TOOTH PREPARATION  FOR CAST METAL   RESTORATIONS       INDIAN DENTAL ACADEMY    Leader in Continuing Dental Education    w...
   INTRODUCTION   DEFINITONS OF INLAY AND ONLAY   BRIEF LOOK AT CASTING METALS   INDICATIONS AND    CONTRAINDIACTIONS...
    Types of margins, design features and functions     of occlusal and gingival bevels.    Types and design features of...
      TOOTH PREPARATION FOR ONLAY CAST       RESTORATIONi)     Indications.ii)    General shape.iii)   Internal anatomy. ...
INTRODUCTIONThe cast metal restoration is versatile and the  procedure requires meticulous care both in  preparation and l...
DEFINITIONSINLAY      It is primarily an intracoronal cast restoration that is fabricated outside the oral cavity and pla...
Brief look at casting metals :    Gold alloy is most commonly used, however due to its  expense other metals which are in ...
INDICATIONS FOR CAST RESTORATIONSA) Extensive tooth involvement        Ultimate in both efficiently replacing lost tooth s...
C) Correction for occlusion:-               If any drastic change is planned for the occlusal  table or occluding parts of...
F) Low incidences of plaque accumulation or decay :              patients to receive a cast restorations should   have the...
b) High Plaque and caries indices :                 Patients with rampant caries and  poor oral hygiene should not be give...
Advantages and Disadvantages of cast metal               RestorationsBetter yield, compressive, tensile and   Being a ceme...
Instrumentation for tooth preparations for               cast restorationsA) Removal of undermined enamel and  gaining acc...
c) Defining the facial and lingual marginal and axial  parameters of the extra coronal portion of the  preparation :      ...
D. Bur no.271 : tungsten   carbide tapering fissure with   0.8mm widthE. Bur no. 169L tapering   fissure with 0.5 mmF. Pre...
   G .Boxing up :              Using a tapered fissure bur, wall    proper, e.g., for cast alloy onlay, the    inner(pulp...
H. Establishing circumferential tie    constituents:        Gingival bevels are best created with    gingival margin trimm...
A hallow-ground bevel  can be prepared either  with a torpedo-shaped  stone or bullet shaped  stone, followed by  round bu...
I)   Finishing and establishing the continuity     between the circumferential tie     constituents:                   Smo...
PRINCIPLES OF CAVITY PREPRATION I) Outline form:     i) External outline form:          The external outline for inlay sh...
ii) Internal outline form:               The Pulpal floor and the axial wall  of the inlay preparation must be placed in ...
 It is sometimes desirable to incline the cutting  instrument so that it forms either an exaggerated taper  from cavosurf...
 Removal of wax pattern and insertion of the casting is  facilitated by the taper. A range between 4 to 6 degrees is use...
 The occlusal interlock or dovetail is a major factor in  resistance and retention form. Specially designed features lik...
IV) Convenience form : This form provides accessibility and visibility  required to complete operative procedures  thorou...
V) Finishing enamel walls and margins       If Coarse or medium grit diamond  instruments have been used during cavity  p...
 a bevel on the cervical margin of a box preparation  for the direct technique should be uniform about 1/4  to ½ of mesio...
Primary tooth preparations are more less the same as   mentioned above and the dissimilar features are ;1.Path of insertio...
Taper depends on : 1.Length of the preparation: Longer the wall, increased     taper and shorter wall, minimal taper and p...
Types of margins in a cast restorationBevel, Chamfer, Shoulder are commonly used  margins for cast restorations, how ever ...
Advantages and DisadvantagesBevel           Removes            Extends                unsupported        preparation into ...
BEVELSBevels are the “flexible extensions” of a cavity   preparation.This peripheral marginal anatomy of the preparation  ...
FUNCTIONS OF BEVELS1)To increase the bulk of the material at the margins of   the preparation.2)By increasing the bulk, bu...
The bevels available for cast restoration1)   Partial: it involves part of     enamel2)   Short: It involves entire     en...
5)   Hollow ground: It is concave in     form, truly it is not a bevel,     some times given to increase     retention.5) ...
7)   Counter bevel : in case of capping     the cusps. It is started from inner     dentine involves enamel with a flat   ...
Types and design features of facial and     lingual flares.a) The Primary Flare:        This is the conventional and basic...
Functions and indications : Brings proximal facial and lingual walls to self cleansable and finishable areas. They are ind...
The secondary flare :It is a flat plane superimposed    peripherally to a primary    flare. usually it is prepared    on e...
Functions of secondary flareIn a very widely extend lesion bucco-lingually ,the buccal   and lingual structure will be bad...
In very broad contact areas, the   primary flare will not bring facial   and/or lingual areas to self   cleansable areas, ...
Surface defects or decalcifications, facial or lingual to the primary flare’s facial and lingual margin respectively, can ...
   In ovoid teeth peripheral margin    undercuts esp. apt to be present    occluso-apically on the facial and/or    lingu...
Tooth Preparation for Inlay castrestoration :   Indications :     cavity width does not exceed 1/3 inter cuspal      dis...
   General shape :              Outline of occlusal preparation is dove    tailed. the proximal portion is usually boxed ...
