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etter to the Editor

esponse to Dr Kühnisch

© 2012 Academy of Dental Materials. Published by Elsevier

am writing in reference to the paper, Longevity of materialsor pit and fissure sealing—Results from a meta-analysis, byünisch et al., Dental Materials 2012;28:298–303. The authorsuggest two conclusions based on their meta-analysis: firstlyhat resin-based sealants are to be recommended (no problemith that); secondly that light-polymerizing materials are pre-

erred over the auto-polymerizing types. This latter conclusions based on the assumption that light-polymerizing materialsre “faster and less error-prone”. Both the preference and theeasoning are incorrect, in my opinion.

I would argue that most light-polymerizing materials takeonger to finish if one takes into account the need to fully irra-iate each surface for the required minimum time for full curet full depth (unless, possibly, only one surface of one tooth isddressed). Similarly, the assumption that auto-polymerizingaterials are less error-prone is false. The example concerned

he incorporation of bubbles in the mixing process. Apartrom the fact that careful mixing precludes the incorpora-ion of most bubbles (and that more advanced methods wouldreclude it entirely), the far more important issue of stress-elaxation during polymerization being much more favorableor the auto-polymerizing materials was ignored. In addition,he disadvantage of a costly light that requires regular test-ng and maintenance for full output was ignored, as was theifficulty of knowing that any particular aliquant of sealer isully polymerized, especially for opaque sealants, and in sitesf limited access. Nevertheless, this preference and reasoningmerges out of the blue: neither was supported by data; nei-her was the subject of the study. Gratuitous opinions cannote conclusions.

Secondly, it seems that the authors relied on wildly implau-

ible data for light-polymerizing sealants in their rush tonoint these materials as the best—one of the graphs in Fig. 1howed that light-polymerizing sealants possess the remark-ble aptitude to improve in terms of retention over time!

DOI of original article:10.1016/j.dental.2011.11.002.

This, of course, is patently ridiculous, yet the authors do notaddress this glaring impossibility (their model gave 2-, 3-,and 5-year fitted retention rates of 77.8%, 80.4% and 83.8%respectively [Authors’ Table 1]). There must either be a mis-calculation (Bayes notwithstanding), or their adopted modelinvalidated itself. No sealant can improve in retention overtime unless defects are regularly rectified, but this of coursewould render a study of longevity of retention null and void.In any event, the ‘ground truth’ of the data has not been recog-nized. To report fitted-model estimates as facts is unhelpful,at best.

There are other concerns as well (such as the non-independence of repeated observations), but I find itdisappointing that neither our colleagues nor the reviewerscould see the incomprehensibility of this last point and, at thevery least, prompt some discussion of it in the text, if not theabandonment of their meta-analysis in favor of some othermore realistic model.

Using an unquestioned impossible result to justify unsub-stantiated opinion cloaked as a definitive conclusion for asupposedly authoritative clinical recommendation is not whatI would expect in such an important analysis, from such anhonorable team of authors, in such a respected scientific jour-nal.

Richard J. SimonsenFaculty of Dentistry, Kuwait University, Kuwait

E-mail address: richardsimonsen@me.com

0109-5641/$ – see front matter

Ltd. All rights reserved.doi:10.1016/j.dental.2012.03.007