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.

It is well-known that self-etching primers can be altered. However, the effects from altered primers on the dentin bond durability have yet to be thoroughly identified. In this study, we examined the effects from 5 altered Liquid A primers in different stages of degradation-where 2-hydroxyethylmethacrylate (HEMA) and 10-methacryloyloxydecyl dihydrogen phosphate (MDP), used in Liquid A primers, were altered by the hydrolysis of the methacryloxy ester portion in the HEMA and MDP-on the hybrid layer's quality and dentin bond durability. The hypothesis was that degradation stages of altered Liquid A primers have no effect on the hybrid layer's quality and on dentin bond durability. Bond strengths, obtained after thermo-cycling, were strongly dependent on the degradation stage of the altered Liquid A primer. Alterations of self-etching primers reduced dentin bond durability and decreased the created hybrid layer's quality.

Purpose : In this study, we investigated the conditioning efficacy of a self-etching primer consisting of methacrylamide, N-methacryloyl-w-amino acid (MƒÖA) derivatives for enhancing the bond strength of resin to crown and root dentins. Methods : A series of four MƒÖA derivatives, with different methylene chain numbers, were synthesized, as follows. 1 : N-methacrylole glycine (Gly) ; 2 : N-methacrylole-fl-alanine ( fiAla) ; 3 : N-methacrylole-

We designed self-etching primers consisting of a series of four N-methacryloyl-ω-amino acids, MωA, of different methylene chain numbers for resin core construction. The interacted amount of MωA's carboxylic acid with root or crown dentin apatite was determined, and its effects on dentin bond durability examined.The addition of both dentin particles to the MωA solutions caused the carbonyl carbon peak of carboxylic acid in MωA to shift to a lower field, chiefly because of an acid-base interaction between carboxylic acid and calcium. Then, as the pKa value of MωA's carboxylic acid increased, the amount of carboxylic acid that interacted with calcium decreased. In terms of dentin bonding durability, the four tested MωA adhesives provided noticeably higher bond strengths of resin to root or crown dentin than ED Primer II. Therefore, from the perspective of restoring pulpless teeth with minimal intervention, carboxylated MωA adhesives seemed to be very useful as functional monomers for self-etching primers.