Influence of ridge type on mandibular removable partial denture

Objectives: The aim of this research was to analyze, by photoelastic models, the stress distribution formed by load incidence on free end mandibular removable partial dentures, on abutment teeth and residual ridge in the following manners: distal ascendant, descendant-ascendant, horizontal and distal descendant. On the different types of ridge, the best clip type and location of the smallest connector were found to be on the last abutment tooth of the free end.

Methods: Four photoelastic resin models were constructed ( PL-1 for the teeth and PL-2 for the alveolar ridge), one model for each ridge type. For each model, 4 removable partial dentures were made (total of 16 removable partial dentures) with roach clip and smallest connector on the distal, roach clip and smallest connector on the mesial, and circumferential clip and smallest connector on the mesial face. The models were placed in a circular polariscope and 100 N load points were applied on the denture pre-molars and molars. The images were photographed and transferred to the ADOBE Photoshop 7.0 program.

Results: The results were qualitatively analyzed and one could observe that when the force was applied on the second molar, there was greater stress on the last abutment tooth, the descendant distal ridge presented the highest stresses, irrespective of the clip type and smallest connector location, and the descendant–ascendant ridge presented the greatest stress variations when the type of clip was changed.

Conclusion: 1 – The Roach clip presented the most favorable stress distribution; 2 - The most unfavorable ridge was the distal descendant and the most favorable the horizontal; 3 – Location of the smallest connector presented similar behaviors, except on the descendant distal ridge; 4 – Clip type had no influence on the horizontal ridge.