Operative Dentistry - Anterior teeth composite restoration -Part 1
Anterior teeth composite restoration
Resistance form
• Extending the external walls pulpally to an initial depth of 0.75 mm thus providing adequate dimension for composite strength, placement of a retention groove (if necessary), and maintenance of strength of the gingival wall and margin.
• The portion on the root surface that has no enamel margin-would be prepared in this manner.
The Access of Class III:
•The lingual approach is preferable, unless such an approach would necessitate excessive cutting of tooth structure, such as in instances of irregular alignment of the teeth or facial positioning of the lesion.
•Use a round carbide bur (No. 1/2, 1, or 2) or diamond stone, the size depending on the extent of the caries to prepare the outline form.
•The point of entry is within the incisogingival dimension of the carious lesion or defective restoration and as close to the adjacent tooth as possible, without contacting it.
•Direct the cutting instrument perpendicular to the enamel surface, but at an entry angle that places the neck portion of the bur as far into the embrasure (next to the adjacent tooth) as possible.
•Prepare the enamel walls perpendicular to the external tooth surface, with the enamel margin beveled.
. The axial wall depth approximately 0.75 to 1.25 mm (0.2 mm inside the dentinoenamel junction
•Extend the external walls to sound tooth structure during preparation
of the outline form.
•The axial wall will be outwardly convex, Following normal external tooth contour and the DEJ, both incisogingivally and faciolingually.
•Any remaining infected dentin or old, defective restorative material on the axial wall will be removed during the final tooth-preparation stage.
•Usually retention is obtained by bonding to the enamel and dentin and no groove retention is necessary.
•When replacing a large restoration or restoring a large Class III lesion, the operator may decide that retention form should be enhanced by placing groove (at gingival) and/or cove (at incisal) retention features in addition to the bonded tooth structure.
•For most Class III using the beveled conventional preparation, the cavosurface bevel provides more surface area for end-on etching of the enamel rods.
•The cavosurface bevel or flare is best prepared with either a flame-shaped or round diamond instrument, resulting in an angle approximately 45 degrees to the external tooth surface all accessible enamel margins usually are beveled, with the exception of the gingival margin.
The gingival margin is usually not beveled if little or no enamel is present or access is difficult for finishing procedures. In addition, bevels may not be recommended on lingual surface margins that are in areas of centric contact or subjected to heavy masticatory forces because composite has less wear resistance than enamel for withstanding heavy attritional forces.
The advantages of restoring the proximal lesion from the lingual approach include:
1. The facial enamel is conserved for enhanced esthetics.
2. Some unsupported, but not friable, enamel may be left on the facial wall of a Class III or Class IV preparation.
3. Color matching of the composite is not as critical.
4. Discoloration or deterioration of the restoration is less visible.
-Retention form
•Because the bond of composite to enamel and dentin is so strong, most Class III composite restorations are retained only by the micromechanical bond from acid-etching and resin bonding, so no additional preparation retention form is usually necessary.
•Using diamond stones for the
tooth preparation leaves the prepared surfaces rougher, thereby increasing the
surface area and the micromechanical retention.
Anterior cavity preparation :
(Class III, Class IV and Class V)
•Almost
all Class III and Class IV restorations are appropriately restored with
composite.
• Most
Class V restorations that are in esthetic prominent areas are also
appropriately restored with composite.
•Tooth
preparations for composite materials should be as conservative as possible.
Class III tooth preparations:
By definition, are located on proximal surfaces of anterior teeth.
Conventional Class III Tooth Preparation:
•The
primary indication for this type of Class III preparation is for the
restoration of root surfaces, preparation the portion on the root surface that
has no enamel.
Beveled conventional Class III Tooth Preparation:
•The
beveled conventional tooth preparation for composite restorations is indicated
primarily for replacing an existing defective restoration in the crown portion
of the tooth.
•It
also
may be used when restoring a large carious lesion for which the need for
increased retention and/or resistance form is anticipated.
•Class III beveled conventional
tooth preparations are prepared as conventional preparations with the addition
of a cavosurface bevel or flare of the enamel
rather than a butt joint margin.
