The value of a quality improvement programme for panoramic radiography: A cluster randomised controlled trial

The value of a quality improvement programme for panoramic radiography: A cluster randomised controlled trial

Journal of Dentistry, 2013-04-01, Volume 41, Issue 4, Pages 328-335, Copyright © 2013 Elsevier Ltd

Abstract

Objectives

To assess the value of a quality improvement programme for panoramic radiography.

Methods

A prospective, cluster randomised controlled trial was conducted in 40 dental practices in England. Practices were randomly assigned into two groups, an ‘active’ practice receiving regular feedback on film quality and a ‘control’ practice receiving no feedback until the completion of the study.

Results

800 panoramic radiographs were examined for technical and processing faults. Following the first feedback to the ‘active’ practices, 100 films showed that the films taken were a significant predictor of a reduction in the number of technical (effect coefficient 0.51 (standard error SE 0.06); P < 0.001) and processing (effect coefficient 0.42 (SE 0.08); P < 0.001) faults compared to those in ‘control’ practices ( n = 400). The ‘active’ practices continued to benefit from the second round of feedback, showing a marked reduction in technical (effect coefficient 1.31 (SE 0.06); P < 0.001) and processing (effect coefficient 1.18 (SE 0.11); P < 0.001) faults. Two months after completion of the study, a further 120 panoramic radiographs from 12 practices in each group were examined for quality. Significant differences between the two groups for both technical faults (effect coefficient 0.62 (SE 0.22); P = 0.02) and processing faults (effect coefficient 0.65 (SE 0.17); P < 0.001) were found.

Conclusions

This cluster randomised controlled trial showed that distance feedback is an effective method in instructing dental practitioners to correct technical and processing errors experienced in producing panoramic radiographs. This intervention was effective in the short term whilst the practitioners were actively receiving feedback and for 8 weeks afterwards.

Clinical significance

Panoramic radiography quality is often poor due to a lack of knowledge of correct patient positioning. A failure to comply with manufacturers’ instructions regarding the changing frequency for processing chemistry also compounds the problem. Distant feedback is effective in improving film quality in the short term and after 8 weeks.

Introduction

Panoramic radiography has become a routine radiographic technique in many dental practices. In 2004/2005, 1.3 million panoramic films were taken in National Health Service dental practices in both England and Wales whilst in private dental practice, it has been estimated that a further 0.5 million panoramic films were executed.

The quality of many of these panoramic films is often less than optimal which several studies have highlighted. One study has suggested that panoramic technical and processing faults may remain uncorrected as the operator has not recognised the cause of the error. In acknowledging this, the aim of this study was to assess the efficacy of detailed quality feedback to general dental practitioners with regard to improving the quality of their panoramic radiographs.

The aim of this paper is to

  • 1.

    assess the value of a quality improvement programme for panoramic radiography and

  • 2.

    assess the long term (8 week) benefit of distance feedback on correcting the technical and processing faults found on panoramic radiographs.

Materials and methods

Ethical approval was obtained on 11 January 2002 from Manchester Local Ethics committee. The trial has also been registered with ISRCTN with trial registration number 54934084.

Participants

The Dental Practice Board (DPB), the then overseeing body for the implementation, financing and governance of National Health Service Dentistry in England and Wales, was approached for assistance in recruiting practices which routinely used panoramic radiography. Letters explaining the details of the study were sent to practitioners using this type of equipment which explained that the research was aimed at improving the quality of panoramic radiographs in general dental practice. The letter was circulated to 820 practices in England and Wales of which 542 replies were received showing an interest, a response rate of 66.1%. Pursuant to this, the respondees were contacted by letter which outlined the basic parameters of the research. From this cohort, 40 practices were selected, solely on the basis of numbers of radiographs taken over a specific time span, to participate in the study.

Piloting the study

Prior to the commencement of the study, the methodology had been piloted using two volunteer dental practitioners who were not involved in the study itself and no problems were noted regarding the study design.

Randomisation and interventions

Using computer generated random numbers the statistician for the study randomised the forty practices into two groups, an ‘active’ group who were to receive regular feedback and a ‘control’ group that were to receive none until the end of the study. Each practice was asked to forward twenty consecutive panoramic radiographs to the study co-ordinator. The group allocations were sent to the study co-ordinator who also handled all the radiographs to ensure allocation concealment and that the researchers assessing the radiographs were blinded to study group when doing so.

As the policy of each of the practices was to take a panoramic radiograph on all new patients, panoramic films taken of dentate patients, new to the practice, over the age of 18 years were sent to the principle researcher and a consultant in dental and maxillofacial radiology. On receipt of these films, each radiograph was simultaneously viewed by the researchers. Standardised viewing conditions were employed to evaluate the radiographs using a dental light-box with a 30 cm × 15 cm viewing area (Rinn Dentsply Ltd., Weybridge, UK) in a room with low lighting and the periphery of the light box viewing screen masked using matt black card to eliminate peripheral light that might affect the researchers’ evaluation of the film. The viewing surface of the light box was cleaned prior to each session and a new bulb fitted after every 10 h of use in order to ensure reproducibility of viewing conditions. Using consensus agreement, the researchers viewed each panoramic radiograph for the presence of technical and processing faults. These faults were recorded on custom designed proformas. The flow chart ( Fig. 1 ) indicates the procedures for the ‘active’ and ‘control’ practices. The films were scored for quality using national guidelines. Tables 1 and 2 detail the technical and processing faults which were assessed on each of the panoramic radiographs submitted by the general dental practitioners.

