This document discusses the critical process of access cavity preparation in endodontics, highlighting its importance in achieving successful root canal treatment. It covers objectives, guidelines, and instruments necessary for effective access, along with anatomical considerations and classifications of root canal configurations. It concludes by providing details on the morphology and cavity preparation techniques for various types of teeth.

1. ACCESS CAVITY
PREPARATION
The journey of a thousand miles begins with a single small step.
- Lao Tzu
Presented by
Dr Aswin S
1st Yr PG
Dept of Conservative Dentistry and
Endodontics

2. “Of all the phases of anatomic
study in the human system, one
of the most complex is the pulp
cavity morphology.”
- M T BARRETT

3. Contents
• Introduction
• Definition
• Objectives of access cavity preparation
• Instruments for access cavity preparation
• Guidelines for access cavity preparation
• Laws of access cavity preparation for locating canal orifices
• Classification of root canal configurations
• Morphology and access cavity preparation for individual teeth
• Newer concepts in access cavity preparation and case reports
• Conclusion
• Bibliography

4. Introduction
•The fundamental aim of root canal treatment is to remove bacteria and to treat apical periodontitis using biomechanical
preparation, infection control and complete obturation of the root canal system. In order to be able to effectively carry
out any of the above technical stages, adequate access to the root canal system is required.
•In order to be able to carry out successful endodontic treatment, it is fundamentally important to have an adequate
understanding of the canal anatomy of the tooth being treated and of the potential anatomical variations that may be
encountered
• An access cavity is the opening prepared in a tooth to gain entrance to the root canal system for the purpose of
cleaning, shaping and obturating. Essentially, the access cavity is vital for allowing the effective cleaning, shaping and
obturation of the root canal system.
•Traditionally the technical stages of root canal therapy have been described as clean, shape and fill. The significance of
the access cavity in this process is too frequently overlooked.
• As the key technical phase governing the success/ease of the subsequent treatment stages, it is of paramount
importance. A poorly executed access cavity will compromise the remaining technical stages and result in an increased
risk of procedural errors or failure to carry out a satisfactory treatment.

5. Definition
Access cavity preparation is defined as the 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 of access cavity preparation
The main objectives of coronal access preparation are to
• Provide a straight line access to the root canals
•Confirm the etiology of pulp pathosis
•Assess restorability of the tooth
A straight access is necessary to allow unhindered introduction of instruments, irrigants, and
medicaments to the entire length and circumference of the canal , with minimum loss of dental
structural integrity.
- Ingle

7. Instruments for access preparation
1. Front surface mouth mirrors
2. Airotor and slow speed rotary handpieces
3. Burs
• Round carbide burs (No.2, No.4 and No.6) for caries removal and defining the external outline shape
•Diamond burs with round cutting ends for axial wall extensions
•Fissure carbide burs and diamond burs with safety tips
•Round diamond burs for entry into teeth with porcelain or ceramometal restorations and transmetal burs
for teeth with metal restorations
•Extended long shank burs such as Mueller burs (Brasseler, USA) and LN burs (Dentsply Maillefer, USA) for
calcified teeth.

8. 4. Endodontic spoon excavators
5. Endodontic explorers
6. Additional aids
- Magnification and illumination aids
- Ultrasonic tips
- Micro-openers and microdebriders

10. Diamond burs with rounded cutting ends Fissure carbide burs with non-end cutting
safety tips
Endodontic excavator DG–16 endodontic explorer
Start X ultrasonic tips 1, 2, 3, and 5 for access refinement

11. Guidelines for preparation of access
cavities
1. Determination of the point of penetration : Usually, entry is in the center of the occlusal table but in certain teeth (e.g. ;
maxillary molars) it is deceiving , as the center of the occlusal table does not reflect the center of the pulp chamber.
2. Assessment of occlusal and external root form : Once the point of entry has been determined, the bur’s angulation has to be
mentally envisioned. This is determined by taking into account the angulation of the teeth in the jaws and assessing the
external root surface at the level of CEJ.
3. Radiographic measurement of the depth of the pulp chamber roof from the occlusal table
4. Assessment of complicating factors : This includes rotated / malpositioned teeth, tipping / mesial tilting of the teeth, grossly
decayed teeth, calcifications, teeth with full coverage restorations, and abutment teeth with fixed prostheses.
5. Radiographic assessment : The preoperative radiographic assessment helps to visualize , mesial tilt of the teeth, size and shape
of the pulp chamber, thickness of the roof of the pulp chamber, presence of pulp stones, variations in the number of canals
and / or roots, extent of root and canal curvature and radiographic changes in the furcation and / or periapical region.

12. Clinical Considerations
A. Complete removal of carious tooth structure and other restorative material
While preparing the access cavity in a cariously involved teeth, start removing the carious tooth structures irrespective of the
the location of the carious lesion.
B. Complete deroofing and removal of dentinal shoulders The
overhanging roof of the pulp chamber misdirects the instrument, which results in ledge formation in the canal. Hence
complete deroofing must be done to obtain unrestricted access to the canals. Using a round bur and working from inside out
out will accomplish this end. Removal of the dentinal shoulders present between root canal orifices will help in achieving
straight line access and improve the clinical access to the root canals.
C. Evaluation of cementoenamel junction (CEJ) and root canal orifices Krasner and
Rankow in a study 500 pulp chambers determined that the CEJ is the most important anatomic for determining the location of
of pulp chambers and root canal orifices. They demonstrated that specific and consistent pulp chamber floor and wall
anatomy exist and proposed laws for assisting clinicians to identify canal morphology.
D. Significances of straight line access Removal of the
coronal tooth structure is necessary to allow complete freedom of endodontic instruments in the coronal cavity and direct
access to the apical canal.

