Cavity design (3) Flashcards
Pathologic dental cavity:
Cavity in the tooth produced by a congenital, traumatic or pathological
processes.
Therapeutic cavity:
Artificial cavity shaped into a tooth, to later build it up with the correct materials and techniques, in order to restore the anatomy, function and aesthetics.
Extensions.
Objetives
specific preparation to accomplish a goal
Extension for caries prevention? (3)
- First way to remove cavitie
- we dont do it anymore
- remove all the fissures even they are not affected
Extension for caries prevention: Nowadays
So we leave the unaffected fissures
Only if the surrounding tissues are defective or affected.
Extension for support:
we extend the cavity for support
- if the caries is deeper, we just remove the caries where it is
Extension for retention
To provide mechanical lock or retention
Extension: amalgam (2)
- for retention because does not bind to the tooth
- Converge slightly pulp-occlusally. Depth > width
Extension: composite
Composite: Adhesion (bonding to enamel better than dentin).
Do we need extension for composite?
No it sticks without
Bevel
rough the surface
For a better adhesion and aesthetics
Increase the surface etching, remove fragile enamel, expose the head of the prisms,
hide tooth restoration junction. Flat, concave, mixed
Extension for resistance of the material:
Avoid fracture of the material. Extend the margins of the cavity beyond the contact point with the antagonist tooth.
if the preparation is too thin and the preparation might break, so we have to extend the preparation a bit more
Extension for resistance of the teeth:
To avoid fracture of the remaining tooth. To resist structural failure from occlusal loading stresses. Fragile walls must be removed if mechanical conditions are not positive.
same if the tooth is too thin, so the wall is too thin, there might be a fracture, so always protect the cusp, the top of the cusp in order to protect the wall
cusp protection
Extension for convenience:
Ensure access for instrumentation, removal of defective tooth structure, insertion and finish of the restorative material.
Make the obturation easier
sometimes we have to extend the obturation to reach the caries better, if we leave it we cannot clean the caries
Protection of the dentin-pulp
complex:
Restrict depth. Axial angle more rounded to prevent pulp exposure.
During a preparation we always have to think about the pulp, always make it more round around
Extension for aesthetics:
- bevel
- access from lingual
What is bevel?
anrauen
for the aesthetics we have the bevel (on buccal and palatal walls)
From where do we do the acess?
Access from lingual
we always do bevels when we do restauration on the anterior teeth, when we have caries on the frontal tooth, its down the contact point, we clean the surface from palatal
cavity elements:
- boxes
- walls
- angles
Boxes:
Well-defined spaces in the cavity that retain the material.
ex. amalgam
How is it called when there is more than one box?
Their union is calles Isthmus
Walls
Side or surface of the cavity preparation that encloses the restorative material.
around the box there is the wall, they get the name where its close to
How is the wall called that is close to the pulp?
Pulp wall or floor of the cavity/ axial wall
Angles
Where the cavity wall meet
- Confluence of the cavity walls.
- They can be dihedral or trihedral: line or point.
- They take the name of the walls that form it.
- The angle of the tooth formed by the junction of a prepared wall in the cavity and the intact tooth surfaces (outline) is called cavosurface line angle.
Classification
- material
- area
- location
- Etiology (blacks classification)
1.Material
- plastic
- rigid
- adhesive
What do we understand by plastic?
retentive shape. Amalgam.
What do we understand by rigid?
obturation that are made by the lab
expulsive shape, indirect technique
What do we understand by adhesive?
Obturation we shape in the special way
minimal shape, composite resins
Area
According to the sides of the tooth affected (number
of surfaces affected):
just the number that is affected
- simple
- compound
- complex
Whats a simple area?
those which occur on one surface of the tooth.
Whats a compound area?
two surfaces of the tooth involved.
Whats a complex area?
three or more surfaces involved.
location
according to the name of the surface affected
Whats a simple location?
occlusion
Whats a compound location?
mesio occlusal
its just compound when the cavity join together
Whats a complex location?
Mesio- occlusal- distal
Etiology (Black`s)
Class I- VI
Whats class I
pits and fissures
Whats class II?
Proximal surfaces of posterior teeth
just for posterior teeth
Whats class III?
Proximal surfaces of anterior teeth, does not involve the incisal edge.
Whats class VI?
Proximal surfaces of anterior teeth involving the incisal edge.
Whats class V?
Gingival third of facial or lingual surfaces
buccal or lingual but just on the surfaces
Whats class VI?
Incisal edge of anterior/ cusps of posterior teeth
Initially (Black’s):
- Caries was an aggressive process.
- The action of fluoride or other prevention mechanisms was not known.
- Restoration materials and instruments were limited.
- The lesions were classified in 5 according to the location, without taking into account the size and difficulty.
Basic principles in cavity design:
- Remove tooth structure to improve access and visibility.
