Electric knife is convenient for dental treatment, particularly periodontal surgery. However, it is reported that the use to the titanium implant must be avoid. In this study, influence of the stimulus of the electric knife was investigated on the surrounding bone of the titanium (Ti) and hydroxyapatite (HA) implants. Ti and HA implants were inserted into the tibiae of the 16 rats. Six weeks later, the heads of the implants were stimulated by the electric knife and the surrounding bone around implant was investigated at just before the stimulus and 2, 4, 6 weeks after the stimulus. The surrounding bone was damaged by the stimulus of the electric knife in all implants. However, bone contact to the Ti was lost, whereas that to the HA was maintained.

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Gold alloy has been normally chose for fabricating superstructures on dental implants because of easy manufacturing and good fit. The aim of this study was to apply titanium castings for those restoration. Three kinds of commercial investment for titanium (Titavest CB, code:CB, Titanmold, code:TM, T-invest, code:TI) and an experimental calcia mold (code:CaO) were investigated and used for castings. Using a metal die for fabricating the full crown, fit of each MOD crown obtained from investments was evaluated.
Results were as follows:
1. MOD crowns obtained from CaO mold and CB were unnecessary to sandblast due to less reaction at casting. However, fused mold components were observed on the surface of those from TM and TI.
2. CB showed the largest thermal expansion in the investment tested although it was found to contract at setting. The value of total expansion was approximately 2.3%.
3. The thermal expansion of CaO depended on additional expander. In this study, sound castings with an excellent fit were fabricated when the mold was expanded about 1.6%.
4. MOD crowns obtained from commercial investments were not good enough on the fit. It from CB was oversized, and those from TM and TI were undersized.

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From 1994 to 1998, implant installation was done in 15 cases of guided bone regeneration (GBR) combined with autobone graft.
Materials and methods: Fifteen patients, 12 females and three males, age 18 to 65 years old. The patterns of bone defects of the alveolar ridge were divided into a narrow type (ten cases) and a concave type (five cases). The extent of the GBR treatment area was distributed from two-teeth to five-teeth in width.
Surgical procedure:
1. One or two pieces of cortical bone fragment and some chips of cancellous bone were gathered from the mentum or the anterior region of the mandibular ramus.
2. The bone surface of the alveolar ridge was exposed and several small holes were made on the lateral surface by a small drill.
3. The cortical bone was fixed to the lateral wall of the alveolar ridge by a mini-screw.
4. The e-PTFE membrane was fixed to the top of the alveolar ridge by two mini-screws for covering with grafted bone.
5. The space around cortical bone was filled with pieces of cancellous bone and the lower end of the membrane was fixed to the alveolar ridge by mim-screws.
6. Fixtures were installed about six months after the initial GBR surgery.
Evaluation of bone formation was classified into three grades. If enough bone formation beneath the membrane was found, it was evaluated as “ excellent.” If the bone volume was almost the same as that of grafted bone, it was evaluated as “not good.” If absorption or reduction of grafted bone was observed, it was evaluated as “poor.”
Results: In five of 15 cases, no trouble occurred during the entire treatment course until implant installation. In the other ten cases, mucus wounds ruptured and the e-PTFE membrane was exposed after surgery; therefore, the membrane was partially cut and the mucus wound was resutured. In four of ten cases, preimplant surgery rerupture did not occur, but in the other six cases, the membrane was reexposed. Therefore, in four cases, the whole membrane was removed and in two, the whole membrane and a part of the grafted bone, which partially necrosed, were removed. In the concave type to which this GBR method was applied, the incidence of membrane exposure was higher than in the narrow type.
In ten of 15 cases, bone formation was evaluated as “ excellent, ” in three it was “not good,” and in two “poor.” Fixtures could be installed in all of the cases.

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There are many issues involved about subperiosteal implant. One of such issues will be the problem of initial fixation. We have developed a method of penetrating screw fixation with metal framework into jaw bone to solve this problem. By penetrating screw, metal framework is fixed to jaw bone with both labial or buccal and palatal or lingual cortical bones. We enrolled 12 patients (12 maxillas and 1 mandible) who were not able to receive endosseous implant due to severe alveolar bone resorption. The median length of follow-up period of the 12 patients was 11 months. If we define a clinically functioning patient who is symptom-free as a successful case, the 11 months success rate is 100%. All patients could ingest normal diet. Subperiosteal implant of penetrating screw fixation with metal framework into jaw bone has advanced its safety by stable fixation.

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The purpose of this study was to examine the relationships between peri-implant sulcus depth (PISD) variations, results of a Periocheck diagnosis (PCD) test for activity of periodontopathic bacteria in subgingival plaque around peri-implant sulcus and four major factors (i.e., implant placement time, implant cervical form, fixture material and pontic design) of fixed implant prostheses.
Those who participated in this study were a total of 75 patients-31 men (mean age:64.6±8.8 yrs) and 44 women(mean age:58.3±10.2 yrs). All the patients had undergone implant surgery 1 to 17 years before.
In 85.3% of the 75 subjects, peri-implant sulcus depths measured 2 mm or less, which was categorized as PISD_a. Nevertheless, the PCD evaluations were divided into negative and positive reactions,and the results of the Periocheck diagnostic test did not correlate with the PISD evaluation.
When the relationships between PISD distributions and four major factors in fixed prostheses were examined, closed type pontic devices were predominant in those subjects whose peri-implant sulcus depths came under the category of PISD₃.Three other types made up significantly (p＜0.05) larger percentages in the subjects with PISD_a.
Among the sub-factors, the mean PISD value and mean PCD value in the wearers of the rounded(R) cervical type device were 0.51 mm and 0.60 smaller than those in the wearers of the squared(S) cervical type device. The differences were thought to be statistically significant (p＜0.05). The mean PISD value for the sanitary-type pontic devices was also smaller than those for the closed as well as intermediate type devices by a significant 1.76 mm and 0.89 mm, respectively.
From these results, we concluded that closer observation would be necessary as far as the sites where the PISD values are less than 2 mm and their PCD values are positive are concerned.

