1. Kakehashi et al.
    Illustrated the role of pulpal inflammation to apical periodontitis.

    Germ-free rats did not develop apical periodontitis following pulpal exposures, whereas conventional rats with normal oral flora rapidly developed apical pathology.
  2. Bacteria and Apical Pathosis
    Moller et al.

    Sundqvist et al.
    Moller = Monkeys

    Sundqvist = Humans

    Both found bacteria in necrotic pulps with apical periodontitis but not in necrotic pulps without apical disease.
  3. Focal Infection Theory


    Key Figure
    Asserts that localized or generalized infection can result from dissemination of bacteria and toxic byproducts from a focus of infection.

    Weston Price - 1925
  4. How did the following figures refute Focal Infection Theory?
    Easlick - pointed out the fallacies in Price’s research methods, including the inadequate use of controls, large amounts of bacteria in the cases presented, and contamination of root canal–treated teeth studied during extraction.  Doing so, he effectively refuted the associations between endodontically treated teeth and systemic disease.

    Fish - described the encapsulation of infections into the so-called “Zones of Fish”: Infection, Contamination, Irritation, Stimulation extending outward concentrically.  If the nidus of infection is removed, the body can recover, providing a basis for the success of root canal therapy
  5. Culturing Bacteria Limitations
    Certain species are unable to grow outside of physiologic conditions.

    It is difficult to take a truly anaerobic sample for growth in culture.
  6. Molecular Techniques:
    DNA Chekerboard Analysis
    Polymerase Chain Reaction - amplifies DNA, which can subsequently be sequenced to identify the presence of known and novel species.

    Fluorescent In Situ Hybridization and DNA Checkerboard Analysis - allow detection of vast libraries of known species. Molecular techniques are also useful in the detection of nonbacterial infection sources. They can be used to identify the DNA from fungal infections, including candida, and viruses, including viruses in the herpes family.
  7. Gram Positive Bacteria
    Gram Positive Bacteria

    • Labeled as such due to the affinity of the crystal violet dye for their thick peptidoglycan cell walls.
    • Gram-positive bacteria include those in the Streptococcus, Peptostreptococcus, Enterococcus, Lactobacillus, Eubacterium, and Actinomyces genera.
  8. Gram Negative Bacteria
    Gram Negative Bacteria

    • Have a lesser affinity for the crystal violet stain due to the presence of a cell wall containing lipopolysaccharide (LPS), often referred to as endotoxin.
    • LPS is important in the progression of pulpal and periapical inflammation.
    • Gram-negative bacteria include those in the Fusobacterium, Treponema, Prevotella, Porphyromonas, Tannerella, Dialister, Campylobacter, and Veillonella genera.
  9. LPS and Pulpal / Periapical Inflammation

    Dwyer and Torabinejad.
    Dwyer and Torabinejad found that LPS stimulates cytokine production by macrophages.
  10. Endodontic Infections
    When the body’s physiologic microbiome is interrupted, or pathogenic microbes enter normally sterile tissues such as the dental pulp, the balance shifts, and pathogenic infection can occur.

    Regardless of the means of pulp inoculation, endodontic infections are polymicrobial. Both culture-based and molecular methods confirm this finding.
  11. Microcracks - Bergenholtz

    Proposed that microcracks caused by traumatic injuries allow ingress of bacteria to infect an already compromised, inflamed pulp.
  12. Anachoresis 

    Proponents - Gier and Mitchell
    Opponents - Delivanis
    Gier and Mitchell

    • Proposed anachoresis as another means of infection.
    • Anachoresis is the homing of bacteria to traumatized, unexposed pulps.

    Delivanis, PD. Localization of blood-borne bacteria in instrumented unfilled root canals. Oral Surg Oral Med Oral Pathol 1981.

    Effectively disproved anachoresis.
  13. Biofilms - Definition

    Donlan and Costerton.
    Defined biofilms as microbial-derived, sessile communities characterized by cells irreversibly attached to a substratum or interface or to one other, embedded in a self-produced matrix of extracellular polymeric substances, and exhibiting an altered phenotype with respect to growth rate and gene transcription compared with their planktonic counterparts.
  14. Biofilms - Qualities

    Svenstater and Bergenholtz.
    • Qualities unique to biofilms:
    • Metabolic diversity
    • Concentration gradient
    • Genetic exchange
    • Quorum sensing
  15. Biofilms - Qualities

    Metabolic Diversity

    Svenstater and Bergenholtz.
    Metabolic diversity allows for a sharing of nutritional sources and waste products and results in greater overall survival.
  16. Biofilms - Qualities

    Concentration Gradient

    Svenstater and Bergenholtz.
    Concentration gradient created by the mere density of the biofilm community allows for greater physical and chemical resistance to antimicrobials and immune responses.
  17. Biofilms - Qualities

    Genetic Exchange

    Svenstater and Bergenholtz.
    Genetic exchange by the microbiota in close proximity allows for sharing of favorable virulence factors.
  18. Biofilms - Qualities

    Quorum Sensing

    Svenstater and Bergenholtz.
    Quorum sensing serves as a communication method among the microbial community and permits the members to act as a group and increase effectiveness of their actions.
  19. Are abscesses sterile?

