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CHAPTER 3 EPIDEMIOLOGY AND PREVENTION OF DENTAL DISEASES The committee considered dental benefits that are specific to three major oral diseases and conditions--dental caries, periodontal disease, and malocclusion. Central to the recommendation of specific benefits is the question of efficacy of professional interventions at various stages of the disease process. The committee's choices among alternatives are based in part upon the potential impact of services on oral health. The etiology, epidemiology, prevention, and treatment of dental diseases are examined in this chapter. Emphasis is placed on the prevention of caries and periodontal disease because control of the amount and severity of these two major bacteria-related conditions will greatly affect oral health. Malocclusion is also analyzed because it can seriously affect child growth and development in its severe or handi- capping forms. The primary function of human dentition is efficient chewing. Healthy teeth enable consumption of a varied and nutritious diet. Untreated dental disease causes dysfunction and eventual tooth loss. In 1971 about 11 percent of the American population was toothless, including about 51 percent of those aged 65 and over 91/. Although full dentures usually enable one to eat an adequate diet, no denture can approach the efficiency and comfort of healthy natural teeth. In the most recent National Health Interview Survey, about 30 percent of denture wearers indicated that their dentures needed to be refit- ted or replaced 92/. Speech can be affected by tooth loss or deviations in dentition and oral tissues 93/. In children 18 months to 4 years of age, the absence of primary incisor teeth can permanently affect the quality of certain speech sounds 93-95/. Disfigurement and pain caused by oral pathology or abnormali- ties can lead to impaired social function. A number of studies have emphasized the social and psychological importance of facial appear- ance 96-102/. A recent report of the National Research Council stated that dental disease, if left untreated, places an increasing burden 27

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on a person's emotional well-being, because pain and disfigurement lead to diminished comfort and poor self image 103/. Abnormal dento- facial appearance can evoke discrimination and an increased likeli- hood of an individual adopting a dysfunctional social role 104/. Pain is the most common consequence of untreated oral disease and is often the stimulus for seeking professional dental attention. The three most prevalent dental pathologies--caries, periodontal disease, and malocclusion--are discussed in the following pages. Dental Caries Etiology Dental caries (tooth decay) is the progressive destruction of the teeth by organic acids produced locally by bacteria 105/. Carious lesions may begin to appear soon after teeth erupt. Caries has a complex etiology that includes at least three factors--diet (pre- dominately sugars), acid-producing bacteria, and susceptible teeth. Sugars are cariogenic because they are easily fermented to acid. Sucrose may have a special role because some oral bacteria act on sucrose to produce sticky polysaccharides, which in turn enable the acid-producing bacteria to adhere to the surface of the teeth in a film known as dental plaque. Epidemiology Dental caries is the most common dental disease in the United States and is the primary cause of tooth loss through young adulthood: by age 35, the average American has lost five teeth and has 11 more attacked by caries 106/. The most widely used measure of dental caries is the DMF index, which is usually expressed as the total number of decayed (D), missing (M), and filled (F) permanent teeth per person. DMF measures the total cumulative experience with the disease at any one point in time, but the three components reflect different aspects of a person's experience with dental caries. D represents the number of permanent teeth with untreated decay. The F component reflects the number of filled or restored teeth, which indicates experience with dental care received. M theoretically is a measure of teeth extracted be- cause of decay but because teeth can be lost for reasons other than decay, M should be interpreted cautiously. For the over-35 age group, in which severe periodontal disease often causes tooth loss, the M component is an inappropriate indicator of caries experience. The combined DMF may not portray changes in oral health. The F can in- crease and the D decrease, leaving the DMF unchanged, although more filled teeth and fewer untreated decayed teeth mean a change for the better in oral health. 28

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The epidemiological data on dental disease in this report, in- cluding the DMF were obtained in the 1971-74 Health and Nutrition Examination Survey (HARES) 107/ conducted by the National Center for Health Statistics.* The RANKS data show a direct relationship between age and dental caries in a susceptible population. One indication of this relationship is that girls 3 to 5 years old, whose teeth usually erupt earlier than boys, tend to have more caries than boys of the same age 108/. Adult women have a slightly higher DMF rate than men. A review of the incidence and prevalence of dental caries by age is of interest. Thirty-three percent of elementary school children aged 6 to 11 have two or more decayed teeth 109/. Within this age group an average of 2.7 primary teeth have been attacked by caries. In addition, the total DMF for permanent teeth is 1.7 (Table 11~. The prevalence of caries in permanent teeth increases with age among children, and by age 11, more than 75 percent of all children have ex- perienced tooth decay 110/. Table 11. AVERAGE NUMBER OF DECAYED, MISSING, AND FILLED PERMANENT TEETH OF CHILDREN, BY AGE AND SEX, 1971-74 Age Total DMF Decayed (D) Male Female Male Female - Missing (M) Filled (F) Male Female Male Female Total 1.7 0.7 0.1 0.8 6 .2 .3 .1 .1 .0 .15 .1 .1 7 .5 .6 .3 .4 .1 .0 .1 .2 8 1.3 1.2 .6 .6 .1 .0 .6 .6 9 1.9 2.4 1.0 .9 .3 .1 .7 1.4 10 2.5 2.5 .9 .9 .2 .2 1.4 1.5 11 2.6 3.1 1.1 1.1 .4 .3 1.1 1.7 . Source: Health and Nutrition Examination Survey (HARES), National Center for Health Statistics 111/. Table 12 shows the incidence and prevalence of disease, as measured by DME, for adolescents aged 12 to 17. Rising about 1.0 DMF tooth per year, the incidence of caries among adolescents is twice that of chil- dren, although part of the difference is due to the presence of more teeth at risk. . *The BANES study is described in Chapter 2e A description of sampling and standard errors can be found in the appendix e 29

