- Joined
- Jun 18, 2006
- Messages
- 28
- Reaction score
- 0
This is cool notes please refer very helpful it is very good information please save it in a word document and organize it:
GINGIVA
I. DEFINITION
The Gingiva is that subpart of the Oral Mucosa that covers, surrounds and invests the alveolus/tooth complex. The gingiva is attached to the alveolus/tooth complex by both a fibrous connective tissue and an epithelium attachment apparatus; the former is characterized by collagen fiber bundles that connect to cementum and alveolar bone, the latter is characterized by hemidesmosome-mediated attachments to an inner basement membrane lining the hard tissue surface of the tooth. In lay terms, the gingiva are referred to as the "gums."
II. CLINICAL RATIONALE FOR STUDY
The gingiva can be considered as the protective outer part of the periodontium. It constitutes the so-called first line of defense against microbial pathogens. The gingiva is the most readily accessible and easily examined among the 4 tissues of the periodontium. Plaque accumulations can induce infectious/inflammatory alterations in the gingiva that predispose the periodontium to tissue destruction, leading to Gingivitis and Periodontitis. Many clinical indices have been designed to describe the relative state of health or disease in the gingiva.
III. GENERAL OVERVIEW OF ORAL MUCOSA
A. Types of Oral Mucosa
1. Masticatory Mucosa (i.e., the "gums") [Keratinized]
[Clinically referred to as "gingiva" and "palatal mucosa"]
2. Lining Mucosa (i.e., the "alveolar mucosa") [Nonkeratinized]
[Clinically referred to as "mucosa" or "oral mucosa"]
3. Specialized Mucosa (i.e., the "taste buds" of the tongue dorsum) [Nonkeratinized]
a. Fungiform Papillae
b. Filiform Papillae
c. Foliate Papillae
d. Circumvallate Papillae
B. Functions of Oral Mucosa
1. Protection (primarily due to the keratinized mucosa)
a. Masticatory Mucosa
1. Gingiva [Clinical Relevance: gingival graft surgery]
2. Hard Palate [Clinical Relevance: gingival graft surgery]
3. Sensation (ex. taste buds)
4. Secretion (ex. minor salivary glands)
5. Thermal Regulation
C. Clinical Features of Oral Mucosa
1. Pink or red color w/ or w/o pigmentation
2. Moist (in health)
3. Gingiva is comprised of 2 tissue "compartments"[Histologic Description]
a. Keratinized Squamous Epithelium (multilayered)
1) Basement Membrane/Basal Lamina
a) Lamina Lucida
b) Lamina Densa
2) Stratum Basale (basal cell layer)
3) Stratum Spinosum (spiny or prickle cell layer)
4) Stratum Granulosum (granular cell layer)
5) Stratum Corneum (cornified, horny or keratinized layer)
b. Connective Tissue (soft, nonmineralized)
1) Basement Membrane
a) Lamina Reticularis
2) Superficial Papillary Layer (arbitrary designation; associated with the epithelial ridges)
3) Deeper Reticular Layer (arbitrary designation; associated with the bulk of Lamina Propria)
a) [Note: do not confuse with the Lamina Reticularis of the Basement Membrane]
4) Even deeper Submucosa Layer, when present (associated with fatty/glandular tissue, esp. in posterior vs. anterior hard palate)
IV. GENERAL HISTOLOGY OF THE GINGIVA [a subpart of the oral mucosa] (tissue level)
A. Composition of the Gingiva
1. Principle Cells
a. Epithelial cells (of the epithelium compartment)
b. Fibroblasts (of the connective tissue compartment; "Lamina Propria," or "Corium")
2. Ancillary Cells
a. Undifferentiated Mesenchymal Cells (minimal, if any)
b. Immune/Inflammatory cells
c. Pigment cells
d. Sensory cells
e. Neurovascular cells
f. Secretory cells
3. Extracellular Matrix of the Epithelium Compartment ["Basement Membrane"]
a. Collagen proteins
b. Non-collagen proteins (including secreted adhesive proteins of the ECM)
c. Transmembrane adhesive proteins
1) Cadherins & Cell Adhesion Molecules (CAMs) for cell-cell (i.e., intercellular) adhesion
2) Integrins for cell-matrix adhesions (i.e., attachment to the basement membrane)
4. Extracellular Matrix of the Connective Tissue Compartment
a. Collagen proteins
b. Non-collagen proteins (including secreted adhesive proteins of the ECM) [in connective tissue these are referred to as ground substance]
c. Transmembrane adhesive proteins
1) Integrins for cell-matrix adhesions (i.e., fibronexi or "focal contacts") [Note: minimal cell-cell adhesions are found
among fibroblasts in vivo]
5. Neurovascular Elements
a. Nerves (mainly sensory; the nerve endings are unmyelinated and occur in different forms)
b. Blood Vessels (numerous capillaries; more vascular than skin)
B. Functions of the Gingiva [sometimes considered as "Investing" structure of the tooth]
1. Protection, Attachment & Adaptation/Homeostasis (can be considered altogether)
a. Surface Toughness Components [designed primarily to act as a semi-permeable barrier and to resist surface ulceration during mastication]
1) Keratinized Epithelium Surface ("Cornified" or "Horny" outer layer of the multilayered stratified squamous epithelium)
2) Thus, "protection" is mainly a function of the epithelium
b. Tensile Strength Components [designed primarily to connect teeth to gingiva and to resist shearing forces during mastication]
1) Collagen Fiber Bundles
2) Analogy: spliced rope-like tethers
3) Thus, "attachment" (and also "protection") is mainly a function of the collagenous structures within the lamina propria
1) Ground Substance; Tissue Fluid; & the Vasculature
2) Thus, "adaptation/homeostasis" is mainly a function of the non-collagenous structures within the lamina propria
2. Sensory Perception [designed to provide information about external environment]
a. Nociceptors (provide sensation of pain)
b. Mechanoreceptors (provide sensation of touch/pressure)
c. Thermoreceptors (?) (provide sensation of hot/cold)
C. General Characteristics
1. Gingiva is comprised of 2 tissue "compartments" [Functional Description]
a. Epithelium [Stratified Squamous type, with & without keratinization]
1) Oral Epithelium/Gingival Epithelium (OE/GE)- keratinized
2) Sulcular Epithelium (SE)- nonkeratinized
3) Junctional Epithelium (JE)- nonkeratinized
b. Connective Tissue (soft, unmineralized) [Lamina Propria; Corium]
1) Superficial "Instructive" Connective Tissue
2) Deep "Permissive" Connective Tissue
