Composite fillings bond to tooth structure and strengthen weakened teeth. After selecting the best composite color that matches your tooth, the area will be numb and isolated to promote good bonding, decrease post-op sensitivity, and to prevent swallowing of debris. Deeper filling will often require a desensitizer and a base to prevent sensitivity, so there are often multiple layers of material used. Expect good durability with small and medium cavities. Cavities that involve more than 50% of tooth structure may require a stronger solution such as a crown.