[Show abstract][Hide abstract] ABSTRACT: Previously, sex differences among the various tooth types in Japanese skulls were examined to facilitate choosing an implant diameter similar to the cervical diameter of each tooth, and it was found that mesiodistal diameters at the cementoenamel junction were narrower in women than in men. Also interesting and relevant to the selection of implant diameter is the possible existence of racial differences in diameters at the cementoenamel junction. The purpose of this research was to test the hypothesis that the diameter at the cementoenamel junction of the tooth differs in humans of different races. We compared 106 skulls of unknown sex collected from South Asia with the skulls of Japanese women. Our conclusions are as follows: (1) Except for the lower canine, no significant racial differences were found in the labiolingual diameter of any teeth. (2) Except for the upper canine, upper central incisor, lower second premolar, and lower first premolar, a significant racial difference was found in the mesiodistal diameter. In all teeth in which this value differed, the mesiodistal diameters of South Asians were narrower than those of Japanese women, except for the lower canine. (3) The labiolingual and mesiodistal diameters of the lower canine were significantly larger in South Asians than in Japanese women. (4) Among South Asians, no significant left/right differences were found in the diameter at the cementoenamel junction of any tooth.
[Show abstract][Hide abstract] ABSTRACT: Magnets are frequently applied to removable dentures as retentive attachments. A magnet-retained removable overdenture might be slightly shifted from side to side by eccentric movement in the mouth, and the surface of magnetic attachment may be worn as a result. However, the relationship between the retentive force of magnetic attachment and its surface abrasion has not been reported. The purpose of this research is to investigate this relationship. Ten Mgfit DX 400 magnetic attachments for natural tooth roots were used for this experiment. The magnetic attachments were embedded in autopolymerizing acrylic resin, and ten pairs of specimens were fabricated. A 5-mm repeated gliding motion was applied on each pair of specimens until 30 000, 50 000, or 90 000 cycles had been achieved. The abrasion machine was under 5 kg loading, and the slide speed was 60 times/min. The retentive force of magnetic attachment was measured with a tension gauge at (1) before gliding; (2) after 30 000 gliding cycles; (3)after 50 000 gliding cycles; or (4) after 90 000 gliding cycles. The average change of retentive force of ten magnetic attachments after 30 000, 50 000, and 90 000 gliding cycles was 0.016 N, 0.003 N, and -0.008 N, respectively. The change was statistically analyzed using a paired-sample t test, which showed that the number of gliding cycles did not affect the retentive force of magnetic attachment significantly. The surface of magnetic attachment after gliding was observed by a microscope, and the abrasion of this attachment surface is clearly seen.
[Show abstract][Hide abstract] ABSTRACT: This study was conducted to histomorphologically determine the quantity of bone formation induced by TAK-778, a 3-benzothiepin derivative, (Takeda Pharmaceutical Co.Ltd.), in various amounts, using b-tricalcium phosphate granules (beta-TCP; OLYMPUS Corp.) as a carrier for the osteogenetic agent.
Ten-week-old female SD rats were used. An incision was made over the parietal region of the head. The cranial periosteum was ablated and a titanium tube was fixed with an adhesive resin cement to the central part of the head, through which a mixture of TAK-778 and beta-TCP was implanted under various conditions. Tissue specimens were prepared at 4, 8, and 16 weeks after the implantation for histomorphological examination, and the proportion of new bone formation was compared at fixed time points using the NIH imaging software. The amount of new bone formation was examined every week after the implantation of TAK-778 at various doses, and the mean values were compared using Fisher's PSLD test (P< 0.05).
The histomorphological observations revealed new bone formation in all the groups, irrespective of the amount and the duration of implantation of TAK-778. A comparative study revealed that the amount of new bone formation was the largest at 16 weeks following the implantation of a mixture of beta-TCP and 100 mg of TAK-778.