13. Mouse hole Effect
If the lateral wall of the cavity has not been sufficiently extended and the pulp horn portion of the orifice
still remains in the wall, the orifice will have the appearance of a tiny “mouse hole”. This feature occurs due
to the extension of canal orifice to the axial wall. By extending the lateral wall of the cavity, thus removing
all intervening dentin from the orifice, the “mouse hole” in the wall will be eliminated and the orifice will
appear completely on the floor.

14. Krasner and Rankow’s Laws of
Access Opening
•Law of centrality : The floor of the pulp chamber is always located in the center of the tooth at the level of
the CEJ.
•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.
•Law of CEJ : The distance from the external surface of the clinical crown to the wall of the pulp chamber is
same throughout the circumference of the tooth at the level of the CEJ. The CEJ is the most consistent,
repeatable landmark for locating the position of the pulp chamber.
•Law of symmetry 1 : Except for maxillary molars, the orifices of the canal are equidistant from a line drawn in
a mesiodistal direction through the pulp chamber.
•Law of symmetry 2 : Except for maxillary molars, the orifices of the canals lie on a line perpendicular to a line
drawn in a mesiodistal direction across the center of the floor of the pulp chamber.

15. •Law of color change : The color of the pulp chamber floor is always darker than the walls
•Law of orifices location 1 : The orifices of the root canals are always located at the junction of floor and walls.
•Law of orifices location 2 : The orifices of the root canals are located at angles in the floor-wall junction.
•Law of orifices location 3 : The orifices of the root canals are located at the terminus of the root
developmental fusion lines.

16. Law of colour change
•Enamel – White
•Dentin – Yellow
•Floor of the pulp chamber – Gray
•Root canal orifice – Dark gray or black
•Pulp stone – Pearly white/dark yellow

17. Classification of Root canal configurations
The various classifications proposed are as follows:
I. Vertucci’s classification (1974)
•Type I: Single canal extends from the pulp chamber to the apex (1).
•Type II: Two separate canals leave the pulp chamber and join short of the apex to form one canal (2-1).
•Type III: One canal leaves the pulp chamber and divides into two in the root; the two then merge to exit as one canal (1-
2-1).
•Type IV: Two separate distinct canals extend from the pulp chamber to the apex (2).

18. •Type V: One canal leaves the pulp chamber and divides short of the apex into two separate distinct canals with separate
apical foramina (1-2).
•Type VI: Two separate canals leave the pulp chamber, merge in the body of the root, and redivide short of the apex to
exit as two distinct canals (2-1-2).
•Type VII: One canal leaves the pulp chamber, divides and then rejoins in the body of the root, and finally redivides into
two distinct canals short of the apex (1-2-1-2).
•Type VIII: Three separate distinct canals extend from the pulp chamber to the apex (3).

19. Type I(1) Type II(2-1) Type III(1-2-1) Type IV(2) Type V(1-2) Type VI(2-1-2) Type VII(1-2-1-2) Type VIII(3)
(a) (b) (c) (d) (e) (f) (g) (h)
Vertucci’s root canal configurations. Above: diagrammatic representation of eight different root canal configurations found by Vertucci et al. (1974)
using 200 cleared maxillary second premolars, which had their pulp cavities stained with dye. Below: three-dimensional microcomputed
tomographic models of different teeth representing the Vertucci’s root canal configurations.

20. II. Weine’s classification (1969)
•Type I: Single canal from pulp chamber to apex.
•Type II: Two canals leaving from the chamber and merging to form a single canal short of the apex.
•Type III: Two separate and distinct canals from chamber to apex.
•Type IV: One canal leaving the chamber and dividing into two separate and distinct canals.

21. Weine’s classification of root canal anatomy:
(a) Type I. (b) Type II. (c) Type III. (d) Type IV.
(a) (b) (c) (d)

22. III. Classification based on canal cross-section
According to Jou et al., canals can vary based on their anatomy cross-sectionally:
•Round (circular)
•Oval
•Long oval
•Flattened (flat/ribbon)
•Irregular

23. Micro-computed tomographic three-dimensional models
of the most common root canal configurations
in all groups of teeth.

24. Morphology and Access Cavity
preparation for Individual teeth

25. Maxillary Central Incisor
• Average tooth length : 22.5-24 mm ( avg : 23.5 mm)
• Shape of pulp chamber : - Ovoid mesiodistally
- Three pulp horns
• Roots and Root canals : - One root
- One root canal
- Broad labiopalatally, large, conical, centrally located
• Clinically Significant Attributes : - Majority of roots are straight
- Labial perforation is the most common iatrogenic error
- lateral canals may be present (24% of specimens), usually in the apical third
• Shape of Access Preparation : - Rounded triangular shape (base of triangle towards incisal edge)
• Most common Anomalies : - Talon cusp (Dens evaginatus)
- Two roots and two canals

26. Access opening
•The shape, size and coronal extension of the pulp chamber are estimated from a radiograph.
•The internal anatomic structure of the pulp chamber of the maxillary central incisor dictates the shape and size of the
access opening.
•The enamel is penetrated in the centre of the lingual surface at an angle perpendicular to it with a No 4 Round bur in a
high speed contra angle.
•After penetration of the enamel, the bur is directed along the long axis of the tooth until the pulp chamber is reached.
•A “drop” of the bur into the chamber may be felt if the chamber is large enough.
•The overhanging enamel and dentin of the palatal roof of the pulp chamber are removed, including the pulp horns, with
a No 4 round bur in a slow speed contra angle by working from the inside to the outside following the internal anatomy.

