Finite element analysis (FEA) has been used extensively to predict the biomechanical performance of various dental implant designs as well as the effect of clinical factors on implant success. By understanding the basic theory, method, application, and limitations of FEA in implant dentistry, the clinician will be better equipped to interpret results of FEA studies and extrapolate these results to clinical situations. This article reviews the current status of FEA applications in implant dentistry and discusses findings from FEA studies in relation to the bone-implant interface, the implant-prosthesis connection, and multiple-implant prostheses.

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Application of finite element analysis in implant dentistry: A review of the literature

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications.

With an ageing population, war, and sports related injuries there is an ever-expanding requirement for hard tissue replacement such as bone. Engineered artificial scaffold biomaterials with appropriate mechanical properties, surface chemistry and surface topography are in a great demand for enhancing cell attachment, cell growth and tissue formation at such defect sites. Most of these engineering techniques are aimed at mimicking the natural organization of the bone tissues and thereby create a conducive environment for bone regeneration. As the interaction between the cells and tissues with biomaterials at the tissue–implant interface is a surface phenomenon, surface properties play a major role in determining both the biological response to implants and the material response to the physiological condition. Hence surface engineering of biomaterials is aimed at modifying the material and biological responses through changes in surface properties while still maintaining the bulk mechanical properties of the implant. Therefore, there has been a great thrust towards development of Ca–P-based surface coatings on various metallic and nonmetallic substrates for load bearing implant applications such as hip joint prosthesis, knee joint prosthesis and dental implants. Typical coating methodologies like ion beam assisted deposition, plasma spray deposition, pulsed laser physical vapor deposition, magnetron sputtering, sol–gel derived coatings, electrodeposition, micro-arc oxidation and laser deposition are extensively studied at laboratory scale. In the present article, attempts are made to give an overview of the basic principles behind the coating techniques as well as advantageous features such as bioactivity and biocompatibility associated with these coatings. A strong emphasis will be given on laser-induced textured and bioactive coatings obtained by the author's research group [A. Kurella, N.B. Dahotre, Journal of Biomedical Applications 20 (2005) 5–50; A. Kurella, N.B. Dahotre, Acta Biomaterialia 2 (2006) 677–688; A. Kurella, N.B. Dahotre, Journal of Minerals, Metals and Materials Society (JOM) 58 (2006) 64–66; A. Kurella, N.B. Dahotre, Journal of Materials Science: Materials in Medicine 17 (2006) 565–572; P.G. Engleman, A. Kurella, A. Samant, C.A. Blue, N.B. Dahotre, Journal of Minerals, Metals and Materials Society (JOM) 57 (2005) 46–50; R. Singh, A. Kurella, N.B. Dahotre, Journal of Biomaterials Applications 21 (2006) 46–72; S.R. Paital, N.B. Dahotre, Biomedical Materials 2 (2007) 274–281; S.R. Paital, N.B. Dahotre, 2009, Acta Biomaterialia, doi:10.1016/j.actbio.2009.03.004 ; R. Singh, N.B. Dahotre, Journal of Materials Science: Materials in Medicine 18 (2007) 725–751.]. Since cells are sensitive to topographical features ranging from mesoscale to nanoscale, formation of these features by both pulsed and continuous wave Nd:YAG laser system will be highlighted. This can also be regarded as advancement towards third generation biomaterials which are bioinert, bioactive and which once implanted will stimulate cell adhesion, proliferation and growth at the interface. Further, an overview of various bio-implants and bio-devices and materials used for these kinds of devices, performance factors such as mechanical and corrosion behavior and surface science associated with these materials are also explained. As the present article is aimed at describing the multidisciplinary nature of this exciting field it also provides a common platform to understand this subject in a simple way for students, researchers, teachers and engineers in the fields ranging from medicine, dentistry, biology, materials science, biomedicine, biomechanics to physics.

Calcium phosphate coatings for bio-implant applications: Materials, performance factors, and methodologies

Calcium phosphate coatings on magnesium alloys for biomedical applications: a review.

