Development of predictable periapical lesion monitored by subtraction radiography

An in vivo study to determine the effects of early preflaring on the working length in curved mesial canals of mandibular molars

AIM

To evaluate the effects of a preflaring method on the determination of working length in the curved mesial canals of mandibular molars.

MATERIALS AND METHODS

Ninety mandibular molars with apical curvature of 30 to 40° were selected and randomly divided into two groups; each containing 45 teeth. In the first group, the initial instrumentation was performed with preflaring on the mesiobuccal canal (preflared group), and in the second group; the instrumentation was performed without preflaring on the mesiobuccal canal (nonpreflared group). A size 15 K-file was inserted in the mesiobuccal canals until the apical constriction could be felt by tactile sensation and a radiograph was taken to identify the distance between the file tip and radiographic apex. The location of the tip was classified as (a) within 1 mm of the radiographic apex, (b) more than 1 mm of the radiographic apex, or (c) overextended beyond the radiographic apex. The collected data was statistically analyzed and probability value was set to be ≤0.05.

RESULTS

The file tip was significantly closer to the true working length in the canals with early preflaring compared to the canals without early preflaring (p < 0.005). In the preflared group; 75.5% of the cases had the file tip in location 'a', 13.3% in location 'b', and 11.1% in location 'c'. In the nonpreflared group; 33.3% of the cases had the file tip in location 'a', 53.3% in location 'b' and 13.3% in location 'c'.

CONCLUSION

Preflaring the coronal portion of curved canals greatly improved the access to the apical constriction, and thus enhanced correct working length determination. If the coronal portion of the curved canals is not preflared, the clinician cannot discern the accuracy of what they feel apically. Thus, preflaring is a highly recommended procedure especially in curved canals for better determination of correct working length.

Digital Radiograph Registration and Subtraction: A Useful Tool for the Evaluation of the Progress of Chronic Apical Periodontitis

The purpose of this study was to evaluate the suitability of a digital radiograph registration and subtraction software for a sensitive and reliable assessment of the progress of chronic apical periodontitis. Ninety cases of teeth with chronic apical periodontitis have been studied. In each case, a preoperative radiograph was taken, root canals were prepared, and a Ca(OH)2 paste was placed in the root canals. Radiographic control and replacement of Ca(OH)2 paste took place at 15-day intervals. The root canals were obturated 1.5 months after the first appointment. Recall radiographs were taken 0.5, 1.5, 3, 6, and 12 months after the obturation. All radiographs were taken for each case under constant conditions by using a direct digital radiography system. In each case, the preoperative, postoperative, and control and recall radiographs were digitally registered and pairwise subtracted. The resulting images were further processed by using contrast enhancement and pseudocoloring methods. Changes to the periapical tissue structure were easily detectable by using the above-mentioned methodology, even during short time intervals.

Periapical inflammation affecting coronally-inoculated dog teeth with root fillings augmented by white MTA orifice plugs

Placement of orifice plugs has been suggested to augment the seal of conventional root canal fillings. This study assessed in vivo the efficacy of white mineral trioxide aggregate (MTA) plugs in preventing periapical inflammation subsequent to coronal inoculation of root-filled teeth. The two-rooted mandibular premolars of six beagle dogs were conventionally prepared and filled with gutta-percha and sealer. A white MTA orifice plug was placed into one canal in each tooth. Pulp chambers were inoculated with plaque except for 12 teeth (negative control), and restored. Radiographs were taken at regular intervals. At 10 months, dogs were killed and jaw blocks processed for histology. None of the roots revealed radiographic or histologic evidence of severe inflammation. Mild inflammation was observed in 17% and 39% of the roots with and without an orifice plug, respectively (McNemar, p > 0.05). Without development of severe inflammation, the seal augmentation efficacy of MTA orifice plugs could not be determined.

Image processing for enhanced observer agreement in the evaluation of periapical bone changes

AIM

The aim of the present study was to evaluate the effect of root canal treatment on periapical lesions by conventional and subtracted digital radiographic images of clinical cases.

METHODOLOGY

Eleven patients who exhibited clinical or radiological signs of periapical pathology received root canal treatment. Periapical radiographs were obtained immediately postoperatively and recall radiographs at intervals of 3, 6, 9 and 12 months postoperatively were obtained. Identical exposure geometry was maintained. From the standardized radiographs digitized images were produced. Four experienced practitioners interpreted the radiographs and the digitized images. They assessed 59 pairs of images projected at random using a slide projector. On the left side, there was a reference image with no lesion, and on the right an image either with or without a lesion. Each reader was asked to rate each pair of images on a three-point scale: yes, absolutely sure that gain or loss was present; uncertain, if there was gain or loss; no, absolutely sure that no gain or loss was present. There was no time limit for each decision. Inter- and intra-examiner agreement was analyzed using the kappa-statistic for the diagnosis of periapical bone density changes in the periapical region at the different time points either in conventional pairs of radiographs or using digital subtraction images.

