1. Tooth Anatomy
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Topic: Enamel, Dentin, Pulp, Cementum Structures of the Tooth
Speaker: Dr. Elif Ciftçioglu
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Dental Tissues:
Hard dental tissues: Enamel, Dentin, Cementum
Soft dental tissues: Pulp tissue
Dental Tissues Location: Dentin (Coronal, Root), Enamel (Crown), Cementum (Root apex)
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Enamel:
Chemical composition:
96% inorganic (Hydroxyapatite crystals)
4% water and organic (amelogenin & nonamelogenin)
Properties:
Highly calcified and hardest tissue in the body
Insensitive— no nerves
Acid soluble (pH 5.5 or lower)
Can be lost by physical mechanism (abrasion, attrition, abfraction) or chemical dissolution (erosion)
Cannot be rebuilt
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Cementum:
Properties:
Thin layer of mineralized tissue covering the root dentin
Softer than enamel, dentin, and bone
Anchors the tooth to the alveolar bone with periodontal ligament
Non-sensitive
Cement deposition lasts for a lifetime
Chemical structure:
45-50% inorganic (Calcium, hydroxyapatite, phosphate, fluorid)
50-55% water and organic
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Cement Enamel Junction and Cementoenamel Junction:
Enamel: 5-10%
Cement: 30%
Junction: 60-65%
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Dentin:
Properties:
Majority of the mineralized part of the tooth
Covered with enamel in the coronal; with cementum in the root
Softer than enamel, harder than cementum and bone
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Dentin Chemical structure:
Matrix secreted by odontoblasts is calcified
Produced throughout life
Does not have a nerve supply but can be sensitive
70% inorganic hydroxyapatite crystals
15-20% organic collagen
10-12% water
1-2% non-collagen proteins
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Dentin tubules:
Dentin has a tubular structure
Dentin tubules connect the dentin and the pulp
The tubules run parallel to each other in an S-shaped course
Tubules contain fluid and odontoblastic process (extensions of nerve fibers)
External stimuli cause movement of the dentinal fluid, a hydrodynamic movement, which can result in short, sharp pain episodes
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Dentin types:
Peritubular dentin:
Surrounding the dentin tubules
More mineralized than intertubular dentin
Intertubular dentin:
Localized between dentin tubules
Covers a large part of the dentin around the pulp
Contains more organic matter than peritubular dentin
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Types of dentin:
Mantle dentin: The first dentin formed at the enamel-dentin boundary
Primary dentin: Forms the initial shape of the tooth
Secondary dentin: Formed slowly after the root development, continues to form throughout the life of the tooth
Tertiary dentin (irritation dentin): Formed by odontoblasts in response to moderate external influences such as attrition, abrasion, erosion, trauma, dental caries, and some operative procedures
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Pulp:
Innermost part of the tooth
A soft tissue, rich with blood vessels and nerves
The vitality of the tooth is maintained by the vessels and nerves in the pulp tissue
Typically sensitive to extreme thermal stimulation
Responsible for nourishing the tooth
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Morphologic zones of the Pulp:
Pulp
Dentin
Odontoblast layer
Predentin
Cell-poor zone
Pulp proper
Cell-rich zone
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Morphologic zones of the Pulp:
Pulp proper
Odontoblast layer
Cell-poor zone
Cell-rich zone
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Morphologic zones of the Pulp:
Odontoblast layer:
Capillaries, nerve fibers, dendritic cells
Odontoblasts forming dentin
Cell-poor zone:
Cell-free layer of Weil
Traversed by blood capillaries, unmyelinated nerve fibers
Raschow nerve plexus
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Morphologic zones of the Pulp:
Pulp proper:
Many fibroblasts
Undifferentiated mesenchymal cells around the veins may turn into odontoblasts, fibroblasts, or macrophages
Central mass of the pulp
Loose connective tissue
Blood vessels, nerves, fibroblasts
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Functions of the Pulp:
Inductive
Formative
Nutritive
Protective
Defensive
Sensory
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Functions of the Pulp:
Inductive:
