Mikrostruktura je osnovni faktor koji određuje svojstva nekog materijala. Cilj ove
studije je procena mikrostrukturnih promena nakon višestrukog pretapanja dve komercijalne
dentalne legure, Ni-Cr (Wiron 99) i Co-Cr (Dentalit C) i njihov uticaj na fiziološke procese
ćelija, kao i komparacija kvaliteta dve ispitivane legure, od kojih jedna sadrži, a druga ne
sadrži Ni.
U ovom istraživanju pošlo se od pretpostavke da više puta topljenja i livenja dentalna
legura ima promenjenu mikrostrukturu, koja utiče na izmenu fizičko-mehaničkih svojstava
i biološkog kvaliteta legura. Uzorci obe ispitivane legure izliveni su nakon prvog, četvrtog
i osmog topljenja, bez dodavanja nove legure. U cilju mikrostrukturne karakterizacije
optičkom mikroskopijom uočena je tipična dendritna struktura uzoraka Co-Cr, kao i Ni-Cr
dentalne legure, nakon različitog broja topljenja i livenja. Poznato je da dendritna struktura
pokazuje razliku u hemijskom sastavu i da dendritne grane sadrže manje legirajućih i
pratećih... elemenata nego međudendritni prostor. Uočene su promene u mikrostrukturi koje
su znatno izražejnije kod Co-Cr dentalne legure. SEM analiza je dala jasnije podatke o
strukturi ispitivanih uzoraka dentalnih legura. Poznato je na osnovu binarnog dijagrama
stanja da Ni-Cr sistem pokazuje široku oblast rastvorljivosti u čvrstom stanju Cr u Ni. U
složenom sistemu kao što je Wiron 99 pored čvrstog rastvora bogatog Ni uočavaju se i
faze u međudendritnom prostoru nepravilnog oblika, koje menjaju svoj raspored u zavisnosti
od broja ponavljanih topljenja i livenja. EDS analizom utvrđeno je da se razlika u hemijskom
sastavu dendrita i međudendritnog prostora veoma mala za leguru Wiron 99. Kada je u
pitanju legura na bazi Co-Cr, bilo je moguće praćenje razlike u hemijskom sastavu između
dve zone, dendrit-međudendritni prostor. Sa povećanjem broja ponovljenog topljenja i
livenja uočeno je da dolazi do homogenizacije strukture, odnosno do smanjenja razlike u
hemijskom sastavu i da je to najuočljivije za elemente Co i Mo, dok ostali praćeni elemente
Cr, Fe i Si imaju ravnomernu (homegenu) raspodelu u analiziranim zonama.
Rendgenostrukturnom analizom uzoraka Ni-Cr dentalne legure uočene su samo
refleksije površinski centrirane kubne kristalne rešetke čvrstog rastvora α-Ni. Utvrđeno je
da sa povećanjem broja topljenja i livenja legure, menjaju relativni intenziteti difrakcionih
maksimuma. Takođe se menja i preferentna orjentacija kristalita sa povećanjem broja
ponovljenog topljenja i livenja...
Microstructure is the basic factor that determines the properties of any material.
The aim of this study is to evaluate the effect of recasting of two commercially available
dental alloys, Ni-Cr (Wiron 99) and Co-Cr (Dentalit C), on physiology of cells, as well as
comparation those two dental alloys, one containing Ni and the other not.
In this study the it was presumed that many times recasted dental alloy has changed
microstructure, which influences the physical and mechanical properties and biological
quality of the alloy. The specimens of both tested alloys were casted after the first,
fourth and eight melting, without adding any amount of new alloy. The microstructural
characterization by optical microscopy showed typical dendritic structure of Co-Cr and
Ni-Cr alloys after different numbers of recasting. It is well known that the dendritic structure
shows differences in chemical composition and that the dendrite branches contain less
alloying and trace elements than the interdendr...itic zone. There were noticed some
microstructural changes that were much more obvious by Co-Cr dental alloy. SEM analysis
has given more explicit informations about the structure of the examined dental alloys.
Based on the binary phase diagram, Ni-Cr alloy shows a wide region of solubillity in solid
condition Cr in Ni. In a complex system, as it is in Wiron 99, beside the solid solution of
Ni rich phase, there are also phases in the interdendritic zones with irregular shapes,
depending of the number of recasting. EDS analysis showed the differences in chemical
composition of dendritic and the interdendritic zones, that were very small for Wiron 99.
For the Co-Cr alloy it was possible to detect the differences in chemical compositions
between two zones, dentritic and interdendritic. As the number of recasting was increased,
the structure became more homogenous and the difference in the chemical composition
was decreased for Co and Mo, while the rest of the traceing elements Cr, Fe and Si were
homogenous in the analyzed zones.
X-ray analysis of the specimens of the Ni-Cr dental alloy indicate that there were
only reflections of face centered cubic crystal lattice of solid solution of α-Ni phase. It
was established that the increase of the number of recasting changes the relative intensity
of diffraction maximum. Also, there were changes in the preferred orientation of the
crystallites with the increase of the number of recasting...
