Question 1. Describe the macroscopic and microscopic appearance of cementum. (or) Cementoenamel junction
Answer:
Cementum:
- It is a mineralized, hard connective tissue that covers the anatomical roots of teeth.
Macroscopic appearance:
- Cementum provides a medium for tire attachment of collagen fibers that bind tire tooth to, the surrounding structures.
- It is avascular and non-innervated.
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- Cementum can form throughout the life of a tooth.
Extend:
- Cementum begins at the tire cervical portion of the tire tooth at the tire cementoenamel junction and continues to the apex.
- Sometimes, it extends to the inner wall of the dentin for a short distance.
Color:
- Cementum is light yellow in color.
- It lacks luster as present in enamel, n It is lighter in color than dentin.
Microscopic appearance:
- The cementum consists of
1. Fibres.
Types:
- Intrinsic fibers:
- Collagen fibers secreted by tire cementoblast are called intrinsic fibers.
- They are densely packed to the root surface.
- They run parallel.
- Extrinsic fibers:
- Collagen fibers produced by fibroblasts of periodontal ligament are incorporated into the cementum as sharpe/s fibers form extrinsic fibers.
- They are large and haphazardly incorporated.
- They run perpendicular to the root surface.
Function:
- Fibres anchor the tooth to the bone.
- They distribute masticatory forces.
2. Cementoblasts:
- The cells forming the cementum are called cementoblasts.
- They have numerous mitochondria, a well-formed Golgi apparatus, and a large amount of granular endoplasmic reticulum.
- They intermingle with the fibroblasts of the periodontal ligament.
- They have basophilic cytoplasm.
Functions:
- Cementoblasts synthesize collagen and protein polysaccharides which form an organic matrix of cementum.
- This organic matrix of cementum forms a fibrous fringe where collagen fiber bundles of periodontal ligament become anchored.
3. Cementocytes:
- Some cementoblasts become entrapped within their own matrix, they are called cementocytes.
- They have very little cytoplasm and numerous processes called canaliculi.
- They are present in spaces called lacunae.
- Cementocytes in the deeper layers are non-viable.
- They have reduced secretory activity.
4. Incremental lines:
- The incremental lines in cementum are called the lines of salter.
- These lines indicate periodic formation.
- They can be best seen in decalcified specimens.
- They are highly mineralized areas with less collagen and more ground substance than other portions of the cementum.
- These lines are far apart in the cellular cementum and closely placed in the acellular cementum.
- The number of incremental lines is used for the age determination of an individual.
5. Cementodentinal junction:
- It is the interface between cementum and dentin.
- It is relatively smooth in permanent teeth, while scalloped in deciduous teeth.
- It is a wide zone containing large quantities of collagen associated with glycosaminoglycan which increases its water content.
Functions:
- It contributes to the stiffness of cementum
- It helps to redistribute occlusal loads to the alveolar bone.
6. Cementoenamel junction:
- The relation between cementum and enamel at the cervical region of teeth is called a cementoenamel junction.
Types:
- In 30% of cases – the cementum and enamel meet as a butt joint.
- In 10% of cases – a gap exists between the cementum and enamel.
- In 60% of cases – cementum overlaps enamel.
Question 2. Enumerate the difference between cellular and acellular cementum.
Answer:
Question 3. Intermediate cementum.
Answer:
Hertwig’s epithelial root sheath may produce epithelial products that accumulate on the forming root surface to form a layer, referred to as intermediate cementum.
- The cell rests of HERS may be entrapped in the cementum near cementodentinal junction.
- It is a zone that separates dentin from cementum.
- It does not exhibit characteristic features of either dentin or cementum.
Site:
- It usually occurs in the apical half of the roots of molar teeth.
- It is rarely present on incisors and primary teeth.
- It is found only in isolated areas.
Synonym:
- A hyaline layer of Hopewell and Smith.
Structure:
- It contains no tubules but wide spaces that may result due to enlarged terminals of dentinal tubules,
- It contains an amorphous layer of noncollagenous material devoid of odontoblasts and cementoblasts.
- It is a continuous layer.
Functions:
- It might seal the sensitive root dentin.
Question 4. Cementoeenesls.
