Fracture Resistance of Lithium Disilicate Ceramics Bonded to Enamel or Dentin Using Different Resin Cement Types and Film Thicknesses.
OBJECTIVE
To investigate the influence of cement film thickness, cement type, and substrate (enamel or dentin) on ceramic fracture resistance.


METHODS
One hundred extracted human third molars were polished to obtain 50 enamel and 50 dentin specimens. The specimens were cemented to 1-mm-thick lithium disilicate ceramic plates with different cement film thicknesses (100 and 300 μm) using metal strips as spacers. The cements used were etch-and-rinse (RelyX Ultimate) and self-adhesive (RelyX U200) resin cements. Compressive load was applied on the ceramic plates using a universal testing machine, and fracture loads were recorded in Newtons (N). Statistical analysis was performed by multiple regression (p < 0.05). Representative specimens were evaluated by scanning electron microscopy to control the cement film thickness.


RESULTS
The RelyX Ultimate group with a cement thickness of 100 μm cemented to enamel showed the highest mean fracture load (MFL; 1591 ± 172.59 N). The RelyX Ultimate groups MFLs were significantly higher than the corresponding RelyX U200 groups (p < 0.05), and thinner film cement demonstrated a higher MFL than thicker films (p < 0.05). Bonding to dentin resulted in lower MFL than with enamel (p < 0.001).


CONCLUSIONS
Higher fracture loads were related to thinner cement film thickness and RelyX Ultimate resin cement. Bonding to dentin resulted in lower fracture loads than bonding to enamel.


CONCLUSIONS
Reduced resin film thickness could reduce lithium disilicate restoration fracture. Etch-and-rinse resin cements are recommended for cementing on either enamel or dentin, compared with self-adhesive resin cement, for improved fracture resistance.
Esthetic Restorative and Implant Dentistry International Program, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
Thitithorn
T
Rojpaibool
Esthetic Restorative and Implant Dentistry International Program, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
Chalermpol
C
Leevailoj
D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding / Q000379:methods*; D003738:Dental Cements / Q000737:chemistry*; D003743:Dental Enamel; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003804:Dentin; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008963:Molar; D019279:Resin Cements / Q000737:chemistry*; D013499:Surface Properties; D013718:Tensile Strength
D003188:Composite Resins; D003738:Dental Cements; D005899:Glass Ionomer Cements; C587242:RelyX U200; D019279:Resin Cements; C084550:Vitremer; C493120:lithia disilicate; D003776:Dental Porcelain
Lithium disilicate ceramics; cement film thickness; dentin bonding; enamel bonding; fracture resistance; self-adhesive resin cement