Facemask performance during maxillary protraction: a finite element analysis (FEA) evaluation of load and stress distribution on Delaire facemask

Abstract

BackgroundTo evaluate load and stress distribution on Delaire facemask (FM) during maxillary protraction in class III growing patients by means of finite element analysis (FEA). A three-dimensional geometry of a Delaire FM was reconstructed from the original CAD 3D prototype, using software package (ANSYS 5.7). FM presented forehead and chin supports and stainless steel framework characterized by two lateral vertical bars connected to a crossbar with two pawls for elastic attachment. Two traction intensities (7.8 and 9.8 N) were applied on the FM pawls along three different downward inclined directions with respect to the occlusal plane (0°, 30°, or 50°, respectively). Resulting stresses and deformations were then tested through the von Mises yield criterion in order to underline the FM wear performance.ResultsThe analysis showed that higher stresses and deformations are mostly related to axial forces of 9.8 N rather than 7.8 N. Stresses also progressively increased with increasing downward force inclinations (0°, 30°, and 50° with respect to the occlusal plane). The overall tensions were inferior to the limit of the elastic behavior (yield point) characterizing the material they are applied on. Thus, the FM structure absorbed the load applied with an elastic deformation of the lateral and horizontal bars.ConclusionsResulting stresses and deformations were directly proportional to protraction load amounts and to increasing downward inclination of forces. In all tested conditions, protraction forces were not able to determine plastic deformation on FM structure compromising its performance and efficiency.

Effectiveness of the attachment position in molar intrusion with clear aligners: a finite element study

“…A finite element analysis (FEA) can be used to divide the dentition into a finite size and number of units and study the properties of each unit to obtain the overall properties. Several studies have extended the application of FEA in the evaluation of orthodontic forces [ 12 , 13 ]. Currently, it is the best method to analyze orthodontic forces [ 14 ].…”

Stress on facial skin of class III subjects during maxillary protraction: a finite element analysis

“…Stresses and load distribution developed on skeletal structures during orthopedic protraction treatment were widely analyzed [6,7,25]. More recently, in a previous investigation stresses developed during maxillary protraction and their effects on FM structure were evaluated by means of FEM analysis [13]. The absence of permanent plastic deformations and efficacy persistence of FM components highlighted the importance of a careful management of the device during treatment in order to grant its best performance.…”

“…Gautam et al [6] highlighted that the highest loads produced by FM therapy were mostly localized along naso-maxillary, frontonasal and, fronto-maxillary sutures. Gazzani et al [13] evaluated mechanical properties of Delaire FM and the stresses generated on device components during orthopedic treatment, by means of FEA. Some of the major complications related to maxillary protraction treatment are due to poor adaptation and low fit of FM on the face and to skin irritation determined by the extra-oral cups.…”

Evaluation of Finite Element Analysis Studies Related to Maxillary Protraction with Facemask

“…High stress levels were observed with the increase in force values, specially after 5N, and it was suggested that care should be taken at higher forces. 18 Gazzani et al 19 simulated a Delaire facemask and applied force at 0°, 30° and 50° angle to the occlusal plane with 7.8 and 9.8 N force values; high stresses and deformations were mostly observed after 9.8 N with increasing downward forces. They also stated since the total stresses were lower than the elasticity limit that characterizes the materials, facemask absorbed the force and plastic deformation did not occur.…”