Histo- Cementum & Pulp

Dental papilla (derived from ectomesenchyme)

• Cellular- Odontoblasts, Fibroblasts, mesenchymal cells (which make new odontoblasts), and immunologic cells
• Interceulluar- collagen fibers and ground substance

• Blood vessels- for nutrients and oxygen
• Nerve supply- sensory (mediate pain) and motor (supply blood vessels)

Lymphocytes, mast cells, neutrophils, macrophages, and dendritic cells

• Molars have more volume than incisors
• pulp volume decreases with age

• 1. Coronal pulp
• 2. radicular (root canal) pulp

• Coronal pulp- similar in contour to dentin and may possess a roof, pulp horns, and floor in this area
• Radicular pulp- tube shaped (bc in root canal!), is continuous with the periodontal CT at the apical forament

• All zones found w/in the crown of the teeth
• 1. Odontoblastic layer
• 2. Cell free zone of Weil
• 3. Cell rich zone
• 4. Pulp core

• Zone is adjacent to the dentin and is made of a single layer of odontoblasts.
• Fxn: make dentin and be area for sensory nerves to treminate

intercellular matrix, nerve fibers, capillaries and tissue fluid

• Fibroblasts and undifferentiated cells that will become odontoblasts. Also nerve plexus here.
• These cells form reparative dentin or replace odontoblasts.

• Bulk of the pulp.
• Loose CT with fibers, cells and ground substance.

Location and structure

• Free in the pulp.
• Attached to the dentin.
• Embedded in the dentin.

• True denticles
• False denticles
• Diffuse calcifications

• Made of dentin, but formed from induction of remnants of Hertwigs root sheath trapped in the pulp.
• For these, odontoblasts differentiate in the pulp and make dentin= true denticles.

True denticles- big red ovals

• Concentric layers of calcified tissue surrounding dead cells or collagen bundles.
• Pink circles

Made from calcification of collagen bundles. Squamous, irregular looking

similar in that it is 50% mineralized (bone is 60), but different bc cementum is avascular.

• Thinnest- cervix
• Thickest- apex

It serves as an attachment site for PDL fibers

• 1. Anchors root to the socket
• 2. Continuously produces itself throughout life, which helps the tooth continuously erupt through life (helps w/ enamel loss), helps the PDL fibers maintain width, and helps repair root injuries.

• cementoblasts
• cementocytes
• cementoclasts

• Organic matrix
• inorganic matrix
• Sharpey's fibers

• Found at the surface of the cementum
• Lay down organic matrix (cementoid) on the surface of root dentin.

• Cementocytes are cementoblasts that have become embedded in the cementum.
• They live in lacunae and have processes called canaliculi.

• Cementoclasts are large, multinucleated cells that are derived from monocytes.
• They demineralize and remove cementum- they are located in the PDL.
• Similar to osteoclasts.

Cementoid- ground substance and collagen fibers which are produced by and located underneath the cementoblasts

Cementum- formed from hydroxyapatite depositing on the collagen fibers of the cementoid (organic matrix) and of the PDL.

Sharpey's fibers- extrinisic collagen fibers of the PDL that become embedded in the cementum as the cementum grows outward

Dental Sac (follicle) which is derived from ectomesenchyme

• Root shealth breaks down after root detin forms. (reminants called epithelial rests)
• This allows mesenchymal cells, fibroblasts, and collagen, in the dental sac to move toward the dentin.
• Dentin turns these cells into cementoblasts and they then secrete cementoid.

• 1. from fibroblasts in the dental sac
• 2. later, from newly differentiated cementoblasts

Sharpey's fibers of the PDL. These fibers are not really fibers of the true matrix. These fibers are anchored into calcified cementum and help anchor the tooth into the alveolar bone.

The cementoblasts, when mature, lay down the collagen fibers that secrete the organic matrix for the mineralization of cementum.

Cellular and Acellular

• Located in the cervical 1/3 of the root.
• Covered by cementoid and cementoblasts. (NO CEMENTOCYTES). No cells in this matrix, just covered by them.
• This is the first cementum produced, and is usually just a thin layer.

on dentin surface- in upper 1/3 root

• Located in apical 1/3 of root
• Covered by cementoid and cementoblasts (same as acellular), but cementocytes are distributed throughout it in lacunae(different from acellular).
• Cementocytes processes extend toward PDL

• Grows throughout life.
• Most recently formed cementum has Sharpey fibers.
• Grows in Incremental lines that have periods of rest (cementoblasts retreat) and then resumed cementum formation.
• These lines follow the contour of the tooth.

• More layers of cementum are deposited in response to stress- LAMELLAE. This appears as heavier resting lines.
• Can be cellular or acellular.

• 1. Cementum overalps enamel (60% of the time). Happens due to the early degeneration of the REE during development/ early breakdown of epithelial root sheath.
• 2. Cementum and enamel abut eachother (30%) Well formed. Proper.
• 3. Cementum is lacking (10%). Exposed dentin. Due to delayed breakdown of epithelial root sheath.

• Calcified bodies located on or in the cementum or PDL.
• Formed via induction from remnants of epithelial rests.
• May be formed from local trauma, hyperactivity and increasing age.

• 1. Free- lie in the PDL
• 2. Attached- stone is attached to cementum
• 3. Embedded- stone is embedded in cementum

• 1. Anchors teeth in the socket
• 2. Allows for repair at root surface
• 3. Seals the ends of the dentinal tubules
• 4. Is more resistance to resorption than bone
• 5. Permits orthodontic movement