Effect of temporature3.ppt
- 1. Effect of temperature during polymerization on strength of autopolymerizing resin. Takahiro Ogawa,DDS,PhD Mutsuko Tanaka,DDS Kiyoshi Koyano,DDS,PhD J Prosthet Dent 2000;84:222-4
- 2. Introduction Purpose of this study Material and methods Results Discussion Conclusion Clinical implications Critical analysis References
- 3. Introduction Temporary coverage of the prepared tooth is an important step during fabrication of fixed prosthesis. Provisional restoration must satisfy mechanical requirements. Failure of Provisional restorations leads to…… Several techniques have been proposed to increase the strength and life of provisional restorations……. Reinforcement with metal framework,stainless steel wire,polyethylene or carbon graphite fibers. Because heat activates the chemical reaction(auto polymerizing resin), placing in hot water accelerates the reaction.
- 4. Purpose of this study: To examine the effects of the curing environment ,air or water,and water temperature during polymerization on the auto polymerizing resin.
- 5. Material And Methods Transverse strength and transverse modulus analyses were done….. The time schedule simulated the direct technique for formulating provisional restorations. Test material was auto polymerizing methyl methacrylate resin(unifast II,GC Corp,Tokyo).
- 6. Powder to liquid ratio of 2:1….. Mixed for 10 seconds at controlled temperature of 23 deg C and placed in preformed stainless steel mold (2 x 2 x 25 mm) 1 min 50 sec. after mixing,molds were placed under following conditions……. 6 mins. after mixing….. 8 mins. after mixing….transverse test (3-point flexural test)….. Instron testing machine.
- 7. Time diagram of experimental protocol
- 8. Transverse strength =3x20 L/2 w t2 Transverse modulus (E) =20 x 3S/4 x 3 w t 5 samples were tested under each polymerizing conditions. Results were compared using ANOVA.
- 9. Results •Transverse strength increased with increasing water temperature and reached plateau at 60ºC. • Resin polymerized in 10ºC and 23ºC water demonstrated less strength than that of resin polymerized in 23ºC air. •Water conditions of 60ºC to 80ºC produced more than 2 time greater transverse strength of there in compared with 23ºC air.
- 10. Transverse strength of resin in different polymerizing conditions.
- 11. •The transverse modulus of the resin increased with increasing water temperature. • The resin polymerized in 40ºC to 80ºC water demonstrated greater modulus than that of resin polymerized in 23ºC air.
- 12. Transverse modulus of resin in different polymerizing conditions
- 13. Discussion •This study demonstrated that the strength of autopoloymerizing resin in influenced by water temperature during polymerization. •At water temperatures of 40ºC or greater, the strength was significantly increased compared with polymerization in 23ºC air. •Polymerization at 60ºC and 80ºC in water produced resin with twice the transverse strength.
- 14. •Transverse modulus corresponds to stiffness; therefore increased transverse modulus indicates increased resistance to the flexure. •Transverse modulus increased proportionally with an increase in the polymerizing temperature.
- 15. On the basis of the present data …..recommended for the following situations: 1. When fabricating a provisional crown, hot water should be used to reinforce the outer surface of the crown. The inner surface and margin should be readjusted or relined 2. When fabricating a provisional fixed partial denture, the abutments should be first connected by a small amount of resin to maintain their alignment.
- 16. •Polymerization shrinkage of the resin …… readjust and reline a provisional restoration •Using hot water in the appropriate situations when fabricating provisional restorations may help to shorten chair time and improve mechanical properties of provisional restorations.
- 17. Conclusions Study demonstrated that polymerizing the resin in hot water increased its mechanical strength. 60 deg c and 80 deg c water conditions produced….
- 19. References Davidson CL,Feilzer AJ. Polymerization shrinkage and polymerization stress in polymer based restoratives.J Dent 1997;25:435-40. Galindo D, Soltys JL, Graser GN.Long term reinforced fixed provisional restorations.J Prosthet Dent 1998;79:698-701. Gegauff AG.Provisional restorations. In:Rosenstiel SF, Land MF, Fugimoto J,editors.Contemporary Fixed prosthodontics. 2nd ed.St Louis,Mosby;1995.325-60. Larson WR,Dixon DL,Aquillino SA, Clancy JM.The effect of carbon- graphite fiber reinforcementon the strength of provisional crown and fixed partial denture resins. .J Prosthet Dent 1991;61:816-20. Powell DB,Nicholls JI,Yuodelis RA. A Comparison wire- and Kevlar- reinforced provisional restorations.Int J Prosthodont 1994;7:81-9. Ramos V,Runyan DA,Christensen LC.The effect of Plasma-treated polyethlene fiber on the fracture strength of polymethyl methacrylate. J Prosthet Dent 1996;76:94-6