Onlay

The cast metal restoration is versatile and is especially applicable to Class II onlay preparations. The process has many steps, involves many dental materials, and requires meticulous attention to prepration.
Tooth treatment planned to be restored with an intracoronal restoration, but the decay or fracture is so extensive that a direct restoration, such as amalgam or composite, would not be able to sustain or bear forces.
Additionally, when decay or fracture incorporate areas of cusp or remaining tooth structure that undermines perimeter walls of a tooth, an onlay might be indicated.

1. Onlay Presented by:- Dr. Nakul patidar

2. content INTRODUCTION DEFINATION INDICATION CONTRAINDICATION CAST METAL ONLAY RESTORATION MODIFICATION CONCLUSION

3. INRODUCTION The cast metal restoration is versatile and is especially applicable to Class II onlay preparations. The process has many steps, involves many dental materials, and requires meticulous attention to prepration . Tooth treatment planned to be restored with an intracoronal restoration, but the decay or fracture is so extensive that a direct restoration, such as amalgam or composite, would not be able to sustain or bear forces. Additionally , when decay or fracture incorporate areas of cusp or remaining tooth structure that undermines perimeter walls of a tooth, an onlay might be indicated.

4. Types of cast metal restoration ACCORDING TO MARZOUK: Class-I : Gold and platinum group based alloys . Class-II : Low gold alloys (gold content < 50 %). Class-III : Non-gold palladium based alloys . Class-IV : Nickel-chromium based alloys . Castable moldable ceramics

5. CAST METAL ONLAY RESTORATION  “The cast metal onlay restoration spans the gap between the inlay ( intracoronal restoration) and the full crown, which is a totally ( extracoronal restoration)”  

6. DEFINATION:-   ACC TO STUDEVANTS (6th edition) :- “Caps all of the cusps of a posterior tooth and can be designed to help strengthen a tooth that has been weakened by caries or previous restorative experiences. It can be designed to distribute occlusal loads over the tooth in a manner that greatly decreases the chance of future fracture.” ACC TO SHILINBERG (4 TH EDITION):- “ Intracoronal restorations are those that fit within the anatomical contours of the clinical crown of a tooth. BUT when IT IS modified with occlusal coverage, the intracoronal restoration is called an onlay ”

7. INDICATION LARGE RESTORATION:- Better strength Control of contours and contacts Better alternative to a crown to teeth that have been greatly weakened by caries

8. When portions of a facial (lingual) smooth surface and a proximal surface are affected by caries or some other factor the treatment may be a large inlay, an onlay , a three-quarter crown, a full crown, or multiple amalgam or composite restorations. Generally , if carious portions are extensive, the choice between the previously listed cast metal restorations is determined by the degree of tooth circumference involved. A full crown is indicated if the lingual and the facial smooth surfaces are defective, especially if the tooth is a second or third molar. When only a portion of the facial smooth surface is carious, and the lingual surfaces of the teeth are conspicuously free of caries, a mesioocclusal , distofacial , and distolingual inlay or onlay with a lingual groove extension is chosen over the crown because the former is more favorable to the health of the gingival tissues and more conservative in the removal of tooth structure. (ACC TO STURDEVANT 6 TH EDITION)

9. CUSPAL PROTECTION:- Lesion width 1/3 - ½ ( intercuspal distance) = Cusp protection consider Lesion width > ½ ( intercuspal distance) = Cusp protection mandatory CUSP LENGTH/WIDTH RATIO:- If ratio- >1:1 - <2:1 = Cusp protection consider >2:1 = cusp protection mandatory WEAR FACET :- When wear facet is involved cusp tip and triangular crest ridge.

10. ENDODONTICALLY TREATED TEETH:- Molars and Premolars with endodontic treatment can be restored with a cast metal onlay but facial and lingual wall should intact. (ACC TO STURDEVANT 6 TH EDITION) TEETH AT RISK FOR FRACTURE:- The onlay can be designed to distribute occlusal loads over the tooth in a manner that decreases the chance of tooth fracture in the future.