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The DMF increases steadily with age (Table 13). The portion of the DMF representing decay among adults is highest in the 18-to-24 year-old group, with an average of more than two decayed teeth per person; this figure gradually declines to less than one by age 65. The missing (M) component rises with age. The filled (F) component of the DMF reaches a high of around nine teeth in the 25-to-44 age range, dropping to about six among the elderly, largely because of the extraction of filled teeth. Table 12. AVERAGE NUMBER OF DECAYE1), MISSING, AND FILLED PERMANENT TEETH OF ADOLESCENTS, BY AGE AND SEX, 1971-74 - Total DMF Decayed Missing Filled Age Male Female Male Female Male Female Male Female Total 6.4 1.8 0.6 3.7 * 12 3.9 3.7 1.0 1.4 .3 .4 2.6 1.9 13 4.8 5.2 1.9 1.7 .4 .4 2.4 3.0 14 5.1 6.6 1.7 2.0 .5 .9 3.0 3.7 15 5.4 7.1 1.6 1.9 .5 1.0 3.3 4.4 16 7.1 8.3 2.1 1.9 .6 1.6 4.4 5.1 17 8.1 9.4 2.1 2.4 1.6 1.6 5.4 5.4 .. Source: Health and Nutrition Examination Survey (HARES), National Center for Health Statistics 112/. Table 13. AVERAGE NUMBER OF DECAYED, MISSING AND FILLED TEETH OF DENTULOUS ADULTS, BY AGE AND SEX 1971-74 Age Total DMF Decayed Missing Filled Group - Male Female Male Female Male Female Male Female Total 16.9 1.4 7.4 8.1 18-24 10.5 11.0 2.2 1.9 1.7 1.8 6.6 7.3 25-34 14.9 15.8 1.8 1.7 4.1 4.9 9.0 9.2 35-44 18.4 20.0 1.2 1.1 8.4 9.9 8.8 9.2 45-54 19.2 20.5 1.0 0.9 9.9 11.1 8.3 8.5 55-64 20.7 21.5 1.0 0.8 12.4 12.6 7.3 8.1 65-74 21.8 22.5 0.7 0.5 15.6 14.8 5.5 7.2 Source: Health and Nutrition Examination Survey (HADES), National Center for Health Statistics 113/. 30

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Treatment Dental caries is usually treated by removing the decayed portion and reconstructing the tooth. Teeth have limited capacity for self repair, therefore carious lesions become worse with time. The type of treatment depends on how early it is instituted. Reconstructive services fall into three main categories--fillings, inlays and onlays, and crowns. The filling materials generally are sil- ver amalgam for posterior teeth, tooth colored composite resins for anterior teeth, and cast gold inlays/onlays for teeth that have lost sub- stantial amounts of tooth structure. A full crown is the treatment of choice when there is little or no supporting enamel remaining after the decay is removed. If the destruction caused by the decay has affected the tissues of the pulp chamber, endodontics (root canal therapy) may be needed if the tooth is to be retained. When the most extensive treatment (root canal filling and a crown) cannot be performed, the tooth must be extracted. The dental treatment then consists of replac- ing the lost tooth or teeth with either removable partial dentures or fixed bridges. Partial dentures usually are held in place by means of clasps on the adjacent natural teeth. The loss of all teeth calls for full dentures. Because treatment of dental caries increases in complexity as the disease process advances, prevention of disease or early diagnosis and treatment are important. Prevention Several preventive strategies for dental caries are available. These include plaque removal and diet modification and the use of fluorides and tooth sealants. Fluoride There is ample and convincing scientific evidence of the effectiveness of fluoride in reducing dental caries. Fluoride can be administered in treated drinking water, in dietary supplements, or can be applied directly to the teeth by the individual or by professionals. The most effective and efficient method of exposing teeth to fluoride is to consume it in drinking water. A recent symposium speaker on caries prevention stated: Water fluoridation involves a minimum per capita outlay for a tremendous saving in the cost of re- placing decayed and missing teeth. As such, it is one of the few bargains available in health care 122/. 31

