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Amoxycillin with clavulanic acid and tetracycline in periodontal therapy
J. Dent. 1991;
19: 97-99
Amoxycillin tetracycline
97
with clavulanic acid and in periodontal therapy
S. H. Abu Fanas, D. B. Drucker*
and P. S. Hull
Department of Restorative Dentistry University of Manchester, UK
and *Department
of Cell and Structural
Biology,
Turner Dental School,
ABSTRACT The effects of tetracycline and amoxycillin with clavulanic acid on the clinical parameters and subgingival flora of eight patients with rapidly progressive periodontitis was assessed. Subjects received either tetracycline 250 mg four times daily or amoxycillin 250 mg with clavulanic acid 125 mg three times daily for a period of 2 weeks together with subgingival scaling and root planing. Both treatment regimens produced significant reductions in bleeding on probing and probing pocket depths which were still present 16 weeks after the antibiotic therapy. A significant reduction in the mean percentage of black-pigmented Bacreroides spp., Fusobacterium nucfeatum and anaerobic corroding bacilli was also obtained. Both treatment regimens were equally effective in reducing the clinical parameter and altering the subgingival flora. The MIC values for Bacteroides gingivalis (Porphyromonas gingivalis), Bacteroides intermedius (Prevotella intermedia) and F. nucleatum to amoxycillin with clavulanic acid remained constant throughout the period of investigation. The MIC values of these organisms to tetracycline increased. KEY WORDS: Antibiotics, Periodontal therapy .I. Dent. 1991; 1990)
19: 97-99
(Received 23 July 1989;
reviewed 25 September
1989;
accepted 28 October
Correspondence should be addressed to: Mr P. S. Hull, Department of Restorative Dentistry, Turner Dental School, University of Manchester, Manchester Ml 5 6FH. UK.
INTRODUCTION The use of antimicrobial agents as adjuncts to conventional therapy of plaque associated inflammatory periodontal diseases has attracted considerable interest. A number of antimicrobial agents have been investigated (Listgarten et al., 1978; Slots et al., 1979; Loesche et al., 1981; Lindhe et al., 1983; Van-Oosten et al., 1986; Magnussenetal., 1989). Tetracycline is the most extensively used agent as an adjunct in the treatment of periodontal diseases. It is however bacteriostatic and Van Palenstein Helderman (1986) suggested that if there is a place for antibiotics in the treatment of periodontal diseases bactericidal antibiotics would be preferred. Metronidazole has also been widely investigated and is very active against strictly anaerobic microorganisms. However, Actinobacillus actinomycetemcomitans is a facultative capnophilic Gram-negative rod and therefore resistant to metronidazole. It is important in the aetiology of localized juvenile periodontitis’(Slots and Genco, 1984) and severe @1991 ButteMrorth-Heinemann 0300-5712/91/020097-03
Ltd.
periodontitis in young adults (Slots et al., 1986). To overcome some of these limitations, combinations of antibiotics, i.e. metronidazole and amoxycillin, have been used by Van Winkelhoff et al. (1989). They suggested that metronidazole might act synergistically with amoxycillin. Amoxycillin in combination with clavulanic acid is a broad-spectrum bactericidal antibiotic. Its effectiveness against periodontal pathogens has been demonstrated in vitro (Abu Fanas et al., 1991) and in viva (Magnusson et al., (1990). In this latter study the subgingival flora was almost devoid of Gram-negative anaerobes that have been traditionally associated with ‘active’ disease sites (Walker et al., 1988). The purpose of this preliminary investigation was to compare the effect of amoxycillin with clavulanic acid and tetracycline on clinical parameters and anaerobic Gram-negative rods from the subgingival flora in patients with rapidly progressive periodontitis.
98
J. Dent. 1991; 19: No. 2
Tab/e/. Effectsof amoxycillin with clavulanicacid (A + C) ortetracycline (T) on mean percentageof pockets that bleed on probing (+ s.d.) and mean probing pocket depths (+ s.d.)
