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The Lincoln dental caries study I. The incidence of dental caries in persons with various mental disorders
M e n ta lly subnormal persons have a lower incidence of dental caries than m entally normal persons, but the reason for this lower incidence has not been determined. A total of 568 male and fem ale patients, ages 10 to 21, a t the Lincoln State School for the m entally subnormal, Lincoln, III., participated in an investigation of the incidence of dental caries in subdivisions of m ental subnormality. Each subject was assigned to a group in which subjects had a low (20 to 49) or high (50 or more) intelligence quotient. The group of subjects with a lower IQ had a sig n ifican tly lower caries score than the group of subjects with the higher IQ. Results of the study did not indicate the causes of the resistance to d e n ta lc a rie s in m entally subnormal persons.
The Lincoln dental caries study I. The incidence of dental caries in persons with various mental disorders A rn old D. Steinberg,
Investigators who have been working with the mentally subnormal are aware that many of these persons have a lower incidence of dental caries than mentally normal persons. Such empirical clinical observations have been substantiated by documented studies.15 Most of these investiga tions have considered the mentally subnormal as a group and have not been concerned with the incidence of dental caries when the patients were classified according to their specific mental dis orders. The few dental caries studies conducted that were concerned with specific forms of mental subnormality were limited to persons with mon golism,68 cerebral palsy,9 emotional disturb ance,4 and familial dysautonomia.10 A Hungarian study11 did consider several types of mental sub normalities, but it was primarily concerned with the caries rate in all persons who were psy chologically abnormal. It has been substantiated that institutionalization lowers the caries rate in the mentally subnormal12 and normal sub jects.12-15 It has also been found that the caries 1002
MS, DDS, Stu art Z im m e rm an , PhD, Chicago
rate of the mentally subnormal was lower than that of institutionalized and noninstitutionalized normal persons23 (Table 1). The purpose of this study was to investigate the incidence of dental caries in the various sub divisions of mental subnormality at the Lincoln State School for the mentally subnormal at Lin coln, 111.
M a terials and methods
A total of 568 mentally subnormal,' institution alized, male and female patients, ages 10 to 21, with an average age of 16.6, were examined by one examiner by use of mouth mirror, explorer, port able dental light and chair, compressed air, and radiographs. All patients jn this study had an intelligence quotient of 20 or above and were cooperative enough to be examined. Because of the difficulty in obtaining intraoral radiographs
Table 1 "
Review of literature — dental caries and the mentally subnormal
Mentality classification
No. of patients
DMFT
Subnormal Normal
436 250
15.6 15.4
Subnormal
Ï66
3,5
Subnormal Normal
131 129
Subnormal Normal
48 48
Subnormal Normal
68 200
7.3 10.6
Mentally defective Emotionally disturbed
38 20
11.4 13.5
Cerebral palsy Normal
81 81
7.8 5.5
Mongolism No mongolism
99 97
Mongolism No mongolism
106 106
DMFS
DFS
Age
Institutionalized
Author
Yes No
Gustafsson, and others5
15 (Avg.)
Yes
Boyd15
8.5 10.5
16 (Avg.) 16 (Avg.)
Yes Yes
Boyd2
17.0 25.2
30 (Avg.) 30 (Avg.)
Yes No
Ellis1
57
No No
Snyder*
55 101
Yes Yes
Tannenbaum*
6-15 6-15
No No
Shmarak9
1.84 3.55
13-17 13-17
Yes Yes
Winer, and Cohen6
0.47 1.93
10 (Avg.) 9 (Avg.)
Yes Yes
Johnson, and others7
8.3 0.6 6.6 2.2 9.2
14 (Avg.) 9 (Avg.) 13 (Avg.) 20 (Avg.) 14 (Avg.)
Yes Yes Yes Yes Yes
Winer, and others, Acad. Dent, for Handicapped Study Group Report (1962)
No
Reitman, and others 10
32( Avg.) 14 (Avg.)
12.2 19.1
Minnesota group Texas group California group Massachusetts group
15 15 15 35 14
(2 with mongolism) (all with mongolism) (4 with mongolism) (all with mongolism) (none with mongolism)
Familial dysautonomia
19
No index reported; 15 of subjects were caries free.
6.7 9.9
6-17 6-17
5.7 9.5
16 (Avg.) 16 (Avg.)
5-20
Oligophrenic (mentally defective) 248 7.61 ... ... 2-6Q (Caries rate in early age group low. At age 14-19, caries rate increased sharply in this group.) Epileptic
70
Average IQ
11.67
6-60
45
60 60
Not reported
Yes
Yes
Schizophrenic
392
14.07
6-60
Yes
Psychopathic
388
14.48
6-6 0
Yes
Neurological
34
18.67
6-60
Yes
on the majority of these subjects, occlusal film placed extraorally was substituted for bitewing radiographs.16 A dental assistant recorded all data on spe cially designed examination sheets; data were then transferred to IBM punch cards for statistical evaluation. A DFT index for caries was used rather than a DMFT index,6 7 since a large num ber of teeth were missing because of periodontal disease, trauma, bizarre eruption patterns, and congenital absence rather than dental caries. Classification for the mental disorders was that used by this and most other similar institutions and was based primarily on the etiology of the disorder. One year after the initial examination, a similar survey was conducted on all available patients previously examined. All subjects were on an excellent diet, with more than adequate amounts of proteins and vita mins. Food intake was unrestricted, and all pa tients had spending money that was used mostly for candies and other confectionaries so that between-meal snacking was probably as frequent
Toth and Sz ab o "
as that of a normal population. The fluoride con tent of the water was 0.4 ppm, a negligible con sideration. Results and discussion
The average DFT for the group was 3.57 with a 1-year DFT increment of 0.89 (Table 2). This 1-year increment was less than that in published reports for a normal population,5-171s This dif ference was expected since our subjects were mentally subnormal and institutionalized. In this mentally subnormal population, 289 mentally defective patients had, at the initial ex amination, a DFT of 2.90, whereas the 274 mentally retarded patients had a DFT of 4.30, a significant difference (Table 2). A mentally de fective person is one who has organic brain dam age, and a mentally retarded person is one who is congenitally defective in intelligence without demonstrable organic etiology. Although not sta tistically significant, the 1-year DFT increment
Steinberg— Z im m erm a n : L IN C O L N D E N T A L C A R IE S S T U D Y I. ■ 1003
