Endodontic access cavity preparation design

Endodontic access cavity preparation design

1. ACCESS
CAVITY
PREPARATION

2. Contents
•Introduction
•Definition
•Objectives
•Principles
•Armamentarium
•Aids in locating canals
•Steps of access opening
•Errors in access cavity preparation
•Conclusion
•References

3. ““If you If you
consider consider
pulp pulp
chamber as chamber as
a room , a room ,
access access
cavity is the cavity is the
key that key that
opens its opens its
door”. door”.

4. Well begun is half done

5. Definition
“Endodontic coronal preparation
which enables unobstructed access
to the canal orifices, a straight line
access to apical foramen, complete
control over instrumentation and to
accommodate obturation
technique”.

6. Objectives
•Remove all caries
•Conserve sound tooth structure
•De-roof the pulp chamber
•Remove all coronal pulp tissue (vital or necrotic)
•Locate all root canal orifices
•Achieve straight line access into the root canal
•Establish restorative margins to minimize marginal
leakage of the restored tooth
Ingle’s

7. Principles
Coronal Preparation
•Outline form
•Convenience form
•Removal of the remaining carious
dentin
•Toilet of the cavity
Radicular Preparation
•Outline form and convenience form
•Toilet of the cavity
•Retention form
•Resistance form
Greene Vardiman Black

8. Principle 1 - Outline form
•To establish complete access for instrumentation
•Internal outline form should project the external
outline form
3 factors of internal anatomy must be considered.
1.The size of the pulp chamber
2.The shape of the pulp chamber
3.The number of individual root canals, their
curvatures and their position.

9. The size of the pulp chamber
•In younger patients -
extensive than in older
patients

10. Shape of the pulp chamber
•The final outline form
should reflect the shape
of the pulp chamber
•eg: maxillary molar
triangluar in shape

11. Number, position and curvature of root
canals
•To prepare each canal
efficiently without
interferences, the cavity
walls often have to be
extended to allow an
unstrained instrument
approach to the apical
foramen.

12. Principle 2 - Convenience Form
•It makes the preparation & filling of the root canal
more convenient
•Benefits gained are

13. Unobstructed access to the canal orifice
•Enough tooth structure
must be removed to
allow instruments to be
placed easily into
orifices of each canal
without any
interference from
overhanging walls.

14. Shamrock Preparation
According to Leubke
•This preparation is
modification from
routine access cavity
preparation
•When suspecting extra
canal or severely curved
canal – extend only that
access cavity wall than
removing entire wall of
cavity (clover leaf)

15. Direct access to the apical foramen
•To provide direct access
to the apical foramen,
enough tooth structure
must be removed to
allow the endodontic
instruments freedom
within the coronal
cavity.

16. “ The first essential in
getting at any root canal is
to gain direct access, and
not to try to work around
corners, whatever tooth-
structure may have to be
sacrificed”.
R.H.Hofheinz, 1892

17. Complete authority over enlarging
instruments
•Clinician should have
complete authority over
the enlarging root canal
instruments
•Tooth structure is
removed around the
orifices so that the
instruments stands free
Orifice having mouse hole
appearance

18. Principle 3 : Removal of the remaining Carious
Dentin and Defective Restorations
For three reasons to
eliminate
1.Bacteria.
2.Discoloured tooth
structure.
3.The possibility of any
bacteria-laden saliva
leaking into the
prepared cavity.

19. Principle 4: Toilet of the cavity
•Purpose
‐It may act as an obstruction during canal enlargement
‐Bacterial population can increase
‐Stains crown – anterior teeth.

20. •Round burs, endodontic
spoon excavator,
irrigation with sodium
hypochlorite is excellent
means for cleaning of
the cavity.
•Finally wiped out with
cotton & careful flush of
air will eliminate
remaining debris.

21. Radiograph
Radiography before access cavity preparation is mandatory

22. Armamentarium
Must have instruments
a.Burs
i.Round burs ( #2, #4 and
#6)
ii.Tapering fissure bur
with a round head
iii.Safe end burs e.g.: Endo
Z bur
iv.Transmetal bur e.g.:
Trihawk burs

23. b.DG – 16 Endodontic
Explorer
c.Endodontic Spoon
excavator
d.Orifice Enlargers-
Gates Glidden Drills
e.Patency files- K Files
ISO sizes #06, #08 and
#10

24. Nice To Have Instruments
& Equipments
a.Burs
i.LN Bur (Dentsply
Maillefer)
ii.Munce Discovery Burs
b.Ultrasonic Tips-
Start X tips

25. c.Orifice Enlargers
i.X Gates
ii.Rotary orifice shapers
iii.Endodontic Micro
Openers
d.Dental Operating
Microscope for
Magnification and
Illumination

26. Rubber dam placement
•Protect the patients
tissues and seal the
mouth from root canal
irrigants and
disinfectants.
•Prevent patient
ingestion of irrigants
and aspiration of
instruments

