X-ray Beam Angulation Research Articles

A novel method for determining the X-ray beam angulation of the supraspinatus outlet view.

Rapid and accurate quantification of the supraspinatus outlet view (SOV) is a clinical challenge. To quantify the X-ray beam angle of the SOV using the horizontal angle of the subscapular spine line (SSSL) and to further verify the feasibility of this method. A total of 119 patients who underwent shoulder computed tomography (CT) examination were enrolled in the retrospective study. Three-dimensional (3D) CT reconstruction was performed and manually adjusted to provide the position similar to SOV. The rotation angle of the 3D image along the long axis of the human body (marked as β) was obtained. The horizontal angle of SSSL (marked as α) was measured on the anteroposterior localizer image of shoulder CT. Pearson correlation and linear regression correlation analysis were performed. In addition, the first-time success rate between the experience-based group and the measurement-based group were compared to verify the novel method. We found a linear correlation between α and β (r = 0.962; P = 0.000). There was no significant correlation between the experience-based group and the measurement-based group in terms of age (P = 0.500), sex (P = 0.397), and side (P = 0.710), but there was a significant statistical difference in the first success rate between the two validation groups (χ2 = 5.808a, P = 0.016). This novel quantitative measurement method for determining the X-ray beam angle of SOV using the horizontal angle of SSSL is feasible.

X-ray beam angulation can compromise 2-dimensional diagnosis of interradicular space for mini-implants

The aim of this research was to evaluate the influence of x-ray projection geometry on interradicular space of the posterior maxillary arch. Cone-beam computed tomography (CBCT) scans of 32 patients (16.85±4.93years) who met the selection criteria were enrolled. One hundred ninety-two interradicular sites of the posterior maxillary arch were evaluated. Before measurements, each side of the maxillary arch was orientated in all 3 planes of space to obtain CBCT synthesized periapical radiographs with 0° projection geometry (orthogonal x-ray beam-orthogonal X-ray angulation [OX]). Standardized CBCT axial rotations (10°, 20°, -10°, and -20°) were used to simulate periapical radiographs taken with mesial and distal angulation of the x-ray beam (mesial x-ray angulation [MX] and distal x-ray angulation [DX]). Interradicular space widths were measured on OX, MX, and DX CBCT synthesized periapical radiographs. Measurements were performed parallel to the occlusal plane at 3mm and 6mm apical to the midpoint of the alveolar crest. Interradicular distances were statistically compared (P<0.05). Interradicular distances measured on MX and DX CBCT synthesized periapical radiographs were significantly smaller than those measured on OX. Interradicular distance was significantly correlated with the horizontal angulation of the x-ray beam. X-ray projection angle was the most influential variable on interradicular distance. About 30% reduction in interradicular space was observed for every 10° of deviation from orthogonal x-ray. Two-dimensional radiographs obtained away from the 0° projection geometry can reduce the actual interradicular space for mini-implants, inducing misdiagnosis.

Influence of the ankle position and X-ray beam angulation on the projection of the posterior facet of the subtalar joint.

Using digitally reconstructed radiographs (DRRs), we determined how changes in the projection angle influenced the assessment of the subtalar joint. Weightbearing computed tomography (CT) scans were acquired in 27 healthy individuals. CT scans were segmented and processed to create DRRs of the hindfoot. DRRs were obtained to represent 25 different perspectives to simulate internal rotation of the ankle with and without caudal angulation of the X-ray beam. Subtalar joint morphology was quantified by determining the joint space curvature, subtalar inclination angle (SIA), calcaneal slope (CS), and projection of the subtalar joint line on three-dimensional (3-D) reconstructions of the calcaneus. The curvature of the projected joint space was altered substantially over the different DRR projections. Simulated caudal angulation of the X-ray beam with respect to the ankle decreased the SIA and CS significantly. Internal rotation also had a significant impact on the SIA and CS if the X-ray beam was in neutral or in 10° of caudal angulation. An antero-posterior (AP) view of the ankle showed the posterior area of the posterior facet, whereas a more anterior area was visible with internal rotation of the foot and caudal angulation of the X-ray beam. Internal rotation of the foot of 20° is recommended to assess the posterior aspect of the posterior facet, whereas a combined 20° internal rotation of the foot and 40° caudal angulation of the X-ray beam is best to assess the anterior aspect of the posterior facet of the subtalar joint.

The development of new image receptor-holding instruments with appropriate horizontal X-ray beam angulation for periapical radiographs.