did show a tendency for the mentally defective group to have a lower caries increment than the mentally retarded group. When the children were classified into high and low IQ categories, by use of the intelligence test ing criteria prevailing at the institution, a highly significant difference in caries scores between the two categories was evident. The 253 patients with IQs of 20 to 49 had an average DFT score of 2.48, whereas the 315 patients with IQs of 50 or more had a significantly higher DFT score of 4.47 (Table 3,4). The well-known Vipeholm dental caries study5 obtained similar findings in an adult population of mentally subnormal institutionalized patients. A similar finding in a Hungarian study11 of patients from 2 to 60 years of age was reported. Although of borderline significance, the 1-year DFT increment at Lincoln tended to show that the lower IQ group was acquiring cavities at a faster rate than the higher IQ group. The group with the IQ of 20 to 49 had a DFT increment of 1.03, whereas the group with the IQ of 50 and above had a DFT increment of 0.73. The reported caries incidence of persons with a higher than normal IQ is of particular interest in this phase of the investigation. Hutchinson19 reported on a caries study in which 200 normal noninstitutionalized children were found to have a caries score inversely proportional to their IQ. Bruckner and Hill20 reported similar results with 165 normal noninstitutionalized ch'ldren. Kaho,21 in a survey of normal high school children, found that as grade score average increased, the DMF score decreased. These findings correlated with the present results when graphed from the lowest IQ to the highest IQ level, and form a bell-shaped curve showing persons of average IQ to have the highest caries score. Data are being acquired to ascertain the validity of this hypothesis. When the influence of oral hygiene was in vestigated by a one-way analysis of variance of the DFT scores of subjects categorized as poor, fair, or good, a significant result was obtained (Table 5, 6). It was found that the poorer the oral hygiene (more accurately, state of oral clean liness), the lower the DFT index. Miller,22 in studying normal noninstitutionalized children, ages 3 to 15, found a similar correlation. On the assumption that persons with lower IQs would brush teeth less often than persons with a higher IQ because of such physical factors as greater muscular imbalance and various infantile habits in the lower IQ patients, it would seem that a correlation between IQ and oral hygiene should 1004 ■ J A D A , V o l. 74, A p ril 1967
Table 2 H A verag e DFT for entire group Initial examination
5
1-year examination
Mental disorder
Mean DFT
Mentally defective
2*90
Mentally retarded
4.30
274
1.05
107
Average for entire group
3.57
568t
0.89
231
DFT In crement
No. 289 (p <0.001) •
0.77
No. 124 >(p0.10)
*“ t" =4.34. tFive patients were classified as psychotic or emotionally disturbed.
Table 3 m A verag e DFT at initial examination and the 1-year increment for subjects according to IQ level Initial examination
1-year examination
Intelligence level
Mean DFT
No. of subjects
DFT in crement
No. of subjects
IQ 20-49
2.48
253 (p <0.001)
1.03
115 (0.05
IQ 50 and over
4.47
315
0.73
116
Table 4 * One-way analysis of DFT scores of subjects according to IQ level*
Source of variation Between groups
Degrees of freedom
Sum of squares
2
533.56
Within groups (residual)
564
7,884.69
Total
566
Mean square 276.7%
F ratio 19.70 (p <0.001)
13.98
*This analysis of information presented in Table 3 and the analysis of infor mation presented in Table 5 (Table 6} was also confirmed by a one-way analysis of covariance, with age as the covariate. The results were virtually the same; the means adjusted for age were almost identical with the unadjusted means. Apparently, the high correlation between caries level and age in normal children does not exist in the mentally subnormal, probably because of the poor correlation between chronological age and developmental age.
Table 5 * DFT scores o f subjects categorized as having poor, fair, or good oraj hygiene Oral hygiene
Mean DFT
No. of subjects
Poor Fair
3.04 3.92
Good
4.58
277 210 (p <0.005) 81
Table 6 H One-way analysis of DFT scores of subjects categorized as having poor, fair, or good oral hygene
Source of variation
Degrees of freedom
Sum of squares
Mean square
2
185.76
92.889
Within groups (residual)
564
8,252.47
14.632
Total
566
Between groups
F. ratio 6.348 (p <0.005)
exist. In an effort to determine whether the ob served oral hygiene effect was caused by the com parative inability of persons with low IQ to maintain adequate oral hygiene, the data were subjected to a two-way unbalanced analysis of variance23 to investigate the interrelationship of IQ and hygiene on the caries states of these chil dren. The result differed from those previously obtained (Table 7). Significant F value still exists
investigation, the average DFT, the number of caries-free persons, and the 1-year increments are shown. Although there are many conditions listed affecting too few persons to be statistically significant, they add to the overall pattern of caries found in this particular population. The subgroup of conditions caused by prenatal influ ences had the lowest caries score, DFT increment, and number of caries-free persons. Of all the conditions listed, the patients with mongolism had the lowest caries scores (a DFT average of 0.46 in 68 such patients). This finding is in agree ment with that of previous reports.6'8 Further evidence of the caries resistance of the mongolian is indicated by the extremely low 1-year increment (0.07) and the large number of caries-free patients (53 out of a total of 68). The idiopathic epileptics and those persons classified under birth trauma were in groups that contained a significant, num ber of patients and had a DFT rate that was slightly under the average for the total popula tion studied. The extremely low DFT of 0.67 for the three cretins initially examined prompted the examina-
Table 7 * Two-way analysis of variance of oral hygiene and IQ effects on DFT
Source of variation
Degrees of freedom
Sum of squares
Mean squares
F ratio
Hygiene main effects
2
62.191
31.095
2.27 p*»0.1 0
IQ main effects
1
411.916
411.916
30.10 p<.001
Interaction
2
62.649
31.325
2.29 P ~ 0 .1 0
552
7,553.721
13.684
Error
for the IQ effects. The F ratio for the hygiene main effect is not large enough to claim that there are significant differences because of hy giene. Similarly, the interaction F ratio is not significant, having a probability p~0.10, essen tially the same as for oral hygiene. The combina tion of the oral hygiene main effect together with its interaction with the strong IQ main effect gave the same significant oral hygiene effect as in the one-way analysis. Thus, although there is an oral hygiene effect here in the direction re ported by Miller,22 it cannot be regarded as sig nificant. In Table 8, the mental subnormalities under
Table 8 ■ Various mental subnormalities under investigation — ave ra g e DFT, number of caries-free persons, and the 1-year increment Initial examination Classification
1-year examination
Mean DFT
No.
