Infective endocarditis following invasive dental procedures: IDEA case-crossover study
Authors: Thornhill Martin H , Crum Annabel , Rex Saleema , Campbell Richard , Stone Tony , Bradburn Mike , Fibisan Veronica , Dayer Mark J , Prendergast Bernard D , Lockhart Peter B , Baddour Larry M , Nicholl Jon 
Published: June 2022

Background
Infective endocarditis is a heart infection with a first-year mortality rate of ≈ 30%. It has long been thought that infective endocarditis is causally associated with bloodstream seeding with oral bacteria in ≈ 40–45% of cases. This theorem led guideline committees to recommend that individuals at increased risk of infective endocarditis should receive antibiotic prophylaxis before undergoing invasive dental procedures. However, to the best of our knowledge, there has never been a clinical trial to prove the efficacy of antibiotic prophylaxis and there is no good-quality evidence to link invasive dental procedures with infective endocarditis. Many contend that oral bacteria-related infective endocarditis is more likely to result from daily activities (e.g. tooth brushing, flossing and chewing), particularly in those with poor oral hygiene.

Objective
The aim of this study was to determine if there is a temporal association between invasive dental procedures and subsequent infective endocarditis, particularly in those at high risk of infective endocarditis.

Design
This was a self-controlled, case-crossover design study comparing the number of invasive dental procedures in the 3 months immediately before an infective endocarditis-related hospital admission with that in the preceding 12-month control period.

Setting
The study took place in the English NHS.

Participants
All individuals admitted to hospital with infective endocarditis between 1 April 2010 and 31 March 2016 were eligible to participate.

Interventions
This was an observational study; therefore, there was no intervention.

Main outcome measure
The outcome measure was the number of invasive and non-invasive dental procedures in the months before infective endocarditis-related hospital admission.

Data sources
NHS Digital provided infective endocarditis-related hospital admissions data and dental procedure data were obtained from the NHS Business Services Authority.

Results
The incidence rate of invasive dental procedures decreased in the 3 months before infective endocarditis-related hospital admission (incidence rate ratio 1.34, 95% confidence interval 1.13 to 1.58). Further analysis showed that this was due to loss of dental procedure data in the 2–3 weeks before any infective endocarditis-related hospital admission.

Limitations
We found that urgent hospital admissions were a common cause of incomplete courses of dental treatment and, because there is no requirement to record dental procedure data for incomplete courses, this resulted in a significant loss of dental procedure data in the 2–3 weeks before infective endocarditis-related hospital admissions. The data set was also reduced because of the NHS Business Services Authority’s 10-year data destruction policy, reducing the power of the study. The main consequence was a loss of dental procedure data in the critical 3-month case period of the case-crossover analysis (immediately before infective endocarditis-related hospital admission), which did not occur in earlier control periods. Part of the decline in the rate of invasive dental procedures may also be the result of the onset of illness prior to infective endocarditis-related hospital admission, and part may be due to other undefined causes.

Conclusions
The loss of dental procedure data in the critical case period immediately before infective endocarditis-related hospital admission makes interpretation of the data difficult and raises uncertainty over any conclusions that can be drawn from this study.

Future work
We suggest repeating this study elsewhere using data that are unafflicted by loss of dental procedure data in the critical case period.

Trial registration
This trial is registered as ISRCTN11684416.

Funding
This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 28. See the NIHR Journals Library website for further project information.