Effects of particle sizes of pH-10 hydroxyapatite on bony growth have been investigated. Influences of amorphous calcium phosphate were also studied.The following conclusions were obtained.
1. 12 BC and 20 BC have a tendency to flow out from the filling portion.
2. HAP and AP particles were found to be osteoconductive.
Recently, magnetic attachments for implants have been reported to be useful. However, keepers of magnetic attachments have produced metal artifacts on magnetic resonance (MR) imaging in the head and neck regions. The purpose of this study was to evaluate metal artifacts on MR imaging using Magnetic Attachments of a Cap Shape (MACS) removable keepers, in a phantom study and in clinical cases.
The following results were obtained:
1. In the phantom study, the dimensions of metal artifacts were 11.3 centimeters with a keeper,and almost none without a keeper.
2. In clinical case, diagnostic imaging in the head and neck regions was impossible with keepers, and possible without keepers. These results suggested that MACS is useful for MR imaging in the oral region, because it has a removable keeper.
To clarify the improvement of frame fitness for osseointegrated implants, the difference in the horizontal distance of bounded gold cylinder between a one-piece cast frame and a solder joint were compared. Working stone models with abutment replica were made from a simulation model of an edentulous mandible which installed five fixtures in the acrylic resin block, then both five frames including five and four gold cylinders were made. To evaluate the dimensional change during solder joint of these frames, the horizontal dimension of all bounded gold cylinder were measured at the one-piece cast frame before separating them. Then these frames were divided into two to three gold cylinders, or two to two gold cylinders, and then they were solder the put carefully. The horizontal dimension of all bounded gold cylinder was also measured after solder joint of them. The tightness of gold screw that shows good fitting of frame was improved after solder joint in all cases at the end of the frame, but it improved less at the bounded gold cylinder. The mean value of the differences of the bounded gold cylinder, including the solder joint,was 102±56 mm. Results suggested that a solder joint was effective to reduce the total inter gold cylinder distance in a large frame.
Experimental composite films made from chitosan and hydroxyapatite were examined as to if the films could be used as a bone substitute material. Neutralized film, at pH 7.4 (ASF), and the film that was titrated to pH 7.2 (TRF), using malic acid and sodium polyphosphate acid solutions, were prepared. Films soaked in Ringer's solution were also fabricated. These films were immersed in a physiological saline solution for up to 8 weeks.The tensile strength and elongation of test specimens, the pH values of the solution, and the amounts of Ca, P, Na, and K ions from the films into the solution, were determined. The surfaces of films before and after immersion were examined using SEM. The following results and conclusions were obtained:
1. The longer the immersion time, the lower the tensile strength and elongation of the films.
2. The pH values of the solution in which ASF and TRF films were immersed were slightly lower than those in which the films soaked in Ringer's solution were immersed.
3. The dissolved amounts of Ca, P, and K increased with prolonging of the immersion period.
4. The surfaces of film hydroxyapatite particles in film were covered with chitosan before immersion, while no chitosan was found on the hydroxyapatite particles after immersion, and,
5. Although the dried films showed cookie-like brittleness, the films soaked in water had elastic properties like a rubber material. Those elastic films can be trimmed into any forms using scissors or a surgical knife. Thus, these films can be bone filling material between alveolar bone and the alveolar ridge. In addition, the experimental films show radiopacity, because of the hydroxyapatite particles in the film.
The purpose of this study was to identify factors that may effect the clinical results of implant treatment. For this purpose, a long-term follow-up survey was conducted on patients who had undergone endosseous implant surgery during the past 22 years. A total of 5,092 implants placed in 2,261 men and women were assessed clinically and analyzed statistically. The results showed that 83.8% to 93.8% of the subjects maintained stability of their implants.
Among factors related to the outcome of the implant surgery, drinking alcohol was found to have an adverse effect on the clinical results. In the subjects who drank and smoked, the survival rate of implants was significantly low. Patients with implants placed in the mandible or completely edentulous jaws, as well as those with anterior or posterior implants, had favorable results. Generally, the patient-outcome assessments were better in women than in men. However, no gender difference was found whatsoever in the patients who had acquired the habits of both drinking and smoking.
These findings suggest that dentists' proper guidance to their patients, depending on sex;careful selection of patients with no underlying diseases, and effort toward the maintenance of healthy lifestyle and improvement of the mode of life on the part of patients, will reduce risks of a poor outcome and serve to result in a high implant survival rate.
The purpose of the present study was to look into the effects that various factors related to implant-supported prostheses have on clinical outcomes. A total of 2,291 men and women participated in this retrospective study, and 5,092 implants placed in 2,969 cases were examined.