No. caries free
DFT increment
No.
No. caries free
2.33 1.38 0.46 0.00
24 8 68 2
11 6 53 2
0.00 1.00 0.07 0.00
11 Î 30 2
3 0 24 2
Intracraniol infections other than syphilis Epidemic encephalitis Other intracranial infections
3.44 6.56
9 16
4 2
1.17 0.80
6 5
1 2
Intoxication
3.00
1
0
Trauma Birth trauma Birth trauma with gross force
3.21 1.60
43 5
12 2
0.89 1.33
18 3
5 2
Other Idiopathic epilepsy Cretinism Intracranial neoplasm Multiple sclerosis Unknown
3.26 0.67 1.50 5.00 4.54
35 3 2 1 72
7 2 1 0 12
0.86
14
1
0.00 0.00 1.45
1 1 33
1 0 4
Mentally defective Caused by prenatal influences Congenital cranial anomaly Congenital spastic paraplegic Mongolism Prenatal' maternal infectious diseases
Total mentally defective Psychotic disorders Personality disorders Mentally retarded
289
124
114(39%)
4 5 (3 6 % )
2.33 3.50
3 2
0 0
Familial IQ 70 and over IQ 50-69 IQ 49 and less
5.33 4.79 2.65
15 64 37
1 7 10
2.67 0.26 2.17
3 27 23
1 7 1
Idiopathic IQ 70 and over IQ 50-69 IQ 49 and less
4.38 5.14 3.00
26 85 47
2 11 11
0.78 1.131.36
9 31 14
3 1 2
Total mentally retarded
274
42(15 % )
107
15(14% )
Total of all groups
568
156(27%)
231
6 0 (2 6 % )
Steinberg— Z im m erm a n : L IN C O L N D E N T A L C A R IE S S T U D Y I. ■ 1005
tion of all such patients at this institution. An additional six cretins were located, and the total of nine had a DFT average of less than 1.00. If the finding of such a low caries rate remained the same for a larger sampling, it would be con trary to the findings reported for studies in ex perimental animals in which induced hypothyroid ism produced an increase in caries.24 The group classified as unknown had a higher DFT index than the average for this entire popu lation. It was recently discovered that the un known group, listed by the institution under the heading, mentally defective, should have been separately classified. Since any patient with an undiagnosable mental defect was arbitrarily as signed to this group, the entire group could have easily been put in the mentally retarded category. By the elimination of this group from the men tally defective category, the difference in DFT rates between the mentally defective patients and mentally retarded patients would be much greater than that reported. Insufficient numbers of psychotic and emotion ally disturbed persons were present in this popu lation for a proper evaluation. From the reports in the literature, it was learned that stress and some psychotic disturbances increased caries in human beings and experimental animals.25 26 Tannenbaum4 reported that emotionally disturbed children had a higher caries rate than mentally defective children. Toth11 reported that oligophrenics (mentally defective) had a lower caries score than schizophrenic, psychiatric, and neuro logical patients. Familial and idiopathic were the two major subgroupings of mentally retarded. The former had some relative who was also retarded and the latter had no retarded relative. The finding of a lower caries score as the IQ score decreased was valid for the familial subgrouping. The num ber of caries-free persons increased as the IQ score decreased in both groups. No correlation between IQ and caries rate was shown in the idiopathic subgroup, and there was no correlation of the 1-year incremental DFT with the two sub groupings. Out of a total of 568 mentally subnormal pa tients initially examined, 156 (27 percent) were caries free. A similar percentage (26 percent) was maintained in the 1-year examination. Thirty-nine percent of the mentally defective pa tients initially examined were caries free, and a similar percentage (36 percent) was maintained in the 1-year examination. Fifteen percent of the patients in the mentally retarded group were caries free; a similar percentage (14 percent) was 1006 ■ JA D A , V o l. 74, A p ril 1967
obtained from the 1-year examination. The possible cause or causes of the reported resistance to dental caries in some groups can only be speculated. The factor or factors produc ing this resistance could be the result of an al teration in tooth morphology. The central nervous system, enamel, and skin have an ectodermal origin, and some parts of their development occur concomitantly. The factors, genetic or environ mental, responsible for a brain abnormality may operate at the same time that skin patterns are forming, thereby producing dermatologic peculiar ities, such as those often associated with various mental disorders. In mongolism, for example, an elephant-like skin and abnormal fingerprint pat terns occur. These same causative factors could, in a similar manner, affect the protein synthesis of the enamel organ resulting in the deposition of a modified enamel sheet. The apatite crystalline growth follows the organic fiber axis of the en amel matrix, and modifications in this organic fiber could alter the pattern whereby the apatite crystals are deposited and could create a more resistant enamel. The composition of saliva might also promote caries immunity. Steinman27 showed that NaCl levels of the saliva in experimental animals was directly related to the caries rate. Turner28 sim ilarly reported the presence of a higher level of chloride in caries-prone persons than in cariesfree persons. Winer29 said that in the parotid saliva from patients with mongolism there was an increased pH and concentration of Ca and H C03 ion. Each of these studies demonstrated a salivary difference between those with a high and those with a low caries rate. Further inves tigation, however, is necessary before definitive statements about the true relationship between caries' immunity and saliva can be made. A uniqueness in the bacterial flora in these caries-resistant persons, a combination of any or all of the factors discussed, or some cause not discussed in this paper might be the reason for caries immunity. There is something in these peo ple causing an increased caries resistance, and understanding its nature may provide researchers with material with which to study the etiology of dental caries.
Sum m ary
The mentally defective group had a lower caries score than the mentally retarded group, and the 1-year increments tended to show a similar result.
