Polymerization pattern characterization within a resin-based composite cured using different curing units at two distances

  • Afnan O. Al-ZainEmail author
  • George J. Eckert
  • Henry Lukic
  • Spiro Megremis
  • Jeffrey A. Platt
Original Article



To investigate the relationship of the irradiance-beam-profile areas from six different light-curing units (LCUs) with the degree of conversion (DC), microhardness (KH), and cross-link density (CLD) throughout a resin-based composite (RBC) cured at two clinically relevant distances, and to explore the correlations among them.

Materials and methods

A mapping approach was used to measure DC using micro-Raman spectroscopy, KH using a Knoop indentor on a hardness tester, and %KH reduction after ethanol exposure, as an indicator for CLD within a nano-hybrid RBC increment (n = 3) at various depths. These sample composites were cured from two distances while maintaining the radiant exposure, using six different light-curing units: one quartz-tungsten-halogen; two single and three multiple-emission-peak light-emitting-diode units. Irradiance beam profiles were generated for each LCU at both distances, and localized irradiance values were calculated. Points across each depth were analyzed using repeated measures ANOVA. Correlations across multiple specimen locations and associations between beam uniformity corresponding with polymerization measurements were calculated using linear mixed models and Pearson correlation coefficients.


Significant non-uniform polymerization patterns occurred within the specimens at various locations and depths. At 2-mm curing distance, the localized DC = 52.7–76.8%, KH = 39.0–66.7 kg/mm2, and %KH reduction = 26.7–57.9%. At 8-mm curing distance, the localized DC = 50.4–78.6%, KH = 40.3–73.7 kg/mm2, and %KH reduction = 28.2–56.8%. The localized irradiance values were weakly correlated with the corresponding DC, KH, and %KH reduction, with only a few significant correlations (p < 0.05).


Although significant differences were observed at each depth within the specimens, the localized irradiance values for all LCUs did not reflect the polymerization pattern and did not seem to have a major influence on polymerization patterns within the RBC, regardless of the curing distance.

Clinical relevance

Commonly used LCUs do not produce uniform polymerization regardless of the curing distance, which may contribute to the risk of RBC fracture.


Degree of conversion Microhardness Cross-link density Resin composite Beam profile Light-curing unit 



The work is part of the PhD dissertation for Dr. A. O. Al-Zain. The scholarship support from King Abdulaziz University, Jeddah, Saudi Arabia, and the technical assistance received from UITS/PTI Advanced Visualization Lab at Indiana University are acknowledged.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Informed consent

For this type of study, formal consent is not required.

Supplementary material

784_2019_2831_MOESM1_ESM.docx (2.6 mb)
ESM 1 (DOCX 2696 kb)
784_2019_2831_MOESM2_ESM.docx (15 kb)
ESM 2 (DOCX 15 kb)
784_2019_2831_MOESM3_ESM.docx (17 kb)
ESM 3 (DOCX 17 kb)
784_2019_2831_MOESM4_ESM.docx (17 kb)
ESM 4 (DOCX 16 kb)
784_2019_2831_MOESM5_ESM.docx (54 kb)
ESM 5 (DOCX 54 kb)
784_2019_2831_MOESM6_ESM.docx (19 kb)
ESM 6 (DOCX 19 kb)


