Residual lower first premolar extraction space.

Residual lower first premolar extraction space was examined in 43 subjects, 16 male and 27 female, 5 years after extraction; 16 subjects were treated mechanically, 27 had no active treatment. Forty per cent of extraction sites had residual spaces averaging 0.62 mm left and 0.71 mm right. Various parameters were measured to try to establish reasons for non-closure of spaces. These included buccal space condition and incisal space condition measured on the pre-extraction models, and alveolar atrophy assessed on final models. The angulation of second premolars and canine to the maxillary plane and molar space were measured on 60 degrees cephalograms. Changes in these three parameters were measured after superimposing a tracing of the pre-extraction film on the final film. Angulation of lower incisors to the maxillary plane was measured on pre-extraction 90 degrees cephalograms, and change in lower incisor angulation and position measured after superimposing a tracing on the final 90 degrees film.