there is a choice between facial or lingual entry into the tooth
Indications for Lingual Approachto conserve facial enamel for enhanced esthetics.
Color matching of the composite is not as critical.
The lingual area is less subjected to thermal changes.
The discoloration in the future is less visible.
Indications for Facial Approach
1. The carious lesion is positioned facially
2. Teeth is irregularly aligned, making lingual access undesirable.
3. Extensive caries extent into the facial surface.
4. Faulty restoration that was originally placed at the facial.
Cavity designs :-
conventional.
beveled conventional.
modified.
Conventional class 3
indicated for restorations involving the root surface1. using a No. , 1, 2 round bur prepare the outline form on the root surface
2. extend the preparation into sound walls
3. extend pulpally 0.75mm in depth
The gingival/cervical and incisal wall is perpendicular to the root surface (box like design)
A continuous groove retention can be prepared 0.25 mm ( of diameter of bur) into dentin of the gingival and incisal walls with a round bur.
. The groove is placed at the junction of the axial and the external walls.
7. Clean preparation and inspect the final preparation
Beveled Conventional Class III Indicated for replacing an existing defective restoration in the crown portion of the tooth
when restoring a large carious lesion for which the need for increased retention and/or resistance form is anticipated.
Lingual Access
1. Use a round bur No. 1/2, 1. 2 depending on the size of the caries to enlarge the opening sufficiently to allow for caries removal.
2. Extend external walls to sound tooth structure using a straight bur.
3. Extend the gingival and incisal walls up to extent of caries or location of old restoration.
Unless necessary, DO NOT:
include the proximal contact.
extend into the facial surface.
extend subgingivally
4. Create an axial wall depth of 0.2mm into the dentin/DEJ (approximately 0.75 1.25mm in depth)
5. Axial wall is convex, following the external contour of the tooth.
6. Remove all remaining infected dentin, using a round bur or small spoon excavator.
7. Remove friable enamel at the margins.
8. If necessary, prepare retention (grooves or coves)
prepare it along the gingivoxial line angle, and sometimes at the incisoaxial line angle 0.25 mm with a round bur.
9. Place cavosurface bevel or flare at the enamel except at the gingival margin area.
10. Use a flame shape or round bur resulting in a 45 degrees angle to the external tooth surface.
11. Bevel width should be 0.25 to 0.5mm.
12. Clean the preparation of any debris and inspect final preparation.
Facial Access
same stages and steps are followed
procedure is simplified because of easy access
modified class3
most used type of cavity preparation.
indicated for small and moderate lesions or faults.
designed to be as conservative as possible.
preparation walls have no specific shapes or forms other than an external angle of 90 or more degrees
preparation design appears to be scooped or concave
preparation design appears to be scooped or concave
1. Use a 1/2, 1, 2 round bur, point of entry is within the incisogingival dimension of the lesion, perpendicular to the enamel surface.
2. Remove all remaining caries or defect.
3. No attempt is made to create a uniform axial wall.
4. Place cavosurface bevel or flare at the enamel except at the gingival margin area.
5. Use a flame shape or round bur resulting in a 45 degrees angle to the external tooth surface.
6. Bevel width should be 0.25 to 0.5mm.
7. Clean the preparation of any debris and inspect final preparation.
Conventional Class IV cavity preparation
There is no indication for this cavity preparation form except for any portions of the restoration extending on to the root.
The typical conventional preparation design with 90 cavosurface margins and groove retention form is similar to the beveled conventional class IV with the exception of the bevel.
This preparation is indicated for restoring large proximal areas which also involve the incisal surface of an anterior tooth.
Retention of beveled conventional class IV cavity preparation depends on etching enamel margins in addition to the grooves and undercuts, dove tail, threaded pins or a combination of these.
Dove tail extension onto the lingual surface of the tooth may enhance both the restoration's strength and retention but is less conservative.
Beveled Conventional Class IV cavity preparation
Although pins is sometimes necessary, but their use with composite is discouraged for several reasons:
(1) risk of perforation either into pulp or through external surface.
(2) Pins do not enhance the strength of restoration.
(3) Some pins may corrode because of microleakage of the restoration resulting in discoloration of tooth and restoration. Despite these disadvantages when large part of tooth structure is missing pin retention may be necessary to retain the restoration.
Cavity walls are prepared as much as possible perpendicular or parallel to the long axis of the tooth, resulting is a design which provide greater resistance to biting forces that could cause fracture of restoration.
Using an Appropriate size round carbide bur at high speed with water coolant, remove all weakened enamel with axial wall depth at 0.5 mm into dentin.
Bevel the cavosurface margins of all accessible enamel margins at 45 angle to the external tooth surface with a coarse, flame-shaped diamond bur. The width of the bevel should be 0.25 to 2 mm, depending on the amount of tooth structure missing and the retention required.
Retention form is provided primarily by the micromechanical bonding of the composite to the enamel and dentin, additional retention may be obtained by increasing the width of the enamel bevel or placing retention grooves.
If retention undercuts are necessary prepare a gingival retention groove using a No. round bur 0.2 mm inside the DEJ at a depth of 0.25 mm (half of a diameter of the No. bur). The groove should extend the length of the gingival floor and slightly up the facioaxial and linguoaxial line angles.
No retentive undercuts is needed at the incisal area where mostly enamel exists.
Modified class IV cavity preparation
It is indicated for small or moderate sized class IV lesions or traumatic defects and the objective of this cavity preparation is to remove as little tooth structure as possible.
Remove any lesion with a round bur and prepare out line to include weakened, friable enamel.
The cavosurface margins are prepared with a beveled configuration and the pulpal depth is dependant on the extent of the lesion but initially no deeper than 0.2 mm inside DEJ.
Usually no groove or cove retention is indicated instead the retention is obtained primary from the etched enamel and conditioned dentin but in larger cavities retentive grooves and coves might be necessary.
Class V composite cavity preparation
It is located in the gingival one-third of facial and lingual tooth surfaces thus in anterior teeth composite material most frequently be used because of esthetic considerations.
Conventional Class V cavity preparation
Conventional class V cavity preparation is indicated when defect is entirely or partially located on the facial or lingual root surface.
The preparation form is similar to that in class V amalgam restoration, the cavity preparation include 90 cavosurface angle, uniform depth of the axial line angles, and groove retentive form in the incisoaxial and gingivoaxial line angles.
Beveled Conventional Class V cavity preparation
It is indicated either for the replacement of an existed defective class V in which was prepared using conventional cavity preparation or for new large carious lesion in which gingival retention groove will be necessary.
Beveled conventional Class V cavity preparation initially will exhibit 90 cavosurface margins (that subsequently will be beveled) and axial line angles that are uniform in depth in to the dentin only 0.2 mm when no retentive groove is needed or 0.5 where retentive groove is planned and the margins are still in enamel.
Many of the larger preparations will be a combination of beveled enamel margins and 90 root surface margins with a retentive groove on root surface (combined conventional with beveled conventional preparation), the depth of the initial preparation on the root surface should be only 0.75 mm.
Bevel is made at 45 angle on enamel margins with a coarse flame-shaped diamond bur to a width of 0.25 to 0.5 mm.
Modified class V cavity preparation
It is indicated for the treatment of class V lesions that are small to moderate in size (decalcified and hypoplastic areas located in the cervical one third of the teeth). The objective is to restore the defect as conservative as possible.
There is no need to prepare the cavity walls as a butt joint and usually no retentive groove is incorporated. The defect is removed resulting in a cavity form that may have a divergent cavity wall and an axial surface that usually is not uniform in depth.