Introduction:An abfraction lesion is a type of a non-carious cervical lesion (NCCL) that represents a sharp defect on the cervical part of tooth, caused by occlusal biomechanical forces. The largest prevalence of the NCCL is found on the mandibular first premolar. The goal of the study is, by means of a numerical method – the finite element method (FEM), in an appropriate computer program, conduct a stress analysis of the mandibular premolar under various static loads, with a special reference to the biomechanics of cervical tooth region.Material and methods:A three-dimensional model of the mandibular premolar is gained from a µCT x-ray image. By using the FEM, straining of the enamel, dentin, peridontal ligament and alveolar bone under axial and paraxial forces of 200 [N] is analyzed. The following software were used in the analysis: CT images processing–CTAn program and FEM analysis–AnsysWorkbench 14.0.Results:According to results obtained through the FEM method, the calculated stress is higher with eccentric forces within all tested tooth tissue. The occlusal load leads to a significant stress in the cervical tooth area, especially in the sub-superficial layer of the enamel (over 50 MPa). The measured stress in the peridontal ligament is approximately three times higher under paraxial load with regard to the axial load, while stress calculated in the alveolar bone under paraxial load is almost ten times higher with regard to the axial load. The highest stress values were calculated in the cervical part of the alveoli, where bone resorption is most commonly seen.Conclusion:Action of occlusal forces, especially paraxial ones, leads to significant stress in the cervical part of tooth. The stress values in the cervical sub-superficial enamel layer are almost 5 times higher in relation to the superficial enamel, which additionally confirms complexity of biomechanical processes in the creation of abfraction lesions.

Preliminary notesToday's business of manufacturing systems is entirely dictated by the dynamics of the market and every day there is a need for adjustment of the structure and parameters of associated manufacturing systems. Those adjustments should ensure the operation of manufacturing systems in more favourable manufacturing and economic conditions, and often this process is directly linked with the starting of investment process. On the other hand, every day practice proves that evaluation of investment program during selection of structure of manufacturing system with the aim to accomplish production plans and reduction of production costs is often based on insufficient sets of information. Lack of information may result in inappropriate insight into overall techno-economic effects that can be achieved by investment program. Within this paper are presented researches which resulted in development of a new systematic approach in the analysis of potential structures and parameters of manufacturing systems with the aim to plan, project or reengineer manufacturing systems on the basis of minimal production costs.Keywords: equipment structure; investments; material flow; manufacturing system; production costs; simulation Utjecaj strukture proizvodnog sustava i opsega investicije na troškove proizvodnjePrethodno priopćenje Poslovanje današnjih proizvodnih sustava u potpunosti je diktirano dinamikom tržišta te se svakodnevno javlja potreba za prilagodbom strukture i parametara proizvodnog sustava kako bi se poslovalo u što povoljnijim tehnološkim i ekonomskim uvjetima, a nerijetko je ovaj process vezan i s ulaskom u investicijski postupak. S druge strane, praksa dokazuje da je ocjena investicijskog programa pri odabiru strukture proizvodnog sustava u cilju ostvarenja planirane proizvodnje i smanjenja troškova proizvodnje često zasnovana na nedovoljnom skupu informacija, tako da se ne dobiva relevantna slika o tehno-ekonomskim efektima koji će biti posljedica investicijskog programa. U okviru članka prikazani su rezultati istraživanja koji su doveli do razvoja metodičkog pristupa analize mogućih struktura i parametara proizvodnog sustava u cilju planiranja, projektiranja ili reinženjeringa proizvodnog sustava na bazi minimalizacije troškova proizvodnje.