   Location of margins :                   In occlusal portions, the margins are    located on inclined planes of corresp...
   Internal anatomy :                           The wall    proper-taper, should taper from    either 2-5 degrees or be p...
   The occlusal bevel : it is along bevel, almost one    third of the facial and lingual (proximal) walls. This    bevele...
   Pulpal floor : should be flat for    most extent if this is not possible,    atleast the peripheral portions    should...
   Proximal portion: Axial wall should be flat or    slightly rounded in bucco-lingual direction, either    vertical or s...
   Proximally facial and lingual walls : composed    of two planes ,axial half and proximal half.     Axial half (i.e. fa...
   The gingival floor: Proximally should be flat in the    bucco-lingual direction, making a slightly obtuse angle    wit...
   The junction between the occlusal bevel and the    secondary or primary flare proximally and also    the junction betw...
Secondary modes of retention :    1) Luting cement : fills gap between inlay and       tooth giving a physio chemical bond...
2) Grooves : Place two  grooves, one on bucco axial  and other on lingual axial line  angle with #165 bur. It is  totally ...
3)Reverse Bevel :                    It is given on  gingival seat. This bevel has  generally three planes, i) reverse  be...
4) Internal box:                  made on the  pulpal floor, which improves the  retention by 4-5 times. this is  on the u...
5) External box : these are box   shaped preparations opening to   axial tooth surface .they can be   proximal, facial or ...
6) Roughening of pulpal floor : at   specific areas of tooth preparation,   esp. in pulpal floor, is done for   more reten...
   7) Precementation grooves : after casting make    grooves on the walls of the inlay and/or grooves    on the cavity wa...
8)Electrolytic etching of inlay :      This gives hinge like projections.   Procedure : Protect proximal and occlusal surf...
Tooth preparations for onlay cast            restorations  It is partly intracoronal and partly extra coronal type of   re...
5) whenever there is a need to change the dimension, shape   and interrelationship of the occluding tooth surfaces, onlay ...
Onlay Tooth Preparation ProcedureOcclusal preparation:           The initial entry is made in  the central fossa to a dept...
Proximal boxes:         The boxes are createdon the proximal surface. Thefacial and lingual walls shouldexhibit a combined...
The faciolingual dimension  is likely to be  determined by the  presence of a  restoration, caries  lesion. The bevels wil...
Cuspal Reduction:                 A carbide buror diamond bur is used toreduce the cusp. Depth cuts of1.5 to 2 mm are made...
After the depth cuts are  placed, a uniform  reduction of the cusps that  parallels the generally  anatomic contours of th...
The cuspal heights are  reduced to the full extent  of the depth cuts.  Reduction of centric  cusps generally needs to  be...
Shoulder Preparation:                   A shoulder isprepared on the external surface ofthe centric cusp to provide a band...
Non centric cusp :                 A chamferor long bevel is giveninstead of shoulder in noncentric cusp(s). A barrelshape...
Gingival Bevel:   A smooth and distinct bevel isestablished on the gingival margins withno.7901 finishing bur, a thin tape...
Shoulder Bevel:            A 1.0 mm bevel is placed on theshoulder with No.7901 or fine diamond bur. Thisbevel is blend wi...
Retention grooves :   If retention grooves areneeded, grooves are placedin both proximal boxes. Ano.169 bur is used to bis...
TOOTH PREPARATION FOR CAST           RESTORATIONS WITH SURFACE                   EXTENSIONS   Modifications for basic onl...
Skirt: It is more extensive surface extension. It is  also superimposed on the basic intra-coronal  inlay or onlay cavity...
   When the contact areas and the contour of the    proximal surfaces are to be changed in the    contemplated restoratio...
    Every effort should be made to have the axial    reduction of skirt parallel to rest of the cavity    preparation. If...
Collar : Most involving  are surface wise and  depth wise, it can be one of the two  types. Cuspal collars- involve the ...
   Indications :   They help in retention and resistance when an    entire cusp is lost prior to tooth preparation or   ...
   With axial depth of 1.5mm to    2 mm, collar surface extend    gingivally in a beveled    shoulder finishing line,    ...
 The peripheral beveled portion of the collar will have its angulation and extent dictated by same features as those gove...
Conclusion:Cast metal inlays and onlays offer excellent restorations that  may be utilized in dentistry. Even though the t...
References:Art and science of operative dentistry –  sturdevant – 4th edition.Operative dentistry-modern theory and  pract...