27. Aids in locating canals
•Presence of dark lines on the floor of the pulp
chamber(dentinal map).
•Champagne bubble test – 1% Methylene blue dye
performing the Sodium Hypochlorate.
•Use of fiber optic on buccal or lingual surface, either
directly or indirectly.
•Magnification and illumination
•Canal blue:- blue dot indicates canal orifices

28. Steps of access opening
1.Relieve the tooth out of occlusion - “Reduce Post –
operative Discomfort”
2.Use carries as a guide - “Chase the caries”3.Laws of access opening - “Know your Geography”4.De-roofing of pulp chamber - “Most important rule of
access opening”
5.Observe the color change - “Color is the language of
endodontics”
Enamel White
Dentin Yellow
Floor of the pulp chamber Gray
Root canal orifice Dark gray or black
Pulp stone Pearly white Dark yellow
6.Remove dentinal shelves - “Establish straight line
access”
7.Locating the canal orifices - “Eureka Moment!!!”
“Cemento-enamel
junction is the key
anatomical
landmark during
access cavity
preparation”
1.Law of Centrality: The floor of the pulp chamber is always located
in the center of the tooth at the level of the CEJ
2.Law of Concentricity: The walls of the pulp chamber are always
concentric to the external surface of the tooth at the level of the
CEJ
3.Law of the CEJ: The distance from the external surface of the
clinical crown to the wall of the pulp chamber is the same
throughout the circumference of the tooth at the level of the CEJ
Krasner and Rankow
Law of color change:- The color of the pulp chamber floor
is always darker than the walls.

29. Endodontic preparation of maxillary anterior teeth
•Entrance is always through
lingual surface
•Penetration is made exact
centre of the lingual
surface (marked X)
•Initial entry with round
tapered fissure bur - at
a right angle to the long
axis of the tooth at
enamel.
•Rotate the handpiece
toward the incisal
parallels to long axis of
the tooth.
•Outline is funneled &
fanned incisally with a
fissure bur.
•A “nest” is prepared in
the dentin to receive
the round bur for
penetration.
•A surgical-length No. 2
or 4 round bur used to
penetrate the pulp
chamber.
•Working from inside the
chamber to outside.
•Round bur used to
remove lingual and
labial walls of pulp
chamber
•After outline completed
surgical bur is carefully
passed into canal from
inside to outside
•A long, tapering
diamond point to
remove the lingual
“shoulder.”
•No. 1 or 2 round bur
must be used laterally &
incisally to eliminate
pulpal horn, debris &
bacteria to prevent
future discoloration.
•Young tooth with large
pulp chamber - Large
triangular internal
anatomy
•“Adult” teeth - ovoid
preparation.
•Final preparation with
the reamer in place.
•Reduced lingual
shoulder allowing
unstrained approach to
the apical third of canal

30. Endodontic Preparation of
Mandibular Anterior Teeth
•Lingual surface - “X.”
•A common error is to
begin too far gingivally.
•Initial entrance cavity is
prepared with a 701U
tapering fissure bur at a
right angle to the long
axis of the tooth.
•Only enamel is
penetrated at this time.
•rotate the handpiece
toward the incisal - the
bur parallel tothe long
axis.
•Outline is funneled &
fanned incisally with a
fissure bur.
•The enamel has a short
bevel toward the incisal
& a “nest” is prepared .
•A surgical-length No. 2
round bur - penetration
into the pulp chamber.
•A round bur is used to
remove the labial walls
of the pulp chamber.
•The lingual “shoulder” is
removed with a long,
fine, tapered diamond
point.
•The No. 1 round bur
used laterally & incisally
to eliminate pulpal horn
debris & bacteria to
prevent discoloration.
•In a “young” tooth with
a large pulp - Triangular
Preparation
• “Adult” tooth ovoid
preparation .
•Convenience extension
must be advanced
further incisally to allow
the bur shaft to operate
in the central axis.
•Final preparation
showing the reamer in
place.

31. Endodontic Preparation
of Maxillary Premolar Teeth
•Penetration made in
the exact center of the
central groove.
•701 U tapering fissure
bur ideal for
penetrating gold casting
or virgin enamel.
•Amalgam fillings
opened - No. 4 round
bur
•No. 2 or 4 round bur -
to open the pulp
chamber & the drop will
be felt.
•In removing the bur, the
orifice is widened
buccolingually for
exploration for canal
orifices.
•An endodontic explorer
used to locate orifices
to the buccal & lingual
canals in the first
premolar or the central
canal in the second
premolar.
•A round bur - extend
the cavity
buccolingually by
removing the roof of
the pulp chamber.
•701 U fissure bur –
Finishing of cavity walls
& Buccolingual
extension
•Final preparation
provide unobstructed
access to canal orifices
•Outline form will be
identical for both newly
erupted and adult tooth
•Buccolingual ovoid
preparation
• The cavity must be
extensive for
instruments & filling
materials.

