a cess cavity preparation

8/2/2019 A Cess Cavity Preparation

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ACCESS CAVITYPREPARATION OFMAXILLARY TEETH


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The access cavity preparation generally refers to the part ofthe cavity from the occlusion table to the canal orifice. (according toStephen Cohen)

OBJECTIVESWell designed access preparation is essential for a goodendodontic result. Without adequate access, instrumentsand material becomes difficult to handle properly in thehighly complex and variable canal system. To achieve a straight or direct line access to the apical foramen. To locate all root canal orifice. To conserve sound tooth structure. Well prepared and correct access cavity allow complete irrigation, shaping

,cleaning and quality obturation. Ideal access results in a straight entry into the canal orifice, with the line

angles forming a funnel that drops smoothly into the canal.

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GUIDELINESIt is essential for the completion of ideal access preparation.

1. Visualization of internal anatomy because internal anatomy dictates access shape. This requireevaluation of angled peri-apical radiograph, examination of coronal and cervical tooth anatomy.

2. Evaluation of CEJ and occlusal anatomy.traditionally, access cavity is prepared in relation to the occlusal

anatomy.CEJ is the most important anatomical landmark for determining the location of pulp chamber

and root canal orifice.

3. Preparation of the access cavity is through lingual in anterior teeth and on the posterior teeth throughocclusal surface.

4. Removal of unsupported tooth structure.This reduce the tooth's resistance to stress.

5. Creation of access cavity walls. So that sufficient tooth structure must be removed to allow instrument tobe placed in a straight line and easily into canal orifice.

6. Location, flaring and exploration of all root canals orifices. A sharp endodontic explorer used to locate thecanal orifice and to determine their angle of departure from the pulp chamber.

7. Magnification and illumination.These are important in root canal therapy, especially for determiningthe location of canal, curved and calcified canal and debriding and removing tissue from the pulpchamber.

8.Tapering of cavity walls and evaluation of space adequacy for a coronal seal. A proper access cavity hastapering walls and is widest at occlusal surface. At least 3.5 mm of temporary filling material is needed toprovide an adequate coronal seal for a short period.

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MORPHOLOGY AND ACCESS CAVITY PREPARATIONFOR MAXILLARY CENTRAL INCISORDevelopmental and anatomic data

Average time of eruption-: 7-8 Years

Average age of calcification-: 10 Years

Average tooth length-: 23.5mm

Average crown length-: 10.5mm

Average root length-:13mm

M-D of crown-: 8.5mm M-D of crown at cervix-: 7mm

Labio-lingual diameter of crown-: 7mm

Labio-lingual diameter at cervix-: 6mm

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Pulp chamber

It is located in the centre of crown equidistant

from the dentinal wall. It is broad m-d, with its broadest part incisally.

It has three pulp horns that corresponds to the double mammelonsin a young tooth.

Root and root canal

It has one root with one root canal. Root canal is broad labio-palataly, conical shape, and centrally

located.

In cross-section, canal is ovoid m-d in cervical third, rounded inmiddle and apical third.

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INCIDENCE

Rooto Straight : 75%o Distally curved : 8%o Mesially and palatally curved : 4%o Labially curved: 9%

Apical forameno Centrally located in anatomic apex : 12%o Apical delta : 1%

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Anatomic relationship in situLabial surface of the root lies under the labialcortical plate of the maxilla and may fuse with it.It has an average of 2 degree of mesio-axialinclination and 29 degree of palato-axial angulations inits alveolus.


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Access opening Shape, size and coronal extension of pulp chamber are estimated by

diagnostic radiograph.

Enamel is penetrated in the centre of the lingual surface at an angleperpendicular to it, with a number 4 round bur in high speedcontra-angle.

After penetration of the enamel, a No 4 carbide bur in a slow speedcontra-angle is directed along the long axis of the tooth until thepulp chamber is reached.

A drop of the bur into the chamber may be felt if the chamber islarge enough.

The overhanging enamel and dentin lingual surface of the pulpchamber is removed with a No 4 round bur in a slow speed contra-angle by working from inside to outside following internal anatomy.

The lingual extension of the pulp chamber, with a straight linepenetration to the apical root canal.

Direct access can be verified by placing a straight end of theendodontic explorer in the canal orifice.

The access shape is slightly triangular, with the base of the triangleto the incisal edge.

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Anatomic alteration in pulp

The usual anatomic structure of the chamber in the root canalmay be altered in any tooth due to deposition of reparative orsecondary dentin.

This alteration in anatomy may be due to trauma, caries,restorative procedure, aging.

To escape this alteration we can use No 2 round

carbide bur.

Enlarge the enamel portion of the access cavity to an ovoidshape, with greatest diameter incisogingivally.