A+C Week Week Week Week Week
0 1 2 6 18
68.6 39.8 27.0 19.1 22.3
f + f f f
Bleeding on probing T 19.3 5.6* 5.7* 4.1* 10.3*
58.0 39.2 29.2 20.3 23.9
+ f + ? f
Sig.
15.9 15.6* 14.1* 6.7* 7.4*
n.s. n.s. n.s. ns. n.s.
Probing pocket depth (mm) T Sig.
A+C 4.1 3.5 3.1 2.7 2.5
* * * + f
0.2 0.4* 0.5* 0.2* 0.4*
4.3 4.2 3.9 3.3 2.9
+ f f f f
0.7 0.7 0.6* 0.3* 0.6*
n.s. n.s. P :::05 n.s.
n-s., Not significant. *Significant reductionfrom the baseline (P < 0.05).
Tab/e II. Effects of amoxycillin with clavulanic acid (A + C) or tetracycline (T) on the subgingival proportions of selected anaerobes Fusobacterium nucleatum T A+C
Black-pigmented Bacteroides spp. A+C T Week Week Week Week Week
0 1 2 6 18
26 k 2.3 1.1 * 2** 2.8 fN2G4** 5.9 f s:s*
16.3 + 6.5 2.7 f 5.1* 1.5 +Y7** 5.4 f 4:8*
20.2 + 5.8 0.1 1 + 0.3** NG 2.7 + 5.0** 2.5 f 3.4*
15.7 + 8.7 4.2 + 0.7 NG 1.2 * 1.5* 3.1 + 6.8*
Anaerobic corroding bacilli A+C T 12.4 + 6.4 0.08 + 0.2 NG 2.::
6.8
5.5 + 3.9 0.4 f 0.6 NG 0:5 6 4 f+ 0.7 1
*
P < 0.05. ** P
MATERIALS
AND METHOD
selected for this study were referred to the Periodontal Clinic of the University Dental Hospital of Manchester and were diagnosed as having ‘rapidly progressive periodontitis’ using the criteria of Page and Schroeder (1982). None of the patients had received antibiotic treatment in the previous 6 months. At the baseline examination, probing pocket depths and bleeding on probing were assessed using the method described by Torfason et al. (1979). Recordings were made on the mesial and distal aspects of each tooth. A bacteriological sample was removed from the apical portion of two periodontal pockets with a depth of at least 6 mm from each patient using a sterile curette. In an attempt to minimize contamination bacterial plaque was first removed from the supragingival region and the coronal portion of the pocket. Viable counts of blackpigmented Bacteroides spp., Fusobacterium nucleatum and anaerobic corroding bacilli (Bacteroides gracilis) were determined using selective media as described by Abu Fanas et al. (1991). The sensitivity of the subgingival microflora to tetracycline and amoxycillin with clavulanic acid was determined by the method previously described (Abu Fanas et al., 1991). Following these baseline examinations, the patients received a supragingival scale and oral hygiene instruction and were randomly allocated to Group A who received tetracycline hydrochloride 250 mg four times daily for 14 days or Group B who received amoxycillin 250 mg with clavulanic acid 125 mg three times daily for Patients
14 days. In addition, all patients received full mouth subgingival scaling and root planing. Local anaesthesia was used when necessary. Supragingival plaque control was maintained throughout the experimental period with further scaling and oral hygiene instruction where necessary. Clinical assessments and bacteriological sampling were repeated at 7 days, 14 days, 42 days and 126 days from the baseline examination. The results were analysed using Student’s t test for paired and unpaired data.
RESULTS Eight patients completed the study. Each group consisted of three females and one male. No adverse effects from the drug therapy were reported and none of the patients received any other antibiotic therapy during the experimental period. Both treatment regimens resulted in a reduction in the percentage of sites that bled on probing and probing pocket depth measurements (Table I). Reductions in bleeding on probing were obtained at each assessment except at the final assessment when a small but nonsignificant increase over the previous assessment occurred. Reductions in probing pocket depths were significant over the baseline measurements from week 1 in the amoxycillin with clavulanic acid group and week 2 in the tetracycline group. No significant differences between the two treatment regimens was obtained except at week 6 for probing pocket depths.
