Surface roughness and microhardness evaluation of composite resin restorations subjected to three different polishing systems immediately and after 24 h: An in vitro study

Abstract

Background: Finishing and polishing of composite resin restorations can be considered two different procedures or two steps of a single procedure. During the finishing procedure, contours are corrected while margins and irregularities are smoothened. The polishing procedures result in the production of a smooth and lustrous finish. Consensus regarding the correct timing for initiating the steps of finishing and polishing after the curing of the composite resins is divided. Some authors support immediate finishing and polishing while other authors support delaying the finishing and polishing procedures.

Aim: The aim of this study is to evaluate the surface roughness and microhardness of composite resin restoration subjected to finishing and three different polishing systems immediately and after 24 h.

Materials and method: Eighty composite resin samples were prepared. A Teflon mold was made which was customized for this study having dimensions of 10-mm diameter and 2-mm depth. For the first group of specimens, Group I (n = 20) the composite resin surface was covered with Mylar Strips which acted as control. The other specimens (n = 60) were prepared without the use of a Mylar strip, followed by curing. For all the samples, curing was done with a light-emitting diode for 40 s each. Eighty light-cured samples were divided equally into 4 groups, each group containing 20 samples (n = 20). Out of the 20 samples, in the second, third, and fourth groups, (Kenda C. G. I., Shofu Super-snap X-Treme, and Eve Diacomp Plus Twist) 10 samples were finished and polished immediately after curing and the other 10 samples were finished and polished after 24 h of curing. The samples in Groups II, III, and IV were subjected to finishing by a 12-fluted tungsten carbide bur and were polished according to the respective manufacturer's instructions. The samples were then subjected to quantitative analysis of surface roughness by a noncontact three-dimensional optical profilometer (Bruker GT-Q; Ettlingen, Germany) and qualitative analysis of surface roughness by a scanning electron microscope (Zeiss EVO 18 Special Edition; Carl-Zeiss-Strasse; Oberkochen Germany) at ×10,000 magnification. The samples were also subjected to Vickers microhardness measurement using a microhardness tester (Leica VMHT 001; Walter UHL GmbH, Germany) under 100 g load over 10 s.

Conclusion: A. For surface roughness: The samples cured under Mylar strips gave the least surface roughness values (0.25 ± 0.032). Immediate finishing and polishing procedures led to statistically less surface roughness than when finishing and polishing procedures were performed after a delay of 24 h for all polishing systems used B. For microhardness: The samples cured under Mylar strips gave the least microhardness values (57.1 ± 2.03). Delayed finishing and polishing increased microhardness values in all finishing and polishing systems used. Different polishing systems did not have any significant effect on the microhardness values in immediate and delayed finishing and polishing groups.

Keywords: Composite resin; Vicker’s microhardness; finishing; microhardness; polishing; surface roughness; three dimensional optical profilometer; timing.

Graph 1

Intergroup comparison of surface roughness (immediate)

Graph 2

Intergroup comparison of surface roughness (delayed)

Graph 3

Intergroup comparison of microhardness (immediate)

Graph 4

Intergroup comparison of microhardness (delayed)

Figure 1

SEM Analysis of groups at 10,000 X magnification (Qualitative Analysis)