Effect of supragingival air polishing on subgingival periodontitis microbiota

Abstract

Background:

Supragingival air polishing of teeth effectively removes dental plaque and extrinsic stain on coronal tooth surfaces, but its impact on specific periodontal pathogens in adjacent subgingival biofilms is not known. This study assessed the microbiological effect of supragingival air polishing on the subgingival microbiota of individuals with severe periodontitis.

Methods:

Supragingival air polishing with a sodium bicarbonatebased powder was performed on 15 adult test subjects, with the nozzle of the air polishing device aimed apically at a 45° angle onto tooth surfaces immediately coronal to the entrance of periodontal pockets. Supragingival prophylaxis paste polishing, using a slow-speed handpiece, was carried out on 13 adult control subjects. Subgingival specimens were collected from a single 5 mm to 7 mm periodontal pocket with bleeding on probing in each of the study participants before and immediately after supragingival polishing procedures. Viable bacterial counts and selected putative periodontal pathogens (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia/nigrescens, Fusobacterium nucleatum, Parvimonas micra, Campylobacter species) were quantified by microbial culture, and motile morphotypes (spirochetes and motile rods) by phase-contrast microscopy.

Results:

Statistically significant decreases were detected after supragingival air polishing in total viable counts (84.9% decrease), in P. intermedia/nigrescens, F. nucleatum, Campylobacter species, total proportions of red/orange complex periodontal pathogens (82.3% decrease), and in motile morphotypes (85.3% decrease). No statistically significant subgingival microbiological changes occurred with supragingival prophylaxis paste polishing.

Conclusion:

Supragingival air polishing of teeth, but not supragingival prophylaxis paste polishing, may serve as a useful therapeutic adjunct to disrupt and help remove pathogenic biofilms in deep periodontal pockets.

PRACTICAL IMPLICATIONS OF THIS RESEARCH.

• Supragingival air polishing may impact subgingival bacteria.

• Supragingival air polishing can help remove pathogenic subgingival biofilms.

INTRODUCTION

Air polishing was commercially introduced into professional oral care over 45 years ago. Air polishing devices mix a mildly or low abrasive powder, such as sodium bicarbonate or glycine, with compressed air and water into a jet spray directed at coronal tooth surfaces with a standard handpiece nozzle or delivered with low pressure into periodontal pockets using a special thin, wedge-shaped subgingival nozzle.¹ Supragingival air polishing does not remove dental calculus but removes supragingival dental plaque and extrinsic tooth stain more efficiently and with less discomfort to the individual than conventional dental prophylaxis paste polishing.¹

In addition to the effects on coronal tooth surfaces, supragingival air polishing can potentially impact the subgingival environment. Horning² observed subgingival insufflation of sodium bicarbonate particles caused a near total removal of stainable dental plaque up to 5 mm into periodontal pockets after supragingival air polishing with a sodium bicarbonate powder. Similar studies with teeth extracted and examined post-treatment found subgingival dental plaque removal up to 4.2 mm and 4.6 mm into periodontal pockets after supragingival air polishing with sodium bicarbonate and glycine powders, respectively.^{3, 4} Other studies found a reduction of cultivable subgingival anaerobic bacterial counts by ≥99% immediately after a glycine-based supragingival air polishing spray was apically aimed for 5 seconds at the orifice of periodontal pockets with 3 mm to 5 mm probing depths.^{5, 6}

However, the extent to which supragingival air polishing may decrease levels of specific putative periodontal pathogens in subgingival dental plaque biofilms has yet to be evaluated. Consequently, this study determined the immediate effects of supragingival air polishing with a sodium bicarbonate powder on selected periodontal bacterial pathogens and motile morphotypes in the subgingival microbiota of untreated periodontitis lesions.

METHODS

Study subjects and treatment

A total of 15 consecutive systemically healthy adults with untreated Stage III/Grade B periodontitis (severe)⁷ were microbiologically sampled before and immediately after supragingival air polishing of coronal tooth surfaces. Supragingival air polishing was performed with a sodium bicarbonate-containing prophylaxis powder (EMS Air-Flow Classic Prophylaxis Powder, Electro Medical Systems, Le Sentier, Switzerland; 65 μm median particle grain size) applied for 8 to 10 seconds per tooth with an EMS Air-Flow S1 air polishing device (Electro Medical Systems) set at medium (50%) water and powder flow rates with a standard supragingival instrument nozzle (Figure 1). The air polishing nozzle was held 5 mm to 7 mm away from supragingival tooth surfaces and moved in continuous, overlapping, and sweeping brush strokes at a 70° to 90° angle, except on tooth surfaces immediately coronal to the entrance of periodontal pockets, where the nozzle was apically aimed at a 45° angle. A high-volume evacuation tip was held adjacent to the nozzle tip during air polishing procedures.

