This study examined the corrosion resistance of a Ti-Ni alloy used as implant material in the oral cavity, by applying the ELID method on the mirror grinding finish. Comparing the anode polarization curves in artificial body fluid, the anode polarization curve for ELID grinding material was found to be in the low current density area, indicating excellent corrosion resistance compared to a buffing material and SiC waterproof grinding material. Comparing the anodic polarization curves in a 1% lactic acid solution, the ELID mirror grinding finish material was found to be in a lower current density area than the buffing material and SiC waterproof grinding material, indicating better corrosion resistance. Furthermore, the effectiveness of the ELID grinding method was further verified with respect to improved corrosion resistance when compared to conventional grinding methods used for the mirror surface finishing of implant materials in the oral cavity.
It is well known that implant surface characteristics (topography) affect osseointegration. Grit blasting with abrasives is one method of implant surface modification. It was reported that osteogenesis was increased more by roughening implant surface by apatite grit-blast treatment than by using alumina. This study compared the direction and arrangement of bone induction and formation in the boundary area between the implant produced by the following methods and the surrounding bone, using back-scattering image in SEM:Ti alloy rods grit-blasted with alumina abrasive (Group 1), with apatitic abrasive (Group 2), and with alumina abrasive and plasma-sprayed using hydroxyapatite source (Group 3).
Rabbits were used as the experimental animal for this study, in which a 2.8 mm hole was produced in the tibia and implantation was performed under anesthesia. The rabbits were sacrificed 1, 2, and 4 weeks after surgery under anesthesia, and part of the tibia including the implant was collected as non-decalcified tissue specimens. After vacuum evaporation of carbon, BSI of the specimens was observed using a scanning electron microscope. Although it had been difficult to differentiate the formation of new bone by conventional microscopic observation, entire images could be obtained by the use of BSI, and osteogenetic patterns were clearly observed in this study.
Although G l and G 3 showed new bone smoothly developing from the adjoining compact bone toward the implant surface, G 2 exhibited bone growth originating from the medullary cavity, showing different osteogenetic patterns.
These findings revealed that new bone formation was more marked in the early stage by the use of grit-blasted implants than by the use of apatite materials, showing bone growth patterns differing fromthose in G 1 and G 3.
Entire images could be obtained by the use of BSI in which it had been difficult to differentiate the formation of new bone by conventional microscopic observation, and osteogenetic patterns were clearly observed in this study.
For imaging diagnosis in osseointegrated dental implant treatment, cross-sectional images in the bucco-lingual direction, obtained by conventional X-ray tomography or computed tomography (CT), are necessary. Recently, new compact CT systems have been developed and will likely be used in dental implant treatment.
This study investigated the accuracy of mandibular representation of compact CT for dental use using mandibular measurement and image subtraction, and the influences of changing the threshold to obtain the binary image and size of the region of interest (ROI) were evaluated.
Two semi-lateral dried mandibles were used in this study. Images of the mandibular interdental alveolar bone in the premolar and molar regions were obtained using a compact CT system, 3DX (Morita Co., Japan) and a micro-CT unit (SMX-130CT, Shimadzu Co., Japan). The representations of mandible and trabecular bone patterns constructed from compact CT images were compared with those of mic-CT images.
The results were as follows
The mean difference of mandibular length between compact CT images and micro-CT images was 0.23 mm. The mean agreement rate was 73.8%, and the correlation coefficient of the rate of trabecular bone was 0.920 between the images by compact CT and micro CT, when the threshold of two-value images in compact images was set at the value of 60% and ROIs were set at half the size of those in cancelous bone.
In conclusion, the accuracy of mandibular representation in compact CT was high.
We applied atelocollagen sponge into the wounds of tooth extraction of 40 compromised patients and compared the results with those of 26 healthy patients. The degree of hemostasis, pain, infection and wound closing time were compared. The compromised patients were a diabetic patient, dialysis patient, hepatic diseased patient, patient on oral anti-coagulation therapy such as warfarin or hepar in for circulatory disorders, and cerebrovascular diseased patient. It is known that these compromised patients are prone to bleeding, infection and delayed wound healing.
Atelocollagen sponge indicated high hemostasis, high alleviation of pain, infection control and the wounds closed at 1.72±1.45 weeks in healthy patients. Although hemostasis was slightly inferior to that of healthy patients, the alleviation of pain and infection control were equal to those of healthy patients, and the wounds closed at 1.34±0.52 weeks (T-test;p=0.22) in compromised patients. There were no side effects in both patients.
