Journal of Periodontal Research 17: 210-218, 1982

Artificial periodontal defects aroundincisor teeth of beagle dogs

A clinical and histometrical analysis

JAN JANSEN

Department of Periodontology, University of Groningen, The Netherlands

The aim of the present experiment was to investigate if it is po^ible to create deepperiodontal defects around incisor teeth of beagle dogs with the use of orthodontic elasticbands, to investigate if this method is reproducible and predictable, and to evaluate if suchdefects possess the histopathological characteristics of naturally occurring periodontitis.

In eight beagle dogs the dentogingival fibres around four upper incisors, 313 and 212 werecut to the level of the aiveolar bone. Orthodontic elastic bands were placed in thesedeepened sulci and removed after 8 weeks. Clinical data (probing depth and gingivalrecession) were recorded at the start of the experiment, immediately following removal ofthe elastic bands, and 2, 6, 14, and 30 weeks thereafter. The dogs were sacrificed on dif-ferent dates so that is was possible to analyse defects histometrically 3, 7, 15, or 31 weeksafter elastic removal. Contralateral defects one week after elastic band removal served ascontrok. Micrographic color slides of the histoiogical sections were analysed using aFerranti-Cetec digitizer.

Immediately after elastic band removal mean values for probing depth and gingivalrecession were approximately 5.5 mm and 2.0 mm, respectively. Histometrical assessmentsreveziled a loss of attachment of approximately 3.0 mm.

The differences in probing depths between contralateral defects in the same dog weresmall indicating rather high reproducihility of the method. Because of wide variations inprobing depth and histometrical dimensions between dogs, it was concluded that thepresent method is not fully predictable.

Upon elastic removal values for probing depth decreased with approximately 1.5 mm, theresult being a moderately deep detect of around 4 mm. Histometrically there was no evi-dence that the apical positioning of the junctional epithelium was reversible after elasticremoval. However, alveolar bone repair could be demonstrated in the 7, 15, and 31 weeksspecimens.

It was concluded that because of this bone repair, the present defects do not possess allhistopathological characteristics of naturally occurring periodontitis.

(Accepted for publication September 30, 1981)

in this area, such as the broad interdentalIntroaiicHon alveolar bone septum atid the absence of

When in periodontal research a dog model contacts between nei^boring teeth, onlyis used, premolars are usually selected as allows for the institution of shallow orexperimental teeth. However, the anatomy moderately deep pockets due to recession

A R T I F I C I A L P E R I O D O N T A L D E F E C T S 211

of the interdental gingiva (Lindhe & Erics-son 1978, Jansen & Pilot 1981). In thebeagle dog incisor teeth often have contactpoints, and the interdental periodontium isnarrow. Furthermore, these teeth are single-rooted, and the roots have a conical shape.These anatomical features wouid favor arapid artificial periodontal breakdown withthe formation of deep pockets providedthat the marginal gingiva does not retract.Deep experimental pockets would be avaluable extension to the dog model, notonly in evaluating preventive or therapeuticprocedures but also e.g. in studying micro-biological aspects of subgingival plaque.

In monkeys, Caton and Zander (1975)very elegantly produced deep periodontaldefects in incisor teeth with the use oforthodontic elastic bands. They concludedthat the created loss of attachment and thealveolar bone loss was irreversible uponelastic band removal. Furthermore, Catonand Kowalski (1976) indicated that thesedefects were fully reproducible.

Material and Methods

Eight beagle dogs approximately 18 monthsold and weighing ± 15 kg were used.Throughout the experiment the dogs werefed on a diet which favors gross plaque ac-cumulation on the teeth, and no oral hy-giene procedures were performed.

Before the start of the experiment smallamalgam fillings were made at the level ofthe gingival margin to serve as referencepoints for gingival recession. Periodontaldefects were created using a modificationof the method described by Caton and Zan-der (1975). The dentogingivai fibres aroundupper incisors ' P and ^P were cut to thelevel of the alveolar bone. Orthodonticelastic bands (Unitek, Englewood CliffsN.J. 1/8 inch) were placed in these deep-ened sulci helow the gingival margin andremoved after 8 weeks. Upon removal of

the elastic bands a notch was made with theuse of a smalt excavator on the mesial anddistal root surfaces to indicate the apicalextent of the soft tissue defects. The instru-ment was placed into the defects with lighthand pressure until definite resistance wasfelt. The notch was then made in the rootsurface with one bucco-lingual stroke.

