Cavity Preparations

							Operative Dentistry


    Cavity Preparations
Indication of Operative Dentistry
 Caries;
 Malformed, discolored,
   or fractured teeth;
 Restoration replacement.
   Tooth-colored restoration
For Class Ⅲ，Ⅳ and Ⅴ，
— Esthetic Dentistry

For Class Ⅰand Ⅱ，
What are Tooth-colored materials?

What is their working mechanism?

What are the cavity preparation
futures for tooth-colored restoration?
What are steps for tooth-colored
restoration?

What are the advantage & disadvantage
of tooth-colored restoration?
   Tooth-Colored Materials

 Composite resin

 Glass ionomer cement

 Compomer
        Composite Resin

Traditional composites

Hybird composites

Flowable composites
Condensable composites    Packable
Universal composites
       Glass Ionomer


Chemical adhesion to dentin

Release Fluoride
      Compomer


Compomer =

Composite + Ionomer
        Dental Adhesion
               or
        Dental Bonding

Adhesion is a process of solid and/or
liquid interaction of one material with
another at a single interface.
  Enamel bonding system

Enamel bongding depends on resin tags
becoming interlocked with the surface
irregularities created by etching.
Macrotags: form between enamel rod
           peripheries.

Microtags: smaller tags form across
           the end of each rod.

Macrotags and microtags are the basis
for micro-mechanical bonding.
 Dentin bonding system

The difficulties of dentin bonding:

More water---wet bonding
Lower calcification
Richer organic---collagen network
Smear layer
The bond strength is primarily related
to micro-mechanical bonding to the
intertubular dentin which occures
between tubules along the cut dentin
surface.
 Dentin Bonding Agent, DBA

Early DBA were hydrophobic, bonded
directly to the dentin smear layer.
Bond strengths＜6MPa.

Later DBA removed the smear layer but
tended to over-etch dentin.
Bond strengths≈10~12MPa.
DBA were chemically modified to be
more hydrophilic.
Bond Strengths≈18~20MPa.


Careful dentin conditioning,
Coupled with hydrophilic primer,
Bond Strength≈22~35MPa.
The Development of DBA
      Enamel etch (1955)

      Dentine etch (1960)

Treatment of smear layer (1980)


 Wet Bonding technique(1990)
First generation
Second generation

Third generation
Fourth generation: Total etch technique
Fifth generation: One bottle system

Sixth generation: All in one,2000
Seventh generation
     Cavity Preparation
Three designs of cavity preparation:

1.Conventional
2.Beveled conventional
 3.Modified
Beveled conventional cavity preparations
are similar to conventional preparation,
in that the outline form has external,
“box-like” walls, but with beveled
enamel margin.
Beveled enamel margin
Beveled conventional cavity designs for
   Class Ⅲ, Ⅳ and Ⅴ preparations
The advantages :

The ends of enamel rods are more etched
The increase in etched surface results in
a stronger bond
Increase the retention and reduce marginal
leakage and discoloration.
More esthtically
Modified cavity preparation

Have neither specified cavity wall structure
nor specified pulpal depth, and have enamel
margins.

Conserve more tooth structure.
Modified cavity preparation
   Initial Clinical Procedure

Local anesthesia
Preparation of the operating site
Shade selection
Isolation of the operating site
   with rubber dam or cotton rolls
Rubber dam
       Clinical Procedure

Cavity preparation
Acid etching enamel & conditioning dentin
Matrix application
Application of bonding agent
Insertion of composite
Finishing procedures
Matrix application
Final procedures
Cases
Conservative Operative Dentistry
 Minimal intervention dentistry


   is regards as a main stream
   in caries treatment in the 21st
   century.
Principles of Minimal Intervention
             dentistry

 Remineralization of early lesions
 Reduction in cariogenic bacteria, to
  elminate the risk of further demi-
  neralization and cavitation
 Minimum surgical intervention of ca-
  vitated lesions
 Repair rather than replacement of
  defective restorations
“The day is surely coming, and perhaps
within the lifetime of you young men
before me, when we will be engaged in
practicing preventive, rather than
reparative, dentistry. ”

                   — GV Black in 1896