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4th year > Endodontics > Flashcards

Endodontics Flashcards

1
Q

Compare the two types of primary dentine:

A

Mantle dentine- 1st layer formed closest to enamel/ cementum.

Pre-dentine- The layer of dentine that still has to be mineralised.

This is found between the odontoblast layer and mineralised dentine.

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2
Q

What type of The vertucci canal classification is shown in this picture?

A

Vertucci type 1.

1 canal.

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3
Q

What type of The vertucci canal classification is shown in this picture?

A

Vertucci type II

(2-1)

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4
Q

What type of The vertucci canal classification is shown in this picture?

A

Vertucci type III.

1-2-1

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5
Q

What type of The vertucci canal classification is shown in this picture?

A

Vertucci type IV

2

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6
Q

What type of The vertucci canal classification is shown in this picture?

A

Vertucci type V

(1-2)

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7
Q

What type of The vertucci canal classification is shown in this picture?

A

Vertucci type VI

2-1-2

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8
Q

What type of The vertucci canal classification is shown in this picture?

A

Vertucci type VII

(1-2-1-2)

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9
Q

What type of The vertucci canal classification is shown in this picture?

A

Vertucci type VIII

3

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10
Q

What is the most common number of roots and canals found in:
Maxillary central incisor

A

roots: 1

Canals: 1

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11
Q

What is the most common number of roots and canals found in:

Maxillary lateral incisor

A

Roots: 1

Canals: 1

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12
Q

What is the most common number of roots and canals found in:

maxillary canine

A

Roots: 1

Canals 1

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13
Q

What is the most common number of roots and canals found in:

Maxillary 1st premolar

A

Roots: 2

Canals: 2

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14
Q

What is the most common number of roots and canals found in:

maxillary 2nd premolar

A

Roots:1

Canals: 1

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15
Q

What is the most common number of roots and canals found in:

Maxillary 1st molar

A

Roots: 3

Canals: 4

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16
Q

What is the most common number of roots and canals found in:

maxillary 2nd molar

A

Roots:3

Canals:3

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17
Q

What is the most common number of roots and canals found in:

Mandibular central incisor

A

roots: 1

Canals: 1

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18
Q

What is the most common number of roots and canals found in:

mandibular lateral incsior

A

root: 1
canal: 1

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19
Q

What is the most common number of roots and canals found in:

mandibular canine

A

root: 1

Canal: 1

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20
Q

What is the most common number of roots and canals found in the mandibular 1st premolar.

A

root: 1
canal: 1

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21
Q

What is the most common number of roots and canals found in:

mandibular 2nd premolar

A

roots: 1
canals: 1

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22
Q

What is the most common number of roots and canals found in:

mandibular 1st molar

A

Roots: 2

Canals 3

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23
Q

What is the most common number of roots and canals found in:

mandibular 2nd molar

A

Roots; 2

Canals: 3

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24
Q

State the law of centrality

A

That the pulp chamber floor lies at the centre of the tooth at the level of the CEJ

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25
Q

State the law of concentricity

A

The walls of the pulp chamber are always concentric to the external surface of the tooth at the level of the CEJ.

(the undulations of the pulp chamber match the external undulations)

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26
Q

State the law of the CEJ?

A

You use the CEJ to identify the pulp chamber.

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27
Q

What is the 1st law of symmetry?

A

The orifices of the canal are equidistant from a line (PINK) drawn in a mesial distal direction from the pulp chamber floor.

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28
Q

What is the law of symmetry II

A

The orifices of the canals lie on a line perpendicular to the line drawn in the law of SI.

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29
Q

What are the exceptions to the laws of symmetry and why?

A

Maxillary molars as they do not have any planes of symmetry.

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30
Q

What is the law of colour change?

A

That the colour of the pulp chamber is always darker than the walls.

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31
Q

What is the 1st law of orifice location?

A

That the orifices are always located at the junction of the wall and the floor.

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32
Q

What is the 2nd law of orifice location

A

The orifices are located at the angles in the floor wall junction (i.e. the corners)

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33
Q

What is the third law of orifice location.

A

That the orifices are located at the terminus of the root developmental fusion lines.

