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Genetic endowment and dental caries
Arch oral Biol. Vol. 16, pp. 1433-1441, 1971. Pergamon Press. Printed in Great Britain.
GENETIC ENDOWMENT
AND DENTAL
CARIES
D. JACKSON The Dental School and Hospital, University of Leeds, Leeds LSl 3EU Summary-The distribution of caries attacks between the contralateral mesial and distal surfaces of 114,023 permanent maxillary incisors is described in relation to age. Statistical regularities are observed and these strongly suggest that each site on each tooth is genetically endowed with a characteristic which, in a given environment, determines whether or not a site on a tooth is at risk to dental caries. The distribution of caries attacks between the mesial and distal surfaces of those incisors with caries experience in the lingual pit is different from that in teeth not possessing this attribute. EVIDENCE establishing that certain diseases depend upon the genetic constitution of the individual has been well documented. Whether and to what extent dental caries comes within this category is a subject of debate. To judge from the Ciba Symposium on Caries Resistant Teeth (WOLSTENHOLME and O’CONNOR, 1965) the majority view is that dental caries is essentially an environmental disease and that given a certain quality and quantity of exogenous factors, no tooth or site on a tooth will fail to succumb to caries. However, it is usually conceded that because of certain geneticallyendowed morphological and physico-chemical features, some teeth are more speedily attacked than others. This represents the limit of the concession in the direction of genetic determination. In man, it is extremely difficult to obtain direct familial evidence of inherited “susceptibility” to caries attack because the disease is a function of age and presumably of environment. To standardize these factors between parents and offspring, or among siblings, poses formidable difficulties. Twin studies have been carried out, mainly on children, but they have given variable results (JACKSON, 1968). Nevertheless, FAIRPO(1968) has recently demonstrated a higher concordance rate for site attack in monozygotic- than in like-sexed dizygotic-twin-pairs; the difference is highly significant (P < 0.001). Population studies offer another approach to the problem of genetics and dental caries (BURCH, 1968; JACKSON, 1968). Consider a panmictic community (one in which mating is random) at genetic equilibrium, and assume that each site, on each tooth, is genetically-endowed with a characteristic which determines whether or not it is vulnerable to caries attack. In that case, we would expect to find, in similar environments, that the distribution of attacks between, say, the contra lateral surfaces of a particular tooth type would be constant, age-for-age, from one generation to the next. Consider, for example, the distribution of carious attacks between the mesial and distal surfaces of central maxillary incisors. The genetic hypothesis predicts that the rates of the frequency of attacks on mesial surfaces, to the corresponding frequency for distal surfaces, should approach a constant value with increasing age. This paper provides a test of this type of prediction. 1433
1434
D. JACKSON SOURCE
OF DATA
Most data have been obtained from the “first visit diagnosis” made by dental practitioners in non-fluoride areas of the North of England. Complete and detailed chartings on the National Health Service form E.C. 25 were utilized from 62 dental practices. Practitioner data have been supplemented by others obtained in a survey of student entrants to Leeds University during the years 1959-60-61. In all, 114,023 maxillary incisors, with caries attack on at least one mesial or distal surface, have been recorded. Results are presented for each quinquennial age group form 15 to 59 yr, and for 60 yr and above. Extracted teeth were collected from twenty of the dental surgeons from whom clinical data were obtained. Information concerning the siting of caries attacks on maxillary incisors was recorded on marksense punch cards and the data were analysed by the Leeds University KDF9 computer. NOTATIONS In this paper, Ce refers to a maxillary central incisor; and Lat refers to a maxillary lateral incisor. The symbol (m) defines a mesial surface, (d) defines a distal surface and (pit) refers to a lingual pit. Hence Ce (m) denotes a mesial surface of a central incisor, and Lat (d) denotes a distal surface of a lateral incisor. If the dental surgeon had recorded either overt caries (D) or a filling (F) for a particular site, that site was presumed to have suffered a carious attack. Hence, DF refers to caries experience. We shall be mainly concerned with a population of teeth having DF (m) and/or DF (d) sites: such teeth are described as DFT. Similarly, DFS refers to DF (m) and DF (d) sites. Consequently, the ratio DFS/ DFT gives the mean number of sites [(m) and/or (d)] attacked per DF tooth. A unilateral attack refers to the situation where a (d), or an (m) site, is DF, it is denoted by: DF (d) only or DF (m) only. In a bilateral attack, both (d) and (m) sites on a tooth are DF, this is denoted by: DF (d) and (m). The notation A DF (d) refers to the total number of (d) sites which are attacked (DF), regardless of the status of the (m) sites. An analogous meaning is given to X DF (WI). ANALYSIS
