Applied Chemistry at Protein Interfaces

13 Surface Chemistry of Dental Integuments

Downloaded via UNIV OF ARIZONA on July 22, 2018 at 15:38:17 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

RONALD P. QUINTANA Department of Medicinal Chemistry, College of Pharmacy, University of Tennessee Center for the Health Sciences, Memphis, Tenn. 38163

The acquired pellicle, a proteinaceousfilmadsorbed onto tooth surfaces, plays a significant role in the development of dental plaque which is a prime etiologic factor in dental caries and in periodontal disease. The chemical nature and function of pellicle in plaque genesis are reviewed along with the interactivities contributing to the integrity of plaque. Among antiplaque agents under current investigation is chlorhexidine, 1,1'-hexamethylenebis[5-(p-chlorophenyl)biguanide]. The relevance of surface chemistry to the compound's efficacy is summarized.

^

r e c e n t l y p u b l i s h e d m o n o g r a p h ( 1 ) d e a l t w i t h t h e r e l e v a n c e o f surf a c e c h e m i s t r y a n d p h y s i c s i n the c o n t r o l of d e n t a l - d e p o s i t - m e d i a t e d

diseases, w i t h t h e characteristics a n d n a t u r e o f d e n t a l deposits, t h e i r p r e d i l e c t i o n f o r pathogenesis,

w i t h demographic

and

with

prevalence

patterns o f disorders associated w i t h d e n t a l i n t e g u m e n t s , a n d w i t h c o n -

ORAL

ENVIRONMENT

DENTAL PLAQUE

Miaoflora Matrix

ACQUIRED PELLICLE ////TOOTH SURFACE ' / / / / / / //////^MEL) / / / / / / / / / Figure

1.

Schematic representation integuments

of dental

290

Baier; Applied Chemistry at Protein Interfaces Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

13.

Q U I N TA N A

Dental

291

Integuments

v e n t i o n a l p r o p h y l a c t i c practices.

T h i s p a p e r s u m m a r i z e s the c h e m i s t r y

of d e n t a l i n t e g u m e n t s , i n c l u d i n g p e r t i n e n t n e w

findings.

W h i l e there has b e e n c o n s i d e r a b l e c o n f u s i o n i n r e g a r d to n o m e n c l a t u r e of d e n t a l i n t e g u m e n t s , F i g u r e 1 delineates the terms a c q u i r e d p e l l i c l e a n d d e n t a l p l a q u e as t h e y are u s e d i n this c h a p t e r . T h e a c q u i r e d p e l l i c l e is a structureless, colorless, t r a n s l u c e n t , almost i n v i s i b l e

film,

0.05—1μ t h i c k , w h i c h forms r a p i d l y a n d s p o n t a n e o u s l y o n c l e a n t o o t h surfaces a n d adheres there r a t h e r t e n a c i o u s l y ; i t has a s a l i v a r y o r i g i n a n d a p r o t e i n n a t u r e . Its f o r m a t i o n is i n d e p e n d e n t of b a c t e r i a . W h i l e i t m a y b e r e m o v e d b y abrasives or b y s c a l i n g , i t reforms q u i c k l y ( 2 , 3, 4, 5,

6).

D e n t a l p l a q u e , o n the other h a n d , constitutes " a soft a m o r p h o u s g r a n u l a r deposit w h i c h a c c u m u l a t e s o n the surfaces of t e e t h " ( 3 )

(see

Figure 2).

W h e n m a t u r e , i t comprises " a m y r i a d of m i c r o o r g a n i s m s e m b e d d e d i n a r e l a t i v e l y i n s o l u b l e m a t r i x t h a t is l a r g e l y of m i c r o b i a l o r i g i n , b u t is at least p a r t i a l l y of s a l i v a r y o r i g i n . It contains little f o o d d e b r i s a n d o n l y a few epithelial cells" (2).

A

Β

Figure 2. Dental plaque on human teeth: A , unstained dentition; B, the same teeth stained with solution disclosing the presence of plaque (dark areas on tooth surfaces) M a n y factors affect the d e v e l o p m e n t of p l a q u e o n a tooth, i n c l u d i n g ( a ) the l o c a t i o n of the t o o t h i n the m o u t h , ( b ) the a n a t o m y of the t o o t h a n d t h a t of s u r r o u n d i n g tissues, ( c )

the n a t u r e of t h e t o o t h

surface,

(d)

the presence of nutrients f r o m the diet, s a l i v a , a n d g i n g i v a l

fluid,

(e)

the t i m e of exposure of the t o o t h i n the o r a l e n v i r o n m e n t , etc.

(7).

