Access cavity preparation

Seminar On-: Access Cavity PreparationSubmitted To-:Dr Anurag Singhal Submitted By-:Dr Anurag Gurtu Kapil Yadav(25)Dr Naveen Chhabra Shailendra Singh(44)Dr Raju Chauhan 1

ACCESS CAVITY PREPARATION

INTRODUCTIONThe major factor involved in the development ofthe apical periodontitis are loss of integrity ofcoronal tooth substance and the entry ofmicroorganisms into the dentine and pulpspace.The chemo-mechanical removal ofmicroorganisms, their substrate and products formthe dentine and pulp space is primary aim of rootcanal treatment, with the second being the threedimensional obliteration and sealing of the pulpspace to prevent bacterial recontamination. 3

A clear understanding of the anatomy of humanteeth becomes an essential prerequisite forachieving the objectives of access, throughcleaning, disinfection, and obturation of the pulpspace.in this seminar we have tried to describe theaccess opening of the teeth. 4

• The access cavity preparation generally refers to the part of the cavity from the occlusion table to the canal orifice. (according to Stephen 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. 5

• 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.GUIDELINESIt is essential for the completion of ideal accesspreparation.7. Visualization of internal anatomy because internal anatomy dictates access shape. This require evaluation of angled peri-apical radiograph, examination of coronal and cervical tooth anatomy. 6

2. Evaluation of CEJ and occlusal anatomy.traditionally, access cavity is prepared in relationto the occlusal anatomy. CEJ is the mostimportant anatomical landmark for determiningthe location of pulp chamber and rootcanal orifice. 7

According to Krasner and Rankow, five guidelinesor laws, of pulp chamber anatomy to helpclinicians determine the number and location oforifices on the chamber floor First Law of Symmetry It states that except for the maxillary molars, canal orifices are equidistant from a line drawn in mesio-distal direction through the pulp chamber floor. Second Law of Symmetry It state that except for the maxillary molars, canal orifices lie on line perpendicular to a line drawn in a mesio-distal direction across the center of the pulp chamber floor 8

 First Law of Orifice Location It states that the orifices of the root canal are always located at the junction of the walls and the floor. Second Law of Orifice Location It states that the orifices of the root canals are always located at the angles in the floor-walls junction. Third Law of Orifice Location It states that the orifices of the root canals are always located at the terminus of the roots developmental fusion lines. Law of Color Change It states that the pulp chamber floor is always darker in color than the walls. 10

3. Preparation of the access cavity is throughlingual in anterior teeth and on the posterior teeththrough occlusal surface.4. Removal of unsupported tooth structure.Thisreduce the tooths resistance to stress.5. Creation of access cavity walls. So thatsufficient tooth structure must be removed toallow instrument to be placed in a straight lineand easily into canal orifice. 11

6. Location, flaring and exploration of all root canals orifices. A sharp endodontic explorer used to locate the canal 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 determining the location of canal, curved and calcified canal and debriding and removing tissue from the pulp chamber. 12

8.Tapering of cavity walls and evaluation of space adequacy for a coronal seal. A proper access cavity has tapering walls and is widest at occlusal surface. At least 3.5 mm of temporary filling material is needed to provide an adequate coronal seal for a short period. 13

ANATOMY OF THE PULP CAVITY Pulp cavity is the central cavity within the tooth and is entirely enclosed by dentin except at the apical foramen. Pulp cavity may be divided into a coronal portion, pulp chamber, radicular portion and root canal. In anterior teeth the pulp chamber gradually merges into root canal. In multirooted teeth, the pulp cavity consists of a single pulp chamber and usually three root canal. 14

 A pulp horn is an accentuation of the roof of the pulp chamber directly under a cusp or developmental lobe. Orifices are continuation with both pulp chamber and root canal. A root canal may be divided into three sections namely coronal, middle, apical third. Accessory canal or lateral canal is a lateral branch of main root canal, generally occur in the apical third or furcation area of a root. 15

 In most cases number of root canal depends upon the number of roots of the tooth. In young age, apical foramen is funnel shaped in a incompletely developed teeth. With the development of the root, the apical foramen becomes narrower. The shape and size of pulp cavity is influenced by age. In young people, pulp chamber is large and with increase of age, it gets smaller. 17