Flow chart for randomisation.
Fig. 1
Flow chart for randomisation.
Table 1
Details of the technical faults assessed.
Faults Active 1st batch ( n = 100) percent in parentheses Active 3rd batch ( n = 200)
Static discharge on the radiograph 2 (2) 1 (0.5)
Poor screen/film contact 0 (0) 1 (0.5)
Images of foreign objects 11 (11) 14 (7)
Ghost image present 4 (4) 0 (0)
Anterior/posterior positioning error 64 (64) 77 (38.5)
Occlusal plane error 48 (48) 65 (32.5)
Sagittal plane error 44 (44) 56 (28)
Spinal column shadow 27 (27) 25 (12.5)
Head tipped laterally 31 (31) 61 (30.5)
Tongue not in contact with the palate 72 (72) 106 (53)
Film orientation markers not present 7 (7) 20 (10)
Incorrect lip position 85 (85) 95 (47.5)
Bite-block absent 41 (41) 37 (18.5)
Symphysis menti missing from image 22 (22) 25 (12.5)
Table 2
Details of the processing faults assessed.
Faults Active 1st batch ( n = 100) percent in parentheses Active 3rd batch ( n = 200)
Faults in density 32 (32) 42 (21)
Faults in contrast 28 (28) 28 (14)
Developer/fixer splashes 4 (4) 0 (0)
Film fogging present 21 (21) 66 (33)
Chemical streaks/contamination 6 (6) 4 (2)
Screen damage/artefacts 83 (83) 35 (17.5)
Inadequate fixation/washing 7 (7) 9 (4.5)
Processor roller marks 35 (35) 19 (9.5)
Pressure marks 18 (18) 31 (15.5)

Standardisation of the interventions

Following assessment of the faults evident, the clinician in the ‘active’ practices received a proforma detailing the technical and processing faults observed by the researchers and how to correct them for each of the panoramic films received. In addition, the researchers provided the participating clinicians with detailed diagrams to assist in the recognition and also the remedial actions necessary for all types of panoramic technical and processing film faults. Obviously, each feedback was tailored to the specific problems that individual practitioners were encountering.

After assessment of the first batch of 5 radiographs from each of the ‘active’ practices, the films were returned accompanied by a report detailing any faults in technique and/or processing. Guidance on how the faults could be recognised and rectified was provided by written instructions. The practice was asked to act upon the recommendations and provide another batch of 5 radiographs. An identical format was followed for this second batch. Having reviewed the feedback for this second batch, the ‘active’ practices were asked to provide a final batch of 10 radiographs which were assessed and written feedback provided.

The twenty ‘control’ practices were asked to provide 20 panoramic radiographs taken on dentate patients, new to the practice, over the age of 18 years. Each practice submitted twenty radiographs in one batch. This was facilitated by the co-ordinator to ensure blinding of the researchers with regard to possible practice group identification. Feedback was provided similarly as in the ‘active’ practices.

Reassessment of film quality

After a period of 2 months, a reassessment of film quality was undertaken. This was possible as 60% of the ‘active’ and ‘control’ practitioners were involved in another study which, while not connected with panoramic film quality, did involve providing further panoramic radiographs for assessment. The practitioners were randomly selected and unaware of this reassessment as it may have caused them to change their routine working practices. From these subsequent panoramic radiographs, the researchers were able to assess 10 panoramic radiographs taken from each of the 12 ‘active’ and 12 ‘control’ practices. These 240 panoramic films were subsequently assessed for technical and processing quality using the same criteria as that in the initial assessment.

Analysis of the data

The numbers of individual faults on all the radiographs were recorded for each practice in both practice groups. An intention to treat analysis was performed by the study statistician. Statistical methods to account for the clustering of radiographs within each practice were used throughout. For the effect of the intervention, a multiple linear regression model was fitted for the dependent variables, number of technical faults and number of processing faults, with study group as an explanatory variable. Robust standard errors were used to the account for the clustering of radiographs within the practices using Stata Statistical Software: Release 11.1 (StataCorp, College Station, TX, USA). Ten percent of radiographs were re-examined by the researchers 1 month after completion of the study to determine the repeatability of the assessments. This was assessed by the calculation of the kappa ( κ ) statistic for inter- and intra-observer repeatability.

Sample size calculation

From the review of the literature, it was assumed that the quality of the panoramic radiographs could be improved in approximately 80% of those films. As the study wished to detect a reduction due to the ‘feedback’ process intervention to 65% and assuming that the films were independent, the following sample size was calculated.

A sample size of 20 practices in each group and 15 radiographs per cluster (practice) (300 radiographs per group, 600 in total) would have 90% power to detect a difference in proportions of 0.80 to 0.65, assuming an intra-practice correlation coefficient of 0.04.

Results

All the practices provided all the films that they had been asked to provide for the study so there was no loss to follow-up of either practices or films in either group. Eight hundred panoramic radiographs were examined for both technical and processing faults. Of these, general dental practitioners took 468 (58.5%) films whilst the remaining 332 (41.5%) were taken by dental surgery assistants. Statistical analysis, fitting a multiple regression model to predict differences in the numbers of technical and processing film faults between the 20 ‘active’ practices for the first baseline batch of 5 films (prior to any feedback), the second batch of 5 films (after feedback) and the third batch of 10 films (after two sets of feedback) with the 20 ‘control’ practices, each who had 20 films assessed. A comparison between technical and processing faults for films at baseline ( Table 3 ) found the film being taken in an ‘active’ practice was a predictor for more technical faults ( P = 0.02) but practice type (active or control) was not a predictor of a difference in processing faults ( P = 0.84). However, following feedback to the ‘active’ practices on the methods to correct these problems, the second batch of films showed that the film being taken in an active practice was a significant predictor for a reduction in both technical (effect coefficient 0.51 (standard error SE 0.06); P < 0.001) and processing (effect coefficient 0.42 (SE 0.08); P < 0.001) faults compared to the ‘control’ practices. The ‘active’ practices continued to benefit from feedback with the third batch of 200 films, showing the film being taken in an active practice was a strong predictor of a marked reduction in the number of both technical (effect coefficient 1.31 (SE 0.06); P < 0.001) and processing (effect coefficient 1.18 (SE 0.11); P < 0.001) faults ( Table 3 ) compared with the film being taken in ‘control’ practices.

