Effect of photoinitiator level on properties of a light-cured and post-cure heated model resin system.

Frederick Rueggeberg, J. W. Ergle, P. E. Lockwood

Research output: Contribution to journalArticle

63 Citations (Scopus)

Abstract

OBJECTIVES: This study evaluated the effect of increased levels of photoinitiator components on biaxial flexural strength, monomer conversion, and dynamic thermal properties of an unfilled model resin system in both the light-cured only state as well as after post-cure heating. METHODS: Unfilled polymer discs were made using 50/50 mole% Bis-GMA and TEGDMA and were rendered photo-curable using a common (normal) concentration of photoinitiators (camphorquinone 0.3 wt% and DMAEMA 0.75 wt%) as well as twice and four-fold this amount. Specimens were light-cured and left unheated or were post-cure heated in a commercial unit. Biaxial flexural strength was obtained at a constant stressing rate (100 MPa/s), monomer conversion was determined using FTIR, and dynamic mechanical thermal properties (E', E", and Tg) were measured with DMA. Data were analyzed using ANOVA and Turkey-Kramer post-hoc test (p < 0.05). RESULTS: Increased levels of photoinitiator above normal significantly increased monomer conversion and Tg values for unheated as well as for post-cure heated specimens. Biaxial flexural strength for light-cured only groups remained unaffected by change in initiator concentration, but was significantly increased by post-cure heating. Increase in initiator concentration did not affect E' values for post-cured specimens, but significantly increased values for the unheated, light-cured only groups. E" values for post-cure heated specimens were significantly lowered by increasing initiator concentration. SIGNIFICANCE: The clinical implications of these results indicate that increasing photoinitiator levels results in post-cure heated restorations with significantly higher Tg and monomer conversion values. Use of elevated initiator concentrations for post-cured resins could result in restorations with enhanced resistance to deformation at elevated oral temperatures as well as significantly lower amounts of leachable components.

Original languageEnglish (US)
Pages (from-to)360-364
Number of pages5
JournalDental materials : official publication of the Academy of Dental Materials
Volume13
Issue number6
StatePublished - Jan 1 1997

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Resins
Monomers
Bending strength
Light
Heating
Restoration
Thermodynamic properties
Hot Temperature
Bisphenol A-Glycidyl Methacrylate
Dynamic mechanical analysis
Fourier Transform Infrared Spectroscopy
Analysis of variance (ANOVA)
Turkey
Analysis of Variance
Polymers
Temperature

ASJC Scopus subject areas

  • Materials Science(all)
  • Dentistry(all)
  • Mechanics of Materials

Cite this

Effect of photoinitiator level on properties of a light-cured and post-cure heated model resin system. / Rueggeberg, Frederick; Ergle, J. W.; Lockwood, P. E.

In: Dental materials : official publication of the Academy of Dental Materials, Vol. 13, No. 6, 01.01.1997, p. 360-364.

Research output: Contribution to journalArticle

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abstract = "OBJECTIVES: This study evaluated the effect of increased levels of photoinitiator components on biaxial flexural strength, monomer conversion, and dynamic thermal properties of an unfilled model resin system in both the light-cured only state as well as after post-cure heating. METHODS: Unfilled polymer discs were made using 50/50 mole{\%} Bis-GMA and TEGDMA and were rendered photo-curable using a common (normal) concentration of photoinitiators (camphorquinone 0.3 wt{\%} and DMAEMA 0.75 wt{\%}) as well as twice and four-fold this amount. Specimens were light-cured and left unheated or were post-cure heated in a commercial unit. Biaxial flexural strength was obtained at a constant stressing rate (100 MPa/s), monomer conversion was determined using FTIR, and dynamic mechanical thermal properties (E', E{"}, and Tg) were measured with DMA. Data were analyzed using ANOVA and Turkey-Kramer post-hoc test (p < 0.05). RESULTS: Increased levels of photoinitiator above normal significantly increased monomer conversion and Tg values for unheated as well as for post-cure heated specimens. Biaxial flexural strength for light-cured only groups remained unaffected by change in initiator concentration, but was significantly increased by post-cure heating. Increase in initiator concentration did not affect E' values for post-cured specimens, but significantly increased values for the unheated, light-cured only groups. E{"} values for post-cure heated specimens were significantly lowered by increasing initiator concentration. SIGNIFICANCE: The clinical implications of these results indicate that increasing photoinitiator levels results in post-cure heated restorations with significantly higher Tg and monomer conversion values. Use of elevated initiator concentrations for post-cured resins could result in restorations with enhanced resistance to deformation at elevated oral temperatures as well as significantly lower amounts of leachable components.",
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