Influence of recasting different types of dental alloys on gingival fibroblast cytotoxicity.
BACKGROUND
Surplus alloy from the initial casting is commonly reused with the addition of new alloy. This recasting procedure could affect the cytotoxicity of dental alloys.


OBJECTIVE
The purpose of this in vitro study was to evaluate the effect of repeated casting of high-noble and base metal alloys on gingival fibroblast cytotoxicity.


METHODS
Disk-shaped specimens (5 × 2 mm, n=60) of a high-noble (Au-Pt) and 2 base metal (Ni-Cr and Cr-Co, n=20) alloys were prepared with 100% new alloy and 50%, 65%, and 100% once recast alloy. The elemental composition of specimens was analyzed with X-ray energy-dispersive spectroscopy. Five specimens from each group were conditioned in saline with 3% fetal bovine serum albumin. The conditioning media were analyzed for elemental release with atomic absorption spectroscopy. Cytotoxic effects were assessed on human gingival fibroblast with a 3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyl tetrazolium bromide (MTT) colorimetric assay. The data were analyzed with 1-way and 2-way ANOVA and Tukey's HSD multiple comparison test (α-=.05).


RESULTS
Elemental compositions of Co-Cr and Au-Pt alloys were significantly different among casting protocols. Elemental release of Co-Cr and Ni-Cr alloys was significantly different between new and recast specimens (P<.001). Nickel release increased with recast alloy addition. The 2-way ANOVA showed a significant effect of the casting procedure (P<.001) alloy group (P<.001) and their interaction for cytotoxicity (P<.001). The Ni-Cr alloy groups with 65% and 100% recast alloy had lower cellular activity than all other specimens (P<.001).


CONCLUSIONS
The results of this study indicated that alloys containing nickel have increased cytotoxic effects and that composition of the alloys affected the cytotoxicity. Furthermore, recasting nickel-containing alloys with 65% surplus metal addition significantly increased the cytotoxic activity.
Department of Prosthodontics, Başkent University, School of Dentistry, Ankara, Turkey.
Pervin
P
Imirzalioglu
Emine
E
Alaaddinoglu
Zerrin
Z
Yilmaz
Bahar
B
Oduncuoglu
Burak
B
Yilmaz
Stephen
S
Rosenstiel
D000328:Adult; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002857:Chromium / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry / Q000633:toxicity; D003035:Cobalt / Q000737:chemistry; D003124:Colorimetry / Q000379:methods; D004396:Coloring Agents; D017077:Culture Media, Conditioned; D003722:Dental Alloys / Q000032:analysis / Q000633:toxicity*; D003735:Dental Casting Technique; D004058:Diffusion; D017743:Equipment Reuse; D005347:Fibroblasts / Q000187:drug effects*; D005881:Gingiva / Q000166:cytology / Q000187:drug effects*; D006046:Gold / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry / Q000633:toxicity; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry; D010984:Platinum / Q000737:chemistry / Q000633:toxicity; D013052:Spectrometry, X-Ray Emission; D013054:Spectrophotometry, Atomic; D013778:Tetrazolium Salts; D013844:Thiazoles
D002858:Chromium Alloys; D004396:Coloring Agents; D017077:Culture Media, Conditioned; D003722:Dental Alloys; D006047:Gold Alloys; D013778:Tetrazolium Salts; D013844:Thiazoles; D002857:Chromium; D003035:Cobalt; D010984:Platinum; D006046:Gold; D009532:Nickel; C022616:thiazolyl blue