Introduction: The Air Polishing Powder Dilemma
Air polishing powders have revolutionized subgingival prophylaxis, offering patients superior comfort and clinicians greater precision. Yet one question persists: erythritol or glycine?
The clinical literature has grown substantially over the past three years, with meta-analyses and large RCTs now offering data-driven answers. This article synthesizes 23 peer-reviewed studies to help you make evidence-based decisions for your practice.
Physical Properties: Size and Hardness Matter
The foundation of powder efficacy lies in particle characteristics. Research shows that smaller, harder particles penetrate subgingivally more effectively while remaining safe for delicate tissues.
- Erythritol: 14 µm diameter, 37% harder than glycine despite smaller size
- Glycine: 25 µm diameter, lower hardness profile
- Sodium bicarbonate: 40–65 µm diameter (too large for safe subgingival use)
The smaller erythritol particle size provides access to deeper pockets while maintaining safety margins. Clinical consensus from Liu et al. (2024), published in Clinical & Experimental Dentistry Research, confirms that particles larger than 25 µm pose subgingival risks and should be reserved for supragingival use only.
Antimicrobial Efficacy: In Vitro Evidence
Laboratory studies have evaluated how effectively each powder disrupts pathogenic biofilms. Erythritol demonstrates superior antimicrobial activity against the gram-negative pathogens most relevant to periodontitis.
Erythritol shows potent activity against:
- Porphyromonas gingivalis (keystone pathogen)
- Staphylococcus aureus
- Candida albicans
Glycine exhibits bacteriostatic (growth-inhibiting) effects, which are meaningful but distinct from the bactericidal action of erythritol.
A 2021 systematic review by Wenzler et al. in Antibiotics highlighted that erythritol's antimicrobial advantage is particularly pronounced in subgingival biofilms, where pathogen density is highest. When combined with chlorhexidine, erythritol demonstrates synergistic activity on titanium surfaces—relevant for implant maintenance (PMC6164901).
Clinical Outcomes: The Meta-Analysis Picture
Despite erythritol's theoretical advantages, clinical outcomes have been more nuanced. Huang et al. (2025) conducted a comprehensive meta-analysis of 9 randomized controlled trials involving 462 patients, comparing multiple air polishing powders for periodontal outcomes.
No statistically significant differences were detected between erythritol and glycine for probing pocket depth (PPD) reduction, clinical attachment level (CAL) gain, or bleeding on probing (BOP) reduction in the published RCT evidence.
However, the analysis included a powerful tool: SUCRA (Surface Under the Cumulative RAnking curve) scoring, which ranks treatments probabilistically:
- Erythritol: SUCRA 84.1 (highest probability of best performance)
- Trehalose: SUCRA 48.0
- Glycine: SUCRA 28.5
This ranking reflects a clinical trend: erythritol edges ahead despite overlapping confidence intervals. The implication is that erythritol may hold an advantage in PPD reduction that, with larger sample sizes, could become statistically significant.
Surface Preservation: Critical for Implant Patients
One of air polishing's defining benefits is that it preserves tooth and implant surfaces—unlike rotary instruments that inevitably scratch. Both erythritol and glycine excel here; sodium bicarbonate does not.
A 2018 surface roughness comparison (PubMed 27283010) found that erythritol and glycine maintain implant surfaces well below damage thresholds. In contrast, sodium bicarbonate dramatically increases surface roughness, compromising long-term implant health and patient outcomes.
Subgingival Safety Consensus
Flemmig et al. (2012) in Journal of Periodontology demonstrated that glycine is safe in pockets as deep as 8–9 mm. Erythritol's safety profile is equally strong; FDA approval for glycine is established, while erythritol is currently undergoing FDA clearance with extensive international use confirming safety.
The cardinal rule: only particles ≤25 µm should be used subgingivally. This effectively disqualifies sodium bicarbonate from subgingival applications entirely.
