title: Effect of pH on in vitro biocompatibility of orthodontic miniscrew implants.
abstract: BACKGROUND
  Although 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.
  
  
  METHODS
  Four 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).
  
  
  RESULTS
  When 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.
  
  
  CONCLUSIONS
  The 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.
authors: Department of Pediatric Surgery, Bambino Gesù Children's Hospital, Rome, Italy. vincenzo.danto@unina.it.
authors: Angela
authors: A
authors: Galeotti
authors: Roberto
authors: R
authors: Uomo
authors: Gianrico
authors: G
authors: Spagnuolo
authors: Sergio
authors: S
authors: Paduano
authors: Roberta
authors: R
authors: Cimino
authors: Rosa
authors: R
authors: Valletta
authors: Vincenzo
authors: V
authors: D'Antò
mesh_terms: D000328:Adult; D001672:Biocompatible Materials / Q000633:toxicity*; D001863:Bone Screws; D018929:Cell Culture Techniques; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003343:Corrosion; D003722:Dental Alloys / Q000633:toxicity; D003764:Dental Materials / Q000633:toxicity*; D005347:Fibroblasts / Q000187:drug effects; D005881:Gingiva / Q000166:cytology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015603:Keratinocytes / Q000187:drug effects; D008904:Miniaturization; D008928:Mitochondria / Q000187:drug effects; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D012965:Sodium Chloride / Q000737:chemistry; D013193:Stainless Steel / Q000633:toxicity; D013997:Time Factors; D014025:Titanium / Q000633:toxicity; D055815:Young Adult
chemical_list: D001672:Biocompatible Materials; D003722:Dental Alloys; D003764:Dental Materials; D013193:Stainless Steel; D012965:Sodium Chloride; D014025:Titanium