Recently, we showed that a cementum-impregnated gelatine membrane (CGM) could form periodontal ligament-like tissues around hydroxyapatite (HA) implants. This pilot study was carried out to evaluate the effects of CGM with various amounts of cemental partitles on the healing of peri-implant tissues. Hydroxyapatite (HA) implants compounded with and without CGM were placed in experimentally created edentulous ridges of monkey jaws. After 3 months the animals were sacrificed, and implants were retrieved and studied following preparation with a cutting-grinding system. Histological examination of undecalcified sections revealed that epithelial downgrowth was suppressed by applying CGM to the HA implants, whereas considerable epithelial downgrowth was observed with a large amount of inflammatory cells on HA implants without CGM. The results thus suggest that HA implants compounded with CGM suppress epithelial downgrowth.
The bone augmentation method for dental implants has become a main means of controlling the prognosis of dental implants in clinical treatment. Platelet-rich plasma (PRP) has been accepted as a safe material which can be extracted from the blood of patients. Furthermore, PRP is used in many treatments to enhance bone formation.
The aim of this study was to identify what kind of growth factor was affected by PRP on bone formation in an animal experiment.
Six adult dogs were selected, and four implants were placed in the lower jaw of each dog; two implants were located on the right side and the other two on the left side, to obtain control and experimental sides respectively. After that, an artificial bony defect was made between two implants on both sides, and then the defect on the experimental side was filled up with PRP extracted from the same dog. Radiographic, histological and immunohistochemical methods were used for a comparative analysis.
The results showed new bone formation due to PRP at the first week after the operation, and it was identified by both radiographic and histological methods. In addition, positive reactions of PDGF in immunohistochemical qualitative analysis and quantitative search were confirmed.
From the data it was concluded that PDGF was the main growth factor for the bone formation when PRP was applied to the artificial bony defects of the studied dogs.
Hydroxyapatite (HAp) has been used as a biomaterial for hard tissues because of its excellent biocompatibility and osteoconduction. However, the non-absorbable HAp remains as a foreign body in a living body and may trigger inflammation. The aim of this study was to develop biomimetic ceramics from bovine bone and to estimate the absorbable property in vivo histomorphometrically.
Spongy and cortical bones in bovine femur were used as starting materials and calcined at 500～800℃ to obtain b-HAp. The spongy b-HAp was partially dissolved in HNO3 solution, and the cortical b-HAp was completely dissolved in the other HNO3 solution. After the two solutions were mixed, HAp (r-HAp) crystals were precipitated on the macropores and micropores of spongy b-HAp at pH 10.5 and 25℃. The modified spongy b-HAp was filtrated and dried to fabricate the functionally graded HAp (fg-HAp) ceramics. The fg-HAp ceramics were characterized by pore sizes of 100～600 µm, porosities of 70～80%, and small amounts of metal ions. SEM photograph of the fg-HAp showed spherical moss like-grains of about 1.0μm in size, which consisted of about 10 nm r-HAp microcrystals. Micro-XRD analyses indicated that the crystallinity of fg-HAp single phase was better from the surface layer to bulk region in the ceramics. fg-HAp (3×3×3 mm)/rhBMP-2 were implanted into the subcutaneous tissue in 4-week-old Wistar rats. At 1, 2, 3, 4 and 8 weeks after the implantation, the ceramics were explanted and stained with hematoxylin-eosin and evaluated histopathologically. The ceramics were covered by a thin connective tissue. At 4 weeks, body fluid was well invaded and diffused into the micropores and microcracks of the ceramics and there was new bone formation and marrow in the macropore spaces. The fluid invaded into the HAp was stained with albumin antibody. At 8 weeks, the remaining HAp was retained by bone. Mature bone and fatty marrow were observed. Morphometric analysis showed the HAp volume diminished from 27% at 4 weeks to 25% at 8 weeks. These results indicated that fg-HAp/rhBMP-2 was a bioceramic with characteristics of superior new bone formation, bioabsorption and biocompatibility.
The use of magnetic attachments in implant-supported overdentures has been attempted in a variety of forms. Magnetic attachments for two implants inserted in the canines area between both mentale foramen in the edentulous mandible in particular are highly regarded for their simplicity and usefulness. Nevertheless, the distribution of force acting on the residual ridge differs depending on the shape of the upper surface and has yet to be clarified.
