title: Effect of Preoperative Occlusal Matrices on the Vickers Microhardness of Composite Disks Polymerized with QTH and LED Lamps.
abstract: OBJECTIVE
  This study aimed to assess the reliability of the preoperative occlusal matrix technique in terms of the surface Vickers microhardness (VMH) of the underlying composite restorative material.
  
  
  METHODS
  Two hundred microhybrid composite cylinders were built up and light-cured in a single-layer step, forming two experimental groups (N = 100) according to their heights (1.5 mm/2 mm). Each group was divided into five subgroups (N = 20) depending on the matrix thickness (no matrix/0.5 mm/1 mm/2 mm/3 mm). Half the specimens per subgroup (N = 10) were randomly polymerized with a quartz-tungsten-halogen (QTH) light-curing unit (LCU). The remaining half were cured using a light-emitting diode lamp. The top and bottom samples' sides were tested for VMH at 1 hour and 24 hours post-curing using a universal VMH machine. A multiple analysis of variance with repeated measurements for the "surface" factor and the Student-Newman-Keuls test were run (α = 0.05). Bottom/top microhardness ratios were compared with the empirically accepted limit (0.8). Surface topography was analyzed under a scanning electron microscope.
  
  
  RESULTS
  The thinnest matrices provided the significantly best VMH values. LCU, disc height, and time also contributed to VMH. At 24 hours, 2-mm high discs polymerized with QTH resulted in inadequate microhardness ratios when 1-mm thick to 3-mm thick matrices were used.
  
  
  CONCLUSIONS
  The thinnest matrices are the most recommendable ones.
  
  
  CONCLUSIONS
  The esthetics and occlusal reproducibility achieved with customized occlusal matrices fabricated before cavity preparation have been widely demonstrated. However, their effect on the physical properties of the restorations deserves further investigation. Although more studies are necessary, the thinnest matrices seem to be the most suitable to preserve the composite surface VMH and the curing depth.
authors.affiliation: Department of Buccofacial Prostheses, Faculty of Dentistry, Complutense University of Madrid (U.C.M.), Pza. Ramón y Cajal, s/n, Madrid, 28040, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Castillo-Oyagüe
authors.affiliation: Department of Prosthetic Dentistry, University Dental School, Heath Park, Cardiff, CF14 4XY, UK.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Milward
authors.affiliation: Department of Dentistry for Adults, European University (U.E.), C/ Tajo, s/n, Villaviciosa de Odón, Madrid, 28670, Spain.
authors.forename: Alicia
authors.initials: A
authors.lastname: Martín-Cerrato
authors.affiliation: Department of Adult Dental Health, University Dental School, Heath Park, Cardiff, CF14 4XY, UK.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Lynch
mesh_terms: D003188:Composite Resins; D055117:Curing Lights, Dental; D006245:Hardness Tests; D006801:Humans; D008855:Microscopy, Electron, Scanning; D058105:Polymerization; D057234:Preoperative Period; D013499:Surface Properties
chemical_list: D003188:Composite Resins