title: Depth of cure and mechanical properties of nano-hybrid resin-based composites with novel and conventional matrix formulation.
abstract: OBJECTIVE
  This study's purpose was to evaluate the depth of cure (DOC) and the variation of mechanical properties with depth of two nano-hybrid resin-based composites (RBCs) containing a novel monomer composition based on dimer-acid derivatives (h-Da) or rather tricyclodecane-urethane structure (TCD-urethane) compared to three conventionally formulated nano-hybrid RBCs based on hardness-profile measurements.
  
  
  METHODS
  Specimens were produced through different layering techniques (bulk, incremental) and curing times (10, 20, and 40 s). Mechanical properties (Vickers hardness (HV), modulus of elasticity (E)) were evaluated every 100 μm longitudinally throughout the bisected samples using an automatic micro-hardness indenter. DOC was determined as the depth at which the 80% hardness cutoff value in relation to the surface hardness was reached. Results were compared using one- and multiple-way ANOVA, Tukey HSD post-hoc test (α = 0.05) and partial eta-squared statistic.
  
  
  RESULTS
  Increasing curing time resulted in a significant increase in DOC. Generally, the novel-formulated materials showed higher DOC values. "Curing time" and "material" showed the strongest effect on DOC. Starting in 4 mm depth, significantly higher HV and E was reached for incremental compared to bulk-curing technique. Values in 0.1 and 2 mm depth (bulk, incremental) as well as in 4 mm depth (incremental) were independent from curing time, while in greater depths, values generally increased with curing time. "Filling technique" and "material" performed the strongest influence on mechanical properties.
  
  
  CONCLUSIONS
  Within the limits of this study, the novel-formulated RBCs showed better performance concerning DOC compared to conventional materials.
  
  
  CONCLUSIONS
  For cavities deeper than 3 mm, all tested materials should be placed incrementally to ensure adequate polymerization. In large cavities (≥6 mm), the lowest increment should be cured at least 40 s. The novel-formulated RBCs might be cured in comparatively bigger increments.
authors: Department of Restorative Dentistry, Dental School of Ludwig-Maximilians-University, Goethestr. 70, 80336 Munich, Germany.
authors: Karina E
authors: KE
authors: Frauscher
authors: Nicoleta
authors: N
authors: Ilie
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D055119:Elastic Modulus; D006244:Hardness; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D053761:Nanocomposites / Q000737:chemistry*; D058105:Polymerization; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D008689:Methacrylates; C000602431:Miris 2; C551012:N'Durance composite resin; C510232:Simile composite resin; C488393:Venus (composite resin); C507210:premise composite resin