Investigation of the Effect of Variation of Cross- Linking Agents and two Heating Rates on Glass Transition of a Denture Base Acrylic Resin

Svrha istraživanja bila je ispitati učinak dviju stopa zagrijavanja na određivanje visine temperature staklastog prijelaza akrilata od kojih se izrađuju baze proteze. U radu su uporabljeni umrezivači etilenglikol- dimetakrilat, tetra-etilen-glikol-dimetakrilat i poli-etilen-glikol-dimetakrilat, koji su dodavani u koncentracijama od 0 do 30% volumena monomerske komponente akrilata. Kao polimerska komponenta korišten je nepigmentirani homopolimer. Kontrolna skupina pripravaka izrađena je pomoću monomera bez umrezivaća. Pripravci su napravljeni u standardnoj toplopolimerizirajućoj tehnici kivetiranja i polimeriziranja. Prijelazna temperatura mjerila se termomehaničkim postupkom, aparatom Stanton Redcroft TMA, model 790 (PL Thermal Sciences Ltd., Epsom, UK). U radu su primijenjene dvije stope zagrijavanja pripravaka: 5 0C/min i 10 0C/min. Rezultati su pokazali da prijelazna temperatura raste kada se povećava stopa zagrijavanja, uz jaku statističku značajnost. Dodatak od 10 - 15% etilen-glikol-dimetakrilat a ili t etr a-etilen-glikol-dimetakrilat a u protezne polimetilmetakrilatne materijale neznatno mijenja prijelaznu temperaturu, te nema laboratorijsku i kliničku važnost. Dodavati tetra-etilen-glikol-dimetakrilat u većim koncentracijama ili poli-etilen-glikol-dimetakrilat bilo koje koncentracije, pa i najmanje, ne preporučuje se jer snizuje vrijednost prijelazne temperature, čime protezni polimer postaje podložniji mogućim termičko- mehaničkim deformacijama.The purpose of the study was to investigate the effect of two different heating rates used in order to evaluate the transition glass temperature of dough-moulded poly (methylmethacrylate) denture base materials. Cross-linking agents ethylene glicol dimethacrylate (EGDMA), tetra (ethylene glycol dimetacry late) (TEGDMA) and poly (ethylene glycol dimethacrylate) (PEG 600 DMA) were added to the MM A monomer component in concentrations o f 0 - 30% according to the volume o f monomer liquid concentration. The polymer component was an unpigmented PMMA homopolymer. The comparison group of specimens was made by using the monomer liquid without a cross-linking agent. Specimens were produced in moulds according to conventional dental- flasking and curing procedures. Measurements o f Tg were determined by thermomechanical analysis using a Stanton Redcroft TMA, Model 790 (PL Thermal Sciences Ltd., Epsom, UK) Heating rates o f 5 °C/min and 10 °C/min were selected for this investigation. It was concluded that Tg values were highly dependent o f the heating rates used in thermomechanical analysis, being very significantly increased with the increase in heating rate. It was also concluded that the addition of a cross-linking agent would affect Tg o f denture base resins