title: Small-diameter titanium grade IV and titanium-zirconium implants in edentulous mandibles: five-year results from a double-blind, randomized controlled trial.
abstract: BACKGROUND
  The aim of this study was to compare the 5-year survival and success rates of 3.3 mm dental implants either made from titanium-zirconium (TiZr) alloy or from Grade IV titanium (Ti Grade IV) in mandibular implant-based removable overdentures.
  
  
  METHODS
  The core study had a follow-up period of 36 months and was designed as a randomized, controlled, double-blind, split-mouth multicenter clinical trial. Patients with edentulous mandibles received two Straumann Bone Level implants (diameter 3.3 mm, SLActive®), one of TiZr (test) and one of Ti Grade IV (control), in the interforaminal region. This follow-up study recruited patients from the core study and evaluated the plaque and sulcus bleeding indices, radiographic crestal bone level, as well as implant survival and success 60 months after implant placement.
  
  
  RESULTS
  Of the 91 patients who initially received implants, 75 completed the 36 month follow-up and 49 were available for the 60 month examination. Two patients were excluded so that a total of 47 patients with an average age of 72 ± 8 years were analysed. The characteristics and 36-month performance of the present study cohort did not differ from the non-included initial participants (p > 0.05). In the period since the 36-month follow-up examination, no implant was lost. The cumulative implant survival rate was 98.9 % for the TiZr group and 97.8 % for the Ti Grade IV group. Crestal bone level changes at 60 months were not different in the test and control group (TiZr -0.60 ± 0.69 mm and Ti Grade IV -0.61 ± 0.83 mm; p = 0.96). The cumulative implant success rate after 60 months was 95.8 and 92.6 % for TiZr and Ti Grade IV, respectively.
  
  
  CONCLUSIONS
  After 60 months, the positive outcomes of the 36 month results for TiZr and Ti Grade IV implants were confirmed, with no significant differences with regard to crestal bone level change, clinical parameters and survival or success rates. TiZr implants performed equally well compared to conventional Ti Grade IV 3.3 mm diameter-reduced implants for mandibular removable overdentures.
  
  
  BACKGROUND
  Registered on www.clinicaltrials.gov: NCT01878331.
authors.affiliation: Division of Gerodontology and Removable Prosthodontics, University of Geneva, Geneva, Switzerland. frauke.mueller@unige.ch.
authors.forename: Frauke
authors.initials: F
authors.lastname: Müller
authors.affiliation: Johannes-Gutenberg University Mainz, Mainz, Germany. al-nawas@mkg.klinik.uni-mainz.de.
authors.forename: Bilal
authors.initials: B
authors.lastname: Al-Nawas
authors.affiliation: University of Milan, Dental Clinic, San Paolo Hospital, Milan, Italy. stefano.storelli@studioplinio.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Storelli
authors.affiliation: School of Dentistry, Catholic University Leuven, Leuven, Belgium. marc.quirynen@uz.kuleuven.ac.be.
authors.forename: Marc
authors.initials: M
authors.lastname: Quirynen
authors.affiliation: University of Bern, School of Dental Medicine, Bern, Switzerland. stefan.hicklin@zmk.unibe.ch.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hicklin
authors.affiliation: University of Regensburg Clinic, Regensburg, Germany. Jose.Castro-Laza@klinik.uni-regensburg.de.
authors.forename: Jose
authors.initials: J
authors.lastname: Castro-Laza
authors.affiliation: Cantonal Hospital Lucerne, Clinic for Oral and Maxillofacial Surgery, Lucerne, Switzerland. renzo.bassetti@luks.ch.
authors.forename: Renzo
authors.initials: R
authors.lastname: Bassetti
authors.affiliation: Division of Gerodontology and Removable Prosthodontics, University of Geneva, Geneva, Switzerland. martin.schimmel@zmk.unibe.ch.|University of Bern, School of Dental Medicine, Bern, Switzerland. martin.schimmel@zmk.unibe.ch.
authors.forename: Martin
authors.initials: M
authors.lastname: Schimmel
mesh_terms: D000497:Alloys; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D017267:Dental Prosthesis Design; D003828:Denture, Overlay; D004311:Double-Blind Method; D005500:Follow-Up Studies; D006801:Humans; D007575:Jaw, Edentulous; D008334:Mandible; D014025:Titanium; D015040:Zirconium
chemical_list: D000497:Alloys; D015921:Dental Implants; D015040:Zirconium; D014025:Titanium