In vitro biocompatibility of orthodontic miniscrews with human gingival fibroblast and SAOS-2 osteoblast cultures.

Purpose: Miniscrews are an important choice for orthodontic anchorage. Yet reports on failures do exist, and attempts have been made to elucidate the causes. Clinical outcomes may be compromised not only by the mechanical implications of miniscrew design and the location of anchorage but also by poor biocompatibility. Hence, this study deals with the surface roughness and elemental composition of miniscrews and how these properties may affect the in vitro biocompatibility of four commercially available miniscrews.

Methods: Most of the currently available miniscrews are made of TiAl6V4, an alloy widely considered to be biocompatible. The samples tested in this study included four similarly dimensioned TiAl6V4 products from different manufacturers: tomas® by Dentaurum, OrthoEasy® by Forestadent®, Dual Top™ by Jeil Medical/Promedia, and LOMAS by Mondeal®. The surface properties of these products were characterized by scanning electron microscopy (SEM) and energy-dispersive X‑ray spectroscopy (EDX). Cytotoxicity was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and agar overlay assays according to ISO 10993-5.

Results: The miniscrew products were found to show variations in surface-finish quality pertaining to topography and chemical composition, with the latter departing slightly from the manufacturers' specifications. MTT assays yielded rates of cell culture viability in excess of 90%, and agar overlay assays did not reveal decoloration beyond the specimen outlines in any of the experimental groups tested.

Conclusions: The four miniscrew products exhibited some minor, but statistically significant, differences in microtopography, alloy composition, and biological inertness. Cytotoxicity testing revealed that all four products should be considered non-cytotoxic, thus, ruling out poor biocompatibility as a cause of miniscrew failure.