Defense mechanisms of gingiva

1. DEFENSE MECHANISMS
OF GINGIVA
Dr Jaffar Raza Syed

3. INTRODUCTION
Defense Mechanisms
The mechanisms by which health is preserved in the face of
potential disease.
The innate immunity system :
Acts as a first line of defense against infections,
Present since birth.
Resistance to infection, which an individual possesses by virtue of
his genetic and constitutional make up.
The adaptive immune system:
Activated when innate fails to protect the host.
Produces a specific reaction to each infectious agent
Also remembers the infectious agent and can prevent it from
causing disease later.

4. What’s the need for defense mechanisms?

5. Gingiva is constantly subjected to a PLETHORA of mechanical,
chemical and antigenic challenges from bacteria and other foreign
bodies.
During mastication of food the bolus passes over the gingival surface
with force. Gingiva is also exposed to extreme variations in temperature
and pH.
Over 300 bacterial species, some of them pathogenic, have been
recognized as commensals of the oral cavity.
Inspite of all these adverse environmental conditions, periodontal
tissues remain in a state of health, normally. & This is because of these
host defense systems..
The gingiva is able to withstand all of these adverse environmental
conditions, with the help of certain defense mechanisms.

6. Defense
mechanisms
Nonspecific Specific
Host-
microbial
symbiosis
Adaptive
immunity
Tissue
Resistance
Local
inflammatory
response
Anatomical
factors
Mucous
barrier
Epithelial
barrier
Ging
crevi
Saliva
fluid
Eshan V, Apurv J. Defense Mechanisms of Gingiva. Journal of Orofacial Research.2014
April-June;4(2):111-114
CLASSIFICATION

7. Host-Microbial Symbiosis
Close, prolonged association between two or more organisms of
different species, regardless of the benefit to the members.
• Presence commensal habitats essential for host immune
system protects periodontium from pathogenic microbes.
• Bacteria associated with periodontal health include: various
facultative gram-positive bacteria Streptococcus sanguis,
Streptococcus mitis, Actinomyces naeslundii and Actinomyces
viscosus.

8. Proposed mechanisms for commensal bacteria
in maintaining health of host tissue
• Commensals promote host tolerance to pathogenic bacteria by:
Suppressing inflammatory cytokine production.
Inducing generation of suppressive T-lymphocytes
Favoring secretion of Th2 cytokine
• Certain commensals are capable of inducing release of
antimicrobial peptides from epithelial cells.
F. nucleatum protects oral ep. From P.gingivalis invasion by
inducing release of antimicrobial peptides
• They also prevent over colonization of pathogenic/exogenous
bacteria and compete with them for resources.
Zhimin Feng & Aaron Weinberg. Role Of Bacteria In Health And Disease Of
Periodontal Tissues Periodontology 2000, Vol. 40, 2006, 50–76.

9. Tissue Resistance
Tissue resistance consists of four barriers:

10. Anatomical Factors:
• Anatomy of gingival tissues is designed for effective mastication and
clearance of food debris.
• Any poor functional tissue relations lead to plaque accumulation.
• Stippling: functional adaptation resistance to mechanical trauma.
• Attached gingiva: contoured to allow for proper deflection of food.

11. • Gingival fibers:
braces marginal gingiva firmly against tooth surface,
provides rigidity to combat forces of mastication and
tends to throw out any foreign material into the sulcus.
This expulsion is aided by the movement of teeth and
gingival tissues during function of dentition and pulse beats.

12. Mucus barrier:
• Mucus barrier is formed by
Saliva washing the gingival surface and
Gingival crevicular fluid flowing through junctional
epithelium (JE) into the gingival sulcus.

13. Saliva
• Saliva has been defined as “the fluid secreted by the salivary glands
that begins the digestion of foods”.
• Salivary secretions protective maintain the oral tissues in a
physiologic state.
• Saliva exerts a major influence on
plaque by mechanically cleansing the exposed oral surfaces,
by buffering, the acids produced by bacteria,
by controlling bacterial activity.

15. Composition of Saliva

16. Schematic presentation of the main functions of saliva in relation to
its constituents

17. Antibacterial Factors
• Saliva contains numerous inorganic and organic factors that
influence bacteria and their products in the oral
environment, aiding in the defense of the host.
• They are:
Salivary antibodies
Enzymes
Glycoproteins
Buffer system
Saliva pH

18. Salivary Antibodies:
• First line of defense in saliva, mucous layer of epithelium &
acquired pellicle.
• Salivary Ab:
o Secretory IgA – gland derived
o IgG – Serum/ local plasma cells
o Non- secretory IgA- serum/local plasma cells
o Traces of other Ig like: IgM,D,E
• Functions:
Antibacterial, fungal, viral
Helps in phagocytosis, Ag presentation, degranulation,
cytokine production.

