Fundamentals of Tooth Preparation
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Transcript of Fundamentals of Tooth Preparation
FUNDAMENTALS OF TOOTH PREPARATION
DR ASMA NAWAZ CHANNA
TOOTH PREPARATION
It is the mechanical alteration of defective, injured or diseased tooth to receive a restorative materials that reestablished a healthy state for tooth including esthetic correction where indicated and normal form and functions
CONVENTIONAL TOOTH PREPARATION Preparations that require specifics
wall forms,depths and marginal form owing to the properties of the restorative materials
E.g 1 amalgam 2 gold 3 ceramic
MODIFIED TOOTH PREPARATION Preparations that needs less
specifics depth,and wall and marginal form
E.g 1 composite 2 GIL
OBJECTIVES OF TOOTH PREPARATIONS No friable tooth structure can be
left All faults or carries is removed Remaining tooth structure is left
as strong as possible and should be supported by sound dentine
Underlying pulpal tissue is protected where indicated
Restorative materials is retained in a strong, esthetic and fundamental manners
NEED FOR RESTORATION
To repair a tooth after destruction from carious lesion
Replacement or repaired of restorations with serious defects such as gingival excess, defective open margins or poor esthetics
For fructure teeth ,to restore proper form and funtion
PRINCIPALS OF CAVITY PREPARATION Outline form Resistance and retention form Convenience form Removal of remaning carious
dentine Finishing of the enamel walls
and margins toilel of cavity
TOOTH PREPARATION TERMINOLOGYSimple, compound, complex 1. Simple:A tooth preparation is termed simple if only one tooth
surface is involved. 2. Compound: Two surfaces are
involved. 3. Complex: preparation
involving three or more surface
Tooth preparation walls:
Internal wall: prepared surface that does not extend to the external tooth surface
Axial wall: internal wall parallel with the long axis of the tooth
Pulpal wall: internal wall that is perpendicular to the long axis of the tooth
External wall: prepared(cut) surface that extend to external tooth surface
Floor: prepared wall that is reasonably flat and perpendicular to the occlusal forces that are directed occlusogingivally.
Externalwalls:
I nternalwalls:
Tooth preparation angles
Line angle: the junction of two planal surface of different orientations along a line.
Point angle: the junction of three planel surface of different orientation
Cavosurface angle
Cavosurface angle is the angle of the tooth structure formed by the junctions of the prepared walls and the external surface of the tooth
STAGES AND STEPS OF TOOTH PREPARATIONS Initial cavity preparation stages
final cavity preparation stages:
Initial cavity preparation stages
Step 1:Outline form and initial depthStep 2:Primary resistance formStep 3:Primary retention formStep 4:Convenience form
Step 1:Outline form and initial depth 1. placing the preparation margins in
the positions that will occupy in the final preparation except for finishing walls and margins
2.initial depth should be .2 to.8 pulpaly of DEJ (fig 6-1)
Principles:
Step 2:Primary resistance form Defined as the shape and placement
of the preparation wall that best enable the restoration and tooth to with stand without fructure during masticatry forces delivered principally in the long axis of the tooth
Resistance forms must consider resistance of tooth to fracture from forces exerted on restoration. Flat floor (A) will help prevent restoration movement, whereas rounded pulpal floor( B) may allow a nonbonded restoration rocking action producing a wedging force, which may result in shearing of tooth structure.
Principles:1.To use box shape with a
relatively fiat floor which help the tooth to resist occlusal loading during masticatory forces
2.internal line angles shoulid be round to reduce stress concentration in tooth stucture
3.To provide enough thickness to restorative material to prevent its fructure under loading
Step 3:Primary retention formPrimary retention form is the
shape or form of conventional preparation that resist displacement or removal of the restoration by tipping or lifting forces
Principles: principles of primary retention
form vary depending on the materials
E.G For amalgam external walls should be
converge occlusaly
Step 4: Convenience Form
Convenience form is that shape or form of the preparation that provides for adequate observation, accessibility, and ease of operation in preparing and restoring the tooth.
final cavity preparation stages:
Step 5:removal of any remaining carious or infected dentine
Step 6:pulp protection if indicatedStep 7:secdondary resistance and
retention form Step 8:finishing of the external wallsStep 9:cleaning,inspecting and sealing