27. •This procedure makes the access cavity walls confluent with the lateral and incisal walls of the pulp chamber and
renders the access cavity a lingual extension of the pulp chamber, with a “straight line” penetration to the apical
root canal.
•A Gates Glidden drill of appropriate size (usually No 3) or any other suitable orifice enlarger is used to remove the
palatal shoulder by working from inside to outside with light strokes.
•The palatal shoulder is not an anatomic entity itself, but rather is a prominence of dentin created when the
palatal roof is removed.
•One gains direct access to the apical area of the root canal by removing the palatal roof and palatal shoulder of
the pulp chamber in an anterior tooth.
•Direct access can be verified by placing the straight end of the endodontic explorer into the canal orifice. The
explorer should follow the path of the canal without impedance from the walls the surrounding access
preparation.

28. Steps in the access opening of a maxillary central incisor
(a) (b) (c) (d)
(e) (f) (g) (h)

29. Maxillary Lateral Incisor
•Average tooth length : 21.5-23 mm (avg : 22 mm)
•Shape of pulp chamber : - Similar maxillary central incisor
- Two pulp horns
•Roots and Root canals : - Conical
- Finer diameter than that of maxillary central incisor
•Clinically Significant Attributes : - Majority of roots have distal curve (53%); others have straight (30%)
- Labial perforation most common iatrogenic error
•Shape of Access Preparation : - Similar to central incisors
•Most common Anomalies : - Dens invaginatus
- Talon cusp ( Dens evaginatus)
- Palatogingival groove

30. Access opening
The access opening of maxillary lateral incisor is similar to that for the maxillary central incisor, but it is
smaller and usually more ovoid.
The technique for entry is the same, except that a No 2 round bur may be used instead of a No 4.

31. Maxillary canine
•Average tooth length : - 26-28 mm (avg : 27 mm)
•Shape of pulp chamber : - Largest of any single rooted tooth
- Labiopalatally triangular, mesiodistally narrower
•Roots and Root canals : - Single root, large (Straight roots in 39% of cases, whereas in 32% the roots curved distally)
- Wider labiopalatally than mesiodistally
•Clinically Significant Attributes : - Straight root
- Lateral canal present (30% cases)
•Shape of Access Preparation : - Circular to ovoid
•Most common Anomalies : - Two roots in rare cases

32. Access opening
•The access opening for the maxillary canine is basically the same as that for the maxillary central and
lateral incisors.
•The only variation is that the shape of the access opening is circular to ovoid, as directed by pulp
chamber anatomy.
•The technique for entry is same as that for the maxillary central and lateral incisor.

33. Common errors in access openings of maxillary anterior teeth: (a) Gouging. (b) Perforation of crown.
(a) and (b) are caused by not directing the bur parallel to the long axis of the tooth after initial penetration.
(c) Discoloration. (d) Ledge with inadequate cleaning and shaping of canal. (e) Perforation of root.
(a) (b) (c) (d) (e)

34. Maxillary First Premolar
•Average tooth length : -21.5-23 mm (22.5 mm)
•Shape of pulp chamber : - Narrower mesiodistally
- Wider buccopalatally
- Pulp horn under each cusp
- Floor of pulp chamber convex
- Two canal canal orifices (buccal and palatal)
•Roots and Root canals : - Two roots and two canals
•Clinically Significant Attributes : - Two distinct canals
•Shape of Access Preparation : - Ovoid buccopalatal diameter wider while mesiodistal diameter narrower
•Most common Anomalies : - Three roots and three canals

35. Access opening
•By measuring the shape, size and extension of the pulp chamber mesially, distally and coronally in the diagnostic
radiograph, one can determine the approximate size, shape, depth and location of the coronal access cavity to be
prepared.
•The internal anatomic structure of the pulp chamber of the maxillary first premolar dictates the shape and size of the
access opening.
•Using a No 2 round carbide bur in a high speed contra angle, one penetrates the enamel in the center of the occlusal
surface between the buccal and lingual cusps, and the bur is directed into the long axis of the tooth.
•Then a bur aligned to the long axis to the tooth is used to penetrate through the dentin into the pulp chamber.
•The operator frequently feels the bur drop into the pulp chamber when the pulp chamber is large.
•Using the radiographic measurement, one penetrates deep enough to remove the roof of the pulp chamber without
cutting into the chamber floor; one should avoid an access opening that is too shallow and exposes only the pulp horn
tips, which may appear to be root canal orifices.

36. •To remove the roof of the pulp chamber, one should place the bur alongside the walls of the chamber and
cut occlusally.
•A tapered cylinder, self limiting diamond bur is used to remove the remaining roof of the pilp chamber.
•The walls of the pulp chamber are smoothened and are sloped slightly towards the occlusal surface with
this diamond.
•The divergence of the access cavity walls creates a positive seat for the entrance filling.
•The access cavity preparation for endodontic treatment of a premolar tooth differs from Black’s cavity
preparation for an occlusal restoration.
•In Black’s preparation, the ovoid shape runs mesiodistally and encompasses all the pit and fissures ,
whereas the endodontic preparation runs ovoid in a buccolingual direction and permits direct access to the
root canal.

