Good
Morning
Good morning
Contents
 Introduction
 Classification
 Biological requirements
 Mechanical requirements
Esthetic requirements
 Planning and evaluating tooth
preparation
 Frequently encountered errors in
tooth preparation
 ...
Introduction
Carious, traumatised or worn out teeth
require preparation
Preparations based on fundamental
principles
A ...
Tooth preparation -“ mechanical treatment of
dental disease or injury to hard tissues that
restore a tooth to original for...
Objectives of tooth preparation
Reduction of tooth in miniature to provide retainer
support
Preservation of healthy toot...
Factors to be considered before
preparing teeth
•Size and position of the pulp
•Rotation or tilting of teeth
•Provision of...
•Finishing margin
•Degree of metal to be displayed
•Treatment of any opposing teeth
Classification
According to Rosenstiel, Land and
Fujimoto (1988)
biologic mechanical
esthetic
According to Shillingburg et al (1987)
•Preservation of tooth structure
•Retention and resistance
•Structural durability
...
The Rosenstiel classification
Biological considerations
I. Prevention of damage during tooth preparation
II.Conservation of tooth structure
III.Consider...
I.Prevention of damage during
tooth preparation
Adjacent teeth-
 A metal matrix band around adjacent tooth
 A thin taper...
Soft tissues-
 Prevent damage to tongue and cheeks
Careful retraction with aspirator tip and
mouth mirror or flanged sal...
Pulp-
Extreme temperature, chemical irritation or
micro organisms cause irreversible pulpitis
Pulp size decreases with a...
Causes of injury-
Temperature -
excessive pressure
high rotational speeds
type, shape, condition of cutting instrument
all...
water spray prevent
overheating of the tooth
removes debris
prevents clogging
prevents dessication of dentin
Chemical action-
bases, restorative resins, solvents and luting
agents-cause pulpal damage
Bacterial action-
all carious...
II.Conservation of tooth structure
 partial coverage
complete coverage
 Axial walls - minimal taper
 Occlusal reduction...
 Retain maximal thickness surrounding
pulpal tissues
 conservative margin geometry
 Avoid unnecessary apical extension
III.Considerations affecting
future dental health
Axial reduction-
 sufficient space for good axial contours
 margin - s...
adequate less over
reduction reduction reduction
Margin placement-
Supra gingival margins –
 No trauma to soft tissues
 On enamel
 Kept plaque free
 Impressions made e...
Equigingival margins-
At the level of the crest of the gingiva
Maintain the health of periodontium
Subgingival margins-
dental caries,cervical erosion extend subgingivally
crown lenghthening procedure not indicated
 pr...
margin of metal ceramic crown to be hidden
 root sensitivity
 modification of the axial contour indicated
Margin adaptation-
casting to fit within 10 micrometre
porcelain margin to fit within 50 micrometre
smooth and even margin...
Margin geometry-
Ease of preparation without overextension or
unsupported enamel
Ease of identification in the impressio...
Sufficient bulk of material
Conservation of tooth structure
margin design advantages disadvantages indications
margin design advantages disadvantages indications
margin design advantages disadvantages indications
Feather edge chisel edge chamfer beveled shoulder 120 deg sloped beveled
shoulder shoulder
Occlusal considerations-
Reduction to compensate for supra erupted or
tilted abutment teeth
Reduced retention and resist...
Preventing tooth fracture-
The tooth preparation design- minimise the
potentially destructive stresses
Mechanical considerations
I. Providing retention form
II.Providing resistance form
III.Preventing deformation of the resto...
I. Providing retention form
Retention
The quality of a preparation that prevents the
restoration from becoming dislodged b...
 Magnitude of dislodging forces
 Geometry of tooth preparation
 Roughness of the fitting surface of the
restoration
 M...
A)Magnitude of the dislodging forces-
Pulling with floss under the connectors
When exceptionally sticky foods( caramel ) i...
B) Geometry of the tooth preparation-
 A single path of placement
 Preparation restrains free movement
 The occlusoaxia...
