DISCUSSION
The ambition to restore ad integrum the lost oral structures often leads us to select a fixed implant-supported option. Clinicians thus hope to restore esthetics, function and comfort for these edentulous patients. However, this vision is often unrealistic in a context of UADT cancer. The clinical conditions of the prosthetic management, the need for an easy access to oral hygiene, but also for the supervision of possible cancer recurrence on the surgically treated sites modify the prosthetic choice. Studies have shown (3) that patient satisfaction would be equivalent between patients wearing a complete implant-supported bar-retained overdenture or a fixed implant-supported prosthesis. Moreover, oral hygiene maintenance (often difficult in patients treated surgically for UADT cancers) is easier with a complete implant-supported bar-retained overdenture compared to a fixed implant supported prosthesis.
In these complex clinical situations, the limited mouth opening (LMO) restricts easy access to prostheses. Excessive retention of the clips must be avoided despite the great number of implants. Therefore, we will prefer the Dolder CB rather than the Hader CB.
The CBs were made of titanium for all our clinical cases because titanium CBs achieve better stress distribution on implants and peri-implant tissues than the cobalt-chromium CBs (13).
The main difficulty of the prosthetic rehabilitation is the vertical dimension paradox : Patient N°1 presented a severe bone resorption, and Patient N°2 had an oversized reconstruction. Initially, for both cases, we could therefore expect an increased prosthetic space ; however, given the microstomia / mouth opening limitation (and the oversized fibula in the mandible for Case N°2), the prosthetic space is reduced. Therefore, determining an esthetic and functional VOD becomes difficult. Tissue sclerosis leads to labial inocclusion at rest which can prove to be unesthetic. In Case N°2, this tissue sclerosis could have been limited if we had implemented a complete removable prosthesis immediately after the surgery. But, given the context (fibula graft/ UADT cancer), placing a prosthesis immediately after the surgery could lead to flap necrosis. The complete removable bar-retained overdenture remains a good alternative to the esthetic challenge (lip support, gummy smile) often observed in patients treated surgically for UADT cancer.
Another problem frequently encountered (15) in patients grafted with a fibula is mucosal hypertrophy around the implants. It consists of granulomatous mucous tissue which may complicate the implant-supported prosthetic rehabilitation (16). In Case N°2, we could have considered achieving a bar contacting the mucosa in order to reduce the stress on the implants and the bar. However, this option limits the access for good oral hygiene, and may aggravate peri-implant tissue proliferation which can become chronic. Grafting palatal gingiva in the concerned zones could be an alternative.
For Patient N°1, in the maxilla, we fabricated a CB spaced 1mm from the mucosa because his oral hygiene was good despite the limited mouth opening (LMO) and microstomia, but also to limit the stress on the peri-implant bone. Otherwise, we could have fabricated a complete prosthesis with full palate coverage. Indeed, Kim MJ and Hong SO showed that a prosthesis with full palate coverage provided a better stress distribution on the implants (particularly the most distal ones which receive the most of the loads), than a partial palate coverage). (18)