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Approximately half of the American people have drinking water that is either naturally fluoridated or has had fluoride added.* Children who from birth have drunk fluoridated water have, on the average, 50 to 70 percent less teeth decay than those who have not 114-121/. Loss of first permanent molars can be reduced as much as 75 percent; and caries on the proximal surfaces of upper incisor teeth can be reduced 95 percent. The economic benefits of fluoridation vary with such factors as the age of the subjects when fluoridation was initiated, the total number of years they have been drinking fluoridated water, and the size of the city. A conservative estimate, based on number of tooth surfaces saved, is an annual saving in treatment costs of $11 to $16 per capita, resulting in an average cost-benefit ratio of approximately l:SO after 12 to 15 years of fluoridation 122/. In other words, for every dollar spent on water fluoridation, 50 dollars are saved in treatment costs. One of the advantages of community water fluoridation is that it does not require active cooperation from individuals for its benefits to be conferred. Children in such communities receive fluoride from birth, which is expected to maximize the benefit. A recent report to Congress by the General Accounting Office stated that the U.S. Public Health Service was not actively promoting fluoridation 123/. Subsequent- ly, the Public Health Service, through the Center for Disease Control, has increased its efforts to promote community water fluoridation. There is a need to educate the public on the benefits of fluoridation. A national survey taken in 1977 revealed that 76 million adults--about 51 percent of the adult population--do not know what fluoridation is. About 45 million adults served by public water systems do not even know that the water they drink is fluoridated 124/. The fluoridation of school water supplies is effective in rural communities that lack a central water supply. But because children do not attend school until some of their permanent teeth are partially or fully mineralized, the benefits of school water fluoridation are less than for community fluoridation. School water is usually fluori- dated at levels higher than the concentration recommended for community fluoridation, because children consume only part of their daily intake of water at school. The maximum benefit reported has been a 10 to 40 percent reduction in caries 125-131/. The approximate cost per person is $1.50 a year, with a cost-benefit ratio of 1:5.3 (one dollar spent for fluoridation saves $5.30 in dental costs). This figure varies *A report that cancer mortality was higher in cities with fluoridated water than in those without fluoridation appeared in 1975 132-133/. How- ever, subsequent analyses have repudiated these findings 134-135/. When the crude death rates for fluoridated and non-fluoridated cities were adjusted for demographic characteristics and for variables such as population density, median education and income level, and percentage of the population employed in manufacturing, no association was found between fluoridated water supplies and increased mortality 136/. 32

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with the size of the school; fluoridation is more efficient for larger schools and requires no individual compliance. Dietary supplements of fluoride, in tablet form, can effectively reduce caries. It has been estimated that a 50 to 70 percent reduction in caries results from ingestion of fluoride tablets from birth. When tablets are administered at school, the caries-inhibiting effect has been estimated at 20 to 40 percent 122,120/. A six-year clinical trial of chewable fluoride tablets administered at school showed that children who chewed one tablet a day during the school year had 28 percent fewer cavities than a control group 338/. The cost-benefit ratio of tablets distributed at school is about 1:17.5 122/, or one dollar spent for tablets saves $17.50 in dental care costs. Administration of tablets at home is less effective for lack of parental compliance. Table 14 displays the cost-benefit comparison of community and school water fluoridation and distribution programs of fluoride tablets in a school setting. Table 14. ESTIMATED ANNUAL COST-BENEFIT RATIOS OF SYSTEMIC FLUORIDES a/ Estimated Cost- percent caries Cost per Saving per benefit Method reduction capita capita ratio b/ Community Water Supply Fluoridation 50 $0.20 $10.00 1:50 School Water Fluoridation 40 1.50 8.00 1:5.3 Fluoride Tablets Distributed at School 35 0.40 7.00 1:17.5 a/ Estimates represent maximum benefits, which would not be attained until program has been operating for more than 12 years. b/ Assuming caries increment of 2~0 DMF/year in nonfluoridated community and cost of restoring a surface at $10. Source: University of Michigan Workshop on Caries Prevention 137/. Table 15 shows the recommended dosages of dietary fluoride supple- ments adjusted for children's ages and content of fluoride occuring naturally in the drinking water. 33

