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The Deterioration of Human Teeth
The deterioration of human teeth' Peter ] . Brekhus, D .D .S ., Minneapolis
Given only the methods known at pres ent for preventing the loss of human permanent teeth, can those teeth be saved? O r is there a force at work, an evolutionary or degenerative force, that is slowly but surely eliminating certain teeth from the human dentition? Workers at the School of Dentistry of the University of Minnesota are asking these questions as the result of their find ings in three successive studies that began 20 years ago. These findings are por trayed in Figure 1. The 3,388 freshman students, both men and women, who entered the University of Minnesota in 1929 averaged 9.95 teeth affected by dental caries.1 T h e 4,348 stu dents who entered 10 years later, in 1939, had 11.8 teeth so affected .2 T h e 4,412 who came to the University in 1949 averaged 13.7 teeth affected by caries. All differences are statistically significant. Though started only 20 years ago, these decennial reviews of the dental con dition of university freshmen really cover a period of approximately 40 years. The young people who entered the University in 1929 at an average age of about 19 years were born in 1910 or thereabouts. T h e period since that time has produced more benefits for dental health than any other period in the world’s history. N u trition, particularly among the American people, has greatly improved. Dental hy giene has become an almost universal practice, at least by the majority of per
sons in the higher socioeconomic levels to which university students belong. Den tal health education has been carried on at a constantly accelerating rate since 1910, and its emphasis has been increas ingly on the desirability of early and fre quent dental care to prevent the de terioration and loss of teeth. Nor has all this good advice been dis regarded by the public. T h e teeth of most of these university students had been given good care. These young people keep their teeth clean and they go to their dentists to obtain fillings and other re pairs or replacements when these are needed. T h e point is that they are needed. Despite all the care and attention that has been and is being given to the teeth of university students, these teeth are now decaying to a greater degree than they were 10 years ago and a still greater degree than they were 20 years ago. The majority of permanent teeth in cluded in the 1929 study were in process of formation between 1910 and 1919; those of the 1939 study between 1920 and 1929; those of the 1949 study between 1930 and 1939. W h at influences may have been at work during those periods
Professor Emeritus, School of Dentistry, University of Minnesota. 1. Brekhus, P. J., Report on dental caries in 10,445 university students. J.A.D.A. 18:1350 (July) ¡931. 2. Brekhus, P. J. A second census of dental conditions in University of Minnesota freshman students. J.A.D.A. 28:1126 (July) 1941.
BREKHUS . . . V O LU M E 42, APRIL 1951 • 425
to influence the caries susceptibility of children’ s permanent teeth? T h e first period included W orld W ar I. Possibly a slightly less than optimum de gree of nutrition was enjoyed by some of the children who grew up during that period, but to offset this there was a re duction in sugar intake due to the re strictions of the war years. T h e second period, 1920 to 1929, was the most pros perous in our nation’s history— the era of the two chickens in every pot. The third period, 1930 to 1939, included the depression years, when nutrition may have been reduced to some extent, but hardly to a degree that would have inter fered with the normal development of children in the group represented by uni34.8%
42.1%
4 8 .9 %
T a b le 1 • Com parative mean heights and weights of University o f Minnesota freshman students, 1929, 1939, and 1949* M en Year
1929 1939 1949
Height In Inches 68.64 68.87 69.57
|
W eight In pounds 142.45 147.75 153.80
Women Height in inches 63.48 64.36 64.45
W eight in pounds 123.01 124.44 126.30
*A1I differences are statistically significant.
Table 2 • Dental findings for the three groups of freshmen
Year of examination
1929 1939 1949
Number Average no. fillings of freshmen per student
3,388 4,348 4,412
7.837 8.858 11.410
Unfilled carious lesions
1.245 1.439 1.213
Number extractions per student
.7077 .7812 1.1124
versity students. Nor did the conditions
k.
