Análise fotoelástica da distribuição de tensões cisalhantes em segundos molares inferiores inclinados
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Data
2019-02-13
Autores
Pinheiro, Carolina Leão
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A perda de primeiros molares permanentes é uma situação clínica frequente levando a uma inclinação gradual no sentido mesial de segundos molares. O primeiro estudo avaliou por meio da técnica da fotoelasticidade as tensões geradas por três mecanismos ortodônticos de verticalização: Cantilever, Mola de correção radicular e Mola de Sander (NiTi- SE- Stahl-Aufrichtefeder) com ativação a 90°e a 135°. No segundo estudo, foram avaliados a inserção de seis tipos fios contínuos de Níqueltitânio (NiTi), separados em 2 grupos: fios redondos e fios retangulares. No primeiro estudo foram utilizados 7 modelos fotoelásticos e no segundo 5 modelos fotoelásticos. Todos os modelos fotoelásticos seguiram o mesmo padrão de confecção: A réplica de uma má oclusão de perda de primeiro molar inferior com segundo molar inferior inclinado a 30° e a presença dos dentes adjacentes, pré-molares e caninos. Utilizouse um polariscópio circular de transmissão plana da Universidade Estadual de Campinas (Faculdade de Odontologia de Piracicaba, FOP/UNICAMP). Todos os testes, de ambos os estudos, foram realizados de forma randomizada. Para a análise quantitativa e qualitativa utilizou-se o software Fringes® demarcando no total 18 pontos ao longo das raízes de todos os dentes. Primeiramente foi aplicado o teste de normalidade Shapiro-Wilk em todos os dados, todos as análises foram feitas com o teste não-paramétrico Kruskal-Wallis seguido do pós teste Dunn, com nível de significância de 5%. No primeiro estudo foi verificado não haver diferença estatística entre todas as molas de verticalização na região do molar. No segundo estudo, não houve diferença significativa no grupo dos fios redondos, no grupo de fios retangulares em alguns pontos os fios de Copper Niti (Morelli®) e Thermo-Plus Niti (Morelli®) apresentaram valores de tensões cisalhantes menores do que os fios de Niti convencionais (Morelli®). Conclui-se a importância de ser conhecer a localização e valores de tensão das áreas estudas para uma melhor decisão clínica.
Loss of first permanent molars in adult patients is very commonly encountered. Frequent consequences are mandibular second molars tipped mesially. The aim of the first study was to analyze and compare the stress distributions in three molar uprighting techniques: cantilever, uprighting spring and Sander’s Spring, using quantitative and qualitative photoelastic analysis (NiTi- SE- Stahl-Aufrichtefeder) bended 90° and 135°. The aim of the second study was to analyze and compare the stress distributions of six types of nickel-titanium wires: round wires and rectangular wires, using a quantitative and qualitative photoelastic analysis. Seven photoelastic models were used in the first study, five was used in the second. In all models used we made the same replication of malocclusion: second mandibular molar was tipped forward 30º and the mandibular right canine and the first and second premolars were present. We used a circular polariscope of horizontal transmission to do the analyzes (Piracicaba Dental School, University of Campinas, Sao Paulo, Brazil). All tests were randomly. A software Fringes® was used to quantify the model’s shear stress and qualify the fringe order. Eighteen points of interest were determined along all the roots of the teeth. All quantitative data included in this study were tested concerning normality by Shapirowilk test. When normality was not found in the data, thus opting for the nonparametric Kruskal-wallis test and the post hoc test by Dunn) were performed to verify the types of mechanical differences. The test was performed with a significance level of 5%. The results of the first study showed there was no statistically significant difference between the uprighting mechanisms in all regions analyzed of the molar. On the second study there was no statistically significant difference in the group of round NiTi wires. The Cooper Niti (Morelli®) and Thermo-plus (Morelli®) presented lower shear stress than the regular Niti Wire (Morelli®). These researchers corroborate to a good clinical practice.
Loss of first permanent molars in adult patients is very commonly encountered. Frequent consequences are mandibular second molars tipped mesially. The aim of the first study was to analyze and compare the stress distributions in three molar uprighting techniques: cantilever, uprighting spring and Sander’s Spring, using quantitative and qualitative photoelastic analysis (NiTi- SE- Stahl-Aufrichtefeder) bended 90° and 135°. The aim of the second study was to analyze and compare the stress distributions of six types of nickel-titanium wires: round wires and rectangular wires, using a quantitative and qualitative photoelastic analysis. Seven photoelastic models were used in the first study, five was used in the second. In all models used we made the same replication of malocclusion: second mandibular molar was tipped forward 30º and the mandibular right canine and the first and second premolars were present. We used a circular polariscope of horizontal transmission to do the analyzes (Piracicaba Dental School, University of Campinas, Sao Paulo, Brazil). All tests were randomly. A software Fringes® was used to quantify the model’s shear stress and qualify the fringe order. Eighteen points of interest were determined along all the roots of the teeth. All quantitative data included in this study were tested concerning normality by Shapirowilk test. When normality was not found in the data, thus opting for the nonparametric Kruskal-wallis test and the post hoc test by Dunn) were performed to verify the types of mechanical differences. The test was performed with a significance level of 5%. The results of the first study showed there was no statistically significant difference between the uprighting mechanisms in all regions analyzed of the molar. On the second study there was no statistically significant difference in the group of round NiTi wires. The Cooper Niti (Morelli®) and Thermo-plus (Morelli®) presented lower shear stress than the regular Niti Wire (Morelli®). These researchers corroborate to a good clinical practice.
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Palavras-chave
Ortodontia, Dente molar, Técnicas de movimentação dentária, Orthodontics, Molar, Tooth movement techniques