W h i l e p l a q u e forms o n almost a n y s m o o t h e n a m e l surface w h e r e a b r a s i o n is m i n i m a l , i t seems to a c c u m u l a t e m o r e r e a d i l y i n i n t e r p r o x i m a l areas adjacent to g i n g i v a l m a r g i n s , i n e n a m e l defects, a n d at other sites w h i c h are n o t s e l f - c l e a n s i n g . Its a d h e r e n c e to the u n d e r l y i n g s u r f a c e is r e l a t i v e l y strong.

R i n s i n g or s p r a y i n g w i t h w a t e r w i l l n o t r e m o v e i t c o m -


292

A P P L I E D C H E M I S T R Y A T PROTEIN I N T E R F A C E S

p l e t e l y , b u t m e c h a n i c a l c l e a n s i n g s u c h as t o o t h b r u s h i n g w i t h dentifrices (2, 3) can. Formation

of Acquired

"Pellicle

P e l l i c l e is b e l i e v e d to result f r o m selective a d s o r p t i o n of s a l i v a r y proteins

and

glycoproteins

onto the

p r i s i n g t h e e n a m e l surface. Ca

1 0

(PO )6(OH)2 4

properties). further

(see

hydroxyapatite

crystallites

P u r e h y d r o x y a p a t i t e has the

com-

composition

R e f . 8 for details of its c r y s t a l s t r u c t u r e a n d

W h i l e m a n y details of the c o m p o s i t i o n of p e l l i c l e r e q u i r e

investigation, a

sialic-acid-containing glycoprotein

in

human

s a l i v a appears to h a v e a h i g h affinity for h y d r o x y a p a t i t e , even i n c o m p e t i t i o n w i t h other and

Sonju reported

glycoproteins sulfated

f o r m e d o n teeth in vivo;

(9)

(cf.

glycoproteins

Ref. 5 ) . to

be

Moreover,

present

Rolla

in pellicle

e v i d e n c e was a l r e a d y a v a i l a b l e for the

occur-

rence of s u c h c o m p o u n d s i n s a l i v a a n d for t h e i r affinity for h y d r o x y a p a tite ( J O ) . C o n s i d e r i n g t h e p r o m i n e n t a d s o r p t i o n characteristics of a c i d i c p r o t e i n s or g l y c o p r o t e i n s , a n i m p o r t a n t factor i n the a d s o r p t i o n process m a y be t h e affinity b e t w e e n

c a l c i u m of h y d r o x y a p a t i t e a n d n e g a t i v e l y

c h a r g e d c a r b o x y l a t e ( o r s u l f a t e ) groups of s a l i v a g l y c o p r o t e i n s

(9,

11).

A n a l y s e s for t h e c a r b o h y d r a t e c o m p o n e n t s of p e l l i c l e g l y c o p r o t e i n have

r e v e a l e d the p r e s e n c e of

s i a l i c a c i d , fucose, glucose,

galactose,

m a n n o s e , N - a c e t y l g l u c o s a m i n e , a n d N - a c e t y l g a l a c t o s a m i n e (2, 4). a c i d a n d fucose t y p i c a l l y o c c u r i n t e r m i n a l positions of the

r i d e c h a i n , w h e r e a s N - a c e t y l g l u c o s a m i n e or N - a c e t y l g a l a c t o s a m i n e ties l i n k the s a c c h a r i d e segment to the p r o t e i n core (2).

Sialic

oligosacchamoie-

Schrager and

O a t e s ' studies o n the p r i n c i p a l g l y c o p r o t e i n f r o m h u m a n m i x e d s a l i v a h a v e i n d i c a t e d the latter to possess " a b a s i c h o m o g e n e o u s

composition

a n d s t r u c t u r e b u t [to b e ] p o l y d i s p e r s e w i t h respect to r e a c t i v e e n d groups [sulfate; s i a l i c a c i d ] a n d c h a r g e " (12). a n d q u a n t i t a t i v e differences

It w a s also n o t e d that q u a l i t a t i v e

exist a m o n g

carbohydrate

components

of

t h e p r i n c i p a l s a l i v a r y g l y c o p r o t e i n a n d those d e r i v e d f r o m p l a s m a . G a l a c t o s a m i n e was f o u n d i n the s a l i v a r y g l y c o p r o t e i n b u t n o t i n p l a s m a g l y c o p r o t e i n s ; conversely, mannose was absent i n s a l i v a r y b u t present i n p l a s m a glycoproteins.

T h u s pellicle glycoproteins

comprise

both salivary and

p l a s m a types. T h e a m i n o a c i d c o m p o s i t i o n of the p r o t e i n p o r t i o n of a 2-hour p e l l i c l e a c q u i r e d in vivo o n h u m a n teeth was the subject of a c o m m u n i c a t i o n b y S o n j u a n d R o l l a (13).

