Thermal GP obturation

Question 1

Aim of obturation (2)

Answer 1

Establishment of a fluid tight barrier with the aim of protecting the periradicular tissues from microorganisms which reside in the oral cavity
A hermetic seal is required from the coronal orifice of the canal to the apical foramen at the cemento-dentinal junction.

Question 2

The establishment of a well obturated system would serve three main functions (3)

Answer 2

Prevent coronal leakage of microorganisms or potential nutrients to support their growth into the dead space of the root canal system
Prevent periapical or periodontal fluids percolating into the root canals and feeding microorganisms
Entomb any residual microorganisms that have survived the debridement and disinfection stages of treatment in order to prevent their proliferation and pathogenicity

Question 3

Ideal properties of a root filling material (lots)

Answer 3

Easy handling and ample working time 
Seal the canal laterally and apically conforming to the complex internal anatomy
Dimensionally stable
Non-irritant 
Does not stain tooth structure
Anti-microbial
Impervious and non-porous
Unaffected by tissue fluid
Radiopaque
Easily removed

Question 4

What is gutta percha and what does it traditionally contain? (5)

Answer 4

Naturally occurring rubber
Traditional GP contains:
-Zinc oxide (65%)
-Gutta percha (20%)
-Radio opacifier (metal sulphate) (10%)
-Plasticiser (5%)

Question 5

Forms of GP (5)

Answer 5

GP occurs in 2 crystalline forms – alpha phase and beta phase
-below 42⁰C – beta phase
-42-49⁰C – alpha phase
-Above 49⁰C – GP becomes amorphous
Upon cooling it returns to the beta phase

Question 6

Role of an endodontic sealer (4)

Answer 6

Seal the space between the obturating core material and the internal root surface
Fill the space between core and accessory filling materials in lateral condensation
Seal the irregularities of the complex canal anatomy (lateral canals, tubules, etc)
Lubricate and facilitate seating of the core and accessory filling material

Question 7

Types of endodontic sealers (6)

Answer 7

Zinc-oxide/Eugenol-based
-most popular with long track record eg Tubliseal
Calcium hydroxide-based
-less antimicrobial, but also less toxic than zn-ox/Eug eg Sealapex
Glass ionomer-based
-not commonly used, difficult to remove eg Ketac-Endo
Resin-based
-superior sealing ability, adheres to dentine and antimicrobial eg AHPlus
Calcium silicate-based
-e.g. smartphase bio, MTA Fillpex – limited research at this stage
Silicone-based
-e.g. RoekoSeal – limited research at this stage

Question 8

Obturation techniques (6)

Answer 8

Lateral compaction (cold and warm) 
Single cone
Thermomechanical compaction
Warm vertical compaction (continuous and interrupted wave)
Carrier-based
Apical ‘barrier’

Question 9

Cold lateral compaction steps (lots)

Answer 9

Choose an ISO master GP point that fits snugly with tug-back
Coat with sealer and place to WL
Place finger-spreader down to 1mm from the WL
Place an accessory point where the finger spreader was removed from ensuring it extends to 1mm from the WL
Continue the process – the finger spreader will get further from the WL
After placing 2/3 accessory points consider taking a mid-fill radiograph
Continue until the accessory points fill to just below the canal orifice
Once complete, sear the cones off at orifice level and compact vertically

Question 10

Warm lateral compaction technique (3)

Answer 10

A k type file is inserted into a peizoelectric ultrasonic unit
The file is activated and introduced into the GP generating heat to soften it
A finger spreader is then placed followed by an accessory point, as in the cold lateral technique

Question 11

Warm lateral compaction advantage (1)

Answer 11

May have an advantage over cold lateral as the thermoplasticised GP may flow into accessory anatomy

Question 12

Warm lateral compaction uses (1)

Answer 12

‘Energised spreading’

Question 13

Single cone technique - what is it and pros and cons

Answer 13

Where only the master GP point, with sealer is used to obturate
Only applicable with greater taper GP points matched to the preparation file (eg F1,2,3 GP points for Protaper)
Does not provide good 3-dimensional seal
Not recommended

A newer material “Smartseal” uses a single cone which expands when coated in a hydrophilic polymer
It is a resin-based system with a calcium silicate-based cement “”Smartpastebio”
Not enough evidence yet to assess its effectiveness

Question 14

Thermomechanical compaction (4)

Answer 14

Uses heat generated from a reverse Hedstrom file which is driven with a slow handpiece into the GP
A master point is placed with sealer and the instrument placed 3-4mm from the working length
The GP is driven apically and laterally and the file driven coronally
Can cause extrusion from the apex and its possible for the instrument to fracture in the canal

Question 15

Warm vertical compaction types (2)

Answer 15

Continuous wave compaction

Interrupted wave compaction

Question 16

Continuous wave compaction stages (2)

Answer 16

Downpack – Aims to create an apical ‘plug’ of GP which seals and fills the apical 3-4mm of the canal, thereby providing apical control
Backfilling – Aims to fill the remainder of the canal by squirting molten GP through a GP ‘gun’

Question 17

Continuous wave compaction - technique (10)

Answer 17

Step 1 – choose a GP point which fits the apical preparation completed and displays tug-back just before the apical constriction.

