Effect of fluorosis on shear bond strength of glass ionomer-based restorative materials to dentin.
BACKGROUND
Several studies have investigated the adhesion of glass ionomer-based restorative materials to nonfluorotic teeth, but there appears to be no information on the bond strength of these restorative materials to dentin in fluorotic teeth.


OBJECTIVE
This study investigated the effect of dental fluorosis on the bond strength of Ketac-fil conventional glass ionomer cement, Vitremer resin-modified glass ionomer cement, and Dyract polyacid modified resin to dentin.


METHODS
Ninety posterior teeth were classified according to the severity of fluorosis, by using the Thylstrup and Fejerskov index, TFI. The teeth were divided into 3 equal groups (TFI = 0,TFI = 1-3, TFI = 4+) of 30 teeth, which were again divided into 3 equal subgroups for testing each of the3 restorative materials. Occlusal surfaces of mounted teeth were ground flat to expose dentin. Cylindrical specimens (4 mm diameter and 4 mm high) of the restorative materials were bonded to the middle of the cleaned exposed dentin surfaces, according to the manufacturers' instructions. After storing the specimens in 100% humidity at 37 degrees C for 24 hours, shear bond strengths of the restorative materials were measured with an Instron testing machine at crosshead speed of 0.5 mm/min.


RESULTS
Two-way analysis of variance and Tukey-B test revealed that Dyract had significantly higher shear bond strength to dentin than Ketac-fil or Vitremer cements, regardless of severity of fluorosis (P <.05). Furthermore, there was an inverse relationship between shear bond strength and the severity of fluorosis for each of the restorative materials. Cohesive mode of failure was most prevalent in nonfluorotic teeth (TFI = 0), especially with Ketac-fil cement, whereas Dyract cement had the greatest propensity for adhesive failure.


CONCLUSIONS
Fluorosis reduces the shear bond strength of glass ionomer-based restorative materials to dentin.
Awliya
W Y
WY
College of Dentistry, King Saud University, Riyadh, Saudi Arabia.
Akpata
E S
ES
D000268:Adhesiveness; D000704:Analysis of Variance; D020770:Compomers; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000503:physiopathology* / Q000648:ultrastructure; D009050:Fluorosis, Dental / Q000145:classification / Q000503:physiopathology*; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D006813:Humidity; D008298:Maleates / Q000737:chemistry; D008689:Methacrylates / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature
D020770:Compomers; D003188:Composite Resins; C088486:Dyract; D005899:Glass Ionomer Cements; D008298:Maleates; D008689:Methacrylates; D017640:Silicates; C084550:Vitremer; C040964:Ketac-Fil