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Bacteriology of Most Frequent Oral Anaerobic Infections
Anaerobe (1999) 5, 221±227 Article No. anae.1999.0204
ORAL MICROBIOLOGYAND RELATED INFECTIONS (FACULTY PRESENTATION)
Bacteriology of Most Frequent Oral Anaerobic Infections S. Piovano School of Dentistry, MaimoÂnides University, Buenos Aires, Argentina
Key Words: oral anaerobic infections
The anaerobic infections most frequently found in the oral cavity are gingivoperiodontal diseases and pulpal and periapical infections. Gingivitis and adult periodontitis are the most frequent forms. In adult periodontitis the subgingival microbiota are complex and there is a prevalence of Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Peptostreptococcus micros, Campylobacter rectus, and species of Fusobacterium, Eikenella and Treponema. The microflora associated with peri-implant infections are similar to the microflora found in periodontal diseases, particularly in partially edentulous patients. Implant placement is therefore not recommended in patients presenting with uncontrolled periodontal disease. Likewise, there is a similarity between the genera identified in periodontal pockets and infected root canals, and in periapical infections. However, some species are more prevalent than others in both infections. The following were predominantly observed inside the root canals: Prevotella intermedia, Prevotella nigrescens, Peptostreptococcus anaerobius, Peptostreptococcus micros, Eubacterium lentum, Eubacterium alactolyticum and Porphyromonas endodontalis, with strong associations among some species. Pericoronaritis is another infection associated with anaerobic Gramnegative bacilli and treponeme. There are a great number of methods for microbiological diagnosis, and treatment of some oral infections depends on close interaction between the microbiologist and the dentist. # 1999 Academic Press
Introduction The oral cavity is the habitat of numerous microbial species. It has been observed that 1 g of dental plaque contains more than 1011 micro-organisms [1]. Many indigenous flora are anaerobes and these microorganisms can be associated with oral infections and be the origin of distant infections [1±9]. The most frequent oral anaerobic infections include gingivoper1075±9964/99/030221 + 07 $30.00/0
iodontal diseases, pulpal and periapical infections, peri-implantitis and pericoronarities.
Gingivoperiodontal Diseases Gingivoperiodontal diseases, including gingivitis and periodontitis, are caused by dental plaque, which is a biofilm [10,11]. # 1999 Academic Press
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Microbial species associated with gingivitis Studies have demonstrated that the dental plaque associated with gingivitis presents a high burden of micro-organisms (104±106) and an increase in anaerobic Gram-negative organisms (15±50%) [10]. Culture studies of the plaque near the marginal gum have demonstrated a prevalence of Actinomyces species [12]. Likewise, culture studies indicate that Fusobacterium nucleatum, Prevotella intermedia, Campylobacter species and Veillonella are frequently isolated from plaque samples associated with gingivitis [12]. Spirochaetes can be found mainly at the apical subgingival area. Gingivitis can be worsened by steroid hormones. In puberty, pregnancy and women taking oral contraceptives, it has been shown that gingival disease is associated with an inadequate plaque control, worsened by steroid hormones that stimulate the growth of Prevotella intermedia [13±15]. Acute necrotizing ulcerative gingivitis is a destructive inflammatory disease associated with species of Selenomonas, Porphyromonas, Prevotella, Fusobacterium and Treponema [4,16]. The prevalent bacteria are Prevotella intermedia and spirochaetes and Prevotella intermedia represents between 8% and 15% of the microbiota. Spirochaetes represent approximately 30% of the morphotypes that are present with medium and large spirochaetes being prevalent. Studies by Transmission Electron Microscopy have shown the invasion of tissues by spirochetes [17±19]. Microbial species associated with periodontitis Adult periodontitis. An increase in the total microbial burden (105±108 micro-organisms) and high levels of Porphyromonas gingivalis have been observed in adult periodontitis [10]. Porphyromonas gingivalis, Bacteroides forsythus and Actinobacillus actinomycetemcomitans have been identified as causative agents, and not as agents merely associated with disease [10]. The micro-organisms specifically implied are Porphyromonas gingivalis, Bacteroides forsythus, P. intermedia, Prevotella nigrescens and Actinobacillus actinomycetemcomitans. A second group of micro-organisms include F. nucleatum, Campylobacter rectus, Eikenella corrodens, Eubacterium nodatum, Selenomonas noxia, Peptostreptococcus micros, Streptococcus intermedius and Treponema denticola [2,20±33]. Adult periodontitis is associated with a group of bacteria and different microbial complexes have been described from subgingival plaque samples [10,34,35]. Many transmission studies have demonstrated that the same clonal types of P. gingivalis, A. actinomycetemcomitans and T. denticola can be found in members
of the family [36±40]. Porphyromonas gingivalis, A. actinomycetemcomitans and T. denticola penetrate the gingival epithelium, and they have endotoxins, active compounds and cytotoxic enzymes which act upon the host [21,41±44]. Spirochetes constitute 37±56% of the flora [19] and all morphogroups are detected with a prevalance of small and medium spirochetes [25,26,45]. The microflora are necessary to produce and allow progression of disease, modulated by host factors and lifestyle [33,46].
