Centering the header in Datatable v2.3.0

I started using Bootstrap version of the Datatable Plugin and I am unable to center the text of header using the text-center class of the bootstrap(included in v2.3.0, that just's center the text), although using the same code of css inside the style tag of the element works fine?
what is the problem?please shed some light?

                       //this is <script> part
                                $('#tbl').dataTable({
					"aoColumns" : [ 
						{"bSortable" : false}, 
						null, 
						null,
						{"bSortable" : false}, 
						{"bSortable" : false}
					],
				});


                 <table  class="table table-striped table-bordered table-hover"  id="tbl" width="100%">
			<thead>
				<tr>
					<th width="3%"><input type="checkbox"></th>
					<th>GaCode</th>
					<th>Ga Phone</th>
					<th>Distance</th>
					<th>Address</th>
				</tr>
			</thead>
			<tbody>
				<tr>
					<td><input type="checkbox"></td>
					<td>Ankur</td>
					<td>12345678</td>
					<td><button class="btn btn-small">Distance</button></td>
					<td><button class="btn btn-small">Address</button></td>
				</tr>
						
				<tr>
					<td><input type="checkbox"></td>
					<td>Reva</td>
					<td>12345678</td>
					<td><button class="btn btn-small">Distance</button></td>
					<td><button class="btn btn-small">Address</button></td>
				</tr>
			</tbody>
		</table>