Periodontology 2000, Val. 19, 1999, 164-1 72 Printed in Denmark . All rights reserved

C o p y r i g h t 0 Munksgaard 1999

PERIODONTOLOGY 2000 ISSN 0906-6713

Infectious aspects of periodontal regeneration J 0 R G E N SLOTS, ERIKA SMITH MACDONALD & HESSAM NOWZARI

The development of predictable procedures to facili- tate the formation of new periodontal ligament, ce- mentum and bone over previously diseased root sur- faces remains an important goal in periodontal ther- apy. Periodontal regeneration has been attempted using extraoral or intraoral autogenous bone grafts, allografts, various alloplasts, growth factors, nonre- sorbable or resorbable barrier membranes, or their combinations (2).

Regenerative approaches to treat periodontitis lesions offer exciting possibilities; however, they fre- quently fail to produce the desired clinical outcome due to infectious complications (27). Because re- generative periodontal devices are placed in a poten- tially highly infected environment, their successful application depends upon the prior removal or marked suppression of microbial pathogens at the treated site(s). Infection control may be particularly important with barrier membranes because they may induce a foreign body-like reaction with re- duced host defenses (53) .

This chapter reviews the microbiota that may in- terfere with periodontal regeneration. It also pro- vides guidance on antimicrobial therapies that may reduce the risk of infectious failures with periodontal regeneration. Emphasis is placed on infections as- sociated with expanded polytetrafluoroethylene bar- rier membranes because most of the available data are concerned with this type of regenerative device.

Microbiota of failing periodontal regeneration

Table 1 presents studies that have examined the ef- fect of microbial biofilms or specific bacteria on re- generative periodontal therapy.

Oral bacteria have a propensity to colonize barrier membranes (26, 38). Moreover, in vitro data suggest that bacterial species vary in ability to attach to bar-

rier membranes of different materials. Wang et al. (50) compared the in vitro attachment of 15 oral microorganisms to expanded polytetrafluoroethy- lene, polyglactin 910 and collagen barrier mem- branes. Streptococcus mutans revealed the strongest attachment in all experiments except for Porphyro- monas gingivalis, which exhibited higher cell counts on collagen membranes. S. mutans attached signifi- cantly more to the expanded polytetrafluoroethylene and the collagen barrier membranes than to the po- lyglactin 9 10 membrane. Actinobacillus actinomyce- temcomitans, Actinomyces viscosus, Fusobacterium nucleatum and Selenomonas sputigena showed simi- lar attachment to the 3 barrier membranes studied. S. sputigena revealed the lowest attachment poten- tial of the test bacteria.

Ricci et al. (34) demonstrated varying in vitro af- finity for J? gingivalis to attach to 6 types of bioab- sorbable and nonbioabsorbable barrier membranes. A polyglactin and two collagen barrier membranes demonstrated high I? gingivalis counts. Polylactic acid and synthetic glycolide and lactide copolymer barrier membranes showed lowest J? gingivalis counts. Expanded polytetrafluoroethylene barrier membranes revealed I! gingivalis cells mainly in the fibrillar areas of both the internal and external sides of the membrane. Ricci el al. (34) also showed the in vitro ability of I? gingivalis to penetrate barrier mem- branes from one side to the other. Simion et al. (40) reported that an expanded polytetrafluoroethylene barrier membrane had to be exposed for at least three weeks for complete bacterial penetration.

Using scanning electron microscopy, Selvig et al. (38) identified cocci, filaments and short curved rods in the outer and inner surfaces of retrieved barrier membranes. The patients had been prescribed tetra- cycline for 2 weeks postsurgically and chlorhexidine rinses during the period of membrane insertion. Sel- vig et al. (39) showed an inverse relationship be- tween the extent of barrier membrane microbial contamination and gain in clinical attachment level.

164

Infectious asDects o f Deriodontal regeneration

Grevstad & Leknes (14) detected gram-negative rods and spirochetes in the occlusive and apical por- tions of expanded polytetrafluoroethylene barrier membranes despite systemic penicilllin therapy and chlorhexidine rinses. The authors attributed the mi- crobial growth on barrier membranes to ineffective antimicrobial therapy.

