3D Finite Element Analysis Of Maxillary Protraction With Bone Anchorage In Patients With Unilateral Cleft Lip And Palate

Objective:CLP(cleft lip and palate)is a kind of congenital craniomaxillofacial malformations with high morbidity,which is more common in unilateral.Most patients have sagittal hypoplasia of the maxilla and the maxillary protraction with bone anchorage is often used to treat patients who have passed their peak of growth.However,the biomechanical effect of protraction with bone anchorage on patients with UCLP(unilateral cleft lip and palate)needs further study.In this study,the craniomaxillary complex with UCLP was modeled by the three-dimensional finite element method,aiming to research the biomechanical effects of different force directions,the position of implants,and bone anchorage systems on maxillary protraction.The study can lay the foundation for further biomechanical studies and provide the theoretical basis for clinical application.Methods:A 12-year-old male patient with UCLP and unilateral alveolar cleft in late mixed dentition was selected as the study object.The CBCT(cone beam computed tomography)data of the patient was imported into the modeling software to construct the 3D finite element models of the craniomaxillary complex containing miniscrew implants and titanium miniplates,and they were assembled into model A with miniscrew implants anchorage in the infrazygomatic buttresses of the maxilla,model B with miniscrew implants anchorage between the premolars,and model C with titanium miniplates in the infrazygomatic buttresses of the maxilla.The displacement of maker nodes and the stress distribution of the sutures were analyzed by changing the traction direction,traction position,and bone anchorage.Results:1.The 3D finite element models of the UCLP craniomaxillary complex with bone sutures and the bone anchorage systems were successfully established,with complete related structures and strong geometric similarity.2.The craniomaxillary complex moved forward and counterclockwise rotated under all loading conditions,and the stress magnitude and distribution of each suture were different.3.The horizontal and vertical dislocation of the bone segments on both sides of the alveolar cleft was aggravated,and the alveolar cleft decreased during the maxillary protraction with bone anchorage.4.The sagittal displacement and counterclockwise rotation of the maxilla reached the peak when protracting in the direction of 15°.5.The dental arch narrowed with maxillary protraction.The area of arch retraction became smaller and less severe with the direction of protraction increased.6.In the process of maxillary protraction,there were differences in the displacement and the distribution of suture stress of the healthy and affected sides of the UCLP craniomaxillary complex.7.The titanium miniplates produced greater sagittal displacement,counterclockwise rotation,arch narrowing,and suture stress than miniscrew implants,and the horizontal and vertical dislocation of the bone segments on both sides of the alveolar cleft was also more serious.8.The anterior sagittal displacemen of the craniomaxillary complex was greater and the degree of counterclockwise rotation of the maxilla was less when the miniscrew implants were placed between premolars than placed in the infrazygomatic buttresses of the maxillaConclusions:1.The maxillary protraction with bone anchorage can effectively stimulate the growth of the suture around the maxilla of UCLP.Under the protraction directions of-60° to 60° in the infrazygomatic buttresses of the maxilla,the maxilla moves forward with counterclockwise rotation,which is suitable for patients with deep reverse overjet with vertical overgrowth of the maxilla.2.The maxillary protraction with bone anchorage affects the width of the dental arch in UCLP patients and the degree of change is closely related to the direction of traction.3.The displacement and the stress of sutures on the cleft and noncleft sides are asymmetric,and the maxillary protraction with bone anchorage can cause increased misalignment of the bone segments on both sides of the alveolar cleft.4.Compared with the miniscrew implant system,the titanium miniplate system can obtain more three-dimensional displacement and stress of sutures during maxillary protraction,and the bone segment malposition on both sides of the alveolar cleft is more serious.5.When maxillary protraction with-30° angle is performed between premolars,the force line was closer to the center of the maxillary complex than that in the infrazygomatic buttresses of the maxilla.