Aim To quantitatively assess the degree of conversion and the water-leaching targeted compound from 3D-printed aligners. Materials and methods 3D-printed aligners were made of photopolymerized resin (Tera Harz TC85A). The molecular structure and degree of conversion of the set resin were investigated by ATR-FTIR spectroscopy (n = 5). The aligners (n = 10) were immersed in double distilled water for 1 week at 37°C and the eluents were analysed using liquid chromatography/mass spectrometry methods (LC–ESI-MS/MS for urethane dimethacrylate [UDMA] and LC–APCI-MS/MS for bispenol-A [BPA]). Results The resin was composed of aliphatic vinyl ester-urethane monomers, with acrylate and/or methacrylate functionalization. The degree of conversion was estimated as to 83%. There was no detection of BPA in any of the assessed samples (0.25 µg/l). Quantifiable amounts of UDMA were detected in all the exposed samples, ranging from 29 to 96 µg/l. Conclusions Although efficiently polymerized and BPA free, the great variability in the amount of UDMA monomer leached from the examined samples may raise concerns on potential health hazards after repeated intraoral exposure, which is indicated for this class of materials.

Situated at the crossroads of comparative philology, classics, and general historical linguistics, this study is the first ever attempt to outline in full the developments which led from the remotest recoverable stages of the Indo-European proto-language to the complex verbal system encountered in Homer and other early Greek texts. By combining the methods of comparative and internal reconstruction with a careful examination of large collections of primary data and insights gained from the study of language change and linguistic typology, Andreas Willi uncovers the deeper reasons behind many surface irregularities and offers a new understanding of how categories such as aspect, tense, and voice interact. Drawing upon evidence from all major branches of Indo-European, and providing exhaustive critical coverage of scholarly debate on the most controversial issues, this book will be an essential reference tool for anyone seeking orientation in this burgeoning but increasingly fragmented area of linguistic research.

The origin of the Umbrian perfect suffix ‐nç‐/‐ns`‐ has been variously explained, but none of the theories proposed so far is satisfactory at the same time from a philological, semantic, typological, and word‐formational point of view. After a critical review, the present paper proposes a derivation from a periphrastic structure {(action) noun in the accusative + perfect of *fak‐‘to make, do’}, which was univerbated and underwent a series of regular sound changes in Umbrian. A number of close parallels in various Indo‐European languages are pointed out, and it is suggested that the Umbrian periphrasis became so successful because its phonological shape at some point allowed a syntactic reanalysis as {part.pres.act. + perfect of *fak‐}.

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