The survival rate for removable implant-supported prostheses, which can be taken care of easily, and which readily keep peri-implant tissues clean, was 97.7%, while the rate for implant-to-implant connected prostheses, in which biomechanical loading is not applied through the periodontal ligament, was 97.6%. These connection-type and implant-supported prostheses exceeded other types in survival rate. The survival rate for implant superstructures loaded three months and upward after first surgery was significantly high (96.7%). As was found in the cases of screw-type and cylinder-type implant (96.4% and 97.3%), the survival rates for titanium plasma sprayed-and hydroxyapatite-coated implants with surface roughness were also as high as 98.2 and 96.7%. The survival rate of 95.9% for implants of 10 to 15 mm in length was high, compared with the rates for plants longer than 15 mm and shorter than 10 mm. The survival rates for implants 3 mm and 4 mm in diameter were as high as 96.7% and 96.2%, respectively, but the rates dropped sharply for those 5 to 6 mm wide. Implant survival rates reached 95.9% and 96.1% in the regions where bone was satisfactory in both quality and quantity. Where these alveolar bone conditions were insufficient, the rate became low. A combination of implants and GBR (guided bone regeneration) did not contribute to raising the survival rate.
In conclusion, the present retrospective study suggested that, if it is to achieve a good result and a high survival rate, implant treatment should be done with our findings taken into due consideration.
Statistical analyses were made to work out the frequency of occurrence of unstable conditions (UST) in implant patients, cases, and implants themselves. The subjects and materials were 2,261 implant patients,2,969 cases, and 5,092 implants. UST was observed in 8.3% (185/2,226) of the patients, 8.6% (251/2,923) of the cases, and 7.3% (368/5,023) of the number of implants. About 45% of the patients with UST were found to have circular disease. The number of smokers with UST was larger than that of non-smokers with UST by 1.8%. The occurrence of UST in the implants placed into completely edentulous jaws was 5.0% less than in the implants placed into partially edentulous jaws. UST occurrence was less in removable supported implant prostheses, overdentures, single tooth implant crowns, and implant-implant supported prostheses, than in all the other types of prostheses. UST occurred less in screw and cylindrical type implants than in plate(blade) type implants, and less in HA-coating and TPS implants than in Ti implants. Regarding the length of the implants, UST appeared frequently in implants longer than 15 mm. However, the implant diameter and the presence or absence of GBR (guided bone regeneration) had nothing to do with the occurrence of UST. Implants placed into alveolar bone that was satisfactory in quality and quantity were less unstable. Gender had no bearing on UST whatever. Most of the implants were stable at the time of examination,but many implants developed UST over time as follow-up continued. These findings could be useful for a prospective clinical study taking stock of EBD (evidence-based dentistry).
Human platelets have effects that not only stop bleeding but also heal wounds. The effect of wound healing depends on many kinds of growth factors in platelets, e.g. PDGF, TGF-β, IGF-Ⅱ.PRP (platelet rich plasma) is the condensation of platelets, so that numerous growth factors are included. Therefore, PRP perform the acceleration of cell growth and healing of the wound rapidly. Recently, there is increased concern in PRP as its function and hearing process relates to bone graft surgery in implant treatment. This article present about the clinical ability of PRP for autologous bone graft, which suffered severe alveolar bone resorption in the maxilla. We performed surgery on 5 patients of which 4 cases of veneer graft in anterior and 2 cases of onlay graft in posterior. Three to four months later, a CT scan was taken, and we examined about the bone volume. Four to five months later, fixtures were implanted, and we took specimens from the bone graft area. In those results, CT images revealed resorption of grafting bone, however, adequate bone remained for the implant. During implant surgery, graft bones were consolidated to original bones completely, and fixtures could be placed according to plan. In microscopic findings, these specimens showed immature tubeculae, which liked weben bone. Despite the short term of wound heal, all cases were successful without infection and wound exposure, and we were able to obtain sufficient bone quantity. In the above mentioned, we knew that PRP was useful for wound healing and bone regeneration without membrane, however, we could not prevent postoperative bone resorption.
We evaluated the validity, using the Dental Prescale system®, of implant-retained fixed prosthesis on masticatory efficiency in unilateral free-end partial edentulism, compared with a removable partial denture. The population of this study was as follows: implant-retained fixed prosthesis for unilateral free-end dentition, 7; removable partial denture for unilateral free-end dentition, 7; upper or lower single complete denture and the natural dentition on the opposite side, 5; complete edentulism with complete denture wearing, 5; natural dentition, 7.
In the present study, total occlusal force, the occlusal force support rate of the rehabilitation area, the change of occlusal forces on the teeth nearest the edentulous area, and the asymmetry index were evaluated, and the results were as follows:
1. Both the total occlusal force and the occlusal force support rate of the implant prosthesis were superior to the removable partial denture.
2. The occlusal force on the teeth nearest the edentulous area was increased with the removable partial denture, while the implant-retained prosthesis decreased.
3. The implant-retained prosthesis showed more symmetrical occlusal force than the removable partial denture.
In summary, it was suggested that the implant-retained prosthesis is more suitable than a removable partial denture to obtain the appropriate occlusal force and to protect the residual teeth.
The esthetic aspect is one of the most important factors in the anterior maxilla, but this region also easily causes alveolar ridge resorption following tooth extraction.
Immediate implant placement will inhibit the alveolar ridge resorption that normally occurs following tooth extraction. Therefore, we decided to take the immediate implant placement using tooth extrusion for an upper left front tooth that had a root microfracture detected longitudinally along the root surface.
