In three adult dogs,4 molars of mandibular bone were extracted. Three months later, the three bone cavities in the extracted area were prepared.Bone crushed dust at preparation of bone cavities was transplanted into the mesial cavity, and bone smashed tips from the top of the surrounding alveolar bone into the distal cavity, while the central cavity was filled with only blood clot. Tissue specimens at 1,3, and 5 weeks after surgery were made for observation under a light microscope and a polarizing microscope.
1.New bone trabeculae were not observed after 1 week, in all of the cavities. Bone trabeculae were observed after 3 weeks, and the bone was immature.After 5 weeks, lamellae were obviously observed,and bone was mature.
2.In the case of blood clot, the trabeculae were slender, and the percentage of occupation of bone was 41.2±4.87% after 3 weeks, and 42.8±3.3 after 5 weeks.
3.In the case of bone crushed dust, the trabeculae were large, and the percentage of occupation of bone was 64.5±5.34% after 3 weeks, and 71.1±6.4% after 5 weeks.
4.In the case of bone smashed tips, the trabeculae were large, as in the case of bone crushed dust. The percentage of occupation of bone was 66.1±6.45% after 3 weeks, and 65.9±6.91% after 5 weeks.
5.At 3 and 5 weeks later, the gross square measure of bone trabecule was significantly larger in the case of bone crushed dust or bone smashed tips, compared with the case of the blood clot(percentage of danger＜0.1%).
One of the possible complications of dental implant treatment is fracture of implant components. Metal fatigue and biomechanical overload seem to be the most common causes of fractured implant components.
We experienced a case of retaining screw loosening and consequent fracture of an implant. In this case, implants had been installed in the mandibular molar region, with an inferior alveolar nerve repositioning procedure. Five years after functional loading, a fracture of the distally placed implant fixture was observed.
The fractured surface was observed by scanning electron microscope(SEM). The SEM analysis showed evidence of metal fatigue, which is thought to be the most common cause of implant fracture.The finite element methods(FEM)model was established based on this case, and then the stress distribution in and around the implants was investigated. The results showed that the non-fractured fixture had a higher concentration of stresses than the fractured one. Higher tensile stress concentration was observed at the abutment-superstructure interface of the non-fractured implant. Clinically,the superstructure is connected to the abutment with a retaining screw. Therefore, the retaining screw in the non-fractured implant might have loosened, resulting in a fracture of the other fixture due to the anterior cantilever condition.
It is important to check for screw loosening during the maintenance period, to prevent serious damage, such as implant fracture.
Dental implant materials have certain/numerous drawbacks:bacterial deposits form easily between the fixture and alveolar bone surface, and mirror surface polishing is required to obtain resistance to corrosion, to enhance the appearance, and to realize contamination-free conditions. Achieving this,however, involves considerable time and labor.The titanium alloy, etc., used commonly for metal dental materials also has the drawback of poor workability, and it is important to resolve this problem. In this study, the authors applied ELID grinding to polish the neck between the fixture of a titanium-nickel alloy artificial dental root and alveolar bone, and studied the grinding efficiency of the method and the surface properties obtained. By applying ELID grinding using a CBN grinding wheel, it was found that superior surface properties could be obtained. Results of analyzing the grinding surface by SEM, EPMA, and AES indicated comparatively good surface properties. Also, no surface contamination or harmful elements to the human body were detected with the use of ELID grinding. These results suggest that ELID grinding can be applied for polishing metal dental materials.
The application of enamel matrix derivative(EMD)has recently been reported to be effective in periodontal regeneration. EMD appears to induce both periodontal tissue and calcified tissue. EMD has been recognized to be useful in tooth replantation and autotransplantation, both experimentally and clinically.
Dental implant and autotransplantation have been used in the recovery of missing teeth. These procedures may also be effective for orthodontic treatment.
The objective of the present study was to determine if EMD could stimulate the regenerative potential of connective tissue, such as periodontium,dental pulp and calcified tissue such as cementum,alveolar bone after intentional replantation of teeth.
