没有使用symfony 2.8的枝条下拉？

I have a proyect with symfony 2.8. When I add a dropdown on mi navbar in twig, is added correctly. But when I click on it the dropdown not drop... The url change adding the # of href, but this not dropdwon.

My code is:

<ul class="nav navbar-nav navbar-right">
                <li class="dropdown">
                    <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button"
                       aria-expanded="false">  <img src="" height="40" width="40" class="profile-photo img-circle">
                        {{ app.user.username }} <span class="caret"></span></a>

                    <ul class="dropdown-menu" role="menu">
                        <li>
                            <a href="#">Edit</a>
                        </li>
                        <li class="divider"></li>
                        <li>
                            <a href="{{ path('logout') }}">Logout</a>
                        </li>
                    </ul>
                </li>
            </ul>

How can implement this on twig to work?? Thanks!