Decortication Vs Microperforations: A Finite Element Analysis

Abstract

Introduction: Adjunctive corticotomies such as decortication and microperforations reportedly reduce the duration of orthodontic treatment, but their effectiveness remains controversial.

Aims: 1. Compare the stresses and displacements generated by canine distalization against orthodontic miniscrews with and without decortication and microperforations. 2. Determine the conditions under which both techniques lead to similar effects. 3. Test the influence of individual variation in cortical bone properties through thickness and stiffness. Our hypothesis was that increasing the extent of the corticotomy leads to higher stress and initial displacement, and that cortical bone thickness and stiffness influence stress generation.

Methods: A 3D model of the maxilla containing teeth, PDL, cortical and trabecular bone was prepared for finite element analysis (FEA) using first ScanIP™ 7.0 software (Simpleware Ltd., Exeter UK) to construct the model and later ABAQUS 6.13 for mechanical modeling. Distalization of the buccal segment was simulated with a force (150 grams) directed from a miniscrew placed between the 2nd premolar and 1st molar to the canine bracket. With DEC and MOP introduced distal to the canine, six models were generated: Control, DEC, and 4 MOP (with 3, 4, 5 and 6 perforations). Initial canine and first premolar displacement and stress distribution on the PDL of the canine, first premolar, and trabecular bone were compared.

Results: The stress distribution pattern was similar in all the models, being highest on the canine, more precisely on the cervical region, and progressively decreasing in magnitude from the canine to the second molar. Stresses on all PDL surfaces and displacement of the canine were significantly higher (with the highest stress registered on the distal surface) than the stresses and displacement of the 1st premolar except for the palatal surface. Statistically significant differences were found for the stress and displacement between modalities in both the stiffness and thickness variations. Stress and displacement increased as the number of perforations increased. The 6MOP modality yielded the highest initial displacement and stress on all PDL surfaces and the trabecular bone. However, when compared with decortications, greater stresses and displacements were found except for the stress on the buccal surface where it was significantly reduced. DEC and 6MOP led to almost the same effect on distal surface stress and initial canine displacement (25% increase). The difference was in the stress on the buccal surface. High correlations where present between the total stress on the PDL and initial tooth displacement. No correlations where found between PDL stress and thickness, and between initial displacement and cortical bone properties. At the 1st premolar, high and negative correlations were present with the palatal stiffness components of the premolar. Moreover, stress on the trabecular bone underlying the corticotomy showed a negative correlation with the buccal cortical bone stiffness and a positive correlation with the thickness in the microperforation modalities.

Conclusions: 1. By removing a continuous shear band of cortical bone with decortication, resistance to tooth movement is decreased thereby facilitating initial displacement 2. Six microperforations could be as efficient as decortication when extended over the same distance. 3. By introducing individual variation in cortical bone properties, we were able to determine the effect of stiffness and thickness on stress generation, proving that the response of the dentoalveolar structures depends not only force magnitude and vectors, but also on individual anatomy. 4. Future research should elucidate other clinical setups and time-dependent orthodontic movement, beyond the present initial static FEA conditions.