Comparative Finite Element Analysis of Endocrowns and Traditional Restorations for Endodontically Treated Mandibular First Molars.

BACKGROUND This study evaluated 2 endocrown designs and traditional restoration with a conventional crown using post and core to find the best restoration design for endodontically treated mandibular first molars. MATERIAL AND METHODS Three 3D finite element models were constructed: (1) post and core restoration, (2) endocrown butt joint margin design, and (3) endocrown with shoulder finish line. The intact tooth geometry was extracted with computed tomography, then modified to the selected restoration designs. Bone and mucosa geometry was simplified and represented as 3 cylinders. Two loading cases were examined on E-max crowns as 400N and 200N vertically and 45º oblique, respectively, that were located at buccal cusp tips and central fossa by nodal force distributed on circular areas with 0.5-mm diameter in each location. RESULTS Traditional restoration kept crown deformation and stresses at lower levels than did endocrowns. Results of the butt joint margin design were comparable to that of shoulder finish line design. Cement had the lowest stress values under shoulder finish line design, while the remaining tooth indicated the superiority of butt joint margin design, with less stresses by 20% and 24%, compared with traditional and shoulder finish line restorations, respectively. CONCLUSIONS The 3 tested restoration designs worked well. Although the differences were small, according to stress analysis results, conventional restoration by post and core achieved the best performance, followed by butt joint margin, which ensures lowest level of stresses on dentine. Finally, the shoulder finish line endocrown can replace the other designs but with higher stress levels.

Recent Advances in Material and Geometrical Modelling in Dental Applications.

This article touched, in brief, the recent advances in dental materials and geometric modelling in dental applications. Most common categories of dental materials as metallic alloys, composites, ceramics and nanomaterials were briefly demonstrated. Nanotechnology improved the quality of dental biomaterials. This new technology improves many existing materials properties, also, to introduce new materials with superior properties that covered a wide range of applications in dentistry. Geometric modelling was discussed as a concept and examples within this article. The geometric modelling with engineering Computer-Aided-Design (CAD) system(s) is highly satisfactory for further analysis or Computer-Aided-Manufacturing (CAM) processes. The geometric modelling extracted from Computed-Tomography (CT) images (or its similar techniques) for the sake of CAM also reached a sufficient level of accuracy, while, obtaining efficient solid modelling without huge efforts on body surfaces, faces, and gaps healing is still doubtable. This article is merely a compilation of knowledge learned from lectures, workshops, books, and journal articles, articles from the internet, dental forum, and scientific groups' discussions.

Advanced Computational Methods in Bio-Mechanics.

A novel partnership between surgeons and machines, made possible by advances in computing and engineering technology, could overcome many of the limitations of traditional surgery. By extending surgeons' ability to plan and carry out surgical interventions more accurately and with fewer traumas, computer-integrated surgery (CIS) systems could help to improve clinical outcomes and the efficiency of healthcare delivery. CIS systems could have a similar impact on surgery to that long since realised in computer-integrated manufacturing. Mathematical modelling and computer simulation have proved tremendously successful in engineering. Computational mechanics has enabled technological developments in virtually every area of our lives. One of the greatest challenges for mechanists is to extend the success of computational mechanics to fields outside traditional engineering, in particular to biology, the biomedical sciences, and medicine. Biomechanics has significant potential for applications in orthopaedic industry, and the performance arts since skills needed for these activities are visibly related to the human musculoskeletal and nervous systems. Although biomechanics is widely used nowadays in the orthopaedic industry to design orthopaedic implants for human joints, dental parts, external fixations and other medical purposes, numerous researches funded by billions of dollars are still running to build a new future for sports and human healthcare in what is called biomechanics era.

Effect of surface modification of zirconia on cell adhesion, metabolic activity and proliferation of human osteoblasts.

Titanium dental implants with sandblasted and/or acid-etched surfaces have shown clinical superiority in comparison to their smooth, machined counterparts, and are now state of the art. Sandblasting of finished, sintered zirconia implants, however, will damage the surface structure and affect the mechanical properties. To improve osseointegration of zirconia dental implants without impairing the original mechanical strength by crack initiation and partial phase transformation from tetragonal to monoclinic, roughening of the zirconia surface by sandblasting before the final sintering step was employed. Impact of the treatments on cellular reactions of SAOS-2 human osteoblast-like cells was investigated. Sandblasting of Yttrium-stabilized zirconia (Y-TZP) with 120 µm and 250 µm Al2O3 enhanced average roughness (Sa) from 0.28 µm to 4.1 µm and 5.72 µm, respectively. Cell adhesion of SAOS-2 osteoblasts was enhanced up to 175% on sandblasted surfaces, compared to the machined zirconia reference (100%). Metabolic activity and proliferation in the logarithmic growth phase (24-48 h) were not significantly affected. Sample surface coverage by the cells after prolonged incubation (72 h) was markedly decreased on the roughened samples, indicating a shift towards increased differentiation on these surfaces. The approach investigated here to roughen zirconia implants by sandblasting before sintering shows potential to improve the clinical performance of ceramic dental implants.