Histological DesignPairs of dogs were sacrificed 3, 7, 15, and31 weeks after elastic band removal fromthe right side of the jaw (Fig. 1). Contra-lateral defects were created 9 weeks beforesacrifice was planned. One week beforesacrifice the elastic bands were removedfrom this side and notches prepared. Thesedefects on the left side of the jaw, one weekafter ligature removal, served as controls.The dogs were sacrificed and histometri-cally analysed as described in detail byJansen, Van Dijk and Pilot (1981).

Three sections 40 ^m apart were selectedfrom the midsagittal region of each inter-proximal block. Micrographic color slideswere made and projected with a totalmagnification of 70 on a Ferranti-Cetecdigitizer table connected to a Digital P.D.P.-11/0.5 computer.

The following distances were calculatedfor each section:- the distance from the cemento-enamel

junction to the apical termination of thejunctional epithelium (CBJ to ATJE),

- the distance from the cemento-enameljunction to the alveolar hone level (CEJto bone),

- the distance from the notch to the al-veolar hone level (notch-hone), and

- the distance from the ATJE to the al-veolar bone level (ATJE-bone).The mean of the three sections was taken

for further analysis.Two additional beagle dogs of the same

age in which no periodontal defects hadheen created were sacrificed, and the di-

212 J A N S E N

* ciinicai measurementst sacfilice.histometricai assessments

Fig. 1. Schematic representation of tlie design of Ihe experiment.

mensions of the periodontium of the upperincisors were analysed as described above(baseline situation).

Cliniccd DesignClinical recordings were made before thestart of the experiment (baseline) imme-diately after removal of the elastic bandsand 2, 6, 14, or 30 weeks thereafter (Fig.1). The reason for collecting the final clin-ical data one week prior to sacrifice wasthat it was expected that probing imme-diately prior to sacrifice would disturb thehistological picture. Only mesial and distalsurfaces of the experimental teeth were in-vestigated.

Probing depth was assessed with the useof a University of Michigan 0 prohe with aterminal diameter 0.35 millimeter whidiwas inserted with light hand pr^sure. Re-

cession of the clinical margin was measuredusing the same probe. The level of the gin-gival margin was related to the apical bor-der of the amalgam filling which indicatedthe original position of the gingiva. All clin-ical measurements were made to the nearesthalf millimeter.

The Student's t test was used to analyzedifferences between mean values at dif-ferent intervals using the dog as a unit.Th number of histometrical data at eachtime point was limited. In every evaluationphase only 2 dogs with at most 3 defectson each side of the jaw were available.Furthermore, these defects cannot be con-sidered strictly independent, mandatory forstatistical analysis (Pilot et al. 1980). There-fore, results are presented as mean vaiuesper side of the jaw for each pair of dogs,and no effort was made to subject the histo-metrical results to statistical analysis.

A R T I F I C I A L P E R I O D O N T A L D E F E C T S 213

Fig. 2. Specimen (before decaScification) of an inter-dental area between 1 and P at the end of the ac-tive phase of creating defects. The interdentai areadoes not provide enough space tor two eiastic bandsto be situated next to each other. Since the elasticswere first placed around ^i^ and subsequently around^i^ the elastics at the mesial aspect of H^ werealways situated more apical than at the distal aspectof 2|J, This explains why deeper defects were createdat the mesial aspect of ^ l^ . The dog from which theabove section was taken was not included in thepresent experiment. E ~ elastic band; ES = spaceformerly occupied by an elastic band.

Fig. 3. Clintcal aspect of an elastic induced defect atthe end of the active phase.

Results

In this experiment it was impossible tocreate pedodontal breakdown at the distalaspect of I*. Data from this area were notincluded in the present material in ordernot to disguise the effect of elastic bandplacement at the mesial aspect of ''P andthe distal and mesial aspect of ^P.

Clinical Re.suJtsThe elastic bands were situated subgin-givaliy, both immediately after placementand after 8 weeks (Fig. 2). The clinicalaspect of a defect at the end of the activephase is shown in Fig. 3.

