Upload
eri-lupitasari
View
48
Download
5
Embed Size (px)
DESCRIPTION
akses kavitas
Citation preview
1FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
ACCESS CAVITY PREPARATION – AN ANATOMICAL AND CLINICAL PERSPECTIVEDr. V. Gopi Krishna, MDS, FISDR is a clinician, researcher and academician of national acclaim. He is the Co-Editor of Grossmans Endodontic
Practice - 12th Edition (Wolters Kluwer – Lipincott) and Editor of Preclinical Manual of Conservative Dentistry (Elsevier). He is also the Editor-
in-Chief of the Journal of Conservative Dentistry (www.jcd.org.in) and is working as Professor, Dept. of Conservative Dentistry & Endodontics
at Thai Moogambigai Dental College. He runs the Root Canal Centre - an exclusive endodontic training and treatment centre at Chennai,
which mentors more than 100 dentists every year in improving their endodontic skills. For more information on microscope aided clinical
endodontic training modules with live patient demonstrations you can contact Dr. Gopi Krishna at [email protected] (Ph: 91-
9840218818) and on Facebook Root Canal Centre.
“You don’t know how much you know until you know
how much you don’t know”
“Access is success”. These three words in a nutshell convey the
significance of a proper access opening on the overall quality and
success of endodontic treatment. In this era of instrument driven
endodontics it is important that one understands that the efficacy
of cleaning and shaping is effective only if employed after a good
access opening.
Anatomy of Pulp Cavity
The pulp cavity is the central cavity within a tooth and is entirely
enclosed by dentin except at the apical foramen (Fig. 1). The pulp
cavity may be divided into a coronal portion, the pulp chamber,
and a radicular portion, the root canal. In anterior teeth, the pulp
chamber gradually merges into the root canal, and this division
becomes indistinct. In multi-rooted teeth, the pulp cavity consists
of a single pulp chamber and usually three root canals, although
the number of canals can vary from one to four or more. The roof
of the pulp chamber consists of dentin covering the pulp chamber
occlusally or incisally (Fig. 1).
A pulp horn is an accentuation of the roof of the pulp chamber
directly under a cusp or developmental lobe. The term refers more
commonly to the prolongation of the pulp itself directly under a
cusp. The floor of the pulp chamber runs parallel to the roof and
consists of dentin bounding the pulp chamber near the cervix of
the tooth, particularly dentin forming the furcation area. The canal
orifices are openings in the floor of the pulp chamber leading into
the root canals. The canal orifices are not separate structures, but
are continuous with both pulp chamber and root canals. The walls
of a pulp chamber derive their names from the corresponding walls
of the tooth surface, such as the buccal wall of a pulp chamber. The
angles of a pulp chamber derive their names from the walls forming
the angle, such as the mesiobuccal angle of a pulp chamber.
(Fig. 1)
Anatomy of Root Canals
The root canal is that portion of the pulp cavity from the canal
orifices to the apical foramen. It may be divided for convenience
into three sections, namely: coronal, middle, and apical thirds.
Accessory canals, or lateral canals, are lateral branching of the
main root canal generally occurring in the apical third or furcation
area of a root (Fig. 1). A distinction sometimes made between an
accessory canal and a lateral canal is that a lateral canal is an
accessory canal that branches to the lateral surface of the root and
may be visible on a radiograph. Lateral canals occur 73.5% of the
time in the apical third, 11.4% of the time in the middle third and
6.3% of the time in the cervical third of the root. The apical foramen
is an aperture at or near the apex of a root through which the
blood vessels and nerves of the pulp enter or leave the pulp cavity.
Accessory foramina are the openings of the accessory and lateral
canals in the root surface (Fig. 1).
Although variations are the norm in root canal configurations;
various researchers have classified them according to the number
of canals, intracanal branching & fusion and exit from the canal.
The most widely accepted clinical classification was proposed by
Vertucci and his classification is as follows: (Fig. 2)
GROSSMAN’S Corner
Dr. V. Gopi Krishna
Fig. 1 Various views of the root canal system: (a) Labial view of a central incisor. (b) Apical third of a root. (c) Buccal view of a maxillary first molar. (d) Buccal view of a mandibular first molar.
2FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
3. To de-roof the pulp chamber
4. To remove the coronal pulp tissue including vital pulp, necrotic
pulp and pulp stones.
5. To locate all the root canal orifices
6. To achieve straight line access into the root canal
7. To remove the dentinal shelves between the canal orifices
Armamentarium
I would like to classify the instruments and equipments required for
access cavity preparation into two separate lists:
I. Must Have Instruments & Equipments
a. Burs
i. Round burs ( #2, #4 and #6) (Fig. 3)
ii. Tapering fissure bur with a round head (Fig. 4)
iii. Safe end burs e.g.: Endo Z bur (Fig. 5)
iv. Transmetal bur e.g.: Trihawk burs (Fig. 6)
• TypeI(Fig.2a) Single canal extends from the pulp chamber
to the apex
• Type II (Fig. 2a) Two separate canals leaving the pulp
chamber and join short of the apex to form one canal (2-1)
• Type III (Fig. 2a) 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 (Fig. 2b) Two separate, distinct canals extend from
the pulp chamber to the apex
• Type V (Fig. 2b) One canal leaves the pulp camber and
divides short of the apex into two separate, distinct canals with
separate apical foramina (1-2)
• Type VI (Fig. 2b) Two separate canals leave the pulp
chamber, merge in the body of the root, and re-divide short of
the apex to exit as two distinct canals (2-1-2)
• Type VII (Fig. 2b) One canal leaves the pulp chamber,
divides and then rejoins in the body of the root and finally re-
divides into two distinct canals short of the apex (1-2-1-2)
• Type VIII (Fig. 2c) Three separate, distinct canals extend
from the pulp chamber to the apex (3)
Thus, a clinician must be familiar with the various pathways the root
canals take to the apex.
Fundamental Objectives of Access Cavity Preparation
The following are the fundamental objectives which one has to keep
in mind while preparing the pulpal access cavity after achieving
profound local anesthesia:
1. To remove all decay, leaking restorations and undermined tooth
structure
2. To conserve healthy tooth structure
INDUSTRY WATCHACCESS CAVITY PREPARATION – AN ANATOMICAL
AND CLINICAL PERSPECTIVE
Fig. 2 Vertucci’s classification.
Fig. 3 Round bur
Fig. 5 Endo Z – Safe end cutting bur
Fig. 6 Trihawk bur
Fig. 4 Tapering fissure bur with a round head
3FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
b. DG – 16 Endodontic Explorer (Fig. 7)
c. Endodontic Spoon excavator (Fig. 8)
d. Orifice Enlargers
i. Gates Glidden Drills (Fig. 9)
e. Patency files
i. K Files ISO sizes #06, #08 and #10
II. Nice To Have Instruments & Equipments
a. Burs
i. LN Bur (Dentsply Maillefer) (Fig. 10)
ii. Munce Discovery Burs (CJM Engineering) (Fig. 11)
b. Ultrasonic Tips
i. Start X tips (Dentsply Maillefer) (Fig. 12)
c. Orifice Enlargers
i. X Gates (Fig. 13)
ii. Rotary orifice shapers
iii. Endodontic Micro Openers (Dentsply Maillefer)
(Fig. 14)
d. Dental Operating Microscope for Magnification and Illumi-
nation (Fig. 15)
The use of surgical telescopes of greater than 2.5X magnification
(ideally 4X or greater) and accompanying coaxial high-intensity
illumination or an operating microscope is highly recommended.
Access Cavity Guidelines For Permanent Teeth
I. Maxillary Incisors
Steps of access cavity preparation:
• Divide the tooth into nine boxes. The box in the centre is the
region for penetration of the bur. This is usually just incisal to the
cingulum,
• The lingual surface is entered perpendicular to the lingual
surface,
• The bur head is then oriented parallel to the long axis to the
tooth,
Fig. 7 DG 16 Fig. 13 X gates
Fig. 14 Micro opener
Fig. 15 Dental operating microscope greatly enhances both the illumination and magnification during access cavity preparation
Fig. 8 Endodontic excavator
Fig. 10 LN bur
Fig. 12 Start X ultrasonic tips
Fig. 9 Gates Glidden drills
Fig. 11 Munce discovery burs
INDUSTRY WATCHACCESS CAVITY PREPARATION – AN ANATOMICAL
AND CLINICAL PERSPECTIVE
4FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
• A round bur on slow speed contra-angled handpiece is used to
de-roof the pulp chamber,
• Completed access preparation must have a triangular outline
with the base towards the incisal edge and apex towards the
cingulum.