Their data (Table I)

are significant because,

u n l i k e p r e v i o u s studies i n w h i c h p e l l i c l e films w e r e o b t a i n e d b y

acid

d e m i n e r a l i z a t i o n of t o o t h e n a m e l , t h e i r p e l l i c l e p r e p a r a t i o n w a s r e m o v e d b y c a r e f u l s c a l i n g o n l y . N o significant differences w e r e o b s e r v e d i n

find-

ings f o r v a r i o u s teeth, a n o b s e r v a t i o n that supports selective a d s o r p t i o n


13.

Dental

QUINTA N A

293

Integuments

of the s a l i v a r y proteins. S m a l l amounts of g l u c o s a m i n e a n d galactosamine, i n d i c a t i v e of g l y c o p r o t e i n s , w e r e also d e t e c t e d ; no d i a m i n o p i m e l i c a c i d or m u r a m i c a c i d w a s f o u n d , h o w e v e r , p o i n t i n g to the absence of

bac

t e r i a l c o n t a m i n a t i o n . Sonju a n d R o l l a f u r t h e r o b s e r v e d t h a t the a m o u n t of p e l l i c l e d e p o s i t e d o n h u m a n teeth c o n t i n u e d to increase for 1.5 hrs a n d then l e v e l e d off. film

T h i s is consistent w i t h p r i o r findings of others that the

adjacent to the e n a m e l surface h a d a m a x i m u m thickness of

about

1μ e v e n after s e v e r a l days. Table I.

Amino A c i d Composition of 2 - H o u r Pellicle"

Amino

Acid

Content* moles/100 moles

Asp Thr Ser Glu Pro Gly Ala Val Cys He Leu Tyr Phe Orn Lys His Arg

7.3 3.7 9.6 12.8 2.2 17.0 7.3 4.1 0.9 2.9 6.1 1.6 2.9 6.4 7.0 4.1 4.1

« F r o m R e f . 13. A v e r a g e values. h

U s i n g contact angle measurements, B a i e r d e t e r m i n e d the c r i t i c a l surface tension of the s p o n t a n e o u s l y a c q u i r e d films d e p o s i t e d o n a c l e a n i n o r g a n i c s o l i d p l a c e d i n h u m a n m o u t h s for p e r i o d s of 30 sec, 2 m i n , a n d 15 m i n (14)

(see

T a b l e I I ) . C o n c u r r e n t d e t e r m i n a t i o n of m u l t i p l e a t t e n

u a t e d i n t e r n a l reflection I R spectra of the a d s o r b e d films p r o v i d e d e v i d e n c e for the presence of p r o t e i n m a t e r i a l . W h i l e the spectra r e v e a l e d Table II.

D a t a From Contact Angle Experiments on Surface Film Adsorbed onto Clean Solid Placed in the M o u t h α

Exposure in Mouth, min

Critical Surface Tension,* dynes/cm

Slope, cm/dyne

0.5 2 15

33.3 34.3 36.1

-0.014 -0.012 -0.008

« F r o m Ref. h

6

14.

D e t e r m i n e d f r o m Z i s m a n plots

(14)·


294 no

APPLIED CHEMISTRY

major

changes

i n composition,

the

AT PROTEIN

progressive

INTERFACES

surface-chemical

changes—i.e., increase i n c r i t i c a l surface tension, decrease i n slope

of

t h e Z i s m a n p l o t s — w e r e i n t e r p r e t e d to m e a n that the c o n f i g u r a t i o n r a t h e r t h a n the c o m p o s i t i o n of the film c o m p o n e n t s

was changing.

S i n c e the

o b s e r v e d changes reflected a t r e n d t o w a r d s g e n e r a l l y greater surface free energies, i t w a s suggested " t h a t d e n t a l i n t e g u m e n t s b e c o m e m o r e a n d m o r e a ' c o m f o r t a b l e ' substrate for a t t a c h m e n t , a d h e s i o n , a n d c o l o n i z a t i o n b y o r a l b a c t e r i a as t i m e lapses." B a i e r also c o n d u c t e d teeth in situ (14).

p r e l i m i n a r y c o n t a c t - a n g l e studies o n h u m a n

H e d e t e r m i n e d values of c r i t i c a l surface t e n s i o n to be

a p p r o x i m a t e l y 32 d y n e s / c m for teeth w h i c h h a d b e e n r e c e n t l y c l e a n e d w i t h toothpaste. cleaned.

A s i m i l a r v a l u e was o b t a i n e d for teeth n o t as r e c e n t l y

T a k i n g other factors i n t o c o n s i d e r a t i o n , a surface energy

30 to 40 e r g s / c m

2

of

represents the n a t u r a l s i t u a t i o n . T h e exact v a l u e s are

c o n t i n g e n t u p o n i n d i v i d u a l e a t i n g a n d o r a l h y g i e n e practices.