Rapidly progressing periodontitis. It affects young individuals and has a rapid evolution. Prevalent bacteria in active sites are A. actinomycetemcomitans, P. gingivalis, P. intermedia, F. nucleatum, T. denticola, B. forsythus and Campylobacter species [47]. Kamma et al. [47] have examined the microflora of severe, moderate and minimal lesions in young adults with rapidly progressing periodontitis, and have observed microbial complexes associated with severe and moderate lesions, while in small lesions species of Antinomyces and Streptococcus, Capnocytophaga ochracea, Haemophilus segnis and Veillonella parvula were identified.
Juvenile periodontitis. Juvenile periodontitis affects adolescents and is characterized by a rapid destruction of periodontal tissues [4]. The major microorganism related to juvenile periodontitis is A. actinomycetemcomitans [4,44,48]. A. actinomycetemcomitans has been considered as an agent of exogen infection in periodontitis [31,44], in patients with early-onset periodontitis and adult periodontitis it has been frequently isolated from periodontal pockets and other ecological niches of the oral cavity [44,48,49]. Epidemiological studies have shown that this microorganism can be transmitted by members of the family [36±39]. The introduction of the bacteria into the oral cavity is facilitated by the presence of frequent contacts and high inoculation doses [38]. Although A. actinomycetemcomitans is the major species related to juvenile periodontitis, high rates of P. gingivalis, Capnocytophaga, E. corrodens, F. nucleatum and Eubacterium brachy have been observed.
Prepubertal periodontitis. The main features are a rapid and severe destruction of deciduous teeth. In the generalized form the patients have defects in polymorphonuclear neutrophils and macrophages [4]. They usually present with other infections as well as periodontal lesions. The prevalent micro-organism is A. actinomycetemcomitans frequently associated with
Frequent oral anaerobic infections Capnocytophaga sputigena, P. intermedia and E. corrodens [4]. Refractory periodontitis. The species identified in active sites have been: P. gingivalis, A. actinomycetemcomitans, F. nucleatum, P. micros, C. rectus, B. forsythus, P. intermedia and E. corrodens. Some of these bacteria were isolated inside the gingiva in samples from biopsies of the active disease sites [50,51]. Periodontal abscess. There is a wide range of bacteria present in abscesses, which can exist in the plaque adhered to the tooth, or be free at the apical portions or adhered to the soft wall of the pocket. The prevailing micro-organisms are: P. micros, P. gingivalis, Fusobacterium spp., Capnocytophaga spp., Actinomyces spp. and species of oral streptococcus. Periodontal microbiota and halitosis. Halitosis has frequently been associated with gingivoperiodontal infection [52]. T. denticola, P. gingivalis, Veillonella species and Fusobacterium have all been associated with halitosis [53,54]. Halitosis can also be associated with flora of the tongue and flora lower down the gastro-intestinal tract. A direct relation between halitosis, the tongue's covering, and subgingival plaque has been observed [55].
