The Tipping Point for Air Polishing

What does it take for a new technology and treatment modality to become an accepted therapy? In an era where dental hygienists have joined other health care providers in employing evidence-based practice, dental hygienists need to thoroughly assess all products and therapies before adopting them. The evolution of air polishing may require some clarification to determine how it may best be integrated into practice. Additionally, a practitioner needs to identify the patients whose oral condition will benefit from air polishing. Finally, the practitioner needs to evaluate the various delivery vehicles and powders to determine the appropriate use for different clinical conditions.

Air polishing as a device to remove extrinsic stain and dental plaque biofilm from the teeth first became available in 1976.¹ The device operates through the movement of pressurized air via the powder bowl, which forces a stream of air and powder toward an outlet, where it then combines water with the air and powder to form a slurry.² The abrasiveness of the slurry is influenced by the powder particle size, shape, and hardness, measured on the Mohs scale of mineral hardness from 1 to 10. Hardness is determined by whether a substance can be scratched by another substance of known hardness. A score of 1 is represented by talc and 10 by diamond. The effectiveness of air polishing is increased by higher air pressure and water settings.

A specially formulated version of sodium bicarbonate was the original powder used in air polishing devices and is still the most common powder on the market today.^2,3 While sodium bicarbonate is nontoxic and water soluble, early evaluations of its effect on hard and soft tissues resulted in recommendations for use on enamel, but not on cementum and dentin.² Sodium bicarbonate encompasses particle sizes up to250 μm, with an average size of74 μm and a Mohs hardness index of 2.5.^1,2 With these characteristics, studies demonstrated that it could be used safely and effectively on enamel.⁴ Studies examining the use of sodium bicarbonate for air polishing, however, showed extensive loss of root surface when used on cementum and dentin.^5,6,8 The larger and harder the particle impacting the root surface, the greater the erosion of cementum or dentin through the increased size of the defects created. More recent studies have confirmed the same results with sodium bicarbonate air polishing.^9,10

Additionally, contact with the gingiva during sodium bicarbonate air polishing causes severe erosion of the epithelium, though the tissue recovers rapidly.^4,11 In a systematic review on the effects of air polishing devices on oral tissues, Buhler et al¹⁰ suggested that sodium bicarbonate powder should not be used in periodontally involved patients because of the risk of harm to the cementum, dentin, and gingiva.

A further consideration is the care that must be taken when air polishing restorative materials. Sodium bicarbonate air polishing may erode the surface of restorative materials, resulting in a rough, dull appearance.^2,12 Yet at least one study has found that sodium bicarbonate air polishing was less abrasive to amalgam, composite, and ceramic surfaces than piezoelectric ultrasonic devices.¹³ When considering the results of studies evaluating the effects of air polishing on restorative materials, consideration must be given to the fact that these are invariably conducted as in vitro studies. Sodium bicarbonate air polishing safely and effectively removes biofilm from orthodontic brackets.¹⁴ It has also been demonstrated as safe for use on titanium implants in several studies.^15,16 In addition, air polishing is more effective than rubber cup polishing when cleaning the tooth surface prior to etching for sealant placement, resulting in enhanced bond strength.¹⁷ Once placed, however, air polishing of sealants should be avoided as it can lead to loss of sealant material.^18,19

Despite these limitations, supragingival air polishing is beneficial for patients undergoing routine prophylaxis because supragingival polishing with prophy paste is more abrasive than the use of air polishing powder.¹ Prophy paste contains pumice, which has a Mohs hardness index of 6.1 Air polishing is also less time consuming than removing stain and plaque biofilm with the traditional rubber cup polish and hand instrumentation.⁴ The decrease in appointment time may increase patient comfort and acceptance of the procedure and result in less operator fatigue.