The group with a lower IQ had a significantly lower caries score than the group with the higher IQ. The 1-year increment result indicated that the group with the lower IQ was acquiring new lesions faster than the group with the higher IQ. A one-way analysis of variance showed that the poorer the oral hygiene, the lower the caries score. More detailed analysis, however, indicated that oral hygiene effect .was mainly caused by dis proportionate IQ distributions in the oral hygiene levels. Significant differences for oral hygiene could not be shown when this distribution was corrected. The mentally defective group, classified under conditions caused by prenatal influences, had a low decay index, a large number of caries-free patients, and a low 1-year increment. The familial subgrouping of the mentally re tarded group showed that the lower the IQ the lower the decay rate and that the lower the IQ the greater the number of caries-free patients. The idiopathic subgroup did not show any such relationship. No correlation could be made from the 1-year increments. Thirty-nine percent of the mentally defective patients were caries free, whereas 15 percent of the mentally retarded patients were caries free. The 1-year increment results for both groups maintained similar percentages. A portion of this paper was presented a t the 43rd a n nual meeting of the International Association of Dental Research, Toronto, C an ad a, 1965. T h e authors th a n k Doctor Joseph A lb aum , director of the Lincoln S tate School, and his s ta ff for their cooperation and assistance. This investigation was supported by a grant from the Carbonated Beverage M a n u fa ctu re rs of Illinois. C om putation was made with the assistance of the B io logical Sciences C om putation C enter, U n iversity of C h i cago, under U S P H S grant FR 0 0 1 3 from the Division of Research Facilities and Resources of the N atio n al Insti tutes of H ealth . Doctor Steinberg is an instructor in the departm ent of biochemistry, U n iversity of Illinois, College of M edicine, Chicago, and an associate attending a t the dental depart ment, M ich ael Reese Hospital and M ed ical Center, C h i cago. Doctor Zim m erm an is an assistant professor a t the W a lte r G. Z o ller M em o rial Dental C lin ic and a research associate (assistant professor), C om m ittee on M a th e m a t ical Biology, U n iversity of C hicago. 1. Ellis, R. G. Dental infections and mental health. O ral H ealth 33:71 1 Dec., 1943. 2. Boyd, J . D., and Cheyne, V . D. Epidemiologic stud ies in dental c a rie s ;:incidence of caries am ong institution alized children. J P e d ia t 31 :306 Sept., 1947. 3. Snyder, J . R .; Knopp, J . J . , and Jo rd a n , W . A. Dental problems of non-institutionalized m entally retard ed children. Northw est Dent 3 9 :1 2 3 M a rch , 1960. 4. Tannenbaum , K. A ., and M ille r, J . W . O ral condi tions of m entally retarded patients. J Dent C h ild 27 :2 7 7 4th quart., 1960.
5. Gustafsson, B. E., and others. Vipeh olm dental caries study. T h e effect of different levels of carbo h y d rate intak e on caries a c tiv ity in 4 3 6 individuals observed for fiv e years. A cta Odont Scand 1 1 :232 Sept., 1954. 6. W in e r, Richard, and Cohen, M ich a e l. D ental caries in mongolism. Dent Prog 2 :2 1 7 A p ril, 1962. 7. Johnson, N . P.; Young, M . A ., and Gallios, J . A. Dental caries experience o f mongoloid children. J Dent C h ild 2 7 :2 9 2 4th quart., 1960. 8. W in e r, Richard, and others. Dental treatm ent of the m entally subnormal. Bull A c a d D ent H an d icap 1 :9, 1962. 9. Shm arak, K. L., and Berstein, J . E. C aries incidence among cerebral palsy child ren : a prelim inary study. J Dent Ch ild 2 8 :1 5 4 2nd quart., 1961. 10. Reitm an, A . A .; Blacharsh, C., and Levy, J . M . C lin ical evaluation of the dental aspects of fa m ilia l dysauto n o m ia : a p relim inary report. J A D A 71 :14 3 6 Dec., 1965. 1 1. Toth, Karoly, and Szabo, Im re. Elme-es idegbetegek fogcaries viszonyai. Fogorv Szem le 5 6 :2 9 3 Oct., 1963. 12. Suher, Theodore; Dickson, J . P., and H adjim arkos, D. M . Caries experience among institutionalized children in the P a cific N . W . J Dent Res 3 3 :5 5 2 A ug., 1954. 13. H adjim arkos, D. M ., an d Storvick, C. Geographic variatio ns of dental caries in Oregon. II. D ental caries among institutionalized children and the possible influence of certain ecological factors on its incidence. J D ent Res 2 8 :5 9 4 Dec., 1949. 14. H arris, Robert. Biology of the children o f Hopewood House, Bowral, A u stralia. 4. O bservations on dentalcaries experience extending over five years ( 1 9 5 7 - 6 1 ) . J Dent Res 4 2 :1 3 8 7 Nov.-Dee., 1963. 15. Boyd, J . D. Long term studies of dental caries progression among teen-aged inm ates of a custodial in stitution. J C a lif Dent Assn (sup p l.) 2 6 :3 0 M a y - Ju n e , 1950 Abstract. 16. Bram er, M . L., and Steinberg, A . D. N ew concept in extra and intra-oral radiographs. J Dent C h ild 31 :34 1st quart., 1964. 17. Klein, H .; Palm er, C., and Knutson, J . W . Studies on dental caries: I. Dental status and dental needs of ele m entary school children. Public H ealth Rep 53:751 M a y 13, 1938. 1 8. Knutson, J . W ., and Scholz, G. C. E ffe c t of topically applied fluorides on dental caries experiences. N ew Y o rk Dent J 2 0 :7 2 Feb., 1950. 19. Hutchinson, G. T . Intelligence a n d dental health. A u st D ent J 4:31 Feb., 1959. 20. Bruckner, R. J., and H ill, T. J . Intelligence quo tients and dental caries experience. J D ent C h ild 19:64 2nd quart., 1952. 21. Kaho, Noel. Dental conditions and related psycho logical factors. J O kla Dent Assn 4 8 :5 Ju ly , 1958. 22. M iller, J . Relationship of occlusion and oral c le a n liness with caries rates. A rch O ral Biol 6 :7 0 , 1961. 23. Scheffe, Henry. A na lysis of va rian ce. N ew Y o rk, Jo h n W ile y & Sons, I 959, p. 112. 24. Bixler, D avid, and M u hler, J . C. Relation of th y roid gland a c tiv ity to the incidence of dental caries in the rat. II. A comparison o f caries incidence under pairedfeeding technic. J Dent Res 3 6 :8 8 0 Dec., 1957. 25. M anhold, J . Dental caries and psychological f a c tors. J Clin Psych 14:319 Ju ly , 1951. 26. Steinm an, R. R. E ffe c t of stress upon the incidence of dental caries. J S C a lif Dent Assn 2 8 :3 6 7 N ov., 1960. 27. Steinm an, R. R. Th e incidence of dental caries as altered by electrolyte a n d w ater balance. J S C a lif Dent Assn 2 9 :1 2 2 A p ril, 1961. 28. Turner, N. C. Biochem ical pattern basic to tooth decay. J A D A 61 :20 Ju ly , 1960. 29. W in e r, Richard, and others. T h e composition of hum an saliva from the parotid gland secretion rate and the electrolytic concentration in the m entally subnormal. J D ent Res 4 4 :6 3 2 Ju ly - A u g ., 1965.
