effect of temprature

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….

18. Critical Analysis

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