Thank youwww.indiandentalacademy.com
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Tooth preparation for cast metal restoration / endodontic courses by indian dental academy

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Tooth preparation for cast metal restoration / endodontic courses by indian dental academy

  1. 1. TOOTH PREPARATION FOR CAST METAL RESTORATIONS INDIAN DENTAL ACADEMY Leader in Continuing Dental Education www.indiandentalacademy.com
  2. 2.  INTRODUCTION DEFINITONS OF INLAY AND ONLAY BRIEF LOOK AT CASTING METALS INDICATIONS AND CONTRAINDIACTIONS ADVANTAGES AND DISADVANTAGES INSTRUMENTATION FOR TOOTH PREPRATION FOR CAST RESTORATION PRINCIPLES OF TOOTH PREPRATION FOR CAST RESTORATIONS www.indiandentalacademy.com
  3. 3.  Types of margins, design features and functions of occlusal and gingival bevels. Types and design features of facial and lingual flares. TOOTH PREPARATION FOR INLAY CAST RESTORATION i) Indicationsii) General shapeiii) Internal anatomy www.indiandentalacademy.com
  4. 4.  TOOTH PREPARATION FOR ONLAY CAST RESTORATIONi) Indications.ii) General shape.iii) Internal anatomy. TOOTH PREPRATION FOR CAST RESTORATIONS WITH SURFACE EXTENSIONSi) Skirtii) Collar CONCLUSION. REFERENCES. www.indiandentalacademy.com
  5. 5. INTRODUCTIONThe cast metal restoration is versatile and the procedure requires meticulous care both in preparation and laboratory procedures. The practice of restorative dentistry improved permanently on cast metal restorations when it was first introduced by Taggart for cast gold restorations.Today, cast metal restorations and its applications have become basic treatment modalities in dentistry both for strengthening the tooth structure and maintaining the functional value. www.indiandentalacademy.com
  6. 6. DEFINITIONSINLAY It is primarily an intracoronal cast restoration that is fabricated outside the oral cavity and placed in the prepared cavity.ONLAY An onlay is combination of intracoronal and extra coronal cast restoration when one or more cusps are covered. www.indiandentalacademy.com
  7. 7. Brief look at casting metals : Gold alloy is most commonly used, however due to its expense other metals which are in use are : Noble Noble Base Base (Gold (Palladium metals metals based) based) (Cobalt (Nickel based) based)Major Gold Palladium Cobalt Nickelconstituents ‘’ Silver Silver Chromium Chromium ‘’ Copper Copper Tungsten Iron ‘’ Gold Molybdenum www.indiandentalacademy.com
  8. 8. INDICATIONS FOR CAST RESTORATIONSA) Extensive tooth involvement Ultimate in both efficiently replacing lost tooth structure and supporting remaining tooth structure.B) As an adjuvant to successful periodontal therapy i) physiologically restoring the dimensions of the contact contour, marginal ridges and embrasures. ii) Splinting of teeth loosened by periodontities to a better bone supported teeth. The rigid connection of several cast restoration assures distribution of the applied forces to the best supported teeth and minimises force on disabled teeth. www.indiandentalacademy.com
  9. 9. C) Correction for occlusion:- If any drastic change is planned for the occlusal table or occluding parts of a tooth, cast restorations are ideal.D) Restoration of Endodontically treated teeth:- After endodontically treated, the tooth become brittle. Almost always the clinical crown portion of these teeth will need reinforcing restoration.E) Support for and preparatory to partial or complete dentures:- Weather they are a clasp type, over denture type, bar attachment. Most removable prosthesis will need cast restorations. www.indiandentalacademy.com
  10. 10. F) Low incidences of plaque accumulation or decay : patients to receive a cast restorations should have their plaque accumulation in rigid control.G) Esthetics : Of all metal restorations properly fitted cast restorations enhance esthetic appearance.CONTRAINDICATIONS :a) Developing and deciduous teeth: Growth or resorption may be affected by the traumatic nature of the procedures of the cast restorations. www.indiandentalacademy.com
  11. 11. b) High Plaque and caries indices : Patients with rampant caries and poor oral hygiene should not be given cast restorationsc) Occlusal Disharmony : Cast restorations should not be used in patients with severe occlusal interference or other defects .d)Dissimilar Metals : Gold-based castings are avoided in patients already having silver restorations. www.indiandentalacademy.com
  12. 12. Advantages and Disadvantages of cast metal RestorationsBetter yield, compressive, tensile and Being a cemented restorations,sheer strengths of alloy. interphase leading to leakage around and under cast restoration will be a common problem.Reproduces precise form and minute Extensive tooth involvement createsdetail. hazards to vital tooth structures.Metals that are usually used are not The cathodic effect of dental alloyssignificantly affected by tarnish and towards other metals used in the samecorrosion . mouth will lead to galvanic deterioration.Fewer voids, no layering effects, less Lengthy procedures, requiring manyinternal stress will lead to strong visits, temporary coverage betweenstructure. visits, expense of alloy.Cast restorations can be finished, Some cast alloys exhibit high abrasivepolished or glazed outside the oral resistance which may lead tocavity. www.indiandentalacademy.com imbalance occlusion.
