Aims:
The overall aim of this work was to study the use of Laser Doppler flowmetry for the assessment of the dental pulp in permanent teeth. The thesis is presented as four distinct studies; 1) A systematic review was carried out to assess the published evidence on the use of laser Doppler flowmetry in the assessment of the pulp status of permanent teeth, 2) A cross-sectional survey was carried out in order to understand the use of dental pulp tests by paediatric dentists and general dental practitioners in children with dental trauma in the United Kingdom, 3) The first clinical study aimed to assess whether laser Doppler flowmetry was more accurate than the conventional pulp sensibility tests (Electric pulp test and ethyl chloride) in assessing the pulp status of permanent anterior teeth in children, and 4) The second clinical study aimed to prospectively monitor pulp sensibility/vitality of traumatised teeth using laser Doppler flowmetry, electric pulp testing and ethyl chloride, and to prospectively investigate the accuracy of each test.
Methods:
Systematic review: A systematic literature search, using MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, www.clinicaltrials.gov and www.controlled-trials.com, in addition to citation and manual reference list searches, was conducted up to 15th January 2018. A risk of bias assessment was performed using the quality assessment for diagnostic accuracy studies tool (QUADAS-2) with all steps performed independently by two reviewers.
Survey: A cross-sectional study utilising an 18-item questionnaire that was developed using the Bristol Online Survey (BOS) tool and circulated electronically to the members of the British Society of Paediatric Dentistry between June and August 2017.
Clinical study 1: A cross-sectional cohort diagnostic accuracy study with randomisation was carried out in 8-16-year-old children. Participants had one maxillary central or lateral incisor with either a completed root canal treatment or pulp extirpation and a contra-lateral tooth with vital pulp. The outcome measures included the cut-off threshold for LDF and the sensitivity, specificity and predictive values as well as the repeatability of each test. The Receiver Operating Characteristic (ROC) curve and the contingency 2X2 table were used for analysis. Kappa scores were used to assess the repeatability of EPT and ethyl chloride while inter-class correlation was used for LDF.
Clinical study 2: Children who sustained dental trauma to an anterior permanent tooth with uncertain pulp vitality requiring monitoring for a minimum of 12 months were included in the study. Recordings of dental pulp tests were carried out at baseline and at the end of the follow-up period.
Results
Systematic review: Only four studies all with a high risk of bias were included in the final systematic review for analysis. Laser Doppler flowmetry was reported to be more accurate in differentiating between teeth with normal pulps and pulp necrosis with a sensitivity of (81.8-100%) and specificity of 100 % in comparison to other vitality tests such as pulp oximetry (sensitivity = 81.3 %, specificity = 94.9 % ) and sensibility tests such as electric pulp testing (EPT) (sensitivity = 63.3 – 91.5 %, specificity = 88 – 100 %).
Survey: One hundred and forty-one respondents, both, paediatric dental specialists (56%) and GDPs (44%) were included in the analysis. Almost all specialists (93.7%) reported using sensibility tests routinely in comparison to 80.6% of GDPs. Child perception and cooperation were the most commonly reported barriers. GDPs mainly used cold testing, while specialists used cold and electric pulp tests equally. Inconsistencies in recording as well as documentation the results varied among respondents. Only a few specialists reported having some experience in using laser Doppler flowmetry.
Clinical study 1: There was a significant difference between the Flux values for teeth with vital and non-vital pulps. The best cut–off ratio for LDF was 0.6 yielding a sensitivity of 54 % and a specificity of 32 % which were lower than the values of electric pulp test (Sensitivity = 83.8 – 94.6 %, Specificity = 89.2 – 97.6 %) and ethyl chloride (Sensitivity = 81.1 – 91.9 %, Specificity = 73 – 81.1 %). The repeatability of LDF, EPT and ethyl chloride were 0.85, 0.86 and 0.81, respectively.
Clinical study 2: The study included a convenience sample size of 15 participants with a mean age of 10.7 years (SD=1.66), age range 8-14 years. The mean follow-up period was 7.29 months (SD 1.9) with a range of 6-12 months. All traumatised teeth remained vital at the end of follow-up except one tooth. The specificity of LDF at baseline was 80% compared to 66.6% and 60-73.3% for EPT and ethyl chloride, respectively. At the end of the follow-up period, LDF showed lower specificity (71.4 %) than EPT (78.5 – 85.7 %) and ethyl chloride (71.4 – 78.5 %).
Conclusion: Despite the high reported sensitivity and specificity of laser Doppler flowmetry in the systematic review, these data were found to be based on studies with a high level of bias and serious shortfalls in study designs. The survey of specialists and GDP’s showed that the use of pulp sensibility tests was relatively high amongst respondents while those of vitality tests were very low. Barriers and inconsistencies in the technique and recording of the results of sensibility tests were evident. The frequency and timing of using sensibility tests in line with international guidelines were stressed. The use of standardised techniques involving methods considered to improve reliability was highlighted. The results of the clinical studies showed that there was a high probability of false results when using LDF in assessing the pulp blood flow/pulp vitality. LDF was unable to differentiate between teeth with vital and non-vital pulps in children between the ages of 8-16 years with an acceptable level of confidence in the first clinical study. Within the limitations of the second clinical study, LDF showed better specificity than both EPT and ethyl chloride in predicting the outcome of the pulp at baseline but less at the end of follow-up. Due to the small sample size and relatively short follow-up period, the results of the second clinical study have been interpreted with caution.
Therefore, the published data on the accuracy of LDF can not be accepted as they are based on studies with unacceptable flaws in study design. Our studies have shown that not only the use of LDF or even the experience of clinicians with its use is extremely low, but also its specificity and sensitivity were of a level which is unacceptable for recommending its meaningful clinical use
