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The effect of preheating of nano-filler composite resins on their degree of conversion and microfiltration in dental fillings


The study assessed microhardness, microleakage of Class I, and the degree of conversion of composite resins preheated at 55 °C. This in vitro study evaluated two nanofilled composite resins (NCR), Filtek™ P60 and Filtek™ Z350 XT, used in the restorations. The degree of conversion (DC) was determined by Raman spectroscopy; the study compared the vibrational bands of the residual unpolymerized methacrylate C=C stretching band at 1640 cm−1 to the aromatic C–C stretching band at 1610 cm−1, used as an internal standard. Microleakage tests considered standard Class 1 cavities prepared on human premolars randomly divided. Preheating Filtek™ P60 and Filtek™ Z350 XT increased significantly VMH values (p = 0.0001). The highest microleakage occurred in preheated Filtek™ Z350 XT, while the lowest was in unheated Filtek™ P60. Unheated Filtek™ Z350 XT showed a significant increase of microleakage than unheated Filtek™ P60. (p = 0.024). Preheating of composite resins improved mechanical properties increasing DC and VMH. However, it also increases microleakage promoting bacterial penetration, secondary caries, marginal discoloration and hypersensitivity.

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The authors would like to thank to the laboratory of nanospectroscopy (LAB-NANOSPECT) (UdeC). National Agency for Research and Development of Chile (ANID) by project: FONDEQUIP Project N°EQM150139, VRID-UdeC Project 216.098.004-1.0. The authors thank Joanna Tereszczuk and Germán Osorio of the Center for Advanced Microscopy of the University of Concepción for their technical support and CMA Bío-Bío, Project ECM-12. MFM would like to thank Valentina Lamilla for her enormous support. All the authors thank Professor Alfonso Catalan for all his contribution to science throughout his life. Although he is no longer with us, his teachings will remain and transcend from generation to generation. Forever Dr. A. Catalan (R.I.P).

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A.E, A.M and C.M designed the experiments. A.E and A.M performed the experiments. T.M helped for grammar revising and language checking. A.M and A.C. wrote the paper. C.M performed the mechanical tests. A.J. carried out the Raman spectra. M.F.M analyzed the Raman spectra and prepared the composites. All authors discussed the results and commented on the manuscript. All authors read and approved the final manuscript.

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Correspondence to A. Catalán.

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Catalán, A., Martínez, A., Muñoz, C. et al. The effect of preheating of nano-filler composite resins on their degree of conversion and microfiltration in dental fillings. Polym. Bull. 79, 10707–10722 (2022).

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  • Dental material
  • Composite resins
  • Preheating
  • Raman spectroscopy
  • Degree of conversion
  • Vickers microhardness
  • Microleakage
  • Confocal laser microscopy