Researchers and clinicians have sought to improve and expand on the opportunities for use of the air polishing technique. The working parameters—including the powder and water settings, distance and angle that the delivery device nozzle is held from the surface being treated, and time of treatment—have all been examined. These may all affect the size, depth, and extent of defects that result from air polishing. In a study that examined the relationship of these factors, the amount of treatment time (number of seconds the air polishing device was directed at a surface) had the greatest impact on surface erosion.⁹

New powders have been developed for use in air polishing devices. These include aluminum trihydroxide, calcium carbonate, calcium sodium phosphosilicate, glycine, and, most recently, erythritol (currently not available in the United States). Aluminum trihydroxide was developed for use with patients on sodium-restricted diets who needed an alternative to sodium bicarbonate air polishing powder. It is harder than sodium bicarbonate with a Mohs hardness index of 4, but the particle size is comparable, ranging from80 μm to 325 μm.¹ Aluminum trihydroxide should not be used on composites, glass ionomers, luting cements, and cast restorations.²⁰

A calcium carbonate particle is more uniform in shape than the particles of other air polishing powders.²¹ Its Mohs hardness index is 3 and it is45 μm in size.^1,21 Calcium sodium phosphosilicate powder is considered a bioactive glass composed of silica, calcium, phosphorus, and sodium.²¹ It has a Mohs hardness index of 6 and particle size ranges from25 μm to 120 μm.¹ In addition to removing stain and plaque biofilm, it may reduce dentinal hypersensitivity.

Glycine powder air polishing (GPAP) was developed for use in subgingival air polishing. As such, a powder was needed that would not damage root surfaces. Glycine is an amino acid with a particle size of20 μm  and a Mohs hardness index of 2.¹ Research has shown that glycine powder is significantly less abrasive than sodium bicarbonate powder when used on root surfaces.²² It is also less damaging to restorative materials.¹⁸ GPAP use results in minimal erosion of the gingival tissues at the time of treatment compared to sodium bicarbonate powder air polishing or hand instrumentation.^10,11

Equally important, glycine powder is effective at subgingival plaque biofilm removal. Researchers demonstrated its ability to eliminate plaque biofilm at buccal and lingual sites and the interproximal surfaces of teeth in patients with moderate to severe periodontal disease.^23,24 These studies also compared GPAP to hand instrumentation and found that the sites treated by GPAP had a significant reduction in plaque biofilm as compared to the sites instrumented with curets.^23,24

INSTRUMENTATION ARMAMENTARIUM

Supra- and subgingival air polishing do not remove calculus and, therefore, are not a replacement for ultrasonic and/or hand instrumentation. However, plaque biofilm disruption is a critical aspect of periodontal maintenance appointments. The ability of GPAP to effectively remove subgingival plaque biofilm compared to hand instrumentation adds an alternative modality for this procedure to the dental hygienist’s armamentarium. In addition, a study comparing GPAP to ultrasonic instrumentation during maintenance therapy found that GPAP was equally as effective in reducing periodontal bacteria immediately and 2 days after treatment in patients with moderately deep pockets (5 mm to 8 mm).²⁵ Furthermore, both treatments demonstrated significant reductions at 2 months in clinical parameters: bleeding on probing, pocket depth, and attachment levels.²⁵

When GPAP was compared to hand instrumentation or ultrasonic instrumentation for the treatment of peri-implant mucositis or peri-implantitis, the results were similar to those for treatment of the natural dentition.²⁶ In a study of GPAP compared to hand instrumentation and chlorhexidine for maintenance treatment of peri-implant tissues over 6 months, GPAP treatment resulted in significant improvement in probing depth, plaque and bleeding indices, and bleeding score.²⁷ The results of a 12-month study evaluating GPAP treatment on peri-implant mucositis compared to ultrasonic debridement demonstrated an equivalent and significant reduction in plaque scores, bleeding on probing, and number of pockets greater than or equal to 4 mm.²⁸

