title: The influence of finishing/polishing time and cooling system on surface roughness and microhardness of two different types of composite resin restorations.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of finishing time and polishing time on surface roughness and microhardness of nanofilled and hybrid resin composites.
  
  
  METHODS
  Hundred disk composite specimens from micro hybrid composite and nanohybrid composite were prepared, 50 for each type of composite. The specimens were divided into five groups according to the time of finishing and polishing (immediate, 15 min, 24 h and dry). Composite under the Mylar strip without finishing and polishing was taken as the control group. Surface roughness was measured with environmental scanning electronic microscope (ESEM) and microhardness was determined using Vickers Microhardness Tester. Data collected were statistically analyzed by t-test and one-way analysis of variance (ANOVA) followed by Turkey's post hoc test.
  
  
  RESULTS
  Smooth surface with low hardness was obtained for the group under Mylar strip without finishing and polishing. The highest roughness was recorded for delayed finishing and polishing for both composites. Immediate finishing and polishing increased the surface hardness more than that in the control group in both types of composites. Dry finishing reduced the hardness significantly for micro hybrid composite, but resulted in the highest surface hardness for nanofilled composite.
  
  
  CONCLUSIONS
  Immediate finishing and polishing under coolant resulted in the best surface smoothness and hardness values in micro hybrid composite; however, immediate dry finishing and polishing gave the best smoothness and hardness values in nanohybrid composite.
authors.affiliation: Department of Restorative Dental Sciences, Al-Farabi College, Riyadh, Kingdom of Saudi Arabia.
authors.forename: Raja Rajeswari
authors.initials: RR
authors.lastname: Kaminedi
authors.affiliation: Department of Pedodontics, College of Dentistry, Salman Bin Abdul Aziz University, Alkharj, Kingdom of Saudi Arabia.
authors.forename: Narendra Varma
authors.initials: NV
authors.lastname: Penumatsa
authors.affiliation: Department of Conservative and Endodontics, Mamatha Dental College, Khammam, Telangana, India.
authors.forename: Tulasi
authors.initials: T
authors.lastname: Priya
authors.affiliation: Department of Restorative Dental Sciences, Al-Farabi College, Riyadh, Kingdom of Saudi Arabia.
authors.forename: Kusai
authors.initials: K
authors.lastname: Baroudi
keywords: Microhardness; resin composite; roughness