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Table 15. RECOMMENDED DOSAGES OF DIETARY FLUORIDE SUPPLEMENTS, BY AGE AND LEVEL OF FLUORIDE IN WATER SUPPLY OF LOCALITY Natural Fluoride Content as Per- cent of Optimal 0-2 Years 2-3 Years 3 Years and Older a/ Fluoride Dosage in ma. Greater than 70% None None None 30% to 70% 0.125 0.25 0.5 Less than 30% 0.250 0.50 1.0 a/ Dietary fluoride supplements should be continued until at least ages 12 to 14, or until all permanent teeth other than third molars have erupted. Sources: Community Programs Section, National Caries Program, National Institute of Dental Research, National Institutes of Health (memorandum to Dental Public Health Professionals, 1979) Weekly fluoride mouthrinsing has proved to be an effective method of self-application when carried out in schools. More than 20 large- scale clinical trials have shown that frequent mouthrinsing with diluted fluoride solutions inhibits dental caries 138/. Caries reduction in these programs has ranged from 20 to 50 percent. Mouthrinsing in school can be done in the classrooms and can be supervised by properly trained teachers, aides, or volunteers. The Food and Drug Administra- tion does not require professional dental personnel to supervise this activity. About 8 million children in the United States are participating in school fluoride mouthrinsing programs 139/. Assuming a conservative 25 percent caries reduction, the cost-beneit ratio of a weekly fluoride rinse in school has been projected at approximately $1 for each tooth surface saved, or about 1:10. If payment is made for supervision, the cost would increase to $1.60 per surface saved. Even in an opti- mally fluoridated community, a weekly mouthrinse at school combined with periodic applications of a fluoride gel tray resulted in 30 percent fewer new DMF surfaces 140/. However, this method requires much more organization than does systemically administered fluoride. Other methods of self-application of fluoride include supervised brushing with solutions and pastes, and the above-mentioned application of fluoride gel in trays customfitted to each chills mouth. These procedures are usually supervised by professional dental personnel, such as a dental hygienist, and are more complicated than the mouth- rinse. Although brushing can be done less frequently than mouthrinsing (every two to six months depending on the type and concentration of fluoride used), its cost-effectiveness is less favorable because of

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the professional time required to supervise the procedure. The gel- tray technique has produced an 80 percent reduction in caries, when used dally, but the cost of producing the trays and the professional time required to supervise the application makes the total cost-benefit ratio unfavorable. Even if done in large groups in a school setting, the cost is an estimated $21.30 per surface saved 141/. Table 16 com- pares cost-effectiveness of various topical fluorides. . . ~ . . Use of fluoride-containing dentifrices will reduce caries to 40 percent in areas with fluoride-deficient water 142-144/. from 15 Studies have shown that supervised brushing at school with fluoride dentifrices does not provide more anti-caries protection than normal home use. More than 70 percent of all dentifrices sold in the United States contain fluoride. Because home use of these products is already widespread, it probably is not economical to provide fluoride dentifrices at public expense 145/. On the other hand, it may be worth while to encourage brushing with fluoride dentifrices as part of a broader program of pre- ventive measures 146/. ~ . Table 16. ESTIMATED COST-EFFECTIVE~SS OF TOPICS FLUORIDE PROCEDURES ~ . Estimated Cost per percent tooth surface Procedure reduction saved Weekly mouthrinse 25 $1.00 Professional application of solution (multiple- chair method) 25 to 40 2.60 to 4.40 Annual professional . application or gel in preformed trays 40 4.40 Toothbrush~ng at home 20 10.00 Daily self-application of gel in custom trays 80 21.30 Source: University of Michigan Workshop on Caries Prevention, 1978 147/ Professionally administered fluoride treatments usually consist of a prophylaxis followed by exposure to a fluoride solution or gel for several minutes. Performed annually, this procedure can reduce caries 35

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from about 25 to 40 percent, according to various investigators 148-150/. The cost, when the procedure is performed by a hygienist, has been esti- mated to be from $2.60 to $4.40 per tooth surface saved. Professional application of fluorides is a cost-effective preven- tive treatment for those who receive the treatment. If the goal of a public health program is to reach the maximum number of children, how- ever, a less costly self-administered procedure may be desirable. For example, a weekly school mouthrinse that produces a 25 percent reduction in caries for a large number of children may be considered preferable to a professionally administered program, which, because of manpower and money constraints, would be available to a smaller number of child- dren. Tooth sealants Adhesives have come into use recently to seal the biting surfaces of teeth. Although these surfaces represent only 12.5 percent of all tooth surfaces at risk for caries, studies of school- children have shown that as much as 45 percent of carious activity occurs in the "pit and fissures" of these surfaces 151/. Several types of sealants have been tested with varying degrees of effectiveness. Teeth are usually carefully prepared by trained personnel in order for the adhesive to be bonded successfully with tooth enamel. Although a first-year reduction in caries of 80 to 100 percent has been reported with the use of sealants 152-158/, the application is time- consuming and therefore relatively expensive. For maximum effectiveness, sealants must be applied soon after tooth eruption. Children must visit a dental professional at regular intervals to seal newly erupted teeth and to replace lost sealant; The results of clinical trials vary great- ly, depending on the type of sealant used and how well it is retained on the teeth 159/. It is unrealistic to attempt to estimate a cost- benefit ratio, but this method might be cost-effective if performed by trained auxiliaries rather than dentists, and if done during the same visit as other preventive procedures. Plaque removal Theoretically, the regular removal of plaque should decrease dental caries, because the presence of plaque is necessary to initiate carious lesions. However, few studies sub- stantiate this relationship. Experimental programs for mass control of plaque in the United States have tended to focus on gingival health or oral hygiene status as outcome criteria 160/. A Swedish study did monitor caries reduction 161-163/. School- children in an experimental group were given regular prophylaxes, while those in a matched control group were not. At the end of four years, the control group had 15 times as much caries as those in the experimental group. The prophylaxes were performed once every two weeks during the first year and every three weeks the second 36

