29 Prevention of Periodontal Diseases
Although our understanding of periodontal conditions is growing rapidly (see Chapter 21), prevention and control of periodontal conditions still must be based on the periodic removal of plaque and calculus, whether by the individual or by a dental professional. There is no parallel in prevention of periodontal diseases to a public health measure such as water fluoridation.
Our current understanding that only some 5%-15% of the population suffers from serious periodontitis has led some to downplay the importance of prevention; this is the view that “periodontal disease doesn’t matter anymore.” This view is clearly faulty, because this level of prevalence still means that some 30 million Americans suffer from serious periodontitis. Based on the data given in Chapter 21, eight times that number have moderate adult periodontitis, much of which requires treatment and could probably be prevented. Prevention of periodontitis still is clearly a worthwhile public health endeavor; the problems and the frustrations come with our limitations in how to accomplish it. Even though our understanding of periodontitis has expanded greatly over recent years, the only practical approach to prevention of periodontitis (as opposed to its control through clinical treatment) is to prevent and control gingivitis.
The rationale for controlling periodontal conditions by regular plaque removal is based on the premise that supragingival plaque, if undisturbed, will become subgingival plaque,92 and subgingival plaque has the potential to be colonized by periodontopathogenic bacteria. Although relatively few gingivitis sites progress to periodontitis (see Chapter 21), we still cannot identify those sites that will. Accordingly, the principle for prevention has not changed for years: the regular and consistent control of plaque buildup, supragingival and subgingival, soft and mineralized (calculus), on the teeth and in the gingival crevices. This approach is bacteriologically nonspecific, for it seeks to control the buildup of all plaque. It also depends strongly on individual motivation for success. Plaque control is therefore unlikely ever to be completely effective in preventing periodontal diseases in a population, although individual success is common. Until research produces methods of controlling periodontal infection, enhancing host response, and identifying susceptible individuals, however, mass plaque control by personal, professional, or chemical means is the best we can do.
This chapter deals with methods for controlling the deposition of dental plaque, an approach that can effectively prevent gingivitis. As was detailed in Chapter 21, however, the role of plaque in periodontitis is not so straightforward. Plaque deposits may be a necessary condition for periodontitis, but clearly they are not sufficient. In other words, susceptible people may have to be stringent about oral hygiene, but there are millions of people with poor oral hygiene who do not have serious periodontitis. There is an analogy here with the role of consumption of sugars in the development of caries: caries-susceptible persons have to restrict their intake of sugars, but there are many people who consume a lot of sugars but have little or no caries as a consequence.
Although dental plaque is commonly depicted as the root cause of both caries and periodontitis, one should remember that it must have evolved in humans for some purpose. Commercial advertising would have us believe that oral health depends on the complete removal of all plaque at all times, but clearly that is not only not possible but also not desirable. Dental plaque forms naturally on the teeth and benefits the host by helping to prevent intraoral colonization by exogenous species.88 Plaque’s role in promoting remineralization of demineralized lesions was described in Chapter 20.
Dental plaque is a natural biofilm that forms on the tooth surface and consists of a diverse microbial community embedded in a polymer matrix of bacterial and salivary origin.89 After a tooth surface is cleaned, the pellicle, a conditioning film of proteins and glycoproteins, is adsorbed rapidly onto the tooth surface. The interactions between pellicle and early bacterial colonizers are the first steps in plaque formation. Secondary bacterial colonizers adhere to these early colonizers through specific molecular interactions, a process that contributes to the pattern of bacterial succession. The biofilm character of plaque allows the survival of a diverse bacterial flora.24 Although microbial adhesion is how plaque formation begins, microbial multiplication is thought to be the dominant factor in the buildup of dental plaque, and the nature of this microbial proliferation is highly dependent on the local environment. Because environmental conditions vary from place to place within the oral cavity, each site with plaque represents its own distinct ecosystem, and the dominant microbial composition at the site depends on the outcome of numerous host-microbe and microbe-microbe interactions.106
The clinical picture of all this activity has been well described. After plaque has been completely removed, it re-forms slowly on the supragingival tooth surface for about 3 days, and then if left undisturbed it increases rapidly to reach a maximum bulk after 7 days. The various microbial interactions actually keep the bacterial composition of plaque relatively stable, but when this homeostasis breaks down, the shifts in microbial balance can set up conditions for caries or gingivitis to begin. Plaque accumulation around the gingival margin leads to an inflammatory host response and an increased flow of gingival crevicular fluid.88 Few bacteria can be isolated from around healthy gingival tissue, although with gingivitis there is a considerable increase in the numbers and complexity of bacteria as the lesion develops.92 Subgingival plaque microflora shift from being predominantly gram positive to including increased levels of anaerobic gram-negative organisms; the character of subgingival plaque is thus quite different from that of supragingival plaque. Specifically, the gram-negative anaerobes Porphyromonas gingivalis and Bacteroides forsythus in subgingival plaque have been associated with both loss of periodontal attachment and bone loss.48,49 Frequent professional supragingival cleaning, added to good personal oral hygiene, has a beneficial effect with regard to subgingival microbiota in moderately deep pockets.54,120 Subgingival plaque is also characterized by oral spirochetes, whose role in periodontitis is still not clear, although their presence in the subgingival plaque is seen as a marker for disease.118
Calculus was formerly viewed only as an “irritating factor” in the development of periodontitis64 and did not get much research attention. Today, however, calculus is recognized as a calcified matrix that can harbor periodontopathogenic bacteria, and subgingival calculus is closely associated with gingivitis and periodontitis.33 Therefore, the initial formation and continued presence of both supragingival and subgingival calculus are to be prevented to the extent possible. The only known method is to control the initial formation of supragingival plaque and calculus.
