Block Bone Graft or Particulate Ridge Augmentation? Why Most Ridges No Longer Need a Block

In the Austin area? Dr. Verrett provides this care in North Austin. See Bone Grafting for Dental Implants, or request a consult.

Some patients come to a consult having been told they need a “block graft” before an implant: a piece of their own bone, cut from the chin, the back of the jaw or the hip, and screwed onto the thin part of the ridge. For decades that was the standard way to rebuild a jaw that had shrunk. It is no longer the only way, and for most ridges it is no longer the first choice. This article explains the two approaches, what the research shows about each, and why this office rebuilds ridges with particulate grafts.

Why a Ridge Needs Rebuilding

After a tooth is removed, the bone that held it starts to shrink. In a 12-month study of 46 patients, Schropp and colleagues found that the major changes in width and contour happened within the first year after extraction. A ridge that has been without a tooth for several years, or that lost bone to gum disease or an injury, is often too thin or too short to hold an implant. An implant needs bone around it on every side, and in the smile line the shape of that bone also decides how natural the gum looks.

There are two broad ways to rebuild it.

Why a 3D Scan Comes First

A ridge has width, height and shape in three dimensions, and an ordinary X-ray shows only two. A cone-beam CT scan shows how wide the bone is at every level, where the nerve and the sinus sit, and whether the defect has walls that will contain a graft. Those findings decide which graft is needed, how large it must be, and whether the implant can go in at the same visit. The European Association for Osseointegration’s imaging guidelines, by Harris and colleagues, describe diagnostic imaging as an essential part of patient selection and treatment planning for implants, provided the scan is justified and the dose kept as low as reasonably achievable. In a 2025 survey of 324 German oral and maxillofacial surgeons by Pabst and colleagues, 87.7 percent named cone-beam CT as their preferred imaging for ridge augmentation. Every ridge graft in this office is planned on a 3D scan.

Two Ways to Rebuild a Ridge

A block graft is a solid piece of bone, usually the patient’s own, taken from a second surgical site: the chin, the back of the lower jaw near the wisdom teeth, or for large rebuilds the hip. It is shaped, fixed to the ridge with small screws, and left to fuse for several months before the implant goes in.

Particulate ridge augmentation, also called guided bone regeneration, uses bone granules instead. These can be processed donor bone, bovine bone mineral, the patient’s own bone shavings, or a mix. The granules are packed against the ridge and covered with a membrane that keeps the gum from growing into the space while new bone fills it. The granules act as a scaffold; over the healing months the body replaces them with its own bone. No second surgical site is needed.

What the Comparisons Show

For height, particulate grafting comes out ahead. The 2019 meta-analysis by Urban, Montero, Monje and Sanz-Sánchez, prepared for the European Workshop on Periodontology, pooled 36 studies of vertical ridge augmentation:

• Guided bone regeneration gained 4.18 millimeters of height on average, with a complication rate of 12.1 percent.
• Bone blocks gained 3.46 millimeters, with a complication rate of 23.9 percent.
• In the studies that compared the two directly, particulate grafting gained 1.34 millimeters more.

For width, both work, and blocks gain a little more on average. A 2016 systematic review by Troeltzsch and colleagues found particulate grafts added 3.7 millimeters of width on average, and blocks about a millimeter more. A 2018 meta-analysis of randomized trials by Elnayef and colleagues found a similar gap: 4.18 millimeters with blocks against 3.61 with particulate grafting. For most implant sites, 3 to 4 millimeters of added width is enough. Even in thin, knife-edge ridges, the particulate approach has done well. In two prospective case series, Urban and colleagues gained 5.56 millimeters of width with no complications in 22 patients, and 5.68 millimeters with one complication in 31 sites in 25 more.

Overall, the consensus report of the 2019 European Workshop on Periodontology, by Jepsen and colleagues, concluded that rebuilding a ridge’s width before an implant is a predictable procedure, and that complication rates are high for every method. That last point is the practical one: when two approaches gain similar bone, the one with fewer complications and one surgical site instead of two is the better choice for most patients.

Blocks have not disappeared. In the 2025 survey of German oral and maxillofacial surgeons, 73 percent still used block augmentation. But the research has moved: a bibliometric analysis of 4,386 papers on ridge augmentation published between 1990 and 2024, by Hu and colleagues, found guided bone regeneration with particulate grafts was by far the most extensively studied technique.

The Cost of a Block: A Second Surgery

A block has to come from somewhere, and the place it comes from heals as a second wound.