Table 3
Comparison of technical and processing faults between the ‘Control’ and ‘Active’ practices.
Number of films Mean number of faults Effect coefficient (robust standard error) 95% confidence interval P- value
Technical faults
Baseline
Control 400 4.27 −0.15 (0.06) −0.27–−0.02 0.02
Active (1st batch) 100 4.71
Control 400 4.27 0.51 (0.06) 0.317–0.71 <0.001
Active (2nd batch) 100 3.25
Control 400 4.27 1.31 (0.06) 1.02–1.59 <0.001
Active (3rd batch) 200 2.96
Processing faults
Baseline
Control 400 2.42 −0.01 (0.05) −0.10–0.09 0.84
Active (1st batch) 100 2.45
Control 400 2.42 0.42 (0.08) 0.26–0.58 <0.001
Active (2nd batch) 100 1.58
Control 400 2.42 1.18 (0.11) 0.96–1.40 <0.001
Active (3rd batch) 200 1.24

On completion of the study, written feedback had been sent to each of the ‘control’ practices detailing their technical errors and how to correct them. A statistical model was fitted for data from a further 120 films to determine whether the film being taken in an ‘active’ or ‘control’ practice was a predictor for technical and processing faults 2 months later. This was possible as these practitioners were participants in another panoramic study which allowed the researchers to monitor film quality without alerting the practitioners to this fact. This was considered important as knowledge of this assessment may have caused them to change their normal practices during panoramic radiographic or processing technique. The regression models showed that the film being taken in an ‘active’ practice was still a predictor of reductions in the numbers of both technical (effect coefficient 0.62 (SE 0.22); P = 0.02) and processing faults (0.65 (SE 0.17); P < 0.001)( Table 4 ).

Table 4
Comparison of the technical and processing faults after 2 months between the ‘Control’ and ‘Active’ practices.
Number of films Mean number of faults Effect coefficient (robust standard error) 95% confidence interval P -value
Technical faults Control 120 3.88 0.62 (0.22) 0.19–1.04 0.02
Active 120 3.26
Processing faults Control 120 1.85 0.65 (0.17) 0.32–0.98 <0.001
Active 120 1.20

The technical faults recorded as contributing to the unacceptability of a panoramic radiograph are listed ( Table 1 ) and of these only three showed a continuing reduction. These were incorrect patient positioning in the sagittal plane which reduced from 44% to 28%, absence of a biteblock falling from 41% to 18.5% and the number of spinal column errors which decreased from 27% to 12.5%.

It was surprising that the two most common faults, the tongue not being placed against the palate (72%) and the lips not closed (85%), should be so prominent as they are the most simple faults to eliminate simply by clear patient instruction before positioning them in the panoramic unit. It also illustrates a lack of fundamental knowledge of the requirements to produce a satisfactory panoramic radiograph. These faults decreased to 53% and 47.5% respectively. Other faults, such as incorrect positioning of the patient in the anterior focal trough, are more difficult for the operator if a bite block and/or other positioning aids are not available. It was noticable that almost one quarter of the 400 panoramic radiographs were taken with the bite block missing from the panoramic unit, with this action continuing even after feedback. There were reductions in some of the categories of technical faults assessed on the 120 films, 2 months on, by the ‘control’ practices. These included a 15.3% reduction in the incorrect positioning of the tongue and a 10% reduction in the incorrect open lip position. However, it was disappointing to find a 10% increase with regard to incorrect patient positioning relative to the occlusal plane.

Table 2 details the processing faults that contributed to a radiograph as not being of diagnostic value. Feedback to the ‘active’ practices was successful in reducing the majority of processing faults in varying degrees. The faults which showed the greatest reduction were screen damage and screen artefacts (83% to 17.5%), roller marks (35% to 9.5%), film contrast (28% to 14%)) and film density (32% to 21%). Certain faults such as film fogging and pressure marks remained unaddressed for the duration of the study. A comparison of the processing faults found on the 400 panoramic films by the ‘control’ practices and 120 panoramic films 2 months after the conclusion of the study ( Table 4 ) found differences between the two groups ( P < 0.001). The ‘control’ practices had addressed some of the processing problems highlighted by the researchers, but the problems of poor density and contrast remained largely unresolved.

The kappa statistic relating to technical and processing faults for inter- and intra-observer reliability are shown in Tables 5 and 6 respectively. The kappa statistic defines the values of 0.21–0.40 as exhibiting only fair agreement, values of 0.41–0.60 moderate agreement and values of 0.61–0.80 and 0.81–1.00 substantial and almost perfect agreement. For the majority of technical faults ( Table 5 ), the agreement between repeat assessments was either good or substantial except for the discerning of head tipping. For processing faults ( Table 6 ), inter-observer agreement was only moderate in identifying chemical contamination/streaks whilst intra-observer agreement showed substantial and above agreement for the majority of categories with screen damage and artefacts showing only fair reliability.

Table 5
Inter- and intra-observer agreement for the assessment of technical faults.
Technical faults Inter-observer Intra-observer
Kappa (standard error) 95% confidence interval Kappa (standard error) 95% confidence interval
Static discharge on the radiograph All yes Unable to estimate All yes Unable to estimate
Poor screen/film contact All yes Unable to estimate All yes Unable to estimate
Images of foreign objects 1.00 (0.0) 1.00 (0.00)
Ghost image present 0.93 (0.07) 0.78–1.00 1.00 (0.00)
Anterior positioning error 0.75 (0.11) 0.54–0.95 0.75 (0.11) 0.54–0.95
Occlusal plane error 0.67 (0.12) 0.43–0.91 0.73 (0.11) 0.51–0.94
Sagittal plane error 0.65 (0.12) 0.41–0.89 0.80 (0.09) 0.62–0.98
Spinal column shadow 0.77 (0.15) 0.47–1.00 0.77 (0.15) 0.47–1.00
Head tipped laterally 0.53 (0.17) 0.21–0.86 0.73 (0.12) 0.49–0.98
Tongue not in contact with the palate 0.79 (0.10) 0.59–0.98 0.95 (0.05) 0.85–1.00
Absence of film orientation markers 0.83 (0.12) 0.59–1.00 0.73 (0.15) 0.44–1.00
Lips open 0.69 (0.12) 0.47–0.92 0.80 (0.09) 0.61–0.99
Bite block present 1.00 (0.00) 0.93 (0.07) 0.80–1.00
Symphysis menti missing from image 1.00 (0.00) 1.00 (0.0)
Table 6
Inter- and intra-observer agreement for the assessment of processing faults.
Processing faults Inter-researcher Intra-researcher
Kappa (standard error) 95% confidence interval Kappa (standard error) 95% confidence interval
Faults in density 0.84 (0.90) 0.66–1.00 1.00 (0.0)
Faults in contrast 0.81 (0.11) 0.60–1.00 1.00 (0.0)
Developer/fixer splashes All yes Unable to estimate All yes Unable to estimate
Film fogging present 0.66 (0.13) 0.41–0.91 0.94 (0.60) 0.82–1.00
Chemical streaks/contamination 0.48 (0.31) 0–1.00 1.0 (0.0)
Screen damage/artefacts 0.67 (0.12) 0.43–0.91 0.56 (0.14) 0.03–0.83
Inadequate fixation/washing All yes Unable to estimate All yes Unable to estimate
Roller marks 0.63 (0.15) 0.34–0.92 0.86 (0.09) 0.67–1.00
Pressure marks 0.93 (0.07) 0.80–1.00 0.93 (0.07) 0.78–1.00

