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Background/Aim. There is limited published evidence on the cytotoxicity of 3D printed polymer materials for dentistry applications, despite that they are now widely used in medicine. Stereolithography (SLA) is one of the foremost 3D processes used in 3D printing, yet there are only a small number of resin materials reported to be suitable for medical applications. The aim of this study was to investigate, in vitro, the cytotoxic effect of the 3D printed resin in order to establish the suitability for its usage in dentistry and related medical applications such as surgical dental guides, occlusal splits and orthodontic devices. Methods. To examine the cytotoxicity of the 3D printed polymer-based epoxy resin, Accura® ClearVue™ (3D-Systems, USA), two cell cultures were used: mouse fibroblasts L929, and human lung fibroblasts MRC-5. The cell viability was determined by the Mosmann's colorimetric (MTT) test and the agar diffusion test (ADT). Results. Direct contact of the tested material with the ADT test showed nontoxic effects of tested material in any cell culture. The tested material showed no cytotoxic effect after 3 days of extraction of the eluate by the MTT, but mild cytotoxic effect after 5, 7 and 21 days on both cell lines. The cytotoxicity increased with increasing the time of the eluate extraction. Conclusion. The 3D printed polymer-based epoxy resin, Accura® ClearVue™ (3D-Systems, USA) is considered appropriate for making surgical dental implant guides according to the cytotoxic behavior. According to the mild level of cytotoxicity after the longer extraction periods, there is a need for further evaluation of biocompatibility for its application for the occlusal splints and orthodontic devices., Uvod/Cilj. Malo je objavljenih dokaza o citotoksičnosti 3D štampanih polimernih materijala za upotrebu u stomatologiji, bez obzira na njihovu sve širu primenu u medicini. Stereolitografija (SLA) jedan je od najvažnijih 3D procesa koji se primenjuje za 3D štampu, ali postoji samo Mali broj materijala na bazi smola za koje je dokazano da su pogodni za medicinsku primenu. Cilj ove studije je bio da se ispita, in vitro, citotoksični efekat 3D štampanog polimera kako bi se utvrdila mogućnost za njegovu upotrebu u stomatologiji i srodnim medicinskim oblastima, kao što su hirurške dentalne vođice, okluzalni splintovi i ortodontski aparati. Metode. Da bi se ispitala citotoksičnost 3D štampanog polimera na bazi epoksi smole, Accura® ClearVue ™ (3D-Sistems, USA), korišc'ene su dve c'elijske kulture: fibroblasti miša L929 i humani fibroplasti pluc'a MRC-5. Vijabilnost c'elija utvrđena je Mosmannovim kolorimetrijskim testom (MTT) i testom difuzije agara (ADT). Rezultati. Direktan kontakt testiranog materijala ispitan pomoću ADT pokazao je da materijal nije imao citotoksičan efekat ni na jednu ćelijsku kulturu. Testitrani materijal je imao blag citotoksični efekat posle 5, 7 i 21 dana ekstrakcije eluata primenom MTT na obe ćelijske linije. Citotoksičnost je rasla sa produženjem vremena ekstrakcije eluata. Zaključak. 3D štampani polimer na bazi epoksi smole, Accura® ClearVue ™ (3D-Sistems, USA) se može smatrati pogodnim za izradu hirurških dentalnih implantnih vođica sa tačke gledišta njegovog citotoksičnog uticaja. Zbog pokazanih blagih citotoksičnih efekata nakon dužih ekstrakcionih perioda eluata potrebna su dalja istraživanja u oblasti biokompatibilnosti materijala da bi se taj polimer mogao koristiti za izradu okluzalnih splintova i ortodontskih aparata.

