title: Effect of configuration factor on gap formation in hybrid composite resin, low-shrinkage composite resin and resin-modified glass ionomer.
abstract: OBJECTIVE
  Polymerization shrinkage is one of the important factors in creation of gap between dental structure and composite resin restorations. The aim of this study was to evaluate the effect of configuration factor (C-factor) on gap formation in a hybrid composite resin, a low shrinkage composite resin and a resin modified glass ionomer restorative material.
  
  
  METHODS
  Cylindrical dentin cavities with 5.0 mm diameter and three different depths (1.0, 2.0 and 3.0 mm) were prepared on the occlusal surface of 99 human molars and the cavities assigned into three groups (each of 33). Each group contained three subgroups depend on the different depths and then cavities restored using resin modified glass ionomer (Fuji II LC Improved) and two type composite resins (Filtek P90 and Filtek Z250). Then the restorations were cut into two sections in a mesiodistal direction in the middle of restorations. Gaps were measured on mesial, distal and pulpal floor of the cavities, using a stereomicroscope.
  
  
  RESULTS
  Data analyses using Kruskal-Wallist and Mann-Whitney tests. Increasing C-factor from 1.8 to 3.4 had no effect on the gap formation in two type composite resins, but Fuji II LC Improved showed significant effect of increasing C-factor on gap formation. Taken together, when C-factor increased from 1.8 up to 3.4 had no significant effect on gap formation in two tested resin composites. Although, Filtek P90 restorations showed smaller gap formation in cavities walls compared to Filtek Z250 restorations.
  
  
  CONCLUSIONS
  High C-factor values generated the largest gap formation. Silorane-based composite was more efficient for cavity sealing than methacrylate-based composites and resin modified glass ionomer.
authors.affiliation: Department of Restorative Dentistry, Faculty of Dentistry, Islamic Azad University Khorasgan Branch, Isfahan, Iran.
authors.forename: Parvin M
authors.initials: PM
authors.lastname: Boroujeni
authors.forename: Sayyed M
authors.initials: SM
authors.lastname: Mousavinasab
authors.forename: Elham
authors.initials: E
authors.lastname: Hasanli
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000145:classification; D003764:Dental Materials / Q000737:chemistry*; D003804:Dentin / Q000648:ultrastructure; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000295:instrumentation / Q000379:methods; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry; D062047:Silorane Resins / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C444701:Filtek Z250; C431351:Fuji II LC cement improved; D005899:Glass Ionomer Cements; D008689:Methacrylates; D019279:Resin Cements; D012117:Resins, Synthetic; D062047:Silorane Resins; C544925:filtek P90
keywords: configuration factor; gap formation; glass ionomer; resin composite