Enhanced Verifiable CPD from the
University of Birmingham

Direct Restorations: Composite
MOB with SuperMat Matrix

magnify Before     magnify After
Before and after: click to magnify

The slide show below demonstrates use of the SuperMat Matrix System

Slide show: MOB composite restoration

  • Amalgam has failed due to insufficient thickness of material. Over-eruption of the opposing premolar has occurred.

  • Note the Plunger Cusp on 15, contacting the amalgam on 46.

  • The cusp has been shortened. (Ameloplasty, or Enameloplasty). There is now a space between the upper cusp and lower amalgam.

  • Previous restoration is removed. The mesiobuccal cusp has been slightly reduced. Care is taken to preserve an enamel margin all round the cavity (especially gingivally).

  • The occlusal contacts are marked (ICP and excursions). This occlusal scheme is to be retained.

  • Rubber dam, SuperMat matrix system, and wedge are applied

  • Total etch (10 - 15 seconds). Remember to agitate the etchant - bubbles can prevent it working.

  • Cavity is washed / excess water is removed Dentine should be left slightly (and visibly) moist. This can be done by wiping a damp bit of cotton wool onto the dentine.

  • Adhesive is applied.

  • After bond has been applied, place first composite increments.

  • After bond has been applied, place first composite increments.

  • Use a contact-forming instrument to adapt the matrix to the neighbouring tooth during placement. (Trimax, by Optident)

  • Restoration after removal of Matrix.The shape is refined with burs & discs

  • Removal of wedge and rubber dam

  • Surface sealer is applied (Biscover - Optident)

  • Inspect margins

  • Check occlusion .

  • Finished restoration.

Show all slides

b r a i n j u c e . . .

Plunger Cusp
The original restoration failed because it was too thin to withstand the occlusal forces. To make space for a new thicker restoration, this dentist chose to reduce a cusp on the opposing tooth. An alternative would have been to deepen the cavity on this tooth.

An over-erupted cusp that lies directly over a contact point (called a Plunger Cusp) can cause many problems, like food impaction and wall-cracking on excursions, so the decision was made to reduce it.

Complete Enamel Margins

The bond between composite and enamel is much mure durable than the bond between composite and dentine.
Be very careful not to remove the enamel at the bottom of the box, at the gingival floor.
If this happens (accidentally, or during caries removal), consider using the C/GI Open Sandwich techniqe (described here)

Damp Dentine

Prior to applying bond, the dentine must be moist.
Dry dentine will repel the bonding liquid, preventing penetration into tubules.
But note this is not the case with enamel: dry enamel takes bond OK.

Composite Finishing

99% of occlusal shaping should be done with hand instruments before curing the final layer.
If you do most of it with rotary instruments, you risk damaging the enamel, and causing micro-cracks to appear in the bond and the composite.
Freshly set composite is full of internal stresses due to polymerisation contraction. Try to leave rotary finishing for a week, when water absorbtion by the composite will have relieved the stresses and strains.

SuperMat Transparent

SuperMat matrices are available in thin stainless steel, and transparent plastic.
Stainless steel: Easier to adapt to create a broader contact point.
Transparent: Allow light penetration, so easier to cure the composite from the sides.

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Wow. I actually understand occlusion now, thank you so much. I saw those BDJ articles years ago when newly qualified and I didn't understand any of it. It is all so much more understandable now, thank you.

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