MICROBIOLOGY OF

ENDODONTICS

TEXTBOOKS:

• Endodontics. Principles and practice. 4th ed,2009, M.Torabinejad & R.Walton

Chapter 3• Pathways of the pulp. 8th ed,2002. S.Cohen, R.C. Burns. Chapter 13• Endodontics. 5th ed, 2002. J.I.Ingle & LK

Bakland. Chapter 3

Learning objectives:• Define terms associated with endodontic microbiology• Understand the significance of bacteria in pulpal and PR

diseases• Describe portals of entry of microorganisms (mo) to the

pulp and periradicular (PR) tissues• Recognize the different types of endo infections and the

main microbial spc involved in each one• Understand the bacterial diversity within infected RC• Describe the reactions of pulp and PR tissues to bacteria• Discuss the rationale for debridement of root canal system

Terminology• Colonization: the phenomenon of establishment of bacteria or other

organisms in a living host occurs if: - appropriate physical or biochemical conditions

are available for growth - inhibitory factors are inadequate to destroy moNormal oral flora: result of permanent colonization of mo in a symbiotic

relationship with the host->produce beneficial resultsOpportunistic pathogens : gain access to normally sterile area of the body

and produce disease such as dental pulp or PR tissueInfection : mo damage the host & produce clinical signs and

symptomsPulpal&PR pathoses: opportunistic pathogens infect the pulp cavity & PR

tissues

• Pathogenicity : the capacity of mo to produce disease within a particular host

• Virulence : the degree or pathogenicity in a host under defined circumstances

• Anachoresis : a process by which mo are transported in the blood to an area of inflammation where they establish an infection

• Stage in development of an endodontic infection:microbial invasion, colonization, multiplication and pathogenic activity

• History perspective of endodontic microbiology : - 1890 WD Miller, the first to identify bacteria in the

diseased pulp - 1939 EW Fish, investigated and related bone destruction

to infections from dental pulpthe basis for success ful endodontic therapy

- 1965 Kakehashi et al; no lesions in germ-free (gnotobiotic) rats; dental pulps induced bacteria pulpal and PR lesions developed

Sunqvist : the role of aerobe and anaerobe mo in the PR pathoses Kobayashi et al: sulcus of perio pocket->source of bacteria in

root canal infections (similar species)

Portal of entry of mo to the pulp

• Exposed dentinal tubules - dental caries - missing enamel or cementum - fracture of the tooth/cracks - microleakage under or around restoration - restorative procedures - external or internal root resorption

• Direct pulp exposure• Periodontal diseaseperio pocket reaches the AF• Anachoresisblood/lymphatic route mediated by cytokines

Types of endodontic infection

• According to anatomic location:

- Intraradicular infection: Primary, secondary or persistent infection <-depends on the time - Extraradicular infection

Primary intraradicular infection

• Initially invade and colonize the necrotic pulp tissue

• Referred as initial infection or virgin infection• Mixed infection ~ 10-30 bacterial species• Predominant bacteria: anaerob bacteria and some

facultative anaerob

Secondary intraradicular infection- Not present in the primary infection but introduced

into the RCS after professional intervention- Can be during treatment, between appointment or after

root canal filling (loss or leakage of temporary/perma nent restorative materials, fracture,recurrent decay)- Species oral or non oral mo, depends on the cause of

infection- Main cause remnants of dental plaque, calculus or

caries on the tooth crown, leaking rubber dam, contamination of endo instruments, irrigants, intracanal medication.

Persistent intraradicular infection• MO that can resist intracanal antimicrobial proceed• Also termed recurrent infection• MO involved remnants of 1° or 2° infection• Composed of fewer species than 1° infection, mostly

gram + facultative or anaerob, fungi↑• Responsible for several clinical problems: persis tent exudation & symptoms, interappointment flare

–ups, failure of endo treatment PA lesion

Extraradicular infection• Invasion and proliferation in the inflamed PR tissue almost as a sequel of intraradicular infection• Can be dependent on the intraradicular infection acute apical abscess managed by root canal

therapy can be independent on the intraradicular infection

apical actinomycosis treated by endodontic surgery

Bacterial genera represented in endo infections Gram Negative Bacteria Anaerobes Facultatives Rods:- Dialister* - Capnocytophaga - Porphyromonas * - Eikenella - Tannarella * - Haemophilus - Prevotella* - Fusobacterium * - Campylobacter - Synergistes - Catonella - Selenomonas - Centipeda