OF DATA
From previous evidence (JACKSON,1968), it was found that the frequency of attacks on mesial and distal sites on teeth with DF lingual pits differed from the corresponding frequency for teeth without DFlingual pits. For this reason, separate analyses of the distribution of caries attack have been made for those teeth with, and for those-without, DF lingual pits. No consistent sex differences have been observed and hence data for the sexes have been combined. The distribution of(m) and (d) attacks on a tooth on the right side has been found to be effectively the same as that on a corresponding tooth on the left side and hence data for right and left Ce teeth, and for right and left Lat teeth have been combined. RESULTS
Central incisors
(a) DF lingualpit absent (Population Ce. Table 1). At all ages from 25 yr and upwards, the frequency of caries attacks on Ce (6) closely resembles that on Ce (m). This is shown by the stability of the ratio Z DF (6)/E DF (m), which, from 25 yr and upwards, varies little from the mean value of 1.06. One might therefore expect that the proportion of DFT with attacks on both surfaces (i.e. with bilateral attacks) would increase with advancing age. The increase is not observed. The proportion of DF teeth with bilateral attacks is effectively constant from the age of 25 yr and above at a mean level of 29 per cent. From 25 yr and above, the ratios DF (6) only: DF (6) and (m): DF (m) only change little from the mean values of 37:29: 34. It follows that the ratio of the number of teeth with a unilateral attack, to the number with a bilateral attack, is fairly constant at about 2 -40. Another feature is the ratio DFSIDFT which stays effectively constant from the age of 25 yr and above at a mean level of 1.29. This means that, for
Surfaces attacked WF)
DFT DFS DFS/DFT C DF(d)/E DF(m) Unil./Bil. Ratio
(nz) only
(d) and (m)
(4 only
N % N %
N %
4490 (41) 3099 (28) 3311 (31) 10966 14065 1.28 l-17 2.54
4229 (42) 2923 (29) 2943 (29) 10095 13018 1.29 1.22 2.45
3138 (37) 2542 (30) 2902 (34) 8582 11124 1.30 1.04 2.38
25-29
2703 (36) 2242 (30) 2611 (35) 7556 9798 1.30 1.02 2.37
30-34
2161 (38) 1710 (30) 1866 (33) 5737 7447 1.30 1.08 2.35
35-39
ATTACK(DF)BETWEENTHEMESIAL(WI)AND DO NOT POSSESS A DF(Ce) LINGUAL
20-24
WHICH
15-19
TABLE~.THEDISTRIBUTIONOFCARIES
1621 (37) 1312 (30) 1481 (34) 4414 5726 1.30 1.05 2.36
4C-44
1151 (39) 821 (28) 963 (33) 2935 3756 1.28 1.11 2.57
4549
55-59
452 (42) 280 (26) 355 (33) 1087 1367 1.26 1.15 2.88
50-54
697 (38) 532 (29) 597 (33) 1826 2358 1.29 1.09 2.43
DISTAL(~)SURFACESOFMAXILLARY PIT (POPULATION Ce)
25f
12219 (37) 9707 (29) 11053 (34) 32979 42686 1.29 1.06 2.40
60+
296 (35) 268 (32) 278 (33) 842 1110 1.32 1.03 2.14
a
1.08 2.46
2 g u z 4 $ 0 5
4217 (38) 3213 (29) 3674 (33)
40+
11104 14317 1.29
CENTRALINCISORS
Cm) only
(DF)
Unil./Bil. Ratio
DFSIDFT r, DF(d)/T. DF(m)
DFT DFS
(d) and (m)
Surfaces attacked
(4 only
N %
% N %
N
1.40 1.01 1.52
1022
983 1.40 1.10 1.50
(30) 219 732
(Z
20-24
(27) 187 702
(40)
15-19
961 1.43 0.93 1.31
($ z 1.42 0.96 1.41
177 (28) 266 (42) 197 (31)
174 (26) (:q
30-34
25-29
i:z 1.47
861
(5
G
171 (28)
35-39
(43) 143 (28) 505 723 1.43 l*Oo 1.32
40-44
-4s ti)
127 (30) 177 (42) 114 (27) 418 595 1.42 1.04 1.36
45-49
G 331 484 I.46 1.08 1.16
153 (46)
50-54
(5:; (2:; 167 251 I.50 0.97 0.99
(2:; 178 255 1.43 1.06 1.31
60-i-
(4::
55-59
(29) 3523 5036 1.43 0.98 l-33
(43) 1025
1513
(28)
985
25+
TABLE 2. THE DISTRIBUTION OFCARIESATTACK(DF)BETWEENTHEMESIAL(~)AND DI~TAL(~)S~~RPACESOFMAXILLARYCENTRALINCISORS POSESSINQA DF LJ.NGUALPIT(POPIJLATION Ce-DFpit)
GENETIC
ENDOWMENT
AND DENTAL
CAFUl2.S
1437