• The chin. In a follow-up of patients one to three years after chin bone was harvested, Raghoebar and colleagues found that almost half reported decreased sensation in the chin area. A review of 24 studies by Nkenke and Neukam found chin harvesting caused considerable morbidity, including pain, skin sensation changes and wound-healing problems. Patients accepted it so poorly that they preferred bone from the hip, which needs general anesthesia and a hospital stay.
• The back of the jaw. Harvesting from behind the last molars is better tolerated, but it is still a second surgical site, close to the nerve that supplies the lower lip and chin. Raghoebar’s comparative study recorded temporary sensory disturbances at both mandibular sites.
• Graft loss. In a consecutive series of 279 patients treated with their own bone, Sakkas and colleagues found 4.4 percent of grafts failed and had to be redone or abandoned.

Do Block Grafts Shrink?

Unprotected blocks often do, and sometimes a great deal.

• In Cordaro’s 2002 series of mandibular blocks, the width gained shrank by 23.5 percent and the height by 42 percent in the six months before implants were placed.
• In a CT study by Sbordone and colleagues, chin and hip blocks lost 35 to 51 percent of their volume within a year.
• In a six-year CT follow-up of hip-bone blocks, the same group found 87 percent of the grafted volume resorbed in the lower jaw, and essentially all of it in the upper jaw. The authors advised anchoring implants in the native bone below the graft.

The evidence is not one-sided, and it is worth knowing why. When blocks are covered with particulate bone mineral and a membrane, they hold their shape much better. That covering cut resorption from 0.89 to 0.25 millimeters in a randomized trial by Cordaro and colleagues. In a ten-year study by Chappuis and colleagues, covered blocks lost only 7.7 percent of their surface. Across randomized trials, the Elnayef meta-analysis found blocks lost less volume in the first months than particulate grafts did. In other words, the modern block technique protects the block with the same granules and membrane that particulate augmentation uses on its own. Particulate grafts also lose some volume as they mature, which is why surgeons build them slightly larger than the final ridge needs.

Why Stabilizing the Graft Matters

A particulate graft only works if the granules stay where they are placed while bone grows through them. A laboratory study by Mir-Mari and colleagues showed how much this matters. Simply suturing the gum closed over a loose particulate graft pushed the top of it in by 43 percent of its thickness. When the membrane was fixed in place, the loss was 23 percent, about the same as with a solid block.

Exposure of the membrane is the other common problem. In a meta-analysis by Garcia and colleagues, ridges where the membrane stayed covered gained 74 percent more width than ridges where it became exposed. Careful flap design, closing the gum without tension, and a stable graft all reduce that risk.

Membranes are commonly held still with small titanium pins or screws. Dr. Verrett uses the Ribroast Technique™, described by Fien, Puterman and colleagues in 2023. It stabilizes a resorbable collagen membrane over the graft with a row of single horizontal mattress sutures anchored in the tissue covering the bone (the periosteum) along the length of the defect. The sutures hold the membrane taut the way butcher’s twine holds a rib roast, without metal pins that have to be placed and later removed. The 2023 paper describes the technique and two cases rather than a trial. The principle it serves, a stable graft under a stable membrane, is the one the studies above support.

Grafting at the Same Visit as the Implant

Most bone added in this office goes in at the same visit as the implant. When an implant is placed, there is often a thin wall of bone on the cheek side, a small area where the implant surface is not fully covered, or a gap between the implant and the walls of a fresh extraction socket. Grafting it then, rather than leaving it to heal on its own, is well supported.

• Grafting the gap at an immediate implant. In a randomized trial of 86 patients with implants placed straight into extraction sockets in the upper front jaw, Sanz, Lindhe and colleagues filled the gap with bovine bone mineral in half of them. The bone on the cheek side shrank by 1.1 millimeters (29 percent) with the graft and 1.6 millimeters (38 percent) without it, and the difference was larger where that bone was thin. In a CT study by Levine and colleagues, grafting gaps wider than 2 millimeters left a cheek-side wall averaging 1.9 millimeters thick, against 0.5 millimeters without a graft, and bone covered 95 percent of the implant’s height on that side against 59 percent. An earlier animal study by Araújo and colleagues showed the same effect under the microscope. A 2025 systematic review by Ahamed and colleagues found bone mineral grafts preserved volume better than PRF alone in these gaps, while noting that the studies differ too much for a single standard technique.
• Grafting a thin or exposed area at placement. A meta-analysis by Sanz-Sánchez and colleagues found grafting at the time of implant placement reduced these defects by an average of 4.28 millimeters, with a bone graft under a membrane giving the largest reduction. Over the long term, Jung and colleagues followed 265 implants for 12 to 14 years. Those placed with a graft and membrane survived at 91.9 to 92.6 percent, compared with 94.6 percent for implants that needed no graft, a difference that was not statistically significant, and bone levels were the same.

