Background : Relation between insertion torque and tactile, visual, and rescaled gray value measures of bone quality: a cross-sectional clinical study with short implants [1]

The early clinical success of short implants can be affected by poor bone quality and low primary stability because implant micromovement can promote the formation of a fibrous capsule during the osseointegration process. It has been reported that the greater the insertion torque, the greater the resistance of the bone-implant interface to the shear forces that tend to rotate the implant [1]. Clinically, insertion torque is the most practical method for measuring primary stability and can be recorded with the manual torque wrench or contra-angle and motor used for implant placement. Resonance frequency and damping capacity have also been used to measure the primary and secondary stability of short implants in research [2], but the procedures are more complex and require sophisticated equipment and extra clinical time.

Bone quality is a generic term for the characterization of bone tissue in three dimensions: the structural quality, related to the amount of the cortical bone and to the trabecular bone pattern; the bone density, related to the amount of bone mineralization and/or the amount of bone by its volume; and the amount of bone, related to the volume of bone available [3]. Bone quality varies intra- and inter-subject depending on the thickness of cortical bone, the amount of trabecular bone, and the amount of bone tissue mineralization in the region of interest for implant placement [4]. Some classifications of bone quality have considered cortical bone thickness and trabecular bone structure based on preoperative panoramic radiographs and tactile perception during exploratory drilling of the implant site; bone density based on the tactile sensation and Hounsfield units of computed tomography (CT) images; radiographic pattern of trabecular bone; and intra-surgical bone density and biopsy with histomorphometric evaluation [5,6,7,8]. However, most classifications of bone quality for routine clinical use still are not validated by using objective and subjective assessment methods.