Dietary Chemicals vs. Dental Caries

3

Amino Acids, Proteins, and Dental Caries

ABRAHAM E. NIZEL

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School of Dental Medicine, Tufts University, Boston, Mass. 02111

Amino acids and proteins have the potential of being classified as anti-caries nutrients, like fluorides and phosphates. Animal and in vitro studies clearly show that natural protein foods like fish flour, purified compounds like casein, or amino acids like glycine have significant caries-inhibitory and cariostatic effects. The major question that needs to be resolved is whether these findings can be extrapolated to man. Also, we need to determine and understand the mechanisms responsible for producing this effect. It is conceivable that enrichment of sugar and sugar products with amino acids or protein concentrates to reduce their cariogenicity may soon be a reality if we expend more research efforts in this direction.

On

the basis of data obtained from in vitro studies and animal-feeding experiments, it appears that amino acids and dietary proteins may have an effect on dental caries development. However, in human subjects, a direct cause and effect relationship between protein and dental caries has yet to be demonstrated. Furthermore, very few of the studies reviewed in this section suggest the mechanism by which proteins and amino acids influence caries development. Both the lack of clinical studies and paucity of animal or in vitro experiments which deal with possible mechanisms of action indicate the urgent need for more research in protein-dental caries relationship, so that the full potential of protein as an anti-caries nutrient for the human may be realized. Influence of Protein on Dental Caries in Human Beings Population Studies. Ockerse (29) noted that dental caries developed in only 20% of the children who were raised in the Northwest Cape Section of South Africa, an area where the intake of both dietary protein and fluoride are relatively high. This was in sharp contrast to a 23 In Dietary Chemicals vs. Dental Caries; Harris, R.; Advances in Chemistry; American Chemical Society: Washington, DC, 1970.

24

DIETARY

C H E M I C A L S

VS.

D E N T A L

CARIES

1 0 0 % i n c i d e n c e o f caries f o u n d i n c h i l d r e n n a t i v e to the S o u t h e r n R e g i o n of t h e C a p e , a r e g i o n w h e r e the i n t a k e of p r o t e i n a n d fluorides w a s correspondingly lower. T o substantiate his i m p r e s s i o n that p r o t e i n foods a n d fluorides w e r e r e l a t e d to this

finding

of l o w e r caries i n c i d e n c e , O c k e r s e c o n d u c t e d a n

a n i m a l - f e e d i n g e x p e r i m e n t i n w h i c h f e m a l e a l b i n o rats w e r e f e d d u r i n g gestation a n d l a c t a t i o n one of the f o l l o w i n g d i e t s : ( 1 ) c o n t r o l d i e t , ( 2 ) h i g h c a r b o h y d r a t e - l o w p r o t e i n diet, ( 3 ) l o w c a r b o h y d r a t e - h i g h p r o t e i n Downloaded by UNIV OF PITTSBURGH on October 15, 2015 | http://pubs.acs.org Publication Date: June 1, 1970 | doi: 10.1021/ba-1970-0094.ch003

d i e t , ( 4 ) c o n t r o l d i e t p l u s 100 p p m F i n w a t e r , a n d ( 5 ) l o w c a r b o h y d r a t e - h i g h p r o t e i n d i e t p l u s 100 p p m F i n w a t e r .

A t 35 days of age,

a l l t h e o f f s p r i n g w e r e c h a n g e d to a coarse c o r n d i e t , a n d c o n t i n u e d o n i t f o r 45 days m o r e . T h e m e a n caries i n d e x f o r e a c h g r o u p w a s ( 1 ) 5.7; ( 2 ) 8.8; ( 3 ) 3.0; ( 4 ) 2.8; ( 5 )

1.3.

Thus, high carbohydrate and l o w

fluorine

intakes r e s u l t e d i n h i g h e r caries, w h i l e h i g h p r o t e i n a n d h i g h

fluorine

intakes r e s u l t e d i n l o w e r caries.

Clinical Studies. A t t e m p t s have b e e n m a d e b y i n d e p e n d e n t i n v e s t i gators to correlate the l e v e l of p r o t e i n i n the sera a n d s a l i v a of h u m a n s w i t h t h e i r d e n t a l caries experience.

F o r example, Shannon a n d G i b s o n

( 3 5 ) m e a s u r e d t h e t o t a l p r o t e i n , a l b u m i n , a n d g l o b u l i n levels i n the sera of 505 r a n d o m l y - s e l e c t e d h e a l t h y y o u n g m e n . T h e y w e r e f e d a r a t i o n w h i c h w a s a d e q u a t e i n a l l r e q u i r e d nutrients.

