Comparing Degree of Polymerization of 3D Printed and Dental Composite Material

Objectives: To evaluate the degree of polymerization of 3D printed (3DP) resins vs. conventional resin composite.
Methods: In this study, degree of conversion(DoC) was tested using Fourier-transform infrared spectroscopy with Attenuated total reflectance(FT-IR ATR) and compared with conventional dental restorative material, Beautifil II, (Group1)(Shofu, Kyoto, Japan) versus 3DP resin C&B MFH, (Group2)(NextDent, Soesterberg, the Netherlands). The 3DP specimens were designed on open source software MeshMixer into cylinders with 15mm diameters and printed with the compatible printer Moon Ray S(SprintRay, Los Angeles, CA). IsoMet 1000 Precision Cutter saw (Buehler, Lake Bluff, IL) was used to section samples suitable for FT-IR ATR scanning using Nicolet Magna 760 FT-IR scanner (Nicolet Instrument Co., Madison, WI). Group1 samples were measured unpolymerized, then pressed between two glass slides and cured for 20 seconds with a Demi Plus(Kerr Hawe, Middleton, WI) LED light with light intensity of 800mW/cm². Unpolymerized 3DP samples were measured as well.
Results: Area under the peaks at 1620-1650cm^-1 unique to C=C stretch was used to estimate DoC by taking the ratio of alkene bond at polymerized sample to unpolymerized sample. Summarized results are presented in the TABLE. Independent sample t-test was used to compare the means to analyze the results. The absorbance values were normalized using area under the peak at 2800-3000cm^-1 unique to C-C stretch. The highest DoC estimated was Group2 with a mean of 93.36% compared to Group1 with a mean DoC of 58.41%.
Conclusions: From this pilot study, we conclude that the levels of DoC were higher(Group2)compared to DoC of a conventional light-cured direct restoration composite but with no statistical significance. DoC is closely related to shrinkage and resorption in restorative materials. It is possible that in the future 3DP could be used to restore areas with indirect restorations that would have originally contained direct without as many complications.