Grafting at the same visit avoids a separate surgery and its months of healing. Larger rebuilds still need to heal first; the 3D scan shows which case is which.

What About Bone From the Hip?

For the largest rebuilds, bone was once routinely taken from the hip (the iliac crest). It is now uncommon in implant dentistry, for reasons that are easy to see in the research.

• Complications. A systematic review of 92 studies and 6,449 patients by Dimitriou and colleagues found a complication rate of 19.37 percent after iliac crest harvesting. Infection, blood collections under the skin (hematoma), fracture and thickened scars were more common when bone came from the front of the hip.
• Pain and walking. In a prospective study of 50 patients by Nkenke and colleagues, 7 of 25 patients had trouble walking a week after bone was taken from the front of the hip, and 3 of 25 after the back. Skin sensation over the thigh and buttock was measurably reduced at one week, recovering over the following month.
• Anesthesia, hospital and cost. Harvesting bone from the hip needs general anesthesia and, usually, a hospital stay, as the Nkenke and Neukam review notes. That adds an anesthesiologist, an operating room and time off work, on top of the oral surgery itself.
• Shrinkage. In the six-year CT study by Sbordone’s group cited above, hip blocks lost 87 percent of their volume in the lower jaw and essentially all of it in the upper jaw.

The Alternatives to a Large Graft

Today a severely thin or short ridge usually has several options that avoid the hip altogether:

• Particulate grafting for height as well as width. In Urban’s meta-analysis, guided bone regeneration gained 4.18 millimeters of height on average, more than blocks did.
• Titanium mesh or tenting. A rigid mesh or tenting screws can hold a particulate graft in shape for larger vertical rebuilds. A review of onlay grafts and tenting by Aloy-Prósper and colleagues found tenting gained 6.17 millimeters of height with a complication rate of 24.6 percent. Meshes became exposed through the gum in about one case in five in a meta-analysis by Gu and colleagues. These are reserved for defects that need them.
• Shorter implants. Implants 5 to 6.6 millimeters long can sometimes avoid vertical grafting entirely. In a review of randomized trials with five years of follow-up, Esposito and colleagues found short implants failed no more often than longer implants placed in grafted bone. Complications were about 4.7 times as likely, and bone loss around the implants greater, with the longer implants in grafted bone.
• A sinus lift for the upper back teeth, where the sinus rather than the ridge is what limits height. Sinus lift explains it.
• Angling the implants in a full-arch case, so they reach existing bone instead of needing new bone. In a series of 471 patients followed for 10 to 18 years, Maló and colleagues reported 98.8 percent of the full-arch bridges still in use, with 93 percent implant survival. Full-arch implants covers that approach.
• Distraction osteogenesis, which slowly stretches bone apart to grow height. It gained the most height in Urban’s meta-analysis, 8.04 millimeters, but with complications in 47.3 percent of cases, and it is rarely used.

When a ridge needs more than these can reliably provide, the consult says so plainly.

Questions Worth Asking

If you have been told you need a block graft, these are fair questions:

• How much width and height does my ridge need, in millimeters?
• Could a particulate graft gain that, and if not, why not?
• Where would the block come from, and what are the risks at that site?
• How much shrinkage should I expect, and how is the graft protected against it?
• Will the implant go in at the same visit or after healing, and when?

A second opinion is reasonable before any graft that involves a second surgical site.

Ridge Augmentation in North Austin

Dr. Andrew Verrett is a Diplomate of the American Board of Periodontology and the only doctor at Austin Periodontal Associates. He rebuilds thin and short ridges with particulate grafts under a resorbable collagen membrane, stabilized with the Ribroast Technique™, and does not harvest bone blocks. Every ridge is planned on a 3D scan before surgery, and most grafting is done at the same visit as the implant, including filling the gap around implants placed in fresh extraction sockets. Bone grafting for dental implants describes the procedure and recovery, and how long implant treatment takes covers the timeline. Request a consult or call (512) 346-6097.