ORIGINAL ARTICLE Ultrasonic activation of irrigants increases growth factor release from human dentine M. Widbiller 1 & A. Eidt 1 & K.-A. Hiller 1 & W. Buchalla 1 & G. Schmalz 1,2 & K. M. Galler 1 Received: 12 January 2016 /Accepted: 13 April 2016 /Published online: 25 April 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract Objectives Bioactive proteins are sequestered in human den- tine and play a decisive role in dental pulp regeneration and repair. They can be released and exposed on the dentine surface by acids, but also chelators, such as ethylenediaminetetraacetic acid (EDTA). The objectives of this study were (i) to evaluate whether ultrasonic activation of irrigants in the root canal will promote growth factor release from dentine and (ii) to collect bioactive proteins in a physiological solution. Materials and methods Human dentine disks underwent irriga- tion with and without ultrasonic activation. The protocols includ- ed treatment by either a single or two consecutive steps with 10 % EDTA and phosphate-buffered saline (PBS), where each sample was treated three times. To mimic clinical conditions, selected irrigation regimens were applied to root canals of ex- tracted human teeth after preparation. Amounts of transforming growth factor β1 (TGF-β1) in solution were quantified using enzyme-linked immunosorbent assays. Nonparametric statistical analysis was performed to compare different groups as well as repetitions within a group (Mann-Whitney U test, α = 0.05). Additionally, morphological changes of dentine surfaces were visualized by scanning electron microscopy (SEM). Results TGF-β1 was not detectable after irrigation of dentine with PBS, neither with nor without ultrasonic activation. Irrigation with EDTA released TGF-β1, and ultrasonic activation of EDTA enhanced this effect. However, preceding EDTA con- ditioning enabled the release of bioactive proteins into PBS so- lution. Similar results were observed in dentine disks and root canals. Visualization of dentine surfaces after different treatment revealed superficial erosion after ultrasonic activation irrespective of the irrigant solution, but different degrees of exposure of or- ganic substance. Conclusions Ultrasonic activation enhances growth factor re- lease from human dentine. Bioactive proteins can be isolated in physiological solvents and may act as autologous supplements for regenerative endodontic treatment or pulp tissue engineering. Clinical relevance Autologous growth factors from human dentine can advance treatment strategies in dental pulp tissue engineering. Keywords Ultrasonic activation . Dentine . Transforming growth factor beta1 . Ethylenediaminetetraacetic acid . Tissue engineering . Regenerative endodontic procedure Introduction During dentinogenesis, growth factors and other bioactive proteins are secreted by differentiated odontoblasts and em- bedded in the extracellular matrix of dentine [1, 2], where they preserve their ability for biochemical signaling. The entrapped molecules can be released later by lactic acid in carious lesions [3], by dental materials such as mineral triox- ide aggregate [4], calcium hydroxide [5], or self-etching ad- hesives [6], and stimulate reactive or reparative dentine for- mation, repair, or regeneration. Furthermore, these growth factors can be liberated from dentine by demineralizing agents such as EDTA [1, 7], which is a hexadentate chelator and commonly used for smear layer removal from the root canal during endodontic therapy [8]. A variety of bioactive * M. Widbiller matthias.widbiller@ukr.de 1 Department of Conservative Dentistry and Periodontology, University Hospital Regensburg, Franz-Josef-Strauß-Allee 11, 93053 Regensburg, Germany 2 School of Dental Medicine, University of Bern, Freiburgstrasse 7, CH-3010 Bern, Switzerland Clin Oral Invest (2017) 21:879–888 DOI 10.1007/s00784-016-1824-1