Optical impression method to measure three-dimensional position and orientation of dental implants using an optical tracker

OBJECTIVES

The aim of this study was to devise an optical impression method that could make impressions of dental implants accurately and rapidly.

MATERIALS AND METHODS

Four paper markers (4 × 3 mm, 8 × 6 mm, 16 × 12 mm, and 24 × 18 mm) and one titanium marker (8 × 6 mm) were prepared to determine the measuring accuracy of the three-dimensional optical tracker. For a proposed and conventional impression taking method, we compared the reproduction accuracies of the positions and orientations of dental implants and the times to obtain impressions. Finally, we fabricated computer-aided designing (CAD)/computer-aided manufacturing (CAM) superstructure frameworks to determine the adaptation accuracy.

RESULTS

The 8 × 6-mm titanium marker was optimal among the prepared markers. Dental implants made by the proposed and conventional impression taking methods had measurement errors of 71 ± 31 μm and 32 ± 18 μm, respectively. The proposed method took a significantly shorter time to obtain an impression than did the conventional method. The connection between the CAD/CAM superstructure frameworks and four implant analogs had uplifts of 55 ± 10 μm, 94 ± 35 μm, 2 ± 1 μm, and 66 ± 3 μm.

CONCLUSION

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.

Application of virtual reality force feedback haptic device for oral implant surgery

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.

A novel method of removing artifacts because of metallic dental restorations in 3-D CT images of jaw bone

CT images, especially in a three-dimensional (3-D) mode, give valuable information for oral implant surgery. However, image quality is often severely compromised by artifacts originating from metallic dental restorations, and an effective solution for artifacts is being sought. This study attempts to substitute the damaged areas of the jaw bone images with dental cast model images obtained by CT. The position of the dental cast images was registered to that of the jaw bone images using a devised interface that is composed of an occlusal bite made of self-curing acrylic resin and a marker plate made of gypsum. The patient adapted this interface, and CT images of the stomatognathic system were filmed. On the other hand, this interface was placed between the upper and lower cast models and filmed by CT together with the cast models. The position of the marker plate imaged with the dental casts was registered to those adapted by the patient. The error of registration was examined to be 0.25 mm, which was satisfactory for clinical application. The damaged region in the cranial bone images as an obstacle for implant surgery was removed and substituted with the trimmed images of the dental cast. In the method developed here, the images around the metallic compounds severely damaged by artifacts were successfully reconstructed, and the stomatognathic system images became clear, and this is useful for implant surgery.

3D Shape Measurement of Dental Casts Using Medical X-ray CT

Three-dimensional (3D) digitizing and computerization of dental casts is a trend in dentistry especially for orthodontics to substitute stone casts. Generally used laser scanners have a blind side in the measurement of undercuts. As alternative equipment that can digitize regardless of the undercut, the potential of recent multi-slice medical CT was examined. In 3D shape reconstruction, the CT window level affects the size of the object. It was examined, and a CT window level of 800 was found to be suitable. However, the size became slightly smaller than the real object. Then, a correction ratio of 1.002, 1.015 and 1.013 on the X-, Y- and Z-axis was given, and error within 0.08% was accomplished. The measurement and 3D imaging of dental casts was completed within 10 min. The reproducibility of the complicated morphology of dental casts was slightly inferior to that of the latest laser scanners, but the accuracy and operationality regardless of the undercut is noteworthy for clinical application.

Purification of ferredoxins and their reaction with purified reaction center complex from the green sulfur bacterium Chlorobium tepidum

Four ferredoxin (Fd) fractions, namely, FdA-D were purified from the green sulfur bacterium Chlorobium tepidum. Their absorption spectra are typical of 2[4Fe-4S] cluster type Fds with peaks at about 385 and 280 nm and a shoulder at about 305 nm. The A(385)/A(280) ratios of the purified Fds were 0.76-0.80. Analysis of the N-terminal amino acid sequences of these Fds (15-25 residues) revealed that those of FdA and FdB completely agree with those deduced from the genes, fdx3 and fdx2, respectively, found in this bacterium (Chung and Bryant, personal communication). The N-terminal amino acid sequences of FdC and FdD (15 residues) were identical, and agree with that deduced from the gene fdx1 (Chung and Bryant, personal communication). The A(385) values of these Fds were unchanged when they were stored for a month at -80 degrees C under aerobic conditions and decreased by 10-15% when they were stored for 6 days at 4 degrees C under aerobic conditions, indicating that they are not extremely unstable. In the presence of Fd-NADP(+) reductase from spinach, and a purified reaction center (RC) preparation from C. tepidum composed of five kinds of polypeptides, these Fds supported the photoreduction of NADP(+) at room temperature with the following K(m) and V(max) (in micromol NADP(+) micromol BChl a(-1) h(-1)): FdA, 2.0 microm and 258; FdB, 0.49 microM and 304; FdC, 1.13 microM and 226; FdD, 0.5 microM and 242; spinach Fd, 0.54 microM and 183. The V(max) value of FdB was more than twice that previously reported for purified RC preparations from green sulfur bacteria.

