Dentomaxillofacial Radiology (2007) 36, 224–228 q 2007 The British Institute of Radiology http://dmfr.birjournals.org
RESEARCH
Comparison of re-exposure rates of intraoral radiographs between dental students and trained dental assistants in an oral and maxillofacial radiology clinic M Mupparapu*,1, S Jariwala1, SR Singer1, IH Kim1 and M Janal2 1 Department of Diagnostic Sciences, UMDNJ – New Jersey Dental School, Newark, NJ 07101-1709, USA; 2Department of Psychiatry, UMDNJ – New Jersey Medical School, Newark, USA
Objective: To compare the re-exposure rates of dental radiographs taken over a period of 1 year between dental students and trained dental assistants at a university-based oral and maxillofacial radiology clinic. Methods: Detailed records of the number and type of intraoral radiographs taken by the students and staff members and the number of re-exposures that were required from July 2003 to July 2004 were used. Statistical analyses were performed on the data. Results: A x 2 test showed that re-exposure rates of radiographic series between students and staff were statistically different. When comparing the students’ re-exposure rates during each of the four quarters of their radiology rotation, one-way analysis of variance test showed that the results were not statistically significant for reduction in the number of re-exposures over the entire year. Conclusions: There were significant differences in the re-exposure rates between staff dental assistants and students. Film re-exposure rates for the students during the four quarters were expected to decrease with time. Instead, the consistency of the re-exposure rates of the students during the four quarters demonstrates the need to recognize why the students did not perform better as the year progressed. The percentage of films that needed to be re-exposed by either group (students or the staff dental assistants) was not extremely high. Dentomaxillofacial Radiology (2007) 36, 224–228. doi: 10.1259/dmfr/91136616 Keywords: re-exposure rate, radiographs, rectangular collimator, dental student, dental assistant Introduction It has generally been observed that radiology staff dental assistants have lower re-exposure rates than the third year dental students, and it is assumed that the third year dental students reach the level of expertise of staff dental assistants after a yearlong radiology clinic rotation. Nixon and colleagues1 from the United Kingdom audited film reject rates in a dental radiology department and found an overall dental radiographic film reject rate of 3.06% in their facility. The authors commented that there was a significant difference in the reject rates between qualified staff and those in training. These findings could not be confirmed as no other studies were found in the literature that recorded the re-exposure rates and compared the *Correspondence to: Dr Muralidhar Mupparapu, DMD, MDS, Diagnostic Sciences, D-860, UMDNJ – New Jersey Dental School, 110 Bergen Street, Newark, NJ 071011709, USA; E-mail:
[email protected] Received 21 September 2005; revised 10 April 2006; accepted 23 May 2006
performance of dental students and staff dental assistants over time. It is known from the literature that, although dental students had problems in identification of film faults initially, they had the fund of knowledge and competence in the assessment and correction of faults once identified.2 However, there is limited literature on this topic as well. This crucial information is valuable for the efficient clinical training of dental students. In addition, this information can assist dental educators to understand the quality control issues and limitations within the oral and maxillofacial radiology (OMFR) clinic. The objective of this study was to compare the reexposure rates of intraoral radiographs between the dental students attending the radiology clinical rotation (OMFR clinic) and the staff dental assistants over a period of 1 year. This study was also intended to observe performance trends among the dental students’ intraoral radiographic
Comparison of re-exposure rates M Mupparapu et al
technique utilizing rectangular collimation while attending the clinical rotation during this 1-year period. It is anticipated that the data obtained from this study will be useful for the implementation of future clinical training protocols for dental students.