Steinb erg-Z im m erm an: L IN C O L N D E N T A L C A R IE S S T U D Y I ■
1007
The Lincoln dental caries study I. The incidence of dental caries in persons with various mental disorders A rn old D. Steinberg,
Investigators who have been working with the mentally subnormal are aware that many of these persons have a lower incidence of dental caries than mentally normal persons. Such empirical clinical observations have been substantiated by documented studies.15 Most of these investiga tions have considered the mentally subnormal as a group and have not been concerned with the incidence of dental caries when the patients were classified according to their specific mental dis orders. The few dental caries studies conducted that were concerned with specific forms of mental subnormality were limited to persons with mon golism,68 cerebral palsy,9 emotional disturb ance,4 and familial dysautonomia.10 A Hungarian study11 did consider several types of mental sub normalities, but it was primarily concerned with the caries rate in all persons who were psy chologically abnormal. It has been substantiated that institutionalization lowers the caries rate in the mentally subnormal12 and normal sub jects.12-15 It has also been found that the caries 1002
MS, DDS, Stu art Z im m e rm an , PhD, Chicago
rate of the mentally subnormal was lower than that of institutionalized and noninstitutionalized normal persons23 (Table 1). The purpose of this study was to investigate the incidence of dental caries in the various sub divisions of mental subnormality at the Lincoln State School for the mentally subnormal at Lin coln, 111.
M a terials and methods
A total of 568 mentally subnormal,' institution alized, male and female patients, ages 10 to 21, with an average age of 16.6, were examined by one examiner by use of mouth mirror, explorer, port able dental light and chair, compressed air, and radiographs. All patients jn this study had an intelligence quotient of 20 or above and were cooperative enough to be examined. Because of the difficulty in obtaining intraoral radiographs
Table 1 "
Review of literature — dental caries and the mentally subnormal
Mentality classification
No. of patients
DMFT
Subnormal Normal
436 250
15.6 15.4
Subnormal
Ï66
3,5
Subnormal Normal
131 129
Subnormal Normal
48 48
Subnormal Normal
68 200
7.3 10.6
Mentally defective Emotionally disturbed
38 20
11.4 13.5
Cerebral palsy Normal
81 81
7.8 5.5
Mongolism No mongolism
99 97
Mongolism No mongolism
106 106
DMFS
DFS
Age
Institutionalized
Author
Yes No
Gustafsson, and others5
15 (Avg.)
Yes
Boyd15
8.5 10.5
16 (Avg.) 16 (Avg.)
Yes Yes
Boyd2
17.0 25.2
30 (Avg.) 30 (Avg.)
Yes No
Ellis1
57
No No
Snyder*
55 101
Yes Yes
Tannenbaum*
6-15 6-15
No No
Shmarak9
1.84 3.55
13-17 13-17
Yes Yes
Winer, and Cohen6
0.47 1.93
10 (Avg.) 9 (Avg.)
Yes Yes
Johnson, and others7
8.3 0.6 6.6 2.2 9.2
14 (Avg.) 9 (Avg.) 13 (Avg.) 20 (Avg.) 14 (Avg.)
Yes Yes Yes Yes Yes
Winer, and others, Acad. Dent, for Handicapped Study Group Report (1962)
No
Reitman, and others 10
32( Avg.) 14 (Avg.)
12.2 19.1
Minnesota group Texas group California group Massachusetts group
15 15 15 35 14
(2 with mongolism) (all with mongolism) (4 with mongolism) (all with mongolism) (none with mongolism)
Familial dysautonomia
19
No index reported; 15 of subjects were caries free.
6.7 9.9
6-17 6-17
5.7 9.5
16 (Avg.) 16 (Avg.)
5-20
Oligophrenic (mentally defective) 248 7.61 ... ... 2-6Q (Caries rate in early age group low. At age 14-19, caries rate increased sharply in this group.) Epileptic
70
Average IQ
11.67
6-60
45
60 60
Not reported
Yes
Yes
Schizophrenic
392
14.07
6-60
Yes
Psychopathic
388
14.48
6-6 0
Yes
Neurological
34
18.67
6-60
Yes
on the majority of these subjects, occlusal film placed extraorally was substituted for bitewing radiographs.16 A dental assistant recorded all data on spe cially designed examination sheets; data were then transferred to IBM punch cards for statistical evaluation. A DFT index for caries was used rather than a DMFT index,6 7 since a large num ber of teeth were missing because of periodontal disease, trauma, bizarre eruption patterns, and congenital absence rather than dental caries. Classification for the mental disorders was that used by this and most other similar institutions and was based primarily on the etiology of the disorder. One year after the initial examination, a similar survey was conducted on all available patients previously examined. All subjects were on an excellent diet, with more than adequate amounts of proteins and vita mins. Food intake was unrestricted, and all pa tients had spending money that was used mostly for candies and other confectionaries so that between-meal snacking was probably as frequent
Toth and Sz ab o "
as that of a normal population. The fluoride con tent of the water was 0.4 ppm, a negligible con sideration. Results and discussion
The average DFT for the group was 3.57 with a 1-year DFT increment of 0.89 (Table 2). This 1-year increment was less than that in published reports for a normal population,5-171s This dif ference was expected since our subjects were mentally subnormal and institutionalized. In this mentally subnormal population, 289 mentally defective patients had, at the initial ex amination, a DFT of 2.90, whereas the 274 mentally retarded patients had a DFT of 4.30, a significant difference (Table 2). A mentally de fective person is one who has organic brain dam age, and a mentally retarded person is one who is congenitally defective in intelligence without demonstrable organic etiology. Although not sta tistically significant, the 1-year DFT increment
Steinberg— Z im m erm a n : L IN C O L N D E N T A L C A R IE S S T U D Y I. ■ 1003
