A human dentin after teeth extraction was demineralized for recycle use, and its efficacy as a carrier matrix for recombinant human bone morphogenetic protein-2(rhBMP-2) was evaluated histomorphometrically. The shape of demineralized dentin matrix (DDM) was prepared as a particle, and its size varied from 400 to 800μm. In 50 male Wistar rats, the dose-response and time-course of bone induction by rhBMP-2, in 70 mg of DDM in subcutaneous tissue, was estimated. The rhBMP-2/DDM induced bone and cartilage in a dose dependent manner (0, 0.5, 1.0, 2.0, 5.0μg of rhBMP-2). Histological examination in the time‐course study showed that the BMP-2(5.0μg)/DDM (70 mg) induced active bone and cartilage formation between particles of DDM, while the DDM (70 mg) alone resulted in the accumulation of undifferentiated mesenchymal cells and fibroblasts. The morphometric analysis demonstrated that the BMP‐2/DDM showed 66.9% in the volume of bone and marrow, and 32.4% in that of DDM at 8 weeks.
These results indicate that the DDM derived from extracted human teeth may be recycled as a carrier matrix for rhBMP‐2. It provides a cell‐anchorage for differentiation of chondro‐osteogenic cells and is absorbed as bone matures.
Evaluation of jawbone quality and quantity is very important for successful implant treatment. Especially, computed tomography is very useful in pretreatment examination.
The purpose of this study was to evaluate bone mineral densities (BMD) in mandibular unilateral free end saddle patients, with quantitative computed tomography (QCT). Trabecular and cortical BMD of 14 patients (7 males and 7 females), of ages 40 to 60 years, were measured using QCT (CT numbers ＜ 500 HU:trabecular bone, CT numbers＞500 HU:cortical bone). The statistical difference between two groups was estimated using a 2-sample t-test.
The obtained results were as follows.
1. Trabecular BMD of the defect site was significantly higher than trabecular BMD of the no defect site.
2. No significant difference was seen between cortical BMD of the defect and no defect sites.
3. Male trabecular BMD was significantly higher than female trabecular BMD.
4. No significant difference was seen between male cortical BMD and female cortical BMD.
Conclusively, it would be important to consider these tendencies of mandibular BMD in important treatment.
Purpose:In an attempt to evaluate osseointegration of an implant body, a comparison was done on the influence of differences in the material of the superstructure body, on the results of vibration analysis.
Materials and Methods:The measurement sample was a model in which a fixture had been implanted in super-hard plaster. A manufactured conical abutment (CA) and a gold UCLA abutment were placed in the top of the same metal frame. Then, a super porcelain AAA(PFM),Estenia(ES), and UNIFASTⅡ(UⅡ),manufactured for the superstructure body in the form of a mandibular small molar, was connected by torque according to the directions of the manufacturer. The conical abutment was then connected with the fixture. The sample in which the superstructure body was connected with the screw,was the CA. The sample in which the superstructore body was made, was connected with a screw using the gold UCLA abutment. To measure each sample, an acceleration sensor was installed on the side of the tongue. An FFT analyzer was used for Periotest measurement from the buccal side. Differences in torque for the various kinds of abutment were compared according to the influence exerted on the vibration in continuous time, and also in terms of peak frequency.
Results and Discussion:The CA was influenced by differences in the property of the superstructure body material, buffering the vibration resulting from a hammer. In the case of the UA, because an upper structure body was connected with the fixture directly, the vibration characteristics may have been influenced by differences in the property of the material.
When natural teeth and implants coexists in the same oral cavity,it is thought that peri-implantitis may occur owing to periopathic bacterial transmission from periodontal pockets of natural teeth to peri-implant sulci.
In this study,we assessed the validity of bacteriological examination to evaluate implants in a maintenance period. We collected subgingival plaque from 108 implants and 39 natural teeth of partially edentulous patients searched from the detection rate of representative 6 periopathic bacteria by means of PCR, and performed quantitative analysis of Porphyromonas gingivalis, which was isolated from subgingival plaque by means of Real-Time PCR.
In addition, we investigated the possibility of bacteria transmission from natural teeth to implants in the same oral cavities, by arbitrarily primed PCR (AP-PCR). As for clinical parameters, probing depth (PD) and bleeding on probing (BOP) were detected in all teeth tested. The validity of all results of bacterial examination was determined by comparison with clinical parameters.
The results from the direct detection of 6 periopathic bacteria by the PCR method in the subgingival plaque of peri-implant sulci and natural tooth pockets, revealed that both groups had the same bacterial pattern, especially for Bacteroides foysythus and P. gingivalis, showing high frequencies.
The mean numbers of 6 periopathic bacteria in pockets deeper than 3 mm, for both groups, were significantly higher than those in shallower pockets.
The investigation of P. gingivalis transmission from natural teeth to implants by the AP-PCR method was not informative because of the low sensitivity of cultivation. On the other hand, quantitative analysis by Real-Time PCR method showed a high positive correlation in the number of P. gingivalis between natural teeth and implants in the same oral cavities.
Moreover, a tendency was shown:the incidence of P. gingivalis in the subgingival plaque of implants was higher than that of natural teeth. However, a difference in the mean number of P. gingivalis between over and under 3 mm pockets, in both groups, was not shown. The mean numbers of P. gingivalis and 6 periopathic bacteria showed significantly high positive correlation in the same oral cavities.