Chen et al. (4) compared the rate at which 11 com- mon oral bacterial species colonized expanded poly- tetrafluoroethylene, collagen and polylactic acid bar- rier membranes in vivo. Total bacterial attachment increased over the 2-week study period, but the 3 barrier types did not differ in numbers or species of colonizing bacteria.

Tempro & Nalbandian (45) recovered predomi- nantly Streptococcus and Actinomyces species and occasionally Haemophilus and Capnocytophaga spe- cies from the microstructure and the occlusive por- tions of expanded polytetrafluoroethylene barrier membrane. They proposed that barrier membrane infections may in part be responsible for the varying clinical outcome with guided tissue regeneration.

De Sanctis et al. (8, 9) evaluated bacterial colon- ization of expanded polytetrafluoroethylene and po- lyglicolactic barrier membranes at 4-6 weeks after membrane insertion. In scanning electron micro- scopy, 57% of exposed and only 17% of nonexposed barrier membranes revealed bacteria in the mid-part of the tooth-facing surface of the barrier membrane (8). De Santis et al. (8) associated bacterial coloniza- tion in the mid-part of the inner surface of the bar- rier membrane with an almost 50% reduction in po- tential gain of clinical attachment.

Nowzari & Slots (25) demonstrated an inverse re- lationship between microbial counts on expanded polytetrafluoroethylene barrier membranes and gain of probing attachment in treatment of furcation and two- to three-wall intraosseous periodontal lesions. Eighty percent of teeth having membranes with less than lo8 total viable counts gained 3 mm or more in probing attachment, whereas teeth with membranes harboring more than lo8 total viable counts either lost attachment (50%) or showed increases in attach- ment of only 1 or 2 mm.

Mombelli et al. (21) recovered specific bacterial species from barrier membranes retrieved from peri- odontal sites showing 1-5 mm gain in clinical attachment. The patients performed strict plaque control and rinsed with chlorhexidine but received no systemic or topical antibiotic therapy. Gram- negative anaerobic rods made up 31% of total mem- brane isolates at 6 weeks postsurgery. One site yielded high proportions of I? gingivalis, 6 sites dem-

onstrated Prevotella intermedia and 6 sites showed Prevotella melaninogenica. Fusobacterium and Cap- nocytophaga species were also frequent membrane isolates. No analysis was performed to determine the possible role of specific microorganisms on clinical outcome.

Specific bacteria seem to assume particular im- portance in failing periodontal regeneration. Nowza- ri & Slots (25) detected I? gingivalis in 3 periodontal sites that experienced a net loss of clinical attachment after membrane removal. A. actinomycetemcomitans was recovered from a periodontal site that gained as little as 1 mm of probing attachment. Campylobacter rectus comprised 14% of the membrane microbiota at a tooth that demonstrated 1 mm gain of clinical attachment. Total microbial counts and percentage of Peptostreptococcus micros, Capnocytophaga species and motile rods on barrier membranes seemed also negatively to affect periodontal regeneration. Nowzari et al. (28) found most gain in clinical attachment in sites that showed no periodontal pathogens on the tooth-facing surface of the barrier membrane. Sites exhibiting little or no gain in clinical attachment dem- onstrated several species of periodontal pathogens on both sides of the barrier membrane.

Machtei et al. (17) implicated A. actinomycetem- comitans in failing regenerative periodontal therapy. Demolon et al. (10) found an association between I? gingivalis and Bacteroides forsythus on polyte- trafluoroethylene barrier membranes and clinical signs of inflammation.

Microbial colonization of barrier membranes may already start at the time of membrane insertion (29). Also, periodontal pathogens that contaminate a bar- rier membrane during insertion may persist on the membrane for a prolonged period (29). Pathogen colonization of barrier membranes during the initial intraoral manipulation has been associated with re- duced gain of clinical attachment (29). Bacteria col- onizing barrier membranes during the time of inser- tion probably originate from saliva or, in case of in- sufficient debridement, from the membrane-treated lesion itself. Patients having high subgingival counts of periodontal pathogens in periodontitis lesions other than the site receiving regenerative therapy ex- hibit an increased risk for barrier membrane colon- ization by motile rods, I? gingivalis, I? intermedia, I? micros, Propionibacterium species and spirochetes (29). Most likely, the membrane infecting pathogens are transferred via saliva from infected periodontal lesions or tongue dorsum to the regenerative-treated periodontal site(s).

