  The relevance of encounters on the destruction of protoplanetary discs in the
Orion Nebula Cluster (ONC) is investigated by combining two different types of
numerical simulation. First, star-cluster simulations are performed to model
the stellar dynamics of the ONC, the results of which are used to investigate
the frequency of encounters, the mass ratio and separation of the stars
involved, and the eccentricity of the encounter orbits. The results show that
interactions that could influence the star-surrounding disc are more frequent
than previously assumed in the core of the ONC, the so-called Trapezium
cluster. Second, a parameter study of star-disc encounters is performed to
determine the upper limits of the mass loss of the discs in encounters. For
simulation times of $\sim$ 1-2 Myr (the likely age of the ONC) the results show
that gravitational interaction might account for a significant disc mass loss
in dense clusters. Disc destruction is dominated by encounters with high-mass
stars, especially in the Trapezium cluster, where the fraction of discs
destroyed due to stellar encounters can reach 10-15%. These estimates are in
accord with observations of (Lada et al. 2000) who determined a stellar disc
fraction of 80-85%. Thus, it is shown that in the ONC - a typical star-forming
region - stellar encounters do have a significant effect on the mass of
protoplanetary discs and thus affect the formation of planetary systems.
