Gingival health and frequency of

J. A. H. Tromp, J. Jansen and T. . Pilot

tooth brushing in the beagle dog

Groningen, The Netherlands

Department of Periodontology, University of

model Clinical findings

Tromp JAH, Jansen J and Pilot T: Gingival health and frequency of tooth brushing in the beagle dog model. Clinical.findings. J Clin Periodontology 1986; 13: 164-168. Abstract. The aim of this experiment was to study clinical parameters when 3 different frequencies of plaque removal were applied to healthy gingivae in the beagle dog model. The maxillary first, second and third premolars of 12 beagle dogs, at the start of the experiment 2 years of age, were, after a thorough cleaning, submitted to daily plaque.removal during a pre-experimental period of 8 weeks. At the start of the experiment, the dogs were distributed into 3 groups of 4 dogs each: one group was brushed 7 times a week, a second group was brushed 3 times a week and another group was brushed only once a week. Brushing was executed over a period of 24 weeks, on the right sides of the upper jaws. The left upper jaws served as controls. At regular intervals, the plaque index, the gingival index and probing depths were assessed. A "brushing effect" was calculated for each dog, to include information on all within-dog and between dog variations. Comparison of brushing effects revealed that in this experimental model, plaque removal with a frequency of 3 times a week was sufficient to preserve gingival health, whereas tooth brushing once a week resulted in gingival inflammation. Therefore it can be concluded that 3 times a week is the critical brushing frequency in the beagle dog model with healthy gingiya at baseline.

In periodontal research, the beagle dog is frequently used to study the aetiology, pathogenesis and therapy of chronic in­ flammatory periodontal disease. One of the basic areas of interest in periodontal research is the influence of plaque and plaque removal. A causal relationship between plaque and gingi­ vitis has been demonstrated in man (Ash et al. 1964, Loe et al. 1965, Theila­ de et al. 1966). The relation between plaque and periodontitis has been dem­ onstrated in dogs (Lindhe et al. 1973, 1975). Furthermore, it has been shown, both in humans and in dogs, that a healthy periodontium can be main­ tained by regular plaque removal (Egel­ berg 1965, Loe et al. 1965, Theilade et al. 1966, Saxe et al. 1967, Lindhe & Hugoson 1969, Hamp et al. 1972, Lang et al. 1973, Lindhe et al. 1973, 1975). Clinically healthy gingivae in the bea­ gle dog can be established by different modalities of plaque removal using va­ rying intervals. In a number of studies,

the teeth of the dogs were cleaned twice a day (Hamp et al. 1973, Lindhe et al. 1973, 1975, Ericsson et al. 1975, Lind­ he & Rylander 1975, Schroeder & Lind­ he 1975, Lindhe & Ericsson 1978, Lind­ he et al. 1978, Heijl & Lindhe 1980, Dahlen et al. 1982), thus establishing, in a period of 7 to 8 weeks, gingiva with a clinical aspect, "almost identical to a gingiva never exposed to gross plaque accumulation" (Lindhe et al. 1978). In other experiments with dogs, brushing was carried out once a day (Hock & Tinanoff 1979, Nyman et al. 1979, Heijl & Lindhe 1982). This brush­ ing frequency resulted in clinically healthy gingivae after 2 months (Nyman et al. 1979) or a return to a previous healthy status of the periodontal tissues (Heijl & Lindhe 1982). Hock & Tinan­ off (1979), however, stated that daily brushing did not result in complete re­ moval of dental plaque and no healthy gingiva was found. Attstrom (1970), Attstrom & Egelberg (1970, 1971),

Key words: Beagle dog model - frequency of

brushing - gingival health - brushing effect. Accepted for publication Jan 17, 1985

Attstrom et al. (1975), Schroeder et al. (1975) and Nuki et al. (1981) demon­ strated that gingival health could be es­ tablished even with lower frequencies of plaque removal. It should be noted, however, that all the above-mentioned experiments are difficult to compare with one another because the methods of plaque removal and the devices used in the experiment were seldom identical. Sometimes ad­ ditional measures were performed, e.g., initial and/or weekly or biweekly scaling and polishing, or a hard diet (Egelberg 1965). The comparison of different fre­ quencies of plaque removal in one ex­ periment has been carried out in hu­ mans (Alexander 1970, Lang et al. 1973, Kelner et al. 1974) and in monkeys (Ca­ ton 1979). To the best of our knowledge, similar studies in dogs have not so far been reported. The aim of the present experiment was to study clinical parameters when 3 different frequencies of tooth brushing