These results indicated that the bacterial examination using PCR and quantitative PCR method is useful for evaluating dental implant in a maintenance period.
To clarify the effects of clinical factors on the failure (early failure) of osseointegration establishment of titanium implants, we statistically carried out a clinical examination on 373 fixtures of Brånemark implants. Fifteen fixtures (4.0%) failed to establish osseointegration before the fitting of superstructures.
Results are summarized as follows:
1.Age and sex did not affect early failure.
2.Although there was no significant difference in the rate of early failure between the maxilla and the mandible, the prognosis of the maxilla, in women, was poorer than that of the mandible. No difference among regions in the maxilla or mandible was detected.
3.Variations of diameters and kinds of fixtures did not affect early failure.
4.In the length of fixture, the prognosis of 10 mm or less of the fixtures was poor, and the prognosis of fixtures of 13 mm or less was poorer in the maxilla.
5.The initial stability of fixtures at installation was deeply relevant to early failure.
6.The healing period between fixture installation and abutment connection did not affect early failure.
7.There was no significant difference in the rate of early failure between smokers and non smokers.
Osseointegrated implants have been used for general dental treatments with high predictability. On the other hand, a possible complication of this method is implant fractures happening at a part of implant body to abutment joint and a superstructure. However, a solid-type fracture is rare.
The purpose of this study is to find the cause of fractures of two connected freestanding implant abutment of solid implants, which occurred 18 months after they were sat on a one-piece superstructure. This clinical case was examined from first visit to recovery, and analyzed by electric microscopy(SEM)on the fracture surface.
Consequently, it is important for an implant to be created according to a well-considered design that has taken into account not only strength of materials but also the composition, possible locations where stress risers may be created, and flaws that can initiate cracks, in order to avoid fatigue fractures.
Also, it is important that a superstructure be constructed in consideration of strength of materials, as well as a reduction in lateral stress during lateral excursion, by proper occlusion of the prosthesis, and by the use of a night guard for bruxism.
Currently, dental implants are being widely used in clinics as a method of prosthetic dentistry for missing-teeth. It is certain that further demand for dental implants will be increasingly great from now on. It has often become known to us, however,such cases that implants had to removed resulting from incorrect pre-examinations, complications occurred during and/or after surgeries, and bad progress due to inproper supervision.
We conducted a clinical examination of 52 failing cases of dental implant treatment performed by the Department of Oral and Maxillofacial Surgery,Nihon University School of Dentistry, from 1995 thru 1999. Fifty-two cases consisted of 18 men and 34 women, ranging in age from 41 to 82 years. The average age was 58.6 years. Seven months was the shortest, and 20 years the longest, as spans of time between implanting and removing of those implants,with an average span of 8 years and 10 months.
Details of reasons why 52 men and women had decided to come to the hospital were as follows:5 persons made their own decisions;45 persons were introduced by other dental clinics;1 person was introduced by another department of our school hospital;1 person was introduced by an otorhinological clinic, and no people were introduced to us by dental clinics where implant surgeries had been conducted.
The dental implant has been utilized in increasing numbers since the publication of long-term data on osseointegration. However, only a few reports have been made on the actual situation of implant treatment in clinical practice and laboratory work.The authors conducted a questionnaire survey with a view to studying the actual situation of implant applications from the viewpoint of prosthetic laboratory procedure with prosthodontics concept, lab customer, systems which used, and details of laboratory procedure. One hundred twenty dental laboratories were selected who actually doing implant laboratory work from the members of the Japanese Society of Oral Implantology and other academic society as subjects to whom questionnaires were mailed with a request to fill out the form and return it to us. Seventy-eight questionnaires were returned, 65% response rate. An analysis on questionnaire answer were conducted to look into the situation of clinical and laboratory application of implants in Japan. This survey is quite meaningful for understanding the tendency of the implant prosthetic situation and the relationship between clinical and laboratory sides. The results of this survey indicated high anticipation that the dental implant will be established more predictable treatment with high quality prosthetic modality.
The osseointegrated implant™ was introduced more than 30 years ago by Prof. Brånemark. Since then, its application in dental implant therapy has made much progress. And many implants of this type have had the longest observation time and have proven efficacy for dental rehabilitation of totally and partially edentulous patients.
We performed a clinical study on the POI® 2-piece implant, which was developed by our group and Kyocera Co. in 1991, and placed from 1991 to 1999 in our clinic.
The results were as follows:
1. The total number of patients was 165:72 males and 93 females, whose ages widely ranged from 19 to 79 years.
2. The total number of POI®2-piece implants was 425.
3. The classification of implantation part:The number of implants placed in maxillae was 114;the number placed in mandibles was 311.
Especially, the number of implants used in mandibles was three times as many as that used in maxillae.
4. The classification of treatment stages:The number of implants that received post-prosthetic treatment was 381, and that in healing stage was 22. The other 22 implants were considered failures:18 implants failed in osseointegration before prosthetic treatment, and 4 implants lost their osseointegration after prosthetic treatment.
5. The classification of prosthetic types:The number of implants of screw- or cement-fixing type was 362;19 were removable type.
6. The survival rate of POI® 2-piece implants was 94.8% (22 failures out of 425). The part of middle piece was 95.8%, free end was 97.9%, and completely edentulous jaw was 65.2%.
The POI® 2-piece implant was proved satisfactory in our clinical results of this study.