  1. 1.
    Demarco FF, Collares K, Coelho-de-Souza FH, Correa MB, Cenci MS, Moraes RR, Opdam NJ (2015) Anterior composite restorations: a systematic review on long-term survival and reasons for failure. Dent Mater 31:1214–1224. CrossRefGoogle Scholar
  2. 2.
    Alvanforoush N, Palamara J, Wong RH, Burrow MF (2017) Comparison between published clinical success of direct resin composite restorations in vital posterior teeth in 1995-2005 and 2006-2016 periods. Aust Dent J 62:132–145. CrossRefGoogle Scholar
  3. 3.
    Leprince JG, Palin WM, Hadis MA, Devaux J, Leloup G (2013) Progress in dimethacrylate-based dental composite technology and curing efficiency. Dent Mater 29:139–156. CrossRefGoogle Scholar
  4. 4.
    Ferracane JL (2013) Resin-based composite performance: are there some things we can’t predict? Dent Mater 29:51–58. CrossRefGoogle Scholar
  5. 5.
    Cramer NB, Stansbury JW, Bowman CN (2011) Recent advances and developments in composite dental restorative materials. J Dent Res 90:402–416. CrossRefGoogle Scholar
  6. 6.
    Ferracane JL, Mitchem JC, Condon JR, Todd R (1997) Wear and marginal breakdown of composites with various degrees of cure. J Dent Res 76:1508–1516CrossRefGoogle Scholar
  7. 7.
    Soh MS, Yap AU (2004) Influence of curing modes on crosslink density in polymer structures. J Dent 32:321–326. CrossRefGoogle Scholar
  8. 8.
    Li J, Li H, Fok AS, Watts DC (2009) Multiple correlations of material parameters of light-cured dental composites. Dent Mater 25:829–836. CrossRefGoogle Scholar
  9. 9.
    Durner J, Obermaier J, Draenert M, Ilie N (2012) Correlation of the degree of conversion with the amount of elutable substances in nano-hybrid dental composites. Dent Mater 28:1146–1153. CrossRefGoogle Scholar
  10. 10.
    Santini A, Miletic V, Swift MD, Bradley M (2012) Degree of conversion and microhardness of TPO-containing resin-based composites cured by polywave and monowave LED units. J Dent 40:577–584. CrossRefGoogle Scholar
  11. 11.
    Leprince JG, Leveque P, Nysten B, Gallez B, Devaux J, Leloup G (2012) New insight into the “depth of cure” of dimethacrylate-based dental composites. Dent Mater 28:512–520. CrossRefGoogle Scholar
  12. 12.
    Selig D, Haenel T, Hausnerova B, Moeginger B, Labrie D, Sullivan B, Price RB (2015) Examining exposure reciprocity in a resin based composite using high irradiance levels and real-time degree of conversion values. Dent Mater 31:583–593. CrossRefGoogle Scholar
  13. 13.
    Rencz A, Hickel R, Ilie N (2012) Curing efficiency of modern LED units. Clin Oral Investig 16:173–179. CrossRefGoogle Scholar
  14. 14.
    Ilie N, Stark K (2014) Curing behaviour of high-viscosity bulk-fill composites. J Dent 42:977–985. CrossRefGoogle Scholar
  15. 15.
    Schneider LF, Moraes RR, Cavalcante LM, Sinhoreti MA, Correr-Sobrinho L, Consani S (2008) Cross-link density evaluation through softening tests: effect of ethanol concentration. Dent Mater 24:199–203. CrossRefGoogle Scholar
  16. 16.
    Alshali RZ, Salim NA, Satterthwaite JD, Silikas N (2015) Post-irradiation hardness development, chemical softening, and thermal stability of bulk-fill and conventional resin-composites. J Dent 43:209–218. CrossRefGoogle Scholar
  17. 17.
    Yap AU, Soh MS, Han TT, Siow KS (2004) Influence of curing lights and modes on cross-link density of dental composites. Oper Dent 29:410–415Google Scholar
  18. 18.
    Price RB, Ferracane JL, Shortall AC (2015) Light-curing units: a review of what we need to know. J Dent Res 94:1179–1186. CrossRefGoogle Scholar
  19. 19.
    Rueggeberg FA (2011) State-of-the-art: dental photocuring--a review. Dent Mater 27:39–52. CrossRefGoogle Scholar
  20. 20.
    Rueggeberg FA, Giannini M, Arrais CAG, Price RBT (2017) Light curing in dentistry and clinical implications: a literature review. Braz Oral Res 31:e61. CrossRefGoogle Scholar
  21. 21.
    Megremis SJ, Ong V, Lukic H, Shepelak H (2014) An ada laboratory evaluation of light-emitting diode curing units. J Am Dent Assoc 145:1164–1166. CrossRefGoogle Scholar
  22. 22.
    Jandt KD, Mills RW (2013) A brief history of LED photopolymerization. Dent Mater 29:605–617. CrossRefGoogle Scholar
  23. 23.
    Harlow JE, Sullivan B, Shortall AC, Labrie D, Price RB (2016) Characterizing the output settings of dental curing lights. J Dent 44:20–26. CrossRefGoogle Scholar
  24. 24.
    Michaud PL, Price RB, Labrie D, Rueggeberg FA, Sullivan B (2014) Localised irradiance distribution found in dental light curing units. J Dent 42:129–139. CrossRefGoogle Scholar
  25. 25.
    Price RB, Labrie D, Rueggeberg FA, Sullivan B, Kostylev I, Fahey J (2014) Correlation between the beam profile from a curing light and the microhardness of four resins. Dent Mater 30:1345–1357. CrossRefGoogle Scholar