Abu
Fanas
et al.: Antibiotics
in periodontal
therapy
Table 111. Minimum inhibiting concentration in milligrams per litre of 6. intermedius, B. gingivalis nucleatum to amoxycillin with clavulanic acid (A + C) and tetracycline (T) A +B6 intermedius
B. gingivalis T
Week Week Week
0 6 18
0.03-0.06 0.03-0.06 0.03-0.06
0.03-0.125 0.06-8.0 0.03-8.0
A+C 0.015-0.06 0.03-0.06 0.03-0.06
The changes in the subgingival microflora are given in Table II. A significant reduction in the mean percentage of black-pigmented Bacteroides spp., F. nucleatum and anaerobic corroding bacilli at the end of week 1 over the baseline levels was obtained in the amoxycillin with clavulanic acid group. No growth was obtained at week 2. A significant reduction in the percentage of test organisms was obtained at weeks 6 and 18. In the tetracycline group a significant reduction was obtained only for blackpigmented Bacteroides spp. at the week 1 assessment. No growth of the test organisms was obtained at the week 2 assessment and a significant reduction in black-pigmented Bacteroides and E nucleatum was obtained at weeks 6 and 18.A non-significant reduction in anaerobic corroding bacilli was found at weeks 1, 6 and 18. No significant differences were detected between the groups. The MIC values for B. gingivalis (Porphyromonas gingivalis), B. intermedius (Prevotella intermedia) and F. nucleatum to amoxycillin with clavulanic acid remained constant throughout the study (Table III). The MIC values of these organisms to tetracycline increased from the baseline and with the exception of F. nucleatum the increase was present at week 18.
DISCUSSION
This study demonstrated that both tetracycline and amoxycillin with clavulanic acid significantly altered the clinical and microbiological parameters of rapidly progressive periodontitis. Magnusson et al. (1989) suggested that amoxycillin with clavulanic acid was a useful adjunct in the treatment of a subset of patients ‘refractory’ to conventional therapy and harbouring a tetracycline-resistant microflora. They were unable to demonstrate whether this antimicrobial agent would prove as effective against a predominantly Gramnegative microflora. In this study, amoxycillin with clavulanic acid proved equally as effective as tetracycline against the Gram-negative bacteria studied and in addition no resistant strains developed. The complete elimination of the anaerobic Gram-negative bacteria was a surprising result. Although this was mainly due to the effectiveness of the antibacterial agents, it may in part reflect the difficulty of sampling and culturing anaerobic Gram-negative rods in relatively small numbers. Some evidence of recolonization of the pockets by the Gramnegative bacteria was observed at the final visit and at the same time some increase in bleeding on probing occurred.
99
and F.
F. nucleatum T
A+C
T
0.06-0.08 0.06-8.0 0.06-8.0
0.03-0.06 0.03-0.06 0.03-0.06
0.06-0.5 0.06-8.0 0.06-0.5
Although the size of this study precludes long term conclusions, amoxycillin with clavulanic acid would appear to be suitable for use as an adjunctive antibacterial agent in the management of some plaque-associated inflammatory periodontal diseases. Long term studies are required. References Abu Fanas S. H., Drucker D. B. and Hull P. S. (1991) Identification and susceptibility to seven antimicrobial agents of 61 Gram-negative anaerobic rods from periodontal pockets. J. Dent. 19,46-50. Lindhe J., Liljenberg B., Adielson B. et al. (1983) Use of metronidazole as a probe in the study of human periodontal disease. J Clin. Periodontal. 10, 100-l 12. Listgarten M. A., Lindhe J. and Hellden L. (1978) Effect of tetracycline and/or scaling on human periodontal disease. J Clin. Periodontal. 