What is the burden of oral disease?
Oral disease burdens and common risk factors
Despite great achievements in oral health of populations globally, problems still remain in many communities all over the world - particularly among under-privileged groups in developed and developing countries. Dental caries and periodontal diseases have historically been considered the most important global oral health burdens. At present, the distribution and severity of oral diseases vary among different parts of the world and within the same country or region. The significant role of socio-behavioural and environmental factors in oral disease and health is evidenced in an extensive number of epidemiological surveys.
Dental caries is still a major oral health problem in most industrialized countries, affecting 60-90% of schoolchildren and the vast majority of adults. It is also a most prevalent oral disease in several Asian and Latin-American countries, while it appears to be less common and less severe in most African countries. Figure 1 highlights the dental caries experience among 12-year-old children in the six WHO regions in the year 2000, based on the DMFT (Decayed, Missing and Filled Teeth) Index, an index that measures the lifetime experience of dental caries in permanent dentition. Currently, the disease level is high in the Americas but relatively low in Africa. In light of changing living conditions, however, it is expected that the incidence of dental caries will increase in many developing countries in Africa, due particularly due to a growing consumption of sugars and inadequate exposure to fluorides.
In many developing countries, access to oral health services is limited and teeth are often left untreated or are extracted because of pain or discomfort. Throughout the world, losing teeth is still seen as a natural consequence of ageing. While in some industrialized countries there has been a positive trend of reduction in tooth loss among adults in recent years, the proportion of edentulous adults aged 65 years and older are still high in some countries (Table 1).
Globally, most children have signs of gingivitis and, among adults, the initial stages of periodontal diseases are prevalent. Figure 2 illustrates the periodontal health status of 35-44-year-olds by WHO region, using the so-called Community Periodontal Index. Severe periodontitis, which may result in tooth loss, is found in 5-15% of most populations. Juvenile or early-onset aggressive periodontitis, a severe periodontal condition affecting individuals during puberty that leads to premature tooth loss, affects about 2% of youth.
Mean percentages of 35-44-year-olds by maximum Community Periodontal Index scores according to WHO region
In industrialized countries, studies show that smoking is a major risk factor for adult periodontal disease, responsible for more than half of the periodontitis cases among this age group. Risk decreases when smokers quit and the prevalence of periodontal disease has decreased in countries experiencing reductions in tobacco use.
While oral and pharyngeal cancers are both preventable, they remain a major challenge to oral health programmes. The prevalence of oral cancer is particularly high among men, the eighth most common cancer of the world (Figure 3). Incidence rates for oral cancer vary in men from 1-10 cases per 100,000 inhabitants in many countries. In South Central Asia, cancer of the oral cavity ranks amongst the three most common types of cancer. However, sharp increases in incidence rates of oral/pharyngeal cancers have been reported for several countries such as Germany, Denmark, Scotland, Central and Eastern Europe and, to a lesser extent, Japan, Australia, New Zealand and USA.
In Asia, the age standardized incidence rate per 100,000 population ranges from 0.7 in China to 4.6 in Thailand and 12.6 in India. The high incidence rates relate directly to risk behaviours such as smoking, use of smokeless tobacco (e.g. betel nut or miang chewing) and alcohol consumption. In Thailand, for example, the prevalence of smoking is about 60%, betel nut chewing 15% while alcohol consumption is 35%.
Qat is a leafy narcotic substance that is popular in several countries in East Africa and the Arab Peninsula. Qat can be consumed as a liquid in the form of tea or smoked like tobacco. However, the most common mode of ingestion is by chewing the fresh leaves. Consumption of Qat can lead to adverse oral effects including oral mucosal lesions, dryness of the mouth, discoloration of teeth, poor oral hygiene and periodontal disease.
There are variations in oral health profiles across regions. In some developing countries, oral diseases are increasing and countries in Africa and Asia must urgently address a number of very serious oral conditions including Noma (Cancrum Oris), ANUG (Acute Necrotizing Ulcerative Gingivitis), oral pre-cancer and cancer. Cases of Noma are reported for young children aged 3-5 years in Africa, Latin America and Asia (Figure 4); with 90% of them dying without having received any care. Also, Africa and Asia have the highest prevalence of HIV/AIDS, oral manifestations of which are widespread.
In contrast to dental caries and periodontal disease, reliable data on the frequency and severity of oro-dental trauma are still lacking in most countries, particularly in developing countries. Some countries in Latin America report dental trauma for about 15% of schoolchildren whereas prevalence rates of 5-12% are found in children aged 6-12 years in the Middle East. However, recent studies from certain industrialized countries revealed that the prevalence of dental traumatic injuries is on the increase, ranging from 16-40% and 4-33% among 6-year-old and 12-14-year-old children respectively. A significant proportion of dental trauma relates to sports, unsafe playgrounds or schools, road accidents or violence. In industrialized countries, the costs of immediate and follow-up care for dental trauma patients are high.
Estimates of the frequency of different traits of malocclusion are available from a number of countries, primarily from Northern Europe and North America. For example, prevalence rates of dento-facial anomalies are reported at 10%, according to the Dental Aesthetic Index. Malocclusion is not a disease but rather a set of dental deviations which in some cases can influence quality of life. There is insufficient evidence that orthodontic treatment enhances dental health and function. Treatment is often justified by the potential enhancement of social and psychological wellbeing through improvements in appearance.
Diagnosis and treatment of cranio-facial anomalies such as cleft lip and palate present a number of challenges to public health. Orofacial clefts occur in around 1 per 500-700 births; the rate varying substantially across ethnic groups and geographical areas. Other conditions that may lead to special health care needs include Down’s syndrome, cerebral palsy, learning and developmental disabilities, and genetic and hereditary disorders with oro-facial defects. Oro-facial clefts appear to have substantial environmental causes, the higher risk first of all associated with maternal tobacco, alcohol and nutritional factors. There is no consistent evidence of time trends, nor is there consistent variation by socioeconomic status but these aspects have not been adequately studied. 14 Also, there are many parts of the world in which there is little or no information available on the frequency of cranio-facial anomalies, in particular parts of Africa, Central Asia, Eastern Europe, India and the Middle East.
Given the extent of the problem, oral diseases are major public health problems. Their impact on individuals and communities, as a result of pain and suffering, impairment of function and reduced quality of life, is considerable. Moreover, traditional treatment of oral disease is extremely costly, the fourth most expensive disease to treat in most industrialized countries. In low-income countries, if treatment were available, the costs of dental caries alone in children would exceed the total health care budget for children.
A core group of modifiable risk factors are common to many chronic diseases and injuries. The four most prominent noncommunicable diseases (NCDs) - cardiovascular diseases, diabetes, cancer and chronic obstructive pulmonary diseases - share common risk factors with oral diseases, preventable risk factors that are related to lifestyle. For example, dietary habits are significant to the development of NCDs and influence the development of dental caries. Tobacco use has been estimated to account for over 90% of cancers in the oral cavity, and is associated with aggravated periodontal breakdown, poorer standards of oral hygiene and thus premature tooth loss.
The greatest burden of all diseases is on the disadvantaged and socially marginalized. A major benefit of the common risk factor approach is the focus on improving health conditions for the whole population as well as for high risk groups; thereby reducing inequities. The solutions to the chronic disease problems are to be found through shared approaches. The WHO Global Strategy for the prevention and control of noncommunicable diseases is a new approach to managing the prevention and control of oral diseases. Continuing surveillance of levels and patterns of risk factors is of fundamental importance to planning and evaluating community preventive activities and oral health promotion.