    • Shindell
    • Historical


    • Tronstad et al.
    • Sunde et al.
    • Haapasaolo et al.
    • Sassone et al.
    • Sabeti and Slots.
  20. Abscesses are NOT Sterile

    Tronstad et al.
    Tronstad et al performed one of the first culture studies demonstrating the presence of bacteria, particularly anaerobes, in extraradicular infections.
  21. Abscesses are NOT Sterile

    Sunde et al.
    Sunde et al (2000) confirmed the findings of Tronstad by using molecular techniques and noted the presence of certain species in periapical infections, in particular Aggregatibacter actinomycetemcomitans and Tannerella forsythia.
  22. Haapasalo et al.
    Haapasalo et al cultured anaerobic bacteria in sinus tracts.
  23. Abscesses are NOT Sterile

    Sassone et al.
    Sassone et al reported a higher prevalence of Porphyromonas gingivalis and Fusobacterium nucleatum when a sinus tract was present.
  24. Abscesses are NOTE Sterile

    Sabeti and Slots.
    Sabeti and Slots reported the presence of human cytomegalovirus and Epstein-Barr virus in apical periodontitis.
  25. Most, though not all, teeth exhibiting pulpal necrosis are infected.

    Wittgow and Sabiston.
    Andreasen demonstrated that periapical healing could occur despite pulpal necrosis in traumatically lunated teeth without bacterial contamination.

    Wittgow and Sabiston found that 64% of teeth with pulpal necrosis were infected.

    Bergenholtz found that teeth with pulpal necrosis AND periapical lesions were more often infected.
  26. Endodontic infections are comprised of frequently isolated species, and these are repeatedly noted in the literature.
    Streptococcus, Enterococcus, Prevotella, and Porphyromonas species.
  27. Streptococcus

    • Gram positive
    • Generally facultative anaerobic bacteria
    • Classified as alpha or beta based on their reaction with hemoglobin molecules on blood agar in a laboratory
    • Particularly, those further classified into groups F, G, C, and minority D, were common isolates in endodontic infections (Winkler and Van Amerongen)
  28. Enterococcus faecalis
    E. faecalis

    • Gram positive
    • Facultative anaerobe
    • Exhibits anti-microbial resistance
  29. E. faecalis Anti-microbial Resistance

    Evans et al.
    Bystrom et al.
    Evans et al. - E faecalis possesses a proton pump that allows it to adapt to harsh environments.

    Bystrom et al. - Proton pump is theorized to contribute to E faecalis’ unique resistance to calcium hydroxide, an intracanal medicament known for its effectiveness against most known endodontic pathogens. Presumably, the proton pump prevents the ionization calcium hydroxide requires for effectiveness.

    Love - E faecalis possesses the ability to survive for long periods of time in dentinal tubules without nutrients.

    Distel et al. - Found that E. faecalis could form biofilms.
  30. E. Faecalis Properties proposed to increase its resistance to eradication:

    • May form biofilms
    • Can enter dentinal tubules
    • Can survive starvation
    • Possesses a proton pulp
  31. Black Pigmented Bacteroides

    In the 1980s, microbiologists recognized that this group comprised a relatively heterogenous group of bacteria and further split the genus of Bacteroides into Prevotella and Porphyromonas.
    Gram negative

    Obligate anaerobes

    Differentiated in their ability to ferment carbohydrates:

    • Prevotella - Saccharolytic
    • Porphymonas - Asaccharolytic
  32. Bae et al. - Prevotella nigrescens

    Gomes et al. - Prevotella melaninogenica
    Bae et al reported that Prevotella nigrescens was the most common isolate from endodontic infections of those previously categorized as Bacteroides.

    Gomes et al reported that Prevotella melaninogenica was commonly associated with painful infections.
  33. Atypical Species

    Gram positive

    Form cohesive colonies often described clinically as "sulfur granules" because of their yellow granular presentation (Sunde).

    Common cause of persistent endodontic infection (Nair).
  34. Atypical Species


    Sunde et al.
    Xia and Baumgartner.
    Sunde et al. - Histologic analysis of these “sulfur granules” noted that they indeed contained large quantities of clumped bacteria. 

    Nair - Described difficulties in culturing the organism. Modern research methods, on the other hand, more frequently isolate this genus.

    Xia and Baumgartner - Noted Actinomyces israelii, Actinomyces naeslundii, and Actinomyces viscosus in infected root canals and aspirates from associated abscesses and cellulitis.

    Nair reviewed Actinomyces’ ability to survive and thrive in the periapical area, often called periapical actinomycosis, and cites this entity as a common cause of persistent endodontic infections.

