REVIEW ARTICLE

https://doi.org/10.5005/jp-journals-10015-2165
World Journal of Dentistry
Volume 14 | Issue 1 | Year 2023

Efficacy of Subgingival Glycine Powder Air-polishing in Nonsurgical Therapy of Periodontitis Patients: A Systematic Review of Randomized Controlled Trials

Mona Awad Kamil

Department of Preventive Dental Science, College of Dentistry, Jazan University, Jazan, Kingdom of Saudi Arabia

Corresponding Author: Mona Awad Kamil, Department of Preventive Dental Science, College of Dentistry, Jazan University, Jazan, Kingdom of Saudi Arabia, e-mail: munakamil@yahoo.com

Received on: 14 December 2022; Accepted on: 03 January 2023; Published on: 25 March 2023

ABSTRACT

Objectives: To evaluate the efficacy of subgingival glycine powder air polishing (subGPAP) in nonsurgical periodontal therapy in systemically healthy periodontitis patients.

Materials and methods: Scopus, Web of Science, and PubMed databases were searched using predetermined keywords for randomized controlled clinical trials published between 1st January 2000 and 31st August 2022 in the English language. Probing depth (PD) was considered the primary outcome. The risk of bias was assessed using the Cochrane Collaboration’s Tool for Assessing Risk of Bias Version 2.0, and the certainty of the evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) assessment tool. The recorded data were subjected to narrative synthesis as meta-analysis was not possible due to the heterogeneity of the data.

Results: Seven randomized controlled trials were selected from 45 studies obtained in the electronic search, including a total of 232 participants. The risk of bias for six studies was rated as having some concerns, and one had a low risk of bias. The overall quality of evidence was determined to be low as per GRADE guidelines. There was a significant reduction in clinical parameters, especially pocket PD, between baseline and after treatment in both test and positive control groups in all of the studies. However, subGPAP and conventional scaling and root planning (SRP) demonstrated similar results in six of the seven studies, and only one study reported subGPAP to be more effective. The total microbial count and reduction in Porphyromonas gingivalis (Pg) counts were seen to be more significant after subGPAP.

Conclusion: Subgingival glycine powder air polishing (subGPAP) was observed to be equally effective as SRP in reducing periodontal clinical parameters. Total microbial count and reduction in gingival crevicular fluids (GCF) volume levels were seen to be more significant after subGPAP. However, large, multicentric randomized controlled trials with standard diagnostic protocols evaluating the efficacy of subGPAP alone versus other standard treatment modalities are required before formulating clinical guidelines.

Clinical significance: Subgingival glycine powder air polishing (subGPAP) has been reported to reduce the amount of tooth structure lost during conventional SRP and causes less patient discomfort and pain. The present review highlights its effectiveness in improving periodontal clinical parameters. Even though the outcomes with subGPAP were comparable with SRP, clinical variables such as pocket PD and clinical attachment level were seen to improve significantly with subGPAP in all of the seven studies included in this review.

How to cite this article: Kamil MA. Efficacy of Subgingival Glycine Powder Air-polishing in Nonsurgical Therapy of Periodontitis Patients: A Systematic Review of Randomized Controlled Trials. World J Dent 2023;14(1):88-96.

Source of support: Nil

Conflict of interest: None

Keywords: Air-polishing, Glycine air powder polishing, Mechanical debridement, Nonsurgical periodontal therapy, Periodontitis.

INTRODUCTION

The periodontal microflora is the primary etiological factor in the development and progression of periodontitis. Therefore, the initial step in managing periodontitis is the removal of this primary etiology, that is, the oral biofilm.1 Subgingival biofilm generally consists of microorganisms, pathogenic and commensals, enclosed in an extracellular polymeric matrix. This complex, microscopic ecosystem induces local and systemic immune-inflammatory reactions, ultimately leading to chronic inflammatory periodontal destruction. The success of periodontal therapy depends on the disruption of the biofilm to prevent the inflammatory response.2 Over the years, various techniques have been investigated for their efficacy in removing the subgingival biofilm. Hand and ultrasonic instrumentation is the most commonly used method by periodontists and dentists worldwide to date.3 However, in addition to causing root damage and patient discomfort, they are time-consuming and sometimes unable to remove the microflora from hard-to-reach niches such as furcation areas.4-6

