[Finite element analysis of the angulation designment of implant planning in the anterior maxilla]

To provide theoretical reference for maxillary anterior restoration designment in clinics by observing the masticatory stress distribution of the implant-bone interface and the displacement of implant.

This study built simplified 3 dimensional finite models with different angles, which included partial implant (4.3 mm×11.5 mm), abutment and all ceramic crown (Zirconia) and combined with angle of implant A between the long axis of ideal implant and factual implant (0°, 5°, 10°, 15°, 20°, 25°), as well as angle of abutment B between the long axis of abutment and implant (0°, 5°,10°,15°,20°,25°). A force load of 178 N was applied 2 mm below the incisal edge on the palatal surface of the crown, with an approximately 130° angle to the long axis of the crown. The displacement of implant maximum principal stress value and distribution of the implant-bone interface were determined by using Ansys 13.0 software.

Sixteen 3-dimensional models of different implant restoration plan of implant dentures of maxillary incisor were built. When the angle of abutment was increasing with the same labial inclination of implant, the objective functions were enhanced. When the labial inclination of implant was increasing with the same angle of abutment, the objective functions were also improved. With the change of labial inclination of implant and angled abutment, the labial inclination of implant concentrated more than the angle of abutment on the objective functions. When the angle of abutment was between 0 degree and 20 degree, the amplitude of all the objective functions were gentle, while the labial inclination of implant and amplitude of all the objective functions were increased when the angle of abutment increased to 25 degree.

A positive correlation is found between the value of stress of the bone around the implant, and the displacement of implant and the labial inclination of the implant and the angle of abutment. It is necessary to decrease the labial inclination of the implant and the angle of abutment, especially strictly control the labial inclination of the implant. Taking the stress and displacement into consideration, both of two angles ranging from 0 degree to 20 degree are the best optimal choice for the anterior implants. When both of two angles increase to much greater than 20 degree, the value of stress increase remarkably, which will decrease the chance of successful implant.