Microhardness of composite resins at different depths varying the post-irradiation time

Ciccone-Nogueira, Juliane Cristina; Borsatto, Mariana Cristina; Souza-Zaron, Wanessa Christine de; Ramos, Renata Pereira; Palma-Dibb, Regina Guenka

doi:10.1590/s1678-77572007000400012

Cited by 35 publications

(29 citation statements)

References 22 publications

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“…This may explain the slight increase in hardness after 1 day, which is in agreement with previous studies 28,31 . Change in the hardness property may reflect the state of curing the material and the continuation of the setting reaction 32 . The polymerization reaction cannot be considered finished after exposure to light due to the presence of what is called "dark polymerization".…”

Section: Discussionmentioning

confidence: 99%

“…This can be explained by the higher degree of polymerization that occurs as a result of the closest contact of the light-curing guide to the top surface. When the curing light is applied to composite resin, some of the light rays are absorbed while others are scattered by the composite resulting in reduction or attenuation of light intensity which deceases the effectiveness of cure at the base surface 23,32 . At the relatively high temperature (37 °C), the base surface of the specimens showed an increase in the microhardness values, which may be attributed to the dark polymerization of the resin.…”

Section: Discussionmentioning

confidence: 99%

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Post-irradiation vickers microhardness development of novel resin composites

Marghalani

2010

Mat. Res.

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The aim of this study was to evaluate the effect of post-irradiation dry aging at different periods of time on Vickers microhardness of some dental composites based on various resin matrices. Sixty four disc-shaped specimens of the resin composites were prepared in a split Teflon mold (8 × 2 mm) and irradiated by Optilux 501 light cure (500 mW.cm -2 for 40 seconds) on their top side. The specimens were aged-dry in dark at 23 and 37 °C for the following storage periods; immediate, 1/2 an hour, 1, 6, 12, 24, 48 and 168 hours. The microhardness values were recorded using a Vickers Hardness Tester at 300 g load for 15 seconds. Results showed that Filtek ® P90 and Definite expressed the highest hardness value followed by Tetric Evoceram and then Premise Enamel. At each aging period, all materials demonstrated significant differences between hardness values of top and base surfaces as well as both temperatures examined (P < 0.05). In conclusion, surface hardness developed gradually in most of the materials reaching optimum after 168 hours post-irradiation aging. Dental composites based on silorane and ormocer resin matrices achieved higher Vickers microhardness than those based on dimethacrylates resin.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Post-irradiation vickers microhardness development of novel resin composites

Marghalani

2010

Mat. Res.

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“…The material was covered with another celluloid strip, and the glass slide weighed of 200 g for 1 minute until the slide touched the mold completely, thus allowing excess composite to flow prior to curing. [18][19][20] Next, the excess restorative material was removed. The tested restorative material was light cured for 20 seconds on each side using a light-curing unit QHL75 (505 mW/cm 2 ) (Dentsply, York, PA, USA).…”

Section: Specimen Preparationmentioning

confidence: 99%

The Effects of Mouth Rinses on the Color Stability of Resin‐Based Restorative Materials

ElEmbaby

2014

J Esthet Restor Dent

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Patient use of mouth rinses should be subject to dental supervision to control their adverse effects on the aesthetic quality of the restoration. Knowing the composition of the restorative material is important, as is its polymerization cycle and the promotion of adequate surface texture in order to select the appropriate material for each clinical application, and to use it in an effective way to promote its best properties.

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“…Both resin cements types showed an increase in strength from 15 minutes to 24 hours storage, when polymerized using the indirect light‐curing method, suggesting that the polymerization mechanism may need time to complete in attenuated light conditions. Previous research reports that the polymerization of resin‐based materials may continue, even up to 24 hours after being light‐cured, due to the delayed action of unreacted free radicals that may continue to react within the polymer . Thus, it is possible that, when light reaching the specimen is scant, the chemical curing reaction may contribute, in a synergic manner, along with photo‐curing, to increase BFS values after 24 hours storage, as this mechanism is slow and may take longer to complete its reactive cycle.…”

Section: Discussionmentioning

confidence: 99%

Effect of light absence or attenuation on biaxial flexural strength of dual‐polymerized resin cements after short‐ and long‐term storage

Lima

Murillo-Gómez

Sartori

et al. 2018

J Esthet Restor Dent

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Objective To evaluate whether biaxial flexural strength (BFS) of dual resin cements is affected by light absence or attenuation, storage time, or cements' chemical nature. Materials and methods One hundred and twenty disk‐shaped specimens were made from each cement (non‐self‐adhesive cement and self‐adhesive cement) using Teflon molds on a controlled temperature surface (35°C). Specimens were polymerized as follows (N = 30): self‐cured, directly light‐cured, light‐cured at a distance of 6 mm between the light tip and the specimen, and through a 6‐mm thick composite resin barrier (indirectly light‐cured). Each group was divided (N = 10) for storage purposes (15 minutes, 24 hours, and 6 months). Specimens were placed into a biaxial‐flexure jig and a vertical load was applied until failure. The BFS values were subjected to generalized linear models statistical analysis and Weibull distributions (α = 0.05). Results After 15 minutes aging, neither material achieved enough polymerization to perform the BFS test when polymerized using the self‐curing mode. The self‐adhesive product demonstrated much lower variation in strength with storage time than did the non‐self‐curing cement. Conclusions Attenuated/light‐curing reduced BFS values only for 15‐minutes storage period for both materials. Flexural strength of the self‐adhesive cement was less affected by light absence/attenuation and storage time. Clinical significance Biaxial flexural strength of a self‐adhesive resin cement is less sensitive to variation in light application and storage time than is a non‐self‐adhesive cement.

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Microhardness of composite resins at different depths varying the post-irradiation time

Cited by 35 publications

References 22 publications

Post-irradiation vickers microhardness development of novel resin composites

Post-irradiation vickers microhardness development of novel resin composites

The Effects of Mouth Rinses on the Color Stability of Resin‐Based Restorative Materials

Effect of light absence or attenuation on biaxial flexural strength of dual‐polymerized resin cements after short‐ and long‐term storage

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