Ozone Application in Endodontics

Introduction

Ozone (O3) is a triatomic molecule consisting of three oxygen atoms. Its molecular weight is 47.98 g/mol. Thermodynamically, it is a highly unstable compound and, depending on system conditions like temperature and pressure, decom-

Z. Mohammadi, DMD, MSD

Iranian Center for Endodontic Research (ICER), Research Institute of Dental Sciences,

Shahid Beheshti University of Medical Sciences, Tehran, Iran

A. Azarpazhooh, DDS, MSc, PhD, FRCD(C) (*)

Division of Endodontics, Department of Dentistry,

and Clinician Scientist, Lunenfeld-Tanenbaum

Research Institute, Mount Sinai Hospital,

Toronto, ON, Canada

Dental Public Health and Endodontics, Faculty of Dentistry, University of Toronto, 515-C, 124 Edward St, Toronto,

ON M5G 1G6, Canada

e-mail: amir.azarpazhooh@dentistry.utoronto.ca

poses to pure oxygen with a short half-life [1]. Ozone is 1.6 times denser and 10 times more soluble in water (49.0 mL in 100 mL water at 0 °C) than oxygen. Although ozone is not a radical molecule, it is the third most potent oxidant after fluorine and persulfate. Ozone is an unstable gas that cannot be stored and should be used at once because it has a half-life of 40 min at 20 °C [2]. It is naturally produced by the photodissociation of molecular oxygen (O2) into activated oxygen atoms, which then react with oxygen molecules. This transient radical anion rapidly becomes protonated, generating hydrogen trioxide (HO3), which, in turn, decomposes to an even more powerful oxidant, the hydroxyl radical (OH) [2]. It is the fundamental form of oxygen that occurs naturally as a result of ultraviolet energy or lightning, causing a temporary recombination of oxygen atoms into groups of three. In the clinical setting, an oxygen/ozone generator simulates lightning via an electrical discharge

field. Ozone gas has a high oxidation potential and is 1.5 times more powerful than chloride when used as an antimicrobial agent [3, 4].

Applications of Ozone in Medicine

Ozone was discovered by Christian Friedrich Schönbein in 1839 [5]. In 1857, Werner von Siemens designed an ozone generator [6]. Ozone was first used in medicine in 1870 [3]. Medication forms of gaseous ozone are somewhat unusual, and that is why special application techniques have had to be developed for its safe use. According to the European Cooperation of Medical Ozone Societies, direct intravenous injections of ozone/oxygen gas may produce air embolisms [7]. In local applications, as in the treatment of external wounds, ozone application in the form of a transcutaneous gas bath has been established as a practical method – for example, at low (subatmospheric) pressures in a closed system guaranteeing no escape of ozone into the ambient air [8].

Apart from rectal insufflation, principally used in the treatment of intestinal conditions, but also applied systemically, autohemotherapy has established itself as a systemic therapy of choice [2]. A corresponding dosage of ozone gas is passed through or, more correctly, transferred (in the form of microbubbles) to 50–100 ml of the patient’s blood in a sealed, pressureless system, thereby assuring the finest possible distribution to reach the greatest possible number of red and white blood cells with the aim of activating their metabolism [1, 2]. In treating pain in the locomotor system, ozone can be applied supportively in the form of intramuscular or intra-articular injections [2]. Ozone can also enhance both lung function and inflammatory airway responses in subjects with preexisting allergic airway diseases [7]. However, its use is contraindicated for the following conditions: acute alcohol intoxication, recent myocardial infarction, hemorrhaging from any organ, pregnancy, hyperthyroidism, thrombocytopenia, and ozone allergy [2–4].

Ozone in Dentistry

Fisch used ozonated water in dentistry in 1930 for the first time [1]. Following him, the German surgeon Erwin Payr used ozone in surgery and reported his results at the 59th Congress of the German Surgical Society in Berlin [3].

Ozone has been used in various disciplines of dentistry. Ozone is applied to oral tissues in the following forms: ozonated water, ozonated olive oil, and oxygen/ozone gas. Ozonated water and olive oil have the capacity to trap and then release oxygen/ozone which is an ideal delivery system. These forms of application are used singly or in combination to treat dental diseases [8].

Ozone may temporarily arrest the progression of caries by killing bacteria in active carious lesions. This results in preventing or, at the very least, in delaying the need for tooth restorations [8–11]. Our previous systematic review of the applications of ozone in dentistry showed that ozone can be used to manage primary occlusal and root carious lesions [9]. For example, using a KaVo HealOzone device, Baysan et al. [10] showed that ozone exposure for 10–20 s reduced the total levels of Streptococcus mutans and Streptococcus sobrinus in the primary root caries lesions (PRCLs) to <1 % of the control values. Holmes [12] assessed the effect of a KaVo HealOzone device on PRCLs followed by a professionally applied remineralizing solution containing xylitol, fluoride, calcium, phosphate, and zinc and found that after 18 months, 100 % of PRCLs had improved. However, the clinical application has yet to achieve a strong level of efficacy and cost-effectiveness [8]. Filippi [12] observed the influence of ozonated water on the epithelial wound healing process in the oral cavity. It was found that ozonated water applied daily can accelerate the healing rate in the oral mucosa. This effect can be seen in the first two postoperative days. A comparison with wounds without treatment showed that daily treatment with ozonated water accelerates the physiological healing rate. Ozone has also been used to treat TMJ dysfunctions and trismus [4].