Clinical Oral Investigations

, Volume 22, Issue 5, pp 2111–2119 | Cite as

Clinical and histologic evaluation of different approaches to gain keratinized tissue prior to implant placement in fully edentulous patients

  • Daniel S. ThomaEmail author
  • AbdulMonem Alshihri
  • Alain Fontolliet
  • Christoph H. F. Hämmerle
  • Ronald E. Jung
  • Goran I. Benic
Original Article



This work aimed to investigate the effectiveness and predictability of different treatment modalities for gain of keratinized tissue (KT) in fully edentulous jaws prior to dental implant placement: apically positioned flap (APF), APF plus xenogeneic collagen matrix (XCM), and APF plus free gingival graft (FGG).

Materials and methods

In fully edentulous patients with insufficient zones of KT at the prospective implant positions, four treatment modalities were performed in the lower jaw: APF, XCM, FGG, and an untreated control group (control). APF and XCM were applied in the first molar positions, FGG and control in the canine positions. Assessed outcomes up to 3 months post-surgery included changes in width of KT (over a 3-month period), histomorphometric analysis of harvested soft-tissue biopsies (at 3 months postoperatively), and patient-reported outcomes measures (PROMs).


For the primary outcome, changes in KT width demonstrated an increase of 1.93 ± 1.6 mm (APF), whereas XCM and FGG showed an increase of 4.63 ± 1.25 mm and 3.64 ± 2.01, respectively. Histomorphometric analyses revealed a thickness of the epithelium ranging between 375 ± 122 μm (APF), 410 ± 116 μm (XCM), 336 ± 122 μm (FGG), and 413 ± 109 μm (control). All biopsies showed a regular muco-periosteal structure with a keratinized epithelium of comparable thickness in all groups.


All three methods were suitable to increase the width of KT, although APF alone rendered roughly 50% less gain compared to XCM and FGG.

Clinical relevance

The use of XCM in conjunction with an APF represents a valuable treatment option for the gain of keratinized tissue in edentulous sites.


Collagen Matrix Augmentation Keratinized tissue Keratinized mucosa Autologous Gingival graft Transplantation Patient-reported outcome measures 


Funding information

The present study was supported by the Clinic of Fixed and Removable Prosthodontics and Dental Material Science, University of Zurich and by a research grant of Geistlich Pharma AG, Wolhusen, Switzerland.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2017

Authors and Affiliations

  • Daniel S. Thoma
    • 1
    Email author
  • AbdulMonem Alshihri
    • 1
    • 2
  • Alain Fontolliet
    • 1
  • Christoph H. F. Hämmerle
    • 1
  • Ronald E. Jung
    • 1
  • Goran I. Benic
    • 1
  1. 1.Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Dental SchoolUniversity of ZurichZurichSwitzerland
  2. 2.Department of prosthodontics and biomaterialsKing Saud UniversityRiyadhSaudi Arabia

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