The effect of changes in tooth position of unerupted canines on cephalograms

Although many radiographic procedures have been described to localize an impacted canine, they all submit the patient to extra radiation. The purpose of the entire study was to evaluate if the combined interpretation of cephalograms and dental panoramic tomograms (DPTs), which are used in orthodontic practice, can provide adequate information as to the position of impacted canines. In a previous study the radiographic image of impacted canines on DPTs was evaluated. In this investigation, the effect of changes in position and inclination of an impacted canine on cephalograms was studied in an experimental set-up. An upper canine was removed from a human skull and placed in a positioning device to imitate various positions of impaction. Starting from a buccally impacted position, three different displacements were simulated: 10 mm frontally, 10 mm sagittally, and 5 mm vertically. In each of these positions nine different changes in inclination (in the sagittal and the frontal plane) were registered, resulting in 36 different cephalographic exposures. Analysis revealed the following: the degree of vertical and sagittal displacement of the incisal point of the impacted canine, the angulation of the tooth as well as the tooth length, measured on a cephalogram, appeared to give an accurate representation of the experimental set-up. Combining these findings and those from the previous study, it became possible to define a series of points to enable an adequate three-dimensional (3D) estimation of the canine's position. A clinical case of an impacted canine is used as an illustration of this experimental set-up.     

Association between the inclination of the lateral incisors and the position of the erupting canines on panoramic radiographs

OBJECTIVE. To analyze correlations between the inclination of the permanent maxillary lateral incisors and the intraosseous position of the erupting permanent maxillary canines on panoramic radiographs. MATERIAL AND METHODS. The inclination of the lateral incisor to the midline, the mesiodistal position of the crown of the canine, and the inclination of the canine to the midline and to the long axis of the adjacent incisor were measured on panoramic radiographs of 1013 subjects aged 8-11 years. RESULTS. The distal inclination of the lateral incisor crown increased until 10 years, after which no significant changes occurred. The canine erupted with increasing mesial inclination of the crown until 9 years, after which it began to progressively right itself. As a result, inclination of the canine to the adjacent incisor increased between 8 and 9 years and decreased between 10 and 11 years. Until the children reached 9 years of age, the more mesial the crown of the unerupted canine, the greater the decrease in the distal inclination of the lateral incisor crown. CONCLUSIONS. The inclination of the crown of the lateral incisor varies during eruption of the canine, increasing distally until 10 years as a physiological stage in the mixed dentition. The inclination of the lateral incisor is also associated with the mesiodistal position of the canine crown. The mesial intraosseous location of the canine crown results in righting of the lateral incisor.     

The use of panoramic radiographs to localize displaced maxillary canines.

OBJECTIVE: The purpose of this investigation was to develop a reliable method of diagnosing the position of a displaced maxillary canine on the basis of a single panoramic radiograph. STUDY DESIGN: A total of 115 panoramic radiographs depicting 164 displaced maxillary canines were evaluated. The ratio of the width of the displaced canine to the width of the homolateral central incisor (the canine-incisor index) and the ratio of the width of the displaced canine to the width of the contralateral canine (the canine-canine index) were calculated. The height of the crown of each displaced canine was classified in the vertical plane, relative to the adjacent incisor, as apical, middle, or coronal. RESULTS: There was an overlap in the canine-incisor index ranges of the buccal (0.94-1. 45) and palatal (1.15-1.29) canines in the apical zone. In the middle and coronal zones, a clear difference could be seen between the canine-incisor indices of labially (0.78-1.11) and palatally (1.15-1.7) located canines. A cut-off point of 1.15 was determined. CONCLUSIONS: Provided that vertical restriction and the canine-incisor index are used, the panoramic radiograph can serve as a useful indicator for determining the position of an unerupted maxillary canine.     