Development

of Dental

Plaque

S u b s e q u e n t to the d e p o s i t i o n of p e l l i c l e , p r e d o m i n a n t l y

coccoidal

bacteria appear a n d proliferate. T h e y originate, apparently, from enamel defects, f r o m adjacent o r a l tissues, a n d f r o m the s a l i v a (2, 15). c o n n e c t i o n , s c a n n i n g e l e c t r o n m i c r o s c o p e studies (16)

I n this

suggest that g i n g i -

v a l fluid is i m p o r t a n t for tooth-surface c o l o n i z a t i o n . B a c t e r i a l a c c u m u l a tions o c c u r r e d o n a c l e a n e d t o o t h w i t h i n five m i n u t e s w h e n r e a d i l y a v a i l a b l e ( f r o m severely i n f l a m e d g i n g i v a e )

fluid

was

whereas, i n other

instances, m i c r o o r g a n i s m s w e r e e v i d e n t after a f e w h o u r s , " s m a l l colonies of

organisms

[being]

readily observed

after 24 hours of

continuous

exposure to the o r a l e n v i r o n m e n t . " More

specifically, streptococci

c o l o n i z e o n the t o o t h surface.

are a m o n g

the

first

organisms

to

I n the o r a l c a v i t y of m a n , Streptococcus

mutans is p a r t i c u l a r l y i m p o r t a n t since some correlations b e t w e e n caries a c t i v i t y a n d the presence of this o r g a n i s m i n p l a q u e h a v e b e e n m a d e

(17).

A s n o t e d b y G i b b o n s a n d S p i n e l l , t w o m o d e s of a d h e s i o n o c c u r i n the d e v e l o p m e n t of d e n t a l p l a q u e : ( a )

a d h e s i o n of the m i c r o o r g a n i s m s

to the tooth surface ( o r to t h e a c q u i r e d p e l l i c l e ) a n d ( b ) the m i c r o b i a l cells to one a n o t h e r (18).

a d h e s i o n of

O n e of the m o s t d i s t i n g u i s h i n g

characteristics of S. mutans is the a b i l i t y to p r o d u c e e x t r a c e l l u l a r p o l y saccharides f r o m sucrose, a n d a v a i l a b l e d a t a suggest that these

com-

p o u n d s p l a y a significant r o l e i n p l a q u e genesis. T h e m e c h a n i s m r e q u i r e s e l u c i d a t i o n , b u t one e x p l a n a t i o n proposes that the a b i l i t y of h i g h - m o l e c u l a r - w e i g h t dextrans to t r i g g e r a g g l u t i n a t i o n of S. mutans is i n v o l v e d


(19).

13.

Q U I N TA N A

Dental

295

Integuments

S i n c e l o w - m o l e c u l a r - w e i g h t dextrans d o n o t p r o m o t e

aggregation,

the

process r e q u i r e s m o l e c u l e s of d i m e n s i o n s so as to effect b i n d i n g of m o r e t h a n one s t r e p t o c o c c a l c e l l p e r m o l e c u l e of d e x t r a n . T h e n a t u r e of the r e c e p t o r sites o n the surface of the m i c r o o r g a n i s m s is not clear, b u t they m a y b e associated w i t h dextransucrase, the e n z y m e r e s p o n s i b l e for dext r a n synthesis. It is present as a cell-associated f o r m a n d is k n o w n to h a v e a h i g h affinity for dextrans (19). t r e a t m e n t of

oral streptococci

L i l j e m a r k a n d Schauer's w i t h proteolytic enzymes

finding

that

reduced

the

m i c r o o r g a n i s m s ' a d h e r e n c e to s a l i v a - c o a t e d or d e x t r a n - c o a t e d h y d r o x y apatite supports p r o t e i n i n v o l v e m e n t o n t h e b a c t e r i a l c e l l surface i n the r e a c t i v e site b i n d i n g the b a c t e r i a to h y d r o x y a p a t i t e (20). ments

also

demonstrated

that m i c r o o r g a n i s m s

not

Their experi-

subjected

to

any

p r e t r e a t m e n t a d h e r e d c o n s i d e r a b l y better to s a l i v a - c o a t e d a n d to d e x t r a n c o a t e d h y d r o x y a p a t i t e t h a n to u n c o a t e d h y d r o x y a p a t i t e . A c c o r d i n g to R o l l a , i o n i c b o n d s are i m p o r t a n t i n the associations b e t w e e n b a c t e r i a l p o l y s a c c h a r i d e s a n d p r o t e i n - c o a t e d t o o t h surfaces T h i s w a s b a s e d o n in vitro hydroxyapatite powder

(21).