Answer:
- All types of the century are produced by cementoblasts,
- Cornell turn formation is preceded by the formation of HERS followed by the deposition of dentin along the inner aspect of this sheath.
- later fenestrations occur in the root sheath and cementoblasts are aligned along the newly formed unmineralized mantle dentin surface.
- Cenientoblasl exhibits fibroblastic characteristics, extend cell processes into the unmineralized dentin, and deposit collagen fibrils with it so that the dentin and cementum fibrils intermingle.
- Mineralization of the mantle dentin starts internally and then spreads across into the century under the influence of noncollagenous matrix protein, thereby establishing the cementodentinal junction.
- The cement thus formed as acellular momentum,
- Cemontoblasts then migrate away from the surface but continue to deposit collagen so that the fine fiber bundles lengthen and thicken.
- These cells also secrete non-collagenous matrix proteins that fill in the spaces between the collagen fibers.
- Once the tooth is in occlusion, a more rapidly formed and less mineralized variety of cementum, cellular cementum is deposited on the acellular cementum.
- This cementum is formed by cementoblasts which differentiate from the dental follicle.
- As cementum deposition progresses, cementoblasts become entrapped in the extracellular matrix they secrete.
- These entrapped cells are called cemenlocytes.
Question 5. Enumerate types of cementoenamel junctions and write their development.
Answer:
Types of the cementoenamel junction and its development:
1. In approx. In 30% of cases, the cementum and enamel meet as a butt joint, forming a distinct cementoenamel junction at the cervical margin.
- This junction is a relatively sharp line
2. In about 10% of cases, enamel and cementum do not meet.
- This occurs when enamel epithelium in the cervical portion of the root is delayed in its separation from dentin.
- A zone of the root is formed which is devoid of cementum and is covered by reduced enamel epithelium.
- The exposure of root dentin at the cervical margin can lead to sensitivity, increased risk for root resorption, and root surface caries.
3. In approx. In 60% of cases, cementum overlaps enamel.
- This occurs when the enamel epithelium generates at its cervical end permitting connective tissue to come in direct contact with the enamel surface.
- When cementoblast comes in contact with enamel they produce a fibrillar cementum.
- If such fibrillar cementum remains in contact with connective tissue cells for a long enough time, fibrillar cementum may be deposited on its surface.
- Thus, the thickness of cementum that overlies enamel increases.
Question 6. Cellular cementum.
Answer:
Cellular cementum is formed after the tooth reaches the occlusal plane.
- It is more irregular
- It is always thick around the apex
Synonym:
- Secondary cementum.
Site:
- It is more frequent on the apical half of the root.
Histology:
- It is a less calcified structure.
- It contains cells called cementocytes, thus it is known as cellular cementum.
- It has a collagenous matrix.
- Sharpey’s fibers are less mineralized.
- Incremental lines are fewer in number, irregular, and widely spaced.
- It is rapidly formed.
Types:
1. Cellular intrinsic fiber cementum.
- Contains cementocytes and intrinsic fibers but no extrinsic fibers.
2. Cellular mixed fiber cementum.
- It contains cementocytes along with both intrinsic and extrinsic fibers
Functions:
- Cellular cementum is mainly involved in the adaptation and repair of cementum.
Question 7. Acellular cementum. (or)
Answer:
It is first formed cementum.
- It is formed before the tooth reaches the occlusal plane.
Synonym:
- Primary cementum.
Site:
- It covers the cervical third of the root.
Histology:
- It is a highly calcified structure.
- It doesn’t contain any cells thus called acellular cementum.
- It has no collagenous matrix and Sharpey’s fibers are the only collagen fibers.
- These fibers are more mineralized than those of cellular cementum.
- Incremental lines are more in number and placed closer to each other.
- Collagen fibrils make up the bulk of the organic portion of the tissue.
- Between these collagen fibrils, there is the presence of a ground substance of polysaccharide.
Function:
- The main function of acellular cementum is anchorage, especially in single-rooted teeth.