Materials and methods Radiology clinical training for junior (third) year dental students begins with a mandatory 12 h training session towards the end of the sophomore (second) year. Dental radiograph teaching and training replicas (DXTTR; RINN Corporation, Elgin, IL) are used for the training before the students attend the clinical rotation in radiology. Dental students rotate through the radiology clinic once every 4 weeks in their junior year at the New Jersey Dental School. Junior year students normally spend both morning and afternoon sessions in radiology patient care. After obtaining a thorough medical and dental history and completion of a clinical examination, students are trained to independently perform the radiographic examinations. Staff dental assistants in the clinic have had at least 10 years of
Figure 1
225
experience in clinical radiography after their initial training and license. All radiographic studies were performed using a long cone, rectangular collimator using intraoral positioning devices (RINN XCP instruments, DENTSPLY/RINN Corporation). A Kodak Insightw film (speed group F; Eastman Kodak, Rochester, NY) was used with the X-ray machine operating at 70 kV and 15 mA, and processed in automatic processors (DentX 9000; Dent-X Corp., Elmsford, NY). Calibrated OMFR faculty used standard technique error assessment forms for student teaching (Figure 1) to help identify the radiographs that were inadequate for interpretation and subsequently recommended re-exposures when necessary. The radiographs were mounted on standard RINN mounts (RINN Corporation) and viewed on a fluorescent light box (Star X-Ray Inc., Amityville, NY) in a dimly lit room after masking all extraneous light with a specially designed cardboard mask. This is a standard procedure for radiographic studies that are completed within the OMFR clinic. The students were then graded on the number and type of technique errors as well as interpretation using the standard grading form. Faculty underwent calibration exercises
Radiographic technique evaluation form that is used for all intraoral radiographic series Dentomaxillofacial Radiology
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quarterly using the same error assessment forms and grade sheets within the 24-month period prior to the study. Two types of radiographic film series were used for this study: full mouth radiographic series (FMS) and select film series (SFS). A FMS typically has 14 periapical (14 PA) and 4 bitewing radiographs (4 BW films) obtained using size 2 intraoral films. SFS ranged anywhere from 10 films to 17 films with a combination of periapical and/or bitewing films. If the radiographs failed to record and display the desired information, a re-exposure was made. The decision to re-expose was made by the OMFR faculty based on following criteria: (1) (2) (3) (4) (5) (6) (7) (8) (9)
missing apices of teeth due to film positioning or vertical angulation error; missing contact points due to film positioning error; overlap of contact points due to horizontal angulation error; collimator cut through the area of interest; missing distal of the canines and canine-premolar contacts in premolar bitewings; any exposure error that makes the films less than ideal to view; any processing error that makes the films unacceptable; blurred images due to patient movement; and if the desired area of anatomy was not at all recorded in any other views within the series.
A daily log was kept by the OMFR clinic in which students and staff members were asked to record their status, the number of radiographs exposed and the number of reexposures required at the end of each study. Radiology faculty screened all the radiographic series, adhering to the criteria as outlined previously. Patient and student data from 25 July 2003 to 26 July 2004 were used for this study. The data were compiled and summarised into a table by type of examination, number of radiographs obtained, number of re-exposures required for the type of error and status of the operator. This study complied with federally mandated Health Insurance Portability and Accountability Act regulations to protect the confidentiality of patient data. An approval from the Institutional Review Board was obtained. Data analysis Differences between the students and staff dental assistants in the average re-exposure rates were assessed with independent sample t-tests, while the differences in the probability of at least one re-exposure were assessed with the x 2 statistic. Comparisons over time within the student group employed one-way analysis of variance (ANOVA). Results Out of 20 158 radiographs obtained in the OMFR clinic by the junior year dental students, 998 films were re-exposed due to faulty technique, resulting in a 4.9% film reexposure rate for the students. Out of 14 154 films exposed in the clinic by the staff members, only 19 films had to be Dentomaxillofacial Radiology
re-exposed to achieve a diagnostically acceptable study, resulting in a 0.2% film re-exposure rate for the staff members (Table 1). Independent t-test samples revealed that the third year dental students had a significantly higher average film re-exposure rate than staff dental assistants (P , 0.001). Radiographic series included both the FMS and SFS. Out of 797 radiographic series, staff dental assistants required at least one re-exposure in 19 cases and none in the other 778. Thus, 97.6% of the radiographic series done by the staff members did not require any re-exposures. Out of 1154 series completed by the students, there were 518 (44.9%) instances in which at least one re-exposure was required. Thus, only 55.1% of the radiographic series completed by the students did not need any re-exposures (Table 1). x 2 test (424 557 with 1 degree of freedom and the two-tailed P value , 0.0001) indicated that staff dental assistants had a statistically significant lower re-exposure rate than the third year dental students. Table 2 summarises the mean re-exposure rate for students (at least one re-exposure per radiographic series) during the four quarters with an average re-exposure rate of 45%. Table 3 summarises the mean overall total film reexposure rate during the same 12-month period with an average re-exposure rate of 4.9%. ANOVA on the data from Tables 2 and 3 revealed that the rates between the quarters varied only between 3% and 6% during the four periods. The re-exposure rates did not vary significantly (Figure 2). The re-exposure rates for the third year students did not show a consistent trend towards improvement during their 1-year rotation in dental radiology.
