One of the most important factors when considering using an all-ceramic material like zirconia or lithium disilicate (e-max) is the presence of adequate space for the connectors. Fabricating an all ceramic bridge with connectors that are too small based on the strength of the material is a recipe for premature failure. It is common to see fractures of the porcelain right through the connectors. Connector size is determined by measuring the height from gingival to incisal or occlusal as well as the width measured from buccal to lingual. Some patients present with insufficient inter-occlusal space to gain the appropriate height of the connectors recommended. The shape of the interproximal connector is typically an oval or a circle. In areas of increased load or tension it is reasonable to consider increasing the connector size. For example when increasing the connector size in an anterior zirconia bridge from 3mm by 2mm to 3mm by 3mm the fracture resistance went up by 20%. Your ceramist should be able to help you treatment plan the use of differing materials if you have concerns based on the clinical situation.
The guidelines for a single pontic are:
- 9 Square mm in the posterior
- 7 Square mm in the anterior
- 16 Square mm in the posterior
- 12 square mm in the anterior
When we add additional pontics then the requirement for connector size increases. When using zirconia, the addition of a single pontic in the posterior increases the recommended connector size from 9 square mm to 12 square mm.