Setting Time and Solubility of Thymol Incorporated Zinc Oxide-Guaiacol Root Canal Sealer: An in Vitro Study

Aims : This study aimed to establish whether changes in setting time and solubility of the locally prepared zinc oxide-guaiacol endodontic sealer when incorporated with thymol crystals as an antibacterial agent.

among investigators owing to their safety and risk-free; thymol displays the possible to restrain dental infection (4) .
Setting time and solubility consider having importance according to ANSI/ADA specifications in controlling all actions of root canal sealer materials during and after manipulation (5) .
The setting time of zinc oxide-guaiacol sealer allow sufficient working time for better obturation, radiographical assessment, and perform any adjustment if needed (6) .
Perfectly, the endodontic sealer materials must have low solubility, appropriate flow rate, and film thickness that efficiently obturate the auxiliary canals and holes between the master and accessory cones (7) .
Based on this important standard (ADA specification No. 57), the locally prepared zinc oxide-guaiacol root canal sealer with low solubility (ADA did not exceed 3%) related to the presence of natural resin content and bismuth subcarbonate (6) .
The present study aimed to compare and evaluate the effect of (2%, 5%, and 10%) thymol crystals incorporation on the setting time and solubility of the locally prepared zinc oxide-guaiacol endodontic sealer.

Thymol incorporation
The thymol crystals (BDH, England) crushed with an electrical grinder (Geepas,China) and sieved to standard the particles size, and incorporated in the locally prepared zinc oxide-guaiacol root canal sealer in three formulas, Table (1).

Setting time test
Regarding ANSI/ADA specification No.57, Three samples were organized as follows: using a mold of stainless steel ring form with an inner distance of (10 mm) with (2 mm) height, placed on the glass plate (slide of the microscope),

Water solubility test
Ten samples for trial material prepared as follows: the mold with an inner distance of (20±0.1) mm and a height of (1.5±0.1) mm were used for sample planning, Figure   ( In an incubator, all samples were left to set for 24 hours at 37˚ C and 100% qualified moisture. The samples were assessed 3 times and the typical evaluation was noted using an investigative balance to an accurateness of ± 0.001 g (9) . Then, each sample was suspended and fixed by nylon filament inside a plastic bottle having (50 ± 1) ml of distilled water at (37 ± 1) ºC for 24 hrs., Figure (4). the sample was then detached and splashed with 2-3 ml of fresh distilled water (10) . Permit the samples to

Setting time test
The mean of the net setting time (minutes) was showed in, Table (

Water solubility test
The mean of the solubility value and standard deviation of the experimental endodontic sealer are presented in, Table (4).

Setting time
The perfect root canal sealer setting time should allow sufficient working time.
While, a slow setting time can end in tissue irritation, with most endodontic root canal sealers generating a certain degree of toxicity till being totally set (11) .
Setting time is the time essential for the endodontic sealer to accomplish its definitive actions. It rests on the ingredients, size of particles, ambient temperature, and proportional humidity.
There is no specified standard setting time for endodontic sealers, but clinical benefit loads that it must be long enough to permit the application and modification of core root filling when required (12) . usage (8) . The setting of root canal sealer happens due to the reaction between the two constituents of the material (powder with liquid or base paste with catalyst paste), therefore, the adding of particles that do not share in the reaction of set or polymerization may rise the setting time (13) . The water solubility is clearly based on the molecular weight as it declined; the solubility rise at nearly pH 7; Thymol theorizes with low molecular weight (14) .

Water solubility
The result of the present study agreement with Nunez-Flores (15)  According to Nostro (16) , thymol is as much hydrophilic as hydrophobic, which can support the diffusion of this compound. The low solubility of the crosslinked gelatin films; is raised slightly but not very large in the existence of thymol (17) .