Background/Aim. Dental impressions present a negative imprint of intraoral tissues of a patient which is, by pouring in gypsum, transferred extraorally on the working cast. Casting an accurate and precise working cast presents the first and very important step, since each of the following stages contributes to the overall error of the production process, which can lead to inadequately fitting dental restorations. The aim of this study was to promote and test a new model and technique for in vitro evaluation of the dental impression accuracy, as well as to asses the dimensional stability of impression material depending on the material bulk, and its effect on the accuracy of working casts. Methods. Impressions were made by the monophasic technique using the experimental master model. Custom trays with spacing of 1, 2 and 3 mm were constructed by rapid prototyping. The overall of 10 impressions were made with each custom tray. Working casts were made with gypsum type IV. Measurement of working casts was done 24 h later using a coordinate measuring machine. Results. The obtained results show that the working casts of all the three custom trays were in most cases significantly different in the transversal and sagittal planes in relation to the master model. The height of abutments was mainly unaffected. The degree of convergence showed certain significance in all the three custom trays, most pronounced in the tray with 3 mm spacing. Conclusion. The impression material bulk of 1-3 mm could provide accurate working casts when using the monophasic impression technique. The increase of the distance between abutment teeth influences the accuracy of working casts depending on the material bulk., Uvod/Cilj. Otisak predstavlja negativ intraoralnih tkiva, čijim se izlivanjem u gipsu njihova morfologija prenosi ekstraoralno na budući radni model. Sa laboratorijskog aspekta izrade zubnih nadoknada, izlivanje tačnog i preciznog radnog modela predstavlja prvi i veoma bitan korak, pošto svaka sledeća faza doprinosi daljem povećanju greške tokom izrade, što za krajnji ishod može imati neodgovarajuću zubnu nadoknadu. Cilj istraživanja bio je da se ispitaju novi model i tehnika za in vitro procenu preciznosti zubnih otisaka, kao i da se odredi uticaj količine otisnog materijala na dimenzionu stabilnost otisaka i preciznost izrade radnih modela. Metode. Za uzimanje otisaka korišćena je monofazna tehnika otiskivanja. Individualne kašike sa međuprostorom od 1, 2 i 3 mm napravljene su aditivnom tehnologijom za brzu izradu prototipova. Sa svakom kašikom napravljeno je po 10 otisaka. Radni modeli izlivani su u gipsu tipa IV. Merenje radnih modela vršeno je nakon 24 sata na koordinatnoj mernoj mašini. Rezultati. Rezultati pokazuju da radni modeli napravljeni pomoću sve tri individulane kašike u transverzalnoj i sagitalnoj ravni značajno odstupaju od glavnog dela modela. Visina patrljaka je u većini slučajeva bila kao na glavnom modelu. Stepen konvergencije pokazao je određena odstupanja samo kod kašike sa međuprostorom od 3 mm. Zaključak. Monofazna tehnika otiskivanja i otisni materijal debljine od 1 do 3 mm obezbeđuju izradu preciznih radnih modela. Rastojanje između zubnih patrljaka utiče na preciznost izrade radnih modela u zavisnosti od količine otisnog materijala.

Bacground/Aim. Retentive force of removable partial denture (RPD) directly depends on elastic force of stretched retentive clasp arms (RCAs). During deflection RCA must have even stress distribution. Safety factor is the concept which can be applied in estimating durability and functionality of RCAs. This study was based on analyzing properties of clasps designed by conventional clasp wax profiles and defining the optimal shapes of RCAs for stress distribution and safety factor aspects. Methods. Computer-aided-design (CAD) models of RCAs with simulated properties of materials used for fabrication of RPD cobalt-chromium-molybdenum (CoCrMo) alloy, commercially pure titanium (CPTi) and polyacetale were analyzed. Results. The research showed that geometrics of Rapidflex profiles from the BIOS concept are defined for designing and modeling RCAs from CoCrMo alloys. I-Bar and Bonihard clasps made from CPTi might have the same design as Co- CrMo clasp only by safety factor aspect, but it is obvious that CPTi are much more flexible, so their shape must be more massive. Polyacetale clasps should not be fabricated by BIOS concept for CoCrMo alloy. A proof for that is the low value of safety factor. Conclusion. The BIOS concept should be used only for RCAs made of CoCrMo alloy and different wax profiles should be used for fabricating clasps of other investigated materials. The contribution of this study may be the improvement of present systems for defining the clasps shapes made from CoCrMo alloys. The more significant application is the possibility of creating new concepts in defining shapes of RCA made from CPTi and polyacetale., Uvod/Cilj. Retenciona sila parcijalne