Taper:
Convergence of two opposite external walls of
a tooth preparation as viewed in a given plane
Angle of convergence
...
Undercut- any irregularity in the wall of the
prepared tooth that prevents the withdrawal or
seating of a wax pattern or c...
Surface area:
Crowns with tall axial walls - more retentive
Wider tooth – more retentive
Stress concentration:
Stresses are not uniform throughout the
cement
Are concentrated around the junction of axial
and o...
Type of preparation:
Retention of complete crown is more than
double of that of partial coverage
Addition of grooves and...
Roughness of the surfaces being cemented:
Retentive failure -cement restoration interface
Air abrading the fitting surfa...
Materials being cemented:
type of casting alloy
core build up material
Base metal alloys better retained
Cement adheres...
Type of luting agent:
Film thickness of the luting agent:
Important if slightly oversized casting is made
II. Providing resistance form
Lateral forces displace by causing rotation
Rotation is prevented by resistance areas
Depends on:
•Magnitude and direction of the dislodging
forces
•Geometry of tooth preparation
•Physical properties of the l...
A)Magnitude and direction of dislodging
forces-
 In normal occlusion , biting force mostly is
axially directed
 If patie...
B) geometry of tooth preparation-
 Taper of 5 to 22 degrees
 Short tooth with large diameters- less
resistance
 On mola...
 Increasing taper and rounding off axial angles
reduce resistance
 Proximal grooves and boxes enhance resistance
 Parti...
C) Physical properties of luting agents-
Properties such as compressive strength and
modulus of elasticity
Adhesive resin ...
III. Preventing deformation
A)Alloy selection-
 Type I and II gold alloys -intra coronal cast
restorations
 Type III and...
B) Adequate tooth reduction –
 Alloy thickness of 1.5 mm over functional
cusps and 1 mm over non functional cusps
 Occlu...
Esthetic considerations
Determining the esthetic expectations of the
patient
At the initial examination, a full assessment...
All ceramic restorations –
 most pleasing esthetic restoration
 mimic tooth original color better
 greater risk of brit...
Metal ceramic restorations-
 a metal cast sub structure that in visible areas
has an esthetic porcelain veneer
 a minimu...
Partial coverage restorations-
 maintain an intact labial or buccal surface
 tooth structure is conserved
Planning & evaluating tooth
preparations
Diagnostic tooth preparations-
 selecting path of placement
deciding on the amo...
Diagnostic waxing procedures-
establish the optimum contour and occlusion
Alteration of occlusal scheme or anterior
guid...
Evaluative procedures during tooth
preparation-
Detecting undercuts during tooth
preparation
Complex preparations - evaluated by making an
alginate impression and pouring it in fast setting
stone.
A dental surveyor ...
Checking occlusal reduction -
use the contra angle handpiece as both a
cutting and measuring instrument.
top surface of the turbine head is
perpendicu...
Patient and operator positioning-
Direct view preferred
Having the patient rotate the head -improves
visibility of molar...
Maxillary right posterior –
buccal or buccal half of occlusal-
operator at 9 to 11 o’clock position
patient turns head to...
Maxillary left posterior-
buccal or buccal half of occlusal-
operator at 9 o’clock position
patient turns head to right
...
Frequently encountered errors in
tooth preparations
Inadequate tooth reduction on incisal or
occlusal surfaces
Inadequat...
Inadequate build ups
Indistinct margins
Excess gingival extension
Undercuts in the preparation’s axial
walls
Sharp an...
Conclusion
Successful restoration- accurate diagnosis
thoughtful Rx planning
preparation design
On tooth preparation depends-
pulp vitality
periodontal health
good esthetics
proper occlusion
protection of remainin...
References
•Contemporary fixed prosthodontics –
Rosenstiel, Land and Fujimoto
4th edition pages 209- 257
•Fundamentals of ...
•Tylman’s fundamentals of fixed
prosthodontics
8th edition pages 113-143
•JADA oct 2007 vol 138 pages 1373- 1375
•JPD june...
