Casting accuracy greatly depends upon the setting expansion of the phosphate investment material. However, setting expansion is obstructed by the wax pattern. In this study, the flow of paraffin wax was and the relationship between flow and casting shrinkage was investigated.
The results were as follows:
1. Casting shrinkage decreased with an increasing flow of wax pattern.
2. Gypsum investment material had a lower setting gypsum expansion than two kinds of phosphate bonded investment materials, but its heat expansion was higher than that of the other two.
3. The setting expansion of the investment material was considerably influenced by the load, with the GC investment material being influenced the most.
4. The casting shrinkage of phosphate bonded investment material was more affected by the flow of wax than the gypsum bonded investment material.
It is important to obtain exact fitting of the abutment supported restoration cases to maintain the longevity of osseointegration. In order to reveal the influence of laboratory temperature on the properties of the quick heating investment, the calorific values of mold, the setting expansion, heat expansion and casting shrinkage were measured at 16℃,23℃ and 30℃ under 60% humidity.
The results were as follows:
1. With a rise in room temperature, the calorific value increased.
2. WM had higher calorific value than Q1 and Q2.
3. With a rise in room temperature, the setting expansion was increased.
4. With a rise in room temperature, the heat expansion of Q1 and WM were decreased.
5. With a rise in room temperature, the wax pattern was melted inside the mold.
6. With a rise in room temperature, the casting shrinkage was decreased.
Mechanical stress due to occlusal force is one of the most important factors that will decide the success or failure of oral implant treatment.
Excessive load ont the superstrucures will cause not only the destruction of implant components but also bone resorption or micro-fracture of the surrounding bone. A treatment plan based on the knowledge of the behavior of implant components and surrounding bone structures under occlusal force and masticational movement of the jaws should be made.
As for the effect of number and placement alignment of implant fixtures on the stress formation caused by the implant, several estimations based on clinical treatment results have already been reported. Furthermore, some finite element methods, that is, qualitative analysis, on the strain distribution around implant fixtures have been studied using two-dimensional models. However, a quantitative mechanical analysis using an actual model and strain gauges had not been carried out.
Thus, in this paper, we describe experiments conducted with epoxy-resin replicate models of edentulous mandible to determine the safest way to place implant fixtures. Two-or threefixture implants of Branemark system implants® were placed with the fixtures in a straight line of offset line for three fixtures, and in an extension-type or long span-type configurarion for two fixtures, at the posterior portion of replica models. The fixtures were designated F1, F2, and F3 for medial, central, and distal portions, respectively. Superstructures were fabricated from a silver palladium alloy to have a flat-type or roof-rype occlusal surface. A static load was applied to the part of the superstructucture above each of the three points, and then the surface strains at the corresponding abutment and surrounding bone and the internal strain of the corresponding fixture were measured with strain gauges.
The results and conclusions were as follows:
1. In the extension-type model, when a load applied to the extension portion of the superstructure, a large compression strain was measured on the surface of the central abutment;and a large tensile strain, at the medial abutment. These results indicad the possibility of deformation of the superstructure by such a loading condition.
2. With respect to the surface strain around the fixtures on the replica when the roof-type superstructure was supported by the long span-type fixtures, at the lingual site of F 1 under a load at the medial portion and at the lingual site of F 3 under a load at the distal portion, the strain surpassed 1,820 ,μ strain which is reported as the threshold level for bone resorption. Further, when the support was made with the extension-type fixtures, strain larger than the bone-bearable stress were measured equally at the lingual site of F 1 under a load at the central portion and at the lingual portion of F2 under a load at the distal portion. The results suggeed the possibility of bone resorption around the fixtures at the portions mentioned above.
3. As for the strain inside the fixtures, the largest compression strain was measured in the fixture beneath each loading point. The strains inside the fixtures were found to be smaller in the three-fixture models than in the two-fixture ones. In conclusion, it was concluded that the models having three fixtures are more suitable for use than those having two fixtures.
The Er:YAG laser has been used for dental caries treatment, periodontal and root canal treatment. The purpose of this study was to clarify the effect of the Er:YAG laser on implant fixtures that had three types of surfaces (TI: polished blasted titanium, TPS: titanium plasma splayed implant, HA: hydroxyapatite coated implant). The Er:YAG Laser (The KaVo KEY Laser® 1242, KaVo,Germany)irradiated the implant fixture surface under the energy conditions of 32,75,97,135 and 270 mJ using contactfiber. The irradiated surface was observed by OPTIPHOTO (Nikon, Tokyo) and EPMA-8705(Shimadzu, Kyoto). The affected surfaces were analyzed by EPMA-8705. The results were as follows:
1. The color of TI became brown, black-brown and brown-gold. The center of melted area of 270 mJ was blue.
2. TPS surface was melted, the color was brilliant-blue, black-brown. The melted area increased with increasing irradiating energy.
