Principles of Periodontal Surgery
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FLAP DESIGN
A flap is a section of periodontal tissue that has been surgically separated from its underlying support and blood supply. A surgical flap is useful for providing access, facilitating effective debridement, pocket reduction, and many regenerative procedures. A flap is outlined by a surgical incision and carries its own blood supply.
A full thickness (mucoperiosteal) flap is most commonly used in oral surgery. Also known as a blunt dissection, this flap includes the surface mucosa (epithelium, basement membrane, and lamina propria) and the periosteum.
A partial thickness (mucosal) flap refers to a flap that only includes the surface mucosa.
A surgical flap can be classified based on the flap placement after surgery. When sutured to its original position it is called a “non-displaced” flap. A flap that has been moved and sutured is called a “displaced” flap. For a displaced flap to be repositioned the attached gingiva has to be totally separated from the underlying bone. A surgical flap can also be classified based on the management of the papilla.
A conventional flap splits the papilla beneath the contact point of two neighboring teeth to allow the buccal and palatal/lingual flaps to be reflected independently. A papilla preservation flap incorporates the entire papilla in one of the flaps. Though the end result is more aesthetic, papilla preservation flaps are difficult when tooth contacts are tight.
Flap design and management are important considerations for optimum outcome. Basic principles of flap design include:
- The base of the flap needs to be wider than the free margin to provide adequate blood supply.
- The length of the flap should remain less than the width of the flap.
- Incisions should not be placed over any bony defects, pathology or bony eminences. Only over intact, sound bone.
- Care should be taken when making incisions close to important structures. This includes the mental foramen (mental nerve), disto-lingual mandibular area (lingual nerve), and posterior palate (greater palatine vessels).
- Flap corners should be rounded.
- The flap should not be placed under excessive tension.
Types of of mucoperiosteal flaps include:
- Envelope flap (without releasing incision).
- Envelope flap with single releasing incision (three corner flap).
- Envelope flap with two releasing incisions (four corner flap).
- Semilunar incision (no longer popular).
- Y-incision.
- Pedicle flap.
Incisions can be classified according to their orientation.
1. Horizontal incisions – directed along the margin of the gingiva in a mesial-distal direction:
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- Internal bevel incision:
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- Also known as a reverse bevel incision.
- Usually the first incision.
- Aimed at the crest of the alveolar bone.
- Initiated 0.5-3mm from gingival margin:
- For apically displaced flap – 0.5-1.0mm from the free gingival margin.
- For non-displaced flap – just coronal to the base of the pocket.
- For modified Widman flap – no more than 1-2mm apical to the gingival margin.
- A #11 or #15 scalpel blade is commonly used.
- Conserves the outer gingiva which is relatively unaffected by pathology.
- Produces a sharp, thin flap margin.
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- External bevel incision:
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- Typically used in gingivectomy procedures.
- Approximately 45 degrees to the tooth surface.
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- Crevicular incision:
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- Second incision.
- From the base of the gingival sulcus (pocket) to the crest of the bone.
- When preceded by the internal bevel incision it creates a “V” shaped wedge (collar) that contains most of the inflamed and infected granulation tissue as well as the lateral wall of the pocket, compromised (long) junctional epithelium, and supra-crestal fibers.
- A #12 scalpel blade is commonly used.
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- Interdental incision:
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- Once the initial flap is elevated.
- An orban knife (or similar) is used.
- Allows for the removal of a tissue collar around the tooth.
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2. Vertical incisions:
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- Also known as relieving incisions, oblique incisions, or releasing incisions.
- Can be on one or both sides of the flap.
- A flap that has no vertical incisions is termed an envelope flap.
- Usually placed at line angles of papilla.
- Usually any flap technique that involves vertical repositioning includes at least one vertical incision.
