Glycine: New dimension in subgingival biofilm removal

Repeated intervention, however, is not without disadvantages in that a fine balance exists between root surface debridement and disturbance of the epithelial attachment with loss of root substance. Repeated use of traditional methods (hand scalers, curettes, sonic and ultrasonic scalers) can result in significant loss of root substance and surface smoothness,[2,3,4] thus limiting the frequency of such intervention.

Until now, air polishing has been indicated for only supragingival application. With the advent of a glycine-based prophylaxis powder designed for subgingival use, a new dimension in the removal of subgingival plaque and biofilm deposits has arrived.

Air polishing

Surprisingly, air polishing is not a new technology. It's been used for almost 50 years.[5] In contrast to air-abrasive techniques, air polishing employs a mixture of air, powder and water. This fine jet is directed toward the tooth surface at an air pressure of 4–8 bar and a water pressure of 1–5 bar,[6] leading to the removal of surface deposits.

Until now, the powder of choice has been sodium bicarbonate (NaCOH3); however, with a particle size of 100–200 µm (micromillimeters), it has proven too abrasive for subgingival application. Compared with conventional instrumentation, NaCOH3 is more effective in the supragingival removal of plaque deposits and extrinsic staining;[7] however, because of its high abrasive quality, it is contra-indicated for root surface application and subgingival deposits.[8]

Abrasion of dental tissues

Intact enamel surfaces appear not to be significantly affected by NaCOH3 air polishing techniques; however, pits and fissures or markings from dental instrumentation appear to be abraded more quickly and easily. Enamel surfaces subjected to significant plaque colonization and areas of demineralization (white spots) appear to be particularly affected.[5, 7, 8]

Root surfaces (cementum and root dentine) are lower in hardness compared with enamel, and therefore the removal of subgingival plaque deposits with NaCOH3 results in substantial wear of the root surface. In vitro experiments on root surfaces9 have shown significant defects of more than 600 µm following air polishing with NaCOH3.[10]

Histological evaluation of the epithelium, epithelial layers and base membrane of the periodontal pocket have shown significant disruption of epithelial attachment and loss of basal membrane following either hand scaling or NaCOH3 in the removal of subgingival plaque and associated micro organisms.[10]

While NaCOH3 application is a useful and efficient way of removing plaque and biofilm deposits from supragingival enamel surfaces, it is therefore not indicated in the disinfection and maintenance of the periodontal pocket.

Glycine

Glycine is a non-essential amino acid with one of the simplest structures of all the amino acids. Glycine is found in proteins of all life forms, and is important in the synthesis of proteins as well as adenosine triphosphate (ATP). Glycine is water soluble, has a naturally sweet taste and is completely biocompatible. The choice of glycine is because of its physical properties, in that it produces very fine, round soft particles. In contrast to NaCOH3, glycine has a particle size of less than 63 µm, making this powder ideal for use along the gingival margins and in deep subgingival pockets.

An in vitro evaluation of glycine powder on subgingival cementum and dentine showed that subgingival application resulted in significantly smaller defect depths compared with NaCOH3 powder (19.6 µm and 71.1 µm, respectively).[11]

Laboratory test data also confirm that in comparison with NaCOH3, in vitro evaluation of enamel surface roughness and enamel wear after treatment with glycine powder was considerably less and resembled the untreated enamel control surface.[12] An in vitro evaluation and comparison of the surface roughness of human enamel after air polishing with glycine powder and conventional polishing procedures found that while conventional polishing leaves grooves and scratches on the enamel surface, glycine powder resulted in a smooth enamel surface similar to untreated enamel.[13]

Plaque removal

A number of studies have evaluated the plaque removal efficacy of glycine powder and the subsequent effect on the soft tissues. Two studies[14,15] looked at interdental plaque removal and buccal and lingual sites respectively. Both studies compared subgingival plaque removal with glycine powder and traditional hand instrumentation (curettes) in periodontal pockets of 3 to 5 mm in depth. Using a split-mouth design in 23 and 27 patients respectively, plaque samples were taken before and after treatment with either glycine powder or hand curettes. Plaque samples were also taken from untreated sites as a negative control. Anaerobe cultivation was used to assess the mean reduction of total colony-forming units (CFU’s) immediately after treatment. In both studies, test treatment with glycine powder resulted in significantly greater reduction in CFUs at interproximal sites (two times more) and buccal and lingual sites (three times more) compared with hand instrumentation.

