Citation Information :
Ramachandran G, Madhusudanan P, Pillai R, Varghese NO, George S, Sujathan U. Effect of Thermocycling on Microhardness of Two Nanohybrid and One Microhybrid Composites Cured at Different Durations: An in vitro Study. Cons Dent Endod J 2018; 3 (1):27-33.
Aim: The aim of this study was to evaluate the effect of thermocycling on microhardness of three composites cured at different durations.
Materials and methods: One hundred and twenty disks (N = 120) were made with a dimension of 5 mm diameter and 2 mm height using a metal mold from three composites (Filtek Z350 XT, Tetric N Ceram, Z100 Universal Restorative). Forty disks each were made with each composite, which were again divided into two subgroups according to the duration of curing, 20 and 40 seconds. Microhardness test was done before and after thermocycling using Vickers microhardness test. Thermocycling was done at –5 and at 55°C for 250 cycles. Values were analyzed using analysis of variance (ANOVA) test, Tukey's simultaneous comparison.
Results: Among the groups cured for 40 seconds, in the control group, Z100 restorative showed higher microhardness. After thermocycling, even though there was a significant reduction in microhardness in all three composites, Tetric N Ceram showed minimal change in values compared with the other two composites.
Conclusion: It was concluded that after thermocycling, the composite resins are susceptible to significant reduction in microhardness.
Clinical significance: Patient's oral conditions, such as the cyclic thermal gradient and humidity can have negative effects on the mechanical properties of restorative materials. This is one of the factors contributing to a future need for replacement of dental restorative materials.
Cunha LG, Sinhoreti MA, Consani S, Sobrino LC. Effect of different photoactivation methods on the polymerization depth of a light-activated composite. Oper Dent 2003 Mar-Apr; 28(2):155-159.
Imazato S, Tarumi H, Kobayashi K, Hiraguri H, Oda K, Tsuchitani Y. Relationship between the degree of conversion and internal discoloration of light-activated composite. Dent Mater J 1995 Jun;14(1): 23-30.
Cavalcante LM, Peris AR, Amaral CM, Ambrosano GM, Pimenta LA. Influence of polymerization technique on microleakage and microhardness of resin composite restorations. Oper Dent 2003 Mar-Apr;28(2):200-206.
Kim KH, Ong JL, Okuno O. The effect of filler loading and morphology on the mechanical properties of contemporary composites. J Prosthet Dent 2002 Jun;87(6):642-649.
Litkowski LJ, McDonald NJ, Swierczewski M. A comparison of thermalcycling methods for evaluation microleakage. J Dent Res 1989;68:207.
Souza RO, Ozcan M, Michida SM, de Melo RM, Pavanelli CA, Bottino MA, Soares LE, Martin AA. Conversion degree of indirect resin composites and effect of thermocycling on their physical properties. J Prosthodont 2010 Apr;19(3): 218-225.
Yýlmaz EC, Sadeler R. Effect of thermal cycling and microhardness on roughness of composite restorative materials. J Restorative Dent 2016;4(3):93-96.
Okida RC, Da Silveira Okida DS. Effect of thermocycling on the color stability of different shades of composite resins, Int J Clin Dent 2013 Nov;6(4):341.
Sakaguchi RL, Douglas WH, Peters MC. Curing light performance and polymerization of composite restorative materials. J Dent 1992 Jun;20(3):183-188.
Erickson RL, Barkmeier WW, Halvorson RH. Curing characteristics of a composite-Part 1: Cure depth relationship to conversion, hardness and radiant exposure. Dent Mater 2014 Jun;30(6):e125-e133.
Polydorou O, Mönting JS, Hellwig E, Auschill TM. Effect of inoffice tooth bleaching on the microhardness of six dental esthetic restorative materials. Dent Mater 2007 Feb;23(2):153-158.
Campos I, Briso AL, Pimenta LA, Ambrosano G. Effects of bleaching with carbamide peroxide gels on microhardness of restoration materials. J Esthet Restor Dent 2003;15(3): 175-182.
Turssi CP, Ferracane JL, Vogel K. Filler features and their effects on wear and degree of conversion of particulate dental resin composites. Biomaterials 2005 Aug;26(24):4932-4937.
Abuelenain DA, Neel EAA, Al-Dharrab A. Surface and mechanical properties of different dental composites. Austin J Dent 2015;2(2):1019.
Karimzadeh A, Ayatollahi MR, Asgharzadeh Shirazi H. Mechanical properties of a dental nano-composite in moist media determined by nano-scale measurement. Int J Mater Mech Manufacturing 2014 Feb;2(1):67-72.
Medina Tirado JI, Nagy WW, Dhuru VB, Ziebert AJ. The effect of thermocycling on the fracture toughness and hardness of core buildup materials. J Prosthet Dent 2001 Nov;86(5): 474-480.
Villalta P, Lu H, Okte Z, Garcia-Godoy F, Powers JM. Effects of staining and bleaching on color change of dental composite resins. J Prosthet Dent 2006 Feb;95(2):137-142.
Tabatabaee MH, Arami S, Ghavam M, Rezaii A. Monomer release from nanofilled and microhybrid dental composites after bleaching. J Dent Tehran Univ Med Sci 2014 Jan;11(1):56-66.
Aguiar FHB, Braceiro A, Lima DANL, Ambrosano GMB, Lovadino JR. Effect of light curing modes and light curing time on the microhardness of a hybrid composite resin. J Contemp Dent Pract 2007 Sep;6(8):001-008.