N o correlations b e t w e e n

caries i n c i d e n c e a n d the levels of t o t a l p r o t e i n , a l b u m i n , a n d g l o b u l i n i n the sera w e r e f o u n d . M a n d e l et al. (18)

s t u d i e d a g r o u p of 63 c a r i e s - i m m u n e adults w i t h

a c o m p a r a b l e g r o u p of caries-active a d u l t s b y a n a l y z i n g p a r o t i d s a l i v a f o r content of t o t a l p r o t e i n a n d p r o t e i n - b o u n d hexosamine a n d b y c o m p a r i n g t h e d i s t r i b u t i o n of v a r i o u s p r o t e i n fractions a n d t h e ratios of fucose a n d hexosamine to n i t r o g e n i n the t w o m a j o r c a r b o h y d r a t e - p r o teins.

N o differences w e r e f o u n d .

Stack ( 3 9 ) c o u l d find n o c o r r e l a t i o n b e t w e e n the levels of s a l i v a r y t r y p t o p h a n a n d the D M F indices of 55 patients, e v e n t h o u g h s u c h a correlation h a d been Crowell

suggested

b y a n earlier r e p o r t of T u r n e r a n d

(44).

Influence of Natural

Food Protein on Animal Caries

Cereals. M c C l u r e (22) c o m p o u n d e d diets c o n t a i n i n g 8 0 % cereals w h i c h h a d b e e n either heat-processed, c o o k e d , o r d r i e d at 1 0 0 ° C , a n d f e d t h e m to rats, w h o d e v e l o p e d smooth-surface caries. S i n c e these finely p u l v e r i z e d diets w e r e l o w i n sugar content, h e c o n c l u d e d that the c a r i o g e n i c i t y of this d i e t w a s related to its l o w - q u a l i t y p r o t e i n content rather than the sugar.

In Dietary Chemicals vs. Dental Caries; Harris, R.; Advances in Chemistry; American Chemical Society: Washington, DC, 1970.

3.

N I Z E L

Amino Acids,

25

Proteins

I n subsequent experiments, M c C l u r e (20)

demonstrated a h i g h i n -

c i d e n c e of smooth-surface caries i n rats f e d w h e a t flour, d r y or toasted b r e a d , or s h r e d d e d w h e a t b i s c u i t .

W h e n these cereal p r o d u c t s

were

a u t o c l a v e d i n the presence of cerelose or starch, the caries p o t e n t i a l w a s i n c r e a s e d a n d supplements of 1 %

lysine counteracted

this effect.

c o n c l u d e d that this a m i n o a c i d ( l y s i n e ) is the k e y cariostatic

He

nutrient

that is i m p a i r e d d u r i n g the p r o c e s s i n g or h e a t i n g of cereals. D o d d s ( 5 ) was u n a b l e to c o n f i r m the report of M c C l u r e that heatDownloaded by UNIV OF PITTSBURGH on October 15, 2015 | http://pubs.acs.org Publication Date: June 1, 1970 | doi: 10.1021/ba-1970-0094.ch003

p r o c e s s i n g of cereals increases their c a r i o g e n i c i t y , p r e s u m a b l y because of r e d u c e d a v a i l a b i l i t y of their l y s i n e content.

She r e p o r t e d that rats

f e d diets c o m p o s e d m o s t l y ( 8 0 % ) of either c o r n , rice, or oats d e v e l o p e d smooth-surface caries, a n d that the relative c a r i o g e n i c i t y of e a c h of these cereals decreases as f o l l o w s : w h e a t > Dried M i l k .

corn >

M c C l u r e a n d F o l k (24)

rice >

oats.

f o u n d that diets c o n t a i n i n g

roller-processed s k i m m e d m i l k p o w d e r s w e r e m o r e c a r i o g e n i c t h a n sprayprocessed s k i m m e d m i l k p o w d e r s w h e n f e d i n the diets of rats.

Since

h i g h e r temperatures are u s e d i n r o l l e r - p r o c e s s i n g t h a n i n s p r a y - p r o c e s s i n g , a n d since l y s i n e is p a r t i a l l y i n a c t i v a t e d w h e n d r y casein is heated, they c o n c l u d e d that the increased c a r i o g e n i c i t y of the r o l l e r - d r i e d m i l k p r o b a b l y w a s r e l a t e d to l y s i n e i m p a i r m e n t . M c C l u r e a n d F o l k (23)

f e d to rats diets i n w h i c h the p r o t e i n w a s

s u p p l i e d b y three different nonfat m i l k p o w d e r s (freeze-dried, s p r a y - d r i e d , a n d r o l l e r - d r i e d ) , a n d they d e v e l o p e d smooth-surface

caries.

The inci-

dence of severity of the caries c o r r e l a t e d w i t h the degree of heat p r o c essing.

L e a s t caries d e v e l o p e d i n the g r o u p f e d the f r e e z e - d r i e d m i l k

a n d the most severe caries i n the g r o u p f e d the r o l l e r - d r i e d m i l k p o w d e r . T h e y later (25)

d e m o n s t r a t e d that caries d e v e l o p m e n t c a n be r e d u c e d

b y the a d d i t i o n of l y s i n e to this t y p e of diet. T h e effect of d r y w h o l e m i l k o n e x p e r i m e n t a l caries has also b e e n s t u d i e d b y M a u r o n et al.

