MATERIALS AND METHODS: A random sample of 200 permanent molars from 10 deceased sheep was selected. Each received one of the five standard clinical procedures, including no preparation, preparation but restoration, glass ionomer cement restoration (GIC), resin modified glass ionomer cement restoration (RMGIC) as well as composite resin restoration (CR), and followed by topical APF application at a daily interval and a predetermined frequency ranging from zero to three times. Staining formation on teeth and restorations was evaluated and determined by three trained examiners.
RESULTS: Fluoride staining on the teeth and/or the restorations varied, appearing with a distinguishable darker shade, an orange-coloured surface or a deep brown margin. The fluoride staining rates of GIC, RMGIC and CR were 50%, 27.5% and 17.5% respectively. GIC had a higher staining potential than RMGIC (chi square=4.266, df=1, p=0.039) and CR (chi square=9.448, df=1, p=0.002), while difference of staining potential between RMGIC and CR was indiscernible (chi square=1.147, df=1, p=0.284). The occurrence of staining increased with the frequency of topical APF application on RMGIC (chi square=8.436 df=1, p=0.004) and CR (chi square=6.873, df=1, p=0.009) but GIC (chi square=0, df=1, p=1). Staining was not associated with frequency of APF application on teeth without preparation and/or restoration (chi square=2.627, df=1, p=0.105).
CONCLUSION: The staining of APF gels reported in the literature was confirmed in vitro. GIC was more susceptible to fluoride staining than RMGIC and CR. This study suggested aesthetic implications when topically applying fluorides to restored teeth. Further investigation on human teeth is indicated.