title: Evaluation of proximal contact tightness of Class II resin composite restorations.
abstract: OBJECTIVE
  The objective of the current study was to compare in-vitro the proximal contact tightness (PCT) of Class II resin composite restorations (RCR) placed with different established and new placement techniques.
  
  
  METHODS
  105 ivorine lower left first molars with standardized MO cavities were randomly divided into seven groups (n = 15) as follows: SRing: sectional matrix and separation ring (Garrison Dental); CRing: circumferential matrix (1101-c, KerrHawe SA) with separation ring; CWedge: circumferential matrix with a wedge only; COptra: circumferential matrix and OptraContact (Vivadent); CCerana: circumferential matrix and a Cerana insert (Nordiska Dental); CElliot: circumferential matrix and Elliot separator (PFINGST & Co) and Walser: Walser matrix O-type (Dr Walser Dental GmbH). In all the groups, the matrix band was secured using a wooden wedge except for the Walser group, following manufacturer's recommendations. A Tofflemire retainer (Kerr Corporation) was used to apply the circumferential matrix band whenever it was used. All the prepared teeth were restored with resin composite (Premise, Kerr) mounted in a manikin head to simulate the clinical environment. PCT was measured using the Tooth Pressure Meter (University of Technology, Delft). The data were analyzed using one-way ANOVA and Tukey post-hoc tests (p < 0.05).
  
  
  RESULTS
  Compared to the control group (SRing) (6.64 +/- 1.06N), all other systems resulted in significantly lower PCT values (p < 0.001). Within the circumferential matrix groups, CRing (4.01 +/- 0.53N) and CElliot (4.29 +/- 1.08N) showed significantly tighter contacts compared to the CWedge (0.37 +/- 0.22N), COptra (0.91 +/- 0.49N), CCerana (2.99 +/- 1.98N) and Walser (1.34 +/- 0.55N) (p < 0.05) group. Between CWedge and COptra, no significant difference was found (p = 0.57).
  
  
  CONCLUSIONS
  The use of separation rings with sectional matrices provides superior contacts when placing Class II RCRs.
authors.affiliation: Faculty of Dentistry, Cairo University, Department of Operative Dentistry, Cairo, Egypt.
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Saber
authors.forename: Bas A C
authors.initials: BA
authors.lastname: Loomans
authors.forename: Ahmed
authors.initials: A
authors.lastname: El Zohairy
authors.forename: Christof E
authors.initials: CE
authors.lastname: Dörfer
authors.forename: Wafa
authors.initials: W
authors.lastname: El-Badrawy
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D003737:Dental Cavity Preparation / Q000145:classification / Q000295:instrumentation; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000145:classification* / Q000295:instrumentation; D004867:Equipment Design; D006801:Humans; D008348:Manikins; D008422:Materials Testing; D008434:Matrix Bands; D013499:Surface Properties; D014093:Tooth, Artificial
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C507210:premise composite resin