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

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