When considering which modality to employ during periodontal maintenance, several other factors should be considered. A treatment time of 5 seconds per site is recommended with GPAP to ensure that gingival erosion is minimal.¹¹ Subgingival air polishing requires, in addition to the proper powder selection, the use of a nozzle specifically designed for subgingival insertion.²⁹ The improper adaptation of handpieces designed for supragingival air polishing can lead to iatrogenically induced facial emphysema when air is introduced into the subcutaneous tissues. Symptoms include facial swelling, tenderness, and pain.^1,29 Patient acceptance of the procedure has been evaluated in a systematic review that included nine studies, six of which compared GPAP to either hand instrumentation or an ultrasonic device.³⁰ The conclusion was that patients experienced less discomfort during treatment with air polishing devices compared with hand instruments or ultrasonics.

Lastly, erythritol powder is the most recent addition to the air polishing armamentarium; however, it is not yet available in the US. Erythritol is a sugar alcohol derived from plants that is capable of use in subgingival air polishing because its small14 μm particle size makes it the least abrasive of the powders used in air polishing. Erythritol also appears to be more effective than hand instrumentation at reducing bleeding on probing and probing depths while decreasing treatment times and discomfort based on a randomized clinical trial.³¹

The clinician must select the proper air polishing device for the type of powder that will be used and the appropriate nozzle and handpiece if the powder is to be used subgingivally. For example, air polishing powders such as glycine and erythritol cannot be used in devices that are not designed for low-abrasive powders. Clinicians should check with the manufacturer of the device before attempting to switch to a low-abrasive powder.

EVALUATION

Before deciding to proceed with air polishing, the clinician will need to evaluate the patient to determine if it is an appropriate procedure. An oral evaluation is key to ensuring the powder chosen will not be detrimental to the patient’s hard or soft tissues. Further, some patients are contraindicated for the use of air polishing. These include those with respiratory or swallowing problems; communicable diseases; end-stage renal disease; Addison’s or Cushing’s disease; and patients who are immunocompromised or taking steroids or potassium anti-diuretics. Sodium bicarbonate should not be used for air polishing with patients on sodium-restricted diets or who have hypertension. Though research has shown that the levels of sodium bicarbonate ingested during the air polishing procedure are not sufficient to elevate blood levels of sodium or blood pressure, air polishing powders without sodium are preferred.³² Standard infection control procedures should be used during air polishing. Additionally, to control the aerosols generated during air polishing, high-volume evacuation should be used whenever possible along with a preprocedural antimicrobial rinse by the patient.

CONCLUSION

Air polishing has been demonstrated to be faster and more effective at stain and plaque biofilm removal than the conventional prophy angle and rubber cup polishing. The technique requires a careful assessment of the patient’s oral and general health and the objectives of treatment by the clinician prior to proceeding. Powders and devices developed for subgingival air polishing offer the opportunity to accomplish both full-mouth plaque biofilm debridement and an esthetic polish without damage to the root surfaces or restorations in essentially one procedure. The efficacy, comfort, and effectiveness of this procedure may induce more clinicians to investigate the integration of air polishing into their periodontal maintenance programs.

REFERENCES

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3. Focus on prophy pastes and air polishing powders. Dimensions of Dental Hygiene. 2016;14(06):30&dnash;35.
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28. Riben-Grundstrom C, Norderyd O, Andre U, Renvert S. Treatment of peri-implant mucositis using a glycine powder air-polishing or ultrasonic device: a randomized clinical trial. J Clin Periodontol. 2015;42:462&dnash;469.
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31. Hagi TT, Hofmanner P, Salvi GE, Ramseier C, Sculean A. Clinical outcomes following subgingival application of a novel erythritol powder by means of air polishing in supportive periodontal therapy: A randomized, controlled clinical study. Quintessence Int. 2013;44:753&dnash;761.
32. Snyder JA, McVay JT, Brown FH, et al. The effect of air abrasive polishing on blood pH and electrolyte concentrations in healthy mongrel dogs. J Periodontol. 1990;61:81&dnash;86

From Dimensions of Dental Hygiene. October 2016;14(10):30,32,35.