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Master's Dissertation
DOI
https://doi.org/10.11606/D.25.2019.tde-25112019-210835
Document
Author
Full name
Daniella Cristo Santin
Institute/School/College
Knowledge Area
Date of Defense
Published
Bauru, 2019
Supervisor
Committee
Mondelli, Rafael Francisco Lia (President)
Bombonatti, Juliana Fraga Soares
Brondino, Nair Cristina Margarido
Schmitt, Vera Lucia
Title in English
Influence of volume and thickness on shrinkage stress and depth of cure of conventional and bulk fill composites
Keywords in English
Composite resins
Dental stress analysis
Hardness
Polymerization
Abstract in English
Objective: The present study investigated, in vitro, the influence of volume on shrinkage stress and the influence of thickness on the depth of cure by microhardness of convencional and bulk fill composite resins. Material and methods: Six commercial composite resins were selected: conventional (Filtek Z350 Z350; Vittra APS VAPS), high viscosity bulk fill (Filtek One Bulk Fill ONE; Opus Bulk Fill APS OBF) and low viscosity (Filtek Bulk Fill Flowable BFF; Opus Bulk Fill Flow APS OBFF). For the shrinkage stress analysis, specimens (n=5) were made varying the volume/C-factor (24 mm3/0.75 and 48 mm3/0.375). The contraction forces (N) generated from LED light-curing (30s; 1200mW/cm2) were recorded for 300s in an UTM and the shrinkage stress was calculated (MPa). For microhardness, using two molds with 4mm diameters, 2 and 4mm thicknesses (n=5), the specimens were made and light-cured for 30s. After 24h, Knoop microhardness measures (KHN) on the top and bottom surfaces were obtained and the ratio of bottom/top microhardness was calculated determining the depth of cure. After confirming normality (Shapiro-Wilk), all data were evaluated by two-way ANOVA, followed by Tukeys test (p<0.05). Results: The increase of composite resin volume resulted in higher shrinkage stress for the Z350, VAPS and ONE, regardless of the C-factor employed (p<0.05). The Z350, VAPS, BFF and OBF showed a decrease in microhardness (depth of cure) when the thickness was increased (p<0.05). Overall groups showed adequate polymerization (bottom/top microhardness >80%) at 2mm depth, except for the OBFF, while only the ONE presented adequate polymerization at 4mm depth. Conclusion: The volume and thickness of the increment influenced the stress and the depth of cure, respectively. The bulk fill ONE composite resin showed lower tension maintaining cure efficiency independent of volume compared to the other tested materials.
Title in Portuguese
Influência do volume e da espessura no estresse de contração e profundidade de cura de compósitos convencionais e bulk fill
Keywords in Portuguese
Análise do estresse dentário
Dureza
Polimerização
Resinas compostas
Abstract in Portuguese
Objetivo: O presente estudo investigou, in vitro, a influência do volume no estresse de contração e a influência da espessura na profundidade de cura por microdureza de resinas compostas convencionais e bulk fill. Materiais e métodos: Foram selecionadas seis resinas compostas comerciais: convencional (Filtek Z350 Z350, Vittra APS - VAPS), bulk fill de alta viscosidade (Filtek One bulk fill - ONE, Opus bulk fill APS - OBF) e baixa viscosidade (Filtek Bulk Fill Flowable - BFF, Opus bulk fill Flow APS OBFF). Para a análise do estresse de contração, espécimes (n=5) foram confeccionados variando o volume/fator C (24 mm3/0,75 e 48 mm3/0,375). As forças de contração (N) geradas a partir da fotoativação (30s, 1200mW/cm2) foram registradas durante 300s em UTM e o estresse de contração (MPa) foi calculado. Para microdureza, utilizando dois moldes com 4mm de diâmetro, 2 e 4mm de espessura (n=5) espécimes foram preparados e polimerizados por 30s. Após 24h, leituras de microdureza Knoop (KHN) nas superfícies superior e inferior dos espécimes foram obtidas e a razão percentual de microdureza inferior/superior foi calculada determinando a profundidade de cura. Após confirmação da normalidade (Shapiro-Wilk), a análise dos dados foi realizada utilizando ANOVA a dois critérios e Tukey (p<0.05). Resultados: O aumento do volume de resina composta resultou em um maior estresse de contração para Z350, VAPS e ONE, independentemente do fator C empregado (p<0,05). As resinas compostas Z350, VAPS, BFF e OBF apresentaram diminuição na microdureza (profundidade de cura) quando a espessura foi aumentada (p<0,05). Com exceção da OBFF, todos os grupos mostraram adequada polimerização (microdureza base/topo >80%) a 2mm de profundidade, enquanto somente a ONE apresentou polimerização adequada a 4mm de profundidade. Conclusão: O volume e a espessura do incremento influenciaram o estresse e a profundidade de cura, respectivamente. A resina composta bulk fill ONE mostrou menor tensão mantendo eficiência de cura independente do volume em comparação aos outros materiais testados.
 
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Publishing Date
2019-11-27
 
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