DENT11

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Lecture (7)

» Class I cavity preparation for amalgam restoration«

done by:

operative dentistry group

(^_^)

Summary of

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Indications: Moderate to large restorations

Restorations are not in a highly esthetic area Restorations that have heavy occlusal forces When good isolation can not be achieved As foundations

As abutments.

Contraindications : " not to be use"

Esthetic areas

Small to moderate cavities which can be well isolated

Small class VI lesions. Class III, IV and V in anterior teeth.

Class 1 cavity preparation

Characters of caries:

Two opposite cones with their base at the DEJ.

Cone shaped spread in enamel with the base at the DEJ and small opening. Cone shaped spread in dentin with base at the DEJ. Rapid lateral spread at DEJ.

4.Class one

lingual

cavity in

anterior

teeth

2. class 1 extension cavity

3. class 1 buccal pit cavity

1. Class 1 simple cavity

Designs of class 1 cavity preparation

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Clinical technique/tooth preparation : Outline form:

Place margins in sound tooth structure Cavity margins must be placed at contact –free areas Conserve ridges involved in occlusal contacts Include all defective pits and fissures.

Resistance form Create flat pulpal floor perpendicular to the long axis of the tooth. Prepare walls that create 90 degrees cavo-surface margins of amalgam Prepare pulpal floor so that adequate depth exists

for strength of amalgam (1.5mm) Preserve adequate bulk of mesial and distal marginal ridges(minimum of 1.6mm width): FLARED

Extend lateral walls minimally. Round all internal line angles( prevent stress areas).

Retention form Create walls that are parallel to each other, or slightly convergent in an occlusal direction

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Finishing and planing of enamel walls Remove all unsupported enamel rods Enamel rods forming Cavo-Surface angle must be full length rods resting on sound dentin (or shortened

rods resting on sound dentin and covered and supported by the restoration (Noy's principles) Place Cavo-Surface margins so that amalgam can be adequately carved and finished.

Features of prepared cavity : Outline of the cavity is placed equidistant from the center of the groove.

Buccolingual width of 1.5mm through central groove.

Buccolingual width of 1mm in other extensions.

Pulpal floor is placed in dentin, 1.5mm from the enamel

surface of the central groove or 0.5 to 1mm below DEJ.

Pulpal floor is flat

*Parallel to the occlusal plane of the tooth

*Perpendicular to the long axis of the tooth

Extremities of facial and lingual grooves, and walls adjacent to mesial

and distal marginal ridges are prepared at 95 degrees to the

pulpal floor.

This results in a slight flare in these areas.

Note: Retention for composite is not the same as amalgam ,,,Composite has

(Micromechanical retention –by acid etching &bonding that flows in the dentinal

Tubules& attaches the composite to the tooth bulk ) Whereas the Amalgam is

bonded by Mechanical retention.

**The shape of preparation gives stability to the restoration .

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Cavity preparation: Pencil the defective grooves on the occlusal surface of

the tooth.

Do not include supplemental grooves.

Position the round bur above the central pit so that the bur is

perpendicular to the occlusal surface for gaining access.

Switch to fissure bur (1mm in diameter).

Move the bur along the fissures and grooves where the pencil

markings are, maintaining your depth of 1.5mm, applying

intermittent pressure.

Make sure that the bur is always PERPENDICULAR to the

occlusal surface.

Do not make the cavity wider than the width of the bur.

Do not go deeper than indicated (1.5mm).

Walls must be parallel or convergent occlusaly except at(M&D).......

Eliminate any sharp corners of the cavosurface outline (reduce

the speed of the hp).

Remove any debris.

Central pit

Notes : Before doing the preparation We use the (Waxing paper ) &

ask the patient to Bite ,then the cusps will demark on the paper , So I can

not put the margins of Amalgam in this area .& I avoid this area because the

force consuntrated in this area .

