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DIRECT CLASS IV COMPOSITE RESTORATION
TYPES OF COMPOSITE RESINS
BEVELED CONVENTIONAL CLASS IV PREPARATION
Class IV restoration is usually required when an accident or extensive caries destroys or severely weakens the incisal angle
Initial Clinical Procedures
Disadvantages of Composites 1. Gap formation on margins may occur, usually on root surfaces. This occurs because the force of polymerization shrinkage is greater than the initial bond strength of composite to dentin.
2. More difficult, time consuming and costlier than amalgam.
3. More technique sensitive. 4. Greater occlusal wear in areas of high occlusal stress.
MODIFIED (CONSERVATIVE) CLASS IV PREPARATION
BONDING GENERATIONS
First Generation Dentin Bonding Agents-Bonding was pitifully low, hence was useful only for class III and class IV cavities.
Second Generation Dentin Bonding Agents -These products attempted to use the smear layer as a bonding substrate. The smear layer because of its comparatively loose attachment to dentin surface was the weakest link in this system.
Third Generation Dentin Bonding Agents
Fourth Generation Dentin Bonding Agents-The high bond strength to dentin (17 to 25 MPa) and decreased postoperative sensitivity in posterior occlusal restorations, encouraged the switchover from amalgam to direct posterior composite fillings.
Fifth Generation Dentin Bonding Agents-These combine the priming and bonding steps but etching is performed separately
Sixth Generation Dentin Bonding Agents-Since 2000 these single bottle adhesives are available which combine etching, priming and bonding in a single solution and as a single step. Etching as a separate step is eliminated.
Seventh Generation Dentin Bonding Agents-Both the sixth and seventh generation adhesives are self-etching, self-priming adhesives which are minimum technique sensitive
Eighth Generation In this there is stable nanofiller that will not settle out of dispersion. It is suitable for direct and indirect restorations
Tooth Preparation Conventional Class IV Preparation
Composite resin can be divided into three types based on the size, amount and composition of the inorganic filler:
Contraindications of Composites Composite restorations are contraindicated in the following conditions:
1. When operating field cannot be maintained dry.
2. Where very high occlusal forces are present (especially in case of class I, class II and class VI)
3. Some class V restorations that are not esthetically critical.
4. When proper technic cannot be applied.
5. The restorations that extend up to the root surface.
6. Invisible, very small lesions on distal surface of canines where metallic restoration is treatment of choice.
7. Patients with high caries susceptibility and poorly controlled caries activity.
Advantages of Composites
1. Maximum conservation of tooth structure is possible.
2. Esthetically acceptable.
3. Less complex cavity preparation is required.
4. Insulative, have low thermal conductivity hence no insulation base is required.
5. Restorations are bonded with enamel and dentin hence have good retention.
6. Can be finished immediately after curing.
7. It is reparable.
8. Has low microleakage.
9. Can be used almost universally.
Advantages of condensable composites over the conventional composites are as follows:
A. Increased wear resistance: Wear resistance is directly proportional to the amount of ceramic fibers present.
B. Deeper depth of cure : Due to light conducting property of the individual ceramic fibers depth of cure is more.
C. Increased flexural modulus due to presence of more ceramic fibers per unit area : Flexural modulus is directly proportional to number of the ceramic fibers present.
D. Decreased polymerization shrinkage: Polymerization shrinkage is indirectly proportional to the number of ceramic fibers present. E. Reduced stickiness: Stickiness is indirectly proportional to the number of ceramic fibers present
Acid Etch Technique
RESTORATIVE TECHNIQUE