Stress Distribution Patterns within Viscero- and Neurocranium during Nasoalveolar Molding: a Finite Element Analysis

Abstract

Background:The purpose of this study was to evaluate the stress distribution patterns within the viscero- and neurocranium of neonates during nasoalveolar molding.Methods:Finite element models of 3 different healthy neonates at different times of life (date of birth, 4 weeks, and 3.5 months) were generated on the basis of computed tomography scans. A validated workflow, including segmentation, meshing, setting of boundary conditions, and implementation of a bone density–dependent material model, was carried out for each model. A small and a large unilateral alveolar and hard palatal cleft were virtually cut in each model. The stress distribution pattern in each model was then analyzed by using Ansys APDL.Results:Convergence analysis validated the results. The virtual experiments at the date of birth showed a stress pattern above a previously defined threshold value of 30,000 Pa in the ipsilateral naso-orbital-complex, frontal sinus, and the anterior fossa of the base of the skull, with von Mises values > 35,000 Pa. Stress patterns at the age of 4 weeks and 3.5 months showed reduced von Mises values at < 15,000 Pa.Conclusions:Nasoalveolar molding therapy is a safe presurgical treatment modality without significant influence on the viscero- and neurocranium of neonates. Treatment, considering the stress distribution at the naso-orbital-complex and anterior fossa of the base of the skull, should begin in the second week of life, and treatment initiation of preterm infants should be adapted respectively.

Comparative Photographic, Retrospective Analysis of Nonsyndromic Cleft Noses Treated with or without NAM

“…In cases of NAM therapy, the procedure was started within the first two weeks of life and with respect to a corrected age in the case of preterm birth. 2 NAM therapy consisted of alveolar molding (6–8 weeks) and subsequent nasal molding (until operation). 14 , 22…”

“… 1 But NAM therapy should not be started too early and must be adapted in preterm birth because undesired force conduction to the anterior skull base might occur. 2 NAM is commonly performed according to the treatment algorithm described by Grayson et al, but several modifications are also reported in the literature, including CAD/CAM solutions. 3 – 6 …”