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MORPHOLOGY AND ACCESS CAVITY PREPARATION FORMAXILLARY LATERAL INCISORMAXILLARY LATERAL INCISOR

Developmental and anatomic data

Average time of eruption-: 8-9Years

Average age of calcification-: 11Years

Average tooth length-: 22mm

Average crown length-: 9mm

Average root length-: 13mm

M-D of crown-: 6.5mm

M-D of crown at cervix-: 5mm



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Pulp chamber

The shape of the pulp chamber is similar to the maxillary

central incisor. It only has two pulp horn, corresponding to the

developmental mamelons.

Root and root canal

Configuration of the root canal is conical but it has a finerdiameter than maxillary central incisor.

In cross-section, the canal is ovoid labio-palataly in thecervical third and middle third, round in apical third.

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INCIDENCE

Root

o Straight : 30%

o Distally curved : 53%o Mesially and palatally curved : 3%

o Labial curved: 4%

o S-shaped or bayonet curved: 6%

Apical foramen

o Centrally located in anatomic apex : 22%

o Apical delta : 3%

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Anatomic relationship in situ It has an average of 16 degree of mesio-axial inclination and

average of 29 degree of palato axial angulations in its alveolus.

Access opening It is similar to that for a maxillary central incisor, but is smaller and

usually more ovoid.

Except a No 2 round bur may be used instead of a No 4.

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MORPHOLOGY AND ACCESS CAVITY

PREPARATION FOR MAXILLARY CANINE



Average age of calcification-: 13-15Years Average tooth length-: 27mm



M-D of crown-: 7.5mm M-D of crown at cervix-: 5.5mm



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Pulp chamber

It has the largest pulp chamber than any single rooted tooth.

Labio-palatally triangular in shape, apex is toward the singlecusp and base toward the cervical third of crown.

Mesio-distally it is narrower and may resemble like flame.

In cross-section it is ovoid in shape, with greater diameterlabio-palatally.

Only one pulp horn is present.

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Root and root canal

Single root canal of maxillary cuspid is larger than that of

maxillary incisor.

It is wider labio-palatally than its mesio-distal diameter, and on

reaching middle third, it taper gradually to an apical constriction.

In cross-section, root canal is ovoid in the cervical and middle

third and generally round in the apical third

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INCIDENCE

Root

o Straight : 39%

o Distally curved : 32%

o Palatally curved : 7%

o Labially curved: 13%


Apical foramen

o Centrally located in anatomic apex :14%

o Apical delta : 3%

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Anatomic relationship in situ The root of maxillary cuspid is positioned in the cancellous bone of the maxilla

between the nasal cavity and the maxillary sinus, called the canine pillar.

It has an average of 6 degree disto-axial inclination and an average of 21 degreepalato-axial angulation in its alveolus.

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Access opening

External access outline form is oval or slot shaped because nomesial or distal pulp horn are present

Mesio-distal slope is determined by the mesio-distal width of pulpchamber.

Inciso-gingival diameter is determined via straight line access factorand removal of the lingual shoulder.

Incisal extension is approached with in 2-3 mm of the incisaledge to allow for straight line access.

All internal walls funnel to the orifice.

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MORPHOLOGY AND ACCESS CAVITYPREPARATION FOR MAXILLARY 1ST PREMOLARDevelopmental and anatomic data


Average age of calcification-: 12-13YearsAverage tooth length-: 22.5mmAverage crown length-: 8.5mmAverage root length-: 14mm

M-D of crown-: 7mmM-D of crown at cervix-: 5mm Labio-lingual diameter of crown-: 9mm Labio-lingual diameter at cervix-: 8mm

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Pulp chamber

It is narrow M-D, wider bucco-palatally.

The buccal pulp horn is more prominent than the palatal in youngtooth.

The floor of the pulp chamber is convex usually with two canal orifices

with one buccal and other palatal, it lies deep in the coronal third of theroot.

The roof of the pulp chamber is coronal to the cervical line.

Root and root canal

It may have one, two, or three roots and canals.

It most often has two roots namely buccal and palatal. The roots are considerably shorter and thinner than the canine. The palatal orifice is slightly larger than buccal orifice. In the cross-section at the CEJ, the palatal orifice is wider bucco-lingually

and kidney shaped because of the mesial concavity.

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Anatomic relationship in situ

The tooth lies in the alveolar socket below the maxillary sinus and is separatedfrom it by a thin layer of spongy and compact bone. It has an average of 10 degree of disto-axial inclination with average of 6 degree

of bucco-axial angulation in its alveolus

INCIDENCE

Root( Single rooted)

o Straight : 38.4%

o Distally curved : 36.8%

o Buccally curved : 14.4%

o Palatally curved: 2.4%o S-shaped or bayonet curved: 8%

Apical foramen


o Apical delta : 3%

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Double Rooted Teeth Buccal Root

o Straight : 27.8%


o Buccally curved : 14%

o Palatally curved: 36.2%

o S-shaped or bayonet curved:

8%

Apical foramen

o Centrally located in anatomic

apex : 12%

o Apical delta : 3.2%

Palatal Root

o Straight : 44.4%


o Buccally curved : 27.8%

o Palatally curved: 8.3%

o S-shaped or bayonet curved:

5.5%

Apical foramen


apex : 12%


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Access opening The diagnostic radiograph is used for measuring the shape and

extension of the pulp chamber mesially, distally and coronally.

