The relationship between uninstrumented root canals and endodontic treatment failure has been studied extensively. Locating all the canals, then subsequently shaping and cleaning them in their entirety has shown to be essential for predictable clinical and biological success.1-4
High visual magnification and fibre optic illumination incorporated in the surgical operating microscope (SOM) has revolutionized endodontic therapy. The use of the SOM has facilitated the ease with which root canals are found in their typical as well as aberrant positions during orthograde endodontic treatment.5,6
Although the SOM is an indispensable aid in visualizing the detailed anatomy of the pulp chamber, it is essential to develop the visual acuity to appreciate the subtle differences that aid in the location of the root canals. The inherent color differences between the axial dentin and pulpal floor dentin, the coronal dentin and radicular dentin, as well as the differences in color and consistency between soft tissue and hard tissue will assist in locating the root canal orifices.7
This is of even greater significance in teeth with full coverage where the orientation markers of the natural tooth cannot be seen, such as cusp tips, grooves and the external contours of the root outlines. Other situations where the “pulpal road map” has been altered are teeth that have been previously endodontically treated where canals have been missed, where prior occlusal access has been made, altering the chamber floor anatomy, and teeth with pulp chamber obliterations and canal calcifications.
Any help in terms of “marking” the pulp tissue in canal orifices will facilitate the location of canals in both conventional and retreatment cases.
It is the purpose of this article to illustrate the significance and use of ophthalmic dyes in the location of root canal orifices.7
Ophthalmic dyes (e.g. Fluorescein sodium, rose bengal) are currently being used in opthamological diagnostic procedures and for locating damaged areas of the cornea due to injury or disease.
Other uses for these dyes in ophthalmology include detection of epithelial defects, evaluation of the nasolacrimal system, determination of tear breakup time, angiography, location of non-epithelialized foreign bodies and contact lens pressure points.8
Fluorescein sodium is available in pharmacies as a clear, orange-red solution as sterile, single-dose disposable eye drops in cartons of 10 units. Each unit contains approximately 0.5 ml. It is also available as individual strips. When the strips are used, the agents can be reconstituted by immersion in a dappen dish that contains sterile water or 90% alcohol (Figs. 1 & 2).
There are no serious contraindications reported for its use topically except possible hypersensitivity. No serious side effects have been reported except for nausea.8
There are few references for the use of ophthalmic dyes and fluorescence in dentistry. Those that of are significance have studied the use of ultra-violet induced fluorescence spectroscopy in diagnosis, pulp and root canal location, as well as using fluorescent spectroscopy to measure the relative sealing efficiency of root canal sealers.9-11
HOW THEY WORK
When these dyes come into contact with vital or nonvital pulp tissue they are readily absorbed by the connective tissue elements of the pulp in the chamber and root canal system. When exposed to blue light, these dyes dramatically fluoresce showing scattered tissue segments that contrast with the surrounding monochromatic dentin. It is this quality that makes them useful in the location of pulp tissue in root canals especially in those that are calcified and have tissue remnants within.7
TECHNIQUE
Once straight-line access is achieved and the coronal pulp tissue us removed, the pulp chamber is flooded with fluorescein sodium and allowed to contact all the walls for a couple of minutes. The excess is then suctioned away. With the incident light from the SOM turned off, blue light (dental curing light) is used to illuminate the chamber. With the aid of SOM the operator can now visualize the bright green fluorescence emitted by the pulp tissue that has absorbed the dye (Figs. 3 – 6).
CASE REPORT 1
A 25-year-old healthy female patient reported at the primary author’s private practice with the chief complaint of “toothache” in the upper left first molar. After clinical and radiographic examination completed, a diagnosis of irreversible pulpitis subsequent to dental caries had been made and endodontic treatment was advised.
Access into the pulp chamber revealed a hemorrhagic pulp which was removed. Three canals (mesiobuccal [MB], distobuccal [DB] and palatal [P]) were readily detected and straight-line access was directed to these canals.