Herpesviruses have recently been implicated in

165

Tab

le 1

. Rel

atio

nshi

p be

twee

n ba

rrie

r m

embr

ane

biof

ilm a

nd f

ailin

g pe

riod

onta

l re

gene

ratio

n

Ref

eren

ce

-_

__

N

oppe

, Wac

htel

, Ber

nim

oulin

, E

bert-

Kay

ser

(23)

Selv

ig, N

ilveu

s, Fi

tzm

orri

s,

Ker

sten

, Kho

rsan

di (3

8)

Val

letta

, Sbo

rdon

e, R

arna

glia

, C

iagl

ia, S

pagn

uolo

, Len

ci (

48)

Type

of

mem

bran

e E

xpan

ded

poly

tetr

aflu

oroe

thyl

ene

-__

__

- ~

-

Type

of

peri

odon

tal d

efec

t Pl

aque

ana

lysi

s 40

intr

aoss

eous

R

etrie

ved

defe

cts

mem

bran

es

for l

ight

and

tr

ansm

issi

on

elec

tron

ic

mic

rosc

opy

Exp

ande

d 14

intr

aoss

eous

and

R

etrie

ved

poly

tetr

aflu

oroe

thyl

ene

6 fu

rcat

ion

defe

cts

mem

bran

es fo

r

-~

-

~_

_

-_

__

scan

ning

ele

ctro

n m

icro

scop

y

Mic

robi

olog

ical

fin

ding

s an

d cl

inic

al o

utco

me

His

tolo

gica

lly, a

ll ex

pose

d pa

rts

of t

he b

arri

er m

embr

ane

wer

e co

ntam

inat

ed b

y m

icro

orga

nism

s, w

hich

wer

e fo

und

be-

twee

n ne

utro

phds

, deg

ener

ated

col

lage

n fi

brils

and

nec

rotic

ce

ll co

mpo

nent

s. C

linic

ally

, mos

t ca

ses

show

ed m

embr

ane

ex-

posu

re w

ith g

ingi

val r

eces

sion

and

poc

ket f

orm

atio

n be

twee

n m

embr

ane

and

ging

iva.

B

acte

rial

col

onie

s ex

tend

ed in

to th

e m

idpa

rt o

f th

e m

em-

bran

e. F

ibro

blas

t-lik

e cel

ls, b

lood

ves

sels

and

fib

rous

str

uc-

ture

s w

ere

also

foun

d. T

he o

cclu

sive

por

tion

of t

he m

embr

ane

had

a sp

arse

ness

of

adhe

rent

tis

sue

elem

ents

. No

corr

elat

ion

was

mad

e be

twee

n m

icro

biol

ogic

al a

nd c

linic

al fi

ndin

gs.

~-

-

Exp

ande

d C

lass

I1 f

urca

tion

defe

cts

poly

tetr

aflu

oroe

thyl

ene

Sbor

done

, Cia

glia

, Spa

gunu

olo,

L

enci

, Bar

one,

Ram

aglia

(37

) 1

nona

bsor

babl

e an

d 1

abso

rbab

le

2 pe

riod

onta

l def

ects

__ ~

Selv

ig, K

erst

en, C

ham

berl

ain,

E

xpan

ded

12 in

trao

sseo

us d

efec

ts

Wik

esjo

(39

) po

lyte

traf

luor

oeth

ylen

e

Gui

llem

in, M

ello

nig,

E

xpan

ded

30 in

trao

sseo

us d

efec

ts

Bru

nsvo

ld (

15)

poly

tetr

aflu

oroe

thyl

ene

__

~

.