experiments o n the affinity of d e x t r a n for

c o a t e d w i t h s a l i v a r y g l y c o p r o t e i n ; specifically,

a d s o r p t i o n of d e x t r a n was i n h i b i t e d b y 0 . 5 M . P r i o r t r e a t m e n t of the c o a t e d h y d r o x y a p a t i t e w i t h n e u r a m i n i d a s e also r e d u c e d a d s o r p t i o n of d e x t r a n . N e u r a m i n i d a s e w o u l d be e x p e c t e d to r e d u c e the negative c h a r g e of the p r o t e i n coat b y r e m o v i n g i o n i z e d sialic a c i d moieties. O f course, r e d u c e d a d s o r p t i o n of d e x t r a n c o u l d result f r o m c o n f o r m a t i o n a l changes i n d u c e d i n the p e l l i c l e p r o t e i n b y the n e u r a m i n i d a s e t r e a t m e n t , as w a s a p p a r e n t l y effected b y 4M or 8 M u r e a , i n o t h e r e x p e r i m e n t s . W h i l e i m p o r t a n t , d e x t r a n - m e d i a t e d a d h e s i o n is not the o n l y f a c t o r i n v o l v e d i n d e n t a l p l a q u e f o r m a t i o n . I n fact, most types of p l a q u e b a c teria n e i t h e r elaborate

d e x t r a n n o r are a g g l u t i n a t e d b y i t .

Thus, in

e x p l o r i n g other m o d e s of i n t e r b a c t e r i a l a d h e s i o n i n the e v o l v i n g p l a q u e , G i b b o n s a n d S p i n e l l h a v e o b t a i n e d e v i d e n c e suggesting a r o l e for s a l i v a r y proteins (18).

T h e s a l i v a r y p o l y m e r s t h e y s t u d i e d i n t e r a c t e d w i t h the

m i c r o o r g a n i s m s ' surfaces w h i l e effecting a g g r e g a t i o n .

The

composition

of the c o m p o u n d s a n d the m e c h a n i s m of t h e i r interactions w e r e t h o u g h t to b e " v i t a l for a n u n d e r s t a n d i n g of p l a q u e f o r m a t i o n . " Thus, i n plaque, both carbohydrate and protein material contribute to the m a t r i x . W h i l e the origins of these components h a v e b e e n i n d i c a t e d , other hypotheses

w e r e a d v a n c e d to e x p l a i n i n c o r p o r a t i o n of s a l i v a r y

proteins i n p l a q u e (18).

F o r e x a m p l e , L e a c h has p r o p o s e d that p l a q u e

proteins arise as a result of the a c t i o n of glycosidases dase) on salivary glycoproteins ( 5 ) .

(e.g., n e u r a m i n i -

D a t a of B r i s c o e et al. suggest, h o w -

ever, that n e u r a m i n i d a s e does not m o d i f y a d s o r p t i o n b e h a v i o r of s a l i v a r y proteins

(22).


296

APPLIED CHEMISTRY

Surface-Chemical

Aspects of Chlorhexidine

A T PROTEIN

INTERFACES

in Plaque Control

D e n t a l p l a q u e constitutes a p r i m a r y e t i o l o g i c factor i n b o t h d e n t a l caries a n d i n p e r i o d o n t a l diseases; a n d since these c o n d i t i o n s a r e a m o n g the most p r e v a l e n t affecting m a n k i n d (23), one c o u l d n o t o v e r e s t i m a t e the v a l u e o f t r u l y effective p l a q u e - c o n t r o l agents

Among

(24, 25, 26).

c o m p o u n d s u n d e r c u r r e n t i n v e s t i g a t i o n f o r c l i n i c a l use is t h e b i s b i g u a n i d e chlorhexidine biguanide]

(Structure I ) , lJ'-hexamethylenebisCS-p-ichlorophenyl)-

(e.g., 24, 27-37).

I t is n o r m a l l y u s e d

as a d i g l u c o n a t e ,

diacetate, or d i h y d r o c h l o r i d e salt. NH C I - \ 0 / ¥ ' ^

'

Η

C

^

N H N

/

Η

C

X

N

N H

—° ^Η ΟΗ ΟΗ ΟΗ Η

2

2

2

2

C H r - N ^

Η

Η

C

v

N H N ^

Η

C

x

N y Q V c i

Η ^

'

I C h l o r h e x i d i n e has a b r o a d s p e c t r u m of a n t i m i c r o b i a l a c t i o n w h i c h , u n d o u b t e d l y , is associated w i t h its a n t i p l a q u e effects.

T h e mechanism

has b e e n s t u d i e d extensively b y H u g o a n d L o n g w o r t h w h o r e p o r t t h a t c h l o r h e x i d i n e behaves s i m i l a r l y to c a t i o n i c a n t i b a c t e r i a l agents s u c h as surface-active quaternary a m m o n i u m compounds

(38, 39, 40; cf. 41).

