An in vitro study to identify a ceramic polishing protocol effecting smoothness superior to glazed surface

Ceramic prostheses often require adjustments after fabrication, which can compromise the glazed surface. While reglazing is a common solution, polishing is proposed as an alternative. Prior research has shown that glazing provides a smooth and esthetically acceptable surface. However, no prior work had resolved whether polishing methods could match or exceed the smoothness of glazed surfaces. This gap motivated the current investigation into in vitro polishing techniques. It was already known that surface roughness affects both aesthetics and long-term durability. The challenge lies in balancing smoothness with minimal color change. Traditional polishing tools include wheels, kits, and wax-based systems. Yet, the effectiveness of these methods compared to glazing remains unclear. This study aimed to address this uncertainty by evaluating multiple polishing protocols.

The goal was to determine if any polishing method could produce a surface smoother than a glazed ceramic surface. Specifically, the study aimed to compare three polishing systems and their combinations. The motivation stemmed from the need for a reliable alternative to reglazing. Adjustments to ceramic prostheses often damage the glazed layer, requiring a secondary treatment. Polishing is a potential solution, but its efficacy is not well established. The research focused on feldspathic porcelain, a common material in dental prosthetics. The study tested whether polishing alone or in sequence could match or exceed glazing. The hypothesis was that a two-step polishing method might yield superior results. This approach could reduce the need for reglazing and improve clinical outcomes.

The study used 77 glazed porcelain discs, each 12.5 mm in diameter and 2 mm thick. These were divided into seven groups of 11 specimens each. One group remained glazed and unpolished as a control. The remaining groups underwent deglazing before polishing. Three single-step polishing methods were tested: a polishing wheel, an adjustment kit, and diamond-impregnated wax. Two two-step methods combined the adjustment kit with diamond wax in different sequences. Each polishing step lasted 40 seconds, totaling 80 seconds for the two-step groups. One specimen from each group was analyzed via scanning electron microscopy. The remaining ten were tested for color and surface roughness. Colorimetry used a Minolta CR-200b ChromaMeter, while profilometry used a Talysurf CLI 2000. Statistical analysis included one-way ANOVA and Tukey HSD tests.

Color differences in all polished groups remained within the acceptable range of 3.3 units. The single-step methods produced surfaces as smooth as the glazed control. The two-step method using an adjustment kit followed by diamond wax achieved the smoothest results. Surface roughness (Ra) in this group was significantly lower than the glazed surface. The polishing wheel followed by diamond wax also produced smooth surfaces but not as smooth as the adjustment kit method. SEM images supported the profilometry findings, showing fewer surface irregularities. The adjustment kit alone and diamond wax alone were both effective but not superior to the two-step method. These results suggest that a two-step polishing sequence may be more effective than glazing alone.

The study found that polishing with an adjustment kit followed by diamond-impregnated wax created surfaces significantly smoother than glazed specimens. This method did not produce a noticeable color change, making it a viable alternative to reglazing. The two-step approach outperformed single-step methods and the control group. The findings support the use of this polishing sequence in clinical settings. The authors proposed that this technique could reduce the need for reglazing after adjustments. The results were consistent across both profilometry and SEM analyses. The study did not suggest that all polishing methods are equally effective. It emphasized the importance of method sequence in achieving optimal smoothness.