Effect of cariogenic biofilm challenge on the surface hardness of direct restorative materials in situ.
OBJECTIVE
The presence of cariogenic biofilm could result in surface degradation of composite and ionomeric restorative materials. Thus, this study evaluated in situ the alterations in the surface microhardness of these materials under biofilm accumulation and cariogenic challenge.


METHODS
In a split-mouth, double-blind, cross-over study, 10 volunteers wore palatal intra-oral devices containing bovine enamel slabs restored with composite resin (CR - Z250) or resin-modified glass ionomer (RMGI - Vitremer). Two phases of 14 days were carried out, one for each restorative material. In one side of the device, biofilm was allowed to accumulate under a plastic mesh, whereas in the opposing side, regular brushing was carried out 3 times/day with a dentifrice containing 1100 μg F/g as NaF. A 20% sucrose solution was applied extra-orally 10×/day on each restored dental slab. Knoop microhardness was used to calculate the percentage of surface hardness loss (%SHL).


RESULTS
All materials showed a decrease in surface hardness after the in situ period. The restorative materials presented the following average for %SHL: RMGI without biofilm accumulation=8.9 and with biofilm accumulation=25.6, CR without biofilm accumulation=14.7 and with biofilm accumulation=17.0.


CONCLUSIONS
Biofilm accumulation and the presence of cariogenic challenge promoted faster degradation of ionomeric materials, but this was not observed for composite resin.


CONCLUSIONS
The oral environment affects the surface hardness of aesthetic restorative materials. Biofilm accumulation and cariogenic challenge promote surface degradation for ionomeric materials, but not for composite resin.
Graduate Program in Dentistry, Federal University of Pelotas, Pelotas, RS, Brazil.
Renata Pereira de Sousa
RP
Barbosa
Tatiana
T
Pereira-Cenci
Wagner Missio da
WM
Silva
Fabio Herrmann
FH
Coelho-de-Souza
Flávio Fernando
FF
Demarco
Maximiliano Sérgio
MS
Cenci
D000328:Adult; D000818:Animals; D018441:Biofilms / Q000187:drug effects; D002326:Cariogenic Agents / Q000494:pharmacology; D002327:Cariostatic Agents / Q000627:therapeutic use; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry; D018592:Cross-Over Studies; D003731:Dental Caries / Q000382:microbiology*; D003743:Dental Enamel / Q000382:microbiology; D003764:Dental Materials / Q000737:chemistry*; D003773:Dental Plaque / Q000382:microbiology; D003793:Dental Restoration, Permanent; D003802:Dentifrices / Q000627:therapeutic use; D004311:Double-Blind Method; D005260:Female; D005899:Glass Ionomer Cements / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008297:Male; D019279:Resin Cements / Q000737:chemistry; D012969:Sodium Fluoride / Q000627:therapeutic use; D013395:Sucrose / Q000494:pharmacology; D013499:Surface Properties; D014099:Toothbrushing; D055815:Young Adult
D002326:Cariogenic Agents; D002327:Cariostatic Agents; D003188:Composite Resins; D003764:Dental Materials; D003802:Dentifrices; C444701:Filtek Z250; D005899:Glass Ionomer Cements; D019279:Resin Cements; C084550:Vitremer; D013395:Sucrose; D012969:Sodium Fluoride