If you continue browsing the site, you agree to the use of cookies on this website. Prophylactic odontotomy is no longer advocated as a preventive measure.42Enameloplasty and Prophylactic Odontotomy• BOX 4.2Initial Tooth Preparation StageFinal Tooth Preparation StageSteps of Tooth Preparation• BOX 4.3 Fundamental principles of Tooth Preparation prezi com. Simple tooth prep: 1 surface involved. No. e pulpal and axial caries removal of an advanced lesion should therefore extend to approximately 1 mm from the pulp with the recognition that dentin in this deep region may still be soft (soft dentin) to tactile sense. The number one dental title in the world, STURDEVANT'S ART & SCIENCE OF OPERATIVE DENTISTRY, is the book of choice for dental students and practitioners. In general, the appearance, restorative material to be used. Oper Dent 29:261–268, 2004.28. Fundamentals of cavity Preparation PDF docplayer net. 4.5 The external and internal walls (oors) for Class II tooth prepa-ration required to treat occlusal and mesioproximal caries lesions. Red arrowheads indicate the nuclei of the aspirated odontoblasts. e placement and orientation of the preparation walls are designed to resist fracture of the tooth or restorative material from masticatory forces principally directed parallel to the long axis of the tooth and to retain the restorative material in the tooth (except for a Class V preparation and Class III preparations with no component involving the occlusion).Occasionally, very narrow grooves or fossae (that do not penetrate to any great depth into enamel) at the periphery of the preparation prevent the creation of preparation margins that are clearly dened and easily restored. 4.17 A, Excessive drying (desiccation) of tooth preparations may cause odontoblasts to be aspirated into dentinal tubules. Scribd will begin operating the SlideShare business on December 1, 2020 When caries (or any defect) has com-, promised the DEJ, then associated supercial enamel becomes, minimum, oriented 90 degrees to the external surface of the enamel, so as to maintain a continuous connection with the essential, the preparation has full-length enamel rods buttr, enamel rods on the preparation side of the wall (. Severe vertical loss of structure associated with the line angles of the tooth may require the placement of metal pins. e extracoronal restoration generally reestablishes the anatomy of the crown of the tooth (clinical or anatomic crown, depending on whether any enamel is remaining) and is therefore termed a “crown.” e crown must extend well clinical crown knowing that the tooth has already been weakened from the carious loss of tooth structure. Objectives of Tooth Preparation  Remove all defects and provide necessary protection to the pulp. 4.14 Basic primary retention form in Class II tooth preparations for amalgam (A) with vertical external walls of proximal and occlusal por-tions converging occlusally and for inlay (B) with similar walls slightly diverging occlusally. erefore mastery of the techniques of optimal groove design and placement is indicated.Preparation Extensions. STURDEVANT'S ART AND SCIENCE OF OPERATIVE DENTISTRY - SOUTH ASIAN EDITION erefore routine use of medica-ments to occlude the dentinal tubules (i.e. J Am Dent Assoc 119:725, 1989.38. 4.1 and 4.2C). For example, preparation of a proximal caries lesion on a posterior tooth will frequently result in facial, lingual, and gingival walls that diverge proximally. e periphery of preparations for polycrystalline, (edges) of the planned restoration. e external line angle is the line angle whose apex points away from the tooth. Severe caries destruction may necessitate the extension of distal, mesial, facial, or lingual walls so as to gain adequate access to deeper areas of the preparation. Carious dentin that has had some mineral loss, but not to the point of collagen exposure, is not as clinically hard as normal dentin and is referred to as rm dentin. Tooth Prep Terminology. e outline form is designed, regardless of the type of tooth preparation, such that (1) all unsupported or weakened (friable) enamel is usually removed, (2) all faults are included, and (3) all preparation margins are usually placed in a position that allows inspection and nishing of the subsequent restoration margins. Fejerskov O, Nyvad B, Kidd E, editors: Dental caries: e disease and its clinical management, 3rd ed, Oxford, 2015, Wiley Blackwell.13. 4.1, a). Additionally, retention form may be slightly improved when opposing bevels are present. d, dentin; od, odontoblasts; p, pulp. However, this natural occlusion of the dentinal tubules only will occur beneath a slowly progressing caries lesion. 4.1 All enamel walls must consist of either full-length enamel rods on sound dentin (a) or full-length enamel rods on sound dentin supported on preparation side by shortened rods also on sound dentin (b). Diamond instruments are utilized to create the bevel so as to maximize the surface area for bonding. Likewise, the adjacent tooth contour may dictate specic preparation exten-sions that enable the creation of appropriate proximal restoration form. In addi-tion, weakened remaining tooth structure is retained and bonded to the amalgam instead of reduced and covered with amalgam. 