Universal Research Journal of Dentistry September-December 2014 Vol 4 Issue 3158

INTRODUCTION

Dental ceramic has been used in dentistry for over 150 years.[1] Currently, dental ceramic is used extensively as a restorative material in a variety of dental restorations, including allceramic restorations, metal ceramic crowns, fixed partial dentures, and even in complete dentures in some cases because of its aesthetic properties, durability, and biocompatibility.[2]

It is a common clinical practice to adjust the glazed surface of ceramic restorations before insertion by grinding.[3] Surface modifications are essential for correcting occlusal interferences and inadequate contours, finishing the margins of ceramic restorations, and improving the

The Effects of Porcelain Finishing and Polishing Systems on the Surface Roughness of Feldspathic Porcelain: An In Vitro Study

Manoj Shetty, Raghavendra Jaiman, Prasad D KrishnaDepartment of Prosthodontics and Crown and Bridge, Attavar Balakrishna Shetty Memorial Institute of Dental Sciences, Nitte University,

Mangalore, Karnataka, India

esthetic appearance and surface smoothness of ceramic restorations.[4]

A rough surface may abrade the opposing tooth or restorative materials. Abrasiveness is more correlated with ceramic roughness[5] than with hardness.[6] Several studies have shown that finished ceramic can produce equal or less enamel wear than glazed ceramic.[7,8] The roughness of intraoral hard surfaces has a major impact on the initial adhesion and retention of oral microorganisms.

The current study deals with the efficiency of surface polishing systems after the glaze layer of the ceramic has been altered using a medium grit diamond to simulate the chairside adjustment of a restoration. It is aimed to analyze the relative efficiency of each of the four polishing systems by comparing them with roughened samples, keeping glazed samples as control.

O R I G I N A L A R T I C L E

Introduction: This in vitro study deals with the efficiency of surface polishing systems after the glaze layer of the ceramic has been altered using a medium grit diamond to simulate the chairside adjustment of a restoration. Materials and Methods: Forty porcelain discs measuring 10 mm 3 mm with a metal substructure of 10 mm 1 mm were used. Ceramco 3(ultralow fusing feldspathic porcelain) porcelain system was used to fabricate the discs on the metal substructure. A medium grit diamond was used to simulate the chairside adjustment procedures. Ten samples were glazed (control group) and 30 samples were finished and polished using three finishing and polishing agents. (experimental group; Shofu Ceramaster, Kohinoor diamond polishing paste and SofLex discs).These 40 samples and the initial roughened samples were subjected to a profilometer evaluation to obtain results in Ra (Average roughness in m) and Rz (Mean maximum peak tovalley height in m). Results: One way ANOVA revealed a statistical significant difference amongst Ra values of the group. Amongst the finished and polished group of samples, the samples polished with Shofu Ceramaster diamondimpregnated silicon showed the highest efficiency among the three finishing and polishing systems followed by samples polished with Kohinoor L highly filled diamond polishing paste and the least efficient polishing system was the samples polished using SofLex discs. The Rz (Mean peaktovalley height) values showed the same results as the Ra values. Conclusion: The study concluded that among the three finishing and polishing systems tested, Shofu Ceramaster diamond impregnated silicon rubbers are the most efficient with significant differences in surface roughness compared to roughened samples

KEY WORDS: Feldspathic porcelain, profilometry, surface roughness

ABSTRACT

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DOI:10.4103/2249-9725.140676

Address for Correspondence: Dr. Manoj Shetty,

Department of Prosthodontics and Crown and Bridge, A. B Shetty Memorial Institute of Dental Sciences,

Nitte University, Deralakatte, Mangalore, Karnataka 575 018, India.

Email: drmanojshetty@gmail.com

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Shetty, et al.: Effects of porcelain finishing and polishing systems on surface roughness

159Universal Research Journal of Dentistry September-December 2014 Vol 4 Issue 3

MATERIALS AND METHODS

The porcelain discs consisted of metal substructures prepared by casting metal discs of 10 1 mm size using Fornax casting machine by Bego. Girobond CBS, a carbonfree NiCrMobonding alloy, was used for casting the metal substructure for the required 40 discs. [Figures 1 and 2] The porcelain was then layered on all 40 metal substructures using Ceramco3 (ultralow fusing feldspathic porcelain) porcelain system. The buildup was done using purely enamel crystals as the occlusal adjustment requires reduction of enamel layer of the prosthesis. The final porcelain discs along with the metal substructure measured 10 3 mm. All 40 discs were glazed with overglaze followed by which a medium grit diamond rotary instrument was used on all discs to emulate the chairside occlusal adjustment of prosthesis [Figure 3]. Out of the 40 roughened porcelain discs, 10 discs were glazed with overglaze and the remaining 30 discs were finished and polished using 3 finishing and polishing systems and 1 system for a group of 10 discs.

