- Email: [email protected]
Plaque Control in Periodontal Disease
P la q u e c o n tr o l in p e r io d o n ta l d is e a s e Harald Ld'e, DDS, Dr. Odont, Ann Arbor, Mich
Contrary to previously held concepts it has become increasingly evident during the past 25 years that systemic influences, malnutrition, and lack of specific dietary compounds play a m inor role in the actual development o f periodontal disease, and that bacterial plaque and its products form the p ri mary link in the chain of events leading to destruc tion of the periodontium. Substantial evidence for this has been found in experiments showing that, in man, gingivitis will develop within a few days after cessation o f oral hygiene measures, and that it reverts to normal again after reinstitution o f good oral hygiene. This is no less than a documentation of a cause and effect relationship between bacterial plaque and gingivitis. As a matter of fact, no other fac tor or group of factors has been shown to pro duce and to maintain chronic gingivitis in man. Although not substantiated in humans, repeat ed studies of the sequential development of the periodontal lesion in animals strongly suggest that the progression o f the lesion into the deeper parts of the periodontium is preceded by gingivitis, and that regular removal of plaque also prevents this development. Indeed, many subtleties of the periodontal disease syndrome are still unknown or unex plained. Therefore, it is im portant that funda mental research into the detailed mechanisms of the defense and destruction in this disease con tinues. However, some o f us believe that perio dontal research has reached a crucial point in its disentangling of these complex problems, and that along with a continued research program, it is possible and entirely legitimate to apply avail able knowledge to the prevention and treatment of periodontal disease. The initial bacterial colonization o f the tooth surface takes place in the gingival area. During a normal day the number o f organisms on this sur 1 0 3 4 ■ S P E C I A L IS S U E /J A D A , V ol. 8 7 , O c t o b e r 1 9 7 3
face increases through m ultiplication and by re tention o f new organisms. If not dislodged, this plaque continues to grow by addition o f more bac teria and may, especially around the gingival m ar gin and interdentally, reach a considerable thick ness. Despite widespread belief, dental plaque contains little and frequently no food debris. The clinical entity that we now call plaque is, to all practical purposes, a m at of mixed microorganisms. Plaque bacteria do not produce disease by in vading the periodontal tissues, but by elaborating substances known to produce inflammatory reac tions. Although the pathogenic potential o f plaque as a whole is well documented, little information is available as to the relative significance o f the various types of organisms. It is possible that not all elements of the plaque are bad and that some bacteria may actually provide protection against worse destruction of tissues than that usually ex perienced. As more definitive knowledge of the pathogenicity becomes available, it is conceivable that therapeutic methods may be developed that address themselves to specific factors within the plaque. For lack of such information and in view o f the overall harmful effect of plaque on the teeth and periodontium, emphasis must presently be placed on factors or measures that bring about total plaque control.
F a c to rs in flu e n c in g p la q u e fo rm a tio n L ittle factual knowledge exists as to the role of saliva in controlling plaque formation, although the formation may be influenced to some extent by the amount, physical characteristics, and chem ical composition of saliva. There is also some basis for the opinion that mastication has a lim it ing effect on the occlusal or incisal growth o f
plaque. However, during mastication, the cervical areas of the teeth, the gingival margin, and most of the attached gingiva are not subjected to physi cal stress from food particles. Excessive chew ing o f coarse food seems to have no effect on ag gregations of plaque interdentally and in the gingi val area, and systematic consumption of fibrous vegetables does not prevent plaque from forming. Indeed, the presence or absence of plaque at the cervical circumference o f the teeth is seemingly independent of the passing o f food through the oral cavity. In young, healthy individuals with complete dentitions and normal gingiva, salivation, occlu sion, and mastication, who eat standard diets in cluding coarse bread and ample amounts of fruits and vegetables, plaque formation is so great that heavy deposits are present in the gingival and in terdental areas a few days after cessation of oral hygiene. Therefore, although self-cleansing of teeth may have been a valid principle in the past, in most civilized populations today, natural cleans ing o f the dentition is seemingly nonexistent. Consequently, if plaque is to be controlled, it must be actively prevented from forming or removed,at regular intervals.
