Key points
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Alveolar bone resorption after tooth loss is especially challenging in the anterior maxilla due to ridge curvature and esthetic demands.
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The Khoury split bone block technique is effective for stable augmentation but limited by the use of straight plates in curved defects.
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The kerfing modification allows controlled bending of cortical bone plates, improving anatomic conformity and bucco-palatal bone volume.
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Achieving at least 2 mm of buccal bone over implants is critical for long-term stability and esthetics.
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The technique reduces the need for multiple plates and screws, minimizes donor site morbidity, and adapts to complex ridge anatomies.
Abbreviations
| 3D | 3 dimensional |
| SBBT | split bone block technique |
Introduction
Alveolar bone resorption following tooth loss is a well-documented phenomenon that poses significant challenges for implant therapy. In the anterior maxilla, resorption is particularly problematic because of the natural curvature of the ridge and the high esthetic demands of this region. Restoring adequate ridge dimensions often requires bone augmentation, but recreating the native contour of the anterior arch remains technically challenging. ,
Autogenous bone grafting remains the gold standard in augmentation due to its osteogenic, osteoinductive, and osteoconductive properties. Among the various approaches, the Khoury split bone block technique (SBBT) has gained prominence for its ability to provide stable augmentation with relatively low resorption rates. Thin cortical plates are harvested, split, and secured to the recipient site, creating a housing for particulate autogenous bone. This produces predictable healing and high-quality bone. However, the original technique has limitations when applied to curved anterior defects. Straight plates, when used with a convex ridge, tend to create a flat profile, requiring additional grafting, greater donor volume, and often supplementary soft-tissue procedures.
To overcome these limitations, a modification based on the principle of kerfing has been introduced. Kerfing, derived initially from woodworking, involves making a series of parallel cuts to allow a rigid material to bend predictably without fracturing. Applied to cortical bone plates, this technique permits controlled bending to recreate the curvature of the anterior maxilla. The result is improved anatomic conformity and, critically, greater bucco-palatal bone volume for implant placement.
Rationale for bone bending
The ability to bend autogenous bone plates extends the use of the SBBT in several essential ways. A curved graft reproduces the natural ridge anatomy more closely than multiple straight plates fixed together. More importantly, bending increases the volume of bone on the buccal aspect of future implant sites. Since the bone plates are solid cortex with minimal osteocytes within them, they should not be counted in the volume of buccal bone, as this has a high risk of resorption and remodeling over time. The only parts that will remain stable are the bone chips, as they will turn over completely and be replaced with new cancellous bone. The presence of osteocytes enables the bone to perceive pressure from the bite forces applied to the implants, thereby maintaining homeostasis and minimizing remodeling and resorption.
This additional bucco-palatal volume is not merely an esthetic consideration, but a biological requirement. Spray and colleagues , demonstrated that the presence of at least 2 mm of buccal bone overlying an implant is strongly associated with long-term stability of the peri-implant tissues. , Conventional straight plates frequently fail to meet this threshold in the anterior maxilla. The kerfed Khoury technique, by contrast, enables consistent achievement of this dimension, thereby reducing the likelihood of mid-term to long-term resorption and soft tissue recession ( Fig. 1 A and B ).
( A and B ) Reduced the gap between the implant and the bone plate. Narrow ridges do not allow greater palatal placement of the implant, thereby limiting the distance between the implant and the block. The plate is bent outward using a bone wedge to increase the space between the bone plate and the implant to allow a higher volume of autogenous bone chip to be inserted.
Additionally, bending allows fewer plates and screws, thereby reducing the need for extensive donor harvesting and lowering morbidity. The adaptation of plates to the curved ridge surface also minimizes the risk of sharp junctions or steps between graft segments, which can compromise flap integrity.
Application
This technique is ideal for the natural curves of the anterior maxilla or mandible. It can be used for horizontal augmentation buccally or buccally and palatally in both horizontal and vertical dimensions if needed. Both buccal and palatal plates can be bent to shape the buccal and palatal side. The technique can also be for vertical and horizontal augmentation.
In cases where there are no roots or a contour to help curve the bone only with the correct screw placement, an occlusal plate can be used and shaped to the correct contour and then the bone can be bent around this contour. This is ideal for cases with a vertical component and or a buccal and palatal component ( Fig. 2 A–E ). If no vertical grafting is necessary and there is no curve to help bend the plate, it is possible to cut a wedge from the bone plate, which can be used to bend the plate around. The wedge is anchored by the bending plate, so no screws are necessary to secure it. This is often necessary in single tooth sites or in cases where the adjacent teeth are in the same plane and there is no natural curve ( Fig. 3 A–I ).
( A–E ) ( A ) Split bone block shaped to fit between the roots. It is essential that the bone does not touch the root surface. ( B ) Plate screwed into place with 2 bone screws. It is imperative that the plate is solid and has no mobility at all to allow the buccal plate to bend around it. ( C ) The buccal portion of the bone plate is shaped according to the ideal outer contour of the jaw. ( D , E ) the buccal plate is screwed in distally with 1 or 2 bone screws and then again mesially to bend around the occlusal plate.
( A–I ) The use of a bone wedge to create a curvature of the bone. ( A ) Minimal curvature in the bone and the reduced length of the plate make bending difficult without a midsupport. ( B ) A bone wedge is cut to size around which the bone will bend. It is placed centrally in the area required to develop the bone. ( C ) The second screw is placed, which bends the bone around the wedge, curving the bone plate. ( D ) Autogenous bone chips are used to fill the space between the host bone and the bone plate. ( E ) Four months later, the area has healed well with solid bone formation. At this time, the screws are removed and the implant is placed. ( F ) Implant placed in position with excellent buccal bone volume created by the curvature. ( G , H ) A de-epithelialized connective tissue graft is placed over the grafted bone and implant to improve the final esthetic outcome and protect the newly formed bone. ( I ) Peri-apical radiograph showing the implant in the correct position.
Surgical technique
The surgical approach begins with harvesting a cortical block from the mandibular ramus, which offers ample bone volume with low donor-site morbidity compared with the symphysis. The block is harvested before the host site is opened. Once the block is harvested, it is sutured closed after PRF (Platelet Rich Fibrin) membranes are added to the area. The block is sectioned into thin plates, generally 1 to 2 mm thick, using a microsaw. Particulate bone generated during thinning of the plates using a Safescraper or an Automax (Megagen Korea) is collected and stored in platelet-rich fibrin for later use. This will be used to fill the space created by the host bone and the bone plate.
Only once bone plate preparation has been completed, a full-thickness flap is raised at the recipient site, with careful attention to the release incisions to ensure a tension-free closure. Once the defect is exposed, the degree of curvature required is assessed. One should get an idea of where the bend should take place and then cuts made slightly wider than the bend area. The same microsaw is used to create the kerfs in the bone. Holding the plate and microsaw at eye level. Kerfing cuts are made into the bone. They should be about 1.5 to 2 mm apart and should be as parallel as possible, although this is not always possible freehand. The depth of the cuts should not be more than half the thickness of the plate to ensure that they do not fracture on bending. These cuts reduce stiffness and permit predictable bending. In areas where the teeth roots are in a parallel line, a small wedge of bone can be cut from the plate in order to facilitate the bend in the bone at the correct position (see Figs. 1 B, 4 A–D ).