,So We have to be very conservative maintain the main tooth criteria (like

Cusps, transverse &oblique ridges) involve in occlusal contact should be

preserved ,

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Procedures Gaining access is done using a suitable sized round bur the direction of cutting is parallel to the long axis of the tooth until reaching the dentin. The cutting is done through the weakest portion of the tooth,i.e: Central or proximal triangular fossa.

Lateral extension of the cavity to include all pits and fissures is done using inverted cone bur.

Proximally; the extension is done midway between the marginal ridge and the proximal triangular fossa . Buccally and lingually , the extension should not exceed the intercuspal distance. The cutting is performed through the dentin upward to remove enamel, which becomes undermined.

Finishing of the cavity walls and margins is performed using a cylindrical fissure bur . the bucco-lingual dimension of the cavity is 1/4 – 1/3 the intercuspal distance . while the depth cavity is from 0.5-1 mm beyond the DEJ.

The direction of the buccle and lingual walls of the finished cavity are converging occlusally, while the distal and mesial walls are diverging occlusally.

parallel or perpendicular All walls in the cavity should be smooth , Notes:

on tooth to prevent analysis of masticatory forces, for instance the pulpal floor

should be perpendicular on to the Long axis of the tooth & Parallel to the occlusal

surface .

** Amalgam is Brittlness that mean its compressive strength High & tensile

strength Low ..,So the Amalgam should put in abulk cavity at least (1.5mm -

2mm).,otherwise ,Amalgam will be Fracture .

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The cavo-surface angle of the finished cavity is 90°

- Note :

Cavity wall should follow the enamel rods direction ..

**What are or( How many factor in the outline forms ??

-extention of the lesion

- Pits & Fissure which reach to Dentin .

- Occlusal anatomy.

**Pulp & Dentin ..act as aUNIT.

Resistance form”>>it a form given to cavity to prevent tooth fracture of

restoration..

Resistance >>>>buccal -lingual wall (straight or converge) mesial-distal wall

(diverge)

**Class1 cavity preparation is sweeping cures (no sharp angels)(MCQ)

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DENT11

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Lecture (12)

» Class I Cavity Preparation for Amalgam (2) “with extension” «

done by:

operative dentistry group (^_^)

Summary of

DENT11

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Class I Cavity Preparation for Amalgam

Indications of amalgam restoration:

- Moderate to large restorations.

- Restorations are not in a highly esthetic area.

- Restorations that have heavy occlusal forces.

- When good isolations cannot be achieved.

- As foundations.

- As abutments.

Contraindication of amalgam restoration:

- Esthetic areas (anterior teeth).

- Small to moderate cavities which can be well isolate.

- Small class VI lesions.

- Class III, IV and V in anterior teeth.

- when other dissimilar metallic restoration is present in the oral cavity due

to galvanic action.

Notes :Clinical indications for amalgam : Class I , II & V of lower teeth or upper teeth when

isolation for a composite restoration can't be achieved .

There is a big controversy about the distal of the canine , Now 80% we use composite , some

use amalgam due to its small size and its location by an angulation that doesn’t make amalgam

appear and rune the aesthetic appearance .

Forces are subjected on the canine by an angulation , so wear of a restoration on the distal side

can occur . If the contact of the canine with the tooth number 4 is not properly closed it may lead

to drifting of the upper teeth , especially when 8 starts to erupt but doesn’t find place for its

eruption , so it pushes 7 which pushes 6 --- 5 --- 4 on the canine , If the canine wasn’t strong

enough crowding of the anterior teeth will occur .

Notes : The contraindications for the use of amalgam: In any aesthetic area even if it

was on the occlusal side . (That’s why laughter and opening of both male and female patients

mouth should be examined before starting , and don’t forget to put it mind the patients

economic state he/she might not be able to pay for the composite).

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1) Class I cavity preparation:

Characters of caries:

- Two opposite cones with their base at the DEJ.

- Cone shaped spread in enamel with the base at the DEJ and small openings.

- Cone shaped spread in dentin with the base at the DEJ.

- Rapid lateral spread at DEJ.