Key Rules for Maxillary Anteriors:
1. Entry slightly incisal to the cingulum
2. “Go palatal”- Always ensure a Palatal orientation of the bur
after crossing the DEJ
3. No variations – Single orifice with a single canal
II. Mandibular Anteriors
Fig. 16 a – f: Steps of access cavity preparation for mandibular anteriors
Fig. 18 Maxillary canine. (a) Ovoid funnel-shaped preparation. (b) Clinical image
Fig. 19 Mandibular central and lateral incisor. The preparation is ovoid in shape, which is more lingual in order to ensure the tracing of the second lingual canal
Fig. 20 Mandibular canine. The preparation should be ovoid, funnel-shaped. The cavity should be extended inciso-gingivally for room to find the orifice and enlarge the apical third without interference.
Fig. 17 Maxillary lateral incisor. It is similar to maxillary central incisor, but the size is smaller in dimensions.
(F) Clinical Image
(a) (b)
(a) (b)
(a) (b)
INDUSTRY WATCHACCESS CAVITY PREPARATION – AN ANATOMICAL
AND CLINICAL PERSPECTIVE
5FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
Key rules for mandibular anteriors
1. Change the bur Use the smaller round diamond No. 2
Preserves the tooth structure
2. Change the operator seating position 12 o’clock position
Better orientation
3. Change the radiographic position (exaggerated mesial shift)
Helps in identification of extra lingual canal
III. Maxillary Premolars
Key Rules:
1. Bucco - lingual orientation of cavity preparation
2. Oval shaped access
3. In case of bulkier roots suspect extra canals
IV. Mandibular Premolars
Key rules:
1. Ovoid / Round shaped access’
2. In case of bulbous roots suspect bifurcation of canals
V. Maxillary Molars
Maxillary molars generally have three roots and can have as many
as three mesial canals, two distal canals, and two palatal canals.
The mesiobuccal root of the maxillary first molar has generated
more research and clinical investigation than any root in the mouth.
It generally has two canals and they are called mesiobuccal (MB-1)
and second mesiobuccal (MB-2)
Fig. 21 Maxillary premolars. The ovoid coronal preparation need not be as long bucco-lingually as the pulp chamber. Final preparation should provide unobstructed access to canal orifices. Cavity walls should not impede complete authority over enlarging instruments.
Fig. 23 Mandibular premolars. The preparation is ovoid in shape which is less extensive bucco-lingually than that of the maxillary premolar
Fig. 24 Maxillary first molar. The outline is trapezoidal in shape with the broader base towards the buccal surface. The cavity is entirely within the mesial half of the tooth and need not invade the transverse ridge but is extensive enough, buccal to lingual, to allow positioning of instruments
Fig. 22 (a) Incomplete de-roofing of a maxillary premolar access cavity preparation(b) De-roofing allows access to the isthmus area which contains pulp tissue(c) Completed access opening allowing straight line access to both the buccal and palatal canals
(a) (b)
(c)
INDUSTRY WATCHACCESS CAVITY PREPARATION – AN ANATOMICAL
AND CLINICAL PERSPECTIVE
6FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
Key Rules for tracing the canals:
1. All canals are present in mesial 60% of tooth
2. Trace the palatal canal under the palatal cusp
3. Straight line up from palatal canal orifice towards buccal
wall Disto buccal canal
4. Mesial line from Disto buccal canal Mesio buccal canal
Most Common Variations:
i. If Mesio-buccal canal not present at the expected area then
trough for the canal more buccally towards buccal wall
ii. If Mesio-buccal canal is present near the buccal wall, trough for
the second canal MB2 below it. MB2 is consistently located
mesial to or directly on a line between the MB-1 and the palatal
orifices, within 3.5mm palatally and 2 mm mesially from the
MB-1 orifice.
iii. If Disto-buccal canal is not present at the expected area, always
trace it towards the mesial direction, towards a line joining
Mesio-buccal canal and palatal canal.
