Elasticity of alveolar bone near dental implant–bone interfaces after one month's healing

Abstract

Information is scarce about Young's modulus of healing bone surrounding an implant. The purpose of this preliminary study is to quantify elastic properties of pig alveolar bone that has healed for 1 month around titanium threaded dental implants, using the nanoindentation method. Two 2-year-old Sinclair miniswine were used for the study. Nanoindentation tests perpendicular to the bucco-lingual cross section were performed on harvested implant–bone blocks using the Hysitron TriboScope III. Nomarski differential interference contrast microscopy was used to identify pyramidal indentation measurements that were from bone. Reduced moduli, averaged for all anatomical regions, were found to start low (6.17 GPa) at the interface and gradually increase (slope=0.014) to a distance of 150 μm (7.89 GPa) from the implant surface, and then flatten to a slope of 0.001 from 150 to 1500 μm (10.13 GPa). Mean reduced modulus and its relationship to distance did not differ significantly by anatomic location (e.g., coronal, middle, and apical third; P⩾0.28 for all relevant tests) at 1 month after implantation.

Introduction

Early loading on oral implants to promote osseointegration has not been consistently successful (Szmukler-Moncler et al., 1998), partly because the biomechanics of the interfacial bone are ill-understood. At early healing stages prior to maturation, microproperties of healing bone may depend on distance from the implant interface and on anatomic location. The physical properties (e.g., ultrasound propagation and microhardness) of such tissues are, in fact, microscopically heterogeneous across the interface (Zimmerman et al., 1989; Huja et al., 1998). Young's modulus—which differs from hardness, determining stress and strain distributions around the implant and is thus more important in studying osseointegration—has not been measured near the implant–bone interface (Brunski, 1999).

The present study used the nanoindentation method (Ko et al., 1995; Rho et al (1997), Rho et al (1999); Turner et al., 1999; Zysset et al., 1999) to measure interfacial elasticity of pig alveolar bone that has healed for 1 month around threaded titanium dental implants. Young's moduli were measured at μm scale for multiple distances from the interface. Confirmation of data from tissue indents was obtained using Nomarski differential interference contrast (DIC) light microscopy.