The agents used for polishing the three groups of samples were Group 1: Shofu Ceramaster: Diamondimpregnated silicone polishers [Figure 4], Group 2: Reinfert Kohinoor: Highly filled diamond particle polishing paste [Figure 5], Group 3: SofLex finishing and polishing system [Figure 6].

Finally, all samples were tested for their surface roughness using Surtronic 3+ surface roughness analyzer by Taylor Hobson Ltd. (distance travelled by the stylus 2.5 mm) for parameters Ra and Rz [Figures 7 and 8]. Each sample was analyzed three times. The values were digitally displayed on the profilometer and then tabulated.

Statistical analysisStatistical analysis was performed by a oneway ANOVA (SPSS version 16.0) to compare the three finished and polished group of samples (experimental

groups) and the glazed samples (control group) with the roughened samples to find if there was any statistical significance between the five groups. Also, a posthoc analysis using Tukey HSD was performed to compare each of the three finished and polished group of samples with the roughened and glazed group of samples and with every other group.

RESULTS

The mean and standard deviation was calculated and tabulated for a oneway ANOVA test of the samples [Table 1].

A oneway ANOVA revealed that a statistically significant difference exists between the five groups. It compared the five groups to reveal that the highest Ra and Rz values were obviously seen for the roughened samples with a mean Ra of 5.23 m and mean Rz of 26.31 m. Among the three finished and polished groups of samples, the most efficient finishing and polishing system was Shofu Ceramaster (Grp 1). Grp 1 samples had a mean Ra of 3.89 m and mean Rz of 18.57 m. Second most efficient was Kohinoor L highly filled diamond polishing paste (Grp 2). Grp 2 had a mean Ra of 4.66 m and mean Rz of 24.08 m. The least efficient amongst the three groups was the SofLex finishing and polishing system (Grp 3). Grp 3 had a mean Ra of 4.83 m and mean Rz of 24.64 m. Finally, the glazed group, which was the control group, revealed a mean Ra of 1.06 m and a mean Rz of 3.43 m.

The posthoc analysis Tukey HSD was done to compare Ra (average roughness) values of the roughened group of samples and the three polished groups of samples (experimental groups) and glazed group of samples (control group) [Table 2].

It was found that the Ra values of Grp 1 samples (mean Ra 3.89 m) and those of the roughened samples (mean Ra 5.23 m) showed a statistically significant

Table 1: Oneway ANOVA test (Grp 1Shofu, Grp 2Kohinoor and Grp 3Soflex)Descriptive N Mean Std. Deviation Statistic df1 df2 Sig.Ra (in microns)

Roughened samples 30 5.232667 1.197083 165.879 4 68.715

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difference (P < 0.05) whereas the Ra values of Grp 2 samples (mean Ra 4.65 m) and the Grp 3 samples (mean Ra 4.82 m) did not show a statistically significant difference (P > 0.05) when compared to the roughened samples (mean Ra 5.23 m).

Furthermore, the Ra values of glazed samples (Control group) (mean Ra 1.06 m) were compared to the Ra values of all three polished groups of samples (experimental group) (mean Ra 3.89 m, 4.65 m, and 4.82 m) and it revealed a statistically significant difference (P < 0.05).

Figure 7: Surtronic 3+ surface roughness analyzer by Taylor Hobson Ltd. Figure 8: Measurement of surface roughness of a sample

Figure 6: SofLex finishing and polishing system

Figure 5: Reinfert Kohinoor: Highly filled diamond particle polishing paste

Figure 4: Shofu Ceramaster Diamondimpregnated silicone polishers

Figure 3: Glaze surface removal using mediumgrit diamond

Figure 1: All samples (40 glazed samples)Figure 2: Thickness of (a) Metal substructure; (b) Porcelain buildup

ba

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Shetty, et al.: Effects of porcelain finishing and polishing systems on surface roughness

161Universal Research Journal of Dentistry September-December 2014 Vol 4 Issue 3

When Ra values of the various polished samples were compared to each other, it was revealed that the Ra values of Grp 2 samples (mean Ra 4.65 m) did not have a statistically significant difference to the Ra values of Grp 1 samples (mean Ra 3.89 m) and Grp 3 samples (mean Ra 4.82 m). Whereas the Ra values of the Grp 1 samples (mean Ra 3.89 m) had a statistically significant difference compared to the Ra values of the Grp 3 samples (mean Ra 4.82 m).

The Rz (mean peaktovalley height) values showed the exact same correlation as the Ra values except the Rz values of Grp 2 samples (mean Ra 24.08 m) and Rz values of Grp 1 samples (mean Ra 18.57 m), which showed a statistically significant difference unlike the Ra values.

DISCUSSION

With the increased use of ceramic materials in dentistry, one must pay careful attention to the efficacy of different polishing systems and techniques, the brittle nature of this material and whether the intraoral polishing techniques using rotary instruments, such as diamond burs and rubber abrasives, can provide a clinically acceptable smoothness due to the high hardness of ceramic materials. It is a wellknown fact that post adjustment can be overcome using overglaze or various finishing and polishing systems available.