Gre

vsta

d, L

ekne

s (1

4)

Exp

ande

d 8

intr

aoss

eous

po

lyte

traf

luor

oeth

ylen

e pe

riod

onta

l def

ects

Tem

pro,

Nal

band

ian

(45)

E

xpan

ded

6 pe

riod

onta

l po

lyte

traf

luor

oeth

ylen

e in

trao

sseo

usde

fect

s and

2

furc

atio

n de

fect

s

Ana

erob

ic c

ultu

re

Mic

robi

olog

ical

dat

a un

ders

core

d th

e si

gnif

ican

ce of

sur

gica

l in

stru

men

tatio

n in

inte

r-ra

dicu

lar t

reat

ed s

ites

and

con-

fi

rmed

the

need

to m

aint

ain

heal

ing

site

s fr

ee o

f pe

riod

onta

l pa

thog

ens.

N

o cl

inic

al d

iffe

renc

e bet

wee

n ty

pe o

f m

embr

anes

em

ploy

ed.

The

aut

hors

sug

gest

ed th

at h

ealin

g si

tes

shou

ld b

e fr

ee o

f pe

riod

onta

l pat

hoge

ns.

Ret

rieve

d C

ompa

riso

ns b

etw

een

ultr

astr

uctu

ral f

indi

ngs a

nd c

linic

al o

b-

mem

bran

es

serv

atio

ns re

veal

ed t

hat

the

exte

nt o

f ba

cter

ial c

olon

izat

ion

for

scan

ning

of

the

mem

bran

e co

rrel

ated

inve

rsel

y w

ith c

linic

al a

ttach

men

t el

ectr

on m

icro

scop

y ga

in. E

xten

t of

oral

exp

osur

e may

be

an in

dica

tor o

f lo

ng-t

erm

su

cces

s or

failu

re o

f gui

ded

tissu

e re

gene

ratio

n.

30 r

etri

eved

N

o cl

ear p

atte

rn o

f m

icro

bial

col

oniz

atio

n or

cel

l adh

eren

ces

mem

bran

es b

y in

eith

er s

ide

of t

he m

embr

ane.

The

pre

senc

e of

pla

que

on

scan

ning

ele

ctro

n th

e m

embr

ane

did

not

ham

per

clin

ical

hea

ling

duri

ng th

e fi

rst

mic

rosc

opy

4-6

wee

ks.

4 pa

rtia

lly e

xpos

ed

3 s

truc

tura

lly d

iffe

rent

gro

ups

of b

acte

rial

agg

rega

tions

wer

e m

embr

anes

by

obse

rved

1) g

ram

-pos

itive

coc

ci a

nd r

ods

in th

e ex

tern

al

elec

tron

ic

part

of

the

open

mic

rost

ruct

ure,

2)

cocc

i, ro

ds a

nd fi

lam

en-

mic

rosc

opy

tous

mic

roor

gani

sms

embe

dded

in

fibr

in-m

ed s

pace

s, a

nd

3) g

ram

-pos

itive

coc

ci a

nd ro

ds, g

ram

-neg

ativ

e m

icro

orga

n-

ism

s an

d sp

iroc

hete

s in

the

occl

usiv

e pa

rt o

f th

e m

embr

ane.

N

o co

rrel

atio

n w

as m

ade

with

clin

ical

out

com

e.

6 re

trie

ved

Tra

nsm

issi

on e

lect

ron

mic

rosc

opy

show

ed n

umer

ous

bact

eria

m

embr

anes

for

incl

udin

g co

cci,

rods

and

fila

men

ts. A

naer

obic

cul

ture

yie

lded

tr

ansm

issi

on e

lect

ron

Stre

ptoc

occu

s and

Act

inom

yces

spe

cies

, and

gra

m-n

egat

ive

fa-

mic

rosc

opy

and

culta

tive

rods

, mai

nly

Hue

rnop

hilu

s spe

cies

. It w

as a

ssum

ed

anae

robi

c cu

lture

th

at b

acte

rial

col

oniz

atio

n of

mem

bran

e af

fect

s pe

riod

onta

l co

nnec

tive

tissu

e re

gene

ratio

n.

Not

kno

wn

- __

D

emol

on, P

erss

on, M

oncl

a,

Exp

ande

d 19

cla

ss I1

fur

catio

n Sc

anni

ng e

lect

ron

Aug

men

tin"

grou

p sh

owed

less

bar

rier

-mem

bran

e ex

posu

re

John

son,

Am

mon

s (1

0)

poly

tetr

aflu

oroe

thyl

ene

defe

cts

mic

rosc

opy

than

con

trol

s. B

. jor

syth

us a

nd E

! gin

givu

lis w

ere

asso

ciat

ed

with

gin

giva

l inf

lam

mat

ion

duri

ng in

itial

hea

ling.