2. Wound Healing responses
a. Moderate-to-high repair potential
b. Minimal-to-moderate regeneration potential
3. Forms 3 types of junctions with other tooth & oral mucosa tissues
a. Mucocutaneous Junction (MCJ)
1) Is the junction between the lining mucosa of the lips and the skin of the face
2) Very commonly referred to clinically as the "vermilion border" of the lip
3) Clinical Relevance: dysplastic and neoplastic conditions (ex. actinic keratosis)
b. Mucogingival Junction (MGJ)
1) Is the junction between the masticatory mucosa and the lining mucosa (i.e., between gingiva & alveolar mucosa); sometimes a groove or depression demarcates the MGJ
2) Clinical Relevance: important anatomic landmark for determining the amount of keratinized gingiva (very commonly referred to clinically as the "width" of keratinized gingiva)
3) Located on the labial/facial surface of maxillary and mandibular gingiva, and on the lingual surface of mandibular gingiva
4) Not found on palatal surface of maxillary gingiva in humans (but is found in non-human primates); on the palatal surface, the masticatory mucosa of the hard palate is continuous with the masticatory mucosa of the gingiva [Clinical Relevance: (1) the design of palatal flaps during periodontal surgery must take into account the generally thicker & tough fibrous masticatory mucosa as well as the lack of freely moveable alveolar lining mucosa; and
2) for the same reasons, the palate is the prime donor site for harvesting tough fibrous tissue to be used in gingival transplant surgery (ex. free gingival autografts)]
c. Dentogingival Junction (DGJ)
1) Is the attachment of the gingiva to the tooth and alveolar bone
2) Sometimes referred to histologically as "attachment apparatus"
3) Very commonly referred to clinically as the "biologic width"
a. Includes the non-attached "sulcus" dead space (≤ 3 mm)
(via sulcular epithelium (SE) )
b. Includes the "epithelial attachment" portion (~1 mm)
(via junctional epithelium (JE) )
c. Includes the "connective tissue attachment" (~1-2 mm)
(via supracrestal collagen fiber bundles)
4) The col is the interdental gingiva, as viewed in the buccal-lingual direction
a) Is no longer considered more susceptible to periodontal disease than other aspects of the DGJ
4. Width of the gingiva
a. Refers to the apicocoronal dimension; is actually a measure of vertical height [Note: this is counterintuitive and often leads to confusion among beginning dental students]
b. Measured clinically as the vertical distance, in millimeters, between the MGJ and the crest of the gingiva (the crest of the gingiva is also very commonly referred to clinically as the gingival "free margin" or more simply as the gingival "margin")
[Clinical Relevance: the initial incisions made during periodontal surgery are located in some pre-defined relationship to the gingival margin (i.e., "marginal," or "submarginal," or "intrasulcular")]
c. This vertical measurement between the MGJ and the gingival crest gives the total width of the gingival masticatory mucosa at any particular tooth
1) Recall that the gingival masticatory mucosa is keratinized
2) Therefore, this vertical measurement between the MGJ and the gingival crest gives, by definition, the total width of the "keratinized gingiva" at any particular tooth
3) The keratinized gingiva consists of 2 subparts: 1) the attached gingiva and 2) the free gingiva which encloses the gingival sulcus/pocket (also called the marginal/papillary gingiva)
a) the "attached gingiva"
i) is measured from the MGJ to the base of the sulcus
ii) Clinical Relevance: in determining "gum recession"
b) the "nonattached gingiva" or "free gingiva"
i) is measured from the gingival crest to the base of the sulcus; sometimes a clinical feature called the "free gingival groove" can be seen that corresponds more or less to the base of the sulcus
c) the "dead space" between the tooth and the free gingiva is very commonly referred to clinically as the gingival sulcus (in health) or the gingival pocket (in disease); an older term for the gingival sulcus is gingival crevice
i) Clinical Relevance: in determining "gum disease"
d. The width of the gingiva is variable
1. Varies from tooth-to-tooth (normally ranges ~2-7 mm; the thinnest area is the buccal aspect of the mandibular premolars)
2) Varies from patient-to-patient (increases with tooth eruption; may also decrease in older adults [termed "passive eruption"])
5. Thickness of the gingiva
a. Refers to the buccolingual dimension; is actually a measure of horizontal width
b. Measured clinically as the horizontal distance, in millimeters, between the outer cortical plate of the alveolar bone and the external surface of the gingiva (sometimes referred to as "sounding"); However, this is not a routine clinical measurement & is done only after the gingiva are appropriately anesthesized (this hurts!)
6.Blood Supply/Lymphatics
a. Arterial Supply
1) Very well vascularized
2) Derived from respective branches of Maxillary and Mandibular aa.
a) Hard Palate: major palatine, nasopalatine & sphenopalatine
b) Maxillary Gingiva: major palatine, buccal, PSA, MSA & ASA
c) Mandibular Gingiva: inf. alveolar, incisive, sublingual, mental & buccal
3) Arterial branches run parallel to the surface, in either:
a) submucosa layer (in thicker areas), or
b) deep reticular layer (in thinner areas)
4) These vessels give off progressively smaller branches that anastomose with adjacent vessels in the reticular layer before forming an extensive interconnecting capillary network (referred to as capillary loops) in the papillary layer immediately subjacent to the basal epithelial cells
5) This network of capillary loops is much more profuse in gingiva than in skin, which partly explains the deeper color of the gingiva
6) Also, the rich anastomoses of arterioles and capillaries allows the gingiva to heal from injury more rapidly than skin
7) Among all the types of oral mucosa, blood flow is greatest in the gingiva
8) Blood flow through the oral mucosa, as a whole, is greater than in the skin
9) Inflammation in the gingiva (i.e., Gingivitis) may be partly responsible for this greater blood flow in gingiva.
