Working Length

[Name of the Institute]

Working Length

Introduction

Accurate determination of working length during endodontic therapy is a crucial step in achieving a predictable outcome. This is determined by the use of electronic apex locators, dental radiography, tactile perception, and knowledge of average tooth lengths. Currently, conventional films remain the gold standard in which all other imaging methodologies are compared. Recently, digital radiology has gained popularity among general dentists and endodontists and is challenging this gold standard. The advantages of digital radiography are many, including [3]:

Decreased exposure to radiation.

Faster acquisition of images.

Decreased cost over time.

Environmental compatibility due to lack of processing chemicals.

Enhanced patient education.

Ease of image manipulation to a certain degree.

However, many studies have examined the diagnostic quality of digital images versus conventional film, and the findings conflict.

Radel et al.1 recently compared Kodak RVG 6000, Schick CDR, and Kodak InSight digitized film with regard to working length determination. They found that Kodak RVG 6000 was significantly more accurate in determining working lengths. Some studies have shown that conventional film was superior in length measurements compared with older digital systems, whereas other studies show them to be comparable. Friedlander et al.2 compared phosphor plate-based digital images with conventional radiographs and found that perceived clarity of fine endodontic files and periapical lesions was significantly less with phosphor plate-based digital images than conventional films. Mentes and Gencoglu3 compared direct digital and conventional film for working length determination in curved canals and concluded that both systems were comparable. Loushine et al.4 determined that calibrated digital images were more accurate than uncalibrated images. Several other studies have examined the utilization of digital imaging for file length measurements with positive results [12].

Altering the projection geometry, kilovolt peak (kVp), milliampere (mA), exposure time, source-film distance and source-object distance, can affect the interpretability of any image. Specifically, increasing the exposure time causes the image to be darker, whereas decreasing the exposure time causes the image to be lighter. Magnification is a factor of the source-film distance and source-object difference. Specifically, source-film distance is directly proportional to magnification, whereas the source-object distance is indirectly proportional. Although increasing the source-film distance decreases magnification, it also causes the image to be lighter; therefore, exposure time, kVp, or mA must be increased.

Many of the studies evaluating image quality use standard source-film/sensor distance and exposure time. Kaeppler et al.12 altered the tube potential setting from 60kV to 90kV as well as by reducing the milliampere setting at unchanged tube potential. They evaluated peri-implant and decayed lesions and they found that intraoral films and storage phosphor plates demonstrated equal quality regardless of exposure at 60kV or 90kV [1].

History Of Endodontics

The presence of a toothache has plagued mankind for centuries. Its description has been found on Egyptian tablets, Hebrew books, and Chinese, Greek, and Roman medical writings. Fu Hsi (2953 BC) is credited with one of the earliest descriptions of toothaches. In the European and Mediterranean Basin, root canal treatments were performed in antiquity, and the Greeks describe attempts at hermetically sealing root canal systems.

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