Periodontology Quiz: Gingival Anatomy & Function

Clinical Correlations of Periodontal Anatomy

• This presentation covers the anatomy of the periodontium, focusing on its clinical and microscopic features.
• Key components of the periodontium are oral mucosa, gingiva, periodontal ligament, cementum, and alveolar process.
• The presentation also discusses correlations of normal clinical and microscopic features.

Oral Mucosa and Gingiva

• Oral mucosa includes masticatory, specialized, and lining mucosa.
• Masticatory mucosa: Gingiva and hard palate
• Specialized mucosa: The dorsum of the tongue
• Lining mucosa: Oral mucosa covering the soft tissues.

Gingiva

• Definition: Gingiva is the oral mucosa that covers the alveolar processes of the jaws and surrounds the necks of the teeth. It forms a collar-like fashion around the teeth.
• Anatomically: Divided into marginal gingiva, attached gingiva, and interdental gingiva.
• Marginal gingiva (Free gingiva): The portion of the gingiva that borders the tooth.
• Attached gingiva: The portion firmly attached to the underlying alveolar bone.
• Interdental gingiva: The gingiva in between the teeth.
• Includes the Gingival sulcus, Marginal (free) gingiva, Free gingival groove, Attached gingiva, Mucogingival junction, Alveolar mucosa.

Anatomical Areas of Gingiva

• Diagrams and labels of MGJ (Mucogingival junction), MG (Marginal gingiva), AG (Attached gingiva), and IDG (Interdental gingiva) are presented.

Gingival Sulcus

• A V-shaped crevice surrounding the tooth.
• Ideal depth: 0 mm or close to 0 mm, typical of clinically healthy gingiva.
• Normal depth: 1.8 mm (histological), average 1 to 3 mm.

Attached Gingiva

• Firm, resilient, and tightly bound.
• Mucogingival junction is part of this section
• Width varies by location.

Interdental Gingiva

• Occupies gingival embrasure between teeth
• Pyramidal or collar-shaped

Microscopic Features

• Gingiva is composed of epithelial and connective tissues.
• The epithelial component includes the oral epithelium, sulcular epithelium, and junctional epithelium.
• Gingiva turnover rate varies by location.
• Palate, tongue, and cheeks: 5-6 days
• Gingiva: 10-12 days
• Junctional epithelium: 1-6 days
• Oral epithelium is a primary barrier that is stratified squamous epithelium; keratinized or parakeratinized.
• Sulcular epithelium is non-keratinized, stratified squamous epithelium, without rete pegs, and semipermeable.
• Junctional epithelium is a collar-like band of stratified squamous non-keratinizing epithelium; length ranges from 0.25-1.25 mm; widest portion at crown; thin by the cement-enamel junction.
• Note that junctional epithelium is unique because possesses two basement membranes (internal and external basal lamina)

Keratinization

• Keratinization is a series of biochemical and morphological events that occur in cells as they migrate from the basal layer.
• Keratinocytes comprise 90% of the cells.
• Other cell types, include melanocytes, Langerhans cells, and Merkel cells.

Non-keratinization

• Lining mucosa is non-keratinized.
• It is thicker than keratinized mucosa, with larger cells and intercellular bridges.
• It consists of three layers: stratum basale, stratum intermedium, and stratum superficiale/distendum.

Lamina Propria

• Two layers (superficial/papillary and deep/reticular) of the gingival connective tissue.
• Components include gingival connective tissue composed of cells(blood vessels, neural elements, fibers, ground substance).

Gingival Connective Tissue

• Mostly dense collagen fibers (Type I, followed by Type III).
• Fibers are classified by location.

Function of Gingival Fibers

• Support and stabilize the marginal gingiva against forces of mastication.
• Connect free marginal gingiva to cementum and adjacent attached gingiva.
• Gingival fibers arranged in three groups: gingivodental, circular, and transseptal.