Modified Class III tooth Preparation:
•A
modified
tooth preparation is the most used type of Class III tooth preparation. It is
indicated for small and moderate lesions or faults and is designed to be as
conservative as possible.
•Thus,
the preparation design appears to be "scooped" or concave, the cavosurface
margins in a beveled configuration.
• The retention
of the material in the tooth will result from the bond created between the
composite material and the etched peripheral enamel.
For all types of Class III :
If possible, the outline form should not :
(1)Include
the entire proximal contact area.
(2) Extend onto the facial surface.
(3) Or be extended subgingivally
The outline form on the root surface :
•
Box-like design may be considered, extending the external walls to sound tooth
structure while extending pulpally
to an initial depth of 0.75 mm.
•
Any remaining infected dentin on the axial wall will be removed during the
final tooth-preparation stage.
•The
external walls are prepared perpendicular to the root surface.
•The
cavosurface
margins exhibit a 90-degree cavosurface
angle and provide butt joints between the tooth and the composite material.
• Extending the external walls pulpally to an initial depth of 0.75 mm thus providing adequate dimension for composite strength, placement of a retention groove (if necessary), and maintenance of strength of the gingival wall and margin.
• The portion on the root surface that has no enamel margin-would be prepared in this manner.
The Access of Class III:
•The lingual approach is preferable, unless such an approach would necessitate excessive cutting of tooth structure, such as in instances of irregular alignment of the teeth or facial positioning of the lesion.
•Use a round carbide bur (No. 1/2, 1, or 2) or diamond stone, the size depending on the extent of the caries to prepare the outline form.
•The point of entry is within the incisogingival dimension of the carious lesion or defective restoration and as close to the adjacent tooth as possible, without contacting it.
•Direct the cutting instrument perpendicular to the enamel surface, but at an entry angle that places the neck portion of the bur as far into the embrasure (next to the adjacent tooth) as possible.
•Prepare the enamel walls perpendicular to the external tooth surface, with the enamel margin beveled.
. The axial wall depth approximately 0.75 to 1.25 mm (0.2 mm inside the dentinoenamel junction
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•The axial wall will be outwardly convex, Following normal external tooth contour and the DEJ, both incisogingivally and faciolingually.
•Any remaining infected dentin or old, defective restorative material on the axial wall will be removed during the final tooth-preparation stage.
•Usually retention is obtained by bonding to the enamel and dentin and no groove retention is necessary.
•When replacing a large restoration or restoring a large Class III lesion, the operator may decide that retention form should be enhanced by placing groove (at gingival) and/or cove (at incisal) retention features in addition to the bonded tooth structure.
•For most Class III using the beveled conventional preparation, the cavosurface bevel provides more surface area for end-on etching of the enamel rods.
•The cavosurface bevel or flare is best prepared with either a flame-shaped or round diamond instrument, resulting in an angle approximately 45 degrees to the external tooth surface all accessible enamel margins usually are beveled, with the exception of the gingival margin.
The gingival margin is usually not beveled if little or no enamel is present or access is difficult for finishing procedures. In addition, bevels may not be recommended on lingual surface margins that are in areas of centric contact or subjected to heavy masticatory forces because composite has less wear resistance than enamel for withstanding heavy attritional forces.
The advantages of restoring the proximal lesion from the lingual approach include:
1. The facial enamel is conserved for enhanced esthetics.
2. Some unsupported, but not friable, enamel may be left on the facial wall of a Class III or Class IV preparation.
3. Color matching of the composite is not as critical.
4. Discoloration or deterioration of the restoration is less visible.
•Because the bond of composite to enamel and dentin is so strong, most Class III composite restorations are retained only by the micromechanical bond from acid-etching and resin bonding, so no additional preparation retention form is usually necessary.
•Sometimes
a groove or cove may be necessary for Class III restorations that either extend
onto the root surface or are very large. Usually, however, additional needed
retention form can be achieved simply by increasing the surface area with a
wider enamel bevel or flare along the margin.
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