Data for probing depths and gingivalrecession are presented in Table 1. Probingdepth at baseline varied from 2.0 to 3.0mm. At the end of the active phase ofcreating defects, after 8 weeks, the prob-ing depths most commonly recorded were5.0, 5.5, 6.0, and 7.0 mm. Without excep-

214 JANSEN

tion the deepest defects were found at themesial aspect of ^P (x = 6.21 mm SD =0.96 mm) and the shallowest at the distaiaspect of sp (x = 4.71 mm SD = 0.85 mm).Mean probing depth at the mesia! aspect of2P was X = 5.59 mm SD = 0.63 mm.

Table 1

Clinical results: individual recordings forprobing depth and mean values (x) and stan-dard deviations (s.d.) for probing depths and

gingival recessions

ind

ivid

ual

rec

ord

ing

s(o

r pro

bin

g d

«p(h

i

gmgwarrecMSKM

1

2

3

*

5

7

a

».a.i

Baul

contrMt

S S I

irw

Mp.

« • -

D.Si

Ictt

u™ . .4440

S.6B1.11

i.i;

•n -

*•

4»<I.B

0,91

E.p«-

WMkl«lai1ii

•

3.88

o.nZ.il

a ?7

irwnta

: rwno

UpA

•• a

•••s

3 TT

C-.&l

3.03

a 66

tt>h*M

M l

•

• « »

. .

3.6?O.-M3..J41-Q!

MqLSO

>e4

2, 7b

D,6e

1,9;0.95

The differences between mean probing depths atbaseline and at the end of the active phase weresignificant (p < 0.05).The differences between mean probing depths at theend of the active phase and during all stages ofthe experimental phase were aiso significant (p <D.DS).

Differences between mean probing d^ths during allstages of the experimentai phase and baseline re-cordings remained significant {p < 0.05).

Differences between dimensions in con-tralateral defects in one dog at the end ofthe active phase were small. Out of 24defects, 9 contralateral defects differed 0.0mm or 0.5 mm in probing depth, 12 contra-lateral defects differed 1.0 or 1.5 mm, andonly 3 contralateral defects differed 2.0 mm.Between dogs the variation in clinical datain the same area was much greater. Probingdepth values at the mesial aspect of Pranged from 4.5-8.0 mm, at the distalaspect of 2IS from 3.0-5.5 mm and at themesial aspect of sp from 4.5-7.0 mm.

Two weeks after elastic band removalmean values for probing depths had de-creased by approximately 1.5 mm. Meanvalues for probing depth in the experimen-tal phase remained greater than at base-line (p < 0.05). Six weeks after elastic bandremoval a decrease in gingival recessionwas noted, indicating a crownwise shift ofthe gingival margin; however, the differ-ences at different intervals were not signifi-cant.

Histometrical ResultsMeasurements of the baseline sections inthe two additional dogs revealed negligibleloss of attachment (x = 0.08 mm, S.D. =0.13 mm). The mean distance from theATJE to the alveolar bone level was 1.28mm (S.D. = 0.40).

The results of the measurements in thecontrol and experimental sides are pres-

Table 2

Histometrical results: mean values and standard deviations in millimeters for the left(control) and the right (experimental) side of the jaw for each pair of dogs

<>og Rf.

1*2

3 1 4

sts7 * 8

•raaksi*la>tlcfsinovi

contr.

•"

1

1

1

Mp.

3

7

15

31

loss of attach

(C.E.J.-A.T.J.

conlr.

3.26 + 0.92

3.OB * 1.09

3.04 + 0.62

3.?0 . 0.67

nwnt

E.)

np.3.4B

3.30

3.44

3.!8

t "

1 °* 0

• 0

./2

.76

.56

.44

borw tmnl

iC.E.J..b<ini

contr.

5.41 ^ [).S7

5.01 . 0.49

4.93 f 0.61

5.0Z + 0.40

)

•up.

4.96

4.61

4.S3

4.13

+ 1.03

* 0.60

t 0.76

• 0.71

(notch, bo Its

contr.

-0.80 •

-0.61 4

-0.34 .

-0.62 •

0.46

0.2?

0.36

0.45

M p .