To clarify the optimal shape of the upper surface for attachment, we geometrically analyzed the compression force acting on the residual ridge, bearing capacity of the residual ridge, and the effects of two types of upper surfaces, a dome shape and a reverse dome shape. We inserted an implant fixture in the portion corresponding to the canines between both foramen mentale in a standard model of the edentulous mandible and attached a dome attachment. We fabricated a plaster model and measured the slope and area of the residual ridge. In accordance with Young's modules, we calculated the compression force on the residual ridge mucosa by the denture with respect to a fixed amount of sinking and determined the ratio of the supportable occlusal force as support efficiency.
In addition, symmetrical to the dome shape, a reverse dome shape with the same radius of curvature was analyzed in a similar manner.
As a result, the dome shape was able to support occlusal force 10.7% greater than the reverse dome shape at a fixed amount of sinking. With respect to fixed occlusal force, the dome shape had 11.1% less sinking of the residual ridge mucosa than the reverse dome shape. In addition, the dome shape displayed maximum support efficiency at the portion distal to the first molar, and support capacity was evenly distributed. In contrast, the reverse dome shape displayed maximum support efficiency at the portion corresponding to the second premolar, and the range of support efficiency tended to be concentrated.
These results suggest that the dome shape is superior to the reverse dome shape by effectively and evenly bearing a large occlusal force on the residual ridge mucosa.
It has been reported that periopathic bacterial colonization occurs in peri-implant sulci as well as periodontal pockets. When natural teeth and implants co-exist in the same oral cavity, peri-implantitis may occur, owing to periopathic bacterial transmission from periodontal pockets of natural teeth to peri-implant sulci.
In this study, we investigated the possibility of transmission of four periopathic bacteria (Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Fusobacterium nucleatum) from natural teeth to implants in the same oral cavity.
We collected subgingival plaque from 113 implants and 92 natural teeth of 50 partially edentulous patients, and the four periopathic bacteria were detected by arbitrarily primed polymerase chain reaction (AP-PCR). The matched strains existed in more than 70%. This suggests that the bacterial transmission occurs from the remaining natural teeth to peri-implant sulci. Therefore, implant should be done after periodontal treatment of the remaining natural teeth.
When periopathic bacteria were detected within the subgingival plaque obtained from either natural teeth or implants, the same bacterial species were also found with high frequency of more than 80% within saliva. So, the bacterial transmission by saliva may occur from the remaining natural teeth to implants within the same oral cavity. This result suggests that saliva is useful for bacterial examination to predict peri-implantitis without injury of peri-implant sulci caused by probing.
Purpose:We evaluated occlusal contacts in the intercuspal position (ICP) of prostheses without stress absorbing elements on osseointegrated implants (the prostheses) and natural teeth.
Materials and methods: We selected 13 subjects who had shown excellent clinical progression for three years or more after placement of the prostheses on either an IMZ implant (5 subjects) or Brånemark implant (8 subjects) in mandibular unilateral free-end cases from whom informed consent had been obtained for the purpose of this research. The registration of occlusal contacts using silicone impression materials was made during clenching in ICP at two levels (10 and 30%MVC) under maximum EMG amplitude (100%MVC). To read the silicone occlusal records quantitatively, we used the addpicture inspection method which visualized occlusal contacts by digital image processing. We observed variations in the number and area of occlusal contacts between the two occlusal strengths. Statistical analysis was performed using the Wilcoxon test to compare between the two levels.
Results:The number and area of occlusal contacts increased with occlusal strength both on natural teeth and on the prostheses. However, the location of the contacts remained the same in both the healthy dentulous subjects and those with the prostheses. For each tooth, with the increase in occlusal strength, the number of occlusal contacts on natural teeth and the prostheses did not increase significantly, and thus the area of occlusal contacts on natural teeth and the prostheses increased significantly (p＜0.05). There was no significant difference between natural teeth and the prostheses in the rate of increase of the area of occlusal contacts with the increase in occlusal strength.
Discussion: The prostheses and the remaining teeth in ICP cooperated with each other, though there were no stress absorbing elements. These results were probably due to displacement of opposing teeth and strain on their supporting tissue.
