5. Access cavity and Root Canal Preparation Flashcards
what are the Stages of Preparatio?
- Preparation of the tooth for for root canal treatment
- Access cavity preparation and canal orifice identification
- Creating straight-line access
- Initial negotiation
- Coronal flaring
- Working length determination
- Apical preparation
how do you prepare the tooth for
for a root canal treatment?
A thorough clinical and radiographic assessment
is required to:
-Determine the restorability of the tooth
-Pre-empt any possible difficulties of
treatment
-Consider suitable management of the tooth
what should be done following the clinical and radiographic assessment and prior to root canal treatment:
-The periodontal status of the tooth must be stable
-Caries and defective restorations should be removed to prevent infected dentine and restorative materials entering the root canals—Restorability must be assessed
-Isolation of the tooth must be achievableProvisional restoration should be placed where
required
-the tooth should be protected against fracture if necessary using an orthodontic band or
copper ring (posterior teeth)
What is an access cavity?
An opening created in the crown of
the tooth which permits unimpeded
access to the tooth’s pulp chamber
and canal orifices.
What are the objectives of access
cavity preparation?
- Complete removal of the pulp chamber roof to facilitate thorough disinfection of this space
- Allow direct access to and visualisationof the root canal orifices
- Produce a smooth walled preparation with no overhangs of dentine
- Create no damage to the pulp floor (in anterior teeth the
pulp chamber merges into the root canal) - Facilitate the secure placement of a temporary seal between visits
what is the equipment for isolation
- Rubber dam punch creates a hole in the rubber dam sheet to allow the sheet to be pulled over the tooth
- The rubber dam clamp secures the rubber dam sheet over the tooth
- The forceps is used to place the clamp over the tooth
4.The frame is used to provide rigidity to the rubber dam sheet
look at slide 19
How do you create an access cavity?
- The outlineof the access cavity is
made with a tungsten carbide or
diamond bur according to the
anatomy of the specific tooth - The bur is advanced toward the pulp horn of the largest canaluntil the pulp chamber roof is penetrated.
- A safe-tipped endodontic access bur (EndoZ cutting edge is on the side to widen access cavity) is introduced into the pulp chamber and the
entire roof of the pulp chamber is removed - The non cutting tip is allowed to passively follow the contours of the pulp chamber floor
- A steel rose head bur in a slow hand-piece, used in a pulling motion can be also used to
remove the roof of the pulp chamber) - Remaining pulpal tissue and other debris is removed from the floor of the pulp chamber with an excavator
- The pulp chamber is flooded with
sodium hypochlorite - The canal orifices are located, if
necessary, with the aid of a long pointed probe (DG16)
look at slide 22,23,25
what is the removal of the
coronal interferences?
Once the canal orifices are located, any necessary modifications to the access cavity are made to ensure unimpeded (straight line access) to the coronal two thirds of the canals.
what is the Access cavity shape for Maxillary central incisor?
- Start access at cingulum and proceed toward the incisal
edge - Access cavity is tringular in shape to encompass the pulp
horns
there is 1 canal and Average root length 23mm
what is the Access cavity shape for the Maxillary lateral incisor?
- Start access at cingulum and proceed toward the incisal edge
- Access cavity is tringular in shape to encompass the pulp horns
there is 1 canal and the Average root length 22mm
what is the Access cavity shape for Maxillary canine?
- Rounder access cavity than incisors
- Only one pulp horn so no need for flared (triangular) access of incisors
there is 1 canal and the Average root length 26m
what is the Access cavity shape for Maxillary first premolar?
1.Initial point of access centre of occlusal fissure
- Access cavity is extended bucco-palatally to locate the canal orifices under the buccal and
palatal cusp tips
there is 1 canal 5%, 2 canals 90% (B,P), 3 canals 5% (MB, DB, P)
what is the Access cavity shape for Maxillary secondary premolar?
Access cavity will resemble that for the maxillary first premolar
there is 1 canal 75%, 2 canals 25% (B,P) and the Average root length 21m
what is the Access cavity shape for Maxillary first molar?
- Rhomboid access cavity shape
- Distal aspect of the access cavity is on the mesial aspect of the transverse ridge
- Palatal canal is largest and initial penetration should be aimed toward this canal
3 canals 40% (MB, DB, P), 4 canals 60% (MB, DB, P) and the average root length 22mm
what is the Access cavity shape for Maxillary secondary molar?
- Rhomboid access cavity shape
2.Access cavity is narrower than first molar in a mesio-distal direction reflecting the closer
proximity of the canals to each other
there are 3 canals 60% (MB,DB,P), 4 canals 40% (MB1,MB2,DB,P) and the Average root length 20mm
what is the Access cavity shape for the mandibular central incisor?
- Starts at the base of the cingulum
2.Access cavity shape is narrow mesio-distally and oval (bucco-lingually)
- The cavity should be extended almost on to the incisal edge to aid location of a possible lingual canal
there is 1 canal 60%, 2 canals 40% the Average root length 21m
what is the Access cavity shape for the mandibular canine?