1. The present study confirmed the acceleration of new bone formation soon after TAK-778 implantation. 2. The results suggested that the action of TAK-778 could be maintained over time if the agent was used in combination with beta-TCP. 3. The time-course of bone formation differed depending on the proportion of TAK-778 and beta-TCP in the mixture used. 4. TAK-778 at the dose of 10 mg or 50 mg was more effective than that at the dose of 100 mg for the early formation of new bone. These results indicate that TAK-778 accelerates the formation of new bone and that beta-TCP is a useful carrier for TAK-778.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to evaluate the combination of TAK-778-SR which was sustained-release microcapsules of a bone formation stimulant, TAK-778, and its carrier beta-tricalcium phosphate (beta-TCP) blocks (pore rates 60%, 75% respectively). The difference of their abilities in bone-formation was evaluated histomorphologically by varying the following conditions: with or without TAK-778, pore ratio of carrier and embedding period.
Nine-week-old female SD rats were used. After removing the parietal bone from the head with a trephine bar, the defects were refilled by beta-TCP blocks immersed with or without TAK-778 under the following conditions: saline solution, release microcapsules only, and release microcapsules with TAK-778 (TAK-778-SR). These rats were sacrificed after 5 and 10 weeks and their histological specimens were prepared. Morphological change was observed and the formation rates of each new bone were compared using an NIH imaging program.
A significant amount of new bone was morphologically observed in all beta-TCP samples that were treated with TAK-778-SR. A high rate of new bone formation was confirmed in the 10-week samples (pore rate 75%, with TAK-778-SR) with the NIH imaging.
1. beta-TCP and release microcapsules did not disturb the recovery process. 2. Five- and 10-week samples (pore rate 60%) were absorbed marginally. 3. Absorption was observed in the 5-week samples (pore rate 75%), and it was accelerated further at 10 weeks. 4. An accelerating bone-formation effect of TAK-778-SR was confirmed and beta-TCP block was proved to be highly useful as a carriage material.
No preview · Article · May 2005 · Nihon Hotetsu Shika Gakkai Zasshi
[Show abstract][Hide abstract] ABSTRACT: The selection of the appropriate alignment of an implant and the position of implantation are vital for its longterm success. Excessive load is generated around inclined implants, causing microcracks in the bone, which result in implant loosening and eventual failure. This study was designed to analyze the stress distribution caused by varying the degree of inclination of an implant body and varying the loading position and direction, using the finite-element method of stress analysis. Buccal and lingual two-dimensional simulation models of a cylinder implant, embedded in the first molar edentulous cross-section of the mandible, were prepared, and the stress distribution and maximum principal stresses were recorded. Regardless of the point and direction of loading, compressive stresses were relatively greater when the implant was inclined. This tendency became more pronounced when a 45 degrees loading direction and eccentric loading were tested. For the inclined model, with a 45 degrees loading direction, the compressive stress was observed on the cortical bone adjacent to the direction of inclination, while tensile stress was observed on the opposite side.
[Show abstract][Hide abstract] ABSTRACT: This clinical report describes the retrieval of a malpositioned mandibular implant with a severe lingual inclination. A replacement implant was inserted with an emphasis on its relationship with the maxillary antagonist, resulting in a buccal inclination of approximately 10 degrees. The treatment review highlights the importance of thorough communication among all members of the dental implant team.
No preview · Article · Oct 2002 · Journal of Prosthetic Dentistry
[Show abstract][Hide abstract] ABSTRACT: A highly skilled surgical technic is an important factor for the success of implant. But the heat generation during bone preparation will greatly affect the healing process of bone and prognosis of implant. In this study, the heat occurrence and distribution during bone preparation which performed on an in vitro mandible model (ribs of pig) were considered with the aid of a real-time thermography. IMZ implant drills and bur, designed for cylindrical type implant were used for the bone preparation. The conclusion are as follows: 1. Any drill or bur generates higher heat without water irrigation. 2. Heat distribution produced different shape of range according to different type of drills. 3. On a relationship of preparating time to heat generation, spiral drill takes the longest time to complete drilling but heat rising ratio is slow. Round bur and Canon drill take short time to complete drilling but it is accompanied with rapid heat rising.
No preview · Article · Mar 1990 · Nihon Hotetsu Shika Gakkai Zasshi