165

Gingival health and plaque in beagles 0 1 2 34

-8 cleaning

24weeks

18

start experiment

1-c:-----

I J

1

-

end experiment experimental side: brushing 7x, 3x or 1x I week

__ brushing __

7x/week

12

8

control side:

------- n o brushing

____ _

_______ _

Fig. J. Outline of the experiment.

Results

Die Organisation des Experimen/es. Organigramme du plan de /'experience.

were applied to healthy gingivae in the beagle dog model. Material and Methods

The upper jaws of I 2 beagle dogs, at the start of the experiment 2-years-old, were used. The outline of the exper­ iment is illustrated in Fig. l . During the whole experiment, the dogs were fed a soft, plaque-promoting diet. At the start of the pre-experimental period of 8 weeks, the maxillary left and right first, second and third premolars were scaled and polished with pumice and a rubber cup. During the pre-experimental 8 weeks, all dogs were brushed in the left and right maxillae once a day in order to obtain healthy gingivae. After the pre­ experimental period, the dogs were dis­ tributed into 3 groups of 4 dogs each: one group continued to be brushed once a day, another group was brushed 3 times a week and a third group was brushed only once a week. During the experimental period, brushing was per­ formed only in the right upper jaws. The left upper jaws were not brushed during the experimental period and served as contro.ls. All tooth brushing was ex­ ecuted by skilled dental students using a soft tooth brush (Butler 41 I Adult). No toothpaste, pumice or other aids were used. The dogs were brushed as long as was thought to be necessary to remove the plaque. Plaque-disclosing agents, to test the efficacy of the brush­ ing procedure, were not applied. The experimental period lasted for 24 weeks. The following assessments were made at weeks 0, 1, 2, 3, 4, 8, 12, 18 and 24: plaque index, according to Si.lness & Loe (1964); gingival index, according to Loe & Silness (1963); probing depth: assessment of the probing depth was performed with a constant force probe, developed at the University of Groningen (Tromp

extensive description of this method has been given by Corba et al. (1986). A comparison of the differences between the brushing effects of the different brushing groups was made at week 24, using the Student t-test for 2 indepen­ dent samples, P5. 0.05 being the level of significance.

et al. 1979, Borsboom et al. 1981). All measurements were taken the day after all dogs, including the dogs from the once a week brushing group, were brushed. Registrations were made at the mesial and distal surfaces of the first, second and third right and left upper premolars. Data analysis

Data were analysed in two different ways. (1) Frequency distributions of the plaque index and the gingival index were calculated per brushing group and for all control sides. Histograms were made to visualize the %s of the different indices during the experiment. With re­ gard to probing depths for the same groups, means were calculated and pre­ sented in graphs. (2) A brushing effect was calculated for each dog. A brushing effect can be described as a figure indicating the ef­ fect of brushing in a dog after correc­ tions are made with regard to values of these measurements in the same dog at baseline and at control side. A more

% 100

start

4weeks

Bweeks

During the experiment, one of the dogs from the once a week brushing group resisted brushing attempts and had to be excluded from the study. The data presented in this study therefore deal with I I dogs, 4 in the 7 and 3 times a week brushing groups and 3 in the once a week brushing group. Although measurements were performed at more points of time, for the sake of clarity, the results presented relate to critical time points which, after preliminary data analysis, appeared to be weeks 0, 4, 8, 12 and 24. Plaque accumulation

Plaque index data are presented as fre­ quency distributions in Fig. 2. In the control group, an increase in plaque in­ dex was scored until maximum scores were attained at week 12. In the once a week brushing group, there was some increase in plaque index. Only small amounts of plaque were found through­ out the experiment in the 7 and 3 times a week brushing groups. With regard to the plaque index, the maximum range of the mean brushing effect is theoretically between - 6 and + 6 (Corba et al. 1986). The baseline situation in both experimental and control groups was,

12 weeks

�

24weeks interproximal

80 '

60

Pf.I.