all Ce teeth in situ with caries at (m) and/or (d) sites, only about 65 per cent (129 out of 200) of the mesial and distal sites are ever observed to be attacked. (b) DF lingual pit present (Population Ce-DF pit. Table 2). In this population of Ce teeth, each tooth had a DF lingual pit and a DF (m) and/or DF (d) site. At all ages of 20 yr and above, the probability of caries attack (DF) at a (d> site is effectively the same as that at an (m) site; the ratio C DF (d&Z DF (m) varies little from unity. The distribution of attacks between (m) and (d) sites in this tooth population differs from that found in the Ce population. The attack ratios: DF (6) only: DF (d) and (m) : DF(m) only are effectively stabilized by at least the age of 25 yr at 28 :43 : 29. The stabilized ratio of unilateral to bilateral attacks is approximately 1.33. In this tooth population, the ratio DFS/DFTfor (m) and (d) sites stays effectively constant at about l-43. Hence only about 76 per cent (143 out of 200) of(m) and (d) sites are observed to be attacked in this population of DF teeth. Lateral incisors (a) DF lingual pit absent (Population Lut. Table 3). In this population of teeth the ratio of caries attacks, E DF (d)/C DF (m) rises from 0.48 at 15 yr to 0.91 at 40 yr. At ages of 40 yr and above, this ratio is close to unity and hence the probability of attack on a distal surface is similar to that on a mesial surface. By the age of 50 yr (or perhaps earlier), the ratios DF (6) only: DF (6) and (m): DF (m) only; the ratio of unilateral to bilateral attacks and the ratio DFS/DFT have all stabilized at approximately 37:31:32, 2.25, and 1.31 respectively. It will be noted that the stabilized ratios for Lat are very similar to those for Ce, namely, 37:29 : 34; 2 -40; and l-29. (b) DF Iingual pit present (Population Lat-DF pit. Table 4). In the Lat-DF pit population the ratio of caries attack, DF (d)/DF (m) d oes not stabilize at unity until about 45 yr. At ages of 50 yr and above, the two ratios DF (6) only: DF (6) and (m): DF(m) only, the ratio of unilateral to bilateral attacks and the ratio DFSIDFT become age-independent; these stabilized ratios are approximately 27 : 50 : 24, 1 *O,and l-5 respectively. It will be observed that these ratios are quite different from those for lateral teeth without a DF lingual pit and from those for central teeth without a DF pit. They are closer to those for central incisors with a DF lingual pit, which were found to be 28 :43 : 29, 1.33, and 1.43 respectively. Although over 5000 extracted teeth of all types were collected, the number of maxillary incisors in each clinically defined sub-group became critically small particularly at the upper end of the age range. To obtain sufficient numbers, for a reasonably homogeneous group, the comparison between extracted teethand in-situ teeth is made for combined Ce and Lat teeth without a DF lingual pit, over the age-range of 40 yr and above. Tables 1 and 3 show that, from the age of 40yr and above, the distribution of DF (m) and DF (d) sites in Ce teeth without a DF lingual pit is similar to that in Lat teeth without a DF lingual pit. There were 238 extracted teeth with a DF mesial and/or DF distal site and no caries experience at the lingual pit. The findings for extracted teeth are compared with those for the teeth in situ. Although the data for extracted teeth are relatively few, the distributions of DF (d) and DF(m) sites in them are virtually identical to those for the teeth in situ.
Surfaces attacked (DF3
%
(m) only
DFT DFS DFSIDFT C DF (d)/c DF (m) Unil./Bil. Ratio
% N
(d) and (m)
N
% N
((4 only
20-24
2026 (23) 2062 (23) 4897 (55) 8985 11047 1.23 0.59 3.36
15-19
1424 (18) 1785 (22) 4864 (60) 8073 9858 1.22 0.48 3.52
(28)
(27)
3058 (45) 6777 8596 1.27 0.76 2.73
2233 (42) 5378 6864 1.28 0.85 2.62
1390 (33) 1198 (28) 1659 (39) 4247 5445 1.28 0.91 2.55
1659 (31) 1486
1900 (28) 1819
2012 (27) 1917 (26) 3555 (48) 7484 9401 1.26 0.72 2.90
40-44
30-34
25-29
35-39
1010 (36) 782 (28) 980 (35) 2772 3554 1.28 1.02 2.54
45-49
As W
679 (38) 541 (30) 580 (32) 1800 2341 1.30 1.09 2.33
50-54
380 (38) 300 (30) 322 (32) 1002 1302 1.30 1.09 2.34
55-59
282 (35) 267 (33) 254 (32) 803 1070 1.33 1.05 2.01
60+
1341 (37) 1108 (31) 1156 (32) 3605 4713 1.31 1.08 2.25
50+
3741 (35) 3088 (29) 3795 (36) 10624 13712 1.29 0.99 2.44
40-k
TABLE3. THE DISTRIBUTION OFCARIES ATTACK(DF) BETWEEN THEMESIAL (HZ)AND DISTAL(d) SURFACES OF MAXILLARY LATERAL INCISORS NOTPOSSESSING A DF LINGUALPIT(POPULATION LAT)
p 2 $j 8 z
3
7 5 a G E
6
2
! is E E s 3
(8’3
7% VIP (80 L6E (zz) SEZ
zzs (00 OZE (zz) zvz
LLL (LZ) POP bZ) 96Z
(ES)
LEL (6Z) OOV CL11 9zz
(vs)
(zu)
da BH.L N33MEIE
.LId 7Vil9NI-I 1vIS3~
&a)
%3VwIV
V ONISSBSSOd
IV-Z ss.0 62.1 E9LI E9E I
(Lf)
WC (90 IZE (9z) 622
aNv
99.z 65.0 LZ.1 1881 LLPI
ZEZ (LO OEZ (9z) 191
61-51
6E.Z L9.0 OE.1 ml 9801
EP*I IO.1 IV-1 8EL EZS (62) ES1 (IV) SIZ toc1 SSI
PZ-OZ
E9.I 8L.O 8E.I EWI
EO.1 ZO.1 6'k.I 815 LPE Gz) 98 t6t7) IL1 (9z) 06
6Z-SZ
6L.I ES.0 9E.I SIZI t768
IZ*I PO.1 SP.1 262 IOZ (9z) zs w 16 (62) 8s
WOE
IL-1 58.0 LE.1 ES8 EZ9
SL-0 60.1 LS.1 8ZZ SPI (81) 9z (LS) E8 (sz) 9E
6E-SE
mxIa
t8l7)
IO.1 PO.1 6P.I 8EOI C69 6z) WI (OS) SPE (LZ) PSI
#-OV aw
6V-SP w
V-OS
(p)
(qdga-m-r do S33VdWS
NOIl.V-IIldOd)
6S-SS
AXVTIIXVMI
+09
WllEuV?