(there are dark lines on the cavity floor that lead us to the orifice)

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34
Q

What is the most commonly isolated bacteria for endodontic disease?

A

Candida albicans.

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35
Q

Describe the main ways that bacteria infect the pulp:

A

By exposing dentinal tubules- This allows bacteria to reach the pulp.

By direct pulp exposure

Loss of periodontal attachment- allowing alternative routes via pockets in the pulp (ONLY affects non-vital pulp).

Anachoresis- when blood borne bacteria is attracted to inflamed or necrotic tissue during bacteraemia (causing the infection)

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36
Q

What is the clinical objective of root canal treatment?

A

The removal of canal contents to eliminate infection and allow the patient to retain their tooth.

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37
Q

Define the AEE definition of a normal pulp?

A

The pulp is symptom free and normally responds to testing

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38
Q

Define the AEE definition of reversible pulpitis

A

Findings indicate that the inflammation should resolve and the pulp return to normal after managment of the cause:

Characterised:

  • Discomfort when stimulus (cold/sweet) is applied- This goes away after removal.
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39
Q

Define the AEE definition of symptomatic irreversible pulpitis

A

Findings indicate that the inflamed pulp is incapable of healing.

Features include:

Sharp pain upon thermal stimulus

Lingering thermal pain (>30s after removal of stimulus)

Spontaneous pain

Referred pain.

Increased pain at night (lying down increases pressure in the pulp chamber)

Ineffective over the counter analgesics.

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40
Q

Define the AEE definition of Asympotomatic irrreversible pulpitis

A

Findings indicate that the vital inflamed pulp is incapable of healing.

There has been pulpal exposure (Caries/ caries extraction/ trauma) so inflammation is present but there are no clinical symptoms.

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41
Q

Define the AEE definition of pulp necrosis

A

Death of the dental pulp.

The pulp is normally non-responsive to pulp testing.

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42
Q

Define the AEE definition of previously treated

A

The tooth has been endodontically treated and the canals are filled with filling materials.

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43
Q

Define the AEE definition of previously initiated therapy

A

The tooth has been previously treated by partial endodontic therapy e.g. pulpotomy or pulpectomy.

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44
Q

Define the AEE definition of normal apical tissues

A

This is teeth with normal peri-radicular tissues that are not sensitive to percussion or palpitation testing.

The lamina dura surrounding the tooth is intact.

The periodontal ligament space is uniform.

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45
Q

comapre the AEE definitions of

Symptomatic apical periodontitis and

Asymptomatic Apical periodontitis

A

Inflammation of the apical periodontium.

symptomatic- painful response to biting, percussion and palpitation.

Asymptomatic- No clinical but appears as an apical radiolucent area.

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46
Q

Compare the AEE definitions of

Acute Apical abscess and

Chronic apical abscess

A

They are inflammatory reactions to pulpal infection and necrosis

Acute- characterised by rapid onset, spontaneous pain, tenderness of the tooth to pressure, pus formation and swelling of the associated tissues.

Chronic- characterised by gradual onset, little or no discomfort and intermittent discharge of pus through an associated sinus tract.

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47
Q

Describe the AEE definition of:
Condensing osteitis?

A

A diffuse radiopaque lesion representing a localised bony reaction to a low grade inflammatory stimulus. (usually seen at the apex of the tooth)

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48
Q

Compare the pain from A-delta fibres to C fibres.

A

A fibre pain- sharp prickling sensation.

C fibre pain- dull aChing or burning pain.

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49
Q

Define an endodontic emergency?

A

Pain or swelling caused by various stages of inflammation or infection of the pulp or peri-apical tissues.

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50
Q

How can you get post treatment disease after the nerve is removed from a tooth?

A

The tooth still sits on the PDL or alveolar bone which could cause inflammation or infection of the peri-apical tissue.

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51
Q

What is characteristic of referred pain in dentistry?

A

Pain always radiates to the ipsilateral side.

Anterior teeth seldomly refer pain to other teeth or the opposite arch.

Posterior teeth refer pain to the opposite arch or periauricular area(ear)

Seldomly to anterior teeth.

Mandibular posterior teeth refer pain to the periauricular area more than maxillary teeth.