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BIOLOGICAL WIDTH
It is essential that a proper biologic width is maintained after any treatment. The biologic width refers to the collar of junctional epithelium and connective tissue attached to the root surface of a tooth. The biological width does not include the gingival pocket depth, only the soft tissue attachment to the tooth. It can be found between the deepest point of the gingival sulcus and the alveolar bone crest, and provides a natural seal that protects the alveolar bone from infection and disease. For optimum longevity, any restoration placed on a tooth must respect this anatomical zone. The biologic width is unique to every patient, ranging from 0.75 to 4.3 mm, but averages ~2mm (Connective tissue ~1.00 mm + Junctional epithelium ~1.00 mm). In health the gingival pocket depth can vary from 1-3mm, but generally is found to be about 1mm deep. This places the free gingival margin at 3mm coronal to the alveolar bone crest height:
Connective tissue (~1mm) + junctional epithelium (~1mm) + sulcus depth (~1mm) = 3mm
Restorative margin placement can be supragingiva, equigingival, or subgingival. The former will have the least impact on periodontal health, the latter the greatest. For optimum health and longevity, subgingival margins should not impinge on the attachment apparatus (periodontal ligament, cementum, and alveolar bone). Biologic width impingement describes a restorative margin that is placed within 2 mm of the alveolar bone, which will likely lead to inflammation and localized bone loss.
BONE GRAFTING
Regenerative surgical therapies may be effective in cases with localized two or three-walled bony defects. Bone grafting materials may be used independently or in combination. Root resorption is the most common side effect of osseous grafting. Bone grafting materials can characterized by their source:
- Autograft – Bone harvested from the patient’s own body. These could be from extra-oral sources, such as the iliac crest, or intra-oral sources, such as:
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- Osseous coagulum – mixture of bone dust and blood obtained from cortical bone.
- Bone blend – obtained from a predetermined site that is triturated in an autoclaved capsule and packed into bony defects.
- Cancellous bone marrow – obtained from the maxillary tuberosity, edentulous areas, or healing sockets.
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- Allograft – Bone harvested from another individual of the same species. Examples include:
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- Freeze-dried bone allograft (FDBA) – osteoconductive material that maintains a strong osteogenic effect because of the presence of bone morphogenetic proteins (BMPs).
- Decalcified freeze-dried bone allograft (DFDBA) – osteoconductive and osteoinductive factors.
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- Xenograft – Bone-like material harvested from another individual but not the same species. Examples include:
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- Bovine bone.
- Chitosan – sugar that comes from the outer skeleton of shellfish, including crab, lobster, and shrimp.
- High-strength silk protein.
- Phytogenic materials such as gusuibu
- Algae/coral based materials.
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- Alloplast – Synthetic bone substitutes. Examples include:
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- Hydroxyapatite minerals.
- Metals.
- Beta-tricalcium phosphate ceramics.
- Biphasic calcium phosphate ceramics.
- Calcium sulfates.
- Synthetic polymers.
- Bioactive glasses.
- Calcium phosphate cements.
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Bone grafting materials can characterized by their action:
- Osteogenic potential – ability to induce the formation of new bone by cells contained in the grafting material.
- Osteoinductive potential – ability of molecules contained in the graft to induce neighboring cells to convert into osteoblasts.
- Osteoconductive potential – ability of the graft material to serve as a scaffold favorable to outside cells to help form new bone.
Bone substitutes with infused living osteogenic cells use autologous sources of mesenchymal stem cells (MSCs) with an appropriate scaffold (Bioseed-Oral Bone, Osteotransplant DENT). Growth factor based bone substitutes aim to accelerate healing of the bone graft in the bony defect. Many variations utilizing platelet and fibrinogen concentrations are available, including Sticky bone, Augment, Osigraft, and Infuse. Platelets are known to contain high concentrations of growth factors which stimulate cell proliferation and regulate angiogenesis. These growth factors include:
- Transforming growth factors β1 (TGFs-1).
- Platelet-derived growth factor (PDGF).
- Epithelial growth factor (EGF).
- Insulin growth factor-I (IFG-I).
- Vascular endothelial growth factors (VEGF).