The access preparation is oval or slot shaped.

It is also wide bucco-lingually, narrow mesio-distally and centeredmesio-distally between the cusp tips.

Using a No 2 round bur in a high speed contra angle onepenetrates the enamel in the center of the occlusal surface andthe bur is directed into the long axis of the tooth.

Than a No 2 round carbide bur in a slow speed contra angle, alignin the long axis of the tooth is used to penetrate through thedentin into the pulp chamber.

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Using the radiographic measurement, one penetrate deep enough

to remove the roof of the pulp chamber without cutting into thechamber floor.

To remove the roof of the pulp chamber, one should place the buralong the side of walls of the chamber and cut occlusally.

A tapered cylinder, self limiting diamond in slow speed contraangle is used to remove the remaining roof of the pulp chamber.

The walls of the cavity are smoothened and sloped slightly to theocclusal surface.

The divergence of the access cavity creates a positive seal for thetemporary filling such as cavity.

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The border of the ovoid access cavity should not exceed beyond

half the lingual inclined of the facial cusp and half the facial inclineof the palatal cusp.

Any loose debris is removed by irrigating the access cavity with5.2% sodiumhypochlorite solution.

Excess solution is removed by suction with 2 x 2 gauge. The anatomic dark lines in the pulpal floor should be examined

with an endodontic explorer.

The orifice of the buccal canal lies beneath the buccal cusp andthe orifices of the palatal canal lies beneath the palatal cusp.

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Schematic representation

of three canal access

preparation.


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MORPHOLOGY AND ACCESS CAVITYPREPARATION FOR MAXILLARY 2ND PREMOLARDevelopmental and anatomic data


Average age of calcification-: 12-14YearsAverage tooth length-: 22.5mmAverage crown length-: 8.5mmAverage root length-: 14mm

M-D of crown-: 7mmM-D of crown at cervix-: 5mm Labio-lingual diameter of crown-: 9mm Labio-lingual diameter at cervix-: 8mm

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Pulp chamber

It is like maxillary 1st premolar

It is wider bucco-lingually than the maxillary 1st pre molar and

shows two pulp horn in this projection, a buccal and a palatal. In cross-section, the pulp chamber has a narrow ovoid shape.

Root and root canal

Single rooted tooth but may be two or three root and canal .

The majority of canal may be curved. They may be curved distally, buccally, palatally or bucco-palatally.

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INCIDENCERoot (single root 90.3%)

o Straight : 37.4%

o Distally curved : 33.9%

o Buccally curved : 15.7%o Palatally curved: 2.4%


Apical foramen



Only 2% have two well developed root.

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Access cavity preparation

Nearly identical to 1st maxillary premolar. If three canals are present, the external access outline form are

triangular in shape.

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MORPHOLOGY AND ACCESS CAVITYPREPARATION FOR MAXILLARY 1ST MOLAR



Average age of calcification-: 9-10Years

Average tooth length-: 20.8mm


Average root length-: 12mm(b) 13mm(p)

M-D of crown-: 10mm

M-D of crown at cervix-: 8mm


Labio-lingual diameter at cervix-:10mm 32


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Pulp chamber

It has four pulp horns m-b, d-b, m-p, d-p, the arrangement of thefour pulp horn gives the pulpal roof of a rhomboidal shape in

cross-section. The four walls forming the roof converge towards the floor where

the lingual wall almost disappear.

The floor of the pulp chamber thus has a triangular form in cross-section.

The orifices of the root canal are located in the three angles ofthe floor.

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Palatal orifice is the largest, round or oval in

shape and easily accessible for exploration.

The mesio-buccal orifice is under the mesio-buccal is long bucco-palatally.

The mesio-buccal orifice is located by insinuating the tip of long

shank explorer. The disto-buccal orifice is located slightly distal and palatal to the

mesio-buccal orifice and is accessible from the mesial forexploration.

The floor of the pulp chamber in the cervical third of the root andthe roof is in cervical third of crown.

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Root and root canal

It has three root with usually 3 canal situated mesio-buccally,

disto-buccally, palatally.

Mesio-buccal root

It is broad in the bucco-palatal direction.

Majority of the m-b roots have a distal curve and some are s

shaped or bayonet shaped.