I <0 I
of either W orld W ar I or the depression affect adversely the general health of these youngsters. The students of 1939 rated a little bet ter in general health than those of 1929. They were a little taller and a little heavier than their counterparts of a decade earlier. Y et they had more tooth decay .3 The weights and heights of the 1949 freshmen show a similar increase over those of 1939, as shown in Table 1. T h e dental findings for the three groups of freshmen, a little more in detail, are shown in Table 2. A definite pattern is shown in the de generation of teeth as shown in Figures 2 and 3 as represented in these three large groups of students, and exactly the same pattern is evident in all three groups. E x clusive of the third molars, which were not included in the records, the teeth most affected by caries are the first
F ig. 1 • A v e r a g e n u m b er o f tee th p e r stu dent a ffe c te d b y d en ta l c a r ie s ; 19 29 (3 ,3 8 8 stu d en t, 9 , 9 5 ) ; 1 9 3 9 (4 ,3 4 8 stu d en ts, 1 1 .8 ) ; 19 49 (4 ,4 1 2 stu d en ts, 1 3 .7 )
3. Brekhus, P. J., Your Teeth—Their Past, Present, and Probable Future. Minneapolis: University of Minnesota Press, 1941, p. 31.
426 • THE J O U R N A L OF THE A M E R IC A N DENTAL A S S O C IA T IO N
molars, next the second molars, then the second and first bicuspids. Little decay is fou n d in the cuspids and only a neg ligible am ount in the lower incisors. This pattern differs in certain respects from the one found in recent studies of congenitally missing teeth.4 T h e teeth most frequently found to be congenitally absent are the third molars, the upper laterals, and the second bicuspids. These observations suggest that some force
which is not yet understood may be at work in reducing the number o f human teeth. T h e human dentition may be un dergoing a process o f gradual change. A few centuries hence the majority o f p e o ple may have no molars, and their bi-
4. Brekhus, P. J .; O liv e r, C. P., and M ontelius. G e o rg e . A s tu d y , o f the p a tte rn and c o m b in a tio n s o f c o n g e n ita lly m issing teeth in m an. J. D. Res. 23-117 ( A p r il) 1944.
7
H Sound
H F llle d
0 C a r io u s
d E x tra c te d
F ig . 2 • C o m p a ra tiv e d en ta l con d itio n s in right h a lf o f d en tition s o f m ale fresh m en w h o e n te r e d th e U n iversity o f M in n e so ta in 19 29, 1 9 39 and 1 9 4 9 . C olu m n s la b eled A rep resen t con d itio n s in 1 9 2 9 ; th o se la b eled B , 1 9 3 9 ; and th o se la b eled C , 19 49
6
■ Sound
5
H Filled
4
3
2
I
£3 Carious [^E xtracted
F ig . 3 • C om p a ra tiv e d en ta l con d ition s in right h a lf o f d en tition s o f fem a le fresh m en w h o e n te r e d th e U n iversity o f M in n eso ta in 1 9 2 9 , 1 9 3 9 and 19 49. C olu m n s la b eled A r e p resen t c o n d itio n s in 1 9 2 9 ; those la b eled B, 1 9 3 9 ; and th ose la b eled C , 19 49
BREKHUS . . . VOLUME 42, APRIL 1951 • 427
cuspids and upper lateral incisors may be following the molars into oblivion. In the 1929 group of university fresh men there were 3,388 individuals, of whom 61, or about 1.8 per cent, had teeth entirely unaffected by caries.1 In the 1939 group, consisting of 4,348 stu dents, there were only 51 who showed no evidence of caries, about 1.15 per cent .2 In the 1949 group, consisting of 4,412 students, only 30 had perfect teeth, a percentage of 0.68. And this so-called “perfection” refers only to the absence of caries. It does not take into consideration congenitally missing teeth, periodontal conditions, the degree of occlusion or any other factors that should properly be in cluded in evaluating the condition of the teeth. Few significant differences were found between men and women students in any of the three studies. In all three groups of students, the degree of deterioration was somewhat greater among women than among men. The total number of affected teeth in the three groups are shown in Table 3. W ith the single exception of untreated caries in 1949, every one of these evi dences of deterioration of teeth by decay shows an increase as time goes on. It is apparent that, despite all the numerous scientific advances of the modern age, the dental benefits available remain just a step or two behind the force or tendency that is working steadily and slowly against all the efforts to pre vent the loss of human permanent teeth. W ith the present extensive use of fluo ridated drinking water, the topical appli cation of sodium fluoride to children’ s teeth and the widespread use of ammoniated dentifrices, it is possible that the next 10 years will show a reversal of the present tendency. I f such a reversal occurs, will it be permanent or only temporary? Only a continuance of these studies will answer that question. It is hoped that the studies will be con-
Table 3 • Total number o f affected teeth in the three groups o f freshmen
Year o f exam ination
Total fillings
Total caries
1929 1939 1949
26.552 38.516 50.341
4.217 6.258 5.352
Total Total DMF* extractions conditions
2.398 3.357 4.908
33.167 48.171 60.601
*Decayed, missing, or fille d .