Electron transfer kinetics in purified reaction centers from the green sulfur bacterium Chlorobium tepidum studied by multiple-flash excitation

Reaction center preparations from the green sulfur bacterium Chlorobium tepidum, which contain monoheme cytochrome c, were studied by flash-absorption spectroscopy in the near-UV, visible, and near-infrared regions. The decay kinetics of the photooxidized primary donor P840(+), together with the amount of photooxidized cytochrome c, were analyzed along a series of four flashes spaced by 1 ms: 95% of the P840(+) was reduced by cytochrome c with a t(1/2) of approximately 65 micros after the first flash, 80% with a t(1/2) of approximately 100 micros after the second flash, and 23% with a t(1/2) of approximately 100 micros after the third flash; after the fourth flash, almost no cytochrome c oxidation occurred. The observed rates, the establishment of redox equilibrium after each flash, and the total amount of photooxidizable cytochrome c are consistent with the presence of two equivalent cytochrome c molecules per photooxidizable P840. The data are well fitted assuming a standard free energy change DeltaG degrees of -53 meV for electron transfer from one cytochrome c to P840(+), DeltaG degrees being independent of the oxidation state of the other cytochrome c. These observations support a model with two monoheme cytochromes c which are symmetrically arranged around the reaction center core. From the ratio of menaquinone-7 to the bacteriochlorophyll pigment absorbing at 663 nm, it was estimated that our preparations contain 0.6-1.2 menaquinone-7 molecules per reaction center. However, no transient signal due to menaquinone could be observed between 360 and 450 nm in the time window from 10 ns to 4 micros. No recombination reaction between the primary partners P840(+) and A(0)(-) could be detected under normal conditions. Such a recombination was observed (t(1/2) approximately 19 ns) under highly reducing conditions or after accumulation of three electrons on the acceptor side during a series of flashes, showing that the secondary acceptors can stabilize three electrons. From our data, there is no evidence for involvement of menaquinone in charge separation in the reaction center of green sulfur bacteria.

[Protection of cultured mammalian cells by rebamipide]

Rebamipide which is used as a drug for gastritis and stomach ulcer has large capability for OH radical scavenging. It is expected that rebamipide has protective effect against ionizing radiations. The present paper deals with protective effect of rebamipide for cultured mammalian cells exposed to ionizing radiations. As rebamipide is insoluble in water, three solvents were used to dissolve. Rebamipide dissolved in dimethyl sulfoxide (DMSO), dimethyl formamide (DMFA) and 0.02 N NaOH was added to the cells in Eagle's minimum essential medium (MEM) supplemented with 10% fetal calf serum and the cells were irradiated with X-rays. After irradiation, the cells were trypsinized, plated in MEM with 10% fetal calf serum and incubated for 7 days in a CO2 incubator to form colonies. Rebamipide dissolved in 0.02 N NaOH exhibited the protective effect expected its OH radical scavenging capability. However, the protective effect of rebamipide dissolved in DMSO was about half of that expected by its radical scavenging capability and that of rebamipide dissolved in DMFA was not observed. Uptake of rebamipide labeled with 14C increased with increasing contact time with rebamipide. These rebamipide mainly distributed in nucleous rather than cytoplasm.

Electronic and vibrational structure of the radical cation of P840 in the putative homodimeric reaction center from Chlorobium tepidum as studied by FTIR spectroscopy