Aug

men

tin@

se

emed

to h

ave

little

eff

ect o

n ba

rrie

r-m

embr

ane

mic

ro-

biot

a.

Tabl

e 1.

Con

tinue

d N

owza

ri, S

lots

(25

) E

xpan

ded

11 2

- to

3-w

all a

nd

Sele

ctiv

e an

d In

vers

e re

latio

nshi

p be

twee

n m

icro

bial

cou

nts

and

gain

of

poly

tetr

aflu

oroe

thyl

ene

furc

atio

n de

fect

s no

n-se

lect

ive

prob

ing

atta

chm

ent.

80%

of t

eeth

hav

ing

mem

bran

es w

ith

less

than

lo8

tota

l via

ble

coun

ts g

aine

d 3

mm

or

mor

e in

at

tach

men

t; te

eth

with

mem

bran

es h

avin

g m

ore

than

lo8

bac-

te

ria

lost

or h

ad s

mal

l pro

bing

atta

chm

ent i

ncre

ases

of 1

-2

mm

. N

ovae

s, G

utie

rrez

, Fra

ncis

chet

to,

Cel

lulo

se

10 c

lass

I1 fu

rcat

ion

Scan

ning

ele

ctro

n Sc

anni

ng e

lect

ron

mic

rosc

opy

and

DN

A p

robe

ana

lyse

s di

d N

ovae

s (2

4)

defe

cts

mic

rosc

opy

and

not

reve

al p

erio

dont

al p

atho

gens

at

the

time

of m

embr

ane

anae

robi

c cu

lture

an

d D

NA

pro

be

DN

A p

robe

ex

posu

re. N

o cl

inic

al re

sults

wer

e re

port

ed.

ari,

Mat

ian,

Slo

ts (2

8)

Exp

ande

d 18

two-

to th

ree-

wal

l Se

lect

ive

and

The

Aug

men

tine

grou

p ha

d an

incr

ease

in m

ean

prob

ing

poly

tetr

aflu

oroe

thyl

ene

intr

aoss

eous

def

ects

no

n-se

lect

ive

atta

chm

ent o

f 36

.5%

of

pote

ntia

l gai

n as

com

pare

d w

ith

anae

robi

c an

d DN

A e

22.4

% fo

r con

trol

gro

up. T

he A

ugm

entin

@ gr

oup

show

ed 9

- fo

ld fe

wer

org

anis

ms t

han

cont

rols

. D

e Sa

nctis

, Zuc

chel

i, C

laus

er (9

) E

xpan

ded

poly

tetr

aflu

oroe

thyl

ene

Zuc

chel

i, C

laus

er (8

) Po

lygl

ycol

actic

aci

d

Mac

htei

, Gro

ssi,

Dun

ford

, E

xpan

ded

10 a

ngul

ar b

ony

defe

cts

Scan

ning

ele

ctro

n m

icro

scou

v 10

ang

ular

bon

y de

fect

s Sc

anni

ng e

lect

ron

mic

rosc

opy

Bac

teri

al c

olon

izat

ion

in th

e m

id-p

art

of b

arri

er m

embr

ane

redu

ced

pote

ntia

l pro

bing

atta

chm

ent

by 5

0%.

Gai

n of

pro

bing

atta

chm

ent w

as g

reat

er fo

r non

-exp

osed

than

for

expo

sed

mem

bran

es (

4.22

0.5

mm

vs

3.3k

0.6

mm

resp

ec-

tivel

y). S

cann

ing

elec

tron

mic

rosc

opy

show

ed th

at 4

1% of

ex-

D

osed

mem

bran

es h

ad b

acte

rial

col

oniz

atio

n.

