Set a checkbox to unchecked from angularJs factory

I have a list(master) of element which contains also a list(child) of elements. what I want is : If I choose an element from the first list(master) I get a list of checkbox alimented with the appropriated element from the list child

My problem is that when I check an element for example "1" the first element in child list for the first element in master list, and I return to choose the second element I found that the first element in the child list (for the second element in the master list) is also checked. how can I manage this knowing that I feed my child list with a factory and this is my factory:

app.factory("Fctr", ["Restangular", function(Restangular) {
    var currentObj = {};

    currentObj.testz = function(myObj){
        var selectedVersion = [];
        var masterElements = [];
            var params = {
                query: {
                    "id": myObj.id
                }
            };
            var service = Restangular.all('mycollection');
            selectedVersion = service.getList(params).then(function(response) {
                var selectedVersions = response[0].refVersions;
                    for (var k in selectedVersions) {
                        if (selectedVersions[k].vCode == myObj.vCode) {
                            masterElements = selectedVersions[k].masterElements;
                        }
                    }
                    currentObj.masterElements = masterElements;
            }); 
    };

    return currentObj;
}]);

in the controller I'm using factory with this function:

$scope.beginPreparation = function(myObj){
    $scope.Fctr.testz(myObj);
};