Light-induced FTIR difference spectra of P840 upon its oxidation (P840+/P840) have been measured with the reaction center complex from the green sulfur bacterium Chlorobium tepidum. A broad band centered near 2500 cm-1 was observed in P840+, which is comparable to the band near 2600 cm-1 previously observed in P870+ of purple bacteria and assigned to the electronic transition in the bacteriochlorophyll a (BChla) dimer (Breton et al. (1992) Biochemistry 31, 7503-7510]. The intensity of this electronic band found in P840+ was about the same as that in P870+. The P840+ spectrum also showed several intensified vibrational modes, which are characteristic of the P870+ spectrum as well. These similar features of the electronic transition and the intensified lines indicate that P840+ is a BChla dimer whose electronic structure is similar to P870+. Based on the previous theoretical works, the possibility that P840+ has an asymmetric structure as P870+ was suggested. Also, two strong positive bands at 1707 and 1694 cm-1 probably assigned to the keto C9 = O stretching modes of P840+ were observed in the P840+/P840 spectrum. Three different interpretations are possible for the presence of the two C9 = O bands: (i) P840+ is an asymmetric dimer cation. (ii) P840+ has a symmetric structure, and the time constant of positive charge exchange between the two BChla molecules coincides with that of IR spectroscopy (10-13 s). (iii) The electric field produced by the positive charge on P840+ affects the C9 = O frequency of the neutral BChla in P840+ itself (when the charge exchange time is slower than the time scale of 10-13 s) or of a BChla in the close proximity of P840+. The negative bands at 1734 and 1684 cm-1 were assigned to the ester C10 = O and the keto C9 = O of neutral P840, respectively, both of which are free from hydrogen bonding. These results and interpretations regarding the structural symmetry and the molecular interactions of P840 and P840+ are discussed in the framework of the "homodimeric" reaction center of green sulfur bacteria.

Large sequential outbreaks caused by influenza A (H3N2) and B viruses in an institution for the mentally handicapped

During the mixed epidemic caused by influenza A (H3N2) and B in the 1992-1993 season in Japan, large sequential outbreaks occurred in an institution for mentally handicapped people where none of the residents or staff members had been immunized. During the influenza A outbreak (A/ Beijing/32/92-like strain) in January, 37.0% of the residents (85/230) and 31.4% of the staff (75/239) had an influenza-like illness. During the influenza B outbreak (B/Panama/45/90- and B/Beijing/184/ 93-like strain) in late February, 59.0% of the residents and 24.3% of the staff had an influenza-like illness. As many as 25.2% of the residents had two episodes of influenza-like illness during the season, as opposed to only 5.4% of the staff members. Mixed epidemics probably have a severe impact on institutionalized high-risk people, adversely affecting them almost twice as much as influenza epidemics caused by a single virus.

Spectroscopic studies of bound cytochrome c and an iron-sulfur center in a purified reaction center complex from the green sulfur bacterium Chlorobium tepidum

Flash-induced optical kinetics at room temperature of cytochrome (Cyt) c 551 and an Fe-S center (CFA/CFB) bound to a purified reaction center (RC) complex from the green sulfur photosynthetic bacterium Chlorobium tepidum were studied. At 551 nm, the flash-induced absorbance change decayed with a t 1/2 of several hundred ms, and the decay was accelerated by 1-methoxy-5-methylphenazinium methyl sulfate (mPMS). In the blue region, the absorbance change was composed of mPMS-dependent (Cyt) and mPMS-independent component (CFA/CFB) which decayed with a t 1/2 of ∼400-650 ms. Decay of the latter was effectively accelerated by benzyl viologen (Em -360 mV) and methyl viologen (-440 mV), and less effectively by triquat (-540 mV). The difference spectrum of Cyt c had negative peaks at 551, ∼520 and ∼420 nm, with a positive rise at ∼440 to ∼500 nm. The difference spectrum of CFA/CFB resembled P430 of PSI, and had a broad negative peak at 430∼435 nm.

Ocular distribution of carteolol after single and repeated ocular instillation in pigmented rabbits

To investigate the distribution and elimination of carteolol in pigmented rabbits, 14C-carteolol eye drops were instilled singly and repeatedly. After single ocular instillation, the radioactivity in the iris and ciliary body reached maximum levels at 24 h. The elimination rate of pigmented tissues decreased at a half-life of approximately 15 days. The concentration of radioactivity in pigmented tissues increased markedly by repeating the ocular instillation and reached a maximum after the 80th repeated instillation. The concentration of radioactivity at 1 h after 80th instillation was 63.7 times that in the iris, 61.1 times that in the ciliary body and 17.2 times that in the retina & choroid after single instillation. No accumulation of radioactivity was found in other ocular tissues.

[Injury of the coronary artery following non-penetrating chest trauma--a case report]

A previously healthy 71-year-old man sustained a non-penetrating chest trauma. The chest CT scan revealed cardiac tamponade and then emergent operation was performed. We opened the pericardium through median sternotomy and found a laceration of the distal left anterior descending coronary artery (seg. 8). We ligated the artery and he showed signs of a limited myocardial infarction on the postoperative ECGs, but echocardiography revealed symmetric contraction and normal ejection fraction. His postoperative course was uneventful. We think that injuries of distal coronary arteries could be successfully ligated.