VI. Mandibular Molars
Key Rules:
1. Quadrilateral / Trapezoidal shape access
2. Suspect for the fourth canal
Common variations:
1. Possibility of a 2nd distal canal which can be in the following
configuration
• ‘C’shapedcanals
• 2canalswithorificesveryclosetogether
• 2distinctorifices
Fig. 25 The two most common locations of the MB2 canal
Fig. 27 Quadrilateral outline form reflects the anatomy of the pulp chamber. Both mesial and distal walls slope mesially. The cavity is primarily within the mesial half of the tooth but is extensive enough to allow positioning of instruments. Further exploration should determine whether a fourth canal can be found in the distal. In that case, an orifice will be positioned at each angle of the rhomboid.
Fig. 28 Single distal canal – oval shaped
Fig. 29 Single Distal canal - C shaped
Fig. 26 Clinical image of a maxillary first molar with four canals
INDUSTRY WATCHACCESS CAVITY PREPARATION – AN ANATOMICAL
AND CLINICAL PERSPECTIVE
7FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
2. Possibility of 2nd mesial canal (Between the 2 mesial canals)
3. Possibility of an extra root having a canal which is referred to as
Radix entomolaris / Radix paramolaris
4. Teeth having two canals in a straight line do not have any third
or extra canals and this configuration is seen in the second and
the third molars.
Steps of Access Opening
We can divide the complete process of access cavity preparation
into seven distinct steps :
STEP # 1 Relieve the tooth out of occlusion “Reduce
Post – operative Discomfort”
STEP # 2 Use caries as a guide “Chase the caries”
STEP # 3 Laws of Access Opening “Know your
Geography”
STEP # 4 De-roofing of pulp chamber “Most important
rule of access opening”
STEP # 5 Observe the color change “Color is the
language of endodontics”
STEP # 6 Remove dentinal shelves “Establish straight
line access”
STEP # 7 Locating the Canal Orifices “Eureka
Moment!!!”
STEP # 1 Relieve the tooth out of occlusion “Reduce
Post – operative Discomfort”
This is the first step of access cavity preparation in relation to
premolars and molars. This crucial step is recommended for the
following reasons:
i. Establishes stable occlusal reference points for working length
determination
ii. Reduces post operative discomfort by minimizing trauma to the
apical periodontium from occlusal loads
iii. Improves convenience form for the operator
STEP # 2 Use caries as a guide “Chase the caries”
The thumb-rule to follow while doing access opening in a cariously
involved tooth is to start removing the dental decay immaterial of
the location of the decay. Invariably the dental decay would lead
into the pulp chamber. Hence in cases of a tooth with distal decay
the access opening commences from the distal side towards the
mesial pulp chamber.
STEP # 3 Laws of Access Opening “Know your
Geography”
The biggest fear an operator has while preparing an access cavity
is the “Fear of Perforation”. This fear stems from the fact that many
operators are not clear of the internal map / geography of the pulp
chamber. One of the key landmarks, which help the operator in
avoiding procedural errors and helps in determining the location of
Fig. 30 Two distal canals – Orifices next to each other
Fig. 32 Single mesial canal which is in line with the distal canal in a mandibular second molar.
Fig. 33 Relieving the occlusion with a Tapering Fissure diamond
Fig. 34 Occlusal view after completion of relieving the occlusion
Fig. 31 Two distal canals – Distinctly separate orifices
INDUSTRY WATCHACCESS CAVITY PREPARATION – AN ANATOMICAL
AND CLINICAL PERSPECTIVE
8FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
the pulp chamber and root canal orifices, is the Cemento-enamel
Junction. (Fig. 35)
Krasner and Rankow proposed guidelines or laws that are of
immense help to a clinician during access cavity preparation. The
laws are:
i. Law of Centrality: The floor of the pulp chamber is always
located in the center of the tooth at the level of the CEJ
ii. 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, that is, the external root surface anatomy reflects the
internal root canal anatomy.
iii. 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, making the CEJ the most consistent repeatable landmark
for locating the position of the pulp chamber.