In order to locate the mesiolingual (MB2) canal, the pulp chamber was flooded with fluorescein sodium. After suctioning the excess, a blue curing light was used to fluoresce the pulp tissue in the chamber including the isthmus between the MB and MB2 canal. The MB2 canal was readily located by the uptake of the dye that emitted bright green fluorescence. All four canals were then cleaned, shaped and obturated and the access subsequently restored (Figs. 7–19).
CASE REPORT 2
A 42-year-old male patient was referred to the primary author’s private practice after the referring dentist could not locate any of the buccal canals in a maxillary right first molar.
Radiographic examination revealed the canals appeared to be calcified in the coronal two millimeters. Once access was achieved, the pulp chamber was cleaned thoroughly with 5.25% sodium hypochlorite, rinsed with 100% ethyl alcohol, and then dried to visualize the anatomy of the chamber floor. There were no hints of the”pulpal road map” leading to the buccal canals. The access was then extended to below the cusp tips to facilitate straight-line access and pulp chamber was flooded with fluorescein sodium. After suctioning the excess, the chamber floor was examined through the SOM with a blue curing light (with the SOM light turned off). There was a dramatic bright green florescence where the remnants of pulp tissue were. On troughing further with ultrasonic tips (Endotips.com, San Diego, California) and exploration with DG-16 endodontic explorers (Hu-Freidy, Chicago, Illinois) MB, MB2, and DB canals were located. All canals were cleaned, shaped and obturated and the access cavity subsequently restored (Figs. 20 through 27).
There is no one single technique that will allow all canals to be found predictably 100% of the time. Keeping an open mind to new ways of thinking and accumulating the knowledge from different sources will allow new methods to emerge. The use of ophthalmic dyes in finding hidden and calcified canals is another useful tool to be included in the endodontic armamentarium to guide our pathway to predictable clinical and biological success.
Acknowledgement
The authors would like to thank Dr. Gary Carr (PERF) and members of “ROOTS” the Internet based endodontic discussion forum, for their invaluable support.
Dr. Sashi Nallapati graduated from the University of Health Sciences, Govt. Dental College, Hyderabad, India. He is currently in general practice with special interest in endodontics in Ocho Rios, Jamaica.
Dr. Glassman is the endodontic Editorial Board member for Oral Health.
Oral Health welcomes this original article.
REFERENCES
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2.Siqueira Junior JF, Etiology of root canal treatment failure: why well-treated teeth can fail. Int Endod J 2001 Jan; 34(1): 1-10
3.S Crump, M. C. (1979). “Differential diagnosis in endodontic failure.” Dental Clinics of North America 23(4): 617-35.
4.Cheung, G. S. (1996). “Endodontic failures–changing the approach.” Int Dent J 46(3): 131-8.
5.Carr GB Retreatment, Pathways of the Pulp 7th edition, 1998, page 810,832.
6.Ruddle CJ, Microendodontic Non-surgical Retreatment den
t.clin North America 41(3); 429,1997
7.Stephen Niemczyk, Intrinsic and extrinsic aids in root canal location, Endodontic Therapy, vol 2 number 1, pg 7.
8.Newell FW.Ophthalmology; Principles and Concepts. 6th Ed St.Louis, MO, CV Mosby Co; 1986:124.
9.Foreman PC, Ultra-violet light as an aid to diagnosis. Int Endod J (1983 Jul) 16(3): 121-6
10.Pini R, Salinbeni R, Vannini M, Cavalieri S, Barone R, Clauser C, Lasers: Root canal diagnostic technique based on ultra-violet induced fluorescence spectroscopy. Surg Med (1989) 9(4); 358-61
11.Taher, M, E. Sidky, et al. (1973). “The use of fluorescent dye for detecting the relative sealing efficiency of various root canal sealers. II. Qualitative assessment for the effect of aging.” Egyptian Dental Journal 19(2): 197-210.
