Preparation of caries cavities Type class II
OC Course for 2nd Year Dental Students
Dr BEHAR .K
Academic year 2023/2024
Introduction :
These are caries cavities located on the proximal surfaces of premolars and molars.
Site II decay on 14 Site II decay on 46
Depending on their size, number, and the presence or absence of the neighboring tooth, the preparations can concern either the proximal faces only or the proximo-cruturating faces.
I/ Class II A:
1: Definition:
It is a simple restoration of a loss of substance of carious origin, located on a proximal face of the premolar or molar and developed under the point of inter-dental contact,
Such restoration is possible only:
If the practitioner finds direct access to the proximal face thanks to the absence on the arch of the contiguous tooth (at least) which allows the lesion to be seen and the instruments to be passed.
Such a restoration can also be performed when access is provided by the occluso-proximal preparation of the neighboring tooth, but in this case, access is a little narrower and more delicate.
As long as its development does not alter the marginal ridge (restricted volume).
2: Cavity size:
The lesion is generally small in volume (2 to 3 mm)
It often appears as a small brown spot and in this case it is necessary to check whether or not the enamel has been broken, using a probe.
The restoration cavity is a circular cavity; it is generally wider than it is deep, retention is ensured by widening the bottom with a reverse cone bur
II/Class II B:
1: Definition:
It is a two-sided composite restoration of a tooth generally affected by a loss of substance, of carious origin located at the level of one of the proximal faces.
This composite restoration is justified in the following cases:
– Purely proximal caries cavity with presence of the neighboring tooth.
– Occlusal caries cavity, born in the proximal fossa having undermined the marginal ridge.
– Presence on the same tooth of an occlusal caries cavity and a proximal cavity.
2: Preparation of the composite cavity (HESS class II B):
The class II B cavity will be composed of a main cavity located on the proximal face: “BOX” and a secondary cavity on the occlusal face; the two cavities are connected to each other by an ISTHMUS.
The main cavity presents :
– Cervical wall which forms the bottom of the cavity.
– Axial wall;
– V wall; L wall / are divergent from each other (moved towards the areas accessible for brushing).
The secondary cavity presents:
– Pulp wall or bottom of the cavity is perpendicular to the axis of the tooth.
– Proximal wall is parallel to the corresponding face.
– Wall V and L are parallel to each other and parallel to the axis of the tooth.
– The main cavity has a depth twice that of the secondary cavity.
A: Cavity opening:
■Trepanation (the corresponding marginal dimple, using a diamond ball burr mounted on a turbine).
■ In the absence of the neighboring tooth, a groove is made at the proximal face (fissure bur).
B: Carrying out the actual preparation:
■ At the proximal level: (main cavity):
Using a cylindrical cutter mounted on a turbine,
– Destroy the remainder of the marginal ridge,
– Laterally we realize the divergence of the walls.
– At the cervical level: a flat bottom must be obtained with a fissure bur mounted on a contra angle.
■ At the occlusal level (the secondary cavity):
– Open at the level of the furrow with a cylindrical cutter to a depth which corresponds to half the height of the main cavity.
– The opening axis will always be parallel with that of the tooth.
– A rough rounded tail is made at the opposite proximal level.
C- The finishes:
1-For the main cavity (the proximal box)
– Walls V and L are parallel to each other.
– The axial wall is parallel to the axis of the tooth.
– The cervical wall is perpendicular to the axis of the tooth, or inclined towards the center of the tooth.
2-For the secondary cavity:
– Pulp floor or wall must be parallel to that of the main cavity
– Walls V and L are perpendicular to the bottom and parallel to each other.
– Proximal wall parallel to the corresponding face (oblique)
– The isthmus must not be too narrow, its width will always be greater than 2 mm (the amalgam is fragile at low thicknesses).
Class II cavity on upper molars on PM on lower molars
- Main cavity retentions:
VL direction: walls V and L provide retention.
Direction M – D: the wall present (M or D).
the secondary cavity.
Axial direction: by the depth of the cavity.
The edges of the cavity must be rounded (removal of sharp corners).
III/Class II C:
a-For upper molar:
When there is a robust enamel bridge, the creation of 2 separate cavities remains justified.
b-For lower molar:
A single cavity encompassing the 2 proximal faces through the occlusal face = MOD.
Preparation of caries cavities Type class II
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