Surface hardness of light-cured and self-cured composite resins

Helvatjoglou-Antoniadi, M.; Papadogianis, Y.; Koliniotou-Kubia, E.; Kubias, S.

doi:10.1016/0022-3913(91)90164-r

Cited by 22 publications

(16 citation statements)

References 18 publications

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“…12,13 In our study, the microhardness of the celluloid strip-finished composite sur- face increased more progressively. The finding is in partial agreement with the observation of Helvatjoglou et al, 3 who reported a progressive increase of microhardness of the celluloid strip-finished composite surface at 4 weeks. In a study that measured the shear bond strength between precured composite with various surface properties and a newly cured composite increment, Li 14 found that the surface that had been cured against a cover glass resulted in a significantly higher bond strength than any other preparation.…”

Section: Discussionsupporting

confidence: 82%

Hardness of celluloid strip-finished or polished composite surfaces with time

Park¹,

Krejci²,

Lutz³

2000

Journal of Prosthetic Dentistry

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THE JOURNAL OF PROSTHETIC DENTISTRY VOLUME 83 NUMBER 6The smoothest composite surface that is important in esthetic restorations can be obtained with a celluloid strip. 1 However, a discoloration study revealed that composite surfaces polymerized under matrix discolored more than surfaces polished after 48 hours of light curing. 2 Higher tendency of discoloration on the celluloid strip-covered composite surface, even though it has a smoother surface, may be related to lower physical property on the surface.A previous study showed microhardness of the celluloid strip-finished composite to be lower than the polished subsurface, 3 and the celluloid strip-covered composite surface showed lower conversion than the composite bulk. 4 Thus, it was recommended that composites should be finished and polished, despite the smooth finish of the celluloid strip. 5-8 However, from a clinician's point of view, he is reluctant to polish the celluloid strip-finished composite surface with an instrument, especially when an esthetic result is the prime concern to the patient.It would be helpful for the clinicians to find a way to minimize the drawbacks of celluloid strip-finished composite surface. Discovering the physical properties of the celluloid strip-finished composite surfaces would be the first step in minimizing these disadvantages. In the composite, the physical property is closely related to the degree of conversion, and the hardness measurement is an effective way to evaluate the degree of composite cure. 9 The purpose of this study was to evaluate the changes in the microhardness of composite surface over time, which was cured under celluloid. Purpose. This study tested the hypothesis that the celluloid strip-finished composite surface did not cure enough compared with the polished composite surface.Methods and material. The composite was placed in a 1.5-mm thick aluminum mold and the upper surface was covered with a celluloid strip. Composite was light cured for 60 seconds, then a layer of approximately 200 µm thick was ground away from the lower surface and polished. The hardness of the upper composite surface that was polymerized under a celluloid strip and the polished lower surface were measured with Vickers hardness measuring instrument 15 minutes, 6 hours, and 6 days after light curing. The hardnesses of polished and celluloid strip-finished surfaces were compared using a paired t test. Oneway ANOVA and Tukey was used for tests for the significant differences in hardnesses between 15 minutes, 6 hours, and 6 days after light curing for a given surface.Results. Microhardness of the celluloid strip-finished composite surface was 380.6 N/mm 2 at 15 minutes, 442.5 N/mm 2 at 6 hours, and 519.2 N/mm 2 at 6 days after light curing. Microhardnesses of the polished composite surface was 476.6 N/mm 2 at 15 minutes, 511.7 N/mm 2 at 6 hours, and 535.0 N/mm 2 at 6 days after light curing. The hardness of the celluloid strip-opposed composite surface was significantly lower than that of the polished surface 15 minutes...

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Section: Discussionsupporting

confidence: 82%

Hardness of celluloid strip-finished or polished composite surfaces with time

Park¹,

Krejci²,

Lutz³

2000

Journal of Prosthetic Dentistry

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“…This additional polymerization by free radicals occurs considerably during the first hour and has been reported to persist over the course of one month. [13][14][15] In the unpolished specimens, the surface hardnesses of the group that used a Mylar strip and the group cured with glycerin were similar five days after curing. These two methods resulted in greater hardness than that achieved through supplemental curing with glycerin after the initial cure.…”

Section: Discussionmentioning

confidence: 89%

“…This indicates that additional polymerization occurred during the five days in which the specimens were stored, in agreement with the results from several previous studies. 4,[13][14][15] Non-reacted free radicals remain in composites even after light activation and react with free monomers to produce a continued polymerization chain reaction. This additional polymerization by free radicals occurs considerably during the first hour and has been reported to persist over the course of one month.…”

Section: Discussionmentioning

confidence: 99%

“…Polishing results in a higher surface hardness than that produced when a matrix is used, 13 is effective in preventing discoloration, 17 and is advantageous in achieving a satisfactory surface and marginal adaptation. 18 Clinically, however, the OIL may not be able to be completely removed and can remain in deep pits and fissures even after polishing.…”

Section: Discussionmentioning

confidence: 99%

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Effect of glycerin on the surface hardness of composites after curing