A total of 13 consecutive clinically similar and systemically healthy adults were also microbiologically sampled before and immediately after polishing of supragingival tooth surfaces with a fine grit, pumice-based, sodium fluoride-containing de,ntal prophylaxis paste (NUPRO^® Prophy Paste, Dentsply International, Incorporated, York, Pennsylvania, USA), which was applied with a rubber cup in a slow-speed handpiece and rinsed from the study subjects’ mouths post-treatment. Supragingival prophylaxis paste polishing of teeth is a standard professional plaque-removing technique frequently employed in clinical dental practice.⁸

Figure 1.

Air polishing spray for supragingival tooth polishing

None of the study subjects had a history of sodium dietary intake restriction, hypertension, asthma, chronic bronchitis, upper respiratory infection, diabetes mellitus, blood dyscrasias, anomalies of the immune system, or required prophylactic antibiotics for dental treatment, were pregnant, received immunosuppressive drug therapy within the previous 6 months, or presented with localized molar-incisor forms of periodontitis, gingival pain or acute periodontal conditions. A single experienced and calibrated periodontist (author TER)⁹ performed all diagnostic assessments, microbiological sampling, and clinical procedures on the study subjects. The study was conducted in accordance with ethical principles of the 1964 Declaration of Helsinki and its later amendments, with subjects providing written informed consent for periodontal therapy and microbiological testing. The Temple University Human Subjects Institutional Review Board determined that no action was applicable on their part because the study data were obtained from de-identified patient records without any additional contact, interaction or intervention with the subjects.

Microbial sampling

Subgingival biofilms were collected from a single periodontal pocket in each study subject who exhibited a probing depth of 5 mm to 7 mm and bleeding on probing. Each periodontal site was located on teeth free of crowns, proximal dental restorations, and gingival recession. Most (85.7%) of the 28 total sampled sites were on interproximal surfaces of posterior teeth, which were evenly distributed between the 2 supragingival polishing groups. Both before and immediately after completion of supragingival tooth polishing, 2 sterile, absorbent paper points (Johnson & Johnson, East Windsor, New Jersey, USA) were inserted to the depth of each selected periodontal pocket after isolation with cotton rolls and removal of saliva and supragingival deposits. Care was taken to introduce the paper points into the same periodontal pocket location per subject during pre-treatment and post-polishing subgingival sampling. After subgingival placement for 10 seconds, pre-treatment and post-polishing paper points from each subject were placed into separate glass vials containing anaerobically prepared and stored VMGA III transport medium,¹⁰ resulting in 1 pre-treatment and 1 post-polishing microbial sample per study subject. The sample vials were maintained at room temperature and processed within 24 hours. After completion of supragingival tooth polishing, all study participants received conventional non-surgical periodontal therapy and oral hygiene instructions/training.

Microbial isolation and identification

The subgingival specimens were transported to the Oral Microbiology Testing Laboratory at the University of Southern California School of Dentistry, Los Angeles, California, USA, which was licensed for high-complexity bacteriological analysis by the California Department of Public Health. In brief, sample dilution aliquots were spread onto nonselective enriched Brucella blood agar¹¹ and incubated anaerobically at 35°C for 7 days for recovery of total subgingival viable counts, Porphyromonas gingivalis, Prevotella intermedia/nigrescens, Parvimonas micra, and Fusobacterium nucleatum. Additional aliquots were applied onto a selective medium for Campylobacter species¹² with anaerobic incubation at 35°C for 7 days, and onto trypticase soy-bacitracin-vancomycin (TSBV) agar,¹³ with incubation at 35°C for 3 days in 5% CO₂–95% air, for isolation of Aggregatibacter actinomycetemcomitans, gram-negative enteric rods/pseudomonads, and Candida species. Microbial species were identified with methods previously described,^14-18 with the percentage recovery of each bacterial species per study subject calculated using colony counts of each organism in relation to total subgingival viable counts as determined from nonselective enriched Brucella blood agar plates. The proportional distribution of motile morphotypes (spirochetes and motile rods) in the subgingival specimens was enumerated with phase-contrast microscopy.¹⁹ All microbiology laboratory procedures were performed by personnel who were blinded to the clinical status of the study subjects, the nature of their periodontal treatment, and their inclusion in the present analysis.