Discussion

The initial contact letter outlining the purpose of this study to the dental practitioners informed that the researchers were undertaking a programme to improve panoramic film quality in general dental practice. In taking part in this study, a need was recognised for improvement in this field by the practitioners and hence the selected cohort may be more motivated to learn or change practice than a random sample from the population of dentists in general. However, it has been shown that 99.2% of panoramic radiographs taken in general dental practice exhibit one or more faults and of that percentage 33.0% were diagnostically unacceptable. It would therefore be safe to assume that the practitioners in this survey are similar to other practitioners working in the NHS who are taking reasonable numbers of radiographs. Of the 820 practioners contacted by the DPB, 542 replied showing an interest. Forty practitioners were selected solely on the basis of the number of radiographs which they advised the researchers were taken each week and were then assigned to ‘active’ and ‘control’ groups on a random basis. As all the practitioners were aware of the nature of the research and were assigned to the two groups on a random basis, any selection bias can be discounted when interpreting the results.

The study specified radiographs were to be taken on adult dentate patients over the age of 18 as using this age group removed any errors from possible movement in younger patients which relates to the patient rather than the technique. The films in this study were assessed by two researchers working together using optimal viewing conditions. One of the researchers was a consultant in dental and maxillofacial radiology and the principal researcher a general dental practitioner with a long standing involvement and knowledge of dental and maxillofacial radiology.

A review of the literature showed that a number of previous studies have assessed panoramic film quality, a direct comparison with these being impossible due to differences in study methodology. These related to the number of researchers used, the use of trained radiographers and the criteria adopted for determining the presence of a film fault. A number of studies have used a single researcher to assess film quality which has been shown to be less reliable than the use of consensus viewing adopted by this study. Also it is obvious that the use of trained radiographers working in a hospital environment cannot accurately reflect the personnel working in dental practice therefore a comparison with previous studies is inappropriate as the criteria adopted for acceptability of technical and processing faults were unknown.

The panoramic equipment used by the practitioners in this study employed a variety of positioning aids which are required to accurately localise the patient in the panoramic unit. Thirty-five panoramic units (87.5%) were equipped with a light beam facility, all units had a chin rest, 32 (80%) had a bite block, 37 (92.5%) had lateral head supports and 24 (60%) had front positioning guides. Examination of the processed films revealed that (41.0%) of radiographs taken by the ‘active’ practices in their first tranche of films were taken without the use of a bite-block which after two sets of feedback had reduced to 18.5%. The reasoning behind this decision to not use the biteblock is difficult to understand unless the importance of this positioning device was not fully understood or perhaps at the point of commissioning of the unit into service, no instruction on the use of these aids was given.

Member States of the European Union are directed to ensure that all dental practitioners and their ancillary staff who routinely work with ionising radiation have to undertake adequate theoretical training. In the UK, statutory regulations are specific in requiring that this knowledge is regularly reviewed and updated. A recent study has found that the continuing education programmes employed to deliver updates on radiation protection leave participating practitioners with a low knowledge level of exposure factors, radiographic equipment and quality assurance. This lack of knowledge of quality assurance is not solely confined to postgraduate clinicians as a recent study found, discerning that final year dental students in two UK dental schools had difficulties in recognising panoramic film faults. This highlights a need to change the way that the profession, both at undergraduate and postgraduate levels, is adequately educated. A recent systematic review of continuing education found that didactic teaching was not effective in improving clinical skills whereas the use of a combined interactive and clinically integrated approach was more succesful.

The feedback given to the ‘active’ practices in this study was effective as there was a degree of motivation in the participants to improve clinical practice. In general dental practice, practitioners tend to operate in their own environment with limited unbiased sources with which to update their clinical knowledge. The information received from the researchers had an effect on changing panoramic film quality in dental practice but it was disappointing that the effects of the feedback reduced after conclusion of the study. However, other studies in medical practice have mirrored these findings and other workers have shown that the intervention has to be applied regularly in order that specific intervention becomes routine practice amongst clinicians and ancillary staff.

In the United Kingdom, dental radiography represents the most common radiographic examination producing 30% of all examinations allied to which a study conducted in the United Kingdom found that one third of panoramic radiographs were diagnostically unacceptable. Unfortunately, the number of radiographic examinations undertaken precludes any attempt, in the same manner as this study, at improving poor radiographic technique and inadequate processing to rectify this problem. The current provision of poor radiographs should not be accepted as there are implications for the patients in that the dose received, the financial cost and the paucity of diagnostic yield are not in their best interests. The latter is compromised by technical and processing faults, either singly or in conjunction, which may add little or no benefit to their treatment plan and subsequent dental treatment.

Conclusions

This study has shown that distance feedback is an effective method in instructing practitioners in general dental practice to correct the technical and processing errors that they experience in producing a panoramic radiograph. This intervention was shown to be effective both in the short term whilst the practitioners were receiving feedback and for 8 weeks afterwards. Assessment of 120 radiographs of the ‘active’ practices, 2 months later, showed that the improvement had been maintained in both the technical or processing aspects of producing a panoramic radiograph. The ‘control’ practices showed no improvement in the technical aspect of taking panoramic radiographs although paradoxically an improvement ( P < 0.001) was made in the area of processing proficiency for which the researchers can offer no logical explanation. It could be surmised that the feedback may have induced a re-evaluation of processing procedures but it would appear illogical for that facet of panoramic radiography to be addressed and the technical one to be ignored.

It has been shown that interventions are effective in the short term and for those interventions to have longevity requires reinforcement. It would appear that unless funding is available for strategies to be implemented for practitioners to update their competencies in panoramic radiography on a regular basis, then the overall standard of films taken in general dental practice will remain low.

