fundamentals of tooth preparation in fpd

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FUNDAMENTALS OF TOOTH PREPARATIONS : 

FUNDAMENTALS OF TOOTH PREPARATIONS Praveen V Badwaik

FUNDAMENTALS OF TOOTH PREPARATIONS : 

FUNDAMENTALS OF TOOTH PREPARATIONS According to Rosenstiel et al To achieve Optimal Restoration/Success BIOLOGIC CONSIDERATIONS (Health of oral tissues) MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) ESTHETIC CONSIDERATIONS (Appearance)

FUNDAMENTALS OF TOOTH PREPARATIONS : 

FUNDAMENTALS OF TOOTH PREPARATIONS According to Shillingburg et al Preservation of tooth structure Retention & Resistance Structural Durability Marginal Integrity Preservation of Periodontium

FUNDAMENTALS OF TOOTH PREPARATIONS : 

FUNDAMENTALS OF TOOTH PREPARATIONS According to Rosenstiel et al To achieve Optimal Restoration/Success BIOLOGIC CONSIDERATIONS (Health of oral tissues) MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) ESTHETIC CONSIDERATIONS (Appearance)

BIOLOGIC CONSIDERATIONS (Health of oral tissues) : 

BIOLOGIC CONSIDERATIONS (Health of oral tissues) Conservation of Tooth structure Avoidance of Overcontouring Supragingival Margin Harmonious Occlusion Protection against tooth fracture

MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) : 

MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) Retention Form Resistance Form Deformation

ESTHETIC CONSIDERATIONS (Appearance) : 

ESTHETIC CONSIDERATIONS (Appearance) Minimal display of Metal Maximum thickness of Porcelain Porcelain Occlusal Surface Subgingival Margin

Principles of Tooth Preparation : 

Principles of Tooth Preparation Concave Cingulum Reduction (Structural Durability) Flat Incisal Edge & Rounded Angles (Structural Durability) Vertical Lingual Wall (Retention & Resistance) Radial Shoulder (Marginal Integrity) (Periodontal preservation) (Structural Durability) (Resistance) Axial Reduction (Retention & Resistance) (Structural Durability)

BIOLOGIC CONSIDERATIONS (Health of oral tissues) : 

Prevention of damage during tooth preparation Adjacent teeth – Reshape & polish – to reduce chances of caries (as outer surface of enamel has more content of fluoride) Use of Metal Matrix / produce Enamel LIP/FIN Soft tissue – Retraction with Aspirator tip, mouth mirror, Flanged Saliva ejector BIOLOGIC CONSIDERATIONS (Health of oral tissues)

BIOLOGIC CONSIDERATIONS (Health of oral tissues) : 

Prevention of damage during tooth preparation Pulp – Can be damaged by Increased temp., Chemical irritation & Microorganisms Causes of Injury Temperature – Air rotor with proper water spray Chemical Action – (use Cavity Varnish, Dentin bonding agent) Bacterial Action – (use ZnPO4 & Consepsis- chlorhexidine gluconate) BIOLOGIC CONSIDERATIONS (Health of oral tissues)

BIOLOGIC CONSIDERATIONS (Health of oral tissues) : 

BIOLOGIC CONSIDERATIONS (Health of oral tissues) Conservation of tooth structure Taking into Mechanical & Esthetic Considerations -- conservation – reducing Pulpitis Partial coverage Minimal taper between Axial walls Anatomical planes (Occlusal surface) Axial surfaces (Orthodontic repositioning) Margins Unnecessary apical exposure

BIOLOGIC CONSIDERATIONS (Health of oral tissues) : 

BIOLOGIC CONSIDERATIONS (Health of oral tissues) Considerations affecting future dental health Overcontouring – Plaque accumulation – periodontal problem/ caries Reduced Occlusal preparation – Occlusion problem, Ceramic chipping / fracture Axial reduction – avoid overcontouring Preparation should be even, uniform, smooth without ledges Flat surfaces are better & easy to clean Sufficient preparation – correct axial form, provide fluting