-

40 20 0

7 7 3 1 0 brushing frequency

3

1

0

7

3

1

0

7

3

1

0

7

3

1

0

Do 0 1 • 2 • 3

Fig. 2. Plaque index scores. Frequency distributions during the experimental period. 7, 3 and

1 indicate the frequency of brushing per week, 0 indicates the control group. Die Beurteilungseinhei1e11 (Scores) des Plaque-Index. Die Hiiuflgkeitsvert.ei!ungen 1viihrend der Versuchsperiode. 7, 3 und 1 bezeic/111et die Hiiufigkeit. des Ziil111eputzens pro Woche, 0 bezeicl111e1. die Kontrollgruppe. Repartition

(%)

durant les 24 semaines des scores de /'indice de plaque pour des frequences de

brossage hebdomadaire de 7, 3, 1 ou 0 (contro/e) fois.

Tromp, Jansen and Pilot

166

4."

Probing

4.0

Pl.I.

G.I.

depth

3.6

7-3

n.s.

n.s.

n.s.

3.2

7-1

n.s.

n.s.

2.8

3-1

n.s.

n.s.

2

Explanation of the symbols:

.4

T 1 MES R WEEK 3 TIMES R WEEK ONCE R WEEI\ CONTROL 7

--=

2.0

7-3: comparison between brushing 7 and 3

--=

--= --= --= _-; -

1.6

times a week.

1.2

7-1: comparison between brushing 7 times and once a week.

0.8

3-1: comparison between brushing 3 times

0.4

and once a week.

O .OOL_�-� 2 ������---: 1 �8 ������--:2;:;-4 4 �� �������1� 2 -3 ��

n.s.: not significant. *:

I NTERPAOX. OBSERVRT JONS

PROB I NGOEPTH

Table J. Statistical analysis on brushing ef-

feels at week 24

WEEKS

p!>0.05.

Fig. 4. Mean probing depths during the experimental period for the 3 brushing groups and

the control group. The vertical lines indicate the standard deviations.

Mitt/ere Sondierungstiefen der 3 Ziihneputzgruppen und der Kontrollgruppe wiihrend der Ver­ suchsperiode. Die vertikalen Linien bezeic/men die Standardabweichungen.

however, almost equally healthy. The range in the present experiment was

Repartition(%) durant les 24 semaines des profondeurs de poche moyennes pour des frequences de brossage hebdomadaire de 7, 3, 1 ou 0 (contr6/e) fois. Les traits verticaux indiquent /es deviations standard.

therefore between about -3.0 and 0. The closer the value of the· mean brush­ ing effect reaches -3.0, the more effect a brushing frequency has on the plaque index score. The calculated mean brush­

the development of gingivitis seemed to

tically significant difference was scored

ing effects at week 24 were

-1.25,

between the brushing effects of the 7

-0.92 and -0.5 for the 7, 3 and

1 times

be slower. The gingival index scores in the 7 and 3 times a week brushing

a week brushing groups, respectively.

groups remained low during the entire

At week 24, no statistically significant differences were found between the

experimental period.

brushing effects in the different brushing

gingival index were

groups (Table

-0.61 for the 7, 3 and

The mean brushing effects for the

1).

Gingivitis In Fig. 3, frequency distributions of the gingival index scores are presented. At the start of the experiment, minor in­ flammation was present. No brushing resulted in a rapid increase in gingival index to maximum scores at week 4, after which the scores seemed to stabi­ lize. In the once a week brushing group,

-

1 . 25 ,

1 2 1 and 1 times a week -

.

and 3 times a week brushing groups.