The root canal system is highly complex andcanal may branch, divide and rejoin.Vertucci et al identified and classified eight pulpspace configuration which are following as -: Type I : A single canal extends from the pulp chamber to the apex. Type II : Two seprate canal leaves the pulp chamber and join short of the apex to form canal. Type III : One canal leaves the pulp chamber and divides into two in the root: the two then merge to exit as one canal. 18

 Type IV : Two separate, distinct canals extend from the pulp chamber to the apex. Type V : One canal leaves the pulp chamber and divides and divides short of the apex into two separate, distinct canals with separate apical foramina. 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. Type VII : One canal leaves the pulp chamber, divides and then rejoins in the body of root, and finally redivides into two distinct canals short of the apex. 19

 Type VIII : Three separate, distinct canals extend from the pulp chamber to the apex. 20

Access Cavity PreparationsAnterior access cavity preparationsMany of the same steps are used in similar toothtypes to prepare an access cavity.The following discussion outlines the steps formaxillary and mandibular anterior teeth.1. Removal of Caries and Permanent Restorations Caries is typically removed early, before the pulp chamber is entered. This minimizes the risk of contamination of the pulp chamber or root canal with bacteria. 22

 Removal of defective permanent restorations also permits straight line access and prevents the restorative fragments from becoming lodged in the root canal system. If recurrent decay is detected or suspected, the permanent restoration must be removed entirely to prevent coronal contamination of pulp chamber.2. Initial External Outline Form Once caries and restoration have addressed, the clinician create an initial external outline opening on the lingual surface of the anterior teeth 23

 For an intact tooth, the clinician should begin in the center of lingual surface of anatomic crown. No 2 or 4 round bur or tapered fissure bur is used to penetrate the enamel and slightly into the dentine with a high speed hand piece. 24

 The bur is directed perpendicular to the lingual surface as the external outline opening is created.3. Penetration of the Pulp Chamber Roof Penetration of the pulp chamber roof is continuing with the same round or tapered fissure bur, we change the angle of the bur from perpendicular to the lingual surface to parallel to the long axis of the tooth. Penetration into the tooth is accomplished along this roots long axis until the roof of the pulp chamber is penetrated, frequently a drop- in effect is felt when the penetration occurs. 25

Complete Roof Removal Once the pulp chamber has been penetrated, the remaining roof is removed by catching the end of a round bur under the lip of the dentin roof and cutting on the bur ‘s removal stroke. Each tooth has a unique pulp chamber anatomy, working in this manner allow the internal pulp anatomy to dictate the external outline form of the access opening. In vital cases pulp tissue hemorrhage can impair the clinician”s ability to see the internal anatomy. In such cases, as soon as enough roof has been removed to allow instrument access, 26

 The coronal pulp should be amputated at the orifice level an endodontic spoon or round bur and the chamber irrigated copiously with sodium hypo chlorite. After hemorrhage has been controlled, allowing visibility, all of the pulp chamber roof, with pulp horns, must be removed and all internal walls must be flared to lingual surface of the tooth. 27

Identification of All Canal Orifices After the pulp chamber has been unroofed, the canal orifice are located with an endodontic explorer Positioning the explorer in an orifices allows the clinician to check the shaft for clearance from the axial walls an d determine the angle at which a canal depart the main chamber.Removal of lingual shoulder, orifice and coronalflaring Once the orifice has been identified, the lingual shoulder is removed. Lingual Shoulder-: this is the lingual shelf of dentin that extends from the cingulum to a point approximately 2mm apical to the orifice. 28

Straight line access determination After the lingual shoulder has been removed and the orifice, the clinician must determine whether straight line has been achieved. Ideally, an endodontic file can approach the apical foramen or the first point of the canal curvature.Visual inspection of the access cavity The clinician should inspect and evaluate the access cavity using appropriate magnification and illumination. 29

Refinement and smoothing of restorating margins The final step in the preparation of an access cavity is to refine and smooth cavosurface margin. Rough margins can cause of coronal leakage. Proper restorative margins are important because anterior teeth may not require a crown as a final restoration 30

Posterior Access Cavity Preparation The process of preparing access cavity on posterior teeth is similar to that for anterior teeth, but enough difference exists to warrant a separate discussion.Removal of caries and permanent restoration Same as anterior teeth but in posterior teeth, the root canal therapy require a typically have been heavily restored or carious process is extensive. Such conditions, along with the complex pulp anatomy of the posterior teeth, can make access process challenging. 31