M e c h a n ic a l re m o v a l o f p la q u e Today, toothbrushing and other mechanical cleans ing procedures are considered to be the most reli able means of controlling plaque, provided the cleansing is sufficiently thorough and performed regularly. Probably, most civilized people exercise some measure o f oral hygiene, and toothbrushing seems to be the accepted method. However, wide variations exist in brush design, brushing tech niques, frequency o f brushing, and brushing time; and little scientific work in this field is available to guide the interested dentist or patient. Such a simple question as, “How often should I brush my teeth?” has just recently been partly answered. Complete removal o f plaque only once every sec ond day is compatible with the m aintenance of gingival health. But since we do not know how often plaque must be removed to control caries, it is difficult to design a scientifically founded pro gram for the mechanical removal of plaque that could control both diseases. F or most patients, even a well-performed brush ing at frequent intervals may be insufficient to m aintain proper plaque control. Therefore, addi tional techniques and materials such as toothpicks
and dental floss are recommended, according to the patient’s need. In recent years, power-driven brushes, water irrigation devices, and a m ultitude o f other gadgets have been introduced, but they have not had much impact on the general standard o f oral hygiene. The fact that the public does purchase these items shows general dissatisfaction with the handbrush-level o f technology and a defi nite interest in improving the state of oral hygiene — provided it can be done without too much p er sonal effort. This is somewhat encouraging. What is not encouraging at all is the lack of constructive imagination on the part of the dental profession and industry in developing mechanical devices for the swift and effective cleansing o f teeth that would approach the technological level of the space age to some degree. W ithout doubt, for the well-motivated and prop erly instructed patient who is willing to invest the necessary time and effort, mechanical measures are effective in controlling plaque. However, clinical practice and several group studies indi cate that the technical skill, time, effort, and per severance required to continually m aintain a high standard of oral cleanliness exceed the ability of the average person. Many physically and mentally handicapped patients are unable to manage the techniques involved. M otivation and instruction also make demands on professional and auxiliary personnel that cannot be met by any country at present. Therefore, the existing mechanical pro cedures for plaque control do not offer a complete solution to the problem. This is, o f course, unfortu nate since today mechanical cleansing of teeth is the only known method that can be widely ap plied for the prevention of this disease.
A n tib a c te ria l a g e n ts In view of the new knowledge of the true bacterial nature of plaque, several antibiotic and antiseptic agents have recently been tested for their plaqueinhibiting capacity. Although some antibiotics show plaque-reducing properties and even though some inhibit plaque formation completely, the po tential danger of m aintaining a continuous anti biotic regimen cannot be doubted. It is therefore difficult to see how antibiotic agents can offer a practical means of life-long plaque control in man. During the past five years our laboratory has in vestigated some of the fundamental biological principles connected with the use of a general disinfectant in controlling dental diseases. Since Lôe: PLA Q U E C O N T R O L ■ 1035
the initial report o f our work appeared in 1969, m ore than 75 articles have been published on the clinical effect of chlorhexidine, its mechanism of action, its effect on the oral environment, its tox icology, and possible side effects. The initial short-term studies demonstrated that, in the absence of any form of mechanical hy giene, two daily mouthrinsings with 0.2% chlor hexidine gluconate completely inhibited the de velopment of plaque and gingivitis. Form ation of supragingival calculus was prevented, and smooth surface caries did not develop. Heavy accumula tions o f plaque disappeared, and overt clinical gingivitis resolved. These findings have since been confirmed by others in both man and animals. W ritten reports on the long-term effects are still pending; however, the prelim inary analyses of a two-year study comprising 150 Danish medical and dental students show the performance of chlorhexidine is highly satisfactory. Also, on the basis of results from that study, the microbiologic or environmental problems o f the oral cavity as sociated with the regular use of chlorhexidine seem to be much smaller than anticipated. This study has suggested that a substantial reduction in the number o f oral organisms is quite compatible with oral and systemic health. M etabolic studies have shown that chlorhexi dine is poorly absorbed and that almost all of it is excreted in the feces. The small amounts that may pass through the epithelial barrier are cleared through the usual metabolic pathways. During its passage through the body, chlorhexidine is subject to minimal degradation, and no parachloraniline has been detected. Extensive studies of the safety o f chlorhexidine gluconate, including acute, sub acute, and chronic tests show extremely and un usually low levels of toxicity, both locally and systemically. No teratologic or reproductory changes have been seen. At this point in time, the major problem in the use of chlorhexidine in the oral cavity seems to be the formation of stain on the teeth. On the whole, the research in this area is prom is ing and indicates that the day may not be far dis tant when chemical adjuncts to the usual toothbrushing procedures may substantially change the pattern of dental diseases in our population.
