Reaction rate of NaOCl in contact with bovine dentine: effect of activation, exposure time, concentration and pH.

AIM: To determine the influence of activation method (ultrasound or laser), concentration, pH and exposure time on the reaction rate (RR) of NaOCl when in contact with dentinal walls. METHODOLOGY: The walls from standardized root canals in bovine incisors were exposed to a standardized volume of sodium hypochlorite (NaOCl) with different concentrations (2% and 10%), pH (5 and 12) and exposure times (1 and 4min). Two irrigation protocols were tested: passive ultrasonic irrigation or laser activated irrigation with no activation as the control. The activation interval lasted 1min followed by a rest interval of 3 min with no activation. The RR was determined by measuring the iodine concentration using an iodine/thiosulfate titration method. RESULTS: Exposure time, concentration and activation method influenced the reaction rate of NaOCl whereas pH did not. CONCLUSIONS: Activation is a strong modulator of the reaction rate of NaOCl. During the rest interval of 3min, the consumption of available chlorine increased significantly. This effect seems to be more pronounced after irrigant activation by laser. pH did not affect the reaction rate of 2% NaOCl.

Light activated disinfection: an alternative endodontic disinfection strategy.

BACKGROUND: An improved light activated disinfection technique utilizing a specific photosensitizer formulation, liquid optical-conduit, oxygen-carrier and light energy of appropriate wavelength has been introduced recently. This study tested the efficacy of this improved light activated disinfection on ex vivo biofilms of Enterococcus faecalis at two different stages of maturation. METHODS: Eighty-five tooth sections were prepared and endodontic biofilm of E. faecalis were grown within the root canal. In stage 1, conventional light activated disinfection (LAD), chemical disinfectant (sodium hypochlorite) and improved LAD were tested on four-day-old (immature) biofilms. In stage 2, conventional LAD, improved LAD and chemomechanical disinfection (alone and in combination with improved LAD) were tested on four-week-old (mature) biofilms. RESULTS: Sodium hypochlorite and improved LAD showed the ability to significantly inactivate bacteria in four-day-old biofilms when compared to the control and LAD (p < 0.05). Inactivation of bacteria from deeper dentine was higher in improved LAD than sodium hypochlorite. In four-week-old biofilms, a combination of chemomechanical disinfection and improved LAD produced significant bacterial killing compared to either chemomechanical disinfection or improved LAD alone. CONCLUSIONS: This study highlighted the potential of improved LAD to kill bacteria within dentinal tubules. In combination with chemomechanical preparation, the improved LAD significantly inactivated four-week-old biofilm bacteria.

Corrosive effect of disinfection solution containing hydroxyl radicals generated by photolysis of H(2)O(2) on dental metals.

The purpose of the present study was to evaluate the corrosive effect of disinfection solution containing hydroxyl radicals generated by photolysis of H(2)O(2)on dental metals. Static immersion test was performed on four different dental metals: Ti, Type 316L stainless steel, Ag-Pd-Cu-Au alloy, and Co-Cr alloy. Metal specimens were immersed in 1 M H(2)O(2)(=3.4%) with or without light-emitting diode (LED) light irradiation (wavelength: 400 nm) for 1 week, and then the amounts of released ions were analyzed. Corrosive effect of the disinfection solution containing hydroxyl radicals on any dental metals tested in the present study never exceeded that of H(2)O(2) alone. Therefore, disinfection systems based on the photolysis of H(2)O(2) for the cleaning of dentures and treatment of oral infectious diseases would not cause problematic metal corrosion whenever the concentration of H(2)O(2) does not exceed 3%, which is a concentration used as an oral disinfectant.

Some factors influencing the stability of Sterilox(®), a super-oxidised water.

Super-oxidised waters, particularly Sterilox(®), have been suggested for the disinfection of dental unit water lines and dental impression materials owing to their antimicrobial efficacy. One of the previously suggested characteristics is their short shelf life. The purpose of this investigation was to understand the effect of storage conditions on Sterilox(®)'s stability. Eight bottles (four completely full, four half-full) of freshly prepared solution were divided into four groups and subsequently stored by being either exposed to or protected from sunlight. The chlorine concentration was monitored using chlorine test strips until the concentration reached zero, or until the thirteenth week. Statistically significant differences between the groups exposed to sunlight and the non-exposed groups (p <0.001) were found. The mean loss of chlorine per day for the non-exposed samples was 1.01 mg/L, whilst the mean for the exposed samples was 2.42 mg/L. The presence of air did not affect the chlorine decomposition in the bottles. The results of this investigation indicate that when the solution is exposed to sunlight, the decrease of chlorine starts at day 4, whilst for the groups sheltered from sunlight, the process started after day 14. Therefore, Sterilox(®) solutions appear to be more stable than previously surmised.