What are the indications for split-thickness flap vs full-thickness flap in root coverage surgeries in Periodontology?

Flap Thickness Selection in Root Coverage Surgery

Use a split-full-split approach for coronally advanced flap procedures: split-thickness for surgical papillae, full-thickness for soft tissue immediately apical to root exposure, and split-thickness for vertical releasing incisions and apical areas. 1

Primary Surgical Approach Based on Flap Design

Split-Full-Split Technique (Recommended Standard)

• Elevate split-thickness flaps for the surgical papillae to preserve blood supply and prevent necrosis 1
• Use full-thickness dissection for the area immediately apical to the root exposure to maintain periosteal attachment and support regeneration 1
• Return to split-thickness dissection for vertical releasing incisions and areas apical to exposed bone to maximize flap mobility 1
• This approach provides optimal balance between flap mobility for coronal advancement and blood supply preservation 1

Full-Thickness Flap Indications

• Use full-thickness flap elevation when performing rhPDGF-BB-mediated regenerative procedures, as this allows access to the periosteum and prevents flap collapse against the root surface 1
• Full-thickness elevation is necessary when placing bone graft materials (beta-tricalcium phosphate) to prevent new bone formation collapse 1
• Full-thickness flaps achieve equivalent root coverage outcomes (97% coverage) compared to partial-thickness approaches (95% coverage) when combined with subepithelial connective tissue grafts 2

Superficial-Layer Split-Thickness Technique (Advanced Mobilization)

• When maximal flap release is required, dissect following the external surface contour of the flap toward the lip/cheek, separating epithelium and connective tissue from underlying muscular and periosteal layers 3
• This technique leaves muscle and periosteum attached to bone rather than the traditional approach of leaving periosteum on bone with muscle on the flap 3
• Provides extreme flap release allowing complete passive coverage and eliminates muscle pull during healing, preventing flap retraction 3

Critical Decision Points

Flap Thickness as a Predictor

• Flap thickness >0.8mm is directly associated with 100% root coverage when using coronally advanced flap alone 4
• Mean flap thickness of 0.7±0.2mm results in only 82±17% root coverage 4
• Gingival thickness of at least 1.46-1.5mm at 6 months is the main determinant of long-term gingival margin stability 5

When to Avoid Full-Thickness Elevation

• Avoid creating full-thickness flaps or releasing incisions unnecessarily in procedures where blood supply is critical, as this jeopardizes outcomes 6
• Partial-thickness dissection in apical areas maintains periosteal blood supply to the flap 1

Common Pitfalls

• Creating partial-thickness flaps throughout the entire procedure risks perforation or overthinning of the flap 2
• Traditional split-thickness technique that follows alveolar plate contour limits flap mobilization and allows muscle pull during healing, leading to flap retraction 3
• Relying on full-thickness flaps alone without addressing soft tissue thickness leads to significant recession recurrence (from 89.85% coverage at 6 months to 74.10% at 5 years) 5
• Proceeding with coronally advanced flap alone in thin phenotype cases (<0.8mm) results in incomplete root coverage 4

Adjunctive Considerations

• When using L-PRF membranes with coronally advanced flap, the split-full-split approach remains the standard technique 1
• Full-thickness elevation is mandatory when incorporating growth factors (rhPDGF-BB) with bone grafts to prevent material displacement 1
• Connective tissue grafts demonstrate superior long-term stability (89.35% coverage at 5 years) and should be considered when initial flap thickness is inadequate 5