skeletirane proteze (PSP) direktno zavisi od elastične sile rastegnute kukice. Da bi uspešno obavile svoju ulogu, retencione ručice kukice (RRK) prilikom defleksije moraju imati što ravnomerniju raspodelu napona. Stepen sigurnosti je pojam koji se može primeniti u proceni trajnosti i funkcionalnosti RRK. Ciljevi ove studije bili su analiziranje svojstava kukica koje su urađene pomoću konvencionalnih voštanih profila za izradu RRK, kao i definisanje optimalnih oblika RRK sa aspekta raspodele napona i stepena sigurnosti. Metode. Analizirani su CAD (computer aided design) modeli RRK kojima su simulirana svojstva gradivnih materijala koji se koriste za izradu legura: CoCrMo, komercijalno čist titan (CPTi) i poliacetal. Rezultati. Rezultati su pokazali da je geometrija Rapid-flex profila, korišćenih u okviru BIOS, definisana za projektovanje i modeliranje RRK koje se izrađuju od legure (CoCrMo). I Bar i Bonihard kukice od CPTi mogu se uraditi po istom konceptu kao i legure CoCrMo sa aspekta stepena sigurnosti, međutim, titanijumske kukice bile su znatno elastičnije i stoga su morale biti masivnije. Kukice od poliacetala ne smeju se modelovati po BIOS konceptu za leguru Co-CrMo. Dokaz za to je vrlo mali stepen sigurnosti. Zaključak. BIOS koncept može da se koristiti samo za RRK koje se izrađuju od legure CoCrMo. Za izradu kukica od ostalih ispitivanih materijala neophodni su drugačiji voštani profili. Doprinos studije predstavlja i poboljšavanje postojećih sistema za definisanje oblika RRK izrađenih od legura CoCrMo. Značajnija primena rezultata je i mogućnost stvaranja novih sistema za definisanje oblika RRK od CPTi i poliacetala.

Uvod/Cilj. Retenciona sila parcijalne skeletirane proteze (PSP) direktno zavisi od elastične sile rastegnute kukice. Da bi uspešno obavile svoju ulogu, retencione ručice kukice (RRK) prilikom defleksije moraju imati što ravnomerniju raspodelu napona. Stepen sigurnosti je pojam koji se može primeniti u proceni trajnosti i funkcionalnosti RRK. Ciljevi ove studije bili su analiziranje svojstava kukica koje su urađene pomoću konvencionalnih voštanih profila za izradu RRK, kao i definisanje optimalnih oblika RRK sa aspekta raspodele napona i stepena sigurnosti. Metode. Analizirani su CAD (computer aided design) modeli RRK kojima su simulirana svojstva gradivnih materijala koji se koriste za izradu legura: CoCrMo, komercijalno čist titan (CPTi) i poliacetal. Rezultati. Rezultati su pokazali da je geometrija Rapid-flex profila, korišćenih u okviru BIOS, definisana za projektovanje i modeliranje RRK koje se izrađuju od legure (CoCrMo). I Bar i Bonihard kukice od CPTi mogu se uraditi po istom konceptu kao i legure CoCrMo sa aspekta stepena sigurnosti, međutim, titanijumske kukice bile su znatno elastičnije i stoga su morale biti masivnije. Kukice od poliacetala ne smeju se modelovati po BIOS konceptu za leguru Co-CrMo. Dokaz za to je vrlo mali stepen sigurnosti. Zaključak. BIOS koncept može da se koristiti samo za RRK koje se izrađuju od legure CoCrMo. Za izradu kukica od ostalih ispitivanih materijala neophodni su drugačiji voštani profili. Doprinos studije predstavlja i poboljšavanje postojećih sistema za definisanje oblika RRK izrađenih od legura CoCrMo. Značajnija primena rezultata je i mogućnost stvaranja novih sistema za definisanje oblika RRK od CPTi i poliacetala., Bacground/Aim. Retentive force of removable partial denture (RPD) directly depends on elastic force of stretched retentive clasp arms (RCAs). During deflection RCA must have even stress distribution. Safety factor is the concept which can be applied in estimating durability and functionality of RCAs. This study was based on analyzing properties of clasps designed by conventional clasp wax profiles and defining the optimal shapes of RCAs for stress distribution and safety factor aspects. Methods. Computer-aided-design (CAD) models of RCAs with simulated properties of materials used for fabrication of RPD cobalt-chromium-molybdenum (CoCrMo) alloy, commercially pure titanium (CPTi) and polyacetale were analyzed. Results. The research showed that geometrics of Rapidflex profiles from the BIOS concept are defined for designing and modeling RCAs from CoCrMo alloys. I-Bar and Bonihard clasps made from CPTi might have the same design as Co- CrMo clasp only by safety factor aspect, but it is obvious that CPTi are much more flexible, so their shape must be more massive. Polyacetale clasps should not be fabricated by BIOS concept for CoCrMo alloy. A proof for that is the low value of safety factor. Conclusion. The BIOS concept should be used only for RCAs made of CoCrMo alloy and different wax profiles should be used for fabricating clasps of other investigated materials. The contribution of this study may be the improvement of present systems for defining the clasps shapes made from CoCrMo alloys. The more significant application is the possibility of creating new concepts in defining shapes of RCA made from CPTi and polyacetale.