T h e p r i m a r y a c t i o n i n v o l v e s a d s o r p t i o n of the c o m p o u n d

onto t h e c e l l

surface, t h e r e a c t i v e sites b e i n g a n i o n i c . T h i s is f o l l o w e d b y a d i s r u p t i v e effect o n t h e c y t o p l a s m i c m e m b r a n e ,

changes i n p e r m e a b i l i t y of t h e

latter, a n d l e a k a g e of i n t r a c e l l u l a r c o m p o n e n t s . chlorhexidine,

however,

m a y inhibit

leakage

H i g h concentrations of b y inhibiting

autolytic

e n z y m e s , b y f o r m i n g a s e a l i n g l a y e r ( o r l a y e r s ) o n t h e c e l l surface, b y c o n g e a l i n g t h e c y t o p l a s m i c m e m b r a n e , or b y p r e c i p i t a t i n g i n t r a c e l l u l a r components (proteins, nucleic a c i d ) . O t h e r studies h a v e s h o w n a p p r o p r i a t e concentrations of c h l o r h e x i d i n e to i n h i b i t adenosine t r i p h o s p h a t a s e of Streptococcus faecalis m e m b r a n e . E l e c t r o n m i c r o g r a p h s h a v e s h o w n a s o - c a l l e d b l i s t e r i n g of b a c t e r i a l c e l l w a l l s (42) b y c h l o r h e x i d i n e . T h i s w a s a t t r i b u t e d to " c e l l u l a r e x t r u sion o r to t h e a c c u m u l a t i o n of d r u g aggregates o n t h e c e l l s u r f a c e "

(43).

I n a d d i t i o n to a n t i m i c r o b i a l a c t i v i t y , c o n t i n u i n g i n v e s t i g a t i o n reveals other i m p o r t a n t m o d e s of a n t i p l a q u e efficacy.

F o r example:

( a ) C h l o r h e x i d i n e adsorbs onto t o o t h surfaces, p e l l i c l e a n d p l a q u e , and provides an antimicrobial milieu for a period of time through gradual release of t h e c o m p o u n d (28). ( b ) T h e agent m a y also affect a d h e r e n c e of o r a l s t r e p t o c o c c i to teeth, as K o r n m a n et al. h a v e f o u n d t h a t c h l o r h e x i d i n e s i g n i f i c a n t l y r e d u c e d affinity of d e x t r a n - e n c a p s u l a t e d S. mutans f o r p r o t e i n - c o a t e d h y d r o x y a p a t i t e (44). T h e c o m p o u n d m a y r e a c t w i t h a n i o n i c f u n c t i o n s o f


13.

Q U I N TA N A

Dental

297

Integuments

the p r o t e i n , b l o c k i n g sites of a t t a c h m e n t n o r m a l l y a v a i l a b l e to the d e x t r a n e n c a p s u l a t e d b a c t e r i a . C h l o r h e x i d i n e , a d s o r b e d onto t o o t h surfaces, m a y act as a s u r f a c e - m o d i f y i n g agent (24). ( c ) I n v i e w of the i m p o r t a n c e of s a l i v a r y g l y c o p r o t e i n s i n p l a q u e d e v e l o p m e n t , the c o i n c i d e n c e (45) of c h l o r h e x i d i n e concentrations p r e c i p i t a t i n g s a l i v a r y g l y c o p r o t e i n s a n d those effecting c l i n i c a l efficacy is significant. T h e p H - d e p e n d e n c e of c h l o r h e x i d i n e - p r o t e i n i n t e r a c t i o n suggests the i m p o r t a n c e of the n e t n e g a t i v e c h a r g e of the proteins. ( d ) I n a d d i t i o n to c h l o r h e x i d i n e ' s efficacy i n p r e v e n t i n g a c c u m u l a tions of p l a q u e a n d c a l c u l u s , the c o m p o u n d has c a p a b i l i t i e s of affecting a l r e a d y f o r m e d p l a q u e o n teeth (24). I n this c o n n e c t i o n , T a n z e r et al. n o t e d p a r t i a l d i s r u p t i o n of in vitro p l a q u e p r e p a r a t i o n s w h e n these w e r e t r e a t e d w i t h c h l o r h e x i d i n e (46). A d e t a i l e d s t u d y of c h l o r h e x i d i n e ' s s u r f a c e - c h e m i c a l was u n d e r t a k e n i n our laboratories.

characteristics

T h i s i n c l u d e d w o r k w i t h a series of

c a r e f u l l y selected analogs c o m p r i s i n g segments of the p a r e n t

molecule

( S t r u c t u r e I I ; R = n - h e x y l , η-propyl, or H ) or extensions of these ( S t r u c ture I I ; R =

n - o c t y l or n - d o d e c y l ) .

II

T h e g r a d u a l changes i n the c h e m i c a l s t r u c t u r e a n d p h y s i c a l properties of the congeners f a c i l i t a t e d i d e n t i f i c a t i o n of m o l e c u l a r

functions

and/or

physicochemical

characteristics associated w i t h c h l o r h e x i d i n e ' s

surface-

active b e h a v i o r .