tinued. Such recordings, at 10 year in tervals, of the dental conditions of large groups of healthy young people from the top economic levels, can be of inestimable value in plotting long-term trends and in indicating the effects of various factors that may enter into the picture from time to time. Thus they serve, for teeth, a purpose similar to that served by the 10 year censuses of the total population and the death rates for that population. Though those who contributed to the present study may not be here to see the findings of the next 40 years, the chart that will show the degree of dental de terioration over a. half century will con stitute an invaluable record for future generations. Th e present report is not presented in a spirit of pessimism. Even though there does seem to be a trend toward the reduc tion and deterioration of human teeth, that tendency is not necessarily irre versible. And, even if it cannot be re versed, it may indicate merely that a portion of the human anatomy that is no longer of very much use is on its way to disappearing, like the vermiform appen dix at present and the caudal appendage of the past. Moreover, the findings of these three successive studies should serve as a challenge to both dental research workers and practicing dentists. I f teeth are worth saving, it must be these groups that will find and apply the means of saving them. University of Minnesota
Given only the methods known at pres ent for preventing the loss of human permanent teeth, can those teeth be saved? O r is there a force at work, an evolutionary or degenerative force, that is slowly but surely eliminating certain teeth from the human dentition? Workers at the School of Dentistry of the University of Minnesota are asking these questions as the result of their find ings in three successive studies that began 20 years ago. These findings are por trayed in Figure 1. The 3,388 freshman students, both men and women, who entered the University of Minnesota in 1929 averaged 9.95 teeth affected by dental caries.1 T h e 4,348 stu dents who entered 10 years later, in 1939, had 11.8 teeth so affected .2 T h e 4,412 who came to the University in 1949 averaged 13.7 teeth affected by caries. All differences are statistically significant. Though started only 20 years ago, these decennial reviews of the dental con dition of university freshmen really cover a period of approximately 40 years. The young people who entered the University in 1929 at an average age of about 19 years were born in 1910 or thereabouts. T h e period since that time has produced more benefits for dental health than any other period in the world’s history. N u trition, particularly among the American people, has greatly improved. Dental hy giene has become an almost universal practice, at least by the majority of per
sons in the higher socioeconomic levels to which university students belong. Den tal health education has been carried on at a constantly accelerating rate since 1910, and its emphasis has been increas ingly on the desirability of early and fre quent dental care to prevent the de terioration and loss of teeth. Nor has all this good advice been dis regarded by the public. T h e teeth of most of these university students had been given good care. These young people keep their teeth clean and they go to their dentists to obtain fillings and other re pairs or replacements when these are needed. T h e point is that they are needed. Despite all the care and attention that has been and is being given to the teeth of university students, these teeth are now decaying to a greater degree than they were 10 years ago and a still greater degree than they were 20 years ago. The majority of permanent teeth in cluded in the 1929 study were in process of formation between 1910 and 1919; those of the 1939 study between 1920 and 1929; those of the 1949 study between 1930 and 1939. W h at influences may have been at work during those periods
Professor Emeritus, School of Dentistry, University of Minnesota. 1. Brekhus, P. J., Report on dental caries in 10,445 university students. J.A.D.A. 18:1350 (July) ¡931. 2. Brekhus, P. J. A second census of dental conditions in University of Minnesota freshman students. J.A.D.A. 28:1126 (July) 1941.
