Oral Histology and Biology

• Oral histology involves using microscopes at high magnification to study tissues at the cellular and organelle levels.

Why Study Oral Histology and Biology?

• Understanding the structure and function of oral tissues is crucial for treating them.
• Studying the development of oral tissues aids understanding tissue-related pathologies.
• It is important to comprehend general oral physiology.
• It is important to understand oral diseases.

How To Study Oral Histology and Biology

• Studying Gross Anatomy involves macroscopic observation with the naked eye.
• It is important to study Physical properties by observing reactions to forces from different sources.
• Studying Chemical composition includes identifying compounds responsible for tissue formation.

Histological Sections

• Oral cavity tissues are divided into hard and soft tissues.
• Hard tissues are studied using ground or decalcified sections.
• Soft tissues are prepared with different stains, mainly H&E stains.

Ground Section vs. Decalcified Section

• Ground sections burn organic substances, leaving inorganic substances.
• Decalcified sections dissolve inorganic substances, leaving organic substances.
• Ground sections display enamel, dentine, and cementum, but the pulp is burned out.
• Decalcified sections dissolve the enamel, creating an "enamel space," but allow dentine and cementum observation owing to higher organic content.

Additional Points

• Enamel, cementum, and dentine are hard tissues composed mostly of inorganic materials.
• Enamel has the highest percentage of inorganic materials at 96%.

Oral Structures

• Teeth are composed of enamel, dentine, cementum, and pulp.
• The periodontium attaches teeth to bone and includes gingiva, alveolar bone, periodontal ligament, and root cementum.
• Jaw bones support teeth and attach to the periodontium.
• The temporomandibular joint (TMJ) is part of the oral structure.
• Oral mucosa covers bones with underlying submucosa.
• Sub-mucosa contains blood vessels and nerves.
• Salivary glands are also part of the oral structures.

Classification of Oral Tissues

• Soft tissues include pulp, periodontal ligament, oral mucosa, sub-mucosa (blood vessels, nerves), and salivary glands.
• Hard tissues include enamel, dentine, cementum, alveolar bone, jaw bones, and the temporomandibular joint.

Tooth Structure

• The main components are the crown, root(s), pulp chamber, and root canal(s).
• Enamel, dentine, pulp tissue, and cementum make up a tooth.

Enamel

• It’s the most highly mineralized and hardest tissue in the body.
• Enamel consists if 96% inorganic material
• It’s non-vital, insensitive, and cannot regenerate.
• Ameloblasts produce enamel and die after it's fully formed, this is why enamel does not regenerate.

Dentine

• It forms the bulk of the tooth.
• It’s rigid yet elastic - ideal for supporting enamel.
• It protects enamel from breaking because it is rigid (unbreakable, unlike enamel) and yet elastic.
• Dentine in the crown area is covered by enamel, while in the root area, it's covered by cementum.
• It’s sensitive and has a nerve supply, making it vital.
• Dentine is capable of repair.
• During the embryonic stage, odontoblasts form dentine, move inward, and remain alive, this enables dentine regeneration.

Pulp

• It forms, nourishes, innervates, and repairs dentine.
• It is responsible for setting odontoblasts at the end of the dentine.
• It is a soft connective tissue located within the pulp chamber (coronal pulp) and root canal (radicular pulp).

Maxilla and Mandible

• Except for different ossification, there is not much difference between the maxilla, mandible, and other bones in the body.

Temporomandibular Joint

• The synovial articulation between the mandible and cranium, covered by a capsule.
• It is the only articulation found in the oral cavity which makes it very important.

Oral Mucosa

• It represents the lining of the oral cavity that includes the gingiva.
• It is composed of oral epithelium, underlying connective tissue (lamina propria), and a basement membrane.

Oral Sub-mucosa

• It is a layer of loose, fatty, or glandular connective tissue.
• It contains major blood vessels and nerves for the mucosa, and separates it from underlying bones and muscles.

Salivary Glands

• Major and minor salivary glands exist.
• Major salivary glands include parotid, submandibular, and sublingual glands.

Tooth Supporting Structures (Periodontium)

• Periodontium’s function is to attach the tooth to the alveolar bone.
• It consists of the gingiva, root cementum, periodontal ligament, and alveolar bone.

The Gingiva

• It is part of the oral mucosa that forms a collar around the tooth from all sides.
• It has two regions: attached gingiva (attached to the bone) and free gingiva (not attached to anything).

Root Cementum

• It is the hard tissue covering dentine, though less hard than enamel and dentine.
• It is a thin layer of calcified tissue covering the root dentine that can be repaired and regenerated.
• The cells forming cementum live in or on its surface.

Periodontal Ligament

• It is the connecting tissue between the cementum and the alveolar bone.
• It is connected by a group of ligaments that penetrate the cementum and connects it with the alveolar bone.
• It's a dense fibrous connective tissue attaching the tooth to the alveolar bone.

Alveolar Bone

• It is the part of the maxilla and mandible that supports the teeth.
• It is composed of outer and inner -cortical plates, with spongy bone in the middle.
• The part where teeth sit is the socket.
• Individual tooth sockets are separated by inter-dental septa. The histology: compact and spongy bone.