Cocci : - Veillonella - Megasphaera

Spirilla :Treponema *

Gram Positive Bacteria• Anaerobes Facultatives Rods:- Actinomyces -Actinomyces * - Pseudoramibacter * -Corynebacterium - Filifactor * -Lactobacillus - Eubacterium - Mogibacterium - Propionibacterium * - Eggerthela - Olsenella * - Bifidobacterium - Slackia - Atopobium - Solobacterium - Lactobacillus

Gram Positive Bacteria Anaerobes Facultatives Cocci : - Micromonas * - Streptococcus - Peptostreptococcus * - Enterococcus - Finegoldia - Granulicatella - Peptoniphilus - Anaerococcus - Streptococcus * - Gemella

Other MO in endodontic infections

• Fungi, sporadically found in primary infection• Virusescan’t survive in the root canal with

necrotic pulp (just DNA/RNA) - found in root canal of non inflamed vital pulps

of HIV patients - Human cytomegalovirus and Epstein-Barr virus have been detected in symptomatic apical periodontitis lesions

Reaction of pulp to bacteria• Pulp response to irritants : - non specific/innate inflammationneutrophil,

macrophages - specific/adaptive immunologic reactionsproduction of IgG (deep) Response to caries : - formation of peritubular dentin decreased pemeability of tubular dentin - production of irregular secondary dentin• Exposed pulp by caries : accumulation of PMN liquefaction necrosis

The dynamics of pulp reaction is related to:

• Virulence of the bacteria• The ability to release inflammatory fluids to avoid the increasing of intrapulpal pressure• host response/host resistance• Amount of pulpal circulation• Degree of lymph drainage

• Microbes have numerous virulence factors protect them from phagocytosis :

- bacterial capsules resistance factor for bacteria, protect the bacteria from phagocytosis - fimbriae ( pili) exchange DNA during conjugation/synergy relationships between bacteria resistance to antibiotic, important for attachment to surfaces and to other bacteria

- lipopolysccharides (LPS) released from outer membrane of gram (–) bacteria called endotoxin . effect in bone resorption, induce periradicular pathosis . Have non-specific antigen that are not well neutralized by antibodies - enzymes spreading factors that neutralize immunoglobulin and the complement components

- extracellular vesicles formed from outer membrane of gram (-) bacteria free endotoxin

. Able to neutralize antibodies . Involves in hemagglutination, hemolysis, bacterial

adhesion and proteolytic action on host tissues

- Short - chain fatty acids found in infected root canals, propionic, butiric and isobutiric acids bone resorption

affect neutrophil chemotaxis degranulation, chemiluminescence, phagocytosis

- Polyamines biologically active involved in the regulation of growth, regeneration of tissues and modulation of inflammation, incld : spremine, spermidine, cadaverin, putrescine

. Produced by both bacteria and host cells - ammonia & hidrogen sulfides low-

molecular-weight products

• Necrotic pulp : - fertile environment for bacterial growth and colonization moist, warm, nutritious, anaerob - lack of active microcirculation protected from the host defense

Key ecologic factors that influence the composition of the MO in the necrotic root canal:

- oxygen tension and redox potential (lack of oxygen) - type and amount of available nutrients - bacterial interactions

• Patterns of microbial colonization: - as planktonic(unattached) cells suspended in the fluid phase of the main root canal - as aggregates or coaggregates adhered to the root canal walls

forming multilayered biofilms Dynamics of microorganism: MO can disturb disease and treatment process : - resist to antibacterial agents bacteroides fragilis, staphyl.aureus, strepto.faecalis - synthetize by products (toxins,capsules,metabolic irritants & extracellular enzymes) that change infection process which benefit mo by destroying tissues and inactivating antibiotics - spread infection and bacterimia

Bacteria invasion/daya invasi bakteri

• Depends on - antiphagocytosisavoid local host defense by forming capsules (streptoc,bacteroides,fusiformis) Phagocytosis is enhanced by forming specific anticapsule antibodies - adapt metabolic to pulp condition, from normal to inflammation/necrotic . need enzyme to grow and reproduce. The availability of enzyme is induced by complex mechanism of bacteria Enzyme produced by bacteria neutralize immunoglobulin and their components

Infection control• Is treated as transmissible disease which needs precautions/

protections The protections : - avoid cross infection between patients and health providers - the use of physical barriers :rubber dam, masks, gowns, gloves and safety glasses Also reduces accident of instrument exposure such as bur etc - desinfects operation area and root canal with NaOCl or other desinfectants