Acknowledgement

The principal researcher would like to thank the PPP Healthcare Medical Trust for the award of a Mid-Career Award for Established Practitioners which enabled this research to be undertaken.

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The value of a quality improvement programme for panoramic radiography: A cluster randomised controlled trial Michael N. Rushton , Vivian E. Rushton and Helen V. Worthington Journal of Dentistry, 2013-04-01, Volume 41, Issue 4, Pages 328-335, Copyright © 2013 Elsevier Ltd Abstract Objectives To assess the value of a quality improvement programme for panoramic radiography. Methods A prospective, cluster randomised controlled trial was conducted in 40 dental practices in England. Practices were randomly assigned into two groups, an ‘active’ practice receiving regular feedback on film quality and a ‘control’ practice receiving no feedback until the completion of the study. Results 800 panoramic radiographs were examined for technical and processing faults. Following the first feedback to the ‘active’ practices, 100 films showed that the films taken were a significant predictor of a reduction in the number of technical (effect coefficient 0.51 (standard error SE 0.06); P < 0.001) and processing (effect coefficient 0.42 (SE 0.08); P < 0.001) faults compared to those in ‘control’ practices ( n = 400). The ‘active’ practices continued to benefit from the second round of feedback, showing a marked reduction in technical (effect coefficient 1.31 (SE 0.06); P < 0.001) and processing (effect coefficient 1.18 (SE 0.11); P < 0.001) faults. Two months after completion of the study, a further 120 panoramic radiographs from 12 practices in each group were examined for quality. Significant differences between the two groups for both technical faults (effect coefficient 0.62 (SE 0.22); P = 0.02) and processing faults (effect coefficient 0.65 (SE 0.17); P < 0.001) were found. Conclusions This cluster randomised controlled trial showed that distance feedback is an effective method in instructing dental practitioners to correct technical and processing errors experienced in producing panoramic radiographs. This intervention was effective in the short term whilst the practitioners were actively receiving feedback and for 8 weeks afterwards. Clinical significance Panoramic radiography quality is often poor due to a lack of knowledge of correct patient positioning. A failure to comply with manufacturers’ instructions regarding the changing frequency for processing chemistry also compounds the problem. Distant feedback is effective in improving film quality in the short term and after 8 weeks. 1 Introduction Panoramic radiography has become a routine radiographic technique in many dental practices. In 2004/2005, 1.3 million panoramic films were taken in National Health Service dental practices in both England and Wales whilst in private dental practice, it has been estimated that a further 0.5 million panoramic films were executed. The quality of many of these panoramic films is often less than optimal which several studies have highlighted. One study has suggested that panoramic technical and processing faults may remain uncorrected as the operator has not recognised the cause of the error. In acknowledging this, the aim of this study was to assess the efficacy of detailed quality feedback to general dental practitioners with regard to improving the quality of their panoramic radiographs. The aim of this paper is to 1. assess the value of a quality improvement programme for panoramic radiography and 2. assess the long term (8 week) benefit of distance feedback on correcting the technical and processing faults found on panoramic radiographs. 2 Materials and methods Ethical approval was obtained on 11 January 2002 from Manchester Local Ethics committee. The trial has also been registered with ISRCTN with trial registration number 54934084. 2.1 Participants The Dental Practice Board (DPB), the then overseeing body for the implementation, financing and governance of National Health Service Dentistry in England and Wales, was approached for assistance in recruiting practices which routinely used panoramic radiography. Letters explaining the details of the study were sent to practitioners using this type of equipment which explained that the research was aimed at improving the quality of panoramic radiographs in general dental practice. The letter was circulated to 820 practices in England and Wales of which 542 replies were received showing an interest, a response rate of 66.1%. Pursuant to this, the respondees were contacted by letter which outlined the basic parameters of the research. From this cohort, 40 practices were selected, solely on the basis of numbers of radiographs taken over a specific time span, to participate in the study. 2.2 Piloting the study Prior to the commencement of the study, the methodology had been piloted using two volunteer dental practitioners who were not involved in the study itself and no problems were noted regarding the study design. 2.3 Randomisation and interventions Using computer generated random numbers the statistician for the study randomised the forty practices into two groups, an ‘active’ group who were to receive regular feedback and a ‘control’ group that were to receive none until the end of the study. Each practice was asked to forward twenty consecutive panoramic radiographs to the study co-ordinator. The group allocations were sent to the study co-ordinator who also handled all the radiographs to ensure allocation concealment and that the researchers assessing the radiographs were blinded to study group when doing so. As the policy of each of the practices was to take a panoramic radiograph on all new patients, panoramic films taken of dentate patients, new to the practice, over the age of 18 years were sent to the principle researcher and a consultant in dental and maxillofacial radiology. On receipt of these films, each radiograph was simultaneously viewed by the researchers. Standardised viewing conditions were employed to evaluate the radiographs using a dental light-box with a 30 cm × 15 cm viewing area (Rinn Dentsply Ltd., Weybridge, UK) in a room with low lighting and the periphery of the light box viewing screen masked using matt black card to eliminate peripheral light that might affect the researchers’ evaluation of the film. The viewing surface of the light box was cleaned prior to each session and a new bulb fitted after every 10 h of use in order to ensure reproducibility of viewing conditions. Using consensus agreement, the researchers viewed each panoramic radiograph for the presence of technical and processing faults. These faults were recorded on custom designed proformas. The flow chart ( Fig. 1 ) indicates the procedures for the ‘active’ and ‘control’ practices. The films were scored for quality using national guidelines. Tables 1 and 2 detail the technical and processing faults which were assessed on each of the panoramic radiographs submitted by the general dental practitioners. Fig. 1 Flow chart for randomisation. Table 1 Details of the technical faults assessed. Faults Active 1st batch ( n = 100) percent in parentheses Active 3rd batch ( n = 200) Static discharge on the radiograph 2 (2) 1 (0.5) Poor screen/film contact 0 (0) 1 (0.5) Images of foreign objects 11 (11) 14 (7) Ghost image present 4 (4) 0 (0) Anterior/posterior positioning error 64 (64) 77 (38.5) Occlusal plane error 48 (48) 65 (32.5) Sagittal plane error 44 (44) 56 (28) Spinal column shadow 27 (27) 25 (12.5) Head tipped laterally 31 (31) 61 (30.5) Tongue not in contact with the palate 72 (72) 106 (53) Film orientation markers not present 7 (7) 20 (10) Incorrect lip position 85 (85) 95 (47.5) Bite-block absent 41 (41) 37 (18.5) Symphysis menti missing from image 22 (22) 25 (12.5) Table 2 Details of the processing faults assessed. Faults Active 1st batch ( n = 100) percent in parentheses Active 3rd batch ( n = 200) Faults in density 32 (32) 42 (21) Faults in contrast 28 (28) 28 (14) Developer/fixer splashes 4 (4) 0 (0) Film fogging present 21 (21) 66 (33) Chemical streaks/contamination 6 (6) 4 (2) Screen damage/artefacts 83 (83) 35 (17.5) Inadequate fixation/washing 7 (7) 9 (4.5) Processor roller marks 35 (35) 19 (9.5) Pressure marks 18 (18) 31 (15.5) 2.4 Standardisation of the interventions Following assessment of the faults evident, the clinician in the ‘active’ practices received a proforma detailing the technical and processing faults observed by the researchers and how to correct them for each of the panoramic films received. In addition, the researchers provided the participating clinicians with detailed diagrams to assist in the recognition and also the remedial actions necessary for all types of panoramic technical and processing film faults. Obviously, each feedback was tailored to the specific problems that individual practitioners were encountering. After assessment of the first batch of 5 radiographs from each of the ‘active’ practices, the films were returned accompanied by a report detailing any faults in technique and/or processing. Guidance on how the faults could be recognised and rectified was provided by written instructions. The practice was asked to act upon the recommendations and provide another batch of 5 radiographs. An identical format was followed for this second batch. Having reviewed the feedback for this second batch, the ‘active’ practices were asked to provide a final batch of 10 radiographs which were assessed and written feedback provided. The twenty ‘control’ practices were asked to provide 20 panoramic radiographs taken on dentate patients, new to the practice, over the age of 18 years. Each practice submitted twenty radiographs in one batch. This was facilitated by the co-ordinator to ensure blinding of the researchers with regard to possible practice group identification. Feedback was provided similarly as in the ‘active’ practices. 2.5 Reassessment of film quality After a period of 2 months, a reassessment of film quality was undertaken. This was possible as 60% of the ‘active’ and ‘control’ practitioners were involved in another study which, while not connected with panoramic film quality, did involve providing further panoramic radiographs for assessment. The practitioners were randomly selected and unaware of this reassessment as it may have caused them to change their routine working practices. From these subsequent panoramic radiographs, the researchers were able to assess 10 panoramic radiographs taken from each of the 12 ‘active’ and 12 ‘control’ practices. These 240 panoramic films were subsequently assessed for technical and processing quality using the same criteria as that in the initial assessment. 2.6 Analysis of the data The numbers of individual faults on all the radiographs were recorded for each practice in both practice groups. An intention to treat analysis was performed by the study statistician. Statistical methods to account for the clustering of radiographs within each practice were used throughout. For the effect of the intervention, a multiple linear regression model was fitted for the dependent variables, number of technical faults and number of processing faults, with study group as an explanatory variable. Robust standard errors were used to the account for the clustering of radiographs within the practices using Stata Statistical Software: Release 11.1 (StataCorp, College Station, TX, USA). Ten percent of radiographs were re-examined by the researchers 1 month after completion of the study to determine the repeatability of the assessments. This was assessed by the calculation of the kappa ( κ ) statistic for inter- and intra-observer repeatability. 2.7 Sample size calculation From the review of the literature, it was assumed that the quality of the panoramic radiographs could be improved in approximately 80% of those films. As the study wished to detect a reduction due to the ‘feedback’ process intervention to 65% and assuming that the films were independent, the following sample size was calculated. A sample size of 20 practices in each group and 15 radiographs per cluster (practice) (300 radiographs per group, 600 in total) would have 90% power to detect a difference in proportions of 0.80 to 0.65, assuming an intra-practice correlation coefficient of 0.04. 3 Results All the practices provided all the films that they had been asked to provide for the study so there was no loss to follow-up of either practices or films in either group. Eight hundred panoramic radiographs were examined for both technical and processing faults. Of these, general dental practitioners took 468 (58.5%) films whilst the remaining 332 (41.5%) were taken by dental surgery assistants. Statistical analysis, fitting a multiple regression model to predict differences in the numbers of technical and processing film faults between the 20 ‘active’ practices for the first baseline batch of 5 films (prior to any feedback), the second batch of 5 films (after feedback) and the third batch of 10 films (after two sets of feedback) with the 20 ‘control’ practices, each who had 20 films assessed. A comparison between technical and processing faults for films at baseline ( Table 3 ) found the film being taken in an ‘active’ practice was a predictor for more technical faults ( P = 0.02) but practice type (active or control) was not a predictor of a difference in processing faults ( P = 0.84). However, following feedback to the ‘active’ practices on the methods to correct these problems, the second batch of films showed that the film being taken in an active practice was a significant predictor for a reduction in both technical (effect coefficient 0.51 (standard error SE 0.06); P < 0.001) and processing (effect coefficient 0.42 (SE 0.08); P < 0.001) faults compared to the ‘control’ practices. The ‘active’ practices continued to benefit from feedback with the third batch of 200 films, showing the film being taken in an active practice was a strong predictor of a marked reduction in the number of both technical (effect coefficient 1.31 (SE 0.06); P < 0.001) and processing (effect coefficient 1.18 (SE 0.11); P < 0.001) faults ( Table 3 ) compared with the film being taken in ‘control’ practices. Table 3 Comparison of technical and processing faults between the ‘Control’ and ‘Active’ practices. Number of films Mean number of faults Effect coefficient (robust standard error) 95% confidence interval P- value Technical faults Baseline Control 400 4.27 −0.15 (0.06) −0.27–−0.02 0.02 Active (1st batch) 100 4.71 Control 400 4.27 0.51 (0.06) 0.317–0.71 <0.001 Active (2nd batch) 100 3.25 Control 400 4.27 1.31 (0.06) 1.02–1.59 <0.001 Active (3rd batch) 200 2.96 Processing faults Baseline Control 400 2.42 −0.01 (0.05) −0.10–0.09 0.84 Active (1st batch) 100 2.45 Control 400 2.42 0.42 (0.08) 0.26–0.58 <0.001 Active (2nd batch) 100 1.58 Control 400 2.42 1.18 (0.11) 0.96–1.40 <0.001 Active (3rd batch) 200 1.24 On completion of the study, written feedback had been sent to each of the ‘control’ practices detailing their technical errors and how to correct them. A statistical model was fitted for data from a further 120 films to determine whether the film being taken in an ‘active’ or ‘control’ practice was a predictor for technical and processing faults 2 months later. This was possible as these practitioners were participants in another panoramic study which allowed the researchers to monitor film quality without alerting the practitioners to this fact. This was considered important as knowledge of this assessment may have caused them to change their normal practices during panoramic radiographic or processing technique. The regression models showed that the film being taken in an ‘active’ practice was still a predictor of reductions in the numbers of both technical (effect coefficient 0.62 (SE 0.22); P = 0.02) and processing faults (0.65 (SE 0.17); P < 0.001)( Table 4 ). Table 4 Comparison of the technical and processing faults after 2 months between the ‘Control’ and ‘Active’ practices. Number of films Mean number of faults Effect coefficient (robust standard error) 95% confidence interval P -value Technical faults Control 120 3.88 0.62 (0.22) 0.19–1.04 0.02 Active 120 3.26 Processing faults Control 120 1.85 0.65 (0.17) 0.32–0.98 <0.001 Active 120 1.20 The technical faults recorded as contributing to the unacceptability of a panoramic radiograph are listed ( Table 1 ) and of these only three showed a continuing reduction. These were incorrect patient positioning in the sagittal plane which reduced from 44% to 28%, absence of a biteblock falling from 41% to 18.5% and the number of spinal column errors which decreased from 27% to 12.5%. It was surprising that the two most common faults, the tongue not being placed against the palate (72%) and the lips not closed (85%), should be so prominent as they are the most simple faults to eliminate simply by clear patient instruction before positioning them in the panoramic unit. It also illustrates a lack of fundamental knowledge of the requirements to produce a satisfactory panoramic radiograph. These faults decreased to 53% and 47.5% respectively. Other faults, such as incorrect positioning of the patient in the anterior focal trough, are more difficult for the operator if a bite block and/or other positioning aids are not available. It was noticable that almost one quarter of the 400 panoramic radiographs were taken with the bite block missing from the panoramic unit, with this action continuing even after feedback. There were reductions in some of the categories of technical faults assessed on the 120 films, 2 months on, by the ‘control’ practices. These included a 15.3% reduction in the incorrect positioning of the tongue and a 10% reduction in the incorrect open lip position. However, it was disappointing to find a 10% increase with regard to incorrect patient positioning relative to the occlusal plane. Table 2 details the processing faults that contributed to a radiograph as not being of diagnostic value. Feedback to the ‘active’ practices was successful in reducing the majority of processing faults in varying degrees. The faults which showed the greatest reduction were screen damage and screen artefacts (83% to 17.5%), roller marks (35% to 9.5%), film contrast (28% to 14%)) and film density (32% to 21%). Certain faults such as film fogging and pressure marks remained unaddressed for the duration of the study. A comparison of the processing faults found on the 400 panoramic films by the ‘control’ practices and 120 panoramic films 2 months after the conclusion of the study ( Table 4 ) found differences between the two groups ( P < 0.001). The ‘control’ practices had addressed some of the processing problems highlighted by the researchers, but the problems of poor density and contrast remained largely unresolved. The kappa statistic relating to technical and processing faults for inter- and intra-observer reliability are shown in Tables 5 and 6 respectively. The kappa statistic defines the values of 0.21–0.40 as exhibiting only fair agreement, values of 0.41–0.60 moderate agreement and values of 0.61–0.80 and 0.81–1.00 substantial and almost perfect agreement. For the majority of technical faults ( Table 5 ), the agreement between repeat assessments was either good or substantial except for the discerning of head tipping. For processing faults ( Table 6 ), inter-observer agreement was only moderate in identifying chemical contamination/streaks whilst intra-observer agreement showed substantial and above agreement for the majority of categories with screen damage and artefacts showing only fair reliability. Table 5 Inter- and intra-observer agreement for the assessment of technical faults. Technical faults Inter-observer Intra-observer Kappa (standard error) 95% confidence interval Kappa (standard error) 95% confidence interval Static discharge on the radiograph All yes Unable to estimate All yes Unable to estimate Poor screen/film contact All yes Unable to estimate All yes Unable to estimate Images of foreign objects 1.00 (0.0) 1.00 (0.00) Ghost image present 0.93 (0.07) 0.78–1.00 1.00 (0.00) Anterior positioning error 0.75 (0.11) 0.54–0.95 0.75 (0.11) 0.54–0.95 Occlusal plane error 0.67 (0.12) 0.43–0.91 0.73 (0.11) 0.51–0.94 Sagittal plane error 0.65 (0.12) 0.41–0.89 0.80 (0.09) 0.62–0.98 Spinal column shadow 0.77 (0.15) 0.47–1.00 0.77 (0.15) 0.47–1.00 Head tipped laterally 0.53 (0.17) 0.21–0.86 0.73 (0.12) 0.49–0.98 Tongue not in contact with the palate 0.79 (0.10) 0.59–0.98 0.95 (0.05) 0.85–1.00 Absence of film orientation markers 0.83 (0.12) 0.59–1.00 0.73 (0.15) 0.44–1.00 Lips open 0.69 (0.12) 0.47–0.92 0.80 (0.09) 0.61–0.99 Bite block present 1.00 (0.00) 0.93 (0.07) 0.80–1.00 Symphysis menti missing from image 1.00 (0.00) 1.00 (0.0) Table 6 Inter- and intra-observer agreement for the assessment of processing faults. Processing faults Inter-researcher Intra-researcher Kappa (standard error) 95% confidence interval Kappa (standard error) 95% confidence interval Faults in density 0.84 (0.90) 0.66–1.00 1.00 (0.0) Faults in contrast 0.81 (0.11) 0.60–1.00 1.00 (0.0) Developer/fixer splashes All yes Unable to estimate All yes Unable to estimate Film fogging present 0.66 (0.13) 0.41–0.91 0.94 (0.60) 0.82–1.00 Chemical streaks/contamination 0.48 (0.31) 0–1.00 1.0 (0.0) Screen damage/artefacts 0.67 (0.12) 0.43–0.91 0.56 (0.14) 0.03–0.83 Inadequate fixation/washing All yes Unable to estimate All yes Unable to estimate Roller marks 0.63 (0.15) 0.34–0.92 0.86 (0.09) 0.67–1.00 Pressure marks 0.93 (0.07) 0.80–1.00 0.93 (0.07) 0.78–1.00 4 Discussion The initial contact letter outlining the purpose of this study to the dental practitioners informed that the researchers were undertaking a programme to improve panoramic film quality in general dental practice. In taking part in this study, a need was recognised for improvement in this field by the practitioners and hence the selected cohort may be more motivated to learn or change practice than a random sample from the population of dentists in general. However, it has been shown that 99.2% of panoramic radiographs taken