I think many people underestimate how much work goes into planning a fixed removable combination case. There are many factors to consider logistically as well as making sure the patient knows what to expect during the process. For patients needing this type of treatment, they are obviously missing enough teeth that need to have a removable prosthesis. And for these patients, they may already be wearing a partial…that is defective and inadequate requiring replacement. In addition to that, the remaining teeth are broken down requiring full coverage restorations….and before you know it, it is actually a full mouth reconstruction.
Personally, I believe these are the more difficult cases to plan and to manage. As one of my mentors would used to say, you have two different animals to deal with (fixed vs. removable) and trying to merge them into one treatment plan requires one to draw on many skills, knowledge and understanding of the principles behind removable and fixed partial prosthodontics. And if you want to get real fancy, throw in some attachments to the case as well.
When I have a case that requires fixed removable prosthodontic treatment, I like to plan my thoughts and ideas into three phases:
1/Treatment planning phases:
- Take the time to perform a full mouth examination and obtain your pre-treatment records including pictures, models, complete odontogram and periodontal charting. You will need to go back to these as you finalize the treatment plan.
- Evaluate your incisal/occlusal plane and decide if you want to keep the existing plane or modify/improve it. What would it take to do that? Is it some simple enameloplasty? Some minor re contouring or redoing some of the existing restorations? Or more crowns? How is that going to improve the aesthetic outcome of the case? Is your patient very aesthetically aware?
- Is the vertical dimension of occlusion adequate? Are you keeping it or can you afford to modify it somewhat to improve the aesthetic and functional relationship?
- Most cases will require a diagnostic wax up using occlusion rim to mount the case properly.
- Survey the case and have a design in mind. Know exactly where you want the rest seats, guide plane, undercut and the type of major connector etc etc.
- Be critical to your core restorations of potential abutment teeth. I am more critical and inclined to replace the core restorations of all my abutments teeth than to leave them. They have to withstand a lot more in the past as well as in the future. I always treatment plan to redo all the core restorations, rather than to find out they are inadequate at the time of preparation and be burnt to spend more time then intended and then decide if I want to absorb the cost of the core restoration or to transfer that cost back to the patient. Include that in the treatment plan and if it is not needed, you just saved time on your schedule and your patient’s pocket. Both you and the patient will be happy.
- Go through the logistics if the patient’s existing denture can be worn during the restorative and prosthodontic phase while the new crown and denture are being fabricated. Keep in mind, the new crown(s) will unlikely fit around the old denture and if the patient is aesthetically conscious, you have to inform and plan well. If you plan to adjust the old denture to fit the new crown, know that it will compromise the fit and the retention of the denture and sometimes the aesthetics as well. Inform the patient in advance. Sometimes, I make an acrylic partial denture that is easily adjustable to deal with this temporary issue. But then that also adds more time and lab costs to your case.
2/Restorative (fixed) phase
- Make sure you use the diagnostic teeth set up to guide your tooth preparation especially in a case where the VDO or occlusal plane will altered. You should keep in mind the path of insertion for your planned RPD so to guide your tooth preparation reduction and path of draw for the abutment teeth
- After you take the final impression for the abutment teeth, you will likely have insufficient occlusal stops to hand articulate the case. The case will likely require another occlusion rim for mounting. Inform the lab in advance so they don’t start trimming your palatal portion of the impression where soft tissue support is required for your occlusion rim.
- Jaw relation record will likely involve a two step approach: keeping the temporary crowns on as your vertical stop while you obtain the record on the edentulous areas where the occlusion rims are. Once that is obtained, you may have to remove the temporary crowns and record the relationship between the abutment teeth and the opposing dentition using your occlusion rim records as your stop. Check the records are as accurate as can be.
- When you send the crown to the lab for fabrication, make sure you have indicated the path of insertion, the location of the rest seats, guideplane and undercut. Any diagnostic teeth set up done during treatment planning phase should be sent along as well to guide the technician in making your crown(s).
- When you get the case back, make sure the lab has followed your instruction especially the location and the depth of undercut requested. I find that lab frequently forgets to check that before they finish it off and send the case back to me.
- Do your usual try in of the crown(s) and decide if you want to insert the crown(s) now or at the time of the insertion of the removable prosthesis. I usually insert at the end but that makes it more complicated at the next phase in impression taking.
3/Prosthodontic (removable) phase:
- By now, if you have planned and managed the previous phases adequately, doing the removable phase is now a breeze. All the abutment teeth should be in good condition and ready to go.
- If the case previously had unfavorable incisal/occlusal plane, if you have not corrected already, this is the time to make some more final modification to improve the aesthetic and functional outcome.
- The usual steps in denture fabrication will be followed through and you will notice that all your initial hard work will allow you to deliver the fixed and removable prosthesis with predictability and with confidence.
I hope you find the information here useful in managing your patients requiring fixed removable combination treatment.
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