N e w p ro p h y la c tic p rin c ip le To me, one of the most intriguing features of the work with chlorhexidine is its selective adsorption 1 0 3 6 a S P E C I A L I S S U E /J A D A , V ol. 8 7 , O c t o b e r 1 9 7 3
to the tooth surface. During an early stage o f the research, we realized that the total lack of bacterial colonization on the teeth could not be ascribed solely to its general antibacterial effect during the actual rinsing. Indeed, a reduction of the num ber o f organisms in the saliva by 50% to 90% would still provide a sufficient basis for proliferation and recolonization o f the teeth between applica tions. The fact that bacteria, although few in num bers, continued to colonize the gingival tissues essentially proved this point and strongly sug gested that the tooth surface had been conditioned in such a way as to reject bacterial retention and growth. Subsequent research revealed that chlorhexi dine, besides acting immediately on the oral bac teria because of its cationic properties, binds to the hydroxyapatite of the tooth enamel, to the o r ganic pellicle at the tooth surface, and to salivary proteins at large. In vitro and in vivo experiments have shown that the adsorbed chlorhexidine is re leased from the teeth as the concentration in their environment decreases for several hours after the initial application, thereby preventing bacterial colonization on the tooth surfaces. This reversible reaction of an antibacterial agent with the teeth represents an entirely new principle in the prevention of both periodontal disease and caries. This concept may lead to the develop ment of other drugs that may have an even strong er affinity for the organic or inorganic com po nents of the tooth surfaces and that may be re leased over extended periods, permitting far less frequent applications of the antimicrobial agent. During the 25 years o f research into the biology, chemistry, and bacteriology of plaque and its clinical ramifications, we have come a long way. Many unanswered questions and problems still w arrant further research, but I venture to suggest on this im portant occasion, that today, our level of knowledge is sufficient to formulate imaginative research programs and to develop carefully con ceived clinical trials to find means and measures for the eradication of periodontal disease — and caries. In the history of medicine are many ex amples in which large-scale clinical programs for the prevention and cure of a disease have been launched on considerably less evidence than that available on these two plaque diseases. Dr. Löe is directo r of the D ental R esearch Institute at the U niversity of M ichig an, A nn A rbor, 48104.
Contrary to previously held concepts it has become increasingly evident during the past 25 years that systemic influences, malnutrition, and lack of specific dietary compounds play a m inor role in the actual development o f periodontal disease, and that bacterial plaque and its products form the p ri mary link in the chain of events leading to destruc tion of the periodontium. Substantial evidence for this has been found in experiments showing that, in man, gingivitis will develop within a few days after cessation o f oral hygiene measures, and that it reverts to normal again after reinstitution o f good oral hygiene. This is no less than a documentation of a cause and effect relationship between bacterial plaque and gingivitis. As a matter of fact, no other fac tor or group of factors has been shown to pro duce and to maintain chronic gingivitis in man. Although not substantiated in humans, repeat ed studies of the sequential development of the periodontal lesion in animals strongly suggest that the progression o f the lesion into the deeper parts of the periodontium is preceded by gingivitis, and that regular removal of plaque also prevents this development. Indeed, many subtleties of the periodontal disease syndrome are still unknown or unex plained. Therefore, it is im portant that funda mental research into the detailed mechanisms of the defense and destruction in this disease con tinues. However, some o f us believe that perio dontal research has reached a crucial point in its disentangling of these complex problems, and that along with a continued research program, it is possible and entirely legitimate to apply avail able knowledge to the prevention and treatment of periodontal disease. The initial bacterial colonization o f the tooth surface takes place in the gingival area. During a normal day the number o f organisms on this sur 1 0 3 4 ■ S P E C I A L IS S U E /J A D A , V ol. 8 7 , O c t o b e r 1 9 7 3
face increases through m ultiplication and by re tention o f new organisms. If not dislodged, this plaque continues to grow by addition o f more bac teria and may, especially around the gingival m ar gin and interdentally, reach a considerable thick ness. Despite widespread belief, dental plaque contains little and frequently no food debris. The clinical entity that we now call plaque is, to all practical purposes, a m at of mixed microorganisms. Plaque bacteria do not produce disease by in vading the periodontal tissues, but by elaborating substances known to produce inflammatory reac tions. Although the pathogenic potential o f plaque as a whole is well documented, little information is available as to the relative significance o f the various types of organisms. It is possible that not all elements of the plaque are bad and that some bacteria may actually provide protection against worse destruction of tissues than that usually ex perienced. As more definitive knowledge of the pathogenicity becomes available, it is conceivable that therapeutic methods may be developed that address themselves to specific factors within the plaque. For lack of such information and in view o f the overall harmful effect of plaque on the teeth and periodontium, emphasis must presently be placed on factors or measures that bring about total plaque control.
