ACRYLIC PARTIAL DENTURES................

acrylic partial dentures

1. TEMPORARY ACRYLIC PARTIAL DENTURES DR VEENA PAUL DEPT.OF PROSTHODONTICS

2. An acrylic partial denture (APD) is one of the options available for replacing missing teeth and is also the most cost effective treatment option

3. One of the disadvantages of APD’s is its poor strength. Dentists and dental technicians tend to design and construct acrylic partial dentures with little or no tooth support . This can have a detrimental effect on the surrounding hard as well as soft tissue.

4. Generally not considered a permanent treatment option for replacing missing teeth. The provision of metal-based removable partial dentures, fixed partial prostheses or implant supported prostheses to replace missing teeth is considered to be more permanent treatment solutions.

5. In many less affluent societies, APD’s are commonly used in private practice as permanent prostheses owing to the cost-effectiveness of the material – acrylic – used as a major connector, as well as low cost laboratory procedures involved in the construction of this partial denture. In a National Health Survey conducted over a 9 -year period (1992 to 2001) in the UK, it was found that for every metal-based partial denture constructed, five APD’s were made.

6. A metal-based partial denture constructed in private practice will cost the patient in the region upto Rs5000, whereas an APD will cost in the region of Rs1000 to Rs2000 . APD’s thus offer a cheaper alternative to metal-based partial dentures as it is relatively easy to construct in the laboratory, it is easier to repair and reline and wrought wire components can be added to the framework for retention and support.

7. susceptibility to fracture--  usually compensated for by increasing the bulk of the material -  potential of traumatizing the soft tissues as well as periodontal tissues.

8. All removable partial dentures should utilize the existing teeth for support and retention as teeth have a much better response to loading when compared to soft tissue and bone. This is easily achievable with the metal-based partial denture as the entire denture is cast as one and support and retention gained from rests and clasps extending from the major connector

9. For an APD to be tooth-supported, additional material such as stainless steel rests and clasps have to be added to the acrylic major connector. There is no chemical bond between stainless steel and acrylic and clinically this can present itself as a weak area which is prone to fracture. However, with proper patient selection, optimal clinical and laboratory procedures, the disadvantages of APD’s can be minimized. The design of the removable partial denture is more important than the material to be used for its construction.

10. Every designed an upper mucosa-borne denture for bounded saddles and with specific features such as gingival margin relief and clasps distally to provide horizontal stability This design however, cannot be applied to all acrylic partial denture patients as it requires bounded saddles and patients do not necessarily present with these criteria .

11. Potential disadvantages of acrylic partial dentures Acrylic due to its nature is a porous material and thus has an increased area for plaque accumulation . Upper APD’s appear to have a better prognosis mainly due to the larger surface area that is covered-repeated review regimens advised else tissue damage

12. Poor laboratory technique: Should block out unwanted undercuts and interdental spaces on the master model (pour a duplicate cast and process the denture on the duplicate cast. ) Failure to block out these unwanted undercuts usually lead to problems in seating the denture with the dentist adjusting the acrylic and inevitably grinding away too much of the acrylic and thus compromising the acceptability of the denture.

13. as a space between the denture and the abutment teeth with subsequent trauma to gingival tissues

14. Lower APDs present an additional problem: the surface area is much smaller compared to an upper denture and there can be no relief of gingival margins. The acrylic major connector has to cover all the abutment surfaces to provide additional strength to the acrylic. Support must be gained from the remaining teeth otherwise the denture will tend to “sink” into the tissues with a resultant stripping of the gingivae

15. PRINCIPLES IN ACRYLIC PARTIAL DENTURE DESIGN AND CONSTRUCTION Surveying the diagnostic cast The casts should be articulated to assist with the designing of the dentures. Design sheets with the appropriate design for the APD must accompany the study casts to the laboratory

16. The same principles as for the design of the metal-based partial denture are applied when designing an APD. These include: • the edentulous areas / saddles • support • retention • reciprocation • connector • horizontal stability

17. Every removable partial prosthesis should be tooth supported (Kennedy Class III and IV) or tooth-and-mucosa supported (Kennedy Class I and II), but never only mucosa–supported

18. Retention is gained from the abutment teeth and can be passive (depending on a long and single path of insertion) or active (wrought clasps engaging undercuts on abutment teeth). For any prosthesis to be retentive it requires a single long path of insertion and this is usually determined by the edentulous saddles and the degree of parallel surfaces that can be obtained on the abutment surfaces.

19. Guiding planes are 2 or more parallel surfaces prepared on the abutment teeth which can be used to limit the path of insertion and improve the stability of a removable prosthesis. Guiding planes must have a minimum length of 3 mm to provide adequate passive retention

20. THANK YOU..