SOS
SIOSI3NI
smIv3
10
%
(u)
sda ua
ww 'WIm (4 da d~3~gg
mo
mom
&a) paqXlW s=ws
*p s-IavL
(4 Puv 04
Yz N
?lHL
G
NOIu-lflIxLSla
1440
D. JACK.WN
Extracted teeth (Table 5) TABLE~.T~DISTRIBU~ONOFCARIESA?TACK(DF)BETWEENMESIAL(~)DISTAL(~) SITESOFMAXILLARY CENTRAL (@AND LATERAL(L~~)IN EXTRACTED TEETH AND IN i?lSitUTEETH FOR AGESmyrAND ABOVE
Ages 40yr and above Extracted teeth In situteeth Ceand Lat Ce and Lat
Surfaces attacked W9
(4 only (d) and (m) (m) only
N % N % N %
DFT DFS DFSIDFT C DF(d)/C DF(m) Unil./Bil. Ratio
(Z) (E) 238 310 1.30 I.04 2.30
7958 (37) 6301 (29) 7469 (34) 21728 28029 l-29
DISCUSSION
The expression “susceptibility to caries attack” can be interpreted in more than one way. For example, it might be said that Lat (m) is more susceptible to caries attack than Lat (6) because the average rate at which the former site becomes attacked is greater than that at which the latter becomes attacked. On the other hand, above the age of 40 yr, the age-specific prevalence of attack at Lat (d) is effectively the same as that at Lat (m). Hence, if we use the age-specific prevalence of site attack as an index of susceptibility at ages of 40 yr and above, we find that Lat (d> and Lat (m) are almost equally “susceptible”. That a tooth or a site on a tooth may be completely resistant to caries attack has never been fully accepted; hence the expression “susceptibility to caries attack” has been used mostly to describe a graded quality. The evidence which has been presented in this paper and elsewhere (JACKSON, 1968 ; JACKSON and BURCH, 1969, 1970) suggests that, in a given environment, there are two kinds of sites-those at risk and those not at risk to caries attack. If the evidence is accepted, then it must be agreed that the proportion of sites attacked to those not attacked converge towards limiting values. This is completely in accord with the hypothesis that each site on each tooth is genetically endowed with a characteristic which, in a given environment, determines whether or not it is at risk to caries attack. The all-or-nothing nature of this characteristic, associated with sites of similar morphology, does not accord with traditional concepts of caries aetiology. The genetic hypothesis is enhanced by the differing distribution of mesial and distal surface attack in those incisors with and in those incisors without a DF lingual pit. Those incisors predisposed to attack in the lingual pit and also at a mesial and/or distal surface have an appreciably higher proportion of double attacks. A possible explanation of the relationship between genes and dental caries has been described
GENETIC! ENDOWMENT
AND DENTAL
CARIES
1441
elsewhere (BURCH and JACKSON, 1965; JACKSON, 1968; BURCH, 1968; JACKSON and BURCH, 1969, 1970).
Acknowledgements-The author is indebted to the Joseph Rowntree Memorial Trust for a grant of money which has made possible this investigation. To the many dental practitioners who made available their records, I wish to extend my sincere thanks. RBsurne-La repartition de l’attaque carieuse au niveau des surfaces m&ales et distales de 114.023 incisives permanentes sup&ieures est decrite en fonction de l’lge. Des distributions statistiques regulieres sont observers : ce qui indique nettement que chaque cot& dune dent est genetiquement conditiomre, avec une caracteristique qui determine ou non, dans M enviromrement don& le risque de carie dune surface dentaire. La repartition de l’attaque carieuse entre lea surfaces m&ales et distales d’incisives, atteintes de caries des sillons palatins ou linguaux, est differente de celles des dents prealablement indemnes.
Zusammenfaasung-Beschrieben wird die altersabhagige Verteihmg kariiiser L%ionen zwischen den kontralateralen mesialen und distalen ObertXchen von 114.025 bleibenden Oberkieferschneidetihnen. Es werden statistischeRegelml8igkeiten beobachtet ; diese deuten eindringlich darauf hm, da8 jede Stelle an jedem Zahn genetisch verursacht mit Eigenheiten behaftet ist, welche in einem gegebenen Milieu AnlaD dafiir ist, ob eine Stelle an einem Zahn kariesgefardet ist oder nicht. Die Verteilung karioser Lhionen zwischen den mesialen und distalen Obertlachen von solchen Schneidexahnen, die in der lingualen Fissur Karies haben, unterscheidet sich von der Verteihmg bei jenen Zlhnen, die an dieser Stelle nicht karios sind.
REFERENCES BURCH, P. R. J. 1968. An Inquiry concerning Growth, Disease and Ageing. Oliver & Boyd, Edinburgh. Buacrz, P. R. J. and JACKSON,D. 1965. Periodontal disease and dental caries: Some new aetiological considerations. Br. dent. J. 120, 127-134. FAIRPO, C. G. 1968. Comparison of dental caries experience in identical and like-sexed fraternal twins. J. dent. Res. 47,971. JACKSON,D. 1968. Genes and dental caries. Proc. Roy. Sot. Med. 61,265-269. JACKSON,D. and BURCH, P. R. J. 1969. Dental caries as a degenerative disease. Gerontologia 15,203216. JACKSON,D. and BURCH, P. R. J. 1970. Dental caries: distribution by age-group between (right-left) mesial and distal surfaces of permanent maxillary incisors. Archs oral Biol. 15,1059-1067. WOLSTENHOLME, G. E. W. and O’CONNOR,M. (Editors). 1965. Caries Resistant Teeth-Ciba Foundation Symposium. Churchill Ltd., London.