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52
Q

Describe thermal pulp testing

A

Cold test- Apply ethyl chloride to the tooth near the pulp horn.

Heat- use hot gutta percha.

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53
Q

Why are sensibility tests unreliable with multirooted teeth?

A

If one canal was necrotic and the other canal was vital.

The vital nerve would provide a response, so we would not know there was necrosis of the other canal.

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54
Q

What is selective anaesthesia?

A

When you anaesthetise a particular tooth to see if the pain or symptoms diminish. This tells us the pain is coming from that tooth.

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55
Q

How can you use sinus tract tracing to find the source of the infection.

A

By putting a gutta percha cone in the sinus and seeing if it leads to a particular root.

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56
Q

What would be a complexity 1 root canal treatment?

A
  • Single or multiple RC with curvature <15* to the root axis. (with Negotiable root canals for their entire length -From radiograph or clinical evidence) (No root canal obstruction or damaged access)
  • incision or drainage required.
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57
Q

What would be a complexity 2 root canal treatments?

A
  • Single or multiple root canals with curvature >15° or <40° to the root axis. (with Negotiable root canals for their entire length-from radiograph or clinical evidence)
  • Teeth with incomplete dental development.
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58
Q

What would be a complexity 3 root canal treatment

A
  • single or multiple root canals with curvature >40°
  • NOT negotiable (from radiographic or clinical evidence)
  • peri-radicular surgery
  • Teeth with iatrogenic damage or pathological resorption.
  • Teeth with difficult root morphology.
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59
Q

List the 3 main aims of cavity design in endodontics

A
  • Continuously tapered funnel shape.
  • Maintain the apical foramen
  • Keep the apical foramen as small as possible.
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60
Q

Why do we taper our cavities?

A

To create space for the introduction of irirgants while maintaning sufficient tooth structure (to prevent the weakening of the tooth)

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61
Q

List the stages of the Root canal process?

A
  1. Coronal access to the root canal system.
  2. Root canal instrumentation and preparation.
  3. Obturation of the root canal system.
  4. Coronal seal.
  5. Final restoration.
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62
Q

Whydo we remove all the caries in a defective restoration?

A

The caries would be a source of re-infection after you have disinfected it.

You need to assess to see if the tooth can be restored after RCT. If the tooth cannot be restored there is no point of the RCT.

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63
Q

Discuss the ideal cavity.

A

It has:

  • The entire roof removed
  • A smooth walled preparation with no overhangs.
  • Straight line access
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64
Q

Why do you remove the entire roof of the cavity?

A

To allow

  • Complete removal of the pulpal tissue.
  • Visualisation of the root canal entrance.
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65
Q

What is straight line access?

A

Where there is straight access to the first point of curvature or apex of the tooth.

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66
Q

Why do we require straight line access?

A

Without it the instruments will curve, which causes fatigue and eventually breakage.

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67
Q

What is recapitulation, why do we do it & what do we use?

A

what? Filing to remove debris from the canal.

Why? To ensure you are not packing debris apically.

With what? a #10 K file.

68
Q

What is watchwinding?

A

When you rotate clockwise and then anti-clockwise.

This cuts by engaging then breaking dentine each time.

69
Q

What is balanced force motion?

A

This file motion is used when we move onto larger diameter instruments.

Turn file 90º clockwise and then 180º anti-clockwise

70
Q

Why do we irrigate?

A
  • To impact the areas we cannot reach with filing.
  • Root canal disinfection
  • Dissolving organic debris.
  • Flushing out debris (to prevent blockage of the root canal)
  • Lubricate root canal instruments.
  • Remove the endodontic smear layer.
71
Q

What do we use to administer root canal irrigant and why?

A

A luer lock syringe with a 27 gauge endodontic tipped needle.

To reduce the pressure of the syringe in the root canal to prevent a hypochlorite accident.

72
Q

Why do we coronal flare early in our root canal treatment?

A

To avoid hydrostatic pressure in the canal.

For early disinfection of the root canal space.

To improve straight line access to the apical 1/3

73
Q

Why do we want to avoid hydrostatic pressure in the RC?

A

To allow a reservoir of irrigant to form and allow space for the irrigant to move while we instrument.

74
Q

Why is it beneficial to disinfect the root canal space early?

