Ounsi et al
Figure 5: This is the case of agenesia of the lower right second premola . Lower right second primary molar had conventional root canal therapy performed with gutta-percha obturation.
Contra-indications They are generally linked to the overall health of the child (special needs, disabled or cardiac patients), or to clinical considerations such as severely broken down teeth, unrestorable teeth, complex root canal morphology, internal or external resorptions, physiological resorption involving more than 2/3 of the root, perforated pulp floor with or without pathological bone resorption32.
Modus Operandi The pulpectomy technique in itself is rather similar to that performed on the permanent tooth. Following anesthesia and rubber dam placement, the access cavity is performed and the pulpal roof is removed. The bulky shape of temporary teeth helps reducing the enlargement required during access preparation to reach the canal entrances or infandibulum. Nevertheless, all overhanging dentin should be eliminated.
As for their permanent counterparts, Shaping and cleaning are the heart of the endodontic treatment. Estimated root canal length is obtained using a preliminary radiograph and subtracting 1-2mm from the length of the root canal as seen on the radiograph; it is then adjusted by placing a file to the actual length and confirming radiographically. Electronic working length determination is impossible as apex locators are useless on deciduous teeth with regards to their electrical and morphophysiological characteristics33. It is often preferable to reduce working length by 1-2mm to avoid overinstrumentation and overfilling as these teeth often present with apical resorption phenomena, and preserving the integrity of the apical area is paramount6. In general, wide canals (incisors and canines) are shaped to #30 and curved or narrow canals are shaped to #25.
Shaping is done in the conventional manner (step-back) while avoiding ultrasonic shaping instrumentation to
preserve the relatively thin root canal walls. Similarly, Gates- Glidden drills should be avoided because of the increased risk of stripping. Nickel-titanium rotary instruments are ideal for shaping deciduous teeth7. Irrigation is more crucial for cleaning since shaping is kept to a minimum and we rely on chemical cleaning to reach areas that were not addressed by mechanical instrumentation34. Using 5.25% sodium hypochlorite combined to 17% aqueous EDTA is capable of cleaning most complexities and irregularities of the root canal system.
Even though a conical shape is preferable, it is not necessary. This is directly related to the fact that the lifespan of such teeth is limited and to the characteristics of the filing material34. Contrary to permanent teeth, filling materials used for root canal sealing of deciduous teeth should be resorbable so they can be eliminated during the physiological root resorption process and not impede the eruption of the permanent tooth. Hence after cleaning and shaping, root canals are rinsed a last time with sodium hypochlorite, dried with paper points, and filled using a zinc oxide-eugenol paste34. Using medicamented paste as iodoform paste is also described although a retrospective study proved that the antibacterial activity of iodoform paste is less than that of ZOE paste while retaining more direct and indirect toxicity35-36. The root canal filling paste is placed using a spiral Lentulo-type paste filler and packed in the access cavity using a wet cotton pellet. Using pluggers or syringes (Messing Root Canal Gun, PD, Vevey, Switzerland) is also possible although there are no significant differences between these filling procedures37. Nevertheless, irrespective of the filling material or technique, the only constant is that overfilling should be avoided. The coronal access is then sealed using a glass- ionomer and a preformed metallic stainless steel pedodontic crown is placed to avoid tooth fracture. In case the tooth is to be maintained on the arch, root canal filling
INTERNATIONAL DENTISTRY SA VOL. 11, NO. 2