Implant Stability Measurements Using Resonance Frequency Analysis in the Grafted Maxilla: A Cross-Sectional Pilot Study zy Lars Rasmusson, DDS, PhD;*t Goran Stegersjo, DDS;* Karl-Erik Kahnberg, DDS, PhD;* Lars Sennerby, DDS, PhDtS zyxwvut ABSTRACT zyxwvutsrqpo Background: High failure rates have been presented for implants placed in grafted bone. The bone graft-implant interface constitutes a most complex healing situation, where the time scale for osseointegration and development of implant stability currently is not known. Purpose: The zyxwvuts aim of the study was to measure the stability of implants placed in grafted bone after various follow-up periods. Methods: Implant stability measurements by means of resonance frequency analysis were performed in 10 patients previously treated zyxwvutsr with a Le Fort I osteotomy and interpositional bone grafts. The implants were placed 3 to 4 months after the grafting procedure. Sixty-seven Branemark implants were subjected to resonance frequency analysis measurements at fixture place- ment and up to 5.5 years after implant surgery. Periapical radiographs were used for assessment of margmal bone levels. Results: The radiographic examinations showed marginal bone loss with time during the 5.5-year follow-up. The resonance frequencies varied from 5860 to zyxwvuts 8440 Hz. When accounting for abutment length and marginal bone level, there was a ten- dency of increasing resonance frequency with time. Two implants with low resonance frequencies failed during the pros- thetic phase. Conclusion: The results indicate an increased implant stability with time, which may reflect bone formation, remodeling, and maturation at the implant interface. KEY WORDS: bone grafts, implant stability, Le Fort I osteotomy, resonance frequency analysis, titanium implants rosthetic reconstruction of the severely resorbed P maxilla using implants often requires autogenous bone grafting to increase the load-bearing bone vol- ume. The bone graft-implant interface constitutes a complex healing situation and involves revasculariza- tion and incorporation of the grafts as well as integra- tion of the implants. The optimal timing for placement of implants in grafted bone to achieve maximal stability currently is not known. Primary implant stability is achieved at implant placement surgery and is a result of the surgical technique, implant design, and mechanical *Department of Oral and Maxillofacial Surgery, Brinemark Clinic, +Department of BiornateriaMHandicap Research, Goteborg Univer- sity, and *Department of Oral Rehabilitation, Brinemark Clinic, Gothenburg, Sweden Reprint requests: Lars Rasmusson, DMD, PhD, Department of Oral and Maxillofacial Surgery, Goteborg University, Box 450, SE-405 30 Gothenburg, Sweden 01999 B.C. Decker Inc. properties of the bone. Secondary implant stability also is determined by the result of the repair process initi- ated by the surgical preparation of the bone, that is, for- mation and maturation of the bone at the implant interface. Thus, the final implant stability is determined by mechanical properties and the healing capacity of the bone bed. Experimental investigations have demon- strated a better integration of implants in bone grafts if a delayed technique is used compared to simultaneous For instance, Ramusson et a1 showed a higher degree of bone-implant contact and stability for implants placed in onlay bone grafts after healing of the graft compared to a simultaneous approach in which implants and bone graft were placed in one session.2 Histology of titanium microimplants placed and retrieved from 10 patients treated with autogenous bone grafts showed more bone when a delayed approach was used.3 It was speculated that the favorable results were achieved because the delayed implants were placed 70