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We report a case in which osseointegrated implant treatment was utilized to correct missing anterior teeth and severe mandibular bone defects caused by a traffic accident.
X-ray examination revieled severe alveolar bone defects in the anterior part of the mandible, and four metal plates fixed to the mandibular bone by plastic surgery. Since remaining bone height seemed to be sufficient for implant insertion, we intended to perform the dental implant therapy.
The patient was informed about the two different treatment options and informed concent was obtained.
The patient underwent two stage operation using three IMZ implants. Four months after the second operation, the implant supportted prosthesis was placed. Eighteen months after operation, there are no clinical or radiographic signs of bone loss around the implants.

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It is frequently difficult to treat a resorbed edentulous maxilla with a conventional removable prosthesis, and then an application of dental implant is required. We reported a case of a 52-year-old man with a chief complaint of a poorly fitting maxillary full denture where previous dentists tried to restore the case using the fixed implant bridge with 8 ITI and 5 IMZ implants. He had experienced failures of implant treatments two times, but he requested an implant bridge again. We restored his maxilla with an implant-supported fixed detachable prosthesis using 4 Brånemark implants, and also supplementally the remaining other system implants, one ITI and two IMZ implants, previously placed by his dentists.

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Destruction in osseointegrated bone-implant interface occurred due to special torque wrench (STERI-OSS®) after five months reverse-torque failure.
The purpose of this study was to evaluate the wrench action with the torque measurement system. The results were as follows:
1. Measurement of torque wrench action revealed
1) to fast torque speed (0.7s/ratchet point) was 2.894 kgf・cm (28.38 Ncm).
2) to slow torque speed (2.3s/ratchet point) was 3.296 kgf・cm (32.30 Ncm)
2. Measurement of loading torque wrench revaled that slow torque speed was loading more powerful than fast.
The data of torque wrench in companies shows that power of torque wrench classified into three categories.
The most powerful group showed 3.059 kgf・cm (30Ncm) or more, second group showed 2.039～2.957kgf・cm(20～29 Ncm), and least powerful group showed 1.937 kgf・cm (19 Ncm)less.
In our experience, power of torque wrench indicated 3.568 kgf・cm (35 Ncm). The power corresponded to the most powerful group in the company data.
The user must be careful to use the torque wrench.

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In clinical practice, unilateral mandibular free-end edentulous cases are often seen.
However, it has been recognized as a more favorable method to establish a posterior centric stop using implant. Further, it is out of the question when considered from both functional and esthetic viewpoints that the most comfortable prosthesis that patients wish to have would be the fixed one.
In this study, periapical radiographs of implants and surrounding tissues of the remaining natural teeth were examined focusing on 2 typical cases of POI 2-piece type Implant 7 years after placement in order to comparatively evaluate their time-wise changes.
In addition, analyses using“Occluzer” were also performed as to what values of and how the occlusal stresses were loaded on implants and remaining teeth.
The results were as follows:
1. The periapical radiographs of the implant and remaining natural teeth surrounding tissues for up to 7 years after placement suggested that the postoperative course was uneventful without any remarkable changes or abnormal findings such as radiolucency by bone resorption.
2. By the analyses using“Dental Prescale”and “Occluzer”it is considered that the occlusal forces for left and right sides were maintained in good balance. The center of occlusal stresses seemed to be located at ideal position and the mandibular position seemed to be stable.
3. For both the implants-natural teeth occlusion and the natural-natural teeth at opposite sites,almost the same values of occlusal stresses were obtained.
The results demonstrated that the implant supported prostheses were durable enough to play a role in occlusion and considerably efficient masticatory functions were obfained.

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The purpose of the present study was to investigate the actual conditions for oral implant therapy in the Hokkaido region. Self-administered questionnaires were mailed to dentists who belong to the North Japan Oral Implant Society in the Hokkaido region to gather information. A total of 44 of the 134 questionnaires were returned. All completed surveys were analyzed through questionnaires collected from 44 general dentists (32.8 percent).
The participants were asked,“How many implant systems do you use in your clinic？” It was found that the majority of responses was one system (28.6percent), followed by three systems (21.5percent), and two systems (19.0 percent). The most commonly used implant systems were AQB (24.4 percent), followed by ITI (17.8 percent), Calcitek and Paragon (15.6 percent). Porcelain fused to metal crowns were used more than resin veneered crowns on the implant supported prostheses. At the incisor and canine, porcelain fused to metal crowns were commonly used. At the premolar, porcelain fused to metal crowns were more used than full cast crowns. At the molar, full cast crowns were commonly used. The most popular retaining method of the prostheses used by dentists was cement retaining, followed by screw retaining, and temporary retaining. The results of this survey suggested that the aesthetic treatment is important in latel implant therapy.

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