To analyse the mechanism of apical epithelialization at the implant/tissue interface, the cell contact and adhesive strength of epithelial like cells (ELC) and fibroblastic cells (FLC) derived from human gingival tissue to evaporated titanium film were investigated under four different medium conditions containing plaque extracts:no filtered (original plaque extract), 5.0 μ m-Millipore filtered, 0.45 μm-Millipore filtered, and 0.05 μm-Millipore filtered.
The plaque extracts had a greater effect upon decreasing the growth rate of the FLC cells compared to the ELC. The ELC exhibited greater adhesive strength compared to FLC in the medium with four plaque extracts. These differences in the cellular responses of both cells to the plaque extracts were also observed in their morphological changes by using phase contrast microscopy.
The 0.05 μm-Millipore filtered plaque had no decreasing effect upon the growth rate and adhesive strength, although the no filtered, 5.0 μm-Millipore filtered and 0.45 μm-Millipore filtered plaque extracts significantly demonstrated clear evidence of the decreasing effects. It was thus revealed that apical epithelialization develops by symbiosis of microorganisms including virus and both cells.

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The aim of this study was to assess the efficacy of chlorine dioxide (ClO₂) gas against Porphyromonas gingivalis strain smeared on three different materials for experimental purposes. The experimental materials comprised titanium implant fixtures (TIFs) (Steri-Oss ®threaded implant, 3.8 mm in diameter, 13 mm in length), titanium pellets (TPs) (4 mm in diameter, 1 mm in thickness) and paper disks (PDs) (5.6 mm in diameter, 1.1 mm in thickness). The microorganism used in this study was anaerobic Porphyromonas gingivalis ATCC 33277 strain. P.gingivalis-tainted TIFs (TPs/Pds) were inserted into the test tube to dilute the P.gingivalis broth to 10^-1–10^-9 concentration. TIF (TP/PD) polluted with P.gingivalis was transferred to sterile Petri dishes with the cover removed, and exposed to CIO₂ gas with concentrations of minimum 1 ppm to maximum 6.5 ppm in a door-closed and sealed room (7.4 m³) for 60 minutes each. Then, the TIF (TP/PD) placed in Petri dishes was put into a test tube containing sterilized BHI (Brain Heart Infusion) broth and cultured for 48 hours at 37℃. The degree of antimicrobial effect on P.gingivalis was determined based on macroscopic assessment of the extent to which the broth in the test tubes became turbid.
P.gingivalis on TIFs in the 10^-1to 10^-6 dilution group did not perish completely even when exposed to 6.0–6.5 ppm ClO₂ gas. On the other hand, P.gingivalis on TPs and PDs were destroyed regardless of the dilution group by exposure to concentrations of 5 ppm and 3 ppm CIO₂ and above in the same room, respectively.
The results showed that higher concentrations over 6.5 ppm ClO₂ gas were needed to kill all the P.gingivalis ATCC 33277 cells growing on the implant fixtures than those on the other two materials. Therefore, it is suggested that for materials having a smooth surface and/or a plain form, the open method is effective in order to disinfect tools and implant materials contaminated with P.gingivalis, but is inadequate in latter materials having a complicated form.

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Objective: Various types of implant-supported overdentures have been developed as prosthetic treatments for edentulous patients. However, comparison of the treatment outcomes among the complete dentures has not been sufficiently examined, because oral conditions such as denture-supporting tissues differ markedly. Previously, these differences were assessed using X-ray CT and cast measurements, but these techniques are complicated and not widely used.
This study compared treatment outcomes of implant-supported overdentures using magnetic and bar attachment with complete dentures using chair-side functional evaluation charts by matching of age, sex, duration of denture usage, and denture-supporting tissues.
Methods: Ten patients with implant-supported overdentures (IOD group, mean age:60.8, sex:3 men and 7 women, duration of denture usage:27.0 months) and 35 patients with complete dentures (mean age:71.7. sex 15 men and 20 women, duration of denture usage:38.1 months) participated in this study. First, in both groups, the chair-side functional evaluation charts were used to compare treatment outcomes in relation to ①complete denture quality,②chewing function, and③overall satisfaction. Next, ten subjects (CD Group) out of the 35 complete denture patients were selected who were matched for the four items (age, sex, duration of denture usage, and denture-supporting tissues) to the IOD Group. Denture-supporting tissues were quantitatively assessed (0-100) with an examination protocol. Lastly, these scores of CD and IOD groups were compared using the Student's t-test and chi-squared test.
Results: Denture supporting tissue scores of the 35 complete denture patients and IOD Group were 36.6 vs.20.0 points. The average fit for the above four items of the 35 complete denture patients and IOD Group was 70.1%.
The average fit for the above four items of the CD group selected from the 35 complete denture patients (mean age:65.3, sex:3 men and 7 women, duration of denture usage:24.2 months and denture supporting tissue score:20.1 points) and IOD Group was very good (95.4%).
Overall satisfaction scores of the 35 complete denture patients and IOD Group indicated no difference. However, complete denture quality score (93.9), chewing function score (77.0), and overall satisfaction score (80.8) of the IOD Group were higher than those of the CD Group (67.3, 38.5, 54.7) (p＜0.05).
Conclusion: In this study, the matching test including an assessment of denture supporting tissue made it possible to compare treatment outcomes of implant-supported overdentures using magnetic and bar attachment with complete dentures. Furthermore, it was clarified that treatment outcomes of the IOD Group were higher than those of the CD Group.