37. Steps in the access opening of a maxillary first premolar
(a) (b) (c) (d) (e) (f) (g)
(h) (i)

38. Access opening of a maxillary premolar: (a) Circular access opening in the central groove would lead to
missing one of the two canals. (b) Buccolingual extension of the access preparation would lead to straight line access
of both the canals. (c) Buccal and palatal canals after orifice enlargement.
(a) (b) (c)

39. maxillary first premolar with three canals

40. Maxillary Second Premolar
• Average tooth length : - 21.5 – 23 mm
• Shape of pulp chamber : - Narrow mesiodistally
- wider buccopalatally
• Roots and Root canals : - Single root with two canals in most cases
- Rarely two roots
• Clinically Significant Attributes : - If one root, one orifice.
But 50% cases will have two canals and 46% cases have single canal.
- If two roots, two orifices
- The root(s) of the maxillary second premolar are situated below and therefore closer to the maxillary sinus.
• Shape of Access Preparation : - Ovoid buccopalatal diameter wider while mesiodistal diameter narrower
• Most common Anomalies : - Three roots and three canals

41. Access opening
•The access opening for the maxillary second premolar is basically the same as that for the maxillary
first premolar.
•It is varied only as dictated by the anatomic structure of the pulp chamber.

42. Maxillary second premolar with two canals

43. Common errors in access openings of maxillary premolars: (a) Gouging. (b) Perforation. (a) and (b) are caused by not
directing the bur parallel to the long axis of the tooth. (c) Broken instrument. Caused by failure to remove the
dentinal shoulders before placing instruments in the canals. (d) Missing extra canals. Caused by failure to funnel
access openings and not following the outline of the pulp chamber.
(a) (b) (c) (d)

44. Maxillary First Molar
•Average tooth length : - Buccal canals – 18-20 mm (average : 19 mm)
- Palatal canal – 19-21 mm (average : 20.5 mm)
•Shape of pulp chamber : - Largest in dental arch
- Four pulp horns
•Roots and Root canals : Three roots with three to four root canals - Mesiobuccal canal 1 (MB1)
- Mesiobuccal canal 2 (MB2)
- Distobuccal canal (DB1)
- Palatal canal (P)

45. •Clinically Significant Attributes : - Tooth with highest anatomic canal variations
- Tooth with highest incidence of missed canals seen clinically during retreatment
•Shape of Access Preparation : - Rhomboid shape
- Floor triangular in shape in cross section
•Most common Anomalies : - Three roots and four canals
- One root, one canal
- Two distal canals
- Two palatal roots
- Three mesiobuccal canals

46. Access opening
•The internal anatomy of the pulp chamber of the maxillary first molar dictates the shape and size of the access opening.
•By determining the shape and size of the chamber, by measuring the extension of the pulp chamber mesially, distally,
and coronally on the diagnostic radiograph, and by transposing these measurements to the tooth, one can estimate the
approximate size, shape, depth, and location of the coronal access cavity to be prepared.
•The enamel is penetrated with a high-speed bur by positioning the instrument in the central fossa and angling it towards
the palatal root. The bur is directed towards the palatal canal, where the pulp chamber of this tooth is largest.
•After penetration into the enamel, one uses the bur to penetrate the dentin; the bur is angled toward the palatal root
until the pulp chamber is reached.
•A “drop” of the bur into the pulp chamber may be felt if the chamber is large.
•In partially calcified chambers, the drop of the bur is not felt, and the operator has to rely on the measurements made
from the radiograph to avoid penetration beyond the chamber roof.

47. •A tapered-cylinder, self-limiting diamond bur is used to remove the remaining roof of the pulp chamber.
•The walls of the access cavity are refined with this diamond to be divergent towards the occlusal surface,
and this divergence creates a positive seat for the temporary filling that prevents its displacement by
occlusal forces.
•The walls of the access cavity should be confluent with the walls of the pulp chamber and
slightly divergent towards the occlusal surface.
•The access opening is usually triangular, with round corners extending toward, but not including, the
mesiobuccal cusp tip, marginal ridge, and oblique ridge. This triangular preparation permits direct access to
the root canal orifices.

48. (a) (b) (c)
(d) (e) (f)
(g) (h) (i)
Steps in the access opening of a maxillary first
molar
(D, distal; F, facial; M, mesial; P, palatal)
f
m
d
p

49. •The triangular access preparation in a maxillary molar is modified into a rhomboidal shape whenever the
MB-2 canal is suspected or traced.
• According to Nallapati the following are the possible locations of the MB-2 canal in the maxillary first
molar:
- Present on the developmental line that connects MB-1 and palatal canal.
- Present mesial to the developmental line that connects MB-1 and palatal canal
- Appears as a groove on the palatal wall of the MB-1 canal
- Splits off the MB-1 canal in the middle third of the canal
- Splits off the MB-1 canal in apical third of the canal
- Comes off the buccal wall of the palatal canal

50. Clinical tracing of the MB-2 canal: (a) MB-1 canal traced. (b) Ultrasonic tip (BUC-1) used to trough the
developmental groove below the MB-1 canal. (c) Orifice of the MB-2 visualized under the microscope. (d) Canal
traced using an ISO size 6 K-file. (e) and (f) MB-1 and MB-2 under higher magnifications.
(a) (b) (c)
(d) (e) (f)

51. Maxillary first molar with two palatal roots: (a) Access opening showing two distinct
palatal orifices and a single buccal orifice. (b) Spiral CT confirming the unusual anatomy
(a) (b)

52. Maxillary molar with three mesiobuccal canals.

53. (a) Preoperative radiograph of maxillary first molar. (b) Access opening showing eight canals. (c)–(e) Working length radiographs of maxillary
first molar in eccentric angulations. (f) Post obturation radiograph of maxillary first molar with eight root canals. (Adapted from Kottoor, J., et
al. Endodontic management of a maxillary first molar with eight root canal systems evaluated using cone-beam computed tomography
scanning: A case report.
J. Endod., 37(5), 715, 2011.)
(a) (b) (c)
(d) (e) (f)

