As the bone sustained implant directly, even a little error of the fitness between abutments and a superstructure will cause large stress around a prosthesis or the bone. Therefore, it might become the cause of breakage of a prosthesis or recession of bone. Fitness of a prosthesis depends largely on the accuracy of a working cast, and reproducible accuracy of an impression is needed as the most important factor for making it. It is difficult to place multiple implants parallel to each other. The angles formed where implants cross each other may affect reproducibility of an impression, and also, the difference of impression techniques may affect it. Three models, on which implants (CAMLOGTM) were placed under three kinds of inclined angles (0°,10°,15°), were made impressions for making working cast. Reproducibility of the implant position on the working cast, which was made through five kinds of impression techniques, were compared,and results were as follows.
1. The parallel placed implants model was more accurate than the inclined placed implants model. And the displacement of the model with an inclination of 15 degrees was markedly larger than the one of 10 degrees.
2. In comparing impression techniques, a closed tray with a transfer cap was compared with one without a transfer cap, and the latter showed less displacement.
3. On an open tray impression technique, an impression with transfer coping was compared with one without it, and the latter showed more accuracy.
4. On the factor of closed tray impression technique with and without a transfer cap, the parallel placed implants model with a transfer cap showed more accuracy than the 10 or 15 degrees inclined placed implants model.
As described above, when multiple implants are placed, it is recommended that the angle formed by each implant be less than 10 degrees. And impression technique for the CAMLOGTM implant, closed tray without a transfer cap is the most recommendable technique.
The recent advent of improved low-level laser irradiation (LLLI) therapy has promoted interest in clinical implantology. It has been reported that LLLI on bony implant sites might have positive effects on the integration of implants. The biostimulatory effect of cell proliferation and bone formation by LLLI has been investigated, but little is known about the molecular basis of biostimulatory mechanisms. Since LLLI will be useful to support implant therapy, it is important to elucidate the mechanism of the biostimulatory effect of LLLI on bone formation.
We previously constructed the cDNA library of mouse osteoblastic cells (MC 3 T 3-E 1), which enhanced gene expression by LLLI using a subtracted gene cloning technology. In the present study, we further analyzed the DNA nucleotide sequence of gene clones, and focused on a gene clone designated MCL-174. The nucleotide sequence of MCL-174 insert was determined and assessed in the standard nucleotide-nucleotide BLAST (blastn) homology-search using NCBI DNA databases. DNA nucleotide sequences of clone MCL-174 inserted DNA exhibited 99% homology with Mus musculus annexin Ⅲ gene. Reverse-transcription PCR analysis showed that the mRNA level was enhanced by LLLI. These findings suggest that LLLI may enhance mRNA transcription and play a role in stimulating proliferation of osteoblasts through the enhancement of annexin Ⅲ gene expression. Annexin Ⅲ was detected in secretory ameloblasts and odontoblasts, and it was thought to be involved in the regulation of cell calcium. These findings suggest that the biostimulatory effect of LLLI on bone formation may relate through gene expression of annexin Ⅲ.
Physical properties (including shrinkage, melting point, and thermal expansion) and mechanical properties (such as strength) of inlay wax can influence casting accuracy.
Using three different types of paraffin waxes with different melting points, inlay waxes were prepared at a trial base. The melting points, shrinkage, and thermal expansion of these prepared inlay waxes were measured.
The bending strength, as well as strain, was also measured from these inlay waxes when the ambient temperature was controlled to 16,23, and 30℃.
Main results are as follows:
1. If a paraffin wax having a higher melting point was used, the resultant inlay wax showed a higher melting point and smaller shrinkage.
2. On the other hand, when a paraffin wax with a lower melting point was used, the resultant inlay wax had a larger thermal expansion.
3. The bending strength of prepared inlay waxes was lower when tested at a higher ambient temperature.
4. Strain of inlay waxes were recorded to be larger when the testing ambient temperature was higher.
Among many dental metallic materials used for superstructures to be placed on Ti implant abutments,12% Au-Ag-Pd alloy can be considered one of the best material choices, based on both electrochemical and mechanical properties. In this study,the relationship between the wall thickness of cast and fitness of 12% Au-Ag-Pd alloy was investigated, using waxes prepared at a trail base. The wall thickness of cast was varied with 0.4,0.6, and 0.8mm. The investment material used in this study was a raid heating-type gypsum bonded investment.Surface roughness of casts was also measured.The solidification expansion of the investment and its related stress, and the thermal expansion coefficient of the investment, were also measured.
Main results were as follows:
1. The stress that developed in the investment after the mixing increased over time. But the wax pattern was not deformed by force.
2. The trial wax C exhibited the best accuracy,because of large flow, a low melting temperature,and large thermal expansion.
3. It was also found that the fitness got worse when the wall thickness of the cast became thicker.
Due to a remarkable deterioration of material properties when chitosan film is dry-heat-sterilized,chitosan film is conventionally sterilized with the gas sterilization method.
However, there is a potential risk of adverse effects of gas residue on a living body system. In this study, the film was sterilized under 60Co γ-ray irradiation, and changes in properties were investigated.
The main conclusions were as follows:
1.The tensile strength of chitosan film D70(Deacetyl 70%)with a lower level of deacetyl degree markedly decreased. On the other hand, films D85 (Deacetyl 85%), and D99(Deacetyl 99%)did not show any reduction in tensile strengths.
2. The tensile elongation of all films after the 60Co γ-ray irradiation decreased. Among them,the film(Deacetyl 70%)showed the largest reduction in tensile elongation.
