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Effect of pH on in vitro biocompatibility of orthodontic miniscrew implants

Angela Galeotti1, Roberto Uomo1, Gianrico Spagnuolo2, Sergio Paduano3, Roberta Cimino2, Rosa Valletta2 and Vincenzo D’Antò12*

Author Affiliations

1 Department of Pediatric Surgery, Bambino Gesù Children's Hospital, Rome, Italy

2 Department of Neurosciences, Reproductive Sciences and Oral Sciences, University of Naples “Federico II”, Naples, Italy

3 Department of Clinical and Experimental Medicine, University of Catanzaro “Magna Graecia”, Catanzaro, Italy

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Progress in Orthodontics 2013, 14:15  doi:10.1186/2196-1042-14-15

Published: 1 July 2013



Although the clinical use of miniscrews has been investigated on a large scale, little is known about their biocompatibility. Since low pH can affect corrosion resistance, the aim of this study was to evaluate the cytotoxic effect of orthodontic miniscrews in different pH conditions.


Four orthodontic miniscrews of stainless steel and grade IV and grade V titanium were immersed in a pH 7 and pH 4 saline solution for 1, 7, 14, 21, 28, and 84 days. Human osteogenic sarcoma cells (U2OS), permanent human keratinocytes (HaCat), and primary human gingival fibroblasts (HGF) were exposed to eluates, and the mitochondrial dehydrogenase activity was measured after 24 h to assess the cytoxicity. The results were analyzed using the Mann-Whitney U test (P < 0.05).


When exposed to pH 7-conditioned eluates, the cell lines showed an even greater viability than untreated cells. On the contrary, the results revealed a statistically significant decrease in U2OS, HaCat, and HGF viability after exposure to eluates obtained at pH 4. Among the cell lines tested, HGF showed the most significant decrease of mitochondrial activity. Interestingly, grade V titanium miniscrews caused highest toxic effects when immersed at pH 4.


The results suggested that at pH 7, all the miniscrews are biocompatible while the eluates obtained at pH 4 showed significant cytotoxicity response. Moreover, different cell lines can produce different responses to miniscrew eluates.

Biocompatibility; Miniscrew implants; TADs; Titanium alloy; Stainless steel