  13. 13. Instrumentation for tooth preparations for cast restorationsA) Removal of undermined enamel and gaining access: undermined enamel is easily removed with hand cutting instruments like chisel, hatchet, wedelstaedt.B) Removal of caries dentin and placing intermediary basing : Decayed dentin is usually excavated using spoon excavators, cleared of the diseased tissue ,proper intermediary base is placed and locked in place. www.indiandentalacademy.com
  14. 14. c) Defining the facial and lingual marginal and axial parameters of the extra coronal portion of the preparation : using #3,4, or 5 round bur or ball shaped diamond stone, gauge out the axial surface near contemplated circumferential tie, Several of these gougings may be made within the parameters of the extracororonal preparation. They will serve as guide lines in over all axial reduction. www.indiandentalacademy.com
  15. 15. D. Bur no.271 : tungsten carbide tapering fissure with 0.8mm widthE. Bur no. 169L tapering fissure with 0.5 mmF. Preliminary Shaping: Tapered fissure burs or diamond stones with or without rounded ends, are used to reduce the axial surface to the depth of the gouges, cutting strokes should be preplanned in starting and ending points, their angulations and their direction of pressure. www.indiandentalacademy.com
  16. 16.  G .Boxing up : Using a tapered fissure bur, wall proper, e.g., for cast alloy onlay, the inner(pulpal) half to two-thirds of the facial or lingual wall occlusally , the axial half of the facial to two-thirds of the facial or lingual walls proximally, and the axial half two thirds of the gingival floor proximally. Care is taken in this step as it retains the resistance and retention form and hence angulation of cutting tool is very influential. www.indiandentalacademy.com
  17. 17. H. Establishing circumferential tie constituents: Gingival bevels are best created with gingival margin trimmers. primary and secondary flares are done so with chisels or hatchets. occlusal bevels are prepared with cone shaped aluminum oxide stone. A feather-edge finishing line is prepared with filamentous stone . A beveled shoulder is prepared with a tapered fissure bur and a GMT. www.indiandentalacademy.com
  18. 18. A hallow-ground bevel can be prepared either with a torpedo-shaped stone or bullet shaped stone, followed by round bur. For the reverse secondary flare, the preparation can be done using taper end diamond stone followed by hand instrument hatchet or bi angle chisel. www.indiandentalacademy.com
  19. 19. I) Finishing and establishing the continuity between the circumferential tie constituents: Smoothing of the tie can be done with hand instruments and 12 fluted or 40 fluted carbide burs. Also fine grit sand paper discs, if access allows can be used effectively. Establishing the continuity between the circumferential tie constituents is best done by wedelstaedt chisel, biangle chisel or any other sharp chisel. www.indiandentalacademy.com
  20. 20. PRINCIPLES OF CAVITY PREPRATION I) Outline form: i) External outline form:  The external outline for inlay should consists of straight lines and smooth flowing curves, avoiding any short angles.  Enamel rods at the cavosurface margin should be supported by dentin and supported laterally by rods that lie within the preparation.  The cavosurface margin is placed in sound, unbroken tooth tissue to obtain a well fitting casting.  The placement of bevels make the outline form slightly wider for cast restorations. www.indiandentalacademy.com
  21. 21. ii) Internal outline form: The Pulpal floor and the axial wall of the inlay preparation must be placed in dentin. Care must be taken to protect the pulp. Pulpal floor will be usually positioned 0.5mm into dentin below the central groove. In shallow preparations, parallelism enhances the resistance and retention form of the preparation. line angles in both occlusal and proximal portions of the preparations should be well defined. The axio-pulpal line angle should be slightly rounded. www.indiandentalacademy.com
  22. 22.  It is sometimes desirable to incline the cutting instrument so that it forms either an exaggerated taper from cavosurface to pulpal floor or a long bevel on that area of the wall. This procedure protects the thin wall of enamel that remains at the cavosurface by maintaining a supporting edge of dentin.II) Resistance and retention forms : The preparation of the tooth for a cast restoration must be so designed that will resist dislodging forces of compression and tension.Inlay taper: Cavity walls must diverge from the floor of the preparation externally forms a basic design for all cast restorations www.indiandentalacademy.com
  23. 23.  Removal of wax pattern and insertion of the casting is facilitated by the taper. A range between 4 to 6 degrees is used as it provides adequate retention of the cemented casting. The axial length of the preparation will influence the amount of taper. longer preparations require taper in higher range, short preparations in the lower range. Pulpal and cervical floors ideally should be perpendicular to lines of force that will influence the restoration. Floors positioned perpendicular to these lines of force will absorb the stress over a broad area of the tooth. Well defined line angles are also important in obtaining resistance and retention form. www.indiandentalacademy.com
  24. 24.  The occlusal interlock or dovetail is a major factor in resistance and retention form. Specially designed features like pinholes or postholes are placed parallel to the line of draw of the preparation and with appropriate concern for the pulp Tapered grooves extending from cervical floor to the occlusal surface, are sometimes placed in the dentin portion of the proximal walls to form a locking key to aid in preventing lateral dislodgement of the restoration.III) Removing carious dentin : Removal of deeper carious lesion frequently precedes the establishment of resistance and retention form. www.indiandentalacademy.com
  25. 25. IV) Convenience form : This form provides accessibility and visibility required to complete operative procedures thoroughly. Opening the preparation to its approximate final outline form establish an intact dentin enamel junction enhances access and visibility for removing carious dentin and old restoration. Extension, taper and flare of proximal walls to permits access for disking and bevel placement, and extension to allow proper finishing and adaptation of the margins of the restorative material are all examples of convenience form. www.indiandentalacademy.com
  26. 26. V) Finishing enamel walls and margins If Coarse or medium grit diamond instruments have been used during cavity preparation the walls and margins should be finished with carbide finishing burs or fine abrasive discs. The cervical bevel of indirect preparation is most frequently placed with the flame shaped extra fine finishing bur or gingival marginal trimmers for convenience and they provide a steeper bevel to prepare for an effective adaptation of the metal margin. A bevel placed with a flame shaped rotary instrument will establish excellent cervical margin and will further blend together with the buccal andwww.indiandentalacademy.com lingual proximal finish lines.