3. The color of HA became white, brown, black‐brown and black.
4. The results of EPMA analysis suggested that the Er:YAG laser irradiation ablated the hydroxyapatite of HA surface.
It was reported that osseointegrated implant prosthesis, when applied to partially or totally edentulous cases, could recover better occlusal and masticatory function than conventional removable dentures. This clinical experience of increasing the function is beter when the osseointegrated implant prosthesis is adapted for the reconstructed jaws following the resection of oral tumors. However, the quantitative analysis concerning the recovery of masticatory function has not been performed yet. The masticatory function in 5 patients was evaluated using color-changing chewing gum. The recovery rate of masticatory function accounted for 15.5% in mean data. Furthermore, the mean value was almost equal to that of normal dentulous people. The function was recovered more in the maxillary resected case than mandiblar resected cases. Among the mandiblectomized cases, masticatory function of condyle-preserved cases were recovered more than condyle-resected cases. From the results, it was concluded that the osseointegrated implant prosthesis can recover the nasticatory function of jaw bone resected patients to close to the normal level.
In this paper, spontaneous bony growth of the mandible in the posterior region associated with reconstruction using osseointegrated implants was reported.
In this study, there were 27 patients who had totally edentulous mandible and have had fixed bridge supported by osseointegrated implants placed between mental foramina. Patients who had undergone mandibular resection for treatment of tumor and had systemic or metabolic disorder were not included in this study.
The analysis of this study consisted of evaluation of panoramic radiograph. The follow-up period was over 9 months. In 5 of 27 patients, the increase in the bony height of mandible was observed in the posterior region.
The primary objective of this study was to examine the changes in peri-implant sulcus depth (PISD) and bacterial activity levels in subgingival plaque for over a year. The activity of periodontopathic bacteria was determined by means of the Periocheck diagnostic (PCD) test. A total of 56 patients who had undergone endosseous implant surgery 2 to 22 years before participated in this study. The subjects consisted of 22 males (mean age:66.1±9.0 years) and 34 females (mean age:59.4±10.3 years). The number of participants in the current trial accounted for 74.7% of the number of those in the initial trial, which was carried out one year earlier. There was no significant difference in the rates between males and females who participated in the trial one year after.
PISDa was observed in 87.5%of the subjects. Nevertheless, PCD0 showed a similar distribution to that of PCDb. This tendency was noted both in the initial trial and the trial performed one year after. As for the sub-factors, significant differences were observed only in the mean PISD values. Namely, the mean PISD value was 0.68 mm smaller in stage III than in stage I; 0.51 mm smaller in Rounded (R) type than in Square(S) type; and 0.95 mm smaller in HA-coated implant than in Bioceram implant (Al2O3). Some difference was also observed between the results of the two trials.
In conclusion, the results of PISD evaluation did not necessarily agree with those of the PCD test.Moreover, a slight change was found in the results between the two trials, suggesting that a follow-up study should be made.
In oral implant treatment, panoramic radiography is neccessary. It is important that horizontal light beam agrees with occlusal plane for good panoramic radiography. Thns, in order to investigated changes of shape and location in the mandibular area using SCANORA®, an ideal arch was nade of polimethylmethacrylate, the steel balls were set at the points of Cuspid, second Premolar and second Molar of right side and panoramic radiography was peifored with differences of zero, 10, 20 and 30 degree between horizontal light beam and occulusal plane. As for changes of shape, from zero to 20 degree, change rates of shape were nearly equal, but at 30 degrees, they were different from the others. As for changes of location, horizontal change rates of location between steel balls increased in the mesial area with the increase of incline of the occlusal plane.
Vertical change rates of distance between stell balls reduced with the increase of the incline of the occlusal plane. The resalts were charcteristic of the rebolution orbit of panoramic radiography.
There was a case with a screw-retained retrievable prosthesis connected with remaining teeth. The patient complained of severe pain and food impaction around implants while eating. Two IMZ implants have been placed at missing frontal teeth. Two implants were not removed because there was no percussion pain and spontaneous pain and X-ray indicated no bone loss around the implant.Implants were connected with each other by a new CM-bar. The detachable prosthesis retained with the bar and clip attachment was connected semirigidly with the remaining teeth. Pain and food impaction decreased.
In this case, the rigid connection with the remaining teeth brought about an unexpected moment,which caused the pain around the implant while eating.
The socket lift technique, a version of osteotome sinus floor elevation (OSFE), in which the sinus floor in raised through the implant socket and bone graft is added, is simpler, less invasive, and requires less quantity of bone graft material compared with previous sinus lift methods, in which the access is obtained through the lateral wall of the alveolus. This report presents a case of oral rehabilitation performed in the edentulous region of teeth Nos 25 to 27 using FLIALIT®-2 (F-2) with a socket lift technique in proportion to Summers osteotome sinus floor elevation technique.
Case report:A 59-year-old female presented for implantology in the maxillary left posterior segment of teeth Nos 25 to 27. Implant sockets were prepared using BoneCondenser and the sinus floor was partially malleted upward. The space created between the raised sinus membrane and the alveolus was filled with bone graft material, and then 3 F-2 implant bodies were inserted. The bone graft was harvested from the buccal region along the oblique line of the mandible.