Gingival Collagen Fibers

• List of fibers: Dentogingival, Alveologingival, Interpapillary, Transgingival, Circular & Semicircular, Dentoperiosteal, Transseptal, Periostogingival, Intercircular, and Intergingival

Cell Types

• Fibroblasts (65%), neutrophils, lymphocytes, plasma cells, macrophages, mast cells comprise the cells, by volume
• Ground substance consists of glycosaminoglycans (most common dermatan sulfate -60%, followed by chondroitin 4-sulfate 28%).

Vascular Supply

• Supraperiosteal arterioles, vessels of the PDL, and arterioles from the alveolar crests.
• Juxta-epithelial plexus: capillary plexus adjacent to the papillary projections of the gingival epithelium.

Correlations of Normal Clinical and Microscopic Features

• Color is produced by vascular supply, epithelial thickness, keratinization, and presence of pigment-containing cells.
• Color varies among people and may correlate with cutaneous pigmentation (lighter in fair-complected individuals).
• Size correlates with the total bulk of cellular and intercellular elements plus vascular supply.

Gingival Biotypes

• Ochsenbein and Miller described the importance of thick versus thin gingiva in restorative treatment planning.
• Populations are predominantly 85% thick and flat periodontal biotypes and 15% thin and scalloped periodontal biotypes.

Thick Gingival Biotype

• Characterized by relatively flat soft tissue and bony architecture.
• Dense fibrotic tissue.
• Large amount of attached gingiva
• Thick underlying osseous form
• Resistant to acute trauma
• Reacts to disease with pocket formation and infrabony defects.

Thin Gingival Biotype

• Characterized by highly scalloped soft tissue and bony architecture.
• Delicate and friable soft tissue.
• Minimal amount of attached gingiva
• Thin, dehiscence, and fenestration underlying osseous form
• Reacts to disease or insults with gingival recession.

Gingival Zenith

• The most apical point of the marginal gingival scallop.
• Examples include central and lateral incisors, canines, and premolars with their respective tooth regions.

Surface Texture

• Gingiva is stippled (textured like an orange peel).
• Attached gingiva exhibits stippling; marginal gingiva does not.
• Less prominent on the lingual surface compared to the facial surface and can be absent in some individuals

Stippling of Attached Gingiva

• Orange peel-like appearance, best viewed in dried gingiva.
• Variations in fineness or coarseness may exist between individuals and correlate with age and sex.
• Primarily located in the attached gingiva and the central part of the interdental papillae.

Passive Eruption (Gottlieb & Orban 1933)

• Four stages of connective tissue growth and healing after tooth eruption.
• Stage 1: junctional epithelium and the base of the sulcus are on the enamel.
• Stage 2: part of the junctional epithelium is on the cementum, the base of the sulcus remains on the enamel.
• Stage 3: the entire junctional epithelium lies on the cementum, with the base of the sulcus at the cemento-enamel junction.
• Stage 4: Both the junctional epithelium and the base of the sulcus are on the cementum.

Periodontal Grafts

• Gingiva can have a stable connection with restoration margin than alveolar mucosa.
• Grafts are used to regenerate or repair deficient gingival tissue.

Periodontal Probing

• Probing depth typically overestimates the actual depth of the sulcus or pocket due to penetration into inflamed tissues.

Gingival Crevicular Fluid

• Inflammatory exudate containing serum, structural cells, proteins, and electrolytes.
• Increased level in presence of inflammation; a protective role.
• Transudate/exudate with cleaning, antibacterial, and adhesive properties

Interdental COL

• The interdental col is not a powerful barrier against bacteria since it has non-keratinized epithelium.
• A site for initiation of disease.

Periodontal Ligament

• Composed of highly cellular connective tissue surrounding the tooth root.
• Connects the root to the alveolar bone.
• Width: 0.2 mm, narrower in nonfunctional teeth and wider in hyperfunctional teeth.

Periodontal Ligament Fibers

• Collagen in bundles, arranged in a wavy pattern.
• Sharpey's fibers: Collagen portion attached to the cementum and bone, undergo calcification.
• Related non-collagenous protein: Osteopontin and bone sialoprotein.
• Oxytalan & eluanin fibers are other fiber types.

Principle Fibers

• Includes groups such as Transseptal, Alveolar crest, Horizontal, Oblique, Apical, and Interradicular fibers.