This study aimed to develop new image receptor-holding instruments with appropriate horizontal X-ray beam angulation, based on the anatomical data of posterior region interproximal surfaces derived from archived CT images. CT images of 92 patients with sound upper and lower dental arches were collected from our CT database and analyzed to determine the angles between the tangential interproximal contact line and the central groove line of posterior teeth. The average angle for each site was calculated and used to modify instruments using a three-dimensional printer. The utilities of the conventional and the modified instruments for viewing proximal surfaces were compared using two dry skulls. The right and left sides of each site, except for the lower second premolar and first molar sites, did not differ significantly. The difference between the sites was 2.0°; hence, we calculated mean values for the two sides at each site. In the maxilla, the angles of the first and second premolar, second premolar and first molar, and first and second molar to the groove line were 83.9° (±5.4°), 84.4° (±3.9°), 81.6° (±5.1°), while those in the mandible were 85.0° (±9.2°), 85.0° (±4.0°), and 90.6° (±4.9°), respectively. The holding instruments modified to 80° demonstrated better proximal viewing ability in the upper molar region than conventional instruments. The mean angles of the interproximal surfaces were determined from CT data. The image receptor holding-instruments were modified according to these angles to allow appropriate X-ray angulation, which facilitated improved observation of the proximal surfaces of teeth in the posterior region in this pilot in vitro study.

In vitro effect of changing the horizontal angulation of X-ray beam on the detection of proximal enamel caries in bitewing radiographs.

Bitewing radiography is an important modality useful for the evaluation of teeth in patients of various ages and in different stages of tooth eruption. Clinical examination of proximal surfaces for caries may result in false negative results, especially in tight contact areas. Thus, radiography, as an adjunct to clinical examination, is used as a routine diagnostic modality for caries detection. The objective of this study was to assess the in vitro effect of changing the horizontal angulation of X-ray beam on the detection of proximal enamel caries in bitewing radiographs. This in vitro study was conducted on 150 caries-free human premolars (code: p/16/35/9/210). The teeth were randomly divided into 3 groups (n = 50). Group 1 served as the control group and no carious lesions were induced in this group. Teeth in groups 2 and 3 were immersed in demineralizing solution for 2 and 4 months, respectively. After induction of caries and its radiographic confirmation, the teeth were mounted in wax in groups of 3 and bitewing radiographs were obtained at 0°, 5°, 10° and 15° horizontal angles. The sensitivity values of bitewing radiographs at 0°, 5°, 10° and 15° horizontal angles were 88%, 90%, 88%, 92% in group 2 and 88%, 94%, 94% and 94% in group 3, respectively. The specificity values of bitewing radiographs at 0°, 5°, 10° and 15° horizontal angles were 92%, 86%, 84% and 76%. The accuracy of bitewing radiographs at 0°, 5°, 10° and 15° horizontal angles was 89.3%, 90%, 88.7% and 87.3%, respectively. The highest diagnostic accuracy was obtained at 5° horizontal angle for caries detection; however, the difference in this regard among the tested horizontal angles was not statically significant (p = 0.846). Based on the results of this study, changing the horizontal angulation has no significant effect on the detection of proximal enamel caries in bitewing radiographs.

Influence of X-ray beam angulations on the detection of horizontal root fractures

Aims: The aim of this study was to evaluate the variation of vertical angle for detection of fractures. Materials and Methods: Twenty-five (25) single-rooted premolar teeth were divided into two groups, fractured teeth (n = 15) and non-fractured teeth (n = 10). Artificially fractured teeth were classified according to location, number of fragments, and direction of fracture line: Horizontal, oblique, or complex. The tooth fragments were juxtaposed with cyanoacrylate, and the specimens (fractured and non-fractured) were placed individually in the dental alveolus of a human jaw with the aid of silicone rubber impression material and submitted to eight periapical radiographs in a digital sensor with a vertical range of 10 degrees (−40, −30, −20, −10, 0, +10, +20, +30). Three examiners evaluated the characteristics of the fractures and their correlation with the radiographic diagnosis (perceived or not) by varying the vertical angle. Statistical Analysis: Descriptive analysis was performed through the analytical comparison and Kappa test inter-examiner. Results: Among the three examiners, inter-examiner Kappa value was 0.536. The radiographic identification of root fracture in the 15 prepared samples was 60% (nine) at angle 0, and at the angles of +10, −10, and −20, it was less than 50%. Conclusions: Multiple radiographs with variations of vertical angle are fundamental to facilitate the diagnosis of horizontal root fractures in premolars.

