Journal of Peking University (Health Sciences) ›› 2024, Vol. 56 ›› Issue (1): 25-31. doi: 10.19723/j.issn.1671-167X.2024.01.005

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Histopathological characteristics of peri-implant soft tissue in reconstructed jaws with vascularized bone flaps

Jiayun DONG,Xuefen LI,Ruifang LU*(),Wenjie HU,Huanxin MENG   

  1. Department of Periodontology, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digi-tal Medical Devices, Beijing 100081, China
  • Received:2023-10-10 Online:2024-02-18 Published:2024-02-06
  • Contact: Ruifang LU E-mail:kqrflu@bjmu.edu.cn
  • Supported by:
    the National Natural Science Foundations of China(82071116);the Clinical Research Foundation of Peking University School and Hospital of Stomatology(PKUSS-2023CRF305)

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Abstract:

Objective: To analyze the histopathological characteristics of peri-implant soft tissue in reconstructed jaws and the changes after keratinized mucosa augmentation (KMA) with free gingival graft (FGG). Methods: Twenty patients were enrolled in this study. Five patients of them, who were periodontal and systemic healthy and referred for crown lengthening before restoration with healthy keratinized gingiva collected were enrolled as healthy controls. 15 patients of them were with fibula or iliac bone flaps jaw reconstruction (10 with fibula flap and 5 with iliac flap), who were referred to FGG and implant exposures before restoration. Soft tissue was collected before FGG in reconstructed jaws, and in 5 patients (3 with fibula flap and 2 with iliac flap) 8 weeks after FGG if a second surgery was conducted. Histological analysis with hematoxylin-eosin stain and immunological analysis to interlukin-1 (IL-1), interlukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were performed. Results: Thickness from the bottom of stratum basale to the top of stratum granulosum and thickness of keratinized layer in reconstructed jaws were significantly lower compared with that of natural healthy keratinized gingiva [0.27 (0.20, 0.30) mm vs. 0.36 (0.35, 0.47) mm, P<0.05; 16.49 (14.90, 23.37) μm vs. 26.37 (24.12, 31.53) μm, P<0.05]. In the reconstructed area, thickness from the bottom of stratum basale to the top of stratum granulosum increased after KMA with FGG [0.19 (0.16, 0.25) mm vs. 0.38 (0.25, 0.39) mm, P=0.059] and the thickness of keratinized layer significantly increased after KMA with FGG [16.42 (14.16, 22.35) μm vs. 28.57 (27.16, 29.14) μm, P<0.05], which was similar to that in the control group. Furthermore, the number of positive cells of IL-1, IL-6 and TNF-α significantly increased after KMA [0.67 (0.17, 8.93) vs. 11.00 (9.16, 18.00); 13.00 (8.50, 14.14) vs. 21.89 (15.00, 28.12); 0.22 (0.04, 0.63) vs. 2.83 (1.68, 5.00), respectively, P<0.05] as well as the average optical density value [0.15 (0.14, 0.17) vs. 0.18 (0.17, 0.21); 0.28 (0.26, 0.33) vs. 0.36 (0.33, 0.37); 0.23 (0.22, 0.29) vs. 0.30 (0.28, 0.42), respectively, P<0.05], which was similar to that in the healthy keratinized gingiva. Conclusion: The lack of rete pegs and inflammatory factors were common in soft tissue with jaw reconstruction. FGG can improve the quality of the epithelium and may improve the stability of the mucosa around implants.

