Microbial aetiology of pulp and periapical disease

Question 1

Aetiology of pulpitis (Kakehashi et al 1965)

Answer 1

Maxillary molars of conventional and germ-free animals exposed
Left for 1-42 days
Conventional animals –> necrotic pulps
-periapical abscess and granulomas by 8 days
Germ-free animals –> no devitalised pulps
-evidence of healing by 14 days

Question 2

Routes of entry to the pulp

Answer 2

Carious dentine (via dentinal tubules)
Subgingival plaque bacteria present in deep periodontal pockets via lateral canals
Gingiva
Lateral root canal
Anachoresis
Abscess

Question 3

What leads to bacteraemia?

Answer 3

Accute inflammation –> abscess –> bacteraemia

Question 4

What leads to cyst?

Answer 4

Chronic inflammation –> granuloma –> cyst

Question 5

Invasion of dentinal tubules

Answer 5

Bacteria invading from oral cavity into pulp space

Or invading radicular dentine from infected root canal

Question 6

Dentinal tubules

Answer 6

Produced during dentin formation by odontoblast migration
Wider and contain more collagen at pulpal side
Dentinal fluid within tubules (albumin, trnasferrin, proteoglycans)
Bacterial infection - change in hydrostatic pressure within tubules increasing sensitivity
Bacteria within tubules are protected

Question 7

Example mechanism of invasion

Answer 7

Streptococci bind to collagen type I in tubules
Adhesin in ‘antigen I/II’ family of proteins
Bacteria move along tubules by growth and fluid flow
Some streptococci can ‘carry’ other bacteria with them
-e.g. S.gordonii co-aggregates with P.gingivalis via protein I/II

Question 8

Co-operative invasion

Answer 8

P.gingivalis needs to cooperatively invade with S.mutans

Question 9

Pulp response to infection

Answer 9

Rapid acute inflammation involving whole pulp –> pulp necrosis
Development of chronic localised abscess (most pulp remains viable)

Question 10

Micro-organisms in caries v. pulp infection

Answer 10

Enamel caries and dentine caries: Strep and Lactobacillus

Necrotic pulp: (anaerobic organisms) Peptostreptococcus, fusobacterium, black pigmented anaerobes

Question 11

Specificity of oral disease-associated microbiota

Answer 11

Slight overlap between caries and endodontic infections, slight overlap with endodontic and periodontal infections, but overall all 3 have different species due to different environments

Question 12

Bacteria recovered from infected pulps by culture

Answer 12

Anaerobes (57)
-black-pigemented **
-eubacterium
-peptostreptococcus
Facultatives (43)
-streptococcus**
-actinoyces

Question 13

Overview of bacteria in pulpal infection

Answer 13

Polymicrobial infections
Propertions of groups of bacteria in 7 pulp infection
-not all the same but trend

Question 14

Treatment of pulpal infection

Answer 14

Endodontic treatment - pulp removed, cleaning, decontamination, pulp replaced by inert material, restoration
Extraction - esp. if there is insufficient coronal tissue remaining for restoration once root canal therapy is complete

Question 15

Bacteria associated with endodontic treatment failure

Answer 15

Enterococcus faecalis
S. anginosus*
S. constellatus*
S. intermedia*
A. israeli
B. gracilis
*Milleri group

Question 16

Dentoalveolar infections

Answer 16

Pus-producing infections associated with teeth and surrounding suppoerting structures
Periapical abscesses
Clinical presentation depends on

Question 17

Locations of common dental abscesses

Answer 17

Palatal abscess

Periodontal abscess

Question 18

Spread into fascial spaces

Answer 18

Follows path of least resistance
Dependent on anatomical location of original abscess to adjacent tissues
Infection via fascial planes often spreads rapidly and for some distance
May occasionally cause severe respiratory distress as result of airway occlusion by oedema

Question 19

Where can abscesses spread to

Answer 19

Submandibular space

Question 20

Micro-organisms in caries v. pulp and periapical infection

Answer 20

Streptococcus
Peptostreptococcus
Fusobacterium
Black-pigmented anaerobes
-succession of species
-related to their ability to use local nutrients (e.g. by proteolytic activity and avoid host defences)

Question 21

Bacteria genera in periapical abscesses

Answer 21

Anaerobes

• gram-: prevotella, porphyromonas, fusobacterium, campylobacter
• gram+: peptostreptococcus, eubacterium

Question 22

Link between whether patients are symptomatic or not

Answer 22

With symptoms: P. gingivalis, Prev. intermedia

Without symptoms: Prev. denticola

Question 23

Pathogenic factors

Answer 23

Enzymes
-proteases (e.g. trypsin-like)
-phospholipases
Metabolic by-products
-acids (e.g. butyric)
-H2S
-Amines (e.g. putrescine)
Bacterial structures 
-capsules
-peptidoglycan 
-endotoxin (LPS - gram-s)