W h i l e the s t u d y e x p l o r e d p r i n c i p a l l y interactions

be

t w e e n the évaluant entities a n d m o n o m o l e c u l a r films p r o v i d i n g c a r b o x y l , h y d r o x y l , a n d a m i d e groups at the m o n o l a y e r / w a t e r interface, the c o m p o u n d s ' c o m p a r a t i v e effects at a i r / w a t e r , n - h e x a n e / w a t e r , a n d h y d r o x y a p a t i t e / w a t e r interfaces w e r e also i n v e s t i g a t e d (47, 48, The work w i t h monolayer N-octadecylacetamide)

systems

(stearic

49).

acid, stearyl alcohol,

r e v e a l e d the i m p o r t a n c e of interactions

d i c a t i o n i c c h l o r h e x i d i n e molecules

and anionic carboxylate

between

groups

in

effecting s u b s t a n t i a l increases i n the surface pressure of the films, a n d , i n the i n s t a n c e of the c h l o r h e x i d i n e analogs, also p o i n t e d to the significance of a sufficiently l e n g t h y N - a l k y l substituent ( S t r u c t u r e I I , R = 5

n-hexyl)

i n effecting film p e n e t r a t i o n . L a c k i n g the structure of a c l a s s i c a l surfactant, c h l o r h e x i d i n e , w i t h its a l t e r n a t i n g h y d r o p h o b i c

and hydrophilic

moieties, has b e e n designated as a specific surface-active

agent,


some

298

APPLIED CHEMISTRY A T PROTEIN

specific (50).

INTERFACES

g r o u p ( s ) b e i n g r e s p o n s i b l e f o r its a c c u m u l a t i o n at interfaces T h e c o m p a r a t i v e e v a l u a t i o n o f t h e effect o f c h l o r h e x i d i n e a n d t h e

d e l i n e a t e d congeners o n surface a n d i n t e r f a c i a l tension a n d o n a d s o r p t i o n o n t o h y d r o x y a p a t i t e suggested that t h e h e x a m e t h y l e n e c h a i n is a m a j o r c o n t r i b u t o r to t h e surface a c t i v i t y of c h l o r h e x i d i n e . D e t a i l s o f studies o n the c o m p o u n d s '

a n t i p l a q u e efficacy in vitro

(51) w i l l be reported

else

where. Acknowledgment T h e a u t h o r thanks James W . C l a r k f o r t h e p h o t o g r a p h s c o n s t i t u t i n g F i g u r e 2.

Literature Cited 1. Lasslo, Α., Quintana, R. P., Eds., "Surface Chemistry and Dental Integu ments," Charles C. Thomas, Springfield, Illinois, 1973. 2. Burnett, G. W., Pennel, Β. M., "Surface Chemistry and Dental Integu ments," A. Lasslo and R. P. Quintana, Eds., pp. 3-73, Charles C. Thomas, Springfield, Illinois, 1973. 3. Glickman, I., "Clinical Periodontology," 4th ed., pp. 291-314, W. B. Saunders, Philadelphia, 1972. 4. Mayhall, C. W., Aeromed. Rev., Review 5-71, United States Air Force School of Aerospace Medicine, Aerospace Medical Division (AFSC), Brooks Air Force Base, Texas, 1971. 5. Leach, S. Α., Ala. J. Med. Sci. (1968) 5, 247-255. 6. Meckel, A. H., Arch. Oral Biol. (1965) 10, 585-597. 7. Egelberg, J., "Dental Plaque," W. D. McHugh, Ed., pp. 9-16, E. and S. Livingstone, Edinburgh, 1970. 8. Zimmerman, S., "Dental Biochemistry," E. P. Lazzari, Ed., pp. 70-91, Lea and Febiger, Philadelphia, 1968. 9. Rölla, G., Mathiesen, P., "Dental Plaque," W. D. McHugh, Ed., pp. 129140, E. and S. Livingstone, Edinburgh, 1970. 10. Rölla, G., Sönju, T., J. Dent. Res. (Special Issue) (1973) 52, 133, 193. 11. Bernardi, G., Kawasaki, T., Biochim. Biophys. Acta (1968) 160, 301-310. 12. Schrager, J., Oates, M. D. G., Arch. Oral Biol. (1971) 16, 287-303. 13. Sönju, T., Rölla, G., Caries Res. (1973) 7, 30-38. 14. Baier, R. E., "Surface Chemistry and Dental Integuments," A. Lasslo and R. P. Quintana, Eds., pp. 337-391, Charles C. Thomas, Springfield, Illinois, 1973. 15. Kleinberg, I., "Advances in Oral Biology," Vol. 4, P. H. Staple, Ed., pp. 43-90, Academic, New York, 1970. 16. Saxton, C. Α., Caries Res. (1973) 7, 102-119. 17. Krasse, B., Ala. J. Med. Sci. (1968) 5, 267-268. 18. Gibbons, R. J., Spinell, D. M., "Dental Plaque," W. D. McHugh, Ed., pp. 207-215, E. and S. Livingstone, Edinburgh, 1970. 19. Gibbons, R. J., Fitzgerald, R. J., J. Bacteriol. (1969) 98, 341-346. 20. Liljemark, W. F., Schauer, S. V., J. Dent. Res. (Special Issue) (1973) 52, 130. 21. Rölla, G., Arch. Oral Biol. (1971) 16, 527-533. 22. Briscoe, Jr., J. M., Pruitt, Κ. M., Caldwell, R. C., J. Dent. Res. (1972) 51, 819-824.


