Surface Characteristic of Direct Resin-based Composites

  • Gaetano Paolone

Student thesis: Doctoral Thesis

Abstract

This thesis explores, reflects upon, analyses, and connects together a portfolio of ten selected papers investigating the surface characteristics of direct resin-based composites in restorative dentistry, abbreviated below which I have published between 2014 and 2021, details of which are on pages 5-7 below.
Under different curing conditions, the type of resin-based composite (RBC) significantly influenced biofilm formation . Significantly higher biofilm formation was found on a Bis-GMA based RBC. The RBC with lower amount of biofilm, is characterized by a matrix composed primarily of an ester monomer with high molecular weight intended to minimize polymerization shrinkage. The surface restructuring of this RBC occurring during different curing environments, may have been opposed by the steric hindrance of this large monomer or by its interaction with oxygen thus affecting biofilm formation. However, these effects were eliminated when saliva pre-conditioning was applied. [#1(2018)].


Different finishing and polishing procedures can significantly influence RBCs surface properties /roughness and gloss [#2(2017); #3(2019)] but did not significantly affect S. mutans biofilm formation [#2(2017)]. Conversely, different RBCs can significantly influence S. mutans biofilm formation. The material characteristics and composition play a greater role than the surface roughness [#1(2018); #2(2017)].
Different finishing and polishing procedures were also tested [#3(2019)] on bulk-fill materials. The combination of tested bulk-fill and polishing systems provided clinically acceptable results in terms of roughness, while poor results were achieved in terms of gloss. The multistep finishing/polishing systems tested in the present study showed a higher polishing ability on high viscosity bulk-fill resin composite than the single step systems [#3(2019)].

When a clinician is not able to properly finish and polish composite surface restorations, the application of a light-curing protocol performed in the absence of oxygen may improve the overall properties, as well as the polishability of resin-based composites [#4(2020)]. The use of glycerin may be suitable, to avoid the presence of oxygen, for light-curing procedures of occlusal surfaces in posterior teeth, as well as in all those zones of the composite restoration that cannot be covered by a mylar matrix [#4(2020)].
From a clinical perspective, the modification of the internal or external surface of a composite restoration before its completion could be compared to an immediate repair procedure. These surface modifications allow the clinician to achieve more predictable results in terms of shade and translucency management.
Modification of the composite frame during layering procedures can be, therefore, considered a safe and reliable approach to enhancing the esthetic outcome of anterior composite restorations [#5(2021)]. After completing layering procedures, conventional finishing and polishing procedures are performed [#9(2018); #10(2027)]. These allow the clinician to provide symmetry between teeth and the proper surface texture. The latter may be particularly important in some clinical situations to increase the superficial scattering of light as a strategy to counteract the lower value of composite restorations [#8(2017)].
Date of Award24 Apr 2023
Original languageEnglish
Awarding Institution
  • University of Portsmouth
SupervisorChris Louca (Supervisor) & Alessandro Vichi (Supervisor)

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