A novel support system for implant surgery was tried out, which involves manipulating a three-dimensional (3-D) computed tomography (CT) image of a jawbone with a virtual reality force feedback haptic device. Through this virtual system, the haptic experience of bone drilling with vibration and the sound of the contra-angle handpiece could be realized. It is expected to be useful for training inexperienced dentists and educating dental students. The simulation of oral implant insertion was also focused on. A simple cylindrical implant model was inserted into a 3-D image of the jawbone by operating the haptic device, with consideration of bone condition. A rectangular solid object that served as a bone-supported surgical template was adopted, and the shapes of the bone and the implant were subtracted from the object. In this manner, the CAD of the surgical template with impressions of the bone and the implant guide holes for insertion was realized. The surgical template was milled with a computer-controlled milling machine (CAM). Surgical template accuracy was examined with an edentulous gypsum bone model having six holes for implant insertion. Simulation of the oral implant insertion and CAD/CAM of the surgical template were conducted. The milled surgical template was fitted on the gypsum bone model, and CT images were taken. Cross-sections of the guide holes in the surgical template were imaged, and misalignment between the guide holes of the surgical template and the drilled holes on the jawbone was measured. The average misalignment is less than 0.2 mm, and it indicates that the present system is potentially applicable to oral implant surgery.

The generation and the reaction of 8-copper(II) ketones via electrophilic ring opening of siloxycyclopropanes with copper(II) tetrafluoroborate (CuiBF^) were studied. Treatment of siloxycyclopropane with Cu(BF4)2 resulted in desilylative dimerization to give a 1,6-diketone in good yield. The ring opening took place regioselectively across the bond between the methylene and siloxy carbons. The reaction is reasonably interpreted by assuming the electrophilic ring opening by cupric ion to form 8-copper(II) ketone and trimethylsilylfluoride, followed by dimerization. With dimethyl acetylene dicarboxylate (DMAD) and water, 8-(acyl)alkyls were captured to give dimethyl 2-(3-oxoalkyl)maleate with high degree of stereoselectivity. The stereoselective transfer of 8-(acyl)alkyl arises from syn addition across the triple bond followed by in situ protonation of the resulting vinylcopper species with retention of configuration. The stereoselective transfer of 8-(acyl)alkyls to acetylenic sulfones, which gives 8-(acyl)alkylated vinylic sulfones, was also successful.Since their first appearance in the early 1970s,* 1 siloxycyclopropanes 1 have been widely investigated, and a variety of synthetically useful transformations have been developed ,2 Some of the remarkable aspects of siloxycyclopropane chemistry are based on the metal-induced ring-opening reactions (eq 1), which give stable or intermediary 8-metal-substituted ketones 3, organometallics having considerable synthetic potential.3 4The reaction results in the loss of the trialkylsilyl moiety as a cationic leaving group and site-selective ring cleavage of bond a is observed in the case of l-siloxybicyclo[n. 1.0] alkanes. This regioselectivity may be explained by attack of a metal ion at the least hindered site or by the formation of a metalacycle. Nakamura, Kuwajima, and co-workers have reported some impressive achievements in the ring-opening reaction of 1 -alkoxy-1 -siloxycyclopropanes with metal salts to give 8-metallo esters.3b-d Some of these function as versatile ß-carbanion of esters.* Due to the electron donation by the extra alkoxy group, a large number of metal salts are able to cleave the cyclopropane ring, compared to simple siloxycyclopropane 1. However, it should be noted that the reactivities of siloxycyclopropanes and 1-alkoxy-1-siloxycyclopropanes with the same metal salt are not uniformly equivalent.5

Our proposed method and fabricated titanium markers enabled us to measure the positions and orientations of dental implants both accurately and rapidly. We then used the reproducible measurement results for the positions and orientations of the dental implants to fabricate CAD/CAM superstructure frameworks within an acceptable accuracy range.

The present simulation and drilling support using the surgical template may help to perform safe and accurate implant surgery.

To enable accurate implant placement and precise drilling following preoperative simulation, we developed the BoneNavi system. To realize more precise drilling when the holes are upsized, two methods of surgical guiding were attempted in the present study. One involved using multiple surgical guides with titanium tubes of different diameters, and the other involved using a single surgical guide but employing titanium drill guide tubes with different diameters. Drilling accuracy of the two newly developed methods was examined and compared with the results of drilling into a pig bone using only the initial surgical guide. Deviations of the position and angle with the two novel methods were similar: 0.17 mm and 1° respectively. As for the control group whereby drilling was done using only the initial surgical guide, the deviations were 0.25 mm and 3.50° -which were significantly larger than those achieved with the two novel methods. In light of the results obtained, our newly developed BoneNavi system is especially applicable for severe clinical cases that require precise implant placement.