A

As this portion contains most of the contaminated contents.

75
Q

How do we achieve the Flare shape?

A

By sequentially reducing the Gates-glidden burr size as we penetrate deeper into the canal.

76
Q

What do we want for our working length preparation?

A

The preparation should:

  • End at the junction of the pulpal and peri-apical tissues.
  • Be as close as possible to the CDJ .(cementodentinal junction)
77
Q

What is the apical constriction?

A

The narrowest part of the root canal, where the root canal becomes the PDL.

78
Q

What is the master apical file?

A

The largest diameter file taken to working length.

This represents the final prepared size of the apical portion of the canal at working length.

79
Q

Describe the basis of the stepback technique?

A

K files are used that are sequentially 1 size greater in diameter but 1mm shorter in working length to create steps in the root canal.

You then use the master apical file to smooth out the steps.

80
Q

How do you know when the stepback technique is complete?

A

When the file goes straight to the canal depth (so you don’t need to file anymore)

81
Q

Why do we use safe ended burrs when cutting our cavity?

A

To ensure that you do not perforate the floor of the canal.

82
Q

What happens if you use a gate’s glidden burr too deep when aiming for straight line access?

A

You will get a coke bottle appearance (when there is an overexpanded coronal preparation)

83
Q

Why do we not need the water on, when using a handpeice during Root canal treatment?

A

As the irrigation fluid cools the file and the tooth.

84
Q

What causes the formation of the smear layer?

A

When a metallic endodontic instruments touches the mineralised dentinal wall in the root canal.

85
Q

What is the smear layer?

A

a layer of organic pulpal material and inorganic dentinal debris.

86
Q

Why do we not want the smear layer?

A

It weakens the effects of the disinfecting agents in dentine.

It hides the opening of the dentinal canals (preventing sealer penetration and causing a weaker bond to the canal wall)

87
Q

Why do we use NaOCl?

A

It:

  • has potent anti-microbial activity.
  • dissolves pulp remnants and collagen.
  • dissolves necrotic and vital tissues.
  • disrupts the smear layer.
88
Q

What is a hypochlorite accident

A

When the high pressure in a needle squirts hypochlorite through the end of the canal. (Causing tissue damage)

89
Q

Why do we agitate the root canal?

A

To ensure that fluid gets in all the nooks and crannies of the root canal.

90
Q

Compare the types of agitation?

A

Endoactivator is a vibrating polymer tip that causes debris removal and biofilm disruption.

Manual dynamic irrigation- when a GP point is clasped with tweezers, placed in the root canal and manually pumped in and out.

91
Q

Discuss the problems with using NaOCl?

A
  • Effect on dentine- Too high a concentration could cause damage (rather than just cleaning the cavity)
  • It cannot remove the smear layer on its own- You also have to use EDTA.
92
Q

How do you remove the smear layer?

A

By using NaOCl and EDTA.

93
Q

Why do you need to use both NaOCl and EDTA to remove the smear layer?

A

Because EDTA exposes the collagen to make dentine more susceptible to NaOCl.

94
Q

Why do we not often use chlorohexidine digluconate as a final rinse?

A

Because it interacts with NaOCL to form Para-Chloroanaline which is:

  • Cytotoxic
  • Carcinogenic
  • Brown and sticky - stains teeth.
95
Q

What are the symptoms of sodium hypochlorite extrusion?

A
  • Pain
  • Swelling
  • Ecchymosis
  • haemorrhage.
  • Neurological Complications
  • Airway obstructions.
96
Q

What is this?

A

Ecchymosis which is discolouration classically manifesting along the course of the superficial venous vasculature.

Symptom of Sodium hypochlorite extrusion.

97
Q

How would you manage NaOCl extrusion:

A

Pain relief- Ibruprofen 400-600 mg QDS

Paracetamol 1000mg QDS

Swelling- Cold compress for 1st few days

Warm compress to resolve soft tissue swelling and eliminate haematoma.

Prevent secondary infection- Antibiotics

98
Q

Why do we use intra-canal medicaments?

A

To:

  • destroy micro-organisms
  • Prevent re-infection
  • Reduce inflammation and exudate.
  • Control root resorption. (Non-setting calcium hydroxide)
99
Q

Compare intra-canal medicaments.