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year. The interval was gradually increased to 8 weeks during the fourth year for younger children and 16 weeks for older children. In a similar study, children's teeth were deplaqued every three weeks for three years. This regimen produced a 51 percent decrease in new caries 164/. These studies have shown that the mechanical removal of plaque can successfully control caries; however, the frequency with which the procedure must be performed to be effective makes this method of caries prevention expensive. Further, some researchers suggest this procedure may remove the outer enamel that is rich in fluoride content. Therefore, it might well be undesirable from the standpoint of public health programs designed to reach large numbers of people. Diet Modification The annual per capita consumption of sucrose in the United States increased 15 percent between 1960 and 1977. Sucrose now constitutes between 16 and 25 percent of the calories in the average American diet. About 76 percent of the sugar consumed occurs naturally or is added to foods and beverages by processors; a growing proportion of that is consumed in the form of between-meal snacks. Only 24 percent of the sugar consumed in the United States is added to foods by consumers 165/. The consumption of sugars, particularly between meals, contri- butes to tooth decay. An experimental program in Sweden showed that discontinuing the practice of eating sticky sweets between meals could reduce caries as much as 90 percent 166/. A review of 17 studies points up the importance of the frequency of consumption of snack foods in causing caries 167/. In a recent symposium on caries prevention, three public health approaches to diet modification were suggested 168/. 1. Reduction of the availability, intake, and desire for sweets. 2. Fortification of sugars with anticaries nutrients like phosphates. Substitution of refined sugars by less fermentable carbohy- drate sweeteners or by other natural or synthetic sweetness. Positive clinical data supporting the second approach--fortification of sugars--do not seem to be available. With regard to the other alternatives, some actions have already been taken to reduce the availability and desire for sugar. Processors of baby food have eliminated some sugar from their products, and a campaign has been organized against advertisements for sweets on children's television. Another approach could be to teach nutrition in the public schools, the lessons being reinforced by private dental practitioners and their auxiliaries. 37

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There are several natural and artificial sweeteners that could be used as substitutes for sugar. Saccharin is the only synthetic sweetener available, but it has been shown to cause bladder cancer in animals, and so its carcinogenicity in man is suspected. Research is currently being conducted on the suitability and safety of a number of other sweeteners, although none will likely be ready for public consumption for several years. Percentage ingredient labelling on food packages would tell the consumer exactly what proportion of the food is sugar. Presweetened foods might be eliminated from government funded school lunch and break- fast programs. School boards or other official bodies could curtail the use of vending machines that dispense sugar-rich foods in schools. In Alabama, an elementary school cannot receive state accreditation if it contains vending machines that dispense sweet foods 169/. There are many ways that the consumption of cariogenic food could be reduced. Discouraging the frequent consumption of sugar rich food may be, in the long run, an effective strategy for the primary preven- tion of dental caries, although extensive efforts would be required to achieve long-lasting change in eating habits. Periodontal Diseases Periodontal diseases are pathological conditions of the surround- ing and supporting structures of the teeth. Periodontal diseases are almost as prevalent as dental caries in the American population. They affect nearly 75 percent of the adult population and are the most com- mon cause of tooth loss in persons over 35 years of age 170/. Etiology The initiating factor for periodontal diseases is similar to that for dental caries: bacterial colonizations in dental plaque 171/. Although it is not known which of the many organisms in the mouth are responsible for the various forms of periodontal disease, a number of studies have found a direct relationship between the amount of bacterial plaque on teeth and the severity of gingivitis 172-175/. It is clear that the bacteria residing in the human gingival crevice can produce a variety of enzymes capable of destroying many of the constituents of human gingiva 176-181/. There is specific evidence from more recent studies that implicate various microorganisms as primary contributors to the formation of periodontal disease 182-184/. However, studies so far have failed to show a direct relationship between periodontal diseases and either genetic or nutritional factors 185-186/. Hard deposits on teeth (calculus) have not been shown to cause inflammation by their mere physical presence 187-188/. A series of 38