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The clinical measurement of implant stability is very important for predicting the success of implants. Resonance frequency analysis (RFA) has been reported as a method of measuring implant stability as a non-invasive procedure. The aim of this study was to evaluate the correlation between cortical bone thickness, bone mineraldensity (BMD) and RFA value.
After measuring the thickness and BMD of pig's mandibular cortical bone by quantitative computed tomography, 20 screw-shaped dental implants were installed, then RFA was examined. The correlation between different parameters was statistically analyzed.
The results were as follows.
1. Relatively high RFA value was obtained even in the case of a small bone-implant contact.
2. The RFA value was not correlated with the thickness of the cortical bone.
3. The RFA value was correlated significantly with the BMD of the cortical bone.
These results indicate that BMD of the cortical bone predominantly affects initial stability of the implant.

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Human bone marrow derived mesenchymal stem cells (hMSC) have the ability to differentiate into osteoblasts. It has been emphasized that MSC should be used for osseointegrated dental implant therapy. It has been reported that insulin-like growth factor-II (IGF-II) and insulin-like growth factor binding proteins (IGFBP-2) were useful for osteoporosis through increase of bone mineral density. Although the actions of IGF-II and IGFBP-2 have been studied, differentiation of hMSC into osteoblasts is poorly understood. To identify genes involved in the commitment of hMSC differentiation into osteoblasts, gene-expression changes were examined in hMSC cultured with osteogenic induction medium using the Affymetrix Gene Chip analysis system. As expected, IGF-II and IGFBP-2 mRNA levels were elevated during the differentiation process. Furthermore, those gene expression changes were successfully confirmed by real-time polymerase chain reaction (PCR) and endpoint-PCR. Thus, gene expression profiling of in vitro differentiation cultures of hMSC using Gene Chip analysis should be useful for defining the lineage-specific differentiation of hMSC into osteoblasts. Since the stimulation of differentiation and transplantation of hMSC will be useful and a significant approach for the development of bone tissue regeneration, our findings suggest a novel anabolic treatment using IGF-II/IGFBP-2 for dental implant therapies.

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A new Video Overlay Monitoring System (VOLMS) has been developed to secure safe implant placement environments, through accurate monitoring and recording of the patients, where the operators are responsible also for the whole body control of the patients. In preparation for this research, the system has been set to output the display values on BP-88 (a monitor manufactured by Colin Medical Technology Corporation) as serial data and electrocardiogram (ECG) as analog data. The system is configured with an H8-type microprocessor (Hitachi,Ltd.) and a display controller. ECG is converted from analog to digital at the sampling rate of 1.25 msec to meet the sampling theorem and scrolled for display lasting 6 seconds on a zonal area at the resolution of 480×64 dots.The software has been programmed to proactively support the decision-making process of the operators through audio-visual aids and controls in monitoring the implant placements.
Prior to utilizing the system in a clinical setting, we ran a simulation by entering pseudo living body information into data and function generators, and then analyzed the response data on the display. As a result, it has been confirmed that the system operates properly in simulated settings, showing reasonable values for both vital signs and ECG. With preoperative and alarm level values preset, the system displays a stable mark if the measured values are proximate to the preoperative values or an advisory mark if they show a slight change. If the measured values exceed the alarm level values, the system automatically switches to the remeasurement mode and lists values including the current and preoperative values, the upper and lower limit alarm values and a rate of change for RPP (Rate Pressure Product)over its preoperative value.
In times of alarm or predefined statuses, the system changes the colors on the display and activates an audio guidance function. The data recorded on paper and shown on the display during the monitoring has verified that the variance in similarities of ECG falls within±5%. The system has proved useful in clinical testing as well, having precisely traced abnormal conditions like ventricular extrasystole and atrial fibrillation. Specifically, it was extremely helpful in sinus lift, promptly and accurately reflecting the conditions of the patients. Thus, the system has proved to be effective in improving safety during implant placements and providing information valuable for a variety of researches.