A

Anti-microbial paste- Contains corticosteroid and tetracycline.

It is used for pain relief with hot pulp and helps reduce pulpal inflammation.

Effective for 5-7 days

Non setting calcium hydroxide- (GOLD STANDARD)

pH of 12.5 makes it antibacterial.

It removes tissue debris .

Reduces inflammation by affecting the hydrolysis of the lipopolysaccharide.

Treatment lasts 7 days.

100
Q

What is hot pulp?

A

A tooth that has been diagnosed with irreversible pulpitis and Local anaesthetic is not reduce the patient’s pulpal pain.

101
Q

Why do we use an inter appointment temporary dressing?

A

To seal the root canal from contamination between visits.

102
Q

What do we use for the inter-appointment temporary dressing?

A

calcium hydroxide in the root canal.

A small cotton wool pledjet.

A layer of coltosol

3mm of self cure glass ionomer (to prevent displacement)

103
Q

discuss the advantages and disadvantages of using coltosol.

A

Advantage- It can be removed using an ultrasonic so we are less likely to cause extra tooth surface loss when reaccessing the cavity.

Disadvantage- It is not strong enough to sit in the oral cavity.

104
Q

What does the envelope of motion mean?

A

That we need to debride all of the root canal, not just one wall.

105
Q

Discuss nickel titanium dental instruments:

A

Advantages- Increased cutting efficency

increased flexibility.

Disadvantages- instrument fracture

More expensive.

106
Q

What is reciprocation?

A

This means to move back and forth.

107
Q

why do we use reciprocation?

A

To negotiate the curved canals, as if we only wound the file in one direction it would move in a straight line instead of negotiating the curves. This would create a ledge or perforation.

108
Q

Discuss the movements in a reciproc system?

A

The first movement is anti-clockwise and the second movement is clockwise.

109
Q

Compare the types of reciproc system?

A

True reciprocation- equal anti-clockwise and clockwise turning.

Modified reciprocation- e.g. reciproc rotates 150° anti-clockwise and then 30º clockwise

110
Q

Why do we create a glide path?

A

To :

  • Confirm straight line access
  • Allow you to safely explore the anatomy.
  • Ensure the tips of instruments are not overloaded when we take them to length.
111
Q

How does torsional stress cause instrument separation?

A
  • Using too big an instrument too early which results in the instrument being locked in too narrow an area.
  • Extensive instrument surface encounters (cause excessive friction on the canal walls)
112
Q

Discuss the effect of torsional fatigue on instruments?

A

If the instrument binds, it is subject to stress and torsion. This causes a change in metal structure. The bound part of the instrument does not rotate at the same speed as the ubound bit- causing the file to twist (and eventually fracture)

113
Q

Why does flexural stress cause instrument separation

A

The repeated cyclic metal fatigue allows deformation due to the cyclic movements. (This leads to work hardening and then cyclic failure)

Causing the file to unwind.

114
Q

What are hand protapers?

A

A series of Nickel titanium files of greater taper.

These allow us to create shapes in the canal that would be very complex with a stainless steel instrument.

115
Q

What is apical gauging?

A

Testing that you have control of the file by taking the file to working length.

116
Q

How do we know if we have control?

A

The file will not go any deeper.

This tells us the K file is sufficently large and advises us on which size of obturation material to select. (preventing us from losing control i.e. it passes apically)

117
Q

What is obturation and why do we do it?

A

Obturation is filing the root canal system to prevent the passage of micro-organisms and fluid along it after disinfection.

118
Q

Discuss the 2 part system of obturation?

A

There are two parts:

  • semi solid core (gutta percha)
  • Seal (this is more fluid to fill the voids between the semi-solid core and the root canal wall)
119
Q

What is gutta percha?

A

A trans isonomer of polyisoprene which contains:

20% GP

65% zinc oxide

10% radiopacifiers

5% plasticizers

120
Q

What is cold lateral compaction?

A

The process where we use multiple points of GP to fill the root canal.

121
Q

What is the purpose of a finger spreader?

A

To apply apical and lateral pressure to force the master GP cone to the side of the canal, making space for the accesory GP cones.

