Comparative Evaluation of the Surface Roughness and Surface Polishability of a Ceramopolymer Restoration: A Profilometric Analysis

INTRODUCTION

Achieving good surface characteristics is a key objective in composite restorations, driven not only by aesthetic concerns but also oral health considerations. Inadequate finishing and polishing techniques can result in surface irregularities, leading to issues such as staining, plaque retention, gingival irritation, recurrent caries, and altered tactile perception.^[1] Secondary caries is a major reason behind the replacement of composite resin restorations.^[2] Gingival irritation and subsequent caries may result from biofilm growth and bacterial buildup on these restorations.^[3]

In the oral environment, post-polymerisation, the unpolished composite surface may generate a resin-rich surface layer, which exposes the surface to abrasion, revealing rough, inorganic filler material. Maintaining such a finish is challenging; additional contouring and finishing are often required.^[4] Although the clinical performance of composite restorations is on par with that of ceramic restorations, composite resin-based indirect restorations are increasingly being used due to their lower cost and intrinsic low brittleness, especially in the posterior region.^[5]

Many variables, including filler particle size, filler loading, content of resin, and type of filler, affect the surface quality of composite resin. When the surface roughness surpasses 0.2 µm, it can increase plaque retention, thereby heightening the possibility of periodontal inflammation and cavities. Moreover, surface roughness influences the restoration’s natural shine and stain resistance.^[6] Polishing is performed to reduce the surface roughness of the restorative material, effectively eliminating any scratches formed during the finishing process. However, the effectiveness of polishing systems on composites largely depends on the specific product utilised.

The direct technique involves placing the composite directly into the prepared cavity, providing advantages such as a single, relatively inexpensive appointment. Nevertheless, in terms of resistance to wear and polymerisation shrinkage, the indirect approach outperforms the direct method. This is attributed to the fact that indirect composites are polymerised in laboratory-controlled light, heat, and pressure conditions.^[7] When it comes to biofilm growth and compromised composite restorations, surface roughness is a major factor. Numerous investigations have reported lower bacterial adhesion on composites with decreasing surface roughness.^[8,9]

Therefore, the rationale for this study was to evaluate and compare direct and indirect composite resins using different polishing systems. To ascertain the difference in surface roughness when choosing to use a direct or indirect composite resin. A straightforward comparison between direct and indirect composites was only performed in a few studies.

MATERIAL AND METHODS

RESULTS

According to the results of our study, the group with the indirect composite Ceramage showed the lowest surface roughness value when polished using the Ceramage Polishing Kit Hp with a mean value of 0.21 ± 0.15. The highest surface roughness was exhibited by the control group of the direct composite Beautifil II with a mean value of 1.21 ± 0.91. The direct composite group on polishing had a mean value of 0.55 ± 0.16, and the indirect composite control group showed a mean value of 1.13 ± 0.72.

The findings of the present study revealed that additional polishing treatments applied to the surfaces of various composites led to a reduction in surface roughness, regardless of the composite type. One-way ANOVA analysis indicated a statistically significant difference in surface roughness among the four groups, as outlined in Table 1.

To further investigate these differences, a Tukey’s post hoc test was employed for multiple group comparisons, as detailed in Table 2. The results indicated a statistically significant difference in surface roughness between the indirect composite group, using Ceramage with Ceramage Polishing Kit HP, and the control group employing Beautifil II for direct composite (P value = 0.03), signifying a meaningful distinction. However, no statistically significant differences were observed among the other groups apart from the comparison above.

DISCUSSION

It has been shown that the size, hardness, and number of filler particles affect the surface micromorphology of composites after they are finished and polished. It is vital to keep in mind that through the polishing process, the polishing armamentarium must be able to have the resin matrix and filler particles of composites together be consistently removed.^[10] The diamond particles within the polishing paste may provide smoother surfaces on composites compared to the aluminium oxide particles present on the polishing discs due to their higher hardness. ^11]

Within the current study, two distinct types of composites were assessed concerning their surface properties after employing different polishing materials. The control groups underwent no polishing, while the experimental groups for Ceramage and Beautifil II were subjected to polishing using the Ceramage Polishing Kit HP and Super-Snap X-Treme, respectively.

According to the results, the smoother surface is produced by the Ceramage Polishing Kit HP polishing system. This result could be attributed to the use of diamond polishing paste (Dura-Polish Dia), which produces a smoother surface in the indirect composite Ceramage despite being a microhybrid composite containing zirconium silicate filler particles. Our results suggest that the material of the surface plays a more significant role in determining its final smoothness than the specific steps involved in the polishing process. For an effective polishing system, the abrasive particles need to possess higher degrees of hardness than the fillers used.^[12] Suppose the abrasive particles lack sufficient hardness compared to the fillers; in that case, they may selectively remove the softer resin matrix, leaving behind protruding filler particles on the surface, resulting in a rougher finish.^[13]

As per the manufacturer’s specifications, the direct composite utilised in this study was composed of nanohybrid fillers, while the indirect composite featured microhybrid fillers. This distinction may explain why the indirect composite, despite being composed of zirconium disilicate and polished with diamond polishing paste, did not exhibit a superior surface roughness compared to the direct composite. The latter was polished using aluminium oxide polishing discs across more comparison groups. This observation aligns with findings from other studies that suggest that nanohybrid resin composites tend to result in smoother surfaces than their microhybrid counterparts following various polishing procedures.^[14] It can also be taken into consideration that the flexibility of the aluminium oxide discs of the Super Snap X-TREME polishing kit helped maintain a uniformly smooth surface.^[15] While the Ceramage Polishing Kit HP used a silicone point for gross reduction followed by a pivot brush and Felt Wheel for polishing, which may have caused the indirect composite, which is composed of a microhybrid fillers not to produce as smooth a surface as could have been produced had the indirect composite used was one containing nanohybrid fillers. In clinical scenarios necessitating intraoral adjustments for both direct and indirect composites, the use of diamond paste for polishing appears to be a favourable option. This technique has shown superior results in terms of improving surface characteristics and decreasing the production of biofilms.^[16]

Interestingly, none of the materials achieved the desired surface smoothness of 0.2 µm despite undergoing polishing procedures. This finding highlights the crucial role of polishing duration in influencing the outcome. For resin-based composites specifically, Jones et al. suggest using the Super-snap aluminum polishing disc system for 25 seconds per step to achieve optimal results.^[17] The present study employed a 20-second application time for each polishing disc, as recommended by the manufacturers. This relatively short duration might be a contributing factor to the observed surface roughness exceeding the clinical standard of 0.2 mm for all materials.^[18]

Within the constraints of this study, the findings may imply that indirect resin composites are more suitable for restorations requiring adjustments after cementation, particularly in achieving a smoother final surface compared to direct resin composites.

CONCLUSION

Considering the limitations of the study, it can be deduced that the finishing and polishing procedures applied to the indirect composite Ceramage, specifically using the Ceramage Polishing Kit HP, result in a lower surface roughness when compared to the direct composite Beautifil II.