- Remove all traces of affected dentin.
- Open space to insert the restorative material.
- Improve mechanical retention elements.
- Extension of the cavity to self-cleaning areas to prevent recurrent caries.
Result: excessively large cavities
Current situation:
it would be good to do a saliva test, when they still have caries, also mouth breather
- Caries is a more controlled process.
- Importance of early diagnosis and early treatment.
- Knowledge and use of mechanisms of remineralization and prevention.
- More and better restoration materials and instruments.
- Adhesion to enamel and dentin.
Current situation. Basic principles in cavity design:
It is not necessary to eliminate all unsupported enamel.
It is not necessary to remove the affected (non-infected) dentin.
End of the concept of extension to self-cleaning areas.
minimally invasive dentistry
Operative methodology
objective
- Replace the lost dental structure.
- Cavity sealing: perfect adaptation to the dental structure. Prevention of recurrent caries.
(that bacteria dont leak if we get a good seal, so the bacteria that are down will not grow) - Restoration: anatomy, function and aesthetics.
(ex. if its a grinder, doesnt make sense to do a good anatomy) - Remaining tooth’s protection: avoid fracture.
- Protection dentin-pulp complex: dentin tubules sealing. Biocompatible materials.
(we want contact points that the food doesnt go through but we can still go through with the dental floss in order to clean) - Periodontal protection: good adaptation and contacts.
Steps in cavity preparation:
Previous steps
ex. if we have an inflammed gum, treat the gum first
- Cleaning and disinfection of the oral cavity. Anesthesia if necessary.
- Assessment of the specific characteristics of the tooth: Reach the cavity.
- Limits in the cavity.
Steps in cavity preparation:
- Cavity preparation (Opening and conformation).
- Isolation.
- Restoration.
- Modeling.
- Finishing
- Polishing.
I- Cavity preparation:
Different according to the material used.
- Opening
- Conformation:
- External cavity shape.
- Internal cavity shape.
- Use of special forms of retention
Cavity preparation: conformation
External shape:
always follow the cavity ex. if the caries is in the fissure, just follow the fissure but not go straight
Objective: Define the preparation, following the anatomical contour of the tooth.
Extension for prevention
The margin should not coincide with enamel defects and functional occlusal contact points.
Cavity preparation: Conformation
Internal shape:
Objectives: remove all the injured tissues . Make sure: - Stable and long-lasting restoration. (we have to make the floor flat)
- Prevent fracture of tooth and the material. - Prevent the recurrence of the disease.
- Prevent the loss of pulp vitality
Internal shape:
Cavity DEPTH
- Use x-ray.
- The necessary, avoid weakening the tooth. - Supported by healthy tissues.
- Beware of the anatomy of chamber and pulp horns.
- Avoid iatrogenesis.
(depends on how much the cavity is affected by the caries, when we accidentally expose the pulp = iatrogenic)
Internal shape:
cavity FLOOR
- Proximal boxes (gingival floor) flat to prevent rotation or displacement of restoration material. Flat surface.
- Perpendicular to the axis of the tooth.
- Perpendicular to the direction of the chewing forces.
Internal shape
Cavitary walls:
Cavitary walls:
• Remove all the affected tissue and facilitate access, instrumentation and insertion of the restorative material.
Internal shape
Internal angles:
Internal angles:
Rounded to decrease tensions.
Isolation
- complete: rubber dam
- relative: cotton rolls
Cavity cleaning with water or chlorhexidine
which is good cause we get a better adhesion
Restoration
- Replacement of the lost tissues: Artificial dentin. Artificial enamel.
- Restoration of: anatomy, aesthetics, function.
Steps in cavity restoration
- Insert and adapt material (composite resins: 2 mm. Incremental technique.)
- Specific instruments.
- Polymerization or setting time.
dont touch all the wall of the tooth with the same layer
Modelling
- Configuration required to allow the restoration to restore health, function and aesthetics.
- Not only in occlusal surfaces.
- Materials: brushes, spatulas, plastic instruments.
Finishing
Remove excess of material.
Amalgam: manual.
Resins: Rotary instruments
Polishing
Objektive:
Smooth and polished surfaces. Prevent bacterial plaque retention. Uniform light reflection.
Polishing
Instruments
- Fine and extra-fine diamond burs (red, yellow, white ring).
- Turbine tungsten burs.
- Polishing discs (anterior), rubber burs. Brushes and pastes.
What should we avoid during polishing?
Avoid heat: Irrigate!!!!
What colour do the polishing burs have?
- pink
- green
- blue
What kind of burs do we use for the cavites?
Diamand burs
What colour of disks do we have?
- blue
- green
- yellow
- white
What steps do we have to follow in cavity preparation?
1. cavity preparation 2- Isolation 3. Restoration 4. Modelling 5. Finishing 6 Polishing