STEP # 4 De-roofing of pulp chamber “Most important
rule of access opening”
Any permanent tooth not worn down occlusally/incisally has a pulp
chamber that is situated approximately 7 mm from a cusp tip or an
incisal edge. To slowly gain depth by small degrees leading up to
7 mm is needlessly inefficient, but to go beyond 7 mm in one fell
swoop is needlessly dangerous. You have a landmark: 7 mm. By
sticking to it, you will gain access in a predictable way without the
concern of perforating the floor of the chamber.
Once we enter into the roof of the pulp chamber then the operator
has to change to a lateral cutting motion instead of proceeding
in an apical direction. Care must be taken to slowly completely
remove the roof over the pulp chamber.
Fig. 35 Cemento-enamel junction is the key anatomical landmark during access cavity preparation
Fig. 36 Starting the access cavity preparation with a tapering fissure bur with a round head
Fig. 37 Initial access cavity outline. Note the color change as we enter into the dentin
Fig. 39 A, B, C & D: Sequential de-roofing the pulp chamber using a lateral cutting motion
Fig. 38 Note the grayish color change as we gradually near the roof of the pulp chamber.
39 (a) 39 (b)
39 (c) 39 (d)
INDUSTRY WATCHACCESS CAVITY PREPARATION – AN ANATOMICAL
AND CLINICAL PERSPECTIVE
9FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
STEP # 5 Observe the color change “Color is the
language of endodontics”
Table 1: Color chart of endodontic access cavity preparation
Law of color change: The color of the pulp chamber floor is always
darker than the walls.
Pulp stones take on a yellow / pearly white color and while in
intimate mechanical relationship with the floor of the pulp chamber,
they do not fuse with the floor like secondary dentin does. For this
reason, they can often be picked away from the floor with a sharp
explorer. Once through the secondary dentin and pulp stones, the
canals of a calcified canal may still not be readily apparent.
STEP # 6 Remove dentinal shelves “Establish straight
line access”
STEP # 7 Locating the Canal Orifices “Eureka
Moment!!!”
Enamel White
Dentin Yellow
Floor of the pulp chamber Gray
Root Canal Orifice Dark gray or black
Pulp stone Pearly white / Dark Yellow
Fig. 40 Pearly white color of the pulp stone
Fig. 43 The probe pointing into the distal canal while straight line access is not present for the mesial canals
Fig. 44 The DG 16 endodontic explorer is pointing towards the Dentinal Shelves protruding from the respective walls
Fig. 45 Refining the access preparation with the help of Start X ultrasonic tips to remove the dentinal shelves and in planing of the walls. These tips can also be used to trace extra canals and to dislodge calcified pulp stones.
Fig. 42 Note the dome shaped floor having a distinct gray color after the partial removal of pulp stones
Fig. 41 Pulp stone, which is more yellowish than the surrounding dentinal walls.
INDUSTRY WATCHACCESS CAVITY PREPARATION – AN ANATOMICAL
AND CLINICAL PERSPECTIVE
10FAMDENT PRACTICAL DENTISTRY HANDBOOK Vol. 10 Issue 3 Jan. - Mar. 2010
The following laws will help the clinician in locating the canal
orifices:
Law of symmetry 1: Except for maxillary molars, the orifices of the
canals are equidistant from a line drawn in a mesio-distal direction
through the pulp chamber floor.
Law of symmetry 2: Except for maxillary molars, the orifices of the
canals lie on a line perpendicular to a line drawn in a mesio-distal
direction across the center of the floor of the pulp chamber.
Law of orifices location 1: The orifices of the root canals are
always located at the junction of the walls and the floor.
Law of orifices location 2: The orifices of the root canals are
located at the 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.
The above laws were found to occur in 95% of the teeth examined.
Five percent of mandibular second and third molars did not
conform to these laws because of the presence of C-shaped canal
anatomy.
Conclusion:
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. In my opinion,
mastering the art of access cavity preparation is the single most
important operator variable that ultimately determines both the
prognosis and quality of the endodontic therapy
Fig. 46 Access cavity preparation completed
Fig. 47 Under higher magnification
Fig. 49 Representation of first and second laws of symmetry and first, second and third laws of orifice location
Fig. 48 Mesial canal orifices
INDUSTRY WATCHACCESS CAVITY PREPARATION – AN ANATOMICAL
AND CLINICAL PERSPECTIVE