Pulpal and Periapical Infections Micro-organisms reach the pulp in various ways. The most frequent are: fracture of dental tissues, as a result of natural history of dental caries; or through tubules of exposed dentine in the surface of root as a result of fissures or radicular caries. Likewise, the pulp can be infected by the microbial flora of the periodontal pocket and by dental procedures [56]. When anaerobic Gram-negative bacilli are prevalent in an endodontic infection, they release lipopolysaccharides and a periapical periodontitis is initialized at the periapex [5,57±62]. Sundqvist [63] analysed the microflora of root canals of teeth with apical periodontitis according to the frequency of occurrence and the analysis of association between bacteria. Results have shown that the most frequent species isolated was F. nucleatum, present in 45% of the root canals. Likewise, P. intermedia, P. micros, Peptostreptococcus anaerobius, Eubacterium alactolyticum, Eubacterium lectum and Capnocytophaga rectus were the prevalent species in this kind of infections. F. nucleatum showed a positive association with P. micros, Porphyromonas endodontalis, Selenomonas sputigena and C. rectus. A positive association was seen between P. intermedia and P. micros, P. anaerobius and E. lectum, and E. alactolyticum and C. rectus.
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Many authors have reported that the presence of species of the genera Porphyromonas, Prevotella and Peptostreptococcus are associated with an increase in the incidence of clinical symptoms of pain and sensitivity to pressure on the teeth [63±71]. Acute symptoms have been associated with Prevotella buccae, P. intermedia, P. gingivalis, P. endodontalis and Peptostreptococcus magnus [66,67,71]. Conrads et al. [72] analysed samples from nectrotic root canals using PCR and have observed species of Actinomyces, F. nucleatum, Streptococcus milleri and B. forsythus, the latter having not been shown previously in endodontic samples. Nair Ramachandran et al. [73] examined through microscopic studies the apex of endodontically treated teeth presenting a periapical lesion in the radiography after a post-treatment period of 4 to 10 years. Extraradicular presence of bacteria and yeast was observed in the teeth with infection following endodontic therapy [62,73,74]. Gomes et al. [65] observed the presence of Prevotella, Peptostreptococcus, Eubacterium and Propionibacterium spp. in these refractory lesions. In periapical abscesses, 75% to 94% of the flora are anaerobes. Species of Prevotella and Porphyromonas have frequently been isolated. P. gingivalis, P. endodontalis and P. intermedia are the prevalent species [68,75] and other Prevotella species identified in abscesses are Prevotella oralis, Prevotella oris, and Prevotella buccae [68,75]. P. anaerobius, P. micros, Peptostreptococcus prevotti and P. magnus are the prevalent Peptostreptococcus species [65]. Species of Veillonella, Eubacterium, Actinomyces and Fusobacterium are frequently isolated [64,65]. `Viridans streptococci', facultative anaerobes, are present in periapical infections associated with anaerobes [56]. Figure 1 shows the micro-organisms most frequently isolated from endodontic infections.
Peri-implantitis Various criteria originally used for the study of periodontal diseases have been applied to implantology [29,76,77]. The sulcus of relatively healthy implants with stable probing depth (3±5 mm for 1 year) has shown by MCO a prevalence of non-mobile bacteria. Cocoid cells prevail in those sites (64.2%). In culture, the microbiota are poor, dominated by facultative anaerobic Gram-positive cocci [78±83]. The microbial infection can lead to two different clinical manifestations: (1) a lesion limited to inflammation of superficial soft tissues (mucositis); and (2) a lesion comprising soft tissues and the marginal portion of the implant±bone interface (peri-implantitis) [77]. The presence of remnant teeth with any untreated or badly controlled periodontal disease enhances
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Figure 1. Prevalent species in pulpal and periapical infections.
