Ferrule in a Partial Denture Abutment: A Higher Number or a Higher Quality?

In “Ferrule in a Partial Denture Abutment” I said that this tooth works under the worst kind of oblique loading, and that a borderline ferrule that works in fixed prosthodontics may not be enough under a partial denture. The next question is what our criterion should be once we have removed the crown and seen the ferrule. The first thing that comes to mind is raising the height from 2 to 3 mm, but the scientific literature has not proposed a separate figure for partial denture abutments, and greater height is usually gained through crown lengthening, which worsens the crown-to-root ratio in a tooth that is already under lever-like loading.

In my view, what has to go up in a partial denture abutment is the quality of the ferrule, not its number. In ordinary teeth we can often work at the borderline. For example, we restore a tooth that has only two walls and argue that a particular wall, because it lies in the path of the force, matters more than the others and is enough on its own. In a partial denture abutment there is no room for such compromises. The ferrule has to be 360 degrees and continuous, its wall should be as much thicker than the 1 mm minimum as possible, and whatever remains of the coronal walls should be preserved. Alongside this, the design and seating of the partial denture itself are part of the same equation, because a loose base or a rest in the wrong place multiplies the load on that very ferrule.

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