Abstract
BackgroundAlthough 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.MethodsFour 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).ResultsWhen 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.ConclusionsThe 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.
Highlights
The clinical use of miniscrews has been investigated on a large scale, little is known about their biocompatibility
Since orthodontic miniscrews are fixed to the bone, through soft tissues, it is essential to determine the relative levels of biocompatibility of the various mini-implants. As such information is not available, the aim of this work was to study the cytotoxic effects on primary human oral gingival fibroblasts (HGFs), a permanent human osteogenic sarcoma cell line (U2OS), and a permanent human keratinocyte cell line (HaCaT) of four orthodontic miniimplants made of different alloys which were stored under different pH conditions
The morphology of the cells appeared to have been maintained subsequent to mini-implant immersion media exposure
Summary
The clinical use of miniscrews has been investigated on a large scale, little is known about their biocompatibility. Removable miniscrews are available in a range of body lengths and diameter, and are mainly made of pure titanium, titanium alloy, and stainless steel (SS) [2]. Literature in this regard has reported a great number of clinical studies suggesting that TADs may provide stable anchorage during the orthodontic treatment without requiring patient cooperation [3]. Miniscrews are exposed to a number of potentially damaging physical and chemical agents Such conditions may contribute to corrosion of the metal components of any intraoral appliance, and an increasing number of studies have demonstrated that the oral cavity, owing to its peculiar physical, chemical, enzymatic, and microbial characteristics, may play a significant role in the biodegradation of metallic biomaterials [4,5]. The majority of them, in different experimental conditions, report ion release increase on decrease of the pH [9,10,11,12,13,14,15]
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