title: Surface deterioration and elemental composition of retrieved orthodontic miniscrews.
abstract: BACKGROUND
  This study provides insight into surface and elemental analyses of orthodontic retrieved miniscrew implants (MSIs). The sole purpose was to investigate the behavior of MSIs while they are in contact with bone and soft tissues, fluids, and food in the oral cavity. The information thus gathered may help to understand the underlying process of success or failure of MSIs and can be helpful in improving their material composition and design.
  
  
  METHODS
  The study was carried out on 28 titanium-alloy MSIs (all from the same manufacturer) split into 3 groups: 18 MSIs were retrieved after successful orthodontic treatment, 5 were failed MSIs, and 5 were as-received MSIs serving as the controls. All MSIs were subjected to energy dispersive x-ray microanalysis to investigate the changes in surface elemental composition and to scanning electron microscopy to analyze their surface topography. Data thus obtained were subjected to suitable statistical analyses.
  
  
  RESULTS
  Scanning electron microscope analysis showed surface manufacturing imperfections of the as-received MSIs in the form of stripes. Their elemental composition was confirmed to the specifications of the American Society for Testing of Materials for surgical implants. Retrieved MSIs exhibited generalized surface dullness; variable corrosion; craters in the head, neck, body, and tip regions; and blunting on tips and threads. Energy dispersive x-ray analyses showed deposition of additional elements: calcium had greater significance in its proportion in the body region by 0.056 weight percent; iron was seen in greater proportion in the failed retrieved MSIs compared with the successful miniscrews; cerium was seen in greater proportions in the head region by 0.128 weight percent and in the neck region by 0.147 weight percent than in the body and tip regions of retrieved MSIs.
  
  
  CONCLUSIONS
  Retrieved MSIs showed considerable surface and structural alterations such as dullness, corrosion, and blunting of threads and tips. Their surfaces showed interactions and adsorption of several elements, such as calcium, at the body region. A high content of iron was found on the failed MSIs, and cerium was seen in the head and neck regions of retrieved MSIs.
authors.affiliation: Postgraduate student, Division of Orthodontics and Dentofacial Deformities, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Pradnya
authors.initials: P
authors.lastname: Patil
authors.affiliation: Professor and head, Division of Orthodontics and Dentofacial Deformities, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India. Electronic address: opk15@hotmail.com.
authors.forename: Om Prakash
authors.initials: OP
authors.lastname: Kharbanda
authors.affiliation: Professor, Division of Orthodontics and Dentofacial Deformities, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Ritu
authors.initials: R
authors.lastname: Duggal
authors.affiliation: Additional professor, Department of Anatomy; officer in charge, Electron Microscope Facility, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Taposh K
authors.initials: TK
authors.lastname: Das
authors.affiliation: Assistant professor, Centre for Biomedical Engineering, Indian Institute of Technology, Delhi; assistant professor, Department of Biomedical Engineering, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Dinesh
authors.initials: D
authors.lastname: Kalyanasundaram
mesh_terms: D000293:Adolescent; D000327:Adsorption; D000497:Alloys; D000535:Aluminum / Q000032:analysis; D001863:Bone Screws; D002118:Calcium / Q000032:analysis; D002563:Cerium / Q000032:analysis; D002648:Child; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D004577:Electron Probe Microanalysis; D004868:Equipment Failure; D005260:Female; D006801:Humans; D007501:Iron / Q000032:analysis; D008297:Male; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008904:Miniaturization; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D013499:Surface Properties; D014025:Titanium / Q000032:analysis / Q000737:chemistry*; D014639:Vanadium / Q000032:analysis; D055815:Young Adult
chemical_list: D000497:Alloys; D003722:Dental Alloys; D014639:Vanadium; C031462:titanium alloy (TiAl6V4); D002563:Cerium; D000535:Aluminum; D014025:Titanium; D007501:Iron; D002118:Calcium