  26. 26.
    Haenel T, Hausnerova B, Steinhaus J, Price RB, Sullivan B, Moeginger B (2015) Effect of the irradiance distribution from light curing units on the local micro-hardness of the surface of dental resins. Dent Mater 31:93–104. CrossRefGoogle Scholar
  27. 27.
    Price RB, Fahey J, Felix CM (2010) Knoop microhardness mapping used to compare the efficacy of LED, QTH and PAC curing lights. Oper Dent 35:58–68. CrossRefGoogle Scholar
  28. 28.
    Platt JA, Price RB (2014) Light curing explored in Halifax. Oper Dent 39:561–563. CrossRefGoogle Scholar
  29. 29.
    Price RB, Labrie D, Whalen JM, Felix CM (2011) Effect of distance on irradiance and beam homogeneity from 4 light-emitting diode curing units. J Can Dent Assoc 77:b9Google Scholar
  30. 30.
    Al-Zain AO, Eckert GJ, Lukic H, Megremis SJ, Platt JA (2018) Degree of conversion and cross-link density within a resin-matrix composite. J Biomed Mater Res B Appl Biomater 106:1496–1504. CrossRefGoogle Scholar
  31. 31.
    Albino LG, Rodrigues JA, Kawano Y, Cassoni A (2011) Knoop microhardness and FT-Raman evaluation of composite resins: influence of opacity and photoactivation source. Braz Oral Res 25:267–273CrossRefGoogle Scholar
  32. 32.
    Palin WM, Senyilmaz DP, Marquis PM, Shortall AC (2008) Cure width potential for MOD resin composite molar restorations. Dent Mater 24:1083–1094. CrossRefGoogle Scholar
  33. 33.
    Mousavinasab SM, Meyers I (2011) Comparison of depth of cure, hardness and heat generation of LED and high intensity QTH light sources. Eur J Dent 5:299–304Google Scholar
  34. 34.
    Beun S, Bailly C, Dabin A, Vreven J, Devaux J, Leloup G (2009) Rheological properties of experimental Bis-GMA/TEGDMA flowable resin composites with various macrofiller/microfiller ratio. Dent Mater 25:198–205. CrossRefGoogle Scholar
  35. 35.
    Leprince JG, Hadis M, Shortall AC, Ferracane JL, Devaux J, Leloup G, Palin WM (2011) Photoinitiator type and applicability of exposure reciprocity law in filled and unfilled photoactive resins. Dent Mater 27:157–164. CrossRefGoogle Scholar
  36. 36.
    Vasudeva G (2009) Monomer systems for dental composites and their future: a review. J Calif Dent Assoc 37:389–398Google Scholar
  37. 37.
    Watts DC, Cash AJ (1994) Analysis of optical transmission by 400-500 nm visible light into aesthetic dental biomaterials. J Dent 22:112–117CrossRefGoogle Scholar
  38. 38.
    Ikemura K, Endo T (2010) A review of the development of radical photopolymerization initiators used for designing light-curing dental adhesives and resin composites. Dent Mater J 29:481–501CrossRefGoogle Scholar
  39. 39.
    Vaidyanathan TK, Vaidyanathan J, Lizymol PP, Ariya S, Krishnan KV (2017) Study of visible light activated polymerization in BisGMA-TEGDMA monomers with type 1 and type 2 photoinitiators using Raman spectroscopy. Dent Mater 33:1–11. CrossRefGoogle Scholar
  40. 40.
    Sampaio CS, Atria PJ, Rueggeberg FA, Yamaguchi S, Giannini M, Coelho PG, Hirata R, Puppin-Rontani RM (2017) Effect of blue and violet light on polymerization shrinkage vectors of a CQ/TPO-containing composite. Dent Mater 33:796–804. CrossRefGoogle Scholar
  41. 41.
    Moore BK, Platt JA, Borges G, Chu TM, Katsilieri I (2008) Depth of cure of dental resin composites: ISO 4049 depth and microhardness of types of materials and shades. Oper Dent 33:408–412. CrossRefGoogle Scholar
  42. 42.
    Corciolani G, Vichi A, Davidson CL, Ferrari M (2008) The influence of tip geometry and distance on light-curing efficacy. Oper Dent 33:325–331. CrossRefGoogle Scholar
  43. 43.
    ISO (2007) 10650-2:2007 dentistry-powered polymerizationactivators: part 2: light-emitting diode (LED) lamps. Geneva,Switzerland: International Standards Organization.:7Google Scholar
  44. 44.
    Harlow JE, Rueggeberg FA, Labrie D, Sullivan B, Price RB (2016) Transmission of violet and blue light through conventional (layered) and bulk cured resin-based composites. J Dent 53:44–50. CrossRefGoogle Scholar
  45. 45.
    Shimokawa C, Sullivan B, Turbino ML, Soares CJ, Price RB (2017) Influence of emission spectrum and irradiance on light curing of resin-based composites. Oper Dent 42:537–547. CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Restorative Dentistry DepartmentFaculty of Dentistry, King Abdulaziz UniversityJeddahSaudi Arabia
  2. 2.Department of Biostatistics, Indiana University School of MedicineIndiana University Purdue University IndianapolisIndianapolisUSA
  3. 3.Research and StandardsAmerican Dental Association Science InstituteChicagoUSA
  4. 4.Department of Biomedical and Applied Sciences, Indiana University School of DentistryIndiana University Purdue University IndianapolisIndianapolisUSA

Personalised recommendations