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Endodontic cavity preparation


Endodontic cavity preparation

Endodontic cavity preparation

Published in Health & Medicine
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  • 1. Endodontic Cavity PreparationCareful cavity preparation and canal obturation . are the keystones to successful root canal. therapyApical moisture – proof seal, the first essential for . success, is not possible unless the space to befilled is carefully prepared and debrided to. receive the restorationEndodontic cavity preparation begins the instant . the involved tooth is approached with a cutting instrument, and the final obturation of thecanal space will depend on the care and. accuracy exercised in this initial preparation Ass.Prof.Dr.Mohamed ALsakkaf 1
  • 2. Divisions of Cavity PreparationFor descriptive convenience, endodontic cavity preparation may be separated into : two anatomic divisions.a. Coronal preparation.b. Radicular preparationIf one thinks of an endodontic preparation . as a continuum from enamel surface to apex, Blacks Principle of Cavity Preparation –Outline, convenience,retention, and resistance forms – may be .applied 2
  • 3. The entire length of the preparation is the .full outline form. In turn, this outline mayhave to be modified for the sake ofconvenience to accommodate canal. anatomy or curvature and/or instrumentsResistance must be developed at the apical .terminus of the preparation, the So –Called "apical stop", the barrier againstwhich virtually every canal filling must be.compacted 3
  • 4. Basic Coronal Instruments.Two handpieces are usually required.The ideal cutting instrument is the round – end. Carbide Fissure bur, with this instrument, enamel,resin, ceramic, or metal perforation is easily accomplished, and surface. extensions may be rapidly completedPrecious metal alloys can be cut with tungsten . . carbide burs 4
  • 5. Tapered instruments should never be forced, . but should be allowed to cut their own way with a light touch by the operator. If a tapered instrument is forced it will act as a wedge. This causes the enamel to "chech" .or "craze" and will weaken the toothIf a Porcelian Jacket Crown is to be entered, . a small diamond bur should be used. Again care must be exercised not to split the . Jacket by forcing the action 5
  • 6. penetration and minor surface extensions are complete, the high – speed handpiece is put aside, and the slow – speed with a round buris used. Three sizes of round burs No. 2, 4, 6, and two lengths, regular and surgical are routinely used.. The regular – length round bur in a conventional latch – type contra – angle handpice will "reach" 9.0mm from the nose 6
  • 7. The surgical – length bur will "reach" 14 or. 15mm and is necessary in some deep .preparationsThe round burs are for dentin removal in both . anterior and posterior teeth – these burs arefirst used to drill through the dentin and"drop" into the pulp chamber. The same buris then used in the removal of the roof of the. pulp chamberThe size of the round bur is made by estimating . the canal width and chamber size and depth .apparent in the initial radiograph 7
  • 8. The No.2 round bur is generally used in .preparing mandibular anterior teeth andmost maxillary premolar teeth with.narrow chambers and canalsThe No.4 round bur is generally used the .maxillary anterior teeth and mandibularpremolar teeth, and in "young" maxillarypremolars and "adults" molars in both . arches 8
  • 9. The No.6 round bur is used only in molars .. with large pulp chamberA No.1 round bur is used in the floor of the .pulp chamber to seek additional canal.orificesUltraSonic units with specially designed . endodontic tips, allow clinicians to moreprecisely remove dentin and expose.orifices 9
  • 10. As soon as the bulk of the overhanging dentin is . removed from the roof of the chamber, theLaw – speed round bur is put aside, and,once again the high – speed fissure bur is usedto finish and slope the side walls. EndozCarbide fissure bur is recommended. It is safe– ended and will not scar the pulpal floor.Moreover it is longer bleded (9mm) for .sloping the access cavityHigh – Speed burs should not be used topenetrate into, or initially enlarge, the pulpchamber unless the operator is skilled in .endodontic preparation 10
  • 11. Principles of Endodontic Cavity PreparationBy slightly modifying G.V. Black Principles . of Cavity Preparation, a list of principles of endodontic cavity preparation may be.establishedBlack G.V dealt with cavity preparation . limited to the crowns of teeth, however hisprinciples can be applied to radicular .preparations as well 11
  • 12. Endodontic preparations deal with both .coronal and radicular cohorts – eachprepared separately but ultimately flowing.together into a single preparationFor convenience of description, Blacksprinciples are therefore divided into the.following 12
  • 13. Endodontic Coronal Cavity Preparation .I. Outline Form .II. Convenience form III. Removal of the remaining carious dentin ). ( and defective restoration .IV. Toilet of the cavity 13
