Well, if the 2 front teeth needs to be replaced, I definitely would advise against going with the Monodont bridge system. There is no way the Monodont design can hold up for #8 & 9 for an extended period of time, especially if we're going to rely on #7 & 10 for support, which are the 2 smallest teeth in the upper arch.
And if the lab rep is recommending a metal-based partial, then that would mean there's should be no space issue between the two arches. Given that you're 46, we want to make sure this partial is completely tooth-supported and apply very minimal pressure on the underyling gum tissue. We want to retain as much bone as possible so that when you're able to go forward with implant restorations, that we'll have sufficient bone for the implant fixtures. You might still need sinus lift for your posterior molars
(depending on the location and size of your maxillary sinugs), but at least we don't want to jeorpardize bone loss for your 2 front teeth.
The good thing about a metal framework partial on the upper arch is that the palate is rather strong and can help in the distribution of the chewing forces. And using the metal framework, we can use the palate as an additional "rest" for support.
I am going to assume that you're missing teeth #2, 3, 8, 9, 14, & 15. (2-3 are the upper right side back 2 molars, 8-9 are your front teeth, and 14-15 are the upper left side molars). There should be 4 "rest seats" designed for this partial. Mesial rest seat designed on teeth #4 & 13, and cingulum rests on teeth #6 & 11. This would mean that there will be minimal drilling on teeth #4 & 13 (your 2nd pre-molars), as well as minor grooves drilled into the tongue-side of #6 & 11 (your upper canines
). So when you chew with the partial, the biting forces will be redirected and distributed mainly to these 4 teeth and not directly on the soft tissue. This will help reduce the amount of bone loss. Then I-bars or flex resin clasps can be specifically designed to help retain the partial and keep it from coming off too easily.
Of course this is just a preliminary design for the metal framework and how viable it is would depend on the health and conditions of #4, 6, 11, & 13. As long as these teeth aren't periodontally involved, then they should be great candidates for placement of rest seats.
However, ultimately, it will be up to your restoring dentist to try and provide you with the best design that will help you retain the most bone and ridge height as to optimize your eligibility for implant placement down the road. It is also possible that since you've had 2 failed partials, to ask your general dentist if it's possible to refer you to a "prosthodontist". A prosthodontist is a specialist in more complex restorative cases. They go through additional years of training specifically in the areas of implant restoration, as well as removable complete and partial dentures. Although you may have to pay a slightly higher fee for a partial they will provide for you, in my opinion, it's worth the additional cost because I'd pay for having the additional bone support down the road. Once the bone is gone, it's nearly impossible to grow back.
I'll leave that at your discretion, whether you feel it's time to ask for a prosthodontic referral. As long as the partial is primarily tooth-supported, then the prospect of minimizing bone-loss would be really good. It's the completely soft-tissue supported dentures that we need to stay away from, even though they are extremely comfortable and look great.
Jul***** *****, DDS