A removable partial denture on implants.

Rationale:

Free-ending mandibular removable partial dentures yield poor patient acceptance and are generally considered uncomfortable by the patient. Problems caused by the rotational movement of the denture become more frequent. Implants placed in the posterior parts of the mandible can help overcome these problems. Fixed, implant-supported non-removable restorations are not always feasible, both from a surgical and from a financial point of view. As an alternative, implants can also provide retention and support for a Removable Partial Denture (RPD).

There is a lack of evidence in the literature to demonstrate the effectiveness of implant-supported RPD. Well-controlled clinical trials, to the best our knowledge, have not been performed. For a selective population of patients, implant-supported RPD’s may well be a viable treatment option that thus far has not yet been fully explored.



Objective: The primary objective of this study is to investigate the improvement of masticatory function of implant-supported RPD treatment in free-ending, bilateral mandibular partial edentulism depending on the implant position. The secondary objectives include patient satisfaction (OHIP-NL49, SF36 and a Visual Analogue Scale), clinical and radiographical parameters (peri-implant health, marginal bone loss) and the required amount of maintenance.

We expect an improvement in function, denture stability and patient satisfaction whereas prosthetic maintenance and implant complications are minor.

1. TIntake: Before active treatment: MI both with and without current RPD, if present, OHIP-NL49, SF36, VAS;

2. T0: Implant placement, X-ray, submerged healing;

3. T3: 3 months after implant placement: Second stage surgery, placement locator®abutments and start procedure new RPD;

4. T5: 5 months after implant placement: Placing new prostheses (RPD in mandible in conjunction with complete maxillary denture). No measurements;

5. T8: 8 months after implant placement: MI with new RPD without attachment, OHIP-NL49, SF-36, VAS. Changing loading conditions of RPD. Mounting 2 matrices into RPD (A or P) to give support and retention to RPD;

6. T11: 11 months after implant placement: MI with new RPD with attachment, OHIP-NL49, SF36, VAS, PPD, REC, BOP, MBL. Changing matrices;

7. T14: 14 months after implant placement: MI with new RPD with changed attachment, OHIP-NL49, SF36, VAS, PPD, REC, BOP, MBL (X-ray). Changing locator abutments depending on wish subject.

The present study is a randomized cross-over trial.
For this study two groups of fifteen patients with complaints regarding their RPD in the mandible and a maxillary complete denture are selected. In all patients four single implants are placed in the mandible: two directly behind the most distal abutment teeth and two at the location of the first molar. The implants are first provided with covering screws conform a two stage surgery approach.

Three months after placing the implants the second stage surgery takes place. All four implants will be provided with locator abutments. Subsequently a new RPD in the mandible and new complete maxillary denture are made. The first three months after placement of the RPD, none of the locator®abutments will provide retention and support to the RPD. After another three months two locator®abutments are loaded (A or P) by mounting the matrices into the RPD. And after another three months the loading conditions are changed to the other 2 locator®abutments. The sequence of loading depends on the group the patient will be directed to at random.