    Jeansonne - Recommended treating periapical actinomycosis via a surgical approach along with a relatively long, 6-week course of systemic penicillin.
  35. Atypical Species

    Gram negative

    Anaerobic bacteria with flagella for motility

    Difficult to culture, requiring molecular techniques to detect them.
  36. Atypical Species


    Siqueira et al.
    Sakamoto et al.
    Siqueira et al. - Noted Treponema subspecies in endodontic infections.

    Sakamoto et al. -  Identified a variety of Treponema species present in endodontic infections, particulary Treponema denticola, Treponema socranskii, and Treponema maltophilum.
  37. Atypical Species


    Vianna et al.
    Vianna et al first reported their presence in endodontic infections.

    Also known as extremophiles

    Known to be present in hot springs and can be localized to the gastrointestinal and vaginal tracts as well as in periodontal plaque.
  38. Atypical Species

    Candida albicans

    Baumgartner et al.
    Baumgartner et al. - Found Candida albicans in primary endodontic infections.
  39. Atypical Species


    Giardino et al.
    Giardino et al. - Reported a case of an Aspergillus fungal infection associated with extruded zinc oxide–based endodontic sealer in the maxillary sinus potentially related to the zinc, an Aspergillus metabolite, present in the sealer.
  40. Atypical Species 

    Viruses, particularly those in the herpesvirus family, are commonly reported in endodontic infections.

    Recent data indicates that viruses may play an active role in pulpal death.
  41. Atypical Species

    Herpetic Viruses

    Ferreira et al.
    Sabeti et al.
    Goon and Jacobsen.
    Von Arx
    Ferreira et al. - Noted herpes simplex virus (HSV) types 1 and 2; human herpesvirus (HHV) types 6, 7, and 8; and varicella zoster virus (VZV) in aspirated samples of acute apical abscesses.

    Sabeti et al. - Reported the presence of Epstein-Barr virus (EBV) and cytomegalovirus (CMV) in periapical lesions, especially larger and symptomatic lesions.

    Li et al. - Also reported a possible association of EBV with irreversible pulpitis. 

    Goon and Jacobsen - Case report which described devitalization of the dental pulp associated with a trigeminal VZV infection. 

    Von Arx et al. - Reported a potential association between feline herpesvirus and cases of invasive cervical root resorption in both humans and cats.
  42. Atypical Species

    Non-herpetic Viruses

    Ferreira et al. (HPV)
    Glick et al. (HIV)
    Elkins et al. (HIV)
    Ferreira et al. - Found human papillomavirus (HPV) in endodontic abscesses. 

    Glick et al. - Located HIV in the dental pulp of individuals with clinical AIDS.

    Elkins et al. - Found HIV in periradicular lesions of patients known to be carriers of the virus.

    NOTE: human immunodeficiency virus (HIV) has not been correlated with the pathogenesis of endodontic disease.
  43. Primary vs. Secondary Endodontic Infections

    • Equal numbers of gram positive and gram negative species.
    • More anaerobes than aerobes.


    • Varying ratios of gram positive and gram negative species.
    • Equal numbers of anaerobes and facultative species.
  44. Primary vs. Secondary Endodontic Infections

    Primary Infections

    Figdor and Sundqvist.
    Fabricius et al.
    Figdor and Sundqvist - Reported differences in the composition of primary versus secondary infections. Primary infections consisted of an equal mix of gram-positive and gram-negative bacteria and contained mostly obligate anaerobes.

    Fabricius et al. - Described the progression of primary endodontic infections from largely aerobic species to anaerobic species, a process he termed microbial succession. This results from a reduction in oxygen tension in the necrotic pulp tissue due to aerobic metabolism by early colonizers.
  45. Primary vs. Secondary Endodontic Infections

    Secondary Infections

    Figdor and Sundqvist
    Figdor and Sundqvist - Reported that secondary infections contained mostly gram-positive bacteria with a more equal distribution of facultative and obligate anaerobes.

    Murad et al. - Conversely, reported a higher prevalence of gram-negative than gram-positive species in secondary infections, particularly in the presence of a large periapical lesion.
  46. Primary vs. Secondary Infections

    Secondary Infections - E. faecalis

    Rocas et al.
    Rocas and Siqueira.
    Murad et al.
    Rôças et al. - Reported that E. faecalis was nine times more likely to be present in secondary than primary infection.

    Murad et al. - Using checkerboard DNA hybridization, reported that Enterococcus faecium and Streptococcus epidermidis were the most prevalent species in secondary infections.
  47. Bacteria and Clinical Symptoms

    Siiqueira et al.
    Sassone et al.
    Gomes et al.
    Sabeti et al.
    Siqueira et al. - Reported an increased prevalence of Fusobacterium in symptomatic infections.

    Sassone et al. - Reported an association between T forsythia and painful infections.

    Gomes et al. - Noted an increased prevalence of peptostreptococci and P melaninogenica with pain.

    Sabeti et al. - Found that EBV and CMV were also associated with painful infections.
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