One technique for controlling many of the variables in the diagnostic quality of conventional radiography has been the advent of digital radiography. This technology has been around for about 20 years but has recently been refined with better hardware and more user-friendly software. Digital radiography has the ability to capture, view, enhance and store radiographic images in an easily reproducible format that does not degrade over time.
Digital radiography uses no x-ray film and requires no chemical processing. Instead, a sensor is used to capture the image created by the radiation source. This sensor is either directly or remotely attached to a local computer, which interprets this signal and, using specialized software, translates the signal into a digital image that can be displayed and enhanced. The image is stored in the patient's file, typically in a dedicated network server, and can be recalled as needed. Further information about digital radiography may be found in Chapters 5 and 26.
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Figure 1-25 Digital radiography has as an advantage over conventional film in that the image can be enhanced and colorized, a useful tool for patient education.
The viewing of a digital radiographic image on a high resolution monitor allows for rapid and easy interpretation for both the clinician and the patient. The image appears almost instantly, with no potential for image distortion from improper chemical processing, since there is none. The clinician can zoom in to different areas on the x-ray image, digitally enhance the image in order to better visualize certain anatomic structures, and in some cases, the image can even be colorized, a useful tool for patient education (Fig. 1-25).
Until recently, x-ray film has had a slightly better resolution than most digital radiography images, at about 16 line pairs per millimeter (lp/mm).57 However, some sensor manufacturers are now claiming to have resolutions beyond that of film and up to 22 lp/mm. However, under the best of circumstances, the human eye can only see about 10 lp/mm, which is the lowest resolution for most dental digital radiography systems. The digital sensors are much more sensitive to radiation than conventional x-ray film and thus require 50% to 90% less radiation in order to acquire an image, an important feature for generating greater patient acceptability of dental radiographs.
The diagnostic quality of this expensive technology has been shown to be comparable to, but not necessarily superior to, perfectly exposed and perfectly processed conventional film-based radiography.22,47,61 However, digital radiography has the advantage over conventional film in that there is no diminution in diagnostic quality caused by developing and processing errors, and it has the ability to enhance, magnify, store, and electronically send the images, as well the ability to duplicate the original radiograph as a perfect copy. In 1998, the American Association of Endodontists stated that "digital radiography will rapidly replace conventional dental X-rays."2 The reader is referred to Chapter 26 for more information on digital radiography.
Date Added: 20 February 2007
Karl Keiser, DDS, MS, University of Texas Health Science Center at San Antonio
A novel use for ultrasonography-differentiating periapical cysts from granulomas
Radiography is an essential tool in the delivery of endodontic care. At a minimum, radiographs are exposed and interpreted as an aid in preoperative diagnosis, in working length estimation, and to evaluate obturation during nonsurgical endodontic therapy. Later, radiographs provide information as to the health of the periradicular tissues when endodontic recall is performed. Several studies have addressed the poor performance of conventional intraoral radiography in determining the exact nature of periapical disease1-4 and, particularly, the inability to differentiate between granulomatous tissue and cysts.5 This has implications for preoperative treatment planning and postoperative determination of healing.
A recent clinical study by Gundappa et al.6 has assessed the potential use of ultrasonography in differentiating periapical lesions. Fifteen patients who were scheduled for root-end surgery on mandibular or maxillary anterior teeth with histopathologic examination were included in the sample. Preoperative radiographic evaluations included conventional and direct digital imaging with standard techniques. Interpretation of the radiographs was provided by two oral radiologists and one endodontist. Ultrasound examination was performed by an ultrasonographer using a high-definition, multifrequency, 40-mm linear foot print ultrasound probe operating at a frequency of 8-11 MHz. When sufficient vestibular space was available, the probe was placed against the labial mucosa intraorally. In all cases, the probe also was placed extraorally on the skin overlying the periapical region of interest. The probe position was changed as needed to obtain an adequate number of scans to outline the bony defects. The echo characteristics of the bony lesions also were noted. After surgery, apical specimens were processed for routine histopathologic evaluation.
Radiographic and ultrasonographic imaging showed the presence of periapical lesions in all 15 cases. Ultrasound examination disclosed seven cysts, seven granulomas, and one combined lesion; these results agreed completely with the biopsy evaluation.
Although these study results are promising, the diagnosis of periapical cyst is variable, depending on the criteria used by the oral pathologist. The present study found nearly a 50% prevalence of cysts and granulomas. This is in concert with early investigations by Lalond and Luebke7 and Bhaskar.8 Contemporary studies with more stringent criteria have found closer to a 15% prevalence of cysts.9,10 Curettage of periapical lesions during surgical endodontic therapy results in a high rate of success, regardless of the presence of cystic or granulomatous lesions, especially when the source of continued apical inflammation (bacteria and their by-products in the root canal) is addressed.
