RADIOGRAPHIC ERRORS IN DENTISTRY

Radiographic errors in dentistry represent a significant clinical concern, as they can compromise diagnostic accuracy, increase radiation exposure due to retakes, and lead to improper treatment planning. These errors can be broadly categorized into technique/positioning errors, processing errors, and equipment-related errors, with different manifestations across intraoral radiography (periapical and bitewing), extraoral radiography (panoramic and cephalometric), and advanced 3D imaging (cone beam computed tomography, CBCT).

1. Intraoral Radiographic Errors

1.1. Periapical Radiography

Studies have consistently shown that intraoral radiographic errors are highly prevalent. Patel and Greer (1986) evaluated 24,150 radiographs from complete-mouth surveys taken by dental students and found that 2,238 radiographs (approximately 9.3%) were clinically unacceptable due to technical errors. The four major errors identified were:

• Incorrect film placement (64.9% of errors)
• Incorrect vertical angulation (11.75%)
• Cone cutting (11.17%)
• Incorrect horizontal angulation (4.8%) [1]

In an earlier study, Patel (1979) reported that out of 6,763 exposures from 283 complete-mouth surveys, 890 radiographs were clinically unacceptable, yielding an error rate of 13.1 errors per 100 radiographs. The three most common errors were incorrect film placement (49.9%), cone cutting (20.8%), and incorrect vertical angulation (12.5%) [2].

Film placement errors occur when the receptor does not cover the intended anatomical area. In periapical radiography, this often results in the apex of the tooth not being visible (missing the periapical region). Senior et al. (2018), studying digital intraoral imaging re-exposure rates among dental students, found that inadequate capture of the periapical area was the most common error requiring re-exposure for periapical images, accounting for 37% of retakes with solid-state sensors and 6% with photostimulable phosphor (PSP) plates [3].

Cone cutting occurs when the x-ray beam is not properly aligned with the receptor, resulting in a portion of the film not being exposed. This error is directly related to improper positioning of the x-ray tube head relative to the film/sensor holder.

Vertical angulation errors cause elongation or foreshortening of the tooth image. Excessive vertical angulation (too steep) results in foreshortened tooth images, while insufficient vertical angulation (too flat) produces elongated teeth. Patel and Greer noted incorrect vertical angulation as a significant source of error (11.75%), with improvement observed as students progressed through their training [1].

Horizontal angulation errors cause overlapping of proximal surfaces, particularly problematic for diagnosing proximal caries and assessing periodontal bone levels. This error was identified in 4.8% of cases in the Patel and Greer study [1].

1.2. Bitewing Radiography

Bitewing radiographs are essential for detecting proximal caries and assessing alveolar bone levels, but they are highly susceptible to errors. Nysether and Hansen (1983) examined 2,409 pairs of bitewing films from public dental clinics and found that only 4.6% fulfilled all criteria for correct bitewing radiographs. The errors identified included:

• Incorrect film position – 42.7% of films
• Wrong horizontal angulation – 10.6%
• Cone cutting – 4.3%
• Under/overaxial exposures – 2.2%
• Disturbing spots – 88.1% (most common artifact)
• Insufficient washing – 7.7%

The study highlighted that unnecessary errors reducing the readability of bitewing radiographs were frequently found, and steps should be taken to improve radiographic standards [4].

In the digital era, Senior et al. reported that the most common error requiring re-exposure for bitewing images was incorrect placement of the receptor too far mesially or distally (29% for sensors, 18% for PSP) [3].

1.3. Digital Intraoral Imaging Errors

The transition from film-based to digital radiography has introduced new categories of errors while reducing others. Yeung and Wong (2021) conducted a literature review of reject rates in dentomaxillofacial radiology and reported an average reject rate of 11.25% for bitewings and 16.38% for periapical radiographs [5].

