Analysis of stress distribution and displacement based on the miniscrews positions of the palatal slope bone-borne expander: a finite element study

Objectives: The study aimed to investigate the stress distribution pattern of the palatalslope bone-borne expander on the maxillary area according to a differentanteroposterior position of anchored miniscrews using finite element analysis.Materials and Methods: Nasomaxillary stereolithography files with 3 differentanteroposterior anchored miniscrew positions of the palatal slope bone-borne expanderwere determined as models A, B, and C. Each model consists of four supportedminiscrews. Model A: two anterior miniscrews were located between the maxillarycanine and the first premolar, and two posteriors between the second premolar and thefirst molar. Model B: two anteriors were between the lateral incisor and the canine, andtwo posteriors were the same as in model A. Model C: two anteriors were the same asin model A, and two posteriors were distal to the first molar. One turn of expanderscrews was applied. Maximum principal stress, equivalent elastic strain, equivalent vonMises stress, and transverse displacement were evaluated.Results: The maximum principal stress was mostly found at the bone-miniscrewinterface. Model A exhibited an intersecting area of stress between the supportedminiscrews. The highest value of principal stress was in model B, while model Cshowed a uniform distribution pattern. The elastic strain pattern was similar to theprincipal stress in all models. The highest value of equivalent von Mises stress waslocated on the expander screw. The largest amount of transverse displacement of teethwas in model A, while model C exhibited a more consistent transverse displacementthan other models. Vertical displacement of posterior teeth was also noticed.Conclusions: Finite element research revealed that the various anteroposteriorminiscrews placements of the palatal slope bone-borne expander had various patternsof stress distribution and resulted in various outcomes. It may be inferred that modelA's miniscrew location was advantageous for obtaining expansion quantities, but modelC's miniscrew position was advantageous for maintaining consistent biomechanics.