Photo-Activated Disinfection

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Published: Wednesday, 18 September 2013 11:45 Written by 

George Freedman DDS, FAACD, FACD and Edward Lynch, PhD, Lond, MA, BDentSc, TCD, FDSRCSEd, FDSRCSLond

The preparation of the tooth is complete. The walls of the cavity seem hard to the explorer. There is no telltale brown decay visible, even under magnification. Therefore, the cavity must be clean, and ready for restoration. FIG. 1 Or is it?

 If cariogenic bacteria are retained at or below the tooth-restorative interface, the long-term health of the remaining tooth structures, as well as the longevity of the restoration will be compromised. 1For the practitioner, this is a significant issue that will determine short and long term clinical success and one that is not readily diagnosable with currently available tools and technologies. Ozone treatment has been proven to be an excellent antimicrobial agent and is now in use many thousands of practices around the world.20-23 Photo-Activated Disinfection (PAD) is an innovative technology that utilizes two non-toxic components, a photo-activating liquid and an LED light source to selectively tag and destroy cariogenic bacteria and periodontal pathogens. PAD instruments have been evolving for two decades, and the Aseptim Plus (SciCan, Toronto, Canada) is the current state of the art in the photo-activation treatment category. FIG. 2

Current Clinical Problems
Dental Caries

Dental caries is a disease that initially demineralizes the enamel and then progresses slowly into the dentin. The advancing zone of demineralization is preceded by a layer of partially demineralized dentin infected with bacteria.2 During clinical evaluation and/or treatment, it is difficult to differentiate these two zones, and as a result, significant quantities of sound but demineralized tooth tissue are removed during cavity preparation. As well, it is conservatively advantageous to retain the partially demineralized dentin, but only if the bacteria can be reliably eliminated.

There are two possible approaches to conserving remaining

sound tooth structure:

  1. The use of bacterial detection agents that assist in the removal of the infected (and only the infected) tissues.
  2. The use of photo-activated disinfection to eliminate bacteria and then to remineralize the partially infected dentin.

Given the high levels of bacteria in the oral environment, the general assumption must be that even cavities freshly prepared to the level of sound tooth structure have microorganisms lurking in the dentinal tubules and enamel lattices.Research has recently demonstrated that photo-sensitized cariogenic bacteria can be killed by directly applied visible light.3,4,5 The technique involves applying a photo-active solution that is absorbed selectively by cariogenic bacteria to the operative surfaces. This sensitizes them to the application of visible illumination which causes cytotoxic bacterial reactions that result in selective destruction of the target microorganism. 6 FIG. 3

fig 1-5

Periodontal therapy

A similar problem exists in periodontal pockets; scaling and root planing (SRP) can remove the alculus and plaque but has little effect on the acidogenic and aciduric bacterial presence that is the cause of these deposits, and the ensuing periodontal disease that has been associated with numerous systemic health problems. As soon as traditional SRP is completed, the bacteria resume their damaging activities. Additional research has indicated that an identical PAD mechanism functions to combat the bacteria that are largely responsible for periodontal disease.7,8 In fact, it has been observed that PAD treatment can reduce bone loss.9

Photo-Ac tivated Disinfection:Mode of Action
Scientific Model

Photosensitization is a treatment that involves the interaction of two non-toxic factors, such as a photo-active compound (tolonium chloride) and a directly applied visible light (LED illumination at 635nm).10,11 They form metachromatic complexes with lipopolysaccharides that can be photo-activated to cause oxygen ion release.12 The oxygen ions are specifically toxic to a vital structural component of the target cells.13,14 The interactions between the phenothiazine dyes, including toluidine chloride and methylene blue, and many bacteria are well documented.15 Bacterial cells are typically composed of a variety of cytoplasm materials enclosed by a cell wall. Many “traditional” anti-microbial

substances must enter and accumulate inside the bacterium in order to destroy their targets. Since this process requires a transport mechanism through the cell wall, it gives the bacteria an opportunity to build up a resistance by modifying the transport mechanism required by the drug. This also applies to

photo-activated drugs that must accumulate within the cell.16 Some PAD compounds, on the other hand, target the cell wall structures and membranes, and do NOT need to enter the cell. Only specific adhesion to the targets is required for the light-activated destruction of the cell. As a result, target cells cannot develop resistance by stopping uptake, metabolic detoxification, or increasing export of the drug.

Clinical Model

In the illustration, the bacterial cytoplasm is enclosed by the cell wall. FIG. 4 The micro-organism must have both structures in order to survive. A magnification of the cell wall indicates the substructures in the cell wall. A further magnification identifies that some of these components are liposomes. The image at the right is that of a stylized liposome that has been magnified further still, and sectioned to illustrate what occurs within. The dissolved tolonium chloride is released by the practitioner in the general environment of the area to be disinfected FIG. 5 and worked into the tissues for up to 60 seconds. The target areas may be hard or soft dental tissues, or both. The photo-activator is a good wetting agent, and quickly flows to all accessible areas, including surfaces (gingiva) and penetrable structures (enamel and dentin). The absorption is very selective, however. No absorption of the photo-activator can be seen (and therefore no adverse effects from light application) on adjacent healthy tissues.17,18 The tolonium chloride is selectively and rapidly absorbed into the liposomes in the bacterial cell walls, as indicated by the small blue circles within the liposome. In looking at the cell wall again, it can be seen that many liposomes throughout the structure have absorbed the tolonium chloride dye. Then the tolonium chloride specific 635nm LED is applied to the