Designs of class I cavity preparation:

It may be:

1. Class I simple cavity.

2. Class I extension cavity (compound).

3. Class I facial pit cavity (simple).

4. Class I lingual cavity in anterior teeth.

Clinical technique / tooth preparation: Outline form:

- Place margins in sound tooth structure.

- Cavity margins must be placed at contact - free areas.

- Conserve ridges involved in occlusal contact.

- Include all defective pits and fissures.

Outline form:

-Should include:

- All carious and undermined enamel.

- All pits & fissures.

-Should be:

- Extended to area self-cleansable.

- Multi curved without any sharp line angles to prevent stress concentration.

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-Bucco - lingually:

- Should not extend beyond the inter-cuspal line except if there is caries.

- Minimal width of the cavity about 1/4 - 1/3 the inter-cuspal distance.

-Mesio - distally:

- Should be extended midway between the triangular and the crest of the marginal

ridge.

Resistance form:

- Maximum conservation of sound tooth structure.

- CSA = 90 degrees.

- Minimal cavity width.

- Flat and smooth pulpal floor parallel to the occlusal plane.

- Roundation of axial line angles.

- Providing bulk through the cavity depth (0.5 - 1mm beyond the DEJ).

- Create flat pulpal floor perpendicular to the long axis of the tooth.

- Prepare walls that create 90 degrees cavosurface margins of amalgam.

- Prepare pulpal floor so that adequate depth exists for strength of

amalgam (1.5mm).

- Preserve adequate bulk of mesial and distal marginal ridges (minimum of

1.6 mm width): flared.

- Extend lateral walls minimally.

- Round all internal line angles (prevent stress areas).

Retention form:

- Only against axial displacement in the form of mechanical undercuts in

dentin by converging the cavity walls.

- Create walls that are parallel to each other, or slightly convergent in an

occlusal direction.

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Convenience form:

- No need for convenience in class I cavity preparation as it is easily seen

and instrumented.

Finishing of enamel wall:

- The enamel wall should take the same direction of enamel rods without

undermining.

- CSA should be 90 degrees.

- Buccal and lingual wall will be converging occlusally.

- Mesial and distal will be diverged occlusally.

- Remove all unsupported enamel rods.

- Enamel rods forming CSA must be full length rods resting on sound dentin

or shortened rods resting on sound dentin and covered and supported by

the restoration (Noy's principles) .

- Place cavosurface margins so that amalgam can be adequately carved and

finished.

Features of prepared cavity:

- Outline of the cavity is placed equidistant from the center of the groove.

- Bucco-lingual width of 1.5 mm through central groove.

- Bucco-lingual width of 1 mm through other extensions.

- Pulpal floor is placed 1.5 mm from the enamel surface.

- Pulpal floor is flat :

Parallel to the occlusal plane of the tooth.

Perpendicular to the long axis of the tooth.

- Extremities of facial and lingual grooves and walls adjacent to mesial and

distal marginal ridges are prepared at 95 degrees to the pulpal floor.

- This results in a slight flare in these areas.

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Cavity preparation:

- Pencil the defective grooves on the occlusal surface of the tooth.

- Do not include supplemental grooves.

- Position the round bur above the central pit so that the bur is perpendicular to

the occlusal surface.

- Enter with the bur to approximately 1.5 mm.

- Switch to fissure bur (1mm in diameter).

- Move the bur along the fissures and grooves where the pencil markings are,

maintaining your depth of 1.5mm, applying light intermittent pressure.

- Make sure that the bur is always perpendicular to the occlusal surface.

- Do not make the cavity wider than the width of the bur.

- Do not go deeper than indicated (1.5mm).

- Walls must be parallel or convergent occlusally except at mesial & distal.

- Eliminate any sharp corners of the cavosurface outline (reduce the speed

of the hp).

- Remove any debris.

2) Class 1 extension cavity:

Indications:

- Deep caries in buccal or/and lingual pits.

- Deep fissure or groove extended from the occlusal to the lingual or/and

facial surfaces.

- Fissure crossing the oblique ridge in upper molars.

