Objectives: Limited cone-beam CT (CBCT) has recently become popular in dentistry, but there has been no collective opinion on the accuracy of length measurement using CBCT. Some studies suggest that CBCT is superior to conventional CT, but others disagree and believe that CBCT is associated with considerable measurement errors. The purpose of this study was to assess the measurement accuracy of image examination for dental implant treatment.
Material and Methods: A mandibular phantom was designed with precise geometrical morphology and 6 implants (Replace® Select Tapered, Nobel Biocare). The phantom was made with a Teflon sheet surface imitating the cortical bone and internal acrylic resin imitating the cancellous bone. Six implants were placed in the following respective positions: right first molar, right first premolar, right lateral incisor, left second molar, left second premolar, and left canine. The phantom was set in a cylinder-type water tank made of acrylic resin and scanned with an output of 80 kV and 3 mA, and an interval thickness of 1.0 mm using a CBCT apparatus (3DX multi-image micro CT FPD, Morita: 3DX-FPD). The diameter and length of the implants, the distance between the implants, the buccolingual bone width, the lingual cortical bone width, and the vertical length from the apex of the dental implant to the upper rim of the mandibular canal were measured on the CT images and compared to the actual length of the implant.
Results: The measured length of the implants was statistically longer than their actual lengths although the diameter in measurements was very accurate. The measured distance between the outside/center of the two implants was also statistically longer although the internal measurement was very accurate. Noise such as poor granularity and image distortion of the lingual cortical margin shifting buccally were observed in the images of a case with no implant in the image region and implants in the opposite site. Therefore, the patterns of implant placement affected both the measurement of bone width in the horizontal plane and also the measurement of vertical length from the implant to the mandibular canal to a lesser extent.
Conclusion: It was concluded that the vertical length and the distance between implants measured by a CBCT apparatus (3DX-FPD) were longer than their actual length and distance, the existence of a dental implant affected the measurement of bone width in the horizontal plane, and the degree of influence depended on the number of implants and the sites at which they were placed.
Objective: The purpose of this study was to compare the functional properties of attachments for implant overdentures in vitro.
Materials and methods: A mandibular model with two implant replicas in the left and right canines and with pseudo mucous membrane was fabricated. Five types of attachment, which were a magnetic attachment (dome type, flat type, and self-adjusting type, Aichi Steel Corporation, Aichi, Japan), an anchor-type attachment (locator attachment, Zest Anchors Inc., USA), and a ball attachment (DalRo, Biomet 3i, USA), were attached to the model and denture and compared in this research. Lateral forces were measured with strain gauges attached to the implant while a vertical force of 49 N was applied to the occlusal surface.
Result: Mean lateral forces were 0.8 N in the flattype magnetic attachment, 0.6 N in the dome-type magnetic attachment, 0.25 N in the self-adjusting-type magnetic attachment, 0.56 N in the locator attachment, and 1.8 N in the ball attachment.
Conclusion: The functional properties of attachments for implant overdentures varied among the attachments and the self-adjusting-type magnetic attachment had a highly attenuating effect on the lateral force in the implant.
Objectives: Currently available surface modification technologies for endosseous implants seem to have reached a plateau for enhancing the biological potential of implants for better osseointegration. Nano-structuring technology has proven to create unique biological properties in various biomaterials. We recently discovered a self-assembly of uniform nano-scale nodular structures that specifically occurs during physical and chemical depositions of metal or non-metal onto specifically-conditioned micro-textured surfaces of various materials. The formation of these nano-nodules can be controlled in size from under 100 nm to over 1,000 nm, and can even mimic biological molecules. The objective of this study was to examine the protein adsorption and osteoblast cell attachment capacities of titanium surfaces with this nano-nodular structure.
Materials and methods: Ti rods with three different surface topographies were prepared: machined, acid-etched and 200 nm nano-nodular surfaces. The nano-nodular surface was created by sputtering TiO2 onto the acid-etched titanium surface. Protein adsorption capacity of titanium surfaces was examined by placing a Ti rod in the rat femur for 3 h. Cell attachment was evaluated by incubating rat bone marrow-derived osteoblastic cells round the Ti rod for 6 h.
Results: The quantity of cells attached to a titanium rod during incubation for 6 h was 2-fold greater for the nano-nodular surface than for the acid-etched surface. The difference between the nano-nodular and machined surfaces was 6～8 times. Protein adsorbed to the nanonodular surface during incubation for 3 h was 5 and 2 times increased compared to those for the machined and acid-etched surfaces, respectively.
Conclusion: The titanium surface with unique nano-nodular structure substantially enhanced the protein adsorption and cell attachment capacities of titanium over the acid-etched micro-textured surface, providing a groundbreaking route to novel and effective Ti functionalization. Future in vivo studies should be designed to test its osseointegration capability and to determine the usefulness of this nano-structuring technology for clinical application.
Laser welding has been widely used to repair prosthetic appliances as well as joints between similar or dissimilar metals due to its ease of use. The welding of dissimilar metals, particularly cobalt-chromium alloy and gold alloy, is frequently performed in clinical cases. In the present study, the dissimilar metals of cobaltchromium alloy and Type 4 gold alloy were welded using a laser welder to assess the state of the joint by a bending test, its hardness, welding area, fractography and EPMA analyses.
Bending strength and strain after laser welding were significantly lower than in the non-welded specimen group. Bending strength and strain when each weld area was overlapped were significantly larger than when not non-overlapped. Bending strength and strain after welding dissimilar metals were similar to those after welding gold alloys and cobalt-chromium alloys, respectively. EPMA showed a uniform distribution of the dissimilar-metal welded area. In addition, the hardness in the weld was similar to that after welding either cobalt-chromium alloys or gold alloys.
Sufferers of cerebral palsy with total or partial edentulous jaw have difficulty in mastication, speaking, and swallowing because of involuntary muscle spasms and the inability to insert removable dentures. The case of a 56-year-old patient with cerebral palsy was treated using implant-supported fixed prostheses. He suffered from missing bilateral posterior teeth of the mandible. Eight implants were placed in his posterior mandible, and hybrid resin crowns were connected 7 weeks after the implant placement. His masticatory dysfunction improved after dental implant restoration.
The occlusal height had decreased by about 3 mm caused by wear of artificial teeth of superstructures at the follow-up observation at 6 years and 4 months. However, a decrease of bone level around the implants was not observed.