As a result, we consider that atelocollagen sponge is not only a good material for the wounds of tooth extraction in healthy patients, but is also useful for compromised patients.
Tooth loss in the regions of implants is the result of numerous factors. This study observed the microflora within pockets surrounding the implant following tooth extraction.
Forty-two peri-implantitis patients were divided into two groups based on the cause of tooth loss:the periodontal disease group and the nonperiodontal disease group. All patients had natural teeth on the contralateral side, which acted as controls, and the implant had pockets deeper than 4 mm. After removing plaque from the implant and tooth, bacteria were sampled from the pockets of four line angles of the experimental implant and control teeth using sterilized paper points. Specimens were anaerobically cultured on HK agar culture medium for 7 days. The number of colonies was counted and PCR was used to identify black colonies. Furthermore, probing depths were measured in the bacterial picking region. Colonies were also examined bacteriologically and Student's t-test as a statistical analysis was performed on data related to the number and types of isolated bacteria.
Bacteria were obtained from all experimental regions. Bacteria of 2.1×106 CFU/ml on average was picked from the pocket around the implant, whereas bacteria of 9.7×106 CFU/ml on average was picked from the periodontal pockets as a control in the periodontal disease group. In the non-periodontal disease group,bacteria of 3.2×104 CFU/ml on average was picked from the pocket around the implant, whereas bacteria of 6.8×104 CFU/ml on average was picked from the periodontal pockets as a control. The average BPR was 1.3×102CFU/ml in the pocket around the implant in the periodontal disease group. In the non-periodontal disease group, the average BPR was 4.1×102 CFU/ml in the pocket around the implant.
There were differences with the microflora inside pockets surrounding the implant between loss of teeth with periodontal disease and fracture or dental caries.
In recent years, dental implant treatment has been credited with being highly predictable. However, since its prognosis depends on local or systemic factors and surgical techniques, there are some implants that need to be removed due to unknown causes.
Therefore we classified those cases with an unfavorable prognosis over the last five years, into early-type abnormalities, delayed-type abnormalities and abnormalities after fitting the implant prosthesis. Out of these three categories, we paid particular attention to the early-type abnormalities and, as a result of investigating this category, we found 17 implants. Furthermore, from these abnormal cases, we selected and examined 5 cases where oval characteristic radiopaque image, gingival fistula and infection were identified at the upper or central part of the implant body during observation.
The standard procedure for the placement of multiple implants was performed on each of these cases. However, 5 implants eventually had to be removed. One of the possible causes was considered to be overheating from the drilling procedure to create the implant holes, but the definite cause is still under study. As for surgical methods, in all the cases the standard implant procedure (without GBR) was performed.
Socket lift is a useful method for patients who have a limited amount of bone volume in the edentulous posterior maxilla. Depending on the traditional views, using this technique we need 4 to 5 mm of bone volume beneath the sinus and the sinus floor can be elevated by several millimeters at most. We therefore investigated the modified socket lift method that is equal to the effect of sinus lift. The method requires an implant which has a neck shape in order to achieve an initial fixation of less than 4 mm bone volume beneath the sinus, to make use of the anatomical shape of the sinus floor and to elevate the sinus membrane with curettes.
Thirteen implants in 8 patients were placed using this method. Of these patients, 6 were women and 2 were men. Patient age ranged from 43 to 61 years. The mean age was 53 years 4 months at the time of surgery. The mean remaining bone height between sinus floor and alveolar ridge was 3.2±1.0 mm (range 2 to 5 mm). The mean distance of elevation was 10.8±1.7mm (range 8 to 13 mm). All abutments were connected to the fixtures at 30 Ncm, 4 to 5 months postoperatively and had temporization or restoration accomplished. In some cases after restoration we could confirm with radiographic evaluation that the cortical bone lining beneath the sinus membrane existed above the implants.
Osseointegrated Implant with Cam Connection (CAMLOG Implant System) is an osseointegration based system and has been reported to be outstanding particularly in case of tooth reconstruction; however, there are no reports on clinical cases conducted in Japan in this respect.
At the Department of Oral and Maxillofacial Surgery of the hospital attached to Tokyo Women's Medical University, a total of 75 implants was placed during the period from June 2000 to December 2002 for 15 male and 15 female patients aged between 42 and 64. Among those cases 71 implants were set with superstructures for at least 6 months.