19. • Many bacteria coated with IgA,
• bacterial deposits contain both IgA and IgG
• IgA antibodies present in parotid saliva can inhibit the
attachment of oral Streptococcus species to epithelial cells.
• Gibbons and colleagues suggested that antibodies in
secretions may impair the ability of bacteria to attach to
mucosal or dental surfaces.

20. Enzymes:
Derived from the salivary glands, bacteria, leukocytes, oral tissues,
and ingested substances;
Major enzyme parotid amylase.
Certain salivary enzymes have been reported in increased
concentrations in periodontal disease:
↑ hyaluronidase and lipase,
↑ β-glucuronidase and chondroitin sulfatase,
↑ aspartate aminotransferase and alkaline phosphatase,
↑ amino acid decarboxylases, catalase, peroxidase, and
collagenase.

21. • Proteolytic enzymes in the saliva are generated by both the
host and oral bacteria.
• These enzymes have been recognized as contributors to the
initiation and progression of periodontal disease.
• To combat these enzymes, saliva contains:
Antiproteases cysteine proteases such as cathepsins
Antileukoproteases elastase.
Tissue inhibitor of matrix metalloproteinase, activity
of collagen-degrading enzymes.

22. Lysozyme:
• Hydrolytic enzyme
• cleaves the linkage between structural components of the
glycopeptide muramic acid–containing region of the cell wall
of certain bacteria in vitro.
• It works on both gram-negative and gram-positive organisms;
its targets include Veillonella species and Actinobacillus
actinomycetemcomitans.
• It probably repels certain transient bacterial invaders of the
mouth.

23. Lactoperoxidase–thiocyanate system:
Bactericidal to some strains of Lactobacillus and Streptococcus by
preventing the accumulation of lysine and glutamic acid, which are
essential for bacterial growth.
Lactoferrin:
Effective against Actinobacillus species.
Myeloperoxidase:
• similar to salivary peroxidase,
• released by leukocytes;
• bactericidal for Actinobacillus,
• inhibits the attachment of Actinomyces strains to
hydroxyapatite.

24. Glycoproteins:
• Bind specifically to many plaque-forming bacteria.
• Facilitate bacterial accumulation on the exposed tooth surface.
• selectively adsorb to the hydroxyapatite to make acquired
pellicle.
• Glycoproteins with blood group reactivity inhibit the sorption of
some bacteria to the tooth surface and to epithelial cells.
• Glycoproteins and a glycolipid, serve as receptors for the
attachment of some viruses and bacteria.

25. Salivary Buffers and Coagulation Factors:
• The maintenance of the pH important function of salivary
buffers.
• The primary effect of these buffers is on dental caries.
• the bicarbonate–carbonic acid system important buffer
system.
• Saliva also contains coagulation factors (i.e., factors VIII, IX, and
X; plasma thromboplastin antecedent; and Hageman factor)
that hasten blood coagulation and that protect wounds from
bacterial invasion.
• An active fibrinolytic enzyme may also be present.

26. Saliva buffer system protects oral cavity in 2 ways:
1 many bacteria requires specific pH for their growth, &
altering optimal environment conditions prevents colonization.
2 plaque organisms produce acids which if not rapidly
buffered can cause demineralization of tooth.
Salivary pH:
• Normally mixed saliva has a pH of 5.6-7.0, average 6.7.
• pH increases with flow due to increased bicarbonate
concentration.
• Low ph favors survival of bacilli, yeasts and streptococci.
• High ph favors proteolytic bacteria.

27. Leukocytes:
• Saliva contains all forms of leukocytes, principal cells are PMNs.
• The number of PMNs varies from person to person at different times
of the day, and it is increased in the presence of gingivitis.
• PMNs reach the oral cavity by migrating through the lining of the
gingival sulcus.
Orogranulocytes:
Living PMNs in saliva
Their rate of migration into the oral cavity is termed the
orogranulocytic migratory rate.
Rate of migration correlates with the severity of gingival
inflammation and is therefore a reliable index for the assessment
of gingivitis

29. Role in Periodontal Pathology:
• Influences: plaque initiation & maturation
calculus formation,
periodontal disease and caries.
↓ SALIVA SECRETION:
↑ inflammatory gingival diseases, dental caries,
→ rapid tooth destruction (cemental and cervical caries).

31. The generation of crevicular fluid
Squier & Johnson (1973)
• Intercellular movement of molecules
and ions along intercellular spaces
• Three routes have been described:
Passage From CT Into The
Sulcus
Passage From The Sulcus Into
The CT
Passage of Substances through
pathological or experimentally
modified gingival sulcus.