5, 246-271. Loesche W. J., Syed S. A, Morrison E. C. et al. (1981) Treatment of periodontal infections due to anaerobic bacteria with short term treatment with metronidazole. J. Clin. Periodontol. 8, 29-44. Magnusson I., Clark W. B., Low S. B. et al. (1990) Effect of non surgical periodontal therapy combined with adjunctive antibiotics in subjects with ‘refractory’ periodontal disease. J. Clin. Periodontol. 16, 647-653. Page R. C. and Schroeder H. E. (1982) Periodontitis in Man and Other Animals. Basel, Karger, 330~~. Slots J. and Genco R. J. (1984) Black pigmented Bacteroides species, Capnocytophaga species and Actinobacillus actinomycetemcomitans in human periodontal disease: virulence factors in colonization, survival and tissue destruction. J. Dent. Res. 63,412-421. Slots J., Mashino P., Levine M. J. et al. (1979) Periodontal therapy in humans. J. Periodontal. 50,495-509. Slots J., Bnagd L., Wikstrom M. et al. (1986) The occurrence of Actinobacillus actinomycetemcomitans, Bacteroides gingivalis and Bacteroides intermedius in destructive periodontal disease in adu1ts.J. Clin. Periodontal. 13,570-577. Torfason T., Riger R., Selvig K. A et al. (1979) Clinical improvement of gingival conditions following ultrasonic versus hand instrumentations of periodontal pockets. .I. Clin. Periodon tol. 6, 165- 176. Van Oosten M., Hug H., Mikx F. et al. (1986) The effect of amoxycillin on destructive periodontitis. A case report. J. Periodontal. 57, 613-616. Van Palenstein Helderman W. H. (1986) Is antibiotic therapy justified in the treatment of human chronic inflammatory periodontal disease? J. Clin. Periodontal. 13,932-938. Van Winkelhoff A. J., Rodenberg J. P., Goene R. J. et al. (1989) Metronidazole plus amoxycillin in the treatment of Actinobacillus actinomycetemcomitans associated periodontitis. J. Clin. Periodontal. 16, 128-131. Walker C., Bueno L. and Van Ness W. (1988) Bacterial flora associated with refractory periodontitis before and after therapy. .I Dent. Res. 67, (Abstr. 211) 786.
19: 97-99
Amoxycillin tetracycline
97
with clavulanic acid and in periodontal therapy
S. H. Abu Fanas, D. B. Drucker*
and P. S. Hull
Department of Restorative Dentistry University of Manchester, UK
and *Department
of Cell and Structural
Biology,
Turner Dental School,
ABSTRACT The effects of tetracycline and amoxycillin with clavulanic acid on the clinical parameters and subgingival flora of eight patients with rapidly progressive periodontitis was assessed. Subjects received either tetracycline 250 mg four times daily or amoxycillin 250 mg with clavulanic acid 125 mg three times daily for a period of 2 weeks together with subgingival scaling and root planing. Both treatment regimens produced significant reductions in bleeding on probing and probing pocket depths which were still present 16 weeks after the antibiotic therapy. A significant reduction in the mean percentage of black-pigmented Bacreroides spp., Fusobacterium nucfeatum and anaerobic corroding bacilli was also obtained. Both treatment regimens were equally effective in reducing the clinical parameter and altering the subgingival flora. The MIC values for Bacteroides gingivalis (Porphyromonas gingivalis), Bacteroides intermedius (Prevotella intermedia) and F. nucleatum to amoxycillin with clavulanic acid remained constant throughout the period of investigation. The MIC values of these organisms to tetracycline increased. KEY WORDS: Antibiotics, Periodontal therapy .I. Dent. 1991; 1990)
19: 97-99
(Received 23 July 1989;
reviewed 25 September
1989;
accepted 28 October
Correspondence should be addressed to: Mr P. S. Hull, Department of Restorative Dentistry, Turner Dental School, University of Manchester, Manchester Ml 5 6FH. UK.
