Some consequences of repeated casting of Co-Cr dental alloy

The effect of multiple recasting of commercial Co-Cr base dental alloy (Dentalite-C) on its structural characteristics and ion release rates in artificial saliva has been investigated. The number of recasting was once, four and eight times. The as-cast microstructure became uniformer as the number of recasting was increased whereby macro-and micro-hardness and electrical conductivity of the castings decreased. Metallic ion release in artificial saliva was monitored in vitro over the period of 22 weeks at the temperature of 37 degrees C and pH 2.3. Only Co and Fe were evidenced in artificial saliva and their release rates are measured. The ion release rates increases with time. The ion release rate of Fe was larger than Co. The ion release rates increases substantially by increasing the number of recasting

The effect of recasting on biological properties of Ni-Cr dental alloy

Introduction Increases in market prices of gold over the last 20 years have led to expansion of basic dental alloys, which, primarily due to their good mechanical properties and acceptable prices, have found their place in everyday dental practice. However, within the procedure of making dental prosthetic restorations, the alloys are melted and cast, which leads to changes in their physical, mechanical and biological properties. Objective The objective of the study was to test biocompatibility of a Ni-Cr dental alloy (WIRON 99) depending on the number of melting and casting processes. Methods The working method included the testing of cytotoxicity of the alloy obtained by casting after one, after four, and after eight successive processes of melting. Cytotoxicity of samples was tested by means of a 24-hour and a three-day cytotoxicity test, done on L929 fibroblasts. Results A repeatedly melted and cast alloy shows a reduced biocompatibility and causes specific responses of the tissues in the surrounding area. Since the cytotoxic effect is more significant in the extended contact with the culture cells, a three-day cytotoxicity test showed discrete changes which were the indicator of cell growth inhibition in the cell culture. Conclusion The obtained results confirm the working hypothesis that repeated alloy melting and casting will decrease biocompatibility of dental alloys and will lead to specific responses of the tissue in the surrounding area

Prosthetic treatment after teeth extractions in patients with type 2 diabetes mellitus

Introduction Good and well balanced diet provided by adequate mastication is part of therapy in patients with type 2 diabetes mellitus (DM). The critical period presents the time immediately after teeth extractions; hence, immediate denture is a rational therapeutical choice for diabetic patients. The presence of immediate denture and its compression might compromise wound healing process, affect chewing ability, food intake and consequently blood glucose level in type 2 DM patients. Objective The objective of this study was to compare socket opening diameters (SOD), chewing ability, changes in blood glucose level and food intake in type 2 DM patients with and without maxillary immediate complete denture (MICD) during a three-week wound healing period. Methods The study comprised 78 type 2 DM partially removable denture wearers (42 candidates for teeth extractions and 36 candidates for teeth extractions and insertion of MICDs). During the three-week period participants were followed for SOD, chewing ability and changes in blood glucose level and food intake. Results Patients with MICD showed significantly lower reduction of SOD (seventh, 14th, 21st day) and higher chewing ability (seventh, 14th, 21st day) in comparison to patients without an MICD. Significantly lower number of patients with an MICD had changes in blood glucose level and food intake. Conclusion Maxillary immediate complete denture presents a good therapeutic choice for type 2 DM patients, as it provides possibility of adequate mastication after teeth extractions and maintenance of nutritional status and blood glucose level.Uvod Redovna i balansirana ishrana obezbeđena adekvatnom mastikacijom je značajan deo terapije pacijenata sa dijabetesom melitusom tipa 2 (DM tip 2). Kritičan period za ove bolesnike jeste vreme neposredno nakon ekstrakcije zuba, pa za njih imedijatna proteza predstavlja terapijski izbor. Prisustvo imedijatne proteze i kompresija koju izaziva mogu kompromitovati proces zarastanja, uticati na sposobnost žvakanja, količinu unete hrane, a time i nivo glikemije kod pacijenata obolelih od ovog tipa dijabetesa. Cilj rada Cilj istraživanja je poređenje dijametra ekstrakcionih alveola (DEA), sposobnosti žvakanja, promene količine unete hrane i glikemije kod DM tipa 2 pacijenata sa gornjom totalnom imedijatnom protezom (GTIP) i bez nje. Metode rada Istraživanje je obuhvatilo 78 DM tipa 2 pacijenata, nosilaca parcijalnih pločastih proteza (42 pacijenta indikovana za ekstrakcije zuba i 36 pacijenata indikovanih za ekstrakcije zuba i dobijanje GTIP). Tokom postekstrakcionog perioda od tri nedelje kod pacijenata su praćeni DEA, sposobnost žvakanja, promena količine unete hrane i glikemije. Rezultati Pacijenti sa GTIP pokazali su značajno manju redukciju DEA (7, 14, 21. dana), veću sposobnost žvakanja (7, 14, 21. dana) u odnosu na pacijente bez GTIP. Značajno manji broj pacijenata sa GTIP imao je promene u glikemiji i unošenju hrane u odnosu na grupu bez GTIP. Zaključak Imedijatna proteza predstavlja terapijski izbor kod pacijenata sa DM tipa 2, budući da omogućava dobru mastikaciju nakon ekstrakcija, uz održanje nutricionog statusa i glikemije

Comparative analysis of unilateral removable partial denture and classical removable partial denture by using finite element method

