Seminar 10: Restoring After RCT

Question 1

What direction does peritubular dentine run?

Answer 1

Outwards radially

Question 2

What direction does the collagen mesh run in dentine?

Answer 2

Perpendicular to tubules

Question 3

Water can be found in two forms in dentine, they are?

Answer 3

Bound

Unbound

Question 4

Where is bound water found in dentine?

Answer 4

Hydrogen bonded to collagen to prevent fibres joining to each other

Question 5

Where is unbound water found in dentine?

Answer 5

Inside the tubules

Question 6

What is the function of unbound water in dentine?

Answer 6

To exert a hydrostatic pressure when pressure is applied to the dentine

Question 7

Why does dehydrated dentine fracture more than hydrated dentine?

Answer 7

Less water

Unable to undergo plastic strain

Question 8

What happens to the calcium in dentine upon dehydration?

Answer 8

Calcium depletes and increase risk of fracture of dentine also when dehydrated

Question 9

What happens to collagen in dehydrated dentine?

Answer 9

The shrink and pull tighter pulling HAP crystals in dentine closer causing it to become brittle

Question 10

Why does dentine lose its cushioning ability once dehydrated?

Answer 10

Due to loss of water

Question 11

What features increase risk of fracture post RCT?

Answer 11

1. Less guarding
2. Altered mechanical properties of dentine
3. Loss of tooth tissue: loss of marginal ridge!!!
4. Loss of proprioceptive feedback
5. Effects of chemicals during RCT

Question 12

What are the three principles of restoring root treated teeth?

Answer 12

1. Preserve remaining tooth - odds ratio of x10
2. Ensure stress is distributed favourably amongst remaining tooth
3. Seal against coronal leakage

Question 13

Survival of RCT teeth at 8-10 years is ?

Answer 13

Gulbivala and Ng 2019
87%

Question 14

Which teeth are at greatest risk of fracture ?

Answer 14

Root treated molars
Those last in the arch
Immature ant teeth
MOD plastic restorations esp premolars

Question 15

What effect does NaOCl have on dentine?

Answer 15

Effects organic matrix
Reduces flexural strength
Osmotic pressure during irrigation drives water out

Question 16

What effect does EDTA have in dentine?

Answer 16

Disrupts inorganic matrix
Exposed collagen matrix to damage by NaOCl

Question 17

To what depth does NaOCl and EDTA affect dentine?

Answer 17

0.3-0.5mm deep

Question 18

What impact does size of dentinal tubules have on depth of NaOCl/EDTA penetration?

Answer 18

Wider tubules greater depth of effect

Younger teeth are more susceptible to chemicals since tubules are wider

Question 19

What effect does CaOH have on dentine?

Answer 19

Deproteinates dentine
Caustic

Question 20

What factors make non root treated teeth fracture ?

Answer 20

Tertiary dentine formation
Ageing
Sclerosis

Question 21

Restorability assessment prior to RCT should be carried out. What should this include?

Answer 21

Space available
Remaining tooth
Occlusion

Question 22

How much ferrule needed for success of restoration ?

Answer 22

2mm height and width around circumference of tooth

Question 23

To increase amount of tooth structure present what can be done to the root?

Answer 23

Extrude

Question 24

In which occlusal circumstance are anterior teeth loaded axially?

Answer 24

In class 3 malocclusion

Question 25

What type of movements should be avoided on root treated teeth?

Answer 25

Excursions

Question 26

What are the features of posts that affect their function?

Answer 26

Length- not longer than height of clinical crown- better stress distribution to the alveolar bone and tensile strength of apical root is greater than coronal root
Diameter
Shape
Surface
Diaphragm

2.Need to leave 4-5mm of GP apical to ensure apical seal maintained
3. Need at least 2mm of ferrule and dentine needs to be 1mm thick helps with resisting lateral forces and fracture resistance
4. Tip should be no more than 1/3 of diameter of the root
5. Not exceed the diameter of the shaped canal 

Question 27

Why do fibre posts offer more favourable characteristics ?

Answer 27

They flex allowing for deformation so root fracture tends to be more coronal in the root

Question 28

What is the benefit of a parallel post?

Answer 28

Offer greater retention per unit length

Question 29

What are the risks with parallel posts?

Answer 29

Can generate greater stresses

Question 30

What are the risks with tapered posts?

Answer 30

• less retentive
• can generate a wedging effect but this can be reduced by placing a shoulder

Question 31

What is the key determinant for retention of a post ?

Answer 31

Post length

Question 32

What should you consider when determining ideal post length?

Answer 32

• Length of root canal filling- always leave 3mm apically
• where bone loss present ensure post extended to beyond bone level
• post should be similar height to crown

Question 33

What is difference between cast and wrought posts ?

Answer 33

Cast: melted and poured
Wrought: this has been worked and shaped

Question 34

Between cast and wrought post which should have a greater diameter?

Answer 34

Cast since they are weaker than wrought

Question 35

What type of metal post would you use in a narrow canal?

Answer 35

Wrought

Question 36

The diameter of post is more important for?

Answer 36

Post strength

Question 37

What type of surface configuration for posts exist ?

Answer 37

Smooth
Rough
Serrated
Threaded

Question 38

What function do diaphragms play in posts?

Answer 38

Can help prevent fracture and stresses concentrating in the apical region

Question 39

Why is it better to have an onlay than crowns in cracked teeth?

Answer 39

• Onlays prevent cusp flexure
• Crowns cause thinning of the walls causing bracing to take place further down the tooth resulting in whole crown snapping off

Question 40

What is the effect of 5.25% of NaOCl on dentine according to Sim et al 2000?

Answer 40

Reduces elasticity and strength

Increases stiffness