did show a tendency for the mentally defective group to have a lower caries increment than the mentally retarded group. When the children were classified into high and low IQ categories, by use of the intelligence test ing criteria prevailing at the institution, a highly significant difference in caries scores between the two categories was evident. The 253 patients with IQs of 20 to 49 had an average DFT score of 2.48, whereas the 315 patients with IQs of 50 or more had a significantly higher DFT score of 4.47 (Table 3,4). The well-known Vipeholm dental caries study5 obtained similar findings in an adult population of mentally subnormal institutionalized patients. A similar finding in a Hungarian study11 of patients from 2 to 60 years of age was reported. Although of borderline significance, the 1-year DFT increment at Lincoln tended to show that the lower IQ group was acquiring cavities at a faster rate than the higher IQ group. The group with the IQ of 20 to 49 had a DFT increment of 1.03, whereas the group with the IQ of 50 and above had a DFT increment of 0.73. The reported caries incidence of persons with a higher than normal IQ is of particular interest in this phase of the investigation. Hutchinson19 reported on a caries study in which 200 normal noninstitutionalized children were found to have a caries score inversely proportional to their IQ. Bruckner and Hill20 reported similar results with 165 normal noninstitutionalized ch'ldren. Kaho,21 in a survey of normal high school children, found that as grade score average increased, the DMF score decreased. These findings correlated with the present results when graphed from the lowest IQ to the highest IQ level, and form a bell-shaped curve showing persons of average IQ to have the highest caries score. Data are being acquired to ascertain the validity of this hypothesis. When the influence of oral hygiene was in vestigated by a one-way analysis of variance of the DFT scores of subjects categorized as poor, fair, or good, a significant result was obtained (Table 5, 6). It was found that the poorer the oral hygiene (more accurately, state of oral clean liness), the lower the DFT index. Miller,22 in studying normal noninstitutionalized children, ages 3 to 15, found a similar correlation. On the assumption that persons with lower IQs would brush teeth less often than persons with a higher IQ because of such physical factors as greater muscular imbalance and various infantile habits in the lower IQ patients, it would seem that a correlation between IQ and oral hygiene should 1004 ■ J A D A , V o l. 74, A p ril 1967
Table 2 H A verag e DFT for entire group Initial examination
5
1-year examination
Mental disorder
Mean DFT
Mentally defective
2*90
Mentally retarded
4.30
274
1.05
107
Average for entire group
3.57
568t
0.89
231
DFT In crement
No. 289 (p <0.001) •
0.77
No. 124 >(p0.10)
*“ t" =4.34. tFive patients were classified as psychotic or emotionally disturbed.
Table 3 m A verag e DFT at initial examination and the 1-year increment for subjects according to IQ level Initial examination
1-year examination
Intelligence level
Mean DFT
No. of subjects
DFT in crement
No. of subjects
IQ 20-49
2.48
253 (p <0.001)
1.03
115 (0.05
IQ 50 and over
4.47
315
0.73
116
Table 4 * One-way analysis of DFT scores of subjects according to IQ level*
Source of variation Between groups
Degrees of freedom
Sum of squares
2
533.56
Within groups (residual)
564
7,884.69
Total
566
Mean square 276.7%
F ratio 19.70 (p <0.001)
13.98
*This analysis of information presented in Table 3 and the analysis of infor mation presented in Table 5 (Table 6} was also confirmed by a one-way analysis of covariance, with age as the covariate. The results were virtually the same; the means adjusted for age were almost identical with the unadjusted means. Apparently, the high correlation between caries level and age in normal children does not exist in the mentally subnormal, probably because of the poor correlation between chronological age and developmental age.
Table 5 * DFT scores o f subjects categorized as having poor, fair, or good oraj hygiene Oral hygiene
Mean DFT
No. of subjects
Poor Fair
3.04 3.92
Good
4.58
277 210 (p <0.005) 81
Table 6 H One-way analysis of DFT scores of subjects categorized as having poor, fair, or good oral hygene
Source of variation
Degrees of freedom
Sum of squares
Mean square
2
185.76
92.889
Within groups (residual)
564
8,252.47
14.632
Total
566
Between groups
F. ratio 6.348 (p <0.005)
exist. In an effort to determine whether the ob served oral hygiene effect was caused by the com parative inability of persons with low IQ to maintain adequate oral hygiene, the data were subjected to a two-way unbalanced analysis of variance23 to investigate the interrelationship of IQ and hygiene on the caries states of these chil dren. The result differed from those previously obtained (Table 7). Significant F value still exists
investigation, the average DFT, the number of caries-free persons, and the 1-year increments are shown. Although there are many conditions listed affecting too few persons to be statistically significant, they add to the overall pattern of caries found in this particular population. The subgroup of conditions caused by prenatal influ ences had the lowest caries score, DFT increment, and number of caries-free persons. Of all the conditions listed, the patients with mongolism had the lowest caries scores (a DFT average of 0.46 in 68 such patients). This finding is in agree ment with that of previous reports.6'8 Further evidence of the caries resistance of the mongolian is indicated by the extremely low 1-year increment (0.07) and the large number of caries-free patients (53 out of a total of 68). The idiopathic epileptics and those persons classified under birth trauma were in groups that contained a significant, num ber of patients and had a DFT rate that was slightly under the average for the total popula tion studied. The extremely low DFT of 0.67 for the three cretins initially examined prompted the examina-
Table 7 * Two-way analysis of variance of oral hygiene and IQ effects on DFT
Source of variation
Degrees of freedom
Sum of squares
Mean squares
F ratio
Hygiene main effects
2
62.191
31.095
2.27 p*»0.1 0
IQ main effects
1
411.916
411.916
30.10 p<.001
Interaction
2
62.649
31.325
2.29 P ~ 0 .1 0
552
7,553.721
13.684
Error
for the IQ effects. The F ratio for the hygiene main effect is not large enough to claim that there are significant differences because of hy giene. Similarly, the interaction F ratio is not significant, having a probability p~0.10, essen tially the same as for oral hygiene. The combina tion of the oral hygiene main effect together with its interaction with the strong IQ main effect gave the same significant oral hygiene effect as in the one-way analysis. Thus, although there is an oral hygiene effect here in the direction re ported by Miller,22 it cannot be regarded as sig nificant. In Table 8, the mental subnormalities under
Table 8 ■ Various mental subnormalities under investigation — ave ra g e DFT, number of caries-free persons, and the 1-year increment Initial examination Classification
1-year examination
Mean DFT
No.
No. caries free
DFT increment
No.
