## 2 Materials and Methods
### Assessment of Ability of Different Powders to Remove Biofilm  
A sterile tube containing 10 mL of BHI was inoculated with a single colony of Streptococcus Sanguinis (_S. sanguinis_) and grown overnight for 24 h at 37 \({}^{\circ}\)C. Absorbance (OD600) of the culture was assessed and the culture transferred aseptically to a 15 mL Falcon tube and centrifuged at 3260 g for 15 min. The supernatant was gently poured off, and the bacteria were resuspended in an appropriate volume of fresh BHI medium containing 0.5% sucrose to yield an absorbance (OD 600) of 0.4. A total of 56 scored contaminated and 2 control-contaminated untreated discs were transferred aseptically to culture plates, and 1 mL of bacterial culture was added to each disc. Discs were incubated at 37 \({}^{\circ}\)C for 72 h, with media being changed at 24 and 48 h. The remaining 4 unscored discs were incubated in 1 ml of fresh BHI + 0.5% sucrose for 72 h,  
Figure 1: Assessment of ability of different powders to remove biofilm—experimental design. Specifically, a total of 34 machined (M) and 34 moderately rough surface (MRS) discs were examined. A total of 28 M and 28 MRS were contaminated, while 6 M and 6 MRS served as controls and were left uncontaminated. Thus, 4 M and 4 MRS discs were treated with sodium bicarbonate powder 65 \(\upmu\)m (group 1), sodium bicarbonate powder 40 \(\upmu\)m (group 2), glycine powder (group 3), erythroid powder (group 4), and the addition of cetylpyridinium chloride (group 5), calcium carbonate (group 6), and distilled water (group 7), respectively; the same treatments were applied to 1 not contaminated disc per group. without changing the medium. The other 12 scored uncontaminated discs (6 M and 6 MRS) were used without immersion in BHI to assess the fluorescence of different powders. After 72 h, each of the 68 scored discs (28 M and 28 MRS incubated in bacterial culture and 12 discs not incubated in any culture) received treatment using different powders. Half of each disc was covered with parafilm, while the other half was left exposed to treatment. An Original AirFlow(r) handpiece (EMS, Nyon, Switzerland) was kept at 5 mm distance from the disc surface. The angle of the handpiece was maintained at 90\({}^{\circ}\)[32; 33; 34], and treatment was standardized using a putty index (Figure 2A). Since the handpiece was stabilized in a perpendicular position in relation to the disk and the treatment was delivered through a stream of high pressured water and powder, most of the powder hit the disk perpendicularly, with some particle powders hitting the disk at a more acute angle which did not exceed 45\({}^{\circ}\). Distilled water was used during treatment with different powders. Settings of the unit were kept to the maximum for both water and powder. Treatment was provided for 20 s in a back-and-forth movement, as follows:  
1. Group 1 (4 M contaminated and 4 MRS contaminated, 1 M not contaminated, 1 MRS not contaminated): treated with air-powder mechanical instrumentation delivering sodium bicarbonate powder (Air flow powder Classic(r), 65 \(\upmu\)m, EMS, Nyon, Switzerland);
2. Group 2 (4 M contaminated and 4 MRS contaminated, 1 M not contaminated, 1 MRS not contaminated): treated with air-powder mechanical instrumentation delivering sodium bicarbonate powder (Air Flow powder Classic Comfort(r), 40 \(\upmu\)m, EMS, Nyon, Switzerland);
3. Group 3 (4 M contaminated and 4 MRS contaminated, 1 M not contaminated): treated with air-powder mechanical instrumentation delivering glycine powder (Air-Flow Powder Perio(r), 25 \(\upmu\)m, EMS, Nyon, Switzerland);
4. Group 4 (4 M contaminated and 4 MRS contaminated,1 M not contaminated, 1 MRS not contaminated): treated with air-powder mechanical instrumentation delivering erythritol powder (Air-Flow Powder Plus(r), 14 \(\upmu\)m, EMS, Nyon, Switzerland);
5. Group 5 (4 M contaminated and 4 MRS contaminated, 1 M not contaminated, 1 MRS not contaminated): Air Flow Plus(r) with 0.05% Cetylpyridinium chloride (CPC);
6.