  27. 27.  a bevel on the cervical margin of a box preparation for the direct technique should be uniform about 1/4 to ½ of mesio-distal width of the cervical floor and must include the proximal cervical cavosurface angles. Such a bevel is placed with GMT prior to finishing the proximal enamel walls.VI) Cleaning and inspection of the cavity : Upon completing the cavity preparation, the walls, floors, margins should be cleaned with water. after drying with cotton pledgets and a gentle stream of warmed air, the cavity should be scrutinized carefully for any imperfections. www.indiandentalacademy.com
  28. 28. Primary tooth preparations are more less the same as mentioned above and the dissimilar features are ;1.Path of insertion : (a) should be parallel to the long axis of the tooth. (b) should be opposite to the occlusal load, this helps the inlay to seat well in the cavity without rocking or to prevent any micro movements.2.Taper :It is the preparation in which the walls of the cavity in intracoronal cast restoration is diverged to occlusal margin and in extracoronal, converged to occlusal margin. The amount of taper should be normally 2˚ to 5˚ for one wall, for both walls should not exceed 10˚.The sum of taper of both walls is called “cone angle taper” and should not exeed 10˚. www.indiandentalacademy.com
  29. 29. Taper depends on : 1.Length of the preparation: Longer the wall, increased taper and shorter wall, minimal taper and parallel the wall. 2.Surface involvement of cavity : More complex the surface involved, less should be taper and more parallelism. 3.Need for retention : reduce the taper to have maximum retention. www.indiandentalacademy.com
  30. 30. Types of margins in a cast restorationBevel, Chamfer, Shoulder are commonly used margins for cast restorations, how ever other margins are feather edge, chisel edge, sloped shoulder, shoulder with bevel. www.indiandentalacademy.com
  31. 31. Advantages and DisadvantagesBevel Removes Extends unsupported preparation into enamel, allows sulcus if used finishing of on apical metal margin.chamfer Distinct margin, Care needed to adequate bulk, avoid easier to unsupported lip control of enamelShoulder Bulk of Less restorative conservative material www.indiandentalacademy.com
  32. 32. BEVELSBevels are the “flexible extensions” of a cavity preparation.This peripheral marginal anatomy of the preparation is called “circumferential tie”, bevels, being the part of the circumferential tie, are one of the major retention forms for a cast restorations. and has following features:a) Enamel must be supported in the sound dentin.b) Enamel rods forming the cavosurface margin should be continuous with sound dentin.c) Enamel rods forming the restorative material and angular cavosurface angles should be trimmed. www.indiandentalacademy.com
  33. 33. FUNCTIONS OF BEVELS1)To increase the bulk of the material at the margins of the preparation.2)By increasing the bulk, burnishing of the cast restoration is possible.3)The cement line is hidden or marked by the bevel thus preventing marginal leakage.4)Discrepancy in the cavity preparation or cast restoration is marked by the bevel.5)It improves the resistance of the tooth structure.6)Improves retention –reverse bevel also called as flexible extension, i.e., any surface defect like attrition can be involved in the preparation. www.indiandentalacademy.com
  34. 34. The bevels available for cast restoration1) Partial: it involves part of enamel2) Short: It involves entire enamel.3) Long: It involves all of enamel but one half of the dentinal wall.4) Full: This involves all of the enamel and dentinal wall. www.indiandentalacademy.com
  35. 35. 5) Hollow ground: It is concave in form, truly it is not a bevel, some times given to increase retention.5) Inverted Bevel: It is indicated only in metal ceramics. it is given on the labial shoulder. www.indiandentalacademy.com
  36. 36. 7) Counter bevel : in case of capping the cusps. It is started from inner dentine involves enamel with a flat plane on enamel and is taken back.8) Reverse bevel: bevel towards axial wall and slopping towards it, made of dentine fully, aids in retention and prevents proximal displacement. www.indiandentalacademy.com
  37. 37. Types and design features of facial and lingual flares.a) The Primary Flare: This is the conventional and basic part of the circumferential tie facially and lingually of the proximal box for an intracoronal preparation. It is very similar to the long bevel formed of an enamel and part on the dentin, on the facial or lingual proximal wall. Primary flares have 45 degree angulation to the dentinal wall proper. www.indiandentalacademy.com
  38. 38. Functions and indications : Brings proximal facial and lingual walls to self cleansable and finishable areas. They are indicated for any facial or lingual proximal wall of any intracoronal cavity preparation. It is prepared on enamel and dentin. www.indiandentalacademy.com
  39. 39. The secondary flare :It is a flat plane superimposed peripherally to a primary flare. usually it is prepared on enamel , but sometimes may involve dentin. Unlike primary flare, secondary flare have different involvements, angulations and extent depending on their functions. www.indiandentalacademy.com
  40. 40. Functions of secondary flareIn a very widely extend lesion bucco-lingually ,the buccal and lingual structure will be badly thinned, the primary flare will end with acute angled marginal tooth structure, here a secondary imposed flare will create the needed obtuse angulation of the marginal tooth structure without any sacrifice to resistance and retention form, because the wall proper and primary flare maintained at their proper location and angulations. www.indiandentalacademy.com