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studies showed that the presence of bacterial plaque was more im- portant histologically in the initiation of severe inflammation than mechanical irritation from calculus 189-193/. Calculus is always - covered by bacterial plaque, however, and by removing the calculus, the plaque is also removed. The incidence of various periodontal diseases is difficult to estimate because of uncertainties in separating the different clinical entities that are grouped under one general heading. In 1956, Russell 194/ developed the Periodontal Index (PI), which scores the clinical manifestations of the periodontal diseases on a scale of 0 to 8. Higher scores indicate gross pathology of bone destruction; lower scores signal more subtle clinical signs of early gingivitis. The PI score is a mean score for each individual, not an absolute count as is the DMF. Thus, a person can have one or more areas with advanced periodontal disease but show a low mean PI score. Another important measure in the assessment of periodontal disease is the Simplified Oral Hygiene Index (OHI-S) developed by Greene and Vermillion 195/ in 1964. The OHI-S is the sum of two component scores, the Simplified Debris Index (DI-S) and Simplified Calculus Index (CI-S). The PI and OHI-S measures have been used in the epidemiological data presented in this section. These data were obtained in the 1971-74 Health and Nutrition Examination Survey 216/ conducted by the National Center for Health Statistics. Epidemiology The incidence of periodontal diseases varies most noticeably with age and oral hygiene 197/. The presence of organisms in dental plaque probably explains the relationship between oral hygiene and periodontal diseases, but the relationship with age is not clearly understood. It would appear that the microorganisms in dental plaque provide a chronic irritation that eventually begins to break down the periodontal tissues. The gingival inflammation of children ages 6-11 is mostly asso- ciated with tooth eruption. Thirty-two percent of American youths aged 12-17 and approximately half of the adult population with at least one remaining natural tooth have some periodontal disease. Thirty-seven percent of adults have chronic disease with pocket formation between gum and tooth. Both income and education are inversely associated with high PI and OHI-S scores. Men have a mean score 40 percent higher than women, and black adults have an 80 percent higher perio- dontal index than whites. In summary, periodontal diseases are a major threat to oral health and account for a significant amount of pain, discomfort and loss of teeth in the adult population. 39

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Treatment The intent of the treatment of periodontal diseases is to interrupt, arrest, or reverse the progressively destructive process of the bacterial colonizations that are the precipitating causes of periodontal diseases. In more advanced diseases, an attempt is made to arrest the progression of the periodontal pockets which lead to the loss of the supporting bone. Treatments of more advanced clinical states of periodontal diseases are aimed at rearranging the forces on the periodontal attachment apparatus which consists of the root cementum, supporting bone, and the periodontal ligament (the connective tissue contents of the space between the bone and root cementum). The specific treatments and the order in which they are given will vary from patient to patient, but the stages in the process often include: 1. Thorough prophylaxis and the establishment of a program of oral hygiene in order to control or eliminate gingival inflammation; thorough root planing and gingival curettage. 2. Reevaluation of the patient's ability to maintain oral hygiene as a condition for more extensive treatments. 3. Restoration of carious lesions that are related specifically to gingival health. 4. Extraction of teeth beyond treatment because of periodontal de- struction. 5. Periodontal surgery. 6. Occlusal adjustment. Extensive surgical therapy for advanced periodontal diseases is usually performed on patients who can maintain their oral hygiene and who understand the disease process which they are being motivated to control. Several studies in which comparisons were made between con- servative treatment (curettage) and periodontal surgery raise some questions about the cost-effectiveness of periodontal surgery. Ramfjord, et a1. 198/, report that in the short term (one to three years after treatment) curettage resulted in a slight gain of attachment, while sur- gery resulted in a slight loss of attachment. For the long term, there was no significant difference in attachment between the two therapies. In another analysis after 15 years, the subsequent loss of teeth was related more to the extent of pathology than the surgery performed 199/. Some investigators suggest that a diligent oral hygiene program that in- cludes toothbrushing, flossing, irrigation, application of certain 40

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saturated salt solutions deep into the gingival sulcus, and periodic courses of systemic tetracycline can eliminate or greatly reduce potentially pathogenic bacterial populations 200/. Their findings suggest that this treatment abates or arrests further periodontal destruction. Prevention Plaque bacteria play a major role in the etiology of both dental caries and periodontal diseases. Since natural mechanisms do not adequately clean teeth, a combination of professional cleaning and personal oral hygiene practices (toothbrushing, flossing, water pres- sure devices and gingival stimulators) is recommended to control dental plaque. This combined approach can reduce the incidence of periodontal diseases by 90 percent 201-202/. But there are many gaps in the knowledge related to plaque control 203/. Plaque may form anew on teeth 24 hours after cleaning; it is not clear how often it must be removed to control or prevent disease. It has been shown in one study that subjects who removed all traces of plaque from teeth every two days can maintain healthy gingiva. However, the subjects' teeth and gums were in excellent condition at the beginning of the study and their teeth were checked after each brushing to be sure plaque had been completely removed 204/. There is additional evidence that supervised self-administered oral hygiene procedures are effective in reducing plaque and gingival inflammation 205/, and that plaque control is important for the success of periodontal treatment 205-206/. Teaching people to brush and floss their teeth correctly and moti- vating them to do it regularly without supervision has proved to be difficult. Formal classroom instruction in dental health for children generally has failed to produce long-term behavioral changes. The New York City Health Department recently terminated a 50-year-old program of classroom instruction in dental health for elementary and junior high school children because it failed to reverse a 20-year decline in the number of children seeking or receiving dental treatment annually 208/. More encouraging results have appeared in studies of instruction and motivation techniques combined with professional dental care. In one three-year study 209/, an experimental group of young adults was given a professional prophylaxis at two, four, six, and nine months during the first year, at three-month intervals during the second year, and at four-month intervals during the third year. They were also instructed repeatedly about personal oral hygiene and periodontal disease, both individually and in groups. A control group was given annual examinations and told to continue with their usual oral hygiene practices. 41