It has one root and one canal, it is narrowest of the 3 canals,

flattened in a m-d direction in the orifice, but round in the apicalthird.

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Disto-buccal root

It is small and is more or less round in shape. It may be straight (54%), distally curved mesial curve or s

shaped.

It is a narrow, tapering canal sometimes flattened in a mesiodistal direction , but generally cone shaped.

Palatal root It has larger diameter and is the longest root of the maxillary 1st

molar.

It may be straight, curved buccally, mesially or distally.

Root may curve in the apical third toward buccal side.

The palatal canal is ovoid m-d and tapers toward apex.

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INCIDENCE Mesio-buccal Root

o Straight : 21%



o S-shaped or bayonet curved:1%

Apical foramen


apex : 14%

Disto-buccal Root

o Straight : 54%


o Mesial curved : 20%

o S-shaped or bayonet curved:10%

Apical foramen


apex : 19%

o Apical delta : 2%

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Palatal Rooto Straight : 40%


o Mesial curved : 4%

o Buccally curved: 55%

Apical foramen


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Access opening Radiograph is used to determine the shape and size as well as

the extension of the pulp chamber mesially, distally andcoronally.

The enamel is penetrated with No 4 round carbide bur in ahigh speed contra angle by positioning the instrument in thecentral fossa and angling it toward palatal root.

After penetration of the enamel No 4 round carbide bur inslow speed is used in a slow speed contra angle to penetratedentin.

The bur is angled toward the palatal root until the pulpchamber is reached.

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A drop of the bur into the pulp chamber may be felt if thechamber becomes large.

The internal anatomy of the pulp chamber guides the occlusalcutting.

A tapered cylinder self limiting diamond in a slow speed contraangle is used to remove the remaining roof of the pulp chamber.

The walls of the access cavity should be in good confluence withthe walls of pulp chamber and should be slightly divergent to theocclusal surface.

The access opening should be triangular for permitting directaccess to the root canal orifice.

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Any loose debris is removed by irrigating the access cavity with

5.2% sodiumhypochlorite solution. Excess solution is removed by suction with 2 x 2 gauge.

The anatomic dark lines in the pulpal floor should be examinedwith an endodontic explorer.

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MORPHOLOGY AND ACCESS CAVITYPREPARATION FOR MAXILLARY 2ND MOLARDevelopmental and anatomic data




Average root length-: 11mm(b) 12mm(p)

M-D of crown-: 9mm M-D of crown at cervix-: 7mm


Labio-lingual diameter at cervix-:10mm44


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Pulp chamber Similar to maxillary 1st molar, except it is narrower m-d.

It is rhomboidal in shape.

The roof of the pulp chamber is more rhomboidal in cross-

section, The floor of the pulp chamber is an obtuse triangle in cross-

section.

The mesio-buccal and disto-buccal root canal are closer togetherand appear to have a common opening.

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Root and root canal It has usually one canal in each root however , it may have two or

three mesio-buccal canal, one or two disto-buccal canal, or twopalatal canal.

The three main orifice ( M-B, D-B, P) usually form a flat triangleand sometimes a straight line.

The mesio-buccal canal orifice is located to the buccal and mesialthan 1st molar.

Disto-buccal orifice approaches the mid point between the m-b

and palatal orifice Palatal orifice usually located at the most palatal aspect of the

root.

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Floor of the pulp chamber is convex which gives the canal orificea slight funnel shape.

When four canal are present, access cavity preparation has arhomboid shape, if three canal are present, it is a roundedtriangle with the base placed buccally.

If two canal are present the access outline form is oval andwidest bucco-lingually.

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INCIDENCE Mesio-buccal Rooto Straight : 22%

o Distally curved : usually

Apical foramen


o Apical delta : 3%

Distal Rooto Straight : usually

o Mesially curved : 17%

Apical foramen


o Apical delta : 3%

Palatal Rooto Straight : usually


Apical foramen

o Centrally located in anatomicapex : 16%

o Apical delta : 3%

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Access cavity preparation

Same as 1st molar.

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MORPHOLOGY AND ACCESS CAVITYPREPARATION FOR MAXILLARY 3RD MOLARDevelopmental and anatomic data





M-D of crown-: 8.5mm M-D of crown at cervix-: 6.5mm


Labio-lingual diameter at cervix-:9.5mm51


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It is considered as a strategic abutment after loss

of maxillary 1st and 2nd molars.

Pulp chamber

Anatomic resemblance to maxillary 2nd molar.

It may also have an odd shaped pulp chamber with four or fiveroot canal orifice.

Conical chamber with only one root canal.

Roots and root canal

Three well developed roots, fused root, one conical root or fouror more independent roots.

Root may be straight, curved or dilacerated.

One may find a C shaped pulp chamber with a C shaped rootcanal.

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a cess cavity preparation

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