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Supragingival calculus consist of 75.9 percent Ca₃ (PO₄)₂, 3.1 percent CaCO3, and traces of Mg3(PO4)2.

At least 2/3rd of the inorganic content is crystalline in nature. The four main crystalline forms are:

1. Hydroxy apatite 58%. 2. Mg whitlockite 21%.

3. Octacalcium phosphate 12%. 4. Brushite 9%.

Organic Content

Mixture of protein polysaccharide complexes, desquamated epithelial cells, Leukocyte and microorganism.

Subgingival calculus is located apical to the gingival margin and is not visible in the oral cavity. It is usually dark brown or greenish black in color. It is typically hard and dense and firmly attached to the tooth surface.

Composition

Subgingival calculus has same composition as supragingival calculus with few differences.

Inorganic Content

It is more homogenous with an equally high density of minerals. The predominant mineral is magnesium whitlockite, containing small proportions of magnesia (3%).

It has the same amount of hydroxyapatite but less brushite and octacalcium phosphate.

The ratio of calcium to phosphate is concomitantly high in subgingival calculus with an increase in the sodium content with the depth of the periodontal pocket.

Organic Content

It is similar to that of supragingival calculus although the salivary proteins are not found in it.

C. Stains

Stains are produced by the action of chromogenic bacteria on food substances such as tobacco, tea coffee etc. or by metallic particles. These pigments become absorbed by plaque or pellicle.

3. ENVIRONMENTAL FACTORS

A. Food and Nutrition

Despite observations like sailors suffering from scurvy [deficiency of vitamin ‘C’] had bleeding gums; no nutritional

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or dietary factors have been shown to be directly related to the prevalence of periodontal disease in the earlier epidemiological studies. Improved understanding of the disease at the cellular level and more stringent nutritional methodologies have brought new interest and provided new insights into the association between nutrition status and periodontal disease. The influence of nutrition on periodontal disease therefore appears to be exerted mainly at 3 different levels.

1. On the metabolism of the gingival crevice-plaque flora. 2. On the repair process in the connective tissue at local site. 3. On the immunologic response to the microbial antigens.

Protein

Protein calorie malnutrition has been associated with osteoporosis of alveolar bone, thinning of periodontal ligament, degeneration of periodontal collagen fibers, retardation in deposition of cementum and delayed gingival wound healing. (Stahl S.S 1966).

Enwonwu (1994) observed the effect of protein –energy malnutrition (PEM) on periodontal disease risk. He observed that aggressive periodontal disease was more prevalent and severe in undernourished population (Table 11.8).

Table 11.8: Proposed mechanism by which PEM enhances

periodontal disease (Gregory 2000)

• Decreased resistance of mucosa to colonization and invasion by pathogens.

• Impaired salivary flow and antibacterial properties.

• Increased prevalence and potency of pathogenic oral microorganism (possibly due to altered bacterial profile) • Cytokines involved in the healing process compromised • Reduced acute phase protein response

Vitamin C

There is a direct relationship between gingival tissue concentration of ascorbic acid and sulcular epithelial function, collagen synthesis and permeability of sulcular epithelial. In vitamin C deficiency, there is an increase in gingival sulcular epithelial permeability and decrease collagen synthesis and poor sulcular epithelial barrier function due to gingivitis by bacterial toxins and antigens to the underlying connective tissue and lamina propria.

Calcium

Calcium and phosphorus have effect on gingival inflammation, calcium formation, pocket depth and tooth mobility. Binkley (1978) Reported that person who had high dietary calcium showed lesser bone resorption. The studies of Wical et al (1974) and Sorensen (1977) showed an inverse relationship between calcium intake and ridge resorption.

Zinc

Deficiency of Zinc leads to:

1. Inhibition of cell mediated immune functions (Sand Stead 1979).

2. Inhibits collagen formation (Prosed et al 1971)

3. Increased sulcular and junctional epithelial permeability (Joseph et al 1982)

4. Increased alveolar bone resorption (Ekund et al 1980)

Iron

There is an inverse relationship between iron and sulcular and junctional epithelial permeability. Iron deficiency reduces the competence phagocytes and depresses myeloperoxidase in macro phages, which is required for killing of bacteria. Also deficiency of iron inhibits hydroxylation of praline in collagen synthesis (Mallek 1978).

B. Geographic Distribution

Certain geographic areas throughout the world are associated with more periodontal disease than others. Russell describes population according to whether disease is relatively high, intermediate or relatively low.

High includes countries like Chile, Lebanon, Jordan, Thailand, Burma, India, and Ceylon.

EPIDEMIOLOGICAL FACTORS IN PERIODONTAL DISEASE I. Host Factors • Age • Sex • Race • Endocrine Changes • Intraoral Distribution • Tooth Malalignment • Restoration • Traumatic Occlusion • Oral Hygiene • Tobacco • Occupational Habits • Systemic Factors • Socio- Economic Status • Psychosomatic Factors

II. Agent Factors

• Dental Plaque • Calculus • Stains

III. Environmental Factors • Food and Nutrition

• Geographic Distribution

Chapter 11

Epidemiology of Periodontal Disease

BACTERIA MOST COMMONLY ASSOCIATED WITH PERIODONTAL DISEASE • Porphyromonas gingivalis • Prevotella intermedia • Actinobacillus actinomycetemcomitans • Fusobacteria • Treponema spp.

It is found to be intermediate in USA black population, Equador, Columbia and Ethopia.

In relatively low group come US white population and primitive Eskimos of Alaska.

It is observed that underdeveloped and dentist deprived areas show greater periodontal disease than developed countries.

C. Urbanization

Periodontal disease is seen less in urban than in rural population particularly at younger ages. This difference could be attributed more to educational background than to rural life.

Data from various surveys on the prevalence of gingivitis and periodontitis is dependent on whom the disease is defined and the age group from which they were taken.

Gingivitis is found in early childhood, is more prevalent and severe in adolescence, and then tends to level off in older age group. Mild to moderate periodontitis affects a majority of adults. Some 5-20 percent of the population suffers from severe, generalized periodontitis. For those who are most susceptible, periodontitis becomes evident in teenage and early adult years rather than the later years.

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Epidemiology, Etiology andPrevention of Oral Cancer