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The oral hygiene score of the control group increased (worsened) at more than four times the rate of the experimental group. Gingival inflation scores were significantly lower and loss of epithelial attachment was significantly less in the experimental group. A follow- up examination 32 months after the end of the original study found that subjects in the experimental group continued to show cleaner teeth, less gingival inflammation, and less detachment of tissues than subjects in the control group 210/. A future alternative to the mechanical cleaning of teeth may be the use of vaccines or antimicrobial agents to eliminate plaque, although clinical trials of antimicrobials so far have yielded ambiguous results 211-215/. At present, however, it would seem that an organized and super- vised program of activities aimed specifically at the prevention of perio- dontal diseases may be the most effective method of prevention. Such a program should consist of multiple components, each of which has some scientific evidence that would suggest its inclusion. The clinical ob- jective of such a preventive program would be to facilitate the removal of bacteria, plaque, and calculus from the teeth. The high prevalence of periodontal diseases among youths provides support for the need for professional intervention to prevent periodon- tal diseases. Among youths 12 to 17 years of age, for example, 32 per- cent have periodontal disease and 6 percent of those show evidence of destructive periodontal disease 216/. Data from the National Nutrition Survey, primarily of low-income families, show that 55 percent of children in junior high school and 65 percent of all high school stu- dents have periodontal disease 217/. In seven cases of every 100 persons so afflicted, the disease had reached an advanced and destructive stage. Thus, because calculus is present in a fairly high proportion of youths, and because there is evidence of destructive (irreversible) periodontal diseases occurring, it would seem prudent to interfere with the progression of the disease in this age group by means of periodic, thorough oral prophylaxis. Because the need for such prophylaxis at specific intervals is not universal, this treatment might be limited to those with the greatest need. The literature on prevention suggests that a combination of pro- fessional cleaning and personal oral hygiene practices can reduce the incidence of the periodontal diseases. However, reliance on individual behavior alone to control the bacterial plaque associated with perio- dontal diseases has not been shown to be effective. Therefore supportive professional attention to remove calcified plaque and reinforce personal oral hygiene habits seem to be necessary components of a successful pro- gram to prevent periodontal diseases. 42

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Malocclusion Although not as prevalent as dental caries or periodontal diseases, severe malocclusion is a handicapping condition for a sub- stantial minority of the population. A malocclusion is considered to be seriously handicapping when the malposition of the teeth and jaws seriously inhibits the ability to chew and/or adversely affects social roles. The term malocclusion refers to ". . . that condition in which dental structures are not in acceptable equilibrium with each other or with the facial structures and/or cranium, thus inter- fering with or posing a potential threat to normal tissue development and maintenance, effective function, or a psychological problem" 218/. Etiology Malocclusion often follows loss of teeth due to poor hygiene. Un- treated dental caries may cause premature tooth loss. The "space loss" resulting from lost tooth structure is considered to be one of the causes of malocclusion 219/. Malocclusion may also be related to child- hood anxiety. Intensive and prolonged thumbsucking has been described by Moyers as "a direct cause of some of the worst forms of maloc- clusion" 220/. The National Health Examination Survey of children 6-11 years of age also found a relationship between thumbsucking and malocclusion 221/. The role of genetics in malocclusion is complex. Studies of twins indicate that heredity and environment are probably of equal importance in the etiology of malocclusion 222/. Epidemiology The Health Examination Survey indicated that orthodontic diagnosis, which includes evaluation of facial proportions and the relation of teeth to the underlying bone structure, is needed for approximately 2.5 million children and 10 million youths (about one out of every two youths in the U.S.) who have Treatment Priority Index (TPI) scores of 7 and above. The Treatment Priority Index combines selected major components of occlusion to obtain a weighted score, which ranges from O (ideal) to 10 (very severe malocclusion) 223/. The average TPI score for children and youths gen- erally does not vary significantly with age, sex, race, family income, parents' education, or region of residence. Tooth displacement (crooked teeth) is probably the most widely recognized sign of malocclusion. Approximately two out of five children have crooked teeth, and one in 10 have tooth displacement scores of 4 or more, which the Health Examination Survey team assumed to be of critical severity. 224/ 43