Initial external outline form The pulp chamber of posterior teeth is positioned in the center of the tooth at the level of CEJ. An access starting location must be determined for an intact tooth. 32

 In maxillary premolar this point is on the central groove between the cusp tip. In mandibular 1st premolar the starting location is half way up the lingual incline of the buccal cusp on the line connecting the cusp tip. In mandibular 2nd premolar the starting location is one third the way up lingual incline of the buccal cusp on a line connecting the buccal cusp tip and lingual groove between the lingual cusp. In maxillary and mandibular molar the starting location is limit with mesial and distal boundary. The mesial boundary for both molar is a line connecting the mesial cusp tip. 33

 The distal boundary for both molar is a line connecting the buccal and lingual groove. Penetration through the enamel into the dentin is performed using a No 2 round bur for premolar and No 4 round bur for molar. The bur is directed perpendicular to the occlusal table and initial outline shape is created. The premolar and maxillary molar outline shape is oval and widest in bucco-lingual dimension and mesiodistal direction is widest in mandibular molar. The final outline shape of molar is triangular or rhomboidal. 35

Penetration of pulp chamber roof Continuing with a same round or tapered fissure bur and angle of bur is changed same as anterior teeth. In case of premolar the direction of penetration angle is towards the mesio-distal and bucco- lingual and in case of molar it is towards the largest canal because pulp chamber space is usually largest just occlusal to the orifice of this canal. 37

Complete Roof Removal Round or tapered fissure bur is passed between the orifices along the axial walls to remove the roof of pulp chamber with pulp horns and create the desired external ouline shape simultaneously.Identification of all Canal Orifices Ideally the orifices are located at the corner of the final preparations to facilitate the shaping and cleaning process. 38

Removal of the Cervical Dentin bulge and Orificesand Coronal flaring The cervical dentine bulge are shelves of dentin that overhang orifices in posterior teeth. These bulge can be removed with carbide bur or Gates-Glidden burs. 39

 After this the orifices and the coronal portion of the canal can be flared with Gates-Glidden bur, which are used in sweeping upward portion with lateral pressure away from the furcation.Straight Line Access preparation It is paramount to successful shaping. Files must have unimpeded access to the apical foramen or the first point of canal curvature. 40

Visual inspection of the pulp chamber floorSame as anterior access cavity preparations.Refinement and smoothing of the restorativeMarginsThe restorative margins are refined and smoothed to minimize the potential of coronal leakage. 41

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR 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 42

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 mammelons in 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 in middle and apical third. 43

INCIDENCERooto 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% 45

Anatomic relationship in situ Labial surface of the root lies under the labial cortical plate of the maxilla and may fuse with it. It has an average of 2 degree of mesio-axial inclination and 29 degree of palato-axial angulations in its alveolus.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 angle perpendicular to it, with a 46

number 4 round bur in high speed contra-angle. After penetration of the enamel, a No 4 carbide bur in a slow speed contra-angle 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 lingual surface of the pulp chamber is removed with a No 4 round bur in a slow speed contra-angle by working from inside to outside following internal anatomy. 47

 The lingual extension of the pulp chamber, with a “straight line” penetration to the apical root canal. Direct access can be verified by placing a straight end of the endodontic explorer in the canal orifice. The access shape is slightly triangular, with the base of the triangle to the incisal edge. 48

Anatomic alteration in pulp The usual anatomic structure of the chamber in the root canal may be altered in any tooth due to deposition of reparative or secondary dentin. This alteration in anatomy may be due to trauma, caries, restorative procedure, aging.To escape this alteration we can use No 2 roundcarbide bur. Enlarge the enamel portion of the access cavity to an ovoid shape, with greatest diameter incisogingivally. 50

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MAXILLARY LATERAL INCISORMAXILLARY LATERAL INCISORDevelopmental 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 Labio-lingual diameter of crown-: 6mm Labio-lingual diameter at cervix-: 5mm 51

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 finer diameter than maxillary central incisor. In cross-section, the canal is ovoid labio- palataly in the cervical third and middle third, round in apical third. 52

INCIDENCERooto Straight : 30%o Distally curved : 53%o Mesially and palatally curved : 3%o Labial curved: 4%o “S-shaped” or bayonet curved: 6%Apical forameno Centrally located in anatomic apex : 22%o Apical delta : 3% 53