54. Maxillary Second Molar
•Average tooth length : Buccal canals – 17.5--19 mm (avg 18 mm)
Palatal canal – 18.5--19.5 mm (avg 19 mm)
•Shape of pulp chamber : Similar to maxillary first molar
Narrow mesiodistally
•Roots and Root canals : Three root canal orifices closely grouped
•Clinically Significant Attributes : Distobuccal canal has high incidence of asymmetrical location
•Shape of Access Preparation : Rhomboid shape. Floor obtuse. Triangular in cross section.
Smaller in dimension than maxillary first molar
•Most common Anomalies : Four rooted molars with two palatal roots

55. Access opening
•The maxillary second molar access opening is basically the same as that for the maxillary first
molar, with the variations that anatomic structure dictates.

56. Maxillary Third Molar
•Average tooth length : 16.5—18 mm (avg 17.5 mm)
•Shape of pulp chamber : Resembles second molar
C shaped pulp chamber
•Roots and Root canals : Three root canal orifices closely grouped
C shaped root canal
•Clinically Significant Attributes : Tooth that is most challenging to access and work on clinically.
Closely related to maxillary sinus and maxillary tuberosity
•Shape of Access Preparation : Rhomboid shape Smaller in dimension than maxillary second molar
•Most common Anomalies : Anomalies are common

57. Access opening
•The access opening is similar to that for the maxillary second molar, with modifications for
variations in anatomic structure.

58. Common errors in access openings of maxillary molars: (a) Ledging. Caused by failure to remove dentinal
shoulder. Another cause is using a large straight instrument in a curved canal. (b) Gouging. Failure to direct
the bur parallel with the long axis of the tooth upon penetration.
(a) (b)

59. Mandibular Central Incisor
•Average tooth length : 21—22 mm ( avg 21.5 mm)
•Shape of pulp chamber : Smallest tooth of the arch
Small and flat mesiodistally Wide and ovoid labiolingually
Three distinct pulp horns (disappear early in life because of constant masticatory stimulus)
•Roots and Root canals : One root, which is flat and narrow mesiodistally but wide labiolingually
•Clinically Significant Attributes : 60% of roots are straight
Buccal performance is the most common iatrogenic error
Second canal normally located lingual to primary canal
•Shape of Access Preparation : Long and Oval
•Most common Anomalies : Two root canals
Talon cusp (Dens evaginatus)

60. Access opening
•The access opening of the mandibular central incisor is made in a similar manner as for the maxillary
anterior teeth, with the variations that its smaller size demands.
• The shape of the access opening of the mandibular incisor is long and oval, with its greatest
dimension oriented inciso gingivally.
• Proper access enables one to explore the cervical third of the root to determine whether a second
root canal is present.

61. Mandibular Lateral Incisor
•Average tooth length : 22.5 – 24 mm ( avg - 23.5 mm)
•Shape of pulp chamber : Similar to mandibular central incisor, but the lateral incisors have larger dimensions
•Roots and Root canals : Similar to mandibular central incisor, but slightly larger
•Clinically Significant Attributes : Majority of roots straight or distally/labially curved (more of distal curvature)
•Shape of Access Preparation : Long and oval
•Most common Anomalies : Two root canals
Talons cusp (Dens evaginatus)

62. Access opening
The access opening is made in the same manner as for the mandibular central incisor

63. Access opening of a mandibular incisor followed by exploration to assess for the
presence of the second lingual canal.
(Second canal is normally located lingual to the primary canal)

64. Endodontic management of mandibular incisors with two canals (Courtesy: Siju Jacob, India.)
(a) (b) (c)

65. Common errors in access openings of mandibular anterior teeth: (a) Gouging. Caused by not directing
the bur parallel to the long axis of the tooth after initial penetration. (b) Missed lingual canal. (c)Discoloration due to
incomplete deroofing of the pulp chamber.
(a) (b) (c)

66. Mandibular Canine
•Average tooth length : 26 – 28 mm (avg 27 mm)
•Shape of pulp chamber : Pulp chamber narrow mesiodistally
Labiolingually tapers to the incisal third and wide at the cervical third
Only one pulp horn
•Roots and Root canals : Single root
•Clinically Significant Attributes : Straight roots (68%)
Distal curvature (20%)
•Shape of Access Preparation : Circular to ovoid
•Most common Anomalies : Two root canals

67. Access opening
The access opening of the mandibular canine is made in a similar manner as for the maxillary canine, with
the variations dictated by a smaller anatomic dimension
(a) Access opening of a mandibular canine. (b) Micro CT image of a mandibular canine with two canals.
(c) Mandibular canine with two canals (Courtesy: Frank Paque, Switzerland.)
(a) (b) (c)

68. Mandibular First Premolar
•Average tooth length : 21.5 23 mm (avg 22.5 mm)
•Shape of pulp chamber : Narrow mesiodistally
Wide buccopalatally
Prominent buccal pulp horn
Prominent buccal cusp and smaller lingual cusp give 30 degree lingual tilt
•Roots and Root canals : Usually short and conical root
Usually straight (48%), distal curve (35%)
•Clinically Significant Attributes : Mental foramen mimic peri radicular pathology radiographically
•Shape of Access Preparation : Ovoid buccolingually
•Most common Anomalies : Bifurcations and trifurcations of the roots or root canals are most common anomalies.