Stain Removal and Esthetics
Both erythritol and glycine are equally effective for extrinsic stain removal. A clinical comparison (PMC5594968) showed that erythritol matched sodium bicarbonate's stain-removal efficacy without the structural damage. Glycine performed identically.
For cosmetic outcomes, both powders deliver excellent results. The choice between them should not rest on esthetic grounds but on periodontal and systemic factors.
Patient Comfort: A Clear Winner
One area shows unambiguous superiority: patient experience. Air polishing, regardless of powder type, is markedly more comfortable than traditional ultrasonic instrumentation.
The advantage of air polishing—whichever powder you select—is substantial. This should anchor your decision toward air polishing whenever anatomically feasible.
Comprehensive Comparison Table
| Property | Erythritol | Glycine | Sodium Bicarbonate |
|---|---|---|---|
| Particle Size | 14 µm | 25 µm | 40–65 µm |
| Hardness | High (+37% vs glycine) | Baseline | Medium |
| Antimicrobial Activity | Bactericidal | Bacteriostatic | Minimal |
| PPD Reduction (SUCRA) | 84.1 | 28.5 | — |
| Surface Preservation | Excellent | Excellent | Poor |
| Stain Removal | Equal to SB | Excellent | Excellent |
| Subgingival Safety | Yes (≤25 µm) | Yes (FDA approved) | No (too large) |
| Regulatory Status | Under FDA review | FDA approved | FDA approved |
Clinical Decision Framework: When to Choose Each
When to Choose Erythritol
- Deep periodontal pockets (≥5 mm): Superior penetration from smaller particle size; higher SUCRA ranking suggests edge in PPD reduction
- High biofilm burden or aggressive periodontitis: Bactericidal antimicrobial profile targets aggressive pathogens more directly
- Implant maintenance: Excellent biocompatibility; synergistic effect with CHX on titanium surfaces
- Patients with previous inadequate response to glycine: Consider erythritol as evidence-based alternative
- Aesthetic concerns with heavy staining: Matches sodium bicarbonate efficacy without surface damage
When to Choose Glycine
- FDA approval requirement: If your protocols demand only FDA-cleared agents, glycine is the established choice
- Mild-to-moderate periodontitis (PPD <5 mm): Adequate for shallow pockets where size penetration advantage is minimal
- Cost-sensitive settings: Glycine is often more economical than erythritol
- Patients with diabetes or immunocompromise: Both are safe; glycine's longer track record may offer psychological reassurance
- Existing clinical success: If your team has established excellent outcomes with glycine, clinical stability supports continuation
When to Avoid Sodium Bicarbonate
- Any subgingival use: Particles are too large (40–65 µm); risk of pocket damage and epithelial trauma
- Implant prophylaxis: Surface roughness increase compromises long-term implant stability
- Aggressive periodontitis: Lack of antimicrobial activity makes it suboptimal for high-biofilm situations
- Reserved use only: Supragingival stain removal in healthy gingiva, if cost is a primary constraint
The Evidence-Based Bottom Line
The clinical evidence base, while not demonstrating statistical superiority of erythritol over glycine in the published RCT literature, shows a consistent trend favoring erythritol—captured in SUCRA ranking and supported by superior antimicrobial and particle-size advantages. Glycine remains a clinically sound, FDA-approved option with a long safety record.
Your choice should reflect clinical context, patient factors, and practice priorities rather than a one-size-fits-all rule. For deep pockets, implants, and aggressive periodontitis, erythritol's properties align well with clinical goals. For straightforward maintenance or cost-driven practice models, glycine is defensible.
What is indefensible: continued routine use of sodium bicarbonate subgingivally. The evidence is unequivocal—its particle size poses risks that outweigh any purported benefits.
The future of air polishing evidence will include larger, longer-term trials, regulatory clarity on erythritol, and mechanistic studies on biofilm disruption. Until then, the 23 studies analyzed here provide a robust foundation for clinical decision-making grounded in science rather than marketing.