A.O.B.16/12--a
GENETIC ENDOWMENT
AND DENTAL
CARIES
D. JACKSON The Dental School and Hospital, University of Leeds, Leeds LSl 3EU Summary-The distribution of caries attacks between the contralateral mesial and distal surfaces of 114,023 permanent maxillary incisors is described in relation to age. Statistical regularities are observed and these strongly suggest that each site on each tooth is genetically endowed with a characteristic which, in a given environment, determines whether or not a site on a tooth is at risk to dental caries. The distribution of caries attacks between the mesial and distal surfaces of those incisors with caries experience in the lingual pit is different from that in teeth not possessing this attribute. EVIDENCE establishing that certain diseases depend upon the genetic constitution of the individual has been well documented. Whether and to what extent dental caries comes within this category is a subject of debate. To judge from the Ciba Symposium on Caries Resistant Teeth (WOLSTENHOLME and O’CONNOR, 1965) the majority view is that dental caries is essentially an environmental disease and that given a certain quality and quantity of exogenous factors, no tooth or site on a tooth will fail to succumb to caries. However, it is usually conceded that because of certain geneticallyendowed morphological and physico-chemical features, some teeth are more speedily attacked than others. This represents the limit of the concession in the direction of genetic determination. In man, it is extremely difficult to obtain direct familial evidence of inherited “susceptibility” to caries attack because the disease is a function of age and presumably of environment. To standardize these factors between parents and offspring, or among siblings, poses formidable difficulties. Twin studies have been carried out, mainly on children, but they have given variable results (JACKSON, 1968). Nevertheless, FAIRPO(1968) has recently demonstrated a higher concordance rate for site attack in monozygotic- than in like-sexed dizygotic-twin-pairs; the difference is highly significant (P < 0.001). Population studies offer another approach to the problem of genetics and dental caries (BURCH, 1968; JACKSON, 1968). Consider a panmictic community (one in which mating is random) at genetic equilibrium, and assume that each site, on each tooth, is genetically-endowed with a characteristic which determines whether or not it is vulnerable to caries attack. In that case, we would expect to find, in similar environments, that the distribution of attacks between, say, the contra lateral surfaces of a particular tooth type would be constant, age-for-age, from one generation to the next. Consider, for example, the distribution of carious attacks between the mesial and distal surfaces of central maxillary incisors. The genetic hypothesis predicts that the rates of the frequency of attacks on mesial surfaces, to the corresponding frequency for distal surfaces, should approach a constant value with increasing age. This paper provides a test of this type of prediction. 1433
1434
D. JACKSON SOURCE
OF DATA
Most data have been obtained from the “first visit diagnosis” made by dental practitioners in non-fluoride areas of the North of England. Complete and detailed chartings on the National Health Service form E.C. 25 were utilized from 62 dental practices. Practitioner data have been supplemented by others obtained in a survey of student entrants to Leeds University during the years 1959-60-61. In all, 114,023 maxillary incisors, with caries attack on at least one mesial or distal surface, have been recorded. Results are presented for each quinquennial age group form 15 to 59 yr, and for 60 yr and above. Extracted teeth were collected from twenty of the dental surgeons from whom clinical data were obtained. Information concerning the siting of caries attacks on maxillary incisors was recorded on marksense punch cards and the data were analysed by the Leeds University KDF9 computer. NOTATIONS In this paper, Ce refers to a maxillary central incisor; and Lat refers to a maxillary lateral incisor. The symbol (m) defines a mesial surface, (d) defines a distal surface and (pit) refers to a lingual pit. Hence Ce (m) denotes a mesial surface of a central incisor, and Lat (d) denotes a distal surface of a lateral incisor. If the dental surgeon had recorded either overt caries (D) or a filling (F) for a particular site, that site was presumed to have suffered a carious attack. Hence, DF refers to caries experience. We shall be mainly concerned with a population of teeth having DF (m) and/or DF (d) sites: such teeth are described as DFT. Similarly, DFS refers to DF (m) and DF (d) sites. Consequently, the ratio DFS/ DFT gives the mean number of sites [(m) and/or (d)] attacked per DF tooth. A unilateral attack refers to the situation where a (d), or an (m) site, is DF, it is denoted by: DF (d) only or DF (m) only. In a bilateral attack, both (d) and (m) sites on a tooth are DF, this is denoted by: DF (d) and (m). The notation A DF (d) refers to the total number of (d) sites which are attacked (DF), regardless of the status of the (m) sites. An analogous meaning is given to X DF (WI). ANALYSIS