1. Bender IB: Roentgenographic and direct observation of experimental lesions in bone. J Am Dent Assoc 62:152, 1961.
2. Kaffe I, Gratt BM: Variations in the radiographic interpretation of the periapical dental region. J Endod 14:330, 1988. MedlineSimilar articles
3. Goldman M, Pearson A, Darzenta N: Reliability of radiographic interpretations. Oral Surg 38:340, 1974.
4. Bender IB: Factors influencing the radiographic appearance of bony lesions. J Endod 23:5-14, 1997. MedlineSimilar articles
5. Shrout MK, Hall JM, Hildebolt CE: Differentiation of periapical granulomas and radicular cysts by digital radiometric analysis. Oral Surg Oral Med Oral Pathol 76(3):356-361, 1993.
6. Gundappa M, Ng SY, Whaites EJ: Comparison of ultrasound, digital and conventional radiography in differentiating periapical lesions. Dentomaxillofac Radiol 35:326-333, 2006. MedlineSimilar articles
7. Lalonde ER, Luebke RG: The frequency and distribution of periapical cysts and granulomas: An evaluation of 800 specimens. Oral Surg Oral Med Oral Pathol 25(6):861-868, 1968.
8. Bhaskar SN: Oral surgery-oral pathology conference No. 17, Walter Reed Army Medical Center. Periapical lesions—types, incidence, and clinical features. Oral Surg Oral Med Oral Pathol 21(5):657-671, 1966.
9. Ramachandran Nair PN, Pajarola G, Schroeder HE: Types and incidence of human periapical lesions obtained with extracted teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 8:93-102, 1996.
10. Simon JH: Incidence of periapical cysts in relation to the root canal. J Endod 6(11):845-848, 1980.
Root Fractures and Cracks
Because of the wide variety of different types of cracks in teeth, there may be a myriad of symptoms and presentations, making the diagnosis of a crack often difficult. The extensiveness of a crack may directly alter the prognosis assessment for a given tooth. Therefore, any possible crack should be examined prior to dental treatment. These cracks may be as innocent as a superficial enamel craze line, or they may be as prominent as a fractured cusp. The crack may progress into the root system to involve the pulp, or it may even split the entire tooth into two separate pieces. The crack may be oblique, extending cervically, such that once the coronal segment is removed the tooth may or may not be restorable. Any of these situations may present with mild, moderate, or severe symptoms or possibly no symptoms at all. Because of the high prevalence of fractures and cracks in teeth and how they can directly alter the prognosis for a tooth, an extensive review is presented.
There have been many attempts in the literature to classify cracks in teeth, trying to differentiate the extent to which the crack has progressed into the tooth structure. By defining the type of crack present, an assessment of the prognosis may be determined and treatment alternatives may be planned as fully described in Chapter 16. Unfortunately, it is often impossible to determine how extensive a crack is until the tooth is extracted. Therefore, the determination of a crack is often more of a prediction, rather than a definitive diagnosis.
Cracks in teeth can be divided into three basic categories:
Fractures (also referred to as cracks)
Craze lines are merely cracks in the enamel that do not extend into the dentin and either occur naturally or develop secondary to trauma. They are more prevalent in adult teeth and usually occur more in the posterior teeth. If light is transilluminated through the crown of such a tooth, these craze lines may show up as fine lines in the enamel with light being able to transmit through them, indicating that the crack is only superficial. Craze lines typically will not manifest with symptoms. No treatment is necessary for craze lines unless they create a cosmetic issue.
Fractures extend deeper into the dentin than superficial craze lines and primarily extend mesially to distally, involving the marginal ridges. Dyes and transillumination are very helpful in visualizing potential root fractures.
Symptoms from a fractured tooth range from none to severe pain. A fracture in the tooth does not necessarily dictate that the tooth has split into two pieces, but left alone, especially with provocations like occlusal prematurities, the fracture may progress to a split root. A fractured tooth may be treated by a simple restoration, endodontics, or even extraction, depending upon the extent and orientation of the fracture, the degree of symptoms, and whether or not the symptoms can be eliminated. This makes the clinical management of fractured teeth difficult and sometimes unpredictable.
A definitive combination of factors, signs, and symptoms that, when collectively observed, allows the clinician to conclude the existence of a specific disease state is termed a syndrome. However, given the multitude of signs and symptoms that fractured roots can present with, it is often difficult to achieve an objective definitive diagnosis. For this reason, the terminology of cracked tooth syndrome13 should be avoided.1 The subjective and objective factors seen in cases of fractured teeth will generally be diverse; therefore a tentative diagnosis of a fractured tooth will most likely be more of a prediction. Once this prediction is made, the patients must be properly informed as to any potential decrease in the prognosis of the pending dental treatment. Since treatment options for repairing fractured teeth have only a limited degree of success, early detection, prevention, and proper informed consent are crucial.4,18,46,59,75,78,87
Split roots occur when a fracture extends from one surface of the tooth to another surface of the tooth, with the tooth separating into two segments. If the split is more oblique, it is possible that once the smaller separated segment is removed, the tooth might still be restorable, e.g., a fractured cusp. However, if the split extends below the osseous level or involves the pulp, the tooth may not be restorable and endodontic treatment may not result in a favorable prognosis.
Proper prognosis assessment prior to any dental treatment is imperative, but is often difficult in cases of cracked teeth. Because of the questionable long-term success from treating cases of suspected or known fractures, the clinician should be cautious in the decision to continue with treatment and should avoid treating cases of definitive split roots.