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

OBJECTIVES: 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). RESULTS: 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 mum (APF), 410 +/- 116 mum (XCM), 336 +/- 122 mum (FGG), and 413 +/- 109 mum (control). All biopsies showed a regular muco-periosteal structure with a keratinized epithelium of comparable thickness in all groups. CONCLUSION: 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.