By adding some function I came a little further. Unfortunately I still can't use the Model::has and Model::whereHas functions, which are quite important.

public function getRestrictedToAttribute()
{
	if(!is_null($this->restricted_to_id) && $this->restricted_to_id !== '')
	{
		$classToType = '';
		list(, $classToType) = explode('\\', $this->restricted_to_type);
		$classToType = snake_case(str_plural($classToType));

		return $this->relations['restricted_to'] = call_user_func_array([$this, 'restricted_to_' . $classToType], [])->getResults();
	}

}


public function restricted_to_materials()
{
	return $this->morphToMany('App\Materials', 'restricted_to', 'options', 'id', 'restricted_to_id');
}

public function restricted_to_material_categories()
{
	return $this->morphToMany('App\MaterialCategories', 'restricted_to', 'options', 'id', 'restricted_to_id');
}

Does someone have an idea?