(19),

w h o f o u n d , c o n t r a r y to M c C l u r e ,

that

this source of d i e t a r y p r o t e i n was not c a r i o g e n i c , a n d that there was no r e l a t i o n s h i p b e t w e e n the content of u t i l i z a b l e l y s i n e a n d the p o t e n c y of m i l k - c o n t a i n i n g diets.

D r e i z e n et al.

(6)

cariogenic

c a m e to a s i m i l a r

c o n c l u s i o n , because i n their a n i m a l - f e e d i n g e x p e r i m e n t they f o u n d that d r y w h o l e m i l k f e d at a 3 9 % l e v e l i n a c a r i o g e n i c diet h a d n o a p p r e c i a b l e effect o n i n c r e a s i n g c a r i o g e n i c i t y . R e c e n t l y , G r e e n (10)

suggested that the c a r i o g e n i c i t y of s k i m m e d

m i l k p o w d e r was r e l a t e d to its stickiness a n d the f r e q u e n c y w i t h w h i c h it was eaten. N a t u r a l s k i m m e d m i l k p o w d e r h a d a pleasanter taste t h a n casein or a c a s e i n - r i c h s i m u l a t e d s k i m m e d m i l k p o w d e r , a n d therefore w a s p r e f e r e n t i a l l y selected a n d eaten m o r e f r e q u e n t l y .

A l l three diets (nat-

u r a l s k i m m e d m i l k p o w d e r , casein, c a s e i n - r i c h s i m u l a t e d s k i m m e d m i l k


26

DIETARY

C H E M I C A L S

VS.

D E N T A L

CARIES

p o w d e r ) w e r e f o u n d b y analysis to h a v e the same p r o t e i n , c a r b o h y d r a t e , a n d fat content. Effect of Fish Protein Concentrate on Animal Caries.

Fish

flour,

w h i c h is c u r r e n t l y b e i n g u s e d as a n e c o n o m i c a l source of h i g h - q u a l i t y p r o t e i n f o r f e e d i n g c h i l d r e n i n u n d e r d e v e l o p e d countries, is a n a t u r a l f o o d p r o d u c t , consisting of p r o v e n anti-caries a c t i n g nutrients, a n d phosphates, i n a d d i t i o n to p r o t e i n . S t e p h a n (26)

(40)

h a v e f o u n d that a n otherwise extremely c a r i o g e n i c

al.

experimental

d i e t c a n b e m a d e significantly less c a r i o g e n i c i f the p r o t e i n Downloaded by UNIV OF PITTSBURGH on October 15, 2015 | http://pubs.acs.org Publication Date: June 1, 1970 | doi: 10.1021/ba-1970-0094.ch003

fluorides

a n d N i z e l et

component

of the diet is p r i m a r i l y , i f not c o m p l e t e l y , fish flour. W h a t has not b e e n d e t e r m i n e d is h o w m u c h the fish p r o t e i n has c o n t r i b u t e d to this cariesi n h i b i t i n g effect vis-a-vis

the

the fact remains that F . P . C .

fluoride

or the p h o s p h a t e .

Nevertheless,

(fish p r o t e i n c o n c e n t r a t e ) has the

strong

p o t e n t i a l to b e a u s e f u l a n d effective s u p p l e m e n t f o r r e d u c i n g the i n c i dence of d e n t a l decay. Influence of Synthetic Proteins on Animal Caries Casein. S c h w e i g e r t et al.

(33,

34)

content of a diet was r a i s e d f r o m 2 4 % to 5 0 %

o b s e r v e d that w h e n the

casein

( w h i c h is a d e q u a t e n u t r i t i o n a l l y )

( w h i c h is i n excess), the caries i n c i d e n c e w a s h a l v e d . It w a s

suggested that this effect w a s c a u s e d i n part b y r e p l a c e m e n t of sugar i n the d i e t b y e q u a l amounts of casein, a c o m p o u n d w h i c h is less susceptible to f e r m e n t a t i o n

b y t h e a c i d - p r o d u c i n g organisms associated

with

the

d e c a y process. T h e i m p o r t a n c e of the casein-sucrose

ratio of the diet to

caries d e v e l o p m e n t i n the rat was s t u d i e d b y S t e p h a n (41).

dental

D u r i n g 56

days, groups of 20 w e a n l i n g f e m a l e rats w e r e f e d one of three synthetic diets, the major components of w h i c h w e r e (A) (B)

12%

casein, 8 3 %

sucrose, or ( C )

16%

8 % casein, 8 7 % casein, 7 9 %

sucrose,

sucrose.

He

d e t e r m i n e d that o n d i e t A, 19 rats d e v e l o p e d m o l a r caries a n d 14 rats d e v e l o p e d i n c i s o r caries; o n diet B, 15 rats d e v e l o p e d m o l a r caries a n d o n l y one rat d e v e l o p e d a carious lesion o n the i n c i s o r t o o t h ; a n d o n diet C , 5 rats d e v e l o p e d m o l a r caries a n d n o i n c i s o r carious lesions.

