title: Marginal ridge strength of Class II tunnel restorations.
abstract: OBJECTIVE
  To test the strength, at the marginal ridge, of the tunnel preparation vs the Class II traditional box preparation when restored with composite or glass ionomer (GI).
  
  
  METHODS
  Eighty-four extracted maxillary molars stored in normal saline and thymol were randomly divided into six groups of 14 each (determined by pilot study where alpha = 0.05, beta = 0.2). Group A and C were tunnel preparations. Group B and D were traditional Class II preparations. Group E-whole tooth (negative control), and Group F-tunnel preparation unrestored (positive control). Group A and B were restored with Scotchbond 2/P-50 composite. Group C and D were restored with Ketac Fil-GI. The marginal ridge of each tooth was loaded at 0.5 mm/minute on the Instron. A loading rod produced a contact point of 1.0 mm in diameter.
  
  
  RESULTS
  The mean compressive loads (kg) required for fracture were: (A): 42.2 +/- 11.9, (B): 53.1 +/- 10.7, (C): 52.0 +/- 10.9, (D): 23.8 +/- 8.4. (E): 79.1 +/- 16.1, (F): 27.0 +/- 10.6. A significant difference was found between whole teeth (E) and all other groups (P < 0.05). The Newman-Keuls test showed a significant difference between Class II composite (B) and tunnel composite (A) (P < 0.05), between tunnel GI (C) and tunnel composite (A) (P < 0.05) but no difference between tunnel GI (C) and Class II composite (B).
authors.affiliation: University of Missouri, School of Dentistry, Kansas City 64108, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Purk
authors.forename: R S
authors.initials: RS
authors.lastname: Roberts
authors.forename: D A
authors.initials: DA
authors.lastname: Elledge
authors.forename: R P
authors.initials: RP
authors.lastname: Chappell
authors.forename: J D
authors.initials: JD
authors.lastname: Eick
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D003737:Dental Cavity Preparation / Q000009:adverse effects; D003793:Dental Restoration, Permanent / Q000009:adverse effects / Q000379:methods*; D003799:Dental Stress Analysis; D004548:Elasticity; D005899:Glass Ionomer Cements; D006801:Humans; D008298:Maleates; D008422:Materials Testing; D019279:Resin Cements; D018709:Statistics, Nonparametric; D014082:Tooth Fractures / Q000209:etiology
chemical_list: D003188:Composite Resins; D005899:Glass Ionomer Cements; D008298:Maleates; D019279:Resin Cements; C065771:P50 composite resin; C067788:scotchbond 2; D017438:Bisphenol A-Glycidyl Methacrylate; C040964:Ketac-Fil