- When the remaining oblique ridge in upper molars or transverse ridge in

lower premolars is weak it must be included in the cavity outline to avoid

its fracture.

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Outline form:

The same as simple class | cavity preparation in addition to :

-Extension to include the carious or retentive area.

Notes: Class I extension cavities : 1) Pits and fissures on the occlusal surface ( center or in the occ. 2/3 coming from the buccal or

lingual , and this is a COMPOUND cavity )

2) Buccal pit or lingual pit of anterior teeth

Notes : The step is mainly to protect the pulp from exposure .

The extension buccaly or lingual is with step or with out

طب ي حذدن ؟ depends on the caries , if it was near the cervical we will need to do a step , If the caries was at

the height of contour step is not needed.

The extension buccaly or lingual is with step or with out

eans that when we are cutting we should not hurt the gingiva mBiological concept :Notes

nor the pulp HOW ?? By cutting in an ( in-out , in-out )way for cooling , use a coolant

ex.water , use new burrs if the burr was blocked it will regenerate heat which leads to formation

of dead tracts and death of the pulp afterward and the patient goes into irreversible pulpitis ,

as the outline ex. in lower 6 the occlusal outline is the same as class I , Mechanical concepts

the extension is between the mesial and central cusp with parallel walls when there is no step

(when the caries is at the same level as the height of contour )

happens when microns of the dentin is removed and the pulp tissue Exposure of the pulp

becomes impact ( The pressure of the pulp is lower than the pressure of the atmosphere so any

exposure of the pulp even if it was microscopicly it will increase the pressure on the pulp and

nourishment does not reach the odontoblasts and the tooth starts to enter the sequence of the

degeneration , necrosis and abscess formation

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-it may be extended : a)with step forming axial wall and gingival floor.

b)without step: in cases showing extended caries or fissure at the level

of the pulpal floor.

** the formed step will provide :including the caries or retentive area

without endangering the pulp.

Resistance form:

The same as simple class I cavity in addition to:

- Roundation ofAxio-pulpal line angle to:

1. Prevent stress concentration.

2. Provide bulk to the restoration.

-The axial wall direction should be parallel to the corresponding external

tooth surface, i.e. convex (mesio - distally), in order to:

1. Prevent pulp exposure.

2. Provide uniform thickness of the restoration.

Retention form:

The same as simple class I cavity in addition to:

- Parallel mesial and distal walls (coefficient of friction).

:Notes

: it’s the form given to the teeth to resist and prevent mainly fracture of the Resistance form

tooth than fracture of the restoration Remember the "" Luggage and home ""

All the walls of the cavity should be parallel or perpendicular to the long axis of the tooth

WHY ?? So analysis of the forces does not occur. And they should be smooth and flat .

When the analysis occur that mean there is a high destructed force has component more than

descending force The concentration of the stress occurs when we have rough surface ,

inclination also leads to fracture of both the tooth and restoration (due to disturbans of the force)

.

The bulk should be at least 2 mm in amalgam to prevent fracture .

No undermined enamel ( Has no SOUND dentin under it ) and no loose enamel rods the rods

should be resting on sound dentin ( we get rid of the loose enamel rods by using the hatchet and

the gingival marginal trimmer)

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- Occlusal lock against lateral displacement.

- Extension for retention to the other opposing surface to provide

lateral retention in extensive cavities. Efficient.

Convenience form:

The same as simple class I cavity.

Finishing of enamel wall:

The same as simple class I cavity in addition to:

- The mesial and distal walls of the extension will be completely parallel

to each other and to the long axis of the tooth.

- The gingival floor will be slightly slanting gingivally to be in the same

direction as the enamel rods.

Note: class I extension can be: with step or without step (done in practical).

in its place screwing ( don’t move right holding the restoration : Retention form =Notes

or left or rotate )to prevent entry of food & axial dislodgment

retention . prevent difference between the tooth & restoration Coefficient of friction

retention . provide lsof the wal parallismIn proximal portion The

retention . provide ) LockingOcclusal restoration (

: (Latrel desplacment is always the proplem in restoration such as amalgam .

