Lec.5 Oral Mucosa2 د.سحرغانم
Masticatory mucosa:The gingiva and hard palate are covered by masticatory mucosa.
Gingiva:
Macroscopic anatomy:
The gingiva is that part of the masticatory mucosa which covers the alveolar process and surrounds the cervical portion of the teeth.
It consists of an epithelial layer and an underlying connective tissue layer called the lamina propria. The gingiva obtains its final shape and texture in conjunction with eruption of the teeth.
In the apical direction the gingiva is continuous with the loose, darker red alveolar mucosa (lining mucosa) from which the gingiva is separated by a, usually, easily recognizable border line called either the mucogingival junction or the mucogingival line.
There is no mucogingival line present in the palate since the hard palate and the maxillary alveolar process are covered by the same type of masticatory mucosa, and the gingiva forms a collar around the tooth,
1-9mm wide, which is attached in part to the tooth and in part to the alveolar bone surface.
Types of the gingiva:
The gingiva is divided into the following three types :
1. The marginal gingiva ( free gingiva) (FG).
3. The interdental papillae .
3.The attached gingiva.. (AG)
1.The marginal gingiva
the marginal gingiva which is also called the free gingiva or unattached gingival(not attached to tooth) is the most coronally positioned portion (terminal border) of the gingiva .*It surrounds the teeth in a collar - like fashion and creates the soft tissue wall of the gingival sulcus .
*The marginal gingiva is separated from the adjacent attached gingiva by the so called free gingival groove .
The free gingival groove: It is a shallow depression in the gingival surface which is approximately 1 mm wide . It corresponds to the level of the cement enamel junction(CEJ) and separates the attached gingiva from the free gingiva (unattached gingival) .
2- The interdental gingiva:
The interdental gingiva or interdental papillae is located in the interproximal space created by adjacent teeth just beneath the area of tooth contact . It consists of the following parts :
The facial papilla .
The lingual(or palatal) papilla.
The "Col" .
Each papilla is pyramidal or wedge shaped and joined by the "col" . This gingival "Col" which is covered by a thin non-keratinized epithelium and is a valley - like depression . It is present only when the gingiva surrounds the gingival surface of the inter proximal contact space.
Col
- Depressinos in interdental (embrasure) area. Similar to outline of depression with buccal and lingual peaks
- Epithelium identical to junctional epithelium and has same origin (dental epithelium)
- Incidences of gingivitis greater interdentally at Col – may be more vulnerable to inflammation.
*Absence of interdental papillae and col where proximal tooth contact is missing .The lateral borders and tips of the interdental papillae are formed by a continuation of the marginal gingiva from the adjacent teeth. The intervening portion consists of attached gingival. the interdental bone and forms a smooth, rounded surface without interdental papillae.
3- The attached gingiva:
The attached gingival is firm but resilient and tightly bound to the tooth or alveolar bone by means of a connective tissue fiber insertion.
* It is of firm texture, coral pink in color, and often shows small depressions on the surface. The depressions crossponding to the center of heavier epithelium ridges, Because portions at the epithelium appear to be elevated and between the elevations there are shallow depressions, the net result of which is called "stippling", give the appearance of orange peel. This phenomina disappear where there is gingivitis .usually inflamed gingival shown with red ,shining ,smooth and edematous due to destruction of collagen fibers.
* It is continuous with the mucous gingival junction , demarcates the beginning of the alveolar mucosa and separates it from the facial aspect of the attached gingiva .
*The width of the attached gingiva varies from area to area .
*The width of the attached gingiva on the facial aspect differs in different areas of the mouth. It is generally greatest in the incisor region (3.5 to 4.5 mm in the maxilla and 3.3 to 3.9 mm in the mandible) and less in the posterior segments, with the least width in the first premolar area (1.9 mm in the maxilla and 1.8 mm in the mandible).
The Gingival sulcus :
A shallow groove between the marginal gingival and the tooth surface, bound by sulcular epithelium laterally and juncitonal epithelium apically.
* It runs from the crest of the marginal gingiva to the coronal level of the junctional epithelium .
*This sulcus (sulcular epithelium) is a non – keratinized epithelium.
*No epithelium ridge and form smooth surface with lamina propria.
*The depth of the gingival sulcus is approximately 0.5 mm but , because of the weakness of the junctional epithelium , this depth may be increased during probing to 2 mm .
The gingival sulcus can be divided in to :
1.The anatomical depth of sulcus : It ranges from 0 mm to 0.5 mm .2.The clinical depth of sulcus : It may range from 0 mm to 2 mm .
The gingival fluid(Sulcular Fluid)
This gingival fluid (crevicular fluid) is found in the gingival sulcus . that seeps into it from the gingival connective tissue through the thin sulcular epithelium.