Thus,

less caries d e v e l o p e d as the sucrose content of the diets was progressively r e p l a c e d w i t h casein. Losee and V a n Reen

(17)

reported an experiment

in which

68

w e a n l i n g rats w e r e d i v i d e d i n t o three groups a n d f e d one of the f o l l o w i n g diets, the major constituents of w h i c h w e r e 2 0 % casein a n d 6 1 . 8 %

or 4 0 %

casein

and

71.8%

30%

sucrose.

S o m e caries d e v e l o p e d i n a l l rats, a n d there w a s n o significant

difference b e t w e e n the groups.

sucrose;

casein a n d

sucrose;

51.8%

H o w e v e r , w h e n the caries f r o m these

e x p e r i m e n t a l groups w e r e c o m p a r e d w i t h a c o n t r o l g r o u p w h i c h w e r e


3.

N I Z E L

Amino Acids,

Proteins

27

f e d g r o u n d R o c k l a n d rat pellets, the latter s h o w e d s i g n i f i c a n t l y m o r e carious teeth a n d m o r e severe caries lesions.

This m a y have been

be-

cause the r e l a t i v e coarseness of the R o c k l a n d d i e t w o u l d t e n d to p r o d u c e f r a c t u r e caries, whereas a diet c o m p r i s e d of sucrose a n d casein has a fine consistency, a n d w o u l d t e n d to p r o d u c e caries o n the s m o o t h B a v e t t a a n d M c C l u r e (1)

o b s e r v e d that i n c r e a s i n g the casein c o n -

tent of the diets of rats r e d u c e d caries.


surfaces.

A similar observation was made

b y S h a p e r n a k ( 3 6 ) , w h o f o u n d that b y e n r i c h i n g a b a s a l d i e t w i t h

15%

casein, the p e r c e n t a g e of carious teeth w a s decreased b y a b o u t 5 0 %

and

the caries i n d e x b y a b o u t

66%.

S e v e r a l other i n d e p e n d e n t investigators r e p o r t e d that casein exerted

( 5 , 28, 30, 43)

a significant cariostatic

have

effect u n d e r

also the

c o n d i t i o n s of t h e i r experiments. Shaw

(38)

has p o i n t e d out that c a s e i n - r i c h diets h a v e

q u a l i t i e s a n d are r e l a t i v e l y i n s o l u b l e i n the o r a l

fluids.

retentive

T h i s stickiness

m a y encourage the f o r m a t i o n of p l a q u e , w h i c h i n t u r n m a y p r o m o t e the d e v e l o p m e n t of smooth-surface caries.

H e n o t e d that w h e n a m i x t u r e of

a m i n o acids w h i c h d u p l i c a t e d casein was f e d to rats, the a m i n o a c i d m i x t u r e p r o d u c e d less smooth-surface caries t h a n casein itself. T h e a f o r e m e n t i o n e d experiments d e a l w i t h the l o c a l effects of casein s u p p l e m e n t u p o n caries d e v e l o p m e n t i n the n e w l y e r u p t e d tooth. w a y et al.

(13)

Hollo-

s t u d i e d the systemic effects of early f e e d i n g of casein

o n d e n t a l caries experience a n d o n t o o t h q u a l i t y b y f e e d i n g a diet deficient

i n casein ( 8 % ) i n c o m p a r i s o n w i t h one a d e q u a t e i n casein ( 2 4 % )

to m o t h e r rats d u r i n g p r e g n a n c y a n d lactation.

T h e y o b s e r v e d that the

p u p s f e d the l o w - c a s e i n diet w e r e m o r e susceptible to caries

develop-

ment. W h e n the p u p s w e r e f e d a p r o t e i n - a d e q u a t e diet b e f o r e w e a n i n g at 21 days of age, f o l l o w e d b y a protein-deficient d i e t , t h e i r caries score was 22.4.

average

C o n v e r s e l y , w h e n the p u p s w e r e f e d a p r o t e i n -

deficient diet b e f o r e w e a n i n g , a n d a p r o t e i n - a d e q u a t e diet after w e a n i n g , the score was 42.0; this w o u l d be i n d i c a t i v e of a m a r k e d systemic effect o n caries d e v e l o p m e n t d u e to the p r o t e i n c o m p o n e n t .

Since the

first

a n d s e c o n d molars of rats e r u p t at 18 to 20 days of age, it is e v i d e n t that the protein-deficient d i e t p e r m i t t e d m o r e caries d e v e l o p m e n t w h e n f e d b e f o r e tooth e r u p t i o n t h a n after e r u p t i o n .

T h e s e authors

commented

that other variables i n a d d i t i o n to the l e v e l of d i e t a r y p r o t e i n , s u c h as i n a n i t i o n a n d the p h o s p h a t e content of the diet, m a y h a v e i n f l u e n c e d these results. S i n c e casein is a p h o s p h o p r o t e i n , it is possible that at least a p a r t of its cariostatic a c t i v i t y is d u e to its p h o s p h o r u s content

(see

p p . 116).

the

E v e n so, the results r e p o r t e d here c l e a r l y i n d i c a t e that

l e v e l of p r o t e i n i n diets f e d to rats d u r i n g t o o t h f o r m a t i o n a n d m a t u r a t i o n c a n influence caries d e v e l o p m e n t p r o f o u n d l y .