Probing depths Fig. 4 represents the mean

probing

depths, at the start of the experiment,

brushing groups, respectively (theoreti­

about 2 mm. On the control sides, high­

cal maximum range for GI between

-6

er probing depths were scored during

and +6; for this experiment between

the whole experimental period. From

about

- 3 and 0). Results of the statisti­ cal analysis are shown in Table 1. At

week 4 onwards in the 7 times a week

week 24, brushing 7 times a week was

were apparent. Compared to baseline,

significantly better compared to the once a week brushing group. The 3

about the same probing depths were

brushing group, lower probing depths

found after 24 weeks in the brushing

times a week brushing group scored

groups, while on the control sides, prob­

significantly better compared

ing depths tended to

to the

once a week brushing group. No statis-

increase.

brushing effects found were

-

The

0 73 , .

-0.88 and -0.33 for the 7, 3 and 1

times a week brushing groups, respec­ % 100 80

start

4weeks

8 weeks

12weeks

tively. As is shown in Table

24weeks interproximal

1, no sig­

nificant differences between the brush­ ing effects of the 3 brushing groups

f-

could be demonstrated at week 24.

60

G.I.

40 20

0

7 3 1 0 7 brushing frequency

3

1

0

7

3

1

0

7

3

1

0

7

3

1

0

Do 01 llill 2

Fig. 3. Gingival index scores. Frequency distributions during the experimental period. 7, 3 and 1 indicate the frequency of brushing per week, 0 indicates the control group.

Discussion

In the present study, the frequency of plaque removal has been related to the state of health of gingivae which were at the baseline clinically healthy. Attempts were made to assess the critical brushing

frequency, i.e., the lowest tooth brush­ ing frequency with which a healthy gin­

Die Beurteilungseinheiten (Scores) des Gingival-lndex. Die Hiiufigkeitsverteilungen wiihrend der Versuchsperiode. 7, 3 uncl 1 bezeichnet die Hiiufigkeit des Ziihneputzens pro Woche, 0 bezeichnet die Kontrol/gruppe.

kept in mind that for all dogs in all

Repartition (%) durant /es 24 semaines des scores de l'indice gingival pour des frequences de brossage hebdomadaire de 7, 3, J ou 0 (contr6/e) fois.

was executed the day before measure-

giva can be maintained. It should be brushing groups, the last toothbrushing

Gingival health and plaque in beagles

ments were recorded. Plaque removal was effected with the same effort and for the same length of time in all dogs as far as possible and independent of brushing frequency. Differences in plaque scores were still found in the second half of the experiment. Io groups with higher brushing frequencies, less plaque was found. This indicates that with low frequencies of toothbrushing, plaque accumulates during intervals in such amounts that not all plaque can be removed in one brushing session, and some residual plaque might remain. The plaque found at registration might therefore be composed of residual p laque on wruch, within l day, ad­ ditional plaque has accumulated rather rapidly. Lang et al. (1973) reported simi­ lar difficulties in the interpretation of plaque scores. In their study (in hu­ mans), only minor differences in the amounts of plaque were found between groups, whether they brushed every 2, 3 or 4 days, but nevertheless gingivitis developed when the frequency of plaque removal exceeded 48 h. This is not likely to be the result of a difference in microbial composition of the plaque at the different points of time but rather of a longer exposme of the gingivae to the micro-organisms of the plaque (Van Palenstein Helderman 1981). In the once a week brushing group, plaque index scores 2 and 3 were very rare. This was probably due to the brushing session that had taken place the day before the plaque index was recorded. Therefore it is very difficult to draw conclusions from the plaque level in this group before a brushing session. The effect of the removed plaque on the gingival tissues, however, was still seen when the gingival index was analysed. In the once a week brush­ ing group, the plaque index was reduced to plaque that could be detected only with a probe (PII= 1) while the gingival index was 2.0 in 30% of the surfaces. This finding stresses the importance of bleeding on probing as a clinical par­ ameter above plaque index scores. In the 7 and 3 times a week brushing groups and the control group, the re­ lation between plaque index and gin­ gival index was more pronounced. In the present experiment, data were analysed by calculating the brushing ef­ fects in the brusrung groups for every parameter. By using brushing effects, the situation at the start of the exper­ iment and on the control side of the same dog are taken into consideration.