In air polishing devices, small particles, such as sodium bicarbonate, erythritol, and amino acid glycine powder (AAGP), are mixed with a jet of water and pressurized air, forming an abrasive slurry. Sodium bicarbonate is highly abrasive and is indicated only for supragingival applications.7 Bühler et al. reported that erythritol and glycine powder cause less patient discomfort during supragingival and subgingival air polishing.8 With advances in the design of subgingival application devices, erythritol and glycine powder have been extensively studied for their effectiveness in removing subgingival biofilm. While most of the trials have investigated the use of air polishing devices as adjuncts to conventional nonsurgical periodontal therapy (SPT), Ng et al. reported that they could also be effective as monotherapy.7 Similarly, other systematic reviews have also stated that the clinical outcomes, reduction in periodontal inflammation, and control of biofilm achieved with air polishing are comparable to conventional techniques in supportive periodontal therapy, but air polishing causes less patient discomfort.9,10 Contradictorily, Onisor et al. reported no greater improvements in periodontal clinical parameters with erythritol powder than with conventional instrumentation.11 Clinpro Prophy powder marketed by 3M ESPE was one of the first glycine powder formulations commercially available for subgingival use. This is used in conjunction with the Perioflow handpiece for Airflow Master by EMS, Switzerland, for optimal effectiveness.

Petersilka et al. reported a higher reduction in colony-forming units with GPAP compared to hand instrumentation.12 GPAP also resulted in fewer gingiva erosions than sodium bicarbonate polishing or hand instrumentation.13 However, Wennstrom et al. compared the clinical and microbiological effects of ultrasonic instrumentation and glycine air polishing and reported no significant differences between the test and control groups.14

Even though the clinical and microbiological results with glycine powder have been mostly positive, some in vitro studies have reported its negative effect on the periodontal soft tissues. The in vitro study by Drago et al. demonstrated that air polishing with chlorhexidine-erythritol powder has more antimicrobial and antibiofilm activity than glycine powder.2 Weusmann et al. reported that glycine and trehalose could regulate cytokine expression, cell viability, and cell proliferation. In the in vitro study, the authors demonstrated that glycine powder triggered the NF-κB pathway, increased the expression of proinflammatory and proapoptotic genes, and had an inhibitory effect on wound healing rate. It had an antiproliferative effect on human gingival fibroblasts. However, analyzing whether these results have any clinical impact is vital.15

The primary aim of this systematic review was to evaluate the effectiveness of AAGP in reducing periodontal clinical parameters, including pocket PD, bleeding on probing, and clinical attachment loss (CAL) in systemically healthy patients with periodontitis.

MATERIALS AND METHODS

Search Criteria

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines were followed in the design and execution of the systematic review.16

The focused question was designed as “what is the effectiveness of (I) subgingival GPAP in nonsurgical periodontal therapy of periodontitis patients (P) when compared to mechanical debridement alone or in combination with techniques other than air polishing (C) in reducing (O) pocket PD (primary outcome parameter) and/or reducing bleeding on probing, clinical attachment level, plaque index (PI), gingival index, microbial flora (secondary outcome parameters) as demonstrated in randomized controlled clinical trials?”

Inclusion criteria:

  • Population: Periodontitis patients.

  • Intervention: Subgingival GPAP in nonsurgical periodontal therapy.

  • Comparison: Patients who received mechanical debridement alone or in combination with techniques other than air polishing.

  • Outcome: Primary outcome—pocket PD; secondary outcomes—bleeding on probing (BOP), CAL, microbiological parameters, PI, gingival index.

  • Study design: Randomized controlled clinical trials.

Exclusion criteria:

  • Studies without primary outcome measure, that is, Probing Pocket Depth (PPD).

  • Studies including patients with systemic diseases.

  • Inaccessibility of digital copies.

  • Studies published in a language other than English.

  • Unpublished studies.

Specific keywords were used to identify randomized controlled trials evaluating the efficacy of sub-gingival GPAP as adjuncts to nonsurgical periodontal therapy in periodontitis patients. Reduction in PD was selected as the primary outcome parameter. Secondary outcome parameters studied included BOP, CAL, microbiological studies, plaque, and gingival indices. The study strategy is summarized in supplementary Table 3.

Screening and Selection of Studies

The initial search was conducted in the electronic databases—MEDLINE (PubMed), Scopus, and Web of Science. Articles published between 1st January 2000 and 31st January 2022 in English with a full-text digital copy available were included. The electronic search was conducted using a random combination of prestated keywords and included periodontitis, glycine air powder polishing, air-polishing, mechanical debridement, and nonsurgical periodontal therapy. The most recent electronic search was conducted on 31st October 2022.