28

DIETARY

Influence of Individual

C H E M I C A L S

VS.

D E N T A L

Amino Acid Supplements on Animal

Lysine. M c C l u r e (22)

CARIES

Caries

f o u n d that heat t r e a t m e n t c a u s e d a n increase

i n c a r i o g e n i c i t y o f cereals, p r e s u m a b l y b e c a u s e t h e a v a i l a b i l i t y of heatl a b i l e l y s i n e w a s decreased.

M c C l u r e a n d F o l k ( 2 5 ) later s h o w e d that

the a d d i t i o n of L - l y s i n e at levels of 2.5 a n d 0 . 2 5 % to t w o c a r i o g e n i c diets r e d u c e d t h e caries score i n t h e rats s i g n i f i c a n t l y . S i m i l a r l y , B a v e t t a a n d M c C l u r e (1)

c o n f i r m e d t h e cariostatic p r o p e r t i e s o f l y s i n e w h e n t h e y


fed a cariogenic

diet containing a considerable

p r o p o r t i o n of r o l l e r -

p r o c e s s e d s k i m m e d m i l k p o w d e r to o n e g r o u p o f rats, a n d f e d t h e same d i e t s u p p l e m e n t e d w i t h 0 . 4 % l y s i n e to a s e c o n d g r o u p . T h e l y s i n e s u p p l e ment

s i g n i f i c a n t l y r e t a r d e d caries

these e x p e r i m e n t a l

development, indicating that

c o n d i t i o n s , l y s i n e exerted

a significant

under

cariostatic

action. I n a n a t t e m p t to d e t e r m i n e w h e t h e r this a c t i o n of l y s i n e w a s l o c a l o r systemic, M c C l u r e (21)

designed an experiment i n w h i c h lysine was

administered i n the diet, i n the water, b y intubation, or b y intraperitoneal injection.

S i g n i f i c a n t r e d u c t i o n i n caries o c c u r r e d w h e n L - l y s i n e w a s a d -

ministered b y diet, b y water, a n d b y intubation. Intraperitoneal injection h a d a v a r i a b l e a n d essentially n e g l i g i b l e effect. McClure

(20)

later r e p o r t e d a h i g h i n c i d e n c e of

caries i n rats f e d w h e a t

flour,

smooth-surface

d r y b r e a d , toasted b r e a d , o r s h r e d d e d

w h e a t b i s c u i t . W h e n these c e r e a l p r o d u c t s w e r e a u t o c l a v e d i n the presence of cerelose o r starch, t h e caries p o t e n t i a l w a s i n c r e a s e d .

Supple-

ments of 1 % l y s i n e c o u n t e r a c t e d this effect. Hennon

(12)

f o u n d that a l y s i n e - d e f i c i e n t d i e t f e d to rats u n d e r

his e x p e r i m e n t a l c o n d i t i o n s p r o d u c e d t h e h i g h e s t caries scores. et al. (36)

Sharpenak

s h o w e d that t h e a d d i t i o n o f D L - l y s i n e H C 1 to a caries-pro-

d u c i n g d i e t c a u s e d a decrease of a p p r o x i m a t e l y 5 0 % i n t h e n u m b e r of carious teeth p e r r a t , i n t h e p e r c e n t a g e of carious teeth, a n d i n t h e caries index. O n t h e other h a n d , D o d d s ( 5 ) r e p o r t e d that L - l y s i n e H C 1 a d d e d to a c a r i o g e n i c d i e t of r a w w h o l e w h e a t h a d n o cariostatic effect. L - A r g i n i n e , L-Histidine, L - O r n i t h i n e , L-Cadaverine.

McClure and

F o l k (23) h a v e r e p o r t e d that 0 . 5 % L - a r g i n i n e , 1 % L - h i s t i d i n e , a n d 0 . 2 5 % L - o r n i t h i n e a n d L - c a d a v e r i n e d e c r e a s e d caries d e v e l o p m e n t i n rats f e d a n a u t o c l a v e d s k i m m e d m i l k p o w d e r diet. DL-Methionine and D L - T h r e o n i n e . D o d d s ( 5 ) has r e p o r t e d that s u p p l e m e n t a t i o n of D L - m e t h i o n i n e a n d D L - t h r e o n i n e to a r a w w h o l e w h e a t c a r i o g e n i c diet d i d n o t affect t h e i n c i d e n c e of caries.


3.

Amino

N I Z E L

Glycine.

Acids,

29

Proteins

A c c o r d i n g to D o d d s ( 5 ) , the a d d i t i o n of 1.6% g l y c i n e to

a w h i t e flour ( w h e a t ) c a r i o g e n i c d i e t r e d u c e d t h e caries score b y a b o u t 23.8%. Furthermore, w h e n 0.20% of the glycine was replaced b y 0.40% D L - m e t h i o n i n e , t h e caries score w a s i n c r e a s e d . H a r r i s et al.