11. DENTAL REHABILITATION WITH CAST METAL ALLOYS:- DIASTEMA CLOSURE AND OCCLUSAL PLANE CORRECTION :- Indicated when extension of mesiodistal dimension of tooth is necessary. Occlusal plane of a slightly tilted tooth. Heavy occlusal contact and attrition of posterior teeth . ( A cc to Nisha garg )

12. REMOVABLE PROSTHODONTIC ABUTMENT :- Teeth that are to serve as abutments for a removable partial denture can be restored with a cast metal restoration. Advantages : The rest seats, guiding planes and other aspects of contour relating to the RPD are better controlled when the indirect technique is used.

13. Contraindications High Caries rate Facial and Lingual tooth surface must be free of caries or previous restorations. If present, the tooth must be restored with a Full crown. Young patients Old age patient Esthetics

14. Amalgam or Composites are the restorative material of choice for Class I and II restorations unless the tooth is severely broken down or endodontically restored . Small restorations Extensive occlusal facet

15. ADVANTAGE Strength Biocompatibility Low wear Control of Contours and Contacts Less chances of voids and internal stress. ( Acc to Nisha garg )

16. DISADVANTAGE Microleakage Number of Appointments and More Chair time Provisional restoration is required Costs Technique sensitive Difficult repair ( Acc to Nisha garg )

17. ONLAY PREPRATION

18. CAST METAL ONLAY RESTORATION Dovetailed internally Follow cuspal anatomy externally. Proximally – Box shaped or cone shaped.

19. Occlusal reduction Improve access and the visibility When the cusps are reduced, it is easier to assess the height of the remaining clinical crown of the tooth Using the No. 271 carbide bur held parallel to the long axis of the tooth crown, a 2-mm deep pulpal floor is prepared along the central groove

20. The groove should not be extended further than two thirds the distance from the central groove to the cusp tips. With the side of the No. 271 carbide bur, uniform 1.5-mm deep depth cuts are prepared on the remaining occlusal surface. Depth cut placed on triangular ridge on facial and lingual surface.

21. Caries and old restorative material that is deeper in the tooth than the desired clearance are not removed at this step in preparation. When completed, this reduction should reflect the general topography of the original occlusal surface. The operator should not attempt to reduce the mesial and distal marginal ridges completely at this time to avoid hitting an adjacent tooth.

22. INTRACORONAL PREPRATION Carbide burs used to develop the vertical internal walls of the preparation for cast metal inlays and onlays . No. 271 bur No.169 L bur No.8862 bur (Flame shaped diamond bur) Throughout the preparation , the vertical walls are oriented to a single “draw” path, usually the long axis of the tooth crown. G ingival-to-occlusal divergence of these preparation walls may range from 2 to 5 degrees

23. For mandibular molars and second premolars whose crowns tilt slightly lingually , bur should also be tilted slightly (5–10 degrees )

24. OCCLUSAL STEP After cusp reduction, a 0.5-mm deep occlusal step should be present in the central groove region between the reduced cuspal inclines and the pulpal floor . Old restorative material or caries that is deeper pulpally than this 0.5-mm step is not removed at this stage of tooth This 0.5-mm occlusal step contributes to the retention of the restoration with additional bulk for rigidity

25. PROXIMAL BOX PREPRATION:- ACC TO STURDEVANTS :- Occlusal step should be extended for creation of proximal box. Continue prepration with 271 bur. Gingival floor should be in width of 0.8 mm (enamel-0.5 & Dentine-0.3mm)

26. Cutting the proximal ditch. Provides a 0.5-mm clearance of the unbeveled gingival margin with the adjacent tooth.

27. Penetration of enamel by side of bur at its gingival end . Breaking away isolated enamel.

28. Planing the distofacial , distolingual , and gingival walls by hand instruments to remove all undermined enamel may be indicated. Depending on access, the operator can use a No. 15 (width ) straight chisel, bin-angle chisel or enamel hatchet . The axial wall may be planned with the side edge

29. Shallow (0.3-mm deep) retention grooves may be cut in the facioaxial and linguoaxial line angles with the No. 169L carbide bur. It should be completely in dentine. It is given when prepared tooth is short.

30. REMOVAL OF INFECTED CARIOUS DENTIN AND DEFECTIVE RESTORATIVE MATERIALS

31. PREPARATION OF BEVELS AND FLARES The slender, flame-shaped, fine-grit diamond instrument is used to place counterbevels on the reduced cusps to apply the gingival bevels, and to create secondary flares on the facial and lingual walls of the proximal boxes . D iamond instrument is used to prepare the counterbevels on the facial and lingual margins of the reduced cusps . B evel should be of generous width and should result in 30-degree marginal metal.