Because plaque has some identifiable health functions and because disease comes more from an upset in the homeostatic balance than from infection with exogenous organisms, disease prevention should be geared more toward plaque control than plaque eradication. This concept is referred to as the ecologic plaque hypothesis.87 The goal in preventing periodontitis is to prevent fresh plaque from becoming established plaque, which permits the growth of specific periodontopathogenic bacteria,102,123 and to prevent supragingival plaque from becoming established subgingivally.
Several approaches to plaque control can be quickly ruled out as having no scientific basis: rinsing with water and chewing a fibrous food (e.g., remove loose food debris but do not affect plaque). There is no evidence to alter the long-held view that preventive benefits cannot be achieved by changes in diet or nutrition,74,110 although, given the importance of the host response in periodontitis and the fact that nutrition is a vital part of the immune reaction, the role of nutrition in periodontitis should continue to be studied.
Primary prevention of gingivitis requires consistent, thorough control of plaque accumulation on a lifetime basis. The rationale is to prevent plaque from reaching the stage of maturity at which gingivitis begins. Some people are capable of maintaining an adequate oral hygiene status largely by their own efforts, but many are not. The dental professional will consistently see some level of gingivitis in the latter patients and may become frustrated in the effort to eliminate gingivitis entirely. For these patients, the dental professional’s goal should be to maintain the gingivitis at as low a level as possible. As long as the lowest possible level of gingivitis can be maintained over time, subsequent loss of periodontal support is likely to be minimized. This is true for the majority of patients who are at low risk of severe periodontitis. It is less the case for those patients with aggressive periodontitis who fit the compromised host model described in Chapter 21. Prevention of disease in these patients is difficult because we do not yet have the means of influencing the deficient host response to a periodontal challenge.
As long as plaque accumulation remains supragingival, it can be controlled by mechanical or chemotherapeutic means.101 Once plaque becomes established subgingivally, however, the individual patient cannot remove it by self-care, and professional intervention is necessary. The goal of prevention of periodontal conditions through plaque control by the individual is to keep supragingival plaque from accumulating.
Self-care is a fundamental part of periodontal health. Unless the individual is able to maintain at least a reasonable level of oral cleanliness by regular and consistent home care, the benefits of treatment by dental professionals will be limited. Individual effort means mechanical plaque removal with a toothbrush and aids such as dental floss, an interproximal brush, and wood points.
Although individual oral hygiene practices are fundamental to the promotion of oral health, it is surprising how little is really known about such basic things as the most efficient type of toothbrush and how often the teeth should be brushed. Research studies in these areas have often been run for only short periods and with atypical populations, such as dental or dental hygiene students. Long-term effects and the validity of projecting results to the general population are thus difficult to assess.
The limited information that is available indicates that a thorough oral cleansing should be carried out at 24- to 48-hour intervals.61,66 Considering the time needed for plaque to mature bacteriologically, brushing after every meal, which was usually impractical anyway, is unnecessary to prevent gingivitis. But because toothbrushing with a fluoride toothpaste is also a major source of fluoride exposure for caries prevention, it is best carried out at least twice per day to maintain oral health. Brushing in the morning and evening fits with most peoples’ daily routines and should be the basis for education of the public and dental patients. Of course, patients who have received treatment for periodontitis are likely to be at high risk for further disease, and more stringent home care regimens may be required for them.120
Little research has been carried out on the best type of toothbrush; what evidence there is suggests that it really does not matter much. Children clearly should use a smaller brush, and the dentist or hygienist may want to recommend different sizes and degrees of softness, depending on each patient’s manual dexterity, enthusiasm, and oral health. Soft brushes generally are preferred to minimize gingival damage with enthusiastic brushing. Manufacturers are constantly coming out with new designs, so anyone can find a toothbrush that is comfortable and efficient. However, these recommendations are based on common sense rather than on firm evidence.
Electric toothbrushes with a rotary action have been found to be more effective plaque removers in closely supervised clinical trials,117 although it is uncertain how well these findings reflect everyday effectiveness. Both manual and power-driven toothbrushes are effective if used properly; differences between individuals’ brushing efficiency are likely to be much greater than inherent differences between types of toothbrushes. New versions of power-driven brushes are constantly being marketed, some with heavy advertising, and most have not been subjected to rigorous testing. Power brushes may be particularly useful for handicapped persons or others with low manual dexterity.