(11)

also f o u n d that 4 % g l y c i n e s u p p l e m e n t s c o u l d

exert significant cariostatic a c t i v i t y w h e n a d d e d to a n o t h e r w i s e c a r i o g e n i c d i e t a n d f e d to rats.

I n t w o successive f e e d i n g trials, caries w a s


r e d u c e d b y 66 a n d 4 3 % b y t h e 4 % g l y c i n e d i e t a r y s u p p l e m e n t . L - G l u t a m i c A c i d and L - A s p a r t i c A c i d . E n g l a n d e r et al. (8)

recently

r e p o r t e d that n e i t h e r L - g l u t a m i c a c i d n o r L - a s p a r t i c a c i d i n f l u e n c e d t h e d e v e l o p m e n t of caries i n hamsters w h e n a d d e d to a d i e t at a 2 % l e v e l . T h e s e hamsters

h a d been

made

h i g h l y susceptible

s w a b b i n g w i t h virulent cariogenic streptococci.

to caries

b y oral

T h e diet w a s r i c h i n

q u a l i t y p r o t e i n , w a s n o t deficient i n l y s i n e , a n d c o n t a i n e d a b o u t 6 5 % sucrose.

Protein and Bacteria Associated with Dental Caries

Relationships

S i n c e d e n t a l caries is a c k n o w l e d g e d to b e a c o m p l e x disease i n w h i c h the m e t a b o l i s m of p l a q u e b a c t e r i a p l a y a significant role, t h e n u t r i t i o n a l r e q u i r e m e n t s of t h e o r a l m i c r o f l o r a , e s p e c i a l l y t h e i r p r o t e i n a n d a m i n o a c i d needs, c o u l d b e q u i t e a n i m p o r t a n t c o n s i d e r a t i o n here. proteinaceous

T h e major

constituent of s a l i v a is the g l y c o p r o t e i n , m u c i n , a n d ac-

c o r d i n g to L e a c h ' s postulate

(15)

c o n c e r n i n g t h e c h e m i s t r y of d e n t a l

p l a q u e , t h e p r o t e i n that is s p l i t f r o m t h e g l y c o p r o t e i n b y n e u r i m i n i d a s e c o u l d c o n t r i b u t e to t h e f o r m a t i o n of p l a q u e m a t r i x . A c c o r d i n g to L o e s c h e a n d G i b b o n s (16),

t h e t o t a l q u a n t i t y of a m i n o acids is b e l o w t h e a m o u n t

necessary f o r m a x i m a l g r o w t h of m i c r o - o r g a n i s m s , b u t since b a c t e r i a i n the m o u t h g r o w s l o w l y a n d d i v i d e o n l y a f e w times e a c h d a y , this a m o u n t is o f significance

to t h e n u t r i t u r e of the organisms.

Unfortunately,

there is v e r y l i t t l e m o r e d e t a i l e d i n f o r m a t i o n a b o u t the r o l e of p r o t e i n o n c a r i o g e n i c b a c t e r i a , w i t h t h e e x c e p t i o n of the f o l l o w i n g three studies. D r e i z e n a n d Spies

( 7 ) i n v e s t i g a t e d t h e p r o d u c t s of p r o t e i n p u t r e -

f a c t i o n i n s a l i v a to d e t e r m i n e w h e t h e r some of t h e m m i g h t b e r e s p o n sible f o r t h e decreased i n c i d e n c e of caries c o m m o n l y seen i n m a l n o u r i s h e d p o p u l a t i o n s . T h e y o b s e r v e d that i n d o l e a n d i n d o l e - 3 - a c e t i c a c i d ( w h i c h m a y be p r o d u c e d b y the bacterial

d e c o m p o s i t i o n of t r y p t o p h a n ) d e -

creased a c i d p r o d u c t i o n a n d i n t e r f e r e d w i t h m a x i m u m g r o w t h of a strain of l a c t o b a c i l l u s a c i d o p h i l u s f o u n d i n the carious lesions. Nordh

(27)

c o m p a r e d t h e s e r u m p r o t e i n patterns

of t w o g r o u p s

of p e o p l e w h o h a d different n u m b e r s of l a c t o b a c i l l i i n t h e s a l i v a . T h e


30

DIETARY

C H E M I C A L S

VS.