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. 54

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MAXILLARY CANINEDevelopmental and anatomic data Average time of eruption-: 10-12Years Average age of calcification-: 13-15Years Average tooth length-: 27mm Average crown length-: 10mm Average root length-: 17mm M-D of crown-: 7.5mm M-D of crown at cervix-: 5.5mm Labio-lingual diameter of crown-: 8mm Labio-lingual diameter at cervix-: 7mm 55

Pulp chamber It has the largest pulp chamber than any single rooted tooth. Labio-palatally triangular in shape, apex is toward the single cusp 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 diameter labio-palatally. Only one pulp horn is present. 56

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 57

INCIDENCERooto Straight : 39%o Distally curved : 32%o Palatally curved : 7%o Labially curved: 13%o “S-shaped” or bayonet curved: 7%Apical forameno Centrally located in anatomic apex : 14%o Apical delta : 3% 58

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 degree palato- axial angulation in its alveolus. 59

Access opening External access outline form is oval or slot shaped because no mesial or distal pulp horn are present Mesio-distal slope is determined by the mesio- distal width of pulp chamber. Inciso-gingival diameter is determined via straight line access factor and removal of the lingual shoulder. 60

 Incisal extension is approached with in 2-3 mm of the incisal edge to allow for straight line access. All internal walls funnel to the orifice. 61

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MAXILLARY 1ST PREMOLARDevelopmental and anatomic data Average time of eruption-: 10-11Years Average age of calcification-: 12-13Years Average tooth length-: 22.5mm Average crown length-: 8.5mm Average root length-: 14mm M-D of crown-: 7mm M-D of crown at cervix-: 5mm Labio-lingual diameter of crown-: 9mm Labio-lingual diameter at cervix-: 8mm 62

Pulp chamber It is narrow M-D, wider bucco-palatally. The buccal pulp horn is more prominent than the palatal in young tooth. 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 the root. 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. 63

 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.Anatomic relationship in situ The tooth lies in the alveolar socket below the maxillary sinus and is separated from 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 64

INCIDENCERoot( 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 forameno Centrally located in anatomic apex : 14%o Apical delta : 3% 65

Double Rooted Teeth• Buccal Root • Palatal Rooto Straight : 27.8% o Straight : 44.4%o Distally curved : 14% o Distally curved : 14%o Buccally curved : 14% o Buccally curved : 27.8%o Palatally curved: 36.2% o Palatally curved: 8.3%o “S-shaped” or bayonet o “S-shaped” or bayonet curved: 8% curved: 5.5%Apical foramen Apical forameno Centrally located in o Centrally located in anatomic apex : 12% anatomic apex : 12%o Apical delta : 3.2% o Apical delta : 3.2% 66

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 centered mesio-distally between the cusp tips. Using a No 2 round bur in a high speed contra angle one penetrates the enamel in the center of the occlusal surface and the bur is directed into the long axis of the tooth. Than a No 2 round carbide bur in a slow speed contra angle, align in the long axis of the tooth is used to penetrate through the dentin into the pulp chamber. 67

 Using the radiographic measurement, one penetrate deep enough to remove the roof of the pulp chamber without cutting into the chamber floor. To remove the roof of the pulp chamber, one should place the bur along the side of walls of the chamber and cut occlusally. A tapered cylinder, self limiting diamond in slow speed contra angle is used to remove the remaining roof of the pulp chamber. The walls of the cavity are smoothened and sloped slightly to the occlusal surface. The divergence of the access cavity creates a positive seal for the temporary filling such as cavity. 68

 The border of the ovoid access cavity should not exceed beyond half the lingual inclined of the facial cusp and half the facial incline of the palatal cusp. 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 examined with an endodontic explorer. The orifice of the buccal canal lies beneath the buccal cusp and the orifices of the palatal canal lies beneath the palatal cusp. 69

Schematicrepresentation of threecanal access preparation. 70

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MAXILLARY 2ND PREMOLARDevelopmental and anatomic data Average time of eruption-: 10-12Years Average age of calcification-: 12-14Years Average tooth length-: 22.5mm Average crown length-: 8.5mm Average root length-: 14mm M-D of crown-: 7mm M-D of crown at cervix-: 5mm Labio-lingual diameter of crown-: 9mm Labio-lingual diameter at cervix-: 8mm 71