After the screening of the abstracts and titles, duplicates and non-relevant articles were discarded manually. Studies not meeting the inclusion and exclusion criteria were excluded from the review. Full text of all remaining studies was obtained. Final inclusion and exclusion decisions were made by the reviewers after the examination of the manuscripts. Studies which met the predefined and explicit criteria regarding population, study outcome and study design were selected for inclusion in the review.

Data Extraction

Data extraction tables were predesigned on Microsoft Excel (Microsoft Inc., Redwood, California, United States of America) and then refined during the recording of the data from the included studies. The data were extracted from the included studies.

For each trial, the following data were recorded:

  • Primary outcome: Pocket PD.

  • Secondary outcomes: BOP, CAL, microbiological parameters, PI, and gingival index.

  • Author and year of publication.

  • Number of participants.

  • Mean age of the participants.

  • Diagnostic criteria of periodontitis.

  • Length of follow-up.

  • Biochemical parameters.

  • Histological analysis.

  • Reported adverse effects.

  • Funding and conflict of interest.

Assessment of Study Quality

The risk of bias in individual studies was evaluated using the Cochrane Collaboration’s Tool for Assessing Risk of Bias Version 2.0.17 The validity of the data was assessed in five different domains, including bias due to randomization, deviation from intended intervention, missing outcome data, bias in the measurement of outcome data, and bias in the selection of the reported result. Each included study was assessed as having low bias, some concerns, or high bias.

Methods to Assess the Quality of Evidence Presented in the Summary of Findings

The quality of evidence for the primary outcome in the summary of the findings table was assessed using GRADE guidelines for rating the overall certainty of evidence.18 Initially, one author (MAK) applied the GRADE ratings, and the final ratings were agreed upon after discussion with two other reviewers. The risk of bias, inconsistency of results, indirectness of evidence, imprecision of results, and publication bias were evaluated and rated. The evidence was initially rated as high and then downgraded if serious concerns were detected in any of the parameters.

RESULTS

An initial search of the electronic databases yielded 45 results. A total of 13 duplicate articles were deleted. Titles and abstracts of the remaining 32 articles were screened, and 19 trials were excluded as they did not meet the study eligibility criteria. The full text of the remaining 13 studies was further evaluated against the study criteria. Only seven articles matched the eligibility criteria, and these were additionally included in the systematic review.

The reference list of the seven selected studies was assessed. However, no other trials matching the study eligibility criteria were identified. Flowchart 1 illustrates the PRISMA flow diagram.

Flowchart 1: PRISMA flow chart

Geographical Location

Seven randomized controlled trials were included in the systematic review. Two studies were conducted in China19,20, while the others were conducted in USA21, Sweden14, Hong Kong22, Greece23, and Turkey.24

The study duration and follow-up period ranged from 30 days in the study by Caygur et al.24 to 6 months in the studies by Kargas et al. and Tsang et al.22,23

Table 1 summarizes the characteristics of the selected studies.