BREKHUS . . . V O LU M E 42, APRIL 1951 • 425
to influence the caries susceptibility of children’ s permanent teeth? T h e first period included W orld W ar I. Possibly a slightly less than optimum de gree of nutrition was enjoyed by some of the children who grew up during that period, but to offset this there was a re duction in sugar intake due to the re strictions of the war years. T h e second period, 1920 to 1929, was the most pros perous in our nation’s history— the era of the two chickens in every pot. The third period, 1930 to 1939, included the depression years, when nutrition may have been reduced to some extent, but hardly to a degree that would have inter fered with the normal development of children in the group represented by uni34.8%
42.1%
4 8 .9 %
T a b le 1 • Com parative mean heights and weights of University o f Minnesota freshman students, 1929, 1939, and 1949* M en Year
1929 1939 1949
Height In Inches 68.64 68.87 69.57
|
W eight In pounds 142.45 147.75 153.80
Women Height in inches 63.48 64.36 64.45
W eight in pounds 123.01 124.44 126.30
*A1I differences are statistically significant.
Table 2 • Dental findings for the three groups of freshmen
Year of examination
1929 1939 1949
Number Average no. fillings of freshmen per student
3,388 4,348 4,412
7.837 8.858 11.410
Unfilled carious lesions
1.245 1.439 1.213
Number extractions per student
.7077 .7812 1.1124
versity students. Nor did the conditions
k.
I <0 I
of either W orld W ar I or the depression affect adversely the general health of these youngsters. The students of 1939 rated a little bet ter in general health than those of 1929. They were a little taller and a little heavier than their counterparts of a decade earlier. Y et they had more tooth decay .3 The weights and heights of the 1949 freshmen show a similar increase over those of 1939, as shown in Table 1. T h e dental findings for the three groups of freshmen, a little more in detail, are shown in Table 2. A definite pattern is shown in the de generation of teeth as shown in Figures 2 and 3 as represented in these three large groups of students, and exactly the same pattern is evident in all three groups. E x clusive of the third molars, which were not included in the records, the teeth most affected by caries are the first
F ig. 1 • A v e r a g e n u m b er o f tee th p e r stu dent a ffe c te d b y d en ta l c a r ie s ; 19 29 (3 ,3 8 8 stu d en t, 9 , 9 5 ) ; 1 9 3 9 (4 ,3 4 8 stu d en ts, 1 1 .8 ) ; 19 49 (4 ,4 1 2 stu d en ts, 1 3 .7 )
3. Brekhus, P. J., Your Teeth—Their Past, Present, and Probable Future. Minneapolis: University of Minnesota Press, 1941, p. 31.
426 • THE J O U R N A L OF THE A M E R IC A N DENTAL A S S O C IA T IO N
molars, next the second molars, then the second and first bicuspids. Little decay is fou n d in the cuspids and only a neg ligible am ount in the lower incisors. This pattern differs in certain respects from the one found in recent studies of congenitally missing teeth.4 T h e teeth most frequently found to be congenitally absent are the third molars, the upper laterals, and the second bicuspids. These observations suggest that some force
which is not yet understood may be at work in reducing the number o f human teeth. T h e human dentition may be un dergoing a process o f gradual change. A few centuries hence the majority o f p e o ple may have no molars, and their bi-
4. Brekhus, P. J .; O liv e r, C. P., and M ontelius. G e o rg e . A s tu d y , o f the p a tte rn and c o m b in a tio n s o f c o n g e n ita lly m issing teeth in m an. J. D. Res. 23-117 ( A p r il) 1944.