b. Venous Drainage
1) Venous drainage tends to follow arterial structures, but is less organized
2) Lacks arteriovenous shunts (unlike skin, which plays a role in body temperature regulation)
c. Lymphatic Drainage
1) Lymphatic vessels tend to follow the venous drainage
7. Nerve Supply
a. Efferent (motor) supply
1) Efferent supply is autonomic (mostly sympathetic, esp. for blood vessels)
b. Afferent (sensory) supply
1) Most of the nerves in gingiva are for afferent sensory supply
2) Derived from respective branches of the 2nd & 3rd divisions of the Trigeminal Nerve
a) Hard Palate: major palatine, nasopalatine & sphenopalatine
b) Maxillary Gingiva: major palatine, PSA, MSA & ASA
c) Mandibular Gingiva: inf. alveolar, sublingual, mental & buccal
3) Sensory nerves lose their myelin sheaths and form a network in the reticular layer of the Lamina Propria, terminating in what is referred to as a subepithelial plexus
c. Type of Termination of the Sensory Nerves (2 general types)
1) Free Nerve Endings [similar to those found in PDL and in other types of joints (ex. TMJ)]
a) Found within the Epithelium [Note: unlike capillaries, free nerve endings do penetrate into the epithelium]
i) frequently associated with Merkel's Cells
😉Merkel's cells are believed to be sensory and respond to touch; associated with nerve fibers by a synapse-like junction
ii) also associated with Keratinocytes rather than Merkel's Cells (this arrangement may be considered a type of mesaxon)
iii) terminate as simple endings in the middle or upper layers of the epithelium
b) Also found in the Lamina Propria
i) frequently associated with Schwann Cells
ii) can be considered to be less numerous than in epithelium (?)
c) Nociceptor Function [1°]
d) Mechanoreceptor Function [2°]
e) Thermoreceptor Function (?) [3°]
2) Organized Nerve Endings [generally characterized by groups of nerve fibers surrounded by a connective tissue capsule]
a) Not found within the Epithelium
b) Found in the Lamina Propria, usually in the papillary region
c) More abundant in anterior rather than posterior & in maxilla rather than mandible [Clinical Relevance: maxillary anterior sextant is usually the most sensitive to periodontal probing]
d) Are classified according to their specific morphology
i) Meissner's Corpuscle Primarily sensitive to touch stimuli
ii) Ruffini's Corpuscles [also found in joints (ex. TMJ), in association with Pacini's corpuscles & Golgi tendon organs]
😉 Primarily sensitive to mechano- receptive/proprioceptive stimuli
iii) Krause's Bulbs
😉 Primarily sensitive to cold stimuli
iv) Mucocutaneous End Organs
😉 Function not described
e) Mixed functions among the free & organized endings likely
E. Classification (already described above)
1. General Comments
a. Gingiva is a keratinized masticatory mucosa
b. Gingiva is the most obvious & clinically measurable of the 4 tissues of the periodontium
c. Therefore, many of the clinical descriptions of the periodontium refer to the appearance of the gingiva
d. The various clinical descriptions of gingiva, in turn, specifically refer to its inflammation status
1) Color
2) Size & Shape
3) Consistency/Texture (ex. "stippling")
4) Pain/Loss of Function
5) [Temperature]
6) Location relative to the CEJ
2. Based on structure-function considerations [most Clinically Relevant]
a. The sulcus acts as a habitat for Gram (+) and Gram (-) bacteria
b. The junctional epithelium (JE) acts as a potentially leaky "seal" due to the wide intercellular spaces [Analogy: discontinuous caulking around a bathtub]
c. The dentogingival collagen fibers act as a type of "fiber barrier" to bacteria/bacterial toxins, in addition to serving a tooth- attachment function
V. CELL BIOLOGY (cell level)
A. Types of Gingival Cells vary according to Different Primary Functions
1. Principle Cells
a. Epithelial cells (commonly referred to as Keratinocytes) [constitute ~90% of all the cells found within the epithelium; ~10% of these are progenitor cells in basal layer]
1) Specialized cells which form the coherent cell sheets known as epithelia; epithelial cells are called keratinocytes because of their characteristic differentiated activity in the synthesis of intermediate filament proteins called keratins; the main cell type in the gingival epithelium compartment
2) Epithelia can be defined, in general, as coherent, dynamic cell sheets, formed from one or more layers of eucaryotic cells covering an external surface or lining a body cavity, that perform a number of varied functions such as constituting a physical barrier, absorbing molecular nutrients, secreting different molecules, and propulsive movement of external substances [Note: not all epithelia exhibit all these functions; for example, the epithelium of the masticatory mucosa is not considered to be an important route for absorption of substances within the oral cavity]
3) Originate from a fusion of Reduced Enamel Epithelium and epithelium of the Dental Lamina [Remember: both of these are originally derived from the Primary EpitheliBand in the early embryo]
4) Considered to be a functionally heterogeneous population of cells in the Dentogingival Junction (DGJ)
a) Oral Epithelium/Gingival Epithelium (OE/GE)
b) Sulcular Epithelium (SE)
c) Junctional Epithelium (JE)
5) Large cells with extensive cytoplasm/organelles for protein synthesis & secretion [Clinical Relevance: critical for both anabolic & catabolic aspects of the Basement Membrane and protective outer layer]
6) Well-developed cytoskeleton for cell movement (for either migration (~0.5mm/day) or in situ shape change) [Clinical Relevance: periodontal wound healing]
a) Actin filaments (i.e., "thin" filaments)
b) Actin-binding proteins (i.e., accessory proteins)
c) Myosin proteins (i.e., "thick" filaments)
d) Microtubules (i.e., "thick" filaments, also)
e) Intermediate filaments (ex. Keratin(s) ); the keratins are a heterogeneous group of intracellular proteins that are differentially expressed among different epithelia and even in different parts of the same one epithelium [Clinical Relevance: typing of carcinoma primary tumors]
7) Form several types of Cell-to Cell functional contacts
a) Occluding Junctions (Tight Junctions)- very rare in gingiva
b) Communicating Junctions (Gap Junctions)- rare in gingiva
c) Anchoring Junctions (Adherens Junctions)- common in the gingiva
i) Adhesion Belts
ii) Desmosomes
8) Form several types of Cell-to-Matrix functional contacts
a) Anchoring Junctions (Adherens Junctions)- common in the gingiva
i) Focal Contacts (sometimes called Fibronexi)
ii) Hemidesmosomes
9) Overall Clinical Relevance: any disease of gingival epithelium leads to a loss of barrier integrity and ulcer formation [Clinical Relevance: mucositis following head & neck cancer radiation therapy]