122
Q

Why do we use a heated plugger after obturation?

A

To remove excess GP and compact GP into the root canal. (we don’t want GP in the pulp chamber)

123
Q

What is the problem with cold lateral compaction?

A

We are limited to how much we can obturate laterally.

124
Q

What is warm vertical compaction?

A

When a cone of GP is placed in the root canal & the coronal portion is severed off using a heated plugger. This transfers heat to the GP which is then plugged apically to fill the area.

Warm peices of GP are placed on top of the apical plug to backfill the root canal.

125
Q

What is continuous wave obturation?

A

The use of guns that contain electrically heated pluggers and GP to remove and deliver the gutta percha in a continuous wave.

126
Q

What is carrier based obturation?

A

An oven is used to warm the GP which is held on a stick with a handle.

This allows placement of warm GP into the root canal space.

127
Q

Why is carrier based obturation not good in wide straight canals?

A

As the warm flowable GP means that we lack apical control

128
Q

Why do we use MTA?

A

To fill large apical diameters (open apexes)

129
Q

What are the advantages and disadvantages of MTA?

A

Adv- It is bioinductive (bone and cementum can grow alongside it thanks to the alkaline conditions it produces)

The white version has reduced particle size and discoloration.

It requires moisture to set.

Disadv- It is not easy to remove if we need to retreat the root canal.

It has a delayed setting reaction .

130
Q

What is the function of sealers?

A
  • To provide a fluid tight seal between the dentinal wall and the core.
  • Fill voids and irregularities in the canal, lateral canals and space between the GP points used in lateral condensation
  • Lubricate during obturation.
131
Q

Compare the different types of sealer that are commonly used in RCT obturation

A

Zinc oxide eugenol - Long lasting antimicrobial effect but is unstable (loses volume over time due to dissolution)
Resin based (good seal that lasts a long time. but initial toxicity)
Calcium hydroxide-
Calcium silicate- expensive and difficult to treat.

132
Q

What sealer do we use in the dental hospital and why?

A

A resin sealer.

adv- it is good seal that remains over time.

Disadv- It has an initial toxicity but this declines after 24 hours (could leave post-operative sensitivity)

133
Q

Why do we use a secondary seal after obturation?

A

We use RMGI or vitrabond to seal the root canal from any ingress of bacteria as the GP becomes rapidily infected if exposed directly to oral bacteria.

134
Q

When do we assess root canal treatment and why?

A

After 6 months to:

  • Give time for signs and symptoms to subside.
  • Allow radiographic evidence of healing to be present. (change to a normal PDL)
135
Q

What is an uncertain root canal outcome?

A

If the radiographic changes remain the same or have diminished in size.

(so the problem has not gone away, it has just reduced)

136
Q

How do you deal with an uncertain root canal outcome?

A

You assess the lesion for a minimum of 4 years or until it has resolved.

137
Q

What is an unfavourable root canal outcome?

A
  • Tooth is associated with the signs and symptoms of infection
  • Lesion has appeared after treatment or increased in size
  • Lesion has not changed size (or has taken 4 years to reduce in size)
  • Root resorption is continuing.
138
Q

What happens if you fail to maintain patency?

A

There will be a blockage.

139
Q

What happens if ledges are produced in the root canal?

A

Access to the root canal is restricted.

140
Q

Compare Treatment of persistant intra-radicular infections and persistant extra-radicular infections

A

Persistant intra-radicular infections are due to complex canals, biofilm and resistant bacteria.- We can RC to help these.

Persistant extra-radicular bacteria -if bacteria make it out of the RC to reside in the peri-radicular tissues disinfection of the RC alone will not work- we need to control the infection.

141
Q

Compare true and pocket cysts?

A

True cysts- These are seperate from the RC.

Pocket cysts- these are continuous with the RC.

142
Q

insoluble resins have been used to obturate the root canal space, what technique do you use for retreatment?

A

Ultrasonic

143
Q

What are the 3 criteria that must be fulfilled before the root canal system on the tooth can be obturated?

A

Tooth is asymtpomatic (no swelling/ TTP)
Canal has been dried
Full biomechnical cleaning

144
Q

Gutta percha has been used to obturate the root canal space, what technique do you use for retreatment?