Conclusion: A harmonious intercuspal position with natural teeth can be established by imparting appropriate occlusal contacts to the prostheses, even if there are no stress absorbing elements.
The aim of this study was to develop a dental implant that is surrounded by periodontal ligament and has an attachment with the ligament in the alveolar socket. After rat maxillary left first molars (ULMI) were extracted, titanium implants which were handmade to be nearly the same size as natural teeth were inserted into the extraction sockets and the support function and structure of newly-formed connective tissue between the implants and alveolar bone were examined.
Male Wistar rats, aged 41～43 days, were used. Under general anesthesia, ULM1 was extracted, and a ULM1-shaped titanium implant was placed into the socket. Mobility of the implant was assessed every week after placement. The tensile strength of the peri-implant connective tissue was measured by extracting the implant from its socket using a materials testing machine. The extracted implants and natural teeth were subjected to scanning electron microscopy to assess their surface characteristics. At 7, 14, 21, and 28 days after placement, rats were sacrificed, and newly-formed peri-implant connective tissue was analyzed with microcomputed tomography (MCT), light microscopy, and polarizing microscopy.
Immediately after placement, the average mobility of the implants was M3. Thereafter, the mobility gradually decreased and became less than M0.3 after 14 days.The tensile strength of the newly-formed peri-implant tissue was low at day 14, but increased markedly at day 28. The mean value at day 28 was 68% of that for the natural tooth. On the surfaces of the extracted implants and natural teeth, collagen fiber bundles, cementoblast-like cells and surrounding amorphous tissue, as in natural teeth, were observed. MCT scans revealed the presence of a periodontal ligament-like radiolucent area between the implants and alveolar bone. Histologically, after one week cementoblast-like cells were seen on the surface of the implants, collagen fiber bundles being seen running perpendicular to the surface of the implants near the alveolar process. After two weeks, extracellular matrix and calcified structures were observed adjacent to the implant surfaces in the middle and apical root levels. Some collagen fibers were aligned parallel to the implant surfaces while the other fibers connected the alveolar bone to the implant as in the periodontal ligament of natural teeth.
These findings suggested that the remaining periodontal ligament adhering to the surface of extraction sockets may induce the formation and attachment of new connective tissue on the implant surface which is similar to the normal support function and structure of periodontal ligament.
Because of the concept of osseointegration proposed by Prof. Brånemark, application of dental implant therapy has made much progress. Currently, various kinds of dental implant systems have been widely used in clinics even for the partial edentulous posterior regions. However, there was only limited information on the long-term success of implants placed in the posterior regions. The purpose of this study was to compare the survival rates of the commercial implant systems with different geometry and surface texture followed for 7 to 14 years after placement.
The subjects were 84 males and 129 females with an average age of 57.9 years. Brånemark Implant System® of 243 implants in 65 patients, ITI Implant System® of 110 implants in 40 patients, and Integral Implant System® of 342 implants in 108 patients were used. The survival rates were assessed according to the implant position and length using the life table analysis method.
The cumulative survival rates were 92.5% for the Brånemark implant system up to 14 years, 92.3% for the ITI implant system up to 14 years, and 91.7% for the Integral implant system up to 12 years. There was no statistical difference between the systems. However, two types of implant failure were identified. The first type of failure was observed in the Brånemark implant system before establishing osseointegration. The second type of failure related to peri-implantitis was observed especially in the Integral implant system during the follow-up periods. In addition, a significantly higher failure rate was observed in all systems using the implants with the length of under 10 mm than with those of above 10 mm.
Purpose: We report that implant treatment for a schizophrenic patient complicated with intellectual disabilities has allowed the patient's masticatory function to improve.
Case: The 53-year-old female patient had been in a mental hospital for the reason of advanced schizophrenia with the complication of intellectual disabilities. The patient was unable to masticate hospital solid food due to the loss of mandibular teeth. No prosthesis was worn at that time because of the risk of mis-deglutition of her denture when using a denture before.
Results: The implants were placed into the sites of the 3223567 three times under local anesthesia. The patient has become able to eat hospital solid food after inserting all superstructures.
Conclusion: It is considered that implant treatment enhances the masticatory capability of schizophrenic patients with intellectual disabilities.