Underperforming light curing procedures trigger detrimental irradiance-dependent biofilm response on incrementally placed dental composites

Haifa Maktabi, Maria Ibrahim, Qoot Alkhubaizi, Michael Weir, Hockin Xu, Howard Strassler, Ana Paula P. Fugolin, Carmem S. Pfeifer, Mary Anne S. Melo

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Objectives: Insufficient radiant exposure (J/cm2) may provide an early trigger in a cascade of detrimental responses on incrementally-place composite, especially the bottom layer. This study aimed to assess the influence of poor radiant exposure, the degree of conversion (%DC), water sorption/ solubility and S. mutans biofilm formation on conventional, incrementally placed composites and to establish a relationship between these factors. Methods: Two light units operating at 600 and 1000 mW/cm2 and four most common operator-dependent curing conditions had the radiant exposure (RE) recorded. All the specimens were subjected to S. mutans biofilm model for 14 days. The %DC, biofilm formation expressed by colony-forming units (CFU), water sorption/ solubility and surface roughness/ SEM were assessed. Data were submitted to two-way ANOVA and Tukey post-hoc test (α = 0.05). Pearson correlation was also determined. Results: The influence of RE on S. mutans CFU values and DC are dependent on the curing conditions and irradiance (p < 0.05). A negative relationship was observed between RE and biofilm formation. The operator-dependent curing conditions have shown RE reduction varying from 49.4% to 73.5% in relation to control. The difference in DC between top/bottom of cylinder varied from 13% to 21% for 1000 mW/cm2and from 29% to 53% for LCU600. The roughness, solubility and salivary sorption were greater for low RE. Conclusion: Poor, deficient curing procedures provide an early trigger in a negative pathway of events for incrementally-place dental composite including a biological response by increased biofilm formation by S. mutans, a relevant factor for secondary caries development. Significance: The susceptibility to variation in the outcomes was RE -dependent. The optimization of the curing procedures ensures the maximum performance in the chain of events involved in the light curing process of resin-based materials and potentially reduce the risk factors of secondary caries development.

Original languageEnglish (US)
Article number103110
JournalJournal of Dentistry
StatePublished - Sep 2019


  • Light curing
  • Oral biofilm
  • Resin composite
  • S. mutans
  • The degree of conversion

ASJC Scopus subject areas

  • Dentistry(all)


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