Class I lesion affects

�The pit and fissures of posterior teeth Surfaces involved are:Surfaces involved are:

–Occlusal surfaces of premolars & molars

–Occlusal 2/3 of the facial & lingual surfaces of molars

� Palatal surfaces of maxillary incisors

Spread of pit &fissure caries in

enamel & dentin

In enamelCone shape

Base towards DEJ

& apex toward the surface& apex toward the surface

In dentin (Spreads more rapidly than enamel)

Cone shape

Base towards DEJ

& apex towards the pulp

Class I could be :• Simple occlusal cavity S.O.C

• Compound class I (two surfaces)

* Occluso buccal O.B.C

* Occluso lingual or palatal O.L.C /O.P.C

• Complex class I (more than two surfaces)

* occluso bucco lingual O.B.L.C

• Buccal pit

• Paltal pit in anterior

CLASS I SIMPLE OCCLUSAL CAVITY

(OCCLUSAL SURFACE ONLY)

Outline form

Varies in shape according to theVaries in shape according to the

number of cusps

and orientation of pits ad fissures

Resistance form is obtained by

• Outline placed equidistance from the defective pits ,fissures on smooth ,soundtooth structure

• Sufficient width to include the defects, • Sufficient width to include the defects,

pits & fissures and permit insertion of small condenser for placement of amalgam

But otherwise as narrow as possible

(preservation of tooth structure)

Extension for prevention

Black suggested that it was necessary to

• remove additional tooth structure to gain access

Resistance

• remove additional tooth structure to gain access

& visibility

• extend the cavity to self-cleansing areas to

AVOID RECURENT CARIES

Black’s cavity width

1/3 intercuspal distance

CONSERVATIVE APPROACHE

Introduction of amalgams with better properties

& the use of smaller instruments

Resistance

� Cavity width (faciolingual width)

,/- intercuspal distance

(not more than ,-,./ mm)

No extension for prevention

A Conservative cavity preparation

• Saves tooth structure

Minimize pulpal irritation

Resistance

• Minimize pulpal irritation

• Strong tooth structure,

marginal integrity &

restoration longevity

� Outline should consist of smooth

curves on occlusal surface

(no sharp line angles)

Resistance

To avoid stress concentration

• Box form (mortis form)

* flat floor

* definite line & point angles

Resistance

Distribution of force

• Cavosurface margin is 90° butt joint

• Remove any undermined enamel (enamel

supported with dentin)

Resistance

• Depth * 0.5mm below DEJ (cavity in dentin)

* The whole cavity depth is about

1.5 - 2 mm

from cavity margin to pulpal floor

Resistance

from cavity margin to pulpal floor

Pulpal floor

D

�Minimal extension into the marginal ridge (only enough to remove the defect) without removing dentinal support

� Mesial & distal walls

* divergent occlusally(≥≥≥≥ 10°) to follow

Resistance

* divergent occlusally(≥≥≥≥ 10°) to follow

the direction of enamel rods & prevent undermining of the marginal ridge

• Join weekend ridge between two cavities (<0.5 mm apart)

Resistance

Retention form

Is obtained through

• Converging Buccal and lingual walls occlusally (undercut)

• Parallelism of the walls

• Griping action of dentin

Extra means of retention

Grooves

Retention

Prepared at the line angle between floor of the cavity & its walls with

a ¼ round bur

• Establishing RESISTANCE & RETENTION

(depth & width of the cavity)

gives adequate convenience

Convenience form

gives adequate convenience

to instrumentation ,removal of

decay & insertion of the

restoration

If there is spot of caries

remaining in the cavity

Infected carious dentin should be removed by:

• Excavators (spoon or discoid) • Excavators (spoon or discoid)

soft caries

• Large carbide Rose head at low speed

hard caries

* Until the tooth structure feels hard & firm

* lesion is lighter in color

The removal of carious dentin should not affect resistance form

Create a flat floor peripheral

to the excavated area

Compound class I

cavity cavity

It involves two surfaces

• Occlusal surface

• Buccal or Lingual grooves OF molars

Compound class I

• Buccal or Lingual grooves OF molars

� Occlusal box follows the same principles for class I simple occlusal cavity

� After preparing the occlusal cavity

* #245 bur is held ⊥ to the pulpal floor &

parallel to the long axis of the tooth crown

Cavity preparation

parallel to the long axis of the tooth crown

* moved towards the buccal/lingual

direction along the fissure maintaining uniform depth until the bur reaches the buccal/lingual surface

• The step is prepared keeping the bur parallel to the buccal/ lingual surface of the corresponding groove

So The axial wall will follow the contour of

the buccal/lingual surface at a the buccal/lingual surface at a

uniform depth of 0.5mm inside

the DEJ (0.2mm is permissible)

• Axiopulpal line angle is

rounded

Resistance

• Extend the lingual box gingivally to terminate at the buccal/lingual groove creating a flat gingival seat for

…………. Resistance …………. Resistance

• Gingival wall meets the tooth surface at 90°& the axial wall makes an obtuse angle with the pulpal floor ……………..Resistance

• Mesial & distal walls of the B/L BOX are made parallel to each other with slight occlusal convergence ………………………………..Retention

• Mesial & distal walls are butt joint with the cavity margins………………… Resistancecavity margins………………… Resistance

Pit & fissure on facial or lingual surface

only(buccal pit /paltalpit)

• Shape varies (oval –round-oblong) depending

upon the extent of caries

• Walls continually joined & slightly convergent • Walls continually joined & slightly convergent

towards the cavosurface margin

• Axial wall follows the contour of the

buccal/lingual surface