colonization of potentially peridontopathic bacteria in the peri-implant area [84]. Differences in the microflora of implants of partially or totally edentulous patients have been observed. Spirochetes have been seen from samples of teeth and implants in partially edentulous patients, but were not detected in implants from totally edentulous patients [81,85]. Apse [85] noticed a higher prevalence of Gram-negative black-pigmented anaerobic bacilli in partially edentulous patients compared with totally edentulous patients. George et al. [86] evaluated implants in partially and totally edentulous patients with implants. P. intermedia and P. gingivalis were observed in 39% of partially edentulous patients and in 19% of totally edentulous patients. In the implants harbouring one of these micro-organisms an increased probing depth, high tendency to bleeding and a higher level of gingival fluid were recorded [86]. A long-term study clinically and microbiologically examined peri-implant infections in totally edentu-
lous patients. High levels of anaerobes were detected 2 weeks after the implantation. Fusobacterium spp. were first detected at day 42; spirochetes at day 120, and during that period increased probing depth and pus formation were observed [79]. Other micro-organisms such as F. nucleatum, P. intermedia, Prevotella melaninogenica, P. micros, Capnocytophaga and C. rectus have been associated with development of peri-implantitis [78,79,87,88]. Likewise, it has been seen that the long-term systemic use of antibiotics or immunosuppressors longterm, can lead less prevalent micro-organisms to play a major role in these infections. This happens with Candida albicans, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Staphylococcus species, and others [77,86]. The failure of an implant can be produced by a periimplant infection, enhanced oclusal forces, incorrect surgical technique or systemic states affecting the bone [76]. Rosenberg [76] stated indicators used to determine the aetiology of implant failures due to
Frequent oral anaerobic infections infections or oclusal trauma. The study of microbial morphotypes by dark-field microscopy and cultures, as well as clinical indicators, have shown that infection and oclusal trauma respond differently. Clinical indicators of infected sites behave in a similar way as periodontitis and the examination of morphotypes led to high rates of spirochetes and mobile bacilli [76]. The micro-organisms identified by culture methods from failed implants due to infections have been associated with periodontitis, while implant failure due to oclusal trauma showed prevalence of Streptococcus sanguis [76]. The diagnosis of peri-implantitis is made clinically and radiographically. However, microbiological studies should be included to examine the associated microbiota. It is now recognized that peri-implant tissues behave in a way similar to periodontal tissues when confronting microbial challenge, and therefore, strict control of the microbiota surrounding the implants is a determinant for long-term success.
Pericoronaritis Pericoronaritis develops during eruption of teeth. Few studies have examined the microflora associated with pericoronaritis, although Gram-negative anaerobic bacilli and treponemes are prevalent [89,90]. It has also been observed that Treponema denticola is prevalent in pericoronaritis [89]. Transmission Electron Microscopic studies have demonstrated that spirochetes can be found in almost all cases of chronic pericoronaritis of the third inferior molar [91].
Oral Micro£ora Associated with Systemic Infections The association of oral infections with infectious endocarditis has been demonstrated [1,92,93]. Recently, periodontal disease has been associated as a high-risk factor for coronal diseases, arteriosclerosis, myocardial infarction, pneumonia, pre-term births and low birth weight [3,7,9,94].
Conclusions The oral cavity is characterized by harbouring indigenous flora. The ability of micro-organisms to colonize the different oral surfaces depends mainly on their binding potential. Various environmental factors and host factors are involved in the harbouring of micro-organisms and microbial composition. Oral infections are predominantly anaerobic. There is a variety of microbiological diagnostic methods for oral
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infections, the therapy of which depends on a close relation between the clinician and the microbiologist. Dentistry should assume this new challenge of team work interaction in order to prevent and solve oral and systemic infections.