INTRODUCTION The use of antimicrobial agents as adjuncts to conventional therapy of plaque associated inflammatory periodontal diseases has attracted considerable interest. A number of antimicrobial agents have been investigated (Listgarten et al., 1978; Slots et al., 1979; Loesche et al., 1981; Lindhe et al., 1983; Van-Oosten et al., 1986; Magnussenetal., 1989). Tetracycline is the most extensively used agent as an adjunct in the treatment of periodontal diseases. It is however bacteriostatic and Van Palenstein Helderman (1986) suggested that if there is a place for antibiotics in the treatment of periodontal diseases bactericidal antibiotics would be preferred. Metronidazole has also been widely investigated and is very active against strictly anaerobic microorganisms. However, Actinobacillus actinomycetemcomitans is a facultative capnophilic Gram-negative rod and therefore resistant to metronidazole. It is important in the aetiology of localized juvenile periodontitis’(Slots and Genco, 1984) and severe @1991 ButteMrorth-Heinemann 0300-5712/91/020097-03
Ltd.
periodontitis in young adults (Slots et al., 1986). To overcome some of these limitations, combinations of antibiotics, i.e. metronidazole and amoxycillin, have been used by Van Winkelhoff et al. (1989). They suggested that metronidazole might act synergistically with amoxycillin. Amoxycillin in combination with clavulanic acid is a broad-spectrum bactericidal antibiotic. Its effectiveness against periodontal pathogens has been demonstrated in vitro (Abu Fanas et al., 1991) and in viva (Magnusson et al., (1990). In this latter study the subgingival flora was almost devoid of Gram-negative anaerobes that have been traditionally associated with ‘active’ disease sites (Walker et al., 1988). The purpose of this preliminary investigation was to compare the effect of amoxycillin with clavulanic acid and tetracycline on clinical parameters and anaerobic Gram-negative rods from the subgingival flora in patients with rapidly progressive periodontitis.
98
J. Dent. 1991; 19: No. 2
Tab/e/. Effectsof amoxycillin with clavulanicacid (A + C) ortetracycline (T) on mean percentageof pockets that bleed on probing (+ s.d.) and mean probing pocket depths (+ s.d.)
A+C Week Week Week Week Week
0 1 2 6 18
68.6 39.8 27.0 19.1 22.3
f + f f f
Bleeding on probing T 19.3 5.6* 5.7* 4.1* 10.3*
58.0 39.2 29.2 20.3 23.9
+ f + ? f
Sig.
15.9 15.6* 14.1* 6.7* 7.4*
n.s. n.s. n.s. ns. n.s.
Probing pocket depth (mm) T Sig.
A+C 4.1 3.5 3.1 2.7 2.5
* * * + f
0.2 0.4* 0.5* 0.2* 0.4*
4.3 4.2 3.9 3.3 2.9
+ f f f f
0.7 0.7 0.6* 0.3* 0.6*
n.s. n.s. P :::05 n.s.
n-s., Not significant. *Significant reductionfrom the baseline (P < 0.05).
Tab/e II. Effects of amoxycillin with clavulanic acid (A + C) or tetracycline (T) on the subgingival proportions of selected anaerobes Fusobacterium nucleatum T A+C
Black-pigmented Bacteroides spp. A+C T Week Week Week Week Week
0 1 2 6 18
26 k 2.3 1.1 * 2** 2.8 fN2G4** 5.9 f s:s*
16.3 + 6.5 2.7 f 5.1* 1.5 +Y7** 5.4 f 4:8*
20.2 + 5.8 0.1 1 + 0.3** NG 2.7 + 5.0** 2.5 f 3.4*
15.7 + 8.7 4.2 + 0.7 NG 1.2 * 1.5* 3.1 + 6.8*
Anaerobic corroding bacilli A+C T 12.4 + 6.4 0.08 + 0.2 NG 2.::
6.8
5.5 + 3.9 0.4 f 0.6 NG 0:5 6 4 f+ 0.7 1
*
P < 0.05. ** P
MATERIALS
AND METHOD
selected for this study were referred to the Periodontal Clinic of the University Dental Hospital of Manchester and were diagnosed as having ‘rapidly progressive periodontitis’ using the criteria of Page and Schroeder (1982). None of the patients had received antibiotic treatment in the previous 6 months. At the baseline examination, probing pocket depths and bleeding on probing were assessed using the method described by Torfason et al. (1979). Recordings were made on the mesial and distal aspects of each tooth. A bacteriological sample was removed from the apical portion of two periodontal pockets with a depth of at least 