essay 26 - fabrication of class III composite restorations - stages, instruments, matrix systems

stages in fabrication of class III composite restorations

1. Initial clinical procedures

• diagnosis and treatment planning: requires full exam, radiographs and case selection

• shade election: always done before rubber dam placement or dehydration of the tooth

• isolation: rubber dam is preferred for moisture control and better bonding

2. tooth preparation

• remove carious lesions and unsupported enamel conservatively

• Tooth prep done conservatively and may involve only enamel or enamel and dentin

• for anterior teeth, lingual access is preferred to rpeserve facial enamel and aesthetics

3. etching and bonding

• prepared surface is etched (phosphoric acid) to create micromechanical undercuts

• etching alters enamel prisms and opens dentin tubules

• after rinsing and drying (but keeping dentin moist), apply primer and adhesive (or self etching system)

• a hybrid layer forms, creating resin tags for strong micromechanical retention

4. Matrix and wedge placement

• use Mylar strip (polyester strip matrix) for anterior teeth

• place strip interproximally, then wedged from gingival embrasure

• Wedges:

— inserted into gingival embrasure

— Functions:

- separate teeth to compensate for matrix thickness

- stabilise the matrix

- prevent gingival overhangs of composite material

5. Composite placement (incremental insertion technique)

• Use either a hand instruments or syringe

• light cured composite is inserted in 1-2mm increments to:

— ensure complete polymerisation

— reduce polymerisation shrinkage

— minimise internal stress

• first increment in line with gingival floor and rise slightly on axial walls

• each increment is light cured, particularly in deeper or more difficult to reach regions

6. finishing and contouring

• matrix and wedge removed

• restoration is cured again from different angles to ensure complete polymerisation

• excess composite is removed and final anatomical contour is established

• use fine finishing burs or diamonds cautiously to prevent damage to adjacent teeth

7. polishing

• achieved using fine polishing discs, rubber cups or diamond-impregnated polishers

• ensure smooth margins, gingival compatibility and aesthetics

• especially critical in anterior teeth for proper reflection and integration with natural enamel

instruments used for fabrication of class III composite restorations

• diagnostics tools: mirror, explorer, probe

• preparation: burs (small round or pear-shaped for conservative access)

• isolation aid: rubber dam, cotton rolls

• etching and bonding applicators: micro brushes or tips

• matrix system: Mylar (celluloid) strip

• Composite placement tools: composite syringes, plastic composite instruments

• curing: LED curing unit for light polymerisation

• finishing tools: fine diamond, finishing discs

• polishing tools: rubber cups, fine paste, composite polishers

matrix systems

• mylar (polyester) strip: transparent, flexible matrix ideal for anterior teeth

• positioned between teeth with a concave edge facing the preparation

• held in place with wooden or plastic wedge from the gingival embrasure

• ensures contour and prevents excess material at gingival margins

• easy to remove after curing and allows curing light penetration

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