32. The counterbevel usually should be wide enough so that the cavosurface margin is beyond (gingival to) any contact with the opposing dentition . A counterbevel is not placed on the facial cusps of maxillary premolars and first molars where esthetic considerations. After beveling and flaring, any sharp junctions between the counterbevels and the secondary flares are rounded slightly

33. This should result in 30- to 40-degree marginal metal This cavosurface design helps seal and protect the margins A strong enamel margin with an angle of 140 to 150 degrees. If >150 degrees is incorrect Its produce a less defined enamel margin (finish line) The marginal cast metal alloy is too thin and weak If <140 degrees or less The metal is too bulky and Difficult to burnish

34. Using the flame-shaped diamond instrument that is rotating at high speed, the dentist prepares the lingual secondary flare. The dentist approaches from the lingual embrasure The wall extends from the linguoaxial line angle into lingual embrasure in two planes. The first is termed lingual primary flare ; and the lingual second is termed lingual secondary flare . During this ( secondary) flaring operation, the long axis of the instrument is held nearly parallel to the line of draw, with only a slight tilting mesially and lingually for the direction of translation of the instrument is that which results in a marginal metal angle of 40 degree.

35. Secondary Flare Places margins in more cleansable finishable areas results in 40 degrees marginal metal. A more blunted and stronger enamel margin is produced May have different angulations, involvement & extent

36. INDICATIONS OF SECONDARY FLARE Broad contact areas , secondary flare brings the facial and lingual margins to finishable , cleansable areas , without sacrificing much tooth structure. In case caries is widely extended in buccolingual dimension. To include surface defects on facial and lingual aspect beyond the primary flare. To overcome undercuts that may be present at the cervical aspect of the facial and lingual proximal walls

37. ACC TO MARZOUK:- Facial and lingual margin of proximal box should correspond the embrasure. All the undermine enamel, surface defect and peripheral margin undercut are eliminated. “The difference in inlay and onlay proximal box prepration is of secondary flare are used in all situation and most cases joining of short or counter bevel facially and lingually with primary flare.”

38. TOOTH PREPARATION WITH SURFACE EXTENSIONS:- INDICATIONS- o Surface extensions are required to include facial or lingual defects beyond the axial angle of the tooth. o Surface extensions are required to eradicate severe peripheral Marginal undercuts, which have not been removed by the maximum angulations and extent of a secondary flare. o A surface extension is necessary to encompass an axial angle for reinforcing and supporting reasons.

39. A surface extensions is needed to add to the retentive capability of the restoration proximally especially with shortened facial and lingual walls or as a reciprocal means of retention More surface extension is required to fulfil the objectives of secondary flares in extremely wide cavities or contact areas

40. REVERSE SECONDARY FLARE:-   This is a surface extension of the basic intracoronal onlay prepration. 2 Indication :- Surface extension require beyond axial angle of tooth , to include facial and lingual defect. 2 Surface extension require to eradicate severe peripheral marginal undercut which have not been removed by the maximum angulation and extent of secondary flare. 2

41. Surface extension is require to add retentive capability of the restoration proximally esp. with short facial and lingual wall. 2 Reverse secondary flare is usually in the form of partial bevel which is in enamel only. It end in facial and lingual surface with a knife edge finishing line and extent of this should not exceed the height of contour of tooth Reverse secondary flare could include only the middle part of periphery . 2

42. REVERSE SECONDARY FLARE

43. The instrument should be tilted slightly mesially to produce a gingival bevel with the correct steepness to result in 30-degree marginal metal. The gingival bevel should be 0.5 to 1 mm wide and should blend with the lingual secondary flare.

44. The gingival bevel serves the following purposes: Weak enamel is removed. :- Gingival declination of the enamel rods. The bevel results in 30-degree metal that is burnishable (on the die) because of its angular design. A lap, sliding fit is produced at the gingival margin . This helps improve the fit of the casting in this region. With the prescribed gingival bevel, if the inlay fails to seat by 50 μm , the void between the bevel metal and the gingival bevel on the tooth may be 20 μm ; however , failure to apply such a bevel would result in a void

45. The operator completes the gingival bevel and prepares the facial secondary flare. T he direction of translation of the instrument is that which results in 40-degree marginal metal T he lingual surface and proceeded to the facial surface. The direction may be reversed, however, starting at the facial surface and moving toward the lingual surface. On the mesiofacial surface of maxillary premolars and first molars where extension of the facial margin should be minimal, it is usually desirable to use the lingual-to-facial direction.