Treatment of endodontic infections• Removal of the reservoir of infection (necrotic tissue,bacteria,

bacterial byproducts) through debridement• Complete obturation of root canal system• Debridement of the root canal system: - cleaning and shaping (biomechanical) followed by irrigation (chemical adjuncts) - intracanal medication

Irrigation Major function is to flush out debris from the canal

Ideal irrigant• Tissue or debris solvent• Low toxicity• Low surface tension• Lubricant• Sterilization or desinfection/antibacterial• Removal of smear layer• Other factors such as, economics,easily got, adequate shelf life, ease of

storage Types of irrigants : - NaOCl [0.5-5.25%] - EDTA remove smear layer - H2O2 popular with bubbling effect. H2O2H2O + On

- ChlorHexidine - MTAD (mixture of tetracycline and detergent)

Irrigation technic

• Prepare irrigant in a dappen dish• Prepare maxiprobe, 28 or 30 gauge • Fill the needle with irrigant• Insert the needle passively to the root canal, ½ root

depth and remove the irrigant slowly. Notice that there is gap between the needle and root canal wall to allow debris to flow out

Intracanal Medication• Mode of action : denaturation of cell proteins• Mode of application: applied on a cotton pellet or

absorbent paper point and placed in pulp space• Toxicity : kills bacteria and host cells• Duration of effectiveness : short term except

calcium hydroxide

Intracanal medicaments usually used :• Phenolics : moderate antimicrobial with short term effect (24 hours) only effective in direct contact with microorganisms

incld:,camphorated parachlorphenol, cresol, thymol, eugenol,creosote,cresatin

• Aldehydes : moderate antimicrobial effect formocresol• Halides : sodium hypochlorit, iodine potassium iodide• Steroides: single use or in combination with antibiotics

reduce pain post treatment except flare up/severe pain• Antibiotics : rarely used as intracanal dressing• Combination : variety substances or mixed by dentist for double action

by single application

CALCIUM HYDROXIDE• Current intracanal dressing of choice

Available in many forms and combinations• Used as intracanal dressing of necrotic pulp• Can be combined with water, saline, anaestheticum, glycerin,

methylcellulose or other medicaments (not very effective due to toxicity from other medicaments)

• Combined with water/glycerinpaste,placed in root canal with plugger or lentulo counter clockwise

• Antibacterial action: pH 12.5, block intracanal bacterial growth and change biological nature of lipopolisaccharide bacteria

WHEN TO CULTURE• Reasons of culturing bacteria of root canal:

- to determine bacteriologic status of root canal before obturation

- to assess the effectiveness of debridement procedure- to isolate flora microbes in order to evaluate the

sensitivity and resistance of antibiotics in persistent infection

When to prescribe antibiotic for endodontic infections

• In conjunction with the appropriate endodontic procedure, when there is :

- systemic involvement, persistent infection or a spreading infection signs and symptoms : fever (>38°C), malaise, cellulitis, unexplained trismus, progressive diffuse swellingAntibiotic as an adjunct to debridement and drainage

Selection of antibiotic regimen• Penicillin narrow spectrum of microbial activity antibiotic of choice for Endo Infec, low toxic, effective, 10%

allergy rate. Oral loading dose 1000 mg, followed by 500 mg/ 6 hours, 6-10 days• Amoxicillin broader spectrum than penicillin, for more

resistant organisms,rapid absorption, more sustained serum level Oral loading dose 1000 mg, followed by 500 mg/ 8 hours, 6-10

days Combination with clavulanate not recommended unless B-

lactamase producing bacteria are the cause of infection.

Clarithromycin and Azithromycin macrolides - mild infection and allergic to penicillin - Clarithromycin dosage : 250-500 mg/12 hours, 6-10 days (with or without meals)- Azithromycin : takes 1 hour before meals or 2 hours after

meals . loading dose 500 mg/1st day, followed by 250 mg/daily . Block the metabolism of a number of drugswarfarin & anisindione, lead to serious bleeding in anticoagulated patients

- Metronidazole : excellent activity against strict anaerobes, but not

facultative bacteria, can be combined with penicillin, with loading dose 500 mg, followed by 250-500 mg/6 hours

during therapy, no alcohol consumption and lithium- Clindamycin recommended for serious infection and allergy to penicillin effective for both facultative and strict anaerobes loading dose : 300 mg, followed by 150-300 mg/6 hours,

6-10 days

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