  41. 41. In very broad contact areas, the primary flare will not bring facial and/or lingual areas to self cleansable areas, however a secondary flare placed peripheral to that primary flare will accomplish this without the change in a 45 degree angulation and the resistance and retention forms. www.indiandentalacademy.com
  42. 42. Surface defects or decalcifications, facial or lingual to the primary flare’s facial and lingual margin respectively, can be involved in the preparation with the secondary flare without to extend or angulate the primary flare more than indicated. www.indiandentalacademy.com
  43. 43.  In ovoid teeth peripheral margin undercuts esp. apt to be present occluso-apically on the facial and/or lingual peripheries of the cavity walls. Elimination of these undercuts via wall proper or primary flare extension will unnecessarily involve and weaken tooth structure. How ever a secondary flare superimposed on primary flare will eliminate these undercuts with only minimal sacrifice to tooth structure. www.indiandentalacademy.com
  44. 44. Tooth Preparation for Inlay castrestoration : Indications :  cavity width does not exceed 1/3 inter cuspal distance.  Strong self-resistance cusps remain.  Indicated teeth have minimal or no occlusal facets and if present limited to occlusal surfaces.  The tooth occlusion or occluding surfaces are not to be changed by restorative procedure.
  45. 45.  General shape : Outline of occlusal preparation is dove tailed. the proximal portion is usually boxed in shape.
  46. 46.  Location of margins : In occlusal portions, the margins are located on inclined planes of corresponding cusps , triangular cusps or marginal ridges. The most peripheral margins of the preparations are located away from contact with the opposing tooth surface during centric closure and extrinsic movements of the mandible. All adjacent wear facets, supplementary grooves, areas of decalcification should be included in beveled portion of the cavity preparation only. The margins of this design fulfill all requirements of extension of prevention.
  47. 47.  Internal anatomy : The wall proper-taper, should taper from either 2-5 degrees or be parallel to each other. Each wall should make right angles/slightly obtuse angle with pulpal floor. Preferably each of wall proper should be parallel to long axis of crown.
  48. 48.  The occlusal bevel : it is along bevel, almost one third of the facial and lingual (proximal) walls. This beveled outer plane of the walls will have angulations of 30-45 degrees to the long axis of the crown. This angulation should increase as the width of the cavity increases to accommodate more bulk of the cast alloy and to resist increased stress near the cusps on inclined planes.
  49. 49.  Pulpal floor : should be flat for most extent if this is not possible, atleast the peripheral portions should be flat .Generally should be 1 to 1.5mm from DEJ. The pulpal floor should meet all surrounding walls at definite line angle except its junction with the axial wall, where it should be rounded.
  50. 50.  Proximal portion: Axial wall should be flat or slightly rounded in bucco-lingual direction, either vertical or slightly divergent(5-10 degrees) towards pulpal floor in the gingivo-occlusal direction. The depth axially should be 1 to 1.5mm from DEJ. However different depths may be necessary according to carcinogenic pattern.
  51. 51.  Proximally facial and lingual walls : composed of two planes ,axial half and proximal half. Axial half (i.e. facial or lingual wall proper ) is completely formed by dentin and meets axial wall at right angle. This is main resistance and retention form of this part. Proximal half: Is formed of primary flare in enamel and dentin ,45 degree angle to wall proper. Secondary flare: Some times it is necessary to impose a third plane in the form of secondary flare, placed on the enamel peripherally .This simplifies impressions and wax patters techniques.
  52. 52.  The gingival floor: Proximally should be flat in the bucco-lingual direction, making a slightly obtuse angle with the buccal and lingual walls. The axio proximal line direction is formed in two planes, the axial half and proximal half. The axial half consists of gingival floor, being perfectly flat, formed of dentin making either right angle or slightly obtuse angle with the axial wall. The proximal half should be beveled in the form of a long bevel inclining gingivally. this bevel is usually angulated on the average of 30-45 degrees.
  53. 53.  The junction between the occlusal bevel and the secondary or primary flare proximally and also the junction between the primary and secondary flares proximally and the gingival bevel should be rounded and smooth.
  54. 54. Secondary modes of retention : 1) Luting cement : fills gap between inlay and tooth giving a physio chemical bonding. Physical – Zinc phosphate, chemical : glass inomer + polycorboxylate. The exposed cement dissolves in the oral cavity and so should not be considered as main retentive factor.
  55. 55. 2) Grooves : Place two grooves, one on bucco axial and other on lingual axial line angle with #165 bur. It is totally placed on dentine. Depth of groove should be 0.3mm at the expense of buccal and lingual walls and never at expense of axial walls.