Question 8. Hypercementosis
Answer:
- It is a prominent thickening of cementum
- It may be diffuse or circumscribed
- It may affect all teeth or single tooth
- Observed often in non-functioning teeth
- It is characterized by a reduction in the number of Sharpey’s fibers embedded in the root
- It is found in teeth exposed to greater stress
- This increases the surface area for the firmer anchorage of the tooth
- An excessive deposition is circumscribed and surrounds the root like a cuff
Types:
- Localized
- Generalized
Etiology:
1. Localized
- Excessive tension
- Excessive occlusal forces
2. Generalized
- Periapical infections
- Paget’s disease
Question 9. Cementocytes
Answer:
- Some cementoblasts become entrapped within their own matrix they are called cementocytes
- They are oval spider-like structures
- They have very little cytoplasm and numerous processes called canaliculi
- Those processes may branch and anastomose with those of neighboring cells
- Most of the processes are directed towards the PDL surface of the cementum which is the site of diffusion for essential nutrients since the cementum is avascular
- They are present in spaces called lacunae
- Cementocytes in the deeper layers are nonviable
- They have reduced secretory activity
- They become progressively further from the nutritive source
- They show few organelles with dilated endoplasmic reticulum
- They are in stages of degeneration
Question 10. Cellular cementum.
Answer:
- It is formed after the tooth reaches the occlusal plane, thus also called secondary cementum.
- It contains cells containing cementocytes, collagenous matrix, and less mineralized Sharpey fibers.
- Incremental lines are widely separated and irregular.
- It is mainly found in the apical half of the root and in furcation areas.
- It is mainly involved in the adaptation and repair of cementum.
Question 11. Cementocytes.
Answer:
- Some cementoblasts become entrapped within their own matrix, they are called cementocytes.
- They are spider-like cells.
- They lie in spaces called lacunae.
- They have very little cytoplasm and numerous periodontal surfaces of cementum.
- These processes may branch and anastomose with those of neighboring cells.
- Cementocytes have reduced secretory activity.
- The cytoplasm of deeper layer cementocytes contains few organelles indicating degenerating cementocytes.
- In the deeper layer of cementum, lacunae appear empty, cementocytes are non-viable suggesting complete degeneration of cementocytes.
Question 12. Hypercementosis.
Answer:
- Hypercementosis is the abnormal thickening of the cementum.
- It may be diffuse or circumscribed.
- It may affect all teeth or a single tooth or many parts of a single tooth.
- It is observed often in non-functioning teeth.
- It is characterized by a reduction in the number of Sharpey fibers embedded in the root.
- In localized hypertrophy, a prong-like extension of the cementum may be formed.
- It is formed in teeth exposed to great stress.
- This increases the surface area for the firmer anchorage of the tooth.
- Localized hypercementosis may sometimes be observed in areas in which enamel drops have developed on the dentin.
- It is occasionally associated with chronic periapical inflammation.
- The excessive deposition is circumscribed and surrounds the root like a cuff.
Question 13. Cementicles.
Answer:
- The calcified bodies found in the periodontal ligament are called cementicles. These bodies are seen in older individuals.
Appearance:
- May remain free in the connective tissue or
- May join with the cementum.
- When adherent to the cementum, they form excementoses.
- May fuse into large calcified masses.
Origin:
- Degenerated epithelial cells form the nidus for the calcification of cementicles.
Question 14. Types of cementum.
Answer:
1. Based on location:
- Radicular cementum:
- It covers the anatomical roots of the teeth.
- It forms the main bulk
- Coronal cementum:
- It covers the enamel at CEJ.
- It is poorly developed.
2. Based on the presence or absence of cementocytes:
- Cellular cementum:
- It contains cementocytes in lacunae.
- It is also known as secondary cementum as it is formed after the tooth reaches the occlusal plane.
- Acellular cementum:
- It does not contain any cells.
- It is also known as primary cementum as it is the first formed cementum.
3. Based on the presence or absence of fibrils in the matrix:
- Fibrillar cementum.
- This contains well-defined and densely packed collagen in the matrix.
- A fibrillar cementum.
- This does not have any fibers – intrinsic/extrinsic.
Question 15. Functions of cementum.
Answer:
1. Anchorage:
- Cementum furnishes a medium for the attachment of collagen fibers that bind the tooth to the alveolar bone.
- The exfoliated teeth are characterized by an almost total absence of cementum.
- Mainly acellular extrinsic fiber cementum helps in anchorage.
2. Adaptation:
- It makes functional adaptation of teeth possible.
- Deposition of cementum in an apical area can compensate for the loss of tooth substance from occlusal wear.