b. Fibroblasts [constitute  90% of all the cells found within the corium]
1) The main cell type in the gingival connective tissue compartment; "Lamina Propria," or "Corium"
2) Originate from the mesenchyme subjacent to the Dental Lamina and peripheral to the Dental Organ/Enamel Organ and the Dental Follicle/Sac
3) Considered to be a functionally heterogeneous population of cells (despite similarities in microscopic appearance among fibroblasts, in general); however, subtypes are not well characterized [Clinical Relevance: Dilantin® "Hyperplasia"]
4) Large cells with extensive cytoplasm/organelles for protein synthesis & secretion [Clinical Relevance: critical for both anabolic & catabolic aspects of the ECM of connective tissue]
5) Well-developed cytoskeleton for cell movement (either for migration or for in situ shape change) [Clinical Relevance: periodontal wound healing]
a) Actin filaments (i.e., "thin" filaments)
b) Actin-binding proteins (i.e., accessory proteins)
c) Myosin proteins (i.e., "thick" filaments)
d) Microtubules (i.e., "thick" filaments, also)
e) Intermediate filaments (ex. Vimentin)
6) Overall Clinical Relevance: any disease of gingival corium fibroblasts leads to a rapid loss of tooth- supporting/tooth-investing tissue
2. Ancillary Cells
a. Undifferentiated Mesenchymal Cells - minimal, if any, present in the gingival corium
b. Immune/Inflammatory cells
1) Mainly associated with acute inflammation
a) Polymorphonuclear leukocytes (PMNs; Neutrophils) [found in both epithelium & corium; PMNs are routinely found in low levels even in clinically healthy gingiva]
2) Mainly associated with chronic inflammation
a) lymphocytes [found in corium]
3) Mainly associated with cellular immunity
a) T-lymphocytes [found in corium]
b) Macrophages/Histiocytes [found in both epithelium & corium (ex. corium melanophages & siderophages]
c) Mast Cells [found in corium]
d) Langerhan's Cells [found only in epithelium]
i) A macrophage-like cell, derived from bone marrow, that functions as an immune cell in skin and related epithelia, such as in gingiva
ii) Characterized by small intracellular granules called the Birbeck granules
4) Mainly associated with humoral immunity (i.e., antibodies)
a) B-lymphocytes & Plasma Cells [found in corium]
c. Pigment cells
1) Melanocyte [found only in epithelium]
a) A pigment cell, derived from neural crest, that produces melanin, the dark substance responsible for the protective and decorative pigmentation of skin and hair; this ancillary to the specialized function of epithelial cells proper [the melanin is found in structures referred to as melanosomes]
b) Melanin is secreted by melanocytes and then taken up by neighboring keratinocytes
c) Clinical Relevance: oral differential diagnosis of the malignant melanoma form of skin cancer vs. a nevus (mole) vs. a melanotic macule
d. Sensory cells
1) Merkel Cell [found only in epithelium] (described above)
a) A cell that is associated with nerve fibers which extend into the epithelium of the epidermis or oral mucosa
e. Neurovascular cells- mainly in lamina propria; some nerve endings within epithelium (described above)
f. Secretory cells
1) Melanocytes
2) Mast Cells
3) [Associated minor salivary & sebaceous gland epithelial cells]
C. Various Structural Proteins
1. General
a. Collagen Proteins (Mainly Type I, III, IV, V & VII collagen)
b. Noncollagen Proteins
1) Gingival Proteoglycans/Glycosaminoglycans
2) Gingival Glycoproteins
a) Laminin
b) Fibronectin
3) Gingival Glycolipids (?)
c. Laminin (is an adhesive glycoprotein of the basement membrane)
d. Others, for example:
1) Entactin
4. Extracellular Matrix of the Connective Tissue Compartment [again, fibroblast secretory products are mainly components of the Lamina Propria]
a. Type I Collagen (is a "fiber-forming" type of collagen, in contrast to Type IV Collagen, which is a "network-forming" type of collagen)
1) Numerous Collagen Fiber Bundles (well defined)
5) Other Ground Substance components
a) Other Proteoglycans/Glycosaminoglycans (PG/GAG)
(ex. dermatan sulfate)
b) Other Glycoproteins (GP)
c) Other Glycolipids (GL)
D. Organized Collagen Fiber Bundles of the Lamina Propria
1. Type I & III mixture, mostly (along with other molecular organizers; ex. Type XII collagen)
2. Individual fibers have a mean diameter of ~100 nm (therefore, generally thicker than in PDL)
3. Help to maintain the functional integrity of the tooth
4. Collectively, the various fiber bundles are occasionally referred to as the "gingival ligament;" however, this term is not completely accepted [Clinically, this is referred to as the "connective tissue attachment"]
5. Arranged in several distinct fiber bundles (forming a "fiber barrier")
a. Dentogingival Group
1) Attach to cervical cementum immediately apical to CEJ and coronal to PDL
2) Run laterally & obliquely into the lamina propria
3) Insert into the lamina propria of both "free" and "attached" gingiva
b. Dentoperiosteal Group
1) Attach to cervical cementum
2) Run apically over the periosteum of the outer cortical plate of bone
3) Insert into either the outer cortical plate or the vestibular muscle and floor of the mouth
c. Transseptal Group
1) Attach to cementum just apical to the base of the JE
2) Run interdentally in a horizontal direction over (i.e., coronal to) the alveolar bone crest
3) Insert into cementum on the adjacent tooth just apical to the base of the JE
4) Collectively form a transseptal fiber system (sometimes referred to as the "transseptal ligament" or "interdental ligament") connecting all the teeth of the arch
5)Clinical Relevance: transseptal fibers of the gingiva are believed also to provide the mechanism for mesial drift (i.e.,anterior component of occlusal forces
d. Alveologingival Group
1) Attach to the alveolar bone crest
2) Run coronally & laterally into the lamina propria
3) Insert into the lamina propria of both "free" and "attached" gingiva
e. Circular Group
1) Do not attach directly to the tooth
2) Run circumferentially around the neck of the tooth, within the lamina propria
3) Interconnect with the other fiber groups to help bind the "free" gingiva to the tooth
f. Other minor fiber bundle groups
GINGIVA
I. DEFINITION
The Gingiva is that subpart of the Oral Mucosa that covers, surrounds and invests the alveolus/tooth complex. The gingiva is attached to the alveolus/tooth complex by both a fibrous connective tissue and an epithelium attachment apparatus; the former is characterized by collagen fiber bundles that connect to cementum and alveolar bone, the latter is characterized by hemidesmosome-mediated attachments to an inner basement membrane lining the hard tissue surface of the tooth. In lay terms, the gingiva are referred to as the "gums."