In this case, we investigated augmentation of the alveolar ridge and the apical alveolar bone using tooth extrusion with a periapical radiograph, and thereafter we investigated bone changes around the implant after immediate implant placement with a periapical radiograph.
As a result of this investigation, it was suggested that immediate implant placement using tooth extrusion was effective in preventing alveolar ridge resorption, and in achieving aesthetic results in the anterior segment with implant-supported restorations.
This case report describes the use of osseointegrated implants as anchorage of intermaxillary fixation for a hemimandibulectomy patient. The patient was a 59-year-old man with an ameloblastoma of the right mandible. We placed two implants in the mandibular anterior edentulous area, so that these implants could assist in retention of his conventional removable denture after tumor resection. Four days later, we performed tumor resection and an immediate mandibular reconstruction using a titanium plate. Three months later, however, failure of the mandibular reconstruction deviated his left residual mandible to the right side. After removal of the reconstruction plate, we performed intermaxillary fixation using an implant-assisted removable denture for one month, and for one more month, his normal occlusion was maintained by intermaxillary rubber traction. These treatments satisfactorily prevented displacement of the left mandible. Since then, the implant-assisted removable denture has been working adequately for masticatory function. During 7 years' postoperative observation, there were no signs such as implant movement or local pain, except, radio-graphically, bone resorption around the one implant. We attribute this bone resorption to heavy loading. This case indicates that we could to use osseointegrated implants as anchorage of intermaxillary fixation.
The authors describe our experience with a patient diagnosed as having essential thrombocythemia after implant surgery. We had no significant abnormality in clinical examination about 4 months ago. Because of postoperative excessive hemorraging, he was admitted to a general hospital, and was diagnosed as having thrombocytopathy. He showed marked improvement by drug therapy, and after ward was inserted overdenture. In our experience of this case, we called some attentions that following. Careful examination should be required before implant surgery.
The care for patient should be prior to everything in unpredictable troubles.
The doctor should understand sufficiently various risks in dental implantation.
Magnetic attachments have various properties not found in other retainers because of their specific retentive force by magnetic energy, and they have received attention as excellent retainers with different functions. However, no sufficient guidelines have been established for designing magnetic attachments used in clinical treatment. In this study, we focused on the ability usefulness of magnetic attachments, and classified them according to their purpose of application, to obtain guidelines for their design:
[Classification of magnetic attachments by purpose of application](Tanaka ＆ Hoshino)
Type R:for retention mainly. Support and bracing are not expected.
Type SR:for support and retention. Bracing is not expected.
Type BSR:for bracing, support, and retention.
Type R should be applied to cases in which the amount of available remaining bone for implantation is insufficient, and the permanent abutment teeth condition is poor. That is, support should be obtained from the mucosa, and mainly retention alone should be obtained from the magnetic attachment abutments;therefore, magnetic attachment abutments should be placed in the area as far as possible from the area to which strong occlusal force is applied. We considered that this approach useful for protecting the abutments.
In cases in which the amount of available remaining bone for implantation is sufficient, and the permanent abutment teeth condition is good, the application of Type SR is possible, and we considered that, by placing magnetic attachment abutments in the area, such as molar areas, where strong support was expected, the magnetic attachments could be used for improving occlusal support.
Furthermore, in cases in which a sufficient number of magnetic attachment abutments are available, the application of Type BSR is possible, and we considered that, by placing magnetic attachment abutments in the anterior and molar areas, not only retention but also support and bracing could be expected.
It is known that the prognosis of dental implant becomes poor not only by excessive lateral force but also by vertical force, and understanding this aspect is important in designing implants. It was suggested that, in applying magnetic attachments to implants, and also in order to bring out many advantages in magnetic attachments, using the above classification, in which not only retention but also support and bracing were considered, was very useful.
Boyne and Brånemark et al. have shown, since 1980, that it is possible to insert implants into sinuses after elevation of the sinus membrane.Conventionally, the floor of the sinus is filled with an autogenous bone graft, hydroxyapatite, or a demineralized freeze-dried bone allograft during this procedure.
The purpose of this study was to establish a procedure using simultaneous elevation of the sinus membrane and implant placement into the sinus,which involves no foreign body graft material and less surgical intervention. Three patients received surgery involving simultaneous sinus lift and implant placement into the sinus without graft material. Bone chips removed from the lateral wall of the maxilla were inserted between the apex of the implanted fixture and the sinus membrane,and they were secured to the membrane by biological tissue bond (Beriplast P®). The augmented space under the sinus was filled with blood clot without the presence of graft material. We expected the blood clot to develop into new bone. In order to evaluate bone development around the fixture, tomographic analysis was performed before and after surgery (at six months and one year). Radiographic examination revealed that the augmented space under the sinus and around the apex of the implant fixture was filled with new bone. All three cases showed no mobility of the implant. Our findings suggest that this procedure increases the indication for implant therapy on posterior maxillary edentulous patients that have a sinus floor near the alveolar ridge.