Step 2 – choose a plugger which extands to approximately 4mm from the apex and binds. Adjust the rubber stopper to this length

Step 3 – turn on the heat source and plunge the plugger through the GP point.

Step 4 – Continue to apply pressure towards the pre-determined binding point. This should be done in one movement and take only 1-2 seconds.

Step 5 – the plugger will slow its apical movement and stop just short of the predetermined binding point. Stop the heat source and maintain apical pressure for 10 seconds to prevent cooling shrinkage of the mass.

Step 6 – activate the heat source again and complete the pressure until the binding point is reached. Then wiggle the plugger tip and remove it from the canal.

Step 7 – as the plugger is removed any GP coronal to the tip is also removed leaving a plug of GP sealing the apical third.

Step 8 – Place the tip of the injectable GP gun against the plug of apical GP and extrude GP in bursts of 3-4mm

Step 9 – after each application of GP use a condenser the compact the GP which has just been placed, then continue placing further GP in this manner until the canal orifice is reached

Step 10 – Completed obturation.

Question 18

Advantages of continuous wave compaction (3)

Answer 18

Has been shown to provide improved 3D obturation compared to cold-lateral condensation
The canal is filled with a homogenous mass of GP with no carrier (see next)
Good for filling internal resorption defects and other anomalous anatomy

Question 19

Disadvantages of continuous wave compaction (2)

Answer 19

Technique sensitive and takes time to master

Requires relatively expensive equipment

Question 20

Interrupted wave compaction (3)

Answer 20

Very similar to continuous wave technique
However, the downpack is carried out in multiple waves rather than one continuous wave
Recommended for wider canals

Question 21

Carrier-based obturation (4)

Answer 21

Consist of a carrier coated in GP
Thermafil is the market leader
Utilise a plastic carrier surrounded by heated GP which is inserted into the canal
The carrier is then cut at the entrance of the canal, leaving the remaining carrier and GP in the canal

Question 22

Technique for carrier-based obturation (lots)

Answer 22

Choose a Thermfil carrier with matches the size of canal preparation undertaken
Use a verifier or a carrier with the GP stripped off to check it can be inserted to the full working length
Take a radiograph if required
Modify the Thermafil point to achieve better length control and reduce the amount of excess GP
Place the rubber stopper at the correct length
Dry the canal
Apply sealer (extra working time) to the entrance of the canal using a probe
Place the Thermafil point into the oven
Press the correct button according to the size and then press start
The oven will beep when the GP is heated correctly
Remove the Thermafil point from the oven
In one swift movement, insert the point into the canal up to the rubber stopper
Use a plugger to condense the GP in the coronal portion of the canal
Use a Thermacut bur to remove the carrier and any excess GP at the entrance to the canal

Question 23

Advantages of carrier-based obturation (2)

Answer 23

Has been shown to provide improved 3D obturation compared to cold-lateral condensation
Quick and relatively easy to learn

Question 24

Disadvantages of carrier-based obturation (4)

Answer 24

Length control can be an issue
Increased post-operative pain has been reported
The plastic carrier can be an issue when removing it during a retreatment case or preparing for an endodontic post
Cannot fill internal resorption defects as well as warm vertical compaction

Question 25

Developments in obturation (3)

Answer 25

Recently, a cross-linked GP core has been developed
This has the advantage of being easier to remove during retreatment and post preparations
The technique used is the same as for the plastic cores

Question 26

Apical barrier technique (3)

Answer 26

When the apex is immature (pulp death before root formation completed) or has been damaged (iatrogenic/resorption etc) then apical control becomes more difficult
If the apical size is 0.7mm (ISO 70) or greater then an apical plug should be considered
This is a specialist technique

Question 27

Apical barrier technique steps (lots)

Answer 27

The material of choice for an apical plug is MTA (calcium silicate)
Undertake endo conventionally, however there will be minimal need to prepare the walls/apex
Be careful of irrigant extrusion
Dry the canal
Use a delivery system to place a plug of MTA in the apical region
Continue to place plugs of MTA, using a paper point to compact it, until a plug of 3-5mm has been achieved
MTA needs moisture to set, therefore a damp cotton wool pledget is placed in the canal next to the MTA
At the next appointment the MTA will have set and the remainder of the canal can be filled with heated GP

Question 28

RealSeal (4)

Answer 28

Looks similar to GP but is actually resin-based
The intention is to bond to the internal structure of the root
Can be used for either lateral or warm vertical compaction
Can be problematic for removal during retreatment

Question 29

Assessment of obturation (4)

Answer 29

Obturation becomes a surrogate marker for quality of canal preparation as it is difficult to asses this clinically and radiographically prior to obturation
The root filling is judged by taper, condensation and length
The aim is to provide a well condensed root filling ending just coronal to the apical foramen, without extrusion of GP into the apical tissues
A recent systematic review (Ng et al 2007) showed that root fillings without voids, extending to within 2mm of the radiographic apex had a significantly improved outcome