Experimental evaluation of bone quality measuring speed of sound in cadaver mandibles

Objectives. To demonstrate in vitro the feasibility of speed of sound (SOS) measurements through the mandible and to investigate the relationships between mandibular SOS, local bone mineral density (BMD), and the ratio between trabecular and cortical thicknesses (Tb.Th/Cort.Th). The long-term goal is to find a safe, simple test for bone quality in sites for dental implant placement. Methods. Excised human mandibles (N=23) were used for the measurement of sound transmission with two 1.6 MHz transducers. Three regions of interest (ROIs) were selected in each of the specimens, namely incisor, premolar, and molar regions. To determine short-term precision, 10 measurements (with repositioning between measures) were performed for each ROI. Local BMD and mandibular cross-sectional morphological characteristics were determined by dual x-ray absorptiometry (DXA) and computed tomography (CT). Results. The coefficient of variation for SOS was found to be 1%. SOS measurements at different sites were significantly different. A significant linear relationship was found between SOS and BMD (r(2)=0.62; P <.0001), whereas a nonlinear relationship was found between SOS and Tb.Th/Cort.Th (r(2)=0.53; P <.0001). Conclusion. This in vitro study demonstrated the feasibility of SOS measurement through the mandible. Mandibular SOS reflects local BMD and Tb.Th/Cort.Th. In vivo studies are now required to confirm the predictive power of SOS measurement for bone quality assessment and its potential usefulness as a clinical diagnostic technique.