Table 1: Summary of the characteristics of the selected studies
Author and year Sample size Study design Intervention Control used Outcome assesment Primary outcome—PD Secondary outcomes Inference
Wennstrom et al., 2011 20 patients; test sites: 40’ control sites: 40. Split mouth RCT; test sites: subgingival GPAP; control sites: ultrasonic scaling. Low abrasive amino acid glycine powder using Perioflow handpiece. A piezoceramic ultrasonic device. PD, BOP, microbiological analysis. No statistically significant between test and control sites. Non-significant differences between test and control sites regarding BOP, RAL, and number of sites positive for periodontal microorgansims inclusing Pg and Aggregatibacter actinomycetemcomitans. SubGPAP and ultrasonic debridement produced similar clinical outcomes.
Flemmig et al., 2012 30 patients; test group: 15; control group: 15. Parallel group RCT; test group: subGPAP in pockets with PD 4 to 9 mm; control groups: SRP and coronal polishing. FM-GPAP with glycine powder of different particle size distribution of Dv10 (5 µm), Dv50 (19 µm), and Dv90 (52 µm). SubGPAP done using handpiece with thin, wedge-shaped nozzle and supraGPAP done using conventional handpiece. SRP using scalers and curets followed by coronal polishing using rubber cups and polishing paste. PD, BOP, PI, microbial counts. Similar reduction in PD in test and control groups. Similar reduction in BOP and PI in test and control groupsTotal viable bacterial counts and Pg counts were lower in test group at day 10. SubGPAP is more efficacious than SRP in removing biofilm and also results in a beneficial shift of oral micoflora.
Kargas et al., 2015 25 patients; group I: 25; group II: 25; group III: 25; group IV: 25. Split-mouth RCT; test group: GPAP; positive control group1: SRP with hand instruments; positive control group II: ultrasonic debridement; negative control: no treatment. Subgingival GPAP using Perioflow handpiece. Positive control group 1 (SRP): SRP using hand instruments; positive control group II (UD): ultrasonic debridement;negative control (NT): no treatment. PD, CAL, GI, PI. Statistically significant lower PPD reduction with GPAP than UD or SRP. Statistically significant higher CAL with GPAP than UD or SRPNo significant differences in GI, PI, microbial counts between groups at any time point. GPAP not more effective than hand or ultrasonic instrumentation.
Caygur et al., 2017 60 patients; test group: 30; control group: 30. RCTtest group: SRP (ultrasonic and hand instrumentation) + GPAP; control group: SRP (ultrasonic and hand instrumentation). Glycine powder (Air-Flow Perio Powder, EMS) applied for 10 seconds in each pocket using Perioflow device. SRP using ultrasonic and hand instrumentation. PD, CAL, BOP, PI, GI. No statistically significant differences between test and control groups. No significant differences in CAL, BOP, PI, and GI. SubGPAP, ultrasonic debridement, and hand instrumentation produced similar clinical outcomes.
Tsang et al., 2018 27 patients (309 sites); test sites: 157; control sites: 152. Split-mouth RCT; test group: SRP + GPAP; control group: SRP + water flushing. GPAP Water flushing using air-flow master. PD, BOP, CAL. No significant difference between test and control sites. No significant difference between test and control sites regarding BOP and CAL. GPAP as an adjunct to SRP is beneficial in the short-term improvement of subclinical inflammation.
Zhang et al., 2020 43 patients; group I:18 group II1:13; group II2:12. RCT; group I: SRP; group II1: subGPAP after FM-SRP; group II2: subGPAP before FM-SRP. SubGPAP done with 25 μm AAGP and a specially designed, thin, flexible nozzle. SRP PD, PI, bleeding index, BOP. No siginificant difference in percentage pocket closure between study groups In initial PPD ≥ 7 mm, group II1 shosed more improvement than group I. Percentage no-bleeding site was higher in group II1 at 3 monthsNo statistically significant differences in PI between the groups; No significant differences in microbial concentrations between groups at 3 months. FM-SRP with and without GPAP demonstrated similar clinical, inflammatory and microbiological outcomes in the management of stage II to IV periodontitis.
Zhang et al., 2021 27 patients;group I = 9;group II1 = 8;group II2 = 10 RCT;group I: SRP; group B1: subGPAP after FM-SRP; group II2: subGPAP before FM-SRP. 65 µm and 25 µm glycine powder used with Perioflow nozzle for subGPAP;group II1: subGPAP after FM-SRP at 1 week visit;group II2: subGPAP before FM-SRP at 1 week visit. SRP PD, PI, BOP, Microbiological analysis of peripheral blood. No statistically significant differences between the groups. No statistically significant differences in BOP and PI between study groups;group II2 had lowest total bacterial count, No significant differences in the relative species abundance and α-diversity of peripheral blood microbiota. SubGPAP before and after SRP as well as SRP produced similar clinical outcomes.

Characteristics of Interventions

All of the studies evaluated subgingival GPAP in systemically healthy patients. In all the studies, SRP with hand or ultrasonic instrumentation was used as a positive control. Tsang et al. combined water flushing with SRP and compared it to SRP with GPAP.22 Conversely, Flemmig et al. used SRP with coronal polishing as a positive control.21 In addition to using hand and ultrasonic instrumentation as a positive control, two studies compared subgingival GPAP right before and after full mouth-SRP (FM-SRP). The authors also used GPAP at three-time points–at baseline for supragingival air polishing, at the 1-week visit along with subgingival SRP, and at the 6-week SPT visit.19,20 Caygur et al. and Wennstrom et al. used conventional SRP with no adjuncts as the positive control.14,24 Kargas et al. and Wennstrom et al. compared GPAP alone with SRP, whereas all the other studies compared GPAP with SRP to positive and negative controls.14,23

Flemmig et al. reported gastrointestinal symptoms and resistance mechanism disorder in patients allocated to the test group. However, some of the patients in the control group also reported similar symptoms.21 Zhang et al. stated that nine of the 27 patients reported systemic symptoms such as low-grade fever, headache, drowsiness, and chills on the day following FM-SRP.20 None of the other five trials reported any adverse events.