Bacground/Aim. Retentive force of removable partial denture (RPD) directly depends on elastic force of stretched retentive clasp arms (RCAs). During deflection RCA must have even stress distribution. Safety factor is the concept which can be applied in estimating durability and functionality of RCAs. This study was based on analyzing properties of clasps designed by conventional clasp wax profiles and defining the optimal shapes of RCAs for stress distribution and safety factor aspects. Methods. Computer-aided-design (CAD) models of RCAs with simulated properties of materials used for fabrication of RPD cobalt-chromium-molybdenum (CoCrMo) alloy, commercially pure titanium (CPTi) and polyacetale were analyzed. Results. The research showed that geometrics of Rapidflex profiles from the BIOS concept are defined for designing and modeling RCAs from CoCrMo alloys. I-Bar and Bonihard clasps made from CPTi might have the same design as Co- CrMo clasp only by safety factor aspect, but it is obvious that CPTi are much more flexible, so their shape must be more massive. Polyacetale clasps should not be fabricated by BIOS concept for CoCrMo alloy. A proof for that is the low value of safety factor. Conclusion. The BIOS concept should be used only for RCAs made of CoCrMo alloy and different wax profiles should be used for fabricating clasps of other investigated materials. The contribution of this study may be the improvement of present systems for defining the clasps shapes made from CoCrMo alloys. The more significant application is the possibility of creating new concepts in defining shapes of RCA made from CPTi and polyacetale., Uvod/Cilj. Retenciona sila parcijalne skeletirane proteze (PSP) direktno zavisi od elastične sile rastegnute kukice. Da bi uspešno obavile svoju ulogu, retencione ručice kukice (RRK) prilikom defleksije moraju imati što ravnomerniju raspodelu napona. Stepen sigurnosti je pojam koji se može primeniti u proceni trajnosti i funkcionalnosti RRK. Ciljevi ove studije bili su analiziranje svojstava kukica koje su urađene pomoću konvencionalnih voštanih profila za izradu RRK, kao i definisanje optimalnih oblika RRK sa aspekta raspodele napona i stepena sigurnosti. Metode. Analizirani su CAD (computer aided design) modeli RRK kojima su simulirana svojstva gradivnih materijala koji se koriste za izradu legura: CoCrMo, komercijalno čist titan (CPTi) i poliacetal. Rezultati. Rezultati su pokazali da je geometrija Rapid-flex profila, korišćenih u okviru BIOS, definisana za projektovanje i modeliranje RRK koje se izrađuju od legure (CoCrMo). I Bar i Bonihard kukice od CPTi mogu se uraditi po istom konceptu kao i legure CoCrMo sa aspekta stepena sigurnosti, međutim, titanijumske kukice bile su znatno elastičnije i stoga su morale biti masivnije. Kukice od poliacetala ne smeju se modelovati po BIOS konceptu za leguru Co-CrMo. Dokaz za to je vrlo mali stepen sigurnosti. Zaključak. BIOS koncept može da se koristiti samo za RRK koje se izrađuju od legure CoCrMo. Za izradu kukica od ostalih ispitivanih materijala neophodni su drugačiji voštani profili. Doprinos studije predstavlja i poboljšavanje postojećih sistema za definisanje oblika RRK izrađenih od legura CoCrMo. Značajnija primena rezultata je i mogućnost stvaranja novih sistema za definisanje oblika RRK od CPTi i poliacetala.