D E N T A L

CARIES

g r o u p w i t h a h i g h c o u n t ( o v e r 1 m i l l i o n / m l o f s a l i v a ) , w h i c h is assoc i a t e d w i t h h i g h caries a c t i v i t y , s h o w e d e l e c t r o p h o r e t i c patterns i n t h e s e r u m , s i m i l a r to those

seen i n i n f l a m m a t o r y disease—i.e.,

decreased

albumin, increased gamma globulin, a n d increased i m m u n o g l o b u l i n concentrations. G r e e n ( 9 ) has suggested that i n n a t e caries resistance i n p e o p l e m a y b e d u e to the presence o f a b a c t e r i o l y t i c agent i n t h e g l o b u l i n f r a c t i o n of t h e s a l i v a . H e c l a i m e d that this agent, w h i c h contains t r y p t o p h a n


a n d s e v e r a l r e l a t e d c o m p o u n d s , w i l l r e d u c e the g r o w t h o f c a r i e s - p r o m o t i n g bacteria (lactobacilli a n d streptococci). Effect of Protein and Amino Acids on Tooth Solubility Interesting in vitro studies of t h e effects of a m i n o acids u p o n t h e rate of e n a m e l a n d d e n t i n e s o l u b i l i z a t i o n w h e n a d d e d to d e c a l c i f y i n g buffers h a v e b e e n c o n d u c t e d at t h e E a s t m a n D e n t a l C e n t e r d u r i n g recent years. B u o n o c o r e a n d S o m n e r ( 3 ) c o m p a r e d aspartic a c i d , g l u t a m i c a c i d , a l a n i n e , a n d v a l i n e , a n d r e p o r t e d that aspartic a c i d w a s t h e most a c t i v e i n r e d u c i n g the s o l u b i l i t y of e n a m e l i n t h e presence

of acetic,

l a c t i c , c i t r i c , a n d p y r u v i c acids, w h i c h a r e t h e o r g a n i c acids c o m m o n l y f o u n d i n d e n t a l p l a q u e a n d o n e n a m e l surfaces.

T h i s result suggested

the p o s s i b i l i t y that t h e aspartic i o n m a y f u n c t i o n to r e d u c e t h e rate at w h i c h these acids dissolve t h e t o o t h structure. I n subsequent studies, K o u l o u r i d e s a n d B u o n o c o r e (14) onocore (2)

and B u -

f o u n d l y s i n e to b e a n effective agent i n r e d u c i n g t h e rate

of e n a m e l d e c a l c i f i c a t i o n . T h e y p o s t u l a t e d that s u r f a c e - b o n d complexes are f o r m e d b e t w e e n a m i n o acids a n d t h e e n a m e l p a r t i c l e s , a n d that these act t o r e t a r d t h e d i f f u s i o n of acids. Significant reductions i n enamel solubility were noted b y Weiss a n d B i b b y (45, 46) w h e n casein solutions w e r e a d d e d to d e c a l c i f y i n g buffers. M i l k p r o t e i n concentrates w e r e at least as g o o d as w h o l e m i l k i n r e d u c i n g e n a m e l s o l u b i l i t y . T h i s result m a y i n d i c a t e that n e i t h e r t h e fat n o r the m i n e r a l i n t h e m i l k c o n t r i b u t e to t h e r e d u c t i o n i n e n a m e l s o l u b i l i t y . T h e i m p o r t a n c e of p r o t e i n to this process w a s e m p h a s i z e d w h e n these authors d e m o n s t r a t e d that m u c o p r o t e i n s , s u c h as gastric m u c i n ,

were

e q u a l l y as effective. M o r e r e c e n t l y , P e a r c e a n d B i b b y (31)

r e p o r t e d that e n a m e l absorbs

p r o t e i n , a n d suggested that p r o t e i n b i n d i n g occurs i n areas w h e r e e n a m e l d e s t r u c t i o n is i n i t i a t e d . T h u s , t h e y d e m o n s t r a t e d that there is a r e a c t i o n b e t w e e n p r o t e i n a n d the e n a m e l surface.

A t t h e b e g i n n i n g of caries

d e v e l o p m e n t ( t h e w h i t e spot s t a g e ) , d e c a l c i f i c a t i o n is greater b e l o w t h e t o o t h surface t h a n at t h e surface. P o s s i b l y this is because proteins cannot diffuse to subsurface sites.


3.

NIZEL

Amino Acids, Proteins

31


Summary and Conclusions (1) It appears that both the amount and quality of protein are important factors in influencing dental caries development in the experimental animal. F o r example, Dodds noted less caries when the level of cereal protein was raised about 16% and when the diets were less deficient in amino acids. A diet which contains limited amounts of poorquality protein w i l l become less cariogenic as the protein content is increased, and/or as the quality of the protein is improved. (2) Dietary additions of casein, a phosphoprotein, appeared to be the most effective of all proteins tested in the reduction of caries development in experimental animals. The relative importance of the phosphate moiety of the casein molecule for exerting this cariostatic action has not been evaluated. (3) Other proteins and amino acids that show some promise as significant cariostatic agents are fish protein concentrate ( F . P . C . ) and glycine. (4) A few in vitro studies seem to show that amino acids can decrease the rate of enamel solubility. (5) N o well-controlled study has been published which proves that dietary supplements of protein can influence the development of dental caries in human beings. (6) The favorable indications that proteins and constituent amino acids may affect caries development should stimulate further search for protein-caries relationships. Literature Cited (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16)

(17)