69. Access opening
•By determining the shape and size and measuring the extension of the pulp chamber mesially, distally, and
coronally in the diagnostic radiograph and by transposing these measurements to the tooth, one can
estimate the approximate size, shape, depth, and location of the coronal access cavity to be prepared.
•The internal anatomy of the pulp chamber dictates the shape and size of the access opening.
•The mandibular first premolar has about a 30° lingual tilt of the crown to the long axis of the root.
•To compensate for the tilt and prevent perforations, the enamel is penetrated at the upper third of the
lingual incline of the facial cusp with a bur in a high-speed contra-angle centered mesiodistally and directed
along the long axis of the root.

70. •The procedure is the same as for the maxillary premolars .
•The resulting access cavity is ovoid, with the walls of the pulp chamber confluent with the access
cavity and divergent occlusally.
•The ovoid preparation should extend buccally and lingually enough to allow the complete removal of
the roof of the pulp chamber.
•This ovoid access preparation permits exploration for bifurcations or trifurcations in the middle and
apical thirds

71. Steps in the access opening of a mandibular first premolar.
(a) (b) (c)
(d) (e) (f) (g) (h)

72. Mandibular Second Premolar
•Average tooth length : 21.5 – 23 mm (avg 22.5 mm)
•Shape of pulp chamber : Similar to mandibular first premolar except that the lingual horn is more prominent
•Roots and Root canals : Single root
Rarely two or three roots
Straight (39%), distal curve (40%)
•Clinically Significant Attributes : Usually exits in one apical foramen (97.5%), in some may exit in two (2.5%)
•Shape of Access Preparation : Ovoid access opening wider mesiodistally (similar to first premolar)
•Most common Anomalies : Bifurcation and trifurcations of the roots or root canals are most common anomalies.

73. Access opening
The access opening for the mandibular second premolar is basically the same as for the mandibular first
premolar, except that the enamel penetration is initiated in the central fossa, and the ovoid access opening
is wider mesiodistally, as dictated by the wider pulp chamber.

74. Common errors in access openings of mandibular premolars: (a) Missing extra canal. (b) Perforation of root.
(a) and (b) are caused by inadequate deroofing of access opening. (c) Perforation of crown. Caused by not
directing the bur parallel to the long axis of the tooth.
(a) (b) (c)

75. Mandibular First Molar
•Average tooth length : 21 – 22 mm (21.5 mm)
•Shape of pulp chamber : Roof of pulp chamber rectangular in shape
Rhomboidal floor
Four pulp horns
Three distinct orifices; mesiobuccal, mesiolingual, distal
•Roots and Root canals : Two well differentiated roots ( one mesial and one distal)
Both roots are wide and flat buccolingually
Third root found either mesially or distally in 5.3% cases called radix entomolaris
•Clinically Significant Attributes : The distal canal has more clinical variations than the mesial canal
•Shape of Access Preparation : Trapezoidal with round corners
•Most common Anomalies : Radix entomolaris
Middle mesial canal

76. Access opening
The access opening for the mandibular first molar follows the anatomic features of the pulp
chamber. The enamel and dentin are penetrated in the central fossa with the bur angled towards
the distal root, where the pulp chamber is largest. The preparation follows the procedures outlined
for the maxillary molar. The access opening is usually trapezoidal with round corners or
rectangular if a second distal canal is present. The access opening extends toward the
mesiobuccal cusp to uncover the mesiobuccal canal, lingually slightly beyond the central groove
and distally slightly beyond the buccal groove.

77. Steps in the access opening of a mandibular first molar.
D, distal; F, facial; L, lingual; M, mesial.
(a) (b) (c)
(d) (e)
(f) (g) (h)
L
F
M
D

78. Clinical access opening in a mandibular first molar: (a) Triangular access opening in a mandibular molar
might lead to missing the second distal canal. (b) Access opening modified to a more trapezoidal form
enabling the tracing of the second canal in the distal root. Note the evidence of secondary caries under
the restoration on the buccal wall. (c) Complete removal of caries from the buccal wall.
(d) Access refined and canals enlarged with orifice enlargers.
(a) (b) (c) (d)

79. Middle mesial canal in mesial root of
mandibular first molar
Radix entomolaris

80. Variations in distal root of mandibular first molar:
(a) Distal root of a mandibular first molar with one canal and one orifice.
(b) Distal root of a mandibular first molar with one canal and two orifices.
(a) (b)

81. Mandibular Second Molar
•Average tooth length : 19 -21 mm (avg 20 mm)
•Shape of pulp chamber : Similar, but smaller than mandibular first molar
•Roots and Root canals : Majority have two roots (71%), but with one root (27%) and three roots (2%) also seen
•Clinically Significant Attributes : C shaped canal significantly higher
C shaped canal system classified into ; merging, symmetrical, asymmetrical
•Shape of Access Preparation : Similar to mandibular first molar
•Most common Anomalies : C shaped canal significantly higher

82. Access opening
The access opening for the mandibular second molar is created as for the mandibular first molar,
with the variations that a smaller tooth demands. Because of the buccoaxial inclination, it is
sometimes necessary to reduce a large portion of the mesiobuccal cusp to clean and shape the
mesiobuccal canal.

83. Type I C-shaped canal system (merging type)
Type II C-shaped canal system (symmetrical type
Type III C-shaped canal system (asymmetrical type

84. Mandibular second molar with two canals Mandibular second molar with a C-shaped
canal and a single conical root

85. Mandibular Third Molar
•Average tooth length : 17.5 – 19.5 mm (avg 18 mm)
•Shape of pulp chamber : Resembles mandibular first and second molar
C shaped root canal orifices
•Roots and Root canals : Usually two roots and two canals ;
Occasionally, one root and one canal or three roots and three canals may present
•Clinically Significant Attributes : Apex of root in close proximity to mandibular canal
•Shape of Access Preparation : Similar to mandibular first and second molar
•Most common Anomalies : Frequently has complex anatomic structure

86. Access opening
The access opening for the mandibular third molar is created as for the mandibular first and
second molars, with the variations that anatomic structure dictates.