The effects of compression on the image quality of digital panoramic radiographs

Size reduction through compression is an important issue that needs to be investigated for possible effects on image quality. The aim of the present study was to evaluate the subjective image quality of digital panoramic radiographs which were lossless and lossy compressed for the visualization of various anatomical structures. Fifty-five digital panoramic radiographs in Tagged Image File Format (Tiff) were used in the study. Two types of lossy (Joint Photographic Experts Group (Jpeg)) and one type of lossless (Lempel?CZiv?CWelch) compression were applied to the original radiographs. These radiographs were evaluated by two observers separately for the visibility of some anatomical structures with visual grading. Mean quality number for each radiograph was obtained. The differences between the mean quality numbers in each compression and original image mode were evaluated with Friedman test. Pair-wise comparisons revealed that there were statistically significant differences between all groups (p?=?0.000) for all comparisons except for Jpeg_1 and Jpeg_2 groups. Kappa statistics was used to evaluate inter- and intra-observer agreements. Intra-observer agreements were ranging from 0.229 to 1.000 and inter-observer agreements were ranging from 0.154 to 1.000. The observers had better inter- and intra-observer agreements in highly compressed Jpeg_1 images. The anatomical structures evaluated in this study had better visibility in Tiff images than Jpeg images except for mandibular canal and mental foramen. While Jpeg compressed images offer high inter- and intra-observer agreements, the visibility of anatomical structures are better in Tiff images except for mandibular canal and mental foramen.     

X-ray diagnosis of impacted upper canines in panoramic radiographs and computed tomographs

Ten orthodontists were asked to diagnose the number of impacted upper canines and the number of resorbed lateral and/or central incisor roots in 30 panoramic radiographs (P1) from 30 patients. In order to objectify these diagnoses, transversal CT images of all 30 patients were examined in addition. Addition of the recordings in the 30 patients revealed that the 10 orthodontists had diagnosed 350 impacted/displaced canines. On comparison of the P1 and CT results, the latter revealed that, in fact, 390 canines were impacted or displaced, not just 350. Addition of the recordings further showed that, based on P1, the investigators had diagnosed 73 resorptions in the 1,200 incisors examined. However, the CT showed 160 resorptions; this corresponds to a sensitivity value of 45.6%. The CT showed 1,040 incisors with no resorptions, whereas the investigators diagnosed only 925 teeth as not resorbed in the P1. The specificity was thus 88.9%. These results show that, due to their low reliability, panoramic radiographs are not an appropriate means of diagnosing resorptions in front teeth in connection with impacted canines.     

The mental foramen: 3. Size and position on panoramic radiographs.

Panoramic radiographs were made of 75 dry, adult human mandibles. The size and position of the mental foramen in relation to the second premolar was determined. The mental foramen on panographic radiographs was slightly larger than reported on periapical radiographs. The average position of the foramen was mesial and below the radiographic apex of the tooth. Panoramic radiography may account for a distal shift of the foramen and a 23% increase in size of the mandibles examined.     

传统全景片和锥形束CT重建全景片测量牙轴近远中倾斜度的对比研究

目的 比较传统全景片和锥形束CT（CBCT）重建全景片用于测量牙轴近远中倾斜度的准确性。方法 收集15名个别正常志愿者的石膏模型,在模型上确定上下颌从左侧第一磨牙到右侧第一磨牙的牙体长轴和平面的标记点,制作放射显影装置,志愿者佩戴放射显影装置拍摄全景片和 CBCT片。分别在石膏模型、全景片和 CBCT重建全景片上测量牙轴近远中倾斜度。利用多元方差分析和 Dunnett-t检验比较3种测量方法的差异。结果 3种测量方法间的差异有统计学意义（P=0.00）。与模型测量相比,全景片组中12个牙位有2个牙位（上下颌第二前磨牙）测量结果的差异有统计学意义（P=0.00）,CBCT组12个牙位的差异均无统计学意义。结论 评价牙轴近远中倾斜度时,传统全景片存在一定误差, CBCT重建全景片是一种更为有效的评价手段。     

An investigation of tooth loss factors in elderly patients using panoramic radiographs

Oral Radiology - The aim of this study was to observe the dental condition in a group of elderly patients over a period of 10 years in order to clarify important risk factors. Participants...     

