Effect of abutment's height and framework alloy on the load distribution of mandibular cantilevered implant-supported prosthesis

Objectives: In cantilevered implant-supported complete prosthesis, the abutments' different heights represent different lever arms to which the abutments are subjected resulting in deformation of the components, which in turn transmit the load to the adjacent bone. The purpose of this in vitro study was to quantitatively assess the deformation of abutments of different heights in mandibular cantilevered implant-supported complete prosthesis.

Material and methods: A circular steel master cast with five perforations containing implant replicas (Ø3.75 mm) was used. Two groups were formed according to the types of alloy of the framework (CoCr or PdAg). Three frameworks were made for each group to be tested with 4, 5.5 and 7 mm abutments. A 100 N load was applied at a point 15 mm distal to the center of the terminal implant. Readings of the deformations generated on the mesial and distal aspects of the abutments were obtained with the use of strain gauges.

Results: Deformation caused by tension and compression was observed in all specimens with the terminal abutment taking most of the load. An increase in deformation was observed in the terminal abutment as the height was increased. The use of an alloy of higher elastic modulus (CoCr) also caused the abutment deformation to increase.

Conclusion: Abutment's height and framework alloy influence the deformation of abutments of mandibular cantilevered implant-supported prosthesis.