87. Common errors in access openings of mandibular molars: (a) Perforation of crown: Caused by failure to direct the bur parallel
to the long axis of the tooth. (b) Perforation in furcation: Caused by using a long-shank bur at high speed and not realizing the
depth of the pulp chamber. The depth of most pulp chambers is approximately 6 mm. (c) Faulty cavity preparation: Caused by
not following the proper anatomy of the occlusal table. The mesiobuccal orifice is present beneath the mesiobuccal cusp. The
fourth canal is usually located buccally to the distal canal and under the distobuccal cusp tip. (d) Gouging and leaving roof of
the pulp chamber: Caused by not directing the bur at right angles to the occlusal table and not penetrating completely. If the
opening appears shallow with openings to the canal separated by light-colored dentin, one should suspect that the opening is
incomplete. The floor of the pulp chamber in a multirooted tooth is somewhat darker and may have grooves connecting the
canal orifices.
(a) (b) (c) (d)

88. Anomalies of Pulp Cavities
Certain developmental anomalies of the pulp cavities may render the execution of endodontic procedures
difficult or impossible.
•In dentinogenesis imperfecta, the pulp cavities may be small or even obliterated.
•Hyperparathyroidism may cause pulp calcification and loss of lamina dura.
•Hypofunction of the pituitary gland may lead to retarded eruption of teeth and to open root apices.
•Dentinal dysplasia is a hereditary condition characterized by obliteration of the pulp chamber and
defective root formation. In some cases of dentinal dysplasia, the root development is disturbed,
with obliteration of the root canals.
•Taurodontism is characterized by a short tooth and a much-larger-than-normal pulp chamber. It is
probably due to a lack of invagination of the epithelial root sheath during development

89. Newer concepts in Access Cavity
Preparation
•Different designs of minimally invasive access cavities have been proposed to improve the fracture
resistance of the endodontically treated teeth by preserving the tooth substance of the peri cervical
dentine and the roof of the pulp chamber.
•Currently, the available evidence, mainly laboratory studies, has shown some improvement in
fracture resistance in posterior teeth with MIECs. However, with the potential risks of procedural
impairment, the use of MIECs is yet to be recommended universally. Proper training and
armamentarium such as Operating Microscope and heat-treated NiTi instruments may be
prerequisites of clinical application.

90. The newer concepts in access cavity preparation includes
•Conservative endodontic access cavity
•Ultra conservative access cavity / ‘Ninja'
•Orifice – directed dentin conservation access cavity / Truss
•Caries driven / Restorative driven
•Cala Lilly enamel preparation
•Image guided endodontic access
•Dynamically guided endodontic access
•Micro guided endodontic access

91. Various Access cavity designs in anterior teeth

92. Various Access cavity designs in posterior teeth

93. Schematic representation of NiTi instruments in Trad-AC, Cons-AC, and Ultra-AC

94. Conservative access cavity
•By David Clark and John Khademi
•Lessen the tooth structure removal.
•Helps the long time survival & function of root canal treated tooth.
•Here, the teeth are accessed at the central fossa and they are extended out to discover canal orifices. This
aids in protecting the pericervical dentin and a part of the chamber floor.

96. Ultra conservative access cavity/
Ninja method
•Here, an oblique projection is made towards the central fossa of the root canal orifices
•This projection is made parallel with the enamel cut of 90 degree or more to the occlusal plane
•This makes simpler to discover the canal orifices from different visual angulations
•Limited line of vision, incomplete removal of infected pulpal tissue is the main limitation leading to failure
of endodontic treatment.

97. Orifice- Directed Dentin Conservation
Access Cavity / Truss
’
•Separate cavities are made to approach the canals
•The point of this methodology is to preserve dentin with the minimally invasive approach i.e. leaving
a truss of dentin between the two cavities that have been prepared
•The restricting components of this methodology which are past the operator’s control are position of
tooth, patients mouth opening capability, degree of calcification & other patient related variables

99. Caries driven
•Entry into the pulp chamber is carried out
by extracting caries and maintaining all the remaining structure of the tooth.
•This access design thus allows for direct conservation of healthy dentin by removing discontinuities in
tooth structure

100. Cala Lilly
enamel preparation
•In Cala Lilly enamel preparation,
shape of the access preparation resembles calalilly flower.
• In this preparation a bevel (45 degree) is given on the enamel portion of access cavity to remove
undermined enamelwhich resembles a calalilly flower.
• This helps to cover the access preparation within the restorative and to involve the entire enamel and
dentinal wall in the restoration, thereby improving the overall resistance and strength of the access
preparation.

101. Guided Endodontic Access
Guided endodontics involves merging a CBCT imaging and surface scan of the tooth to create a guide
(static navigation) (Buchgreitz et al., 2019a) or track a surgical instrument in real time and constantly
visualizing its position (dynamic navigation) in order to create a drill path into the tooth (Moreno-
Rabié et al., 2020) or design a path to reach the apical portion of the root (Fan et al., 2019).

102. Static-guided technique
Static guidance (SG) refers to the use of a fixed surgical stent, which is made using computer-aided
design/computer-assisted manufacture (CAD/CAM), based on a preoperative CBCT scan (Chong et
al., 2019).

