Comparison of Microhardness of a Composite Core in Two Different Placement Techniques - An Invitro Study


1 Assistant Professor of Operative and Esthetic. Department of Operative and Esthetic , Dentistry School, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

2 Resident of Operative and Esthetic.Department of Operative and Esthetic , Dentistry School, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

3 Assistant Professor of Food Hygiene. Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz , Iran.


Background and Objective: The purpose of this study was laboratory comparison of microhardness values in one kind of composite core at complete building tooth with incremental and Bulk placement techniques.
Subjects and Methods: Ten cylindrical samples of clearfil photo core-light cure (Kuraray/Japan), (Translucent, Single Shade) composite were prepared up to 9mm in Insulin syringes. Half of them were built with incremental placement technique by 2 mm increments and the other half were built with bulk placement technique. Light curing was done with output irradiance of 650 mw/cm2 for 40 seconds. Samples were cut in longitudinal position and were mounted in Epoxy resin. Vicker's microhardness was measured from surface of every samples in the 1,2,3,4,5,6,7,8,9 mm depths. Statistical Analyses were done with two-way ANOVA (P<0.05).
Results: The micro hardness values of equivalent depths in bulk placement technique were more than incremental placement. There were not significant diffenences among the hardness of 1 to 9 mm depths, in two placement techniques.
Conclusion: In order to achieve the suitable curing depth in every composite with regard to its composition and color, we should follow the light curing standard conditions of that special composite.


1-He Z, shimada Y, Tagami J. The effects of cavity size and incremental technique on micro –t ensile bond strength of resin composite in class I cavities. Dent Mater 2007;23:533-8.
2-Soh MS, Yap AU, Siow  KS. The effectiveness of  cure of LED and halogen curing lights varying cavity depths. Oper Dent 2003;28:707-15.
3-Moore BK, Platt JA, Borges G, Chu TM, Katsilieri I . Depth of cure of dental resin composites: ISO 4049 depth and microhardness of types of materials and shades. Oper Dent 2008;33:408-12.
4-Amaral CM, de Castro AK, Pimenta LA, Ambrosano GM. Influence of resin composite polymerization techniques on microleakage and microhardness. Quintessence Int 2002;33:685-9.
5-Price RB, Derand T, Loney RW, Andreou P. Effect of light source and specimen thickness on the surface hardness of resin composite. Am J Dent 2002;15:47-53.
6-Asmussen E, Peutzfeldt A. Influence of specimen diameter on the relationship between subsurface depth and hardness of light-cured resin composite. Eur J Oral Sci 2003;111:543-6.
7-Poskus LT, Placido E, Cardoso PE. Influence of placement techniques on Vickers and knoop hardness of class II composite resin restorations. Dent Mater 2004;20:726-32.
8-Kuraray Dental CO. Clearfil photo core light cure composite[Internet]; [Cited 2007]. Available from: compare.Com/Product /Clearfil-photo–core.html.
9-Lazarchik DA, Hammond BD, Sikes CL, Looney SW, Rueggeberg FA . Hardness comparison of  bulk – filled/transtooth and incremental – filled/ occlusally irradiated composite resins. J Prosthet Dent 2007;98:129-40.
10-Lang BR, Jaarda M, Wang RF.Filler particle size and composite resin classification systems. J Oral Rehabil 1992;19:569-84.
11-Cook WD. Factors affecting the depth of cure of UV- polymerized composites . J Dent Res 1980;59:800-8.
12-Resin composite restorative materials. In: Powers JM, Sakaguchi RL, editors. Craig's restorative dental materials. 12th ed. St. Louis,Mo: Mosby Elsevier; 2006. p.191-207.
13-Bayne SC, Thompson J Y. Biomaterials. In:Roberson TM, editor.  Sturdevant's Art and science of operative dentistry. 5th ed. St. Louis, Mo.: Mosby Elsevier; 2006. p.197-201.
14-Atmadja G, Bryant RW. Some factors in fluencing the depth of cure of visible light-activated composite resins.Aust Dent J 1990;35:213-8.
15-Strydom C. Curing lights--the effects of clinical factors on intensity and polymerisation . SADJ 2002;57:181-6.
16-Shortall AC. How light source and product shade influence cure depth of  a contemporary composite .. J Oral Rehabil 2005;32:906-11.
17-Sakaguchi RL, Douglas WH, Peters MC. Curing light performance and polymerization of composite restorative materials. J Dent 1992;20:183-8.
18-Yap AU. Effectiveness of polymerization in composite restoratives claiming bulk placement: Impact of cavity depth and exposure time. Oper Dent 2000;25:113-20.
19-Lindberg A, Peutzfeldt A, van Dijken JW. Effect of Power density of curing unit, exposure duration, and light guide distance on composite depth of cure. Clin Oral Investig 2005;9:71-6.
20-Nomoto R, Asada M, McCabe JF, Hirano S. Light exposure required for optimum conversion of light activated resin systems. Dent Mater 2006;22:1135-42.
21-Santos GB , Medeiros IS , Fellows CE, Muench A,Braga RR. Composite depth of cure obtained with  QTH and LED units assessed by microhardness and Micro– Raman Spectroscopy. Oper Dent 2007;32:79-83.
22-Uhl A, Mills RW, Vowles RW, Jandt KD. Knoop hardness depth profiles and compressive strength of selected dental composites polymerized with halogen and  LED light curing technologies. J Biomed Mater Res 2002;63:729-38.
23-Nitta K. Effect of light guide tip diameter of LED-Light curing unit on polymerization of light–cured composites. Dent Mater 2005;21:217-73.
24-Aguirar FH, e Oliveria TR, Lima DA, Ambrosano G, Lovadino JR. Microhardness of different  thicknesses of resin composite polymerized by conventional photocuring at different distances. Gen Dent 2008;56: 144-8.
25-Abbas G, Fleming GJ, Harrington E, Shortall AC, Burke FJ. Cuspal movement and microleakage in premolar teeth restored with a packable composite resin cured in bulk or in increments. J Dent 2003;31:437-44.
26-Halon G, Levin M, Bimstein E, Grajower R, Eidelman E. Clinical, radiographic, SEM evaluation and assessment of microleakage of  class II  composite restorations. Am J Dent 1989;2:274-8.