Oral diseases affect the most basic human needs: the ability to eat and 
drink, swallow, maintain proper nutrition, smile, and communicate. Oral health and overall health and well-being are inextricably connected. Many systemic conditions such as human immunodeficiency virus (HIV)/AIDS, diabetes, Sjögren’s syndrome, and osteoporosis have important oral symptoms, manifestations or complications. The lips, tongue, gingivae (gums), oral mucosa and salivary glands can all signal clinical disease elsewhere in the body. Long considered to be localized infections only, periodontal or gum diseases are now being investigated as potential risk factors for the development of systemic disease. For instance, accumulating evidence now points to a possible link between periodontal diseases and the incidence of premature, low-birth weight babies, cardiovascular disease, and pulmonary disease. Oral diseases affect not only the health of the oral cavity and associated craniofacial structures, but can be detrimental to the overall health and well-being of individuals.
In the section that follows, we highlight selected oral diseases, disorders, birth defects and conditions that are uniquely within NIDCR’s mission to improve the oral health of the nation.
Health Disparities
The substantial gains in the oral health of the nation over the past generation have not benefited all Americans equally. The burden of oral and dental disease, particularly untreated disease, falls heaviest on individuals from lower socioeconomic groups, which include disproportionately large numbers of racial and ethnic minorities. Individuals in lower socioeconomic status groups also have higher incidences of HIV infection and diabetes, diseases that increase the risk for serious oral, viral, bacterial and fungal infections. Children in low-income families are particularly vulnerable to oral health problems. Their nutrition may be poor, their oral hygiene inadequate, and their access to oral health care lacking. A partial remedy for addressing health disparities lies in improving access to effective and appropriate health promotion, preventive, diagnostic, and treatment services. The research challenges to reducing health disparities include elucidating risk factors, identifying and eliminating barriers to health care, designing better means of care delivery, and designing educational strategies to reduce risk and enhance health promotion that are appropriate to the social and cultural frameworks of the groups in question.
Dental Caries
Dental caries — also known as tooth decay — is not extinct. Despite tremendous declines in the past three decades, tooth decay, the end result of a bacterial infection, remains the single most common chronic disease of childhood in the U.S. A troubling trend that partly explains the continued prevalence of caries is the increasing polarization of oral health in the U.S. — while most children enjoy excellent oral health, about 25 percent of children 5–17 years of age experience 80 percent of all dental caries in their permanent teeth. Dental caries begins early in life: 18 percent of preschoolers in the U.S. have already experienced tooth decay and by age 6–8, more than half have experienced this disease — making it 5–8 times more common than asthma. By age 17, more than 80 percent of the adolescent population is affected by caries. Dental caries is also a problem among adults; recurrent caries and root caries are prevalent among adults and the elderly. The subset of the general population most prone to caries is also the most vulnerable: the poor, the very young and the elderly, and those with compromising medical conditions or disabilities. Continued research to identify the most effective health education messages for the prevention of caries, particularly among underserved populations, is needed. New approaches to diagnose, manage and prevent caries throughout the lifespan may come from further research to understand the molecular consequences of the interaction between host and microbes, and from deciphering the genomic makeup of bacteria implicated in dental caries.
Periodontal Diseases
Periodontal diseases are a result of infections caused by bacteria in the biofilm that forms on the teeth in the cul de sac between the tooth and gum (gingiva). They include a range of clinical variants — from mild forms such as gingivitis to severe disease that can destroy the periodontal ligament and surrounding bone, in some cases leading to the loss of teeth. Almost half of U.S. adults ages 35 to 44 have gingivitis, a reversible inflammation of the gingivae, and about one-fourth have the more severe condition of periodontitis. Severe periodontal disease affects 14 percent of adults ages 45 to 54, and 23 percent of 65- to 74-year olds. Tobacco use is a major risk factor for the development and progression of periodontal diseases. There also is considerable evidence that diabetes, particularly if poorly controlled, increases the risk for periodontal disease. At present, treatment of periodontal diseases includes surgical as well as non-surgical approaches. Substantial advances in our understanding of how cells adhere to one another, and increased knowledge about the molecules that support and regulate nearly all cells are giving clinicians potential new options to manage periodontal diseases through the regeneration of tissues.
Tooth Retention and Edentulism
Vast improvements in tooth retention have taken place in the U.S. over the past three decades. Total tooth loss or total edentulism, once a relatively common condition among middle age adults is now most prevalent in older persons, affecting approximately one-third of adults 65 years and older. There is evidence that people with impaired dentitions due to missing teeth must choose foods that do not provide optimal nutrition; in the elderly, total edentulism and poor oral health can lead to significant weight loss that can affect overall health. The presence of 21 or more natural teeth has been used worldwide as an indicator of functional ability. Yet in the U.S. 58 percent of people 50 years or older and over one-quarter of the population over 19 years of age do not have 21 or more natural teeth. Low-income individuals, and in particular low-income white adults, are most likely to be totally edentulous. The standard treatment for tooth loss involves prosthetic devices such as full or partial dentures. Although these devices initially restore some of the ability to chew, as people age and lose underlying bone, the fit and aesthetics of dental prostheses are often compromised. Replacement of teeth with dental implants provides more natural and stable function than do dentures, but not every patient is an ideal candidate for implants. While continuing efforts to prevent tooth loss, there is a need to evaluate the appropriate replacement of tooth function, and to pursue evolving technologies that are enabling the development of biologic materials to repair and eventually regenerate teeth.
