J Adv Prosthodont.  2019 Feb;11(1):41-47. 10.4047/jap.2019.11.1.41.

Effects of different surface finishing protocols for zirconia on surface roughness and bacterial biofilm formation

• Lee DH
• Mai HN
• Thant PP
• Hong SH
• Kim J
• Jeong SM
• Lee KW

• KMID: 2438930
• DOI: http://doi.org/10.4047/jap.2019.11.1.41

Abstract

PURPOSE
Surface finishing of a zirconia restoration is essential after clinical adjustment. Herein, we investigated the effects of a surface finishing protocol for monolithic zirconia on final roughness and bacterial adherence.
MATERIALS AND METHODS
Forty-eight disk-shaped monolithic zirconia specimens were fabricated and divided into four groups (n = 12) based on initial surface treatment, finishing, and polishing protocols: diamond bur+polishing bur (DP group), diamond bur+stone grinding bur+polishing bur (DSP group), no diamond bur+polishing bur (NP group), and no diamond bur+stone grinding bur+polishing bur (NSP group). Initial and final surface roughness was measured with a profilometer, and shown using scanning electron microscope. Bacterial adhesion was evaluated by quantifying Streptococcus mutans in the biofilm. Kruskal-Wallis and Mann-Whitney U tests were used to compare results among groups, and two-way analysis of variance was used to evaluate the effects of grinding burs on final roughness (α=.05).
RESULTS
The DP group had the highest final Ra value, followed by the DSP, NP, and NSP groups. Use of the stone grinding bur as a coarse-finishing step significantly decreased final Ra values when a diamond bur was used (P < .001). Omission of the stone grinding bur increased biofilm formation on specimen surfaces. Combining a stone grinding bur with silicone polishing burs produced the smallest final biofilm values, regardless of the use of a diamond bur in initial surface treatment.
CONCLUSION
Coarse finishing of monolithic zirconia with a stone grinding bur significantly decreased final Ra values and bacterial biofilm formation when surfaces had been roughened by a diamond bur.

Keyword

Zirconia; Dental finishing; Dental polishing; Biofilm; Bacterial adhesion

MeSH Terms

Bacterial Adhesion
Biofilms*
Dental Instruments
Dental Polishing
Diamond
Silicon
Silicones
Streptococcus mutans
Diamond
Silicon
Silicones

Figure

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  Fig. 1 Workflow of study.

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  Fig. 2 Microscopic views of burs at ×300 magnification. (A) Diamond bur, (B) Stone grinding bur, (C) Silicone polishing bur, (D) Fine silicone polishing bur.

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  Fig. 3 Biofilm formation on zirconia specimen from each group after finishing and polishing. Black lines indicate initial biofilm formation for diamond bur-treated and nontreated specimens.

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  Fig. 4 Scanning electron microscope images of diamond bur-treated specimens. (A) Surface after use of diamond bur alone, (B) Surface after use of diamond and polishing burs, (C) Surface after use of diamond bur, stone grinding bur, and polishing bur.

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  Fig. 5 Schematic image of bacterial adhesion to zirconia; heavy bacterial inhabitation is observed in the partially altered surface treated by diamond and polishing burs. (A) Surface after use of diamond bur alone, (B) Surface after use of diamond and polishing burs, (C) Surface after use of diamond bur, stone grinding bur, and polishing bur.

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