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Frequent oral anaerobic infections 69. Sundqvist G. (1992) Ecology of the root canal flora. J Endod 18: 427±430 70. Sundqvist G. (1994) Taxonomy, ecology and pathogenicity of the root canal flora. Oral Surg Oral Med Oral Pathol 78: 522±530 71. Yoshida M., Fukushima H., Yamamoto K., Ogawa K., Toda T. and Sagawa H. (1987) Correlation between clinical symptoms and microorganisms isolated from root canals with periapical pathosis. J Endod 13: 24±28 72. Conrads G., Charbia S.E., Gualabivala K. and Lampert F. (1997) The use of a 16S r DNA directed PCR for the detection of endodontopathogenic bacteria. J Endod 23: 433±438 73. Nair P.N.R., SjoÈrgren U., Kahnberg K.E., Krey G. and Sundqvist G. (1990) Intraradicular bacteria and fungi in root-filled asymptomatic human teeth with therapy-resistant periapical lesions: a long term light and electron microscopic follow-up study. J Endod 16: 580±588 74. Tronstad L., Barnett F. and Cervone F. (1990) Periapical bacterial plaque in teeth refractory to endodontic treatment. Endod Dent Traumatol 6: 73±77 75. Brook I. Frazier E.H. and Gher M.E. (1991) Aerobic and anaerobic microbiology of periapical abscess. Oral Microbiol Immunol 6: 123±125 76. Rosenberg E.S., Torosian J.P. and Slots J. (1991) Microbial differences in 2 clinically distinct types of failure of osseointegrated implants. Clin Oral Impl Res 2: 135±144 77. Tonetti M.S. (1996) Peri-implantitis: biological considerations. J Periodontologie & d'Implantologie Orale 15: 269±284 78. Mombelli A., Van Oosten M.A.C., Schurch E. and Lang N.P. (1987) The microbiota associated with successful or failing osseointegrated titanium implants. Oral Microbiol Immunol 2: 141±151 79. Mombelli A., Buser D. and Lang N.P. (1988) Colonization of osseointegrated titanium implants in edentulous patients: early results. Oral Microbiol Immunol 3: 113±120 80. Mombelli A. and Lang N.P. (1994) Microbial aspects of implant dentistry. Periodontology 2000 4: 74±80 81. Quirynen M. and Listgarten M.A. (1990) The distribution of bacteria morphotypes around natural teeth and titanium implants ad modum Branemark. Clin Oral Impl Res 1: 8±12 82. Rams T.A., Robert T.W., Tatum H. and Keyes P. (1984) The subgingival microbial flora associated with human dental implants. J Proseth Dent 51: 529±534 83. Sanz M., Newman M.G., Nachnani S., Holt R., Stewart R. and Flemming T. (1990) Characterization of the subgingival microbial flora around endosteal sapphire dental implants in
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ORAL MICROBIOLOGYAND RELATED INFECTIONS (FACULTY PRESENTATION)
Bacteriology of Most Frequent Oral Anaerobic Infections S. Piovano School of Dentistry, MaimoÂnides University, Buenos Aires, Argentina
Key Words: oral anaerobic infections
The anaerobic infections most frequently found in the oral cavity are gingivoperiodontal diseases and pulpal and periapical infections. Gingivitis and adult periodontitis are the most frequent forms. In adult periodontitis the subgingival microbiota are complex and there is a prevalence of Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Peptostreptococcus micros, Campylobacter rectus, and species of Fusobacterium, Eikenella and Treponema. The microflora associated with peri-implant infections are similar to the microflora found in periodontal diseases, particularly in partially edentulous patients. Implant placement is therefore not recommended in patients presenting with uncontrolled periodontal disease. Likewise, there is a similarity between the genera identified in periodontal pockets and infected root canals, and in periapical infections. However, some species are more prevalent than others in both infections. The following were predominantly observed inside the root canals: Prevotella intermedia, Prevotella nigrescens, Peptostreptococcus anaerobius, Peptostreptococcus micros, Eubacterium lentum, Eubacterium alactolyticum and Porphyromonas endodontalis, with strong associations among some species. Pericoronaritis is another infection associated with anaerobic Gramnegative bacilli and treponeme. There are a great number of methods for microbiological diagnosis, and treatment of some oral infections depends on close interaction between the microbiologist and the dentist. # 1999 Academic Press
Introduction The oral cavity is the habitat of numerous microbial species. It has been observed that 1 g of dental plaque contains more than 1011 micro-organisms [1]. Many indigenous flora are anaerobes and these microorganisms can be associated with oral infections and be the origin of distant infections [1±9]. The most frequent oral anaerobic infections include gingivoper1075±9964/99/030221 + 07 $30.00/0
iodontal diseases, pulpal and periapical infections, peri-implantitis and pericoronarities.