4.15).When a preparation has extended onto the root surface (i.e., no enamel present), the root-surface cavosurface angle should be either 90 degrees (for amalgam, composite, or ceramic restorations) or beveled (for intracoronal cast-metal restorations). Hyatt TP: Prophylactic odontotomy: e ideal procedure in dentistry for children. Dent Mater 19:680–685, 2003.24. Polymeric restorative materials (e.g., composite resins) have no minimal thickness.When developing the outline form in Class I and II preparations, the end of the cutting instrument prepares a relatively horizontal pulpal wall of uniform depth into the tooth (i.e., the pulpal wall follows the original occlusal surface contours and the DEJ, which are approximately parallel; see Fig. 4.16).e design of the cavosurface angle depends on the restorative material being used.  Extend restoration as conservatively as possible. Biological principles of cavity preparation is important as well as the mechanical principles and aesthetic principles. Hansen EK, Asmussen E, Christiansen NC: In vivo fractures of endodontically treated posterior teeth restored with amalgam. e objective of this approach is to remove the caries lesion and leave the marginal ridge essentially intact. Careless, iatrogenic removal of healthy dentin further compromises the diseased tooth and must be avoided. Eur J Oral Sci 125:63–71, 2017.36. INITIAL TOOTH PREPARATION STAGE: Step 1: Outline form and initial depth Step 2: Primary resistance form Step 3: Primary retention form Step 4: Convenience form FINAL TOOTH PREPARATION STAGE: Step 5: Removal of any remaining infected dentin and/or old restorative material, if indicated Step 6: Pulp protection, if indicated Step 7: Secondary resistance and retention forms Step … Preservation of the marginal ridge in a strong state is questionable, especially since the dentinal support (essential for enamel durability under occlusal loading) of the marginal ridge is no longer present or is compromised. An even more durable wall conguration results when the preparation has full-length enamel rods buttressed by shorter enamel rods on the preparation side of the wall (Fig. When properly prepared, skirts provide additional, opposing vertical walls that increase retention of the restoration. Nevertheless, these exposures may be large enough to allow direct pulpal access for bacteria or other restorative materials. Frequently tooth preparation leaves much of the clinical crown surface uninvolved and is referred to as an intracoronal tooth preparation. Biological Principles of Tooth Preparation help in preserving the health and integrity of the remaining tooth structure, where the Principles of Tooth Preparation deal with obtaining the proper shape, retention, resistance form of the cavity for restoration. Features that enhance the retention form of a preparation also enhance the resistance form (e.g., slots or pins placed in a manner such that, upon completion of the restoration, the structural integrity of the restoration enhances the structural integrity of the remaining tooth structure).Use of Adhesives to Increase Retention and ResistanceSupercial demineralization of preparation walls and subsequent inltration of the altered surface with resin-based adhesives allows for increased retention and resistance of restorations. e more extensive the preparation, the greater the risk of iatrogenic damage of adjacent structures or restorations during procedures. erefore they are prone to fracture when occlusal loading causes material exure. When caries (or any defect) has com-promised the DEJ, then associated supercial enamel becomes prone to fracture under cyclic occlusal loading. e amalgam is condensed into this adhesive material before polymerization, and a mechanical bond develops between the amalgam and adhesive. J Oral Rehab 39:301–318, 2012.30. Charbeneau GT, Peyton FA: Some eects of cavity instrumentation on the adaptation of gold castings and amalgam. Baratieri LN, Machado A, Van Noort R, et al: Eect of pulp protection technique on the clinical performance of amalgam restorations: ree-year results. The preparation is based on biological and mechanical principles, protecting the pulp vitality and periodontal health while creating a strong restoration that protects the restored tooth. The axis of the initial prepara-tion into the carious ssure is aligned with the long axis of the tooth crown so as to prevent iatrogenic removal of adjacent healthy tooth structure. 4.13) and/or (2) extension of the gingival oors around axial tooth line angles onto facial or lingual surfaces. Looks like you’ve clipped this slide to already. Controlled, conservative, the restorative material, is always accomplished with the awar, and in the smooth surface area on the facial (B). nitial tooth preparation stage for conventional preparations. J Dent Res 89:1063–1068, 2010, doi:10.1177/0022034510376071.41. 