periodontal ligament and cementum semester 1

Question 1

Describe the structure and function of the periodontal ligament

Answer 1

Thin sheet of fibrous connective tissue
* Thickness varies depending on age and
function of tooth
* Fibroblasts are responsible for the
production of fibrous matrix and ground
substance
* Fibres are arranged in bundles located within
the alveolar bone proper and cementum

functions:
* Attaches tooth to its bony socket
* Supportive - suspends tooth in socket
* Sensory- tactile pressure and pain
sensation
* Nutritive- to cementum and bone
* Formative- builds and maintains
cementum and alveolar bone
* Remodelling - severe pressure
initiates osteoclasts

Question 2

Define ankylosis and discuss occurrence and characteristics of it

Answer 2

Defined:
Fusion of cementum and alveolar bone (no presence of periodontal ligaments)
Occurrence:
* Post chronic periapical inflammation
* Tooth re implantation, occlusion trauma, and impacted teeth
* Common in primary dentition
Characteristics:
* Metallic percussion sound
* Infra occlusion
* No pressure receptors
* No drifting
* No eruption of teeth
* Periodontal ligament space is missing

Question 3

Recall the physical properties and functions of cementum

Answer 3

Physical Characteristics
* Thin layer of calcified tissue covering the dentine of the root
* Pale yellow with a dull surface
* More permeable and softer than dentine
* readily removed by abrasion due to softness and thinness of cementum around
the cervical region
Functions
* Maintains the integrity of the root
* Helps maintain the tooth’s functional position in the mouth
* Seals the dentinal tubules
* Involved in tooth repair and regeneration

Question 4

Describe the process of cementum formation

Answer 4

Cementoblasts lay down cementoid,
which is subsequently mineralised to
form cementum
* Uncalcified matrix = cementoid
* As new layer of cementoid is laid down,
the old one is mineralised
* A thin layer of cementoid can always be
found on surface of cementum, which is
lined by cementoblasts
Once the tooth comes into occlusion,
cementum starts to form more
rapidly
Cementoblasts become trapped in
the forming mineralised tissue
This results in two types of
cementum – acellular and cellular
cementum

Question 5

Explain the differences between cellular and acellular cementum

Answer 5

Type 1 Acellular Cementum
* Covers the cervical one
third of the root
* Formed prior to the tooth becoming functional
* Thickness ranges from 20 to 230 μm
* Does not increase in thickness with age
* Laid down in layers resulting in incremental lines
which run parallel to the root surface indicating slow
formation
Type 2 Cellular Cementum
* Covers the apical third and
overlying the acellular
cementum
* Less calcified and up to 10 times thicker than a cell
* Cementoblasts trapped in the rapidly forming cellular cementum are
known as cementocytes
* Incremental lines are further apart, thicker and more irregular

Question 6

Describe the relationship of cementum to enamel at the cementoenamel junction
(CEJ) and recall the classification system used to describe this relationship.

Answer 6

• The cementum – enamel relation is where the enamel and cementum is meet. It is actually significant land mark, most people where the gingival margin seat, but not always the case. The cementum enamel junction is important for the probing or the measuring.
• There are different cementum enamel relationship in different pt
  Pattern 1: enamel just overlap the cementum (most common one)
  Pattern 2 the enamel and cementum meeting each other
  Pattern 3 the enamel fail to meet the cementum ( it is rare)

Question 7

Define hypercementosis and its aetiology

Answer 7

• Thickening of cementum
• Age related phenomenon
• Localised or generalised
• Associated with neoplastic or non neoplastic conditions
• Thickening with nodular enlargement of the apical third of the root
• Excessive tension from
  orthodontic appliances or
  occlusal forces
• Generalised form- keep
  pace with excessive tooth
  eruption (over-eruption)
• Pulp disease –
  compensation for the
  destroyed fibrous
  attachment to the tooth

Question 8

Explain key clinical considerations related to the composition and function of
cementum

Answer 8

Clinical Considerations:
* Cementum is essential for tooth anchorage
* It mediates attachment of the tooth to the gingival connective tissue
as well as the periodontal ligament and alveolar bone
* Cementum protects the tooth as it is less susceptible to resorption
(loss of substance)
* This allows for safe orthodontic movement without damage
* During the removal of calculus and bacterial deposits, thin layers of
cementum are removed

Question 9

sharpey’s fibres

Answer 9

• Ends of the PDL fibres
• Embedded in the
  cementum and
  alveolar bone

Question 10

blood supplies of PDL

Answer 10

PDL has rich blood supplies and heavily anastomosed. Basically, is that mean that it get blood supply from number of the diversion blood vessels.
Nutrition transfer from 3 different blood vessel cells type, gingival, perveriong vessel and epical vessel.
, There are different type of blood vessel and providing nutrition to different type of structure in the teeth

Question 11

nerve supplies to PDL

Answer 11

• PDL has number mechanoreceptors (there are things that react to pressure or tactile stimulation such a food stuck) and pain sensing never endings (relatively high thresholds, we can chewed, eat , but it taking a lot for something to cause pain to the PDL while we are eating or talking or normal daily activity
• These two systems is work together, by transmit the information such as Jaw position in the correct way, whether out teeth are moving, whether there are injuries on our teeth.

Question 12

thickness of cementum

Answer 12

• Continuous process that proceeds at varying rates throughout life
• Most thickness at apical and furcation of multi rooted teeth
• Thicker in the distal surfaces than the mesial surface
• Thickness on coronal half equates to the thickness of one hair