Gingivoperiodontal Diseases Gingivoperiodontal diseases, including gingivitis and periodontitis, are caused by dental plaque, which is a biofilm [10,11]. # 1999 Academic Press
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Microbial species associated with gingivitis Studies have demonstrated that the dental plaque associated with gingivitis presents a high burden of micro-organisms (104±106) and an increase in anaerobic Gram-negative organisms (15±50%) [10]. Culture studies of the plaque near the marginal gum have demonstrated a prevalence of Actinomyces species [12]. Likewise, culture studies indicate that Fusobacterium nucleatum, Prevotella intermedia, Campylobacter species and Veillonella are frequently isolated from plaque samples associated with gingivitis [12]. Spirochaetes can be found mainly at the apical subgingival area. Gingivitis can be worsened by steroid hormones. In puberty, pregnancy and women taking oral contraceptives, it has been shown that gingival disease is associated with an inadequate plaque control, worsened by steroid hormones that stimulate the growth of Prevotella intermedia [13±15]. Acute necrotizing ulcerative gingivitis is a destructive inflammatory disease associated with species of Selenomonas, Porphyromonas, Prevotella, Fusobacterium and Treponema [4,16]. The prevalent bacteria are Prevotella intermedia and spirochaetes and Prevotella intermedia represents between 8% and 15% of the microbiota. Spirochaetes represent approximately 30% of the morphotypes that are present with medium and large spirochaetes being prevalent. Studies by Transmission Electron Microscopy have shown the invasion of tissues by spirochetes [17±19]. Microbial species associated with periodontitis Adult periodontitis. An increase in the total microbial burden (105±108 micro-organisms) and high levels of Porphyromonas gingivalis have been observed in adult periodontitis [10]. Porphyromonas gingivalis, Bacteroides forsythus and Actinobacillus actinomycetemcomitans have been identified as causative agents, and not as agents merely associated with disease [10]. The micro-organisms specifically implied are Porphyromonas gingivalis, Bacteroides forsythus, P. intermedia, Prevotella nigrescens and Actinobacillus actinomycetemcomitans. A second group of micro-organisms include F. nucleatum, Campylobacter rectus, Eikenella corrodens, Eubacterium nodatum, Selenomonas noxia, Peptostreptococcus micros, Streptococcus intermedius and Treponema denticola [2,20±33]. Adult periodontitis is associated with a group of bacteria and different microbial complexes have been described from subgingival plaque samples [10,34,35]. Many transmission studies have demonstrated that the same clonal types of P. gingivalis, A. actinomycetemcomitans and T. denticola can be found in members
of the family [36±40]. Porphyromonas gingivalis, A. actinomycetemcomitans and T. denticola penetrate the gingival epithelium, and they have endotoxins, active compounds and cytotoxic enzymes which act upon the host [21,41±44]. Spirochetes constitute 37±56% of the flora [19] and all morphogroups are detected with a prevalance of small and medium spirochetes [25,26,45]. The microflora are necessary to produce and allow progression of disease, modulated by host factors and lifestyle [33,46].
Rapidly progressing periodontitis. It affects young individuals and has a rapid evolution. Prevalent bacteria in active sites are A. actinomycetemcomitans, P. gingivalis, P. intermedia, F. nucleatum, T. denticola, B. forsythus and Campylobacter species [47]. Kamma et al. [47] have examined the microflora of severe, moderate and minimal lesions in young adults with rapidly progressing periodontitis, and have observed microbial complexes associated with severe and moderate lesions, while in small lesions species of Antinomyces and Streptococcus, Capnocytophaga ochracea, Haemophilus segnis and Veillonella parvula were identified.
Juvenile periodontitis. Juvenile periodontitis affects adolescents and is characterized by a rapid destruction of periodontal tissues [4]. The major microorganism related to juvenile periodontitis is A. actinomycetemcomitans [4,44,48]. A. actinomycetemcomitans has been considered as an agent of exogen infection in periodontitis [31,44], in patients with early-onset periodontitis and adult periodontitis it has been frequently isolated from periodontal pockets and other ecological niches of the oral cavity [44,48,49]. Epidemiological studies have shown that this microorganism can be transmitted by members of the family [36±39]. The introduction of the bacteria into the oral cavity is facilitated by the presence of frequent contacts and high inoculation doses [38]. Although A. actinomycetemcomitans is the major species related to juvenile periodontitis, high rates of P. gingivalis, Capnocytophaga, E. corrodens, F. nucleatum and Eubacterium brachy have been observed.