In 4 male adolescent Beagle dogs, bilateral maxillary and mandibular first premolars(P1)were extracted, by the same operator, with forceps, and they were re-implanted in the presence or absence of EMD. Splinting was performed for a week after replantation, and the animals were fed a soft diet during the entire experimental period. All of the animals were sacrificed at 21 weeks after replantation, and dissected specimens around maxillary and mandibular premolars were decalcified by a conventional method. The specimens from both jaws were cut sagittally, including the crown cusp and root apex of P 1 and P 2, and tissue sections were evaluated histologically. Using each tissue section,the clinical crown root ratio was determined, and the root resorption rate was defined as the area of root resorption/total root area including cementum×100(%),and was calculated by two-dimensional computer analysis.
Statistically significant differences were found between EMD-treated and EMD-nontreated groups in the root resorption rate and the clinical crown root ratio. In addition, the replanted dental pulp treated by EMD seemed to be histologically the same as the dental pulp of the neighboring control tooth(P2). This finding was quite different from EMD-nontreated replanted dental pulp.
These results suggest that the application of EMD into the intentional replanted root surface stimulates the regenerative potential of connective tissue, such as periodontium and dental pulp, as well as calcified tissue, such as cementum and alveolar bone.
An AQB implant is an HA-coating implant and a simple one-piece column type. It is made of pure titanium on which crystalline HA is coated by a plasma spraying technique.
In this clinical case, one AQB implant was removed by bone resorption caused by an infection and inflammation, three years after installation.The HA coating surface of a new AQB and the removed AQB implants was examined crystallographically by SEM, EDS, and XRD. The HA-coating of the new AQB was 35-100μm in thickness, and 1-10μm in pore size, and contained a small amount of β-TCP. The HA-coating was composed of an aggregate of needle-like single crystals and polycrystals. The Ca/P ratio of their HA crystals was 4.5,much higher than the 1.67 of stoichiometric HA. The higher Ca/P originated in containing CaO in the HA-coating. In the removed implant,needle-like crystals dissolved by the inflammation,and the Ca/P ratio decreased to 1.9, slightly higher than 1.67. XRD revealed the dissolution of needle-like crystals and the presence of CaO.
Various materials for sinus lifting have been used for this type of transplantation, including autologous bone, heterogeneous bone, and artificial bone. A number of reports indicate that the transplantation of fresh autologous bone yields excellent results. If the amount of bone needed for transplantation is small, the necessary bone can be harvested from the mandible(the ramus of the mandible, mental region, etc.),and if a larger amount of bone is needed, the iliac bone can be used as the donor site. The iliac bone is a good source, since large amounts of bone can be harvested from it,including both blocks and fragments. However,bone collection from this area requires more complex surgery, which entails many problems, such as the stress associated with the surgical wound and the more complex facilities required for the operation. Large amounts of cancellous bone for transplantation can be collected from the tibia under local anesthesia, and this site is among the more suitable donor sites if the bone is to be harvested during day surgery. In this article, we present a method for collecting bone from the tibia, citing a case in which this method was employed to obtain bone needed for transplantation.
Conclusion:The combination of bone donation from the tibial head and sinus lifting is considered an excellent means for creating a suitable substructure for implants in patients with severe atrophy of the alveolar ridge, associated with less physical stress.
We evaluated the clinical performance of commercial titanium implants (IAT Fit Ⅱ®, ISHIFUKU Co.) treated by wire-type electric discharge machining during the period under function for 3 to 6 years.
We implanted 417 implants with diameter 3.8 mm and lengths of 8,10,13 and 15 mm, in 131 patients,during the years from 1995 to 1998, at three facilities. Eleven implants failed within one year after implantation, because of early failure of osseointegration. Ten of the 11 failures were 8 mm-length implants. There was no failure of implants after that period during the observation. Therefore, the survival rate of the implant during the overall 6 years was 97.4%.
Patients were restored with 145 super-structures,such as 121 bridge-type prostheses,12 single-tooth replacements, and 7 overdentures.
Six of the 75,8 mm-length implants showed marginal bone resorption of over 3 mm during 3 years.However, other implants were observed to be clinically satisfactory in the regions with different bone quality. Therefore, the success rate of implants placed in this study was 95.7% during the period of observation.
These results indicated the current implant system evaluated in this study achieved a high survival and success rate, even in the region with fragile bone, although 8 mm-length implants showed worse prognosis.