Understanding Oral Biofilm
Management hinges on knowing what it is and how it forms
Gregori M. Kurtzman, DDS, MAGD, DICOI
Research has dramatically changed our understanding of periodontal disease and its affects on the body. For decades the information on periodontal disease remained virtually unchanged, but in the last 10 years scientific advances connecting the mouth with systemic health show that periodontal disease is the key to a number of systemic issues, either creating them or complicating them.
Many common health issues have been connected to oral biofilm, such as cardiovascular disease (CVD),1 diabetes,2 pulmonary disease,3 chronic kidney disease,4 and osteoporosis.5 Evidence has also linked prostate disease,6 colon cancer,7 pancreatic cancer,8 and poor pregnancy outcomes (ie, preterm birth and low birth weight)9 to the oral biofilm that induces periodontal disease. But, what exactly is oral biofilm?
Oral Biofilm: What is It?
We used to call it plaque, a soft and sticky deposit containing food particles and bacteria that is continually forming on teeth and gums, but it is now understood that the deposit is more complex than previously thought. A better definition of biofilm is a specific but highly variable entity consisting of micro-organisms and their products embedded in a highly organized intercellular matrix.10 Biofilm consists of a variety of micro-organisms involved in a wide range of physical, metabolic, and molecular interactions. The cooperative nature of the microbial community within the biofilm provides advantages to the participating bacteria, from a broader habitat range enhancing growth to greater resistance to host defenses and antimicrobial agents that also enhance the microbial communities’ pathogenicity.11
Yet to understand how to manage biofilms, we need to understand what a biofilm is. Costerton first introduced the term in 1978, and it was used to emphasize that the bacteria congregated in a “living film” that interacted with the environment.12
Biofilm will form on virtually any surface that is immersed in a natural aqueous environment. A biofilm confers certain properties to the bacteria contained within that are not seen in bacteria in a planktonic state. Bacteria growing in a biofilm are physiologically distinct from planktonic cells of the same organism, which, by contrast, are single cells that are floating in a liquid medium such as saliva or blood.13 The formation of biofilm is a complex process that has several distinct phases (Figure 1). The process begins with adsorption of a sticky film onto the tooth surface derived from bacterial and host molecules. This is followed by a passive transport of bacteria that is mediated by weak long-range forces of attraction. These forces are covalent with hydrogen bonds and create strong, short-range forces that result in an irreversible attachment to the surface. These primary colonizers form a biofilm by autoaggregation between the same bacterial species and coaggregation between dissimilar species of bacteria, which results in a functional organization of the contained bacteria.14 This leads to the microenvironment changing from aerobic to a facultative anaerobic environment with the contained bacteria multiplying and secreting an extracellular matrix, resulting in a mature biofilm.
As the biofilm further matures, incorporation of new bacterial members from other sites into the biofilm leads to the formation of a complex community. Following maturation, portions of the biofilm break off and are dispersed to other sites to initiate new biofilm or exert issues systemically. Biofilm development occurs over a 2- to 3-day period, which means even with professional cleaning and homecare, biofilm reestablishes quickly. Additionally, biofilm can vary from site to site—even when the sites are adjacent to each other—demonstrating different varieties of bacteria in adjacent pockets, complicating their management (Figure 2).
The slime coating encasing the biofilm offers major protection to the bacteria contained within from host defense mechanisms and “toxic” substances such as oral antibacterials or systemic antibiotics. Quorum sensing (cell density-mediated gene expression) that is observed with biofilm-associated bacteria also increases biofilm resistance to host-mediated responses.15 Through quorum sensing, the regulation of genes for antibiotic resistance may provide protection to the bacteria of the biofilm. Additionally, bacterial communication can influence community structure by encouraging the growth of species beneficial to the biofilm and discouraging the growth of competitors.
How Can Oral Biofilm Be Managed?