4.3 Intracoronal preparation with “boxlike” appearance. Chapters that are devoted to the preparation and restoration of specic lesions/defects elaborate on these additional factors. A–C, Extensions in all directions are to healthy, mineralized (“sound”) tooth structure, while maintaining a specic limited pulpal or axial depth regardless of whether end (or side) of rotary instrument is in a caries lesion or old restorative mate-rial. e pulpal and axial caries removal of a moderate lesion should therefore extend to where the dentin is rm to tactile sense (i.e., extend to rm dentin). During the initial tooth preparation, the preparation walls are designed not only to provide for draw (for the casting to be placed into the tooth) but also to provide for an appropriate small angle of divergence (2–5 degrees per wall) from the line of draw (to enable retention of the luted restoration). PRINCIPLES FOR TOOTH PREPARATION PART 1 YouTube. Preparations for polycrystalline materials require removal of diseased tooth structure followed by Patient Factors      Anatomical Factors     Procedural Factors    Lesion/Defect Factors      Restorative Material Factors   Factors to Consider Before and During Tooth Preparation• BOX 4.1ba• Fig. Dr. siddiq 5 General Principles of the cavity preparation: Fundamentals of Description. When the defect results in a preparation outline form that places the marginal interface at the point of contact, then the nal position of the preparation outline is modied slightly so that the marginal junction is away from the occlusal contact (review section Occlusal Contact Identication and Rotary Instrument Axis Alignment).It is appropriate, for clinical practicality, to consider that enamel rods are oriented perpendicular to the external tooth surface. Reeves R, Stanley HR: e relationship of bacterial penetration and pulpal pathosis in carious teeth. Correct alignment of the long axis of the shank limits the likelihood of iatrogenic removal, and thereby weakening, of adjacent healthy (occasionally referred to as “sound”) coronal tooth structure. Primary resistance form is obtained through use of a preparation design that conserves as much healthy tooth structure as possible. e exception to reducing a cusp, where extension has been two thirds from a primary groove toward the cusp tip, is when the operator judges that adequate cuspal strength (adequate dentin support) remains. Factors for Retention- Degree of taper 4.9 A, Enameloplasty on area of imperfect coalescence of enamel. Adhesive bonding of etchable glass-ceramic materials to enamel and dentin increase their resistance to fracture development when under occlusal load.Step 8: External Wall FinishingFinishing the external preparation walls is the further development, when indicated, of a specic design (e.g., degree of smoothness or roughness, the placement of a bevel) immediately adjacent to or including the cavosurface margin such that the anticipated restorative material has the greatest likelihood of clinical success. e dentinal wall is that portion of a prepared external wall consisting of dentin, in which mechanical retention features may be located (see Fig. 4.17). 14.18). e durable attachment between enamel and dentin (the dentinoenamel junction [DEJ]) enables enamel to withstand the rigors of mastication. Teeth that lack natural circumferential morphologic variations after tooth preparation (round teeth) should be modified with the creation of grooves or boxes in axial surfaces. Goracci G, Giovani M: Scanning electron microscopic evaluation of resin-dentin and calcium hydroxide-dentin interface with resin composite restorations. Murray PE, Hafez AA, Smith AJ, et al: Bacterial microleakage and pulp inammation associated with various restorative materials. Sectional view (C) of initial stage of tooth pr, for lesions in A and B when planning for a polycrystalline restorative material such as amalgam. 7). 4.1, b). e sequence of these steps may need to be altered when extensive caries has increased the risk of pulpal involvement (see Chapter 2).e concepts of initial and nal stages of tooth preparation are utilized for caries lesions that have progressed into dentin, have compromised the dentinal support of enamel, and therefore require surgical intervention. Vertically oriented grooves associated with the facial and lingual aspects of a proximal prepara-tion are used to provide additional retention for the proximal portions of some Class II amalgam restorations. dldfdfpfpafpafafgfg ag lgdpdlplpapalpalalg• Fig. is Evaporationresults inrapid outwardtubular fluidmovementDentinPre-dentinPulpOdontoblastAir blastAFluid movementleads to stretchingof odontoblasticprocesses / nerveswith potential for aspiration ofodontoblasticcell bodies intothe tubules• Fig. Any nal changes may then be accomplished, as indicated, followed by steps to disinfect the preparation.the preparation margin to dentin tend to split o, leaving a V-shaped ditch along the cavosurface margin area of the restoration. Using a heavily illustrated, step-by-step approach, Sturdevant’s Art and Science of Operative Dentistry, 7th Edition helps you master the fundamentals and procedures of restorative and preventive dentistry and learn to make informed decisions to solve patient needs. Bacterial proteases are not able to degrade intact, native collagen. In general, the appearance of