BIOLOGIC CONSIDERATIONS (Health of oral tissues) : 

BIOLOGIC CONSIDERATIONS (Health of oral tissues) Considerations affecting future dental health Margin placement – Supragingival Margin Adaptation – Recurrent caries Margin Geometry a) Knife edge, b) Bevel, c) Chamfer, d) Shoulder, e) Shoulder with bevel

BIOLOGIC CONSIDERATIONS (Health of oral tissues) : 

BIOLOGIC CONSIDERATIONS (Health of oral tissues) Occlusal Considerations Sufficient space for Occlusal Scheme (for better functioning) Supraeruption / tilted teeth requires Endodontic treatment Plane Analyzing should be done Preventing tooth fracture Cusps may fracture Intracoronal restorations may increase stresses So, CROWNS are better solution

MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) : 

MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) To avoid Dislodge / Distort / Fracture Retention Form Resistance Form Prevent Deformation

MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) : 

MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) Retention Form Jaws are moved apart (sticky food) Forces parallel to path of withdrawl Failure of FPD - 1 Caries 2 Fracture of ceramic 3 Retention failure Magnitude of dislodging forces should be reduced

Slide 17: 

Retention failure Magnitude of dislodging forces should be reduced Geometry of Tooth Preparation Roughness of fitting surface Material being cemented Film thickness of luting agent MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration)

MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) : 

Dislodging forces – normally small , with sticky food Surface area & texture of restoration Geometry of tooth preparation Cylinder – more retentive Taper : more retention is provided by parallel walls,, but 6* (12:01 – 5.5*) Undercut – Divergence in opposing Axial walls in cervico-incisal direction MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration)

MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) : 

Surface Area : Long axial wall – more retention Molar – more surface area – more retention Stress concentration Rounded internal angles (Axial – Occlusal junction) Type of Preparation Complete Crowns, Grooves, Boxes {limits path of withdrawl} MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration)

Slide 20: 

Roughness of Surfaces being cemented Air – Abrasion = 50 um Alumina, increases retention by 64% Material being cemented Base metal is more retentive than High gold metal Amalgam more retentive than composite Type of Luting Agent Adhesive resin cement is more retentive MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration)

Slide 21: 

Resistance Form Mastication & Parafunctional activities – causes horizontal / oblique forces Magnitude & Direction of Dislodging forces Geometry of tooth preparation Physical properties of luting agent MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration)

Slide 22: 

Deformation Depends on the Strength of the restoration Alloy Selection Type I, II gold alloys – intracoronal restorations Type III, IV gold alloys – Crown & FPD High noble metal (ceramic) has more strength than type IV gold alloys Adequate tooth reduction : Sufficient bulk Prep - 1.5 mm in Centric cusps Supraerupted teeth require more preparation Margin Design – Sufficient bulk Feather edge does not give that strength Grooves, Ledges increases Strength MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration)

ESTHETIC CONSIDERATIONS (Appearance) : 

ESTHETIC CONSIDERATIONS (Appearance) Minimal display of Metal Maximum thickness of Porcelain Porcelain Occlusal Surface Subgingival Margin

Slide 24: 

Depends on the Skill of the Dentist & Esthetic expectations of the patient Teeth has to seen when patient is Smiling, Talking, Laughing Metal-Ceramic are good in esthetics, but if ceramic thickness is less or if restoration is overcontoured then esthetics is reduced Facial tooth reduction has to be done in 2 planes Incisal edge has to be reduced by 2mm Proximally no metal has to be shown Labial margin should be Supragingival but in cases of High lip Line --- Subgingival margin is advised ESTHETIC CONSIDERATIONS (Appearance)

FUNDAMENTALS OF TOOTH PREPARATIONS : 

FUNDAMENTALS OF TOOTH PREPARATIONS To Summarize According to Rosenstiel et al To achieve Optimal Restoration/Success BIOLOGIC CONSIDERATIONS (Health of oral tissues) MECHANICAL CONSIDERATIONS (Integrity & Durability of restoration) ESTHETIC CONSIDERATIONS (Appearance)