  • 14. Endodontic Radicular Cavity PreparationI. and II outline form and convenience form ). (continued).IV. Toilet of the cavity (continued .V. Retention Form .VI. Resistance Form 14
  • 15. Outline FormThe outline form of the endodontic cavity . must be correctly shaped, and positioned to establish complete access for instrumentation, from cavity margin to.apical foramenExternal outline form evolves from the . internal anatomy of the tooth established . by the pulp 15
  • 16. Because of this internal – external . relationship, endodontic preparationsmust of necessity be done in a reversemanner, from the inside of the tooth tothe outside. This means, the externaloutline form is established bymechanically projecting the internalanatomy of the pulp onto the external.surface 16
  • 17. This may be accomplished only by drilling into . the open space of the pulp chamber and thenworking with the bur from the inside of thetooth to the outside, cutting away the dentinof the pulpal floor and walls overhanging the .floor of the chamberIntracoronal preparation is contrasted to the . extracoronal preparation of operativedentistry, in which outline form is always .related to the external anatomy of the tooth 17
  • 18. Factors that govern Endodontic outline form:Size of pulp chamber. 1The outline form affected by the size of the pulp. chamber. In young patients, these preparations must be more extensive than in older patients, in whom the pulp has receded .and the pulp chamber is smallerIn youngsters teeth the root canals are larger, so. . they require larger instruments 18
  • 19. :Shape of pulp chamber. 2Final outline form should reflect the shape of .. the pulp chamberExamplea. The floor of the pulp chamber in a molar tooth is usually triangular in shape, owing to the triangular position of the orifices of the canals. This triangular shape is extended up the walls of the cavity and out onto theocclusal surface, so the final occlusal cavity .outline form is generally triangular 19
  • 20. b. The coronal pulp of a maxillary premolaris flat mesiodistally, but is elongated buccolingually. The outline form is, an elongated oval that extends buccolingually rather thanmesiodistally, as does Blacks operative .cavity preparation 20
  • 21. Number, position and carveture of the . 3. root canalsTo prepare each canal efficiently without . interference, the cavity walls often have to be extended to allow unstrained. instrument approach to apical foramen 21
  • 22. Self Study .Convenience form. 1III Principle (Removal of remaining. 2 (.carious dentin.IV Principle Toilet of the cavity. 3 22
  • 23. Endodontic Preparation Of Maxillary Anterior TeethA. Access opening is always gained through the lingual surface of all anterior teeth. Initial penetration is made in the exact center (X(.. Avoid intering the cavity too far gingivallyB. Enterance is prepared with a round – point tapering fissure bur in high – speed handpice, operated at a right angle to the long axis of thetooth. At this step only enamel is penetrated..Don’t apply any pressure 23
  • 24. C. Convenience extension toword the incisal continues the initial penetrating. Enamel and dentin are beveled toward the incial – Entrance into the pulp chamber should not be made with a high – speed. handpiceD. The outline is fanned incisally with a fissure bur, a "nest" is prepared in the dentin to receive the round bur to be. used in penetration 24
  • 25. E. A surgical – length No 2 or 4 round bur in low – speed is used to penetrate the pulp chamber. Take advantage of convenience extension toward the incisal to allow for the shaft of the bur, operated nearly . parallel to the long axisF. Working from inside the chamber to outside, a round bur is used to removethe lingual and labial walls of the pulp . chamber 25
  • 27. G. When the outline is completed, the surgical – length bur is carefully passed into the . canalWorking from inside to outside, the lingual"shoulder" is removed to providecontinuous, smooth – flowing penetration.Often a long, tapering diamond point bur to .be used for this purpose 27
  • 28. H. A No 1 or 2 round bur must be used laterally and incisally to eliminate pulpal horn debris (This will prevent future (. discolorationI. In a "young" tooth with a large pulp, the outline form reflects a large triangular internal anatomy – an extensive cavity that allows cleansing of the chamber as well as passage of large instruments.Extension incisally provides greater .access to the midline of the canal 28
  • 29. Cavity Access. CanineExtensive ovoid, funnel-shaped coronal preparation 29
  • 30. J. In "adult" teeth with the chamber obturated with secondary dentin, are avoid in shape. The difficalty is to reach to this depth with a round bur. Therefore, when the X – Ray revealsadvanced pulpal recession, convenienceextension must be advanced furtherincisally to allow the bur shaft to operate .in the central axis 30
  • 31. K. Final preparation with the reamer. The shaft clears the incisal cavity margin and reduced lingual "shoulder", providing good approach to the apical third of the canal. An optimal, round, tapered cavity. may be prepared in the apical third 31