a completed extracoronal preparation is reminiscent of a tree stump and is referred to as “stumplike” (Fig. Become a DentistryKey membership for Full access and enjoy Unlimited articles, eeth require intervention (i.e., need some type of preparation), for various reasons: (1) caries lesion progr, in need of reestablishment of form or function; (4) previous r, tion with inadequate occlusal or proximal contact, defective (open), margins, or poor esthetics; or (5) as par, of iatrogenic damage to adjacent tooth surfaces while seeking to, intervention are prepared such that various r, is chapter denes tooth preparation and the historical classica, tion of anatomic locations aected by caries lesions. e external walls of Class III and V preparations diverge so as to provide strong enamel margins (see Figs. e dentin substitute, along with remaining healthy dentin, acts to support the new restorative material that is replacing the enamel. If the excavation extends to within 0.5 mm of the pulp, a liner usually is selected to cover the deepest area of the dentin. Markley MR: Restorations of silver amalgam. Restorative materials that need beveled margins require tooth preparation outline form extensions that must anticipate the nal cavosurface position and form that will result after the bevels have been placed.Step 2: Primary Resistance FormPrimary resistance form may be dened as the shape and placement of the preparation walls (oors) that best enable the remaining tooth structure, as well as the anticipated restoration, to withstand masticatory forces primarily oriented parallel to the long axis of the tooth. J Prosthet Dent 8:514, 1958.9. It is essential that the outline form be visualized (i.e., mentally anticipated) as much as possible before any mechanical alteration of the tooth has begun. e only dierence in the restora-tion is that the thickness of the restorative material, at the enameloplastied margin, is slightly decreased because the pulpal depth of the preparation external wall is slightly decreased. Investigators have veried the presence of bacteria in the dentinal tubules within the preparation walls. For better visualization, these imaginary projections may be formed by using two periodontal probes, one lying on the unpre-pared surface and the other on the prepared external tooth wall (Fig. e use of sharp spoon excavators and sharp rotary instru-ments, with intermittent light pressure, may help limit pulpal irritation. CHAPTER 4 Fundamentals of Tooth Preparation 133 preparation joins an occlusal lesion with a proximal lesion by means of a prepared tunnel under the involved marginal ridge. Complete debridement allows careful inspection of the preparation so as to ensure adherence to all principles of preparation design. e preparation may be complete after the initial tooth preparation stage when the caries lesion (or other defect) is minimal. As of this date, Scribd will manage your SlideShare account and any content you may have on SlideShare, and Scribd's General Terms of Use and Privacy Policy will apply. It has been suggested that this technique may limit the likelihood of the development of postoperative sensitivity, staining of the dental structure, secondary caries, fracture of the tooth, or partial/total loss of the restora-tion. Quintessence Int 27:129–135, 1996.20. We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. If the ends of these grooves were to be included in the tooth preparation, the cusp may be weakened to the extent that it would need to be reduced and covered with restorative material. An exception to this initial depth of 0.2 mm internal to the DEJ is when the enamel is thin and greater depth is necessary for the strength of the restorative material that will be used. Also, it was thought that retention grooves may increase the resistance form of the restoration against fracture at the junction of the proximal and occlusal portions. Another instance in which enameloplasty may be indicated is the presence of a narrow groove that approaches or crosses a lingual or facial ridge. Tooth preparation is the mechanical alteration of a defective, e use of a beveled marginal form increases the surface area available for bonding, which increases the retention form of the preparation. A reasonable compromise may be to make a minor modication of the external enamel contours, in this peripheral area only, by selective removal of the surface enamel associated with the shallow, narrow developmental groove or fossa. is essential, initial step is then followed by inltration of the roughened surface with resin-based adhesive materials. The process of tooth preparation is dfpdlp mlpmfmpmldldpdflpfp mfp• Fig. See our Privacy Policy and User Agreement for details. Hand instruments such as enamel hatchets and margin trimmers may be used in planing enamel walls, cleaving o unsupported enamel, and establishing enamel bevels.Step 9: Final Procedures: Debridement and InspectionDebridement (cleaning) of the tooth preparation involves use of the air/water syringe to remove visible debris with water and then excess moisture with a few light bursts of air. Following preparation of the abutment teeth in accordance