RESULTS

The inter-examiner agreement (P < 0.001) and the intra-examiner agreement (P = 0.02) when digital pictures where evaluated were significantly higher than with conventional radiographs.

CONCLUSIONS

A highly significantly better observer agreement was achieved by digital subtraction radiography during the evaluation of the outcome of root canal treatment on periapical lesions.

Analysis of sensitivity and specificity of a new digital subtraction system: an in vitro study

OBJECTIVE

The purpose of this study was to compare a new digital subtraction system with conventional radiograph images for the detection of periapical and periodontal bone lesions.

STUDY DESIGN

Periapical and periodontal bone lesions were simulated with cortical bone chips of varying sizes placed on a human dry mandible. Radiographic film images were acquired from varying projections and were subsequently digitized, registered, and subtracted. Four clinicians evaluated the subtracted images, and sensitivity and specificity were calculated.

RESULTS

The mean sensitivity and specificity of the Diagnostic Subtraction Radiography system for detecting bone lesions of all sizes with varying projection geometry were 87.90% and 85.23%, respectively. The corresponding results for conventional radiograph images were 47.54% and 97.38%. The difference in sensitivity was statistically significant, whereas the difference in specificity was not.

CONCLUSIONS

These results indicate that, even when radiographs are taken from disparate projection geometries, the Diagnostic Subtraction Radiography system is capable of excellent discrimination between healthy and disease states in this in vitro model.

Detection of mineral loss in approximal enamel by subtraction radiography

The purpose of the present study was to determine whether digital subtraction radiography will improve detectability of small, mechanically prepared defects within dental enamel. Lesions with an extent of 1 mm in vertical direction and representing 5% to 10% mineral loss in the direction of the x-ray beam were prepared in eight extracted molars. Radiographs of teeth with defects were subtracted from radiographs taken before the lesions were prepared. Seven observers evaluated the images using a five-point confidence rating scale (receiver operating characteristic technique). Examination of the original radiographs showed increasing accuracy of radiographic interpretation with increasing mineral loss as judged from the areas beneath the receiver operating characteristic curves. The same observation was made using subtraction images with and without contrast enhancement. There was no indication that subtracted images provided better diagnostic validity than the original radiographs. In conclusion, subtraction images do not seem to improve the diagnosis of well-defined lesions within dental enamel.

Application of computer-aided image interpretation to the diagnosis of periapical bone lesions

An image analysis system was developed for the computer-aided diagnosis of periapical bone lesions in dental radiographs. The system was designed to (1) identify the periapical region, (2) determine the presence of a periapical lesion and (3) estimate the size of the lesion in cases when a lesion had been found. To initiate the procedure, an observer indicates an arbitrary point on the root in a digitized radiograph. From this initial point, the location of the radiographic projection of the apex of the root is automatically computed. Next, the trabecular bone pattern is detected through texture analysis. A local absence of the trabecular bone pattern in the periapical region is marked as a periapical bone lesion. When a lesion has been identified, its size is estimated based on local edge properties. Observer interaction is only allowed to adjust the result of the apex localization procedure if the apex has not correctly been localized. In an experiment with randomly selected radiographs of 111 mandibular roots, the performance of the system was tested against the consensual diagnosis of four expert observers. The sensitivity of the system to identify a lesion was 83.3%, the specificity 75.6% and the diagnostic accuracy 80.2%. The correlation between the size of the lesions as estimated by the system and by the observers was 0.67 (P < 0.01). When the procedure was repeated, the percentage of correctly reproduced lesion sizes by the system was 92.8%. The determination of the presence of a lesion was reproducible in 98.2% of all the cases.

Standardized lateral oblique projection of the mandible for digital subtraction radiography

A special apparatus was developed for standardization of the lateral oblique projection of the mandible (LOPM) in order to apply the digital subtraction method. Geometric reproducibility was examined over an 8-week period using a dry skull. Angulation errors were determined by the relation to image noise in the subtraction image. It was found that the relation between image noise and angulation error was approximated by a second-order polynomial. Geometric reproducibility was within 1 degree over the experimental period. These results suggest that this standardized LOPM is satisfactory for clinical application of digital subtraction. Two cases are presented where this technique was used to demonstrate longitudinal changes in bone density.