Park

Lee

2011

J Korean Acad Conserv Dent

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Objectives:The purpose of this study was to examine the effect of glycerin topical application on the surface hardness of composite after curing. Materials and Methods: A composite (Z-250, 3M ESPE) was packed into a disc-shaped brass mold and light cured according to one of the following protocols. Group 1 (control) was exposed to air and light cured for 40 sec, group 2 was covered with a Mylar strip and light cured for 40 sec, group 3 was surface coated with glycerin and light cured for 40 sec, and group 4 was exposed to air and light cured for 20 sec and then surface coated with glycerin and cured for additional 20 sec. Twenty specimens were prepared for each group. The surface hardnesses of specimens were measured with or without polishing. Five days later, the surface hardness of each specimen was measured again. Data were analyzed by three-way ANOVA and Tukey' s post hoc tests. Results:The surface hardnesses of the unpolished specimens immediately after curing decreased in the following order: group 2 > 3 > 4 > 1. For the polished specimens, there was no significant difference among the groups. Within the same group, the hardness measured after five days was increased compared to that immediately after curing, and the polished specimens showed greater hardness than did the unpolished specimens. Conclusions:The most effective way to increase the surface hardness of composite is polishing after curing. The uses of a Mylar strip or glycerin topical application before curing is recommended.

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“…Chemically-cured resin cements exhibit a shorter working time, but their polymerization is not influenced by the thickness of the indirect restoration. Light-cured resin cements present ideal working characteristics, although they require an adequate amount of light to achieve polymerization 1 . The polymerization of a light-cured cement may be compromised by insufficient light intensity emitted by the light-curing unit, wavelengths emitted outside the spectrum of the photoinitiator within the resin material, and the thickness of the indirect restoration 2 .…”

Section: Introductionmentioning

confidence: 99%

Additional chemical polymerization of dual resin cements: reality or a goal to be achieved?

Umetsubo

Yui

Borges

et al. 2016

Rev. odontol. UNESP

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ResumoIntrodução: Este trabalho serve como um alerta para dentistas e pesquisadores, que alguns cimentos resinosos duais podem não polimerizar completamente sob alguns tipos de coroas protéticas. Objetivo: Analisar o grau de polimerização de cimentos resinos duais, sob barreiras protéticas, por teste de microdureza. Material e método: Três cimentos: Bistite II, RelyX ARC e Variolink II, foram fotopolimerizados através da interposição de vários tipos de barreiras, interpostas entre o cimento e a fonte de luz, formando os grupos: G1: sem barreira; G2: Resina composta Cesead; G3: Inceram alumina/Allceram; G4: IPS Empress; G5: Inceram zircônia/Allceram; G6: fragmento dental. Utilizou-se a luz halógena (650 mW/cm 2 ) para fotoativação e a microdureza foi avaliada: 50gf durante 15s (MicrohardnessTester FM 700), em dois períodos (30min e 24h) pós ativação. Os dados foram submetidos à ANOVA e teste de Tukey (5%). As interposições de Inceram alumina e Inceram zircônia resultaram na polimerização deficiente dos cimentos, impossibilitando a realização dos ensaios. Resultado: Para o fator cimento, o Bistite revelou a maior microdureza, seguido do RelyX e do Variolink (p<0,05). A barreira influenciou a microdureza, sendo que os maiores valores foram obtidos sem barreira, seguida do dente. Empress e Cesead proporcionaram os menores valores de microdureza e não diferiram entre si. Conclusão: A barreira afetou negativamente a microdureza dos cimentos resinosos duais; o período de avaliação não afetou os valores de microdureza para quase todas as condições testadas; existe um fator limitante do ativador químico na polimerização de alguns cimentos resinosos duais, e seu desempenho é dependente do produto.Descritores: Cimentos dentários; microdureza; cimentação; polimerização. AbstractIntroduction: This study serves as a warning to dentists and researchers that dual-cured resin cements may not polymerize completely under some prosthetic crowns. Objective: The aim of this study was to analyse the polymerization degree of dual-cured resin cements under prosthetic barrier, by microhardness test. Material and method: Three cements (Bistite II, RelyX ARC and Variolink II) were light-cured through different barriers, placed between the cement and the light source: G1: without barrier; G2: composite resin (Cesead); G3: Inceram alumina; G4: IPS Empress; G5: Inceram zirconia; G6: tooth fragment. Photopolymerization was carried out using a halogen light unit (650 mW/cm 2 ); microhardness was evaluated using the Microhardness Tester FM 700, under a load of 50gf with a dwell time of 15s, at two evaluation times (30min and 24h). Result: The results were submitted to ANOVA and Tukey tests (5%). Both Inceram alumina and Inceram zirconia ceramic barriers hindered polymerization. Bistite, followed by RelyX and Variolink, exhibited the highest microhardness values (p<0.05). As the highest values were obtained without a barrier, it was determined that the barrier, followed by the tooth, influenced microhardness. Both Empress and Cesead had the small...

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Surface hardness of light-cured and self-cured composite resins

Cited by 22 publications

References 18 publications

Hardness of celluloid strip-finished or polished composite surfaces with time

Hardness of celluloid strip-finished or polished composite surfaces with time

Effect of glycerin on the surface hardness of composites after curing

Additional chemical polymerization of dual resin cements: reality or a goal to be achieved?

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