II. CLINICAL RATIONALE FOR STUDY
The gingiva can be considered as the protective outer part of the periodontium. It constitutes the so-called first line of defense against microbial pathogens. The gingiva is the most readily accessible and easily examined among the 4 tissues of the periodontium. Plaque accumulations can induce infectious/inflammatory alterations in the gingiva that predispose the periodontium to tissue destruction, leading to Gingivitis and Periodontitis. Many clinical indices have been designed to describe the relative state of health or disease in the gingiva.
III. GENERAL OVERVIEW OF ORAL MUCOSA
A. Types of Oral Mucosa
1. Masticatory Mucosa (i.e., the "gums") [Keratinized]
[Clinically referred to as "gingiva" and "palatal mucosa"]
2. Lining Mucosa (i.e., the "alveolar mucosa") [Nonkeratinized]
[Clinically referred to as "mucosa" or "oral mucosa"]
3. Specialized Mucosa (i.e., the "taste buds" of the tongue dorsum) [Nonkeratinized]
a. Fungiform Papillae
b. Filiform Papillae
c. Foliate Papillae
d. Circumvallate Papillae
B. Functions of Oral Mucosa
1. Protection (primarily due to the keratinized mucosa)
a. Masticatory Mucosa
1. Gingiva [Clinical Relevance: gingival graft surgery]
2. Hard Palate [Clinical Relevance: gingival graft surgery]
3. Sensation (ex. taste buds)
4. Secretion (ex. minor salivary glands)
5. Thermal Regulation
C. Clinical Features of Oral Mucosa
1. Pink or red color w/ or w/o pigmentation
2. Moist (in health)
3. Gingiva is comprised of 2 tissue "compartments"[Histologic Description]
a. Keratinized Squamous Epithelium (multilayered)
1) Basement Membrane/Basal Lamina
a) Lamina Lucida
b) Lamina Densa
2) Stratum Basale (basal cell layer)
3) Stratum Spinosum (spiny or prickle cell layer)
4) Stratum Granulosum (granular cell layer)
5) Stratum Corneum (cornified, horny or keratinized layer)
b. Connective Tissue (soft, nonmineralized)
1) Basement Membrane
a) Lamina Reticularis
2) Superficial Papillary Layer (arbitrary designation; associated with the epithelial ridges)
3) Deeper Reticular Layer (arbitrary designation; associated with the bulk of Lamina Propria)
a) [Note: do not confuse with the Lamina Reticularis of the Basement Membrane]
4) Even deeper Submucosa Layer, when present (associated with fatty/glandular tissue, esp. in posterior vs. anterior hard palate)
IV. GENERAL HISTOLOGY OF THE GINGIVA [a subpart of the oral mucosa] (tissue level)
A. Composition of the Gingiva
1. Principle Cells
a. Epithelial cells (of the epithelium compartment)
b. Fibroblasts (of the connective tissue compartment; "Lamina Propria," or "Corium")
2. Ancillary Cells
a. Undifferentiated Mesenchymal Cells (minimal, if any)
b. Immune/Inflammatory cells
c. Pigment cells
d. Sensory cells
e. Neurovascular cells
f. Secretory cells
3. Extracellular Matrix of the Epithelium Compartment ["Basement Membrane"]
a. Collagen proteins
b. Non-collagen proteins (including secreted adhesive proteins of the ECM)
c. Transmembrane adhesive proteins
1) Cadherins & Cell Adhesion Molecules (CAMs) for cell-cell (i.e., intercellular) adhesion
2) Integrins for cell-matrix adhesions (i.e., attachment to the basement membrane)
4. Extracellular Matrix of the Connective Tissue Compartment
a. Collagen proteins
b. Non-collagen proteins (including secreted adhesive proteins of the ECM) [in connective tissue these are referred to as ground substance]
c. Transmembrane adhesive proteins
1) Integrins for cell-matrix adhesions (i.e., fibronexi or "focal contacts") [Note: minimal cell-cell adhesions are found
among fibroblasts in vivo]
5. Neurovascular Elements
a. Nerves (mainly sensory; the nerve endings are unmyelinated and occur in different forms)
b. Blood Vessels (numerous capillaries; more vascular than skin)
B. Functions of the Gingiva [sometimes considered as "Investing" structure of the tooth]
1. Protection, Attachment & Adaptation/Homeostasis (can be considered altogether)
a. Surface Toughness Components [designed primarily to act as a semi-permeable barrier and to resist surface ulceration during mastication]
1) Keratinized Epithelium Surface ("Cornified" or "Horny" outer layer of the multilayered stratified squamous epithelium)
2) Thus, "protection" is mainly a function of the epithelium
b. Tensile Strength Components [designed primarily to connect teeth to gingiva and to resist shearing forces during mastication]
1) Collagen Fiber Bundles
2) Analogy: spliced rope-like tethers
3) Thus, "attachment" (and also "protection") is mainly a function of the collagenous structures within the lamina propria
1) Ground Substance; Tissue Fluid; & the Vasculature
2) Thus, "adaptation/homeostasis" is mainly a function of the non-collagenous structures within the lamina propria
2. Sensory Perception [designed to provide information about external environment]
a. Nociceptors (provide sensation of pain)
b. Mechanoreceptors (provide sensation of touch/pressure)
c. Thermoreceptors (?) (provide sensation of hot/cold)
C. General Characteristics
1. Gingiva is comprised of 2 tissue "compartments" [Functional Description]
a. Epithelium [Stratified Squamous type, with & without keratinization]
1) Oral Epithelium/Gingival Epithelium (OE/GE)- keratinized
2) Sulcular Epithelium (SE)- nonkeratinized
3) Junctional Epithelium (JE)- nonkeratinized
b. Connective Tissue (soft, unmineralized) [Lamina Propria; Corium]
1) Superficial "Instructive" Connective Tissue
2) Deep "Permissive" Connective Tissue
2. Wound Healing responses
a. Moderate-to-high repair potential
b. Minimal-to-moderate regeneration potential
3. Forms 3 types of junctions with other tooth & oral mucosa tissues
a. Mucocutaneous Junction (MCJ)
1) Is the junction between the lining mucosa of the lips and the skin of the face
2) Very commonly referred to clinically as the "vermilion border" of the lip