7
H Sound
H F llle d
0 C a r io u s
d E x tra c te d
F ig . 2 • C o m p a ra tiv e d en ta l con d itio n s in right h a lf o f d en tition s o f m ale fresh m en w h o e n te r e d th e U n iversity o f M in n e so ta in 19 29, 1 9 39 and 1 9 4 9 . C olu m n s la b eled A rep resen t con d itio n s in 1 9 2 9 ; th o se la b eled B , 1 9 3 9 ; and th o se la b eled C , 19 49
6
■ Sound
5
H Filled
4
3
2
I
£3 Carious [^E xtracted
F ig . 3 • C om p a ra tiv e d en ta l con d ition s in right h a lf o f d en tition s o f fem a le fresh m en w h o e n te r e d th e U n iversity o f M in n eso ta in 1 9 2 9 , 1 9 3 9 and 19 49. C olu m n s la b eled A r e p resen t c o n d itio n s in 1 9 2 9 ; those la b eled B, 1 9 3 9 ; and th ose la b eled C , 19 49
BREKHUS . . . VOLUME 42, APRIL 1951 • 427
cuspids and upper lateral incisors may be following the molars into oblivion. In the 1929 group of university fresh men there were 3,388 individuals, of whom 61, or about 1.8 per cent, had teeth entirely unaffected by caries.1 In the 1939 group, consisting of 4,348 stu dents, there were only 51 who showed no evidence of caries, about 1.15 per cent .2 In the 1949 group, consisting of 4,412 students, only 30 had perfect teeth, a percentage of 0.68. And this so-called “perfection” refers only to the absence of caries. It does not take into consideration congenitally missing teeth, periodontal conditions, the degree of occlusion or any other factors that should properly be in cluded in evaluating the condition of the teeth. Few significant differences were found between men and women students in any of the three studies. In all three groups of students, the degree of deterioration was somewhat greater among women than among men. The total number of affected teeth in the three groups are shown in Table 3. W ith the single exception of untreated caries in 1949, every one of these evi dences of deterioration of teeth by decay shows an increase as time goes on. It is apparent that, despite all the numerous scientific advances of the modern age, the dental benefits available remain just a step or two behind the force or tendency that is working steadily and slowly against all the efforts to pre vent the loss of human permanent teeth. W ith the present extensive use of fluo ridated drinking water, the topical appli cation of sodium fluoride to children’ s teeth and the widespread use of ammoniated dentifrices, it is possible that the next 10 years will show a reversal of the present tendency. I f such a reversal occurs, will it be permanent or only temporary? Only a continuance of these studies will answer that question. It is hoped that the studies will be con-
Table 3 • Total number o f affected teeth in the three groups o f freshmen
Year o f exam ination
Total fillings
Total caries
1929 1939 1949
26.552 38.516 50.341
4.217 6.258 5.352
Total Total DMF* extractions conditions
2.398 3.357 4.908
33.167 48.171 60.601
*Decayed, missing, or fille d .
tinued. Such recordings, at 10 year in tervals, of the dental conditions of large groups of healthy young people from the top economic levels, can be of inestimable value in plotting long-term trends and in indicating the effects of various factors that may enter into the picture from time to time. Thus they serve, for teeth, a purpose similar to that served by the 10 year censuses of the total population and the death rates for that population. Though those who contributed to the present study may not be here to see the findings of the next 40 years, the chart that will show the degree of dental de terioration over a. half century will con stitute an invaluable record for future generations. Th e present report is not presented in a spirit of pessimism. Even though there does seem to be a trend toward the reduc tion and deterioration of human teeth, that tendency is not necessarily irre versible. And, even if it cannot be re versed, it may indicate merely that a portion of the human anatomy that is no longer of very much use is on its way to disappearing, like the vermiform appen dix at present and the caudal appendage of the past. Moreover, the findings of these three successive studies should serve as a challenge to both dental research workers and practicing dentists. I f teeth are worth saving, it must be these groups that will find and apply the means of saving them. University of Minnesota