Characteristics of Outcome Measures

All studies assessed pocket PD at the baseline and following treatment. Microbiological analysis was done by Wennstrom et al.,14 Flemmig et al.,21 and Zhang et al.20 Zhang et al. and Tsang et al. also measured the cytokine levels, with the former measuring CRP and interleukin (IL) 6 levels while the latter measured IL-1β and IL-1ra.19,22 Clinical attachment levels were assessed by Tsang et al., Caygur et al., and Kargas et al.22-24

Effect of Interventions

Reduction in probing pocket depth was considered to be the primary outcome parameter for the present review. It was measured as the distance between the gingival margin and the base of the pocket in all seven studies,14,19-24 with four studies using William’s periodontal probe,19,20,23,24 one study using Hu-Friedy PCP15 periodontal probe14 and one study using a computerized periodontal probe.21 PPD was reported to be reduced in all the included studies between baseline and the follow-up visit, indicating the efficacy of subgingival GPAP in periodontitis patients.14,19-24 However, compared to FM-SRP, no significant changes were reported in the experimental groups in six of the studies.14,19-22,24 Contrarily, Kargas et al. reported a statistically significant reduction in PD in patients treated with subGPAP compared to ultrasonic or hand instrumentation.23

Secondary outcome parameters recorded in the study include CAL, BOP, PI, GI, and microbial analysis. Similar to PPD, other clinical parameters also demonstrated similar outcomes between test and control groups in six of the seven studies.14,19-22,24 Kargas et al. reported significantly higher CAL gain with GPAP than with conventional instrumentation.23

Microbiological analysis was conducted by Wennstrom et al.,14 Flemmig et al.,21 and Zhang et al.20 However, while subGPAP was effective in reducing the bacterial counts, no significant differences were demonstrated between the test and control treatments in any of these three studies. Flemmig et al. reported lower total viable bacterial counts in sites treated with GPAP compared to the control sites. The authors also reported a shift in the oral microflora, with a reduction in Pg counts. These results indicate the effectiveness of subgingival GPAP in removing or disrupting the biofilm.21 Tsang et al. reported a more significant decrease in the GCF volume at 3 months after subGPAP than SRP. However, the GCF levels of IL-1β and IL-1ra reduced in both test and control groups similarly.22

Quality of Evidence

Six of the seven studies were assessed as having some concerns about the risk of bias. Several examined studies suffered from methodological insufficiencies and a lack of transparent reporting. The overall risk of bias was also rated as having some concerns due to missing information on the allocation concealment and reporting of the selected result. The study by Flemmig et al. was rated as having an overall low risk of bias.21Figure 1 summarizes the risk of bias.

Fig. 1: Summary of risk of bias assessment

Certainty of Evidence

Our review examined seven studies with a total of 232 periodontitis patients. The overall quality of evidence was assessed as low according to GRADE recommendations.18 Six of the seven included studies showed a null effect for the primary outcome parameter, that is, reduction in pocket PD.14,19,20,22-24 This suggests limited confidence in estimating the reduction in periodontal PD with GPAP and raises doubts regarding the magnitude of the effect of the interventions examined. Table 2 shows the summary of the findings.

Table 2: Summary of findings table
Quality assessment Summary of findings
Outcome Risk of bias Inconsistency Indirectness Imprecision Publication bias Impact No. of participants (studies) Certainty of evidence (GRADE)
Reduction in periodontal PD Seriousa Not serious Not serious Seriousb Not serious Our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect 232 (7) Low ⊕⊕

aSix studies showed some concerns based on ROB2; bSix of the studies showed null effect for primary outcome

