The purpose of this study was to investigate the relationship between immunolocalization of proliferating cell nuclear antigen (PCNA) and newly-formed bone tissue in the space created by GBR.
Nine Sprague-Dawley rats were used in this study. After exposure of the tibia, a defect was developed in the cortical bone. An e-PTFE membrane was cut to the appropriate size and then applied to the defect. Control defects were not covered with membranes on the left side. The animals were sacrificed at 6, 8, and 10 days after the exposure and tibiae were removed and fixed in 20% formalin. Then they were demineralized with 10% EDTA before being embedded in paraffin. Serial sections were cut and stained with HE and immuno-histochemically stained using monoclonal antibody of PCNA. For morphometric analysis, the occupation ratio of newly-forrned bone in the defects was evaluated by measuring the area occupied by newly-formed bone tissue. The PCNA positive score was made by calculating the number of positive cells per 1 mm2. The bone occupation rate of both groups increased up to 10 days, but the experimental group had a significantly higher rate than the control group in each time period. The PCNA positive score decreased with time in both groups but there were no significant differences between the groups. These results suggested that the GBR method promotes the proliferation of cells related to wound healing with new bone by means of the barrier membrane.
The Finite Element Method (FEM) was used for biomechanical studies of the Yamashita Artificial Dental Root (ADR) and the surrounding tissues. The ADR was fabricated from pure gold and autogeneous teeth. Its metal shaft had a gold ring at the apical region, and a sword-guard like wing to support the dentin portion. The studies were conducted using the ISAP structural analysis program running on a SUN 3-80 workstation. Through these analyses, it was observed that the metal portion of the ADR supported the stresses occurring under axial loading. The ADK wing demonstrated tensile stresses, and the fibrous membrane surrounding the metal portion absorbed the stresses. The stress level in the bone around the ADR was near zero. This indicated that the ADR wing and the membrane were effective in mechanically distributing stresses. The biomechanical analysis of the characteristic structure of the ADR indicated that this can be classified as a self-sustaining system.
The influence due to variations in the elastic properties of constituent materials on stress distribution was evaluated using the Finite Element Method. These studies confirmed the viability of using a truss model to simulate the characteristics of the metal part of the Artificial Dental Root.With this truss model, the influence of Young's modulus for bone on stress distribution was evaluated. Variations in the cancellous bone elastic properties ranging from 50 kg/mm2 to 300 kg/mm2 did not affect the stress distribution. With cortical bone elastic properties ranging from 1000 kg/mm2 to 3000 kg/mm2, no significant change was observed.
Versions of the ADR model were built in which the dentin portion was composed of aluminum oxide, titanium, hydroxyapatite, and autogeneous dentin. Under axial loading, the distribution of stress in these models was also evaluated. As for the material constituting the dentin portion of the ADR, autogenous dentin and hydroxyapatite were shown to be biomechanically optimal.
A computer simulation model was used to investigate the relations between the blade opening of shape memory alloy implants (SMI) and factors involved in the heat and temperature of physiological saline solution used for irrigation. The conclusions were as follows
1. Irrigation with physiological saline solution at a temperature of 44℃,1℃ higher than the austenite transformation finishing (Af) temperature, for twice the thermal time constant resulted in the blade opening of SMI.
2. Since the temperature within the slot of the jaw bone decreases drastically after the termination of irrigation, it is important not to discontinue irrigation until completion.
3. During irrigation, factors that lower the temperature of the irrigation solution and the tissue in the slot of the jaw bone should be eliminated.
4. The jaw-slot temperature and the thermal time constant vary depending on the clinical situation of the individual patient. Therefore, it is most important to confirm whether or not the jaw-slot temperature of the nonirrigated side has reached the Af temperature.
The clinical operative procedure that is currently used was found to be optimally suited for the blade opening of SMI in terms of a short time, reliability, and lack of heat-induced injury to the surrounding tissue.
A system for high-frequency dielectric heating and irrigation that has independent reproducibility for time, flow rate, and temperature factors determining the heat work load was trially developed. The system includes a mechanism for automatically terminating irrigation at the time of blade opening of shape memory alloy implants (SMI).