A

Hand files (Hedstroem) (and maybe solvent)

Then protaper D or Reciproc.

145
Q

Soluble pastes have been used to obturate the root canal space, what technique do you use for retreatment?

A

Hand files (maybe solvent)

then protaper D or Reciproc

146
Q

When do we use solvent with the handfiles and why?

A

During retreatment-If the GP is well condensed

& solvent is used to dissolve the GP and allow the files to penetrate deeper.

147
Q

WWhy do we use a headstroem file?

A

To engage the GP and try and withdraw it.

148
Q

Why do we use D files for retreatment?

A

As D files have an active tip used to penetrate the material.

149
Q

What is a disadvantage of using D files?

A

They can cause perforations so we need to be careful of the curves in the root canal.

150
Q

Discuss Nickel titanium hand files (Nitinol)

A

Nitinol can be strained more than stainless steel before permanent deformation- this makes it more suitable for curved canals.

There are 2 forms:
Austenitic- hard and strong used for the file (found at room temperature)

Martensite- (soft and easily deformed)

151
Q

What is the flute of an endodontic instrument?

A

The groove which collects dentine and soft tissue.

152
Q

What is the land of an endodontic instrument?

A

The land is the surface between flutes. This touches the wall causing friction.

This friction can be reduced by reducing the surface of the land.

153
Q

Compare a Post and a core?

A

Post- this is placed in the root canal and retains the core.

Core-this is what the prosthesis is cemented to

154
Q

What is coronal micro-leakage

A

The ingress of bacteria into the root canal- which will cause biological failure.

We seal the GP and pulpal floor with RMGI to prevent this.

155
Q

What is a ferrule and why is it important?

A

A dentine collar (1-2mm of vertical tooth structure)

This allows the crown to be placed on the tooth structure rather than filling structure, preventing fracture.

156
Q

Discuss the ideal post?

A

It should be:

  • Parallel sided- more retentive
  • Non threaded- less stress to the remaining tooth
  • Cement retained - cement acts as a buffer between mastigatory forces and the post/tooth.
  • Joint post and core- to avoid material interfaces.
157
Q

Discuss the material selection for posts:

A

Metal- Poor aesthetics/ can corrode

Ceramic- high flexural strength & fracture toughness/ good aesthetic

Fibre- Flexible/ bonds to dentine with DBA

158
Q

compare the materials used for Cores

A

Composite- Tooth coloured/ bonds to tooth structure (most common)
Amalgam- requires retention/ poor aesthetics /Core needs 24hrs to set.

Glass ionomer- Absorbs water causing expansion in size (prevents restoration from fitting)

Therefore, we chose composite.

159
Q

What is the main reason for post/crown failure?

A

Restorative problems e.g. caries around the crown margins.

160
Q

What do we avoid when restoring posterior teeth and why?

A

Posts because the narrow roots of posterior teeth increase the risk of perforation during post preparation.

161
Q

How should an endodontically treated posterior tooth be restored and why?

A

A cast restoration with occlusal coverage (e.g. an MOD onlay)

This is to provide cuspal protection to

  • Prevent catastrophic fracture
  • maintain the coronal seal
  • Prevent microbial ingress.
162
Q

Compare the terms straight line access and glide path.

A

A glide path is a smooth radicular tunnel from the canal orifice to the apical constriction. This is used to confirm straight line access.

Straight line acess is the straight access to the first point of curvature/apex of the tooth to prevent curving of the instrument which would cause fatigue and eventually breakage.

163
Q

Identify the canals in this radiograph of the upper 1st molar.

A

Longest canal- the palatal.

More curved canal- mesiobuccal.

Straighter canal- Distobuccal.

164
Q

How does a metal post fail and compare this to how a fibre post fails?

A

Metal post fails due to fracture of the root.

Fibre posts can debond at the Post/cement interface which allows recurrent caries.

165
Q

Why does irreversible pulpitis keep a patient up at night?

A

There is increased pain due to an increase in interpulpal pressure due to the patient lying down.

166
Q

compare apical and periapical

A

Apical refers to a problem originating at the root tip. Periapical refers to a problem originating around the root tip.

4th year (51 decks)

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