title: Long-term retention behaviour of resin matrix attachment systems for overdentures.
abstract: OBJECTIVE
  The purpose of this laboratory study was to evaluate the long-term retention behaviour of two resin matrix attachment systems for overdentures and the influence of the implant angulation.
  
  
  METHODS
  Sixteen titanium patrices of each attachment system were connected to their corresponding implant analogues and fixed in an auto curing resin either orthogonally (n=8) or 20° tilted (n=8). The corresponding matrices, one made from polyetherketoneketone (PEKK; CM LOC, Cendres+Métaux, Biel, Switzerland), one made from polyethylene (PE; Locator, Zest Anchors, Escondido, California, USA), were fixed in a stylised unilaterally removable dental prosthesis resulting in 4 groups with 8 specimens in each group. Overall, 30,000 joining and separating cycles of the matrix were performed in a chewing simulator. After each joining movement, the unilaterally removable dental prosthesis was loaded eccentrically with 100N at a distance of 12mm from the attachment to simulate clinical loading conditions. Retentive forces were measured during the test using force transducers. The statistical analysis was performed using Tukey-HSD.
  
  
  RESULTS
  Both attachment systems showed a significant decrease in retention over time, which occurred earlier in the tilted groups than in the orthogonal groups. After 5000-30,000 joining and separating cycles the PE matrix attachment provided significantly lower retention than the PEKK matrix attachment system.
  
  
  CONCLUSIONS
  Within the limitations of this investigation, the combination of a titanium patrix and a matrix made from polyetherketoneketone seems to be a promising material combination for long-term retention, also on tilted implants.
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Arnold-Heller-Str. 16, 24105 Kiel, Germany. Electronic address: npassia@proth.uni-kiel.de.
authors.forename: Nicole
authors.initials: N
authors.lastname: Passia
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Arnold-Heller-Str. 16, 24105 Kiel, Germany.
authors.forename: Muhamad
authors.initials: M
authors.lastname: Ghazal
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Arnold-Heller-Str. 16, 24105 Kiel, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Kern
mesh_terms: D003828:Denture, Overlay; D007659:Ketones / Q000737:chemistry; D008422:Materials Testing; D012117:Resins, Synthetic / Q000737:chemistry*; D013997:Time Factors
chemical_list: D007659:Ketones; D012117:Resins, Synthetic
keywords: Attachment system; Retention; Wear