EPIDEMIOLOGY OF DENTAL CARIES DR. HIDAYATHULLA SHAIKH,

Objectives At the end of the lecture students should be able to – Explain epidemiology Define dental caries explain primary mechanism of caries formation Discuss caries epidemiology

INTRODUCTION Epidemiology Derived from the Greek word Epi – among Demos – people Logos – study. the very old word dating back to 3rd century BC.

Dental caries Latin word meaning ‘rot’ or ‘decay’ Defined as microbial disease of the calcified tissues of the teeth, characterized by demineralization of inorganic portion and destruction of the organic substances of the tooth. Shafer.

History From the Australopithecines (over a million years ago) to the Neolithic ( 12,000-3000 BC), carious lesions have been found in almost every population studied.

There has been a sporadic, but generally increasing caries prevalence over the past 5,000 years. During the first 4,000 years there is a gradual increase in caries prevalence ranging from 2 to 10 carious teeth per 100 teeth, followed by a sharp rise at about the year 1000 A.D. to 24 carious teeth per 100 for 3 out of 4 populations. The year 1000 A.D. is the approximate date for the introduction of sugar cane to the Western world.

CURRENT CONCEPTS ‘multifactorial’ etiology Primary or Essential Factors in the etiology of dental caries (Keyes, 1960) A susceptible host tissue - the tooth Microflora with a cariogenic potential, and A suitable local substrate to meet the requirements of the pathogenic flora

Caries tetralogy (Newbrun, 1982):

Primary mechanism of caries formation Cariogenic bacterial plaque + Suitable local substrate  Organic acids Organic acids (in plaque) + Tooth mineral  Loss of enamel Demineralized tooth + Bacterial proteolytic enzymes  Cavitation

THE ROLE OF DENTAL PLAQUE: G.V. Black in 1899 described ‘plaque’ and regarded it as important factor in the carious process. Dental plaque - soft deposits that form the biofilm adhering to the tooth surfaces or other hard surfaces in the oral cavity including removable and fixed restorations. Appears as a tenacious, thin film, which may accumulate to a perceptible degree in 24 to 48 hours.

Epidemiological triad – dental caries Agent Host Microorganisms Diet & nutrition Transmissibility Age Sex Race Quality and quantity of tooth structure Familial heredity Nutrition Socioeconomic status Geographic variation (latitude, sunshine, rainfall & temperature) Fluoride Trace elements Urbanization Social factors Environment

Host Factors The Tooth factor Significant differences in fluoride content of sound and carious teeth have been reported by the studies. The tooth having optimum level of fluoride tends to be less cariogenic.

Tooth morphology and arch form A susceptible host is one of the factors for carries to occur, certain surfaces of the tooth are more prone for decay, ex pit and fissures of the posterior teeth are more prone decay. Irregularity in the arch form, crowding and overlapping of teeth also favor development of carious lesion.

Tooth position May play an important role in dental caries under certain circumstances. Teeth which are mal aligned, out of position, rotated or other wise not normally situated may be difficult to clean and tend to favor food accumulation and debris. This in susceptible persons would be sufficient to cause caries in tooth which under normal circumstances of proper alignment would conceivably not developed caries, but tooth position seems to be a minor factor in etiology of Dental Caries.

Caries susceptibility of Jaw quadrants many investigators have shown that caries exhibit bilateral distribution between the right and left quadrants of both maxilla and mandible. Scott 1944 found that bilateral caries were present in 95% of a group of 300 persons whose dental radiographs were studied. Among both the jaws caries are more prevalent in maxilla than in mandible. Day and Sedwick in their 1935 study of 433 , 13 year old children, reported that 60% of all caries was in the maxillary arch.

Saliva The complex nature of saliva and the great variation in its composition are premonitory of the difficulties involved in establishing which factors may directly influence dental health. There is no doubt that saliva significantly influences the carious processes evidenced be the animal experimenters in which salivary glands are surgically extirpated, results proved the one in which the salivary glands are removed developed more than 5 times caries as compared to controls in which the glands are not removed.

Salivary flow Any condition that results in xerostomia will predispose the person to increased risk for dental caries. (Stephen R 1971, Driezen et.al 1977)

Salivary composition Calcium phosphorous content of saliva was found to be less in caries active persons (study by Karshan) Ammonia was found in higher concentration in saliva of caries immune persons than with those with caries (Turkheim 1925)

(Demographic Factors) Race or ethnic group: Certain races enjoy immunity or at least high degrees of resistance to caries have been evident in dentistry for a long time. They probably stemmed from the earlier observations that certain non-European races such as African and Asian enjoyed freedom from caries than Europeans. These beliefs have faded as evidence suggests that these differences are more due to environmental factors that inherent racial attributes.

Age - it shows 3 peaks: at ages of 4-8 years, 11-19 years and 55-65 years.

Sex: Many studies have shown higher caries experience in girls than boys during childhood period and also latter at adolescence period. (US public health service 1967, 1987, 1988). However, there are some studies, which have shown no difference between girls and boys. (sloman, 1941 & backer dirks,1961). However, root caries prevalence is more and commonly seen in males

Diet: Diet refers to the customary allowance of food and drink taken by any person from day to day. Thus, diet may exert and effect on caries locally in the mouth by reacting with the enamel surface and by serving as a substrate for cariogenic microorganisms. Sucrose has been indicated as “the arch criminal” in the etiology of caries.

Agent Factors Micro flora: Although there are differences of opinion as to how and which micro organisms produce carious lesion. It is uniformly agreed that caries cannot occur without micro organisms. The classical germ-free animal studies of Orland et al, firmly established principal evidence that had been debated for more than a century, that dental caries is a bacterial infection. These studies demonstrated that germ-free rats on a highly cariogenic diet containing sucrose did not develop caries and on the contrary when the gnotobiotic rats on the same diet were infected with combinations of an enterococcus and a proteolytic bacillus, caries developed.

Environment factors Urbanization - was found to be accompanied by an 11 percent increase in caries. Industrial hazards - Carbohydrate dust is known to be deleterious to the teeth, it promotes dental caries Social factors - Social factors like economic status, social pressure, affordability, provision of good preventive measures etc. might create more demand for better dental care and leads to lesser caries prevalence. However in the absence of these factors especially among poor and disadvantaged population, socioeconomic factors might influence higher dental caries prevalence.

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