46. The flame-shaped, fine-grit diamond instrument also is used for occlusal bevels. The width of the cavosurface bevel on the occlusal margin should be approximately one-fourth the depth of the respective wall but wider bevel is desired to include an enamel defect.

47. MODIFICATION IN ONLAY TOOTH PREPRATION

48. Facial or Lingual Surface Groove Extension :- Faulty facial groove on occlusal surface continues with facial surface on mandibular molar Faulty distal oblique groove on occlusal surface continuous lingual surface of maxillary molar.

49. INCLUSION OF PORTIONS OF THE FACIAL AND LINGUAL SMOOTH SURFACES AFFECTED BY CARIES, FRACTURED CUSPS, OR OTHER INJURY Mandibular first molar with large mesio - occluso -distal amalgam and fractured mesiolingual cusp. No. 271 carbide bur is used to prepare the gingival shoulder and the vertical lingual wall. Reducing cusps for capping and extending out the facial groove improve the retention and resistance forms .

50. Beveling of margins Complete preparation

51. Preservation of oblique ridge. Disto -lingual cusp is preferable in distocclusal restoration. It’s reduced with 271 bur and 1.5 uniform reduction is achived MAXILLARY FIRST MOLAR WITH UNAFFECTED, STRONG OBLIQUE RIDGE.

52. Lingual extension given when only distolingual wall of proximal box is achieved. Occlusogingival dimension of axial wall -2.5 mm. Retention is achieved by mesio and disto axial groove and facial and lingual retention groove. Lingual counterbevel is given

53. Retention form is attained by (1) C reating a maximum of 2-degree occlusal divergence of the vertical walls, (2) Accentuating some line angles (3) Extending the lingual surface groove to create an axial wall height in this extension of at least 2.5 mm occlusogingivally .   Proper resistance form dictates (1) Routine capping of the distolingual cusp (2) Maintaining sound tooth structure between the lingual surface groove extension and the distolingual wall of the proximal boxing.

54. SKIRT PREPARATION:- ACC TO STURDEVANTS:-   Skirts are thin extensions of the facial or lingual proximal margins of the cast metal onlay that extend from the primary flare to a termination just past the transitional line angle of the tooth . Extention are entirely on enamel. If lingual wall is missing than skirt extention of facial margin is to be given.

55. “ This is a specific extension involving a part of the axial angle of tooth” - According to marzouk INDICATION:- ( acc to marzouk ) It is required when involve defect with more dimension(esp. in depth) than those that can be involve in reverse secondary flare. When shorten opposing facial and lingual wall Contact areas and contour of proximal surface are to be changed Essential for facially and linguallly tilted teeth.

56. Indication :- ( acc to sturdevants ) Teeth exhibit split tooth syndrome Spinting of posterior teeth Proximal surface contour and contact are to be extended more than the normal dimension Occlusal plane of a mesially tilted molar Disadvantage:- Increase display of metal on facial and lingual surface of teeth.

57. Collar Preparation:- Acc to marzouk :- “ This is a surface extension completely surrounding a cusp or a surface of tooth .” Types:- Cuspal collars:- involve the facial or lingual surface of one cusp only in multicusped tooth. Tooth collar:- involve facial and ligual surface of tooth.

58. INDICATION OF COLLAR PREPRATION:- ( Acc to M arzouk ) Help in retention and resistance form when entire cusp is lost prior to tooth prepration Help in retention of shorten teeth Help to enhance support for the tooth that is endodontically treated Used when pins are contraindicate for retention Used for cast material with low castability Used for areas in a cast alloy to be veneered by fused porcelain.

59. For preparing mesio-occlusodistal onlay capping all cusps, a facial or lingual “ collar,”or both, may be provided. With the help of 271 bur , collar is prepared and is to be 2-3 mm To provide uniform thickness , occlusal 1 mm reduction should be prepared. A light bevel is given.