32. Permeability of junctional & sulcular epithelium
• Brill and krasse confirmed the permeability by using fluorescein.
• Substances that have been shown to penetrate the sulcular
epithelium:
Albumin
Endotoxin
Indicate that its
Thymidine
permeable to
Histamine molecules upto
1000kd wt.
Phenytoin
Horseradish peroxidase

40. Clinical Significance
• Amount of GCF is greater when inflammation is present.
• Sometimes proportional to the severity of inflammation.
GCF production is:
Not Increased by trauma from occlusion
Increased by :
mastication of coarse foods
Toothbrushing
Gingival massage
Ovulation
Hormonal contraceptives
Prosthetic appliances
Smoking
• Other factors affecting amount of gcf : circadian periodicity &
periodontal therapy

41. Gingival fluid flow and sex hormones:
Lindhe & Lundgren, 1972 (3 groups of females are studied)
• During mensturation: ↑ in GCF because sex hormones cause ↑
in the gingival vascular permeability.
• Females on birth control pills: significant ↑ GCF
• Females during pregnancy: gingival exudates reached max
values during the last trimester and ↓ to min after delivery.
Loe,1965: During pregnancy
↑ levels of gcf due to
exacerbation of gingivitis.
Muhlemann,1948: menstrual cycle
Sutcliffe,1972: at puberty

42. Circadian periodicity:
↑ in GCF from 6:00AM -10:00PM and
↓ afterward.
• Bisada et al. 1967: Average flow was greater in the evening
and minimal early in the morning.

43. Influence of Mechanical Stimuli
Mechanical stimulation of the marginal gingiva, such as
massage by means of a round instrument, causes a significant
increase in the permeability of the blood vessels located below
the junctional and sulcular epithelia.
Brill in 1959: The amount of gingival fluid was shown to
increase significantly under the influence of chewing.
Mcluaghlin WS et al 1993 Smoking produces an immediate but
transient increase in GCF flow.

44. Periodontal Therapy and Gingival Fluid
• Oral prophylaxis:
Gwinnett et al 1978: GCF flow decreases 1 week after oral
prophylaxis and slowly returned to pretreatment values.
• After surgical procedure:
Suppipat et al 1978: increase in GCF flow during the first 2 weeks during
healing period after surgery, followed by a gradual decrease
Tsuchida & Hara 1981. decrease in GCF flow 4 weeks following root
planing & Curettage
Arnold et al., 1966: One week after gingivectomy there was a
striking increase in GCF flow.

45. The Epithelial Barrier
• Continuous epithelial sheath consisting of gingival, sulcular
and junctional epithelium.
• Continuity of the epithelium protective barrier to foreign
agents, including bacteria, their toxic products and
antigenic substances.
• The ability of an epithelial surface to resist penetration of
bacterial toxins is related to:
Thickness of the epithelium.
Degree of keratinization
Rate of turnover of the cell population

46. Thickness of the epithelium:
• oral mucosa respond to irritation hyperplasia
and downgrowth of basal layers.
• The sulcular epithelium (non-keratinised, thin)
easily damaged and less effective barrier to
penetration of the connective tissue by bacterial
products than is the oral mucosa in the other areas.

47. Degree of keratinization
• Protection afforded by the epithelium is
dependent keratinization and its ability to
desquamate or shed epithelial cells.
• Desquamation: process wherein dehydrated and
flattened cells of superficial layers are lost and and
replaced by cells of underlying layers.
• This limits colonization of bacteria and also removes
the already colonized bacteria from the epithelial
surfaces.

48. Rate of turn over of the cell population:
• Constant process of shedding and cell renewal in the oral
epithelium.
• The following have been the reported turn over times time for
different areas in the oral epithelium of experimental animals
Palate, tongue, cheek - 5 - 6 days.
Gingiva
J.E. -
- 10 – 12 days
1 – 6 days. (Skougaard et al 1962).
• The high turn over rate of epithelium as well as the connective
tissue of the periodontium, are important aspects of the
defense mechanism.

49. Components that contribute to various aspects of the
epithelial barrier
Early responders of
innate immunity
Toughened
mechanically
resistant
surface
Wound healing
Tissue turnover

50. These include cell–cell attachments and the overall integrity
of the tissue as well as the process of differentiation
(keratinization) of the tissue leading to the toughened,
mechanically resistant surface.
Desmosomes mediate keratinocyte cell–cell attachment, and
hemidesmosomes mediate keratinocyte–basal lamina
attachment.
Langerhans cells (purple dendritic cells) within the epithelium
do not have desmosomal attachments.
Constant cell renewal is critical to tissue turnover and
continual differentiation.
Cell migration is critical to wound healing and re-
epithelialization.
Constitutively expressed antimicrobial peptides contribute to
the barrier to microbial invasion.

