In yesterday’s post I discussed the factors that impact wear resistance in modern composite materials. The great news is that we only have to think about the wear resistance of composite in areas of direct occlusal contact. The second piece of good news is that very few composite restorations are replaced because of excessive wear. The majority of restorations succumb to marginal breakdown and leakage, secondary caries or other forms of bond failure. Now, the bad news is that bond failure and bond degradation is accelerated under extreme occlusal load. With all of this in mind it makes sense to manage excessive forces and material selection to increase longevity of our restorations.
On the side of managing the composite there are a number of considerations:
- Chose a material with low shrinkage stress so the restoration begins with minimal strain on the bonded interface.
- Chose a material with good wear resistance so that wear does not introduce excursive interferences over time increasing the load on the bonded interface.
- Chose a composite with low surface roughness to reduce the wear of the opposing dentition and minimize production of excursive interferences over time.
- Place the restoration under isolation and manage the creation of the hybrid zone carefully to maximize initial bond strength.
The other side of the equation is managing the force being applied to the restoration:
- Assess patients to identify a high risk from occlusal force.
- Evaluate the four occlusal positions ( End to end, ICP, Excursives, Retruded from ICP) for evidence of attrition.
- Alter the occlusal relationships to minimize force application.
- Alter the occlusal contacts to distribute force.