with the main biomechanical principles of teeth preparation (Davenport et al. e minimal occlusal thickness, for appropriate resistance to fracture, of amalgam is 1.5 to 2 mm and glass-ceramic is 2 mm. However, correctly oriented external walls (i.e., walls that have proper dentinal support of the enamel) may diverge as they approach the external surface of the tooth. ese preparation modications provide resistance to parallel and also obliquely (laterally) directed Initial Tooth Preparation Stage: Steps 1-4Step 1: Initial Depth and Outline Forme rst step in tooth preparation is to establish the initial depth and then, at that depth, extend the walls of the preparation until the junction between the enamel and supporting dentin is uncom-promised (i.e., a “sound DEJ” has been reached; see Fig. Some desensitizers not only are eective disinfectants but also are able to occlude (“plug”) the dentinal tubules by cross-linking and precipitating the proteins in the dentinal tubule uid.32-35 Preparations designed for amalgam restoration should be desensitized with a solution that contains 5% glutaraldehyde and 35% 2-hydroxyethyl methacrylate (HEMA) before amalgam placement.36 e use of this type of desensitizer allows prevention of rapid uid movement associated with osmotic gradients and temperature gradients. Pulpal wall: Internal wall perpendicular to long axis of the tooth, occlusal to pulp. 245 carbide bur) head length, or 1.5 mm, as related to central ssure location. It is currently impossible to clinically identify the specic depth of the bacterial invasion. ere are two types of internal walls. e thin restoration will ex as needed. Recent in vitro evidence is in support of this theory.35 However, potential cytotoxic eects of free glutaraldehyde and HEMA (i.e., not involved in the protein cross-linking and tubular occlusion) raise legitimate patient safety concerns. Removal of carious tissue in a moderate lesion (i.e., a lesion that has not reached the inner one third of dentin) has a low risk of pulpal involvement. Agnihotry A, Fedorowicz Z, Nasser M: Adhesively bonded versus non-bonded amalgam restorations for dental caries. AB• Fig.  Allow for the esthetic and functional placement of the restorative material. is internal wall may also be referred to as the pulpal oor. Fundamentals of Tooth Preparation Flashcards Quizlet. Previous notions of dentin excavation for the purpose of complete removal of all bacteria have resulted in exposure of pulp tissue that was not irreversibly inamed, leading to overtreatment and increased frequency of adverse outcomes. e design of the cavosurface margins for these materials is therefore as close to 90 degrees as possible as this marginal conguration allows maximum thickness of the polycrystalline material that will subsequently be placed in the preparation (Fig. Examples ar, (1) A simple tooth preparation involving an occlusal surface is an, “O”; (2) a compound preparation involving the mesial and occlusal, surfaces is an “MO”; and (3) a complex preparation involving the. Tooth preparation terminology eectively describes preparation aspects with regard to complexity, anatomic location, three-dimensional orientation, and geometry.Tooth Preparation: TerminologyA tooth preparation is termed simple if only one tooth surface is involved, compound if two or three surfaces are involved, and complex if a preparation involves four or more surfaces. 6. is initially creates a strong mechanical bond between the composite and dentin. When discussing or writing a term denoting a combination of two or more surfaces, the -al ending of the prex word is changed to an –o. Removal of remaining old restorative material, when indicated, may be accomplished using sharp rotary instruments and light intermittent pressure with or without water irrigation/cooling. Using a heavily illustrated, step-by-step approach, Sturdevant’s Art and Science of Operative Dentistry, 7th Edition helps you master the fundamentals and procedures of restorative and preventive dentistry and learn to make informed decisions to solve patient needs. Note, in the upper exploded view, that the cavosurface angle (cs) may be visualized by imaginary projections of the preparation wall (w′ ) and of the unprepared surface (us′ ) contiguous with the margin, forming angle cs′. I want NOTHING more than a step by step, how to do each prep, for operative and/or prosthodontics. 130 CHAPTER 4 Fundamentals of Tooth Preparationthe liner from dissolution from the phosphoric acid etchant used prior to composite placement.14,19 Protection of the CaOH2 liner with an RMGI base also prevents inadvertent displacement of the liner during subsequent procedural steps.Very deep excavations may contain microscopic pulpal exposures that are not visible to the naked eye. Examples are as follows: (1) A simple tooth preparation involving an occlusal surface is an “O”; (2) a compound preparation involving the mesial and occlusal surfaces is an “MO”; and (3) a complex preparation involving the mesial, occlusal, distal, and lingual surfaces is an “MODL.”e process of creating a preparation in a tooth results in the formation of preparation walls or oors (Fig. J Dent Res 67:306, 1988.5. e 90-degree root-surface margin provides a butt joint relationship between the restorative material and the dentin (with overlying cementum) preparation wall, a conguration that provides appropriate strength to both.An acute, abrupt change in a preparation wall outline form increases the diculty of optimal adaptation of the restorative material. Oper Dent 29:319–324, 2002.27. e durable attachment between enamel and dentin, (the dentinoenamel junction [DEJ]) enables enamel to withstand, the rigors of mastication. Limiting the activity of the MMPs may help stabilize the hybrid layer, at least in Class I preparations for the short term.39 Chlorhexidine is able to inactive MMPs that are exposed as a result of the etching process. 