Biomechanical study of a prosthetic solution based on an angled abutment: case of upper lateral incisor.

OBJECTIVES To study the complex behaviour of an upper lateral incisor restoration using an angled abutment, a mechanical analysis of the abutment bearing capacity was firstly carried out. The evolution of bone properties around implant was then simulated as a function of time to estimate the maximal load that could be supported by the prosthetic solution without bone damage. MATERIALS AND METHODS According to the Food and Drug Administration procedure, experimental tests were firstly carried out on five samples. A 25 degrees -angled abutment screwed to an implant embedded into a massive steel bloc was submitted to a static loading. Two finite element models were also built: the first one (I) to interpret and complete the results obtained in the experimental part and the second one (II) to simulate bone remodelling around implant considering a strain energy stimulus. RESULTS According to experiments, the abutment straightening was observed for an average force of 869N. Numerical model (I) confirmed this result and indicated that the initial irreversible deformation (yielding) of abutment was obtained for a 283N compressive force. It could thus be deduced that this abutment can safely be used for an incisor restoration. Model (II) showed that, after 26 months, some of the cancellous bone initially present in an approximately one millimetre thick shell surrounding the implant had reached the density of cortical bone. A safe load notion corresponding to the force leading to the maximal admissible strain value for trabecular bone was introduced. It evolved from 44N after surgery to approximately 160N after 26 months.