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. 72

INCIDENCERoot (single root 90.3%)o Straight : 37.4%o Distally curved : 33.9%o Buccally curved : 15.7%o Palatally curved: 2.4%o “S-shaped” or bayonet curved: 13%Apical forameno Centrally located in anatomic apex : 12%o Apical delta : 3.2%Only 2% have two well developed root. 73

 A single root is oval and wider bucco-lingually than m-d. The canal remain oval from the pulp chamber floor and taper rapidly to the apex.Access cavity preparation Nearly identical to 1st maxillary premolar. If three canals are present, the external access outline form are triangular in shape. 74

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MAXILLARY 1ST MOLARDevelopmental and anatomic data Average time of eruption-: 6-7Years Average age of calcification-: 9-10Years Average tooth length-: 20.8mm Average crown length-: 7.5mm Average root length-: 12mm(b) 13mm(p) M-D of crown-: 10mm M-D of crown at cervix-: 8mm Labio-lingual diameter of crown-: 11mm Labio-lingual diameter at cervix-: 10mm 75

Pulp chamber It has four pulp horns m-b, d-b, m-p, d-p, the arrangement of the four 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 of the floor. 76

 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 for exploration. The floor of the pulp chamber in the cervical third of the root and the roof is in cervical third of crown. 77

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 apical third. 79

 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 mesio –distal 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. 80

INCIDENCE• Mesio-buccal Root • Disto-buccal Rooto Straight : 21% o Straight : 54%o Distally curved : 78% o Distally curved : 17%o Buccally curved : 14% o Mesial curved : 20%o “S-shaped” or bayonet o “S-shaped” or bayonet curved: 1% curved: 10%Apical foramen Apical forameno Centrally located in o Centrally located in anatomic apex : 14% anatomic apex : 19% o Apical delta : 2% 81

• Palatal Rooto Straight : 40%o Distally curved : 1%o Mesial curved : 4%o Buccally curved: 55%Apical forameno Centrally located in anatomic apex : 18% 82

Access opening Radiograph is used to determine the shape and size as well as the extension of the pulp chamber mesially, distally and coronally. The enamel is penetrated with No 4 round carbide bur in a high speed contra angle by positioning the instrument in the central fossa and angling it toward palatal root. After penetration of the enamel No 4 round carbide bur in slow speed is used in a slow speed contra angle to penetrate dentin. The bur is angled toward the palatal root until the pulp chamber is reached. 83

 A “drop” of the bur into the pulp chamber may be felt if the chamber becomes large. The internal anatomy of the pulp chamber guides the occlusal cutting. A tapered cylinder self limiting diamond in a slow speed contra angle is used to remove the remaining roof of the pulp chamber. The walls of the access cavity should be in good confluence with the walls of pulp chamber and should be slightly divergent to the occlusal surface. The access opening should be triangular for permitting direct access to the root canal orifice. 85

 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 examined with an endodontic explorer. 86

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MAXILLARY 2ND MOLARDevelopmental and anatomic data Average time of eruption-: 11-13Years Average age of calcification-: 14-16Years Average tooth length-: 19mm Average crown length-: 7mm Average root length-: 11mm(b) 12mm(p) M-D of crown-: 9mm M-D of crown at cervix-: 7mm Labio-lingual diameter of crown-: 11mm Labio-lingual diameter at cervix-: 10mm 87

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 together and appear to have a common opening. 89

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 two palatal canal. The three main orifice ( M-B, D-B, P) usually form a flat triangle and sometimes a straight line. The mesio-buccal canal orifice is located to the buccal and mesial than 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. 90

 Floor of the pulp chamber is convex which gives the canal orifice a slight funnel shape. When four canal are present, access cavity preparation has a rhomboid shape, if three canal are present, it is a rounded triangle with the base placed buccally. If two canal are present the access outline form is oval and widest bucco-lingually. 91

INCIDENCE• Mesio-buccal Root • Palatal Rooto Straight : 22% o Straight : usuallyo Distally curved : usually o Buccally curved : 37%Apical foramen Apical forameno Centrally located in o Centrally located in anatomic apex : 16% anatomic apex : 16%o Apical delta : 3% o Apical delta : 3%Distal Rooto Straight : usuallyo Mesially curved : 17%Apical forameno Centrally located in anatomic apex : 16%o Apical delta : 3% 92