in general dental practice exhibit one or more faults and of that percentage 33.0% were diagnostically unacceptable. It would therefore be safe to assume that the practitioners in this survey are similar to other practitioners working in the NHS who are taking reasonable numbers of radiographs. Of the 820 practioners contacted by the DPB, 542 replied showing an interest. Forty practitioners were selected solely on the basis of the number of radiographs which they advised the researchers were taken each week and were then assigned to ‘active’ and ‘control’ groups on a random basis. As all the practitioners were aware of the nature of the research and were assigned to the two groups on a random basis, any selection bias can be discounted when interpreting the results. The study specified radiographs were to be taken on adult dentate patients over the age of 18 as using this age group removed any errors from possible movement in younger patients which relates to the patient rather than the technique. The films in this study were assessed by two researchers working together using optimal viewing conditions. One of the researchers was a consultant in dental and maxillofacial radiology and the principal researcher a general dental practitioner with a long standing involvement and knowledge of dental and maxillofacial radiology. A review of the literature showed that a number of previous studies have assessed panoramic film quality, a direct comparison with these being impossible due to differences in study methodology. These related to the number of researchers used, the use of trained radiographers and the criteria adopted for determining the presence of a film fault. A number of studies have used a single researcher to assess film quality which has been shown to be less reliable than the use of consensus viewing adopted by this study. Also it is obvious that the use of trained radiographers working in a hospital environment cannot accurately reflect the personnel working in dental practice therefore a comparison with previous studies is inappropriate as the criteria adopted for acceptability of technical and processing faults were unknown. The panoramic equipment used by the practitioners in this study employed a variety of positioning aids which are required to accurately localise the patient in the panoramic unit. Thirty-five panoramic units (87.5%) were equipped with a light beam facility, all units had a chin rest, 32 (80%) had a bite block, 37 (92.5%) had lateral head supports and 24 (60%) had front positioning guides. Examination of the processed films revealed that (41.0%) of radiographs taken by the ‘active’ practices in their first tranche of films were taken without the use of a bite-block which after two sets of feedback had reduced to 18.5%. The reasoning behind this decision to not use the biteblock is difficult to understand unless the importance of this positioning device was not fully understood or perhaps at the point of commissioning of the unit into service, no instruction on the use of these aids was given. Member States of the European Union are directed to ensure that all dental practitioners and their ancillary staff who routinely work with ionising radiation have to undertake adequate theoretical training. In the UK, statutory regulations are specific in requiring that this knowledge is regularly reviewed and updated. A recent study has found that the continuing education programmes employed to deliver updates on radiation protection leave participating practitioners with a low knowledge level of exposure factors, radiographic equipment and quality assurance. This lack of knowledge of quality assurance is not solely confined to postgraduate clinicians as a recent study found, discerning that final year dental students in two UK dental schools had difficulties in recognising panoramic film faults. This highlights a need to change the way that the profession, both at undergraduate and postgraduate levels, is adequately educated. A recent systematic review of continuing education found that didactic teaching was not effective in improving clinical skills whereas the use of a combined interactive and clinically integrated approach was more succesful. The feedback given to the ‘active’ practices in this study was effective as there was a degree of motivation in the participants to improve clinical practice. In general dental practice, practitioners tend to operate in their own environment with limited unbiased sources with which to update their clinical knowledge. The information received from the researchers had an effect on changing panoramic film quality in dental practice but it was disappointing that the effects of the feedback reduced after conclusion of the study. However, other studies in medical practice have mirrored these findings and other workers have shown that the intervention has to be applied regularly in order that specific intervention becomes routine practice amongst clinicians and ancillary staff. In the United Kingdom, dental radiography represents the most common radiographic examination producing 30% of all examinations allied to which a study conducted in the United Kingdom found that one third of panoramic radiographs were diagnostically unacceptable. Unfortunately, the number of radiographic examinations undertaken precludes any attempt, in the same manner as this study, at improving poor radiographic technique and inadequate processing to rectify this problem. The current provision of poor radiographs should not be accepted as there are implications for the patients in that the dose received, the financial cost and the paucity of diagnostic yield are not in their best interests. The latter is compromised by technical and processing faults, either singly or in conjunction, which may add little or no benefit to their treatment plan and subsequent dental treatment. 5 Conclusions This study has shown that distance feedback is an effective method in instructing practitioners in general dental practice to correct the technical and processing errors that they experience in producing a panoramic radiograph. This intervention was shown to be effective both in the short term whilst the practitioners were receiving feedback and for 8 weeks afterwards. Assessment of 120 radiographs of the ‘active’ practices, 2 months later, showed that the improvement had been maintained in both the technical or processing aspects of producing a panoramic radiograph. The ‘control’ practices showed no improvement in the technical aspect of taking panoramic radiographs although paradoxically an improvement ( P < 0.001) was made in the area of processing proficiency for which the researchers can offer no logical explanation. It could be surmised that the feedback may have induced a re-evaluation of processing procedures but it would appear illogical for that facet of panoramic radiography to be addressed and the technical one to be ignored. It has been shown that interventions are effective in the short term and for those interventions to have longevity requires reinforcement. It would appear that unless funding is available for strategies to be implemented for practitioners to update their competencies in panoramic radiography on a regular basis, then the overall standard of films taken in general dental practice will remain low. 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