Discussion One of the guiding principles in teaching radiology to dental students is as low as reasonably achievable (ALARA). Decisions on radiographic prescriptions and re-exposures are based on this principle. Radiographic prescriptions are based on sound selection criteria3,4 that include patient complaint, a detailed medical history and a thorough intra and extraoral examination. Although radiographic selection criteria should be followed universally, a recent study demonstrated that a greater percentage of dental schools in the United States and Canada that used selective radiography in accordance with the FDA guidelines in 1987, switched to routine radiography by 2002 than schools that switched in the opposite direction.5 The 20-year positive trend of using selective radiography for the dental school patient population at dental schools in the United States and Canada had Table 1 Re-exposure rates for staff dental assistants and students
Group
Radiographic series with no re-exposures
Radiographic series with at least one re-exposure
Total number of radiographic series’
Staff Students Total
778 (97.6%) 636 (55.1%) 1414 (72.5%)
19 (2.4%) 518 (44.9%) 537 (27.5%)
797 (100%) 1154 (100%) 1951 (100%)
Comparison of re-exposure rates M Mupparapu et al
Table 2
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Mean rates of at least one re-exposure per set during a 12-month period for students (^SE) 95% Confidence interval for mean
Quarter
Count
Mean
Standard deviation
Standard error (SE)
Lower bound
Upper bound
1 2 3 4 Total
287 289 289 289 1154
0.44 0.36 0.48 0.51 0.45
0.49675 0.48179 0.50050 0.50067 0.49756
0.02922 0.02834 0.02944 0.02940 0.01463
0.3785 0.3075 0.4230 0.4559 0.4199
0.4935 0.4191 0.5389 0.5717 0.4773
plateaued in 1997 and, according to the author, the dental schools are not capitalizing on the dose-sparing and costsaving benefits of selective radiography.5 When a radiograph is rendered non-diagnostic due to a technique or processing error and the area of interest cannot be visualized in another radiograph, a decision to obtain a re-exposure of the same anatomical area is made. Re-exposures should only be made when it is absolutely necessary. The goal of dental radiology teaching programmes is to teach sound decision making with radiographic prescriptions and proper radiographic technique while abiding by ALARA. Students can practice ALARA by using radiographic techniques such as rectangular collimation6 and also by minimizing technique errors requiring re-exposure. It was assumed that rectangular collimation might result in increased collimator cut errors leading to an overall increase in the re-exposure rate. Parks7 had addressed this issue after studying the use of rectangular collimation and the resultant errors generated and found that operator skill did not appear to influence the number or types of errors/re-exposures. Other studies are warranted to identify areas where dental radiology educators can improve their teaching programmes. For example, overall re-exposure rates are very useful data, but a more detailed data collection may reveal outliers that skew the results. In such cases, those students who perform poorly can be identified and an intervention may prove beneficial to all. Although our study found a significant difference in the radiographic series re-exposure rates between the staff (2.3%) and students (44%), it is possible that there were common radiographic errors between the two groups of users that need to be identified. To determine whether this is accurate or not, further studies are needed using detailed data input recording the number as well as the reason for re-exposures in every case. According to Bridgman,8 though faulty techniques in intraoral radiography are hard to categorise, it is important that an organized approach to recording these faulty techniques is implemented so that these technique errors can be analysed Table 3
