Post-retained Restorations for RPD Abutments

This study will be a controlled, randomized, parallel group trial where the survival rate of direct and indirect restorations on removable partial denture abutment teeth will be assessed. For this, individuals with widely destroyed teeth and need for endodontic treatment, with at least one remaining dentin wall, adjacent to edentulous spaces in Kennedy Classes I and II will be selected. After the minimum period of one year the teeth will be reassessed through clinical and radiographic examination annually.

All patients will receive oral hygiene instructions, caries disease control and endodontic treatment according to the need of each case. Prior to post cementation, patients will receive endodontic treatment through routine techniques that include use of rubber dam, mechanized instrumentation with NaOCl 2%, gutta percha and endodontic cement filling and condensation by the McSpadden technique. The preparation for post space will be done with a specific bur compatible with the diameter of root canal, and the same preparation cast post and cores. The glass-fiber posts (will be cleaned with 70% alcohol and receive silane application.

The clinical protocol for direct restoration and confection of the composite resin core will occur in the same way, using the same materials: the dental structure will be etched with 37% phosphoric acid and rinsed, followed by the adhesive system and fabrication of the restoration by incremental technique according to the manufacturer's recommendations. It is important to emphasize that the direct restorative procedure will be carried out in the same consultation of the glass-fiber post cementation.

In order to make the cast metal cores, the indirect impression technique will be done with prefabricated pins associated with addition silicone. In this technique, the lightweight material will be inserted into root canal and then, the pin will be introduced into the canal. Next, a prefabricated tray with the heavy and light material will be positioned for removal of the assembly, being removed after the setting time determined by the manufacturer. The mold obtained will be sent to the dental technician for cast post and core fabrication. All posts will be cemented under rubber-dam isolation using self-adhesive resin cement.

In teeth where randomization is a metalceramic crown, first the composite resin or metal core will be prepared with a 3216 drill, in order to obtain 1.5mm wear on the proximal and free faces and 2mm on the occlusal surface. The margin design in form of a chamfer, preferably at the gingival level whenever possible. The impression procedure will be carried out using a molding cap and polyether, which will be removed in a tray with irreversible hydrocolloid. A temporary crown will also be made for the patient. The metallic infrastructure will be tested in order to verify its adaptation and transferred in irreversible hydrocolloid molding for later ceramic application. After application of the ceramic, the laying and adaptation of the prosthetic piece will be conferred, being the crown luted with self-adhesive resin cement.

Once the restoration / crown of the abutment tooth has been made, the treatment will continue with the preparation of the removable partial denture. The teeth will always be prepared in the mesial proximal area. The delivery of the removable partial denture will be considered the baseline of the study. At this moment, the necessary adjustments and subsequent control of the prosthesis will be made after 24, 72 hours, a week and 15 days in order to check for possible flaws. After 6 months and 1 year of delivery of the removable partial denture, all patients will be recalled for clinical and radiographic evaluation of prostheses / restorations and oral hygiene conditions. This monitoring will be conducted by two evaluators until the end of the trial.

All clinical procedures will follow pre-established protocols and the data of each patient and intervention will be recorded in the individual patient file.