Background/Aim. Fracture toughness determines functional crown strenght and prevents damages on ceramics during mastication. There is a lack of relevant literature data about fracture toughness of crowns made by feather-edge preparation. Mechanical testing of ceramic samples is supposed to show if feather-edge tooth preparation is a successful method for making ceramic crowns without any risk of reduction of their mechanical properties. This research was done to establish effects of feather-edge tooth preparation on fracture toughness of single zirconia ceramic crowns. Methods. The research was performed as an experimental study. Sixty (60) ceramic crowns were made on non-carious extracted human premolars. Thirty (30) crowns were made on the basis of feather-edge preparation (experimental group I). The group II included 30 crowns made on 1 mm rounded shoulder. Crowns fabrication was executed on a copy mill production system 'Zirkonzahn' (Zirkonzahn GMBH, Gais, Germany). The spherical compression test was used to determine fracture toughness, using 6 mm diameter ceramic ball. Fracture load for damaging ceramic crown was recorded on a universal testing machine - Zwick, type 1464, with the speed of 0.05 mm/min. Results. The results of this research introduced significant differences between fracture toughness of ceramic samples in every examined group. However, fracture toughness of crowns from both group was above 2 000 N, what was double beyond a recommended value. The mean value of fracture toughness in the feather-edge group was 2 090 N, and in shoulder group it was 2 214 N. Conclusion. This research showed a high fracture toughness of zirconia crowns made on feather-edge preparation. The examined crowns showed a fracture resistance at a sufficient distance in relation to the minimum values of functional loads. Further research of functional loads of these crown is necessary, as well as research of marginal adaptation of cemented crowns and gingival inflammatory re, Uvod/Cilj. Otpornost na lom uslovljava čvrstoću krune u toku funkcionalnih opterećenja i sprečava oštećenje keramike u toku mastikacije. U literaturi nema podataka o otpornosti na lom kruna izrađenih na bazi linijske preparacije. Mehaničkim testiranjem keramičkih uzoraka treba pokazati da li se linijska preparacija zuba može primeniti bez rizika od degradacije mehaničkih osobina keramičkih kruna. Ovo istraživanje sprovedeno je sa ciljem da se utvrdi uticaj linijske preparacije zuba na otpornost na lom pojedinačnih cirkonijumskih keramičkih kruna. Metode. Istraživanje je obavljeno kao eksperimentalna studija. Izrađeno je ukupno 60 keramičkih kruna na nekarioznim ekstrahovanim humanim premolarima. Ukupno 30 kruna izrađeno je na bazi linijske preparacije (prva eksperimentalna grupa), dok je u drugoj grupi izrađeno 30 kruna na osnovu preparacije oblika pravouglog stepenika sa unutrašnjim zaobljenjem. Za izradu kruna korišćen je kopir-frez sistem 'Zirkonzahn' (Zirkonzahn GMBH, Gais, Germany). Za određivanje otpornosti na lom primenjen je test pritiska sa sferičnim opterećenjem - keramičkom kuglom prečnika 6 mm. Sila potrebna da dovede do loma keramičke krune zabeležena je na univerzalnoj mašini za testiranje materijala Zwick, tipa 1464, koja se kretala brzinom od 0,05 mm/min. Rezultati. Rezultati ovog ispitivanja ukazali su na značajne razlike između otpornosti na lom dve ispitivane grupe kruna. Prosečna otpornost na lom obe grupe kruna bila je iznad 2 000 N, što je dvostruko više od preporučene vrednosti. Krune na bazi linijske preparacije imale su prosečnu vrednost otpornosti na lom od 2 090 N, dok je u drugoj grupi otpornost iznosila 2 214 N. Zaključak Eksperimentalnim ispitivanjem utvrđena je visoka otpornost na lom cirkonijumskih keramičkih kruna izrađenih na osnovu linijske preparacije zuba. Ispitivane krune imale su otpornost na lom na dovoljnoj distanci u odnosu na minimalne vrednosti funkcionalnog opterećenja. Neophodna su dalja istraživanja funkcionalnog optere