Another option for diminishing the velopharyngeal port is posterior wall augmentation. This technique is not often used. Additionally this technique can only be used for small gaps. When this operation is performed there are several advantages. It is possible to narrow down the velopharyngeal port without modifying the function of the velum or lateral walls. Furthermore, the chance of obstructing the airway is lower, because the port can be closed more precisely. Many materials have been used for this closure: petroleum jelly, paraffin, cartilage, adjacent soft tissue, silastic, fat, Teflon and proplast. But results in the long term are very unpredictable. There are problems with tissue incompatibility and migration of the implant. Even migration to the brain is noticed.