PSP plate artifacts are specific to digital radiography. Chiu et al. (2008) analyzed 15,912 scanned digital images and identified 643 image artifacts. The main causes were:

• Operator errors (n = 554, 86.2%) – including improper handling, incorrect positioning, and contamination
• PSP plate defects (n = 60) – scratches, wear and tear
• Scanning errors (n = 29) – laser scanner malfunctions, dust on the scanner

The study emphasized that modified clinical techniques, such as using protective barriers, can greatly reduce artifacts caused by wearing of the sensor plate [6].

2. Extraoral Radiographic Errors

2.1. Panoramic Radiography

Panoramic radiography is the most commonly performed extraoral dental examination, but it requires precise patient positioning due to the narrow focal trough (image layer) [7].

Frequency of errors: Dhillon et al. (2012) evaluated 1,782 panoramic radiographs and found that only 196 (11%) were error-free, while 1,586 (89%) contained positioning errors. Only 11% were judged as "excellent" quality, 64.1% were "diagnostically acceptable," and 24.9% were considered poor quality [8].

Common positioning errors in panoramic radiography, as classified by Rondon et al. (2014), include [7]:

1. Failure to position the tongue against the palate – This is the most common error, creating a dark radiolucent shadow (air space) over the roots of the maxillary teeth. Dhillon et al. found this in 55.7% of radiographs [8].

2. Chin tipped too high – Causes the hard palate and nasal floor to overlap with the maxillary tooth apices; the mandibular incisors appear blurred.

3. Chin tipped too low – The mandibular symphysis overlaps the roots of the mandibular anterior teeth; the condyles may be cut off.

4. Slumped (slouched) position – The patient's spine is not straight, creating a radiopaque shadow over the midline.

5. Patient positioned too far forward – The anterior teeth appear narrow and blurred (in the focal trough but too close to the tube).

6. Patient positioned too far back – The anterior teeth appear widened and blurred.

7. Head tilted – One side of the image appears vertically elongated while the opposite side is foreshortened.

8. Head turned to one side – The side toward the rotation appears narrower.

9. Patient movement – Causes overall blurring of the image; least common but most detrimental to image quality.

10. Failure to remove metal objects/artifacts – Jewelry, eyeglasses, hearing aids, and dental prostheses create radiopaque artifacts that obscure anatomy.

Peretz et al. (2012) compared errors in digital panoramic radiographs of patients with mixed dentition versus permanent dentition. They found significantly fewer errors in the mixed dentition group. However, "positioning too forward" was significantly more prevalent in the mixed dentition group, while "slumped position" and "non-positioning of chin properly" prevailed in the permanent dentition group. The study noted that diagnostic ability could be improved by manipulating brightness or contrast in nearly 45% of all radiographs [9].

Choi et al. (2012) evaluated 297 panoramic radiographs from 99 Korean dental clinics and found that the main causes of image quality degradation were: positioning errors (139 errors), processing errors (135), radiographic unit issues (50), and anatomic abnormalities (13). Only 17 images (5.7%) were deemed "optimal for obtaining diagnostic information" [10].

2.2. Cephalometric Radiography

Cephalometric radiographs are used primarily in orthodontics for growth assessment and treatment planning. Baumrind and Frantz (1986) identified several sources of error, including:

• Projection errors – head positioning variations
• Tracing errors – identification of landmark points
• Measurement errors – digitizer and software inaccuracies

Errors in head positioning (rotation, tilt, or flexion/extension) can significantly alter linear and angular measurements used in cephalometric analysis [11].

3. Processing and Darkroom Errors

Despite the shift toward digital imaging, some practices still use conventional film-based radiography, and even digital systems have processing-related issues.

Film processing errors include:

• Under/overdevelopment – Affects density and contrast
• Under/over-fixation – Incomplete clearing of unexposed silver halide
• Insufficient washing – Leads to yellow-brown stains and image fading over time (7.7% of films in the Nysether and Hansen study) [4]
• Chemical contamination – Developer splashes on undeveloped film cause black spots; fixer contamination causes white spots

Digital processing artifacts can arise from:

• Inappropriate image enhancement (brightness, contrast manipulation)
• Sensor calibration issues
• Exposure indicator (S-number) misinterpretation leading to under- or over-exposure

4. CBCT Imaging Errors and Artifacts

Cone beam computed tomography (CBCT) has become essential for implant planning, orthodontic assessment, and maxillofacial surgery, but it is susceptible to various artifacts.

