Case Study: Replacing an RPD on a Bruxer

A patient presents to my office for a new maxillary removable partial denture.  He’s had the old one for decades and he feels that the cosmetics could be improved.

Here’s what the old RPD looks like:

Old RPD

You can learn a lot from an old crown, CD, or RPD.  The hygiene and wear around the prosthesis to be replaced is like a crystal ball for the work you’re about to do.  Let’s take a closer look:

Wear Facets in Old RPD

Hmm… those are some serious wear facets in the acrylic.  Let’s look at the mounted study models:

Mounted Study Models

Uh oh.  It looks like we have limited occlusal clearance for our new RPD.  What happened?  Let’s look at the lower model more closely:

Lower Mounted Study Model

You can appreciate the significant reverse curve of the plane of occlusion caused by the supra-eruption of the mandibular anterior teeth.  My guess is that he’s a bruxer.  Since acrylic is softer than teeth, the acrylic loses the bruxism battle.  When the acrylic is worn away, the lower teeth have nothing to oppose so they erupt.  Then they touch the acrylic again and wear that down further.  This cycle repeats over and over again, slowly but surely.  After many years, we see the changes to the plane of occlusion and the wear facets in the maxillary RPD that fit perfectly into the mandibular anterior teeth.

So what do we do about it?

It would be a HUGE MISTAKE to open the bite.  His vertical dimension of occlusion probably has not changed significantly because the posterior teeth are still fairly unworn.  Only the mandibular anterior teeth have changed.  Opening the VDO would only cause pain to the TMJ, difficulty during eating and speech, and destruction of the crowns used to open the VDO.

There are two possible solutions.  Ideally, we would put his mandibular teeth back into the correct plane of occlusion.  This would restore the appropriate interocclusal dimension and normalize his bite.  Either orthodontic intrusion or an occlusal adjustment could accomplish this.

The other solution is to keep the mandibular anterior teeth the way they are and try to compensate for the problem with a unique design for the upper RPD.  This is what the patient chose due to limited finances.

I created occlusal stops for the upper RPD in metal rather than acrylic.

New Metal Framework

New Metal Framework Up Close

Now the mandibular anterior teeth will lose the bruxism battle.  Over many years, they will still supra-erupt as they are worn down.  However I won’t have an angry patient who has fractured his relatively new RPD.

I would have preferred to see this patient have his plane of occlusion corrected and implants placed in the maxillary anterior.  That treatment plan was presented to him and he understood the pros and cons of his options.  But financial limitations are very common these days.  The important thing is that the patient made an informed decision and accepts the limitations of the compromise.

An understanding of why his occlusion has changed allowed me to give him an accurate forecast for how our compromised treatment plan will pan out.

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