Three-dimensional Finite Element Study On The Effect Of Perioral Force On Maxilla In Patients With Unilateral Complete Cleft Lip And Palate

Objective:Three-dimensional finite element analysis method was used to study the effect of perioral force on the growth and development of maxilla in patients with unilateral complete cleft lip and palate(UCLP)in mixed dentition.By constructing a threedimensional finite element model of UCLP maxillary complex in mixed dentition,and applying perioral force on the labial and lingual sides of the model in resting and swallowing states,the internal stress distribution and displacement change of the model were studied.In-depth analysis of the relationship between the perioral force and the formation of dentofacial deformities in patients with UCLP to provide a reference for the sequential treatment of patients with UCLP.Methods:1.Modeling: Select a representative UCLP patient in mixed dentition,obtain CBCT image data,import the medical image processing software mimics15.0 in DICOM format,and intercept the maxillary complex(including maxilla,upper dentition,zygomatic bone,part of the orbit,sphenoid bone and part of the skull,etc.),generate a 3D model in STL format,and import it into the reverse engineering software Geomagic Studio10 for optimization and smoothing.The obtained geometric model was imported into Hypermesh modeling and meshing software for format conversing and meshing,and finally imported into Abaqus6.14 finite element modeling and analysis software to obtain a three-dimensional finite element model of the maxillary complex.2.Applying force: Set parameters for the three-dimensional finite element model of the maxillary complex,and establish a three-dimensional coordinate system(X axis represented the horizontal direction,Y axis represented the sagittal direction,and Z axis represented the vertical direction).The molar,the first and second premolar/deciduous molar,the canine,the incisor buccal(labial)/lingual alveolar process area exerted the labial and lingual perioral force obtained from the previous study under the resting and swallowing states value,the direction was perpendicular to the outer surface of the alveolar process.3.Mechanical analysis: After adding the peripheral force,the stress cloud map and the displacement cloud map were obtained,and the changes of Von Mises stress,principal stress and shear stress of the model in two states were studied from the stress cloud map.The displacement changes of the cleft side and the anterior and posterior segments of the model in the horizontal,sagittal,and vertical directions in the two states were compared and analyzed from the displacement cloud map.Results:1.A three-dimensional finite element model of the UCLP-maxillary complex including the maxilla,upper dentition,zygomatic bone,part of the orbit,part of the sphenoid bone and part of the skull was established.The number of nodes was 205,415 and the number of elements was 127,181.The model had three-dimensional solid structure,good biomechanical and geometric similarity.2.The stress change results of the maxilla after loading conditionsThe Von Mises stress,principal stress,and shear stress of the maxilla after loading conditions did not appear red bands,mostly blue and green bands,and there was no stress concentration area.The Von Mises stress and principal stress were slightly larger in the premolar and molar apical regions than in other positions,and the stress values in the swallowing state were higher than those in the resting state.3.The results of the displacement change of the maxilla after the loading condition.After loading the perioral force in resting and swallowing states,both the healthy and cleft sides of the maxilla were displaced in three-dimensional directions,especially in the sagittal direction.In the resting state: the maximum sagittal displacement was 0.008107 mm,the anterior segment moved the most backward,greater than the middle and posterior segments;the displacement of the healthy side was greater than that of the cleft side.The maximum horizontal displacement was 0.004533 mm,and the displacement of the anterior segment was the most obvious.The healthy side of the middle and posterior segment was larger than the cleft side.Both the healthy and cleft sides moved from outside to inside,resulting in the narrowing of the dental arch width.The maximum vertical displacement was 0.004612 mm,the upward movement of the posterior segment was greater than the downward movement of the anterior segment;the displacement of the middle and posterior segments of the healthy side was greater than that of the cleft side.In the swallowing state: the displacement in the three-dimensional direction was greater than that in the resting state,the maximum sagittal displacement was 0.01789 mm,the horizontal maximum displacement was 0.009969 mm,and the vertical maximum displacement was 0.01035mm;The comparison results of displacement changes in threedimensional directions were similar to those in the resting state.4.The displacement of the maxilla before and after applying the force was magnified by 500 times.Zooming in on the contour map 500 times,overlapping found: in the resting and swallowing states,both sides of the maxilla moved from the outer to the midline and from the front to the back,and clockwise occurs.The direction was rotated,the fissure area was narrowed,and the dental arch collapsed.Swallowing was more obvious than the movement of both sides of the maxilla from the lateral to the midline and from the front to the back in the resting state.Conclusion:1.Collect the CBCT data of UCLP patients,and then process them through Mimics,Geomagic,Hypermesh,and Abaqus,and a fast and effective method for establishing a three-dimensional finite element model of the UCLP maxillary complex was obtained,which can reflect the anatomical characteristics of the cleft lip and palate and could be used for finite element experimental analysis.2.Under the action of labial and lingual perioral force in resting and swallowing states,the maxillary complex model of UCLP patients was displaced in three-dimensional directions,the sagittal displacement was the largest,and the displacement was mainly backward and inward.The bilateral alveolar arches collapsed and the alveolar fissure narrowed.The changes in the three-dimensional direction were more pronounced in swallowing than in the resting state.3.The displacement of the healthy side of the model was greater than that of the cleft side,and the displacement of the anterior segment was greater than that of the middle and posterior segments,indicating that the healthy side of the maxilla was more inhibited than the cleft side and the anterior segment than the posterior segment.The imbalance of perioral force could inhibit the growth of maxillary bone in UCLP patients,and the inhibition effect was more obvious in the swallowing state.4.One of the reasons for the undergrowth and asymmetry of the maxilla in UCLP patients may be that the maxilla was subjected to an unbalanced perioral force,and the pressure on the labial and buccal side was too large or(and)the pressure on the lingual side was too small.Therefore,the tension of the labial muscles should be appropriately reduced to increase the strength of the tongue muscles,improve the unbalanced perioral force clinically,and promote the growth of the maxilla.