Schulze et al. (2011) comprehensively reviewed CBCT artifacts, categorizing them as [12]:

1. Beam hardening artifacts – Occur when the polychromatic x-ray beam passes through dense objects (teeth, bone, metal restorations, implants). Low-energy photons are preferentially absorbed, causing dark bands and streaks (cupping artifacts) adjacent to dense structures.

2. Metal artifacts – Particularly severe with high-density materials such as amalgam restorations, gold crowns, and zirconium implants. Fontenele et al. (2018) demonstrated that the magnitude of CBCT artifacts is influenced by the type of implant material and the specific CBCT unit. Zirconium implants produced more pronounced artifacts than titanium implants, with higher standard deviation values and lower contrast-to-noise ratios, especially in regions closer to the implant [13].

3. Patient movement artifacts – Even slight movement during the scan (which typically lasts 10–40 seconds) causes blurring, double contours, and reduced image quality. Movement artifacts in CBCT can significantly reduce diagnostic image quality [14].

4. Partial volume averaging – Occurs when a voxel contains multiple tissue types, resulting in inaccurate gray values at tissue boundaries.

5. Ring artifacts – Caused by defective or miscalibrated detector elements, appearing as concentric rings in the reconstructed image.

6. Aliasing artifacts – Related to undersampling (insufficient number of projections), appearing as fine streak patterns.

7. Cone beam effect – Due to the conical shape of the x-ray beam, structures at the periphery of the field of view (especially in the superior-inferior direction) are less accurately reconstructed.

Yeung and Wong reported an average reject rate of 2.77% for CBCT in clinical practice, which is relatively low compared to intraoral imaging, but positioning errors and patient movement remain common causes for retakes [5].

5. Classification of Radiological Errors

Beyond technical errors, interpretive errors also occur in dental radiology. Onder et al. (2021) provided a comprehensive classification of radiological errors, which is applicable to dentistry [15]:

• Perception errors – Failing to see an abnormality that is present on the image (satisfaction of search, distraction)
• Cognitive errors – Misinterpreting the finding due to knowledge gaps or faulty reasoning
• Technical errors – Poor image quality due to technique, positioning, or equipment issues
• System errors – Communication breakdowns, lost images, or reporting delays

Cognitive biases such as anchoring (fixing on an initial interpretation despite contradictory evidence), confirmation bias (seeking evidence that supports a preconceived diagnosis), and availability bias (overestimating the likelihood of recent or memorable diagnoses) can also contribute to diagnostic errors [15].

6. Clinical Significance and Recommendations

The high prevalence of radiographic errors has significant clinical implications:

• Missed pathology – Caries, periapical lesions, periodontal bone loss, or tumors may go undetected
• Unnecessary radiation exposure – Retakes increase patient radiation dose, violating the ALARA (As Low As Reasonably Achievable) principle
• Increased costs – Wasted time, materials, and equipment usage
• Delayed treatment – Poor-quality images require rescheduling and repeated appointments

Strategies to reduce radiographic errors include:

1. Standardized training – Patel and Greer demonstrated that students showed statistically significant improvement from the first to the third quarter of clinical training, with a minimum of 20–25 complete mouth surveys needed to achieve minimal technical proficiency [1].

2. Quality assurance programs – Regular reject analysis (documenting and analyzing all retaken images) helps identify systemic issues. Choi et al. recommended routine quality evaluation using standardized clinical image quality charts [10].

3. Proper use of positioning aids – Film holders, beam-aiming devices (e.g., Rinn holders), and sensor stabilizers significantly reduce errors.

4. Patient instruction – For panoramic imaging, clear instructions regarding tongue positioning, chin placement, and immobilization are essential [7,8].

5. Equipment maintenance – Regular calibration of x-ray units, processors, and digital sensors prevents equipment-related errors.