103. (a) Radiographic aspects of a maxillary first molar with pulp
canal obliteration in all root canals.
(b–f) Digital planning of a static guide using CBCT and oral
scanning. After merging the images, a virtual copy of the drill
used for the access preparation was superimposed on the root
canals;
(g) Printed guides for individually accessing the root canals
(mesiobuccal, distobuccal, and palatal canals);
(h) Drilling the root canals; (i) Clinical aspect after guided-
access preparation showing the three accessed root canals;
(k) Radiographic image showing the prepared and filled root
canals
(Courtesy of Dr. Warley Luciano Fonseca Tavares)

104. Dynamic-guided technique
•The dynamic-guided technique, also known as dynamic navigation system (DNS), is based on
computer-aided surgical navigation technology.
• This technology allows the use of a computer to guide special burs in real-time based on information
gathered from a CBCT image.
•Motion tracking enables the system by following the position of both the patient and the dental
handpiece throughout the procedure.
•The ideal drill position is planned virtually by the surgeon using the CBCT data set uploaded into the
planning software.

105. (a) Tomographic images of a symptomatic maxillary central left incisor
with chronic apical periodontitis and pulp canal obliteration showing
the access planning with the Navident system;
(b–e) Preoperatory tomographic and radiographic images showing a
patent apical canal, the obliteration of the coronal and middle canal
thirds, and an apical lesion located at the mesial aspect of the root
associated with a large lateral canal;
(f) The use of the dynamic Navident system allowed to locate, prepare,
and
(g) fill the root canal through a conservative access cavity (Courtesy of
Dr. Felipe Restrepo)

106. Case reports
Present status and future directions – Minimal endodontic access cavities / International
endodontic journal
Emmanuel João Nogueira Leal Silva, Gustavo De-Deus, Erick Miranda Souza, Felipe Gonçalves
Belladonna, Daniele Moreira Cavalcante, Marco Simões-Carvalho, Marco Aurélio Versiani
First published: 31 January 2022

107. 1)
Mandibular incisor with apical periodontitis and massive bone
loss referred for root canal treatment
(a–c) Preoperative radiographic and tomographic images (January
2020).
(d) Intracanal medication after preparation procedures performed
through a conservative access cavity (January 2020).
(e–f) Radiographic and tomographic images after 8 months and
(g–h) 13 months, showing the bone repair progression.
(i–j) Immediate post-operative radiographic and tomographic
images demonstrating the complete bone repair after 18 months
from the initial procedures
(Courtesy of Dr. Carlos Bóveda)

108. 2) (a–d) Preoperative radiographic and tomographic
images of a maxillary first right premolar with apical
periodontitis referred for root canal treatment.
(e–g) Root canal preparation and disinfection
through a conservative access cavity preparation.
(h) Intracanal medication after 6 months showing
bone repair.
(i–l) Occlusal view of the tooth after filling
procedures.
(m–p) Radiographic and tomographic images after
4 years of filling procedures demonstrating bone
repair
(Courtesy of Dr. Carlos Bóveda)

109. 3)
(a–d) Preoperative radiographic and
tomographic images of a maxillary first right
molar referred for root canal treatment.
(e–f) Occlusal view of the tooth showing the
conservative access cavity preparation.
(g–j) Immediate postoperative radiographic
and tomographic images of the tooth after
filling procedures.
(k) 4-year follow-up
(Courtesy of Dr. Carlos Bóveda)

110. •The fact that healing is possible in individual cases does not mitigate the necessity of assessing in a
systematic and prospective way how predictable this treatment mode is not only by providing similar
or superior apical healing rates but also proving its value on reducing the fracture rate of filled teeth
compared to standard counterpart treatments.
• It is essential that the minimally invasive access concept passes through populational validation;
otherwise, its clinical application cannot be considered worthwhile.
• In the current context, where the benefit of minimal access cavities is not clear-cut, it should not be
advocated as being superior to the traditional approach.
•Therefore, clinician should strike the right balance between traditional endodontic preparation and
minimal endodontic preparation to achieve the purpose of endodontic treatment.

111. Conclusion
Most apical problems originate coronally ! The severity of coronal problems increases on the way to
the apex !
•The use of magnification, illumination and specialized items of equipment greatly improves the ability of an
operator to identify the root canals entrances in molar teeth, however nothing can substitute the experience and
knowledge gleaned from practice both in a clinical environment and on extracted teeth.
•Successful access cavity preparation relies on a sound knowledge of the internal and external anatomy of teeth.
•The importance of gaining straight line endodontic access cannot be over-emphasized .
•Ultimately poor access cavity design could lead to inadequate cleaning, shaping and obturation compromising
successful outcome.

112. Bibliography
1. Grossman's endodontic practice - 14th edition
2. Ingle's Endodontics 7th Edition
3. A practical guide to endodontic access cavity preparation in molar teeth/ BRITISH DENTAL JOURNAL VOLUME 203 NO. 3 AUG 11 2007
4. REVIEW ARTICLE : Access Cavity Preparations : Classification and Literature Review of Traditional and Minimally Invasive Endodontic
Access Cavity Designs. (J Endod 2021;-:1–16.)
5. REVIEW ARTICLE : Present status and future directions – Minimal endodontic access cavities. International Endodontic Journal
6. ENDODONTIC ACCESS PREPARATION THE TOOLS FOR SUCCESS by Clifford J. Ruddle, DDS / Advanced Endodontics
7. American Association of Endodontists A new look at the endo restorative interface. AAE Endodontics Colleagues for
Excellence. 2020 / Fall;:1–8
8. Review article / A Literature Review of Minimally Invasive Endodontic Access Cavities - Past, Present and Future / European
Endodontic Journal

113. Thank You