To continue our conversation about provisionals let’s discuss interproximal contacts. It is critical to create a contact between the provisional and the adjacent natural teeth to prevent the prepared tooth from drifting. Drifting results in an open contact or an overly tight contact, both if which are challenging to solve chair-side. One of the challenges is to create a tight interproximal contact and the proper size and shape of the contact surface to prevent food impaction and allow for gingival health.
The first dimension to control is the buccal to lingual width of the contact point.When I teach hands on provisionals courses I commonly see a broad flat contact area that ends abruptly at the buccal and lingual line angles. This shape will prevent the tooth from drifting but is sure to create tissue irritation and may even be awkward to the patient’s tongue. The area of the tooth from the flat surface of the contact must emerge into the line angle and create a rounded tooth form to the buccal or lingual. The shape of the embrasure should be a rounded “V” to allow the space to be self cleansing.
The contact must also be gradualized into the gingival embrasure to the apical. This allows adequate room for the papilla, without creating too much room and a space. We also want to avoid the creation of a ledge that traps food and bacteria. I do these adjustments from the contact out to the tooth shape with a silicone polisher and do not run over the main portion of the contact itself to avoid lightening the pressure until I have flossed.