Thank you
For more details please visit
www.indiandentalacademy.com
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
Biomechnics/ dental continuing education online
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Indian Dental Academy: will be one of the most relevant and exciting

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implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic

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Biomechnics/ dental continuing education online

  1. 1. Good Morning Good morning
  2. 2. Contents  Introduction  Classification  Biological requirements  Mechanical requirements
  3. 3. Esthetic requirements  Planning and evaluating tooth preparation  Frequently encountered errors in tooth preparation  Conclusion  References
  4. 4. Introduction Carious, traumatised or worn out teeth require preparation Preparations based on fundamental principles A good preparation ensures that subsequent techniques can be accomplished
  5. 5. Tooth preparation -“ mechanical treatment of dental disease or injury to hard tissues that restore a tooth to original form” Perceptive diagnosis and disciplined tooth preparation determine success
  6. 6. Objectives of tooth preparation Reduction of tooth in miniature to provide retainer support Preservation of healthy tooth structure to secure resistance form Provision for acceptable finish lines Performing axial tooth reduction to encourage favourable tissue responses from artificial crown contours
  7. 7. Factors to be considered before preparing teeth •Size and position of the pulp •Rotation or tilting of teeth •Provision of space for connectors •Use of precision retainers
  8. 8. •Finishing margin •Degree of metal to be displayed •Treatment of any opposing teeth
  9. 9. Classification According to Rosenstiel, Land and Fujimoto (1988) biologic mechanical esthetic
  10. 10. According to Shillingburg et al (1987) •Preservation of tooth structure •Retention and resistance •Structural durability •Marginal integrity •Preservation of periodontium
  11. 11. The Rosenstiel classification
  12. 12. Biological considerations I. Prevention of damage during tooth preparation II.Conservation of tooth structure III.Considerations affecting future dental health
  13. 13. I.Prevention of damage during tooth preparation Adjacent teeth-  A metal matrix band around adjacent tooth  A thin tapered diamond - interdental area  Leave a slight lip or fin of enamel on the proximal side
  14. 14. Soft tissues-  Prevent damage to tongue and cheeks Careful retraction with aspirator tip and mouth mirror or flanged saliva ejector
  15. 15. Pulp- Extreme temperature, chemical irritation or micro organisms cause irreversible pulpitis Pulp size decreases with age
  16. 16. Causes of injury- Temperature - excessive pressure high rotational speeds type, shape, condition of cutting instrument all increase generated heat
  17. 17. water spray prevent overheating of the tooth removes debris prevents clogging prevents dessication of dentin
  18. 18. Chemical action- bases, restorative resins, solvents and luting agents-cause pulpal damage Bacterial action- all carious dentine should be removed
  19. 19. II.Conservation of tooth structure  partial coverage complete coverage  Axial walls - minimal taper  Occlusal reduction - anatomic planes
  20. 20.  Retain maximal thickness surrounding pulpal tissues  conservative margin geometry  Avoid unnecessary apical extension
  21. 21. III.Considerations affecting future dental health Axial reduction-  sufficient space for good axial contours  margin - smooth and free of ledges  anterior crowns –maintain the interproximal papilla
  22. 22. adequate less over reduction reduction reduction
  23. 23. Margin placement- Supra gingival margins –  No trauma to soft tissues  On enamel  Kept plaque free  Impressions made easily with no soft tissue damage  Easy evaluation after placement or at recall appointments
  24. 24. Equigingival margins- At the level of the crest of the gingiva Maintain the health of periodontium
  25. 25. Subgingival margins- dental caries,cervical erosion extend subgingivally crown lenghthening procedure not indicated  proximal contact area extends to gingival crest  additional retention /resistance needed
  26. 26. margin of metal ceramic crown to be hidden  root sensitivity  modification of the axial contour indicated