This system combines functions for the heating and transport of irrigation solution in a single unitand includes an automatic control mechanism. It is indispensable for safe, reliable clinical use of SMI.
The purpose of this study was to examine the applicability of the newly-established method to analyze distribution of occlusal force among implant superstructure and natural teeth at different clench levels.
Dental Prescale (Fuji Film Co. Tokyo) was used to record occlusal contacts and the force loaded on each of them. Four clench levels, which were 25, 50, 75, and 100%MVC, were regulated by visual biofeedback of masseter muscle EMG. This method was applied to five patients who received osseointegrated implants at the prosthodontic clinic of Kyushu University Dental Hospital attached to The Faculty of Dentistry and the applicability of the method was discussed.
The results indicated that the Implant Support Ratio, which was defined in this study, can be used for the quantitative evaluation of the occlusal force distribution among implant superstructure and natural teeth at different clench levels. It was suggested that the distribution of occlusal force depends not only on the patterns of missing teeth but also the occlusal scheme and the conditions of the residual natural teeth.
Occlusion of implant prosthesis has been assessed by measurement of the occlusal force, masticatory efficiency, muscle activity during mastication, and mandibular movement. However, little has been reported about the occlusal contact of an implant that seems most closely related to occlusion. In this study, functional evaluation of implant dentures was carried out by measurement of the occlusal force and occlusal contact area using Dental Prescale®.
From the occlusal force and occlusal contact measured with Dental Prescale®, functional evaluation of implant dentures was possible. The results also suggested that the occlusal force and contact area increased with time after implant prosthodontic treatment.
In this study, evaluation using experimental animals was conducted to determine whether or not a method combining dehydrothermally (DHT) cross-linking collagen sponge hybridized with autologous periosteum and DHT cross-linking collagen-coated lactic acid-glycolic acid copolymer membrane (C-PLA membrane) would be effective in the GBR method as a means of performing intraosseus implantation in an edentulous area with a dehiscence-type bone defect. The edentulous area of the mandible of beagle dogs was used as the experimental site, and the new bone forming function was evaluated histopathologically 8 weeks postoperatively. The results showed significant increases in the height and the area of the new bone formation in the experimental group compared with the control group (C-PLA membrane group). The change with time showed a significant increase in new bone formation from 4 to 8 weeks postoperatively compared with from 2 to 4 weeks postoperatively. No difference was found between the groups in regard to the standard nature of the bone defects, and the C-PLA membrane was confirmed to be present in all of the animals. The above findings suggested that this method will be useful in the GBR method of treating local bone defects.
This study was conducted to investigate the stress distribution of the surrounding bone by two-dimensional finite element methods, and histologically examine the flattening effect of alveolar ridge.
The alveollar bone conditions were classified into three patterns:model-① without alveoplasty of the ridge, model-② with slight alveoplasty of cortical bone, and model-③ with exposed cancellous bone.
The results were as follows
1. Based on the model of no alveoplasty, high stresses were distributed in cortical bone around the neck of the implant.
2. On the model of the alveoplasty within cortical bone, higher stresses concentrated on the remaining cortical bone, and the stresses in cancellous bone around the implant were much lower than those in cortical bone of its neck. These tendencies were similar to the result of the control.
3. The stress distribution of flattening to cancellous bone showed different tendencies in comparison with the two previous models. The stresses in the apical portion of the implant with vertical load greatly increased because of the loss of cortical bone, and compressive stresses occurred in extensive cancellous bone due to opposite horizontal load application.
4. In the animal experiment three months after implant placement with alveoplasty to cancellous bone, the well-matured cortical bone wall was around the implant.
These results suggested that the complete placement in the cancellous bone would be preferable in the case of implantation with flattening.
Hydroxylapatite (HA)-coated implants have been the subject of great interest since the mid 1980s. Various clinical studies have shown that HA coatings lead to good clinical results over a time period of about five years.