ASSESSMENT OF FIVE OBLIQUE RADIOGRAPHIC PROJECTIONS OF THE CANINE TEMPOROMANDIBULAR JOINT

Investigation of temporomandibular joint (TMJ) disease requires a clear diagnostic image, which can be challenging to obtain using conventional radiography. The aim of this study was to compare five different oblique radiographic views with the head in lateral recumbency, assessing the clarity of visualization of the normal TMJ anatomy. The views under investigation were the laterorostral-laterocaudal oblique at a 10° and 20° rotation of the head ("nose-up" view), laterorostral-laterocaudal oblique with a rostrocaudal X-ray beam angulation of 10° and 20°, and a parallax view with the beam centered over C2 and collimated to include the TMJ region, using the divergence of the X-ray beam to project the TMJs separately on the radiograph. The views were performed on both TMJs of thirty canine cadavers and were graded independently by experienced and inexperienced observers. Grading was performed on the mandibular fossa, condylar process, joint space, retroarticular process, and the overall TMJ, and was based on a four-point scale. Mean grades for each component and for the overall joint were compared for each observer and each projection. Mean grades were significantly (P < 0.05) higher for the "Nose-up" projections than the angled beam or parallax projections, as was interobserver agreement, and both observers showed significantly higher (P < 0.05) mean grades for the 20(o) "Nose-up" angulation than the 10(o) "Nose-up" angulation. These results suggest that a latero 20(o) rostral-laterocaudal oblique gives the best representation of the anatomy of the TMJ of the dog of the projections assessed, and should be considered when investigating clinical cases of TMJ disease.

Diagnosis and clinical management of teeth with vertical root fractures: a literature review

The diagnosis of vertical root fracture (VRF) is at times complicated for lack of specific signs, symptoms and/or radiographic features. It constitutes an important threat to the tooth’s prognosis during and after root canal therapy and may result in root or tooth extraction. Early detection and management of VRF remain a vexing issue that has caused needless stress for both the dentist and the patient. This paper presents an overview of the prevalence and multifactorial aetiology of VRF, the clinical and radiographic features of this disorder, the importance of correct diagnosis and treatment options available for both anterior and posterior teeth. An exhaustive review of literature was done using Medline to bring out various etiologic factors, clinical presentations, radiographic features and treatment alternatives available for VRF. There are, however, many specific clinical and radiological signs which when present, can alert clinicians to the existence of a fracture. Even though VRF are commoner in endodontically treated teeth, its occurrence in non-restored teeth has been described. Clinical signs and symptoms vary according to the position of the fracture, tooth type, duration after fracture, periodontal condition of the tooth and architecture of the bone adjacent to the fracture. The radiographic appearance of teeth with VRF is variable depending on the angulation of X-ray beam in relation to the plane of the fracture, the time after fracture and the degree of separation of the root fragments. It is important to recognize the sometimes subtle findings in VRF so that patient can be properly informed about the prognosis and the potential for successful treatment in affected tooth\teeth.

Charge couple ddeviceセンサーを用いたディジタル歯科用X線撮影システムにおけるX線投影角度:隣接面齪蝕診断能に及ぼす影響の検討

Charge couple ddeviceセンサーを用いたディジタル歯科用X線撮影システムにおけるX線投影角度:隣接面齪蝕診断能に及ぼす影響の検討

Comparative dental radiographic identification using flat panel CT

A skull without lower jaw was found and brought in for identification. It was suspected to be that of a man reported missing five years ago. An undated antemortal dental chart and two dental films of the 1st and 2nd dental quadrants, both taken about 4 years before the man went missing, were available for comparison. The method of choice in solving the identity question was comparative dental radiography. Despite numerous attempts, it was not possible to obtain radiographs of the upper jaw that duplicated the X-ray beam angulation of the antemortem dental films. The skull was thus scanned with a multislice computed tomography (MSCT) scanner, and virtual radiographs with the desired angulation were generated from the data with the maximum intensity projection (MIP) technique. The resulting virtual radiographs could, however, not be used for superimposition with the antemortem radiographs because of their poor resolution and the occurrence of artifacts caused by metallic dental fillings. The upper jaw was therefore scanned again, this time with a high resolution eLU-CT (eXplore Locus Ultra flat panel CT). The resulting eLU-CT datasets were visualized with the MIP technique and yielded virtual radiographs that could be compared with the antemortem radiographs. Positive identification could be assumed with near certainty after dental features could be matched in the superimposition of antemortem and postmortem radiographs. In the presented case, eLU-CT was used for the first time for a comparative dental radiographic identification.