56 C

lass

I1 fu

rcat

ion

Ana

erob

ic c

ultu

re

defe

cts

10 m

andi

bula

r fu

rcat

ion

Ana

erob

ic cu

lture

de

fect

s

Site

s col

oniz

ed w

ith l?

int

erm

edia

exh

ibite

d le

ss f

avor

able

cl

inic

al re

sults

com

pare

d w

ith s

ites

free

of

the

orga

nism

. F

usob

acte

rium

, I! i

nter

med

ia a

nd A

ctin

omyc

es o

dons

olyt

icus

w

ere

mos

t com

mon

mem

bran

e is

olat

es. S

ites t

reat

ed w

ith a

ba

mer

mem

bran

e te

n o

be p

ositi

ve fo

r 15

targ

et m

icro

- or

gani

sms m

ore

ofte

n si

tes t

reat

ed w

ithou

t a m

em-

bran

e.

Now

zari,

Sm

ith M

acD

onal

d,

Exp

ande

d 42

man

dibu

lar

post

erio

r Se

lect

ive

and

Patie

nts

trea

ted

with

hll

-mou

th o

sseo

us s

urge

ry re

veal

ed

Lon

don,

Fly

nn, M

orri

son,

po

lyte

traf

luor

oeth

ylen

e 2-

to 3

-wal

l def

ects

no

n-se

lect

ive

low

er le

vels

of

peri

odon

tal p

atho

gens

on

barr

ier

mem

bran

es

Slot

s (2

9)

and

grea

ter g

ain

in c

linic

al a

ttach

men

t th

an c

ontr

ols

(3.4

us

1.4

mm

res

pect

ivel

y).

anae

robi

c cu

lture

an

d D

NA

pro

be

onal

d, N

owza

ri,

Poly

lact

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failing periodontal regeneration. Smith MacDonald et al. (44) studied 4 membrane-treated periodontal sites having human cytomegalovirus or Epstein-Barr type 1 virus. The 4 virally infected sites revealed an average gain in clinical attachment of 2.3 mm com- pared with 16 virally negative sites that showed a mean clinical attachment gain of 5.0 mm (P=0.004). This observation may be important because the two herpesviruses have been associated with adult peri- odontitis (5, 31) and with acute necrotizing ulcer- ative gingivitis in Nigerian children (6) and they pos- sess an array of virulence factors pertinent for de- structive periodontal disease (5). It is also of interest that cytomegalovirus is the most common viral in- fectious complication in patients receiving organ and bone marrow transplants (35). Cytomegalovirus can infect and alter the function of fibroblasts (201, thereby potentially impairing regeneration of the periodontal ligament. More research is warranted on the possible relationship between periodontal her- pesvirus infections and suboptimal healing after re- generative periodontal procedures.

Thus, it seems that several oral microbial species can colonize barrier membranes, that microbial con- tamination of barrier membranes can significantly hamper periodontal tissue regeneration, and that certain microbial species and maybe some herpesvi- ruses are particularly detrimental to periodontal re- generation.

An ti - in fec tive therapy in periodontal regeneration

To prevent infectious failures with regenerative peri- odontal therapy, efforts should be directed towards the elimination or marked suppression of pathogens in the treated site as well as in the entire mouth prior to regenerative surgery and throughout the healing phase.

The dental professional possesses a variety of means to prevent or control barrier membrane-as- sociated infections. Anti-infective therapy in peri- odontal regeneration includes mechanical debride- ment with or without concomitant periodontal surgery, local or systemic delivery of antimicrobial agents, possible application of slow-release anti- microbial agents to the barrier membrane material and proper oral hygiene measures by the patient.

Diligent mechanical instrumentation (that is, seal- ing and root planing) to remove dental plaque, cal- culus, altered cementum and cytotoxic microbial products on the root surface is a prerequisite for op-

timal periodontal healing. Patients may also benefit from treatment of periodontal lesions other than those designated for regenerative therapy before per- forming the regenerative procedures. Nowzari et al. (29) showed that patients who received pocket-re- duction therapy of existing periodontal lesions prior to barrier membrane placement revealed the lowest levels of periodontal pathogens in the membrane and exhibited most clinical attachment gain. A non- surgical approach to periodontal therapy may also be successful in reducing the oral load of periodontal pathogens, provided appropriate considerations are given to the specific pathogenic microbiota of the patient. As discussed by van Winkelhoff et al. (49), systemic antimicrobial therapy may be necessary to suppress A. actinomycetemcomitans and other peri- odontal pathogens in the human oral cavity. Sys- temic antimicrobial treatment allows antibiotics to reach pathogens residing in the depth of periodontal pockets and on the tongue and buccal mucosa.