The effects of image compression on quantitative measurements of digital panoramic radiographs

Objectives: The aims of this study were to explore how image compression affects density, fractal dimension, linear and angular measurements on digital panoramic images and assess inter and intra-observer repeatability of these measurements. Study Design: Sixty-one digital panoramic images in TIFF format (Tagged Image File Format) were compressed to JPEG (Joint Photographic Experts Group) images. Two observers measured gonial angle, antegonial angle, mandibular cortical width, coronal pulp width of maxillary and mandibular first molar, tooth length of maxillary and mandibular first molar on the left side of these images twice. Fractal dimension of the selected regions of interests were calculated and the density of each panoramic radiograph as a whole were also measured on TIFF and JPEG compressed images. Intra-observer and inter-observer consistency was evaluated with Cronbach’s alpha. Paired samples t-test and Kolmogorov-Smirnov test was used to evaluate the difference between the measurements of TIFF and JPEG compressed images.Results: The repeatability of angular measurements had the highest Cronbach’s alpha value (0.997). There was statistically significant difference for both of the observers in mandibular cortical width (MCW) measurements (1st ob. p: 0.002; 2nd ob. p: 0.003), density (p<0.001) and fractal dimension (p<0.001) between TIFF and JPEG images. There was statistically significant difference for the first observer in antegonial angle (1st ob p< 0.001) and maxillary molar coronal pulp width (1st ob. p<0.001) between JPEG and TIFF files. Conclusions: The repeatability of angular measurements is better than linear measurements. Mandibular cortical width, fractal dimension and density are affected from compression. Observer dependent factors might also cause statistically significant differences between the measurements in TIFF and JPEG images. Key words:Digital panoramic radiography, image compression, linear measurements, angular measurements, fractal dimension.     

Interpretation of panoramic radiographs

Panoramic radiography has become a commonly used imaging modality in dental practice and can be a valuable diagnostic tool in the dentist's armamentarium. However, the panoramic image is a complex projection of the jaws with multiple superimpositions and distortions which may be exacerbated by technical errors in image acquisition. Furthermore, the panoramic radiograph depicts numerous anatomic structures outside of the jaws which may create additional interpretation challenges. Successful interpretation of panoramic radiographs begins with an understanding of the normal anatomy of the head and neck and how it is depicted in this image type. This article will describe how osseous structures, soft tissues, air spaces and ghost shadows contribute to the final panoramic image. A systematic and repeated approach to examining panoramic radiographs, which is recommended to ensure that critical findings are not overlooked, is also outlined. Examples of challenging interpretations, including variations of anatomy, artefacts and disease, are presented to illustrate these concepts.     

Prediction of the widths of unerupted canines and premolars

The purpose of this study was to develop, with simple linear regression analysis, equations that could accurately predict the mesiodistal widths of unerupted canines and premolars in both arches of the mixed dentition patient. Clinically useful prediction equations were developed and tested on a sample of orthodontic patients. Performance of the equations in patients was satisfactory. Charts and suggestions for completing a tooth size-arch length analysis in the patient with a mixed dentition were discussed.     

Can adaptive post-processing of storage phosphor plate panoramic radiographs provide better image quality? A comparison of anatomical image quality of panoramic radiographs before and after adaptive processing

Objective: The objective of the present study was to study the effect of adaptive image processing on the visibility of anatomical structures in storage phosphor plate (SPP) panoramic images.

Materials and methods: Three hundred SPP panoramic X-ray radiographs of children and adolescents were used. The radiographs were post-processed using general operator processor (GOP) technology, resulting in both a standard-processed and a GOP-processed radiograph. Four specialists in dental radiology compared the structural image quality of all standard-processed and GOP-processed panorama images for six anatomical structures, using a six-point scale for visual grading characteristics (VGC) analysis.

Results: For three of the anatomic structures – the root canal space of the mandibular left first premolar, mandibular canal left side and periodontal ligament space of the mandibular right first molar – there was a statistically significant difference to the GOP’s advantage. For the three remaining structures – dentino-enamel junction of the maxillary right first molar, crista alveolaris of the mandibular left molar area and floor of maxillary sinus right side – no significant difference between standard processing and GOP processing was obtained.

Conclusions: The study demonstrates that it is possible to improve the quality of SPP radiographs and the visibility of anatomical structures by using the GOP technique. Manufacturers’ image-processing programs can be further developed, as there is a possibility of improving the diagnostic content of an image with external processing.