6 mm from each patient using a sterile curette. In an attempt to minimize contamination bacterial plaque was first removed from the supragingival region and the coronal portion of the pocket. Viable counts of blackpigmented Bacteroides spp., Fusobacterium nucleatum and anaerobic corroding bacilli (Bacteroides gracilis) were determined using selective media as described by Abu Fanas et al. (1991). The sensitivity of the subgingival microflora to tetracycline and amoxycillin with clavulanic acid was determined by the method previously described (Abu Fanas et al., 1991). Following these baseline examinations, the patients received a supragingival scale and oral hygiene instruction and were randomly allocated to Group A who received tetracycline hydrochloride 250 mg four times daily for 14 days or Group B who received amoxycillin 250 mg with clavulanic acid 125 mg three times daily for Patients
14 days. In addition, all patients received full mouth subgingival scaling and root planing. Local anaesthesia was used when necessary. Supragingival plaque control was maintained throughout the experimental period with further scaling and oral hygiene instruction where necessary. Clinical assessments and bacteriological sampling were repeated at 7 days, 14 days, 42 days and 126 days from the baseline examination. The results were analysed using Student’s t test for paired and unpaired data.
RESULTS Eight patients completed the study. Each group consisted of three females and one male. No adverse effects from the drug therapy were reported and none of the patients received any other antibiotic therapy during the experimental period. Both treatment regimens resulted in a reduction in the percentage of sites that bled on probing and probing pocket depth measurements (Table I). Reductions in bleeding on probing were obtained at each assessment except at the final assessment when a small but nonsignificant increase over the previous assessment occurred. Reductions in probing pocket depths were significant over the baseline measurements from week 1 in the amoxycillin with clavulanic acid group and week 2 in the tetracycline group. No significant differences between the two treatment regimens was obtained except at week 6 for probing pocket depths.
Abu
Fanas
et al.: Antibiotics
in periodontal
therapy
Table 111. Minimum inhibiting concentration in milligrams per litre of 6. intermedius, B. gingivalis nucleatum to amoxycillin with clavulanic acid (A + C) and tetracycline (T) A +B6 intermedius
B. gingivalis T
Week Week Week
0 6 18
0.03-0.06 0.03-0.06 0.03-0.06
0.03-0.125 0.06-8.0 0.03-8.0
A+C 0.015-0.06 0.03-0.06 0.03-0.06
The changes in the subgingival microflora are given in Table II. A significant reduction in the mean percentage of black-pigmented Bacteroides spp., F. nucleatum and anaerobic corroding bacilli at the end of week 1 over the baseline levels was obtained in the amoxycillin with clavulanic acid group. No growth was obtained at week 2. A significant reduction in the percentage of test organisms was obtained at weeks 6 and 18. In the tetracycline group a significant reduction was obtained only for blackpigmented Bacteroides spp. at the week 1 assessment. No growth of the test organisms was obtained at the week 2 assessment and a significant reduction in black-pigmented Bacteroides and E nucleatum was obtained at weeks 6 and 18.A non-significant reduction in anaerobic corroding bacilli was found at weeks 1, 6 and 18. No significant differences were detected between the groups. The MIC values for B. gingivalis (Porphyromonas gingivalis), B. intermedius (Prevotella intermedia) and F. nucleatum to amoxycillin with clavulanic acid remained constant throughout the study (Table III). The MIC values of these organisms to tetracycline increased from the baseline and with the exception of F. nucleatum the increase was present at week 18.