3) Clinical Relevance: dysplastic and neoplastic conditions (ex. actinic keratosis)
b. Mucogingival Junction (MGJ)
1) Is the junction between the masticatory mucosa and the lining mucosa (i.e., between gingiva & alveolar mucosa); sometimes a groove or depression demarcates the MGJ
2) Clinical Relevance: important anatomic landmark for determining the amount of keratinized gingiva (very commonly referred to clinically as the "width" of keratinized gingiva)
3) Located on the labial/facial surface of maxillary and mandibular gingiva, and on the lingual surface of mandibular gingiva
4) Not found on palatal surface of maxillary gingiva in humans (but is found in non-human primates); on the palatal surface, the masticatory mucosa of the hard palate is continuous with the masticatory mucosa of the gingiva [Clinical Relevance: (1) the design of palatal flaps during periodontal surgery must take into account the generally thicker & tough fibrous masticatory mucosa as well as the lack of freely moveable alveolar lining mucosa; and
2) for the same reasons, the palate is the prime donor site for harvesting tough fibrous tissue to be used in gingival transplant surgery (ex. free gingival autografts)]
c. Dentogingival Junction (DGJ)
1) Is the attachment of the gingiva to the tooth and alveolar bone
2) Sometimes referred to histologically as "attachment apparatus"
3) Very commonly referred to clinically as the "biologic width"
a. Includes the non-attached "sulcus" dead space (≤ 3 mm)
(via sulcular epithelium (SE) )
b. Includes the "epithelial attachment" portion (~1 mm)
(via junctional epithelium (JE) )
c. Includes the "connective tissue attachment" (~1-2 mm)
(via supracrestal collagen fiber bundles)
4) The col is the interdental gingiva, as viewed in the buccal-lingual direction
a) Is no longer considered more susceptible to periodontal disease than other aspects of the DGJ
4. Width of the gingiva
a. Refers to the apicocoronal dimension; is actually a measure of vertical height [Note: this is counterintuitive and often leads to confusion among beginning dental students]
b. Measured clinically as the vertical distance, in millimeters, between the MGJ and the crest of the gingiva (the crest of the gingiva is also very commonly referred to clinically as the gingival "free margin" or more simply as the gingival "margin")
[Clinical Relevance: the initial incisions made during periodontal surgery are located in some pre-defined relationship to the gingival margin (i.e., "marginal," or "submarginal," or "intrasulcular")]
c. This vertical measurement between the MGJ and the gingival crest gives the total width of the gingival masticatory mucosa at any particular tooth
1) Recall that the gingival masticatory mucosa is keratinized
2) Therefore, this vertical measurement between the MGJ and the gingival crest gives, by definition, the total width of the "keratinized gingiva" at any particular tooth
3) The keratinized gingiva consists of 2 subparts: 1) the attached gingiva and 2) the free gingiva which encloses the gingival sulcus/pocket (also called the marginal/papillary gingiva)
a) the "attached gingiva"
i) is measured from the MGJ to the base of the sulcus
ii) Clinical Relevance: in determining "gum recession"
b) the "nonattached gingiva" or "free gingiva"
i) is measured from the gingival crest to the base of the sulcus; sometimes a clinical feature called the "free gingival groove" can be seen that corresponds more or less to the base of the sulcus
c) the "dead space" between the tooth and the free gingiva is very commonly referred to clinically as the gingival sulcus (in health) or the gingival pocket (in disease); an older term for the gingival sulcus is gingival crevice
i) Clinical Relevance: in determining "gum disease"
d. The width of the gingiva is variable
1. Varies from tooth-to-tooth (normally ranges ~2-7 mm; the thinnest area is the buccal aspect of the mandibular premolars)
2) Varies from patient-to-patient (increases with tooth eruption; may also decrease in older adults [termed "passive eruption"])
5. Thickness of the gingiva
a. Refers to the buccolingual dimension; is actually a measure of horizontal width
b. Measured clinically as the horizontal distance, in millimeters, between the outer cortical plate of the alveolar bone and the external surface of the gingiva (sometimes referred to as "sounding"); However, this is not a routine clinical measurement & is done only after the gingiva are appropriately anesthesized (this hurts!)
6.Blood Supply/Lymphatics
a. Arterial Supply
1) Very well vascularized
2) Derived from respective branches of Maxillary and Mandibular aa.
a) Hard Palate: major palatine, nasopalatine & sphenopalatine
b) Maxillary Gingiva: major palatine, buccal, PSA, MSA & ASA
c) Mandibular Gingiva: inf. alveolar, incisive, sublingual, mental & buccal
3) Arterial branches run parallel to the surface, in either:
a) submucosa layer (in thicker areas), or
b) deep reticular layer (in thinner areas)
4) These vessels give off progressively smaller branches that anastomose with adjacent vessels in the reticular layer before forming an extensive interconnecting capillary network (referred to as capillary loops) in the papillary layer immediately subjacent to the basal epithelial cells
5) This network of capillary loops is much more profuse in gingiva than in skin, which partly explains the deeper color of the gingiva
6) Also, the rich anastomoses of arterioles and capillaries allows the gingiva to heal from injury more rapidly than skin
7) Among all the types of oral mucosa, blood flow is greatest in the gingiva
8) Blood flow through the oral mucosa, as a whole, is greater than in the skin
9) Inflammation in the gingiva (i.e., Gingivitis) may be partly responsible for this greater blood flow in gingiva.