Access cavity preparation Same as 1st molar. 93

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MAXILLARY 3RD MOLARDevelopmental and anatomic data Average time of eruption-: 17-22Years Average age of calcification-: 18-25Years Average tooth length-: 17mm Average crown length-: 6.5mm Average root length-: 11mm M-D of crown-: 8.5mm M-D of crown at cervix-: 6.5mm Labio-lingual diameter of crown-: 10mm Labio-lingual diameter at cervix-: 9.5mm 94

It is considered as a strategic abutment after lossof 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 five root canal orifice. Conical chamber with only one root canal.Roots and root canal Three well developed roots, fused root, one conical root or four or more independent roots. Root may be straight, curved or dilacerated. One may find a “C shaped” pulp chamber with a “C shaped root canal. 96

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MANDIBULAR CENTRAL INCISORDevelopmental and anatomic data Average time of eruption-: 6-7Years Average age of calcification-: 9Years Average tooth length-: 22mm Average crown length-: 9.5mm Average root length-: 12.5mm M-D of crown-: 5mm M-D of crown at cervix-: 3.5mm Labio-lingual diameter of crown-: 6mm Labio-lingual diameter at cervix-: 5.3mm 97

Pulp chamber It is small and flat m-d. Three distinct pulp horns present. Pulp chamber is wide and ovoid labio-lingually and it tapers incisally.Root and root canals It has one root which is flat and narrow mesio- distally but wide labio-lingually. It may have a distal labial curvature. Canal is broad and cervical of middle third of root in labio-lingual aspect, tapers toward apex. Canal is ovoid in labio-lingual direction in the cervical third of root. 98

INCIDENCERooto Straight : 60%o Distally curved : 23%o Labially curved: 13%Apical forameno Centrally located in anatomic apex : 25%o Apical delta : 5% 99

 It is ribbon shaped in labio-lingual direction in middle third and round in the apical third. Apical foramen is central in root in 25%cases.Anatomic relation in situ Average of 2 degree of m-d inclination of average of 20 degree linguo-axial of tooth in its alveolus.Access opening Same as maxillary anterior teeth. 100

Mandibular lateral incisor 101

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MANDIBULAR LATERAL INCISORDevelopmental and anatomic data Average time of eruption-: 7-8Years Average age of calcification-: 10Years Average tooth length-: 23.5mm Average crown length-: 9.5mm Average root length-: 14mm M-D of crown-: 5.5mm M-D of crown at cervix-: 4mm Labio-lingual diameter of crown-: 6.5mm Labio-lingual diameter at cervix-: 5.8mm 102

Pulp chambers Same as mandibular central incisor but it has larger dimension.Root and root canal Larger than mandibular central incisor. Majority of root are straight. It may also have distally , labially curved root as central incisor but the distal curve is sharper.Anatomic relation in situ Average 17 degree of mesio-axial inclination of 20 degree of linguo-axial angulations of tooth in its alveolus. 103

INCIDENCESame as mandibular central incisor except apicalforamen which is located centrally in 20% cases 104

Access opening Same as mandibular central incisor 105

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MANDIBULAR CANINEDevelopmental and anatomic data Average time of eruption-: 11-12Years Average age of calcification-: 13-15Years Average tooth length-: 27mm Average crown length-: 10mm Average root length-: 17mm M-D of crown-: 7.5mm M-D of crown at cervix-: 5.5mm Labio-lingual diameter of crown-: 8mm Labio-lingual diameter at cervix-: 7mm 106

Pulp chamber It is small and flat mesio-distally. Three distinct pulp horn are present. It is wide and ovoid m-d and tapering incisally.Root and root canal It is usually single rooted. It has straight root(68%) may have curved root(20%) Sometimes a “S shaped” bayonate shaped curve is also seen. It usually has a single canal and apical foramen. Root canal is broad in middle third and taper to constriction in the apical third in labio-lingual view. 107

INCIDENCERooto Mesially curved : 1%o Distally curved : 20%o Labially curved: 7%o “S-shaped” or bayonet curved: 2%Apical forameno Centrally located in anatomic apex : 30%o Apical delta : 8% 108

 In cross-section it is ovoid in middle third and round in apical third. Lateral canal are present in 30% casesAnatomic relation in situ Average of 13 degree of mesio-axial inclination of average of 15 degree of linguo-axial angulations of tooth in its alveolus.Access opening Similar to maxillary canine. 110

