Chemomechanical disinfection

Question 1

<p>What are the clinical aims of endodontic therapy?</p>

Answer 1

• Removing the canal contents

- Eliminating infection

Question 2

<p>What are the design objectives when shaping a root canal?</p>

Answer 2

• create a continuously tapering funnel shape
• maintain apical foramen in original position
• Keep apical opening as small as possible

Question 3

<p>What is the mechanical prep in chemo-mechanical disinfections done for?</p>

Answer 3

To create space to allow irrigating solutions and medicaments to more effectively eliminate micro-organisms from the root canal system

Question 4

<p>What are the stages in mechanical preparation?</p>

Answer 4

1. Prep of tooth
2. Access cavity prep
3. Straight-line access
4. Initial negotiation
5. Coronal flaring
6. Working length determination
7. Apical prep

Note: bacteria load decreases

Question 5

<p>The size of the apical preparation is determined by what?</p>

Answer 5

initial size of the root canal apex

Question 6

<p>The actual size to make the apical pre is controversial. What size should it be at least?</p>

Answer 6

At least ISO size 25 but some advocate at least size 30 or larger

Question 7

<p>What aspect of the root canal impacts on what size is safely achievable for the apical prep?</p>

Answer 7

The canal curvature

Question 8

<p>What are the ideal properties of irrigants? (13)</p>

Answer 8

• Killing of biofilm microbes
• Detachment of the biofilm
• Low cost
• Reduction of friction (lubrication)
• Improve cutting of dentine by the instruments
• Temperature control
• Dissolution of organic and inorganic matter
• Good penetration within the root canal system
• Killing of planktonic microbes (free-living bacteria that don’t need to adhere etc)
• Non-toxic to periapical tissue
• Non-allergenic
• Does not react with -ve consequences with other dental materials
• Doesn’t weaken dentine

Question 9

<p>What is the main irrigant used?</p>

Answer 9

<p>Sodium hypochlorite (NaOCl)</p>

Question 10

<p>Why is NaOCl useful as an irrigant?</p>

Answer 10

<p>potent antimicrobial activity
dissolves pulp remnants ad collagen

dissolves necrotic and vital pulp tissue (only irrigant that does this)

helps disrupt smear layer by acting on organic components</p>

Question 11

<p>What concentration of NaOCl should be used?</p>

Answer 11

<p>between 0.5% and 6%</p>

Question 12

<p>What are some problems with NaOCl? (3)</p>

Answer 12

<p>Possible effect on dentine properties (the mechanical, chemical and structure of root dentine)
Inability to remove smear layer by itself

its effect on organic material</p>

Question 13

<p>What increases the risk of NaOCl having an effect on the dentine?</p>

Answer 13

<p>the higher the conc of NaOCl

| the longer it is left on, the deeper it penetrates</p>

Question 14

<p>Describe the smear layer and how its formed in endo.</p>

Answer 14

<p>Formed during prep from organic pulpal material and inorganic dental debris, is superficial and packs into tubes.</p>

Question 15

<p>What problems does the smear layer cause in endo?</p>

Answer 15

<p>It causes bacterial contamination, interferes with disinfection and prevents sealer penetration.</p>

Question 16

<p>What ways can the smear layer be removed in RCT?</p>

Answer 16

<p>17% EDTA
10% citric acid

MTAD

Sonic and ultrasonic irrigation</p>

Question 17

<p>Describe how 17% EDTA is used to remove the smear layer</p>

Answer 17

• Used with NaOcl to remove
• Needs a contact time of 1 min

-NaOCl and EDTA should not be present in the root canal at the same time so don’t put dentine at risk

Question 18

<p>What affects can NaOCl have on organic materials?</p>

Answer 18

<p>* Discolouration of fabrics

* ophthalmic injuries (can lead to blindess)
* Apical extrusion leading to tissue necrosis (as toxic)
* Allergic reaction

Note: intracanal use of NaOCl is not more toxic than saline solution</p>

Question 19

<p>How can ophthalmic injures be avoided?</p>

Answer 19

<p>Use eye protection at all times when handline NaOCl</p>

Question 20

<p>What is the proposed protocol for cleaning and shaping in GDH?</p>

Answer 20

<p>Once canal prep is complete the canal should be finally irrigated with:
1. 3% NaOCl throughout instrumentation and at 30mL after instrumentation complete with MDI – at least 10 mins prior to obturation (don’t start clock will after prep as NaCl wont penetrate properly until prep complete)

2. 17% EDTA 1 min penultimate rinse
3. 3% NaOCl final rinse

Dry the canal with absorbent paper points between irrigants.</p>