(the is NO undercut in buccal extantion because ,if we do the undercut the undermind

enamel will occur so the tooth will be fracture .

( the undercut in class I )

Notes :

why we said " pulpal floor is placed 1.5 mm from the enamel surface "??

Because thiknes of enamel in gingival floor toward the cervical will decres =0.5 ,, with 1mm

below DEJ =1.5mm which give enough bulk to amalgam .

The buccal extantion should be Equedistance between M& D cusps ):Notes

= That mean the distance from the M =the distance from the D ) …this distance = 1.5

mm.

Very Very IMP in MCQ the axial wall in class I with step should be slitly

Convex " mesio distaly "..(why??) to give thiknes to dentin bridge "" dentin bridge

mean the amount of dentin which protect the pulp ..

صم انى احت انبهب "انذتام تبل تتسع كم ياكا انذت بزج سك ..كم ياكا احس ال كم يا أ يالحظ نهفى

..نا تتسع تسح نهبكتزا االاث اا تذخم بسزع ..ع كم يازنا دب خه يجال اسع نهبكتزا اا تصم

كا بعى كم يا DEJنهبهب انذي حتي عهى غذائا انذو )ذا عهى عكس انذتام تبل انضق انجد عذ

()عتذر ع انكتاب بانعزب نك نزادة انفى –االقسم ال كفكس كم ياكا افضم

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3) Class I facial pit cavity:

-Buccal pit mostly occur in lower mandibular molars.

-It is designed as a simple oval cavity limited to the carious pit and having

the following features:

1. Walls of the cavity slight converge buccally to provide retention.

2. Axial wall parallel to the facial surface of the tooth in mandibular

molars , convex mesio-distally.

4) Class I lingual pit cavity:

- While lingual pit mostly occurs in maxillary molars.

- It is designed as a simple round cavity limited to the carious pit and having

the following features:

1. Walls of the cavity slight converge lingually to provide retention.

2. Axial wall parallel to the lingual surface of the tooth, convex mesio-

distally.

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DENT11

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Lecture (18)

» Class V cavity preparation «

done by:

operative dentistry female group

(^_^)

Summary of

DENT11

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Class V Cavity Preparation

Characters of caries:

-Starts as white or chalky line near the center of the gingival third.

(Persisting white chalk = CARIES NOT INCIDEOUS!)

-Marked sensitivity.

-Tendency to spread mesially and distally near the axial line angles of the tooth.

-Teeth with marked convexity are more susceptible for caries , due to food accomulation.

-Less frequent than other types of caries.

-Usually affects multiple teeth not like other classes they may affect one teeth only.

-More frequent among old aged patients and is called "senile caries".

Notes: Introduction :

Nowadays Class V is usually used in anterior.

Class V can be used in posterior restoration in some situations such as bad oral hygiene ,

First we have to treat patients with bad oral hygiene by : going on a special diet ,close & seal all

the cavities , seal pits & fissures and use fluoride .

If the hygiene is better we use aesthetic restorations , If not (if its still bad) we use amalgam

restorations.

How do we know if the oral hygiene is better or not ? By the count of streptococcus meatus

lactobacilli ( which lead to caries).

Notes :White legion(=sensitive tooth) starts at the cervical region facially and

lingualy of all teeth .

The free gingiva acts as a shelf for food and it might extend to the proximal : its

called unilateral extension if it was from one side & Bilateral extension if it was

from both sides. إرا األساس ف هزي الحالة اها Class V and extension occurred .

Frequent among old age WHY ? due to recession of the gingiva (it loses its cells) ----

The root is rough ---- which leads to food accumulation and dental plaque.

تفقذ الخالا والخالا اال داوا تتقسن وتذا خالا جذذة تتحىل الى Fibers (in elderlies) which is hard

& difficult to repair , it takes time . While in young individuals cells are repaired

fast and easily.

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Outline form:

-Usually described as trapezoidal outline with rounded corners , which may

be modified by an added box extension to involve proximal caries.

