Better to avoid FPD  in high masticatory stress areas as it would be more detrimental than advantageous 

The concept of  "splinting" was controversial during my post graduate studies at Wits, with literature often being contradictory,  however, it was common practice during my clinical years prior to that.

I feel that a balanced occlusal distribution with particular emphasis on reducing premature or parafunctional contacts on those teeth which are periodontally compromised is best. Observation of Crown to Root ratio, % bone which is still in the alveolus and the type of mobility all need to be assessed. If the tooth is misaligned and in a parafunctional state one could improve the tooths longevity by addressing this (possibly as part of an FPD).It must be said that the issues acting as "limiting" are multifactorial and unless we observe all of these and decide based on best current evidence we are not offering the patient the optimum treatment.  

Prior to the initiation of any fixed prosthodontic care the clinician must manage or refer for management of the periodontal disease.  Failure to do so will simply lead to more disease progression.  Once management/treatment is provided and the patient demonstrates capacity to maintain the fixed prosthodontic care can be initiated with some degree of confidence.

Simple, short span fixed dental prostheses should perform well as long as there is adequate periodontal support and the occlusion established on the fixed prosthesis is in harmony with the rest of the dentition.  For example, in a patient who has a mutually protected occlusion one should avoid creation of a unilateral group function with a new FDP.  The reverse is also true for conformative care.  If multiple FDP's are to be made and if OVD is to be changed it will not be appropriate to conform to the existing occlusal scheme and then a mutual protection with progressive disclusion would be a good choice for most patients.

If the question is related to complex FDP's with multiple teeth begin splinted it is important for the clinician to identify the patient capacity and willingness to perform meticulous oral hygiene procedures.  Home care must be excellent otherwise  caries at crown margins or progression of the periodontal breakdown secondary to plaque retention in the areas of the splinted teeth may be a risk.

You state that immobilization of teeth with periodontal disease may be favourable for many patients. However, the only advantage of a splint is to reduce the mobility of the participating abutments. On the downside, a splint tends to hinder adequate oral hygiene measures, which is the panacea of most oral diseases. It is therefore only used in modern periodontology for one of two reasons: 1) Because the root /crown ratio is so unfavourable and degree of mobility of a tooth so great that even the stresses of normal masticatory function will progressively increase the width of the periodontal ligament until the tooth is lost, or 2) if essential teeth are lost and somehow have to be restored. In the latter case a splint and an FDP have concurrent functions, and the benefits normally outweigh the added risk.

This should shed some light on the general question of indications and contraindications of using splints in periodontal therapy. The question of limitations, indications and contraindications for fixed dental prostheses (FDPs) is harder to answer concisely because so many other aspects and evaluations come into play – too many to treat comprehensively in this discussion.

However, perhaps the most important ones are:

1) Treat the periodontitis and any other diseases that might be revealed in the initial diagnosis and do not make a definite treatment plan before the tissue response and degree of patient cooperation over quite an extended period of time – sometimes for as much as one year, is evaluated.

2) After this, inform the patient of all possible treatments, including estimated prognoses. Make it clear that aesthetic or functional demands often cannot be met due to irreversible damage to the tissues, and that risk of biological or mechanical breakdown is inherent in extensive restorations on compromised dentitions. The periodontal inflammation may not be entirely resolved, despite efforts by therapist and patient – a situation that will seriously worsen the long-term prognosis of any restoration.

3)  Impart this information to the patient, both to ensure that his expectations agree with reality and to enable him to make an informed choice. Failure to do so and to document it in the journal makes you liable to be sued if the patient should be dissatisfied with the outcome. The informed patient may then choose to have an FDP made, even on a less than optimal biological or mechanical basis, on the clear understanding that the restoration may not last more than a few years. On such premises treatment is ethical to perform. To deny a patient the privilege of having a functional dentition, albeit for a limited period of time, because optimal conditions cannot be obtained is my opinion less ethical. If you want to play it safe, you should limit yourself to 3-unit FDPs on solid, healthy abutments, but then, do you serve your patient’s best interest?

4)  As Käyser has documented, a reduced dental arch (10 tooth pairs in occlusion) is usually sufficient for adequate dental function, provided no visual teeth are lost. So don’t restore lost teeth with FDPs without a definite indication – regardless of whether there is a periodontal problem or not. Remember that any prosthetic intervention is accompanied by an increased risk, which might be biological or mechanical, and one is obliged as a professional to consider if the end result of the treatment benefits the patient or not.

5) Generally speaking the more compromised the dentition, the more extensive the FDP. If you need more stability of the restoration, it may be an advantage to go “round the bend” (literally of course – not metaphorically!) of the dental arch.

6) Try and reduce unfavourable lateral forces to the FDP by reducing cuspal inclines and curvature of the curve of Spee by adjustment grinding. More extensive treatments – among others increasing the vertical dimension may also occasionally be indicated to the same end. For further details, consult textbooks.

Well, healthy periodontium is the foundation for prosthodontic work. In any case, we will have to improve periodontal health before initiating fixed or removable prosthodontic treatment. 

http://www.jresdent.org/article.asp?issn=2321-4619;year=2015;volume=3;issue=3;spage=96;epage=96;aulast=Rashid