Experts offer tips for putting crowns under partials
By Monica F. Anderson, D.D.S.
July 15, 2009
When a patient needs a new crown under an existing removable partial denture (RPD), the dentist faces a dilemma.
Ideally, you would recommend a new partial to go with the crown. But that doesn't sit well with many patients, especially in today's economy. If you need an out-of-stock part for
your year-old car, the mechanic doesn't sell you a whole new car.
Even borrowing the RPD for a day or two to send to the lab -- which is what most of us learned in dental school -- isn't very convenient for the patient. That's like sending your
car in with the order for the new part.
Fortunately, two easy alternatives have very high success rates.
The first is used by prosthodontist Joseph Massad, D.D.S. Dr. Massad lectures internationally and practices in Tulsa, OK. The first step, he told DrBicuspid.com, is to prep the
1. Be certain the RPD fits well and is completely seated. Make sure the occlusion is good. "Use Regisil (Dentsply International) instead of Blu-Mousse (Parkell) [for
bite registration] because it doesn't have any play or bounce," he stressed. "Now, you have your index of the occlusion."
2. Using DuraLay inlay resin (Reliance Dental Manufacturing) (yes, the stuff we made posts with in dental school), fabricate a temporary crown on the preparation
with the RPD in place. It doesn't have to be dental school perfect, but "make sure you're touching the lingual, distal, and labio-buccal surface" of the framework, Dr.
Massad said. This nicely duplicates the shape of the clasps. If there's a rest prep, include that indentation.
3. Take a full-arch polyvinyl impression of the RPD and DuraLay temporary. "If it's a free-ended extension, your impression must be fully anatomical with border
molding" Dr. Massad added. Take an opposing impression and a normal crown and bridge impression of the tooth without the RPD. Send the index and three
impressions to the lab.
4. The technician will put the DuraLay temp inside the polyvinyl impression and pour. The technician uses this "coping" as your die for the wax-up.
This works well, Dr. Massad said, but "the absolute best way to do it is to do your own lab work, but then we wouldn't get any dentistry done!"
The other method comes courtesy of Charles Sallie, C.D.T., the production manager and assistant lab manager for Crown Dental Studios in Shreveport, LA. Sallie, who has 50
years of experience in the business, recommends the Blu-Mousse technique.
"We have a less than 1.5% failure rate with this technique," he said.
When using the Blu-Mousse technique, after creating the
crown/bridge impression, inject Blu-Mousse over the preparation
and continue expressing the material until the clasps and occlusal
rests are completely covered. Because Blu-Mousse has the
consistency of whipped cream, it will not flow, so there is no need