32. Endodontic Preparation
of Mandibular Premolar Teeth
•Entrance made in the
exact center of the
central groove.
•For perforating enamel
surface to the depth of
the dentin. - 702 U
taper fissure bur
•A regular-length No. 4
round bur is used to
open vertically into the
pulp chamber.
•The bur will be felt to
“drop” when the pulp
chamber is reached.
•An endodontic explorer
used to locate the
central canal.
•Tension of the explorer
against the walls of
preparation Indicating
the amount & direction
of extension necessary.
•Working from inside to
outside, a regular-
length No. 2 or 4 round
bur is used to extend
the cavity
buccolingually by
removing the roof of
the pulp chamber.
•Buccolingual extension
& finish of cavity walls
with a 702 U fissure bur
•Final ovoid preparation
- tapered funnel from
the occlusal to the
canal.
•Buccolingual ovoid
outline reflects the
anatomy of the pulp
chamber & position of
the centrally located
canal.
•The cavity is extensive
enough to allow for
instruments & filling.

33. Endodontic Preparation of
Maxillary Molar Teeth
•Initial penetration with
702 U tapering fissure
bur, in the exact center
of the mesial pit with
the bur directed toward
the lingual.
•The No. 4 round bur - to
open into the pulp
chamber
•The bur is directed
toward the orifice of
palatal or mesiobuccal
canal orifice.
• When the pulp
chamber is reached, the
bur is felt to drop.
•An endodontic explorer
-to locate orifices of
mesiobuccal, &
distobuccal canals.
•A round bur - to remove
the roof of the pulp
chamber from inside to
outside.
•Surgical length No. 2
round burs - to explore
the floor of the
chamber.
•Final finish & funneling
of cavity walls 702 U
fissure bur
•Final preparation
provides an obstructed
access to canal orifices.
•Improve ease of access
by “leaning” the
preparation toward the
buccal.
•The base is toward the
buccal & the apex is to
the lingual.
•The cavity is entirely
within the mesial half of
the tooth.

34. Endodontic Preparation
of Mandibular Molar Teeth
•With 702 tapering
fissure bur, initial
penetration is gained in
the exact center of the
mesial pit, with the bur
directed toward the
distal.
•A regular length No. 4
or 6 round bur is used
to open into the pulp
chamber.
•The bur should be
directed toward the
orifice of the
mesiobuccal or distal
canal & will be felt to
“drop” when the pulp
chamber is reached.
•An endodontic explorer
- to locate orifices of
the distal, mesiobuccal,
and mesio
lingual canals.
•Tension of the explorer
indicate the amount &
direction of extension.
•A round bur to remove
the roof of the pulp
chamber from inside to
outside.
• Surgical-length No. 2 or
4 round burs - to
explore the floor of the
chamber.
•Final finish & funneling
of cavity walls 702 U
fissure bur or diamond
point .
•Final preparation
provides unobstructed
access to canal orifices.
• The cavity outline
extend to the height of
mesial cusps.
•“Square” outline form
reflects the anatomy of
the pulp chamber.
•Both mesial & distal
walls slope mesially.

35. Errors in Cavity Preparation
•Endodontic mishaps are those unfortunate
occurrences that happens during treatment
Access related:-
1.Access cavity perforations
2.Treating the wrong tooth
3.Missed canals

36. Perforation
•Perforation at the labio-
cervical caused by
failure to complete
convenience extension

37. Perforation
•Perforation at the
mesiocervical
intentation – failure to
observe distal axial
inclination of the tooth
led to bypassing
receded pulp and
perforation
Maxillary first premolar

38. Perforation
•Perforation at mesial
cervical caused by-
failure to recognise
mesial tilt of morlar.
Precaution
•Orient the bur along the
long axis of tooth

39. Perforation
•Perforation of curved
root using large straight
instrument
Precaution
•Explore & enlarge canal
with a fine curved
instrument

40. Overextended Preparation
•Preparation
undermining enamel
walls
•Failure to observe pulp
recession in the
radiograph.

41. Gauging
Precaution
•Recognize 29 degree
lingual axial angulations
of tooth.

42. •Disoriented occlusal
outline form exposing
only mesiobuccal canal.
Precaution
•Prevented by
recognising the lingual
tip of Molar & preparing
cavity accordingly

43. Cleaning and shaping constitutes the most important phase of Endodontics.However, it is the access cavity preparation that lays the foundation for successful cleaning and shaping.

44. References
•GROSSMAN- Endodontic practice. 11
th
Edition.
•JOHN. I. INGLE. – Endodontics. 5
th
& 6
th
Edition.
•COHEN’S – Pathways of pulp. 10
th
Edition
•FRANKLIN.S. WEINE. – Endodontic therapy. 6
th
Edition
•FAMDENT - Practical Dentistry Handbook. Vol. 10 Issue 3
Jan. - Mar. 2010
•WALTON AND TORABINEJAD - Principles and Practice of
Endodontics.
•JAMES L GUTMAN – Problem Solving in Endodontics, 5
th

Edition
•GULABIVALA – Endodontics. 3
rd
Edition