b. Venous Drainage
1) Venous drainage tends to follow arterial structures, but is less organized
2) Lacks arteriovenous shunts (unlike skin, which plays a role in body temperature regulation)
c. Lymphatic Drainage
1) Lymphatic vessels tend to follow the venous drainage
7. Nerve Supply
a. Efferent (motor) supply
1) Efferent supply is autonomic (mostly sympathetic, esp. for blood vessels)
b. Afferent (sensory) supply
1) Most of the nerves in gingiva are for afferent sensory supply
2) Derived from respective branches of the 2nd & 3rd divisions of the Trigeminal Nerve
a) Hard Palate: major palatine, nasopalatine & sphenopalatine
b) Maxillary Gingiva: major palatine, PSA, MSA & ASA
c) Mandibular Gingiva: inf. alveolar, sublingual, mental & buccal
3) Sensory nerves lose their myelin sheaths and form a network in the reticular layer of the Lamina Propria, terminating in what is referred to as a subepithelial plexus
c. Type of Termination of the Sensory Nerves (2 general types)
1) Free Nerve Endings [similar to those found in PDL and in other types of joints (ex. TMJ)]
a) Found within the Epithelium [Note: unlike capillaries, free nerve endings do penetrate into the epithelium]
i) frequently associated with Merkel's Cells
😉Merkel's cells are believed to be sensory and respond to touch; associated with nerve fibers by a synapse-like junction
ii) also associated with Keratinocytes rather than Merkel's Cells (this arrangement may be considered a type of mesaxon)
iii) terminate as simple endings in the middle or upper layers of the epithelium
b) Also found in the Lamina Propria
i) frequently associated with Schwann Cells
ii) can be considered to be less numerous than in epithelium (?)
c) Nociceptor Function [1°]
d) Mechanoreceptor Function [2°]
e) Thermoreceptor Function (?) [3°]
2) Organized Nerve Endings [generally characterized by groups of nerve fibers surrounded by a connective tissue capsule]
a) Not found within the Epithelium
b) Found in the Lamina Propria, usually in the papillary region
c) More abundant in anterior rather than posterior & in maxilla rather than mandible [Clinical Relevance: maxillary anterior sextant is usually the most sensitive to periodontal probing]
d) Are classified according to their specific morphology
i) Meissner's Corpuscle Primarily sensitive to touch stimuli
ii) Ruffini's Corpuscles [also found in joints (ex. TMJ), in association with Pacini's corpuscles & Golgi tendon organs]
😉 Primarily sensitive to mechano- receptive/proprioceptive stimuli
iii) Krause's Bulbs
😉 Primarily sensitive to cold stimuli
iv) Mucocutaneous End Organs
😉 Function not described
e) Mixed functions among the free & organized endings likely
E. Classification (already described above)
1. General Comments
a. Gingiva is a keratinized masticatory mucosa
b. Gingiva is the most obvious & clinically measurable of the 4 tissues of the periodontium
c. Therefore, many of the clinical descriptions of the periodontium refer to the appearance of the gingiva
d. The various clinical descriptions of gingiva, in turn, specifically refer to its inflammation status
1) Color
2) Size & Shape
3) Consistency/Texture (ex. "stippling")
4) Pain/Loss of Function
5) [Temperature]
6) Location relative to the CEJ
2. Based on structure-function considerations [most Clinically Relevant]
a. The sulcus acts as a habitat for Gram (+) and Gram (-) bacteria
b. The junctional epithelium (JE) acts as a potentially leaky "seal" due to the wide intercellular spaces [Analogy: discontinuous caulking around a bathtub]
c. The dentogingival collagen fibers act as a type of "fiber barrier" to bacteria/bacterial toxins, in addition to serving a tooth- attachment function
V. CELL BIOLOGY (cell level)
A. Types of Gingival Cells vary according to Different Primary Functions
1. Principle Cells
a. Epithelial cells (commonly referred to as Keratinocytes) [constitute ~90% of all the cells found within the epithelium; ~10% of these are progenitor cells in basal layer]
1) Specialized cells which form the coherent cell sheets known as epithelia; epithelial cells are called keratinocytes because of their characteristic differentiated activity in the synthesis of intermediate filament proteins called keratins; the main cell type in the gingival epithelium compartment
2) Epithelia can be defined, in general, as coherent, dynamic cell sheets, formed from one or more layers of eucaryotic cells covering an external surface or lining a body cavity, that perform a number of varied functions such as constituting a physical barrier, absorbing molecular nutrients, secreting different molecules, and propulsive movement of external substances [Note: not all epithelia exhibit all these functions; for example, the epithelium of the masticatory mucosa is not considered to be an important route for absorption of substances within the oral cavity]
3) Originate from a fusion of Reduced Enamel Epithelium and epithelium of the Dental Lamina [Remember: both of these are originally derived from the Primary EpitheliBand in the early embryo]
4) Considered to be a functionally heterogeneous population of cells in the Dentogingival Junction (DGJ)
a) Oral Epithelium/Gingival Epithelium (OE/GE)
b) Sulcular Epithelium (SE)
c) Junctional Epithelium (JE)
5) Large cells with extensive cytoplasm/organelles for protein synthesis & secretion [Clinical Relevance: critical for both anabolic & catabolic aspects of the Basement Membrane and protective outer layer]
6) Well-developed cytoskeleton for cell movement (for either migration (~0.5mm/day) or in situ shape change) [Clinical Relevance: periodontal wound healing]
a) Actin filaments (i.e., "thin" filaments)
b) Actin-binding proteins (i.e., accessory proteins)
c) Myosin proteins (i.e., "thick" filaments)
d) Microtubules (i.e., "thick" filaments, also)
e) Intermediate filaments (ex. Keratin(s) ); the keratins are a heterogeneous group of intracellular proteins that are differentially expressed among different epithelia and even in different parts of the same one epithelium [Clinical Relevance: typing of carcinoma primary tumors]
7) Form several types of Cell-to Cell functional contacts
a) Occluding Junctions (Tight Junctions)- very rare in gingiva
b) Communicating Junctions (Gap Junctions)- rare in gingiva
c) Anchoring Junctions (Adherens Junctions)- common in the gingiva
i) Adhesion Belts
ii) Desmosomes
8) Form several types of Cell-to-Matrix functional contacts
a) Anchoring Junctions (Adherens Junctions)- common in the gingiva