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In youths ages 12 to 17, tooth displacement is far more common than in younger children, because of the greater number of erupted teeth. More than 6 out of every 10 youths have tooth displacement scores of 4 or more. Approximately 17 percent of youths have either lingual or buccal crossbite 225/. The National Research Council Study of Seriously Handicapping Orthodontic Conditions estimated that use of criteria developed during the study "would probably identify approximately five percent of any population of children in this country as having a seriously handi- capping orthodontic condition" 226/. The report, citing the National Center for Health Statistics, finds that an additional nine percent have a handicapping orthodontic condition for which treatment is "highly desirable." Treatment The treatment of malocclusion is accomplished by a variety of minor and major tooth movement techniques. The objective of treatment, which can require up to 24 months, is to move the teeth into more func- tionally and esthetically acceptable alignment and occlusion. The full arch appliance is probably the most common orthodontic treatment technique currently used in the United States. This treatment entails placing of bands on each tooth and attaching a wide variety of brackets, pins, tubes, and wires to these bands in order to place tension on the appropriate teeth, thus causing them to move in a controlled fashion. In addition to the treatment of major malocclusion problems, there are many orthodontic treatment procedures that are applicable to minor tooth movement. Most of the appliances for minor tooth movement are either removable or use a technology that does not require the placement of bands on every tooth. Correction of oro-facial muscle imbalance is a relatively recent development that has emerged from the work of speech pathologists and cleft palate dental teams who were focusing originally on abnormal swallowing, speech defects, and tongue thrusting. Malocclusion is frequent in these cases. The successful treatment of malocclusion in these people is often dependent on the improvement or correction of these detrimental muscular forces. Prevention Prevention of malocclusions 227-228/ is unlikely because of the genetic factors in its etiology. However, some services are described by various authors as interceptive or palliative treatment. These services include 1) procedures to maintain or provide space for natural 44

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tooth movement at critical moments of growth and development, 2) the discouragement of thumbsucking, and 3) minor tooth guidance procedures. After a recent review of such procedures, Dunning concluded that, "Few of the techniques described . . . are within the usual range of the general practitioner" 229/. Perhaps the most clearly defined preventive orthodontic procedure is the use of a space maintainer on elementary school children. When a primary tooth is lost prematurely and the succeeding tooth is not expected to erupt for more than a year, the space should be maintained by an applicance. However, the best space maintainers are healthy primary teeth. Fluoride therapies and the timely restoration of primary teeth can lessen the need for space maintainers. Summary and Conclusions The literature shows that bacteria are associated with the etiology of both dental caries and periodontal diseases, with sugar as a necessary contributory agent in the development of dental caries. Bacterial colonizations in the form of dental plaque are directly asso- ciated with the initiation and progression of dental caries and the periodontal diseases. These bacteria act on sugars and other carbohy- drates to produce acids, which initiate carious lesions in tooth enamel. Both dental caries and the periodontal diseases are nearly pandemic in the U.S. population. Two-thirds of the people of the United States need dental treatment. Thirty-three percent of elementary school children have two or more decayed teeth, and by age 11, more than 75 percent of all children have experienced tooth decay. By age 35, Americans, on the average, have lost five teeth and have 11 more affected by caries. Treatment early in life is essential to improved oral health during adulthood. Periodontal disease is most strongly associated with the presence of bacterial plaque due to poor oral hygiene and with increasing age, probably because long-term chronic irritation from the plaque eventu- ally breaks down the periodontal tissues. The National Nutrition Survey found that 55 percent of junior high students and 65 percent of high school students have some degree of periodontal disease. Approximately 50 percent of adults with teeth have periodontal disease, and about 37 percent have chronic disease with pocket formation. Because of the substantial cost of treating the effects of dental caries and periodontal diseases, much attention has been paid to their prevention. Extensive literature on the prevention of dental caries shows four general strategies--plaque removal, diet modification, use of fluorides, and tooth sealants. Each of these preventive technologies 45

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can be effective under some circumstances, but the systemic fluorides are most easily applied on a community basis and topical flourides are effec- tive in school-based programs. Plaque removal and diet modification entail a marked individual health behavior change; tooth sealants must be applied by a professional, are useful only for chewing surfaces of the teeth, and are less cost-effective than fluorides. A variety of cost-benefit analyses suggest that several of the fluoride strategies are highly cost-effective, providing the basis for the committee's recom- mendation of a foundation of community fluoridation and preventive care as essential to improvement of dental health. - Analyses of dental caries, periodontal diseases, and malocclusions presented in this chapter underlie the recommendations relating to pre- ventive services. These recommendations include a basic public system to assure the delivery of services to all children. The analyses also furnish a basis for emphasis on prevention for adults as a high priority in coverage of dental care services under an insurance program. 1 46