The objective of this study was to investigate the influence of implant/abutment joint designs on abutment screw loosening in a dental implant system, using nonlinear dynamic analysis of the finite element method (FEM). This finite element simulation study used two dental implant systems: the Ankylos implant system (Degusa Dental, Hanau, German) with a taper joint (taper joint-type model), and the Bränemark implant system (Nobel Biocare, Gothenburg, Sweden) with an external hex joint (external hex joint-type model). The nonlinear dynamic analysis was performed using three-dimensional finite element analysis. In comparing the movement of the taper type-joint model and external hex type-joint model, it was found that the external hex type-joint model had greater movement than the taper type-joint model. The external hex joint-type model showed rotation movement, whereas the movement of the taper joint-type model showed no rotation. It was concluded that the nonlinear dynamic analysis used in this study clearly demonstrated the differences in rotation of components in dental implant systems with taper or external hex joints.

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In this study, we examined the effect of the transmitted amount of visible light through a resin composite on the curing depth and polymerization conversion. Transmitted amount of visible light was strongly dependent on the magnitude of refractive index difference that existed between the resin and silica filler. More specifically, the differences arose from the type of base monomer used. The transmitted amount of visible light exhibited a good correlation with the curing depth and Knoop hardness ratio of the bottom surface against the top surface of the resin composite. To improve the polymerization conversion of the cavity floor, it is important to reduce the refractive index difference that exists between the base resin and silica filler.

The influence of surface roughness and calcium phosphate (Ca-P) coating on the bone response of titanium implants was investigated. Four types of titanium implants, i.e. as-machined, grit blasted, as-machined with Ca-P sputter coating, and grit blasted with Ca-P sputter coating, were prepared. The Ca-P sputter-coating, produced by using the RF magnetron sputter technique, was rapid heat-treated with infrared radiation at 600 degrees C. These implants were inserted into the left and right femoral condyles and the left and right tibial diaphyses of the rabbits. After implantation periods of 2 and 12 weeks, the bone-implant interface was evaluated histologically and histomorphometrically. Histological evaluation revealed no new bone formation around different implant materials after 2 weeks of implantation. After 12 weeks, bone healing was almost completed. For both tibial and femoral implants, Ca-P coated implants always showed a higher amount of bone contact than either of the non-coated implants. On the other hand, surface roughness improved only the response to implants inserted into the tibial diaphysis. On the basis of these findings, we concluded that 1) deposition of a sputtered Ca-P coating on an implant has a beneficial effect on the bone response to this implant during the healing phase, and 2) besides implant surface conditions the bone response is also determined by local implant site conditions.

Using finite element method (FEM) , this study sought to investigate how the thickness and Young's modulus of cortical bone influenced stress distribution in bone surrounding a dental implant. The finite element implant-bone model consisted of a titanium abutment, a titanium fixture, a gold alloy retaining screw, cancellous bone, and cortical bone. The results showed that von Mises equivalent stress was at its maximum in the cortical bone surrounding dental implant. Upon investigation, it was found that maximum von Mises equivalent stress in bone decreased as cortical bone thickness increased. On the other hand, maximum von Mises equivalent stress in bone increased as Young's modulus of cortical bone increased. In conclusion, it was confirmed that von Mises equivalent stress was sensitive to the thickness and Young's modulus of cortical bone.

The aim of this study was to bind fibronectin directly to a titanium surface treated with tresyl chloride (2,2,2-trifluoroethanesulfonyl chloride) for the development of a strong connection of a dental implant to subepithelial connective tissues and/or peri-implant epithelia. Basic terminal OH groups of mirror polished titanium were allowed to react with tresyl chloride at 37 degrees C for 2 days. The tresylated titanium disk was then immersed into a fibronectin/phosphate-buffered saline solution for 24 h at 37 degrees C. The activation reaction of the basic OH of titanium with tresyl chloride was confirmed by S2p, F1s, and O1s spectra using X-ray photoelectron spectroscopy and -O-S-O2- bonds using Fourier transform infrared reflection-absorption spectroscopy. After the reaction of fibronectin with titanium, the X-ray photoelectron spectroscopy revealed the remarkable effect of the activation of terminal OH groups with the tresyl chloride treatment. The N1s peak derived from the attached fibronectin still remained after 60 s of argon-ion sputtering after tresyl chloride treatment. In contrast, the N1s peak of the specimen not treated with tresyl chloride almost disappeared after only 10 s of argon-ion etching. Fibronectin, a well-known cell-adhesive protein, could easily be attached to the titanium surface by use of the tresyl chloride activation technique.