Periosteal Fenestration Procedure in Apically Positioned Flap Increases the Attached Mucosal Width: An In Vivo Experimental Study

Aim: To evaluate the efficacy of the apically positioned flap (APF) with periosteal fenestration in increasing the width of the masticatory mucosa (MM, including attached and keratinized mucosa) and to assess the histological properties of the MM gained through this technique. Materials and methods: Six mongrel dogs were treated using a split-mouth design, with APF alone (control) and APF with periosteal fenestration (test) applied from the first to the fourth maxillary premolars on both sides (total of 48 sites). Clinical MM width (cMW) and digitally scanned MM width (dMW) were measured at baseline, post-operatively, and after 8 weeks of healing. Histological observations included measuring the distance from the free gingival margin to the mucogingival junction (MGJ) and the width of non-keratinized attached mucosa (NKAM). A linear mixed model was employed to analyse changes in MM measurements. Results: The mean gain of cMW was 3.17 mm (SD 1.63) in the control group and 4.27 mm (SD 1.91) in the fenestration group with a significant difference in favour of the fenestration group. The estimated mean difference was 1.45 mm (95% CI: 0.57-2.33; p = 0.002). Histologically, the increased mucosal width observed in the fenestration group, compared to the control group, was primarily characterized by non-keratinized epithelium. Conclusion: APF with periosteal fenestration enhances the attached mucosal width; however, this increase is predominantly composed of NKAM rather than orthokeratinized mucosa.