51. Antimicrobial defense of junctional epithelium
1) Rapid turnover cell exfoliation
2) Funneling of JE towards sulcus
hinders bacterial colonization
3) Basement membrane forms an
effective barrier against microbes
4) Release of antimicrobial
substances
5) Release of cytokines from ep. Cells
6) Cytokines & chemokines released
attract LC & PMN

52. Gingival Connective Tissue
The gingival turgor,
• The resilience and pliability of the attached gingiva
withstand frictional forces and pressures that result from
mastication.
The fiber apparatus
• Controls the positioning of teeth within the dental arch
• Biostability of the gingival tissue.
• Protects the cellular defenses located at the
dentogingival interface.
• Maintenance of this fibrous complex connective tissue
turnover rate.
• Consequently, post inflammatory repair of the fiber
apparatus is completed within 40 to 60 days.
Gingival connective tissue protect the root surface and
alveolar bone from the external oral environment.

53. Cells of gingiva involved in defense
mechanism
Immune cells
Neutrophils
Monocytes
Macrophages
Lymphocytes
Basophils
Non-immune cells
Keratinocytes
Langerhans cells
Fibroblasts
Eosinophils
Mast cells
Plasma cells

54. Neutrophils
• the most predominant inflammatory cells in gingiva.
Adhere to the host substrate,
migrate to the site of infection
recognize the bacteria,
Extend Cytoplasmic processes or pseudopodia
Engulf bacteria & bring about phagocytosis.
integrate the pathogen forming a phagosome
Phagosomes fuse with lysosymes phagolysosome
digestion and destruction of pathogen takes place.

55. • PMNs also undergo degranulation and allow extracellular
killing of pathogens which is considered a principle mode
of reducing bacterial count in the gingival crevice.
• The granules found in PMN consist of primary
(azurophilic) and secondary (specific) granules.
• These can bring about oxygen dependent or independent
killing.

56. Keratinocytes:
• Keratinocytes, no longer considered as passive by-standers
• play an active role in the activation of inflammation within
the gingival tissues.
• They synthesize number of cytokines, adhesin molecules,
growth factors and enzymes.
• They also produce Interleukin 1, TNF, prostaglandin E2,
matrix metalloproteinases, that diffuse through JE, enter
the gingival connective tissue and initiate the cellular
immune reaction.
• Recruitment of neutrophils into the JE is mediated by
antigen presenting cells (Langerhans cells), and adhesion
molecules secreted by keratinocytes, promoting diapedesis
of neutrophils along the chemical gradient.

57. Langerhans cells
• Dendritics cells - Modified monocytes
• Reside chiefly in suprabasal layers.
• Act as antigen -presenting cells for lymphocytes.
• Specific elongated g-specific granules called as Birbecks
Granules.
• Have marked adenosine triphosphatase activity.
• Only epidermal cells which express receptors for C3 and
Fc portion of IgG.
• Found in oral ep. of normal gingiva.
• Smaller amounts in sulcular ep.
• Absent in healthy junctional ep.

58. Odland Body / Keratinosome / Membrane – coating
granules:
• The upper most cells of the stratum spinosum
contain numerous dense granules, keratinosomes,
which are modified lysosomes.
• They contain a large amount of acid phosphatase,
an enzyme involved in the destruction of organelle
membranes, which occurs suddenly between the
granulosum and corneum strata and during the
intercellular cementation of cornified cells.

59. Fibroblasts:
• Principal cell type of connective tissue.
• Provide structural framework, maintains CT integrity.
• Many studies shown that,
fibroblasts senses pathogens & PAMPs’
inflammatory mediators
regulate inflammatory response
• Express functional TLR’s

60. PRR
• Cells of epithelium and connective tissue express Pattern
Recognition Receptors (PRRs) that bind Pathogen-
Associated Molecular Patterns (PAMPs), found in a broad
type of organisms.
• These receptor types include:
toll-like receptors (TLR),
nucleotide-binding oligomerization domain (NOD)
proteins,
cluster of differentiation 14 (CD14),
complement receptor-3,
lectins and scavenger receptors.

62. Local inflammatory response
most significant and final barrier to penetration of connective
tissue by bacteria and their toxins.
• This response is stimulated by tissue injury and infection.
• A series of reactions brings about local changes like increased
vascularization leading to increased fluid collection and cellular
exudation that eventually causes accumulation of serum
proteins and phagocytic cells in the affected area.

63. Conclusion
• The oral cavity is well equipped to counterattack any adverse
condition that may harm the gingiva.
• While the innate immunity acts primarily against any foreign
invader, the specific immunity takes a more complex targeted
approach to protect the gingiva.
• Right from its superficial epithelial layer to the innermost
connective tissue, there is a line of defense that acts in harmony
with other oral structures to maintain homeostasis.