Cytotoxicity and Degree of Conversion of Orthodontic Adhesives

Abstract

Objectives:To test the hypothesis that there is no difference in the cytotoxicity related to the modes of polymerization of five commercially available orthodontic bonding resins, with and without an oxygen-inhibited layer (OIL), and to evaluate the degree of conversion (DC) of these resins and correlate this to cytotoxicity. Materials and Methods: Five commercially available orthodontic bonding resins were tested for cytotoxicity and DC. Thirty-six disks of standardized dimensions, for each resin, were used for cytotoxicity assessment. Half of them were washed with 99% acetone to remove the OIL (washed resins), and the remaining disks were left intact (intact resins). Glass disks were used as a control. Vero cells were exposed to intact and washed resins on day 1. Cell viability was determined by tetrazolium bromide reduction assay 1, 3, and 6 days after exposure. The DC of the adhesive specimens of each resin, prepared with a procedure identical to the clinical bonding process, was assessed by Fourier transform infrared spectroscopy. Results: Single-cured systems were comparatively less cytotoxic than dual-cured systems. With removal of the OIL, increased cell viability was noted only with two resins on all three days. Resins tested showed differences in DC. A positive correlation was demonstrated by two resins. Conclusion:The hypothesis is rejected. Single-cured systems are superior to dual-cured systems in exhibiting comparatively less toxicity and higher DC. A significant positive correlation was not established between cytotoxicity and DC.

Influence of the bracket on bonding and physical behavior of orthodontic resin cements

“…We used micro-Raman in situ to determine the CD of dentin adhesives 40) . Our results are slightly greater than reported in other studies with FTIR spectroscopy [41][42][43] . Although a positive correlation has been reported between hardness and DC, high CD does not necessarily mean higher mechanical properties 39) .…”

Uncompleted polymerization and cytotoxicity of dental restorative materials as potential health risk factors

“…In a study by Jagdish et al [23], the authors analyzed the correlation between the degree of conversion of orthodontic adhesives, structurally close to restorative materials, and their cytotoxic effects in vitro. The quoted authors reported no significant association between the conversion degree of the material and impact of its samples on the intensity of metabolism in cultured cells.…”

Biocompatibility of Orthodontic Resins: <i>In vitro</i> Evaluation of Monomer Leaching and Cytotoxic Effects

“…To date many studies focused on their physical properties, such as shear bond strength (Finnema et al, 2010), with less emphasis on RBDM biocompatibility, despite the proximity of their application site to the periodontal tissues which may cause inflammation of gingiva, oral mucosa and alveolar bone (Borra et al, 2009). Different studies, dealing with RBDM biocompatibility, are based on in vitro tests because of the ability to control the environment and cellular responses (Jagdish et al, 2009;Franz et al, 2003;Malkoc et al, 2010). According to the strategies for material testing, presented by Wataha (2012), the purpose of our study, was to determine in vitro material liability, the dynamics of any component release and the potential of released monomers to alter cell metabolism and function.…”

“…Incomplete RBDM conversion and/or their degradation in the oral environment causes the release of monomers which may affect adjacent tissues (Jagdish et al, 2009;Gioka et al, 2005). Light-cured or chemically cured dental composite resins leave a soft, sticky superficial layer upon polymerization, commonly referred to as an Oxygen-Inhibited Layer (OIL) because of its origin (Suh, 2004).…”