Problems deleting rows and the table's style (fnClearTable function)

I want to search in my database and show the results in a datatable. But i have some problems. After the first search, I have to delete the previous rows to show the new results. To remove all rows I am using fnClearTable() but
- it changes the style of the table.
- the footer of the table always shows the quantity is 0 when it is not. It lists the expected result.
- because the "quantity is 0", the previous and next buttons are disabled, it is not possible to sort by columns neither use the search filter.
- the internalization does not work.

If I comment the line $('#displayData').dataTable().fnClearTable(); all these problems disappear but the new rows of the search are added to the current table's data source.

There are my html / javascript codes respectively:

$.ajax({ // search button click
                        url: '../xxx/search.php',
                        type: 'POST',
                        data: 'idxxx=1',
                        dataType: 'json',
                        success: function(response) {
                            var thtml = "";
                            $('#displayData').dataTable().fnClearTable();
                            if(response.length > 0) {
                                $.each(response, function(index, record) {
                                     thtml += "<tr>";
                                     thtml += "<td>" + record.Name + "</td>" ;
                                     thtml += "<td>" + record.BDay + "</td>";
                                     thtml += "<td>" + record.Code + "</td>";
                                     thtml += "</tr>";
                                });
                             }
                             $('#displayData tbody').append(thtml);
                             $('#resultContainer').css({"visibility":"visible"});
                             $('#displayData').dataTable({
                                "bRetrieve": true,
                                "oLanguage": {
                                   "sUrl": "../xxx/DataTables-1.9.4/pt.txt"
                                },
                                "sPaginationType" : "full_numbers"
                             });
                        }
                  });

<table class="display" id="displayData">
            <thead>
                <tr>
                    <th>Name</th>
                    <th>Birthday</th>
                    <th>Code</th>
                </tr>
            </thead>
            <tbody>
            </tbody>
 </table>

Thanks in advance!