References

[1]Patel JR, Greer DF. Evaluating student progress through error reduction in intraoral radiographic technique. Oral Surg Oral Med Oral Pathol. 1986 Nov;62(5):471-474
DOI: 10.1016/0030-4220(86)90300-2[2]Patel JR. Intraoral radiographic errors. Oral Surg Oral Med Oral Pathol. 1979 Nov;48(5):479-483
DOI: 10.1016/0030-4220(79)90081-1[3]Senior A, Winand C, Ganatra S, Lai H, Alsulfyani N, Pachêco-Pereira C. Digital Intraoral Imaging Re-Exposure Rates of Dental Students. J Dent Educ. 2018 Jan;82(1):54-61
DOI: 10.21815/jde.018.011[4]Nysether S, Hansen BF. Errors on dental bitewing radiographs. Community Dent Oral Epidemiol. 1983 Oct;11(5):286-288
DOI: 10.1111/j.1600-0528.1983.tb01895.x[5]Yeung AWK, Wong NSM. Reject Rates of Radiographic Images in Dentomaxillofacial Radiology: A Literature Review. Int J Environ Res Public Health. 2021 Jul 29;18(15):8076
DOI: 10.3390/ijerph18158076[6]Chiu HL, Lin SH, Chen CH, Wang WC, Chen JY, Chen YK, Lin LM. Analysis of photostimulable phosphor plate image artifacts in an oral and maxillofacial radiology department. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008 Oct;106(5):749-756
DOI: 10.1016/j.tripleo.2008.01.003[7]Rondon RHN, Pereira YCL, Nascimento GC. Common positioning errors in panoramic radiography: A review. Imaging Sci Dent. 2014 Mar;44(1):1-6
DOI: 10.5624/isd.2014.44.1.1[8]Dhillon M, Raju SM, Verma S, Tomar D, Mohan RS, Lakhanpal M, Krishnamoorthy B. Positioning errors and quality assessment in panoramic radiography. Imaging Sci Dent. 2012 Dec;42(4):207-212
DOI: 10.5624/isd.2012.42.4.207[9]Peretz B, Gotler M, Kaffe I. Common errors in digital panoramic radiographs of patients with mixed dentition and patients with permanent dentition. Int J Dent. 2012;2012:584138
DOI: 10.1155/2012/584138[10]Choi BR, Choi DH, Huh KH, Yi WJ, Heo MS, Choi SC, Bae KH, Lee SS. Clinical image quality evaluation for panoramic radiography in Korean dental clinics. Imaging Sci Dent. 2012 Sep;42(3):183-190
DOI: 10.5624/isd.2012.42.3.183[11]Baumrind S, Frantz RC. The reliability of head film measurements. 1. Landmark identification. Am J Orthod. 1971 Aug;60(2):111-127.[Note: The DOI I found earlier was - let me use the correct one]
DOI: 10.1016/0002-9416(71)90028-2[12]Schulze R, Heil U, Grob D, Bruellmann DD, Dranischnikow E, Schwanecke U, Schoemer E. Artefacts in CBCT: a review. Dentomaxillofac Radiol. 2011 Jul;40(5):265-273
DOI: 10.1259/dmfr/30642039[13]Fontenele RC, Nascimento EHL, Vasconcelos TV, Noujeim M, Freitas DQ. Magnitude of cone beam CT image artifacts related to zirconium and titanium implants: impact on image quality. Dentomaxillofac Radiol. 2018 Sep;47(6):20180021
DOI: 10.1259/dmfr.20180021[14]Spin-Neto R, Matzen LH, Schropp L, Liedke GS, Gotfredsen E, Wenzel A. Factors affecting patient movement and re-exposure in cone beam CT examination. Dentomaxillofac Radiol. 2015;44(1):20140338
DOI: 10.1259/dmfr.20140338[15]Onder O, Yarasir Y, Azizova A, Durhan G, Onur MR, Ariyurek OM. Errors, discrepancies and underlying bias in radiology with case examples: a pictorial review. Insights Imaging. 2021 Apr 26;12(1):51
DOI: 10.1186/s13244-021-00986-8