Effect of Crestal Soft‐Tissue Augmentation Prior to or Simultaneously With Implant Placement on Peri‐Implant Tissue Dimensions: Histological Outcomes of an Experimental In Vivo Study

Aim To histologically assess the effect of the timing of soft‐tissue augmentation (prior to or simultaneously with implant placement) and the type of grafting material on peri‐implant soft‐tissue dimensions. Materials and Methods Mandibular molars (M1, M2, M3) were bilaterally extracted in six beagle dogs. Eight weeks after extraction, one mandibular side received primary soft‐tissue augmentation with an autogenous subepithelial connective tissue graft (SCTG) or a collagen‐based graft substitute (CG x1D), or no augmentation. At Week 16, implants were placed at these sites without flap. On the contralateral side, implants were placed with flap elevation simultaneously with SCTG or CG x1D, or no augmentation. Animals were sacrificed at Week 36. Histometric outcomes were analysed using linear mixed‐effects models with dog as a random intercept; significant six‐group effects were followed by Tukey‐adjusted pairwise comparisons. Results All six groups showed crestal bone remodelling apical to the implant shoulder. The AFL group consistently exhibited the greatest peri‐implant soft‐tissue dimensions. Significant overall group effects were identified for lingual fBIC‐M ( F = 3.58, p = 0.014) and lingual IS‐M ( F = 4.46, p = 0.005), with AFL significantly exceeding FL and FC at both outcomes. SCTG sites showed significantly greater lingual fBIC‐M and IS‐M than collagen substitute sites ( p = 0.013 and p = 0.012, respectively). Conclusions Prior soft‐tissue augmentation with an autogenous graft before flapless implant placement (AFL) resulted in more favourable peri‐implant soft‐tissue dimensions. Both autogenous grafts and collagen substitutes contribute to soft‐tissue volume gains around implants. Clinical trials are warranted to confirm these findings.