The effect of horizontal X-ray beam angulation on the detection of furcation defects of mandibular first molars in intraoral radiography

The aim was to investigate the effect of changes in horizontal X-ray beam angulation in intraoral radiography on the detection accuracy of furcation defects in the mandibular first molar, and to examine the anatomical relationship between the roots and furcation area as a possible cause of changes in detectability. Simulated furcation defects with various depths were created in five mandibular first molars. Intraoral radiographs were taken at various horizontal angulations of the projection beams. The diagnostic accuracies were determined based on receiver operating characteristic analysis. The geometric relationship that might influence the accuracy was investigated through use of a compact cone beam CT in 59 first molar areas. Although the horizontal angulations showing the highest accuracies were shifted mesially, no differences were found between the angles of -10 degrees and 20 degrees . The relationship between the roots and the furcation area was relevant to the range of angulations showing high detectabilities. The angulations traditionally used for detecting proximal caries are also suitable for detecting furcation defects.

Effects of imaging system and exposure on accurate detection of the second mesio-buccal canal in maxillary molar teeth

The objectives of this study were to determine observer ability to detect the second mesio-buccal canal (MB2) in maxillary molars using analog film, CMOS, and photostimulable phosphor x-ray detectors across a wide range of radiation exposures and to determine the optimal exposures for these modalities accurately detecting presence of the MB2. Using 6 experimental models with 2 maxillary molars in each, images were generated with the 3 detector modalities at nominal x-ray beam angulations of 0 degrees and 10 degrees across a range of radiation exposures. Observers independently assessed presence of the MB2 in images presented in random order. Horizontal root sections were then evaluated to determine true MB2 presence. For single images at optimal exposures, the correct number of mesiobuccal canals could be identified 55% of the time for CMOS (RVG 6000), 44% of the time for analog x-ray film (InSight), and 39% of the time for photostimulable phosphor (DenOptix). Statistically significant differences were observed between the imaging modalities (chi2 = 23.4, crucial value = 5.99, P < or = .05). RVG 6000 CMOS outperformed both DenOptix photostimulable phosphor (z score = -5.5) and InSight analog direct exposure x-ray film (z score = 4). Exposure affected the rate of accuracy for MB2 detection across the exposure range tested for RVG 6000 and for film, but not to any appreciable degree for DenOptix. The CMOS detector (RVG-6000) performed best for evaluating presence of the MB2. This was the only modality to exceed 50% reliability with optimal exposure when single images were considered.

Effect of X-ray beam angulation and intraradicular contrast medium on radiographic interpretation of lower first molar root canal anatomy.

To compare evaluator radiographic interpretation of noncontrasted and contrasted root canal anatomy on radiographs taken at a 0 or 30 degrees mesial angle to the orthoradial orientation. Pulp tissue was removed from 20 mandibular first molar teeth using NaOCl irrigation and hand files. Standardized radiographs at 0 and 30 degrees angulation were obtained of each tooth positioned in a dried mandible. Contrast medium (iohexol) was injected passively into the canals and a second pair of corresponding radiographs was obtained. A third pair of radiographs was taken after infusing canals under vacuum with contrast medium. Using set criteria, three evaluators assessed the canal anatomy of the mesial root on radiographs: (i) the number of visible canals, (ii) whether the canal(s) was visible along the entire length of the root, (iii) the location of the canal terminus in relation to the radiographic apex, (iv) configuration of canal(s), (v) level of multiple canals merging and (vi) the presence of lateral canals. The teeth were then cleared for visual assessment. The data were compared using logistic regression and the intra- and interevaluator reliability assessed with the Kappa test. Noncontrasted 0 degrees images were significantly better (P < 0.05) than noncontrasted 30 degrees images for detecting the number of visible canals, whether the canal(s) was visible along the entire length of the root, the location of the canal terminus in relation to the radiographic apex and level of multiple canals merging. The 0 degrees images contrasted by vacuum or passive injection were significantly better (P < 0.05) than 30 degrees images only for assessing whether the canal(s) was visible along the entire length of the root, whilst the 0 degrees image contrasted by passive injection was also better (P < 0.05) at assessing the location of the canal terminus in relation to the radiographic apex. At 30 degrees, contrast medium passively or vacuum introduced improved (P < 0.05) the detection of the number of visible canals, whether the canal(s) was visible along the entire length of the root and configuration of canal(s), whilst vacuum also improved (P < 0.05) the location of the canal terminus in relation to the radiographic apex. Overall, there was no significant difference (P > 0.05) between images contrasted by passive injection or vacuum. Under the conditions of this study, conventional radiographs taken at a 0 degrees orientation provided more information than 30 degrees radiographs. Contrast medium improved radiographic interpretation of canal anatomy, especially when used with 30 degrees radiographs.

