Oral Mucosa: Types and Functions

Oral Mucosa

• The oral cavity is lined with oral mucosa, also known as the oral mucous membrane
• It is a stratified squamous epithelial lining
• This extends from the margins of the lips to the tonsils

Categories of Oral Mucosa

• Specialized Mucosa: On the dorsum of the tongue adapted for taste
• Masticatory Mucosa: Comprises the gingiva and hard palatal tissue, endures trauma during mastication
• Lining Mucosa: All other areas of oral mucosa

Specialized Mucosa

• It covers the dorsal surface of the tongue
• It accommodates the sensation of taste

Masticatory Mucosa

• The gingiva and hard palate are masticatory mucosa
• It is firmly attached to the underlying structures
• Exhibits parakeratinized or keratinized epithelium
• The pressure from food leads to parakeratinization or keratinization of the tissue

Lining Mucosa

• Exhibits non-keratinized epithelium
• Consists of the mucosa covering the lips, cheeks, floor of the mouth, inferior surface of the tongue, soft palate, uvula, and alveolar mucosa

Keratinization

• The process by which epithelial cells differentiate or mature
• Begins with basal cells moving through epithelial layers
• More keratinized cells are tougher and more resistant

Types of Mucosa

• Keratinized: A layer of dead cells without nuclei on the surface (e.g., hard palate)
• Parakeratinized: Features some dead cells without nuclei and some dying cells with flattened nuclei on the surface
• Nonkeratinized: Cells on the surface tend to have nuclei that appear fairly healthy and normal (e.g., alveolar mucosa)

The Periodontium

• Periodontium consists of the tissues supporting and surrounding the teeth
• The periodontium is divided into two units: Gingival Unit and Attachment Unit

Gingival Unit

• The gingival unit comprises Free gingiva (Gingival margin), Interdental papilla, Attached gingiva, and Alveolar mucosa

Free Gingiva

• It extends from the gingival margin to the base of the gingival sulcus
• It is light pink in color
• Averages 0.5 to 2mm in depth
• Is located next to the enamel approximately 0.5 – 2mm coronal to the CEJ
• Forms collar separated from the tooth via the gingival sulcus
• Can be keratinized or parakeratinized
• It closely fits around the tooth without direct attachment
• Being unattached, it can be stretched away from the tooth with a periodontal probe

Gingival Papilla (Interdental Papilla)

• The free gingiva is located in the triangular interdental spaces
• The apex is sharp in anterior teeth, blunt in posterior teeth
• There are facial and lingual interdental papilla
• The lateral borders and tip are formed by free gingiva
• The center is formed by attached gingiva
• When inflamed, it is redder than normal, puffy, and has a blunted apex

Gingival Sulcus

• A gingival groove that often occurs is on the outside of the free gingiva, corresponding to the base of the sulcus
• Health has sulcus termed
• Inflammation has "pocket" term
• Healthy depth is 1-3 mm when measured with a probe
• The inner portion is nonkeratinized
• The tooth surface and free gingiva have space between
• Outer portion is the free tissue which is keratinized
• Attached tissue starts at the bottom of the pocket

Junctional Epithelium

• It attaches the gingiva to the tooth
• Its length is ~1-2 mm .
• It forms a collar around the tooth's neck
• It is a nonkeratinized stratified squamous epithelium
• The fact that it is a nonkeratinized stratified sqaumous epithelium makes it more permeable to fluids, bacteria and toxins

Attached Gingiva

• Extends apically from the base of the sulcus
• It is attached to the bone by collagenous fibers
• Has a stippled texture, resembling dimpled skin (orange peel)
• Is keratinized
• Covered by stratified squamous epithelium
• Color ranges from light to dark pink
• May contain pigment (Melanin pigmentation)

Alveolar Mucosa

• It joins the attached gingiva at the mucogingival junction
• It is continuous with the tissues to the vestibule
• Tissue is thin and soft
• It's loosely attached to the underlying bone
• Consists of lining mucosa
• Is smooth, thin, and nonkeratinized

Attachment Unit

• The attachment unit comprises cementum, alveolar bone, and the periodontal ligament

Cementum

• A hard mineralized tissue layer covers the root of the tooth
• Without Cementum, a tooth would fall out
• Cementum provides an attachment for periodontal ligament fibers to the tooth
• The outer cementum layer safeguards dentin and prevents the exposure and possible damage from open dentinal tubules

Types of Cementum

• Cellular or acellular
• Acellular always covers the cervical 1/3 with possible root coverage outside of the apical section
• Cellular will cover the apical part and form over acellular when needed

More About Cementum

• Similar qualities as bones
• Can have periods of growth or absorbency
• Grows by apposition (addition)
• Appears with collagen or tissue made of connecting tissue from periodontal area

Alveolar Bone

• Alveolar bone proper lines the sockets holding tooth roots
• Thin, compact
• It lines the sockets where the teeth lie
• It allows blood vessels/nerves to pass through
• The socket is called the alveolus, which supports and protects the roots
• The alveolar process contains both proper bone and alveolus components that surround and support teeth in the maxilla and mandible

Compact & Spongy bone

• Compact (cortical) bone is the exterior portion of the alveolar
• Spongy bone is the interior

Alveolar crest

• The alveolar crest portion is the alveolar bone, varies in size and shape based on the tooth position
• Alveolar bone's existence is dependent on teeth
• Alveolar bone resorbs if teeth are extracted

Periodontal Ligaments

• A connective tissue surrounds/ adheres teeth's root with alveolar bones
• Collagen fibers connect the tissue to cementum (which anchor its teeth in bone socket and prevent movement)
• Anchors with Sharpey's collagen fibers
• Forms/ keeps tissue
• Provides nutrition + sensory messages like pain

Arrangement of Periodontal Ligament Fibers

• Alveolar crest group (cervical to alveolar crest)
• Horizontal group (runs horizontally from tooth to alveolar bone)
• Oblique group (fibers that run diagonally from bone to cementum)
• Apical group (fibers by apex)
• Interradicular group- between roots of multi-rooted teeth

Function of PDL Fibers

• The fiber arrangement gives support
• Prevents teeth being pulled out
• Also serves to protect bone and tissues
• Minimizing damage in pushing
• Constant change/ shift based on the pressures

Pressure exerted that leads to functional change includes the following:

• Active eruption: Eruption to compensate for abrasion
• Mesial drift: Movement of molars to compensate for abrasion
• Masticatory occlusal forces: Tooth movement while chewing
• Orthodontic corrective forces: Dentist placing pressure
• Traumatic occlusal forces: Premature contact during occlusion

Periodontal ligament and tooth Position

• A tooth suspends because of PDL, there is movement w/ a bony cavity
• Expansion allows tipping/ compressing