This method may therefore be prefer­ able to other approaches. Corba et al. (1986) have demonstrated clearly that the use of this method is justified in this kind of experiment. When significant differences between the brushing effects were calculated, a statistically significant difference was found only for gingival index between the 7 and 3 times a week brusl1ing group and between the 3 times and the once a week brushing group. With regard to probing depths, Lind­ he et al. (1973) have indicated that pocket formation, i.e., loss of attach­ ment, cannot be expected in less then 18 months. The present experimental period was only 6 months. Indeed an increase in probing depth was observed only in the control groups. This increase has most probably to be attributed to changes in gingival health, i.e., swelling of the gingivae and less resistance to probing forces (Listgarten 1980, Jansen et al. 1981, Van der Velden & Jansen 1981). In the present study, changes in probing depths would therefore appear to be related to changes in gingival health as expressed by the gingivaJ in­ dex. Statistical analysis of the relation­ ship between brushing effects and prob­ ing depths revealed no significant dif­ ference between the 3 brushing groups.

167

The gingival index therefore appeared the most sensitive clinical parameter in the present study. The conclusion therefore is that plaque removal with a frequency of 3 times a week is sufficient to preserve gingival health in beagle dogs, with clinical healthy gingivae at baseline. This critical brushing frequency for the beagle dog is in agreement with the studies of Lang et al. (1973) in humans and Caton (1979) in rhesus monkeys. Acknowledgements

The authors wish to express their grati­ tude to Drs. V. Fidler for his statistical assistance, to Drs. L. J. van Rijo for his great help in developing computer programs and to the staff of the Central Experimental Animal Laboratory of the University of Groningen for their bio­ technical assistance.

Zusammenfassung Gingivale Gesundheit und Hiiufigkeit des Ziih­ neputzens beim Beagle Hund-Versuchsmode/I. Klinische Beobachtungen Mit diesem Experiment hat man beabsichtigt, im Beagle Hund-Versuchsmodell bei 3 ver­ schiedenen Ha ufigkeiten der Plaqueentfer­ nung, klinische Parameter an der gesunden

References Alexander, A. G. (1970) The effect of frequency of brushing and the type of bristle used on gingival inflammation, plaque and calculus accumulation. The Dental Practitioner 20, 347-355.

Ash, M. M. , Gitlin, B. N. & Smith, W. A. (1964) Correlation between plaque and gingivitis. Journal of Periodontology 35, 424-429. Attstriim, R. (1970) Presence of leukocytes in crevices of healthy and chronically inflamed gingivae. Journal of Periodontal Research 5, 42-47. Attstriim, R. & Egelberg, J. (1970) Emigration of blood neutrophils and monocytes into the gingival crevices. Journal of Periodontal Research 5, 48-55.

Attstriim, R. & Egelberg, J. (1971) Presence of leukocytes within the gingival crevices during developing gingivitis in dogs. Journal of Periodontal Research 6, 110-1 14. Attstriim, R. , Graf-de Beer, M. & Schroeder, H. (1975) Clinical and histologic characteristics of normal gingiva in dogs. Joumal of Periodontal Research 10, 115-127.

Borsboom, P. C. F., ten Bosch, J. J., Corba, N. H. C. & Tromp, J. A.H. (1981) A simple constant-force probe. Journal of Periodontology 52, 390-39 l. Caton, J. (1979) Establishing and maintaining clinically healthy gingivae in rhesus monkeys. Journal of Clinical Periodontology 6, 260-263. Corba, N. H. C., Jansen, J. & Fidler, V. (1986) Artificial periodontal defects and frequency of tooth brushing in beagle dogs. I. Clinical findings after creation of the defects. Journal of Clinical Periodonto/ogy, in press. Dahlen, G. , Heijl, L., Lindhe, J. & Moller, A. (1982) Development of plaque and gingivitis following antibiotic therapy in dogs. Journal of Clinical Periodonto/ogy 9, 223-238. Egelberg, J. (1965) Local effect of diet on plaque formation and development of gingivitis in dogs. I. Effect of hard and soft diets. Odontologisk Revy 16, 31-41. Ericsson, J . , Lindhe, J., Rylander, H. & Okamoto, H. (1975) Experimental periodontal breakdown in the dog. Scandinavian Journal of Dental Research 83, 189-192. Hamp, S.-E., Lindhe, J. & Heyden, G. (1972) Experimental gingivitis in the dog. An enzyme histochemical study. Archives of Oral Biology 17, 329-337.

