Connective Tissue Common Components
Cells: fibroblasts, chondroblasts / chondrocytes, osteoblasts / osteocytes, adipocytes, blood cells.

Fibres: Collagen, Reticular, Elastic

Ground Substance: Gel-like fluid with carbohydrates in chains and proteoglycans

Types of Connective Tissue
Mesynchyme (undifferentiated “stem” cells)
Areolar (mixed cells, fibres, and GS)
Adipose (gel matrix with adipocytes)
Reticular (reticular fibres, support other cells)
Loose Irregular (many fibres, little GS)
Dense Irregular (more parallel fibres)

Examples of Connective Tissues
Hyaline Cartilage (collagen fibres, firm matrix)
Elastic Cartilage (elastic fibres)
Fibro Cartilage (thick collagen fibres)
Bone (calcified collagen matrix, osteocytes)
Blood (fluid matrix, blood cells, )
Dental Pulp
Periodontal Ligament

What is the Dental Pulp?
• Connective tissue infilling of the pulp chamber and upper root
• Remnant of the dental papilla
• Maintains health of dentine
• Repairs dentine
• Provides sensory pathways from dentine
• Pulp is the dentist’s friend



Incisor Longitudinal Section





Molar Longitudinal Section





Radiograph





Bell Stage Tooth





Cell Types in Pulp
  • Odontoblasts
  • Fibroblasts (maintain pulp matrix)
  • Undifferentiated Mesenchyme Cells
  • Macrophages
  • Accessory Cells (T-cells, langerhan cells, etc.)
Plus


• Blood vessels
• Nerve axons







Pulp Cross Section




Pulp Matrix
• Fibres are collagen Type III, Type I, and Type V
• (Type III confers elasticity, Type I gives tensile strength, Type V typical of mesenchymal tissue)
• Ground Substance is made up of proteoglycans (which retain water to form gel)




Close-up of Pulp Margin









Odontoblast Layer









Odontoblast Layer









Blood Supply



• Comes from branches of inferior and superior alveolar artery and vein



• Organized into larger central vessels (large venule and several small arterioles) with a superficial plexus of capillaries around periphery
• Important for maintaining living cells (esp. odontoblasts) and for regulating fluid
• Excess matrix fluid removed by lymphatics




Nerve Supply



• Ultimately stems from Trigeminal Nerve (V) via superior and inferior alveolar nerves
• Contains both mylenated and unmyelinated axons
• Contains both sensory and sympathetic fibres (the latter regulate blood flow)
• Single tooth may contain 2000 mylenated axons (conduct sharp, piercing pain) and 300 unmyelinated ones (conduct dull ache in response to thermal, mechanical, and chemical stimuli)
• Fibres concentrated in plexus beneath odontoblast layer (Rashkov’s plexus)
• Fibres may extend into dentine tubules, most concentrated at pulp horns or in areas undergoing repair




Arterioles and Venules









Root Canal with Pulp









Clinical Issues



• Living pulp is required to maintain dentine and tooth sensitivity
• Small volume of pulp cavity and high fluid content of pulp combine to cause painful swelling to damaged or inflamed pulp
• Injury to dentine (including drilling) can pull nerve fibres and odontoblasts into tubules causing damage and pain
• Severe damage or infection to pulp (or open pulp cavity) may require removal of pulp and filling of chamber and root canal (endodontics)