[Study on method for examining bone quality for dental implant. Relationship between cutting force and bone mineral content].

A number of factors, including, for example, patient jawbone condition, influence prognosis of dental implants. At present, X-ray and intraosseous punctures are employed as means of examining bone quality. But lack of definite criteria makes objective evaluation difficult. In order to develop a more reliable method for making objective evaluations of bone quality for dental implant, this study quantitatively measured the cutting force at an intraosseous puncture and investigated its relation to bone mineral content, a parameter of bone condition. Methods One side of each of 4 mandibles obtained from adult Japanese cadavers was fixed with formalin. The mandibles were free of deformity and injury to the jaw or face but lacked molars (these materials were the property of the Department of Anatomy, the Tokyo Dental College). Drilling tests were made in 5 samples taken from each of the 4 mandibles (20 in all), and bone mineral content was measured. Prior to the drilling test, the dental engine was remodeled to produce an experimental test machine permitting quantitative measurement of the cutting force (cutting torque) exerted on cutting instrument in the direction of rotation. The device was fitted to a universal testing machine and constant-feed-speed drilling tests were performed. Cutting force on the cutting instrument produced during drilling was divided into cutting torque (cm-g) in the direction of rotation and cutting load (gf) in the direction of feeding. Densitometry and image analysis were used to measure bone mineral content. X-ray photograph were taken from each sample with an aluminum reference, the density of which was digitalized and measured. The density value was then image analyzed, and bone mineral content of the drilled site was obtained as relative value calculated in aluminum equivalent (mmAl). Comparative examinations of cutting torque, cutting load, and bone mineral content were made through the same drilled site at every 1.0 mm-depth from surface. Results and Conclusions 1. The experimental test machine permitted quantitative measurements of the cutting force exerted on the cutting instrument in the direction of rotation (cutting torque). 2. Quantitative measurements on the cutting force during drilling produced the following values: cutting torque--0.4 to 56.5 cm-g with an average of 8.7 cm-g; cutting load--1.7 to 1419.7 gf with an average of 169.3 gf. 3. Bone mineral content at the drilled site ranged from 0 to 0.67 mmAl and averaged 0.19 mmAl.(ABSTRACT TRUNCATED AT 400 WORDS)