A variety of toothbrushing methods, some requiring a lot of manual gymnastics, have been described in the dental literature down the years. Proponents of one method or another have traditionally been vehement in the defense of their method’s efficacy, a good example of the rule that the level of passion that people have about an issue is inversely proportional to its scientific basis. In fact there is little difference between the various methods in their ability to remove dental plaque.42,52,100,103 From these studies, limited though some of them are, the scrub method emerges as the simplest technique available and one that is no less effective than any other. It requires minimal manual dexterity and patient concentration, and generally seems best for most persons.
The rationale for supplementing toothbrushing with use of dental floss, interdental brushes, or wood points to clean below the contact areas is that even assiduous use of the toothbrush usually cannot penetrate these areas efficiently. There is some limited evidence that interdental cleaning, by floss or interdental brushes, reduces interdental gingivitis and plaque more than toothbrushing alone.27,78
Many dental health education materials extol the efficacy of dental floss: “brush and floss” long ago replaced the exhortation to just “brush.” There is still little evidence, however, to show that flossing, as practiced by the individual with normal interdental spaces, adds much to the efficiency of brushing,55,100,107 nor are the limited research studies able to find a difference between waxed and unwaxed floss in cleaning efficiency.22,30,40,78 In cases in which papillae have diminished to leave open interdental spaces, interdental brushes are superior to floss.23,32 Many people prefer wood points to floss because floss can break and become stuck in awkward contact areas, and wood points can be effective interdental cleaners.
The individual practice of regular, thorough, and consistent oral hygiene procedures depends largely on the interest of the individual in his or her oral health. Dentally conscious people have this interest already, but many others do not. Oral hygiene practices must fit into the lifestyle of each individual, and lifestyles are rarely changed by exhortation. To illustrate the lifestyle issue, a British study found that schoolchildren who reported more frequent toothbrushing also reported more frequent bathing, use of deodorant, and hand washing after visiting the toilet.85 Information like this comes as no surprise.
Knowledge is usually thought to precede action, although a study of periodontal patients in North Carolina found poor correlation between knowledge of the disease process and periodontal health.16 Carefully thought-out and well-organized motivational programs aimed at schoolchildren have produced poor results in the United States.53,56 A typical finding came from a study of supervised daily toothbrushing by schoolchildren in Sweden: gingivitis was reduced for the duration of the program, but the improvement disappeared when the supervision ended.70,71 Although compliance with periodontitis treatment instructions is related to health beliefs,65 the effects of individual chairside instruction are usually weak.115,122 Doubts are thus raised about what motivational programs really do; they may succeed only in reinforcing existing favorable attitudes and not in altering negative ones.90 A Danish longitudinal study found that oral hygiene behavior in youth was found to predict periodontal health in adulthood,73 a finding which confirms that attitudes and oral health behavior are principally determined by factors outside the dental office. (Issues in health promotion are discussed more fully in Chapter 5.)
For dental professionals who try to induce individual patients to improve their daily oral hygiene performance, greatest success may come from a personal and common sense approach by the dentist or hygienist. Some patients will respond better than others. Objective monitoring by measurement of gingival bleeding, pocket depth, periodontal attachment levels, calculus deposits, and plaque is important because subjective impressions of progress can be misleading. Reinforcement of simple messages and constant encouragement of the individual’s efforts seem to be important factors. Oral health professionals must work within the limitations of the individual patient, and within their own limitations too.
Oral hygiene in the United States is considered by most experts to be constantly improving, a trend thought to result from heightened awareness, heavy advertising, and constantly improving oral hygiene products. Public health education programs intended to produce mass improvement in oral hygiene have had little measurable impact on this trend.43,53 Time given to this form of education in public health programs, especially in populations bombarded by television commercials about oral hygiene, could probably be much better spent on primary prevention or on providing dental care to needy people. This may not be the case, however, in a low-income country, where basic knowledge of oral hygiene may be lacking. “Toothbrush drills” are quite properly a common part of dental public health education in such countries, whereas they may be unnecessary in high-income nations.
Professional care is necessary to remove subgingival plaque and calculus; the patient cannot remove plaque from deep pockets. The benefits of professional plaque removal have been shown in studies of children and adults who were in reasonable periodontal health to begin with, as well as in studies of adults receiving treatment for advanced disease.
The discussion of the Karlstad studies in Chapter 28 was related principally to caries; this section discusses the studies in relation to periodontal diseases. Among children, spectacular success in preventing gingivitis was reported by the Axelsson-Lindhe group in their investigations in Karlstad, Sweden.10,11,13,69 Studying children ages 7-14 years, this research group set out to show that a regimen of intensive prophylactic procedures that went considerably beyond routine prophylaxis would be effective in preventing both caries and gingivitis. The detailed protocol for the Karlstad regimen is given in Box 29-1.