13.

QUINTANA

Dental

Integuments

299

23. Donnelly, C. J., "Surface Chemistry and Dental Integuments," A. Lasslo and R. P. Quintana, Eds., pp. 74-192, Charles C. Thomas, Springfield, Illinois, 1973. 24. Quintana, R. P., Lasslo, Α., Clark, J. W., Baier, R. E., "Surface Chemistry and Dental Integuments," A. Lasslo and R. P. Quintana, Eds., pp. 392413, Charles C. Thomas, Springfield, Illinois, 1973. 25. Clark, J. W., Jurand, J. G., Miller, C. D., "Surface Chemistry and Dental Integuments," A. Lasslo and R. P. Quintana, Eds., pp. 193-275, Charles C. Thomas, Springfield, Illinois, 1973. 26. McHugh, W. D., J. Periodont. Res. (1972) Suppl. 10, 40-41. 27. Ochsenbein, H., Schweiz. Mschr. Zahnheilk. (1973) 83, 819-827. 28. Hamp, S., Lindhe, J., Löe, H., J. Periodont. Res. (1973) 8, 63-70. 29. Warner, V. D., Mirth, D. B., Turesky, S. S., Glickman, I., J. Pharm. Sci. (1973) 62,1189-1191. 30. Turesky, S., Glickman, I., Sandberg, R., J. Periodontol. (1972) 43, 263-269. 31. Cumming, B. R., Löe, H., J. Periodont. Res. (1973) 8, 57-62. 32. Löe, H., Mandell, M., Derry, Α., Schiøtt, C. R., J. Periodont. Res. (1971) 6, 312-314. 33. Löe, H., Int. Dent.J.(1971) 21, 41-45. 34. Löe, H., Schiøtt, C. R., J. Periodont. Res. (1970) 5, 79-83. 35. Schiøtt, C. R., Löe, H., Jensen, S. B., Kilian, M., Davies, R. M., Glavind, K., J. Periodont. Res. (1970) 5, 84-89. 36. Rölla, G , Löe, H., Schiøtt, C. R., J. Periodont. Res. (1970) 5, 90-95. 37. Davies, R. M., Jensen, S. B., Schiøtt, C. R., Löe, H., J. Periodont. Res. (1970) 5, 96-101. 38. Hugo, W. B., Longworth, A. R., J. Pharm. Pharmacol. (1966) 18, 569-578. 39. Ibid. (1964) 16, 751-758. 40. Ibid. (1964) 16, 655-662. 41. Emilson, C. G., Ericson, T., Heyden, G ., Lilja, J., J. Periodont. Res. (1972) 189-191. 42. Franklin, T. J., Snow, G. Α., "Biochemistry of Antimicrobial Action," pp. 51-53, Academic, New York, 1971. 43. Hugo, W. B., Longworth, A. R., J. Pharm. Pharmacol. (1965) 17, 28-32. 44. Kornman, K. S., Clark, W. B., Kreitzman, S. N., J. Periodont. Res. (1972) Suppl. 10, 33-34. 45. Hjeljord, L. G., Rölla, G., Bonesvoll, P., J. Dent Res. (Special Issue) (1973) 52, 191. 46. Tanzer, J. M., Reid, Y., Reid, W., Antimicrob. Ag. Chemother. (1972) 1, 376-380. 47. Quintana, R. P., Fisher, R. G., Lasslo, Α., J. Dent. Res. (1972) 51, 1687. 48. Fisher, R. G., Quintana, R. P., Boulware, Μ. Α., J. Dent. Res., in press. 49. Fisher, R. G., Quintana, R P., J. Dent. Res., in press. 50. Heard, D. D., Ashworth, R. W., J. Pharm. Pharmacol. (1968) 20, 505-512. 51. Dr. J. M. Tanzer, Department of General Dentistry, School of Dental Medi cine, University of Connecticut Health Center, private communication. RECEIVED December 4, 1973. This work was supported by the National Insti tute of Dental Research, National Institutes of Health, through Grant DE-03139.


Applied Chemistry at Protein Interfaces

Recommend Documents