- Starts at the base of the cingulum
- Access cavity is oval with the incisal extension approaching the incisal edge aid location of a
possible lingual canal and the lingual extension must penetrate the cingulum
there is 1 canal 90%, 2 canals 10% (B,L)
*Average root length 24mm
what is the Access cavity shape for the mandibular first premolar?
Starts in the centreof the occlusal fissure
*Access is extended in a bucco-lingual direction
*Access cavity is oval (bucco-lingually) in shape
and located centrally when one canal present
*Extension of the cavity further buccally and lingually will be necessary when 2 canals present
*1 canal 75%, 2 canals 25% (B,L)
*Average root length 22m
what is the Access cavity shape for the mandibular second premolar?
*As for first premolar
*1 canal 90%, 2 canals 10% (B,L)
*Average root length 22mm
what is the Access cavity shape for the mandibular first molar?
*Mesial canal orifices are located below the mesial cusp tips
*Distal canal orifice is located closer to the centre of the tooth
*Access cavity outline is trapezoid or rhomboid in shape to encorporate pulp horns
3 canals 65% (MB, ML, D), 4 canals 35% (MB,ML,DB,DL)
*Average root length 21mm
what is the Access cavity shape for the mandibular second premolar?
*As for first mandibular molar
*Access cavity shape for 2 canal variation will
be narrower bucco-lingually and oval in shape
*3 canals 90% (MB,ML,D), 2 canals 10% (M,D)
*Average root length 20mm
after gaining acess what need to be done now?
Preparation of the root canal is completed using a
‘CROWN DOWN’ technique
This involves:
-Enlargement of coronal and middle third
-Confirm working length
-Prepare the apical third
-Connect apical and middle third
How do we prepare the tooth?
1.Mechanically
Using a variety iofinstruments, both manual and machine driven
- Chemically
Using antimicrobial irrigantsand interappointment medicaments
what is the aim of mechanically preparing the tooth?
- Remove pulpal debris and
microbes - Provide a suitable shape
for effective irrigation - Provide improved access
for the placement of
medicaments - Provide the optimal shape
and resistance form for
the root canal filling
what is the aim of chemically preparing the tooth?
- To flush out remnants of pulp
tissue and debris created during
mechanical instrumentation - To dissolve residual pulpal tissue
- To kill microbes and remove
microbial biofilm - To clean the parts of the root canal system which are inaccessible to mechanical instrumentation
- To act as a lubricant to prevent
blockages furing instrumentation - To remove the smear layer
what is Initial Negotiation
Once orifice is located, explore root canal with size
♯08 and ♯10 stainless steel Flexofiles
what is coronal flaring?
Once the root canals have been located, the coronal half
to two-thirds of the root canal is negotiated and instrumented to produce a tapered preparation, which is widest coronally
what is the aim for coronal flaring?
-Removal of the bulk of infected coronal pulp tissue and Dentine
Less risk of forcing infected debris through to the periradicular tissues
Elimination of interferences in coronal third
Early introduction of irrigant solution into apical portion
Easier negotiation to working length
what equipment is used for coronal flaring?
Gates glidden burs are traditionally used for flaring of the coronal portion of the canal
There are six sizes of gates glidden burs which are designed to enter the canal to varying depths to provide a smooth taper
They are used in a slow handpiece
how to establish the patency of coronal and middle third of the canal?
use File 8-10-15-20-25 passively
when do you irrigate?
Irrigate after each instrument and use lubricant on each instrument
what irrigant solutions are used?
Sodium Hypochlorite (0.5% to 5.25%)
The most commonly used is Chlorhexidine. You may choose to use also 0.2% -2%
Chlorhexidine in infected cases
Iodine potassium iodide (IKI)
EDTA (a chelating agent) to help in removing dentine and also because it has a lubricating effect.
Why is coronal flaring
important?
- Enable unrestricted access to the apical portion of the root canal
- Straightening of the coronal portion of the canal
- Better tactile feedback for instrumentation apically
- Removal of the bulk of infected pulpal tissue and debris to prevent coronal microbes and debris from
being introduced into the apical third of the canal - Provide a reservoir for irrigant coronally
- Minimise risk of creating apical blockages
- Maintenance of working length during subsequent
preparation
what is Working length determination?
Once canal has been flared coronally, the canal should be negotiated to its full length and the “working length” determined
What is the working length?
Working length is the distance between a reference point on the crown of the tooth and the terminus of the root canal that is normally identified with the apical
constriction.
How can the working length be calculated?
use of the electronic
apex locator.
What are the aims of apical
preparation?
1.Apical enlargement:
To allow adequate space for the penetration and exchange of irrigantsand placement of
medication
- Creation of apical taper
To create an optimal shape for effective irrigation and root canal filling
How do we prepare the apical
third?
Go to the working length with instruments up to 15-20
(25 if you can)
Use files sequentially at the established working length
Smallest acceptable apical preparation is usually
equivalent to a size 25 file. The largest file that is used to the full working length is termed the
MASTER APICAL FILE.
Use 3-4 sequentially larger files, each at a slightly shorter length (1 mm shorter than previous file) to
create a taper and blend the apical preparation with the coronal flare
Irrigate between instruments
what are the main types of ss file?
- K-flex
- Flexofile
- Hedstrom
They differ from each other in how they were manufactured, their cross-sec