Prognosis: After 6 months of healing, prosthetic rehabilitaion was accomplished with the PMS method. A dental X-ray taken 4 months after operation revealed radiopacity of the bone graft. Good functional rehabilitation was also obtained at 3 months after prosthesis placement.
Magnets can retain objects with their magnetic force, and have various characteristics that are different from conventional mechanical retainers. They are drawing much attention as improved denture retainers. Furthermore, several problems such as adverse effects during magnetic resonance imaging and deterioration of the retainer (prepared by casting and treated with acids) remain. To resolve these problems and to expand the advantages and use of the magnets, a new magnet system called a magnetic attachment Magnetic Attachments of a Cap Shape (MACS) is being developed. This reports on the application of the MACS to removable crown-bridges and impression taking procedure for implant treatment mainly.
The MACS is composed of the male(positive)portion which is attached to the anchor (natural tooth or implant) and the female (negative) portion which is attached to the prosthetic appliance. The male portion is equipped with a screw or other device which is used to attach it to the anchor and it has a head which mates with the female portion. The female portion has a cap which covers the male portion. When used for removable crown bridges,the MACS makes it easy to prepare the bridge and resolve conventional problems such as loosened screws, difficulties in making a passive-fit super structure, and aesthetically unsatisfactory access holes. When used for impression making procedure, the MACS allows precise impressions to be taken easily, and can be used even in cases where the mouth opening is too small and even at sites where screws are difficult to reach (e. g., molars), thus resolving the problem of complex manipulations required by the open tray method.
A three-dimensional model using light-cured resin has been developed, and it has become possible to perform simulated surgery on the model.
This model was applied to two clinical cases of dental implant in the maxilla with a large number of missing teeth.
The position of the maxillary sinus and complex alveolar bone morphology could be grasped by using 3-D model. The model allows to decide precise position, direction, type, and surgerical method for implantation.
Amons ordinary clinical cases, there are various compromised cases of ideal implant placement without primary stability. The autogenous bone graft or guided bone regeneration (GBR) procedure are used to solve these cases, however, there are some technical problems involved in how to obtain the primary stability with little predictability to obtain the perfect regenerated tissue in the case of severe bone defect. Furthermore, it is necessary to build a sufficient amount of bone for implant placement, when the implant is placed at the ideal position for esthetic reasons. Three cases of implant placement utilizing titanium frame to fix the implant at ideal position and regeneration of sufficient bone height for ideal implant placement are presented. In these cases, the ideal implant position was determined using implant model at the site of bone defect, following elevation of mucoperiosteal flap. The titanium frame was shaped to fix the implant at the ideal position, then this titanium frame with implant was fixed by screws buccally and lingually. In this state, the implant was not in contact with the bone surface because of a large gap between the bone defect basement and the ideal implant head. GORE-TEXTM Augmentation Material membrane was placed over this frame and implant. The mucoperiosteal flap was closed with tension free. About 4～6 months postoperatively,sufficient amount of bone for implant stability and demanding gingival form for esthetic implant margin were obtained, when the membrane and titanium frame were removed. This report presents a technique of three-dimensional ideal implant placement at the site in which primary stability could not be obtained.
In the past, oral implant treatment for the prevalence patient was contained in the area of the contraindication in the range, a factor concerning the whole body. However, to keep those patients from the object of freatment, conventional implant contraindication, because the probability of prevalence patient is rising even thoush the patient is examined in clinical practice and the wide range of age is an impossible situation. It is important to consider the easiness of maintenance without exertins an influence on the basic disease in the prevalence patient during oral implantation.
The oral rehabilitation was applied to the overdenture of the Platon magnet head system (made by Platon Inc.) in the implant placement of the minimum by suppress operation on the body at the minimum to the totally edentulous at the maxilla and the mandible of the prevalence patient. The overdenture-type implant superstructure can rarely set the placement number of the implant. The easiness of the maintenance improves because a magnetic attachment retains and the stress to the implant reduces. In this report the treatment cost was reduced after applying the overdenture of the magnetic attachment for the implant, the Platon magnet head retained the attachment to the totally edentulous maxilla and the mandible of the prevalence patient and there was sufficient function recovery.
This report presents a case of a magnetic attachment being used to enhance the adhesiveness of the upper structure of an implant(Conus). The result was removal of the attachment caused by deteriorating expansion of the magnet. A scanning electron microscope (SEM) was used to verify the cause of deterioration.
Four POI 2-part implants were implanted, two on each side, in a patient lacking mandibular molars on both sides. A Conus-type bridge made of platinum alloy was attached to the implants by using two pieces of High Colex Super J® 4515 on one side and two of 3515 on the other. Two and a half months after adding the upper structure the 4515 magnet corroded. The 3515 magnet corroded into a dome shape after three months. The upper structure was recreated but three weeks later slight but similar corrosion was detected. Using a scanning electron microscope(SEM), scratches and cracks on the laser fused ring section of the magnet were found suggesting contamination to the neodymium center of the magnet which caused demagnetization and ineffectiveness of the magnetic attachment.