Data analysis

Descriptive analyses tabulated selected study subject features and calculated their mean age, clinical probing depths of microbiologically sampled periodontal sites, and the prevalence and proportional cultivable recovery of test bacterial species per subject. Total subgingival viable count data were subjected to log₁₀-transformation, as previously recommended.²⁰ Recovered test periodontal pathogens were grouped for analysis into subgingival bacterial clusters (i.e., red complex, orange complex, and non-clustered species).²¹ Mean total cultivable subgingival proportions of red/orange complex species in pre-treatment and post-polishing microbial samples were determined by summing together individual species data for each study subject, and then calculating total mean values across all subjects, as previously described.²²

A 2-proportion z-test examined proportional data. A Student’s t-test compared mean probing depths of microbiologically sampled periodontal sites in study participants receiving supragingival air polishing as compared to supragingival prophylaxis paste polishing. McNemar’s non-parametric test with Yates’ continuity correction assessed the immediate effects of supragingival air polishing or supragingival prophylaxis paste polishing on the subgingival prevalence of evaluated periodontal pathogens. The nonparametric Wilcoxon matched pairs signed-rank test evaluated immediate post-polishing changes from pre-treatment values for each of the polishing protocols in mean total subgingival viable counts, total cultivable subgingival proportions of red/orange complex species, and for individual bacterial species. A p value ≤ 0.05 was required for statistical significance. Data analysis was performed using a 64-bit statistical software package (STATA/SE 16.1 for Windows, StataCorp PL, College Station, Texas, USA).

RESULTS

Table 1 compares selected features of study subjects in the 2 supragingival tooth polishing groups. No statistically significant differences in age, gender, smoking or periodontal case classification were found between subjects in the 2 treatment groups, and no statistically significant differences in probing depth, bleeding on probing or tooth surface location were found between microbiologically sampled periodontal sites receiving supragingival air polishing or supragingival prophylaxis paste polishing (Table 1).

Tables 2 and 3 present the microbiological findings. Table 2 shows that supragingival air polishing significantly decreased mean total subgingival viable counts, inducing an 84.9% reduction from baseline levels, and significantly decreased the subgingival prevalence of P. intermedia/nigrescens, F. nucleatum, and total red/orange complex species per study subject. Table 3 shows that the percentage of cultivable P. intermedia/nigrescens, F. nucleatum, and Campylobacter species were significantly decreased after supragingival air polishing, contributing to an 82.3% post-air polishing decrease in total subgingival proportions of red/orange complex periodontal pathogens from a baseline mean of 22.4% to 3.9% post air polishing (p < 0.001). Subgingival motile morphotypes were significantly reduced by 85.3% after supragingival air polishing from a pre-treatment mean of 17.7% to 2.6% (Table 3). N,o statistically significant microbiological changes were found after supragingival prophylaxis paste polishing (Tables 2 and 3). Gram-negative enteric rods/pseudomonads and Candida species were not recovered from any of the subgingival samples.

Table 1.

Selected features of study subjects treated with supragingival tooth polishing

	Supragingival air polishing	Supragingival prophylaxis paste polishing	p value
At study subject level:
Mean age, years ± SD	53.0 ± 9.7	51.7 ± 7.8	0.702 (NS)
No. (%) males	10 (66.7)	8 (61.5)	0.772 (NS)
No. (%) current smokers	1 (6.7)	0 (0)	0.342 (NS)
No. (%) subjects with untreated Stage III/Grade B periodontitis	15 (100)	13 (100)	1.000 (NS)
At microbiologically sampled sites:
Mean probing depth, mm ± SD	5.7 ± 0.5	5.6 ± 0.4	0.568 (NS)
No. (%) sites with 5 mm to 7 mm probing depth	15 (100)	13 (100)	1.000 (NS)
No. (%) sites with bleeding on probing	15 (100)	13 (100)	1.000 (NS)
No. (%) sites on posterior interproximal tooth surfaces	13 (86.7)	11 (84.6)	0.158 (NS)

NS = not statistically significant

No adverse clinical events or side effects, such as subcutaneous air emphysema or epithelial abrasions of gingival tissues, were clinically noted by the treating periodontist or symptomatically reported by any of the study subjects, following either supragingival air polishing or supragingival prophylaxis paste polishing.

