INCREASE IN RETENTION OF THE TOTAL REMOVABLE MANDIBULAR PROSTHESIS: ROLE OF THE RHEIN 83 ATTACHMENT

Dr. A. Taouili and Pr. S. Bellemkhannate 1. Resident doctor, Department of Removable Prosthodontics, Faculty of Dentistry, Hassan II University of Casablanca, Morocco. 2. Professor and Head of the Removable Prosthodontics service at the Casablanca dental consultation and treatment center (CCTD). Department of Removable Prosthodontics, Faculty of Dentistry, Hassan II University of Casablanca, Morocco. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 05 July 2020 Final Accepted: 10 August 2020 Published: September 2020

The quality of the periodontal , the favorable bone level and the financial conditions of the patient led us to the realization of a supra-radicular mandibular prosthesis with two axial attachments of the Rhein 83 .  107 Diagnostic and therapeutic approach : Diagnostic phase: The study phase is an essential prerequisite, it allows to analyze the occlusion plane and to assess the functional space. As a result, The models are then mounted on an articulator in order to evaluate the height necessary for good integration of the attachments and prosthetic teeth within the framework of a suitable aesthetics ( fig. 4). The realization of a direct assembly materializing the prosthetic project will make it possible to: (fig. 5,6,7). 1. Validate the aesthetic result 2. Realize the vestibular and lingual keys guiding the positioning of the attachments 3. Validate the occluso-prosthetic scheme

Pre-prosthetic phases:
The canines have long roots, with good bone anchoring. Endodontic preparation is performed followed by a tight filling of the 33and 43 (Fig. 8).

Impression of canal housing
A double-mix impression is made by injecting a low-viscosity elastomer into the canals, placing the stakes and the whole is covered with an impression tray charged with a high-viscosity elastomer (Fig. 11).

Attachment placement
The preparation of the attachments in the laboratory must respect a strict parallelism on the one hand between the two attachments and on the other hand between the attachments and the axis of the anterior ridge ( fig. 12)

Fitting and Validation of the copings topped by the resin cylinders and primary impression of the prosthetic support surfaces.
After validating the adaptation of the copings and the retention has been checked (Fig. 13), a primary plaster impression (Fig. 14) of the entire mandibular support surface is made with a commercial impression tray in order to make an individual impression tray that is notched opposite to the roots (Fig. 15).

Functional secondary impression
The remarginage ( fig. 17) is carried out classically as in conventional PAT after having closed the fenestrations with a high viscosity elastomer, the objective of which is to ensure the continuity of the bead and the hermeticity of the base of the PEI, necessary for check the effectiveness of the sublingual joint ( fig. 16)(3,4) Next, the Light Silicone coated posts are inserted, then the individual impression tray is filled with an Impregumtype polyether is inserted in the mouth, applied to the osteomucosal support surfaces, then a digital pressure is exerted on the beads while the patient is invited to mobilize his peripheral and lingual musculature in extreme functional movements( fig. 18). (5) After the impression material has completely set and the excess material has been removed ( fig. 19) to proceed the bonding of the resin beads to the copings using DURALEY resin ( fig. 20,21)

Recording of RIM and transfer of models to articulator (fig. 23)
The recording of the intermaxillary report is carried out through the polymerized direct assembly of the prosthetic project with the correct vertical dimension and in centered relationship. (7) Aesthetic and functional assembly and fitting in the mouth( fig. 24) the choice of prosthetic teeth is followed by the assembly respecting the aesthetic and functional rules: respect of the prosthetic corridor, orientation of the occlusal curves, inter-arch relations and respect of the fully balanced occlusion scheme. The assembly of the teeth is tested at the same time as that of the cast maxillary partial denture.

Polymerization and insertion in the mouth
The sealing of the copings is carried out using a glass ionomer cement under digital pressure, the excess cement is removed, all validated by a radio control. (fig. 25) Fixation of the female part (Fig. 26) can be carried out in the laboratory or directly in the mouth. (8) In our case, it was done in the laboratory, then the prosthesis is placed in the mouth under occlusal pressure, the patient is not allowed to remove it for 24 hours until the cement has set to avoid any risk of loosening. (fig. 27)

Maintenance and prosthetic follow-up
Prosthetic success in the medium and long term is closely linked to the Control and maintaining rigorous hygiene of both at the level of the dental abutments and at the level of the prostheses using a single tooth brush ( fig. 28) and dento-periodontal-prosthetic maintenance sessions are carried out at 1 week after placement of the prosthesis, then at 1 month and then every 6 months for 2 years and then once a year.
Discussion:- 1. Several factors affect prosthetic stability at the mandibular level, in particular the degree of resorption, the reduced support surface, the presence of the tongue, the disappearance of the desmodontal proprioception as well as the quality of the salivary flow resulting in prosthetic imbalance and a masticatory inefficiency.(9)