title: Interaction of titanium, zirconia and lithium disilicate with peri-implant soft tissue: study protocol for a randomized controlled trial.
abstract: BACKGROUND
  Against the background of increasing use of dental implants, and thus an increasing prevalence of implant-associated complications, a deeper understanding of the biomolecular mechanisms in the peri-implant tissue is needed. Peri-implant soft tissue is in direct contact with transmucosal dental implant abutments. The aim of this trial is to distinguish the biomolecular and histological interactions of various dental abutment materials with peri-implant soft tissue.
  
  
  METHODS
  The study is designed as a prospective, randomized, investigator-initiated clinical pilot trial with blinded assessment. We will ultimately include 24 eligible patients who opt for implant treatment to replace a single missing posterior tooth. Three months after implantation (submerged procedure), the study begins with the second-stage surgery. Each of the 24 patients will be given three different transmucosal abutments (zirconia, lithium disilicate, titanium) consecutively. The sequence in which the three materials are used is randomized. Peri-implant crevicular fluid is sampled weekly around the respective abutment for biomolecular analyses. After one month of wearing time, the stamping press from the second-stage surgery is used to gain a narrow gingival ring biopsy around the abutment for immunohistochemical analyses. The next abutment is then inserted. The same procedure is used for all three abutments. After sampling is completed, the patients will receive a definitive crown. The primary outcome measure of the trial is biomolecular detection of specific markers in the peri-implant crevicular fluid: matrix metalloproteinase 8, interleukin- 1β, polymorphonuclear elastase, and myeloid-related protein MRP8/14 (calprotectin). Secondary outcome measures include immunohistochemical analyses and clinical parameters.
  
  
  CONCLUSIONS
  The study design will allow us to perform correlation analyses between the clinical indices with biomarkers' expression in the interface of the transmucosal abutments and the peri-implant soft tissue. A deeper understanding of the three abutment materials' interactions with peri-implant soft tissue will help us understand the formation mechanisms of implant-associated complications and then develop prevention strategies.
  
  
  BACKGROUND
  The trial is registered at the German Clinical Trial Register and the International Clinical Trials Registry Platform by the WHO under DRKS00006555 (Registered on 27 October 2014).
authors.affiliation: Department of Prosthetic Dentistry, Center of Dentistry, Ulm University, Ulm, Germany. katharina.kuhn@uniklinik-ulm.de.
authors.forename: Katharina
authors.initials: K
authors.lastname: Kuhn
authors.affiliation: Department of Prosthetic Dentistry, Center of Dentistry, Ulm University, Ulm, Germany. heike.rudolph@uniklinik-ulm.de.
authors.forename: Heike
authors.initials: H
authors.lastname: Rudolph
authors.affiliation: Department of Prosthetic Dentistry, Center of Dentistry, Ulm University, Ulm, Germany. michael.graf@uniklinik-ulm.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Graf
authors.affiliation: Department of Prosthetic Dentistry, Center of Dentistry, Ulm University, Ulm, Germany. matthias.moldan@uniklinik-ulm.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Moldan
authors.affiliation: Department of Clinical Chemistry, Ulm University, Ulm, Germany. shaoxia.zhou@uniklinik-ulm.de.
authors.forename: Shaoxia
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Institut für Lasertechnologien in der Medizin und Messtechnik, Ulm University, Ulm, Germany. martin.udart@ilm-ulm.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Udart
authors.affiliation: Institut für Lasertechnologien in der Medizin und Messtechnik, Ulm University, Ulm, Germany. andrea.boehmler@ilm-ulm.de.
authors.forename: Andrea
authors.initials: A
authors.lastname: Böhmler
authors.affiliation: Department of Prosthetic Dentistry, Center of Dentistry, Ulm University, Ulm, Germany. ralph.luthardt@uniklinik-ulm.de.
authors.forename: Ralph G
authors.initials: RG
authors.lastname: Luthardt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D001706:Biopsy; D003442:Crowns; D000044:Dental Abutments / Q000009:adverse effects; D059605:Dental Implant-Abutment Design; D003758:Dental Implantation, Endosseous / Q000009:adverse effects / Q000295:instrumentation*; D019250:Dental Implants, Single-Tooth / Q000009:adverse effects; D003776:Dental Porcelain / Q000009:adverse effects; D005260:Female; D005858:Germany; D005883:Gingival Crevicular Fluid / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D053583:Interleukin-1beta / Q000378:metabolism; D019272:Leukocyte Elastase / Q000378:metabolism; D039841:Leukocyte L1 Antigen Complex / Q000378:metabolism; D008297:Male; D020784:Matrix Metalloproteinase 8 / Q000378:metabolism; D008875:Middle Aged; D010865:Pilot Projects; D011446:Prospective Studies; D012107:Research Design; D013997:Time Factors; D014025:Titanium / Q000009:adverse effects; D016896:Treatment Outcome; D055815:Young Adult; D015040:Zirconium / Q000009:adverse effects
chemical_list: D015415:Biomarkers; C508585:IL1B protein, human; D053583:Interleukin-1beta; D039841:Leukocyte L1 Antigen Complex; C493120:lithia disilicate; D003776:Dental Porcelain; D015040:Zirconium; D014025:Titanium; D019272:Leukocyte Elastase; C488762:MMP8 protein, human; D020784:Matrix Metalloproteinase 8; C028541:zirconium oxide