Mechanical debridement of the pocket only removes 50% of the initial biofilm present.16 But, re-growth of the biofilm occurs within 3 hours, resulting in a 4-fold (400%) increase in biofilm mass.16 Because the sulcular environment is difficult for most patients to reach with brushing and flossing, homecare is compromised no matter how diligent the patient tries to be. Toothbrush bristles, unable to extend more then 3 mm into the pocket, are unable to mechanically contact biofilm located at deeper depths. A similar problem occurs with oral irrigators. Irrigation to the bottom of the pockets on all teeth is technically difficult and most patients are not diligent in daily use. Even when biofilm is removed by mechanical means, the bacteria regrow and replicate so rapidly that they are impossible to control mechanically. Post-cleaning, biofilm redevelopment is more rapid and complex, exceeding pre-cleaning levels within 2 days.17,18
We need a method that is easy for patients to use, improves patient compliance, reaches the depths of the pockets, and effectively breaks down the biofilm while preventing it from rebuilding on a daily basis. Antibiotics offer limited answers to this need. Bacteria embedded in the biofilm are up to 1,000-fold more resistant to antibiotics compared to planktonic bacteria.19 The use of antibiotics either systemically or in oral rinses and site application are unable to eliminate or manage the biofilm bacteria adequately.20,21 This has implications both with natural teeth and also periodontal issues developing around dental implants leading to peri-implantitis.21
Chlorhexidine has been reported to have an effect on young biofilm but the bacteria in mature biofilm and nutrient-limited biofilms are more resistant to its effects.22,23 Hydrogen peroxide, on the other hand, has been documented as a very effective means of not only eliminating the biofilm but also preventing its reformation without the bacterial resistance issues found with other site-specific treatment modalities. Hydrogen peroxide has been documented as being used daily up to 6 years with no adverse effects or carcinogenic activity, and it has been shown to decrease biofilm and enhance wound healing, improving gingival bleeding.24 Further, no allergic reactions have been reported and bacterial strains demonstrate no resistance.
Peroxide debrides the biofilm slime matrix and bacterial cell walls, essentially peeling the biofilm back layer by layer. This functions by irreversible cleaving/converting the amino acids in the protein chains of the bacteria in the biofilm. The peroxide acts to break down the protein pellicle attaching the biofilm to the tooth surface and decreases localized inflammation in the pocket by inhibiting interleukin-8 mRNA.25 Oxygen is required for successful wound healing due to the increased demand of reparative processes such as cell proliferation, bacterial defense, angiogenesis, and collagen synthesis, and the peroxide supplies this oxygen to aid the healing process.26 Additionally, new cell growth requires oxygen, which induces the growth of new blood vessels. These new blood vessels bring an increased flow of oxygenated blood to the wound, beginning the healing process. As healing progresses, new granulation tissue that is exposed to oxygen is better vascularized.27 This leads to collagen with higher tensile strength being formed during wound healing.
Breaking Down Biofilm with Hydrogen Peroxide
Numerous published studies have documented that the ideal concentration of hydrogen peroxide is 1.7%, as this is effective in breaking down oral biofilm and virtually eliminating any irritation issues reported with higher concentrations.28-32 The problem is delivering the hydrogen peroxide to the depth of the pocket and keeping it there to assert its action on the biofilm. As a natural process, fluid is produced in the sulcus/pocket as a means to flush bacteria and other items from the sulcus/pocket. This, unfortunately, also flushes out any materials used for pocket irrigation. Normal crevicular fluid is replaced 40 times per hour. This makes spontaneous inflow in a pocket virtually impossible. In inflamed tissue, this may increase up to 30 times the normal flow.33 This constant outflow of crevicular fluid leads to extremely fast clearance of any topically applied product into the pocket.34 Because the peroxide gel requires sufficient contact time, placing it into the pocket with an irrigation syringe is ineffective due to the crevicular flow and would be very time consuming for the patient, adding compliance issues to the equation.
It has been determined that a 10-minute exposure to a 1.7% hydrogen peroxide gel penetrates the biofilm slime matrix, debriding the bacterial cell walls within. Maintaining the peroxide in the periodontal pocket releases oxygen and changes the subgingival micro-environment, making survival of the anaerobic bacteria more difficult.32,35 As the environment changes and breaks down the slime matrix holding the biofilm together, deeper bacteria is exposed to the oxygenating effects of the peroxide. To treat periodontal disease, the hydrogen peroxide has to get into the bottom of the periodontal pocket and be held there for sufficient time to work on the biofilm. Studies have shown that while rinses and dentifrices with hydrogen peroxide can help, they are not sufficient to deliver the medication deep into periodontal pockets where the infection is localized.36
To maximize the effects of hydrogen peroxide deep in the pocket while making patient compliance easily achievable, a customized prescription tray (Perio Tray®, Perio Protect®, www.perioprotect.com) can be fabricated to deliver hydrogen peroxide deep into periodontal pockets, resisting the force of crevicular fluid flow and creating a hyperbaric oxygen chamber within the pockets. When the trays are worn for 15 minutes with the peroxide gel, the peroxide can reach the bottom of deep pockets > 7 mm (Figure 3 through Figure 5).31
Hyperbaric oxygen has been well documented to be bactericidal for anaerobic bacteria.37 Essentially, when hydrogen peroxide is held in place in the pocket, it oxygenates the pocket, changing the environment from anaerobic to aerobic and creating a hyperbaric oxygen chamber effect in the sulcus to destroy the biofilm’s occupants. Additionally, human neutrophils in the presence of hydrogen peroxide and chloride will produce ozone through the cholesterol ozonolysis process.38 This natural production of ozone has antimicrobial activity by oxidation of biomolecule precursors and microbial toxins that have been implicated in periodontal diseases, leading to healing and tissue regeneration.39 Much like a sealed tray, 1.7% hydrogen peroxide releases 5.7 times the volume of oxygen on decomposition, thus theoretically increasing the pressure in a closed system.
