Content of review 1, reviewed on January 23, 2013

The authors report about the preparation and characterization of an experimental dental restorative composite, which should be promising thanks to its radio opaque and antibacterial actions. Indeed a lot of valuable experimental work has been done and is presented. However, most of it seems not to be novel, as mentioned by the authors themselves. First, the properties of DMMAI itself are well known. Second, the authors themselves have already been deeply investigating the same or little different material. By the way, the authors are extensively self citing (Refs. 24, 32, 39, 47, 55, 65, 66), which is too much (7 occurrences) to be believed to be really necessary to present the background of the work. In fact, the total number of references (66) is also too high, probably made to justify the number of above self citations. Back to the work contents, the novelty of the present composite formulation would be the use of DDMAI (imparting both properties of interest) to BisGMA MMA instead of BisGMA TEGDMA (as in Ref.32), which did not allow to reach a DMMAI concentration higher than 5%, due to miscibility problems with TEGDMA, limiting the useful effects of DMMAI. In this work the authors replaced TEGDMA with MMA, and shifted the BisGMA comonomer relative concentration from 50:50 to 80:20. Thus, given the good mixing properties of the new formulation, they could reach up to 25% DDMAI to monomer. In my personal opinion, this is not sufficient in itself to justify a new research article, especially given the negative results. In fact, even if the DC is not affected by DDMAI, both the mechanical and aging properties (in water) clearly are, in negative way. Additionally to the decrease in these properties, absolute radio-opacity is also not sufficient. Only the antibacterial effect is really interesting. Therefore, probably this work could better fit a microbiological journal or one of those novel journals reporting about negative experimental results. The overall poor performance results are also evident in the actual weak form of section , Conclusion. Altogether, the work is not acceptable.

Detailed comments:

  1. In the Results section, several considerations about the statistical significance of differences are not exact. In fact, even if the general flavor is correct, when speaking of statistical significance of their results the authors should be more precise. For example, they write that (page 4, lines 9-10) “control polymer had higher FS and FM than all polymers with DDMAI (p<0.05)”. Given the error bar plotted in Fig.3, this is probably false in the following cases: for FM, in both “before immersion”and “dried” condition, for control vs 15% DDMAI; for FS, in “dried” condition, for control vs 15%. Similarly, in lines 10 11: “FS and FM of polymers with DDMAI decreased with increase of DMMAI concentration (p<0.05)”, which should be false for: FS, before condition, for 15 vs 20%, and dried condition for 15 vs 20%; for FM, after condition, for 20 vs 25%. The trend is clear, but in these peculiar cases the difference should not be statistically effective.

  2. Fig.4: an in-panel legend placing a distance scale by the side of the images themselves (line with arrow for thickness direction and values of levels, 0.5, 1, 1.5 etc. by the side) would surely help the reader to more easily interpret this figure.

  3. Fig.5: all the right columns images should be removed, as this close up does not add any insight, and the larger view of the left column itself is sufficient to describe the presented effect. (BTW, this way the figure could be made a more compact 2x2 panels one, and no SEM would be justified but an optical microscope would suffice, always choose the easiest option).

  4. Fig.6: because other peaks in the spectrum are changing even more than those two used to evaluate the DC (eg see around 1250 and 1050 cm^-1), either a zoomed region only is showed around the peaks of interest of an inset in top left could show a close up of that region.

Minor text edits follow (demonstrating thoroughful reading by the referee):

  1. Page 2 line 40: “could not over”, change to “could not go over”.

  2. Abstract, line 26: better use Degree of conversion before defining DC acronym, rather than Double bond conversion (which can make non expert reader think the D stands for double).

  3. Page 8, line 2: “vitification”, change to “vitrification: wouldn’t be bad the paper authors always make their document go through a word processor chedckspeller, each and every time.

  4. Page 8, line 31: it is not Fig.5 but is Fig.4.

  5. Page 9, line 10: “into” change to “in”, no motion there.

  6. Page 9 line 17 “days’” change to “days”.

  7. Page 9 line 35:” used” change to “use”.

  8. Page 10 line 24: “according” change to “according to”.

  9. Page 11 line 7: “day” change to “ days”.

  10. Line 9 (equation): “SL” to “WSL”.

Source

    © 2013 the Reviewer (CC BY 4.0).