Systemic administration of amoxicillin-clavulanic acid (Augmentin9 (28) and ornidazole (22) have demonstrated clinical benefits in regenerative peri- odontal therapy. However, since an antibiotic agent may be active against one and demonstrate resist- ance against another periodontal pathogen and since the periodontal microbiota of individual pa- tients often shows several pathogenic species simul- taneously, it is often advantageous to prescribe a combination therapy of two antibiotics. Metronida- zole and ciprofloxacin exhibit synergy and constitute a valuable drug combination for periodontitis pa- tients with anaerobic pathogens together with su- perinfecting enteric bacteria (32, 42). The metronid- azole-ciprofloxacin drug combination is also effec- tive against A. actinomycetemcomitans and several other periodontal pathogens (42). Resistant organ- isms are mainly streptococci (421, which exert antag- onistic activity against several periodontal patho- gens (42, 49). Optimally, systemic antibiotics in peri- odontics should be prescribed on the basis of an appropriate microbiological analysis (41, 46). If mere clinical judgment forms the basis for the selection of antibiotics, the clinician may not choose the optimal drug regimens and may not obtain the desired clin- ical results (43).

Nowzari et al. (29) recommended washing extra- oral skin areas with a iodophor before regenerative periodontal surgery to prevent membrane coloniza- tion by dermal pathogens during membrane inser- tion. Sutures used in regenerative procedures are particularly prone to contacting the lips and the face and thereby adsorbing dermal microorganisms.

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Sander et al. (36) evaluated the effect of local ap- plication of 1 g of a 25% metronidazole gel on peri- odontal healing after guided tissue regeneration. At 6 months postsurgery, significantly more gain of clinical attachment occurred in the metronidazole- treated periodontal sites than in sites treated with barrier membrane alone (36). At 1 week postsurgery, metronidazole-treated sites showed significantly lower levels of total viable bacteria and lower pro- portions of black-pigmented anaerobic rods than control sites (12). However, no microbiological dif- ference between test and control sites was observed at later observation times (12), suggesting that the microbiological benefit of the metronidazole gel was confined to the initial regeneration phase. Local pocket delivery of chemotherapeutic agents other than metronidazole may also help reduce pathogens in barrier membrane-treated sites (33).

Antimicrobial coating of barrier membranes con- stitutes a novel approach to controlling membrane- associated infections. Harvey et al. (16) have described the potential of antibiotic bonding to po- lytetrafluoroethylene by means of the cationic sur- factant, tridodecylmethylammonium chloride (Poly- sciences, Inc., Warrington, PA, USA). Tridodecyl- methylammonium chloride has been safely used for more than a decade in vascular shunt (3) and urinary tract catheter (1 1) surgeries. Our laboratory has studied the clinical benefit of applying tetracycline- HC1 to the surface of expanded polytetrafluoroethy- lene membranes (30). Barrier membranes were sub- merged for 1 minute in a 5% solution in absolute alcohol of tridodecylmethylammonium chloride. After drying at room temperature, the specimens were immersed for 1 minute into a freshly prepared, basic 3% tetracycline-HC1 solution (one 250 mg cap- sule dissolved in 7.5 ml distilled water; pH adjusted from 1.7 to 9.5 using sodium hydroxide) and then dried at room temperature. In vitro studies showed that, despite exhaustive washing, the tetracycline- coated barrier membranes released biologically ac- tive tetracycline for 3-6 weeks (Fig. 1). Tetracycline- coated barrier membranes harbored significantly fewer cultivable pathogens for the first 2 weeks after membrane insertion than non-coated membranes (30). Also, after 6 weeks, tetracycline-coated mem- branes were associated with more gain in clinical attachment than non-coated membranes (30). Most dental offices can readily perform the tetracycline coating described above. Undoubtedly, additional methods for slow release of antibiotics or other bio- logically active agents from regenerative devices will be developed in the future.

