[Progressive pneumatization of the basal maxillary sinus after extraction and space closure].

By superimposing 32 pretreatment and post-treatment orthopantomograms, it proved possible to quantify the progressive pneumatisation of the basal maxillary sinus following extraction and orthodontic space closure. It was shown that if pneumatisation was present prior to treatment (more than 30% of root length), clear extension of the basal antrum could be expected. The tendency towards pneumatisation is significantly higher after molar as compared with premolar extraction. Possible reasons for these findings and their clinical significance are discussed.