.0.87 * 0.46

•O.ZO t- 0

•0.40 • 0

•Q.93 • 0

36

70

30

WiQiri of COf

(*.T.J.E.-bc

2.14 4 0.91

1.S3 f O . 9 7

1.B8 + 0.43

1.82 < 0.64

n*cttn tiMus

•w)

«P1.46

k.31

•1.S5

0.84

h 0.35

. 0.22

^ 1.01

0.52

A R T I F I C I A L P E R I O D O N T A L D E F E C T S 215

ented in Tahle 2. Mean loss of attachmenton the control sides was slightly over 3 mm.Mean values for ioss of attachment on theexperimental sides were at all times greaterthan those of the controls.

The mean distance from the CEJ to thealveolar bone on the experimental side wasat all intervals smaller than on the controlside. This difference was most pronouncedin the 31 week specimens.

The alveolar hone in the controi speci-mens was situated apical to the notch in theroot surface, but in the experimental speci-mens the alveolar bone was situated coronalto the notch, except in dogs 1 and 2 (threeweeks after elastic band removal). From themean values per pair of dogs it appearedthat aiveolar bone height tended to in-crease with experimental time (Table 2,distance notch-bone). As a result the dis-tance from ATJE to hone became graduallysmaller and was in the 31 week specimenshalf that found in the baseline sections.

Discussion

The present experiment has demonstratedthat it is possible to create deep perio-dontai defects at the mesial aspect of *Fand 3I« and at the distal aspect of H^. Thesedefects were characterized hy probingdepths of approximately 5.5 mm and a gin-gival recession of approximately 2.0 mm.

Differences in probing depth betweencontralateral defects in the same dog weresmall, indicating that the method in itself israther reproducible. However, there wasmuch variation in probing depths in thesame area between dogs. This finding indi-cates that the method does not predictablyresult in defects of equal size in a group ofdogs.

In the first weeks after elastic hand re-moval prohing depth values decreasedsharply and from 7 wwks on aiveoiar bonerepair could he observed. BoQi reduction

of probing depth and alveolar bone repairafter creation of an artificial periodontaldefect in the dog have been reported ear-lier (Jansen & Pilot 1981, Jansen et al.1981, Van Dijk 1979).

The decrease in probing depth vaiuesdoes not reflect a true reduction in pocketdepth: the connective tissue attachment lossdid not seem to be reversible (Tabie 2 dis-tance CEJ-ATJE), and the gingival margindid not further retract. The decrease inprobing depth may, however, be explainedby different prohing conditions as a resultof difference in inflammation before andsome time after elastic band removal. Aless severely inflamed lesion would thenresult in a lower probing depth value(Armitage, Svanberg & Loe 1977, Robinson& Vitek 1979, Jansen, Pilot & Corba 1981).Indeed, most of the long term experimentalspecimens in the present study revealed along junctiona! epithelium together withless severe inflammation in the deeper partof the lesion than was found in the controlspecimens (Figs. 4a, b). Tiiis may also ex-plain the alveolar bone repair because it hasbeen reported that reduction of periodontalinflammation stimulates bone repair (Kan-tor, Poison & Zander 1976, Rosling, Ny-man & Lindhe 1976, Kantor 1980).

In contrast to the present dog model,for the Rhesus monkey it was reported thatafter elastic band removal probing depthsdid not decrease and the alveolar bone iosswas irreversible (Caton & Zander 1975). Atleast part of this discrepancy may be ex-plained by the fact that in contrast to thedog most of the long term "elastic-off"specimens in the Rhesus monkeys stillshowed the histopathological characteristicsof active periodontitis. The question whythe periodontai tissues in dogs obviouslyreact differently to elastic band removalthan in monkeys remains obscure hut dif-ference in species and anatomical dimen-sions can not be excluded.

216 J A N S E N

CEJCEJ

. / • . • •

ATJE.' B.

t- :

N

4b

A R T I F I C I A L P E R I O D O N T A L D E F E C T S 217

In spite of qualitative similarities, theamount of periodontal breakdown in thepresent defects around incisors was sub-stantially greater than that found in liga-ttire-induced defects in the premolar regionin beagle dogs (Jansen & Pilot 1981, Jansenet al. 1981). The difference may be ex-plained by differences in technique and dif-ferent anatomical dimensions.

In contrast to premolars, roots of incisorteeth converge in an apical direction. Itcan be expected that in this situation anelastic band under tension easily moves inan apical direction. Furthermore, theamount of periodontal tissue to be brokendown around premolar teeth, including thebifurcation area, is substantially greaterthan that around incisor teeth with a verythin interseptal bone crest. The broad inter-dental bone crest between the third incisorand the cuspid may explain why it was im-possible to create defects at the distal aspectof 318.

