Effect of different topical fluoride applications on the surface roughness of a colored compomer

Objective The aim of this study was to evaluate the effect of neutral sodium fluoride (NNaF) gel and acidulated phosphate fluoride (APF) gel on the surface roughness of colored compomer (Twinky Star), conventional compomer (Compoglass F) and resin-modified glassionomer cement (RMGIC) (Photac-Fil). Material and Methods A total of 45 standardized disc-shaped specimens were prepared for each material. After 24 h, finishing and polishing of specimens were done with aluminum oxide disc. Surface treatments with topical fluoride agents or distilled water (control) were performed four times, and interspersed with 8 pH cycles, simulating high cariogenic challenges. After the treatment, the surface roughness (Ra) was determined using a profilometer. In each group, specimens with Ra closest to the mean were examined with a scanning electron microscope (SEM) at ×1,000 and ×3,500 magnifications. Two-way ANOVA was used to evaluate Ra measurements, and the differences in Ra values between subgroups for each material and each topical applications were compared by Tukey’s highly significant difference pairwise comparisons. Results No statistically significant difference in Ra between the Twinky Star and Compoglass F was found. However, Photac Fil showed significantly higher Ra than these materials after all surface treatments. There was a general trend of Ra increase from controls to NNaF and APF gels for all materials. SEM observations revealed that the surface micromorphology of Twinky-Star did not differ significantly from that of Compoglass F. Conclusion Both the compomers and the RMGIC showed significantly higher surface roughness when subjected to APF gel application.


INTRODUCTION
Polyacid-modified resin composites, commonly known as "compomers" are a group of esthetic materials for anterior and posterior restorations of primary teeth 14,18 . They were introduced in the early 1990s with claims that they combined the mechanical and esthetic properties of composites with the fluoride-releasing advantages of conventional glass-ionomer cements (GICs) 17 .
Colored compomers, which can be produced by adding a small amount of glitter particles (mainly silicates from kali) to conventional compomers, producing materials with pink, green, blue, silver, orange, lemon or gold shades, have been available for the restoration of primary molars for over 4 years 4,14,17 . When they are asked for a choice, some children prefer tooth-colored, imperceptible dental restorations, while other children enjoy a colorful filling material for their primary teeth 11 .
Even though colored compomer is made to be decorative, it has physical properties that apparently are sufficient to hold up in the mouth 2010;18(2):171-7 until the restored primary tooth is lost 5 . In a study of Croll, et al. 5 , a second primary molar restored in a 8-year-old girl with a colored compomer, and reported that the restoration was intact and serving its purpose well 10 months after placement.
Previous studies have shown that topical fluoride application to compomers could increase the surface roughness of this materials 3,7,30-32 . The clinical significance of the increased surface of the materials covers the increased plaque adhesion and its harmful effects on the tooth and periodontium, to surface discoloration and fatigue failure [2][3]12,19,22,29 . The amount of plaque correlates with the surface roughness of compomers, and the fluoride-releasing capacities of these materials do not efficiently prevent the attachment and viability of Streptococcus mutans 23,26 .
No previous study has addressed the effects of topical fluoride agents on colored compomer in the dental literature. Therefore, the aim of the present study was to evaluate the effects of acidulated phosphate fluoride (APF) gel and neutral sodium fluoride (NNaF) gel treatment on the surface roughness of colored compomer.
The tested null hypothesis was that topical fluoride applications have greater influence on the surface roughness of the colored compomer because of the glitter particles added to these materials compared to conventional compomer and resin-modified glass-ionomer (RMGIC).

MATERIAL AND METHODS
The restorative materials used in this study together with information on their basic composition and particle size are listed in Figure   1.

Specimen Preparation
Sixty disc-shaped specimens (4 mm in

Analysis
In each group, specimens with Ra closest to the mean were sputter coated with gold (S150B; Edwards, Crawley, England) and examined under a field emission scanning electron microscope (SEM) (JSM-6335F, JEOL, Tokyo, Japan). The SEM micrographs were made at ×1000 and 3,500 magnification for visual inspection.

Statistical Analysis
The measurements controlled for normality assumptions, they were found to be normally

Surface Roughness
Comparisons of the of surface roughness means among and within the restorative materials are listed in Table 1.
When the surfaces roughness of the groups were compared in terms of the materials, except for the initial groups, significant differences were found between Photac-Fil and Twinky Star (p<0.05), and also between Photac-Fil and Compoglass F for all subgroups (p<0.05).
However there was no significance difference between Twinky Star and Compoglass F (p>0.05).
According to the surface treatments,

DISCUSSION
In the present study, although Twinky Star had visually more surface roughening than Compoglass F, the profilometry data revealed no significant difference between these materials (Table 1). Thus, the null hypothesis was rejected.
There  (Table 1). On the other hand, for Photac-Fil, whose particle size is larger and amount of resin matrix is lesser, showed very rough surface with voids present confirmed by profilometry.
For Photac-Fil, a significant surface roughness was detected for specimens treated both NNaF gel and APF gel (Table 1), as others have reported 13,15,31 . The filler particles were eroded and partially or completely exposed because of the absence of the surrounding matrix, and the matrix also appeared to be severely degraded