Key words: Jaw reconstruction, Vascularized bone flap, Soft tissue, Free gingival graft

CLC Number: 

  • R781.4

Figure 1

Soft tissue collection in reconstructed jaws A, B, soft tissue of left mandibular in reconstructed jaws with fibula bone flap before KMA, the red mark indicates collection of soft tissue before KMA, there is no keratinized tissue before FGG; C, KMA by FGG in both buccal and lingual side of implants; D, peri-implant soft tissue at 8 weeks after KMA, the red mark indicates collection of soft tissue during the second surgery; E, after removing the soft tissue; F, final restoration; G, H, soft tissue of left maxilla in reconstructed jaws with iliac bone flap before KMA, there is no keratinized tissue before FGG, the red mark indicates collection of soft tissue before KMA; I, KMA by FGG in both buccal and palatal side of implants; J, peri-implant soft tissue at 8 weeks after KMA, the red mark indicates collection of the soft tissue covering the implant during the second surgery; K, exposure of the implant after removing the soft tissue covering the implant; L, prothesis screwed into the implants. KMA, keratinized mucosa augmentation; FGG, free gingival graft."

Figure 2

Histopathological characteristics of healthy keratinized gingiva and soft tissue in reconstructed jaws before and after KMA A, healthy keratinized gingiva, presenting normal structures of stratified squamous epithelium (HE ×100); B, soft tissue of a male patient with fibula bone flap before KMA, lack of normal structures of stratified squamous epithelium (HE ×40); C, soft tissue of a female patient with iliac bone flap before KMA, partial vasodilation and congestion in connective tissue(HE ×100); D, soft tissue of a male patient with fibula flap before KMA, irregular arrangement of mucosal epithelial cells (HE ×100); E, soft tissue of a female patient with fibula flap after KMA, forming rete pegs (HE ×40); F, soft tissue of a female patient with fibula flap after KMA, neovascularization and proliferation of fibrous tissue in the lamina propria (HE ×100). KMA, keratinized mucosa augmentation; HE, hematoxylin-eosin stain."

Figure 3

Comparison of the thickness of keratinized layer and thickness from the bottom of stratum basale to the top of stratum granulosum before and after KMA in reconstructed jaws A, comparison of thickness from the bottom of stratum basale to the top of stratum granulosum before and after KMA in reconstructed jaws; B, comparison of the thickness of keratinized layer before and after KMA in reconstructed jaws. * P<0.05. KMA, keratinized mucosa augmentation."

Figure 4

Immunostaining for IL-1, IL-6 and TNF-α before and after KMA of soft tissue in reconstructed jaws A, low expression of IL-1 before KMA (IHC ×100); B, positive immunostaining for IL-6 before KMA (IHC ×100); C, positive immunostaining for TNF-α before KMA (IHC ×100); D, more positive cells (brown cells) in stratum basale, indicating higher expression of IL-1 after KMA (IHC ×100); E, higher expression of IL-6 after KMA (IHC ×100); F, higher expression of TNF-α after KMA (IHC ×100). KMA, keratinized mucosa augmentation; IL-1, interlukin-1; IL-6, interlukin-6; TNF-α, tumor necrosis factor-α; IHC, immunohistochemistry."

Table 1

Comparison of the number of positive cells and AOD of healthy keratinized gingiva and peri-implant soft tissue in reconstructed jaws before and after KMA"

Variables Healthy control (n=5) Before KMA (n=5) After KMA (n=5) P2
M (P25, P75) P1 M (P25, P75) P1
Number of positive cells
  IL-1 13.50 (11.00, 14.60) 0.67 (0.17, 8.93) 0.043* 11.00 (9.16, 18.00) 0.917 0.028*
  IL-6 26.33 (20.17, 28.84) 13.00 (8.50, 14.64) 0.016* 21.89 (15.00, 28.12) 0.251 0.047*
  TNF-α 4.26 (2.75, 5.19) 0.22 (0.04, 0.63) 0.009* 2.83 (1.68, 5.00) 0.347 0.009*
AOD
  IL-1 0.20 (0.18, 0.23) 0.15 (0.14, 0.17) 0.028* 0.18 (0.17, 0.21) 0.465 0.016*
  IL-6 0.33 (0.31, 0.38) 0.28 (0.26, 0.33) 0.175 0.36 (0.33, 0.37) 0.602 0.028*
  TNF-α 0.29 (0.27, 0.35) 0.25 (0.22, 0.29) 0.016* 0.30 (0.28, 0.42) 0.917 0.047*
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