Autogenous bone has been considered the golden standard for bone grafts because of its osteogenic properties, infection resistance, and secondary healing potential with wound dehiscences. Unfortunately, it also has critical disadvantages such as inevitable additional surgeries, limited amount of harvested material, and the possibility of significant resorption. Therefore, many researchers recommend a mixture with other bone substitutes and covering with a resorbable barrier membrane^3-9.

For alternatives to autogenous bone, many studies have been conducted for allogenic, xenogenic, and alloplastic bone substitutes. However, few instances of clinical success have been reported in cases of using them alone for ridge augmentation¹⁰. In particular, block-type bone substitutes were strongly recommended not to be used for bone grafts because of their poor results and high incidence of complications^10-12.

Bone tissue engineering studies have been conducted to overcome several disadvantages of autogenous bone grafts. As a result, many studies have reported successful results with a mixture of an adequate scaffold and bone growth factors such as recombinant human platelet-derived growth factor (rhPDGF) and recombinant human bone morphogenetic protein-2 (rhBMP-2)^13,14. Recently, several studies reported good bone healing after bone grafts with platelet rich plasma (PRP) or platelet rich fibrin (PRF) which could be obtained and prepared from the venous blood of patients¹⁵. Jeon et al.¹⁶ reported a 3.3 mm increase through vertical ridge augmentation using β-tricalcium phosphate with PRP.

There are no clear criteria for the use of barrier membranes, allowing clinicians to select membranes based on their preferences. Membranes could be effective for the stability of grafted bone in cases of particulate-type bone and an abundant amount of bone graft. Each resorbable and non-resorbable membrane has unique characteristics without a significant predominance. However, in one-wall defect reconstruction, titanium meshes have proven to be effective in stabilization of grafts due to its shape, rigidity, and ability to protect the underlying graft material¹⁷.

The sandwich technique was introduced in the following order where autogenous bone is grafted in the contact area with the implant, a demineralized freeze-dried allogenic bone or bovine hydroxyapatite bone is grafted over the autogenous graft, and a collagen membrane covers the graft site²⁰. In clinical practice, many bone augmentation procedures have been performed with similar principles to the sandwich technique. Some surgeons prefer to cover grafts with non-resorbable membranes such as titanium meshes. This method has been known to be effective for vertical and horizontal augmentation results with the stable mechanical properties of the membrane21.(Fig. 2)

Block type autogenous bone, harvested mainly in intraoral sites, is fixed with screws after intimate adaptation to the recipient surface. Particulate autogenous bone or other particulate bone substitutes are then packed in the surrounding empty space. A resorbable membrane is generally used as a cover to provide additional stability to the grafts^22-24.(Fig. 3)

Recently in implant dentistry, minimally invasive horizontal ridge augmentations are widely performed using particulate or block autogenous bone grafts with ridge splitting or ridge expansion combined with guided bone regeneration (GBR). Each procedure has clear advantages and disadvantages with no significantly different clinical results. Surgeon should select adequate techniques based on evidence and principles. Horizontal ridge augmentation has been known to exhibit more predictable outcomes and higher success rates compared to vertical ridge augmentation. The reconstruction amount has an average 3 to 4 mm target in horizontal ridge augmentations²⁵.

For the reconstruction of one-wall defects, onlay grafts are generally performed as GBR with particulate or block type autogenous bone grafts. However, onlay grafts have been reported to have high complication risks such as wound dehiscence, infection, bone resorption, and graft failure²⁵. Alternative techniques such as interpositional bone grafts (sandwich osteotomy) and alveolar bone distraction have been used to avoid these complications. In particular, the sandwich osteotomy is known to have a successful prognosis because of its optimal soft tissue coverage and blood circulation. The vertical portion is positioned on cortical bone, which has the advantage of enduring occlusal loads and absorption. The average increase in onlay grafts is 3 to 4 mm, while sandwich osteotomies are reported to exhibit an increase of approximately 5 to 7 mm. Nevertheless, some cases cannot undergo sandwich osteotomies due to the limitation of anatomical structures such as the inferior alveolar canal and maxillary sinus. On the other hand, a technique (supraplant) was introduced to increase vertical bone height simultaneously with implantation on the top of the alveolar crest. Several reports have shown acceptable results, but long-term clinical results have been rarely reported. With regards to clinical practice with the supraplant technique, the incidence of complications has been high with most of the surrounding grafted bone exhibiting resorption^26-29.