Effect of fluoride-releasing restorative materials on bacteria-induced pH fall at the bacteria-material interface: an in vitro model study.
OBJECTIVE
Inhibition of bacterial acid production by dental restorative materials is one of the strategies for secondary caries prevention. This study aimed to evaluate the effect of fluoride-releasing restorative materials on bacteria-induced pH fall at the bacteria-material interface.


METHODS
Four fluoride-releasing restorative materials, glass-ionomer cement (GIC), resin-modified glass-ionomer cement (RMGIC), resin composite (RC) and flowable resin composite (FRC) were used. Each specimen was immersed in potassium phosphate buffer at pH 7.0 for 10min and 4 weeks, and in potassium acetate buffer at pH 5.5 for 4 weeks. An experimental apparatus was made of polymethyl methacrylate and had a well with restorative materials or polymethyl methacrylate (control) at the bottom. The well was packed with cells of Streptococcus mutans, and the pH at the interface between cells and materials was monitored using a miniature pH electrode after the addition of 1% glucose for 90min, and the fluoride released into the well was quantified using a fluoride ion electrode.


RESULTS
The pH of GIC (4.98-5.18), RMGIC (4.77-4.99), RC (4.62-4.75) and FRC (4.54-4.84) at 90min were higher than that of control (4.31-4.49). The fluoride amounts released from GIC were the highest, followed by RMGIC, RC and FRC, irrespective of immersion conditions. Saliva coating on materials had no significant effect.


CONCLUSIONS
The fluoride-releasing restorative materials inhibited pH fall at the bacteria-material interface. The degree of inhibition of pH fall seemed to correspond to the amount of fluoride detected, suggesting that the inhibition was due to the fluoride released from these materials.


CONCLUSIONS
A little amount of fluoride actually released from the fluoride-releasing materials may have caries preventive potential for oral bacteria.
Division of Oral Ecology and Biochemistry, Department of Oral Biology, Tohoku University Graduate School of Dentistry, Sendai, Japan; Research Unit for Interface Oral Health Science, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Gen
G
Mayanagi
Division of Oral Ecology and Biochemistry, Department of Oral Biology, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Koei
K
Igarashi
Division of Oral Ecology and Biochemistry, Department of Oral Biology, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Jumpei
J
Washio
Division of Oral Ecology and Biochemistry, Department of Oral Biology, Tohoku University Graduate School of Dentistry, Sendai, Japan; Division of Pediatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Hitomi
H
Domon-Tawaraya
Division of Oral Ecology and Biochemistry, Department of Oral Biology, Tohoku University Graduate School of Dentistry, Sendai, Japan. Electronic address: nobu-t@dent.tohoku.ac.jp.
Nobuhiro
N
Takahashi
D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002327:Cariostatic Agents / Q000737:chemistry* / Q000494:pharmacology; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D044622:Dental Pellicle / Q000737:chemistry; D004058:Diffusion; D004566:Electrodes; D005459:Fluorides / Q000737:chemistry* / Q000494:pharmacology; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017736:Ion-Selective Electrodes; D008422:Materials Testing; D019904:Polymethyl Methacrylate / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013295:Streptococcus mutans / Q000187:drug effects*; D013499:Surface Properties
C470433:Beautifil composite resin; D002327:Cariostatic Agents; D020099:Coated Materials, Biocompatible; D003188:Composite Resins; D003764:Dental Materials; C439808:Fuji IX GP Fast; D005899:Glass Ionomer Cements; D019279:Resin Cements; D017438:Bisphenol A-Glycidyl Methacrylate; D019904:Polymethyl Methacrylate; D005459:Fluorides
Fluoride; ISFET pH electrode; Interface; Restorative material; Saliva; Secondary caries; Streptococcus; pH