Induced periapical lesions in ferret canines: histologic and radiographic evaluation

Ferrets have been utilized in endodontic research to study periapical responses. However, various aspects of induction and healing of periapical pathosis in ferrets are unclear. This study evaluated the radiographic and histopathologic features of induced periapical lesions. Periapical pathosis was consistently produced in 8 canines of 2 ferrets by extirpating the pulp, leaving the cavities open for a week, then sealing for 12 weeks. The resulting lesions were evaluated radiographically every two weeks. The animals were then killed and the induced lesions evaluated histologically and histobacteriologically. Four untreated canines from 2 other ferrets were used as controls. Results showed that periapical rarefactions were visible in all teeth in the experimental group within 4 weeks. Histologically, the induced lesions consisted principally of a mononuclear inflammatory infiltrate, dominated by macrophages but with numerous lymphocytes. With Brown & Brenn staining, bacteria were demonstrated in the pulp space of teeth in which the lesions were induced and in the apical arborization of the canal system. Only one specimen had bacteria within the periapical lesion.

Personal computer equipment for dental digital subtraction radiography vs. industrial computer equipment and conventional radiography

A "low-cost" personal computer (PC) system used to digitize dental radiographs was tested by assessing the accuracy of its subtraction images versus those of "high-cost" industrial equipment and conventional radiography. Subtraction images were made of artificial lesions in human femur bone and subsequently evaluated by students and teachers. The observations were analyzed in terms of true positive and false positive reports. "Low-cost" and "high-cost" subtraction images revealed only small differences in diagnostic accuracy. Compared to conventional radiography, the diagnostic accuracy of the subtraction images with the "low-cost" PC system was significantly higher for all observers. The interexaminer variance was similar for the subtraction and the conventional images for both students and teachers, except for a significantly reduced interexaminer variance for the teachers concerning the true positive reports with the "low-cost" PC subtraction technique.

Tissue reaction to endodontic materials: methods, criteria, assessment, and observations

The purpose of this study was to develop methods and criteria for the testing of the biocompatibility of endodontic materials. One hundred twenty-one teeth from 12 baboons (Papio anubis) were used to test three sealers: AH26, Kerr pulp canal sealer, and Kloroperka N.O. Gutta-percha cones were used as solid core in all cases. Under disinfected conditions, access preparation was performed, and with working length approximately 1.0 mm short of the foramen, the instrumentation of the root canal was started, using sodium hypochlorite (1%) for irrigation. After the root canals were cleaned and shaped, they were obturated with gutta-percha cones and the sealer, and by lateral condensation technique. Histologic periapical reactions were evaluated at 1, 7, 30, 365, 730, and 1095 days. The methods and criteria used were adequate for ranking of the biocompatibility of the tested materials in the short and long periods. At short observation periods (1 to 7 days) AH26 caused severe reactions, and Kerr pulp canal sealer and Kloroperka N.O., moderate and mild reactions, respectively. At 2- and 3-year observation periods the ranking was AH26, mild; Kerr pulp canal sealer, moderate; and Kloropercha N.O., severe.

In vivo efficacy of various retrofills and of CO2 laser in apical surgery

The purpose of the present study was to radiographically assess the efficacy of various retrofilling materials and of the use of CO2 laser in apical surgery. The mandibular premolars of six beagle dogs were infected, resulting in periapical lesions. Apical surgery was performed without root canal treatment. Amalgam with cavity varnish, glass ionomer cement and a lightcured composite resin were the retrofilling materials used. In half of the material CO2 laser was used on the root surface and the bone, for occlusion of the dentinal tubuli and sterilization. The healing following surgery was observed radiographically for six months. The highest success rate (89%) was found in the roots retrofilled with amalgam and varnish, and the lowest (60%) in those retrofilled with the composite resin. The difference between these groups was statistically significant. The success rate following retrofilling with glass ionomer cement was 69%, and was not significantly different from both the other groups. Under the conditions of this study, the use of CO2 laser during surgery did not affect the treatment results.

Image analysis of endodontic radiographs: digital subtraction and quantitative densitometry

In this study computerized image analysis procedures were applied to endodontic radiographs. Kontron IBAS 2000 is a commercially available image analysis system with processing routines applicable to radiograph digitizing and transformations. The system was evaluated for: its ability to harmonize blackening and contrast in endodontic radiographs; its ability to compensate for angulation distortion of sequential exposures of individual teeth; its potential for application of digital subtraction methods; and its use in automated gray-level analyses of diseased and healthy bone areas in endodontic radiographs. The Kontron IBAS 2000 system proved suitable for all applications. However, the specificity of the subtraction procedure was limited by some inherent problems in the harmonization of blackening and in the subtraction process itself. On the other hand, automated gray level measurements proved to be a robust method for unbiased and quantitative assessment of healing of apical periodontitis.