- As the most superficial layer of cementum ages, a new layer of cementum gets deposited.
- Cellular cementum is mainly involved in it.
3. Repair:
- Cementum serves as major reparative tissue for the root surface.
- Damage to roots causes by fractures or resorption it is repaired by tire deposition of new cementum.
- Cellular cementum is also involved in it.
Question 16. Cementoblasts.
Answer:
- All types of cementum are produced by cementoblasts which are derived either from HERS or from the dental follicle.
- Cementum formation is preceded by the formation of the HERS followed by the deposition of dentin along the inner aspect of this sheath.
- Later, fenestrations occur in the root sheath.
- Cementoblast derived from HERS come in contact with dentin and lay down ground substance and collagen fibrils forming acellular cementum.
- Later, cellular cementum is deposited over it.
- This cellular cementum is formed by cementoblasts which differentiate from the dental follicle.
Question 17. Intermediate cementum.
Answer:
- It is a zone separating dentin from cementum.
- It is also known as the Hyaline layer of Hopewell and Smith.
- It usually occurs in the apical half of the roots of molar teeth.
- It does not exhibit characteristic features of either dentin or cementum.
- It is a continuous layer.
- It contains an amorphous layer of non-collagenous material.
It might seal the sensitive root dentin.
Question 18. Acellular cementum.
Answer:
- It is the first formed cementum that is formed before the tooth reaches the occlusal plane.
- It is also known as the primary cementum.
- It covers the cervical third of the root.
- It is a highly calcified structure with mineralized sharpey’sfibers.
- It does not contain any cells thus called acellular cementum.
- Incremental lines are closely placed.
- Its main function is the anchorage of teeth.
Question 19. Clinical considerations of cementum.
Answer:
- Cementum is more resistant to resorption than bone. This is used during orthodontic tooth movement.
- Cementum is avascular and thus not damaged by pressure.
- Cementum resorption can occur after trauma or excessive occlusal forces.
- The damage caused by it is repaired, either by the formation of cellular or acellular cementum.
- If the former outline of the root surface is re-establish, it is called anatomic repair.
- But if the tire outline of the alveolar bone follows that of the root surface, it is called functional repair.
- Transverse root fractures are healed by the formation of new cementum.
- Hypercementosis occurs secondary to periapical inflammation or excessive occlusal stress.
- Abnormal cemental deposition can sometimes lead to ankylosis.
- Cementum is found thicker in type 2 diabetic patients.
- Cemental caries can be seen on the exposed surface of the cementum associated with gingival recession.
- Incremental lines in the cementum are used for age determination.
Question 20. Cementum.
Answer:
- It is a mineralized, hard connective tissue that covers the anatomical roots of teeth.
- It is avascular and non-innervated.
- It begins at the CEJ and extends up to the root apex.
- It is light yellow in color.
- It contains 45-50% of inorganic material, 50-55% of organic material, and water.
- It has the highest fluoride content.
Functions:
- Anchorage of the tooth to the alveolar bone.
- Adaptation by deposition and resorption.
- Repair against damage caused by trauma or resorption.
Question 21. Age changes in cementum.
Answer:
- Decreased vascularity.
- Reduction in metabolic rate.
- Reduction in healing capacity.
- Resorption activity is increased
- Continuous deposition of cementum occurs with age.
- Greater irregularity is seen in the surface of both cellular and acellular cementum.
- Cemental width increases more apically and lingually.
Question 22. Cementoid
Answer:
- The growth of cementum is a rhythmic process
- As a new layer of cement is formed, the old one becomes calcified
- A thin layer of cement is usually observed on the cemental surface
- It is formed of an uncalcified cemental matrix consisting of
- Collagen fibers
- Extrinsic from PDL & intrinsic from cementoblast
- Ground substance
- Proteoglycans
- Glycoproteins
- Phospho proteins
- Collagen fibers
Question 23. Incremental line of salter
Answer:
- Incremental salter is seen in cementum
- They indicate the periodic formation
- Best seen in decalcified specimens
- They are highly mineralized areas with less collagen and more ground substance than other portions of the cementum
- These lines are far apart in cellular cementum and closely packed in acellular cementum
- The number of incremental lines is used for the age determination of individual
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