INTRODUCTION Cementum is a specialised hard layer of calcified mesenchymal tissues which forms the outer covering of the anatomical root. It is also called as Substantia Ossea Cementum is the part of Periodontium . Human Cementum is avascular & has no innervation.
1. Hardness :
Hardness less than dentin.
2. Colour :
Light yellow in colour.
Dull surface (Lack of Lusture)
Darker hue than enamel.
3. Permeability :
More permeable than dentin.
Permeability decreases with age.
4. Thickness :
Cellular Cementum : 16-60 micron.
Acellular Cementum : 150-200 micron.
CHEMICAL PROPERTIES Inorganic Matter (45-50%) Organic Matter (50-55%) Mainly Hydroxyapatite Mainly Type-I collagen Ca 10 (PO 4 ) 6 (OH) 2 & interfibrillar ground Fluoride content is highest Substance consist of than other calcified tissues Proteoglycans of body.
I. Based on time of formation
II. Based on Presence or Absence of Cells
III. Based on Fibers
According to above findings cementum classified as :
1. Acellular Afibrillar Cementum
2. Acellular Extrinsic Fiber Cementum.
3. Cellular Mixed Stratified Cementum.
4. Cellular Intrinsic Fiber Cementum.
It is an ill-defined zone near the cementodentinal junction of certain teeth that appears to contain celluar remnants of Hertwig’s sheath embedded in calcified ground substances.
1. First formed Secondary Cementum. 2. Present on cervical third or half of the root. Mainly on apical third of root. 3. It does not contain cells. It contain cells called cementocytes in individual spaces lacunae. 4. It is formed before the tooth reaches the occlusal plane. Formed after the tooth reaches the occlusal plane. 5. More calcified. Less Calcified. 6. Sharpey’s fibers are main compenent which inserted at approximately right angles onto the root surface. Sharpey’s fibers occupy smaller portion & occpy other fibers that are arranged parallel to the root surface.
SHARPEY’S FIBERS :
Terminal portions of the principal fibers that insert into cementum & bone are termed as “Sharpey’s Fibers”.
These have a principal role of supporting the tooth within jaw.
CELLS OF CEMENTUM :
Cementoblasts synthesize collagen& protein polysaccharides that form organic matrix of cementum.
During formation of cellular cementum, the cementoblasts become incorporated into the cemental matrix. These cells are known as cementocytes. The cementocytes lie in spaces known as lacunae.
CEMENTOGENESIS : Cementum develops from the activity of mesenchymal cells of dental follicle after fragmentation of the epithelial root sheath. After formation of dentin, loss of continuity occurs in the epithelial root sheath. This allows adjacent cells of the investing layer of the dental follicle to come to lie on surface of root dentin & these are induced to differntiate into cementoblasts. CEMENTOENAMEL JUNCTION : The interface between the Cementum & Enamel at the cervical region of tooth is known as cementoenamel junction. It is of 3 types
Pattern I : Pattern Pattern III : Overlapping Type (60%) Butt joint (30%) Gap joint (10%) CEMENTODENTINAL JUNCTION It is interface between the dentin & cementum. Scalloped in deciduous teeth & smooth in the permanent teeth. FUNCTIONS OF CEMENTUM : Cementum provide a medium for the attachment to the collagen fibers of periodontal ligament. Cementum is hard & has no blood supply, It does not show resorption under masticatory or orthodontic forces. Thus, during heavy orthodontic forces, tooth integrity is maintained & alveolar bone being elastic in nature changes its shape, fulfilling the orthodontic requirement. Cementum has property of continuous deposition & does the patch work or repair for the damage such as fracture or resorption of tooth surface. Regular Cementum deposition at the root apex, helps to replenish the lost tooth height due to occlusal wear or helps in passive eruption of teeth.
CEMENTAL ANOMALIES :
I. Hypercementiosis means abnormally prominent thickness of the cementum on root surface
Hypercementiosis Localized Generalized Cemental spikes & Paget’s disease Excementosis Chronic periapical infection. Non functional teeth without any antagonist.
CEMENTAL HYPERPLASIA & HYPERTROPHY :
Cementum overgrowth when growth does not help in increasing function of the tooth.
eg. due to periapical infection.
If Cementum overgrowth improves or helps in the functioning of teeth, this is called as cemental hypertophy.
eg. Cemental spike develps from extensive orthodentic force
Cementicles are round lamellated cemental bodies that lie free in the PDL or are attached to the root surface.
Mostly found in aging persons or at the site of trauma.
CEMENTOMA is also called benign cementoblastoma or cemental dysplasia.
These are cemental masses situated at the apex of the root which are slowly growing odontogenic neoplasm and may cause expansion of jaw.
CEMENTAL RESORPTION & REPAIR :
Cementum on the root surface undergoes resorption & repiar alternately according to change in enviroment faced by it.
CAUSES OF CEMENTAL RESORPTION
Local Causes Systemic Causes
Trauma from Occlusion Deficiency of Ca
Cyst & Tumors Deficiency of Vit. A & D
Periapical Pathology Hypothyroidism
Excessive orthodontic forces
Replanted & Transplanted Teeth
CEMENTAL REPAIR : Repair of cementum is a process to heal the damage caused by resorption or cemental fracture. Repair Anatomic Functional Root outline is re-established In case of large cemental as it was before cemental resorption. resorption, repair does not re-establish the same anatomic contour as before.
AGING OF CEMENTUM : Surface become rough. Cemental Resorption. Permeability Decreases. More Cemental deposition may lead to closure of the apical foramen.
CLINICAL CONSIDERATION : I. Ankylosis : Fusion of cementum & alveolar bone with no PDL in between, known as Ankylosis. Causes : Causes : Faulty replantation & transplantation of teeth. Embedded teeth. Chronic Periapical Infection. Trauma to deciduous teeth. II. Importance of Root Planing in Periodontal Treatment. Root planing is a treatment to remove necrotic cementum & smoothening the root surface in order to reduce the pocket depth