F a c to rs in flu e n c in g p la q u e fo rm a tio n L ittle factual knowledge exists as to the role of saliva in controlling plaque formation, although the formation may be influenced to some extent by the amount, physical characteristics, and chem ical composition of saliva. There is also some basis for the opinion that mastication has a lim it ing effect on the occlusal or incisal growth o f
plaque. However, during mastication, the cervical areas of the teeth, the gingival margin, and most of the attached gingiva are not subjected to physi cal stress from food particles. Excessive chew ing o f coarse food seems to have no effect on ag gregations of plaque interdentally and in the gingi val area, and systematic consumption of fibrous vegetables does not prevent plaque from forming. Indeed, the presence or absence of plaque at the cervical circumference o f the teeth is seemingly independent of the passing o f food through the oral cavity. In young, healthy individuals with complete dentitions and normal gingiva, salivation, occlu sion, and mastication, who eat standard diets in cluding coarse bread and ample amounts of fruits and vegetables, plaque formation is so great that heavy deposits are present in the gingival and in terdental areas a few days after cessation of oral hygiene. Therefore, although self-cleansing of teeth may have been a valid principle in the past, in most civilized populations today, natural cleans ing o f the dentition is seemingly nonexistent. Consequently, if plaque is to be controlled, it must be actively prevented from forming or removed,at regular intervals.
M e c h a n ic a l re m o v a l o f p la q u e Today, toothbrushing and other mechanical cleans ing procedures are considered to be the most reli able means of controlling plaque, provided the cleansing is sufficiently thorough and performed regularly. Probably, most civilized people exercise some measure o f oral hygiene, and toothbrushing seems to be the accepted method. However, wide variations exist in brush design, brushing tech niques, frequency o f brushing, and brushing time; and little scientific work in this field is available to guide the interested dentist or patient. Such a simple question as, “How often should I brush my teeth?” has just recently been partly answered. Complete removal o f plaque only once every sec ond day is compatible with the m aintenance of gingival health. But since we do not know how often plaque must be removed to control caries, it is difficult to design a scientifically founded pro gram for the mechanical removal of plaque that could control both diseases. F or most patients, even a well-performed brush ing at frequent intervals may be insufficient to m aintain proper plaque control. Therefore, addi tional techniques and materials such as toothpicks
and dental floss are recommended, according to the patient’s need. In recent years, power-driven brushes, water irrigation devices, and a m ultitude o f other gadgets have been introduced, but they have not had much impact on the general standard o f oral hygiene. The fact that the public does purchase these items shows general dissatisfaction with the handbrush-level o f technology and a defi nite interest in improving the state of oral hygiene — provided it can be done without too much p er sonal effort. This is somewhat encouraging. What is not encouraging at all is the lack of constructive imagination on the part of the dental profession and industry in developing mechanical devices for the swift and effective cleansing o f teeth that would approach the technological level of the space age to some degree. W ithout doubt, for the well-motivated and prop erly instructed patient who is willing to invest the necessary time and effort, mechanical measures are effective in controlling plaque. However, clinical practice and several group studies indi cate that the technical skill, time, effort, and per severance required to continually m aintain a high standard of oral cleanliness exceed the ability of the average person. Many physically and mentally handicapped patients are unable to manage the techniques involved. M otivation and instruction also make demands on professional and auxiliary personnel that cannot be met by any country at present. Therefore, the existing mechanical pro cedures for plaque control do not offer a complete solution to the problem. This is, o f course, unfortu nate since today mechanical cleansing of teeth is the only known method that can be widely ap plied for the prevention of this disease.