Oral and Pharyngeal Cancer
Oral and pharyngeal cancer is the sixth most common cancer in the developed world. Each year, an estimated 28,900 Americans are diagnosed with this disease and more than 7,400 die each year from it4. The most disturbing aspect about oral and pharyngeal cancer is the survival rate. In the U.S. the 5-year survival rate is approximately 50 percent, a statistic that has not improved over the past twenty years. African American men suffer the highest incidence of these cancers and have a much poorer five-year survival rate than do white men regardless of diagnostic stage. Despite the devastating consequences of oral cancer, which include impaired ability to chew, swallow, and speak, and often disfigurement from extensive surgery to remove parts of the face and oral structures, only 14 percent of U.S. adults report receiving oral cancer exams that can detect early disease. Reconstruction and management of the oral cancer survivor come at a high price both economically and socially. Not only are more efforts needed to increase public and professional knowledge about oral cancer and its prevention, there also is a critical need to develop biomarkers and diagnostic tests that can be used to improve cancer diagnosis and more accurately predict the course of the disease. There also is a pressing need to develop more effective, individualized treatments that spare healthy tissues and improve quality of life.
Pain and Chronic/ Disabling Conditions
International epidemiologic studies indicate that orofacial pain occurs in approximately 10 percent of the adult population. Orofacial pain, by itself or as a symptom of an untreated oral problem, is often a major cause of poor quality of life. Toothaches alone are associated with significant morbidity and high economic cost. Sources of orofacial pain include caries, periodontal diseases, and neuropathic and musculoskeletal conditions. Orofacial pain also is a major symptom of temporomandibular muscle and joint disorders (TMJD) that are estimated to affect 10 million people in the United States. Orofacial pain may also be caused by conditions involving the dental pulp (the innermost part of a tooth that contains blood vessels and nerves) and the area around the root, leading to symptoms that can range from sensitivity to thermal changes to severe pain and/or abscesses. Today, pain researchers know that chronic pain can become a disease in itself, causing long-term detrimental changes in the nervous system. These changes may affect resistance to other diseases, as well as effectively destroy quality of life. There is considerable need for research that integrates knowledge gained from cell biology, genetics, molecular biology, imaging technologies, neuroscience, behavioral sciences and epidemiology to better understand the mechanisms underlying the causes and progression of orofacial pain and dysfunction associated with TMJDs and other pain conditions.
Xerostomia
Saliva is a remarkable fluid essential for oral health: it guards against infections by favoring the accumulation of “beneficial” bacteria and helping to eliminate other microorganisms, lubricates the soft tissues of the mouth, buffers acids produced by cariogenic bacteria, aids digestion, and facilitates speech and swallowing. Salivary gland hypofunction or obstruction can result in xerostomia or dry mouth. Xerostomia is a significant health problem, particularly among the elderly, owing to the some 400 over-the-counter and prescription drugs, including tricyclic antidepressants, antihistamines, and diuretics that have xerostomic side effects. The most common disorder involving the salivary glands is Sjögren’s syndrome, an autoimmune condition that affects between 1 and 4 million Americans, mostly middle age women. Over 30,000 individuals who have cystic fibrosis are also at higher risk for salivary gland dysfunction. In addition, each year an estimated 40,000 people lose salivary gland function as a result of radiation treatment for head and neck cancer. Whether salivary glands are irreparably damaged by disease or by radiation for head and neck cancer, the resulting loss of saliva flow markedly impairs quality of life. Without adequate saliva, people may experience difficulty speaking, chewing and swallowing. They may also experience rampant tooth decay, mucosal infections such as candidiasis, loss of taste, and considerable oral discomfort. Currently, there is no effective treatment for this condition. New treatments such as the potential use of adult and embryonic stem cells for regeneration of salivary gland tissue and function, and gene transfer technology may offer new hope for patients with salivary gland damage or disorders.
Craniofacial Birth Defects or Syndromes
Craniofacial defects are among the most common of all birth defects. Birth defects and developmental disorders can be isolated or may be part of complex hereditary diseases or syndromes. Cleft lip and cleft palate are among the more common birth defects in the U.S., occurring in about 1 to 2 of 1,000 births. Numerous other disorders with oral and craniofacial manifestations such as ectodermal dysplasias, Treacher Collins syndrome, Apert’s syndrome, and Waardenburg syndrome, while considerably more rare than cleft lip/cleft palate, also have serious lifetime functional, esthetic and social consequences. These disorders are often devastating to parents and children alike. Surgery, dental care, psychological counseling, and rehabilitation may help ameliorate the problems, but often at a great cost and over many years. In fact, the lifetime cost of treating the children born each year with cleft lip or cleft palate is estimated to be $697 million5. Exciting advances in genetic studies are shedding light on genes that are important in forming the head and face, how these genes function and how they interact with environmental, nutritional and behavioral factors. Such information may ultimately provide the information necessary for prenatal diagnosis, the development of methods to prevent craniofacial birth defects, and the basis for developing better treatments. The development of biocompatible naturally-derived materials and biodegradable scaffolds offer new hope for the treatment of defects resulting from craniofacial birth defects or syndromes.
4Ries LAG, Eisner MP, Kosary CL, Hankey BF, Miller BA, Clegg L, Edwards BK (eds). SEER Cancer Statistics Review, 1973-1999, National Cancer Institute. Bethesda, MD, http://seer.cancer.gov/csr/1973_1999/ ,2002.
5CDC. Economic costs of birth defects and cerebral palsy – United States, 1992. MMWR 1992;44(no . 37). http://www.cdc.gov/mmwr/preview/mmwrhtml/00038946.htm.