(Class V has 4 point angles + 8 line angles)

●Occlusal wall: →Parallel to the occlusal plane and placed at or

just occlusal to the height of contour

.

●Gingival wall: → Straight and parallel to the occlusal plane

→ placed just beneath the gingival margin.

●Proximal walls (Mesial & Distal) : →Straight and parallel to the direction of the corresponding proximal.

→ placed at the line angles of the tooth.

●Axial wall (from inside) : → 1 mm beyond (=bellow) the DEJ.

→ convex mesio-distally.

→straight occluso-gingivally.

Notes: The location of the gingival wall of Class V : Above the cervical (free

gingiva) by 1-2mm.

In Class II : Above the crest of the ridge by 0.5 mm.

RULE: in any class with a gingival floor near the free gingiva it should be

beneath (=at the top of the crest or 0.5mm above the crest of the ridge ; in class

II restorations ) Why don’t we put the restoration lower ?? Because

restorations are considered as a foreign body which may lead to irritation on

free gingival rescission حطتها دام اى لههوا اش كات ىع الشستىسشي ال chemicals فها

or it’s a rough surface

Parallel to the occlusal plane , parallel to the occ. Wall

Notes: The location : Bellow the height of contour or at the height of

contour or maximum at the height of contour.

Notes:Just before the line angles of the tooth , between the faciodistal line angle &

faciomesial line angles of the surface of the tooth .

*Diverge occlusaly (because the line angles are diverge .

Notes: All axial walls are always CONVEX why?? Because if it was straight the

dentin bridge will have less and uneven (Not even) thickness of the restoration than if

it was convex , this may lead to fracture of the restoration (this is in resistance) .

The convexity provides even thickness of the restoration .

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Resistance form:

• CSA→ 90°.

• Bulk of restoration.

• No need for additional resistance, as the force applied on this area is only the lip and cheek musculature force.

Retention form:

-Grooves in the occluso-axial and gingivo-axial line angles are placed in the expense of the occlusal and gingival walls rather than the axial wall. (axio-occlusal and axio-cervical line angles)

Convenience form:

-No need for convenience in class Ⅴ cavity preparation.

Notes : Remember the story of the house & luggage,

, Luggage = the Restoration ) (house = Structure of the tooth ,which is the more important If we increase the amalgam depth the tensile strength multiply by 2 )

Tension)ل)ال لتزيد من مقاومة األملقم

Notes :Retention = to retain the restoration in stability form )

To prevent the retention in class V Retentive groove .:

There is something called 'flexural stresses !! that mean when the

restoration put in class V it press on enamel then dentin but the dentin

have "Visco elasticity property" which help dentin to push the

restoration out of the cavity (Lateral displacement )

If we put the retentive groove in M or D walls the enamel in M

& D walls become under mind So the tooth may be fracture

Notes : the aim of convenience form is :(:

excitability & workability.

Which classes have Convenience form ?? IMP

-Class II -Class III -may be class IV

In class VThe occlusal or incisive wall should be parallel to occlusal or

incisive Why ??

To prevent force analyses -

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Finishing of the enamel wall:

-CSA 90°.

-Occlusal and gingival walls will be straight and parallel to the occlusal plane.

-Proximal walls will be slightly diverging outwards to outward (follow the enamel rods)

class V cavity preparation:

1- Access to dentin is gained by a round bur, then the cavity outline is

extended using an inverted

cone bur or fissure to a trapezoidal shape with rounded corner of a width just enough to include the lesion.

2- The walls are flared and finished parallel to the enamel rods with a fissure bur.

The floor is made convex in all directions following the pulpal anatomy by an inverted cone.

3- An small round bur is used to place incisal and gingival retentive grooves in dentin at the

pulpal line angles and below the DEJ.

Attention plz (the doctor said in any grooves we use small round

bur & tapered bur but in class V we will use small round bur )

Note :

class V have:

line 8Walls ., & 5., wall axialat point angles 4 angles

Notes :

If the material Brittle like amalgam the CSA should be 90 degree .

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