OF DATA
From previous evidence (JACKSON,1968), it was found that the frequency of attacks on mesial and distal sites on teeth with DF lingual pits differed from the corresponding frequency for teeth without DFlingual pits. For this reason, separate analyses of the distribution of caries attack have been made for those teeth with, and for those-without, DF lingual pits. No consistent sex differences have been observed and hence data for the sexes have been combined. The distribution of(m) and (d) attacks on a tooth on the right side has been found to be effectively the same as that on a corresponding tooth on the left side and hence data for right and left Ce teeth, and for right and left Lat teeth have been combined. RESULTS
Central incisors
(a) DF lingualpit absent (Population Ce. Table 1). At all ages from 25 yr and upwards, the frequency of caries attacks on Ce (6) closely resembles that on Ce (m). This is shown by the stability of the ratio Z DF (6)/E DF (m), which, from 25 yr and upwards, varies little from the mean value of 1.06. One might therefore expect that the proportion of DFT with attacks on both surfaces (i.e. with bilateral attacks) would increase with advancing age. The increase is not observed. The proportion of DF teeth with bilateral attacks is effectively constant from the age of 25 yr and above at a mean level of 29 per cent. From 25 yr and above, the ratios DF (6) only: DF (6) and (m): DF (m) only change little from the mean values of 37:29: 34. It follows that the ratio of the number of teeth with a unilateral attack, to the number with a bilateral attack, is fairly constant at about 2 -40. Another feature is the ratio DFSIDFT which stays effectively constant from the age of 25 yr and above at a mean level of 1.29. This means that, for
Surfaces attacked WF)
DFT DFS DFS/DFT C DF(d)/E DF(m) Unil./Bil. Ratio
(nz) only
(d) and (m)
(4 only
N % N %
N %
4490 (41) 3099 (28) 3311 (31) 10966 14065 1.28 l-17 2.54
4229 (42) 2923 (29) 2943 (29) 10095 13018 1.29 1.22 2.45
3138 (37) 2542 (30) 2902 (34) 8582 11124 1.30 1.04 2.38
25-29
2703 (36) 2242 (30) 2611 (35) 7556 9798 1.30 1.02 2.37
30-34
2161 (38) 1710 (30) 1866 (33) 5737 7447 1.30 1.08 2.35
35-39
ATTACK(DF)BETWEENTHEMESIAL(WI)AND DO NOT POSSESS A DF(Ce) LINGUAL
20-24
WHICH
15-19
TABLE~.THEDISTRIBUTIONOFCARIES
1621 (37) 1312 (30) 1481 (34) 4414 5726 1.30 1.05 2.36
4C-44
1151 (39) 821 (28) 963 (33) 2935 3756 1.28 1.11 2.57
4549
55-59
452 (42) 280 (26) 355 (33) 1087 1367 1.26 1.15 2.88
50-54
697 (38) 532 (29) 597 (33) 1826 2358 1.29 1.09 2.43
DISTAL(~)SURFACESOFMAXILLARY PIT (POPULATION Ce)
25f
12219 (37) 9707 (29) 11053 (34) 32979 42686 1.29 1.06 2.40
60+
296 (35) 268 (32) 278 (33) 842 1110 1.32 1.03 2.14
a
1.08 2.46
2 g u z 4 $ 0 5
4217 (38) 3213 (29) 3674 (33)
40+
11104 14317 1.29
CENTRALINCISORS
Cm) only
(DF)
Unil./Bil. Ratio
DFSIDFT r, DF(d)/T. DF(m)
DFT DFS
(d) and (m)
Surfaces attacked
(4 only
N %
% N %
N
1.40 1.01 1.52
1022
983 1.40 1.10 1.50
(30) 219 732
(Z
20-24
(27) 187 702
(40)
15-19
961 1.43 0.93 1.31
($ z 1.42 0.96 1.41
177 (28) 266 (42) 197 (31)
174 (26) (:q
30-34
25-29
i:z 1.47
861
(5
G
171 (28)
35-39
(43) 143 (28) 505 723 1.43 l*Oo 1.32
40-44
-4s ti)
127 (30) 177 (42) 114 (27) 418 595 1.42 1.04 1.36
45-49
G 331 484 I.46 1.08 1.16
153 (46)
50-54
(5:; (2:; 167 251 I.50 0.97 0.99
(2:; 178 255 1.43 1.06 1.31
60-i-
(4::
55-59
(29) 3523 5036 1.43 0.98 l-33
(43) 1025
1513
(28)
985
25+
TABLE 2. THE DISTRIBUTION OFCARIESATTACK(DF)BETWEENTHEMESIAL(~)AND DI~TAL(~)S~~RPACESOFMAXILLARYCENTRALINCISORS POSESSINQA DF LJ.NGUALPIT(POPIJLATION Ce-DFpit)
GENETIC
ENDOWMENT
AND DENTAL
CAFUl2.S
1437
