Patient selection

Patients treated at Hiroshima University Hospital were included in the study if they remained partially edentulous in the planning area for at least 3 months, if one or two splinting fixed prostheses in the mandible posterior area were planned, if they had never been treated for osteoporosis, and if they had no subjective or objective symptoms of osteoporosis, such as back pain caused by a fractured or collapsed vertebra, loss of height over time, or stooped posture. Eighteen patients (11 women, 7 men) fulfilled the inclusion criteria. The study was approved by the Ethics Committee at Hiroshima University Graduate School of Biomedical and Health Sciences. All patients provided written informed consent after receiving a detailed explanation of the study, including its timeline, aims, risks and benefits of participation, and expectations regarding compliance.

Computed tomography and radiographic superposition

Each patient underwent a spiral computed tomography (CT) scan. The data were stored in Digital Imaging and Communications in Medicine format and loaded into implant planning software (Simplant®, Dentsply Implants, Leuven, Belgium). This allowed the implant placement sites to be pinpointed on the corresponding cross-sectional CT slices. Bone density was measured in Hounsfield units on buccopalatal or buccolingual cross-sectional CT slices at the sites of implant placement. The mean bone density values for the internal and external sides were used as the cancellous bone densities (Fig. 1).

Measurement of BTMs

BTM levels were measured in blood samples obtained simultaneously with routine blood testing before implant surgery by using ELISA. Sampling was performed in the morning in fasting subjects who had abstained from physical exercise for 24 h as recommended.