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We prepared two types of bone defect fillers (BDFs) which were made from a mixture of α-tricalcium phosphate (α-TCP) with chitosan or alginate in solution. A solidifier was added to the mixtures. These solutions were then kneaded to be solidified. The solid substances, named chitosan-BDF and alginate-BDF, were implanted in femurs of guinea pig to study the effects of the BDFs on the processes of bone formation by EPMA.
The alginate-BDF was surrounded with growing bone from all directions at 6 months after the operation and seemed to have an affinity to the tissues. However, no degraded or absorbed form of the BDF was observed.
In contrast, most of the chitosan-BDF was replaced by growing bone at 6 months. The adjacent part of the BDF to surrounding cortical bone was especially well-absorbed, probably due to being involved in a reabsorption process after ossification.
According to the data, both BDFs were shown to have excellent mechanical properties for filling bone defects. Especially, the chitosan-BDF would be useful as bone defect filler because of its induction of ossification and its smooth absorption.

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The aim of this study was to estimate the relationship between jaw bone density and total bone density.
The subjects used were patients who desired implant treatment and who were inspected through pre-operative CT examinations. The number of patients was 19. In the maxilla, bone mineral density (BMD) was measured at the cancellous bone between the nasal cavity and the maxillary sinus. In the mandible, BMD was measured at the cancellous bone beneath the mental foramen.The CT numbers were corrected by the QCT method. The bone mineral content of the total body was obtained byΣGS/D through microdensitometry and OSI (Osteo Sono-assessment Index) through QUS(Quantitative Ultrasound).
The following results were obtained.
1. BMD (total of maxilla and mandible) was significantly correlated with OSI.
2. BMD (total of maxilla and mandible) was significantly correlated withΣGS/D.
3. OSI was significantly correlated withΣGS/D.
From the above results, it was concluded that jaw bone density reflected the changes of the total bone density.

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For imaging diagnosis before dental implant treatment,conventional X-ray tomography or computed tomography (CT) has been used. Recently, multislice helical CT has been developed, and detailed two-dimensional (2-D) and three-dimensional (3-D) reconstructed images can be obtained. Double oblique reconstructed images, which are a kind of 2-D image, can be set for free angles of the axial CT plane.
In this investigation, the usefulness of double oblique reconstructed images was assessed for measurement of the mandibular height at the designed implant site.
Subjects included 22 patients with mean age of 56.1 years and the number of designed implant sites in the posterior mandibular region was 73. Mandibular height at the designed sites was measured from the alveolar crest to the superior border of the mandibular canal using multi-planar reconstructed images and double oblique reconstructed images.
As a result, the mean of differences between multi-planar reconstructed images and double oblique reconstructed images was 1.0 mm. This was significantly different from the designed sites over 15 degrees of mesio-distal angle in sites ranging from 0 to 5 degrees (p＜0.01).
It was concluded that the double oblique images were useful for accurate measurement of bone height in the designed implant sites.

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The retentive force of a clip was found to be proportional to its length in experimental results using 10 new CM bars®. The attachment and detachment cycle of the clip repeated 10,000 times resulted in about a 45.9% decrease in the retentive force with no effect of its length. The gradient of S-N (strength vs. number of cycles) curve for the clip of 2-mm length decreased steeply at about 900 repeated cycles and those for clips of 3-mm, 4-mm and 5-mm lengths decreased similarly at about 400 repeated cycles. The spring action of the clip was reduced as a result of these repeated cycles in addition to the normal strength-loss due to metal fatigue. The ones over 3 mm in length still showed a retentive force stronger than 4.90 (N) which was required for the bar attachment after 10,000 repeated cycles. Consequently, the retentive force of the 2-mm length clip seemed to be weak for clinical use, and we should employ a clip of at least 3 mm or longer.

