Root canal therapy is necessary when the dental pulp is damaged irreversibly and has to be removed. The loss of the dental pulp creates a dead space inside the tooth which is colonized by bacteria. The aim of root canal therapy is to clean and shape the root canal after the dental pulp has been removed and then to obturate the root canal to prevent reinfection of this space.
The root canal is obturated with a combination of a solid cone and root canal sealing cement aiming at filling the root canal space mostly with gutta-percha. More recently with the introduction of hydraulic cements that are used for a number of procedures in Endodontics, root canal sealers are playing more an antimicrobial and thus an interactive role in preventing the reinfection of the root canal space after the root canal obturation is complete. These sealer types are being suggested for use with a single gutta-percha standardized cone. For this technique the sealer properties are important since the obturation will be composed of high volumes of sealer.
There are a number of sealers based on tricalcium silicate cement where the latter interacts with water added to the material or fluids taken up from the root canal space and the formation of calcium hydroxide contributes to the antimicrobial properties of these sealers. These sealers are either presented as powder/liquid and need to be mixed and delivered to the root canal using a file or gutta-percha point. The syringable versions require moisture from the environment to set. All water-based sealers cannot be used in warm vertical compaction obturation techniques as they dry out and may not set. The limitations with the sealers available for clinical use necessitates the development of a hydraulic sealer with optimal antimicrobial and biological properties but which can be used both for the single cone obturation technique but is also stable when used with warm vertical compaction of gutta-percha. The aim of this project is the development of such a sealer.
Prototype hydraulic sealers will be developed and their properties compared to hydraulic sealers available in clinical use.
Material formulation and chemical characterization
Preliminary sealer characterization
The calcium-based cement on its own in the different vehicles will be characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses immediately after setting or after 28 days in a protein-based physiological solution. The leachate collected after 28 days will be assessed by inductively coupled plasma mass spectroscopy (ICP-MS).
Effect of additives
The optimal amount of radiopacifier will be determined by preparing sealers with varying amounts of radiopacifier and measuring the radiopacity using a method described in ISO 6876; 2012 thus comparing the radiopacity to a specific standardized thickness of aluminium. This will determine the percentage of radiopacifier necessary for the sealer.
The role of the additives is to enhance the physical and chemical characteristics of the sealer. Different percentages of additives will be added to the radiopacified calcium-based cement and the setting time, film thickness, flow and solubility will be determined following ISO 6876;2012 specifications. All the additives will be tested with different vehicles.
Final sealer characterization
The best formulations will be shortlisted and will be characterized using the methods described for the preliminary sealer characterization namely SEM, EDS and XRD and ICP on the leachate.
The antimicrobial properties of the sealers in contact with irrigated dentine will be assessed by the direct contact method using a multispecies biofilm. The effect of the final rinse of the root canal on the sealer properties such as the setting and antimicrobial properties will also be assessed using a methodology described previously.
The biological characterization will be carried out using a number of cell types and also using molecular methods
Assessment of quality of obturation
The quality of obturation will be assessed by obturating extracted teeth with the test sealers and a number of controls using either single cone or warm vertical compaction. The volume of voids will be calculated by measuring the volume of the prepared canal and subtracting it from the volume of obturated canal. The measurements will be performed by microcomputed tomography after chemo-mechanical preparation, obturation and after storage in protein based physiological solution for 6 months to assess the degree of washout of the sealer.
Assessment of the effect of heat on the sealers
The sealers will be subjected to heating and cooling cycles at temperatures used for warm vertical compaction. The sealer properties according to ISO 6876;2012 specifications will be assessed both before and after the heating and cooling cycles. The effect of the heat on the sealer chemistry will be assessed by Fourier transform infrared (FT-IR) spectroscopy.
Applicants should have a strong background in material science, specifically in biological characterization methods. The student will receive extensive interdisciplinary training and experience in physical and biological techniques in well–equipped state-of-the-art laboratories in the School of Dentistry. In addition, training will be provided in scientific writing and presentational skills. The student will play an active role in the vibrant post-graduate community within the School and the broader College and University. The student will also be encouraged to attend relevant conferences both nationally and internationally. The supervisors operate an “open door” policy in addition to the more formal monthly research meetings used to monitor progress and direct work.
To be considered for this studentship, please send the following documents to Dr Josette Camilleri on [Email Address Removed]:
• A detailed CV, including your nationality and country of birth;
• Names and addresses of two referees;
• A covering letter highlighting your research experience/capabilities;
• Copies of your degree certificates with transcripts;
• Evidence of your proficiency in the English language, if applicable.