Additional study16 has shown that penetration of the pocket with glycine powder is comparable to hand instrumentation, with 80 percent debridement of the root surface in pockets 2–3 mm in depth and 65 percent in pockets of more than 4 mm. Previous studies[17,18] on debridement efficacy of curettes and ultrasonic scalers showed on average, 66 percent of the root surfaces plaque free in pockets of more than 4 mm.

Attachment and tissue trauma

The use of conventional NaCOH3 air polishing powder has been shown to cause significant epithelial erosion with exposure of the underlying connective tissue.19,20 The use of glycine powder is, however, associated with minimal gingival irritation and increased patient comfort.15,16 This finding has also been confirmed by in vivo histological examination of the gingival epithelium following subgingival debridement using an air-polishing device with glycine powder.[11]

Histological analysis revealed that when glycine powder is compared with hand instrumentation, NaCOH3 powder and a negative control, the glycine powder exhibited a tissue appearance comparable with the control specimens. Epithelial attachment, keratinised layer and base membrane all remained intact following the use of glycine powder for subgingival biofilm removal. This was in comparison with hand instrumentation, which displayed loss of the keratinised layer and gingival epithelial layer, loss of prominent papillae in the lamina propria and strands of epithelial ridges extending into the connective tissue because of the stimulus of inflammation.

Patient acceptance.

For periodontal therapy to be successful, regular maintenance and pocket disinfection is paramount. This is greatly influenced by patient acceptance, pain perception and post-operative comfort.

Patient acceptance surveys conducted across five dental practices involving a total of 80 patients, indicate that treatment with glycine air polishing is widely accepted.6 Seventy percent of patients reported either minimal discomfort or no pain at all, with 76 percent of patients willing to undertake the treatment again.

Further study[21] has also reported greater patient acceptance and comfort with glycine air polishing compared with hand instrumentation. This was a single blind, randomised split-mouth trial using a new subgingival delivery system with glycine powder compared with hand instrumentation (curettes). No adverse effects were reported in the test group, with patients perceiving less pain than the hand-instrument group (0.9 versus 2.2 on a score of 1–10). Treatment in the test group was also completed three times more quickly than the control group, with comparable microbial reduction.

Conclusion

Subgingival debridement is considered essential in treating periodontitis and has been shown to be pivotal in arresting disease progression.[22] Biofilm formation occurs rapidly in periodontal pockets following instrumentation, and re-establishment of pathogenic microbial flora occurs after a few months following treatment,[23] indicating frequent maintenance is required.

Regular and repeated debridement of root surfaces with hand instruments and or sonic/ultrasonic instruments has been shown to lead to root surface loss over time. Plaque removal on enamel surfaces can be accomplished effectively with air-polishing devices with little or no abrasive effects. However, this method is not indicated for root surfaces, because conventional air-polishing powders (NaCOH3) are highly abrasive to root dentine and cementum. When repeatedly performed during maintenance therapy, this cleaning method’s cumulative effects may become clinically significant.

The advent of a new glycine-based powder for use with air-polishing devices has been shown to be suitable for root surface debridement, causing little or no surface loss, tissue trauma or patient discomfort. Reduction in pathogenic microbial-colony-forming units is greater than with hand instrumentation and is achieved in less time, with less operator fatigue and with greater patient comfort and compliance.

Precautionary measures for patients with upper respiratory tract conditions remain the same as with conventional air-polishing powders; however, since glycine was first trialled in 2003, no adverse effects have been reported, making it an effective method of removing subgingival biofilm from the root surfaces and disinfection of the periodontal pocket.

Considering the high level of patient acceptance, biocompatibility and efficacy, the use of glycine powder for biofilm removal may greatly enhance the success of periodontal maintenance therapy and has the potential to offer significant benefits in the supportive care of the periodontal patient.

Note: This article was published in Hygiene Tribune U.S. Edition, Vol. 5 No. 3, April 2012. A complete list of references is available from the publisher.