DISCUSSION
This study demonstrated that both tetracycline and amoxycillin with clavulanic acid significantly altered the clinical and microbiological parameters of rapidly progressive periodontitis. Magnusson et al. (1989) suggested that amoxycillin with clavulanic acid was a useful adjunct in the treatment of a subset of patients ‘refractory’ to conventional therapy and harbouring a tetracycline-resistant microflora. They were unable to demonstrate whether this antimicrobial agent would prove as effective against a predominantly Gramnegative microflora. In this study, amoxycillin with clavulanic acid proved equally as effective as tetracycline against the Gram-negative bacteria studied and in addition no resistant strains developed. The complete elimination of the anaerobic Gram-negative bacteria was a surprising result. Although this was mainly due to the effectiveness of the antibacterial agents, it may in part reflect the difficulty of sampling and culturing anaerobic Gram-negative rods in relatively small numbers. Some evidence of recolonization of the pockets by the Gramnegative bacteria was observed at the final visit and at the same time some increase in bleeding on probing occurred.
99
and F.
F. nucleatum T
A+C
T
0.06-0.08 0.06-8.0 0.06-8.0
0.03-0.06 0.03-0.06 0.03-0.06
0.06-0.5 0.06-8.0 0.06-0.5
Although the size of this study precludes long term conclusions, amoxycillin with clavulanic acid would appear to be suitable for use as an adjunctive antibacterial agent in the management of some plaque-associated inflammatory periodontal diseases. Long term studies are required. References Abu Fanas S. H., Drucker D. B. and Hull P. S. (1991) Identification and susceptibility to seven antimicrobial agents of 61 Gram-negative anaerobic rods from periodontal pockets. J. Dent. 19,46-50. Lindhe J., Liljenberg B., Adielson B. et al. (1983) Use of metronidazole as a probe in the study of human periodontal disease. J Clin. Periodontal. 10, 100-l 12. Listgarten M. A., Lindhe J. and Hellden L. (1978) Effect of tetracycline and/or scaling on human periodontal disease. J Clin. Periodontal. 5, 246-271. Loesche W. J., Syed S. A, Morrison E. C. et al. (1981) Treatment of periodontal infections due to anaerobic bacteria with short term treatment with metronidazole. J. Clin. Periodontol. 8, 29-44. Magnusson I., Clark W. B., Low S. B. et al. (1990) Effect of non surgical periodontal therapy combined with adjunctive antibiotics in subjects with ‘refractory’ periodontal disease. J. Clin. Periodontol. 16, 647-653. Page R. C. and Schroeder H. E. (1982) Periodontitis in Man and Other Animals. Basel, Karger, 330~~. Slots J. and Genco R. J. (1984) Black pigmented Bacteroides species, Capnocytophaga species and Actinobacillus actinomycetemcomitans in human periodontal disease: virulence factors in colonization, survival and tissue destruction. J. Dent. Res. 63,412-421. Slots J., Mashino P., Levine M. J. et al. (1979) Periodontal therapy in humans. J. Periodontal. 50,495-509. Slots J., Bnagd L., Wikstrom M. et al. (1986) The occurrence of Actinobacillus actinomycetemcomitans, Bacteroides gingivalis and Bacteroides intermedius in destructive periodontal disease in adu1ts.J. Clin. Periodontal. 13,570-577. Torfason T., Riger R., Selvig K. A et al. (1979) Clinical improvement of gingival conditions following ultrasonic versus hand instrumentations of periodontal pockets. .I. Clin. Periodon tol. 6, 165- 176. Van Oosten M., Hug H., Mikx F. et al. (1986) The effect of amoxycillin on destructive periodontitis. A case report. J. Periodontal. 57, 613-616. Van Palenstein Helderman W. H. (1986) Is antibiotic therapy justified in the treatment of human chronic inflammatory periodontal disease? J. Clin. Periodontal. 13,932-938. Van Winkelhoff A. J., Rodenberg J. P., Goene R. J. et al. (1989) Metronidazole plus amoxycillin in the treatment of Actinobacillus actinomycetemcomitans associated periodontitis. J. Clin. Periodontal. 16, 128-131. Walker C., Bueno L. and Van Ness W. (1988) Bacterial flora associated with refractory periodontitis before and after therapy. .I Dent. Res. 67, (Abstr. 211) 786.