Table 3: Supplementary Search strategy
Source Keywords No. of articles
Pubmed ((“periodontal”[All Fields] OR “periodontally”[All Fields] OR “periodontically”[All Fields] OR “periodontics”[MeSH Terms] OR “periodontics”[All Fields] OR “periodontic”[All Fields] OR “periodontitis”[MeSH Terms] OR “periodontitis”[All Fields] OR “periodontitides”[All Fields]) AND (“glycine”[MeSH Terms] OR “glycine”[All Fields] OR “glycin”[All Fields] OR “glycines”[All Fields]) AND (“air”[MeSH Terms] OR “air”[All Fields]) AND (“powder s”[All Fields] OR “powdered”[All Fields] OR “powdering”[All Fields] OR “powders”[MeSH Terms] OR “powders”[All Fields] OR “powder”[All Fields]) AND (“polished”[All Fields] OR “polisher”[All Fields] OR “polishers”[All Fields] OR “polishing”[All Fields] OR “polishings”[All Fields]) AND “air-polishing”[All Fields] AND (“mechanical”[All Fields] OR “mechanically”[All Fields] OR “mechanicals”[All Fields] OR “mechanics”[MeSH Terms] OR “mechanics”[All Fields] OR “mechanic”[All Fields]) AND (“debride”[All Fields] OR “debrided”[All Fields] OR “debridement”[MeSH Terms] OR “debridement”[All Fields] OR “debridements”[All Fields] OR “debrides”[All Fields] OR “debriding”[All Fields] OR “debridment”[All Fields] OR “debridments”[All Fields]) AND “non-surgical”[All Fields] AND (“periodontal”[All Fields] OR “periodontally”[All Fields] OR “periodontically”[All Fields] OR “periodontics”[MeSH Terms] OR “periodontics”[All Fields] OR “periodontic”[All Fields] OR “periodontitis”[MeSH Terms] OR “periodontitis”[All Fields] OR “periodontitides”[All Fields]) AND (“therapeutics”[MeSH Terms] OR “therapeutics”[All Fields] OR “therapies”[All Fields] OR “therapy”[MeSH Subheading] OR “therapy”[All Fields] OR “therapy s”[All Fields] OR “therapys”[All Fields])) AND ((randomizedcontrolledtrial[Filter]) AND (2000/1/1:2022/8/31[pdat]) AND (english[Filter]))((“periodontal”[All Fields] OR “periodontally”[All Fields] OR “periodontically”[All Fields] OR “periodontics”[MeSH Terms] OR “periodontics”[All Fields] OR “periodontic”[All Fields] OR “periodontitis”[MeSH Terms] OR “periodontitis”[All Fields] OR “periodontitides”[All Fields]) AND “air-polishing”[All Fields] AND “non-surgical”[All Fields] AND (“periodontal”[All Fields] OR “periodontally”[All Fields] OR “periodontically”[All Fields] OR “periodontics”[MeSH Terms] OR “periodontics”[All Fields] OR “periodontic”[All Fields] OR “periodontitis”[MeSH Terms] OR “periodontitis”[All Fields] OR “periodontitides”[All Fields]) AND (“therapeutics”[MeSH Terms] OR “therapeutics”[All Fields] OR “therapies”[All Fields] OR “therapy”[MeSH Subheading] OR “therapy”[All Fields] OR “therapy s”[All Fields] OR “therapys”[All Fields])) AND ((randomizedcontrolledtrial[Filter]) AND (2000/1/1:2022/8/31[pdat]) AND (english[Filter]))((“periodontal”[All Fields] OR “periodontally”[All Fields] OR “periodontically”[All Fields] OR “periodontics”[MeSH Terms] OR “periodontics”[All Fields] OR “periodontic”[All Fields] OR “periodontitis”[MeSH Terms] OR “periodontitis”[All Fields] OR “periodontitides”[All Fields]) AND (“glycine”[MeSH Terms] OR “glycine”[All Fields] OR “glycin”[All Fields] OR “glycines”[All Fields]) AND (“air”[MeSH Terms] OR “air”[All Fields]) AND (“powder s”[All Fields] OR “powdered”[All Fields] OR “powdering”[All Fields] OR “powders”[MeSH Terms] OR “powders”[All Fields] OR “powder”[All Fields]) AND (“polished”[All Fields] OR “polisher”[All Fields] OR “polishers”[All Fields] OR “polishing”[All Fields] OR “polishings”[All Fields]) AND “non-surgical”[All Fields] AND (“periodontal”[All Fields] OR “periodontally”[All Fields] OR “periodontically”[All Fields] OR “periodontics”[MeSH Terms] OR “periodontics”[All Fields] OR “periodontic”[All Fields] OR “periodontitis”[MeSH Terms] OR “periodontitis”[All Fields] OR “periodontitides”[All Fields]) AND (“therapeutics”[MeSH Terms] OR “therapeutics”[All Fields] OR “therapies”[All Fields] OR “therapy”[MeSH Subheading] OR “therapy”[All Fields] OR “therapy s”[All Fields] OR “therapys”[All Fields])) AND ((randomizedcontrolledtrial[Filter]) AND (2000/1/1:2022/8/31[pdat]) AND (english[Filter]))((“periodontal”[All Fields] OR “periodontally”[All Fields] OR “periodontically”[All Fields] OR “periodontics”[MeSH Terms] OR “periodontics”[All Fields] OR “periodontic”[All Fields] OR “periodontitis”[MeSH Terms] OR “periodontitis”[All Fields] OR “periodontitides”[All Fields]) AND (“glycine”[MeSH Terms] OR “glycine”[All Fields] OR “glycin”[All Fields] OR “glycines”[All Fields]) AND (“air”[MeSH Terms] OR “air”[All Fields]) AND (“powder s”[All Fields] OR “powdered”[All Fields] OR “powdering”[All Fields] OR “powders”[MeSH Terms] OR “powders”[All Fields] OR “powder”[All Fields]) AND (“polished”[All Fields] OR “polisher”[All Fields] OR “polishers”[All Fields] OR “polishing”[All Fields] OR “polishings”[All Fields]) AND “air-polishing”[All Fields]) AND ((randomizedcontrolledtrial[Filter]) AND (2000/1/1:2022/8/31[pdat]) AND (english[Filter])) 210317
WOS ((((((ALL=(periodontitis)) AND ALL=(glycine powder air polishing)) AND ALL=(air polishing)) AND ALL=(mechanical debridement)) AND ALL=(Nonsurgical periodontal therapy)) AND LA=(English)) AND ALL=(clinical trial) Timespan: 2000-01-01 to 2022-08-31 ((((ALL=(periodontitis)) AND ALL=(air polishing)) AND ALL=(Nonsurgical periodontal therapy)) AND ALL=(clinical trial)) AND LA=(English) Timespan: 2000-01-01 to 2022-08-31 (((((ALL=(periodontitis)) AND ALL=(glycine powder air polishing)) AND ALL=(Nonsurgical periodontal therapy)) AND ALL=(clinical trial)) AND LA=(English)) Timespan: 2000-01-01 to 2022-08-31(((((ALL=(periodontitis)) AND ALL=(glycine powder air polishing)) AND ALL=(air polishing)) AND ALL=(clinical trial)) AND LA=(English)) Timespan: 2000-01-01 to 2022-08-31 06314
Scopus (TITLE-ABS-KEY (periodontitis) AND TITLE-ABS-KEY (glycine AND powder AND air AND polishing) AND TITLE-ABS-KEY (air AND polishing) AND TITLE-ABS-KEY (mechanical AND debridement) AND TITLE-ABS-KEY (nonsurgical AND periodontal AND therapy) AND ALL (clinical AND trial) AND LANGUAGE (English)) AND PUBYEAR > 1999 AND PUBYEAR > 1999(TITLE-ABS-KEY (periodontitis) AND TITLE-ABS-KEY (air AND polishing) AND TITLE-ABS-KEY (nonsurgical AND periodontal AND therapy) AND ALL (clinical AND trial) AND LANGUAGE (English)) AND PUBYEAR > 1999 AND PUBYEAR > 1999 (TITLE-ABS-KEY (periodontitis) AND TITLE-ABS-KEY (glycine AND powder AND air AND polishing) AND TITLE-ABS-KEY (nonsurgical AND periodontal AND therapy) AND ALL (clinical AND trial) AND LANGUAGE (English)) AND PUBYEAR > 1999 AND PUBYEAR > 1999 (TITLE-ABS-KEY (periodontitis) AND TITLE-ABS-KEY (glycine AND powder AND air AND polishing) AND TITLE-ABS-KEY (air AND polishing) AND ALL (clinical AND trial) AND LANGUAGE (English)) AND PUBYEAR > 1999 AND PUBYEAR > 1999 17223