DISCUSSION

A prime goal of periodontal therapy is to lower or eradicate periodontal pathogens in order to reduce gingival inflammation and subsequently arrest progression of periodontal disease.²³ This therapy has traditionally involved the use of mechanical tooth debridement procedures and antibiotic/antiseptic agents. The present proof-of-principle study findings confirm and extend prior investigations^2-6 supporting the use of supragingival air polishing as an additional therapeutic aid to disrupt subgingival pathogenic bacterial biofilms. The present study data show that a single application of supragingival air polishing with a sodium bicarbonate powder induced an 84.9% reduction in total viable bacterial counts in untreated deep periodontal pockets, a finding that is similar to previously reported effects of supragingival glycine air polishing in shallow to moderate subgingival sites.^{5, 6} Supragingival air polishing with a sodium bicarbonate powder also significantly altered the subgingival microbiota of periodontitis lesions by decreasing the prevalence and proportions of several red/orange complex periodontal pathogens (82.3% decrease from baseline mean of 22.4% to 3.9% post air polishing) and motile morphotypes (85.3% decrease from baseline mean of 17.7% to 2.6% post air polishing).

It is important to emphasize that these immediate subgingival microbial alterations were attained using an air polishing spray (Figure 1) directed at supragingival tooth surfaces with a standard handpiece nozzle, and not via a special subgingival nozzle providing direct deposition of air-polishing powders into subgingival sites.²⁴ The pressurized supragingival jet spray in the present study likely deflected off coronal surfaces near the gingival margin of teeth and insufflated sodium bicarbonate powder into periodontal pockets,² causing the powder abrasiveness and streaming water to physically dislodge and flush out subgingival microorganisms.²⁵ Sodium bicarbonate may exert additional antimicrobial activity in air polishing powders because of its bactericidal effects against many periodontal pathogens^26-29 and established dental plaque biofilms.³⁰ In contrast, supragingival prophylaxis paste polishing in the present study (Tables 1 and 2), along with previous studies of supragingival air polishing performed with water alone,³ and repeated paper point subgingival sampling for 10-second time periods,^{5, 6, 31} revealed no significant effects on subgingival biofilms.

Supragingival air polishing may thus offer an additional treatment modality for rapidly reducing bacterial populations in periodontal pockets.^{2, 4, 5} Adjunctive use of supragingival air polishing during initial and supportive periodontal therapy may facilitate rapid disruption and removal of supra- and subgingival microbial biofilms to augment conventional mechanical-based tooth debridement procedures, which immediately post-treatment often leave residual plaque on supragingival tooth surfaces³² and periodontal pathogens persisting in subgingival sites.^{22, 33, 34}

Concerns have been raised about potential damage to tooth root surfaces from sodium bicarbonate air polishing powders as compared to glycine-based powders, particularly when exposed root surface areas are continuously treated with air polishing for prolonged time periods.²⁴ However, in a recent study where supragingival air polishing was performed with a continual sweeping motion for brief time periods per tooth surface (5 seconds), similar to the present study, a sodium bicarbonate powder (85 μm grain size; larger and more abrasive than used in the present study) created minimal tooth root surface defects and volume loss that were statistically indistinguishable from those induced by a glycine air-polishing powder.³⁵ Supragingival air polishing with sodium bicarbonate powders may cause more localized trauma to marginal gingiva surrounding teeth than glycine-based powders, but the disruption or loss of superficial epithelium layers heals quickly without lasting adverse effects.³⁶

Table 2.

Cultivable subgingival prevalence of periodontal pathogens before and immediately after 2 supragingival tooth polishing procedures

	Supragingival air polishing			Supragingival prophylaxis paste polishing
	Present pre-treatment		Present post-polishing	Present pre-treatment	Present post-polishing
Subgingival species
Mean log10 total viable counts/mL ± SD		8.2 ± 0.9	7.4 ± 1.0b	7.8 ± 0.5	7.4 ± 1.0
Non-clustered species:
Aggregatibacter actinomycetemcomitans		1	1	1	1
Red complex species:
Porphyromonas gingivalis	3		1	3	3
Orange complex species:
Campylobacter species	7		2	9	8
Fusobacterium nucleatum	14		5c	6	6
Parvimonas micra	7		5	9	11
Prevotella intermedia/nigrescens	10		1c	7	6
Total red/orange complex species per subjecta	15		8b	13	13

Values represent number of culture-positive subjects for species.