It is distinct from saliva , but it is similar to serum and its secretion increases during mastication and with inflammation..
It contains , proteins ,electrolytes , enzymes cells and complement.
The main functions of the gingival fluid are:
1. Essential growth factor for many organisms found in the fluid .
2. Flushing action , ( cleaning materials from the gingival sulcus ) .
3. Antimicrobial and antibody properties to defend the gingival.
4. contain plasma proteins It increases the attachment of epitheliums to tooth.
Microscopic features:
1.Gingival epithelium:
The epithelial part presented with there types are follows:
A. Ortho keratinized stratified squamous epithelium in 15%
B. Para keratinized stratified squamous epithelium in75%
C. Non keratinized stratified squamous epithelium in10%
Gingival epithelium (divided into 3 types):
Oral epithelium (OE): Stratified, squamous keratinizing epithelium which lines the oral(masticatory mucosa) (as contrasted to the dental surface of the gingival). It extends from the mucogingival junction to the gingival margin (except for the palatal surface where it blends with palatal epithelium).
Sulcular epithelium (SE) : Stratified, squamous epithelium, generally non-keratinized, which is continuous with the oral epithelium, lines the lateral surface of the gingival sulcus. Apically it overlaps the coronal border of the junctional epithelium to the free margin of gingiva.
Junctional epithelium (JE) : Stratified non-keratinizing epithelium, in the shape of a collar with a cross-section resembling a thin wedge, attached by one broad surface to the tooth and by the other broad surface to the gingival connective tissue. The desquamative surface is at the coronal end which forms the bottom of the sulcus.
Turnover
- High rate of division, migrate 2-3 cell layers from tooth surface, then join main migratory route in coronal direction parallel to tooth surface to be desquamated into gingival sulcus
- Junctional epithelium readily regenerates from sulcular epithelium or oral epithelium if it is damaged.
The principal cell type of the gingival epithelium:
As well as of other stratified squamous epithelia, is the keratinocyte.•
Other cells found in the epithelium are the clear cells or nonkeratinocytes, which include:
1. Langerhans cells.2. Merkel cells3. and Melanocytes
2.Connective tissue(lamina propria)
Gingival fibers :
they are found in the lamina propria of gingival and collectively form the gingival ligment. The majority are composed of collagen fibers, with minor contributions from elastic fibers and oxytalan fibers.
Classification and anatomic distribution of gingival fibers:
1.Dentogingival group: These are the most numerous fibers, extending from cervical cementum to lamina propria of free and attached gingiva.
2.Alveologingival group: These fibers radiate from the bone of the alveolar crest and extend into lamina propria of free and attached gingiva.
3.circular group: this small group of fibers forms aband around the neck of the tooth, interlacing with other groups of fibers in the free gingival and helping to bind the free gingiva to the tooth.
4.Dentoperiosteal group: Running apically from the cementum over the periosteum of the outer cortical plates of the alveolar process these fibers insert into the alveolar process or the vestibular muscle and floor of the mouth.
Functions of the gingival fibers:
The gingival fibers accomplish the following :
1.They hold the marginal gingiva against the tooth
2.They provide the marginal gingiva with enough rigidity to withstand the forces of mastication without distorting.
3.They serve to stabilize the marginal gingiva by uniting it with both the tissue of the more rigid attached gingiva as well as the cementum layer of the tooth.
Ground substance : Occupies the space between cells, fibers and neurovascular elements. Major components are water, glycoproteins and proteoglycans. Allows diffusion of biological substances between various structural elements.
Cells:
Fibroblasts: Synthesis and resorption
Macrophages : Participate in host defense and repair
Mast cells : Participate in early phase of inflammation
Undifferentiated cells : source of new cells
Leukocytes (neutrophils, lymphocytes, plasma cells, etc…) : Participate in host defense.
Osteoblasts, cementoblasts, osteoclasts, cementoclasts (will be described under “Periodontal ligament”).
Blood Supply of gingiva:
The blood supply To gingiva – derived from periosteal vessels in the periosteum and alveolar process.- To dentogingival junction – continuation of interalveolar arteries.
Nerve supply to gingiva :
Terminal branches of periodontal nerve are branches of infra orbital and palatine, or lingual, mental, and buccal nerves.
DEFINITIONS
Gingival margin : The most coronal portion of the gingival.
Marginal gingival : That portion of the gingival just apical to the gingival margin.
Gingival groove : Indentation along the oral or vestibular surface of the marginal gingival which parallels the gingival margin. It is located at about the same level as the apical border of the junctional epithelium. Note : its level does not correspond to that of the bottom of the sulcus.
Mucogingival junction : Demarcation line between masticatory mucosa of the gingival and the lining alveolar mucosa.