Cons lecture-1

2. The Dr. started the lecture by this Qs :
When we say cavity, we are talking about carious lesion ; cavities that took
place because of caries.
 What are the non- carious injuries to teeth ?
❶ Fracture
❷ Tooth wear
❸ Developmental defects
Cavities were classified by an old dentist called G.V.Black , today we’ll talk
about what changes are made to his principles of cavity preparation and what
factors influence cavity design.
- What does the kit consist of ?
- examination kit ( mirror, probe and tweezers ), spoon excavator,
amalgam carrier , condenser, carver , burnisher and an applicator for
placing the liner.
Current concepts about principles of cavity designs
Principles of cavity designs :

3. ① Establishment of outline form
② Establishment of resistance form
③ Establishment of retention form
④ Treatment of residual caries
⑤ Correction of enamel margins
⑥ Cleaning the cavity.
Outline Form of the cavity : the shape which the cavosurface line-angle of the
cavity assumed after preparation ; so the final shape of the cavity is the
outline form.
The shape of the cavosurface line angle is circular, star-shaped or irregular
shape.

4. ❶ Gain the initial access via the most carious part of the tooth.
❷ Remove all unsupported enamel to expose the internal extent of caries,
you are extending the margins of the cavity so the shape or the outline form
is changing all the time, but once you finish your preparation it’s called the
outline form.
Elimination of any infected carious lesions left inside the tooth after the initial
cavity preparation.
Here we have to differentiate between the infected dentine and the stained
dentine by running the probe on the dentine, if it sticks then it’s soft and if
you here like scratch then it’s hard dentine which we don’t cut .. So we only
remove soft dentine using excavator or slow speed bur.
Once the initial access has been gained , you must stop using the high speed
bur and switch to the low speed one.
Sometimes it’s advisable to leave some caries in the floor, then placing a
temporary filling so that secondary dentine will be formed to protect the pulp
and leave the caries away.
NOTE : the minimum layer of dentine that should cover the pulp is 0.75-1
mm.
Access :
Elimination of carious lesion :

5. When the carious lesions is few, no need to put margins in areas of lessen
caries susceptibility, however it’s advisable to include pits and fissures in an
amalgam cavity in case of high caries areas. So assess the condition of the
tooth; if it had less caries then you don’t have to extend cavity margins into
areas of lessen caries susceptibility and if it’s high then you need.
So if we extend the walls buccal and lingual, bring them out of the contact
point so that they can be cleaned easily by the bristles of the brush ,, then we
can decrease secondary caries that results by plaque accumulation.
Which means make the cavity wide enough to admit the instruments you are
using, so the cavity should be able to admit the instruments inside it.
You have to extend the proximal cavities buccally and lingually just outside
the contact area because we want to bring them in self- cleansing area that
the bristles can reach them.
Placement of cavity margins in areas of lessen
caries susceptibility :
Convenience form :
key word  Admit

6. Which means that the design of the cavity in such a way that the remaining
tooth substance and the filled material can withstand the masticatory stresses
without fracture.
In order to achieve the resistance form the prepared cavity should possess
the following requirements :
① Flat floor :
- Make the floor of the cavity at right angle to the direction of the
force.
- Make the floor of the cavity flat.
- No sound structure should be removed to achieve this.
② Adequate bulk of restorative material ( 1.5-2mm for amalgam ):
- If the bulk of the amalgam is less than 2 mm then it’ll fracture on
biting; because amalgam is brittle in thin sections.
- The depth should be enough to take adequate bulk of restorative
material
③ Absence of weak cusps or marginal ridges :
Let’s assume that you are preparing class I cavity and after removing all
caries you discovered that marginal ridge is weak, in this case you have to
remove it because there’s no resistance from and the cavity will be
transformed to class II .
Resistance form :
Key word  withstand

7. ④ Occlusal cavity margins in areas not subjective to excessive occlusal
trauma:
- Occlusal margins shouldn’t been subjected to heavy occlusal stresses
- Place the restoration in the ¼ inter-cuspal distance, but this isn’t always the
rule because sometimes you find caries extending to the cusps so you have
to remove caries because this is the idea of operative dentistry.
⑤ Walls of the cavity parallel to the direction of stress:
Make the walls of the cavity parallel to the corresponding tooth surfaces, if for
example if you have buccal surface tilted 60
◦
then the buccal wall of the cavity
will be parallel to it so it’ll be 60
◦
.
NOTE: if your cavity has deep point then you shouldn’t remove sound dentine to
make the flat floor , here cut the ideal depth which is 2mm and in the deep area use
GIC or any cements to make the floor flat.
It refers to those aspects of cavity preparation which insure that the
restoration isn’t removed or dislodged from prepared cavity.
Retention form :
key word  dislodged

8. ❶ Undercuts
❷ Dovetail
❸ Flat floor
❹ Grooves
❺ Acid etching
❻ Adhesives
 amalgam is retained in the cavity by mechanical locks while we use acid
etching to create micropores ( micro channels ) in the enamel so that the
adhesive get in these pores and then the composite will stick to it,, so :
Amalgam  mechanical
Composite  micromechanical and chemical
I have to look to :
① Amelodentinal junction caries :
Retention form can be achieved by :
These are applies for amalgam
This applies for composite
This applies for composite and dentine bonding agents

9. - The spread of caries here is very fast because of mantle dentine which
is not well-mineralized dentine and because of abundant ramification
of dentinal tubules so the bacteria can spread easily.
② Pulpal caries :
- we talked about this earlier in the lecture.
③ Indirect pulp capping :
- Use a liner to protect the pulp from bacterial acids.
❶ No undermined enamel left
❷ Smooth enamel surface
❸ Cavosurface line angle ( sorry couldn’t hear !! )
❹ No bevel for amalgam but we do it for composite
① The prepared cavity should be clean from any debris

10. ② No disinfectant should be used, just simply use 3 in 1 syringe with water
③ Don’t desiccate dentine just dry it gently
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❶ It doesn’t include root caries
❷ It doesn’t include secondary caries
❸ It doesn’t include non-carious lesions
① Removing diseased tissue
② Restore the integrity of the tooth
③ Restore the function
④ Restore the appearance
G.V.Black :
- 1836–1915
- the grand old man of dentistry
What are the critique of Black’s principles ?

11. ❶ Dental tissues:
- Enamel :
It’s like glass so it’s brittle
 the hardest tissue in the body
Unsupported enamel should be removed in case of amalgam but
shouldn’t be removed in case of composite.
Unsupported enamel can be used to hold the matrix band around it.
- Dentine :
It’s like wood
❷ Disease
❸ Dental materials properties
The Dr. advised us to visit this website
http://www.juniordentist.com/
Just for u 
Mama …
"If you were once connected with someone, does it make sense that the
connection is broken just because of a physical death? No, the connection
stays. You may just have to listen differently. You may just have to talk
differently. The truth is: the connection is never broken. It's quite
impossible to break the most powerful connection in the universe. As long
as you exist, the connection stays."
Done by : Eman Tawalbeh
What determines cavity designs ?