i) Focal Contacts (sometimes called Fibronexi)
ii) Hemidesmosomes
9) Overall Clinical Relevance: any disease of gingival epithelium leads to a loss of barrier integrity and ulcer formation [Clinical Relevance: mucositis following head & neck cancer radiation therapy]
b. Fibroblasts [constitute  90% of all the cells found within the corium]
1) The main cell type in the gingival connective tissue compartment; "Lamina Propria," or "Corium"
2) Originate from the mesenchyme subjacent to the Dental Lamina and peripheral to the Dental Organ/Enamel Organ and the Dental Follicle/Sac
3) Considered to be a functionally heterogeneous population of cells (despite similarities in microscopic appearance among fibroblasts, in general); however, subtypes are not well characterized [Clinical Relevance: Dilantin® "Hyperplasia"]
4) Large cells with extensive cytoplasm/organelles for protein synthesis & secretion [Clinical Relevance: critical for both anabolic & catabolic aspects of the ECM of connective tissue]
5) Well-developed cytoskeleton for cell movement (either for migration or for in situ shape change) [Clinical Relevance: periodontal wound healing]
a) Actin filaments (i.e., "thin" filaments)
b) Actin-binding proteins (i.e., accessory proteins)
c) Myosin proteins (i.e., "thick" filaments)
d) Microtubules (i.e., "thick" filaments, also)
e) Intermediate filaments (ex. Vimentin)
6) Overall Clinical Relevance: any disease of gingival corium fibroblasts leads to a rapid loss of tooth- supporting/tooth-investing tissue
2. Ancillary Cells
a. Undifferentiated Mesenchymal Cells - minimal, if any, present in the gingival corium
b. Immune/Inflammatory cells
1) Mainly associated with acute inflammation
a) Polymorphonuclear leukocytes (PMNs; Neutrophils) [found in both epithelium & corium; PMNs are routinely found in low levels even in clinically healthy gingiva]
2) Mainly associated with chronic inflammation
a) lymphocytes [found in corium]
3) Mainly associated with cellular immunity
a) T-lymphocytes [found in corium]
b) Macrophages/Histiocytes [found in both epithelium & corium (ex. corium melanophages & siderophages]
c) Mast Cells [found in corium]
d) Langerhan's Cells [found only in epithelium]
i) A macrophage-like cell, derived from bone marrow, that functions as an immune cell in skin and related epithelia, such as in gingiva
ii) Characterized by small intracellular granules called the Birbeck granules
4) Mainly associated with humoral immunity (i.e., antibodies)
a) B-lymphocytes & Plasma Cells [found in corium]
c. Pigment cells
1) Melanocyte [found only in epithelium]
a) A pigment cell, derived from neural crest, that produces melanin, the dark substance responsible for the protective and decorative pigmentation of skin and hair; this ancillary to the specialized function of epithelial cells proper [the melanin is found in structures referred to as melanosomes]
b) Melanin is secreted by melanocytes and then taken up by neighboring keratinocytes
c) Clinical Relevance: oral differential diagnosis of the malignant melanoma form of skin cancer vs. a nevus (mole) vs. a melanotic macule
d. Sensory cells
1) Merkel Cell [found only in epithelium] (described above)
a) A cell that is associated with nerve fibers which extend into the epithelium of the epidermis or oral mucosa
e. Neurovascular cells- mainly in lamina propria; some nerve endings within epithelium (described above)
f. Secretory cells
1) Melanocytes
2) Mast Cells
3) [Associated minor salivary & sebaceous gland epithelial cells]
C. Various Structural Proteins
1. General
a. Collagen Proteins (Mainly Type I, III, IV, V & VII collagen)
b. Noncollagen Proteins
1) Gingival Proteoglycans/Glycosaminoglycans
2) Gingival Glycoproteins
a) Laminin
b) Fibronectin
3) Gingival Glycolipids (?)
c. Laminin (is an adhesive glycoprotein of the basement membrane)
d. Others, for example:
1) Entactin
4. Extracellular Matrix of the Connective Tissue Compartment [again, fibroblast secretory products are mainly components of the Lamina Propria]
a. Type I Collagen (is a "fiber-forming" type of collagen, in contrast to Type IV Collagen, which is a "network-forming" type of collagen)
1) Numerous Collagen Fiber Bundles (well defined)
5) Other Ground Substance components
a) Other Proteoglycans/Glycosaminoglycans (PG/GAG)
(ex. dermatan sulfate)
b) Other Glycoproteins (GP)
c) Other Glycolipids (GL)
D. Organized Collagen Fiber Bundles of the Lamina Propria
1. Type I & III mixture, mostly (along with other molecular organizers; ex. Type XII collagen)
2. Individual fibers have a mean diameter of ~100 nm (therefore, generally thicker than in PDL)
3. Help to maintain the functional integrity of the tooth
4. Collectively, the various fiber bundles are occasionally referred to as the "gingival ligament;" however, this term is not completely accepted [Clinically, this is referred to as the "connective tissue attachment"]
5. Arranged in several distinct fiber bundles (forming a "fiber barrier")
a. Dentogingival Group
1) Attach to cervical cementum immediately apical to CEJ and coronal to PDL
2) Run laterally & obliquely into the lamina propria
3) Insert into the lamina propria of both "free" and "attached" gingiva
b. Dentoperiosteal Group
1) Attach to cervical cementum
2) Run apically over the periosteum of the outer cortical plate of bone
3) Insert into either the outer cortical plate or the vestibular muscle and floor of the mouth
c. Transseptal Group
1) Attach to cementum just apical to the base of the JE
2) Run interdentally in a horizontal direction over (i.e., coronal to) the alveolar bone crest
3) Insert into cementum on the adjacent tooth just apical to the base of the JE
4) Collectively form a transseptal fiber system (sometimes referred to as the "transseptal ligament" or "interdental ligament") connecting all the teeth of the arch
5)Clinical Relevance: transseptal fibers of the gingiva are believed also to provide the mechanism for mesial drift (i.e.,anterior component of occlusal forces
d. Alveologingival Group
1) Attach to the alveolar bone crest
2) Run coronally & laterally into the lamina propria
3) Insert into the lamina propria of both "free" and "attached" gingiva
e. Circular Group
1) Do not attach directly to the tooth
2) Run circumferentially around the neck of the tooth, within the lamina propria
3) Interconnect with the other fiber groups to help bind the "free" gingiva to the tooth
f. Other minor fiber bundle groups