Another important difference is the widthof connective tissue attachment in the nor-mal unaffected situation which is twice aswide in the incisor region as in the pre-molar region as reported earlier (Jansen etal. 1981). Since this attachment was severedat the start of the experiment, the initialdefect was already much deeper in the in-cisor region.

The application of the present dog modelin periodontal research should be advocatedwith great care. Reduction of severity ofperiodontal inflammation and alveolar bonerepair are often objectives of periodontaltherapy. Since both phenomena seem tooccur in the present defects, it will be dif-ficult, if at all possible, to demonstratethese effects of periodontal therapy.

Adcnowledgemenl

The authors would like to express theirgratitude to the staff of the Central Experi-mental Animal Laboratory of the Univer-sity of Groningen for their skillfull assis-tance during the actual experiment and tothe staff of the Laboratory of Oral His-tology of the University of Groningen,Head Dr. H. W. B. Jansen, for the prep-aration of the sections.

References

Arttiitage, G. C , Svanberg, G. K. & Loe, H.1977. Microscopic evaluation of clinical mea-surements of connective tissue attachmentlevels. Journal of Clinical Periodontology 4:173-190.

Caton, J. G. & Zander, H. A. 1975. Primatemodel for testing periodontal treatment pro-cedures. I. Histologic investigation of local-ized periodontal pockets produced by ortho-dontic elastics. Journal of Periodontology 46:71-77.

Caton, I. G. & Kowalski. C. J. 1976. Primatemodel for testing periodontal treatment pro-cedures. II. Production of contralaterallysimilar lesions. Journal of Periodontology 47:506-510.

Van Dijk, L. J. 1979. Surgery and oral hygieneon artificial periodontal defects in beagledogs. University of Groningen, Thesis.

Jansen, J., PUot, T. & Corba, N. H. C. !981.Histologic evaluation of probe penetrationduring clinical assessment of periodontal at-tachment levels. Journal of Clinical Perio-dontology 8: 98-106.

Jansen, J. & Pilot, T. 1981. Predictability ofprohing depths in ligature-induced perio-dmital defects in beagle dogs. Journal ofFeriodontal Research 16: 372-378.

Jansrai, J., Van Dijk, L. J. & Pilot, T. 1982.Histometric analysis of ligature-induced pe-riodontal defects in beagle dogs. Journal ofPeriodontal Research 17: 202-209.

Kantor, M., Poison, A. M. & Zander, H. A.

ng . 4at>. • : Control defect, 1 week atter elastic band removal. Mesial aspect of I', b: Experimental defect, 7weeks after elastic band removal. Mesial aspect of ' I . CEJ = Cemento-enamel junction. ATJE = epical ter-mination of juncttonal epithelium. B = most coronal level of aiveotar bone opposite the root surtace at adistance similar to tiiat of the normai width of the periodontai iigament. N = notch. Original magnificationX m.

218 J A N S E N

1976. Alveolar bone regeneration after re-moval of inflammatory and traumatic fac-tors. Journal of Periodontology 47: 487-495.

Kantor, M. 1980. The behaviour of angularbone defects following reduction of iitfiam-mation. Journal of Periodontology 51: 433-436.

Liadhe, J. & Ericsson, I. 1978. Effect of liga-ture placement and dental plaque on perio-dontal tissue breakdown in the dog. Journalof Periodontology 49: 343-350.

Pilot, T., van der Weele, L. T., van Dijk, L. J.& Jansen, J. 1980. Variations in artificialperiodontal defects in beagle dogs. Journal ofDental Research 59: Special Issue B 373.

Robinson, P. J. & Vitek, R. M. }979. The

relationship between gingival inflammationand resistance to probe penetration. Journalof Periodontal Research 14: 239-243.

Rosling, B., Nyman, S. & Lindhe, J. 1976. Theeffect of systematic plaque control on boneregeneration in infrabony pockets. Journal ofClinical Periodontology 3: 38-53.

Address:

Department of PeriodontologyFaculty of DentistryUniversity of GroningenAnt. Deusinglaan 19713 AV GroningenThe Netherlands