A n tib a c te ria l a g e n ts In view of the new knowledge of the true bacterial nature of plaque, several antibiotic and antiseptic agents have recently been tested for their plaqueinhibiting capacity. Although some antibiotics show plaque-reducing properties and even though some inhibit plaque formation completely, the po tential danger of m aintaining a continuous anti biotic regimen cannot be doubted. It is therefore difficult to see how antibiotic agents can offer a practical means of life-long plaque control in man. During the past five years our laboratory has in vestigated some of the fundamental biological principles connected with the use of a general disinfectant in controlling dental diseases. Since Lôe: PLA Q U E C O N T R O L ■ 1035
the initial report o f our work appeared in 1969, m ore than 75 articles have been published on the clinical effect of chlorhexidine, its mechanism of action, its effect on the oral environment, its tox icology, and possible side effects. The initial short-term studies demonstrated that, in the absence of any form of mechanical hy giene, two daily mouthrinsings with 0.2% chlor hexidine gluconate completely inhibited the de velopment of plaque and gingivitis. Form ation of supragingival calculus was prevented, and smooth surface caries did not develop. Heavy accumula tions o f plaque disappeared, and overt clinical gingivitis resolved. These findings have since been confirmed by others in both man and animals. W ritten reports on the long-term effects are still pending; however, the prelim inary analyses of a two-year study comprising 150 Danish medical and dental students show the performance of chlorhexidine is highly satisfactory. Also, on the basis of results from that study, the microbiologic or environmental problems o f the oral cavity as sociated with the regular use of chlorhexidine seem to be much smaller than anticipated. This study has suggested that a substantial reduction in the number o f oral organisms is quite compatible with oral and systemic health. M etabolic studies have shown that chlorhexi dine is poorly absorbed and that almost all of it is excreted in the feces. The small amounts that may pass through the epithelial barrier are cleared through the usual metabolic pathways. During its passage through the body, chlorhexidine is subject to minimal degradation, and no parachloraniline has been detected. Extensive studies of the safety o f chlorhexidine gluconate, including acute, sub acute, and chronic tests show extremely and un usually low levels of toxicity, both locally and systemically. No teratologic or reproductory changes have been seen. At this point in time, the major problem in the use of chlorhexidine in the oral cavity seems to be the formation of stain on the teeth. On the whole, the research in this area is prom is ing and indicates that the day may not be far dis tant when chemical adjuncts to the usual toothbrushing procedures may substantially change the pattern of dental diseases in our population.
N e w p ro p h y la c tic p rin c ip le To me, one of the most intriguing features of the work with chlorhexidine is its selective adsorption 1 0 3 6 a S P E C I A L I S S U E /J A D A , V ol. 8 7 , O c t o b e r 1 9 7 3
to the tooth surface. During an early stage o f the research, we realized that the total lack of bacterial colonization on the teeth could not be ascribed solely to its general antibacterial effect during the actual rinsing. Indeed, a reduction of the num ber o f organisms in the saliva by 50% to 90% would still provide a sufficient basis for proliferation and recolonization o f the teeth between applica tions. The fact that bacteria, although few in num bers, continued to colonize the gingival tissues essentially proved this point and strongly sug gested that the tooth surface had been conditioned in such a way as to reject bacterial retention and growth. Subsequent research revealed that chlorhexi dine, besides acting immediately on the oral bac teria because of its cationic properties, binds to the hydroxyapatite of the tooth enamel, to the o r ganic pellicle at the tooth surface, and to salivary proteins at large. In vitro and in vivo experiments have shown that the adsorbed chlorhexidine is re leased from the teeth as the concentration in their environment decreases for several hours after the initial application, thereby preventing bacterial colonization on the tooth surfaces. This reversible reaction of an antibacterial agent with the teeth represents an entirely new principle in the prevention of both periodontal disease and caries. This concept may lead to the develop ment of other drugs that may have an even strong er affinity for the organic or inorganic com po nents of the tooth surfaces and that may be re leased over extended periods, permitting far less frequent applications of the antimicrobial agent. During the 25 years o f research into the biology, chemistry, and bacteriology of plaque and its clinical ramifications, we have come a long way. Many unanswered questions and problems still w arrant further research, but I venture to suggest on this im portant occasion, that today, our level of knowledge is sufficient to formulate imaginative research programs and to develop carefully con ceived clinical trials to find means and measures for the eradication of periodontal disease — and caries. In the history of medicine are many ex amples in which large-scale clinical programs for the prevention and cure of a disease have been launched on considerably less evidence than that available on these two plaque diseases. Dr. Löe is directo r of the D ental R esearch Institute at the U niversity of M ichig an, A nn A rbor, 48104.