Term
| THESE ALL OCCUR WHILE TOOTH IS IN CROWN STAGE |
|
Definition
| Root Formation and Cementogenesis |
|
|
Term
| Root Formation and Hertwig's Root Sheath |
|
Definition
-Continued proliferation of cervical loop towards apical region of dental papilla - Leads to formation of Hertwig's Epithelial Rooth Sheath which has 2 cells layers -Gradually migrates apically between dental papilla and dental follicle -The rim eventualy encloses the primary apical foramen (encloses some dental papilla inside) |
|
|
Term
| While Hertwig's RS is growing apically... |
|
Definition
1. It induces superficial cells od dental papilla to differentiate into odontoblasts.
->Subsequently leads to creation of root predentin and then dentin 2. Defines the shape or the root (how many roots) |
|
|
Term
|
Definition
-HRS undergoes focal mitotic activity, forming ridges of epithelium that proliferate centrally -These Epithelial Diaphragms fuse near midline of tooth, forming 2-3 roots -These diaphragms also cause odontoblastic differentiation leading to root dentin
|
|
|
Term
|
Definition
-HRS is stretched over surface of root, then indergoes partial degeneration -Network of leftover HRS cells persist thoughout life within the periodontal ligament -Look like clusters called the Epithelial Rests of Malassez -These have no function but cysts and tumors can occur here
|
|
|
Term
|
Definition
-Ones HRS fragments, dental follicle is exposed to root surface/dentin -> causes differentiation into Cementoblasts at outer surface of root
|
|
|
Term
| Formation of Primary Cementum |
|
Definition
-Outer surface root dentin composed of amorphous hypermineralized layer of dentin called Hylain Layer of Hopewell Smith -Newly differentiated cementoblasts insert a cell process into this layer prior to its full mineralization -Begin to deposit collagen fibrils at right angles to root surface as they retreat from the root ->Cementoid (cementum matrix) -Cementoblast also secrete Bone Sialoprotein + Osteocalcin
|
|
|
Term
| Initial Cementum Layer Characterisics |
|
Definition
1. Acellular 2. Forms slowly as tooth erupts 3. Covers the coronal 2/3 of the root |
|
|
Term
| After primary deposition... |
|
Definition
-Cementoblast activity slows -Fibroblasts of developing Perio Lig. then intertwine collagem around existing fibers protruding from primary cementum -Deposit mineral onto root surface -> leads to establishment of Sharpey's Fibers that attach tooth to Perio Ligament
|
|
|
Term
| Formation of Secondary Cementum |
|
Definition
-Additional cementum produced after tooth reaches occlusion -More rapid deposition of less mineralized cementum along apical 1/3 of root and Interradicular areas of multirooted teeth -Collegen fibers in this cementoid ad Parallel to root -Matrix vessicles from cementoblasts then mineralize the cementoid
|
|
|
Term
|
Definition
-Cementoblast activity diminshes and they become entrapped within lacunae of mineralized matris -Knows as Cementocytes -Communicate via canaliculi like osteocytes -HOWEVER, these channels DO NOT reach cementum surface -Cementocytes ONLY found in secondary cementum
|
|
|
Term
|
Definition
-Cemetum that conatins cementocytes -This type continues to form with continuing organization of Perio Lig in this area -Typicallly found in apical 1/3 of roots and in Interradicular areas
|
|
|
Term
|
Definition
-Hard tissue that covers root and provided partial anchor for PDL -Derived from Dental Follicle - Equal parts organic and inorganic -Type I collagen is Main Organic Component |
|
|
Term
|
Definition
1. Acellular - provides attachment to PDL 2. Cellular - contains Cementocytes. Formed in response to minor persistant trauma and/or tooth wear
|
|
|
Term
| How Cementum is Subclassified |
|
Definition
1. Time of formation (primary vs. secondary) 2. Presence of cementocytes (acellular vs. cellular) 3. Origin of its collagen components (intrinsic vs. extrinsic)
|
|
|
Term
|
Definition
1. Primary Acellular Extrinsic Fiber Cementum 2. Secondary Cellular Intrinsic Fiber Cementum 3. Acellular Afibrillar Cementum 4. Mixed Fiber Cementum
|
|
|
Term
| Primary Acellular Extrinsic Fiber Cementum |
|
Definition
-Produced through incorporation of PDL fibers -Serves anchoring function -Is the Major attachment cementum -Only type found on anterior teeth -There is NO surface cementioid |
|
|
Term
| Secondary Cellular Intrinsic Fiber Cementum |
|
Definition
-Contains cementocytes, contributes little attachment -Formed rapidly once tooth is in occlusion -Less mineralized that PAEFC -It is placed against unmineralized dentin -Cementoblast process extend within it, mixing it's collagen with dentin's collagen -Has thin layer of surface cementoid
|
|
|
Term
| Acellular Afibrillar Cementum |
|
Definition
-Seen only on surface of enamel as a thin extention of root cementum or small isolated path near CEJ -Serves no function, considered development abnomality
|
|
|
Term
|
Definition
-Occurs with the development of PDL -Comprised of cellular cementum secreted arounf PDL fiber bundles -Accounts for majority of Secondary Cememtum -Laminated appearance on Light Micro -Has thin layer of surface cementoid |
|
|
Term
|
Definition
-60% of teeth show cemetum overlapping enamel -30% show the two meeting head to head -10% show a gap between cemetum and enamel However, since been demonstrated that these conditions can be found in all teeth when CEJ is traced circumferentially
|
|
|