Four implant types, Screw-cylinder, Cylinder, Root-form and Screw-line, are currently available with the CAMLOG system. Regarding the break-down of implants placed, 58 Screw-cylinder implants (81.7%) were the most numerous among the four types. Forty-four implants (62.0%) were 13 mm in length and 59 implants (83.1%) were 4.3 mm or larger in diameter.
Concerning superstructures, 39 implants (54.9%) received a single crown. In total, 42 straight abutments (59.2%) and 29 angled abutments (40.8%) were used. Forty-six (64.8%) had a crown/implant ratio (CL/IL) of 0.8 or less, and 31 out of them (67.4%) were restored by a single crown. Increasing the CL/IL ratio leads us to use more connecting prosthesis.
The Periotest value was negative in all cases. Its mean value was -4.23 at the time of prosthetic delivery and -4.53 at the time of second measurement (5-9 months later).
These values show the good status of occlusal function from the initial stage of occlusal reconstruction. There has been no screw loosening or prosthetic failure in the CAMLOG Implant System so far. This result suggests that the system can be safely used either in tooth for tooth or connecting reconstructions.
Distraction osteogenesis has been used for vertical alveolar ridge augmentation in implant treatment. This technique has various benefits compared with autologous bone graft. Therefore, alveolar ridge augmentation using distraction osteogenesis is prevailing in inadequate bone cases. This technique involves osteotomy in the alveolar bone to obtain a moving bone fragment. In the conventional method, the lingual mucosa must not desquamate in order to supply blood to bone the fragment during osteotomy. However, osteotomy requires blind surgery in the lingual site, and can injure the lingual tissues. So, we performed osteogenesis distraction without lingual osteotomy at the posterior site of the mandible. When box formed osteotomy was performed by our method, the bone fragment was separated from the mandibular bone completely.
The patient, who had contracted vertical bone resorption, underwent distraction osteogenesis without lingual osteotomy. Total lengthening was 5.0 mm in the vertical direction in 10 days. During the latency period, local infection occurred, but a sufficient bone volume was obtained. Our result suggested that distraction osteogenesis without lingual osteotomy is useful for alveolar bone augmentation.
A case in which a 62-year-old female suffered acute lymphoblastic leukemia (ALL) during dental implant treatment is reported. Combined chemotherapy was used to treat the disease; severe stomatitis and necrosis of mucous membrane around the implants occurred, then one of seven implant fixtures installed was lost. Superstructures including abutments were removed to reduce stimulation as well as to enable cleaning, resulting in the implant fixtures being in the sleeping condition; the local treatment mentioned above could improve the mucosal condition. Not only because the implant patients are mostly aged, the clinicians must aware that unpredictable diseases such as ALL may arise during or after implant treatment, and also must prepare countermeasures.
Mandibular osteomyelitis is one of the most difficult diseases to treat, because the patient sometimes suffers from severe pain or functional disturbance, and it takes a long time to heal.
This paper describes a comprehensive treatment including dental implant after the healing of mandibular osteomyelitis.
The patient was a 41-year-old female. Her chief complaint was a pain in the left mandibular premolar region. X-ray showed radiolucency in the left canine and premolar apical region of the mandible.
After initial anti-inflammatory treatment, extraction of the left mandibular canine and first premolar teeth was carried out. Histopathological diagnosis was acute suppurative osteomyelitis.
Fourteen months after the anti-inflammatory treatment, a chin bone graft was performed to the 34 region, then implants were placed 7 months later. At the same time, orthodontic treatment was performed and those implants were used as absolute anchors. After the orthodontic treatment, the superstructure was fabricated.
Three years have passed since implant placement, and there are no signs of recurrence of mandibular osteomyelitis.
Osseointegrated implants have been clinically applied in prosthetic treatments, and many studies have been advocated to investigate them. Among the results obtained from these studies, post operative failures such as abutment fracture have been mentioned. We carried out a prospective study of two-step titanium and hydroxyapatite coated osseointegrated dental implants (provided by KYOCERA) that were clinically used from March 1989 to March 1992, in order to evaluate their long term prognosis. From our evaluation, we also found some clinical cases in which fractures of the abutment screw had occurred around 7 years after implant placement. Possible reasons for these failures are changes in the occlusal pattern, metal fatigue, etc. However, these can be considered causative factors only when they are examined together but not when presented as single factors. We therefore carried out a comparative examination among those abutments having fractures, those without fracture but which were used during the same period of time, and the screw portion of abutments that have not been used yet.