The visible light-curing posterior composite materials are used extensively due their esthetic charascteistics. Many disadvantages of marginal leakage, wear and poor strength should be overcome through improvement of mechanical properties. It has
been
proved that most of materials could be improved by additional heat curing after light curing. The objectives of this was to estimate the effects fo additional heat curing on the five different commercial posterior light curing resins, P-50,
Herculite
XR, Prisma AP. H, Clearfil Photoposterior. Additional heat(CRC system, Kuraray Co., Japan) of 100℃ was applied for 0, 5, 15 and 25 minutes after light curing with Visilux II(3MCo,. U.S.A.). The diametral tensile strength was measured by using
UTM(Instron 6022, U.S.A.) of cross head speed of 1 cm/.min afters toring in 37℃, 100% humidity for 10minutes and 24 hours. The following conclusions may be deawn from this study. 1) When heat was appled on tested specimens, diametral tensile
strength
was increased in proportion to period of heat applying in early stage. Howenver, there were differences of diametral tensile strength in each tested materials. 2) The highest diametral tensile strength was shown after 5 and 15 minutes of heat
application. 3) When it compared between 24 hours and 10 minutes group, former showed higher values. Heat application after light curing on VLC pwsterior cvomposite resins showed increase of diametral tensile strength on this study. Not only the
temperature applied but period of heat application seemed affect the strength of this materials. The further investigation of proper temperature and period of heat application for each materials was recommended.
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