Since dental implants must withstand relatively large forces and moments in function, a better understanding of in vivo bone response to loading would aid implant design. The following topics are essential in this problem. (1) Theoretical models and experimental data are available for understanding implant loading as an aid to case planning. (2) At least for several months after surgery, bone healing in gaps between implant and bone as well as in pre-existing damaged bone will determine interface structure and properties. The ongoing healing creates a complicated environment. (3) Recent studies reveal that an interfacial cement line exists between the implant surface and bone for titanium and hydroxyapatite (HA). Since cement lines in normal bone have been identified as weak interfaces, a cement line at a bone-biomaterial interface may also be a weak point. Indeed, data on interfacial shear and tensile "bond" strengths are consistent with this idea. (4) Excessive interfacial micromotion early after implantation interferes with local bone healing and predisposes to a fibrous tissue interface instead of osseointegration. (5) Large strains can damage bone. For implants that have healed in situ for several months before being loaded, data support the hypothesis that interfacial overload occurs if the strains are excessive in interfacial bone. While bone "adaptation" to loading is a long-standing concept in bone physiology, researchers may sometimes be too willing to accept this paradigm as an exclusive explanation of in vivo tissue responses during experiments, while overlooking confounding variables, alternative (non-mechanical) explanations, and the possibility that different types of bone (e.g., woven bone, Haversian bone, plexiform bone) may have different sensitivities to loading under healing vs. quiescent conditions.

In vivo bone response to biomechanical loading at the bone/dental-implant interface.

This study investigated the contamination of abraded Ti surfaces. Using a polishing machine, specimens were abraded with waterproof SiC grit papers under water cooling. The abraded surfaces were examined using element analysis, X-ray diffraction, and hardness tests. Contaminant deposits with dimensions reaching about 30 microns were observed throughout the surface. In these deposits, Ti was apparently reduced by about 10% and replaced by Si and O. The chemical bond state of the Si was similar to that of SiC or a titanium silicide. The O was solute in Ti, which increased the surface hardness. The contaminant deposits were amorphous or very thin. The contamination of Ti, the extent of which was related to hardness, resulted from a reaction with abrasives.

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Surface contamination of titanium by abrading treatment.

Surface Contamination of Titanium by Abrading Treatment

Retention of a prefabricated post and composite resin core system was compared with that of a cast post and core restoration in anterior maxillary teeth on which root canal preparations, enlarged in the coronal part, were performed. The effect of cyclic loading on restoration retention was also investigated. Retention of restorations not subjected to cyclic loading was not influenced by post type, but loaded prefabricated post restorations showed lower retention than both loaded cast post and core restorations and nonloaded prefabricated post restorations. After dislodgment, the failure mode was also determined. The results of this study suggest that if a canal requires extensive preparation, a well-adapted cast post and core restoration may be more retentive than a prefabricated post restoration that does not match the canal shape.

Retention and failure mode after cyclic loading in two post and core systems.

PURPOSE This investigation was concerned with the effect of 3 superstructure materials on the strain around an implant under static and nonimpact dynamic loading. MATERIALS AND METHODS Five highly filled composite resin-veneered crown analogs, 5 autopolymerized acrylic resin-veneered crown analogs, and 5 gold-alloy full cast crown analogs were prepared. The resin veneers were applied to gold-alloy frameworks. These crown analogs were prepared to fit an ITI implant-abutment assembly, which was screwed into a block of acrylic resin to simulate implantation in bone. The crown analogs were successively placed on the abutment, and a lateral load of 100 N was applied to the superstructure by a lever-type testing machine. Strains were recorded under static and dynamic loading by a 2mm-long strain gauge bonded to the surface of the bone simulant tangential to the implant. The dynamic load simulated masticatory cycles (75 strokes/min). RESULTS Although the strain values differed significantly between the static and dynamic loading (P .05). DISCUSSION These findings are in agreement with in vivo measurements, thus suggesting that cyclic rather than impact loading should be used in the investigation of occlusal material behavior under functional loading. CONCLUSION Under static and nonimpact dynamic loading, the 3 superstructure materials tested (highly filled composite resin, acrylic resin, and gold alloy) had the same influence on the strain transmitted to a bone simulant that surrounded a single implant.

Osamu Miyakawa

Papers

Surface contamination of titanium by abrading treatment.

Surface Contamination of Titanium by Abrading Treatment

Retention and failure mode after cyclic loading in two post and core systems.

Influence of superstructure materials on strain around an implant under 2 loading conditions: a technical investigation.

Surface texture and composition of titanium brushed with toothpaste slurries of different pHs