Three adult dogs were used in this experiment to investigate the usefullness of baked dental root tips for bone replacement materials. In the experimental method, baked dental root tips (800℃,20 minutes) of the human devitalized teeth and hydroxyapatite (HA) granules were respectively filled in the mandibular bone of the dog. Tissue specimens were taken 1, 3 and 5 weeks post operatively for observation under the light microscope.
1. In the case of filling of baked dental root tips, osseous addition occured 3 weeks after operation. In the case of filling of HA granules, osseous addition occured 1 week after operation.
2. In the both cases, osseous additoion were incessantly observed 5 weeks after operation.
3. The baked dental root tips may be useful as bone replacement materials.
Five cases, to which screw-type Bioceram Implants were applied, were observed to evaluate biophysical behavior of implant-supporting tissues to horizontal stress for six months after implantation. Ten natural teeth were also tested as control.
Results obtained were as follows:
Following the increasing stress, displacement rate in natural teeth declined exponentially, while linear increases were seen in implants. Maximal increase in mobility was seen in the 2nd month after implantation, thenceforth gradually decreased, and the least displacement was indicated in the 6 th month.
Two phasic curves seen in the recovery course after releaseing stress have significantly increased in size in 2nd month.
Mean speed in the 2nd phase of recovery curve (D3/T3) was about twice as rapid as natural teeth were, except in the 2nd month. From above mentioned facts, it might be assumed that supporting mechanism of implants would differ from ones of natural teeth, showing rather elastic response.
Recently, prosthodontic treatment for partially and completely edentulous patients changed with the provision of the prosthesis supported by osseointegrated implants. Osseointegration is a stability concept in which achieving and maintaining implants stability during functional loading are prerequisites for successful long-term function. Implant research has focused on the requirements for successful osseointegration and long-term performance of root components. In contrast, the instruments, abutment attachments and techniques designed for prosthodontic treatment have evolved on the basis of individual experience and professional opinion, with minimal evidence of published prospective laboratory or clinical testing. The purpose of this study was to investigata functional mastication using different intramobile mechanisms to fasten the superstructure of implants. IMZ implants functioning in 6 patients and 20 normal subjects were selected. On each IMZ implant the same superstructure for experiment was fastened with IME, IMC or titanium element(Ti). The horizontal mechanical mobility of each implant was measured three times by T-M (Tooth Mobility) tester. Occlusal contacts and area of patients were measured by the Add-picture system, and muscle activity of the masseter, anterior temporal muscles was evaluated by electromyography. The obtained data were compared with data for normal subjects.
The results were as follows:
1. As for using MI scores, the mechanical mobility of the implants was smaller than those of the tooth, and the difference of the viscoelastic properties were even more marked.
2. In case of IMC or Ti within the IMZ implants,there was significant difference between tooth and implants, but there was on statistically significant difference between tooth and IME within the IMZ implants.
3. The occlusal contacts in intercuspal position differed in percent of increase for occlusal contact scores and contact area from tooth with the increase level.
4. The occlusal contacts differed with any elements in the IMZ implants.
5. The percent of increas for occlusal contacts scores in case of IME within the IMZ implants showed approximately the same as those of tooth,but in case of IMC or Ti within the IMZ implants,there was significant difference between tooth and implants.
6. There was difference of MKG and EMG parameter between tooth and implant side during deliberate unilateral gum chewing.
The results suggested that the intramobile mechauism affects mobility, occlusion and masticatory function.
We studied an osseointegrated two-step type implants made of titaniumaloy and coated with hydroxyapatite, kindly supplied by Kyoto Ceramics.A total of 45 implants were used clinically in 38 patients during the 3 years and 1 month from March 1989 to March 1992. The patients were followed up to 8 years. Three types of superstructures were seated on the implants, and the long-term clinical follow-up was performed. The following results were obtained.
1.Clinically, a good outcome was obtained with all implants, fitted with three types of superstructures.
2.In one patient fitted with an implant-connected, operator-removable type of super structure, bone resorption was seen at the mesial side of the fixture neck, but there has been no evidence of re-resorption up to now, and it has been uneventful since then. However, careful follow-up is considered necessary he reafter.
Between 1992 and 1996 a total of 1597 hydroxylapatite coated cylinder type implants were placed in maxillary and mandibular locations. Fifty eight implant bodies were removed due to excessive bone resorption. Of these,12 were examined in terms of changes in the surface morphology and physical chemistry of the hydroxylapatite layer. Optical microscopy and SEM were employed to study surface and cross sectional features. Wide angle x-ray diffraction was used to determine the crystalline structure of the hydroxylapatite layer. In addition, elemental analysis to ascertain its chemical composition was performed using energy dispersed x-ray spectrometry. Examination of the hydroxylapatite layer of failed implants revealed contamination of the coating including an increase in the transparency of the layer which was in contrast to the characteristic white surface fo new implant body. Although significant changes were not observed in thickness or chemical composition of the HA coating changes in the crystalline structure of failed implants suggested amorphization of the hydroxylapatite.
The present study was aimed to compare the masticatory function of patients was an edentulous lower jaw using an Overdenture with O-ring attachment and patients with an edentulous lower jaw using an Overdenture with a magnetic attachment that we developed.
Integral® implants (Calcitek Inc., U.S.A.) with a diameter of 3.25 mm and a length of 8,10,13 or 15 mm were used. The latter overdenture was produced by shaving an SUS 447 J stainless steel block. HICOREX SUPER J® 3515 (Hitachi Metal Co.) was used on the inner surface of the latter denture.
Masticatory function was high for both the O-ring type overdenture and the magnetic attachment type overdenture, with little difference between the two. The O ring rubber deteriorated markedly after 3 years of use. Magnetic attachments manufactured by casting can be prone to corrode. This problem may be avoided if the attachment is designed to be directly attachable to the implant. If a removable type keeper is used in the magnetic attachment type overdenture, it would be possible to avoid problems when the patient must undergo MRI, and to deal with and for the alteration of Overdenture. The removable type keeper also makes it possible for the patient to use O ring or other types of overdentures when needed, in place of the magnetic type overdenture.
The questionnaires, concerning the content and category of lectures and chair side practical training for dental implantology at all dental schools in Japan, were analyzed in detailed.
As a result, it was becoming clear that the lecture system was adopted in 52% of the dental schools in spite of 86% of the dental schools considered it necessary. In the dental schools which were adopted the lecture for dental implantology,61% of the dental schools had 1～2 hour lectures.
It could be conjectured that each dental school has its own method for the education of dental implantology.
According to the results, it was concluded that it is necessary to make a dental implant curriculum and manual which are based upon collaboration for basic and clinical dental education at dental schools in Japan.