A case of a removed HA-coated blade implant due to breakdown thereof was reported. Bone loss with a radiolucent appearance around the implant by the peri-implant inflammation was observed. A removed HA-coated titanium blade-form implant was examined using scanning electron microscopy (SEM) and electron probe X-ray microanalyzer (EPMA) for analysis of the main constructive elements.
The results were as follows:
1. Macroscopically and microscopically, the removed implant demonstrated loss of the HA-coating with the presence of the smooth titanium substrate.
2. For the EPMA data, the implant material mainly consisted of titanium with loss of the HA-coated layer. The remaining HA-coated layer was chiefly consisted of calcium and phosphate.
3. Analyses by EPMA indicated almost complete loss of mineral (HA) from the surfaces of the failed implant.
From the above results, it was considered that there may be significant depression of pH and the production of proteolytic enzymes along with bone loss and massive granulation tissue that results from the inflammatory process. Such an environment might be one of the causes for removal of the implants. The most important factor for preventing late complications with implant-prosthetic treatment is the peri-implant osseous and soft tissue conditions. A check of the implant-borne suprastructures and a thorough cleaning of the implants and any remaining natural teeth of patients who receive implant-prosthetic treatment are necessary.
The surface of dental implants are designed to achieve implant stabilization and initial anchorage in bone, and also the surface topography influences the differentiation and other characteristics of cultured cells. There have been many investigations on the effects of surface topography on osteogenetic cells, but few on comparable effects with respect to osteoclasts and/or giant cells in vitro. The behavior of osteoclast-like cells cultured on commercially pure titanium with differing surface rugosities was investigated.
Commercially pure titanium plates were produced with 4 different degrees of surface rugosity: 1) Polished grade (ave.0.25 μm), 2) Untreated grade (ave.1.75 μm), 3) Fine sandblasted grade (ave.8 μm) and 4) Rough sandblasted grade (ave.23.2 μm). Primary rat bone marrow (RBM) cells were obtained and cultured using the method of Maniatopoulos et al. Aliquots of 100 μl of cell suspension were distributed in corresponding sequence for each group. On the following day,1.5 ml of the same medium was added to each well, and the cultures were maintained for 7 days being fed 3 times a week. After fixation, these samples were stained for TRAP. Light microscopy was used to examine the changes in cell morphology of these samples and to quantify the multinucleate giant cells. On the polished plates, small round cells were mainly observed. In contrast, multinucleated giant cells with spreading cell processes were seen on the roughened substrata. The number of multinucleated giant cells was 117.0 ±20.5 cells/plate on the polished plates, 271.1±53.9 cells/plate on the untreated plates, 357.1±96.6 cells/plate on the fine sandblasted plates and 314.8±96.2 cells/plate on the rough sandblasted plates. Significant differences were found between the polished plates and the others.
These results indicated that on the roughened substrata, compared to the polished substrata, there is increased differentiation of multinucleated osteoclast-like giant cells from bone marrow precursor cells obtained from the same femur source. This confirms our previous report that the number of multinucleated TRAP positive cells is significantly higher on the roughened hydroxyapatite substrata than that on the smooth substrata.
Surface topography, especially material microstructure, can influence cell morphology, behavior, differentiation and other characteristics. Therefore cellular response to implant surface topography is an important area of investigation in the pursuit of improvement in implant stability and prognosis.
The purpose of this study was to promote bone formation in the bone cavity after insertion of two kinds of partially perified bone morphogenetic protein (BMP). After insertion in the dog mandible, materials evaluated by histological study at 1, 3, and 5 weeks. G-Ext level BMP (G-Ext BMP) alone and Heparin level BMP-Insoluble bone matrixcomposites (SMP-IBM) produced new bone rapidly. G-Ext BMP and Heparin BMP quickly induced differentiation of the mesenchymal cells into osteoblastic cells in bone cavity of the dog mandible.
