RESUMEN
PURPOSE: In the clinical setting, assessing bone quality and quantity at the implant site is the basis to select implant characteristics and the insertion protocol to be applied. However, a quantitative method to classify bone quality and quantity is still lacking. A recently introduced implant placement micromotor that provides site-specific, operator-independent cancellous bone density measurements may be useful for this purpose, but it remains unknown whether this device can detect the presence of a cortical bone layer and measure its thickness and density. MATERIALS AND METHODS: Thus, an in vitro experiment was performed on six double-layer polyurethane foam blocks mimicking the jaw bone with different cortical thickness/cancellous density combinations. The densities were measured using the micromotor, either removing the cortical layer or leaving it intact, with and without irrigation. RESULTS: The results collected in each condition were compared by means of non-parametric statistical tests. Independent of irrigation, the micromotor detected the cortical layer when it was left intact and accurately estimated its thickness. The micromotor did not discriminate each block from the other ones when they were considered separately, but it did when they were grouped into four or three classes. CONCLUSION: The present study suggested that the micromotor may represent a valid device to quantitatively assess bone quality and density. If the micromotor can quantitatively distinguish different cortical/cancellous bone combinations in humans, it may be a helpful tool to define finely-tuned, patient-tailored preparations of the implant seat, making teeth rehabilitation in challenging clinical conditions more predictable.
RESUMEN
The amount of energy necessary to place an implant in its seat, described as the integral of the torque-depth curve at insertion (I), has been validated as a reliable measure of primary stability. This study aimed to investigate whether (I) may detect the variations in primary stability caused by changes in the implant length or diameter better than the insertion torque (IT). Cylindric implants featuring a double-etched, sandblasted surface with different diameters or lengths were placed into monolithic polyurethane foam blocks with different densities that mimicked human bone. (I)-, (I)*-, IT-, IT*-diameter and -length plots ((I)* and IT* were the derived values corrected for undersizing) were drawn and the relation between (I), (I)*, IT, and IT* and the fixture diameter or length was investigated with correlation analysis. (I)* and IT* correlated better than (I) and IT with the fixture diameter; (I), (I)*, IT, and IT* correlated equally well with the fixture length. In all cases, the slopes of the lines best fitting the experimental data were greater for (I) or (I)* than IT or IT*, respectively. (I) or (I)* were better detectors than IT or IT* of the changes in primary stability that can be achieved by increasing the fixture diameter or length.
RESUMEN
Previous results on synthetic blocks mimicking bone indicate that bone density can be measured by the friction encountered by a rotating probe while it descends into bone, and that primary implant stability may be measured through the integral (I) of the torque-depth curve at implant insertion. This study aims to repeat those tests on collagen-preserving equine bone blocks as they better reproduce the mechanical properties of natural bone. Fifteen cancellous equine blocks had their density measured using a measuring probe. This was compared to their known physical density through linear regression analysis. Implant placement was carried out into six cancellous equine blocks and primary stability was measured using (I), as well as the insertion torque (IT), the implant stability quotient (ISQ), and the reverse torque (RT). The relation between (I), (IT), (ISQ), and (RT) was investigated by correlation analysis. Bone density measured using the probe correlated significantly with actual density, both with (r = 0.764) and without irrigation (r = 0.977). (I) correlated significantly with IT and RT under all irrigation conditions, and with ISQ only without irrigation (r = 0.886). The results suggest that the probe provides actual bone density measurements. They also indicate that (I) measures primary implant stability and is more sensitive to density variations than IT, RT, and ISQ. Results are consistent with those obtained on synthetic blocks but suggest that equine bone blocks may better reproduce the mechanical properties of human cancellous alveolar bone. This should be the subject of additional studies.