USC University of Southern California

Herman Ostrow School of Dentistry of USC

Surrounding Tooth Characteristics Don’t Govern Jawbone Graft Outcomes

The genetics of surrounding teeth do not necessarily predict how successful a jawbone graft will be — disputing what dentists and oral surgeons have thought about jaw grafts, according to a clinical study from the USC School of Dentistry.

“This will change the way we have been looking at jaw bone and periodontal tissues,” said Hessam Nowzari, director of the School of Dentistry’s Advanced Periodontics Program.

Fernando Verdugo, diplomate of the American Board of Periodontology and former assistant professor of clinical dentistry at USC, co-wrote the study with Nowzari and Krikor Simonian, School of Dentistry assistant professor.

  Dr. Krikor Simonian

The dental profession has divided patients into categories called “biotypes” based on the characteristics of their jawbone, teeth, and gums. Patients of biotype 1 have thin gums and bones and triangular-shaped teeth, while biotype 2 patients have thicker gum tissue and bone and possess flatter, more rectangular teeth.

The common thought was that if patients’ own bone was used as the graft material, it would adopt the biotype of the surrounding teeth and jaw, Verdugo said, and the individual’s genetics could influence the degree of bone volume loss at the graft site. Thus, biotype 1 patients who required a bone graft to support a dental implant were thought to need bone from an allogenic source, such as donor tissue from a cadaver or bovine bone, in order to prevent the bone tissue from being reabsorbed and becoming as thin as the tissue around it and structurally unsupportive of the implant.

However, after five years of closely following 40 patients who underwent autogenous bone grafts—bone transplanted from other sites on their own jaw — the team saw that the bone grafts maintained their volume and that the implants anchored at the graft sites remained stable, even in biotype 1 patients, Verdugo said. The grafted bones’ phenotypes, or observable physical characteristics, didn’t appear to be affected by the genetics of the teeth and other nearby tissues even after the five-year period; an especially exciting finding as all bone cells in a human adult are replaced about every two years.

“The grafted site phenotype was not influenced by the patient’s tooth biotype and genetic envelope,” he said. “These findings establish the predictability of patient’s own bone to restore function and esthetics.”

  Dr. Hessam Nowzari

Verdugo added that despite the availability of allogenic bone from cadaver and animal sources, the serious risks of disease transmission and slower healing time with such bone sources should encourage more oral health professionals to employ autogenous grafts instead, now that their long-term stability has been demonstrated.

“Autogenous bone is the gold standard,” he said.

The study, “Periodontal Biotype Influence on the Volume Maintenance of Onlay Grafts,” appeared online in February in the Journal of Periodontology and was funded by the USC Advanced Periodontics Research Fund. The USC Advanced Periodontics Symposium, an annual non-commercial scholarly gathering discussing the latest information in periodontics research and clinical practice, supports the fund.