and corrected, eventually allowing patients to be exposed to the minimum amount of radiation possible. Although the re-exposure rate was high for our students when radiographic series were compared, further analysis revealed that the actual number of film re-exposures in total was a mere 4.9%. Our results also show that the students’ re-exposure rate did not significantly improve during their yearlong rotation in the radiology clinic, varying only between 3% and 6%. It is currently not known why there is a lack of significant skills improvement over time among the students. A computer network-based data collection procedure has now been implemented to record film and patient data, as well as student and staff re-exposure data. With this programme, the student’s or staff dental assistant’s performance can be assessed either individually or as a group over time. Nixon and colleagues1 in the United Kingdom did the only other study in the literature that looked into reexposure rates in a dental radiology department. They performed an audit of film reject and repeat rates over a 6-month period in a dental radiology department and reported an overall reject rate of 3.06%. They found a significant difference in reject rates between dental staff and students in training. This is comparable with the present study’s overall re-exposure rate of 2.6% (4.9% for the third year dental students and 0.2% rate for the dental assistants). This study has documented the re-exposure rates of dental radiographic films for the staff dental assistants and the third year dental students over a period of 1 year. The limitation of our study was the lack of detailed film fault data in the entry logs. Patient data were retrospectively studied, and the student work sheets recording the type of film faults from each study were no longer available. This problem has already been addressed in our facility by implementing detailed computer-based entries, documenting film faults and re-exposure data for both students and staff dental assistants. Earlier research showed that even though dental students initially had problems identifying film faults, they had the knowledge and competency in the
Mean rates of film total re-exposure for students during a 12-month period (^SE) 95% Confidence interval for mean
Quarter
Count
Mean
Standard deviation
Standard error (SE)
Lower bound
Upper bound
1 2 3 4 Total
287 289 289 289 1154
0.0600 0.0493 0.0343 0.0518 0.0488
0.0808 0.0665 0.0563 0.0779 0.0715
0.0048 0.0039 0.0033 0.0046 0.0021
0.0506 0.0416 0.0278 0.0428 0.0447
0.0694 0.0570 0.0408 0.0608 0.0530 Dentomaxillofacial Radiology
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Figure 2
Mean film re-exposure values of students in a 1-year period (by quarter)
assessment and correction of faults once identified.2 Future studies similar to this may be directed towards identification of the students that consistently perform inadequately, resulting in an increase in the overall re-exposure rate for the class. Interventions aimed at these students may significantly improve the overall student performance in a given time period. This study was intended to help dental
educators identify limitations of the clinical radiology training of dental students and the results may be helpful for any curricular modifications that may be required. Further studies are warranted to achieve the ultimate goal of providing students with the optimal educational experience in dental radiology while minimizing radiation to the patient.
References 1. Nixon PP, Thorogood J, Holloway J, Smith NJ. An audit of film reject and repeat rates in a department of dental radiology. Br J Radiol 1995; 68: 1304 –1307. 2. Rushton VE, Hirschmann PN, Bearn DR. The effectiveness of undergraduate teaching of the identification of radiographic film faults. Dentomaxillofac Radiol 2005; 34: 337 – 342. 3. ADA Council on Scientific Affairs, An update on radiographic practices: information and recommendations. J Am Dent Assoc 2001; 132: 234 – 238. 4. ADA Council on Dental Benefits programs, US Department of Health and Human Services, Food and Drug Administration. The selection of patients for dental radiographic examinations. Available at: http:// www.fda.gov.cdrh/radhlth/adaxray-1.pdf. Revised 2004. Accessed 10 April 2006, pp. 1 –27.
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5. Kantor ML. Longitudinal trends in the use of individualized radiographic examinations at dental schools in the United States and Canada. J Dent Educ 2006; 70: 160 –168. 6. National Council on Radiation Protection and Measurements (NCRP). Radiation protection in dentistry. NCRP Report No. 145, Bethesda, MD: NCRP; 2003, pp. 14 – 39. 7. Parks ET. Errors generated with the use of rectangular collimation. Oral Surg Oral Med Oral Pathol 1991; 71: 509 – 513. 8. Bridgman JB, Campbell DJ. An update on dental radiology: quality and safety. N Z Dent J 1995; 91: 16 – 21.