Standards of occipitomental radiography for malar bone trauma in a district general hospital

Purpose: There is evidence that unnecessary radiographs are being taken for suspected malar bone trauma. The present study set out initially to examine first, the number of radiographs obtained in a district general hospital for suspected malar bone trauma and whether these could be reduced to one and second, the extent to which the radiographs conformed with the Royal College of Radiologists' (RCR) guidelines on patient selection. However, initial investigation revealed over-prescription by the referring clinicians and deficient radiographic technique by the radiographers. The aim of the study was therefore redefined as an attempt to improve clinical practice and radiographic technique. Material and Methods: A retrospective evaluation (Study I) was undertaken of the radiographs obtained for suspected malar bone trauma of 50 patients, with particular reference to the number and type of the radiographs and the image quality of the occipitomental (OM) views. Blurring was assessed as a measure of patient cooperation. Following an educational programme, Study II was undertaken following the protocol of Study I. The educational programme was repeated and the outcome analysed (Study III). Results: Study I revealed that 98% of the patients had a lateral skull radiograph and 74% more than two radiographs. Eleven different X-ray beam angulations were used for the OM views. Twenty six per cent were unacceptable because of incorrect positioning and inadequate X-ray beam collimation was found in 71%. Results of Study It showed a reduction in the proportion of lateral skull radiographs to 28%: 62% had two radiographs. No significant improvement was noted in image quality. Results of Study III showed a compliance of 76% in reducing the number of unnecessary radiographs. Four per cent had unacceptable positioning and collimation was adequate in 78%. These differences were statistically significant ( P<0·001) in comparison with Study I and II. Conclusions: Effective dose limitation can be achieved in a district general hospital by improving clinical practice and image quality. Further research is needed to evolve improved guidelines for malar bone radiography. A single OM view cannot be recommended until consistent patient positioning is achieved.

Influence of X-ray beam angulation in the detection of proximal caries: Interobserver agreement in the CCD system

The aim of this study was to assess the influence of changes in horizontal and vertical X-ray beam angulation on interobserver agreement in the diagnosis of approximal caries using a charge coupled device-based digital dental imaging system (digital system) in comparison with a conventional film-based radiography (film system).

The effect of alterations in horizontal X-ray beam angulation and bucco-lingual cavity width on the radiographic depth of approximal cavities.

The effects of changes in horizontal X-ray beam angulation and different cavity shape on images of approximal cavities on bite-wing radiographs were examined using a laboratory model. Cylindrical-, rectangular- and cone-shaped bur cut cavities were prepared in the approximal surfaces of 108 teeth and their depth determined using silicone putty impressions. Spatial relationships were controlled by fixing specimens into perspex blocks. Standardized radiographs were taken at baseline (0 degree) and then using pre-angled wedges to imitate horizontal X-ray beam movements of 5, 10 and 15 degrees in both mesial and distal directions. Radiographic cavity depth to the nearest 0.1 mm was measured. Over the range of X-ray beam movements, more than 72% of cavities deepened compared to baseline. As bucco-lingual cavity width increased the magnitude of the depth change increased. For some cylindrical cavities increases equating to 200% over baseline were seen; in some rectangular cavities increases of up to 400% over baseline occurred. The present study suggests that changes in irradiation geometry from baseline are likely to result in a cavity appearing to deepen. In a clinical context over-treatment is therefore the most likely outcome.

Fractal dimension in radiographic analysis of alveolar process bone

This in vitro study examined radiographic fractal dimension changes in alveolar process bone during simulated osteoporosis. Ten specimens of human maxillary alveolar process bone were progressively decalcified, and the percentage of calcium lost at each decalcification stage was quantified. Four radiographs of each specimen, together with an aluminum step-wedge, were exposed at 70 kVp at each stage. The test set of 560 radiographs was digitized, identical bony regions of interest were selected from the density-corrected images of each specimen, the regions were digitally filtered to reduce film-grain noise, and fractal dimension was computed on a line-to-line basis. Correlation analysis quantified the relationship between calcium loss and fractal dimension change. Analysis of variance and Duncan's multiple range test determined whether a difference existed in fractal dimension computed from images at x-ray beam angulations of -5, 0, and +5 degrees. A strong correlation (average r = -0.94, p < or = 0.0037) was found between generalized demineralization and decreasing fractal dimension. In every bone sample fractal dimension changed significantly (p < or = 0.0189) with angular change. Radiographic fractal dimension holds promise for detecting simulated osteoporosis in the maxilla under ideal conditions, but the sensitivity of fractal dimension to small x-ray beam angular change renders its clinical application questionable.

