Dental plaque and Biofilms (6)

Question 1

What is calculus?

Answer 1

mineralised plaque

Calcified or calcifying deposits attached to the surfaces of teeth or other solid structures in the mouth e.g. dentures

Question 2

What always precedes calculus?

Answer 2

plaque

Question 3

What are the 2 types of calculus?

Answer 3

Supragingival (saliva)
Subgingival (GCF)

Question 4

Describe calculus formation?

Answer 4

Plaque deposits become the organic matrix for the subsequent mineralisation of the deposit

Small crystals appear in the intermicrobial matrix; the matrix calcifies and then the bacteria become mineralised

Mineralisation requires nucleation of crystal seeds and then crystal growth

Question 5

What are the 4 crystal types of of calcium phosphate?

Answer 5

Octacalcium phosphate
Hydroxyapatite
Whitlockite
Brushite

Question 6

Where would you find supragingival calculus?

Answer 6

Adjacent to the opening of salivary ducts:
Parotid
Sublingual

Question 7

Where would you find subgingival calculus?

Answer 7

No predilection for certain parts of the mouth
Approximal and lingual parts affected more than buccal

Question 8

What does subgingival plaque appear like?

Answer 8

Creamy-white colour Stained in smokers

Question 9

Is this sub or supragingival plaque?

Answer 9

supragingival

Question 10

Is this sub or supragingival calculus?

Answer 10

subgingival

Question 11

What does subgingival plaque appear as?

Answer 11

Brownish-black due to haemorrhagic elements from GCF and black pigments from anaerobic rods

Question 12

How do you detect supragingival plaque?

Answer 12

*Visible clinically
*Detection may be enhanced by air drying – gives a chalky appearance

Question 13

How would you detect subgingival calculus?

Answer 13

By probing:
Tactile sensation enhanced with the use of a ball ended probe

If located at the entrance of a pocket:

-May be seen as a dark shadow under the gingival margin

-Air-jet from the 3-in-1 syringe may retract the gingivae to provide direct vision

-Following gingival recession subgingival deposits may become supragingival

-Radiopaque calculus wings may be visible on approximal wings on bitewing radiographs

Question 14

How does supragingival plaque form?

Answer 14

• Nucleation, crystal growth and calcification are heterogeneous (non-uniform)
• Deposits build up in layers with variable mineral content in the layers

Question 15

How does subgingival plaque form?

Answer 15

• Nucleation and crystal growth are heterogeneous
• Calcification is more homogenous compared to supragingival
• Deposits build up in layers, each with a high mineral content

Question 16

What is the mineral content and source of supragingival calculus?

Answer 16

Mean 37% by volume Derived from saliva

Question 17

What is the mineral content and source of subgingival calculus?

Answer 17

Mean 58% by volume Derived from GCF

Question 18

What is the composition of supragingival calculus?

Answer 18

70-80% inorganic salts:
Mainly calcium and phosphate

Smaller amounts of:
Magnesium
Sodium
Carbonate
Fluoride

Regular distribution of fluoride
Traces of other elements

Organic matrix
–> Proteins, lipids and carbohydrates

Question 19

What is the composition of subgingival calculus?

Answer 19

• Greater concentration of calcium, magnesium and fluoride compared to supragingival calculus
• Higher calcium to phosphate ration than in supragingival calculus
• Irregular distribution of fluoride

Question 20

What is the crystal type of supragingival calculus?

Answer 20

Mostly octacalcium phosphate and hydroxyapatite
Some whitlockite
Some brushite

Question 21

What is the crystal type of subgingival calculus?

Answer 21

Mostly whitlockite
Some hydroxyapatite and octacalcium phosphate
No brushite

Question 22

What disease is associated with supragingival calculus?

Answer 22

Gingivitis
Gingival recession

Question 23

What disease is associated with subgingival calculus?

Answer 23

periodontitis

Question 24

Why is calculus always covered with an unmineralsied layer of bacteria?

Answer 24

Due to the rough surface

always a layer of plaque around it

Question 25

Is calculus a plaque retentive factor?

Answer 25

YES