Fixation properties of a biodegradable “free-form” osteosynthesis plate with screws with cut-off screw heads: Biomechanical evaluation over 26 weeks

doi:10.1016/j.tripleo.2008.09.034

Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology

Volume 107, Issue 4, April 2009, Pages 462-468

https://doi.org/10.1016/j.tripleo.2008.09.034 Get rights and content

Objective

The aim of this study was to compare the postoperative fixation properties of a biodegradable osteosynthesis “free-form” plate achieved with countersunk screws with those provided by screws with cut-off screw heads.

Study design

Acrylic pipes were fixed together to simulate fracture fixation for tensile testing. Additional plates were fixed to a polyurethane block with a single screw for plate-screw pullout testing. Specimens were incubated in phosphate buffer solution at 37°C, and testing was conducted at various time points during hydrolytic degradation of 26 weeks. In both tests the specimens were loaded at a speed of 5 mm/min until failure. The yield load, maximum load, and stiffness were recorded, and failure mode was visually determined.

Results

Both countersunk screws and screws with cut-off screw heads provided similar plate fixation properties over degradation time.

Conclusion

According to these results, fixation of the biodegradable osteosynthesis free-form plate with screws with cut-off screw heads seems to be feasible.

Section snippets

Materials and Methods

The study groups were: 1) free-form plates fixed with countersunk screws; and 2) free-form plates fixed with screws with cut-off screw heads (Table I). To create the worst-case scenario for the fixations tested, the smallest diameter screw (i.e., 2.0 mm) available for use with the investigated free-form plate was used (Fig. 1, a).

According to the manufacturer's instructions for use, the plates were immersed in a warm water bath at 70°C for 1 min before use, and immediately after rejuvenation

Results

The results of the tensile test are shown in Table II and Fig. 6. No significant difference was found between the groups in any of the parameters at any time point in the tensile test. In the tensile test, all fixations at all time points failed by screws' shaft breakage.

The results of the plate-screw pullout test are shown in Table III and Fig. 7. No significant difference was found between the groups in any parameters at any time point in the plate-screw pullout test. In group 1 of the

Discussion

The results of this study show that the screws with cut-off screw heads provide postoperative fixation strength of the biodegradable osteosynthesis free-form plate equivalent conventional countersunk screws during 26 weeks of hydrolytic degradation. No statistically significant differences were found between the groups in any parameters at any time point in the tensile or plate-screw pullout tests.

Fractures typically heal in 6 weeks. After 6 weeks of hydrolytic degradation in both groups, >99%

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Oral and maxillofacial surgeryFixation properties of a biodegradable “free-form” osteosynthesis plate with screws with cut-off screw heads: Biomechanical evaluation over 26 weeks

Objective

Study design

Results

Conclusion

Section snippets

Materials and Methods

Results

Discussion

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Fixation properties of a biodegradable “free-form” osteosynthesis plate with screws with cut-off screw heads: Biomechanical evaluation over 26 weeks