  27. 27. Margin adaptation- casting to fit within 10 micrometre porcelain margin to fit within 50 micrometre smooth and even margin rough , irregular increased margin stepped junctions length & reduced adaptation accuracy
  28. 28. Margin geometry- Ease of preparation without overextension or unsupported enamel Ease of identification in the impression and on the die A distinct boundary to which the wax pattern can be finished
  29. 29. Sufficient bulk of material Conservation of tooth structure
  30. 30. margin design advantages disadvantages indications
  31. 31. margin design advantages disadvantages indications
  32. 32. margin design advantages disadvantages indications
  33. 33. Feather edge chisel edge chamfer beveled shoulder 120 deg sloped beveled shoulder shoulder
  34. 34. Occlusal considerations- Reduction to compensate for supra erupted or tilted abutment teeth Reduced retention and resistance Endodontic treatment needed Prevent traumatic occlusal scheme
  35. 35. Preventing tooth fracture- The tooth preparation design- minimise the potentially destructive stresses
  36. 36. Mechanical considerations I. Providing retention form II.Providing resistance form III.Preventing deformation of the restoration
  37. 37. I. Providing retention form Retention The quality of a preparation that prevents the restoration from becoming dislodged by such forces parallel to the path of placement
  38. 38.  Magnitude of dislodging forces  Geometry of tooth preparation  Roughness of the fitting surface of the restoration  Materials being cemented  Type of luting agent  Film thickness of the luting agent
  39. 39. A)Magnitude of the dislodging forces- Pulling with floss under the connectors When exceptionally sticky foods( caramel ) is eaten Magnitude depends on -stickiness of foods -surface area -surface texture
  40. 40. B) Geometry of the tooth preparation-  A single path of placement  Preparation restrains free movement  The occlusoaxial line angle - a replica of the gingival margin geometry
  41. 41. Taper: Convergence of two opposite external walls of a tooth preparation as viewed in a given plane Angle of convergence Maximum retention - parallel walls
  42. 42. Undercut- any irregularity in the wall of the prepared tooth that prevents the withdrawal or seating of a wax pattern or casting If cervical diameter at the margin narrower than at occluso axial junction The recommended convergence between opposing walls is 6 degrees
  43. 43. Surface area: Crowns with tall axial walls - more retentive Wider tooth – more retentive
  44. 44. Stress concentration: Stresses are not uniform throughout the cement Are concentrated around the junction of axial and occlusal surfaces Sharp occlusoaxial line angles should be rounded to minimise these stresses
  45. 45. Type of preparation: Retention of complete crown is more than double of that of partial coverage Addition of grooves and boxes limit the path of placement
  46. 46. Roughness of the surfaces being cemented: Retentive failure -cement restoration interface Air abrading the fitting surface with 50 micron of alumina Avoid abrading the polished surfaces or margins
  47. 47. Materials being cemented: type of casting alloy core build up material Base metal alloys better retained Cement adheres better to amalgam
  48. 48. Type of luting agent: Film thickness of the luting agent: Important if slightly oversized casting is made
  49. 49. II. Providing resistance form Lateral forces displace by causing rotation Rotation is prevented by resistance areas
  50. 50. Depends on: •Magnitude and direction of the dislodging forces •Geometry of tooth preparation •Physical properties of the luting agent
  51. 51. A)Magnitude and direction of dislodging forces-  In normal occlusion , biting force mostly is axially directed  If patient has a habit of pipe smoking or bruxism, large oblique forces are generated
  52. 52. B) geometry of tooth preparation-  Taper of 5 to 22 degrees  Short tooth with large diameters- less resistance  On molar crown minimum preparation wall height - 3.5 to 4 mm
  53. 53.  Increasing taper and rounding off axial angles reduce resistance  Proximal grooves and boxes enhance resistance  Partial coverage crowns have less resistance
  54. 54. C) Physical properties of luting agents- Properties such as compressive strength and modulus of elasticity Adhesive resin  glass ionomer  zinc phosphate  polycarboxylate  zinc oxide eugenol
  55. 55. III. Preventing deformation A)Alloy selection-  Type I and II gold alloys -intra coronal cast restorations  Type III and IV gold alloys -crowns and FDPs  Nickel chromium alloys - for long span FDPs
