Vol 21 No. 1

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J Bagh College Dentistry Vol. 21(1), 2009 The influence of posterior ….. (P60 packable / bulk) was statistically non significant, despite that there's an improvement in the fracture resistance force mean for group E(P60 / Bulk) , in contrast to that of group D (P60 / incremental) , even such improvement was not significant. Which revealed that the mode of application technique employed of the packable composite has no difference on the cuspal reinforcement of the weakened teeth to a cavity depth of 5mm? The presence of white lines between successive layers of resin composite or inside layers is an indication for improper adaptation of the layers with each other, which also affects physical properties. In Bulk build up a whole single increment was adapted properly to the floor and cavity walls, which eliminates the possible previous defects correlated to the composite successive increments. This explanation could be more accepted for the packable composite (10, 11). In our study it’s seemed that Z250 and P60 are sharing many of their physical properties and have closure values for each other including the modulus of elasticity (12) . Also using of the same bonding system, these factors for both posterior composite types are approximate from each other which may explain the comparable values of both materials of the cuspal deflection and therefore on the cuspal fracture resistance. The majority of cohesive failure for group D supported the explanation; that successive incremental technique with packable composite resulted in weakening of the flexural strength of the material itself and reduced the surface hardness as a result of dry spots and voids in between the resin layers coming from the improper adaptation of the heavy filled material. Table 1: Descriptive statistics of values of five groups. GA GB GC GD GE Mean (Kg f) 204.5 79.03 158.6 158.1 167.7 S.D 39.01 35.51 42.48 27.82 22.86 S.E 12.34 11.23 13.44 8.799 7.229 C.V% 19.08 44.93 26.79 17.6 13.63 Table 2: Mode of failure observed in the fractured restored specimens of groups C, D, and E. Groups Cohesive Adhesive Mixed Group C 1 3 6 Group D 7 _ 3 Group E 1 6 3 A Figure 2: Bulk technique using P60 packable composite with flowable one 250 204,5 200 158,6 158,1 167,7 150 Mean 100 79,03 Figure 1: Successive cusp builds up technique; A group C using microhybrid Z250composite, B group D using packable P60 composite with flowable composite B 50 0 GA GB GC GD GE Figure 3: Means of fracture forces values in (Kg f) for the five groups Restorative Dentistry 3
J Bagh College Dentistry Vol. 21(1), 2009 The influence of posterior ….. REFERENCES 1. Mackenzie DF. The reinforcing effect of MOD acid– etch composite restoration on weakened posterior teeth. Br Dent J 1984; 161: 410–4. 2. Fortin D, Vargas MA. The spectrum of composites: new technique and new materials. J Am Dent Assoc 2000; 1(131): 26S – 30S. 3. Ghavamnasiri M, Moosavi H, Tahvildarnejad N. Effect of centripetal and incremental methods in Class II composite resin restorations on gingival microleakage. J Contemp Dent Pract 2007; 2(8): 113–9. 4. Sirimai S, Riis DN, Morgano SM. An in vitro study of the fracture resistance and the incidence of vertical root fracture of pulpless teeth restored with post and core systems. J Prosthet Dent 1999; 81(3): 262–9. 5. Franca FG, Worschech CC, Paulillo AM, Martins LR, Lovadino JR. Fracture resistance of premolar teeth restored with different filling techniques. J Contemp Dent Pract 2005; 3(6): 85– 92. 6. Gorgul G, Alacam T, Kivanc B.H, Uzun O, Tinaz C. Microleakage of packable composites used in post spaces condensed using different methods. J Contemp Dent Pract 2002; 2(3): 23–30. 7. Salih M.M. An evaluation of the cuspal fracture resistance using different restorative materials and techniques with reinforcing effect of adhesive bonding system. A master thesis, Conservative Department, University of Baghdad, 2000. 8. Giachetti L, Russo DS, Bambi C, Grandini R. A review of polymerization shrinkage stress: Current techniques for posterior direct resin restorations. J Contemp Dent Pract 2006; 4(7): 79– 87. 9. Fano V, Ortalli I, Pozela K. Porosity in composite resins. J Am Dent Assoc 1995; 16: 1291– 5. 10. Huysmans M, Varst P, Van de Lautenschlager EP, Monaghan P. The influence of simulated clinical handling on the flexural and compressive strength of posterior composite restorative materials. J Dent Mater 1996; 12: 116–20. 11. 3M Dental products; Filtek P60 technical manual. Minneapolis: 1999; 5–33. Restorative Dentistry 4
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