Induces oral epithelial differentiation into dental lamina and enamel organ
Induces the enamel to become a particular type of tooth
Formative
Nutritive
Protective
Defensive
Sensory
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Functions of the Pulp:
Inductive
Formative:
Odontoblasts induce dentin formation
Formation of primary and secondary dentin
Primary dentin formed before root closure, tubular and regularly arranged
Secondary dentin formed after root closure, contains fewer tubules
Nutritive
Protective
Defensive
Sensory
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Functions of the Pulp:
Inductive
Formative
Nutritive:
Maintains the vitality of dentin by providing O2 and nutrients to the odontoblasts
Provides a continuing source of dentinal fluid
Nutrition made possible by a rich peripheral capillary network
Protective
Defensive
Sensory
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Functions of the Pulp:
Inductive
Formative
Nutritive
Protective:
Pulp helps in recognition of stimuli like heat, cold, pressure, chemicals by the way of sensory nerve fibers
Vasomotor innervation controls the muscular wall of blood vessels, regulating blood volume and rate of blood flow
Defensive
Sensory
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Functions of the Pulp:
Inductive
Formative
Nutritive
Protective
Defensive:
Responds to irritation by producing reparative dentin
Mild to moderate irritation results in continued dentin formation, sclerosis, and intratubular calcification
Triggers inflammatory and immune response
Sensory
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Dentin formation
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Functions of the Pulp:
Inductive
Formative
Nutritive
Protective
Defensive
Sensory:
Changes in temperature, vibration, and chemicals affect the dentin and the pulp
Contains both myelinated (A delta) and unmyelinated nerves (C fibers)
The complex sensory system within the pulp controls the blood flow
Responsible for the sensation of pain
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Terminology:
Apical delta
Apical Foramen
Lateral canal
Root canal
Furcation
Furcation canal
Pulp chamber
Pulp horn
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Anatomy of the Root Apex:
Radiographic apex
Apical foramen (Major foramen)
Apical constriction (Minor Foramen)
Apical root anatomy:
Cementodentinal junction
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Apical Foramen (Major Foramen, Anatomic Foramen):
Main apical opening of the root canal
In younger teeth, during development of the apex, it is usually located at the very end of the anatomical root
Page 27: Anatomic Apex / Radiographic Apex
Anatomic apex is the tip or end of the root determined morphologically.
Radiographic apex is the tip or end of the root determined radiographically, which can vary from the anatomic apex due to root morphology and distortion of the radiographic image.
Mostly, the anatomic apex and the apical foramen are not in the same location.
Page 28: Cementodentinal junction (CDJ)
CDJ is the point where dentin and cementum join in the root canal.
It marks the end of pulp tissue and the beginning of the periodontal ligament.
Its location within the canal varies but is approximately 1 mm behind the apical foramen.
CDJ is also known as the apical constriction.
Page 29: Apical Constriction (Minor Foramen, Physiological Foramen)
Apical constriction is considered the narrowest diameter of the root canal.
The distance between the apical constriction and the apical foramen ranges from 0.5 to 1 mm for teeth of different ages.
It serves as the apical limit for root canal preparation and obturation.
Apical constriction cannot be seen in radiography.
Page 30: Apical constrictions
Type A: Traditional single constriction.
Type B: A tapering constriction with the narrowest portion of the canal near the actual apex.
Type C: Presence of multiple constrictions.
Type D: Constriction followed by a narrow, parallel portion of the canal.
Page 31: Apical root anatomy
Pulp space, dentin, cementum, cementodentinal junction, physiological foramen, apical foramen, radiographic apex.
Page 32: Apical root anatomy
Pulp, dentin, cementum, physiological foramen, mixed tissue, radiographic apex, periodontal membrane, alveolar bone.
Page 33: Periodontal ligament
Periodontal ligament connects the cementum of the tooth to the alveolar bone of the socket.
It is composed of elastic fibrils and acts as an elastic barrier between the tooth and the bone.
Contains nerves and blood vessels.