Prepubertal periodontitis. The main features are a rapid and severe destruction of deciduous teeth. In the generalized form the patients have defects in polymorphonuclear neutrophils and macrophages [4]. They usually present with other infections as well as periodontal lesions. The prevalent micro-organism is A. actinomycetemcomitans frequently associated with
Frequent oral anaerobic infections Capnocytophaga sputigena, P. intermedia and E. corrodens [4]. Refractory periodontitis. The species identified in active sites have been: P. gingivalis, A. actinomycetemcomitans, F. nucleatum, P. micros, C. rectus, B. forsythus, P. intermedia and E. corrodens. Some of these bacteria were isolated inside the gingiva in samples from biopsies of the active disease sites [50,51]. Periodontal abscess. There is a wide range of bacteria present in abscesses, which can exist in the plaque adhered to the tooth, or be free at the apical portions or adhered to the soft wall of the pocket. The prevailing micro-organisms are: P. micros, P. gingivalis, Fusobacterium spp., Capnocytophaga spp., Actinomyces spp. and species of oral streptococcus. Periodontal microbiota and halitosis. Halitosis has frequently been associated with gingivoperiodontal infection [52]. T. denticola, P. gingivalis, Veillonella species and Fusobacterium have all been associated with halitosis [53,54]. Halitosis can also be associated with flora of the tongue and flora lower down the gastro-intestinal tract. A direct relation between halitosis, the tongue's covering, and subgingival plaque has been observed [55].
Pulpal and Periapical Infections Micro-organisms reach the pulp in various ways. The most frequent are: fracture of dental tissues, as a result of natural history of dental caries; or through tubules of exposed dentine in the surface of root as a result of fissures or radicular caries. Likewise, the pulp can be infected by the microbial flora of the periodontal pocket and by dental procedures [56]. When anaerobic Gram-negative bacilli are prevalent in an endodontic infection, they release lipopolysaccharides and a periapical periodontitis is initialized at the periapex [5,57±62]. Sundqvist [63] analysed the microflora of root canals of teeth with apical periodontitis according to the frequency of occurrence and the analysis of association between bacteria. Results have shown that the most frequent species isolated was F. nucleatum, present in 45% of the root canals. Likewise, P. intermedia, P. micros, Peptostreptococcus anaerobius, Eubacterium alactolyticum, Eubacterium lectum and Capnocytophaga rectus were the prevalent species in this kind of infections. F. nucleatum showed a positive association with P. micros, Porphyromonas endodontalis, Selenomonas sputigena and C. rectus. A positive association was seen between P. intermedia and P. micros, P. anaerobius and E. lectum, and E. alactolyticum and C. rectus.
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Many authors have reported that the presence of species of the genera Porphyromonas, Prevotella and Peptostreptococcus are associated with an increase in the incidence of clinical symptoms of pain and sensitivity to pressure on the teeth [63±71]. Acute symptoms have been associated with Prevotella buccae, P. intermedia, P. gingivalis, P. endodontalis and Peptostreptococcus magnus [66,67,71]. Conrads et al. [72] analysed samples from nectrotic root canals using PCR and have observed species of Actinomyces, F. nucleatum, Streptococcus milleri and B. forsythus, the latter having not been shown previously in endodontic samples. Nair Ramachandran et al. [73] examined through microscopic studies the apex of endodontically treated teeth presenting a periapical lesion in the radiography after a post-treatment period of 4 to 10 years. Extraradicular presence of bacteria and yeast was observed in the teeth with infection following endodontic therapy [62,73,74]. Gomes et al. [65] observed the presence of Prevotella, Peptostreptococcus, Eubacterium and Propionibacterium spp. in these refractory lesions. In periapical abscesses, 75% to 94% of the flora are anaerobes. Species of Prevotella and Porphyromonas have frequently been isolated. P. gingivalis, P. endodontalis and P. intermedia are the prevalent species [68,75] and other Prevotella species identified in abscesses are Prevotella oralis, Prevotella oris, and Prevotella buccae [68,75]. P. anaerobius, P. micros, Peptostreptococcus prevotti and P. magnus are the prevalent Peptostreptococcus species [65]. Species of Veillonella, Eubacterium, Actinomyces and Fusobacterium are frequently isolated [64,65]. `Viridans streptococci', facultative anaerobes, are present in periapical infections associated with anaerobes [56]. Figure 1 shows the micro-organisms most frequently isolated from endodontic infections.
