JOURNAL OF OSAKA DENTAL UNIVERSITY

Vol. 41 No. 2      OCTOBER - 2007

ISSN: 0475-2058      UBIC: 172

SUMMARY

Bone fixation with miniplates has recently been used for fixation following sagittal spliting ramus osteotomy. We have observed breakage L-shaped titanium miniplates during the postoprerative observation period. We investigated the breakage cases, and performed biomechanical analysis of stress on L-shaped and straight miniplates in a sagittal spliting ramus osteotomy model, which we developed using CT images and the three dimensional finite element method. Breakage was detected in 22 sides (18patients) in miniplates placed on 123 sides between January 2000 and December 2001. The period between surgery and breakage was less than 3 months in 17 of the miniplates, between 3 and 6 months in 3 miniplates, and greater than 6 months in 2 of them. The breakage, when it occurred, was always at the bending site of the L-shaped miniplates. Stress analysis by the three-dimensional finite element method demonstrated that the stress level was greatest at the upper margin of the bending region in the L-shaped plates. Although it is thought that there is no difference in the effectiveness of bone union between L-shaped and straight miniplates, the letter may be better in resisting long-term stress on the jaw bone, such as occurs during relapse. (J Osaka Dent Univ 2007; 41 : 89-96) Key words: Sagittal spliting ramus osteotomy; Titanium miniplate fixation; Three-dimensional finite element method.

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