title: Effect of immediate and delayed dentin sealing on the fracture strength, failure type and Weilbull characteristics of lithiumdisilicate laminate veneers.
abstract: OBJECTIVE
  Adhesion on dentin is less reliable than on enamel, which could affect the durability of laminate veneers (LV). Immediate dentin sealing (IDS) is suggested instead of delayed dentin sealing (DDS) to overcome hypersensitivity and prevent debonding from dentin. This study evaluated the effect of IDS and DDS on the durability of Li2Si2O5 laminate veneers in vitro.
  
  
  METHODS
  Window preparations were made on the labial surfaces of sound maxillary central incisors (N=50). They were randomly divided into five groups: Group 1: Enamel only+H3PO4+Adhesive (control); Group 2: <1/4 dentin+H3PO4+DDS (2 weeks later); Group 3: Complete dentin+H3PO4+DDS (2 weeks later); Group 4: <1/4 dentin+H3PO4+IDS; Group 5: Complete dentin+H3PO4+IDS. Li2Si2O5 laminate veneers (e.max Press) were bonded to the labial surfaces of the teeth with adhesive resin cement (Variolink Veneer). IDS layers were silicacoated (CoJet System) and silanized (ESPE-Sil). The teeth with their bonded laminates were thermocycled (10.000× cycles) and then subjected to static loading (1mm/min). Failure type and location after debonding were classified. Data were analyzed using ANOVA and Tukey's post hoc test (α=0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (0), values were calculated.
  
  
  RESULTS
  Mean fracture strength (N) per group in descending order was as follows: Group 5 (576±254), Group 4 (478±216), Group 1 (473±159), Group 2 (465±186), and Group 3 (314±137). The presence of complete dentin exposure sealed with DDS after 2 weeks on the bonded surface (Group 3) resulted in significantly lower fracture strength results than those in group 5 with IDS (p=0.034). Weibull distribution presented higher shape (0) for Group 1 (3.67), than those of other groups (2.51-2.89). Failure types were predominantly adhesive failure between the cement and the laminate veneer in Groups 1, 2, 4 whereas Group 3 presented more often complete adhesive failures between the cement and dentin. In Group 5, failures showed some IDS and cement with or without ceramic fracture attached on the tooth.
  
  
  CONCLUSIONS
  When laminate veneers are bonded to a large dentin substrate, application of immediate dentin sealing improves adhesion and thereby, the fracture strength of Li2Si2O5 laminate veneers.
authors: University Medical Center Groningen, The University of Groningen, Groningen, Center for Dentistry and Oral Hygiene, Department of Fixed and Removable Prosthodontics, The Netherlands. Electronic address: marcogresnigt@yahoo.com.
authors: Marco M M
authors: MM
authors: Gresnigt
authors: University Medical Center Groningen, The University of Groningen, Groningen, Center for Dentistry and Oral Hygiene, Department of Fixed and Removable Prosthodontics, The Netherlands.
authors: Marco S
authors: MS
authors: Cune
authors: University Medical Center Groningen, The University of Groningen, Groningen, Center for Dentistry and Oral Hygiene, Department of Fixed and Removable Prosthodontics, The Netherlands.
authors: Joanne G
authors: JG
authors: de Roos
authors: University of Zurich, Dental Materials Unit, Center for Dental and Oral Medicine, Clinic for Fixed and Removable Prosthodontics and Dental Materials Science, Zurich, Switzerland.
authors: Mutlu
authors: M
authors: Özcan
mesh_terms: D000134:Acid Etching, Dental; D000179:Acrylates / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate; D003738:Dental Cements / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D003801:Dental Veneers; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D007180:Incisor; D008422:Materials Testing; D011897:Random Allocation; D019279:Resin Cements / Q000737:chemistry*; D013997:Time Factors
chemical_list: D000179:Acrylates; D000538:Aluminum Silicates; D003738:Dental Cements; D017220:Dentin-Bonding Agents; C075815:IPS-Empress ceramic; C076808:Monobond S; C092987:Optibond; D019279:Resin Cements; C078484:Syntac dentine adhesive; C493120:lithia disilicate; D003776:Dental Porcelain; C103502:Variolink; D017438:Bisphenol A-Glycidyl Methacrylate; C033930:Silar (3M); C040415:heliobond
keywords: Adhesion; Bonding; Cementation; Ceramic; Dentin; Immediate dentin sealing; Laminate; Veneer