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