  56. 56. 3)Reverse Bevel : It is given on gingival seat. This bevel has generally three planes, i) reverse bevel plane where inclination is on gingivoaxial plane which prevents proximal displacement. ii) secondly, flat plane made of dentine. iii) thirdly ,plane which is sloping away from the axial wall made of enamel and dentine, this helps in proximal displacement.
  57. 57. 4) Internal box: made on the pulpal floor, which improves the retention by 4-5 times. this is on the uninvolved side. it should not have sharp line and point angles and definite walls. This prevents micromovement of the inlay. Internal box should always be reciprocated with a reverse bevel or groove to avoid micromovement.
  58. 58. 5) External box : these are box shaped preparations opening to axial tooth surface .they can be proximal, facial or lingual. They can be either stepped occlusally or gingivally.
  59. 59. 6) Roughening of pulpal floor : at specific areas of tooth preparation, esp. in pulpal floor, is done for more retentive and laterally locking. irregularities should have no frail or undermined enamel. Creating different levels out of flat, dished up, gingival or pulpal floors could change a mechanically negative situation into a positive one.
  60. 60.  7) Precementation grooves : after casting make grooves on the walls of the inlay and/or grooves on the cavity wall exactly opposite. This will house with solid mass of cement which helps in good retention
  61. 61. 8)Electrolytic etching of inlay : This gives hinge like projections. Procedure : Protect proximal and occlusal surface with sticky wax and keep it in the electrolyte solution of 0.5 normal nitric acid. Inlay is kept in anode and metal with increased EMF as cathode.(316 stainless steel ) current causes microporosities on fitting surface which enables the luting cement to flow into it for better retention. This process takes place for around 10 to 15 mins.
  62. 62. Tooth preparations for onlay cast restorations It is partly intracoronal and partly extra coronal type of restoration, which has cuspal protection as main feature.Indications: 1)cupal protection is to be considered if the lesion width is1/3 or ½ the intercuspal distance. 2) cuspal protection is mandatory, if the width of the lesion exceeds ½ the intercuspal distance. 3) In the tooth preparation. if the length:width ratio of the cusps is more than 1:1 but not exceeding 2:1, cuspal protection to be considered. 4)if the length:width ratio is more than 2:1,cuspal protection is mandated. www.indiandentalacademy.com
  63. 63. 5) whenever there is a need to change the dimension, shape and interrelationship of the occluding tooth surfaces, onlay cast restorations are the ideal, most conservative restorations.6) Onlays are ideal restorations for abutment teeth for a removal partial denture or fixed prosthesis.7) Onlays are a ideal supporting restorations for remaining tooth structure, combined with conservative tooth involvement.8) Onlays are indicated when it is necessary to include wear facets that exceed the cusp tips and triangular ridge crests facially and/or lingually.GENERAL SHAPE : Onlays are dovetailed internally and follow cuspal anatomy externally. Proximally box or cone shaped. The main feature of the design of the tooth preparations are capping of functional cusps and shoeing of the non-functional cusps. www.indiandentalacademy.com
  64. 64. Onlay Tooth Preparation ProcedureOcclusal preparation: The initial entry is made in the central fossa to a depth of approx. 1.00 mm into dentin(2.5mm in the total depth of the tooth). In some cases this may be needed to extend to greater depth because of caries or pervious restoration . The occlusal outline form should be as conservative as the carious lesion permits. The bur is kept in the long axis of the intended depth of the insertion so that the taper of the bur provides the desired 3 to 5 degree divergence for each internal cavity wall. www.indiandentalacademy.com
  65. 65. Proximal boxes: The boxes are createdon the proximal surface. Thefacial and lingual walls shouldexhibit a combined divergenceof 6 to 10 degrees from eachother as was provided in theocclusal area of thepreparation. www.indiandentalacademy.com
  66. 66. The faciolingual dimension is likely to be determined by the presence of a restoration, caries lesion. The bevels will extend the preparations slightly beyond the proximal contact area so that the margins of the restoration will be accessible for finishing with a disk. www.indiandentalacademy.com
  67. 67. Cuspal Reduction: A carbide buror diamond bur is used toreduce the cusp. Depth cuts of1.5 to 2 mm are made for thecentric cusp(s) and cuts 1.0 to1.5 mm are made for the noncentric cusps. www.indiandentalacademy.com
  68. 68. After the depth cuts are placed, a uniform reduction of the cusps that parallels the generally anatomic contours of the occlusal surface is made. www.indiandentalacademy.com
  69. 69. The cuspal heights are reduced to the full extent of the depth cuts. Reduction of centric cusps generally needs to be greater than that for the non centric cusps because less occlusal force tends to be exerted against a non centric cusp. www.indiandentalacademy.com
  70. 70. Shoulder Preparation: A shoulder isprepared on the external surface ofthe centric cusp to provide a bandof metal to protect the tooth. Thebur is held parallel to the externalsurface of the tooth and a shoulderabout 1.0mm in height and 1.0 mmin axial depth is cut. The finish lineshould extend gingivally at atleast1.0mm beyond any occlusalcontacts. The occlusoaxial lineangles are rounded. There must beadequate (1.0 to1.5mm) clearancein all eccentric mandibularmovements. www.indiandentalacademy.com