60. Slot Preparation:- T he vertical walls of the occlusal step portion of the preparation have been reduced so as to provide very little retention form.   The necessary retention can be achieved by cutting a distal slot. Such a slot is preferred over preparing a box in the distal surface because:- The former is more conserving of tooth structure and of strength of the tooth crown The linear extent of marginal outline is less. No . 169L carbide bur whose long axis should parallel the line of draw

61. Slot should have approximate dimension:- (1) M esiodistally , the width (diameter) of the bur; (2) faciolingually , 2 mm (3) 2 mm gingival of the normally positioned pulpal wall.

62. BOX PREPRATION:- The box design is principally used with the proximo -occlusal preparation for the direct method of wax pattern formation. ( Acc to V imal S ikri - 2nd edition) :- It is conventional technique Direct wax technique require proximal margin in a such a wax that can be directly manipulated in mouth Margin provide greater bulk of wax

63. SLICE PREPRATION:- ( Acc to G.T. Charbeneau - 3 rd edition) “A slice referred to the place­ment of extracoronal taper using a disk of adequate diameter to contact nearly the en­tire proximal surface .” It estabilish cervical finishing line for proximal box prepration as well as remove undercut from prepration . D isk­ing of the proximal surface to establish the buccal and lingual extent of the finish lines and provide a lap joint for finishing Teeth with tapering or ovoid forms generally will indicate a slice prep­aration extending short of the cervical floor P roximal slice for the in­direct inlay produces excellent definition for the finishing line.

64. AUXILIARY SLICE PREPRATION:- ( Acc to G.T. Charbeneau - 3 rd edition ) The slice preparation provides external support of weakened tooth tissue or areas subjected to high stresses during function. Partially around the proximal line angles, thus providing additional tooth support . Advantage:- Minimal bulk of tissue is lost Resistance form is greatly en­hanced Reducing the possibility of tooth fracture.

65. MODIFIED FLARE PREPARATION:- A hybrid between the box and slice preparations. Buccal and lingual proximal walls are initially formed with minimal extension, then disked in a plane that only slightly reduces the proximal wall dimension .

66. MODIFICATIONS FOR ESTHETICS ON MAXILLARY PREMOLARS AND FIRST MOLARS On the facial cusps of maxillary premolars and on the mesiofacial cusp of the maxillary first molar , the occlusal reduction should be only 0.75 to 1 mm on the facial cusp ridge to minimize the display of metal . T hickness should increase progressively to 1.5 mm toward the center of the tooth to provide rigidity to the capping metal .

67. The secondary flare is omitted, and the wall and margin are developed with a chisel or enamel hatchet. Cspus do not receive a counterbevel but are “stubbed” or blunted by the application of a sandpaper disk or the finegrit diamond instrument held at a right angle to the facial surface

68. ENDODONTICALLY TREATED TEETH:- Weak teeth are subjected to fracture. If facial and and lingual surfaces are sound it it better to advice mod onlay is given. Skirt extensions and collar preparations onlay more of an extracoronal restoration that encompasses the tooth, such that the tooth is better able to resist lateral forces. Before starting the preparation of an endodontically treated posterior tooth, the pulp chamber should be excavated to the chamber floor. Usually into the canals (1-2 mm) and an amalgam or composite foundation should be placed.

69. RESTORING THE OCCLUSAL PLANE OF A TILTED MOLAR. An onlay is excellent for restoring the occlusal plane of a mesially tilted molar. To increase the height of tooth , the counterbevel is placed and it extend the gingivally more than usual . Often the mesiofacial and mesiolingual margins on the “submerged” proximal surface This skirt extension can be accomplished with a minimal loss of tooth structure.

70. ACC TO MARZOUK:- On functional cusp side, margin are located gingivally , to be away from the contact with apposing tooth surface in centric occlusion. Normally it involve 1/3-1/4 on facial and lingual surface On Non function cusp side, facial and lingual margin located just gingival to tip and ridge crest of involved cusp and away from occlusal contact (static and functional ) Gingival margin should include all facial and lingual groove. It should be parallel to the contour of cusp tip and crest of adjacent ridges.

71. ( ACC TO MARZOUK):- OCCLUSAL BEVEL :- Constitutes 1/3 of total wall height. Hollow ground bevel is given. This bevel have 30-45 degree angulation of tooth crown. It should relieved 1 mm from opposing cuspal element. For each cusp , two hollow ground bevel is given i.e mesial and distal Advantage of hollow ground bevel:- Bulk of restoration Increase surface area of restoration.