Introduction. Various mobile devices are used in the therapy of unilateral free-end saddle. Unilateral dentures with precise connectivity elements are not used frequently. In this paper the problem of applying and functionality of unilateral freeend saddle denture without major connector was taken into consideration. Objective. The aim was to analyze and compare a unilateral RPD (removable partial denture) and a classical RPD by calculating and analyzing stresses under different loads. Methods. 3D models of unilateral removable partial denture and classical removable partial denture with casted clasps were made by using computer program CATIA V5 (abutment teeth, canine and first premolar, with crowns and abutment tissues were also made). The models were built in full-scale. Stress analyses for both models were performed by applying a force of 300 N on the second premolar, a force of 500 N on the first molar and a force of 700 N on the second molar. Results. The Fault Model Extractor (FME) analysis and calculation showed the complete behavior of unilateral removable partial denture and abutments (canine and first premolar), as well as the behavior of RPD under identical loading conditions. Applied forces with extreme values caused high stress levels on both models and their abutments within physiological limits. Conclusion. Having analyzed stresses under same conditions, we concluded that the unilateral RPD and classical RPD have similar physiological values.Uvod. U lečenju jednostrane krezubosti koriste se različiti oblici mobilnih nadoknada. Jednostrane kompleksne proteze sa preciznim veznim elementima nisu često u upotrebi. Radi rasvetljenja problema jednostrano slobodnog sedla i primene proteze koja ne poseduje veliku spojnicu, u ovom radu je prikazano istraživanje funkcionalnosti ove manje poznate nadoknade. Cilj rada. Cilj rada je bio da se ispitaju i uporede dobijeni naponi jednostrane kompleksne i konvencionalne parcijalne skeletirane proteze pod opterećenjem. Metode rada. U kompjuterskom programu CATIA V5 napravljeni su trodimenzionalni modeli jednostrane kompleksne proteze s odgovarajućim potpornim strukturama (retencioni zubi - očnjak i prvi premolar s namenskim krunicama, alveole i parodontalni prostor) i klasične skeletirane proteze s livenim kukicama. Radi validnosti dobijenih rezultata, modeliranje je obavljeno u prirodnoj veličini. Primenom metode konačnih elemenata izvršena je komparativna analiza vrednosti dobijenih napona pri opterećenju silama od 300 N u predelu drugog premolara, 500 N u predelu prvog molara i 700 N u predelu drugog molara. Rezultati. Proračun je dao sliku ponašanja celog modela jednostrane kompleksne parcijalne proteze s retencionim zubima i sliku celog modela klasične skeletirane parcijalne proteze koje su predstavljene u obliku napona pri različitim uslovima opterećenja. Uneta opterećenja izazvala su visok nivo napona na modelu i zubima nosačima, ali u granicama fiziološke podnošljivosti. Zaključak. Naponi na potpornim strukturama jednostrane kompleksne proteze koji su nastali usled dejstva primenjenih sila bili su u podnošljivim fiziološkim granicama. U uslovima istog opterećenja primenom metode konačnih elemenata dobijaju se veoma slične vrednosti napona jednostrane kompleksne proteze i konvencionalne skeletirane proteze

In Vitro Assessment of Ni-Cr and Co-Cr Dental Alloys Upon Recasting: Cellular Compatibility

The aim of this study was to evaluate the effect of recasting of commercially available Ni-Cr (Wiron 99) and Co-Cr (Dentalit C) dental alloys on physiology of microenvironmental cells. The viability of fibrosarcoma (L929) cells, human embrional fibroblasts (MRC-5) and isolated peripheral blood mononuclear cells (PBMC) was measured by MTT and acidic phosphatase tests. Presence of dying cells was estimated by Annexin/PI staining while the production of intracellular nitric oxide (NO), reactive oxygen (ROS) and nitrogen (RNS) species was determined by DAF-FM diacetate and DHR staining. Recasting of Ni-Cr alloy intensified its cytotoxicity manifested through enhanced free radicals production, induction of cell death and permamently diminished cell proliferation. On the other hand, after initial toxic effect cells adapted to the presence of Co-Cr alloys. Independently of recasting, Co-Cr alloys are more compatible with microenvironment then Ni-Cr alloy. Oppositely, recasting of Ni-Cr alloy promoted its toxicity

In Vitro Assessment of Ni-Cr and Co-Cr Dental Alloys Upon Recasting: Cellular Compatibility

The aim of this study was to evaluate the effect of recasting of commercially available Ni-Cr (Wiron 99) and Co-Cr (Dentalit C) dental alloys on physiology of microenvironmental cells. The viability of fibrosarcoma (L929) cells, human embrional fibroblasts (MRC-5) and isolated peripheral blood mononuclear cells (PBMC) was measured by MTT and acidic phosphatase tests. Presence of dying cells was estimated by Annexin/PI staining while the production of intracellular nitric oxide (NO), reactive oxygen (ROS) and nitrogen (RNS) species was determined by DAF-FM diacetate and DHR staining. Recasting of Ni-Cr alloy intensified its cytotoxicity manifested through enhanced free radicals production, induction of cell death and permamently diminished cell proliferation. On the other hand, after initial toxic effect cells adapted to the presence of Co-Cr alloys. Independently of recasting, Co-Cr alloys are more compatible with microenvironment then Ni-Cr alloy. Oppositely, recasting of Ni-Cr alloy promoted its toxicity