all Ce teeth in situ with caries at (m) and/or (d) sites, only about 65 per cent (129 out of 200) of the mesial and distal sites are ever observed to be attacked. (b) DF lingual pit present (Population Ce-DF pit. Table 2). In this population of Ce teeth, each tooth had a DF lingual pit and a DF (m) and/or DF (d) site. At all ages of 20 yr and above, the probability of caries attack (DF) at a (d> site is effectively the same as that at an (m) site; the ratio C DF (d&Z DF (m) varies little from unity. The distribution of attacks between (m) and (d) sites in this tooth population differs from that found in the Ce population. The attack ratios: DF (6) only: DF (d) and (m) : DF(m) only are effectively stabilized by at least the age of 25 yr at 28 :43 : 29. The stabilized ratio of unilateral to bilateral attacks is approximately 1.33. In this tooth population, the ratio DFS/DFTfor (m) and (d) sites stays effectively constant at about l-43. Hence only about 76 per cent (143 out of 200) of(m) and (d) sites are observed to be attacked in this population of DF teeth. Lateral incisors (a) DF lingual pit absent (Population Lut. Table 3). In this population of teeth the ratio of caries attacks, E DF (d)/C DF (m) rises from 0.48 at 15 yr to 0.91 at 40 yr. At ages of 40 yr and above, this ratio is close to unity and hence the probability of attack on a distal surface is similar to that on a mesial surface. By the age of 50 yr (or perhaps earlier), the ratios DF (6) only: DF (6) and (m): DF (m) only; the ratio of unilateral to bilateral attacks and the ratio DFS/DFT have all stabilized at approximately 37:31:32, 2.25, and 1.31 respectively. It will be noted that the stabilized ratios for Lat are very similar to those for Ce, namely, 37:29 : 34; 2 -40; and l-29. (b) DF Iingual pit present (Population Lat-DF pit. Table 4). In the Lat-DF pit population the ratio of caries attack, DF (d)/DF (m) d oes not stabilize at unity until about 45 yr. At ages of 50 yr and above, the two ratios DF (6) only: DF (6) and (m): DF(m) only, the ratio of unilateral to bilateral attacks and the ratio DFSIDFT become age-independent; these stabilized ratios are approximately 27 : 50 : 24, 1 *O,and l-5 respectively. It will be observed that these ratios are quite different from those for lateral teeth without a DF lingual pit and from those for central teeth without a DF pit. They are closer to those for central incisors with a DF lingual pit, which were found to be 28 :43 : 29, 1.33, and 1.43 respectively. Although over 5000 extracted teeth of all types were collected, the number of maxillary incisors in each clinically defined sub-group became critically small particularly at the upper end of the age range. To obtain sufficient numbers, for a reasonably homogeneous group, the comparison between extracted teethand in-situ teeth is made for combined Ce and Lat teeth without a DF lingual pit, over the age-range of 40 yr and above. Tables 1 and 3 show that, from the age of 40yr and above, the distribution of DF (m) and DF (d) sites in Ce teeth without a DF lingual pit is similar to that in Lat teeth without a DF lingual pit. There were 238 extracted teeth with a DF mesial and/or DF distal site and no caries experience at the lingual pit. The findings for extracted teeth are compared with those for the teeth in situ. Although the data for extracted teeth are relatively few, the distributions of DF (d) and DF(m) sites in them are virtually identical to those for the teeth in situ.
Surfaces attacked (DF3
%
(m) only
DFT DFS DFSIDFT C DF (d)/c DF (m) Unil./Bil. Ratio
% N
(d) and (m)
N
% N
((4 only
20-24
2026 (23) 2062 (23) 4897 (55) 8985 11047 1.23 0.59 3.36
15-19
1424 (18) 1785 (22) 4864 (60) 8073 9858 1.22 0.48 3.52
(28)
(27)
3058 (45) 6777 8596 1.27 0.76 2.73
2233 (42) 5378 6864 1.28 0.85 2.62
1390 (33) 1198 (28) 1659 (39) 4247 5445 1.28 0.91 2.55
1659 (31) 1486
1900 (28) 1819
2012 (27) 1917 (26) 3555 (48) 7484 9401 1.26 0.72 2.90
40-44
30-34
25-29
35-39
1010 (36) 782 (28) 980 (35) 2772 3554 1.28 1.02 2.54
45-49
As W
679 (38) 541 (30) 580 (32) 1800 2341 1.30 1.09 2.33
50-54
380 (38) 300 (30) 322 (32) 1002 1302 1.30 1.09 2.34
55-59
282 (35) 267 (33) 254 (32) 803 1070 1.33 1.05 2.01
60+
1341 (37) 1108 (31) 1156 (32) 3605 4713 1.31 1.08 2.25
50+
3741 (35) 3088 (29) 3795 (36) 10624 13712 1.29 0.99 2.44
40-k
TABLE3. THE DISTRIBUTION OFCARIES ATTACK(DF) BETWEEN THEMESIAL (HZ)AND DISTAL(d) SURFACES OF MAXILLARY LATERAL INCISORS NOTPOSSESSING A DF LINGUALPIT(POPULATION LAT)
p 2 $j 8 z
3
7 5 a G E
6
2
! is E E s 3
(8’3
7% VIP (80 L6E (zz) SEZ
zzs (00 OZE (zz) zvz
LLL (LZ) POP bZ) 96Z
(ES)
LEL (6Z) OOV CL11 9zz
(vs)
(zu)
da BH.L N33MEIE
.LId 7Vil9NI-I 1vIS3~
&a)
%3VwIV
V ONISSBSSOd
IV-Z ss.0 62.1 E9LI E9E I
(Lf)
WC (90 IZE (9z) 622
aNv
99.z 65.0 LZ.1 1881 LLPI
ZEZ (LO OEZ (9z) 191
61-51
6E.Z L9.0 OE.1 ml 9801
EP*I IO.1 IV-1 8EL EZS (62) ES1 (IV) SIZ toc1 SSI
PZ-OZ
E9.I 8L.O 8E.I EWI
EO.1 ZO.1 6'k.I 815 LPE Gz) 98 t6t7) IL1 (9z) 06
6Z-SZ
6L.I ES.0 9E.I SIZI t768
IZ*I PO.1 SP.1 262 IOZ (9z) zs w 16 (62) 8s
WOE
IL-1 58.0 LE.1 ES8 EZ9
SL-0 60.1 LS.1 8ZZ SPI (81) 9z (LS) E8 (sz) 9E
6E-SE
mxIa
t8l7)
IO.1 PO.1 6P.I 8EOI C69 6z) WI (OS) SPE (LZ) PSI
#-OV aw
6V-SP w
V-OS
(p)
(qdga-m-r do S33VdWS
NOIl.V-IIldOd)
6S-SS
AXVTIIXVMI
+09
WllEuV?
