title: Pre-heating mitigates composite degradation.
abstract: Dental composites cured at high temperatures show improved properties and higher degrees of conversion; however, there is no information available about the effect of pre-heating on material degradation. Objectives This study evaluated the effect of pre-heating on the degradation of composites, based on the analysis of radiopacity and silver penetration using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Material and Methods Thirty specimens were fabricated using a metallic matrix (2x8 mm) and the composites Durafill VS (Heraeus Kulzer), Z-250 (3M/ESPE), and Z-350 (3M/ESPE), cured at 25°C (no pre-heating) or 60°C (pre-heating). Specimens were stored sequentially in the following solutions: 1) water for 7 days (60°C), plus 0.1 N sodium hydroxide (NaOH) for 14 days (60°C); 2) 50% silver nitrate (AgNO3) for 10 days (60°C). Specimens were radiographed at baseline and after each storage time, and the images were evaluated in gray scale. After the storage protocol, samples were analyzed using SEM/EDS to check the depth of silver penetration. Radiopacity and silver penetration data were analyzed using ANOVA and Tukey's tests (α=5%). Results Radiopacity levels were as follows: Durafill VS<Z-350<Z-250 (p<0.05). The depth of silver penetration into the composites ranked as follows: Durafill VS>Z-350>Z-250 (p<0.05). After storage in water/NaOH, pre-heated specimens presented higher radiopacity values than non-pre-heated specimens (p<0.05). There was a lower penetration of silver in pre-heated specimens (p<0.05). Conclusions Pre-heating at 60°C mitigated the degradation of composites based on analysis of radiopacity and silver penetration depth.
authors.affiliation: Consultório particular, Goiânia, GO, Brasil.
authors.forename: Jessika Calixto da
authors.initials: JC
authors.lastname: Silva
authors.affiliation: Instituto de Ciências da Saúde, Materiais Dentários e Dentística, Faculdade de Odontologia, Universidade Paulista, Goiânia, GO, Brasil.
authors.forename: Reges
authors.initials: R
authors.lastname: Rogério Vieira
authors.affiliation: Instituto de Ciências da Saúde, Radiologia Oral, Faculdade de Odontologia, Universidade Paulista, Goiânia, GO, Brasil.
authors.forename: Inara Carneiro Costa
authors.initials: IC
authors.lastname: Rege
authors.affiliation: Departamento de Materiais Dentários e Prótese, Faculdade de Odontologia, Universidade Estadual Paulista, Araraquara, SP, Brasil.
authors.forename: Carlos Alberto dos Santos
authors.initials: CA
authors.lastname: Cruz
authors.affiliation: Departamento de Materiais Dentários e Prótese, Faculdade de Odontologia, Universidade Estadual Paulista, Araraquara, SP, Brasil.
authors.forename: Luís Geraldo
authors.initials: LG
authors.lastname: Vaz
authors.affiliation: Departamento de Ciências Estomatológicas, Faculdade de Odontologia, Universidade Federal de Goiás, Goiânia, GO, Brasil.
authors.forename: Carlos
authors.initials: C
authors.lastname: Estrela
authors.affiliation: Faculdade União de Goyazes, Trindade, GO, Brasil.
authors.forename: Fabrício Luscino Alves de
authors.initials: FL
authors.lastname: Castro
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D006361:Heating / Q000379:methods*; D006358:Hot Temperature; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D012016:Reference Values; D012834:Silver / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D003188:Composite Resins; D014867:Water; D012834:Silver; C039734:Durafill
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