The future of endodontic diagnosis

The limitations of the use of standard radiography in the practice of endodontics is well known and documented [1], with the ability to detect periradicular disease (sensitivity) and lack of disease (specificity), significantly lower than a practitioner would wish for [2].

Periapical pathology can only be seen on a radiograph once the adjacent cortical plate has started to be eroded, and therefore diagnosis can be a lottery in the positioning of the root apex, with sometimes even bone damage from a pulpitis visible, but a very large lesion undetectable [3].

However, as the periapical radiograph has been the only way to accurately visualise unseen tooth and root anatomy with associated hard tissue pathology, it is considered mandatory before any endodontic procedure is carried out [4].

As it is only a two-dimensional representation of a complex layered composite of calcific materials, a practitioner will need to use all available diagnostic tests, a fair amount of intelligence and sometimes luck, to establish effective diagnosis and treatment planning.
As an endodontist, I am continually frustrated to be dependent on poor quality subjective clinical tests (percussion, palpation, thermal and electrical), with the only objective diagnostic test, a periapical radiograph. I frequently hear of patients with pulpal and periapical disease being told by their dentists that there is ‘nothing wrong’ from the X-ray.

There is frequently something wrong, it is just a failing in the sensitivity of the diagnostic test and the dentist’s over-dependency on a limited medium. Computed tomography (CT) is a medical imaging method employing tomography where digital geometry processing is used to generate a three-dimensional image of the internals of an object, from a large series of two-dimensional X-ray images taken around a single axis of rotation.

Since its introduction in the 1970s, CT has become an important tool in medical imaging to supplement X-rays and medical ultrasonography. It is now the gold standard in the diagnosis of a large number of different disease entities.

In the late 1990s, scanners specifically for maxillo-facial use were developed, producing a cylinder-shaped volume of radiographic data in a single rotation called cone beam computed tomography (CBCT). Thanks to readily available powerful personal computers, the data in the cylinder can now be processed rapidly and reconstructed by software into multiplanar radiographic reconstructions with relatively good resolution. Dental anatomy can be visualised in slices in any plane, rather than the composite view afforded by standard intra-oral radiography.

Limited volume CBCT scanners capture small volumes of data that can include just two or three individual teeth and this was first seen in the Accuitomo 3D scanner launched by Morita in 2001. Recently, Morita has upgraded its OPG machine to include the advanced technology found in the Accuitomo, producing the Veraviewepocs 3D.

This ‘small footprint’ scanner is particularly attractive to endodontists as the combination of a small field of radiation with advanced digital processing reduces the effective dose of radiation to that of 5-6 standard periapical radiograph exposures.

The information gathered in such a scan dramatically increases diagnostic sensitivity, reducing the need for invasive investigation, as well as providing vital information on the anatomy of the roots, root canals and surrounding tissues, for treatment planning.

Two months of routine use of the scanner has revolutionised my practice of endodontics. I believe it has the same potential to change the face of the speciality as the introduction of the operating microscopes and nickel titanium files. Previously invisible periapical pathology under the distal root of a lower molar, reacting positively to an electric pulp test, was discovered and allowed treatment of unexplained pain. Vertical crown fractures of vital teeth extending into roots can be seen in the reactive bone loss and therefore a diagnosis and prognosis can be established.

The extent of areas of internal and external resorption can be correctly gauged and treatment planned. Hidden post or pin perforations, apical transportations and missed canal in the plane of the X-ray beam can be seen through z- and y-plane analysis.

Canal anatomy can be confirmed so time is not wasted looking for possible extra canals. Effective pre-apical surgery planning can be carried out locating anatomical structures such as the maxillary sinus or ID canal for safety, the position of the root apices relative to the surgical access, and the size of the lesion and its association with the apices of adjacent teeth so that damage can be avoided to their apical vessels. Even the effect of toxins from an irreversible pulpitis can be seen in damage to the periapical bone.

However, there are limitations in the use of CBCT scanners for endodontics. Frequently, judgements have to made on the quality of existing restorations and root fillings. These factors will impact significantly on diagnosis and treatment planning.

The presence of any radiopaque material causes artefact that affects the appearance of the tooth and surrounding structures. The denser the material, the more significant is the artefact, causing characteristic streaks (aliasing artefact) that appear as dark lines that radiate away from sharp corners.

One has to effectively ignore the information in the coronal tooth structures where restorations are present in the vicinity of the scan. Even heavily radiopaque structures from further afield can superimpose artefact over the scanned area and can be mistaken for pathology.

Non-metallic root fillings do not cause major artefacts but are seen to have associated shadows within the canal. Metal posts and implants can cause enough artefact to render diagnostic information from adjacent bone obsolete.

Understanding and interpreting CT artefacts as well as using techniques to minimise these, will be important skills in this emerging field of technology and is an area in which I have started to carry out some research. It is important to state that standard periapical and bitewing views are therefore still necessary to fully diagnose and plan endodontic treatment.
In planning the integration of such an expensive piece of equipment into a practice, the financial and practical implications need to be carefully considered. Apart from simple space requirements, health and safety aspects must be paramount, with full compliance of the radiation protection officer. Although the scanner is equipped with two powerful PCs, total scan volumes can be over 500 Mb in size, so network infrastructure will need to be fast enough to sustain these transfers together with a large capacity backup facility.

I decided early on that I would not charge patients a separate fee for a scan, counter to the most common practice nowadays. I am therefore able to take objective decisions on whether to scan a patient based on clinical need rather than financial goals. I am not financially target driven, and consider the equipment to be part of my diagnostic arsenal. I do not charge my patients for each radiograph, for the use of endo-ice, the electric pulp tester or even the tap of my mirror handle!

In summary, the arrival of the Morita CBCT scanner has heralded a new era in my own endodontic practice and teaching. In just a few months I have gathered enough cases to lecture for years on the power of this technology to radically enhance diagnostic and treatment planning in endodontics.

We are currently carrying out research into the ideal settings for periradicular lesion identification, and the recognition and reduction of dental artefact, but with the relentless march of technological innovation these images will continue to improve together with further reductions in radiation. Welcome to the future!

1. Tidmarsh BG (1987). Radiographic interpretation of endodontic lesions – a shadow of reality. International Dental Journal 37: 10-15; Mol A, van der Stelt PF (1992). Application of computer-aided image interpretation to the diagnosis of periapical bone lesions. Dentomaxillofacial Radiology 21: 190-194; Rohlin M, Kullendorff B, Ahlqwist M, Stenstrom B (1991). Observer performance in the assessment of periapical pathology: a comparison of panoramic with periapical radiography. Dentomaxillofacial Radiology 20: 127-131; Molander B, Ahlqwist M, Grondahl H-G (1995). Panoramic and restrictive intraoral radiography in comprehensive oral radiographic diagnosis. European Journal of Oral Science 103: 191-198
2. Bohay R (2000). The sensitivity, specificity, and the reliability of radiographic periapical diagnosis of posterior teeth. Oral Surgery, Oral Medicine Oral Pathology, Oral Radiology, Endodontics 89: 639-642.
3. Bender IB (1997). Factors influencing the radiographic appearance of bony lesions. Journal of Endodontics 23: 5-14
4. Quality guidelines for endodontic treatment: consensus report of the European Society of Endodontology (2006). International Endodontic Journal, 39 (12) 921-930; Patel S, Dawood A, Pitt Ford T, Whaites E (2007). The potential applications of cone beam computed tomography in the management of endodontic problems. International Endodontic Journal 40: 818–830.

alities of incorporating
micro CT in a specialist endodontic practice

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