Biomechanical Aspects of Primary Implant Stability: A Human Cadaver Study Ilser Turkyilmaz, DDS, PhD;* Lars Sennerby, DDS, PhD; † Edwin A. McGlumphy, DDS, MS; ‡ Tolga F. Tözüm, DDS, PhD § ABSTRACT Background: The quality of bone is an important factor in the successful implant treatment, and it is evident that higher implant failure is more likely in poor quality of bone. The primary stability of oral implants related to resistance to micromotion during healing is influenced by bone quality, surgical technique, and implant design. Purposes: The aims of this biomechanical study were to explore the effect of bone quality on initial intraosseous stability of implants, and to determine the correlations between the bone quality and implant stability parameters. Materials and Methods: Twenty-four implants (Neoss Ltd., Mölnlycke, Sweden) were placed into anterior and posterior regions of three human cadaver mandibles. The bone densities of implant recipient sites were preoperatively determined using computerized tomography (CT) in Hounsfield unit (HU). The maximum insertion torque values were recorded, and primary implant stability measurements were noninvasively performed by means of resonance frequency analysis (RFA). Results: The bone density values ranged from -267 HU to 553 HU. It was found that mean bone density, insertion torque, and RFA values were 113 1 270 HU, 41.9 1 5 Ncm, and 70 1 7 implant stability quotient (ISQ), respectively. Statistically significant correlations were found between bone density and insertion torque values (r = 0.690, p < .001); bone density and ISQ values (r = 0.557, p < .05); and insertion torque and ISQ values (r = 0.853, p < .001). Conclusion: CT is a useful tool to assess bone quantity and quality in implant recipient sites, and bone density has a prevailing effect on implant stability at placement. KEY WORDS: bone density, CT, human cadaver, implants, implant stability, insertion torque, resonance frequency analysis C linical success of dental implants is influenced by both the quantity and quality of available bone as they vary from site to site and from patient to patient. 1 Clinical studies showed higher survival rates for implants placed in the anterior region of the mandible with good bone quality and quantity. 2–5 Therefore, an accurate evaluation of bone structure might be neces- sary prior to implant placement. Several bone classification systems have already been introduced. 6,7 Lekholm and Zarb 6 classified bone density radiographically into four types, based on the amount of cortical bone versus trabecular bone. Misch 7 related bone density to the clinical hardness of the bone as subjectively perceived during drilling prior to implant placement. Computerized tomography (CT) is an established method for acquiring bone images before oral implant surgery. 8 It was also used for objective quantification of trabecular and cancellous bone mineral densities, and direct density measurements, expressed in Hounsfield units (HU). 9–11 *Implant prosthodontic fellow, Department of Restorative and Pros- thetic Dentistry, College of Dentistry, The Ohio State University, Columbus, OH, USA; † professor, Department of Biomaterials, Insti- tute of Surgical Sciences, Sahlgrenska Academy, Göteborg University, and private practice, Göteborg, Sweden; ‡ associate professor, Depart- ment of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, OH, USA; § associate professor, Department of Periodontology, Faculty of Dentistry, Hacettepe Uni- versity, Ankara, Turkey Reprint requests: Dr. Ilser Turkyilmaz, College of Dentistry, The Ohio State University, 305 West 12th Avenue, PO Box 182357, Columbus, OH, 43218-2357, USA; e-mail: turkyilmaz.1@osu.edu © 2008, Copyright the Authors Journal Compilation © 2008, Blackwell Munksgaard DOI 10.1111/j.1708-8208.2008.00097.x 113