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MANDIBULAR 1st PREMOLARDevelopmental and anatomic data Average time of eruption-: 10-11Years Average age of calcification-: 12-13Years Average tooth length-: 24.5mm Average crown length-: 8.5mm Average root length-: 14mm M-D of crown-: 9mm M-D of crown at cervix-: 5mm Labio-lingual diameter of crown-: 9mm Labio-lingual diameter at cervix-: 8mm 111

Pulp chamber It is the transition tooth between anteriors and posteriors. The m-d width is narrow. Bucco-lingually the pulp chamber is wide with prominent buccal pulp horn that extend under a well-developed buccal cusp. In cross-section the chamber is ovoid with the greater diameter bucco lingually. Single canal is present. In young tooth a small lingual pulp horn is present in the prominent buccal cusp and smaller lingual cusp give the crown an 30 degree lingual tilt. 112

Root and root canal It has a short conical root which may divide in the apical third into 2 or 3 roots. Root is usually straight (48%) but may be curved also. One canal and and apical foramen is present. Canal is cone shaped and simple in outline. Root canal is m-d narrow and b-l broad and taper towards the apical third. In cross-section, the cervical and middle third are ovoid and apical third is conical. 114

INCIDENCERooto Buccally curved : 2%o Distally curved : 35%o Lingually curved: 7%o “S-shaped” or bayonet curved: 7%o Straight : 48%Apical forameno Centrally located in anatomic apex : 15% 115

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MANDIBULAR 2ND PREMOLARDevelopmental and anatomic data Average time of eruption-: 10-12Years Average age of calcification-: 12-14Years Average tooth length-: 24.5mm Average crown length-: 8.5mm Average root length-: 14mm M-D of crown-: 7mm M-D of crown at cervix-: 5mm Labio-lingual diameter of crown-: 9mm Labio-lingual diameter at cervix-: 8mm 116

Pulp chamber Same as mandibular 1st premolar. Lingual pulp horn is more prominent under well developed lingual cusp.Root and root canal Single root but rarely two or three roots. Root is wider bucco-lingually than the counter tooth. It may curve distally9(40%) and curve(30%). Single canal is present. Lateral canal in (48.3%) cases. 117

INCIDENCERooto Buccally curved : 10%o Distally curved : 40%o Lingually curved: 3%o “S-shaped” or bayonet curved: 7%o Straight : 39%Apical forameno Centrally located in anatomic apex : 60.1% 118

Anatomic relation in situ Similar to mandibular 1st premolar. Average 10 degree of disto-axial inclination of root and average of 34 degree bucco-axial angulations of tooth in its alveolus.Access opening Same as mandibular 1st premolar. Enamel penetration is initiated in the central fossa . Ovoid access cavity is wider m-d and dictated by the wide pulp chamber. 120

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MANDIBULAR 1ST MOLARDevelopmental and anatomic data Average time of eruption-: 6-7Years Average age of calcification-: 9-10Years Average tooth length-: 21.5mm Average crown length-: 7.5mm Average root length-: 14mm M-D of crown-: 11mm M-D of crown at cervix-: 9mm Labio-lingual diameter of crown-: 10.5mm Labio-lingual diameter at cervix-: 9mm 121

Pulp chamber Roof of the pulp chamber is often rectangular. The mesial wall is straight and distal wall converge round. Buccal and lingual walls converge to meet mesial and distal wall to form a rhomboidal floor. The roof of the pulp chamber has four pulp horns m-b, m-l, d-b and d-l. The four pulp horns regress with age. The roof of the pulp chamber is located in cervical third of crown just above the cervix 122

 Floor is located in the cervical third of the root. Three distinct orifice are present in the pulpal floor m-b, m-l and distal. The m-b orifice is located under the m-b cusp and difficult to find. It can be penetrated by a long shank explorer. The mesiobuccal and the mesio-lingual orifice may be close under the mesio-buccal cusp. Distal orifice is oval in shape. The multiple orifice may be present in the distal root or are found in buccal and lingual portion of ovoid root canal. 124

Root and root canal Two roots mesial and distal. The roots are wide and flat, with a depression in the middle of the root b-l. Sometimes third root is present. Mesial root is curved distally. Distal root is straight. Three canals are usually present. Mesial root may have two canals and apical foramina. Distal root has one canal. In cross-section three canals are ovoid in cervical and middle third and round in apical third 125