SOS
SIOSI3NI
smIv3
10
%
(u)
sda ua
ww 'WIm (4 da d~3~gg
mo
mom
&a) paqXlW s=ws
*p s-IavL
(4 Puv 04
Yz N
?lHL
G
NOIu-lflIxLSla
1440
D. JACK.WN
Extracted teeth (Table 5) TABLE~.T~DISTRIBU~ONOFCARIESA?TACK(DF)BETWEENMESIAL(~)DISTAL(~) SITESOFMAXILLARY CENTRAL (@AND LATERAL(L~~)IN EXTRACTED TEETH AND IN i?lSitUTEETH FOR AGESmyrAND ABOVE
Ages 40yr and above Extracted teeth In situteeth Ceand Lat Ce and Lat
Surfaces attacked W9
(4 only (d) and (m) (m) only
N % N % N %
DFT DFS DFSIDFT C DF(d)/C DF(m) Unil./Bil. Ratio
(Z) (E) 238 310 1.30 I.04 2.30
7958 (37) 6301 (29) 7469 (34) 21728 28029 l-29
DISCUSSION
The expression “susceptibility to caries attack” can be interpreted in more than one way. For example, it might be said that Lat (m) is more susceptible to caries attack than Lat (6) because the average rate at which the former site becomes attacked is greater than that at which the latter becomes attacked. On the other hand, above the age of 40 yr, the age-specific prevalence of attack at Lat (d) is effectively the same as that at Lat (m). Hence, if we use the age-specific prevalence of site attack as an index of susceptibility at ages of 40 yr and above, we find that Lat (d> and Lat (m) are almost equally “susceptible”. That a tooth or a site on a tooth may be completely resistant to caries attack has never been fully accepted; hence the expression “susceptibility to caries attack” has been used mostly to describe a graded quality. The evidence which has been presented in this paper and elsewhere (JACKSON, 1968 ; JACKSON and BURCH, 1969, 1970) suggests that, in a given environment, there are two kinds of sites-those at risk and those not at risk to caries attack. If the evidence is accepted, then it must be agreed that the proportion of sites attacked to those not attacked converge towards limiting values. This is completely in accord with the hypothesis that each site on each tooth is genetically endowed with a characteristic which, in a given environment, determines whether or not it is at risk to caries attack. The all-or-nothing nature of this characteristic, associated with sites of similar morphology, does not accord with traditional concepts of caries aetiology. The genetic hypothesis is enhanced by the differing distribution of mesial and distal surface attack in those incisors with and in those incisors without a DF lingual pit. Those incisors predisposed to attack in the lingual pit and also at a mesial and/or distal surface have an appreciably higher proportion of double attacks. A possible explanation of the relationship between genes and dental caries has been described
GENETIC! ENDOWMENT
AND DENTAL
CARIES
1441
elsewhere (BURCH and JACKSON, 1965; JACKSON, 1968; BURCH, 1968; JACKSON and BURCH, 1969, 1970).
Acknowledgements-The author is indebted to the Joseph Rowntree Memorial Trust for a grant of money which has made possible this investigation. To the many dental practitioners who made available their records, I wish to extend my sincere thanks. RBsurne-La repartition de l’attaque carieuse au niveau des surfaces m&ales et distales de 114.023 incisives permanentes sup&ieures est decrite en fonction de l’lge. Des distributions statistiques regulieres sont observers : ce qui indique nettement que chaque cot& dune dent est genetiquement conditiomre, avec une caracteristique qui determine ou non, dans M enviromrement don& le risque de carie dune surface dentaire. La repartition de l’attaque carieuse entre lea surfaces m&ales et distales d’incisives, atteintes de caries des sillons palatins ou linguaux, est differente de celles des dents prealablement indemnes.
Zusammenfaasung-Beschrieben wird die altersabhagige Verteihmg kariiiser L%ionen zwischen den kontralateralen mesialen und distalen ObertXchen von 114.025 bleibenden Oberkieferschneidetihnen. Es werden statistischeRegelml8igkeiten beobachtet ; diese deuten eindringlich darauf hm, da8 jede Stelle an jedem Zahn genetisch verursacht mit Eigenheiten behaftet ist, welche in einem gegebenen Milieu AnlaD dafiir ist, ob eine Stelle an einem Zahn kariesgefardet ist oder nicht. Die Verteilung karioser Lhionen zwischen den mesialen und distalen Obertlachen von solchen Schneidexahnen, die in der lingualen Fissur Karies haben, unterscheidet sich von der Verteihmg bei jenen Zlhnen, die an dieser Stelle nicht karios sind.
REFERENCES BURCH, P. R. J. 1968. An Inquiry concerning Growth, Disease and Ageing. Oliver & Boyd, Edinburgh. Buacrz, P. R. J. and JACKSON,D. 1965. Periodontal disease and dental caries: Some new aetiological considerations. Br. dent. J. 120, 127-134. FAIRPO, C. G. 1968. Comparison of dental caries experience in identical and like-sexed fraternal twins. J. dent. Res. 47,971. JACKSON,D. 1968. Genes and dental caries. Proc. Roy. Sot. Med. 61,265-269. JACKSON,D. and BURCH, P. R. J. 1969. Dental caries as a degenerative disease. Gerontologia 15,203216. JACKSON,D. and BURCH, P. R. J. 1970. Dental caries: distribution by age-group between (right-left) mesial and distal surfaces of permanent maxillary incisors. Archs oral Biol. 15,1059-1067. WOLSTENHOLME, G. E. W. and O’CONNOR,M. (Editors). 1965. Caries Resistant Teeth-Ciba Foundation Symposium. Churchill Ltd., London.
A.O.B.16/12--a