Peri-implantitis Various criteria originally used for the study of periodontal diseases have been applied to implantology [29,76,77]. The sulcus of relatively healthy implants with stable probing depth (3±5 mm for 1 year) has shown by MCO a prevalence of non-mobile bacteria. Cocoid cells prevail in those sites (64.2%). In culture, the microbiota are poor, dominated by facultative anaerobic Gram-positive cocci [78±83]. The microbial infection can lead to two different clinical manifestations: (1) a lesion limited to inflammation of superficial soft tissues (mucositis); and (2) a lesion comprising soft tissues and the marginal portion of the implant±bone interface (peri-implantitis) [77]. The presence of remnant teeth with any untreated or badly controlled periodontal disease enhances
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Figure 1. Prevalent species in pulpal and periapical infections.
colonization of potentially peridontopathic bacteria in the peri-implant area [84]. Differences in the microflora of implants of partially or totally edentulous patients have been observed. Spirochetes have been seen from samples of teeth and implants in partially edentulous patients, but were not detected in implants from totally edentulous patients [81,85]. Apse [85] noticed a higher prevalence of Gram-negative black-pigmented anaerobic bacilli in partially edentulous patients compared with totally edentulous patients. George et al. [86] evaluated implants in partially and totally edentulous patients with implants. P. intermedia and P. gingivalis were observed in 39% of partially edentulous patients and in 19% of totally edentulous patients. In the implants harbouring one of these micro-organisms an increased probing depth, high tendency to bleeding and a higher level of gingival fluid were recorded [86]. A long-term study clinically and microbiologically examined peri-implant infections in totally edentu-
lous patients. High levels of anaerobes were detected 2 weeks after the implantation. Fusobacterium spp. were first detected at day 42; spirochetes at day 120, and during that period increased probing depth and pus formation were observed [79]. Other micro-organisms such as F. nucleatum, P. intermedia, Prevotella melaninogenica, P. micros, Capnocytophaga and C. rectus have been associated with development of peri-implantitis [78,79,87,88]. Likewise, it has been seen that the long-term systemic use of antibiotics or immunosuppressors longterm, can lead less prevalent micro-organisms to play a major role in these infections. This happens with Candida albicans, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Staphylococcus species, and others [77,86]. The failure of an implant can be produced by a periimplant infection, enhanced oclusal forces, incorrect surgical technique or systemic states affecting the bone [76]. Rosenberg [76] stated indicators used to determine the aetiology of implant failures due to
Frequent oral anaerobic infections infections or oclusal trauma. The study of microbial morphotypes by dark-field microscopy and cultures, as well as clinical indicators, have shown that infection and oclusal trauma respond differently. Clinical indicators of infected sites behave in a similar way as periodontitis and the examination of morphotypes led to high rates of spirochetes and mobile bacilli [76]. The micro-organisms identified by culture methods from failed implants due to infections have been associated with periodontitis, while implant failure due to oclusal trauma showed prevalence of Streptococcus sanguis [76]. The diagnosis of peri-implantitis is made clinically and radiographically. However, microbiological studies should be included to examine the associated microbiota. It is now recognized that peri-implant tissues behave in a way similar to periodontal tissues when confronting microbial challenge, and therefore, strict control of the microbiota surrounding the implants is a determinant for long-term success.
Pericoronaritis Pericoronaritis develops during eruption of teeth. Few studies have examined the microflora associated with pericoronaritis, although Gram-negative anaerobic bacilli and treponemes are prevalent [89,90]. It has also been observed that Treponema denticola is prevalent in pericoronaritis [89]. Transmission Electron Microscopic studies have demonstrated that spirochetes can be found in almost all cases of chronic pericoronaritis of the third inferior molar [91].
Oral Micro£ora Associated with Systemic Infections The association of oral infections with infectious endocarditis has been demonstrated [1,92,93]. Recently, periodontal disease has been associated as a high-risk factor for coronal diseases, arteriosclerosis, myocardial infarction, pneumonia, pre-term births and low birth weight [3,7,9,94].
Conclusions The oral cavity is characterized by harbouring indigenous flora. The ability of micro-organisms to colonize the different oral surfaces depends mainly on their binding potential. Various environmental factors and host factors are involved in the harbouring of micro-organisms and microbial composition. Oral infections are predominantly anaerobic. There is a variety of microbiological diagnostic methods for oral
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infections, the therapy of which depends on a close relation between the clinician and the microbiologist. Dentistry should assume this new challenge of team work interaction in order to prevent and solve oral and systemic infections.
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