3. It was also observed that the 60Co γ-ray irradiation caused film discoloration of turning yellowish.
4. The molucules of all chitosans after the 60Co γ-ray irradiation decreased.
Purpose:In an attempt to evaluate osseointegration, a comparison was done on the influence of various kinds of abutment, and on differences in torque, on the results of vibration analysis, as factors that can influence the vibration analysis of an implant body.
Materials and Methods:The measurement sample was a model in which a fixture was implanted in super-hard plaster. A conical abutment was made using a conical gold cylinder, like that used in the UCLA Abutment, and the superstructure body of a lower jaw small molar was made using super gold (referred to as CA and UA hereafter). Both CA and UA were connected to the superstructure body by four values of torque:5,10,20,or 32 Ncm. To measure the face of each sample, an acceleration sensor was installed on the side of the tongue. An FFT analyzer was used to measure the Periotest 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 the peak frequency. The measurement sample was a model in which a fixture was implanted in super-hard plaster. A conical abutment was made using a conical gold cylinder,like that used in the UCLA Abutment, and the superstructure body of a lower jaw small molar was made using super gold(referred to as CA and UA hereafter). Both CA and UA were connected to the superstructure body by four values of torque:5,10,20,or 32 Ncm. To measure the face of each sample, an acceleration sensor was installed on the side of the tongue. An FFT analyzer was used to measure the Periotest 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 the peak frequency.
Results and Discussion:As for the vibration in continuous time, a torque beyond 10 Ncm was not enough to influence the vibration in CA, whereas the vibration was marked in UA when the torque became strong. Vibration in continuous time therefore appeared to become short. In CA, a torque beyond 10 Ncm did not appear to influence the peak frequency, whereas in UA, the peak frequency rose when the torque became strong. Thus, the torque influences an upper structure body that is connected to it directly.
The purpose of this study was to determine whether the healing process in membrane-protected bone defects could be accelerated dose-dependently by basic fibroblast growth factor(FGF-2)using a slow drug-release pellet. Mandibular premolars at both sides were extracted, and bone defects(8×5×5‐7mm)were made in the edentulous area, in beagle dogs. FGF‐2 was administered using specially made collagen pellets. The defects were assigned to be treated in one of four ways:(1)In the FGF (0.1)group, a collagen minipellet containing 0.1μg FGF‐2 was administered;(2)in the FGF(1.0)group, a collagen minipellet containing 1.0μg FGF‐2 was administered;(3)in the Placebo group, a collagen minipellet without FGF‐2 was administered;(4)in the Control group, nothing was administered in the bone defect. All defects were filled up with blood, covered with e-PTFE membranes, and muco-periosteal flaps were then tightly sutured.Bone regeneration was evaluated 10 weeks after the operation by decalcified sections. Histologically,in the FGF(0.1)group, regenerated bone was seen widely in the inner space of membrane-protected defect. In contrast, the bone regeneration seen in the FGF(1.0)group was only adjacent to the border of defect. Morphometric analysis showed that the regenerated bone area ratio of the FGF (0.1)group(42.3±6.6%)was significantly higher than any other groups;on the other hand,the FGF(1.0)group(7.0±1.7%)was significantly higher than any other group (p＜0.05).These results suggest that the effect of controlled local administration of FGF‐2 is biphasic, in that higher doses may be inhibitory, so that we should control the optimal dose in clinical trials.
Success of dental implant treatment is related to accurate placement, such as implant location and/or direction. To determine optimal placement of implants, computed tomography(CT)with a diagnostic stent is used. Then, a surgical template is made with modifications of the location and angle for implants in the CT images.
The purpose of this study was to evaluate the validity of imaging diagnosis using CT in implant design. Differences between the planned placements of the implants, based on measurements of distances and angles before and after CT imaging,were evaluated.
Subjects included 24 patients, with a mean age of 53.8 years. The total number of mandibular implants was 87, classified into anterior and molar regions based on the site of the mental foramen.Thirty-four of 36 anterior implants were treated with overdentures, and the other two implants received a crown prosthesis. All 51 molar implants were placed on the crown prosthesis.
In 18 implants(50.0%) of the anterior implants,the distance was modified a mean of 2.1mm;10(19.6%) of the posterior implants were modified a mean of 1.9mm. Although the rate of modification was significantly different between anterior and posterior implants, the means were not.In the designed angulation,83.3% (n=30) of the anterior implants were modified, with a mean of 10.9 degrees;54.9%(n=28) of posterior implants with the mean of 5.9 degrees. The difference between anterior and posterior implants was significant for both rate and angle of modification.
In conclusion, we found that presurgical design using a working model had its limitations, and CT was essential to determining the optimum positions and angulations of implants in the mandibular anterior region.
An implant-supported overdenture potentially provides a functional and esthetic reconstruction,provided that the implants are precisely placed in a predetermined location and at a predetermined angulation. This article describes a technique in which a guide is fabricated for radiographic evaluation of implant placement, and it also serves as a surgical guide for the placement of implants for a patient with mandible overdenture. A stent was constructed using a clear resin from a duplicate denture or a wax denture.
The stent implements the information from a CT scan, and it was modified to guide the surgical placement of the implant.
A diagnostic stent with radiopaque markers, such as silicone rubber impression materials, indicating the denture space and cylinders of silicone rubber bite materials, were used to determine the best location and angulation of the implant.
Cross-sectional images were selected that contain the silicon cylinders, and the most desirable locations for the implants were decided.
From the angulation of the silicone cylinders with the available bone and the position of the vital structures, the best angulation for the implants were decided.
The surgical stent with the diagnostic information, and the optimum position of the surgical sites,indicated the precise drill access holes. The three-dimensional stent design provided guidance for accurate implant placement for an implant-supported overdenture.