4.2). Tooth preparation features or sections that are parallel (or nearly so) to the long axis of the tooth crown are commonly described as vertical, such as vertical height of cusps, or vertical walls. It may be necessary to reduce cusps that no longer have sucient dentin support and cover (or envelope) them with an adequate thickness of restorative material in order to provide resistance to fracture of the tooth and/or the restorative material. Extreme prudence was exercised in the selection of these areas and in the depth of enamel removed. When a pulpal or axial wall has been established at the proper initial tooth prepara-tion position, and a small amount of carious tissue remains, only this tissue should be removed, leaving a rounded, concave area in the wall. Marzouk MA: Operative dentistry, St Louis, 1985, Ishiyaku EuroAmerica.10. Correcting or improving occlusal relationships also may necessitate altering the tooth preparation to accommodate such changes, even when the involved tooth structure is not faulty (i.e., a cuspal form may need is preparation design may also enhance the resistance form of the remaining tooth by enveloping and contributing reinforcement.Skirts. However, no clinical improvement over normal, routine steps utilized in amalgam restoration has been demonstrated.24-28 Therefore this book does not promote the use of bonded amalgams.Preparation Treatments to Enhance RestorationDisinfection, Desensitization, StabilizationDisinfection of the preparation prior to insertion of the restorative material may be considered. e ability to utilize the information, solid understanding of concepts presented in, that had progressed to the point that ther, surface integrity of the tooth. Polymeric restorative materials may be as thin as is required to replace lost tooth structure and reestablish normal anatomy. book referred : Sturdevant's. erefore it may become necessary to strategically modify internal aspects of the preparation so as to mechanically retain the restoration.Because many preparation features that improve retention form also improve resistance form, and the reverse is true, they are presented together. e peripheral walls determine the overall outline of the preparation, which is referred to as the outline form. An internal wall is a prepared surface that does not extend to the external ddsc• Fig. are structurally either polycrystalline or polymeric. Most proximal caries lesions associated with posterior teeth also require that the shank axis be aligned parallel with the long axis of the tooth crown (Figs. Demineralization of the exposed dentin surface results in exposure of the dentin matrix (collagen), which may then be inltrated with adhesive resin materials. Composite resin materials, which are thermal insulators, do not require the same bulk of material (dentin + liner/base) between the restoration and the pulp. 4.6 and 4.7).e cavosurface angle is the angle of tooth structure formed by the junction of a prepared wall and the external surface of the tooth. J Dent Res 35:25, 1956.32. When the external walls of the preparation converge toward each other, as they approach the external surface of the tooth, then no additional or “secondary” retention is required. Denaturation of the collagen, by host proteolytic enzymes, allows subsequent collagen degradation (of the denatured collagen) by bacterial proteases. Line angles are distofacial (df), faciopulpal (fp), axiofacial (af), faciogingival (fg), axiogin-gival (ag), linguogingival (lg), axiolingual (al), axiopulpal (ap), linguopulpal (lp), distolingual (dl), and distopulpal (dp). Care is taken when choosing the area that will benet from enameloplasty. e smear layer that forms on wall surfaces during preparation is either altered or removed from the enamel and dentin during the etching process. Preparation e thin remaining wall of dentin provides little protection from (1) heat generated by rotary instruments during subsequent steps, (2) noxious ingredients of various restorative materials, (3) thermal changes conducted through restorative materials, (4) forces transmit-ted through materials to the dentin, (5) galvanic shock, and (6) the ingress of bacteria and/or noxious bacterial toxins through microleakage.14,15 Deep dentin also is a very poor substrate for subsequent bonding procedures.

principles of tooth preparation sturdevant

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