^aRepresents cultivable presence per study subject of one or more of the evaluated red/orange complex species

^bValue significantly different from pre-treatment, p = 0.023; ^cp = 0.008

Table 3.

Cultivable subgingival proportions of periodontal pathogens before and immediately after 2 supragingival tooth polishing procedures

	Supragingival air polishing			Supragingival prophylaxis paste polishing
Subgingival species	% pre-treatmenta	% post-polishingb		% pre-treatmenta		% post-polishingb
Non-clustered species:
Aggregatibacter actinomycetemcomitans	0.04 ± 0		0.02 ± 0	0.03 ± 0		2.9 ± 0
Red complex species:
Porphyromonas gingivalis	3.5 ± 5.2	0.5 ± 0.8		9.7 ± 14.0	19.6 ± 19.1
Orange complex species:
Campylobacter species	5.2 ± 6.1	0.3 ± 0.7c		3.3 ± 4.3	3.4 ± 4.9
Fusobacterium nucleatum	8.2 ± 6.1	1.1 ± 2.0c		4.2 ± 3.9	10.5 ± 9.9
Parvimonas micra	6.9 ± 5.1	2.8 ± 3.6		12.3 ± 13.0	8.4 ± 8.5
Prevotella intermedia/nigrescens	10.5 ± 11.6	1.4 ± 4.3c		4.5 ± 5.0	14.7 ± 17.2
Total red/orange complex species	22.4 ± 16.4	3.9 ± 5.7d		18.4 ± 16.1	24.7 ± 21.3
Motile morphotypes	17.7 ± 23.6	2.6 ± 5.2d		10.7 ± 19.0	7.5 ± 9.6

Values are presented as mean ± SD per study subject.

^aThe average percentage of colony-forming units recovered for each species among total subgingival viable counts for species-positive study subjects

^bCalculated for study subjects who were positive for species at pre-treatment

^cValue significantly different from pre-treatment, p < 0.05; ^dp < 0.001

Potentially dangerous subcutaneous air emphysema may develop during supragingival air polishing of teeth, where pressurized air inadvertently penetrates into subepithelial oral tissues and fascial planes.³⁷ Air emphysema did not occur in the present study, consistent with its absence or rare incidence in previous air polishing studies,^{2-6, 37-40} and the primary author’s personal experience of only 3 air emphysema cases encountered in over 40 years of supragingival air polishing clinical use, which resolved under systemic amoxicillin coverage without complication in 2 to 3 days. Nevertheless, caution should be exercised during supragingival air polishing to avoid aiming the device’s pressurized jet stream at oral soft tissues, and clinicians need to be prepared to identify and manage air emphysema events. Alternative approaches, such as air polishing with a specialized subgingival nozzle to deliver glycine powder at low pressure into periodontal pockets and peri-implantitis lesions, may also potentially induce subcutaneous air emphysema.^{24, 37, 41}

The present study has several limitations. The study data were obtained without random assignment of subjects to the supragingival polishing groups, even though microbiological laboratory analysis was performed on a blinded basis. No microbiological or clinical assessments were made beyond the immediate post-polishing point to assess the longevity of the observed subgingival microbiological changes and their clinical impact. Detection of a wider array of microbial species in subgingival biofilm specimens via molecular methods was not performed. No comparisons were made between the sodium bicarbonate-based powder and other types of air polishing powders, nor were they made between the subgingival effects of air polishing and various types of manual and powered scaling instruments. The effects of air polishing on the submucosal microbiota of dental implants were not studied. Further air polishing research addressing these issues is warranted.

CONCLUSION

Supragingival air polishing of teeth with a sodium bicarbonate powder, but not with supragingival prophylaxis paste polishing, induced statistically significant subgingival reductions in total viable microbial counts, red/orange complex periodontal pathogens, and motile morphotypes in untreated deep periodontal lesions. Supragingival air polishing, carefully directed into subgingival sites, may serve as a useful therapeutic adjunct t,o disrupt and help remove pathogenic periodontal biofilms.

CONFLICTS OF INTEREST

The authors declare no conflicts of interest relative to this study.