Non-surgical anterior open bite closure.  Flaring of the upper and/or lower anterior teeth due to orthodontic unraveling of crowded teeth can lead to shallowing of the anterior overbite (called by some the drawbridge effect).  If the overbite was shallow prior to treatment an anterior open bite can result.  This is why I tend to prescribe more premolar removals for crowded cases with shallow overbites and proclined incisors.  If I suspect that first premolar removals may lead to loss of lip support I will suggest removal the second premolars.