72. ACC TO MARZOUK:- COUNTER BEVEL:- Extracoronal part of prepration It should be relieved form opposing cuspal element by at least 1 mm. Angulation of counter bevel is 30-70 degree( as it is measure by embracing angle i.e. formed by bevel and long axis of crown. Emaracing angle is inversely proportional to facial and lingual wall involvement.

73. Uniform 1.5mm deep depth cuts should be prepare on the remaining occlusal surface

74. At this time, mesial and distal marginal ridge should not reduce. For mandibular premolar and molar bur should tilt 5-10 degree. Gingivo occlusal divergence should be 2-5 degree. Taper is directly proptional to length of wall.

75. OCCLUSAL STEP:-   After cusp reduction, there should be a 0.5 mm deep occlusal step in the central groove region between the reduced cuspal inclines and the pulpal floor.  

76. ACC TO MARZOUK:- TABLE:- Transitional are between intra and extra coronal part. It should be relieved by 1.5 mm in both static and functional contact. At any location it should be flat. It provide major resistance form.

77. PROXIMAL BOX PREPRATION:- ACC TO STURDEVANTS :- Occlusal step should be extended for creation of proximal box. Continue prepration with 271 bur. Gingival floor should be in width of 0.8 mm (enamel-0.5 & Dentine-0.3mm)

78. Retention coves are placed with carbide bur to increase retention. Retention grooves on the facioaxial and linguoaxial line angle with 169 bur.

79. Proximal Flares Primary flare:- Part of circumferential tie Similar to a long bevel Formed of enamel and part of dentin Placed on facial and lingual proximal wall. Have 45 o angulation to inner dentinal wall proper Places proximal margins in cleansable finishable areas.

80. Mesial and distal marginal 30 degree marginal metal. Occlusal and gingival bevel 40 degree marginal metal.

81. Class II Preparation for Abutment Teeth and Extension Gingivally to Include Root-Surface:- Extension of facial, lingual and gingival margin is indicated in development of guiding plane. Gingival extension should be achieved by lengthening the gingival bevel.

82. FISSURES IN THE FACIAL AND LINGUAL CUSP RIDGES OR MARGINAL RIDGES:- Preparation margin should not cross such fissures, but should be extended to include them . the No. 271 carbide bur until only 2 mm of tooth structure remains between the bur and the lingual surface of the tooth. Additional extention is achieved through wider bevel

83. CAPPING CUSP:- “ Reduce the cusps for capping as soon as the indication forsuch capping is determined because this improves access and visibility for subsequent steps in preparation .” - Acc to sturdevants When cusp slope >1/2 distance from any primary occlusal groove to cusp tip, cusp should consider. If prepration >1/2 distance , cusp is necessary to Protect from masticatory forces Remove occlusal margin from heavy stress

84. In Maxillary premolar and Molar, Reduction should be 0.75-1 mm Reduction increase progressively toward centre of tooth. Only blunting and smoothing of the enamel margin( a stub margin) should be prepared. Mesiofacial margin minimally extended and secondary flare is omitted.

85. A reverse or counter bevel is prepared on facial (lingual) margin of reduced cusp. Cusp reduction decrease the retention so proximal retention groove is recommended. Occlusal clearance is observed with interocclusal record.

86. INCLUDING PORTIONS OF THE FACIAL AND LINGUAL SMOOTH SURFACES AFFECTED BY CARIES OR OTHER INJURY Tooth is second and third molar and if facial and lingual surface both involved, a full crown is indicated If only portion facial or lingual surface involved and other areas free of caries than an onlay with facial and lingual extention is indicated.

87. CONCLUSION Cast metal inlays and onlays offer excellent restorations but it uses below the optimal level.The technique requires multiple patient visits and excellent laboratory support, but the resulting restorations are durable and long lasting . Cast metal onlays in particular can be designed to strengthen the restored tooth, while conserving more tooth structure than a full crown. Disadvantages , such as high cost and esthetics, limit their use .  

88. REFERENCES Text book of Sturdevant’s Art and science of operative dentistry( 6 th edition) Text book of operative dentistry( Marzouk ) Text book of operative dentistry (Nisha garg 3 rd edition) Text book of operative dentistry ( R amya Raghu) Principle and practice of operative dentistry (G.T. Charbeneau ) (3 th edition) Text book of Shilingburg , Fundamental of fixed prosthodontics (4 th edition)

89. Thank you