  56. 56. B) Adequate tooth reduction –  Alloy thickness of 1.5 mm over functional cusps and 1 mm over non functional cusps  Occlusal reduction should be uniform following cuspal planes of teeth
  57. 57. Esthetic considerations Determining the esthetic expectations of the patient At the initial examination, a full assessment is made of the appearance of the patient ,noting teeth shown in speech , smiling and laughing Related to oral hygiene needs and the potential for development of future disease
  58. 58. All ceramic restorations –  most pleasing esthetic restoration  mimic tooth original color better  greater risk of brittle tooth fracture  minimum material thickness of 1 to 1.2 mm
  59. 59. Metal ceramic restorations-  a metal cast sub structure that in visible areas has an esthetic porcelain veneer  a minimum reduction of 1.5 mm facially  sub gingival margins  porcelain coverage on occlusal surface
  60. 60. Partial coverage restorations-  maintain an intact labial or buccal surface  tooth structure is conserved
  61. 61. Planning & evaluating tooth preparations Diagnostic tooth preparations-  selecting path of placement deciding on the amount of tooth reduction determining the location for the facial and proximal margins
  62. 62. Diagnostic waxing procedures- establish the optimum contour and occlusion Alteration of occlusal scheme or anterior guidance
  63. 63. Evaluative procedures during tooth preparation-
  64. 64. Detecting undercuts during tooth preparation
  65. 65. Complex preparations - evaluated by making an alginate impression and pouring it in fast setting stone. A dental surveyor - precisely measure the axial inclinations of the tooth preparation.
  66. 66. Checking occlusal reduction -
  67. 67. use the contra angle handpiece as both a cutting and measuring instrument. top surface of the turbine head is perpendicular to the shank of the bur. If the top surface is kept parallel to the occlusal surface of the tooth being prepared , the bur is automatically in correct orientation.
  68. 68. Patient and operator positioning- Direct view preferred Having the patient rotate the head -improves visibility of molar teeth partially open jaw -cheek retracted easily lateral excursion - distobuccal line angle and buccal third of the distal wall seen directly the mirror view - visualizing distal surface
  69. 69. Maxillary right posterior – buccal or buccal half of occlusal- operator at 9 to 11 o’clock position patient turns head to left palatal or palatal half of occlusal- operator at 11 o’çlock position patient turns head to right
  70. 70. Maxillary left posterior- buccal or buccal half of occlusal- operator at 9 o’clock position patient turns head to right palatal or palatal half of occlusal- operator at 9 o’clock position patient turns head to left  distal surface reduction- operator at 9 o’clock position patient’s mandible in left lateral excursion
  71. 71. Frequently encountered errors in tooth preparations Inadequate tooth reduction on incisal or occlusal surfaces Inadequate tooth reduction on the preparation’s axial walls Over reduction of tooth structure Excess taper on the tooth preparation
  72. 72. Inadequate build ups Indistinct margins Excess gingival extension Undercuts in the preparation’s axial walls Sharp angles on the preparation
  73. 73. Conclusion Successful restoration- accurate diagnosis thoughtful Rx planning preparation design
  74. 74. On tooth preparation depends- pulp vitality periodontal health good esthetics proper occlusion protection of remaining tooth longevity of the restoration
  75. 75. References •Contemporary fixed prosthodontics – Rosenstiel, Land and Fujimoto 4th edition pages 209- 257 •Fundamentals of fixed prosthodontics – Shillingburg et al 3rd edition pages 119 – 138 •Fundamentals of tooth preparation for cast metal and porcelain restorations – Shillingburg et al. 1991 ed pages 13-45
  76. 76. •Tylman’s fundamentals of fixed prosthodontics 8th edition pages 113-143 •JADA oct 2007 vol 138 pages 1373- 1375 •JPD june 2006 vol 95 no 6 pages 456-461 •JPD aug 2005 vol 94 no 2 pages 105 -107 •JPD dec 2004 vol 92 no 3 page 302 •JPD may 2004 vol 91 no 5 pages 499-500 •JPD may 2001 vol 85 no 5 pages 521-522 •JPD april 2001 vol 85 no 4 pages 363-375
  77. 77. Thank you For more details please visit www.indiandentalacademy.com

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