INCIDENCE• Mesial Root • Distal Rooto Straight : 16% o Straight : 74%o Distally curved : 84% o Distally curved : 21%Apical foramen o Mesially curved : 5%o Centrally located in Apical foramen anatomic apex : 22% o Centrally located ino Apical delta : 10% anatomic apex : 20% o Apical delta : 14% In 5.3% cases a third root may be present which is either mesially or distally, 126

Anatomic relation in situ On average a 58 degree of bucco-axial inclination of roots in the alveolus.Access opening It follows the anatomy of the pulp chamber. The enamel and dentin are penetrated in central fosa. The bur is angled toward the distal root, where the pulp chamber is largest. It is trapezoidal in shape with round corners and rectangular if second distal canal is present. 127

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MANDIBULAR 2ND MOLARDevelopmental and anatomic data Average time of eruption-: 11-13Years Average age of calcification-: 14-15Years Average tooth length-: 20mm Average crown length-: 7mm Average root length-: 13mm M-D of crown-: 10mm M-D of crown at cervix-: 8mm Labio-lingual diameter of crown-: 10mm Labio-lingual diameter at cervix-: 9mm 128

Pulp chamber It is smaller than the mandibular 1st molar. Root canal orifice are small and close to each other.Root and root canal It has mesial and distal root. Rarely three rooted. In the single rooted tooth root is straight but may curve distally, lingually it is “S shaped” or bayout shape In two rooted tooth mesial root curve distally, straight and “S shaped” buccally. 130

INCIDENCE• Mesial Root • Distal Rooto Straight : 27% o Straight : 58%o Distally curved : 61% o Distally curved : 18%o Buccally curved : 4% o Mesially curved : 10%o “S-shaped”: 7% o Buccally curved: 4%Apical foramen o “S-shaped: 6%o Centrally located in anatomic Apical foramen apex : 19% o Centrally located in anatomic apex : 21% In 27% cases a single root may be present and in 2% cases it is three rooted. 131

 Three root canal may be present. The mesial root has one canal and foramina. The distal root has one canal and foramina. In cross-section all three root canal are small and ovoid in cervical and middle third and round in the apical third.Anatomic relation in situ On average -52 degree of bucco axial inclination of the root in the alveolus.Access cavity preparation Same as 1st molar 133

MORPHOLOGY AND ACCESS CAVITY PREPARATION FOR MANDIBULAR 3RD MOLARDevelopmental and anatomic data Average time of eruption-: 17-21Years Average age of calcification-: 18-25Years Average tooth length-: 18mm Average crown length-: 7mm Average root length-: 11mm M-D of crown-: 10mm M-D of crown at cervix-: 7.5mm Labio-lingual diameter of crown-: 9.5mm Labio-lingual diameter at cervix-: 9mm 134

Pulp chamber It is similar to mandibular 1st and 2nd molars. It is large and has an anatomic configuration of a “c shaped” root canal orificeRoot and root canal Two roots with two canals are present. Three roots with three canals are generally large and short.Anatomic relation in situ The alveolar socket may project to the lingual plate of mandible. Apex of root is in close proximity of the mesio- distal canal 135

Access opening It is same as the mandibular 1st and 2nd molars 136

Errors in access cavity preparation• Poor access placement and inadequate mesial extension may lead to uncovered mesial orifice.• Inadequate extension of the distal access cavity may leave the d-b canal unexposed.• Gross over extension of the access cavity weakens the coronal tooth structure and compromises the final restoration. 137

• Failure to remove the roof of the pulp chamber may lead to pulp horn mistaken as canal orifice.• Overzealous tooth removal due to improper angulations of bur and failure to recognize the lingual inclination of the tooth.• Inadequate opening may lead to -: 1. Bur or file breakage 2. Coronal discoloration 3. Root perforation 4. Canal ledging 5. Apical transportation 139

• Furcation perforation leading to the weakening of the tooth and periodontal problems.• Common error in the teeth with full crown is perforation of the mesial surface due to the failure to recognize that tooth is tipped or recognize the alignment of bur along the long axis of tooth.• Entering the wrong tooth is a very serious error and may lead to the medico legal problems.• Any improper motion and excessive pressure may lead to bur and file breakage, broken fragments may lead to excessive tooth removal. 140

Conclusion• The aim of the access preparation is a good endodontic result and with restoration of normal structure and function of the tooth. 142

Access cavity preparation

by Ankita Varshney

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Access cavity preparation Presentation Transcript