The main goal of this study is determining the influence of surface curvature on 3D scanning accuracy of dental castings. The hypothesis is that 3D scanning errors occur on the geometry (surfaces) of a higher curvature on the dental anatomy. Ten dental castings (five mandibular and five maxillar) were 3D scanned with four different dental 3D scanners. As a reference device Atos Core industrial 3D scanner was used. Using a qualitative-quantitative approach of dividing every tooth in three areas (OSocclusal surface, CSBcrown surface buccal side, CSPcrown surface palatal side) and observing the frequency of maximal deviation for each area a deviation map was obtained, which shows on what area, are the biggest deviations and in which frequency they emerge. In total 160 teeth were analysed. To conclude, 3D scanning errors occur more frequently on the geometry (surfaces) of a higher curvature on the dental anatomy. Future work suggests conducting a full numerical analysis to find a correlation between the accuracy of 3D scanned teeth surface and a surface curvature. Comparing the 3D scanning deviation to the calculated curvature of the surface could unveil which curvature is hard to 3D scan and generates errors.

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SAŽETAK: Zbog različitih bolesti i ozljeda šake, potrebno je provesti rehabilitaciju s ciljem postizanja pokretljivosti, koordinacije i povratka funkcije šake. Pri rehabilitaciji pacijenata s parezom šake, koja je posljedica moždanog udara, postupak najčešće obuhvaća fleksijsko i ekstenzijsko gibanje prstiju šake, a terapiju je moguće provoditi pomoću rehabilitacijskih uređaja. Kod fleksije i ekstenzije prstiju šake javljaju se momenti u zglobovima koji predstavljaju pokazatelje aktivnosti pojedinih mišića. Poznavanje potrebnih momenata i sila bitno je za konstruiranje rehabilitacijskog uređaja. Prilikom konstruiranja rehabilitacijskih uređaja moguće je u ranoj fazi, pomoću računalnog modela, analizirati karakteristike uređaja i učinkovitost međudjelovanja uređaja i dijela tijela za koji treba provesti rehabilitaciju. Cilj istraživanja bio je razviti biomehanički model ljudske šake koji opisuje fleksijsko i ekstenzijsko gibanje i ponašanje šake kod međudjelovanja s rehabilitacijskim uređajem te omogućuje analizu karakteristika uređaja za rehabilitaciju u ranoj fazi konstruiranja. Potrebni kinematički podaci utvrđeni su mjerenjem u biomehaničkom laboratoriju. Pomoću razvijenog matematičkog modela moguće je odrediti sile i momente u zglobovima, a time i procijeniti aktivnosti pojedinih mišića. Ovo, na temelju željene mišićne aktivnosti, omogućuje određivanje parametra potrebnog opterećenja koje treba osigurati uređaj u ranoj fazi konstruiranja rehabilitacijskog uređaja.

To determine the biomechanical properties of the distal tendon of the gracilis muscle and the upper third of the quadriceps femoris muscle used for reconstruction of the medial patellofemoral ligament (MPFL), it is necessary to develop a calibration device for specimen preparation for uniaxial tensile tests. The need to develop this device also stems from the fact that there is currently no suitable regulatory or accurate protocol by which soft tissues such as tendons should be tested. In recent studies, various methods have been used to prepare test specimens, such as the use of different ratios of gauge lengths, different gripping techniques, etc., with the aim of obtaining measurable and comparable biomechanical tissue properties. Since tendons, as anisotropic materials, have viscoelastic properties, the guideline for manufacturing calibrator devices was the ISO 527-1:1993 standard, used for testing polymers, since they also have viscoelastic behaviour. The functionality of a calibrator device was investigated by preparing gracilis and quadriceps tendon samples. Fused deposition modeling (FDM) technology was used for the manufacturing of parts with complex geometry. The proposed calibrator could operate in two positions, horizontal and vertical. The maximum gauge length to be achieved was 60 mm, with the maximum tendon length of 120 mm. The average preparation time was 3 min per tendon. It was experimentally proven that it is possible to use a calibrator to prepare tendons for tensile tests. This research can help in the further development of soft tissue testing devices and also in the establishment of standards and exact protocols for their testing.

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