Fig. 1. Tetracycline coating of a section of polytetra- fluoroethylene barrier membrane by means of tridodecyl- methylammonium chloride. After 21 days of washing in double distilled water with frequent water changes, the membrane still released active tetracycline, as evidenced by the zone of inhibition of Escherichia coli growth around the membrane.

The optimal supportive periodontal treatment after regenerative periodontal therapy has not been firmly delineated, and treatment may have to be modified to fit specific individual needs. However, most anti-infective principles of conventional peri- odontal maintenance therapy are applicable to re- generative procedures (52).

Proper oral hygiene is important to decrease plaque levels for the benefit of the tissue healing. Studies have shown regenerative periodontal pro- cedures to be more successful in patients having little or no dental plaque than in patients with high plaque levels (47). Also, patients with good oral hy- giene can preserve the clinical attachment gain after regenerative periodontal therapy for many years (7, 13, 18, 19, 51). Commonly, patients are instructed in twice-daily use of toothbrushing and dental flossing. Chlorhexidine rinses seem to offer therapeutic bene- fits during healing (211, even though in uitro experi- ments have revealed an ability of chlorhexidine to damage fibroblasts (1).

Some clinicians advocate supportive periodontal treatment once a week for the first 6 weeks of barrier membrane treatment and then once a month for the first 6 months after regenerative therapy (29). In bar- rier membrane-treated sites, mechanical plaque re- moval should be performed in a gentle manner in order not to disturb tissue healing. Also, to avoid a foreign body-like reaction, pumice or other particu- lar matter that may remain in regenerative sites dur- ing the healing phase should be used carefully and sparingly.

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Recommendations and concluding remarks

Regeneration of periodontal tissue is predicated upon controlling periodontal pathogens in the bar- rier membrane-treated site and probably also in other parts of the oral cavity prior to the membrane insertion and during initial healing. I! gingivalis, A. actinomycetemcomitans, B. forsythus, I? intermedia, l? micros and C. rectus have been associated with failing regenerative periodontal therapy. Herpesvi- ruses may play a detrimental role in periodontal re- generation as well. Topical antiseptic and systemic antibiotic therapy might be employed to control pathogens in periodontal regeneration.

A practical approach to antimicrobial therapy in regenerative periodontal therapy is outlined below:

institution of effective oral hygiene measures; subgingival scaling and root planing of the entire dentition, possibly combined with periodontal surgery to gain access to affected root surfaces; surgical reduction of periodontal pockets (except for the site(s) of regenerative surgery) or appropri- ate nonsurgical therapy of periodontally affected teeth; possible utilization of a tetracycline-coated bar- rier membrane; thorough root planing of barrier membrane- treated sites using ultrasonic, rotary or hand in- strument; application of antimicrobial agent to diseased root surfaces (iodophor, metronidazole, tetracycline or citric acid, but probably not chlor- hexidine due to its toxic effect on fibroblasts); and suturing of surgical flaps for complete coverage of the barrier membrane; possible systemic antibiotic therapy with an ap- propriate antimicrobial agent to eradicate or markedly suppress periodontal pathogens. Anti- biotic therapy may begin 1-2 days prior to regene- rative surgery and continue for at least 8 days for most antibiotics; 0.12% chlorhexidine rinse (15 ml, twice daily) during the first 2 weeks after regenerative surgery; the anti-inflammatory ibuprofen (400 mg, four times daily) may be prescribed for 3 days post- surgery; frequent professional plaque removal during the healing period. Supportive periodontal treatment may be scheduled once a week for 6 weeks and then once a month for 6 months. Subgingival scal- ing, probing and pumicing of regenerative sites should be minimized or avoided for the first 6

months not to disturb the maturing of newly formed connective tissue; and institution of an individually tailored mainten- ance care program.

This chapter has focused on infectious aspects of membrane-assisted periodontal regeneration. How- ever, the concept of infection control is applicable also to other types of regenerative periodontal ther- apy and to guided bone regeneration. It is important to realize that the formation of new connective peri- odontal attachment is contingent upon the elimin- ation or marked reduction of pathogens at the treated periodontal site.

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