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The purpose of this study was to determine whether clinical success can be achieved with immediate loading in the edentulous maxilla and mandible with Brånemark implants (Nobel Biocare, Goteborg, Sweden) at one year after placement of the implants.
The study sample consisted of 18 patients who were edentulous or about to lose all remaining teeth. A total of 118 fixtures were placed in 7 maxillae and 12 mandibles, including one bimaxillary patient. Ninety seven of the 118 fixtures were immediately loaded and 21 fixtures were submerged. Five to 7 fixtures (mean of 5.9 fixtures) supported the prostheses in the maxilla and 4 or 5 fixtures (mean of 4.7 fixtures) in the mandible. All fixtures immediately loaded were placed in the incisor and premolar regions of both maxilla and mandible. The mean lengths of the fixtures in the maxillae and mandibles were 14.8±1.8 mm and,15.6±2.6 mm, respectively.All of 41 immediate loading fixtures in the maxillae showed a placement torque of more than 35 Ncm. Although 5 of 56 fixtures in the mandibles showed a placement torque of 30 Ncm, remaining fixtures showed more than 35 Ncm. Provisional implant-supported fixed prostheses were fabricated in a laboratory from an impression and were placed on the next day after surgery. After a 4-to 7-month healing period, a definitive prosthesis was fabricated and placed. One implant, although still osseointegrated, was removed owing to bone resorption. In the patient, the provisional prosthesis was supported by 4 remaining fixtures;thus the cumulative survival rates for fixtures and prostheses were 99.0%and 100%, respectively, after one year.
This clinical report suggests that immediate loading of implant-supported fixed prostheses in the edentulous maxilla and mandible can be a safe and successful treatment as long as patients are carefully and strictly selected.

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The purpose of this study was to evaluate the clinical results of implant-supported prostheses following mandibular reconstruction for segmental resected defect. Six patients with mandibular segmental defect were studied in this series. All patients underwent mandibular reconstruction by combination with titanium meshtray and graft of particulate cancellous bone and marrow (PCBM) harvested from bilateral posterior iliac crests. About 6 months later, the titanium mesh tray was removed and fixtures were installed in the non-resected and/or reconstructed mandible. About three to four months later, the abutments were connected. Approximately two weeks after the abutment connection, implant-supported prostheses were fabricated. Masticatory function and speech function were evaluated one month after placement of the implant-supported prostheses. Resorption of the marginal bone around the fixtures was evaluated annually by means of radiographic images.
There was no serious postoperative complication related to the mandibular reconstructive surgery.Twenty-seven fixtures except two were osseointegrated. All patients wore implant-supported overdentures or fixed prostheses, and excellent occlusal reconstruction was completed. There was no complication during the follow-up period.
These results suggest that implant-supported prosthesis following mandibular reconstruction by combination with titanium mesh tray and iliac PCBM graft is useful for oral rehabilitation in patients with mandibular segmental defect.

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Endosseous implant of the mandible has been accepted as an alternative prosthetic treatment for edentulous patients. Unless an exact examination of the jawbone and the general condition is completed and an appropriate implant system is selected, the treatment will be unsuccessful. Herein we report a case of fracture of a highly absorbed mandible possibly due to dental implantation for a patient with osteoporosis.
A 78-year-old female was referred to our hospital for swelling of the left mandibular body region. X-ray showed remarkable atrophy of the mandible and a fracture line along the endosseous implants. The patient was diagnosed as osteoporosis of moderate grade based on measurement of the bone mineral density. The implants were removed, and after the granulation tissue of sockets was removed, the mandible was repositioned and fixed with titanium mini plates.
The prognosis of the fracture was satisfactory. A total denture was made 10 months after surgery by a dentist referred to our hospital.

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The rapid prototyping technique using the binder jet method has recently been established. We investigated the accuracy of the full-scale bone model from CT image data using the binder jet method and discussed its clinical usefulness for dental implants.
Starch and plaster models in three dry mandibles were processed respectively and the accuracy of their size was investigated. The results showed that the accuracy and the reproducibility of two types of models were high enough to be used in dental implant treatment.
As clinical applications, a starch model of maxilla was processed to simulate implant placement surgery. Another plaster model of mandible was processed as the working model to make a surgical template for implant placement.
The starch model was extremely useful for simulating implant operations because the hardness of the model was suitable for using real surgical instruments. To construct an accurate working model for a surgical template, we combined a plaster model of a mandible body with a cast model of a tooth crown from an impression of dentition. The position and direction of implant placement were then designed based on this hybrid model. As the operation succeeded, it is suggested that the plaster bone model is useful in dental laboratory works such as surgical template making.

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