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Assessment of surface roughness and the distribution of mechanical stress on the palate by different pacifiers

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Freitas, Camila Nobre de
Total Authors: 1
Document type: Doctoral Thesis
Institution: Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Defense date:
Advisor: Paula Midori Castelo Ferrua

The prolonged use of pacifiers has deleterious effects on the child, which may impair the growth and development of orofacial structures and occlusion. The aim of this study was to evaluate the distribution of mechanical stresses of three different pacifier geometries on the palate (Article 1) and the effect of two physical disinfection methods (heat) on the surface roughness of silicone pacifiers (Article 2). Article 1 describes the distribution of maximum principal stress and magnitude displacement of three different types of silicone pacifiers: conventional (A), orthodontic (B) and Super Soothie TM (C). The images of the three pacifier nipples were acquired by 3D scanning. The palate structure was recreated by computed tomography of a dry skull of a ~ 3-year-old child, while the tongue structure was reconstructed using software and data available in the literature. The mechanical properties of the pacifier material were determined by the rupture tensile test on a Universal Testing Machine- EMIC DL500, in which 15 standardized samples were removed from each pacifier type (A, B and C). Maximum tongue strength was obtained by evaluating 8 children aged ~ 3 years using the IOPI instrument. Subsequently, the three systems were discretized into finite elements and the force applied to the models for the simulation. It was observed that the nipple B presented the highest values of maximum distributed stress on the palate, followed by the pacifier A. The pacifier B stimulated a displacement in maxillary magnitude forward and to the sides, while the pacifier A promoted an upward deformation, resulting in a more atresic palate. Both types of pacifiers tend to rotate in the sagittal plane, generating tension in the incisors region, which can result in an anterior open bite. The nipple C showed a better distribution of stress on the palate and a more favorable maxillary distribution stimulus, forwards and to the sides without influence on the inclination of the upper incisor teeth. Article 2 presents the variation in surface roughness of three types of pacifiers conventional (A), orthodontic (B) and Super Soothie¿ (C); n=20 each) when subjected to heat disinfection processes. Surface roughness and microscopic morphology were assessed at baseline, 15 and 30 days after boiling water and microwave disinfection (7 and 5 min, respectively), using profilometer and scanning electron microscope. At baseline, higher surface roughness was found in the pacifier C than in the A and B pacifiers. An interaction effect time*pacifier was observed, i.e. an increase in surface roughness after disinfection was pacifier type-dependent, being greater for pacifier C at 15 and 30 days (p <0.001; Three-way mixed model ANOVA), while the effect of the disinfection type (microwave/boil) was not significant. Microscopic analysis showed the presence of more roughness, salience and pores after 15 and 30 days of disinfection in all samples, but they were more prominent in nipple C, which may favor microbial colonization. Thus, the three types of pacifiers differed in the performance evaluation regarding the distribution of mechanical stress on the palate and resistance to heat disinfection methods, information that may help improve the guidance given to parents and caregivers (AU)

FAPESP's process: 16/13867-0 - Longitudinal analysis of the development of orofacial morphology and physiology in children with sucking habits
Grantee:Kelly Guedes de Oliveira Scudine
Support type: Scholarships in Brazil - Doctorate