Spatial resolution and angular alignment tolerance in radiometric analysis of alveolar bone change.

This pilot study was undertaken to determine the effect of x-ray beam alignment and spatial resolution on quantification of alveolar bone using radiometric techniques. Six (6) dry mandibles were radiographed at 70 kVp, 10 mA, 0.6 seconds using D-speed film, with a bone chip (2.64, 4.10, or 6.07 mg) present or absent at 7 x-ray beam alignments (0 degree, 2 degrees horizontal, 2 degrees vertical, 4 degrees horizontal, 4 degrees vertical, 6 degrees horizontal, 6 degrees vertical). This resulted in 28 radiographs per mandible. Radiographs were digitized using 50- and 200-microns pixel spatial resolution. Image gray levels were standardized using a simple look-up table shift. Regions of interest (ROIs) were positioned on the alveolar bone where the bone chips had been placed. Cumulative percent histograms (CPH) were calculated for those ROIs. Regression analysis was used to evaluate the relationships between CPH changes and bone chip size as x-ray beam angulation and spatial resolution was varied. The resulting R2 values for angulation ranges of 0 degree to 1.4 degrees, 1.5 degrees, to 2.4 degrees, and 2.5 degrees to 5.5 degrees were: 0.983, 0.941, 0.891 for 50-microns pixel images and 0.869, 0.909, and 0.774 for 200-microns pixel images. We conclude that 50-microns pixel spatial resolution is apparently superior to 200-microns pixel images if radiometric data is to be evaluated. With 50-microns pixel spatial resolution, alignment variations up to 5 degrees may be acceptable in clinical studies, depending on the magnitude of bone change that is to be detected.

A laboratory model for dental radiographic studies.

Though a number of laboratory models have been developed to study the effects of X-ray geometry on the appearance and relative positions of anatomical landmarks, such as the amelocemental junction and alveolar crest, many have failed to take into account the three-dimensional nature of the alveolus and its spatial relationships with the teeth. As a result, the findings of many ex vivo investigations must be questioned. The aim of this investigation was to develop and refine a new laboratory method for experimental dental radiography utilizing a series of anatomical radio-opaque acrylic models containing extracted teeth. The method allows adjustment of the beam-object relationship through the use of precision-made wedges, which are able to tilt the models through a series of angles thus simulating in vivo changes in both vertical and horizontal X-ray beam angulation. The technique is capable of being used in studies involving assessment of alveolar bone height or the depth of carious lesions. The precision of the method was tested by radiographing in nine different positions a test device consisting of four small amalgam fillings embedded in a perspex sheet. Following removal and replacement, exposures of the test device were repeated for each position. Five linear distances between pairs of fillings were selected and measured on each radiograph to give a total of 45 measurements per set of films. There was exact agreement in 39 of the measurements recorded and a discrepancy of +/- 0.1 mm in the remaining six. The estimated standard deviation for variation on repeat radiography was 0.258 and the 95% confidence interval 0.214 to 0.325. The precision of the apparatus was thus found to be adequate for the measurement of differences in small distances.

Radiographic amelocemental junction and alveolar crest: effect of X-ray beam angulation.

The effect of X-ray beam angulation on the radiographic images of the amelocemental junction (ACJ) and alveolar crest (AC) and their positions relative to one another were assessed using a new laboratory model for radiographic studies. A total of 39 teeth with 62 usable approximal surfaces were included in the investigation. When all tooth types were combined, changes in vertical or horizontal angulation from baseline through 20 degrees had no significant effect on the distance between the marked (true) ACJ and marked (true) AC. However, the distance between the apparent (radiographic) ACJ and apparent (radiographic) AC was significantly reduced by varying the beam angulation in either a vertical or horizontal direction. Results for individual tooth types were qualitatively similar but larger discrepancies were found in molars followed by premolars and incisors. The results emphasize the importance of maintaining the ideal X-ray beam, tooth, bone, film relationship when taking radiographs for the assessment of periodontal destruction.