Hydroxyapatite (HAP) is considered one of the best bioactive ceramics because of high bone conduction/induction in osteogenic tissue. Although it has several characteristics of an ideal bone substitute, it does not have bone induction in heterogenous tissue. On the other hand, partially purified bone morphogenetic protein (BMP), which contains BMP-2 and can induce differentiation of mesenchymal cells into bone, was extracted from bovine bone matrix. In this study, dense HAP-BMP (Heparin-BMP) composites produced new bone faster than dense HAP alone after inserted into the bone cavity of the dog mandible. From the results of this study, HAP-BMP composite was found to have excellent bone induction in osteogenic tissue of the dog.
The panoramic radiograms and x-ray computed tomographic (CT) images of fifteen sinus life patients were studied. The imaging examinations were performed before sinus life operation and during the follow-up stage. The period from the operation to the follow-up examination was varied from a half year to three years.
The statuses of the maxillary sinus mucosa, graft materials and endosseous implants were evaluated. The volume of the maxillary sinus cavity was measured using the three-dimensional reconstructed imaging technique. The volumes of the resorbable and unresorbable graft materials and/or newly formed bone were also calculated.
No significant change in the maxillary sinus mucosa was shown by comparison of pre- and postoperative CT images. Eleven percent of the implant apex in the panoramic radiography and 19% there of in the CT images were found to be exposed to the sinus cavity. The three-dimensional study suggested that the graft materials and/or newly-formed bone occupied 4-18% of the maxillary sinus cavity. The patients having a longer term of prognosis showed a lower occupying rate than the patients soon after sinus lift operation.
To investigate the alimentary conditions of out-patients who underwent implant operation, a questionnaire survey was carried out on foods ingested by 12 patients for five days following endosseous dental implant operation. The masticatory function of each patient was also evaluated by score, using the chewing ability score of Satoh et al. (1988).
Regardless of the number of missing teeth, the daily total calorie intake was approximately 800 kcal until three days after operation, indicating that the amount of food was not enough to supply the daily requirement of calories. In patients with a few missing teeth, the daily calorie intake reached to approximately 1,800 kcal at four or five days after operation. In patients with a large number of missing teeth, however, the daily total calorie intake remained at approximately 850 kcal until five days after operation.
The chewing ability score was less than 40 even five days after operation in patients with a large number of missing teeth. In patients with a few missing teeth, the score remained at approximately 40 until three days after operation but increased to 80 from the fourth day.
Based on these results, an original dietary guidance program was designed using thick liquefied food (Sanet-V, Sanwa Kagaku Kogyo Sho) and blender-processing food (Sanwa Kagaku Kogyo Sho). On actual application of this program to patients who underwent implant operation as outpatients, excellent results were obtained because the amount of heat and/or nutritive elements can be easily adjusted to the conditions of patients. Furthermore, application to the postoperative management of nutrition is also easy as viewed from the preserviability and cooking simplicity.
A digital X-ray device, Compuray®, was applied to the radiological evaluation of endosseous dental implants.
When the amount of exposure to radiation, the time required for image processing and the preserviability of images were compared, Compuray was found superior to conventional dental X-ray devices. However, the resolution of the images obtained by Compuray was slightly poorer than that by conventional dental X-ray devices. In addition, the range of field was narrower because the photosensitive area of CCD sensor was small. The positioning of the CCD sensor was also difficult because the sensor was thick and lacked pliability.
The above results suggested that the scope of clinical application would expand, if the size and thickness of the CCD sensor and the resolution of images are improved.
Edentulous jaws can be reconstructed using Osseointegrated Implant System with predicable long-term success. Initially, 262 fixtures were implanted and 227 remained functional from 1989 to 1994. For 5 years, the cumulative survival rate of implanted fixtures was 92.1%. There were 34 clinical complication cases.
That is, mobility of fixtures in 15, broken artifical teeth in 8, fractures of gold screws in 2, fractures of abutments in 1, inflammation of mucosa around abutment in 1, and radiographic bone resorption lesion at the tip of fixtures in 2 cases.
These problems were due to the poor surgical techniques of the dentists, not the system, and the efficacy of the system was very predictable.