title: Tensile test and interface retention forces between wires and composites in lingual fixed retainers.
abstract: BACKGROUND
  In daily orthodontic clinical practice retention is very important, and lingual retainers are part of this challenge. The failure of lingual retainers may be due to many factors. The aim of this study was to assess the retention forces and mechanical behavior of different types of wires matched with different kinds of composites in lingual retainers.
  
  
  METHODS
  A tensile test was performed on cylindrical composite test specimens bonded to orthodontic wires. The specimens were constructed using four different wires: a straight wire (Remanium .016×.022″ Dentaurum), two round twisted wires (Penta One .0215″ Masel, Gold Penta Twisted .0215″ Gold N'braces) and a rectangular braided wire (D-Rect .016×.022″ Ormco); and three composites: two micro-hybrids (Micro-Hybrid Enamel Plus HFO Micerium, and Micro-Hybrid SDR U Dentsply) and a micro-nano-filled composite (Micro-Nano-Filled Transbond LR 3M). The test was performed at a speed of 10mm/min on an Inström device. The wire was fixed with a clamp.
  
  
  RESULTS
  The results showed that the bonding between wires and composites in lingual fixed retainers seemed to be lowest for rectangular smooth wires and increased in round twisted and rectangular twisted wires where the bonding was so strong that the maximum tension/bond strength was greater than the ultimate tensile strength of the wire. The highest values were in rectangular twisted wires. Concerning the composites, hybrid composites had the lowest interface bonding values and broke very quickly, while the nano- and micro-composites tolerated stronger forces and displayed higher bonding values. The best results were observed with the golden twisted wire and reached 21.46 MPa with the Transbond composite. With the rectangular braided wire the retention forces were so high that the Enamel Plus composite fractured when the load exceeded 154.6 N/MPa. When the same wire was combined with the Transbond LR either the wire or the composite broke when the force exceeded 240 N.
  
  
  CONCLUSIONS
  The results of this study show that, when selecting a lingual retainer in daily clinical practice, not only must the patient's compliance and dependability be considered but also the mechanical properties and composition of different combinations of composites and wires.
authors.affiliation: Viale dei Quattro Venti 233, 00152 Roma, Italy. Electronic address: paolone.mg@gmail.com.
authors.forename: Maria Giacinta
authors.initials: MG
authors.lastname: Paolone
authors.affiliation: Viale dei Quattro Venti 233, 00152 Roma, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Kaitsas
authors.affiliation: 10, place Maréchal-Lannes, 32000 Auch, France.
authors.forename: Patricia
authors.initials: P
authors.lastname: Obach
authors.affiliation: Viale dei Quattro Venti 233, 00152 Roma, Italy.
authors.forename: Vasilios
authors.initials: V
authors.lastname: Kaitsas
authors.affiliation: Viale dei Quattro Venti 233, 00152 Roma, Italy; Department of civil, chemical and environmental studies, University of Genoa, Via Balbi 5, Genoa, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Benedicenti
authors.affiliation: Viale dei Quattro Venti 233, 00152 Roma, Italy; Department of civil, chemical and environmental studies, University of Genoa, Via Balbi 5, Genoa, Italy.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Sorrenti
authors.affiliation: Viale dei Quattro Venti 233, 00152 Roma, Italy; Department of civil, chemical and environmental studies, University of Genoa, Via Balbi 5, Genoa, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Barberis
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D004868:Equipment Failure; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D053761:Nanocomposites / Q000737:chemistry; D016382:Orthodontic Appliance Design; D018704:Orthodontic Retainers; D009969:Orthodontic Wires; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D003722:Dental Alloys; D003764:Dental Materials; D006047:Gold Alloys; D019279:Resin Cements; C481385:Transbond LR
keywords: Dental materials; Orthodontic retainers; Orthodontic wires; Orthodontics