168

Tromp, Jansen and Pilot

Gingiva zu studieren. Bei 12, zu Beginn der Studie 2 Jahre alten BeaglesHunden, wurde beim I. 2. und 3. Priimolaren des Oberkiefers nach sorgfaltiger Reinigung, wiihrend eines 8 Wochen langen vorexperimentellen Zeitab­ sclrnittes, die Plaque sorgfaltig entfernt. Zu Beginn des Versuches wurden die Hunde in 3 Gruppen a 4Hunde eingeteilt. Bei der einen

Hamp, S.-E., Lindhe, J. & Loe, H. (1973) Long-term effect of chlorhexidine on developing gingivitis in the beagle dog. Journal of Periodontal Research 8, 63-70. Heijl, L. & Lindhe, J. (1980) Effect of selective antimicrobial therapy on plaque and gingivitis in the dog. Journal of Clinical Periodontology 7, 463-478. Heijl, L. & Lindhe, J. (1982) The effect of metronidazole on established gingivitis and plaque in beagle dogs. Journal of Periodonto/ogy 53, 180-187. Hock, J. & Tinanoff, N. (1979) Resolution of gingivitis in dogs following topical applications of 0.4% stannous fluoride and toothbrushing. Journal of Dental Research 58, 1652-1653.

Gruppe wurden die Ziihne 7-mal wochent­

Jansen, J., Pi.lot, T. & Corba, N. H. C. (1981) Histologic evaluation of probe penetration

lich, bei einer 2. Gruppe 3-mal in der Woche

during clinical assessment of periodontal attachment levels. An investigation of experimen­

und bei einer anderen Gruppe wurden die Ziihne nur 1-mal in der Woche geputzl. 24

tally induced periodontal lesions in beagle dogs. Journal of Clinical Periodontology 8, 98-106.

Wochen lang wurde die rechte Seite der Ober­

Kelner, R. M., Wohl, B. R., Deasy, M. J. & Formicola, A. J. (1974) Gingival inflammation

kiefer geputzt. Die linke Oberkieferseite dien­

as related to frequency of plaque removal. Journal of Periodontology 45, 303-307.

te der Kontrolle. In regelmiissigen Abstiinden

Lang, N. P., Cumming, B. R. & Loe, H. (1973) Toothbrushing frequency as it relates to

wurde der Plaque Index, der Gingival Index

plaque development and gingival health. Journal of Periodontology 44, 396-405. Lindhe, J. & Ericsson, I. (1978) Effect of ligature placement and dental plaque on periodontal

rcgistricrt und die Taschentiefen sondiert. Fiir jeden Hund wurde ein "Ziihneputzef­ fekt" berechnet,

um

vollstiindige Information

iiber Resultatvariationen bei dem einzelnen Versuchshunde (within dog) und zwischen denHunden (between dog) zu erha.lten. Der Vergleich der Effekte des Ziihneputzens bei

tissue breakdown in the dog. Journal of Periodontology 49, 343-350. Lindhe, J., Hamp, S.-E. & Loe, H. (1973) Experimental periodontitis in the beagle dog. Journal of Periodontal Research 8, 1-10. Lindhe, J., Hamp. S.-E., & Loe, H. (1975) Plaque-induced periodontal disease in beagle dogs. A 4-year clinical, roentgenographical and histometrical study. Journal of Periodontal Research 10, 243-255.

diesem Versuchsmodell zeigte;dass 3-rnal wo­

Lindhe, J. & Hugoson, A. (1969) The influence of estrogen and progesterone on gingival

chentlich vorgenommene Plaqueentfernung

exudation of regenerating dento-gingival tissues. An experimental study on pseudo-pregnant

ausreichte urn die Gesundheit der Gingiva aufrecht zu erhiilten, wiihrend 1-maliges Ziih­ neputzen pro Woche Zahnfleischentziindung zur Folge hatte. Es kann gefolgert werden,