Study On Cyto-genotoxicity Of Five Dental Alloys In Vitro And The Micronuclei In Human Buccal Mucosa Cells Exposed To Dental Alloys

Objective The purposes of present investigation were to detect whether5kinds of dental alloys can induce the cyto-genotoxicity in vitro and to determine whether the increased MNFs of exfoliated buccal cells appear in patients exposed to dental alloys.Methods Human B lymphoblast cells served as target cells in vitro. Vincristine was used as positive control. IMDM was used as negative control. The extracts of five alloys were prepared by being immersed in IMDM culture medium for72hours. The released metal elements of extracts were detected by Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The cytotoxic effects induced by five dental alloy extracts on human B lymphoblast cells were detected using neutral red uptake (NRU) and CCK-8assays in vitro. The genotoxicity induced by five alloy extracts were detected using comet and cytokinesis-block micronucleus (CBMN) assays in vitro. The concentrations of five alloy extracts were56.5s112.5,225,450and900μl extracts/ml. The cells were exposed for48h in four assays. Chromosomal damage of exfoliated buccal cells in68subjects were investigated using micronucleus(MN) assay. Thirty four patients exposed to dental alloys for1-13years (mean5.32years) and34controls were matched with patient group according to age and sex.Results The Ni content (87.6ug/L) in VeraBond (VB) extract was significantly higher than those (57.6ug/L and70.0ug/L) in Kera N (KN) and TILITE"V"(TV) extracts (P<0.05). The Cr content (19.6ug/L) in TV extracts was significantly lower than those (28.7ug/L and29.1ug/L) in KN and N.P. Partial (NP) extracts (P<0.05). The Be content was detectable only in VB extract. The results of NRU assay showed that the cell viability of all groups was significantly lower than that of the negative group (P<0.01or P<0.05) except for the NP alloy extract at the dose of56.5μl extracts/ml. At the doses of112.5-900μl extracts/ml, the cell viability of VB group was significantly lower than that of KN, TV, NP and Starlog C (SC) groups (P<0.01). At the doses of450-900μl extracts/ml, the cell viability of KN group was significantly lower than that of NP group (P<0.01). At the doses of225and900μl extracts/ml, the cell viability of TV group was significantly lower than that of NP group (P<0.01). At the doses of112.5and225μl extracts/ml, the cell viability of SC group was significantly lower than that of NP group (P<0.01). According to the results of CCK-8assay, The cell viability of the NP group was significantly higher than that of the VB group at the doses of112.5-900μl extracts/ml (P<0.01). At the exposure dose of900μl extract/ml, the cell viability of the SC group was significantly higher than that of the VB group (P<0.01). When the exposure dose was900μl extract/ml, the cell viability of NP group was significantly higher than that of KN group (P<0.01). While the DNA damage (%tail DNA) and MNFs induced by VB, KN, TV, NP and SC extracts did not increase significantly when compared with the control (P>0.05) according to the results of comet and CBMN assays. The results of oral buccal cell MN assay revealed that the mean MNF and micronucleated cell frequency (MCF) of oral buccal cells in patient group were1.68±2.04and1.29±1.439‰, respectively.The mean MNF and MCF of oral buccal cells in control group were1.62±1.89and1.09±1.16‰, respectively. There were no significant differences of MNF and MCF between patient group and control group (P>0.05).Conclusion The extracts of the tested five dental alloys did not significantly induce DNA damage and chromosomal damage on human B lymphoblast cells in comet assay and CBMN assay in vitro. Also the genotoxic effects of buccal cells in68cases with dental alloys were not detectable with micronucleus assay of human buccal cells. However, in CCK-8assay and NRU assay in vitro, there were differences of the cytotoxic effects among5dental alloy extracts to some extent, which may be related to the Ni and Be ions released from the dental alloys. The present investigation suggested that the dental alloys with low cytotoxicity should be used for clinical work so that the biocompatibility could be improved and the stimulant effects could be decreased for around tissues of dental alloys.