 0-3. Compressed air must be used to dry the tooth surfaces before the evaluation of the unstained plaque deposits.

Plaque Index (Silness and Loe, 1964)

Assessment of Calcified Deposits

The simplified calculus index is a component of the OHI-S, the scores are assigned according to the following criteria.

Oral Calculus Index

Question 5: Describe the index to assess treatment needs.
Answer:

Community Periodontal Index for Treatment Needs (CPITN, Ainamo et al 1982)

The CPITN data is primarily meant to assist to treatment needs of large samples and must be interpreted with caution when used to determine the prevalence and severity of the periodontal disease.