fig 6-9fig 10-12

photo-activated surface FIG. 6. This relatively intense light not only photo-activates at the surface of application but can penetrate to a certain depth within dental structures as well.16 A 60 second irradiation is sufficient to release the bactericidal oxygen ions for carious and periodontal applications. 19 The liberated oxygen ions are shown within the liposome, and in a more distant view, within the magnified cell wall. The oxygen ions are toxic to the liposomes, and hence the cell wall. The photo-activation begins to break down the bacterial cell walls. FIG. 7 The oxygen ion activity continues as the cell membrane is ruptured. The cell contents escape, killing the bacterium. Photo-activated disinfection is very specific to bacterial cells, and will not affect healthy tissues, even those that are immediately adjacent or surrounding the offending bacteria.

Photo-Ac tivated Disinfection Techniques
Conservative PAD Caries Treatment (Early Decay)

Appropriate anesthesia and isolation are applied to the carioustooth. The sectional matrix system is the Triodent V3 Ring and Matrix, a very effectively designed set of instruments for creating predictably tight interproximal contacts and contour (Triodent, Katikati, New Zealand). The carious lesion is accessed and removed. FIG. 8 The Aseptim solution is applied to the entire lesion with an applicator for 60 seconds. FIG. 9 The Aseptim Plus LED handpiece tip is held close to the tolonium chloride-treated tooth surfaces. FIG. 10 The LED light is activated for 60 seconds, penetrating the illuminated

tissues and disinfecting the remaining tooth structures. FIG. 11 The cavity is treated with a remineralizing agent. The cavity is restored permanently with a resin ionomer or composite resin. FIG.

Conservative PAD Caries Treatment (Advanced Decay)

fig 13-14

  1. Appropriate anesthesia and isolation are applied to the carious tooth.
  2. Only sufficient enamel to access the carious lesion is removed. A
  3. The remaining infected tissue is removed with an excavator or slow dental handpiece until resistance is felt. B
  4. The Aseptim solution is applied to the entire lesion with an applicator for 60 seconds. C
  5. The Aseptim Plus LED handpiece tip is held close to tolonium chloride-treated tooth surfaces. D
  6. The LED light is activated for 60 seconds, penetrating the illuminated tissues and disinfecting the remaining tooth structures. E (If two interproximal surfaces are involved, they must be disinfected separately.)
  7. The cavity is treated with a remineralizing agent. F
  8. The cavity may be restored permanently with a resin ionomer or composite resin, or restored temporarily with a remineralizing agent for later restoration. G

The restorative protocols presented are very similar to currently established ones, with one major difference: with PAD treatment, the remaining tooth surfaces are disinfected, and thus are far more likely to remineralize effectively. Aseptim Plus is used with both routine and deep carious lesions to increase the probability of long-term clinical success.

Conservative PAD Periodontal
Therapy FIG. 14
  1. Routine, thorough SRP debridement is completed, and bleeding is controlled. FIG. 15, 16 and A
  2. The chloride photo-activator solution is inserted to the depth of the pockets. FIG. 17 and B.
  3. The Aseptim Plus handpiece with the light guide is inserted to the bottom of the pocket. FIG. 18 and C.
  4. The Aseptim Plus LED light is activated for 60 seconds to eliminate bacteria in the periodontal pocket. FIG. 19 and D.
  5. The patient’s periodontal status is reviewed at 4 weeks. Repeat PAD if necessary.

The elimination of periodontal pathogens from the depths of the pockets promotes the gingival health far more effectively than SRP debridement alone can. Aseptim Plus periodontal therapy is clinically straightforward, simple to carry out or delegate, and an excellent adjunct to routine SRP. Used together, these treatments offer more predictable longterm clinical results.

fig 15-19


Patients and practitioners have had understandable qualms about the level of disinfection that canbe  ractically and realistically achieved during routine dental procedures. Given the high levels of ambient bacteria in the oral cavity, and the difficulty of isolating surgical treatment sites during and after procedures, it is evident that additional disinfection modalities are welcome additions to the dental armamentarium.

 Photo-activated disinfection offers a heightened level of disinfection during and after operative and periodontal procedures (in addition to endodontic and periimplant treatments that were not discussed above). A relatively rapid and simple procedure which is readily inserted into the treatment routine, the Aseptim Plus destroys bacteria both on the surface and underneath to provide healthier periodontal tissues and more predictable and longer-lasting restorative interfaces.

 Dr. George Freedman is a founder and past president of the American Academy of Cosmetic Dentistry, aco-founder of the Canadian Academy for Esthetic Dentistry and a Diplomate of the American Board of Aesthetic Dentistry. Dr. Freedman sits on the Oral Health Editorial Board (Dental Materials and Technology) is a Team Member of REALITY and lectures internationally on dental esthetics and dental technology. A graduate of McGill University in Montreal, Dr. Freedman maintains a private practice limited to Esthetic Dentistry in Markham, Canada.

Dr. Edward Lynch holds the position of Professor of Restorative Dentistry and Gerodontology of the Queen’s University Belfast as well as Consultant in Restorative Dentistry to the Royal Hospitals. He has just been elected the next President of GORG in the International Association for Dental Research. Oral Health welcomes this original article.

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