Background/purpose: A few studies have compared the osteopromotive effect of different membranes, but soft tissue response to various membranes has not been thoroughly investigated. The purpose of this study was to investigate the impact of various exposed regenerative membranes on gingival soft tissue healing. Materials and methods: Ten adult Taiwan dogs weighing 10-12 kg were used. After administration of local anesthesia, buccal gingival areas of the maxillary canines on both sides were disinfected with β-iodine. Punch-out lesions of 5 mm2 × 5 mm2 were made, 3 mm away from the gingival margin, using a 5-mm punch. Various barrier membranes (7 mm 2 × 7 mm2) were placed under the mucoperiosteal flap. Test membrane materials included collagen, expanded polytetrafluoroethylene (e-PTFE), and high density PTFE (n-PTFE). The sites without barriers served as controls. The lesions were measured and photographed 1 week and 2 weeks after surgery. Histologic sections were prepared at 2 weeks to observe barrier-tissue integration and the inflammatory condition. Results: The lesion size in the collagen group decreased in 1 week and the lesions almost completely healed in 2 weeks as compared with the control group. Lesion size increased 1 week after surgery for both groups of e-PTFE and n-PTFE. ANOVA analysis of the 1-week lesions showed that the differences in defect size among the four groups were statistically significant (P <0.001). A posthoc test (Bonferroni) showed that the differences between collagen and n-PTFE, between control and n-PTFE, and between e-PTFE and n-PTFE were significant. The other three pair-wise comparisons among collagen, control, and e-PTFE were nonsignificant. Lesion size and inflammatory reaction increased for the nonexfoliated sites. Histologic examination of the punch-out tissue margin of e-PTFE group showed ingrowth of fibrous connective tissue. No tissue integration was observed in the n-PTFE group. Compared with the control group, complete regeneration of oral epithelium was observed and the collagen membrane appeared intact 2 weeks following surgery. Conclusion: In the present study, collagen membranes may promote punch-out soft tissue healing whereas e-PTFE and n-PTFE interfered with healing. The impact of soft tissue healing on the efficacy of guided bone regeneration deserves further evaluation.
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