  71. 71. Non centric cusp : A chamferor long bevel is giveninstead of shoulder in noncentric cusp(s). A barrelshaped bur can be used tocreate chamfer. The bur ispositioned at an angle ofapproximately 45 degreesto the axial surface .Thisprovides additionalprotection of the cusp. www.indiandentalacademy.com
  72. 72. Gingival Bevel: A smooth and distinct bevel isestablished on the gingival margins withno.7901 finishing bur, a thin tapereddiamond, or a gingival margin trimmer. This bevel should beapproximately 0.5mm width and at angle ofapprox.45 degrees to the external surfaceof the tooth. www.indiandentalacademy.com
  73. 73. Shoulder Bevel: A 1.0 mm bevel is placed on theshoulder with No.7901 or fine diamond bur. Thisbevel is blend with proximal bevels. Any sharpangles at the junction of the various bevels andacross the occlusoaxial line angles areeliminated.Proximal Bevels: The proximal bevel or flare isestablished with greater disk, a fine tapereddiamond. Divergence is established from thegingival floor occlusally. The proximal bevelshould blend smoothly with the gingival bevel,the buccal and lingual bevels. www.indiandentalacademy.com
  74. 74. Retention grooves : If retention grooves areneeded, grooves are placedin both proximal boxes. Ano.169 bur is used to bisectthe facioaxial and linguoaxialline angles. The grooves mustdiverge toward the occlusalaspect faciolingually and bealigned with the internal partof insertion. www.indiandentalacademy.com
  75. 75. TOOTH PREPARATION FOR CAST RESTORATIONS WITH SURFACE EXTENSIONS Modifications for basic onlay and inlay tooth preparations and restoration involving part or all of the axial surface(s), but short of veneer crown preparation. i) Skirt. ii) Collar. www.indiandentalacademy.com
  76. 76. Skirt: It is more extensive surface extension. It is also superimposed on the basic intra-coronal inlay or onlay cavity preparation facially or lingually. Indications: Skirting is required to involve defects with more dimensions (especially depth). To impart resistance and retention on a cast restoration in lieu of missing or shortened opposing facial/lingual walls. www.indiandentalacademy.com
  77. 77.  When the contact areas and the contour of the proximal surfaces are to be changed in the contemplated restorations. They will allow sufficient cast material to be accommodated without sacrifice of facial and lingual walls. Facially/lingually tilted teeth in order to restore occlusal plane. They will allow for the bulk, resistance and retention of the additional occlusal cast material required in building the occlusal table when so indicated skirts should be prepared on side towards which the tooth is tilted www.indiandentalacademy.com
  78. 78.  Every effort should be made to have the axial reduction of skirt parallel to rest of the cavity preparation. If skirt is to be used to change the contact and contour of the tooth, it should be extended far enough on facial and lingual surfaces of teeth to create sufficient retention and avoid marginal over hangs and over contouring. Like wise, if the skirt is used to create a regular occlusal plane for tilted teeth it should be extended far enough on facial or lingual proximally, away from direction of tilting. This helps in minimize effect of displacing forces in tilted direction. And also accommodation of enough cast material. www.indiandentalacademy.com
  79. 79. Collar : Most involving are surface wise and depth wise, it can be one of the two types. Cuspal collars- involve the facial or lingual surfaces of one cusp in a multi- cusped tooth. Tooth collars – entire facial or lingual surface of the tooth. www.indiandentalacademy.com
  80. 80.  Indications : They help in retention and resistance when an entire cusp is lost prior to tooth preparation or when it is necessary to remove it due to excessive undermining. They help retention in shortened tooth. They help in resistance and enhance support in endodontically treated tooth. They are used in situations where pins are contra-indicated for retention purposes. They are used for cast materials with low castability. www.indiandentalacademy.com
  81. 81.  With axial depth of 1.5mm to 2 mm, collar surface extend gingivally in a beveled shoulder finishing line, making it most reproducible extension. Collars should have less taper toward the cavity preparations than skirts. This improves retention in the shortened tooth or cusp preparations. www.indiandentalacademy.com
  82. 82.  The peripheral beveled portion of the collar will have its angulation and extent dictated by same features as those governing the angulation and extent for gingival bevels of inlays and onlays as more the bevel angulation better will be the marginal seating of cast restorations. www.indiandentalacademy.com
  83. 83. Conclusion:Cast metal inlays and onlays offer excellent restorations that may be utilized in dentistry. Even though the technique is long and posts multiple visits for patient, the resulting restoration is durable and long lasting. High noble alloys are advised for patients with allergy or sensitivity to other restorative materials. Cast metal onlays in particular, can be designed to strengthen the restored tooth structure than a full crown.The high degree of satisfaction and service derived from aproperly made cast metal restoration is a reward for thepainstaking application required. www.indiandentalacademy.com
  84. 84. References:Art and science of operative dentistry – sturdevant – 4th edition.Operative dentistry-modern theory and practice - M.A.Marzouk.Fundamentals of operative dentistry- Richerd.s.Schwartz. -2nd editionText book of operative dentistry-vimal.k.sikriInternet sources. www.indiandentalacademy.com
  85. 85. Thank youwww.indiandentalacademy.com

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