Bavetta, L . A., McClure, F., J. Nutr. 1957, 63, 107. Buonocore, M. G., J. Dent. Res. 1963, 42, 700. Buonocore, M. G., Somner, B., J. Am. Dent. Assoc. 1957, 55, 781. Buxbaum, J. D., Kolin, H . , Proutt, L . M . , Oster, R. H . , J. Dent. Res. 1957, 36, 173. Dodds, M. L., J. Nutr. 1964, 82, 217. Dreizen, S., Dreizen, J., Stone, R. E., J. Dent. Res. 1961, 40, 1025. Dreizen, S., Spies, T. D., J. Dent. Res. 1947, 26, 409. Englander, H . R., Keyes, P. H . , Fitzgerald, R. J., Arch. Oral Biol. 1965, 10, 599. Green, G. E., J. Dent. Res. 1959, 38, 362. Green, R. M., Helv. Odont. Acta 1967, 11, 32. Harris, R. S., Nizel, A. E., Navia, J. M . , Das, S. K., I.A.D.R. Abstracts, March, 1967. Hennon, D . K., J. Dent. Res. 1960, 39, 681. Holloway, P. J., Shaw, J. H . , Sweeney, E . A., Arch. Oral Biol. 1961, 3, 185. Koulourides, T. A., Buonocore, M . G., J. Dent. Res. 1961, 40, 578. Leach, S. A., Brit. Dent. J. 1967, 122, 537. Loesch, W . J., Gibbons, R. J., "Influence of Nutrition on the Ecology and Cariogenicity of the Oral Microflora" in Nizel, A. E., "The Science of Nutrition and its Application in Clinical Dentistry," W. B. Saunders Co., Philadelphia, Pa., 1966. Losee, F. L., VanReen, R., J. Dent. Res. 1957, 36, 904-910.



32

DIETARY CHEMICALS VS. D E N T A L CARIES

(18) Mandel, S. D., Zorn, M., Ruiz, R., Thompson, R. H . , Ellison, S. Α., Arch. Oral Biol. 1965, 10, 471. (19) Mauron, J., Kinkel, H . J., Cremer, H . D., Intern. J. Vitaminforsch. 1959, 30, 19. (20) McClure, F. J., J. Nutr. 1958, 65, 619. (21) McClure, F. J., Proc. Soc. Exptl. Biol. Med. 1957, 96, 631. (22) McClure, F . J., Science 1952, 116, 229. (23) McClure, F. J., Folk, J. E . , J. Nutr. 1955, 55, 589. (24) McClure, F . J., Folk, J. E., Proc. Soc. Exptl. Biol. Med. 1953, 83, 21. (25) McClure, F. J., Folk, J. E., Science 1955, 122, 557. (26) Nizel, A . E., King, G., Harris, R. S., Navia, J., I.A.D.R. Abstract #100, 1969. (27) Nordh, F., Acta Odont. Scand. 1965, 23, 187. (28) Onisi, Ozaki, Hamada, Japan. J. Dent. Health 1966, 16, 85. (29) Ockerse, T. S., African Dent. J. 1941, 15, 353. (30) Osborn, M . O., Carey, J. F., Fisken, A . K., J. Dent. Res. 1966, 45, 1564. (31) Pearce, E . J. F., Bibby, B. G., Arch. Oral Biol. 1966, 11, 329. (32) Russell, A. L., White, C. L . , J. Dent. Res. 1961, 40, 594. (33) Schweigert, B. S., Potts, E., Shaw, J. H . , Zepplin, M., Phillips, P. H . , J. Nutr. 1946, 32, 405. (34) Schweigert, B. S., Shaw, J. H . , Zepplin, M . , Elvehyem, C. Α., J. Nutr. 1946, 31, 439. (35) Shannon, J. L., Gibson, W . Α., Oral Surg. 1964, 18, 399. (36) Shapernak, A. E., Bobyleva, V . R., Gorozanina, L . Α., Vop. Piton 1963, 22, 239-244 (Kaf, bohin. Med. stomatol. Inst. Moscow) Russia. (37) Shaw, J. H . , J. Nutr. 1950, 41, 1. (38) Shaw, J. H., J. Dent. Res. 1966, 45, 1810. (39) Stack, M . V., J. Dent. Res. 1954, 33, 316. (40) Stephan, R. M., I.A.D.R. Abstract #365, 1968. (41) Stephan, R. M., I.A.D.R. Abstract 1956, 34, 77. (42) Sweeney, Ε. Α., Guzman, M., Arch. Oral Biol. 1966, 11, 687. (43) Tamura, S., Kizu, K., Ito, H . , Nahai, K., Bull. Tokyo Dent. Coll. 1965, 6, 15. (44) Turner, N . D., Crowell, G. E., J. Dent. Res. 1947, 26, 99. (45) Weiss, M . E., Bibby, B. G., Arch. Oral Biol. 1966, 11, 59. (46) Weiss, M., Bibby, B. G., Arch. Oral Biol. 1965, 10, 49. RECEIVED August 15,

1968.


Dietary Chemicals vs. Dental Caries

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