Dental matrices: why the contact point is the hardest part of a class II

What determines a correct interproximal contact, why the matrix alone is not enough and a wedge is needed, and how to spot an open contact before the patient reports it.

Restoring a class II cavity is among the most performed procedures in restorative dentistry and, at the same time, the one with the highest redo rate for a precise reason: the contact point. An open or weak contact is not an aesthetic defect but a functional one — it allows food impaction between the teeth, producing papillary inflammation, bleeding, pain on compression during meals and, over time, loss of periodontal attachment. The patient reports it weeks later with a recurring phrase, namely that food gets stuck: at that point the restoration must be redone, however good the filling is in every other respect.

The matrix recreates the missing wall, but on its own it does not recreate the contact. Three elements are needed working together. The matrix provides the shape of the wall, and its morphology matters: a flat band produces a flat wall, which touches the adjacent tooth at a point higher and broader than it should; a contoured matrix reproduces the natural convexity of the proximal surface. The wedge does two distinct things, which is why it is indispensable: it seals the matrix against the cervical margin preventing composite overhang, and it slightly separates the teeth by exploiting the elasticity of the periodontal ligament. That separation is what, on removing the matrix, leaves the space the tooth recovers by closing onto the restoration. Where greater separation is needed, a sectional ring adds the force a wedge alone does not generate.

The commonest error is proceeding with a matrix that does not seal cervically, noticing only at finishing, when the composite has already been cured and the excess has to be removed with burs in an area that is hard to reach. Checking the seal before layering takes seconds: verify that the wedge actually presses the band against the tooth and that there is no light between matrix and margin. A second useful check concerns matrix height relative to the marginal ridge of the adjacent tooth: a band that is too tall leads to building an over-contoured marginal ridge, which becomes a premature contact in occlusion.

Final contact verification is done with dental floss, not by eye: it should pass with clear but surmountable resistance. If it slips through offering nothing, the contact is open and must be corrected immediately, while the patient is still in the chair and the intervention is limited. If it will not pass at all, the contact is too tight and the patient will be unable to clean that area, which is the other way of creating a periodontal problem.

On Oralzon you will find the dental matrices available on the marketplace and, for the later stages of the restoration, also articulating paper for occlusal checking and curing lights.