DISCUSSION

This systematic review evaluated the efficacy of subgingival GPAP in nonsurgical periodontal therapy in improving periodontal clinical parameters, including pocket PD, bleeding on probing, and clinical attachment levels in periodontitis patients. The initial electronic search with the predetermined keywords generated 45 studies. However, only seven were seen to conform to the study eligibility criteria. All of the included studies reported statistically significant changes in clinical parameters, including pocket PD, in the GPAP group between baseline and follow-up visits. These results indicate the effectiveness of subgingival GPAP in improving outcomes of periodontal therapy. However, it is critical to note that when compared to conventional SRP, significant changes were only observed in microbial counts and GCF volume.19,22 Regarding the primary outcome parameter, that is, the reduction in periodontal pocket PD, six studies showed similar outcomes in both test (SubGPAP) and positive control (ultrasonic or hand instrumentation) groups. Also, other than Wennstrom et al.14 and Kargas et al.,23 all the other 5 trials combined SRP with GPAP. The differences in methodology and diagnostic criteria of periodontitis between the seven studies make it difficult to perform a meta-analysis and formulate clinical recommendations.

Periodontitis is a chronic inflammatory disease initiated by the periodontal microflora. Even though the host immune response against these organisms determines the course of the disease, nonsurgical periodontal therapy aimed at removing these organisms is still considered the first step in managing a periodontitis patient.1 Professional mechanical plaque removal is done conventionally using hand and ultrasonic instruments. These instruments are used to mechanically disrupt the plaque biofilm and thereby remove the pathogenic organisms near the periodontal tissues. However, these techniques are associated with undesirable side effects, including tooth structure removal, pain, discomfort, and tooth sensitivity.4-6 Therefore, several alternatives, such as air polishing and photodynamic therapy, were investigated for their effectiveness in improving periodontal clinical parameters.

Even though sodium bicarbonate was one of the first materials to be used effectively as an air-polishing powder, it was demonstrated to be highly abrasive, causing microscopically visible changes in the gingival surface and, therefore, unsuitable for subgingival application. In this vacuum, erythritol, amino acid glycine, and trehalose were investigated for subgingival use. AAGP is a non-toxic, soluble powder with a mean particle size of 20 µm.25

A systematic review by Zhu et al. evaluated the efficacy of GPAP in supportive periodontal therapy. The authors stated that while GPAP may be less painful than conventional SRP, there is insufficient evidence regarding its effect on periodontal clinical parameters.26 Similar results on patient perception were published in the systematic review by Bühler et al. The authors stated that patient-reported discomfort and pain were lower when powder containing glycine was used for air polishing.8

Only two of the studies reported adverse effects. The reported adverse events included gastrointestinal symptoms, resistance mechanism disorder, low-grade fever, headache, and drowsiness.20,27 Emphysema, even though rare, is a severe complication reported after using pressurized air during dental procedures.25 However, none of the studies included in this systematic review have reported emphysema indicating the low probability of occurrence after air polishing in periodontal pockets.

Completeness and Applicability of Evidence

The present systematic review was designed to assess the efficacy of subgingival GPAP in improving periodontal health. However, five of the seven studies combined ultrasonic or handed instrumentation with subGPAP.19-22,24 By contrast, the split-mouth randomized control trials (RCTs) conducted by Wennstrom et al.14 and Kargas et al.23 evaluated the effectiveness of subGPAP with ultrasonic or hand instrumentation, which is more ideal and gives results non-biased with other treatment approaches. The methodology in all the studies varied significantly with different recall intervals, making it difficult to compare the data effectively. Also, the present systematic review only included studies with systemically healthy patients which precludes extrapolating these results onto patients with other co-morbid conditions, including diabetes mellitus. Five of the seven studies had a sample size ranging between 20 and 30 patients.14,20-23 Zhang et al.19 recruited 43 patients, and Caygur et al.24 recruited 60 patients for their studies. However, studies with a much larger, multi-ethnic, multicentric sample would need to be designed before formulating any clinical guidelines.

From the present review, it is evident that subGPAP can significantly improve clinical outcomes, especially when combined with traditional nonsurgical periodontal therapy. However, the question of whether it can be a better alternative to conventional SRP remains to be answered.

Quality of Evidence

All of the included studies were rated as having some concerns about the risk of bias. Per the GRADE guidelines, the quality of evidence for the primary outcome, that is, reduction in periodontal pocket PD, is low, and only a weak recommendation can be made for the applicability of subGPAP. The evidence for the randomized controlled trials was downgraded because of concerns about the risk of bias and imprecision, as six of the seven studies reported a null effect for the primary outcome parameter.

During the selection of articles to be included in the review, only English language studies with full text available were considered. Further high-quality trials adhering to standard reporting guidelines are necessary. It is critical to design and conduct randomized controlled clinical trials comparing the efficacy of subgingival GPAP with mechanical debridement alone. Other adjuncts with SRP, such as water flushing or combining GPAP with SRP in the test groups, could influence the outcome of the trial. Also, comparing the efficacy of GPAP with other air-polishing powders, such as erythritol and trehalose, could provide valuable clinical information. The diagnostic criteria used for periodontitis should be considered and matched across studies.

CONCLUSION

While it is clear that subgingival air polishing with glycine powder improves the periodontal clinical parameters, it could not be determined whether it is better than conventional SRP. Reduction in total viable microbial counts was more significant with subGPAP than with traditional SRP. Similarly, subGPAP was also observed to significantly reduce gingival inflammation and GCF fluid volume more than SRP alone.

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