Adjunctive tray therapy can be used in conjunction with in-office mechanical means and laser therapies to help better manage the biofilm during these treatments. Once the periodontal disease is managed, the tray therapy can become part of the long-term home care solution to control biofilm with home maintenance. Typically, depending on how serious the periodontal disease is, the patient would be instructed to use the trays three to four times daily (for the recommended 15 minutes each time) for 2 weeks. Following mechanical therapy, the patient would be instructed to reduce tray usage to twice daily. This would be continued for a 6- to 12-week period when the patient would be recalled to check their periodontal status. If the gingival margin has remained non-inflamed and there continues to be an absence of bleeding, the patient can reduce usage to once daily. The patient would then be placed on a 3-month perio recall maintenance schedule and the frequency of tray usage would be re-evaluated.
Patients who have active periodontal infection with exudate, significant bone loss, or who are not fully responding to the hydrogen peroxide therapy may benefit from supplementing with Vibramycin syrup. Vibramycin helps decrease oxidative stress during the initial phase of treatment for acute and inflamed tissues, decreases matrix metalloproteinases to reduce connective tissue breakdown, manages long-term osteogenic activity by decreasing osteoclastic activity, and enables osteoblasts to continue to function.40 Clinically, this usage has resulted in decreased bone loss and increased bone healing/repair.41-44 Vibramycin is a doxycycline antibiotic, and the patient is given a prescription for 50 mg/5 ml (2 ounces) to be filled. They are instructed to place the peroxide gel into the tray, apply 3 drops of Vibramycin on top of the gel (a drop in the posterior of the tray bilaterally and one in the anterior), then evenly distribute them before inserting the tray.
The duration of Vibramycin treatment depends on the severity of inflammation and bone loss. Research indicates that during the initial 2 weeks of treatment (eg, the acute inflammatory stage), 3 drops of Vibramycin can be used in the trays four times daily in 15-minute increments to help decrease gingival bleeding. For osteoclast and osteoblast management, the duration of treatment is often longer. Superficial staining has been reported with long-term use of Vibramycin, but can be easily removed with prophylaxis.45 Toothbrushing after application may help prevent staining. While this is a sub-therapeutic dosage, when prescribing Vibramycin syrup as a systemically delivered antibiotic dose, clinicians need to keep in mind that doxycycline could cause adverse reactions for patients who are on Warfarin-type anticoagulant therapy and may require downward adjustments of their anticoagulant dosage.46
Candidates for treatment with adjunctive tray therapy typically have gingival recession or root exposure and the common complaint prior to treatment is root sensitivity. The author has found that having the patient use a neutral sodium fluoride gel in the tray (eg, Pro-DenRx®, DenMat, www.denmat.com; PreviDent®, Colgate®, www.colgateprofessional.com) twice weekly for 15 minutes helps to eliminate root sensitivity, and continuing this over the long term may prevent the return of sensitivity.
Conclusion
Scaling and root planing are still an integral part of periodontal treatment and aid in the disruption of the biofilm within the sulcus. Use of adjunctive tray therapy with 1.7% hydrogen peroxide does not replace its use in periodontal care. The trays enhance in-office care and allow the patient to maintain that care by reaching areas that toothbrushes and proximal cleaners (floss and interdental brushes) are unable to effectively treat. Use of peroxide gel delivered in trays has been documented as an effective long-term maintenance method with good patient compliance because of its ease of use with minimal time out of the day to implement.
Disclosure
The author has no relevant financial relationships to disclose.
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About the Author
Gregori M. Kurtzman, DDS, MAGD, DICOI
Private Practice
Silver Spring, Maryland
