The impact of implementing an enhanced infection control protocol on root canal treatment outcomes
: in vivo and clinical studies

Student thesis: Doctoral ThesisDoctor of Philosophy


This thesis was intended to determine the effectiveness of implementing an enhanced infection control protocol on primary root canal treatment. First, the effect was studied on the outcome of root canal treatment of molar teeth clinically and radiographically; teeth were assigned to one of the two protocols: a standard root canal treatment protocol (SP), and an enhanced infection control protocol (EP). Moreover, this project examined the impact of the EP on the microbial load and the composition of the microbial community after chemomechanical preparation.
Materials and methods:
The pilot study involved samples obtained from teeth diagnosed with irreversible pulpitis (IP). Samples were collected from different sites such as files, endodontic ruler surface, rubber dam surface, gloves and instruments (tip of the tweezer, DG-16 endodontic explorer, plugger and flat plastic instrument), as well as intracanal samples. Microbial load was investigated by quantitative polymerase chain reaction (qPCR). The microbial composition was evaluated by targeting the 16S rRNA V3-V5 hypervariable regions of the 16S rRNA and subjecting to next-generation sequencing (NGS). Moreover, the microbial load and composition of intracanal samples of vital teeth were investigated by similar molecular methods.
The randomised controlled clinical trial involved healthy patients at Guys’ Hospital receiving primary root canal treatments. The patients were block randomised to a standard protocol (SP) and an enhanced infection control protocol (EP). Both treatment arms adhered to current best practice recommendations, while the EP comprised additional steps included replacing rubber dams, gloves, files, all instruments and surface barriers at the time of obturation to reduce the chances of iatrogenic contaminations. CBCT and PA radiographs were taken at baseline and one-year follow-up to assess the outcome of treatment. The outcome was assessed clinically and radiographically using CBCT.
In addition, intracanal samples were taken at baseline (S1) and after completion of chemomechanical preparation (S2). Microbial 16S rDNA copy numbers were enumerated by qPCR. Bacterial composition and identification were performed targeting the 16S rRNA V3-V4 hypervariable regions and subjected to NGS.
Findings of the pilot study showed that around half of the rubber dam surfaces were contaminated with bacteria at time of obturation and 38% of initial files introduced into the canal showed significant levels of bacteria. Bacteria were also detected in 20-30% of gloves, instruments and rulers prior to obturation. Streptococcus, Rothia, Propionibacterium, and Fusobacterium were among the taxa found in such contaminated surfaces. The pilot study findings suggested the risk of introducing bacteria into the root canal space after chemomechanical preparations; higher bacterial loads were more frequently present in intracanal samples before root canal filling when instruments and surfaces were found to be contaminated.
Regarding the intracanal samples of IP teeth, half of the intracanal samples had a substantial bacterial load of bacteria within the vital pulp (≥104 16S rRNA copies), as determined by qPCR. NGS microbial identification yielded 187 bacterial OTUs mainly belonging to the genera Veillonella, Streptococcus, Corynebacterium, Cutibacterium, and Porphyromonas.
At one-year follow-up, 115 teeth were analysed (54 in SP and 61 in EP), as a part of the clinical showed a trend of reduced diversity observed in pre-obturation samples of teeth treated within the EP compared to SP. Contaminants typically arising from saliva, skin or endodontic root canal spaces as Actinomyces, Porphyromonas, Cutibacterium, and Haemophilus were significantly reduced in their abundance in the EP pre-obturation samples.
The evidence from the pilot study highlighted the risk of contamination during root canal treatment and generated a proof of concept to commence a clinical trial. Findings of the clinical randomised trial showed the effectiveness of implementing an enhanced infection control protocol on primary root canal treatment of molar teeth and suggested that the implementation of facile and simple procedural adaptations such as changing instruments, gloves and rubber dams during root canal treatment are important in improving asepsis and have a great impact on treatment outcomes.
Date of Award1 Jul 2021
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorFrancesco Mannocci (Supervisor), Garrit Koller (Supervisor) & Shanon Patel (Supervisor)

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