While some studies have verified that glazing resulted in a smoother surface compared to polishing, other studies

have found comparable final surfaces for both finishing methods.[911] There have also been studies that showed polished ceramic surfaces to be smoother than glazed surfaces.[12,13]

The current study compares the efficacy of three such finishing and polishing agents in polishing samples of feldspathic porcelain after the glaze layer had been removed from them using a mediumgrit diamond keeping the glazed samples as the control group. A mediumgrit diamond was used so as to have a better idea about the relative efficiency of each of the finishing and polishing systems. This removal of the glazed layer simulated the rough surface of porcelain following chairside adjustment of a restoration.

Following the use of medium grit diamond to simulate the chairside adjustment procedures, 10 samples were glazed (Control group) and 30 samples were finished and polished using three finishing and polishing agents (experimental group; Shofu Ceramaster, Kohinoor diamond polishing paste, and SofLex discs). All these 40 samples and the initial roughened samples were subjected to profilometer evaluation to obtain results in Ra (average roughness in m) and Rz (mean maximum peaktovalley height in m). The values from the profilometer evaluation were subjected to statistical analysis. A oneway ANOVA revealed that a statistically significant difference between the five groups. It compared the five groups to reveal that the highest Ra and Rz values were obviously seen for the roughened Samples with a mean Ra of 5.23 m and mean Rz 26.31 m. Amongst the three finished and polished

Table 2: Posthoc analysis tukey HSD (Grp 1Shofu, Grp 2Kohinoor, and Grp 3Soflex)

Tukey HSDDependent variable (I) grp (J) grp Mean difference (IJ) Std. error P valueRa (in microns)

Roughened samples Glazed samples 4.171333 0.283524

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group of samples. The most efficient finishing and polishing system was Shofu Ceramaster. Shofu samples had a mean Ra 3.89 m and mean Rz of 18.57 m. The second most efficient finishing and polishing system was Kohinoor L highly filled diamond polishing paste, which had a mean Ra of 4.66 m and mean Rz of 24.08 m. The least efficient amongst the three groups was the SofLex finishing and polishing system, which had a mean Ra of 4.83 m and mean Rz of 24.64 m. Finally, the glazed group, which was the control group revealed a mean Ra of 1.06 m and a mean Rz of 3.43 m.

When Ra values of the various polished samples were compared to each other, it revealed that the Ra values Kohinoor L (mean Ra 4.65 m) samples did not have a statistically significant difference to the Ra values of Shofu samples (mean Ra 3.89 m) and SofLex samples (mean Ra 4.82 m). Whereas the Ra values of the Shofu samples (mean Ra 3.89 m) had a statistically significant difference compared to the Ra values of the SofLex samples (mean Ra 4.82 m).

The Rz values showed the exact same correlation as the Ra values except the Rz values of Kohinoor L samples (mean Ra 24.08 m) and Rz values of Shofu samples (mean Ra 18.57 m), which showed a statistically significant difference unlike the Ra values.

This finding is in agreement with previous reports on the effect of different polishing techniques on the surface roughness of several dental ceramics. In a study done on refinishing of porcelain by using a refinishing kit, the effects of a group of commercially available finishing kits on Vita VMKbonded porcelain was investigated qualitatively and quantitatively using scanning electron microscope and surface profilometer. The kit proved incapable of restoring a surface glaze to porcelain adjusted using a fine (red band) diamond bur.[14,15]

Another study that was done to assess the effects of porcelain polishing techniques on color and surface texture of different porcelain systems, and it concluded that chairside porcelain polishing systems were not able to provide a porcelain surface as smooth as the glazed surface for Ceramco 3 porcelains.[11]

CONCLUSION

Within the limitations of the study it was concluded that:

Among the three finishing and polishing systems tested, Shofu Ceramaster diamondimpregnated silicon rubbers are the most efficient, showing a statistically significant difference in surface roughness compared to roughened samples.

However, none of the finishing and polishing systems were able to provide a porcelain surface as smooth as the glaze group.

The Kohinoor L highly filled diamond paste and SofLex finishing and polishing system did not show significant difference in surface roughness compared to the roughened samples.

This study made use of a medium grit diamond in order to simulate chairside adjustment since it provides for better evaluation of relative efficiency of the three finishing and polishing systems. However, clinically, a fine grit diamond or a 12fluted carbide bur diamond should be used for chairside adjustment of porcelain restoration.

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How to cite this article: Shetty M, Jaiman R, Krishna PD. The effects of porcelain finishing and polishing systems on the surface roughness of feldspathic porcelain: An in vitro study. Univ Res J Dent 2014;4:158-62.Source of Support: Nil, Conflict of Interest: None declared

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