No. caries free
2.33 1.38 0.46 0.00
24 8 68 2
11 6 53 2
0.00 1.00 0.07 0.00
11 Î 30 2
3 0 24 2
Intracraniol infections other than syphilis Epidemic encephalitis Other intracranial infections
3.44 6.56
9 16
4 2
1.17 0.80
6 5
1 2
Intoxication
3.00
1
0
Trauma Birth trauma Birth trauma with gross force
3.21 1.60
43 5
12 2
0.89 1.33
18 3
5 2
Other Idiopathic epilepsy Cretinism Intracranial neoplasm Multiple sclerosis Unknown
3.26 0.67 1.50 5.00 4.54
35 3 2 1 72
7 2 1 0 12
0.86
14
1
0.00 0.00 1.45
1 1 33
1 0 4
Mentally defective Caused by prenatal influences Congenital cranial anomaly Congenital spastic paraplegic Mongolism Prenatal' maternal infectious diseases
Total mentally defective Psychotic disorders Personality disorders Mentally retarded
289
124
114(39%)
4 5 (3 6 % )
2.33 3.50
3 2
0 0
Familial IQ 70 and over IQ 50-69 IQ 49 and less
5.33 4.79 2.65
15 64 37
1 7 10
2.67 0.26 2.17
3 27 23
1 7 1
Idiopathic IQ 70 and over IQ 50-69 IQ 49 and less
4.38 5.14 3.00
26 85 47
2 11 11
0.78 1.131.36
9 31 14
3 1 2
Total mentally retarded
274
42(15 % )
107
15(14% )
Total of all groups
568
156(27%)
231
6 0 (2 6 % )
Steinberg— Z im m erm a n : L IN C O L N D E N T A L C A R IE S S T U D Y I. ■ 1005
tion of all such patients at this institution. An additional six cretins were located, and the total of nine had a DFT average of less than 1.00. If the finding of such a low caries rate remained the same for a larger sampling, it would be con trary to the findings reported for studies in ex perimental animals in which induced hypothyroid ism produced an increase in caries.24 The group classified as unknown had a higher DFT index than the average for this entire popu lation. It was recently discovered that the un known group, listed by the institution under the heading, mentally defective, should have been separately classified. Since any patient with an undiagnosable mental defect was arbitrarily as signed to this group, the entire group could have easily been put in the mentally retarded category. By the elimination of this group from the men tally defective category, the difference in DFT rates between the mentally defective patients and mentally retarded patients would be much greater than that reported. Insufficient numbers of psychotic and emotion ally disturbed persons were present in this popu lation for a proper evaluation. From the reports in the literature, it was learned that stress and some psychotic disturbances increased caries in human beings and experimental animals.25 26 Tannenbaum4 reported that emotionally disturbed children had a higher caries rate than mentally defective children. Toth11 reported that oligophrenics (mentally defective) had a lower caries score than schizophrenic, psychiatric, and neuro logical patients. Familial and idiopathic were the two major subgroupings of mentally retarded. The former had some relative who was also retarded and the latter had no retarded relative. The finding of a lower caries score as the IQ score decreased was valid for the familial subgrouping. The num ber of caries-free persons increased as the IQ score decreased in both groups. No correlation between IQ and caries rate was shown in the idiopathic subgroup, and there was no correlation of the 1-year incremental DFT with the two sub groupings. Out of a total of 568 mentally subnormal pa tients initially examined, 156 (27 percent) were caries free. A similar percentage (26 percent) was maintained in the 1-year examination. Thirty-nine percent of the mentally defective pa tients initially examined were caries free, and a similar percentage (36 percent) was maintained in the 1-year examination. Fifteen percent of the patients in the mentally retarded group were caries free; a similar percentage (14 percent) was 1006 ■ JA D A , V o l. 74, A p ril 1967
obtained from the 1-year examination. The possible cause or causes of the reported resistance to dental caries in some groups can only be speculated. The factor or factors produc ing this resistance could be the result of an al teration in tooth morphology. The central nervous system, enamel, and skin have an ectodermal origin, and some parts of their development occur concomitantly. The factors, genetic or environ mental, responsible for a brain abnormality may operate at the same time that skin patterns are forming, thereby producing dermatologic peculiar ities, such as those often associated with various mental disorders. In mongolism, for example, an elephant-like skin and abnormal fingerprint pat terns occur. These same causative factors could, in a similar manner, affect the protein synthesis of the enamel organ resulting in the deposition of a modified enamel sheet. The apatite crystalline growth follows the organic fiber axis of the en amel matrix, and modifications in this organic fiber could alter the pattern whereby the apatite crystals are deposited and could create a more resistant enamel. The composition of saliva might also promote caries immunity. Steinman27 showed that NaCl levels of the saliva in experimental animals was directly related to the caries rate. Turner28 sim ilarly reported the presence of a higher level of chloride in caries-prone persons than in cariesfree persons. Winer29 said that in the parotid saliva from patients with mongolism there was an increased pH and concentration of Ca and H C03 ion. Each of these studies demonstrated a salivary difference between those with a high and those with a low caries rate. Further inves tigation, however, is necessary before definitive statements about the true relationship between caries' immunity and saliva can be made. A uniqueness in the bacterial flora in these caries-resistant persons, a combination of any or all of the factors discussed, or some cause not discussed in this paper might be the reason for caries immunity. There is something in these peo ple causing an increased caries resistance, and understanding its nature may provide researchers with material with which to study the etiology of dental caries.
Sum m ary
The mentally defective group had a lower caries score than the mentally retarded group, and the 1-year increments tended to show a similar result.