Cellular Elements of PDL

• Connective tissue (Fibroblasts, cementoblasts, and osteoblasts).
• Undifferentiated mesenchymal cells (UMCs).
• Epithelial rests of Malassez.
• Immune system cells.
• Cells associated with neurovascular elements.

Ground Substance of PDL

• Consists of glycosaminoglycans (GAGs) like hyaluronic acid and proteoglycans.
• Glycoproteins (fibronectin and laminin)
• High water content (70%).
• Calicified structures such as cementicles.

Functions of PDL

• Physical, formative, and remodeling, nutritional, and sensory functions.
• Essential for tooth anchorage.
• Resistant to resorption

Periodontal Ligament Clinical Considerations

• Radiolucent in radiographs
• Thicker in functioning teeth,
• Cell function for remodeling ligament and bone
• Replantable exfoliated teeth.

Cementum

• Hard, calcified connective tissue covering the tooth root, of mesodermal origin.
• Begins at the cemento-enamel junction and extends to the apex.
• Supports periodontal attachment elements.
• Classification: Acellular afibrillar, Acellular extrinsic fibers, Cellular mixed stratified, and Cellular intrinsic fibers

Cementum Characteristics

• Less hard than dentin
• Light yellowish color; less luster than dentin.
• May be permeable to several materials
• Chemical composition; Inorganic portion (45-50%): Calcium and phosphate (hydroxyapatite); the highest fluoride content of all mineralized tissues.
• Organic portion (50-55%): Primarily Type I collagen, protein polysaccharides (proteoglycans), and water.

Schroeders Classification

• Acellular afibrillar, Acellular extrinsic fiber, Cellular mixed stratified, Cellular intrinsic fiber cementum.
• Intermediate cementum - a layer near the cementodentinal junction in some teeth, comprised of calcified ground substance and remnants of the Hertwig's epithelial root sheath.

Acellular Cementum

• The term "acellular" is not precise.
• Does not incorporate cells (spiderlike cementocytes) initially

Cellular Cementum

• Primarily found in the apical third of the root,
• Cells are similar to osteocytes (cementocytes)
• Located in spaces called lacunae.
• Numerous processes (canaliculi) that extend toward the PDL and cementum surfaces.
• Separated from other cementum types by incremental lines, indicative of periodic formation.

Cemento-Enamel Junction (CEJ)

• Region where cementum and enamel meet.
• Varies by individual, with the cementum overlapping the enamel in 60-65%, a sharp line (butt joint) for approximately 30%, and a region devoid of cementum overlapped by enamel epi for ~5-10%.

Cementum Clinical Considerations

• Vital to the tooth's function as an anchorage point
• More resistant to resorption than bone
• Removal of calculus, bacterial deposits in scaling & root planing also removes cementum, potentially exposing dentin and increasing tooth sensitivity.
• Deposition in apical area compensates for occlusal attrition.

Alveolar Process

• Mandibular and maxillary portions supporting tooth sockets (alveoli).
• Formed during tooth eruption; disappears with tooth loss.

Alveolar Process Structure

• External cortical plate made of Haversian bone and compacted lamellae.
• Inner lining of socket walls (alveolar bone proper); seen as lamina dura in radiographs.
• Histology: contains channels (cribriform plates), where neurovascular bundles connect the PDL to the cancellous (central) bone portion.

Alveolar Bone Clinical Considerations

• Remodeling can displace alveolar bone
• Interruptions in lamina dura in the apical region have implications
• Tooth extraction: alveolar bone resorption may occur.
• Dental implant placement: reduces the rate of ridge resorption
• Fenestration may convert to dehiscence, potentially resulting in gingival recession.

Key Points

• Average width of PDL space: 0.2 mm
• Undifferentiated mesenchymal cells (UMCs)
• Functions of PDL
• Cemento-Enamel Junction (CEJ)
• Alveolar Bone terminology

Homework

• Draw the periodontium.

Reference Textbook

• Newman & Carranza's Clinical Periodontology (Chapter 3, Pages 19-49).