Effect of oral exposure on chemical, physical, mechanical, and morphologic properties of clear orthodontic aligners.

INTRODUCTION: The dental industry is heavily committed to developing more esthetic solutions for orthodontic treatments. Invisalign is a system of transparent orthodontic aligners introduced as an alternative to conventional orthodontic fittings with brackets and metal wires. This study aimed to assess the chemical, physical, mechanical and morphologic changes in these polymeric aligners after exposure to the oral environment. METHODS: Twenty-four Invisalign orthodontic aligners were equally divided into 2 groups: an in vivo aged group in which patients used aligners for 14 days and the reference group, unexposed to the oral environment. Different experimental techniques were used to study the chemical structure, the color changes and translucency, the density and subsequent volume of the aligners, mechanical properties, surface roughness, morphology and elemental composition. The data were subjected to several statistical analyses. RESULTS: Clear orthodontic aligners exhibit chemical stability but undergo a statistically significant optical change in color and translucency. There was a gradual increase in the water absorption rate and the dimensional variation of the polymer, indicating a strong correlation among these factors. The mechanical properties of the polymer showed a statistically significant decrease in its elastic modulus and hardness. There was a slight tendency toward increased surface roughness of the material, but no statistical differences were found between reference and aged groups. The surface morphology of the used aligners demonstrates microcracks, distortions and biofilm formation. CONCLUSION: Intraoral aging adversely affected the physical, mechanical, and morphologic properties of the Invisalign appliance.

Nasal bone length in human fetuses by X-ray.

BACKGROUND: To construct a normal range for the prenatal nasal bone length (NBL) in Brazilians irrespective to the knowledge of the ethnic genetic background. STUDY DESIGN: We studied 35 human fetuses (20 males, 15 females) ranging from 14 to 22 weeks of gestation. Gestational age (GA), crown-rump length (CRL), foot length (FL) and body mass (BM) were measured. The X-ray of the head lateral view was made with the specimens placed directly on the film and the NBL was measured. The NBL was correlated with the GA, the CRL, the FL, and the BM using log-transformed data and the allometric model log y=log a+b log x. RESULTS: Correlations of the NBL growth with GA, CRL, FL, and BM were positive and significant (P<0.05), but NBL vs. BM showed the smallest R indicating this correlation as of little practical use. No sexual dimorphism in the NBL growth in the second trimester fetuses was observed. The NBL grew with positive allometry relative to GA, CRL and BM, but it was allometrically slightly negative relative to the FL in both genders. The NBL be allometrically positive against GA, CRL and BM means the bone grew with growth rates higher than those indices in the period analyzed, but not against FL. CONCLUSION: NBL could be considered an auxiliary measurement in the assessment of the 2nd trimester fetal development because its strong correlation with GA, CRL and FL, even when nothing is known about the ethnicity of the population.

Alinhadores Ortodônticos Removíveis Versus Aparelhos Ortodônticos Fixos: uma Revisão da Literatura / Removable Orthodontic Aligners Versus Fixed Orthodontic Appliances: a Literarture Review

Com intuito de pontuar os paralelos entre as técnicas ortodônticas com aparelhagem fixa e alinhadores transparentes, este estudo propôs revisar a literatura científica sobre alinhadores ortodônticos removíveis versus aparelhos ortodônticos fixos. Foram selecionados artigos de 2005 a 2021, utilizando as bases de dados PubMed, Scopus, Web of Science, Cochrane Library, Clinical Trials e Opengrey. Os artigos abordavam temáticas como sensação dolorosa, saúde periodontal, higiene, microbiota, reabsorção radicular, qualidade de vida e efetividade do tratamento. Os alinhadores apresentaram maior aceitabilidade pelos pacientes e vantagens claras em relação à dor, higiene, qualidade de vida, reabsorção radicular e saúde periodontal, sendo inferior aos aparelhos ortodônticos fixos na efetividade do tratamento e na interferência na fala.

In order to point out the parallels between orthodontic techniques with fixed appliances and transparent aligners, this study proposed to review the scientific literature on removable orthodontic aligners versus fixed orthodontic appliances. Articles from 2005 to 2021 were selected, using the PubMed, Scopus, Web of Science, Cochrane Library, Clinical Trials and OpenGrey databases. The articles addressed issues such as pain, periodontal health, hygiene, microbiota, root resorption, quality of life and treatment effectiveness. Aligners showed greater acceptability by patients and clear advantages in relation to pain, hygiene, quality of life, root resorption and periodontal health, being inferior to fixed orthodontic appliances in terms of effectiveness and speech capacity.