The group with a lower IQ had a significantly lower caries score than the group with the higher IQ. The 1-year increment result indicated that the group with the lower IQ was acquiring new lesions faster than the group with the higher IQ. A one-way analysis of variance showed that the poorer the oral hygiene, the lower the caries score. More detailed analysis, however, indicated that oral hygiene effect .was mainly caused by dis proportionate IQ distributions in the oral hygiene levels. Significant differences for oral hygiene could not be shown when this distribution was corrected. The mentally defective group, classified under conditions caused by prenatal influences, had a low decay index, a large number of caries-free patients, and a low 1-year increment. The familial subgrouping of the mentally re tarded group showed that the lower the IQ the lower the decay rate and that the lower the IQ the greater the number of caries-free patients. The idiopathic subgroup did not show any such relationship. No correlation could be made from the 1-year increments. Thirty-nine percent of the mentally defective patients were caries free, whereas 15 percent of the mentally retarded patients were caries free. The 1-year increment results for both groups maintained similar percentages. A portion of this paper was presented a t the 43rd a n nual meeting of the International Association of Dental Research, Toronto, C an ad a, 1965. T h e authors th a n k Doctor Joseph A lb aum , director of the Lincoln S tate School, and his s ta ff for their cooperation and assistance. This investigation was supported by a grant from the Carbonated Beverage M a n u fa ctu re rs of Illinois. C om putation was made with the assistance of the B io logical Sciences C om putation C enter, U n iversity of C h i cago, under U S P H S grant FR 0 0 1 3 from the Division of Research Facilities and Resources of the N atio n al Insti tutes of H ealth . Doctor Steinberg is an instructor in the departm ent of biochemistry, U n iversity of Illinois, College of M edicine, Chicago, and an associate attending a t the dental depart ment, M ich ael Reese Hospital and M ed ical Center, C h i cago. Doctor Zim m erm an is an assistant professor a t the W a lte r G. Z o ller M em o rial Dental C lin ic and a research associate (assistant professor), C om m ittee on M a th e m a t ical Biology, U n iversity of C hicago. 1. Ellis, R. G. Dental infections and mental health. O ral H ealth 33:71 1 Dec., 1943. 2. Boyd, J . D., and Cheyne, V . D. Epidemiologic stud ies in dental c a rie s ;:incidence of caries am ong institution alized children. J P e d ia t 31 :306 Sept., 1947. 3. Snyder, J . R .; Knopp, J . J . , and Jo rd a n , W . A. Dental problems of non-institutionalized m entally retard ed children. Northw est Dent 3 9 :1 2 3 M a rch , 1960. 4. Tannenbaum , K. A ., and M ille r, J . W . O ral condi tions of m entally retarded patients. J Dent C h ild 27 :2 7 7 4th quart., 1960.
5. Gustafsson, B. E., and others. Vipeh olm dental caries study. T h e effect of different levels of carbo h y d rate intak e on caries a c tiv ity in 4 3 6 individuals observed for fiv e years. A cta Odont Scand 1 1 :232 Sept., 1954. 6. W in e r, Richard, and Cohen, M ich a e l. D ental caries in mongolism. Dent Prog 2 :2 1 7 A p ril, 1962. 7. Johnson, N . P.; Young, M . A ., and Gallios, J . A. Dental caries experience o f mongoloid children. J Dent C h ild 2 7 :2 9 2 4th quart., 1960. 8. W in e r, Richard, and others. Dental treatm ent of the m entally subnormal. Bull A c a d D ent H an d icap 1 :9, 1962. 9. Shm arak, K. L., and Berstein, J . E. C aries incidence among cerebral palsy child ren : a prelim inary study. J Dent Ch ild 2 8 :1 5 4 2nd quart., 1961. 10. Reitm an, A . A .; Blacharsh, C., and Levy, J . M . C lin ical evaluation of the dental aspects of fa m ilia l dysauto n o m ia : a p relim inary report. J A D A 71 :14 3 6 Dec., 1965. 1 1. Toth, Karoly, and Szabo, Im re. Elme-es idegbetegek fogcaries viszonyai. Fogorv Szem le 5 6 :2 9 3 Oct., 1963. 12. Suher, Theodore; Dickson, J . P., and H adjim arkos, D. M . Caries experience among institutionalized children in the P a cific N . W . J Dent Res 3 3 :5 5 2 A ug., 1954. 13. H adjim arkos, D. M ., an d Storvick, C. Geographic variatio ns of dental caries in Oregon. II. D ental caries among institutionalized children and the possible influence of certain ecological factors on its incidence. J D ent Res 2 8 :5 9 4 Dec., 1949. 14. H arris, Robert. Biology of the children o f Hopewood House, Bowral, A u stralia. 4. O bservations on dentalcaries experience extending over five years ( 1 9 5 7 - 6 1 ) . J Dent Res 4 2 :1 3 8 7 Nov.-Dee., 1963. 15. Boyd, J . D. Long term studies of dental caries progression among teen-aged inm ates of a custodial in stitution. J C a lif Dent Assn (sup p l.) 2 6 :3 0 M a y - Ju n e , 1950 Abstract. 16. Bram er, M . L., and Steinberg, A . D. N ew concept in extra and intra-oral radiographs. J Dent C h ild 31 :34 1st quart., 1964. 17. Klein, H .; Palm er, C., and Knutson, J . W . Studies on dental caries: I. Dental status and dental needs of ele m entary school children. Public H ealth Rep 53:751 M a y 13, 1938. 1 8. Knutson, J . W ., and Scholz, G. C. E ffe c t of topically applied fluorides on dental caries experiences. N ew Y o rk Dent J 2 0 :7 2 Feb., 1950. 19. Hutchinson, G. T . Intelligence a n d dental health. A u st D ent J 4:31 Feb., 1959. 20. Bruckner, R. J., and H ill, T. J . Intelligence quo tients and dental caries experience. J D ent C h ild 19:64 2nd quart., 1952. 21. Kaho, Noel. Dental conditions and related psycho logical factors. J O kla Dent Assn 4 8 :5 Ju ly , 1958. 22. M iller, J . Relationship of occlusion and oral c le a n liness with caries rates. A rch O ral Biol 6 :7 0 , 1961. 23. Scheffe, Henry. A na lysis of va rian ce. N ew Y o rk, Jo h n W ile y & Sons, I 959, p. 112. 24. Bixler, D avid, and M u hler, J . C. Relation of th y roid gland a c tiv ity to the incidence of dental caries in the rat. II. A comparison o f caries incidence under pairedfeeding technic. J Dent Res 3 6 :8 8 0 Dec., 1957. 25. M anhold, J . Dental caries and psychological f a c tors. J Clin Psych 14:319 Ju ly , 1951. 26. Steinm an, R. R. E ffe c t of stress upon the incidence of dental caries. J S C a lif Dent Assn 2 8 :3 6 7 N ov., 1960. 27. Steinm an, R. R. Th e incidence of dental caries as altered by electrolyte a n d w ater balance. J S C a lif Dent Assn 2 9 :1 2 2 A p ril, 1961. 28. Turner, N. C. Biochem ical pattern basic to tooth decay. J A D A 61 :20 Ju ly , 1960. 29. W in e r, Richard, and others. T h e composition of hum an saliva from the parotid gland secretion rate and the electrolytic concentration in the m entally subnormal. J D ent Res 4 4 :6 3 2 Ju ly - A u g ., 1965.
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