Mechanical and photoelastic analysis of conventional screws and cannulated screws for sagittal split osteotomy fixation: a comparative study.PURPOSE
 The aim of the present study was to use mechanical and photoelastic tests to compare the performance of cannulated screws with solid-core screws in sagittal split osteotomy fixation.


 Ten polyurethane mandibles, with a prefabricated sagittal split ramus osteotomy, were fixed with an L inverted technique and allocated to each group as follows: cannulated screw group (CSG), fixed with three 2.3-cannulated screws; and solid-core screw group (SCSG), fixed with three 2.3-solid-core screws.  Vertical linear loading tests were performed.  The differences between mean values were analyzed through T test for independent samples.  The photoelastic test was carried out using a polariscope.


 The results revealed differences between the two groups only at 1 mm of displacement, in which the cannulated-screw revealed more resistance.  Photoelastic test showed higher stress concentration close to mandibular branch in the solid-core group.


 CONCLUSIONS
 Cannulated screws performed better than solid-core ones in a mechanical test at 1-mm displacement and photoelastic tests.
C