Load transfer by fine threading the implant neck--a FEM study.

ABSTRACT

Osseointegration of dental implants up-to-date is a well-confirmed phenomenon, however the long-term stability and integrity of the bone and soft tissue collar is under discussion. A homogenous distribution of the bone loading is a prerequisite for bone modelling and preservation in the neck area while overload must be avoided. Based on the finite element method (FEM) models of implants without and with a fine thread (implant types Tiolox and tioLogic) with surrounding bone were generated and analysed using the FE program system MSC.Marc/Mentat. The alveolar bone was considered to be an idealized segment with a cortical bone thickness of 2 or 3 mm, respectively with an enclosed spongy bone. The implants were loaded with forces up to 300 N in two different directions, in the first case with a purely vertical force and in other case with an additional lateral force component with a angle of 45 degrees with respect to the occlusal plane. The deflections of the implants ranged from 0.004 to 0.017 mm in the load direction, depending on the implant diameter and the cortical bone thickness. When considering a physiological vertical load of a maximum of 100 N, the highest strains were about 2100 micro strain in the spongy bone. Within the fine thread in the neck area of the implant, the maximum stresses were increased in the cortical bone by 3%. The improvement of implant anchorage in the cortical bone reduced the strains in the spongious bone, at the same time there were no additional stress peaks visible at the fine thread region.